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Photonics West 2011: Presentations on Terahertz Wave Technology and Applications

 

Course: Terahertz Wave Technology and Applications

Date: Wednesday, 26 January 2011
Time: 8:30 AM ?12:30 PM

Instructor(s): Xi-Cheng Zhang, Rensselaer Polytechnic Institute (United States)
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A pulsed terahertz (THz) wave with a frequency range from 0.1 THz to 10 THz is called a "T-ray." T-rays occupy a large portion of the electromagnetic spectrum between the infrared and microwave bands. However, compared to the relatively well-developed science and technology in the microwave, optical, and x-ray frequencies for defense and commercial applications, basic research, new initiatives and advanced technology developments in the THz band are very limited and remain unexplored. However, just as one can use visible light to create a photograph, radio waves to transmit music and speech, microwave radiation (MRI) or X-rays to reveal broken bones, T-ray can be used to create images or communicate information. This course will provide the fundamentals of free-space THz optoelectronics. We will cover the basic concepts of generation, detection, propagation, and applications of the T-rays, and how the up-to-date research results apply to industry. The free-space T-ray optoelectronic detection system, which uses photoconductive antennas or electro-optic crystals, provides diffraction-limited spatial resolution, femtosecond temporal resolution, DC-THz spectral bandwidth and mV/cm field sensitivity. Examples of homeland security and defense related projects will be highlighted.

THz patterned antennas for THz-TDS

Paper 7937-13 of Conference 7937
Date: Sunday, 23 January 2011
Time: 3:00 PM ?3:15 PM

Author(s): Pouya Maraghechi, Abdulhakem Y. Elezzabi, Univ. of Alberta (Canada)
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We report on a comprehensive investigation of radiation characteristic of THz emitters using structures with specific patterns. Such unique geometrical properties in these antennas result in improving the coupling radiation to the free space. It is shown that these novel antennas produce higher radiation power when compared to the bow-tie antenna and their un-complementary structures. It was found that the complimentary structure having the highest structure complexity gave the best radiation power compared to all other antennas. To the best of our knowledge this is the first time that complimentary antennas have been used as emitters for generating THz radiation.

Terahertz holographic interferometry

Paper 7957-42 of Conference 7957
Date: Wednesday, 26 January 2011
Time: 6:00 PM

Author(s): Andrei A. Gorodetsky, Victor G. Bespalov, Saint-Petersburg State Univ. of Information Technologies, Mechanics and Optics (Russian Federation)
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We present our new modeling and research results on terahertz holographic interferometry, a technique allowing to reconstruct changes in inner dielectric object structure. The technique is somehow alike the corresponding one in optics, but allows managing optically opaque objects. Using the broadband pulse THz radiation with a spectrum in the range of 0.1-2.5 THz we can reconstruct object deformations up to several microns in the bulk 3d object.

Stimulated Smith-Purcell semiconductor THz sources

Paper 7953-28 of Conference 7953
Date: Tuesday, 25 January 2011
Time: 4:30 PM ?4:50 PM

Author(s): Don D. Smith, Texas A&M Univ. (United States)
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A simple three-layer planar semiconductor device consisting of a Gunn drift region, a dielectric layer and a metallic grating generates stimulated Smith-Purcell radiation. Frequency is determined solely by the ratio of domain velocity to grating period. The radiation is monochromatic, coherent, and strongly polarized along the axis of the device. Simulations of the device agree well with analytic calculations. InP yields radiated power density of 30nW per micron of device width at 0.27 THz. A hypothetical InN device yields 3.5uW/um at 0.25THz and 21nW/um at 1THz. The device is simple to fabricate, operates at room temperature, and warrants experimental investigation.

Terahertz antiresonant reflecting hollow-core waveguides for sensing applications

Paper 7938-18 of Conference 7938
Date: Thursday, 27 January 2011
Time: 4:40 PM ?5:00 PM

Author(s): Borwen You, Ja-Yu Lu, National Cheng Kung Univ. (Taiwan); Chi-Yu Chan, Chin-Ping Yu, National Sun Yat-Sen Univ. (Taiwan); Hao-Zai Chen, National Cheng Kung Univ. (Taiwan); Tze-An Liu, Jin-Long Peng, Industrial Technology Research Institute (Taiwan)
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A dielectric hollow tube utilized as a terahertz antiresonant reflecting hollow-core waveguide (THz-ARRHW) sensor has been demonstrated to detect the minute variation of both refractive index and thickness in macromolecule layers deposited on the tube wall, and to identify liquid vapors from the various core indices. The minimum detectable variations of sample-quantity and concentration are down to 1.2picomole/mm^2 and 0.2%, corresponding to the variation of 2.9祄-thickness and 0.001-refractive-index, respectively. A THz-ARRHW sensor is also used to identify various volatile liquid vapors in the hollow-core based on different induced core indices, and the detectable vapor density is down to 0.0001g/cm^3.

Recent progress of THz generation and detection in ambient air or gases

Paper 7917-15 of Conference 7917
Date: Tuesday, 25 January 2011
Time: 1:30 PM ?2:00 PM

Author(s): Xiaofei Lu, Benjamin W. Clough, I-Chen Ho, Jingle Liu, Jianming Dai, Xi-Cheng Zhang, Rensselaer Polytechnic Institute (United States)
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THz time domain spectroscopy has been largely applied on the measurement of semiconductor, electro-optic crystals, and selected chemical, biological and explosive materials. Here we will highlight THz gas photonics and its applications, with an emphasis on spectroscopic capabilities. The most recent results of using air (and selected gases) as the emitter and sensor material for both generation and detection of broadband THz waves will also be reported. Air, especially ionized air (plasma), has been used to generate intense peak THz waves (THz field > 1.5 MV/cm) with a broadband spectrum (10% bandwidth from 0.1 THz to 46 THz).

Integrated Terahertz pulse generation and amplification in quantum cascade lasers

Paper 7945-11 of Conference 7945
Date: Sunday, 23 January 2011
Time: 11:20 AM ?11:40 AM

Author(s): Sukhdeep S. Dhillon, Simon Sawallich, Nathan Jukam, Dimitri Oustinov, Julien Madeo, Rakchanok Rungsawang, Ecole Normale Supérieure (France); Stefano Barbieri, Pascal G. Filloux, Carlo Sirtori, Univ. Paris 7-Denis Diderot (France); Xavier Marcadet, Alcatel-Thales III-V Lab. (France); Jerome Tignon, Ecole Normale Supérieure (France)
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We demonstrate an integrated approach to generate and amplify Terahertz (THz) pulses within a quantum cascade laser (QCL). Using an ultrafast interband excitation of a THz QCL, THz pulses are generated via charge carrier acceleration within the QCL miniband. The generated pulses are subsequently amplified at the QCL gain as they propagate through the laser cavity. As well as integrating the generation and amplification of THz pulses, this technique can potentially permit efficient THz pulse injection into sub-wavelength double metal resonators.

Length dependence of forward and backward THz DFG in a strongly absorptive material

Paper 7917-17 of Conference 7917
Date: Tuesday, 25 January 2011
Time: 2:20 PM ?2:40 PM

Author(s): Yen-Chieh Huang, Yen-Hou Lin, Yen-Yin Lin, National Tsing Hua Univ. (Taiwan)
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Owing to the vast difference in wavelengths for THz difference frequency generation (DFG), a nonlinear optical material is often transparent to optical waves but could be highly absorptive to the THz wave. It has been widely believed that, in such a strongly absorptive nonlinear optical material, the useful DFG length is on the order of the THz absorption length. We show in DFG theory and experiment that the THz wave can grow monotonically over cm distance, despite an absorption length of 50 microns at 1.5 THz in lithium niobate.

Encoding terahertz signatures into laser-induced plasma acoustic waves

Paper 7938-3 of Conference 7938
Date: Thursday, 27 January 2011
Time: 8:50 AM ?9:10 AM

Author(s): Benjamin W. Clough, Jingle Liu, Xi-Cheng Zhang, Rensselaer Polytechnic Institute (United States)
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The enhancement of acoustic waves, from audible into the ultrasonic range, is a linear function of the THz intensity incident on a laser-induced plasma, making THz-enhanced acoustics (TEA) useful for THz detection. By using a dual-color laser field to produce the plasma detector, THz spectroscopic information can be encoded into the acoustic emission, making it possible to obtain the electric field profile of the THz pulse by simply "listening" to the plasma at a distance.

Semiconductor plasmons for THz frequency plasmonics

Paper 7937-12 of Conference 7937
Date: Sunday, 23 January 2011
Time: 2:35 PM ?3:00 PM

Author(s): Euan Hendry, The Univ. of Exeter (United Kingdom)
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Surface plasmons (SPs) are electromagnetic waves that propagate along the interface between a conductor and insulator. To date, studies of SPs have been limited to optical frequencies near metallic plasma frequencies, where SP modes are strongly confined to metal surfaces. However, we have shown that certain semiconductors can support confined SPs at THz frequencies. We have demonstrated that SPs play an important role in a variety of physical phenomena, elucidating their role in the transmission of THz radiation through semiconductor structures such as sub-wavelength slits and holes.

Coherent control of ultrafast photocurrents in GaAs

Paper 7937-30 of Conference 7937
Date: Monday, 24 January 2011
Time: 1:55 PM ?2:20 PM

Author(s): Sangam Chatterjee, Kapil K. Kohli, Jan Mertens, Philipps-Univ. Marburg (Germany); Mark Bieler, Physikalisch-Technische Bundesanstalt (Germany)
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The relationship between the electrical field of an optical pulse and its encompassing pulse envelope is characterized by the carrier-envelope phase (CEP). We show, that by using a phase stable pulse pair generated in a pulse shaper we can use the relative CEP between the two pulses as a new degree of freedom in coherent control experiments even for pulses that are not in the single-cycle regime. We demonstrate how to use the CEP to coherently control the shift current generation process in bulk GaAs, by measuring the emitted THz radiation in a standard THz emission setup. A straightforward theoretical model corroborates our experiment.

Using the gene expression profile of jurkat cells to determine whether terahertz (THz) radiation couples to DNA and impacts transcription processes

Paper 7897-13 of Conference 7897
Date: Monday, 24 January 2011
Time: 2:20 PM ?2:40 PM

Author(s): Jessica E. Grundt, Benjamin D. Rivest, Caleb C. Roth, Bennett L. Ibey, Michael L. Doroski, Jason A. Payne, William P. Roach, Gerald J. Wilmink, Air Force Research Lab. (United States)
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Theoretical models suggest that 2.52 THz radiation couples directly to DNA and affects transcriptional processes; however, this phenomenon has not been empirically confirmed. In this study, we hypothesized that if THz radiation does damage DNA then exposed cells will express known damage and repair genes. To test this hypothesis, we irradiated Jurkat cells using a THz laser (2.52 THz, 252 mWcm-2, t=5-50 minutes), and evaluated their response using viability, qPCR, and microarray techniques. We found several genes were markedly upregulated in each THz exposure group; however, the majority encoded for heat shock proteins and few for DNA repair proteins.

One- and two-dimensional THz spectroscopy on semiconductor nanostructures

Paper 7937-32 of Conference 7937
Date: Monday, 24 January 2011
Time: 2:45 PM ?3:10 PM

Author(s): Michael Woerner, Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie (Germany)
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Using our novel high field terahertz source we performed various nonlinear experiments on semiconductor nanostructures. In one-dimensional nonlinear propagation experiments on n-type GaAs we observed ballistic high-field transport and THz-induced interband tunneling of electrons. Two-dimensional THz correlation spectroscopy performed on intersubband transitions of two coupled quantum wells shows distinct polaronic features of the intersubband transitions.

Using nanoscale molecular dynamics modeling and Raman spectroscopy to investigate the direct effect of Terahertz radiation on double-stranded DNA

Paper 7897-15 of Conference 7897
Date: Monday, 24 January 2011
Time: 3:00 PM ?3:20 PM

Author(s): Gerald J. Wilmink, Jessica E. Grundt, Air Force Research Lab. (United States); Brett R. Boyce, U.S. Air Force Academy (United States); James E. Parker III, Air Force Research Lab. (United States) and The Univ. of Texas at San Antonio (United States); Brady Mcmicken, The Univ. of Texas at San Antonio (United States); Caleb C. Roth, Bennett L. Ibey, Michael L. Doroski, Benjamin A. Rockwell, Robert J. Thomas, William P. Roach, Air Force Research Lab. (United States)
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Theoretical models suggest that 2.52 Terahertz (THz) radiation can couple directly to the natural breathing modes of double stranded DNA (dsDNA) resulting in the creation of "bubbles" between dsDNA. In this study, we used Raman spectroscopy and nanoscale molecular dynamics modeling (NAMD) tools to evaluate the effect that 2.52 THz radiation has on the hydrogen bonding in dsDNA. Raman spectra were collected as various wavelengths (414 nm, 514 nm) on both salmon sperm dsDNA (~2-3k base pairs) and custom-designed dsDNA (polyA/T, 50bps). Comparable analyses were also conducted for hyperthermic and UV positive-controls.

Monolithically integrated THz transceivers

Paper 7953-27 of Conference 7953
Date: Tuesday, 25 January 2011
Time: 4:00 PM ?4:30 PM

Author(s): Michael C. Wanke, Mark Lee, Christopher D. Nordquist, Michael J. Cich, Sandia National Labs. (United States); Albert D. Grine, LMATA Government Services (United States); Chuck T. Fuller, John L. Reno, Sandia National Labs. (United States)
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We demonstrate a monolithically integrated THz transceiver consisting of a Schottky diode embedded into a THz QCL waveguide. Besides functioning as a heterodyne receiver for externally incident radiation, the device is a useful tool for characterizing the performance and dynamics of the QCL. This talk gives an overview of the device, demonstrates receiver operation, and presents laser dynamics measurements especially related to feedback of the QCL's emission due to retroreflections. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Ultra-sensitive, room-temperature THz detection based on parametric upconversion by using a pulsed 1550nm optical source

Paper 7917-36 of Conference 7917
Date: Wednesday, 26 January 2011
Time: 4:00 PM ?4:30 PM

Author(s): Mohammad J. Khan, Jerry C. Chen, Zong-Long Liau, Sumanth Kaushik, MIT Lincoln Lab. (United States)
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The paper will detail ultra-sensitive room temperature detection of THz radiation using nonlinear up-conversion. We will describe the experimental setup, focusing on the architecture and performance of the pulsed 1550 nm optical pump, the nature of THz sources that are employed, the quasi phase-matched GaAs crystal and its fabrication process. Temporal and spectral scans showing the up-converted light generated from continuous-wave and pulsed THz sources, using bulk and phase-matched GaAs crystals and different optical detectors, will be presented. Measurements of the noise equivalent power, the phase-matching bandwidth, and temporal resolution of the THz detector will be compared with theoretical calculations.

Optical properties and applications of liquid crystals in the THz frequency range

Paper 7955-25 of Conference 7955
Date: Wednesday, 26 January 2011
Time: 4:30 PM ?5:00 PM

Author(s): Ci-Ling Pan, National Tsing Hua Univ. (Taiwan)
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In the past decade, THz studies ranging from investigations of ultrafast dynamics in materials to medical, environmental sensing and imaging have been actively explored. For these and future applications in THz communication and surveillance, quasi-optic components such as phase shifters are indispensable. The birefringence of liquid crystal (LC) is well known and extensively utilized for the manipulation of optical radiation in the visible and near-infrared range. Recently, there have been increasing interests in the study of liquid-crystal-based devices for application in the sub-millimeter wave or THz frequency range. In this paper, we review recent available optical constants of selected liquid crystals in this important frequency range and recent advances in liquid crystal THz optic and photonic devices.

1/f noise in Schottky diodes

Paper 7939-64 of Conference 7939
Date: Wednesday, 26 January 2011
Time: 6:00 PM

Author(s): Peter H. Handel, Univ. of Missouri-St. Louis (United States); Hadis Morkoç, Virginia Commonwealth Univ. (United States)
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MBE-grown ErAs:InAlGaAs metal-semiconductor Schottky diodes are best suited for use in focal plane arrays for millimeter and sub-millimeter wavelength imaging. The present paper applies the quantum theory of 1/f noise to individual diodes of this type, to back-to-back ErAs contacted diodes without sidewalls, and also to similar diodes fabricated with sidewalls. We start from the quantum 1/f expression of the spectral density S_I(f)= 2 e I_d +(e^3 alpha_H I_0/3 k_T f)[v_r v_d/(v_r+v_d)][2N_d(V_dif-V)/e Epsilon]^1/2. This expression takes into account the image force and is valid both in the diffusion-limited (v_r>>v_d) and thermionic-limited (v_d>>v_r) limiting regimes. Here V_dif-V is the Schottky barrier height, Mu the mobility, N_d the concentration of donors, e the elementary charge, alpha_H the Hooge constant, and Epsilon the permittivity of the semiconductor. For a small, heavily doped semiconductor, our conventional collisional quantum 1/f expression of alpha_H is alpha_H=(4alpha/3Pi)(6kT/m*c^2)=10^-9 Tm/(4m*100K), with v_r=(kT/2Pi m*)^1/2, v_d=Mu[2e N_d(V_dif-V)/Epsilon]^1/2. For larger semiconductor contacts a coherent quantum 1/f contribution may yield a much larger alpha_H. Here alpha is the fine structure constant 1/137, m the electron's mass and m* its effective mass. Quantum 1/f noise is a property of physical cross sections, a new aspect of quantum mechanics.

