WorldWideScience

Sample records for terahertz radiation generation

  1. Detection of Terahertz Radiation

    DEFF Research Database (Denmark)

    2015-01-01

    The present invention relates to a system for detecting terahertz radiation, a camera device, and a method for detecting terahertz radiation.......The present invention relates to a system for detecting terahertz radiation, a camera device, and a method for detecting terahertz radiation....

  2. Generation of phase-locked and tunable continuous-wave radiation in the terahertz regime.

    Science.gov (United States)

    Quraishi, Qudsia; Griebel, Martin; Kleine-Ostmann, Thomas; Bratschitsch, Rudolf

    2005-12-01

    Broadly tunable phase-stable single-frequency terahertz radiation is generated with an optical heterodyne photomixer. The photomixer is excited by two near-infrared CW diode lasers that are phase locked to the stabilized optical frequency comb of a femtosecond titanium:sapphire laser. The terahertz radiation emitted by the photomixer is downconverted into RF frequencies with a waveguide harmonic mixer and measurement-limited linewidths at the Hertz level are demonstrated.

  3. Generation of high-power terahertz radiation by femtosecond-terawatt lasers

    International Nuclear Information System (INIS)

    Nashima, Shigeki; Hosoda, Makoto; Daido, Hiroyuki

    2007-01-01

    We observed electromagnetic waves in the terahertz (THz) frequency range from a Ti foil excited by tabletop terawatt (T-cube) laser pulses. The radiation power was increased drastically with increasing its laser power. We also investigated the polarization characteristics of the sub-terahertz wave. It is found that the polarization of the radiated sub-terahertz waves was parallel to the incident beam plane, which is independent on the pump laser polarization. These results indicate transient electric field to the incident plane is generated by laser-plasma interaction, i.e., laser wake field and coherent plasma wave. (author)

  4. Imaging with terahertz radiation

    Energy Technology Data Exchange (ETDEWEB)

    Chan, W L; Deibel, Jason; Mittleman, Daniel M [Department of Electrical and Computer Engineering, MS-366, Rice University, 6100 Main St., Houston, TX 77005 (United States)

    2007-08-15

    Within the last several years, the field of terahertz science and technology has changed dramatically. Many new advances in the technology for generation, manipulation, and detection of terahertz radiation have revolutionized the field. Much of this interest has been inspired by the promise of valuable new applications for terahertz imaging and sensing. Among a long list of proposed uses, one finds compelling needs such as security screening and quality control, as well as whimsical notions such as counting the almonds in a bar of chocolate. This list has grown in parallel with the development of new technologies and new paradigms for imaging and sensing. Many of these proposed applications exploit the unique capabilities of terahertz radiation to penetrate common packaging materials and provide spectroscopic information about the materials within. Several of the techniques used for terahertz imaging have been borrowed from other, more well established fields such as x-ray computed tomography and synthetic aperture radar. Others have been developed exclusively for the terahertz field, and have no analogies in other portions of the spectrum. This review provides a comprehensive description of the various techniques which have been employed for terahertz image formation, as well as discussing numerous examples which illustrate the many exciting potential uses for these emerging technologies.

  5. Imaging with terahertz radiation

    International Nuclear Information System (INIS)

    Chan, W L; Deibel, Jason; Mittleman, Daniel M

    2007-01-01

    Within the last several years, the field of terahertz science and technology has changed dramatically. Many new advances in the technology for generation, manipulation, and detection of terahertz radiation have revolutionized the field. Much of this interest has been inspired by the promise of valuable new applications for terahertz imaging and sensing. Among a long list of proposed uses, one finds compelling needs such as security screening and quality control, as well as whimsical notions such as counting the almonds in a bar of chocolate. This list has grown in parallel with the development of new technologies and new paradigms for imaging and sensing. Many of these proposed applications exploit the unique capabilities of terahertz radiation to penetrate common packaging materials and provide spectroscopic information about the materials within. Several of the techniques used for terahertz imaging have been borrowed from other, more well established fields such as x-ray computed tomography and synthetic aperture radar. Others have been developed exclusively for the terahertz field, and have no analogies in other portions of the spectrum. This review provides a comprehensive description of the various techniques which have been employed for terahertz image formation, as well as discussing numerous examples which illustrate the many exciting potential uses for these emerging technologies

  6. Terahertz radiation mixer

    Science.gov (United States)

    Wanke, Michael C [Albuquerque, NM; Allen, S James [Santa Barbara, CA; Lee, Mark [Albuquerque, NM

    2008-05-20

    A terahertz radiation mixer comprises a heterodyned field-effect transistor (FET) having a high electron mobility heterostructure that provides a gatable two-dimensional electron gas in the channel region of the FET. The mixer can operate in either a broadband pinch-off mode or a narrowband resonant plasmon mode by changing a grating gate bias of the FET. The mixer can beat an RF signal frequency against a local oscillator frequency to generate an intermediate frequency difference signal in the microwave region. The mixer can have a low local oscillator power requirement and a large intermediate frequency bandwidth. The terahertz radiation mixer is particularly useful for terahertz applications requiring high resolution.

