DOCSLIB.ORG

Pushing Semiconductor Detectors Into the Terahertz Gap

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Pushing Semiconductor Detectors Into the Terahertz Gap TECHNICAL FEATURE Terahertz Detectors An electromagnetic wave that penetrates a US university project is looking to develop clothing could be very useful in looking a range of semiconductor detectors with for concealed weapons and other objects. spectral resolution to support such work. Dr Mike Cooke Terahertz waves offer such a possibility and Pushing semiconductor detectors into the terahertz gap The desire to see hidden threats is one of the concealed weapons and the US military is leading thrusts of the US Homeland Security keen to extend the reach of such devices, effort. Terahertz (1 THz = 1012 Hz) waves along with developing all-weather aircraft penetrate most non-metallic materials, except landing technology (Mike Cooke, “Focusing on water – hence, dry clothing should be trans- high performance and power”, III-Vs Review, parent, while metal and living matter won’t. August 2006, pp. 20–23). Terahertz detectors could also assist in detect- Signals in the terahertz range fall between ing illegal or dangerous materials hidden in conventional radio/microwave frequency elec- baggage or parcels. Spectroscopic informa- tronics up to 100 GHz and photonics above tion from THz waves can also be used to 10 THz (Figure 1). A frequency of 1 THz also detect the binding of inhibitors with protein lies in the far infrared (FIR) range of frequen- targets, allowing for rapid drug screening in cies (~300 GHz–15 THz) with wavelengths pharmaceutical research, and for distinguish- of the order 1 mm–20 µm. Some researchers ing between different tissue types for disease extend the far infrared to ‘extreme infrared’ diagnosis. Secure transmission of signals using with wavelengths of the order 2 mm–100 µm terahertz waves are also under consideration (150 GHz–3 THz). These extreme infrared in some circles. Terahertz airport security photon energies range from around 0.6 systems have already been developed to trap to 12 meV with equivalent temperatures Figure 1. The terahertz gap between electronic and photonic technologies. [From http://electron.physics.buffalo.edu/spec- tre/, the website for Dr Markelz’s group.] 36 III-Vs REVIEW THE ADVANCED SEMICONDUCTOR MAGAZINE VOL 19 - NO 8 - NOVEMBER 2006 iiivs198p36_38.indd 36 31/10/2006 12:24:39 Terahertz Detectors TECHNICAL FEATURE 5–150 K. Transistor technology is only engineering in the University of Buffalo, School now beginning to encroach on the lowest of Engineering and Applied Sciences, focuses terahertz frequencies (Mike Cooke, “Silicon on fabrication and characterization of semicon- transistor hits 500 GHz performance”, III-Vs ductor nanodevices. Review, June/July 2006, pp. 30–31). “We will gain a detailed understanding of how Researchers led by Andrea Markelz, Ph.D., of the electrical properties of semiconductor nan- the University at Buffalo (State University of odevices are modified in the presence of tera- New York) have gained a four-year $1.2m US hertz radiation,” Bird says. National Science Foundation grant to develop There are three types of FIR detector: bolo- semiconductor-based terahertz detectors that metric, photonic and plasmonic. The most can be integrated seamlessly with conventional common are bolometric photoconductors, electronics. where the heating due to absorbed FIR causes The focus will firstly be on the implementa- a net change in conductivity. These detec- tion of frequency-tuneable terahertz detec- tors usually have no frequency resolution. tors based on nanostructured semiconductor Other attempts at photonic detectors (most systems. Among the physical effects to be often resonant tunnelling diodes) are usually explored are plasmons in confined geometries overwhelmed by bolometric effects from free such as quantum dots, as well as photoexcita- carrier absorption. This type of absorption tion of electrons in quantum point contacts normally dominates because one is coupling (QPCs). Both quantum dots and QPCs are built with the electromagnetic field in the plane of in compound semiconductor environments. a two-dimensional electron gas (2DEG) – the The resulting devices are expected to be suita- coupling to the confined transitions is weak ble for integration into large-scale arrays, allow- since the confinement is perpendicular to ing sophisticated temporal and spatial signal the plane. Quantum point contacts (Figures 2 processing functions. A QPC terahertz detector and 3) add further confinement through nega- is likely to be furthest along in development at tively biased metal contacts that raise barriers the end of the grant, according to Markelz. in the 2DEG