THz and millimeter wave vacuum electronic sources

Paper 7938-14 of Conference 7938
Date: Thursday, 27 January 2011
Time: 2:50 PM ?3:10 PM

Author(s): Laurence P. Sadwick, InnoSys, Inc. (United States)
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We will present recent work on a new class of vacuum electronic devices designed for high power operation in the millimeter wave (mm-wave) to low THz frequency region. These vacuum electronic devices are built using microfabrication and micromachining techniques. Power levels ranging from watts to milliwatts can be produced in a reproducible fashion. Some potential applications of these mm-wave and THz sources will also be presented.

Modelling of detector cavities at THz frequencies

Paper 7938-17 of Conference 7938
Date: Thursday, 27 January 2011
Time: 4:20 PM ?4:40 PM

Author(s): Stephen D. Doherty, National Univ. of Ireland, Maynooth (Ireland)
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Work being carried out at NUI-Maynooth is considering a mode matching approach to the simulation of closed cavities. This approach is based operates by cascading the S-matrices across, and conserving power, at each junction. This talk will examine various approaches to simulating closed cavities and will focus primarily on this method. An outline of how the introduction of additional reflection matrices can be employed to model a closed cavity structure will be presented. The introduction of an absorption matrix, determined by the dielectric properties of the material in question, to determine the optical performance of a cavity enclosed absorber will also be examined.

Ultrafast gain switching of quantum cascade lasers

Paper 7937-24 of Conference 7937
Date: Monday, 24 January 2011
Time: 10:35 AM ?11:00 AM

Author(s): Sukhdeep S. Dhillon, Nathan Jukam, Dimitri Oustinov, Rakchanok Rungsawang, Julien Madeo, Ecole Normale Supérieure (France); Stefano Barbieri, Christophe Manquest, Carlo Sirtori, Univ. Paris 7-Denis Diderot (France); Suraj P. Khanna, Edmund H. Linfield, Giles Davies, Univ. of Leeds (United Kingdom); Jerome Tignon, Ecole Normale Supérieure (France)
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Terahertz (THz) time domain spectroscopy is now a widely used technique where it is essential to know both the amplitude and phase of a THz wave. Nonetheless, THz amplifiers, capable of increasing the THz wave field, are presently lacking. In this context THz quantum cascade lasers (QCL) are very promising devices for amplification. Gain clamping in these devices, however, limits the attainable amplification. Here we circumvent gain clamping by coupling a THz QCL and an integrated Auston-switch to perform ultrafast gain switching. The resulting non-equilibrium gain is not clamped above laser threshold and large amplification of input terahertz pulses is demonstrated.

Controlling THz plasmons with the electron spin state

Paper 7937-11 of Conference 7937
Date: Sunday, 23 January 2011
Time: 2:20 PM ?2:35 PM

Author(s): Cameron J. E. Straatsma, Abdulhakem Y. Elezzabi, Univ. of Alberta (Canada)
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We investigate the effects of photonic magnetoresistance on the propagation of terahertz (THz) radiation in multilayered metallic media. These subwavelength plasmonic structures contain alternating layers of ferromagnetic and non-magnetic metal thin films, which allow for control over the electron spin state. In particular, using THz time-domain spectroscopy, a photonic analogous giant magnetoresistance effect is observed and its application in actively controlling THz plasmons is studied. We demonstrate the possibility of implementing this effect to produce active THz guided wave devices.

Ultrafast carrier capture and THz resonances in InGaAs quantum posts

Paper 7937-2 of Conference 7937
Date: Sunday, 23 January 2011
Time: 9:10 AM ?9:35 AM

Author(s): Dominik Stehr, Univ. of California, Santa Barbara (United States) and Forschungszentrum Dresden-Rossendorf e.V. (Germany); Christopher M. Morris, Univ. of California, Santa Barbara (United States); Diyar Talbalyev, Los Alamos National Lab. (United States); Martin Wagner, Forschungszentrum Dresden-Rossendorf e.V. (Germany); Hyochul Kim, Univ. of California, Santa Barbara (United States); Antoinette J. Taylor, Los Alamos National Lab. (United States); Harald Schneider, Forschungszentrum Dresden-Rossendorf e.V. (Germany); Pierre M. Petroff, Mark S. Sherwin, Univ. of California, Santa Barbara (United States)
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Semiconductor quantum posts - nanowire-like InGaAs heterostructures in a GaAs matrix - were investigated with respect to their carrier capture dynamics after photoexcitation into the GaAs matrix. The results of the THz experiment demonstrate that after ultrafast excitation, electrons relax within a few picoseconds into the quantum posts, which act as efficient traps. Saturation of the quantum post states, probed by time-resolved photoluminescence, was reached at approximately ten times the quantum post density. Additionally, possible electronic THz resonances with a dipole moment in the growth direction were probed showing a broad response around 1.5 THz.

Intersubband impact ionization in THz QWIPs: shaping band structure reorganizations to design novel detectors

Paper 7945-33 of Conference 7945
Date: Monday, 24 January 2011
Time: 8:40 AM ?9:00 AM

Author(s): A. Delga, Univ. Paris 7-Denis Diderot (France); F.-R. Jasnot, Ecole Normale Supérieure (France); Amandine Buffaz, Univ. Paris 7-Denis Diderot (France); H. Guo, National Research Council Canada (Canada); Laetitia Doyennette, Univ. Paris 7-Denis Diderot (France); Louis-Anne de Vaulchier, Ecole Normale Supérieure (France); Zbigniew R. Wasilewski, Hui Chun Liu, National Research Council Canada (Canada); Vincent Berger, Univ. Paris 7-Denis Diderot (France)
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In this paper phase transitions and instabilities in Thz QWIPs will be studied. At low temperature, a current phase transition occurs when the voltage reaches a threshold where a quantum well can be depleted by efficient impact ionization. This depletion induces an enhancement of the local electric field and results in a barrier breakdown at the contact, which dramatically increases the current injection in the device. Hysteresis is observed between these two states of the system. It is crucial to understand the physics of the electronic transport in this device in order to be able to design very sensitive Thz detectors, working at the edge of the phase transition. In this paper, we describe in detail the electronic transport, and show how a full calculation of the transport (including the calculation of impact ionization and electronic capture in the wells) leads to the full I(V) curve, despite its very sophisticated shape. Thanks to this modeling, the design of very efficient Thz detectors will be discussed.

Phonon and polaron enhanced IR-THz photodetectors

Paper 7945-34 of Conference 7945
Date: Monday, 24 January 2011
Time: 9:00 AM ?9:20 AM

Author(s): Hui Chun Liu, Chun-Ying Song, Zbigniew R. Wasilewski, Margaret Buchanan, National Research Council Canada (Canada)
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We investigate the active use of phonons and polarons for realizing new optoelectronics devices. We present an application of the concept to photodetection in the infrared-terahertz spectrum. The ability to design a phonon or polaron is the first step in making use of them. We show this by a model system employing the electron intersubband excitation in quantum wells coupled with phonon modes. This results in a photodetector with a high response at the selected wavelength.


GaN for THz sources

Paper 7945-35 of Conference 7945
Date: Monday, 24 January 2011
Time: 9:20 AM ?9:40 AM

Author(s): Michel Marso, Univ. du Luxembourg (Luxembourg)
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In this work we investigate the unique electrical and thermal performance of GaN to improve two different approaches to generate THz radiation. One method is the heterodyne photomixing, where the THz output power is restricted by the thermal and electrical limits of the conventionally used LT GaAs. The aim of our work is to increase the output power by replacing the LT GaAs with low-temperature grown GaN. In the second approach GaN-based ultrafast high electron mobility transistors are developed for use in a high power high frequency oscillator circuit that acts as source for a frequency multiplier chain.

THz techniques for human skin measurement

Paper 7897-12 of Conference 7897
Date: Monday, 24 January 2011
Time: 2:00 PM ?2:20 PM

Author(s): Yu Guan, Takayuki Shibuya, Koji Suizu, Nagoya Univ. (Japan); Shin'ichiro Hayashi, RIKEN (Japan); Kodo Kawase, Nagoya Univ. (Japan) and RIKEN (Japan)
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We are developing several novel THz techniques for skin measurement. A high-resolution tomographic imaging was demonstrated using a reflection-type terahertz time-domain spectroscopy. The wideband spectrum of the terahertz waves provided high-axial resolution of 5?m leading to tomographic imaging of multilayered skin structure. Secondly, we have demonstrated a sensitive THz imaging method using an interference effect. We applied this technique for the thickness measurement of human skin adhered onto a sticky tape. Thirdly, metal-mesh film can be used for sensing when samples adhere to the metal surface. We report on the spectrum change of metal-mesh with horny layer.

Multi-THz fields exceeding 100 MV/cm: an ultrabroadband source for sub-cycle nonlinear optics

Paper 7917-11 of Conference 7917
Date: Tuesday, 25 January 2011
Time: 10:30 AM ?11:00 AM

Author(s): Alexander Sell, Friederike Junginger, Olaf Schubert, Bernhard Mayer, Univ. Konstanz (Germany); Tobias Kampfrath, Martin Wolf, Fritz-Haber-Institut der Max-Planck-Gesellschaft (Germany); Daniele Brida, Marco Marangoni, Giulio Cerullo, Politecnico di Milano (Italy); Alfred Leitenstorfer, Rupert Huber, Univ. Konstanz (Germany)
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We present a table-top source of extremely intense multi-THz transients covering the spectral regime between 0.1 and 140 THz. Electric field amplitudes of up to 108 MV/cm and pulse durations as short as a single cycle are demonstrated with our hybrid Er:fiber-Ti:sapphire laser system. All THz waveforms are electro-optically detected. The multi-branch fiber laser generates gate pulses as short as 4.3 fs. Our high-field THz facility opens the door to extremely nonlinear optics in a previously hard-to-access spectral regime. First applications include THz coherent control and four-wave mixing studies as well as all-magnetic control of coherent spin waves.

Broadband emission from THz quantum cascade lasers

Paper 7953-24 of Conference 7953
Date: Tuesday, 25 January 2011
Time: 2:00 PM ?2:20 PM

Author(s): Dana Turcinkova, Giacomo Scalari, Maria Amanti, Mattias Beck, Jerome Faist, ETH Zurich (Switzerland)
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We demonstrate broadband laser emission at THz frequencies from quantum cascade laser structures based on heterogenous cascades. The active material is composed by five stacks of three different active regions. Each active region is based on a 4-quantum well structure employing a bound-to-continuum transition. Laser emission is observed over a bandwidth of nearly one THz, spanning from 2.24 THz to 3.2 THz. Peak powers of more than 2 mW from a double metal waveguide and maximum operating temperatures of 100 K have been observed with threshold current densities as low as 230 A/cm^2 at 10 K.

Advancements in photomixing and photoconductive switching for THz spectroscopy and imaging

Paper 7938-1 of Conference 7938
Date: Thursday, 27 January 2011
Time: 8:00 AM ?8:30 AM

Author(s): Elliott R. Brown, Wright State Univ. (United States) and Physical Domains, LLC (United States)
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Ultrafast photoconductive devices have been an important breakthrough in THz technology during the past two decades. Photoconductive switches have become the workhorse in moderate-resolution time-domain systems, and photomixers have been widely implemented in high-resolution spectrometers of various types. The primary photoconductive material has been low-temperature-grown GaAs. More recently, this has been rivaled by ErAs-GaAs: a nanocomposite consisting of ErAs nanoparticles embedded in a GaAs matrix. ErAs-GaAs photomixers have produced very useful THz output power levels between 1.0 and 10.0 microwatt when pumped by low-cost DFB lasers operating around 780 nm. ErAs-GaAs photoconductive switches have produced average output power approaching 1 mW, and peak power exceeding 1 W when pumped by frequency-doubled fiber model-locked lasers. The photomixer performance has been utilized in the first U.S. commercial THz photomixing spectrometer which has already been demonstrated on a variety of interesting materials including polar vapors, solid explosives, polysaccharides, nucleic acids, and nonlinear-optical crystals. The photoconductive switch performance has been utilized in a THz impulse radar having a broadband power spectrum centered at around 500 GHz, and a relatively simple gated-receiver to provide pulse averaging and noise reduction. The impulse radar has been used for several applications in biomedical imaging, such as imaging of skin burns, skin cancer, and the ocular cornea.

Semiconductor-coated deep subwavelength spoof surface plasmonic waveguide for THz and MIR applications

Paper 7938-8 of Conference 7938
Date: Thursday, 27 January 2011
Time: 11:20 AM ?11:40 AM

Author(s): Ruoxi Yang, Wangshi Zhao, Zhaolin Lu, Rochester Institute of Technology (United States)
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We propose integrated waveguides for terahertz (THz) and mid-infrared (MIR) applications on wafer platform. Based on the prototype of spoof plasmonic waveguides consisting of textured metallic surface, we explore the possibility of coating periodic metallic pattern with silicon (at 0.6 THz) or germanium (at MIR region of 30 THz) to further shrink the relative mode size of propagation spoof plasmonic waves. Numerical modeling via 3D finite-difference time-domain (FDTD) has shown deep sub-wavelength mode confinement in transverse directions to smaller than ?/50 by ?/50, with an estimated propagation loss of less than 0.1 dB for each repetitive unit.

THz lasing concepts based upon InAs/GaSb broken-gap heterostructures

Paper 7938-10 of Conference 7938
Date: Thursday, 27 January 2011
Time: 1:20 PM ?1:50 PM

Author(s): Dwight L. Woolard, U.S. Army Research Office (United States); Weidong Zhang, North Carolina State Univ. (United States)
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THz thermal emission from a 1D photonic crystal

Paper 7938-12 of Conference 7938
Date: Thursday, 27 January 2011
Time: 2:10 PM ?2:30 PM

Author(s): Ian A. Zimmerman, Ziran Wu, Hao Xin, Richard W. Ziolkowski, The Univ. of Arizona (United States)
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We have experimentally and theoretically investigated a simple 1D, bi-layered electromagnetic crystal structure composed of air and silicon slabs. We have calculated the emissivity using Kirchhoff's thermal radiation law, as well as by calculating the density of states directly, and have compared those results to the experimental values. Our ultimate goal is to be able to control the spectral emission of an electromagnetic crystal in the THz region (or other wavelength ranges, such as the infrared) by engineering its band structure with the desire to develop a cheap, incoherent broadband THz source.

Electromagnetic crystal (EMXT) based THz components

Paper 7938-16 of Conference 7938
Date: Thursday, 27 January 2011
Time: 4:00 PM ?4:20 PM

Author(s): Ziran Wu, Wei-Ren Ng, Michael E. Gehm, Hao Xin, The Univ. of Arizona (United States)
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All-dielectric Terahertz waveguides based on hollow-core EMXT fiber are fabricated via THz rapid prototyping using polymer jetting technique. Several waveguides of identical cross-section and differing lengths are characterized by THz time-domain spectroscopy (THz-TDS) to extract the waveguide intrinsic propagation loss. Measurement results agree very well with simulation. This as an initial example demonstrates a waveguide with low propagation loss of 0.03 dB/mm at 105 GHz. Based on the waveguide, an EMXT antenna is also formed by modifying the defect shape into a horn. Simulation shows good performance of this horn antenna. The antenna is fabricated by the same rapid prototyping method, and its far-field pattern measurement result will be reported.

Nonlinear holographic imaging of terahertz radiation

Paper 7917-12 of Conference 7917
Date: Tuesday, 25 January 2011
Time: 11:00 AM ?11:20 AM

Author(s): Jean-Christophe Delagnes, Patrick Mounaix, Lionel Canioni, Univ. Bordeaux 1 (France)
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We present a theoretical investigation of a non-collinear sum frequency generation in an electrooptic crystal between a visible and a THz radiation. This results in the encoding of the spatial phase of the THz object field onto the visible wave. We can thus record THz scene with conventional optical detector that are much more sensitive than THz sensors. We show that a Nonlinear Snell-Descartes' Lens Formula can be derived from our analysis; in comparison to the classical one this generalized lens formula exhibits an additional magnification factor proportional to the ratio between the optical and THz wavelength.