  7. Generation of tunable narrow-band surface-emitted terahertz radiation in periodically poled lithium niobate.

    Science.gov (United States)

    Weiss, C; Torosyan, G; Avetisyan, Y; Beigang, R

    2001-04-15

    Generation of tunable narrow-band terahertz (THz) radiation perpendicular to the surface of periodically poled lithium niobate by optical rectification of femtosecond pulses is reported. The generated THz radiation can be tuned by use of different poling periods and different observation angles, limited only by the available bandwidth of the pump pulse. Typical bandwidths were 50-100 GHz, depending on the collection angle and the number of periods involved.

  8. Terahertz Pulse Generation in Underdense Relativistic Plasmas: From Photoionization-Induced Radiation to Coherent Transition Radiation

    Science.gov (United States)

    Déchard, J.; Debayle, A.; Davoine, X.; Gremillet, L.; Bergé, L.

    2018-04-01

    Terahertz to far-infrared emission by two-color, ultrashort optical pulses interacting with underdense helium gases at ultrahigh intensities (>1019 W /cm2 ) is investigated by means of 3D particle-in-cell simulations. The terahertz field is shown to be produced by two mechanisms occurring sequentially, namely, photoionization-induced radiation (PIR) by the two-color pulse, and coherent transition radiation (CTR) by the wakefield-accelerated electrons escaping the plasma. We exhibit laser-plasma parameters for which CTR proves to be the dominant process, providing terahertz bursts with field strength as high as 100 GV /m and energy in excess of 10 mJ. Analytical models are developed for both the PIR and CTR processes, which correctly reproduce the simulation data.

  9. Generating high-power short terahertz electromagnetic pulses with a multifoil radiator.

    Science.gov (United States)

    Vinokurov, Nikolay A; Jeong, Young Uk

    2013-02-08

    We describe a multifoil cone radiator capable of generating high-field short terahertz pulses using short electron bunches. Round flat conducting foil plates with successively decreasing radii are stacked, forming a truncated cone with the z axis. The gaps between the foil plates are equal and filled with some dielectric (or vacuum). A short relativistic electron bunch propagates along the z axis. At sufficiently high particle energy, the energy losses and multiple scattering do not change the bunch shape significantly. When passing by each gap between the foil plates, the electron bunch emits some energy into the gap. Then, the radiation pulses propagate radially outward. For transverse electromagnetic waves with a longitudinal (along the z axis) electric field and an azimuthal magnetic field, there is no dispersion in these radial lines; therefore, the radiation pulses conserve their shapes (time dependence). At the outer surface of the cone, we have synchronous circular radiators. Their radiation field forms a conical wave. Ultrashort terahertz pulses with gigawatt-level peak power can be generated with this device.

  10. Terahertz radiation generation by lasers with remarkable efficiency in electron–positron plasma

    International Nuclear Information System (INIS)

    Malik, Hitendra K.

    2015-01-01

    Photo-mixing of spatial-super-Gaussian lasers and electron–positron plasma are proposed for realizing a large amplitude nonlinear current in order to generate an efficient terahertz radiation. An external magnetic field together with a proper index of the lasers helps achieving controllable current and hence, the focused radiation of tunable frequency and power along with a remarkable efficiency of the scheme as ∼6%. - Highlights: • First proposal of photo-mixing of spatial-super-Gaussian (SSG) lasers in electron–positron (e–p) plasma. • Large amplitude nonlinear current due to the contribution of both the plasma species. • Magnetic field as an additional parameter for tunable THz radiation with a remarkable efficiency of ∼6%.

  11. Extremely frequency-widened terahertz wave generation using Cherenkov-type radiation.

    Science.gov (United States)

    Suizu, Koji; Koketsu, Kaoru; Shibuya, Takayuki; Tsutsui, Toshihiro; Akiba, Takuya; Kawase, Kodo