and deplete the electron popula- tion in certain regions. Markelz’s expertise lies in characterizations of terahertz optical systems and materials at “In our device, we combine the high sensitiv- these frequencies while co-principal investiga- ity of a quantum point contact, with the pho- tor Jonathan Bird, Ph.D., professor of electrical tonic transitions of confinement in the plane Figure 2. In research being conducted by Andrea Markelz and Jonathan Bird at the University at Buffalo, the grey and yellow regions create a quantum point contact nanowire device that detects terahertz radiation emitted by a targeted substance. www.three-fives.com 37 iiivs198p36_38.indd 37 31/10/2006 12:24:47 TECHNICAL FEATURE Terahertz Detectors carried out on an initial prototype for a quan- tum dot plasmonic detector. The electron momentum relaxation time was derived using a Drude model and the researchers found an unexpectedly smaller relaxation time compared with that found from DC measure- ments. The normal Drude like response seen in highly doped semiconductors at room tempera- ture evolves to a non-Drude response at low temperatures. The effect begins to be noticeable at 100 K and increases down to 10 K. The differ- ence is also more pronounced at higher frequen- cies. The suggestion is that small-angle scattering processes lead to weaker heating of the 2DEG compared with the results from DC mobility measurements. Figure 3. Close-up of the to allow for maximal coupling and sensitivity,” The money for the research program comes quantum point contact. says Markelz. “We are aiming to operate the QPC from the NSF Nanoscale Interdisciplinary detector at more than 40 K, but higher tempera- Research Teams (NIRT) initiative. The grant tures are likely to suffer reduced sensitivity due is one of only 10 that the NSF has funded to dark currents arising from the thermal from more than 400 applications received. background. The biggest advantage to the quan- In addition to the University at Buffalo, tum point contact terahertz detector that we researchers will come from the University of are developing is that it will provide spectral California at Santa Barbara, and the Queens information, revealing many wavelengths at once, and Kingsborough Community colleges of allowing for far more precise distinctions among the City University of New York (CUNY). This similar objects.” collection of scientists has wide expertise Markelz adds: “We are also continuing to work in semiconductor nanodevice fabrication, on plasmonic devices using both two-dimen- DC and THz characterization, and theoretical sional and three-dimensional confinement. modelling. Some collaboration is also expect- In this case we will have tuneable frequency ed with the Institute of Physical and Chemical resolution through gate defined length Research (RIKEN, Japan) and the US Sandia scales thus changing the confined plasmon National Laboratory. resonances.” Beyond research, the project has educational ‘Hybrid’ devices combining bolometric and and social aims with the inclusion of commu- plasmonic techniques are also being considered. nity-college students and even ‘engagement’ One idea is to have a metal grating rather than with high school teachers. Indeed, the theo- the simple gate structure of the QPC that, when rists on the project are based at the CUNY colleges that do not have graduate programs. negatively biased, creates a grating for the elec- The collaboration aims to provide state-of- tron waves that is tuned to a particular terahertz the-art research opportunities to students at frequency. Improvements over existing technol- these institutions and encourage them to go ogy are expected to include widely-tuneable on to higher degrees in science and engineer- response frequency, low power consumption, ing. Markelz is also keen to use the project to and enhanced sensitivity. attract more women and other under-repre- A recent Applied Physics Letters paper (Kabir sented groups to the sciences, through such et al., Appl. Phys. Lett., 89, 132109, 2006) organisations as the GGems (Girls and Guys involving a number of University of Buffalo Exploring Math and Science) educational pro- researchers (and researchers from the US gram for high school students that she set up Sandia National Laboratory and Arizona State some years ago with NSF backing. University) studies complex conductivity of high mobility GaAs and InAs two-dimensional Mike Cooke is a freelance technology journalist electron gas (2DEG) systems using terahertz who has been reporting on the semiconductor time domain spectroscopy. The tests were industry since 1997. 38 III-Vs REVIEW THE ADVANCED SEMICONDUCTOR MAGAZINE VOL 19 - NO 8 - NOVEMBER 2006 iiivs198p36_38.indd 38 31/10/2006 12:24:47.