Coherent monolithic THz generation based on quasi-phase-matched GaP bonding structures pumped by pulsed fiber lasers at ~ 1.5 祄

Paper 7917-16 of Conference 7917
Date: Tuesday, 25 January 2011
Time: 2:00 PM ?2:20 PM

Author(s): Wei Shi, NP Photonics, Inc. (United States); Eliot B. Petersen, NP Photonics, Inc. (United States) and The Univ. of Arizona (United States); Arturo Chavez-Pirson, NP Photonics, Inc. (United States); Nasser Peyghambarian, NP Photonics, Inc. (United States) and The Univ. of Arizona (United States)
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We report the coherent monolithic THz generation by using GaP QPM bonding structures based on difference-frequency generation (DFG) pumped by the pulsed fiber lasers in the C-band. The highest average power is about 10.9 uW at 1.5 THz by using 6-period GaP QPM bonding structure. Comparing with the single layer GaP crystal, 6-period GaP QPM bonding structure has 26 times of enhancement in THz generation. The azimuthal dependence of the THz generation for the GaP QPM bonding structure has been measured when the polarization directions of two pump beams are orthogonal and parallel, respectively.

Terahertz time-lapse video of hydration in physiological tissues

Paper 7938-20 of Conference 7938
Date: Thursday, 27 January 2011
Time: 10:10 AM ?10:30 AM

Author(s): David B. Bennett, Zachary D. Taylor, Sijun Sung, Borokh Makkabi, Priyamvada Tewari, Neha Bajwa, Rahul S. Singh, Martin O. Culjat, Warren S. Grundfest M.D., Univ. of California, Los Angeles (United States); Elliott R. Brown, Univ. of California, Santa Barbara (United States) and Wright State Univ. (United States)
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This study describes terahertz (THz) imaging and monitoring of physiological tissues over long periods of time based on high sensitivity to hydration levels. A fast-scanning, gated time-domain THz imaging system (centered at 525 GHz; 125 GHz bandwidth) was utilized which uses dynamic pixel acquisition to image a 4-cm2 area in less than two minutes. THz video was taken on three sample systems: (1) a simple binary system of water absorbed into a polypropylene towel, (2) the accumulation of fluid to the site of a sulfuric acid burn on ex vivo porcine skin, and (3) the evaporative dehydration of a porcine cornea. The diffusion-regulating behavior of corneal and skin tissue is elucidated. We conclude from this study that THz imaging can discern the differences between diffusion of liquid water in physiological tissues and that of inanimate, homogeneously-diffusing matter.

Investigation of metamaterials for terahertz frequency range

Paper 7917-13 of Conference 7917
Date: Tuesday, 25 January 2011
Time: 11:20 AM ?11:40 AM

Author(s): Riad Yahiaoui, Univ. Bordeaux 1 (France); Hynek Nemec, Petr Ku瀍l, Filip Kadlec, Christelle Kadlec, Institute of Physics of the ASCR, v.v.i. (Czech Republic); Jörg Schilling, Martin-Luther-Univ. Halle-Wittenberg (Germany); M. Bari, Science and Technology Research Partners Ltd. (Ireland); Jean-Christophe Delagnes, Patrick Mounaix, Univ. Bordeaux 1 (France)
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We have demonstrated theoretical and experimental investigation of fishnet metamaterials at terahertz frequencies. Several prototypes were fabricated using optical lithography or laser micromachining technique. We carried out experiments using terahertz time domain spectroscopy THz-TDS. Moreover, we proposed THz metamaterials showing a tunable spectral interval where the magnetic permeability reaches negative values. This behavior was confirmed both theoretically and experimentally. These demonstrated principles represent a step forward towards a construction of a metamaterial with negative refractive index capable to cover continuously a broad range of THz frequencies and opens a new path for the active manipulation of submillimeter beams.

Upper limits on terahertz difference frequency generation power in quantum well heterostructures

Paper 7953-29 of Conference 7953
Date: Tuesday, 25 January 2011
Time: 4:50 PM ?5:10 PM

Author(s): Yong-Hee Cho, Texas A&M Univ. (United States); Mikhail A. Belkin, The Univ. of Texas at Austin (United States); Alexey A. Belyanin, Texas A&M Univ. (United States)
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We investigate the upper limits on the terahertz (THz) difference frequency generation (DFG) power that can be achieved in intersubband quantum well systems under external mid-infrared pumping. We solve self-consistently three coupled wave equations, the Poisson equation, and density matrix equations including pump depletions and nonlinear saturation effects. The maximal THz DFG power is reached for intermediate pump intensities of the order of the saturation intensity. Further increase of pump intensities degrades the maximum THz DFG power and shifts it to large detunings. We compare our results with recent experiments in GaInAs/AlInAs heterostructures and suggest optimal device designs.

Comparison of GaAs and DAST electro-optic crystals for THz time domain spectroscopy using 1.55 祄 fiber laser pulses

Paper 7938-6 of Conference 7938
Date: Thursday, 27 January 2011
Time: 9:50 AM ?10:10 AM

Author(s): Matthieu Martin, Juliette Mangeney, Paul Crozat, Univ. Paris-Sud 11 (France); Patrick Mounaix, Univ. Bordeaux 1 (France)
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We report terahertz time-domain spectroscopy system based on Er:fiber laser at 1.55 祄 wavelength that integrate an ion-irradiated In0.53Ga0.47As photoconductive antenna as emitter and a GaAs or a DAST electro-optic sensor as detector. Detection using GaAs crystal is performed with an electro-optic sampling detection based on polarization rotation of optical probe beam. We have implemented interferometric scheme to detect the phase change of optical probe beam due to THz-induced electro-optic effect in DAST crystal since the standard electro-optic sampling technique is not applicable to DAST crystal. The detected bandwidth is 3 THz using GaAs crystal and reaches 5 THz using DAST crystal.

A mechanically tunable terahertz modulator based on antiresonant reflecting hollow waveguide

Paper 7938-11 of Conference 7938
Date: Thursday, 27 January 2011
Time: 1:50 PM ?2:10 PM

Author(s): JaYu Lu, Hao-Zai Chen, National Cheng Kung Univ. (Taiwan); Chih-Hsien Lai, Hung-Chun Chang, National Taiwan Univ. (Taiwan); Borwen You, National Cheng Kung Univ. (Taiwan); Tze-An Liu, Jin-Long Peng, Industrial Technology Research Institute (Taiwan)
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We have experimentally demonstrated a broadband tunable terahertz (THz) modulator based on one-dimensional anti-resonant reflecting hollow waveguide (ARRHW), which consisting of a PMMA-made cladding and a pair of motorize-controlled metal plates located outside that. By continually varying the distance d between the PMMA-cladding and the metal plate, it enables dynamical tuning of the transmission band and linear attenuation of THz power for a specific frequency. The measured maximum spectrum tuning range of 60GHz and the power modulating depth of 20dB are achieved. The low loss THz-ARRHW based device is also promising for the polarization filter application with extinction-ratio of 20dB.

Phase-locking and synthesis of terahertz quantum cascade laser emission

Paper 7953-26 of Conference 7953
Date: Tuesday, 25 January 2011
Time: 3:30 PM ?4:00 PM

Author(s): Stefano Barbieri, Marco Ravaro, Pierre Gellie, Univ. Paris 7-Denis Diderot (France); Giorgio Santarelli, LNE-SYRTE, CNRS, UPMC (France); Christophe Manquest, Carlo Sirtori, Univ. Paris 7-Denis Diderot (France); Suraj P. Khanna, Edmund H. Linfield, Univ. of Leeds (United Kingdom)
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We demonstrate that the carrier frequency and the repetition rate of a Terahertz (THz) quantum cascade laser (QCL) can be simultaneously phase-locked to the repetition rate of a mode-locked Er-fiber laser. By combining the two stabilization techniques we show that all the longitudinal modes of a multimode QCL emitting at ~2.4THz can be phase-locked, paving the way to the use of these sources for high power, direct THz frequency synthesis.

High peak power femtosecond pulse VECSELs for terahertz time domain spectroscopy

Paper 7919-38 of Conference 7919
Date: Tuesday, 25 January 2011
Time: 5:00 PM ?5:15 PM

Author(s): Keith G. Wilcox, Aaron L. Chung, Adrian H. Quarterman, Zakaria Mihoubi, Univ. of Southampton (United Kingdom); Ian Farrer, Harvey E. Beere, David A. Ritchie, Univ. of Cambridge (United Kingdom); Vasilis Apostolopoulos, Anne C. Tropper, Univ. of Southampton (United Kingdom)
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We report on a high peak power femtosecond modelocked VECSEL and its application as a driving laser for an all-semiconductor terahertz-time-domain spectrometer. The VECSEL produced near-transform-limited 335 fs sech2 pulses at a fundamental repetition rate of 1 GHz, a centre wavelength of 999 nm and an average output power of 120 mW. We report on the effect that this high peak power and short pulse duration has on our generated THz signal, where an increase in the THz power and bandwidth is observed.

Development of broadband optical frequency resource over 8.4-THz in 1.0-祄 waveband for photonic transport systems

Paper 7958-14 of Conference 7958
Date: Wednesday, 26 January 2011
Time: 5:10 PM ?5:30 PM

Author(s): Naokatsu Yamamoto, National Institute of Information and Communications Technology (Japan); Yu Omigawa, Yuta Kinoshita, Aoyama Gakuin Univ. (Japan); Atsushi Kannno, Kouichi Akahane, Tetsuya Kawanishi, National Institute of Information and Communications Technology (Japan); Hideyuki Sotobayashi, Aoyama Gakuin Univ. (Japan)
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For an enhancing usable optical frequency resources in a future photonic network system, we have recently focused on a use of a novel wavelength band such as a 1-祄 waveband (Thousand-band: T-band) together with the conventional C- and L-bands. In this study, we develop broadband potentialities in the T-band. An error-free 10-Gbps photonic transmission over a few-km long holey-fiber is successfully demonstrated for the wavelength range of 1037-1068-nm, which corresponds to the optical frequency range of 8.4-THz. Pioneering a broadband optical frequency resources is positively applied for a wavelength-division-multiplex network in the T-band.

Reflection modality continuous-wave terahertz imaging of non-melanoma skin cancers

Paper 7883A-19 of Conference 7883A
Date: Saturday, 22 January 2011
Time: 4:30 PM ?4:50 PM

Author(s): Cecil S. Joseph, Anna N. Yaroslavsky, Univ. of Massachusetts Lowell (United States); Victor A. Neel, Harvard Medical School (United States); Thomas M. Goyette, Robert H. Giles, Univ. of Massachusetts Lowell (United States)
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Continuous-wave terahertz imaging has the potential for diagnosing and delineating skin cancers. Specimens of human nonmelanoma skin cancers were obtained from Mohs surgeries at Massachusetts General Hospital. The tissue was sectioned and mounted in between slides of z-cut quartz for terahertz imaging. Reflection measurements of 240祄 thick sections of skin cancer tissue were taken at two frequencies of 1.39 THz and 1.63 THz. The terahertz sources used were two CO2 pumped Far-Infrared molecular gas lasers. For detecting the terahertz radiation liquid Helium cooled Silicon bolometers were used. The resolution of the terahertz imaging system was 0.5 mm. The resulting terahertz images were compared to the H&E histology of adjacent sections of the imaged tissue. The preliminary results of the imaging experiments will be presented and discussed.

Time resolved spectroscopy on quantum dots and graphene at the FELBE free-electron laser

Paper 7937-7 of Conference 7937
Date: Sunday, 23 January 2011
Time: 11:35 AM ?12:00 PM

Author(s): Stephan F. Winnerl, Dominik Stehr, Harald Schneider, Manfred Helm, Wolfgang Seidel, Peter Michel, Forschungszentrum Dresden-Rossendorf e.V. (Germany); Evgeny Zibik, Ben Carpenter, Nathan Porter, Maurice S. Skolnick, Luke R. Wilson, The Univ. of Sheffield (United Kingdom); Thomas Grange, Robson Ferreira, Gerald Bastard, Ecole Normale Supérieure (France); Milan Orlita, Paulina Plochocka, Piotr Kossacki, Marek Potemski, Grenoble High Magnetic Field Lab. (France); Mike Sprinkle, Clair Berger, Walt de Heer, Georgia Institute of Technology (United States)
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The relaxation dynamics in self-assembled quantum dots as well as in graphene is studied by pump probe experiments using the free-electron laser FELBE at the Forschungszentrum Dresden-Rossendorf. This laser provides picosecond radiation pulses in the wavelength range 5 - 280 祄. For the quantum dots long relaxation times (1.5 ns) are found for level separations of 14 meV (3.4 THz), decreasing very strongly to 2 ps at 30 meV (7 THz), in very good agreement with our microscopic theory of the carrier relaxation process. For graphene relaxation times ~ 20 ps are observed for excitations below the optical phonon energy.

Monolithic focal plane arrays for terahertz active spectroscopic imaging: an experimental study

Paper 7945-31 of Conference 7945
Date: Monday, 24 January 2011
Time: 8:00 AM ?8:20 AM

Author(s): Michele Ortolani, Roberto Casini, Fabio Chiarello, Sara Cibella, Alessandra Di Gaspare, Istituto di Fotonica e Nanotecnologie (Italy); Florestano Evangelisti, Istituto di Fotonica e Nanotecnologie (Italy) and Univ. Roma Tre (Italy); Vittorio Foglietti, Ennio Giovine, Roberto Leoni, Guido Torrioli, Istituto di Fotonica e Nanotecnologie (Italy); Alessandro Tredicucci, Scuola Normale Superiore di Pisa (Italy); Miriam S. Vitiello, National Research Council (Italy); Gaetano Scamarcio, Univ. di Bari (Italy)
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Imaging arrays of direct detectors in the 0.5-5 THz range have been developed using three different detector technologies: i) Nb superconducting air-bridge microbolometers; ii) GaAs Schottky diodes with air-bridge sub-micron anodes; iii) AlGaN/GaN field-effect transistors with 0.15 micron Schottky T-gate length. Terahertz active spectroscopic imaging was performed by illuminating the target with two amplitude-modulated quantum cascade lasers (QCL) emitting at 2.5 and 2.8 THz, demodulated at the detector readout level. Performances, requirements and costs of the different detector technologies are compared.

Accelerated 3D FDTD modeling of terahertz propagation in tissue using graphics processing units (GPUs)

Paper 7897-14 of Conference 7897
Date: Monday, 24 January 2011
Time: 2:40 PM ?3:00 PM

Author(s): Michael L. Doroski, Michael Knight, Jason A. Payne, Jessica E. Grundt, Bennett L. Ibey, Robert J. Thomas, William P. Roach, Gerald J. Wilmink, Air Force Research Lab. (United States)
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In this study, we developed 3-D FDTD thermal propagation code to model Terahertz radiation propagation in biological tissues. We used graphics processing units (GPUs) and coded in CUDA, an extension of the C language. We modeled the thermal deposition of THz radiation for both in vitro and in vivo exposures. To determine the speedup provided by GPUs, we compared the performance of simulations performed on a GPU (Tesla C1060) and CPU (Quad-Core,Intel-Xeon-5300). For the in vivo THz exposures, using a six-layer skin model, we found that the GPU performed 3-D simulations roughly 90X faster than the CPU.

Optical pump-terahertz probe studies of AlGaN

Paper 7939-42 of Conference 7939
Date: Tuesday, 25 January 2011
Time: 5:00 PM ?5:20 PM

Author(s): Timothy M. Sweeney, Univ. of Oregon (United States); Grace D. Metcalfe, Gregory A. Garrett, Anand V. Sampath, Paul H. Shen, U.S. Army Research Lab. (United States); Hailin Wang, Univ. of Oregon (United States); Michael Wraback, U.S. Army Research Lab. (United States)
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We report on ultrafast optical pump and terahertz probe studies of free-carrier dynamics in AlGaN materials grown with and without nano-scale compositional inhomogeneities (NCI). We observe an initial fast decrease of the transmitted THz signal in both AlGaN samples due to the generation of photoexcited free-carriers. The NCI AlGaN material shows a subsequent fast decrease in THz absorption, as compared to the NCI-free AlGaN. The faster decay time in the NCI AlGaN sample could be due to the transfer of free-carriers into NCI states from the AlGaN matrix as well as exciton formation and carrier recombination.