    2009-04-13

    Terahertz (THz) wave generation based on nonlinear frequency conversion is promising way for realizing a tunable monochromatic bright THz-wave source. Such a development of efficient and wide tunable THz-wave source depends on discovery of novel brilliant nonlinear crystal. Important factors of a nonlinear crystal for THz-wave generation are, 1. High nonlinearity and 2. Good transparency at THz frequency region. Unfortunately, many nonlinear crystals have strong absorption at THz frequency region. The fact limits efficient and wide tunable THz-wave generation. Here, we show that Cherenkov radiation with waveguide structure is an effective strategy for achieving efficient and extremely wide tunable THz-wave source. We fabricated MgO-doped lithium niobate slab waveguide with 3.8 microm of thickness and demonstrated difference frequency generation of THz-wave generation with Cherenkov phase matching. Extremely frequency-widened THz-wave generation, from 0.1 to 7.2 THz, without no structural dips successfully obtained. The tuning frequency range of waveguided Cherenkov radiation source was extremely widened compare to that of injection seeded-Terahertz Parametric Generator. The tuning range obtained in this work for THz-wave generation using lithium niobate crystal was the widest value in our knowledge. The highest THz-wave energy obtained was about 3.2 pJ, and the energy conversion efficiency was about 10(-5) %. The method can be easily applied for many conventional nonlinear crystals, results in realizing simple, reasonable, compact, high efficient and ultra broad band THz-wave sources.

  12. Echo-enabled tunable terahertz radiation generation with a laser-modulated relativistic electron beam

    Directory of Open Access Journals (Sweden)

    Zhen Wang

    2014-09-01

    Full Text Available A new scheme to generate narrow-band tunable terahertz (THz radiation using a variant of the echo-enabled harmonic generation is analyzed. We show that by using an energy chirped beam, THz density modulation in the beam phase space can be produced with two lasers having the same wavelength. This removes the need for an optical parametric amplifier system to provide a wavelength-tunable laser to vary the central frequency of the THz radiation. The practical feasibility and applications of this scheme are demonstrated numerically with a start-to-end simulation using the beam parameters at the Shanghai Deep Ultraviolet Free-Electron Laser facility (SDUV. The central frequency of the density modulation can be continuously tuned by either varying the chirp of the beam or the momentum compactions of the chicanes. The influence of nonlinear rf chirp and longitudinal space charge effect have also been studied in our article. The methods to generate the THz radiation in SDUV with the new scheme and the estimation of the radiation power are also discussed briefly.

  13. High energy multi-cycle terahertz generation

    International Nuclear Information System (INIS)

    Ahr, Frederike Beate

    2017-10-01

    Development of compact electron accelerators and free-electron lasers requires novel acceleration schemes at shorter driving wavelengths. The Axsis project seeks to develop terahertz based electron acceleration as well as the high energy terahertz sources required. This thesis explores the methods and optical material required for the generation of highenergy multi-cycle terahertz pulses. Two experimental concepts to generate high energy terahertz radiation are presented. In addition the theoretical background and the optical properties of pertinent optical materials in the terahertz range are discussed. Investigations of the materials are performed with a terahertz time domain spectrometer and a Fourier transform infrared spectrometer. The nonlinear optical crystal lithium niobate as well as other crystals suitable for the terahertz generation and in addition polymers and other radiation attenuators are characterized in the range from 0.2 to 1 THz. The theory describing the generation of narrowband terahertz radiation is evaluated. The experimental setups to generate terahertz radiation and to characterize its properties are described. The specific crystals - periodically poled lithium niobate (PPLN) - used in the experiments to generate the multi-cycle terahertz radiation are examined to determine e.g. the poling period. The first experimental concept splits the ultra fast, broadband pump pulses into a pulse train in order to pump the PPLN at a higher fluence while increasing the damage limit. The measurements confirm that a pulse train of ultra short, broadband pump pulses increases not only the terahertz energy but also the energy conversion efficiency. The second experimental concept utilizes chirped and delayed infrared laser pulses. This pulse format makes it possible to pump the crystal with high energy pulses resulting in high energy terahertz radiation. The concept is optimized to reach energies up to 127 μJ exceeding the existing results of narrowband

  14. High energy multi-cycle terahertz generation

    Energy Technology Data Exchange (ETDEWEB)

    Ahr, Frederike Beate

    2017-10-15

    Development of compact electron accelerators and free-electron lasers requires novel acceleration schemes at shorter driving wavelengths. The Axsis project seeks to develop terahertz based electron acceleration as well as the high energy terahertz sources required. This thesis explores the methods and optical material required for the generation of highenergy multi-cycle terahertz pulses. Two experimental concepts to generate high energy terahertz radiation are presented. In addition the theoretical background and the optical properties of pertinent optical materials in the terahertz range are discussed. Investigations of the materials are performed with a terahertz time domain spectrometer and a Fourier transform infrared spectrometer. The nonlinear optical crystal lithium niobate as well as other crystals suitable for the terahertz generation and in addition polymers and other radiation attenuators are characterized in the range from 0.2 to 1 THz. The theory describing the generation of narrowband terahertz radiation is evaluated. The experimental setups to generate terahertz radiation and to characterize its properties are described. The specific crystals - periodically poled lithium niobate (PPLN) - used in the experiments to generate the multi-cycle terahertz radiation are examined to determine e.g. the poling period. The first experimental concept splits the ultra fast, broadband pump pulses into a pulse train in order to pump the PPLN at a higher fluence while increasing the damage limit. The measurements confirm that a pulse train of ultra short, broadband pump pulses increases not only the terahertz energy but also the energy conversion efficiency. The second experimental concept utilizes chirped and delayed infrared laser pulses. This pulse format makes it possible to pump the crystal with high energy pulses resulting in high energy terahertz radiation. The concept is optimized to reach energies up to 127 μJ exceeding the existing results of narrowband