Load more

Recommended publications
  • Half-Cycle Transient Synthesizer in the Terahertz Gap at High Fields
    Intense multi-octave supercontinuum pulses from an organic emitter covering the entire THz frequency gap Authors: C. Vicario1, B. Monoszlai1, M. Jazbinsek2, S.-H. Lee3, O-P. Kwon3 and C. P. Hauri1,4 Affiliations: 1Paul Scherrer Institute, SwissFEL, 5232 Villigen PSI, Switzerland 2Rainbow Photonics, Zurich, Switzerland 3Department of Molecular Science and Technology, Ajou University, Suwon 443-749, Korea 4Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland In Terahertz (THz) technology, one of the long-standing challenges has been the formation of intense pulses covering the hard-to-access frequency range of 1-15 THz (so-called THz gap). This frequency band, lying between the electronically (<1 THz) and optically (>15 THz) accessible spectrum hosts a series of important collective modes and molecular fingerprints which cannot be fully accessed by present THz sources. While present high-energy THz sources are limited to 0.1-4 THz the accessibility to the entire THz gap with intense THz pulses would substantially broaden THz applications like live cell imaging at higher- resolution, cancer diagnosis, resonant and non-resonant control over matter and light, strong-field induced catalytic reactions, formation of field-induced transient states and contact-free detection of explosives. Here we present a new, all-in-one solution for producing and tailoring extremely powerful supercontinuum THz pulses with a stable absolute phase and covering the entire THz gap (0.1-15 THz), thus more than 7 octaves. Our method expands the scope of THz photonics to a frequency range previously inaccessible to intense sources. 1 Coherent radiation in the Terahertz range (T-rays) between 0.1 and 15 THz offers outstanding opportunities in life science and fundamental research due to its non- ionizing nature.
    [Show full text]
  • Terahertz (Thz) Generator and Detection
    Electrical Science & Engineering | Volume 02 | Issue 01 | April 2020 Electrical Science & Engineering https://ojs.bilpublishing.com/index.php/ese REVIEW Terahertz (THz) Generator and Detection Jitao Li#,* Jie Li# School of Precision Instruments and OptoElectronics Engineering, Tianjin University, Tianjin, 300072, China #Authors contribute equally to this work. ARTICLE INFO ABSTRACT Article history In the whole research process of electromagnetic wave, the research of Received: 26 March 2020 terahertz wave belongs to a blank for a long time, which is the least known and least developed by far. But now, people are trying to make up the blank Accepted: 30 March 2020 and develop terahertz better and better. The charm of terahertz wave origi- Published Online: 30 April 2020 nates from its multiple attributes, including electromagnetic field attribute, photon attribute and thermal attribute, which also attracts the attention of Keywords: researchers in different fields and different countries, and also terahertz Terahertz technology have been rated as one of the top ten technologies to change the future world by the United States. The multiple attributes of terahertz make Generation it have broad application prospects in military and civil fields, such as med- Detection ical imaging, astronomical observation, 6G communication, environmental monitoring and material analysis. It is no exaggeration to say that mastering terahertz technology means mastering the future. However, it is because of the multiple attributes of terahertz that the terahertz wave is difficult to be mastered. Although terahertz has been applied in some fields, controlling terahertz (such as generation and detection) is still an important issue. Now- adays, a variety of terahertz generation and detection technologies have been developed and continuously improved.