Synchronized dual wavelength programmable laser with 75nm wavelength difference tuning

Paper 7914-99 of Conference 7914
Date: Tuesday, 25 January 2011
Time: 6:00 PM

Author(s): Bryan Buorgoyne, Youngjae Kim, Alain Villeneuve, Genia Photonics Inc. (Canada)
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Today, most tuneable fiber-based lasers generating dual wavelengths yield identical spacing between the wavelengths while tuning. Having variable spacing between the wavelengths would give way to a tuneable THz source, up to 10 THz, through difference frequency generation. We present here such a source which is a programmable laser based on an actively mode-locked dispersion-tuned picosecond fiber laser delivering two wavelengths in the C and L bands respectively. The difference between these wavelengths is rapidly adjustable over a 75 nm band while the laser is tuning. Laser pulses are as short as 30 ps.


Ultrafast terahertz spectroscopy of few-layer graphene

Paper 7937-64 of Conference 7937
Date: Wednesday, 26 January 2011
Time: 2:40 PM ?3:05 PM

Author(s): Hyunyong Choi, Ferenc Borondics, David A. Siegel, Shuyun Zhou, Michael C. Martin, Alessandra Lanzara, Robert A. Kaindl, Lawrence Berkeley National Lab. (United States)
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Graphene is attracting significant interest due to the unique physics of its 2D charge carriers in a linear electronic bandstructure, and due to possible applications in e.g. high-speed electronics. Here, we discuss the broadband optical conductivity and ultrafast THz dynamics of graphene in the few-layer limit. The equilibrium optical response in epitaxial graphene is consistent with the electrodynamics of a dense Dirac electron plasma, arising from highly-doped layers at the graphene-substrate interface. We will further discuss the transient THz response, which reflects the recombination dynamics and unusual Drude response of graphene and its dependence on the carrier distribution function.

Optical frequency conductance model of teraHertz/infrared emission and detection in quantum wells, quantum dots, and narrow-gap semiconductors

Paper 7938-9 of Conference 7938
Date: Thursday, 27 January 2011
Time: 11:40 AM ?12:00 PM

Author(s): Thomas Szkopek, Elizabeth Ledwosinska, McGill Univ. (Canada)
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The optical frequency conductance is derived for quantum wells and quantum dots, and the optical frequency conductivity of bulk narrow-gap semiconductors is revisited. The teraHertz (THz) and infrared (IR) response of these structures, in free-space and guided-wave geometries, is simply described within the optical frequency conductance formalism. The fine structure constant of quantum electrodynamics sets the natural scale for the optical conductance of semiconductor structures. Rules of thumb and physical limits to THz/IR gain and absorption can be derived. The optical conductance formalism is applied to MCT photodetectors, quantum well IR photodetectors, quantum dot IR photodetectors, and quantum cascade lasers.

Of Light, Electrons, and Metamaterials

Date: Wednesday, 26 January 2011
Time: 10:30 AM ?11:10 AM

Author(s):
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Nader Engheta, Univ. of Pennsylvania (USA)

Abstract: Metamaterials are engineered composite media formed by collections of properly designed subwavelength elements and inclusions. Owing to the ability to tailor their material parameters to desired values, metamaterials may manipulate and control microwave, THz, IR and optical signals at various length scales. When we merge the concept of extreme-parameter metamaterials with the fields of nanooptics and nanoelectronics, various interesting possibilities may arise. These include metamaterial-inspired optical nanocircuitry ("metatronics"), graphene-based metamaterials and transformation optics and electronics for taming and routing photons and electrons on 'flatland' structures, supercoupling in narrow channels, and control of one-way flow of photons and electrons in desired directions. In this talk, I review these concepts and forecast future possibilities and directions.

Biography: Nader Engheta is the H. Nedwill Ramsey Professor of Electrical and Systems Engineering and Professor of Bioengineering at the University of Pennsylvania. He received his Ph.D. from Caltech. Selected as one of the Scientific American magazine 50 Leaders in Science and Technology in 2006, he is a Guggenheim Fellow, an IEEE Third Millennium Medalist, Fellow of IEEE, OSA, APS, and AAAS, and the recipient of the 2008 George H. Heilmeier Award for Excellence in Research, Fulbright Naples Chair Award, NSF Presidential Young Investigator award, and several teaching awards.

Subpicosecond Sub-terahertz soliton laser based on a C-MOS compatible integrated microring resonator

Paper 7945-37 of Conference 7945
Date: Monday, 24 January 2011
Time: 9:55 AM ?10:10 AM

Author(s): Marco Peccianti, Institut National de la Recherche Scientifique (Canada) and Institute for Chemical and Physical Processes (Italy); Alessia Pasquazi, Yongwoo Park, Institut National de la Recherche Scientifique (Canada); Brent Little, Sai-Tak Chu, Infinera Corp. (United States); David J. Moss, Univ. of Sydney (Australia); Roberto Morandotti, Institut National de la Recherche Scientifique (Canada)
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We present a novel subpicosecond, Sub THz -repetition rate, passively mode-locked laser scheme based on high-harmonic four wave mixing in an integrated CMOS-compatible high-Q nonlinear ring resonator.

Modified Sellmeier equation for ZnGeP2 in the 0.97-1640祄 range

Paper 7917-67 of Conference 7917
Date: Tuesday, 25 January 2011
Time: 6:00 PM

Author(s): Nobuhiro Umemura, Chitose Institute of Science and Technology (Japan)
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This paper reports the modified Sellmeier equations for ZnGeP2 (ZGP) that provide excellent reproduction of the phase-matching conditions for DFG between the two CO2 laser wavelengths, and the Nd:YAG laser and the Nd:YAG laser-pumped OPO in the THz region. Model calculations based on these Sellmeier equations strongly indicate that there is no significant difference in the refractive indices of the non-annealed and annealed crystals from 1.0642祄 to 1640祄 (0.18THz).

Novel concept for long-haul ultrashort pulse fiber delivery without pre-chirping

Paper 7912-41 of Conference 7912
Date: Wednesday, 26 January 2011
Time: 8:20 AM ?8:40 AM

Author(s): Tuan Le, Gabriel Tempea, Andreas Stingl, FEMTOLASERS Produktions GmbH (Austria); Kim G. Jespersen, OFS Fitel Denmark ApS (Denmark); Karin Wiesauer, RECENDT GmbH (Austria)
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Ultrashort pulse fiber delivery for Ti:Sapphire lasers is basically restricted to distances below several meters which is due to the application of dispersion compensating devices that are not capable managing third and higher order material dispersion. By the use of a novel fiber delivery concept ultrashort laser pulses in the 800 nm wavelength range can now be transmitted over tens of meters without the need for any pulse pre-compression. For the first time a long-haul fiber delivery module will be demonstrated revealing its potential for remote imaging or THz spectroscopy with femtosecond laser pulses.

Rigorous characterization of surface plasmon modes by using the finite element method

Paper 7941-34 of Conference 7941
Date: Wednesday, 26 January 2011
Time: 8:30 AM ?8:50 AM

Author(s): B. M. Azizur Rahman, Huda Tanvir, Anita Quadir, Ken Grattan, The City Univ. (United Kingdom)
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A rigorous full vectorial finite element-based approach has been developed to characterize a wide range of plasmonic devices, both at optical and terahertz frequencies. Results for wave confinement in gold nanowires, air-core guides and defect-core metal coated photonic crystal fibers and gain threshold optimization of quantum cascaded lasers for terahertz (THz) frequencies will be presented.

Optimization of organic NLO materials for integration with silicon photonic, plasmonic (metal optics), and metamaterial devices (Keynote Presentation)

Paper 7935-1 of Conference 7935
Date: Monday, 24 January 2011
Time: 8:10 AM ?8:50 AM

Author(s): Larry R. Dalton, Univ. of Washington (United States)
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The fast response of organic nonlinear optical materials together with the potential for large optical nonlinearities makes these materials attractive for the integration with silicon photonic, plasmonic, and metamaterial device architectures. For example, incorporation of organic nonlinear optical materials into slotted silicon photonic waveguide device structures leads to dramatic improvement in the "effective" nonlinearity of organic materials. Drive voltages approaching 0.1 V have been realized for electro-optic modulation and low control power all-optical modulation has been demonstrated to approximately 10 THz. While organic nonlinear optical materials in general exhibit excellent processability-being amenable to both solution and vapor phase deposition and to a variety of processing methodologies ranging from crystal growth, to sequential-synthesis/self-assembly, to electrical and optical field poling-the special device architectures of silicon photonics, plasmonics (metal optics), and metamaterials can present challenges to useful integration. New organic nonlinear optical material concepts, materials, and processing options will be introduced and discussed.

The relevance of positive differential conductivity for quantum cascade lasers

Paper 7953-21 of Conference 7953
Date: Tuesday, 25 January 2011
Time: 11:10 AM ?11:40 AM

Author(s): Andreas Wacker, Lund Univ. (Sweden)
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A central feature of Quantum Cascade Lasers (QCLs) is the periodic repetition of identical active structures forming the cascade for the electron flow through the device. For operation, the bias must drop homogeneously over the entire structure which requires the presence of positive differential conductivity in each period as otherwise domains with different electric field will form. As the gain transition itself is associated with a source of negative differential conductivity, this has to be balanced by other processes. This feature is discussed in detail and various strategies are discussed, which help in the classification of existing device concepts. Exemplary simulation results are shown including a new THz design which should operate well above 200 K.

High-temperature performance and broad continuous tunability of terahertz quantum-cascade lasers

Paper 7953-23 of Conference 7953
Date: Tuesday, 25 January 2011
Time: 1:30 PM ?2:00 PM

Author(s): Sushil Kumar, Lehigh Univ. (United States); Qi Qin, Chun W. I. Chan, Qing Hu, Massachusetts Institute of Technology (United States); John L. Reno, Sandia National Labs. (United States)
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We demonstrate a terahertz quantum-cascade laser (QCL) operating significantly above the temperature of hw/kB, which has so-far been an empirical limitation for such devices. A 1.8 THz QCL operating up to a temperature of 1.9hw/kB (163K) is realized, with more than 3mW of peak optical power output at 150K. We also demonstrate broadly tunable terahertz QCLs. Discontinuous tuning over a range of 165GHz is realized for a 4.4THz QCL using an antireflection-coated silicon lens to reduce facet reflection and as a beam-forming element, with an external grating providing frequency selective optical feedback. We have also realized continuous tuning of 137GHz for a 3.8THz QCL with a unique concept of altering the lateral mode profile of terahertz "wire-lasers" to achieve broad tuning.

Trends in nanoplasmonics: ultrasmall, ultrafast, ultrastrong

Paper 7937-42 of Conference 7937
Date: Tuesday, 25 January 2011
Time: 1:30 PM ?1:55 PM

Author(s): Mark I. Stockman, Georgia State Univ. (United States)
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Nanoplasmonics deals with collective electron dynamics on the surface of metal nanostructures, which arises as a result of excitations called surface plasmons. The surface plasmons localize and concentrate optical energy in nanoscopic regions creating highly enhanced local optical fields. They undergo ultrafast dynamics with timescales as short as a few hundred attoseconds. From the latest developments and original work in nanoplasmonics, we will consider SPASER (quantum nanoscale optical generator and ultrafast amplifier), ultrafast coherent control on the nanoscale, generation of EUV radiation by plasmonic enhancement, adiabatic nano-concentration of optical energy, and SPIDER (surface-plasmon-induced drag-effect rectification) that leads to generation of nanoscale THz fields by femtosecond polaritonic pulses in metal nanowires.

Spontaneous and stimulated Raman scattering in planar silicon waveguides

Paper 7943-40 of Conference 7943
Date: Tuesday, 25 January 2011
Time: 3:10 PM ?3:30 PM

Author(s): Sha Wang, Stefan Meister, Shaimaa Mahdi, Bülent Franke, Aws Al-Saadi, Technische Univ. Berlin (Germany); Lars Zimmermann, Harald H. Richter, David Stolarek, IHP GmbH (Germany); Viktor Lisinetskii, Sigurd K. Schrader, Technische Fachhochschule Wildau (Germany); Hans Eichler, Technische Univ. Berlin (Germany)
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Raman scattering in planar silicon on insulator (SOI) waveguides with 2 microm width, 220 nm height and 2 cm length is investigated. Spontaneous Raman scattering is observed with as low as 2.5 mW pump power inside the waveguide. The Raman shift is measured as 15.6 THz, while the FWHM of Raman spectrum is measured as around 100 GHz. Maximum Raman output of around 90 pW is obtained by around 22 mW pump. The stimulated Raman gain coefficient is estimated as around 56 cm/GW from the relationship between spontaneous Raman output power and pump power. A temperature dependence of Raman frequency shift of about 0.6 GHz/K is measured. The spontaneous anti-Stokes Raman scattering output peak at 1253 nm is also observed with around 35 mW pump. Stimulated Raman amplification measurement is carried out with a SLED white light source as probe signal. With 35 mW pump power, around 0.6 dB gain has been determined with both pump and probe being TE polarized.

Novel aspects of pulse propagation in photonic crystal fibers

Paper 7946-33 of Conference 7946
Date: Wednesday, 26 January 2011
Time: 8:50 AM ?9:20 AM

Author(s): Sebastian P. Stark, Alexander V. Podlipensky, Philip S. Russell, Max-Planck Institute for the Science of Light (Germany)
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Unconventional wavelength-dependent group velocity dispersion, designed and realised in solid-core photonic crystal fibers (PCFs), can give rise to unusual pulse dynamics. Broad-band supercontinua can be generated in the visible spectral range, with high conversion efficiencies that can be further enhanced by frequent inter-soliton collisions. The high nonlinearity of small-core PCFs, along with a strongly uncompensated pulse chirp, can be used to trigger pulse breakup, leading to the generation of ultrashort THz pulse trains. Experimental and numerical results on the propagation of femtosecond pulses in axially-varying tapered PCF structures will also be discussed.

Giant lasing effect in magnetic nanoconductors and its detection by DC electrical measurements

Paper 7933-51 of Conference 7933
Date: Wednesday, 26 January 2011
Time: 5:00 PM ?5:20 PM

Author(s): Anatoly M. Kadygrobov, Robert I. Shekhter, Univ. of Gothenburg (Sweden); Sergei I. Kulinich, Univ. of Gothenburg (Sweden) and Institute for Low Temperature Physics and Engineering (Ukraine); Mats Jonson, Univ. of Gothenburg (Sweden)
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We propose a new principle for a solid-state laser in 1-100 THz regime based on a new mechanism for creating spin-flip processes in ferromagnetic conductors. The mechanism is due to the dependence of the electron spin - magnetic moment exchange interaction on the electron momentum. We predict a giant lasing effect which provides the optical gain exceeding the one of conventional semiconductor lasers by 4 or 5 orders of magnitude. This effect may be detected by electrical measurements. We show that the relative change of the resistance of a ferromagnetic point contact under irradiation is proportional to the power of the stimulated emission of photons from the point contact.

Efficient material parameters estimation with terahertz time domain spectroscopy

Paper 7938-4 of Conference 7938
Date: Thursday, 27 January 2011
Time: 9:10 AM ?9:30 AM

Author(s): Osman S. Ahmed, Mohamed A. Swillam, Mohamed H. Bakr, Xun Li, McMaster Univ. (Canada)
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We propose a novel optimization technique for the estimation of material refractive index in the terahertz frequency range. The algorithm is applied for materials with arbitrary frequency dependence. Dispersive dielectric models are embedded for accurate parameter extraction of a sample with unknown thickness. Instead of solving N expensive nonlinear optimization problems with different possible material thickness, our technique obtains the optimal material thickness by solving only one optimization problem. Our approach has been successfully illustrated through a number of examples with different dispersive models. The examples include the characterization of doped semiconductors used in surface plasmon plaritons in the THz regime.

Optical nano-antennas: a new approach for optical imaging and detection

Paper 7945-82 of Conference 7945
Date: Wednesday, 26 January 2011
Time: 2:45 PM ?3:05 PM

Author(s): Jacob Scheuer, Inbal Freidler, Yuval Yifat, Zeev Iluz, Michal Eitan, Yael Hanein, Amir Boag, Tel Aviv Univ. (Israel)
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During the past few years, the field of optical nano-Antennas has experience extensive growth in activity and has been receiving much focus and attention, primarily due to their possible applications in telecommunications, field enhancement, sensing and solar energy harvesting. A Rectenna (Rectifying antenna) is composed of an antenna connected to a rectifying component (e.g. a diode), which enable direct conversion of electromagnetic energy to direct electrical current. The concept, originally proposed in Raytheon during the 60s, was aiming at achieving highly efficient power transfer and indeed, power conversion efficiencies exceeding 80% have been demonstrated in RF frequencies. An attempt to push this concept to the optical domain encounters two primary hurdles: the fabrication of extremely small structures and realizing very high bandwidth (10-1000 THz) diodes. Employing state-of-the-art nano-fabrication tools and extremely high-mobility carbon nano-tubes for the rectification diode, we believe it is possible to realize a rectenna operating at the far to near IR bands and maybe even at the visible band as well. Nano-antenna array operating at telecom wavelength are demonstrated experimentally and their spectral properties are studied in detail exhibiting excellent agreement with the theoretical analysis. Applications in the field of imaging and telecommunications will be presented and discussed.