  15. Terahertz-radiation generation and detection in low-temperature-grown GaAs epitaxial films on GaAs (100) and (111)A substrates

    Energy Technology Data Exchange (ETDEWEB)

    Galiev, G. B.; Pushkarev, S. S., E-mail: s-s-e-r-p@mail.ru [Russian Academy of Sciences, Institute of Ultrahigh-Frequency Semiconductor Electronics (Russian Federation); Buriakov, A. M.; Bilyk, V. R.; Mishina, E. D. [Moscow Technological University “MIREA” (Russian Federation); Klimov, E. A. [Russian Academy of Sciences, Institute of Ultrahigh-Frequency Semiconductor Electronics (Russian Federation); Vasil’evskii, I. S. [National Research Nuclear University “MEPhI” (Russian Federation); Maltsev, P. P. [Russian Academy of Sciences, Institute of Ultrahigh-Frequency Semiconductor Electronics (Russian Federation)

    2017-04-15

    The efficiency of the generation and detection of terahertz radiation in the range up to 3 THz by LT-GaAs films containing equidistant Si doping δ layers and grown by molecular beam epitaxy on GaAs (100) and (111)Ga substrates is studied by terahertz spectroscopy. Microstrip photoconductive antennas are fabricated on the film surface. Terahertz radiation is generated by exposure of the antenna gap to femtosecond optical laser pulses. It is shown that the intensity of terahertz radiation from the photoconductive antenna on LT-GaAs/GaAs (111)Ga is twice as large as the intensity of a similar antenna on LT-GaAs/GaAs(100) and the sensitivity of the antenna on LT-GaAs/GaAs (111)Ga as a terahertz-radiation detector exceeds that of the antenna on LT-GaAs/GaAs(100) by a factor of 1.4.

  16. Theoretical study of the generation of terahertz radiation by the interaction of two laser beams with graphite nanoparticles

    Science.gov (United States)

    Sepehri Javan, N.; Rouhi Erdi, F.

    2017-12-01

    In this theoretical study, we investigate the generation of terahertz radiation by considering the beating of two similar Gaussian laser beams with different frequencies of ω1 and ω2 in a spatially modulated medium of graphite nanoparticles. The medium is assumed to contain spherical graphite nanoparticles of two different configurations: in the first configuration, the electric fields of the laser beams are parallel to the normal vector of the basal plane of the graphite structure, whereas in the second configuration, the electric fields are perpendicular to the normal vector of the basal plane. The interaction of the electric fields of lasers with the electronic clouds of the nanoparticles generates a ponderomotive force that in turn leads to the creation of a macroscopic electron current in the direction of laser polarizations and at the beat frequency ω1-ω2 , which can generate terahertz radiation. We show that, when the beat frequency lies near the effective plasmon frequency of the nanoparticles and the electric fields are parallel to the basal-plane normal, a resonant interaction of the laser beams causes intense terahertz radiation.

  17. Absorber for terahertz radiation management

    Science.gov (United States)

    Biallas, George Herman; Apeldoorn, Cornelis; Williams, Gwyn P.; Benson, Stephen V.; Shinn, Michelle D.; Heckman, John D.

    2015-12-08

    A method and apparatus for minimizing the degradation of power in a free electron laser (FEL) generating terahertz (THz) radiation. The method includes inserting an absorber ring in the FEL beam path for absorbing any irregular THz radiation and thus minimizes the degradation of downstream optics and the resulting degradation of the FEL output power. The absorber ring includes an upstream side, a downstream side, and a plurality of wedges spaced radially around the absorber ring. The wedges form a scallop-like feature on the innermost edges of the absorber ring that acts as an apodizer, stopping diffractive focusing of the THz radiation that is not intercepted by the absorber. Spacing between the scallop-like features and the shape of the features approximates the Bartlett apodization function. The absorber ring provides a smooth intensity distribution, rather than one that is peaked on-center, thereby eliminating minor distortion downstream of the absorber.