    [Show full text]
  • Techniques for Generation of Terahertz Radiation
    TechniquesTechniques forfor GenerationGeneration ofof TerahertzTerahertz RadiationRadiation E.V.Suvorov Institute of Applied Physics of Russian Academy of Sciences 46, Uljanov Str., 603950, Nizhny Novgorod, Russia FNP – 2007 July 3 – 9, 2007 “Georgy Zhukov” N.Novgorod – Saratov - N.Novgorod Russia OUTLINE ♦ Motivation ♦ Generation by means of vacuum electronics ♦ Generation by means of “optoelectronics” ♦ “Exotic” ways ♦ Conclusions TT--RayRay:: NextNext frontierfrontier inin ScienceScience andand TechnologyTechnology Terahertz wave (or T-ray), which is electromagnetic radiation in a frequency interval from 0.1 to 10 THz, lies a frequency range with rich science but limited technology. electronics THz Gap photonics microwaves visible x-ray γ -ray MF, HF, VHF, UHF, SHF, EHF 100 103 106 109 1012 1015 1018 1021 1024 Hz dc kilo mega giga tera peta exa zetta yotta Frequency (Hz) 1 THz ~ 1 ps ~ 300 µm ~ 33 cm-1 ~ 4.1 meV ~ 47.6 oK APPLICATIONS Spectroscopy: Chemistry, Aeronomy, Ecology, Radioastronomy, … Tera-imaging: Biology, Biomedicine, Microelectronics, Technology, Security, … Plasma diagnostics: Interferometry, Faraday, Cotton-Mauton, … … Vacuum electronics ♦Cherenkov generation (BWOs, TWTs, Orotrons) ♦Transition generation (Klystrons) ♦Bremsstrahlung (gyrodevices, FELs) ♦Scattering generation Cherenkov generation P Pin out Pout vgr vgr e e TWT BWO Pout ω = hυ 1 βγλ v Λ = = gr 2π ⊥ 2 2 2π e h = h − k d Orotron, or Diffraction Radiation Generator β = υ/c Commercial BWOs (“ISTOK”, Fryazino, Russia) Tube OB-30 OB-32 OB-80 OB-81 OB-82 OB-83 OB-84* OB-85* Band, GHz 258 - 370 - 530 - 690 - 790 - 900 - 1070 - 1170 - 375 535 714 850 970 1100 1200 1400 Output power (min), 1 - 10 1 - 5 1 - 5 1 - 5 0.5 - 3 0.5 - 3 0.5 - 2 0.5 - 2 mW Power variation (over 13 13 13 13 13 13 13 13 the band), dB Acc.
    [Show full text]
  • Controlling Superconductivity Using Tailored Thz Pulses
    Controlling superconductivity using tailored THz pulses Dissertation zur Erlangung des Doktorgrades an der Fakultät für Mathematik, Informatik und Naturwissenschaften Fachbereich Physik der Universität Hamburg Vorgelegt vor Biaolong Liu aus Hebei, China Hamburg 2020 Gutachter der Dissertation: Prof. Dr. Andrea Cavalleri Prof. Dr. Franz X Kärtner Zusammensetzung der Prüfungskommission: Prof. Dr. Andrea Cavalleri Prof. Dr. Franz X Kärtner Prof. Dr. Markus Drescher Prof. Dr. Alexander Lichtenstein Prof. Dr. Michael A. Rübhausen Vorsitzender des Prüfungskommission: Prof. Dr. Michael A. Rübhausen Datum der Disputation: 27.04.2020 Vorsitzender des Prof. Dr. Wolfgang Hansen Promotionsausschusses: Leiter des Fachbereich Physik: Prof. Dr. Michael Pottho Dekan der Fakultät MIN: Prof. Dr. Heinrich Graener Hiermit erkläre ich an Eides statt, dass ich die vorliegende Dissertationss- chrift selbst verfasst und keine anderen als die angegebenen Quellen und Hilfsmittel benutzt habe. Diese Arbeit lag noch keiner anderen Person oder Prüfungsbehörde im Rahmen einer Prüfung vor. I hereby declare, on oath, that I have written the present dissertation on my own and have not used other than the mentioned resources and aids. This work has never been presented to other persons or evaluation panels in the context of an examination. Hamburg, den Biaolong Liu Abstract Many transition metal oxides show strong electronic correlations that produce functionally relevant properties like metal-insulator transitions, colossal-magnetoresistance, ferroelectricity, and unconventional superconductivity. The development of intense femtosecond laser sources has made possible to control these functionalities and explore unknown out-of-equilibrium phase states of such complex materials by light. In particular, selective excitation of infrared-active phonon modes by intense THz pulses has been demonstrated as a powerful tool to manipulate electronic and magnetic phases.