Recent progress of THz generation and detection in ambient air or gases

Paper 7917-15 of Conference 7917
Date: Tuesday, 25 January 2011
Time: 1:30 PM ?2:00 PM

Author(s): Xiaofei Lu, Benjamin W. Clough, I-Chen Ho, Jingle Liu, Jianming Dai, Xi-Cheng Zhang, Rensselaer Polytechnic Institute (United States)
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THz time domain spectroscopy has been largely applied on the measurement of semiconductor, electro-optic crystals, and selected chemical, biological and explosive materials. Here we will highlight THz gas photonics and its applications, with an emphasis on spectroscopic capabilities. The most recent results of using air (and selected gases) as the emitter and sensor material for both generation and detection of broadband THz waves will also be reported. Air, especially ionized air (plasma), has been used to generate intense peak THz waves (THz field > 1.5 MV/cm) with a broadband spectrum (10% bandwidth from 0.1 THz to 46 THz).

High peak power femtosecond pulse VECSELs for terahertz time domain spectroscopy

Paper 7919-38 of Conference 7919
Date: Tuesday, 25 January 2011
Time: 5:00 PM ?5:15 PM

Author(s): Keith G. Wilcox, Aaron L. Chung, Adrian H. Quarterman, Zakaria Mihoubi, Univ. of Southampton (United Kingdom); Ian Farrer, Harvey E. Beere, David A. Ritchie, Univ. of Cambridge (United Kingdom); Vasilis Apostolopoulos, Anne C. Tropper, Univ. of Southampton (United Kingdom)
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We report on a high peak power femtosecond modelocked VECSEL and its application as a driving laser for an all-semiconductor terahertz-time-domain spectrometer. The VECSEL produced near-transform-limited 335 fs sech2 pulses at a fundamental repetition rate of 1 GHz, a centre wavelength of 999 nm and an average output power of 120 mW. We report on the effect that this high peak power and short pulse duration has on our generated THz signal, where an increase in the THz power and bandwidth is observed.

Multi-THz fields exceeding 100 MV/cm: an ultrabroadband source for sub-cycle nonlinear optics

Paper 7917-11 of Conference 7917
Date: Tuesday, 25 January 2011
Time: 10:30 AM ?11:00 AM

Author(s): Alexander Sell, Friederike Junginger, Olaf Schubert, Bernhard Mayer, Univ. Konstanz (Germany); Tobias Kampfrath, Martin Wolf, Fritz-Haber-Institut der Max-Planck-Gesellschaft (Germany); Daniele Brida, Marco Marangoni, Giulio Cerullo, Politecnico di Milano (Italy); Alfred Leitenstorfer, Rupert Huber, Univ. Konstanz (Germany)
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We present a table-top source of extremely intense multi-THz transients covering the spectral regime between 0.1 and 140 THz. Electric field amplitudes of up to 108 MV/cm and pulse durations as short as a single cycle are demonstrated with our hybrid Er:fiber-Ti:sapphire laser system. All THz waveforms are electro-optically detected. The multi-branch fiber laser generates gate pulses as short as 4.3 fs. Our high-field THz facility opens the door to extremely nonlinear optics in a previously hard-to-access spectral regime. First applications include THz coherent control and four-wave mixing studies as well as all-magnetic control of coherent spin waves.

Reflection modality continuous-wave terahertz imaging of non-melanoma skin cancers

Paper 7883A-19 of Conference 7883A
Date: Saturday, 22 January 2011
Time: 4:30 PM ?4:50 PM

Author(s): Cecil S. Joseph, Anna N. Yaroslavsky, Univ. of Massachusetts Lowell (United States); Victor A. Neel, Harvard Medical School (United States); Thomas M. Goyette, Robert H. Giles, Univ. of Massachusetts Lowell (United States)
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Continuous-wave terahertz imaging has the potential for diagnosing and delineating skin cancers. Specimens of human nonmelanoma skin cancers were obtained from Mohs surgeries at Massachusetts General Hospital. The tissue was sectioned and mounted in between slides of z-cut quartz for terahertz imaging. Reflection measurements of 240祄 thick sections of skin cancer tissue were taken at two frequencies of 1.39 THz and 1.63 THz. The terahertz sources used were two CO2 pumped Far-Infrared molecular gas lasers. For detecting the terahertz radiation liquid Helium cooled Silicon bolometers were used. The resolution of the terahertz imaging system was 0.5 mm. The resulting terahertz images were compared to the H&E histology of adjacent sections of the imaged tissue. The preliminary results of the imaging experiments will be presented and discussed.

Ultrafast carrier capture and THz resonances in InGaAs quantum posts

Paper 7937-2 of Conference 7937
Date: Sunday, 23 January 2011
Time: 9:10 AM ?9:35 AM

Author(s): Dominik Stehr, Univ. of California, Santa Barbara (United States) and Forschungszentrum Dresden-Rossendorf e.V. (Germany); Christopher M. Morris, Univ. of California, Santa Barbara (United States); Diyar Talbalyev, Los Alamos National Lab. (United States); Martin Wagner, Forschungszentrum Dresden-Rossendorf e.V. (Germany); Hyochul Kim, Univ. of California, Santa Barbara (United States); Antoinette J. Taylor, Los Alamos National Lab. (United States); Harald Schneider, Forschungszentrum Dresden-Rossendorf e.V. (Germany); Pierre M. Petroff, Mark S. Sherwin, Univ. of California, Santa Barbara (United States)
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Semiconductor quantum posts - nanowire-like InGaAs heterostructures in a GaAs matrix - were investigated with respect to their carrier capture dynamics after photoexcitation into the GaAs matrix. The results of the THz experiment demonstrate that after ultrafast excitation, electrons relax within a few picoseconds into the quantum posts, which act as efficient traps. Saturation of the quantum post states, probed by time-resolved photoluminescence, was reached at approximately ten times the quantum post density. Additionally, possible electronic THz resonances with a dipole moment in the growth direction were probed showing a broad response around 1.5 THz.

Time resolved spectroscopy on quantum dots and graphene at the FELBE free-electron laser

Paper 7937-7 of Conference 7937
Date: Sunday, 23 January 2011
Time: 11:35 AM ?12:00 PM

Author(s): Stephan F. Winnerl, Dominik Stehr, Harald Schneider, Manfred Helm, Wolfgang Seidel, Peter Michel, Forschungszentrum Dresden-Rossendorf e.V. (Germany); Evgeny Zibik, Ben Carpenter, Nathan Porter, Maurice S. Skolnick, Luke R. Wilson, The Univ. of Sheffield (United Kingdom); Thomas Grange, Robson Ferreira, Gerald Bastard, Ecole Normale Supérieure (France); Milan Orlita, Paulina Plochocka, Piotr Kossacki, Marek Potemski, Grenoble High Magnetic Field Lab. (France); Mike Sprinkle, Clair Berger, Walt de Heer, Georgia Institute of Technology (United States)
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The relaxation dynamics in self-assembled quantum dots as well as in graphene is studied by pump probe experiments using the free-electron laser FELBE at the Forschungszentrum Dresden-Rossendorf. This laser provides picosecond radiation pulses in the wavelength range 5 - 280 祄. For the quantum dots long relaxation times (1.5 ns) are found for level separations of 14 meV (3.4 THz), decreasing very strongly to 2 ps at 30 meV (7 THz), in very good agreement with our microscopic theory of the carrier relaxation process. For graphene relaxation times ~ 20 ps are observed for excitations below the optical phonon energy.

Tapered terahertz plasmonic waveguides

Paper 7937-9 of Conference 7937
Date: Sunday, 23 January 2011
Time: 1:30 PM ?1:55 PM

Author(s): Daniel M. Mittleman, Hui Zhan, Jingbo Liu, Rajind Mendis, Rice Univ. (United States)
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Ultrafast optical control of terahertz surface plasmons in subwavelength hole-arrays at room temperature

Paper 7937-10 of Conference 7937
Date: Sunday, 23 January 2011
Time: 1:55 PM ?2:20 PM

Author(s): Abul K. Azad, Los Alamos National Lab. (United States)
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Ultrafast switching or modulation of the resonant behavior of the 2-D metallic arrays in terahertz frequencies is of particular interest for high speed communication and sensing applications. We demonstrate optical control of surface plasmon enhanced resonant terahertz transmission in two-dimensional subwavelength metallic hole arrays fabricated on gallium arsenide based substrates. Optically pumping the arrays creates a conductive layer in the substrate reducing the terahertz transmission amplitude of both the resonant mode and the direct transmission. Under low optical fluence, the terahertz transmission is more greatly affected by resonance damping than by propagation loss in the substrate. An ErAs:GaAs nanoisland superlattice substrate is shown to allow ultrafast control with a switching recovery time of ~10 ps.

Controlling THz plasmons with the electron spin state

Paper 7937-11 of Conference 7937
Date: Sunday, 23 January 2011
Time: 2:20 PM ?2:35 PM

Author(s): Cameron J. E. Straatsma, Abdulhakem Y. Elezzabi, Univ. of Alberta (Canada)
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We investigate the effects of photonic magnetoresistance on the propagation of terahertz (THz) radiation in multilayered metallic media. These subwavelength plasmonic structures contain alternating layers of ferromagnetic and non-magnetic metal thin films, which allow for control over the electron spin state. In particular, using THz time-domain spectroscopy, a photonic analogous giant magnetoresistance effect is observed and its application in actively controlling THz plasmons is studied. We demonstrate the possibility of implementing this effect to produce active THz guided wave devices.

Ultrafast photoconductors based on subwavelength metallic gratings for the next generation of photoconductive terahertz sources

Paper 7937-14 of Conference 7937
Date: Sunday, 23 January 2011
Time: 3:15 PM ?3:30 PM

Author(s): Christopher W. Berry, Mona Jarrahi, Univ. of Michigan (United States)
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We present a new generation of ultrafast and high quantum efficiency photoconductors fabricated on high quality crystalline semiconductors. The device consists of a metal-semiconductor-metal photoconductor with a subwavelength contact electrode grating at the optical pump wavelength. Ultrafast photocurrent impulse response and high quantum efficiency operation is achieved through the excitation of surface plasmon waves, which significantly enhance the concentration of photo-generated carriers in close proximity to photoconductor contact electrodes. Ultrafast photocurrent impulse response times as low as 100fs FWHM are estimated for the presented photoconductors, which are faster than the photocurrent response of previously demonstrated photoconductors with short carrier lifetime semiconductors.

Correction of tissue perfusion by terahertz waves

Paper 7901-17 of Conference 7901
Date: Sunday, 23 January 2011
Time: 4:45 PM ?5:00 PM

Author(s): Alexey N. Ivanov, Vyacheslav F. Kirichuk, Tatyana S. Kiriyazi, Saratov State Medical Univ. (Russian Federation)
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This work is about influence by electromagnetic therahertz waves at range on frequencies of a molecular spectrum of radiation and absorption nitrogen oxide 150,176 - 150,664 GHz on microcirculation at white male rats, taking place in a condition of sharp stress. It was shown, that waves of the specified range are capable to restore infringements peripheral blood stream, characteristic for sharp stress - reaction.

Monolithic focal plane arrays for terahertz active spectroscopic imaging: an experimental study

Paper 7945-31 of Conference 7945
Date: Monday, 24 January 2011
Time: 8:00 AM ?8:20 AM

Author(s): Michele Ortolani, Roberto Casini, Fabio Chiarello, Sara Cibella, Alessandra Di Gaspare, Istituto di Fotonica e Nanotecnologie (Italy); Florestano Evangelisti, Istituto di Fotonica e Nanotecnologie (Italy) and Univ. Roma Tre (Italy); Vittorio Foglietti, Ennio Giovine, Roberto Leoni, Guido Torrioli, Istituto di Fotonica e Nanotecnologie (Italy); Alessandro Tredicucci, Scuola Normale Superiore di Pisa (Italy); Miriam S. Vitiello, National Research Council (Italy); Gaetano Scamarcio, Univ. di Bari (Italy)
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Imaging arrays of direct detectors in the 0.5-5 THz range have been developed using three different detector technologies: i) Nb superconducting air-bridge microbolometers; ii) GaAs Schottky diodes with air-bridge sub-micron anodes; iii) AlGaN/GaN field-effect transistors with 0.15 micron Schottky T-gate length. Terahertz active spectroscopic imaging was performed by illuminating the target with two amplitude-modulated quantum cascade lasers (QCL) emitting at 2.5 and 2.8 THz, demodulated at the detector readout level. Performances, requirements and costs of the different detector technologies are compared.

Bound terahertz waves on meta-surfaces and active metamaterials

Paper 7945-32 of Conference 7945
Date: Monday, 24 January 2011
Time: 8:20 AM ?8:40 AM

Author(s): Marco Rahm, Fraunhofer-Institut für Physikalische Messtechnik (Germany) and Technische Univ. Kaiserslautern (Germany); Juan Luis Garcia Pomar, Benjamin Reinhard, Jens Neu, Viktoria Wollrab, Oliver Paul, Rene Beigang, Fraunhofer-Institut für Physikalische Messtechnik (Germany)
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Phonon and polaron enhanced IR-THz photodetectors

Paper 7945-34 of Conference 7945
Date: Monday, 24 January 2011
Time: 9:00 AM ?9:20 AM

Author(s): Hui Chun Liu, Chun-Ying Song, Zbigniew R. Wasilewski, Margaret Buchanan, National Research Council Canada (Canada)
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We investigate the active use of phonons and polarons for realizing new optoelectronics devices. We present an application of the concept to photodetection in the infrared-terahertz spectrum. The ability to design a phonon or polaron is the first step in making use of them. We show this by a model system employing the electron intersubband excitation in quantum wells coupled with phonon modes. This results in a photodetector with a high response at the selected wavelength.

GaN for THz sources

Paper 7945-35 of Conference 7945
Date: Monday, 24 January 2011
Time: 9:20 AM ?9:40 AM

Author(s): Michel Marso, Univ. du Luxembourg (Luxembourg)
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In this work we investigate the unique electrical and thermal performance of GaN to improve two different approaches to generate THz radiation. One method is the heterodyne photomixing, where the THz output power is restricted by the thermal and electrical limits of the conventionally used LT GaAs. The aim of our work is to increase the output power by replacing the LT GaAs with low-temperature grown GaN. In the second approach GaN-based ultrafast high electron mobility transistors are developed for use in a high power high frequency oscillator circuit that acts as source for a frequency multiplier chain.

Terahertz emission from Mg-doped a-plane InN

Paper 7945-36 of Conference 7945
Date: Monday, 24 January 2011
Time: 9:40 AM ?9:55 AM

Author(s): Hyeyoung Ahn, Yi-Jou Yeh, National Chiao Tung Univ. (Taiwan); Shangjr Gwo, National Tsing Hua Univ. (Taiwan)
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We report terahertz emission from Mg-doped a-plane indium nitride (a-InN:Mg) films with different carrier density, relative to the Mg-doped InN films grown along the c-axis (c-InN:Mg). While intense terahertz emission (×500 than that of undoped c-InN) from c-InN:Mg sharply decreases as the carrier density increases, terahertz emission from a-InN:Mg is equally strong over the wide variation of the carrier density. The primary terahertz radiation mechanism of both undoped and Mg-doped a-InN film is due to the acceleration of photoexcited carriers under the polarization-induced in-plane electric field perpendicular to the a-axis and that of c-InN:Mg is due to the photo-Dember effect.

Ultrafast gain switching of quantum cascade lasers

Paper 7937-24 of Conference 7937
Date: Monday, 24 January 2011
Time: 10:35 AM ?11:00 AM

Author(s): Sukhdeep S. Dhillon, Nathan Jukam, Dimitri Oustinov, Rakchanok Rungsawang, Julien Madeo, Ecole Normale Supérieure (France); Stefano Barbieri, Christophe Manquest, Carlo Sirtori, Univ. Paris 7-Denis Diderot (France); Suraj P. Khanna, Edmund H. Linfield, Giles Davies, Univ. of Leeds (United Kingdom); Jerome Tignon, Ecole Normale Supérieure (France)
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Terahertz (THz) time domain spectroscopy is now a widely used technique where it is essential to know both the amplitude and phase of a THz wave. Nonetheless, THz amplifiers, capable of increasing the THz wave field, are presently lacking. In this context THz quantum cascade lasers (QCL) are very promising devices for amplification. Gain clamping in these devices, however, limits the attainable amplification. Here we circumvent gain clamping by coupling a THz QCL and an integrated Auston-switch to perform ultrafast gain switching. The resulting non-equilibrium gain is not clamped above laser threshold and large amplification of input terahertz pulses is demonstrated.