  18. Generation of surface electromagnetic waves in terahertz spectral range by free-electron laser radiation and their refractive index determination

    International Nuclear Information System (INIS)

    Bogomolov, G.D.; Jeong, Uk Young; Zhizhin, G.N.; Nikitin, A.K.; Zavyalov, V.V.; Kazakevich, G.M.; Lee, Byung Cheol

    2005-01-01

    First experiments for observation of surface electromagnetic waves (SEW) in the terahertz spectral range generated on dense aluminum films covering the optical quality glass plates are presented in this paper. Coherent radiation of the new free-electron laser covering the frequency range from 30 to 100cm -1 was used. The interference technique employing SEW propagation in the part of one shoulder of the asymmetric interferometer was applied. From the interference pattern the real part of SEW's effective refractive index ae ' was determined for the two laser emission wavelengths: at λ=150μm-ae ' =1+5x10 -5 , at λ=110μm-ae ' =1+8x10 -4 . High sensitivity of the interference patterns to overlayers made of Ge and Si with thickness of 100nm was demonstrated as well

  19. Generation of tunable terahertz out-of-plane radiation using Josephson vortices in modulated layered superconductors

    International Nuclear Information System (INIS)

    Savel'ev, Sergey; Yampol'skii, Valery; Rakhmanov, Alexander; Nori, Franco

    2005-01-01

    We show that a moving Josephson vortex in spatially modulated layered superconductors generates out-of-plane THz radiation. Remarkably, the magnetic and in-plane electric fields radiated are of the same order, which is very unusual for any good-conducting medium. Therefore, the out-of-plane radiation can be emitted to the vacuum without the standard impedance mismatch problem. Thus, the proposed tunable THz emitter for out-of-plane radiation can be more efficient than the standard one which radiates only along the ab-plane

  20. Graphene on nanoscale gratings for the generation of terahertz Smith-Purcell radiation

    International Nuclear Information System (INIS)

    Tantiwanichapan, Khwanchai; Wang, Xuanye; Swan, Anna K.; Paiella, Roberto

    2014-01-01

    Generation of THz radiation based on the Smith-Purcell effect in graphene is investigated numerically. The specific device geometry considered involves an electrically biased single-layer sheet of graphene deposited on a periodic array of holes in a solid substrate. Rigorous electrodynamic simulations combined with a basic model of charge transport are presented, showing that technologically significant output power levels can be obtained at geometrically tunable THz frequencies. These results suggest that graphene is a uniquely suited materials platform for the demonstration of THz electron-beam radiation mechanisms in compact solid-state systems

  1. Graphene hyperlens for terahertz radiation

    DEFF Research Database (Denmark)

    Andryieuski, Andrei; Chigrin, D.; Novitsky, Andrey

    2012-01-01

    We propose the structured graphene terahertz hyperlens that allows overcoming natural diffraction limit and resolving subwavelength features. The proposed hyperlens can have applications in terahertz spectroscopy and imaging.......We propose the structured graphene terahertz hyperlens that allows overcoming natural diffraction limit and resolving subwavelength features. The proposed hyperlens can have applications in terahertz spectroscopy and imaging....

  2. Strong terahertz field generation, detection, and application

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ki-Yong [Univ. of Maryland, College Park, MD (United States)

    2016-05-22

    This report describes the generation and detection of high-power, broadband terahertz (THz) radiation with using femtosecond terawatt (TW) laser systems. In particular, this focuses on two-color laser mixing in gases as a scalable THz source, addressing both microscopic and macroscopic effects governing its output THz yield and radiation profile. This also includes the characterization of extremely broad THz spectra extending from microwaves to infrared frequencies. Experimentally, my group has generated high-energy (tens of microjoule), intense (>8 MV/cm), and broadband (0.01~60 THz) THz radiation in two-color laser mixing in air. Such an intense THz field can be utilized to study THz-driven extremely nonlinear phenomena in a university laboratory.

  3. Strong terahertz field generation, detection, and application

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ki-Yong [Univ. of Maryland, College Park, MD (United States)

    2016-05-15

    This report describes the generation and detection of high-power, broadband terahertz (THz) radiation with using femtosecond terawatt (TW) laser systems. In particular, this focuses on two-color laser mixing in gases as a scalable THz source, addressing both microscopic and macroscopic effects governing its output THz yield and radiation profile. This also includes the characterization of extremely broad THz spectra extending from microwaves to infrared frequencies. Experimentally, my group has generated high-energy (tens of microjoule), intense (>8 MV/cm), and broadband (0.01~60 THz) THz radiation in two-color laser mixing in air. Such an intense THz field can be utilized to study THz-driven extremely nonlinear phenomena in a university laboratory.