    [Show full text]
  • Laser Air Photonics: Beyond the Terahertz Gap
    Laser air photonics: beyond the terahertz gap Through the ionization process, the very air that we breath is capable of generating terahertz (THz) electromagnetic field strengths greater than 1 MV/cm, useful bandwidths of over 100 THz, and highly directional emission patterns. Following the ionization of air, the emitted air-plasma fluorescence or acoustics can serve as an omnidirectional, broadband, THz wave sensor. Here we review significant advances in laser air photonics that help to close the “THz gap,” enabling ultra-broadband THz wave generation and detection, for applications including materials characterization and non-destructive evaluation. The feasibility for remote sensing, as well as the remaining challenges and future opportunities are also discussed. Benjamin Clougha,b, Jianming Daia,b,c, and Xi-Cheng Zhang*a,b,c aHuazhong University of Science and Technology, 1037 Luoyu Road, Wuhan 430074, China bCenter for Terahertz Research, Rensselaer Polytechnic Institute, Troy, New York 12180, USA cThe Institute of Optics, University of Rochester, Rochester, New York 14627, USA *E-mail: Corresponding author: [email protected] Plasma is regarded as the fourth state of matter1 because it exhibits included self-mode-locked femtosecond Ti:sapphire oscillators, unique characteristics that set it apart from solids, liquids, and gases. based on the Kerr effect, and high-power femtosecond Ti:sapphire A bolt of lightning, the glow of the Northern Lights, and the light of amplified laser systems, based on chirped pulse amplification (CPA)3. stars all stem from plasma formation. When a laser pulse is focused These technologies have allowed for critical intensities with pulse into a gas with intensity above a critical value near 1014 W/cm2, the durations on the order of femtoseconds in commercial tabletop laser gas is ionized, yielding positively and negatively charged particles, systems.
    [Show full text]
  • Modulating Fundamental Resonance in Capacitive Coupled Asymmetric Terahertz Received: 2 June 2018 Accepted: 23 October 2018 Metamaterials Published: Xx Xx Xxxx S
    www.nature.com/scientificreports OPEN Modulating Fundamental Resonance in Capacitive Coupled Asymmetric Terahertz Received: 2 June 2018 Accepted: 23 October 2018 Metamaterials Published: xx xx xxxx S. Jagan Mohan Rao 1, Yogesh Kumar Srivastava2, Gagan Kumar1 & Dibakar Roy Chowdhury3 In this work, we experimentally investigate near-feld capacitive coupling between a pair of single-gap split ring resonators (SRRs) in a terahertz metamaterial. The unit cell of our design comprises of two coupled SRRs with the split gaps facing each other. The coupling between two SRRs is examined by changing the gap of one resonator with respect to the other for several inter resonator separations. When split gap size of one resonator is increased for a fxed inter-resonator distance, we observe a split in the fundamental resonance mode. This split ultimately results in the excitation of narrow band low frequency resonance mode along with a higher frequency mode which gets blue shifted when the split gap increases. We attribute resonance split to the excitation of symmetric and asymmetric modes due to strong capacitive or electric interaction between the near-feld coupled resonators, however blue shift of the higher frequency mode occurs mainly due to the reduced capacitance. The ability of near- feld capacitive coupled terahertz metamaterials to excite split resonances could be signifcant in the construction of modulator and sensing devices beside other potential applications for terahertz domain. In the electromagnetic spectrum, terahertz gap exists between microwave and infrared regions and is potentially signifcant to a variety of applications ranging from medical sciences to engineering1. Many natural materials inherently do not respond to terahertz radiation.