Terahertz pulsed imaging in vivo

Paper 7897-11 of Conference 7897
Date: Monday, 24 January 2011
Time: 1:30 PM ?2:00 PM

Author(s): Emma Pickwell-MacPherson, Hong Kong Univ. of Science and Technology (Hong Kong, China)
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Terahertz (10^12 Hz) pulsed imaging is a relatively new technique with high resolution (about 20 祄) and has only emerged in the last five years as a potential new clinical tool for medical imaging. It is a totally non-destructive and non-ionising imaging modality as the average power of the pulse for producing the radiation is as small as 100 nW. We use a prototype terahertz probe to perform reflection geometry in vivo measurements of human skin. The hand-held terahertz probe gives more flexibility than a typical flat-bed imaging system, but it also results in noisier data and requires existing processing methods to be improved.

THz techniques for human skin measurement

Paper 7897-12 of Conference 7897
Date: Monday, 24 January 2011
Time: 2:00 PM ?2:20 PM

Author(s): Yu Guan, Takayuki Shibuya, Koji Suizu, Nagoya Univ. (Japan); Shin'ichiro Hayashi, RIKEN (Japan); Kodo Kawase, Nagoya Univ. (Japan) and RIKEN (Japan)
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We are developing several novel THz techniques for skin measurement. A high-resolution tomographic imaging was demonstrated using a reflection-type terahertz time-domain spectroscopy. The wideband spectrum of the terahertz waves provided high-axial resolution of 5?m leading to tomographic imaging of multilayered skin structure. Secondly, we have demonstrated a sensitive THz imaging method using an interference effect. We applied this technique for the thickness measurement of human skin adhered onto a sticky tape. Thirdly, metal-mesh film can be used for sensing when samples adhere to the metal surface. We report on the spectrum change of metal-mesh with horny layer.

Using the gene expression profile of jurkat cells to determine whether terahertz (THz) radiation couples to DNA and impacts transcription processes

Paper 7897-13 of Conference 7897
Date: Monday, 24 January 2011
Time: 2:20 PM ?2:40 PM

Author(s): Jessica E. Grundt, Benjamin D. Rivest, Caleb C. Roth, Bennett L. Ibey, Michael L. Doroski, Jason A. Payne, William P. Roach, Gerald J. Wilmink, Air Force Research Lab. (United States)
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Theoretical models suggest that 2.52 THz radiation couples directly to DNA and affects transcriptional processes; however, this phenomenon has not been empirically confirmed. In this study, we hypothesized that if THz radiation does damage DNA then exposed cells will express known damage and repair genes. To test this hypothesis, we irradiated Jurkat cells using a THz laser (2.52 THz, 252 mWcm-2, t=5-50 minutes), and evaluated their response using viability, qPCR, and microarray techniques. We found several genes were markedly upregulated in each THz exposure group; however, the majority encoded for heat shock proteins and few for DNA repair proteins.

Accelerated 3D FDTD modeling of terahertz propagation in tissue using graphics processing units (GPUs)

Paper 7897-14 of Conference 7897
Date: Monday, 24 January 2011
Time: 2:40 PM ?3:00 PM

Author(s): Michael L. Doroski, Michael Knight, Jason A. Payne, Jessica E. Grundt, Bennett L. Ibey, Robert J. Thomas, William P. Roach, Gerald J. Wilmink, Air Force Research Lab. (United States)
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In this study, we developed 3-D FDTD thermal propagation code to model Terahertz radiation propagation in biological tissues. We used graphics processing units (GPUs) and coded in CUDA, an extension of the C language. We modeled the thermal deposition of THz radiation for both in vitro and in vivo exposures. To determine the speedup provided by GPUs, we compared the performance of simulations performed on a GPU (Tesla C1060) and CPU (Quad-Core,Intel-Xeon-5300). For the in vivo THz exposures, using a six-layer skin model, we found that the GPU performed 3-D simulations roughly 90X faster than the CPU.

Using nanoscale molecular dynamics modeling and Raman spectroscopy to investigate the direct effect of Terahertz radiation on double-stranded DNA

Paper 7897-15 of Conference 7897
Date: Monday, 24 January 2011
Time: 3:00 PM ?3:20 PM

Author(s): Gerald J. Wilmink, Jessica E. Grundt, Air Force Research Lab. (United States); Brett R. Boyce, U.S. Air Force Academy (United States); James E. Parker III, Air Force Research Lab. (United States) and The Univ. of Texas at San Antonio (United States); Brady Mcmicken, The Univ. of Texas at San Antonio (United States); Caleb C. Roth, Bennett L. Ibey, Michael L. Doroski, Benjamin A. Rockwell, Robert J. Thomas, William P. Roach, Air Force Research Lab. (United States)
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Theoretical models suggest that 2.52 Terahertz (THz) radiation can couple directly to the natural breathing modes of double stranded DNA (dsDNA) resulting in the creation of "bubbles" between dsDNA. In this study, we used Raman spectroscopy and nanoscale molecular dynamics modeling (NAMD) tools to evaluate the effect that 2.52 THz radiation has on the hydrogen bonding in dsDNA. Raman spectra were collected as various wavelengths (414 nm, 514 nm) on both salmon sperm dsDNA (~2-3k base pairs) and custom-designed dsDNA (polyA/T, 50bps). Comparable analyses were also conducted for hyperthermic and UV positive-controls.

Carrier dynamics of Mg-doped indium nitride

Paper 7937-33 of Conference 7937
Date: Monday, 24 January 2011
Time: 3:40 PM ?4:05 PM

Author(s): Hyeyoung Ahn, Chi-Chang Hong, National Chiao Tung Univ. (Taiwan); Yu-Liang Hong, Shangir Gwo, National Tsing Hua Univ. (Taiwan)
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Terahertz emission from Mg-doped InN is strongly influenced by the carrier density in such a way that the strong terahertz emission (×500 than that of undoped InN) is obtained for InN:Mg with a critical carrier density (~1×10^18 cm-3) and it decreases as the carrier density increases. Here we report that the carrier dynamics of InN:Mg, especially the decay time constant, is also closely dependent on the carrier density in the same way as terahertz radiation. The spatial redistribution of carriers in diffusion and drift is found to be responsible for the carrier recombination process as well as terahertz emission mechanism.

Characterization of burn injuries using terahertz time-domain spectroscopy

Paper 7890-25 of Conference 7890
Date: Tuesday, 25 January 2011
Time: 9:00 AM ?9:20 AM

Author(s): M. Hassan Arbab, Trevor C. Dickey, Dale P. Winebrenner, Antao Chen, Pierre D. Mourad, Univ. of Washington (United States)
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The accuracy rates of clinical assessment techniques used in grading burn injuries are significantly low for partial thickness burns. In this paper, we present experimental results from terahertz characterization of burn wounds induced on a rat model. The rats used in this work were divided into two groups for both acute burn characterization and 72-hour survival studies. Reflection measurements were obtained from the surface of both burn wounds as well as normal skin using ultra short pulsed terahertz radiation. Furthermore, spectroscopic signal processing techniques are described for interpretation of the acquired waveform and differentiation of burn wounds.

Nonlinear holographic imaging of terahertz radiation

Paper 7917-12 of Conference 7917
Date: Tuesday, 25 January 2011
Time: 11:00 AM ?11:20 AM

Author(s): Jean-Christophe Delagnes, Patrick Mounaix, Lionel Canioni, Univ. Bordeaux 1 (France)
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We present a theoretical investigation of a non-collinear sum frequency generation in an electrooptic crystal between a visible and a THz radiation. This results in the encoding of the spatial phase of the THz object field onto the visible wave. We can thus record THz scene with conventional optical detector that are much more sensitive than THz sensors. We show that a Nonlinear Snell-Descartes' Lens Formula can be derived from our analysis; in comparison to the classical one this generalized lens formula exhibits an additional magnification factor proportional to the ratio between the optical and THz wavelength.


Investigation of metamaterials for terahertz frequency range

Paper 7917-13 of Conference 7917
Date: Tuesday, 25 January 2011
Time: 11:20 AM ?11:40 AM

Author(s): Riad Yahiaoui, Univ. Bordeaux 1 (France); Hynek Nemec, Petr Ku瀍l, Filip Kadlec, Christelle Kadlec, Institute of Physics of the ASCR, v.v.i. (Czech Republic); Jörg Schilling, Martin-Luther-Univ. Halle-Wittenberg (Germany); M. Bari, Science and Technology Research Partners Ltd. (Ireland); Jean-Christophe Delagnes, Patrick Mounaix, Univ. Bordeaux 1 (France)
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We have demonstrated theoretical and experimental investigation of fishnet metamaterials at terahertz frequencies. Several prototypes were fabricated using optical lithography or laser micromachining technique. We carried out experiments using terahertz time domain spectroscopy THz-TDS. Moreover, we proposed THz metamaterials showing a tunable spectral interval where the magnetic permeability reaches negative values. This behavior was confirmed both theoretically and experimentally. These demonstrated principles represent a step forward towards a construction of a metamaterial with negative refractive index capable to cover continuously a broad range of THz frequencies and opens a new path for the active manipulation of submillimeter beams.

High-temperature performance and broad continuous tunability of terahertz quantum-cascade lasers

Paper 7953-23 of Conference 7953
Date: Tuesday, 25 January 2011
Time: 1:30 PM ?2:00 PM

Author(s): Sushil Kumar, Lehigh Univ. (United States); Qi Qin, Chun W. I. Chan, Qing Hu, Massachusetts Institute of Technology (United States); John L. Reno, Sandia National Labs. (United States)
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We demonstrate a terahertz quantum-cascade laser (QCL) operating significantly above the temperature of hw/kB, which has so-far been an empirical limitation for such devices. A 1.8 THz QCL operating up to a temperature of 1.9hw/kB (163K) is realized, with more than 3mW of peak optical power output at 150K. We also demonstrate broadly tunable terahertz QCLs. Discontinuous tuning over a range of 165GHz is realized for a 4.4THz QCL using an antireflection-coated silicon lens to reduce facet reflection and as a beam-forming element, with an external grating providing frequency selective optical feedback. We have also realized continuous tuning of 137GHz for a 3.8THz QCL with a unique concept of altering the lateral mode profile of terahertz "wire-lasers" to achieve broad tuning.

Broadband emission from THz quantum cascade lasers

Paper 7953-24 of Conference 7953
Date: Tuesday, 25 January 2011
Time: 2:00 PM ?2:20 PM

Author(s): Dana Turcinkova, Giacomo Scalari, Maria Amanti, Mattias Beck, Jerome Faist, ETH Zurich (Switzerland)
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We demonstrate broadband laser emission at THz frequencies from quantum cascade laser structures based on heterogenous cascades. The active material is composed by five stacks of three different active regions. Each active region is based on a 4-quantum well structure employing a bound-to-continuum transition. Laser emission is observed over a bandwidth of nearly one THz, spanning from 2.24 THz to 3.2 THz. Peak powers of more than 2 mW from a double metal waveguide and maximum operating temperatures of 100 K have been observed with threshold current densities as low as 230 A/cm^2 at 10 K.

Terahertz quantum cascade lasers with designer plasmonic collimators

Paper 7953-25 of Conference 7953
Date: Tuesday, 25 January 2011
Time: 2:20 PM ?2:50 PM

Author(s): Nanfang Yu, Harvard Univ. (United States); Qi Jie Wang, Nanyang Technological Univ. (Singapore); Mikhail A. Kats, Jonathan A. Fan, Harvard Univ. (United States); Suraj P. Khanna, Lianhe Li, Alexander G. Davies, Edmund H. Linfield, Univ. of Leeds (United Kingdom); Federico Capasso, Harvard Univ. (United States)
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We explain how semiconductor microstructures can effectively tailor the dispersion properties of surface plasmon polaritons in the terahertz frequency range. The physical principles of three structures are discussed; these are plasmonic Bragg gratings, spoof surface plasmon polariton structures, and channel polariton structures. We demonstrate their effectiveness by solving critical problems associated with terahertz quantum cascade lasers. By integrating plasmonic collimators directly on the semiconductor laser facets, the device power throughput is improved and the beam divergence is reduced by more than one order of magnitude to ~10 degrees. We achieve these improvements without compromising high temperature performance of the lasers.

Terahertz generation with tilted-front laser pulses: dynamical theory

Paper 7917-18 of Conference 7917
Date: Tuesday, 25 January 2011
Time: 2:40 PM ?3:00 PM

Author(s): Michael I. Bakunov, Univ. of Nizhny Novgorod (Russian Federation); Sergey B. Bodrov, Institute of Applied Physics (Russian Federation); Eugene Mashkovich, Univ. of Nizhny Novgorod (Russian Federation)
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A theory of terahertz emission from a femtosecond laser pulse with tilted intensity front propagating through a prism-shaped electro-optic crystal is developed. The theory accounts for transient effects at the entrance boundary of the crystal and allows one to explore the dynamics of terahertz generation in the crystal. Typical experimental situations - LiNbO3 excited with Ti:sapphire laser at room and cryogenic temperatures - are considered, and new schemes - GaAs excited at 1.8 and 3.5 um - are proposed and analyzed. The parameters of the laser pulse (transverse size, tilt angle, and pulse duration) and crystal size maximizing the terahertz yield are calculated.

Optical pump-terahertz probe studies of AlGaN

Paper 7939-42 of Conference 7939
Date: Tuesday, 25 January 2011
Time: 5:00 PM ?5:20 PM

Author(s): Timothy M. Sweeney, Univ. of Oregon (United States); Grace D. Metcalfe, Gregory A. Garrett, Anand V. Sampath, Paul H. Shen, U.S. Army Research Lab. (United States); Hailin Wang, Univ. of Oregon (United States); Michael Wraback, U.S. Army Research Lab. (United States)
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We report on ultrafast optical pump and terahertz probe studies of free-carrier dynamics in AlGaN materials grown with and without nano-scale compositional inhomogeneities (NCI). We observe an initial fast decrease of the transmitted THz signal in both AlGaN samples due to the generation of photoexcited free-carriers. The NCI AlGaN material shows a subsequent fast decrease in THz absorption, as compared to the NCI-free AlGaN. The faster decay time in the NCI AlGaN sample could be due to the transfer of free-carriers into NCI states from the AlGaN matrix as well as exciton formation and carrier recombination.

Low-threshold, quasi-cw terahertz parametric amplification in an external ring cavity with an MgO:LiNbO3 Crystal

Paper 7917-61 of Conference 7917
Date: Tuesday, 25 January 2011
Time: 6:00 PM

Author(s): Shingo Maeda, Tatsuya Ohira, Yuma Takida, Hiroshi Kumagai, Shigeki Nashima, Osaka City Univ. (Japan)
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We developed a terahertz parametric amplifier with an MgO-doped LiNbO3 (MgO: LN) nonlinear crystal in an external ring cavity with the enhancement of pump power. Moreover, the generated idler light was recycled by 2 additional flat mirrors so as to provide a contribution to parametric amplification. As a result, we obtained terahertz wave radiation at high-repetition of 80MHz. We additionally examined seed injection, which seed was provided a continuous-wave diode laser along the generated idler. In this presentation, we will show you the seed injection experimental results together with the effect of terahertz parametric amplification.

Novel terahertz emission devices based on efficient optical frequency conversion in GaAs/AlAs coupled multilayer cavity structures on high-index substrates

Paper 7937-52 of Conference 7937
Date: Wednesday, 26 January 2011
Time: 8:00 AM ?8:25 AM

Author(s): Takahiro Kitada, Fumiya Tanaka, Tomoya Takahashi, Ken Morita, Toshiro Isu, Univ. of Tokushima (Japan)
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GaAs/AlAs coupled multilayer cavity structures have been proposed as novel terahertz emission devices. Two cavity modes with an optical frequency difference in the terahertz region are realized when two cavity layers are coupled by an intermediate distributed Bragg reflector multilayer. Interference between the enhanced light fields of the cavity modes was demonstrated by using an ultrashort pulse laser. We also demonstrated extremely strong sum frequency generation in the (113)B coupled multilayer cavity. Such coupled multilayer cavity structures are promising for use as compact and room temperature operable terahertz emission devices based on difference frequency generation by the cavity-mode lights.