  4. Terahertz-radiation generation in low-temperature InGaAs epitaxial films on (100) and (411) InP substrates

    Energy Technology Data Exchange (ETDEWEB)

    Galiev, G. B., E-mail: galiev-galib@mail.ru [Russian Academy of Sciences, Institute of Ultra-High Frequency Semiconductor Electronics (Russian Federation); Grekhov, M. M. [National Research Nuclear University “MEPhI” (Russian Federation); Kitaeva, G. Kh. [Moscow State University, Faculty of Physics (Russian Federation); Klimov, E. A.; Klochkov, A. N. [Russian Academy of Sciences, Institute of Ultra-High Frequency Semiconductor Electronics (Russian Federation); Kolentsova, O. S. [National Research Nuclear University “MEPhI” (Russian Federation); Kornienko, V. V.; Kuznetsov, K. A. [Moscow State University, Faculty of Physics (Russian Federation); Maltsev, P. P.; Pushkarev, S. S. [Russian Academy of Sciences, Institute of Ultra-High Frequency Semiconductor Electronics (Russian Federation)

    2017-03-15

    The spectrum and waveforms of broadband terahertz-radiation pulses generated by low-temperature In{sub 0.53}Ga{sub 0.47}As epitaxial films under femtosecond laser pumping are investigated by terahertz time-resolved spectroscopy. The In{sub 0.53}Ga{sub 0.47}As films are fabricated by molecular-beam epitaxy at a temperature of 200°C under different arsenic pressures on (100)-oriented InP substrates and, for the first time, on (411)A InP substrates. The surface morphology of the samples is studied by atomic-force microscopy and the structural quality is established by high-resolution X-ray diffraction analysis. It is found that the amplitude of terahertz radiation from the LT-InGaAs layers on the (411)A InP substrates exceeds that from similar layers formed on the (100) InP substrates by a factor of 3–5.

  5. Terahertz Generation & Vortex Motion Control in Superconductors

    Science.gov (United States)

    Nori, Franco

    2005-03-01

    A grand challenge is to controllably generate electromagnetic waves in layered superconducting compounds because of its Terahertz frequency range. We propose [1] four experimentally realizable devices for generating continuous and pulsed THz radiation in a controllable frequency range. We also describe [2-4] several novel devices for controlling the motion of vortices in superconductors, including a reversible rectifier made of a magnetic-superconducting hybrid structure [4]. Finally, we summarize a study [5] of the friction force felt by moving vortices. 1) S. Savel'ev, V. Yampol'skii, A. Rakhmanov, F. Nori, Tunable Terahertz radiation from Josephson vortices, preprint 2) S. Savel'ev and F. Nori, Experimentally realizable devices for controlling the motion of magnetic flux quanta, Nature Mat. 1, 179 (2002) 3) S. Savel'ev, F. Marchesoni, F. Nori, Manipulating small particles, PRL 92, 160602 (2004); B. Zhu, F. Marchesoni, F. Nori, Controlling the motion of magnetic flux quanta, PRL 92, 180602 (2004) 4) J.E. Villegas, et al., Reversible Rectifier that Controls the Motion of Magnetic Flux Quanta, Science 302, 1188 (2003) 5) A. Maeda, et al., Nano-scale friction: kinetic friction of magnetic flux quanta and charge density waves, preprint

  6. Overview of terahertz radiation sources

    International Nuclear Information System (INIS)

    Gallerano, G.P.; Biedron, S.G.

    2004-01-01

    Although terahertz (THz) radiation was first observed about hundred years ago, the corresponding portion of the electromagnetic spectrum has been for long time considered a rather poorly explored region at the boundary between the microwaves and the infrared. This situation has changed during the past ten years with the rapid development of coherent THz sources, such as solid state oscillators, quantum cascade lasers, optically pumped solid state devices and novel free electron devices, which have in turn stimulated a wide variety of applications from material science to telecommunications, from biology to biomedicine. For a comprehensive review of THz technology the reader is addressed to a recent paper by P. Siegel. In this paper we focus on the development and perspectives of THz radiation sources.

  7. Terahertz pulse generation from metal nanoparticle ink

    Science.gov (United States)

    Kato, Kosaku; Takano, Keisuke; Tadokoro, Yuzuru; Phan, Thanh Nhat Khoa; Nakajima, Makoto

    2016-11-01

    Terahertz pulse generation from metallic nanostructures irradiated by femtosecond laser pulses is of interest because the conversion efficiency from laser pulses to terahertz waves is increased by the local field enhancement resulting from the plasmon oscillation. In this talk we present our recent study on terahertz generation from metal nanoparticle ink. We baked a silver nanoparticle ink spin-coated onto a glass coverslip in various temperatures. On the surface of the baked ink, bumpy nanostructures are spontaneously formed, and the average size of bumps depends on the baking temperature. These structures are expected to lead to local field enhancement and then large nonlinear polarizations on the surface. The baked ink was irradiated by the output of regeneratively amplified Ti:sapphire femtosecond laser at an incidence angle of 45°. Waveforms of generated terahertz pulses are detected by electro-optical sampling. The generation efficiency was high when the average diameter of bumps was around 100 nm, which is realized when the ink is baked in 205 to 235°C in our setup. One of our next research targets is terahertz wave generation from micro-patterned metallic nanoparticle ink. It is an advantage of the metal nanoparticle ink that by using inkjet printers one can fabricate various patterns with micrometer scales, in which terahertz waves have a resonance. Combination of microstructures made by a printer and nanostructure spontaneously formed in the baking process will provide us terahertz emitters with unique frequency characteristics.