    [Show full text]
  • Closing the Terahertz Gap at the Speed of Laser How the Protolaser S Enabled Innovation at the Fraunhofer Institute for Applied Solid State Physics
    Closing the Terahertz Gap at the Speed of Laser How the ProtoLaser S enabled innovation at the Fraunhofer Institute for Applied Solid State Physics LPKF ProtoLaser S at Fraunhofer Institute Closing the Terahertz Gap at the Speed of Laser For many years, the terahertz range was something akin to an episode of The Outer Limits. Directly between the microwave and infrared spectrums lurked this mysterious electromagnetic range that was capable of reading organic “fingerprints” and, due to its non-ionizing status, registering medical imagery without the damaging effects caused by X-rays. Yet despite its potential, so little was known about how to utilize the terahertz range that it became known simply as the terahertz gap. Seeking to close this gap, research organizations across switch to the ProtoLaser S, “In-house prototyping facilitates the globe have begun in recent years to scratch the surface several iteration cycles per day and production on of what is possible with the terahertz range. One of the demand.” Indeed, as what used to take the Fraunhofer leading organizations in this quest is the Fraunhofer Institute three days now takes a mere two minutes. Institute for Applied Solid State Physics. The ProtoLaser S uses a patented process to etch design The Fraunhofer Institute, which is named after nineteenth wiring onto circuits. A quick scan of materials processed by century German physicist Joseph von Fraunhofer, has the ProtoLaser S reveals nearly every material one could made waves in its research of the terahertz range, image: FR4, aluminum-coated PET films, TMM, RT/Duroid, specifically when it comes to the development of chips for PTFE, and ceramic substrates.
    [Show full text]
  • Polarization-Maintaining Reflection-Mode Thz Time-Domain Spectroscopy of a Polyimide Based Ultra-Thin Narrow-Band Metamaterial A
    www.nature.com/scientificreports OPEN Polarization-maintaining refection-mode THz time-domain spectroscopy of a polyimide Received: 7 September 2017 Accepted: 18 January 2018 based ultra-thin narrow-band Published: xx xx xxxx metamaterial absorber Maria Denise Astorino 1, Renato Fastampa2,3, Fabrizio Frezza 1, Luca Maiolo4, Marco Marrani4, Mauro Missori3, Marco Muzi1,5, Nicola Tedeschi1 & Andrea Veroli1,6 This paper reports the design, the microfabrication and the experimental characterization of an ultra-thin narrow-band metamaterial absorber at terahertz frequencies. The metamaterial device is composed of a highly fexible polyimide spacer included between a top electric ring resonator with a four-fold rotational symmetry and a bottom ground plane that avoids misalignment problems. Its performance has been experimentally demonstrated by a custom polarization-maintaining refection-mode terahertz time-domain spectroscopy system properly designed in order to reach a collimated confguration of the terahertz beam. The dependence of the spectral characteristics of this metamaterial absorber has been evaluated on the azimuthal angle under oblique incidence. The obtained absorbance levels are comprised between 67% and 74% at 1.092 THz and the polarization insensitivity has been verifed in transverse electric polarization. This ofers potential prospects in terahertz imaging, in terahertz stealth technology, in substance identifcation, and in non-planar applications. The proposed compact experimental set-up can be applied to investigate arbitrary polarization-sensitive terahertz devices under oblique incidence, allowing for a wide reproducibility of the measurements. Terahertz (THz) technology has recently received growing attention, enabling it to overcome the so-called “ THz gap” thus connecting the felds of electronics and optics1.