Novel concept for long-haul ultrashort pulse fiber delivery without pre-chirping

Paper 7912-41 of Conference 7912
Date: Wednesday, 26 January 2011
Time: 8:20 AM ?8:40 AM

Author(s): Tuan Le, Gabriel Tempea, Andreas Stingl, FEMTOLASERS Produktions GmbH (Austria); Kim G. Jespersen, OFS Fitel Denmark ApS (Denmark); Karin Wiesauer, RECENDT GmbH (Austria)
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Ultrashort pulse fiber delivery for Ti:Sapphire lasers is basically restricted to distances below several meters which is due to the application of dispersion compensating devices that are not capable managing third and higher order material dispersion. By the use of a novel fiber delivery concept ultrashort laser pulses in the 800 nm wavelength range can now be transmitted over tens of meters without the need for any pulse pre-compression. For the first time a long-haul fiber delivery module will be demonstrated revealing its potential for remote imaging or THz spectroscopy with femtosecond laser pulses.

Ultrafast carrier and phonon dynamics in graphene: relaxation, recombination, and transport

Paper 7937-61 of Conference 7937
Date: Wednesday, 26 January 2011
Time: 1:25 PM ?1:50 PM

Author(s): Farhan Rana, Haining Wang, Jared H. Strait, Cornell Univ. (United States)
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In this talk we discuss our experimental and theoretical results on the ultrafast dynamics of carriers and phonons in graphene. Ultrafast optical and terahertz spectroscopy results show that photoexcited carriers in graphene exhibit multiple time scales while undergoing relaxation and recombination dynamics. Hot carriers lose most of their energy to optical phonons within few hundred femtoseconds resulting in a hot phonon population which then becomes the main bottleneck for carrier cooling. Hot optical phonons decay into acoustic phonons via anharmonic processes within a few picoseconds. We will discuss the relevance of our experimental and theoretical results to graphene based optoelectronics.

Some aspects of far infrared spectroscopy of explosive materials

Paper 7938-19 of Conference 7938
Date: Wednesday, 26 January 2011
Time: 6:00 PM

Author(s): Norbert Palka, Mieczyslaw Szustakowski, Tomasz Trzcinski, Military Univ. of Technology (Poland)
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This paper presents some potentially interesting aspects of spectroscopic measurements of explosive materials in Far-Infrared (Terahertz) range: preparation of the samples, influence of grain size of particles inside the sample, influence of covering by clothes and influence of phlegmatization of explosives - addition an agent to an explosive material to stabilize or desensitize it. Moreover, two commonly used techniques - Far Infrared Fourier Spectroscopy and Time Domain Spectroscopy are presented and compared.

New experimental methods in terahertz spectroscopy

Paper 7938-2 of Conference 7938
Date: Thursday, 27 January 2011
Time: 8:30 AM ?8:50 AM

Author(s): Elizabeth J. Slingerland, Robert H. Giles, Thomas M. Goyette, Univ. of Massachusetts Lowell (United States)
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Spectroscopic studies are useful in a range of areas, from remote sensing and radio astronomy to the medical community, as spectroscopy can provide information used to identify chemicals. New techniques have been developed for high-resolution measurements of chemical absorption frequencies. These high-resolution measurements not only enhance accuracy of the molecule's energy level transitions, but also allow for environmental information to be gathered through the collisional broadening of the spectral lines. High-resolution measurements, made possible by far-infrared lasers coupled with Schottky diodes, were supplemented with data taken by variable pathlength FTIR measurements in the terahertz region. Chemicals investigated include methanol, nitric acid, and water vapor.

Encoding terahertz signatures into laser-induced plasma acoustic waves

Paper 7938-3 of Conference 7938
Date: Thursday, 27 January 2011
Time: 8:50 AM ?9:10 AM

Author(s): Benjamin W. Clough, Jingle Liu, Xi-Cheng Zhang, Rensselaer Polytechnic Institute (United States)
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The enhancement of acoustic waves, from audible into the ultrasonic range, is a linear function of the THz intensity incident on a laser-induced plasma, making THz-enhanced acoustics (TEA) useful for THz detection. By using a dual-color laser field to produce the plasma detector, THz spectroscopic information can be encoded into the acoustic emission, making it possible to obtain the electric field profile of the THz pulse by simply "listening" to the plasma at a distance.

Efficient material parameters estimation with terahertz time domain spectroscopy

Paper 7938-4 of Conference 7938
Date: Thursday, 27 January 2011
Time: 9:10 AM ?9:30 AM

Author(s): Osman S. Ahmed, Mohamed A. Swillam, Mohamed H. Bakr, Xun Li, McMaster Univ. (Canada)
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We propose a novel optimization technique for the estimation of material refractive index in the terahertz frequency range. The algorithm is applied for materials with arbitrary frequency dependence. Dispersive dielectric models are embedded for accurate parameter extraction of a sample with unknown thickness. Instead of solving N expensive nonlinear optimization problems with different possible material thickness, our technique obtains the optimal material thickness by solving only one optimization problem. Our approach has been successfully illustrated through a number of examples with different dispersive models. The examples include the characterization of doped semiconductors used in surface plasmon plaritons in the THz regime.

Terahertz imaging in dielectric media with quasi-Bessel beams

Paper 7938-5 of Conference 7938
Date: Thursday, 27 January 2011
Time: 9:30 AM ?9:50 AM

Author(s): Takashi Buma, Zhuopeng Zhang, Univ. of Delaware (United States)
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We demonstrate time-domain terahertz imaging with quasi-Bessel beams created with an axicon lens. Experiments with a high density polyethylene axicon confirm that spatial resolution is maintained over a large depth of field. We also demonstrate that quasi-Bessel beams experience reduced spherical aberration when imaging objects embedded in a thick dielectric medium. Metallic objects covered with a 12.5 mm thick plastic slab are imaged clearly with an axicon lens, while an off-axis parabola produces poor image quality. These promising results suggest that Bessel beams are well suited for terahertz nondestructive imaging of thick dielectric objects.

The effects of various approximations on electron-electron scattering calculations in QCLs

Paper 7938-7 of Conference 7938
Date: Thursday, 27 January 2011
Time: 11:00 AM ?11:20 AM

Author(s): Philip Slingerland, Christopher S. Baird, Robert H. Giles, Univ. of Massachusetts Lowell (United States)
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Electron-electron scattering is an essential mechanism involved in electron transport in quantum cascade lasers (QCL's). However, approximations are often made in finding the electron-electron scattering rate in order to simplify calculations. Results will be presented characterizing various effects which are sometimes ignored in calculating electron-electron scattering rates. These effects include state-blocking, electron screening, temperature dependence, as well as the inclusion of all possible transitions that can occur in three periods of the QCL active region. These effects will be presented in the context of several QCL active region designs.

Semiconductor-coated deep subwavelength spoof surface plasmonic waveguide for THz and MIR applications

Paper 7938-8 of Conference 7938
Date: Thursday, 27 January 2011
Time: 11:20 AM ?11:40 AM

Author(s): Ruoxi Yang, Wangshi Zhao, Zhaolin Lu, Rochester Institute of Technology (United States)
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We propose integrated waveguides for terahertz (THz) and mid-infrared (MIR) applications on wafer platform. Based on the prototype of spoof plasmonic waveguides consisting of textured metallic surface, we explore the possibility of coating periodic metallic pattern with silicon (at 0.6 THz) or germanium (at MIR region of 30 THz) to further shrink the relative mode size of propagation spoof plasmonic waves. Numerical modeling via 3D finite-difference time-domain (FDTD) has shown deep sub-wavelength mode confinement in transverse directions to smaller than ?/50 by ?/50, with an estimated propagation loss of less than 0.1 dB for each repetitive unit.

Optical frequency conductance model of teraHertz/infrared emission and detection in quantum wells, quantum dots, and narrow-gap semiconductors

Paper 7938-9 of Conference 7938
Date: Thursday, 27 January 2011
Time: 11:40 AM ?12:00 PM

Author(s): Thomas Szkopek, Elizabeth Ledwosinska, McGill Univ. (Canada)
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The optical frequency conductance is derived for quantum wells and quantum dots, and the optical frequency conductivity of bulk narrow-gap semiconductors is revisited. The teraHertz (THz) and infrared (IR) response of these structures, in free-space and guided-wave geometries, is simply described within the optical frequency conductance formalism. The fine structure constant of quantum electrodynamics sets the natural scale for the optical conductance of semiconductor structures. Rules of thumb and physical limits to THz/IR gain and absorption can be derived. The optical conductance formalism is applied to MCT photodetectors, quantum well IR photodetectors, quantum dot IR photodetectors, and quantum cascade lasers.

A mechanically tunable terahertz modulator based on antiresonant reflecting hollow waveguide

Paper 7938-11 of Conference 7938
Date: Thursday, 27 January 2011
Time: 1:50 PM ?2:10 PM

Author(s): JaYu Lu, Hao-Zai Chen, National Cheng Kung Univ. (Taiwan); Chih-Hsien Lai, Hung-Chun Chang, National Taiwan Univ. (Taiwan); Borwen You, National Cheng Kung Univ. (Taiwan); Tze-An Liu, Jin-Long Peng, Industrial Technology Research Institute (Taiwan)
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We have experimentally demonstrated a broadband tunable terahertz (THz) modulator based on one-dimensional anti-resonant reflecting hollow waveguide (ARRHW), which consisting of a PMMA-made cladding and a pair of motorize-controlled metal plates located outside that. By continually varying the distance d between the PMMA-cladding and the metal plate, it enables dynamical tuning of the transmission band and linear attenuation of THz power for a specific frequency. The measured maximum spectrum tuning range of 60GHz and the power modulating depth of 20dB are achieved. The low loss THz-ARRHW based device is also promising for the polarization filter application with extinction-ratio of 20dB.

THz thermal emission from a 1D photonic crystal

Paper 7938-12 of Conference 7938
Date: Thursday, 27 January 2011
Time: 2:10 PM ?2:30 PM

Author(s): Ian A. Zimmerman, Ziran Wu, Hao Xin, Richard W. Ziolkowski, The Univ. of Arizona (United States)
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We have experimentally and theoretically investigated a simple 1D, bi-layered electromagnetic crystal structure composed of air and silicon slabs. We have calculated the emissivity using Kirchhoff's thermal radiation law, as well as by calculating the density of states directly, and have compared those results to the experimental values. Our ultimate goal is to be able to control the spectral emission of an electromagnetic crystal in the THz region (or other wavelength ranges, such as the infrared) by engineering its band structure with the desire to develop a cheap, incoherent broadband THz source.

Applications of holography in the millimeter-wave and terahertz region

Paper 7938-15 of Conference 7938
Date: Thursday, 27 January 2011
Time: 3:40 PM ?4:00 PM

Author(s): Ian McAuley, Ronan J. Mahon, J. Anthony Murphy, National Univ. of Ireland, Maynooth (Ireland)
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In this paper we report on the holographic techniques developed for applications in a number of areas of interest in the millimeter-wave and terahertz range. An experimental arrangement based on off-axis near-field holography configurations was adapted to digitally record the holograms using two radiating horn antennas fed by a single coherent source to produce the object and reference beams. Among the applications investigated was the measurement of the phase centres of non-standard radiating antennas (such as a planar lens antenna). Using phase retrieval methods, the recorded holographic interference pattern can be used to determine the effective phase centres by numerically propagating the recovered object beam back towards the source plane.

Electromagnetic crystal (EMXT) based THz components

Paper 7938-16 of Conference 7938
Date: Thursday, 27 January 2011
Time: 4:00 PM ?4:20 PM

Author(s): Ziran Wu, Wei-Ren Ng, Michael E. Gehm, Hao Xin, The Univ. of Arizona (United States)
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All-dielectric Terahertz waveguides based on hollow-core EMXT fiber are fabricated via THz rapid prototyping using polymer jetting technique. Several waveguides of identical cross-section and differing lengths are characterized by THz time-domain spectroscopy (THz-TDS) to extract the waveguide intrinsic propagation loss. Measurement results agree very well with simulation. This as an initial example demonstrates a waveguide with low propagation loss of 0.03 dB/mm at 105 GHz. Based on the waveguide, an EMXT antenna is also formed by modifying the defect shape into a horn. Simulation shows good performance of this horn antenna. The antenna is fabricated by the same rapid prototyping method, and its far-field pattern measurement result will be reported.

Integrated Terahertz pulse generation and amplification in quantum cascade lasers

Paper 7945-11 of Conference 7945
Date: Sunday, 23 January 2011
Time: 11:20 AM ?11:40 AM

Author(s): Sukhdeep S. Dhillon, Simon Sawallich, Nathan Jukam, Dimitri Oustinov, Julien Madeo, Rakchanok Rungsawang, Ecole Normale Supérieure (France); Stefano Barbieri, Pascal G. Filloux, Carlo Sirtori, Univ. Paris 7-Denis Diderot (France); Xavier Marcadet, Alcatel-Thales III-V Lab. (France); Jerome Tignon, Ecole Normale Supérieure (France)
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We demonstrate an integrated approach to generate and amplify Terahertz (THz) pulses within a quantum cascade laser (QCL). Using an ultrafast interband excitation of a THz QCL, THz pulses are generated via charge carrier acceleration within the QCL miniband. The generated pulses are subsequently amplified at the QCL gain as they propagate through the laser cavity. As well as integrating the generation and amplification of THz pulses, this technique can potentially permit efficient THz pulse injection into sub-wavelength double metal resonators.

Circuit, antenna-based, and photonic crystal terahertz quantum cascade lasers

Paper 7945-15 of Conference 7945
Date: Sunday, 23 January 2011
Time: 1:35 PM ?1:55 PM

Author(s): Jerome Faist, Christophe Walther, Maria Amanti, Giacomo Scalari, Mattias Beck, ETH Zurich (Switzerland); Hua Zhang, Romuald Houdre, Ecole Polytechnique Fédérale de Lausanne (Switzerland)
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In the Terahertz, MBE-grown structures have demonstrated record low frequency operation, down to 1.2THz. Taking advantage of the tight confinement provided by the metal-metal waveguide, we also have explored third order photonic wire lasers as well as photonic crystal quantum cascade lasers. In a further development, LC resonator cavities enable us to explore the coupling between transport and photon emission in the regime of very subwavelength emitters, as the ratio of volume over lambda cube is much below unity.

Progress in medical applications of terahertz technology in the head and neck

Paper 7883C-176 of Conference 7883C
Date: Sunday, 23 January 2011
Time: 2:40 PM ?3:00 PM

Author(s): Vincent P. Wallace, The Univ. of Western Australia (Australia)
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Subpicosecond Sub-terahertz soliton laser based on a C-MOS compatible integrated microring resonator

Paper 7945-37 of Conference 7945
Date: Monday, 24 January 2011
Time: 9:55 AM ?10:10 AM

Author(s): Marco Peccianti, Institut National de la Recherche Scientifique (Canada) and Institute for Chemical and Physical Processes (Italy); Alessia Pasquazi, Yongwoo Park, Institut National de la Recherche Scientifique (Canada); Brent Little, Sai-Tak Chu, Infinera Corp. (United States); David J. Moss, Univ. of Sydney (Australia); Roberto Morandotti, Institut National de la Recherche Scientifique (Canada)
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We present a novel subpicosecond, Sub THz -repetition rate, passively mode-locked laser scheme based on high-harmonic four wave mixing in an integrated CMOS-compatible high-Q nonlinear ring resonator.

Phase-locking and synthesis of terahertz quantum cascade laser emission

Paper 7953-26 of Conference 7953
Date: Tuesday, 25 January 2011
Time: 3:30 PM ?4:00 PM

Author(s): Stefano Barbieri, Marco Ravaro, Pierre Gellie, Univ. Paris 7-Denis Diderot (France); Giorgio Santarelli, LNE-SYRTE, CNRS, UPMC (France); Christophe Manquest, Carlo Sirtori, Univ. Paris 7-Denis Diderot (France); Suraj P. Khanna, Edmund H. Linfield, Univ. of Leeds (United Kingdom)
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We demonstrate that the carrier frequency and the repetition rate of a Terahertz (THz) quantum cascade laser (QCL) can be simultaneously phase-locked to the repetition rate of a mode-locked Er-fiber laser. By combining the two stabilization techniques we show that all the longitudinal modes of a multimode QCL emitting at ~2.4THz can be phase-locked, paving the way to the use of these sources for high power, direct THz frequency synthesis.