  8. Terahertz radiation generation by beating of two laser beams in a collisional plasma with oblique magnetic field

    Science.gov (United States)

    Hematizadeh, Ayoob; Jazayeri, Seyed Masud; Ghafary, Bijan

    2018-02-01

    A scheme for excitation of terahertz (THz) radiation is presented by photo mixing of two super-Gaussian laser beams in a rippled density collisional magnetized plasma. Lasers having different frequencies and wave numbers but the same electric fields create a ponderomotive force on the electrons of plasma in the beating frequency. Super-Gaussian laser beam has the exclusive features such as steep gradient in laser intensity distribution, wider cross-section in comparison with Gaussian profiles, which make stronger ponderomotive force and higher THz radiation. The magnetic field is considered oblique to laser beams propagation direction; in this case, depending on the phase matching conditions different mode waves can propagate in plasma. It is found that amplitude and efficiency of the emitted THz radiation not only are sensitive to the beating frequency, collision frequency, and magnetic field strength but to the angle between laser beams and static magnetic field. The efficiency of THz radiation can be optimized in a certain angle.

  9. Optical generation,detection and non-destructive testing applications of terahertz waves

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Weili; LIANG; Dachuan; TIAN; Zhen; HAN; Jiaguang; GU; Jianqiang; HE; Mingxia; OUYANG; Chunmei

    2016-01-01

    Optoelectronic terahertz generation and detection play a key role in the applications of non-destructive testing,which involves different areas such as physics,biological,material science,imaging,explosions detection,astronomy applications,semiconductor technology and superconductiong electronics. In this article,we present a reviewof the principle and performance of typical terahertz sources,detectors and non-destructive testing applications. On this basis,the newdevelopment and trends of terahertz radiation detectors are also discussed.

  10. A terahertz-vibration to terahertz-radiation converter based on gold nanoobjects: a feasibility study.

    Science.gov (United States)

    Moldosanov, Kamil; Postnikov, Andrei

    2016-01-01

    The need for practical and adaptable terahertz sources is apparent in the areas of application such as early cancer diagnostics, nondestructive inspection of pharmaceutical tablets, visualization of concealed objects. We outline the operation principle and suggest the design of a simple appliance for generating terahertz radiation by a system of nanoobjects - gold nanobars (GNBs) or nanorings (GNRs) - irradiated by microwaves. Our estimations confirm a feasibility of the idea that GNBs and GNRs irradiated by microwaves could become terahertz emitters with photon energies within the full width at half maximum of the longitudinal acoustic phononic DOS of gold (ca. 16-19 meV, i.e., 3.9-4.6 THz). A scheme of the terahertz radiation source is suggested based on the domestic microwave oven irradiating a substrate with multiple deposited GNBs or GNRs. The size of a nanoobject for optimal conversion is estimated to be approx. 3 nm (thickness) by approx. 100 nm (length of GNB, or along the GNR). This detailed prediction is open to experimental verification. An impact is expected onto further studies of interplay between atomic vibrations and electromagnetic waves in nanoobjects.

  11. A terahertz-vibration to terahertz-radiation converter based on gold nanoobjects: a feasibility study

    Directory of Open Access Journals (Sweden)

    Kamil Moldosanov

    2016-07-01

    Full Text Available Background: The need for practical and adaptable terahertz sources is apparent in the areas of application such as early cancer diagnostics, nondestructive inspection of pharmaceutical tablets, visualization of concealed objects. We outline the operation principle and suggest the design of a simple appliance for generating terahertz radiation by a system of nanoobjects – gold nanobars (GNBs or nanorings (GNRs – irradiated by microwaves.Results: Our estimations confirm a feasibility of the idea that GNBs and GNRs irradiated by microwaves could become terahertz emitters with photon energies within the full width at half maximum of the longitudinal acoustic phononic DOS of gold (ca. 16–19 meV, i.e., 3.9–4.6 THz. A scheme of the terahertz radiation source is suggested based on the domestic microwave oven irradiating a substrate with multiple deposited GNBs or GNRs.Conclusion: The size of a nanoobject for optimal conversion is estimated to be approx. 3 nm (thickness by approx. 100 nm (length of GNB, or along the GNR. This detailed prediction is open to experimental verification. An impact is expected onto further studies of interplay between atomic vibrations and electromagnetic waves in nanoobjects.