    [Show full text]
  • QCL-Based Frequency Metrology from the Mid-Infrared to the Thz Range
    Nanophotonics 2018; aop Review article Luigi Consolino*, Francesco Cappelli, Mario Siciliani de Cumis and Paolo De Natale QCL-based frequency metrology from the mid-infrared to the THz range: a review https://doi.org/10.1515/nanoph-2018-0076 (near-IR), while Doppler-linewidths linearly decrease Received June 25, 2018; revised September 17, 2018; accepted with increasing wavelength. September 20, 2018 Performing molecular precision spectroscopy enables very attractive fundamental physics research about, Abstract: Quantum cascade lasers (QCLs) are becoming a for example, time variation of fundamental constants key tool for plenty of applications, from the mid-infrared (α, m /m , …), electric dipole moment of the electron, (mid-IR) to the THz range. Progress in related areas, such p e and parity violation in molecules [1–5]. At the same time, as the development of ultra-low-loss crystalline micro- mid-IR/THz spectroscopy has a considerable impact in resonators, optical frequency standards, and optical fiber real-world applications spanning from environmental networks for time and frequency dissemination, is paving monitoring to health, from imaging to security [6–15]. the way for unprecedented applications in many fields. Efficient nonlinear generation of mid-IR and THz radi- For most demanding applications, a thorough control of ation with excellent spectral properties, performed since QCLs emission must be achieved. In the last few years, the 1980s of the XXth century, opened the way to metro- QCLs’ unique spectral features have been unveiled, while logical research in these spectral regions [16, 17]. However, multifrequency QCLs have been demonstrated. Ultra-nar- the optical power available for experiments and the com- row frequency linewidths are necessary for metrological plexity of such setups were not suitable for compact and applications, ranging from cold molecules interaction practical applications.
    [Show full text]
  • Terahertz Quantum Cascade Lasers and Electronics—Q. Hu
    Chapter 29. Terahertz Quantum Cascade Lasers and Electronics Terahertz Quantum Cascade Lasers and Electronics Academic and Research Staff Professor Qing Hu Postdoctoral Associates Benjamin S. Williams Graduate Students Hans Callebaut, Steve Kohen, Kostas Konistis, Sushil Kumar, Juan Montoya Introduction Millimeter-wave and THz frequencies (f = 0.1-10 THz) remain one of the most underdeveloped frequency ranges, even though the potential applications in remote sensing and imaging, spectroscopy, and communications are great. This is because the millimeter-wave and THz frequency range falls between two other frequency ranges in which conventional semiconductor devices are usually operated. One is the microwave frequency range, and the other is the near- infrared and optical frequency range. Semiconductor devices which utilize the classical diffusive transport of electrons, such as diodes and transistors, have a high frequency limit. This limit is set by the transient time and parasitic RC time constants. Currently, electron mobility and the smallest feature size which can be fabricated by lithography limit the frequency range to below several hundred GHz. Semiconductor devices based on quantum mechanical interband transitions, however, are limited to frequencies higher than those corresponding to the semiconductor energy gap, which is higher than 10 THz for most bulk semiconductors. Therefore, a large gap exists from 1 to 10 THz in which very few devices are available. Semiconductor quantum-effect devices (which can be loosely termed "artificial atoms"), including both vertically grown quantum-well structures and laterally confined mesoscopic devices, are human-made quantum mechanical systems in which the energy levels can be chosen by changing the sizes of the devices.