Upper limits on terahertz difference frequency generation power in quantum well heterostructures

Paper 7953-29 of Conference 7953
Date: Tuesday, 25 January 2011
Time: 4:50 PM ?5:10 PM

Author(s): Yong-Hee Cho, Texas A&M Univ. (United States); Mikhail A. Belkin, The Univ. of Texas at Austin (United States); Alexey A. Belyanin, Texas A&M Univ. (United States)
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We investigate the upper limits on the terahertz (THz) difference frequency generation (DFG) power that can be achieved in intersubband quantum well systems under external mid-infrared pumping. We solve self-consistently three coupled wave equations, the Poisson equation, and density matrix equations including pump depletions and nonlinear saturation effects. The maximal THz DFG power is reached for intermediate pump intensities of the order of the saturation intensity. Further increase of pump intensities degrades the maximum THz DFG power and shifts it to large detunings. We compare our results with recent experiments in GaInAs/AlInAs heterostructures and suggest optimal device designs.

Course: Terahertz Wave Technology and Applications

Date: Wednesday, 26 January 2011
Time: 8:30 AM ?12:30 PM

Instructor(s): Xi-Cheng Zhang, Rensselaer Polytechnic Institute (United States)
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A pulsed terahertz (THz) wave with a frequency range from 0.1 THz to 10 THz is called a "T-ray." T-rays occupy a large portion of the electromagnetic spectrum between the infrared and microwave bands. However, compared to the relatively well-developed science and technology in the microwave, optical, and x-ray frequencies for defense and commercial applications, basic research, new initiatives and advanced technology developments in the THz band are very limited and remain unexplored. However, just as one can use visible light to create a photograph, radio waves to transmit music and speech, microwave radiation (MRI) or X-rays to reveal broken bones, T-ray can be used to create images or communicate information. This course will provide the fundamentals of free-space THz optoelectronics. We will cover the basic concepts of generation, detection, propagation, and applications of the T-rays, and how the up-to-date research results apply to industry. The free-space T-ray optoelectronic detection system, which uses photoconductive antennas or electro-optic crystals, provides diffraction-limited spatial resolution, femtosecond temporal resolution, DC-THz spectral bandwidth and mV/cm field sensitivity. Examples of homeland security and defense related projects will be highlighted.

Ultrafast terahertz spectroscopy of few-layer graphene

Paper 7937-64 of Conference 7937
Date: Wednesday, 26 January 2011
Time: 2:40 PM ?3:05 PM

Author(s): Hyunyong Choi, Ferenc Borondics, David A. Siegel, Shuyun Zhou, Michael C. Martin, Alessandra Lanzara, Robert A. Kaindl, Lawrence Berkeley National Lab. (United States)
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Graphene is attracting significant interest due to the unique physics of its 2D charge carriers in a linear electronic bandstructure, and due to possible applications in e.g. high-speed electronics. Here, we discuss the broadband optical conductivity and ultrafast THz dynamics of graphene in the few-layer limit. The equilibrium optical response in epitaxial graphene is consistent with the electrodynamics of a dense Dirac electron plasma, arising from highly-doped layers at the graphene-substrate interface. We will further discuss the transient THz response, which reflects the recombination dynamics and unusual Drude response of graphene and its dependence on the carrier distribution function.

Terahertz holographic interferometry

Paper 7957-42 of Conference 7957
Date: Wednesday, 26 January 2011
Time: 6:00 PM

Author(s): Andrei A. Gorodetsky, Victor G. Bespalov, Saint-Petersburg State Univ. of Information Technologies, Mechanics and Optics (Russian Federation)
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We present our new modeling and research results on terahertz holographic interferometry, a technique allowing to reconstruct changes in inner dielectric object structure. The technique is somehow alike the corresponding one in optics, but allows managing optically opaque objects. Using the broadband pulse THz radiation with a spectrum in the range of 0.1-2.5 THz we can reconstruct object deformations up to several microns in the bulk 3d object.

Terahertz time-lapse video of hydration in physiological tissues

Paper 7938-20 of Conference 7938
Date: Thursday, 27 January 2011
Time: 10:10 AM ?10:30 AM

Author(s): David B. Bennett, Zachary D. Taylor, Sijun Sung, Borokh Makkabi, Priyamvada Tewari, Neha Bajwa, Rahul S. Singh, Martin O. Culjat, Warren S. Grundfest M.D., Univ. of California, Los Angeles (United States); Elliott R. Brown, Univ. of California, Santa Barbara (United States) and Wright State Univ. (United States)
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This study describes terahertz (THz) imaging and monitoring of physiological tissues over long periods of time based on high sensitivity to hydration levels. A fast-scanning, gated time-domain THz imaging system (centered at 525 GHz; 125 GHz bandwidth) was utilized which uses dynamic pixel acquisition to image a 4-cm2 area in less than two minutes. THz video was taken on three sample systems: (1) a simple binary system of water absorbed into a polypropylene towel, (2) the accumulation of fluid to the site of a sulfuric acid burn on ex vivo porcine skin, and (3) the evaporative dehydration of a porcine cornea. The diffusion-regulating behavior of corneal and skin tissue is elucidated. We conclude from this study that THz imaging can discern the differences between diffusion of liquid water in physiological tissues and that of inanimate, homogeneously-diffusing matter.

Room temperature Nb5N6 microbolometer for detecting signals at terahertz region

Paper 7938-13 of Conference 7938
Date: Thursday, 27 January 2011
Time: 2:30 PM ?2:50 PM

Author(s): Lin Kang, Xuchou Tu, Jian Chen, Peiheng Wu, Nanjing Univ. (China)
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Onto a double layer, which is made of a Si substrate ( ?> 1000 ?昪m ) and a SiO2 layer 100 nm thick on top of it, a Nb5N6 thin film microbridge is deposited and integrated with an dipole planar antenna. With a SiO2 air-bridge further fabricated underneath the microbridge and operated at room temperature, such a combination behaves very well as a microbolometer for detecting signals at 210 GHz, thanks to a temperature coefficient of resistance (TCR) as high as -0.7% K-1 of the Nb5N6 thin film. According to our measurements and estimations, the best attainable electrical responsivity and the response bandwidth of Nb5N6 microbolometer are about -530 V/W and 21 GHz respectively, at a current bias of 0.35 mA . The electrical noise equivalent power (NEP) is 8.27×10-12 W/Hz1/2 for the modulation frequency above 600 Hz. A quasi-optical receiver based on such a bolometer is constructed and measured.

Terahertz antiresonant reflecting hollow-core waveguides for sensing applications

Paper 7938-18 of Conference 7938
Date: Thursday, 27 January 2011
Time: 4:40 PM ?5:00 PM

Author(s): Borwen You, Ja-Yu Lu, National Cheng Kung Univ. (Taiwan); Chi-Yu Chan, Chin-Ping Yu, National Sun Yat-Sen Univ. (Taiwan); Hao-Zai Chen, National Cheng Kung Univ. (Taiwan); Tze-An Liu, Jin-Long Peng, Industrial Technology Research Institute (Taiwan)
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A dielectric hollow tube utilized as a terahertz antiresonant reflecting hollow-core waveguide (THz-ARRHW) sensor has been demonstrated to detect the minute variation of both refractive index and thickness in macromolecule layers deposited on the tube wall, and to identify liquid vapors from the various core indices. The minimum detectable variations of sample-quantity and concentration are down to 1.2picomole/mm^2 and 0.2%, corresponding to the variation of 2.9祄-thickness and 0.001-refractive-index, respectively. A THz-ARRHW sensor is also used to identify various volatile liquid vapors in the hollow-core based on different induced core indices, and the detectable vapor density is down to 0.0001g/cm^3.

Rigorous characterization of surface plasmon modes by using the finite element method

Paper 7941-34 of Conference 7941
Date: Wednesday, 26 January 2011
Time: 8:30 AM ?8:50 AM

Author(s): B. M. Azizur Rahman, Huda Tanvir, Anita Quadir, Ken Grattan, The City Univ. (United Kingdom)
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A rigorous full vectorial finite element-based approach has been developed to characterize a wide range of plasmonic devices, both at optical and terahertz frequencies. Results for wave confinement in gold nanowires, air-core guides and defect-core metal coated photonic crystal fibers and gain threshold optimization of quantum cascaded lasers for terahertz (THz) frequencies will be presented.

Parametric generation of terahertz wave pumped by picosecond Ti:sapphire laser with MgO-doped LiNbO3 installed in external enhancement cavity

Paper 7917-14 of Conference 7917
Date: Tuesday, 25 January 2011
Time: 11:40 AM ?12:00 PM

Author(s): Yuma Takida, Shingo Maeda, Tatsuya Ohira, Hiroshi Kumagai, Shigeki Nashima, Osaka City Univ. (Japan)
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We built an external enhancement cavity with MgO-doped LiNbO3 (MgO:LN) and then enhanced the pump light in the cavity. Considering that the idler light generated in MgO:LN with the different angle of about 1 degree to the pumping light, we designed carefully the cavity in order to circulating the idler light as well as pump light simultaneously. In the cavity, the circulated idler light could contribute to the terahertz parametric generation induced by the next pumping pulse. As a result, when the idler light circulating the cavity, we demonstrated a clear enhancement of the idler intensity.

Course: Semiconductor Optoelectronic Device Fundamentals

Date: Monday, 24 January 2011
Time: 8:30 AM ?5:30 PM

Instructor(s): Kurt J. Linden, Spire Corp. (United States)
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This provides a review of the basics of semiconductor materials, with primary emphasis on their optoelectronic properties. The motion of electrons and holes is discussed, and photon absorption and generation mechanisms are presented. The course examines basic device structures such as quantum wells and quantum dots, Bragg reflectors, cascade devices, distributed feedback devices, avalanching, tunneling, and various electro-optic effects. Device operating principles are presented, and an overview of current device applications is given. The participants should walk away with a good understanding of semiconductor optoelectronics covering the entire UV to terahertz spectral region, including devices such as diode and cascade lasers, LEDs, SLEDs, VCSELs, modulators, and photodetectors.

Challenges in octave-spanning and short free-spectral-range optical frequency comb generation using monolithic whispering gallery mode resonators

Paper 7913-28 of Conference 7913
Date: Monday, 24 January 2011
Time: 11:50 AM ?12:20 PM

Author(s): Yanne K. Chembo, Institut FEMTO-ST (France) and Jet Propulsion Lab. (United States); Nan Yu, Jet Propulsion Lab. (United States)
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Optical frequency combs find applications in various areas of science and technology, such as time-frequency metrology, aerospace engineering, and ultra-low phase noise microwave and terahertz generation. A new paradigm has recently been proposed for the generation of these combs, and it is based on the excitation of the whispering gallery mode of an ultra-high Q monolithic resonator through the Kerr effect. This communication will review the main challenges that arise from this new perspective, in order to achieve the goal of octave spanning combs whose free spectral range is the shortest possible.

One- and two-dimensional THz spectroscopy on semiconductor nanostructures

Paper 7937-32 of Conference 7937
Date: Monday, 24 January 2011
Time: 2:45 PM ?3:10 PM

Author(s): Michael Woerner, Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie (Germany)
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Using our novel high field terahertz source we performed various nonlinear experiments on semiconductor nanostructures. In one-dimensional nonlinear propagation experiments on n-type GaAs we observed ballistic high-field transport and THz-induced interband tunneling of electrons. Two-dimensional THz correlation spectroscopy performed on intersubband transitions of two coupled quantum wells shows distinct polaronic features of the intersubband transitions.

CUDA based holographic modeling software

Paper 7957-43 of Conference 7957
Date: Wednesday, 26 January 2011
Time: 6:00 PM

Author(s): Andrei A. Gorodetsky, Saint-Petersburg State Univ. of Information Technologies, Mechanics and Optics (Russian Federation)
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We present the result of an upgrade of previously described and used multithreaded software for modeling the process of holographic recording and reconstruction. The software allows 2d and 3d diffraction modeling for near- and far-field radiation of arbitrary spectral composition both for flat and 3d objects. The sofware was successfully applied to holographic nanolithography, terahertz pulse holography and diffraction of ultrashort optical pulses modeling. Today, a considerable upgrade is introduced, allowing referenceless iteration reconstruction of multiple wavelength intensity pictures and GPU calculation functionality.

Fellows Luncheon

Date: Monday, 24 January 2011
Time: 12:00 PM ?1:30 PM

Author(s):
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All Fellows of SPIE are invited to join your colleagues for an SPIE hosted luncheon. The new SPIE Fellows attending Photonics West will be introduced and recognized. Please join us for this informal gathering and a chance to interact with other Fellows. Fellows planning to attend are asked to RSVP to Brent Johnson.

Prof. Federico Capasso
School of Engineering and Applied Sciences at Harvard University

Quantum Cascade Lasers: widely tailorable light sources from the mid-infrared to Terahertz

Quantum Cascade Lasers represent a radical departure from conventional semiconductor lasers in that they don't rely on the bandgap for light emission. This freedom from bandgap slavery has many far reaching implications that will be fully explored in this talk. I will trace the path from invention to exciting advances in the applications of these revolutionary lasers which cover the mid- and far-ir spectrum and are broadly impacting applications ranging from countermeasures to gas sensing and spectroscopy in a wide range of sectors. The talk will conclude with a discussion of the ongoing commercialization.

Federico Capasso is the Robert Wallace Professor of Applied Physics at Harvard University, which he joined in 2003 after a 27 years career at Bell Labs where he did research, became Bell Labs Fellow and held several management positions including Vice President for Physical Research. His research has spanned a broad range of areas including electronics, photonics, material science, nanotechnology and quantum electrodynamics. He pioneered the approach widely known as band-structure engineering in the design of heterostructure materials and devices. He is a co-inventor of the quantum cascade laser, a fundamentally new light source, which has now been commercialized and in recent years has been involved in fundamental studies of forces associated with quantum fluctuations such as the Casimir force, including the first measurement of a repulsive Casimir force. He is a member of the National Academy of Sciences, the National Academy of Engineering, a fellow of the American Academy of Arts and Sciences and an Honorary Member of the Franklin Institute. His awards include the King Faisal International Prize for Science, the Berthold Leibinger Zukunftspreis (the future prize), Julius S

Comparison of GaAs and DAST electro-optic crystals for THz time domain spectroscopy using 1.55 祄 fiber laser pulses

Paper 7938-6 of Conference 7938
Date: Thursday, 27 January 2011
Time: 9:50 AM ?10:10 AM

Author(s): Matthieu Martin, Juliette Mangeney, Paul Crozat, Univ. Paris-Sud 11 (France); Patrick Mounaix, Univ. Bordeaux 1 (France)
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We report terahertz time-domain spectroscopy system based on Er:fiber laser at 1.55 祄 wavelength that integrate an ion-irradiated In0.53Ga0.47As photoconductive antenna as emitter and a GaAs or a DAST electro-optic sensor as detector. Detection using GaAs crystal is performed with an electro-optic sampling detection based on polarization rotation of optical probe beam. We have implemented interferometric scheme to detect the phase change of optical probe beam due to THz-induced electro-optic effect in DAST crystal since the standard electro-optic sampling technique is not applicable to DAST crystal. The detected bandwidth is 3 THz using GaAs crystal and reaches 5 THz using DAST crystal.

III-nitride resonant tunneling devices from growth to fabrication

Paper 7939-50 of Conference 7939
Date: Wednesday, 26 January 2011
Time: 11:30 AM ?11:50 AM

Author(s): Manijeh Razeghi, Northwestern Univ. (United States)
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The resonant tunneling diodes (RTDs) with their strong negative differential resistance (NDR) at room temperature (RT) are promising for high frequency generation up to terahertz enabling many applications such as ultra speed wireless communications, spectroscopy, and imaging. III-nitride materials are emerging candidates for RTD application due to their properties such as high peak electron velocity, saturation velocity, and thermal stability. AlN/GaN RTDs are expected to have high peak-to-valley ratio (P/V) and performance at RT due to large conduction band discontinuity of 2.1 eV. However, high lattice mismatch of conventional substrate such as sapphire which leads to high dislocations density in epilayer and requirement for precise material, thickness, and abrupt interface control are the biggest challenges hindering nitride-based quantum-effect device technology. In the first part of this work, we study metal-organic chemical vapor deposition(MOCVD) of AlN/GaN RTDs. MOCVD growth conditions are optimized to achieve smooth heterojunctions as well as abrupt transition between nano-scale layers with a precise thickness control. Effects of material quality on RTDs' performance are investigated by growing RTD structures on various templates on conventional sapphire substrate. Negative differential resistances with P/V as high as 2.2 are realized in AlN/GaN RTD MOCVD-grown material at RT for the first time. The alternative to reduce dislocation densities in epilayers is homoepitaxial growth on freestanding (FS) GaN substrates. In the second part of this work, we study MOCVD of AlGaN/GaN RTDs on polar (c-plane) and non-polar (m-plane) freestanding GaN substrates. In this talk we compare the performance of MOCVD-grown RTDs on different substrates.

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