    [Show full text]
  • Terahertz Technologies Systems and Accessories
    Terahertz Technologies Systems and Accessories Plastic Inspection Paint and Coating Layers Industrial Quality Control Non-Destructive Testing Material Research Gas Sensing Metamaterials and Micro-Optics Fundamental Physics 1 Wavelength m 10-10 10-9 10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 100 101 Terahertz -rays Ultraviolet VIS Infrared Microwaves Radio waves Contents 1018 1017 1016 1015 1014 1013 1012 1011 1010 109 108 107 Introduction 3 Terahertz Applications 4 Frequency Hz Plastic Inspection 4 Paint Layers 5 Industrial Quality Control 5 Non-Destructive Testing 6 Material Research 6 Gas Sensing 7 Terahertz Waves Fundamental Physics 7 The Final Frontier of the Electromagnetic Spectrum Time-Domain Terahertz Generation 8 Frequency-Domain Terahertz Generation 9 Time-Domain vs. Frequency-Domain 10 Between Microwaves & Infrared tosecond lasers or tunable diode lasers. Applications The terahertz range refers to electromag- Photomixers, photoconductive switches Products · Plastic Inspection TeraFlash pro 12 netic waves with frequencies between or nonlinear crystals convert the near- · Paint and Coating Layers TeraFlash smart 14 100 GHz and 10 THz, or wavelengths be- infrared laser light into terahertz waves, · Industrial Quality Control TeraSpeed 16 tween 3 mm and 30 μm. Light between either broadband or spectrally resolved. microwaves and infrared has some unique The terahertz gap is bridged at last. Imaging Extension 18 · Non-Destructive Testing properties. Terahertz waves can “look Photoconductive Switches 19 · Material Research inside” plastics and textiles, paper and The Complete Portfolio TeraScan 780 / 1550 20 · Gas Sensing cardboard. Many biomolecules, proteins, With more than 150 complete systems TeraBeam 780 / 1550 22 explosives and narcotics also feature char- and 500 lasers for terahertz generation · Hydration Monitoring Tuning Range Extension 24 acteristic absorption lines – so-called spec- in the field, TOPTICA has become one · Ultrafast Dynamics Phase Modulation Extension 25 tral “fingerprints” – at terahertz frequencies.
    [Show full text]
  • Surfing the Electromagnetic Spectrum
    NDE: SURFING THE ELECTROMAGNETIC SPECTRUM Harry I. Ringermacher General Electric Global Research Center, Niskayuna, NY 12309 Abstract. Advances in Nondestructive Evaluation demand an arsenal of techniques. This was as true twenty years ago as it is today. As materials and their associated technologies progress, so must the strategy for evaluating the quality of the product. Nondestructive Evaluation is a constant struggle to extract, from classical and quantum physics, the quintessential elements that will optimally address an inspection requirement, apart from purely academic interest. It must work to be useful and thereby advance the field. The electromagnetic spectrum, from Roentgen to Maxwell/Hertz, lies at the foundation of both classical and quantum physics. Not only has NDE plucked pearls form every nook of the spectrum ranging from X-rays to T-rays but also has managed to utilize virtually every known coupling of the spectrum to the classical mechanics of heat and sound. I will “surf” the spectrum to provide a sampling of what NDE has extracted past and present as well as try to couple to its future. Keywords: Electromagnetic, NDE, Eddy Current, Microwave, Terahertz, Digital Radiography, Laser Ultrasound, Thermal Imaging PACS: 41.20.-q , 41.50.+h , 42.55.-f , 44.10.+1 , 87.63.Hg , 87.59.bf INTRODUCTION In this overview of electromagnetic (EM) NDE we will be “surfing the spectrum” from the low frequency end , namely radio waves - with application to eddy current - to the high frequency end of the spectrum, x-rays and gamma-rays. We will sample the best NDE technologies in these areas seen through my own eyes – so, apologies in advance for anyone not mentioned since a complete review is out of the scope of this presentation.
    [Show full text]