  12. Numerical simulation of terahertz generation and detection based on ultrafast photoconductive antennas

    Science.gov (United States)

    Chen, Long-chao; Fan, Wen-hui

    2011-08-01

    The numerical simulation of terahertz generation and detection in the interaction between femtosecond laser pulse and photoconductive material has been reported in this paper. The simulation model based on the Drude-Lorentz theory is used, and takes into account the phenomena that photo-generated electrons and holes are separated by the external bias field, which is screened by the space-charge field simultaneously. According to the numerical calculation, the terahertz time-domain waveforms and their Fourier-transformed spectra are presented under different conditions. The simulation results indicate that terahertz generation and detection properties of photoconductive antennas are largely influenced by three major factors, including photo-carriers' lifetime, laser pulse width and pump laser power. Finally, a simple model has been applied to simulate the detected terahertz pulses by photoconductive antennas with various photo-carriers' lifetimes, and the results show that the detected terahertz spectra are very different from the spectra radiated from the emitter.

  13. Terahertz radiation in alkali vapor plasmas

    International Nuclear Information System (INIS)

    Sun, Xuan; Zhang, X.-C.

    2014-01-01

    By taking advantage of low ionization potentials of alkali atoms, we demonstrate terahertz wave generation from cesium and rubidium vapor plasmas with an amplitude nearly one order of magnitude larger than that from nitrogen gas at low pressure (0.02–0.5 Torr). The observed phenomena are explained by the numerical modeling based upon electron tunneling ionization

  14. Nonrelativistic electron bunch train for coherently enhanced terahertz radiation sources

    International Nuclear Information System (INIS)

    Li Yuelin; Kim, Kwang-Je

    2008-01-01

    We propose to generate a train of prebunched electron beams for producing coherently enhanced Smith-Purcell radiation [S. J. Smith and E. M. Purcell, Phys. Rev. 92, 1069 (1953)] in the terahertz wavelength range. In this scheme, a train of picosecond laser pulses is produced to drive a photoemission gun to generate a train of 50 keV electron pulses. The parameters are chosen so that the space-charge effect does not destroy the pulse time structure. Smith-Purcell radiation from the electron pulse train is enhanced due both to the short length of the individual electron bunch and to the repetitive structure of the beam. Example systems producing coherent terahertz power at about 1 mW are described

  15. Broadband terahertz generation of metamaterials

    Science.gov (United States)

    Luo, Liang; Wang, Jigang; Koschny, Thomas; Wegener, Martin; Soukoulis, Costas M.

    2017-06-20

    Provided are systems and methods to generate single-cycle THz pulses from a few tens of nanometers thin layer of split ring resonators (SRRs) via optical rectification of femtosecond laser pulses. The emitted THz radiation, with a spectrum ranging from about 0.1 to 4 THz, arises exclusively from pumping the magnetic-dipole resonance of SRRs around 200 THz. This resonant enhancement, together with pump polarization dependence and power scaling of the THz emission, underpins the nonlinearity from optically induced circulating currents in SRRs, with a huge effective nonlinear susceptibility of 0.8.times.10.sup.-16 m.sup.2/V that far exceeds surface nonlinearities of both thin films and bulk organic/inorganic crystals and sheet nonlinearities of non-centrosymmetric materials such as ZnTe.

  16. Graphene hyperlens for terahertz radiation

    DEFF Research Database (Denmark)

    Andryieuski, Andrei; Lavrinenko, Andrei; Chigrin, Dmitry N.

    2012-01-01

    We propose a graphene hyperlens for the terahertz (THz) range. We employ and numerically examine a structured graphene-dielectric multilayered stack that is an analog of a metallic wire medium. As an example of the graphene hyperlens in action, we demonstrate an imaging of two point sources...... separated by a distance λ0/5. An advantage of such a hyperlens as compared to a metallic one is the tunability of its properties by changing the chemical potential of graphene. We also propose a method to retrieve the hyperbolic dispersion, check the effective medium approximation, and retrieve...

  17. Response of asymmetric carbon nanotube network devices to sub-terahertz and terahertz radiation

    International Nuclear Information System (INIS)

    Gayduchenko, I.; Kardakova, A.; Voronov, B.; Finkel, M.; Fedorov, G.; Jiménez, D.; Morozov, S.; Presniakov, M.; Goltsman, G.

    2015-01-01

    Demand for efficient terahertz radiation detectors resulted in intensive study of the asymmetric carbon nanostructures as a possible solution for that problem. It was maintained that photothermoelectric effect under certain conditions results in strong response of such devices to terahertz radiation even at room temperature. In this work, we investigate different mechanisms underlying the response of asymmetric carbon nanotube (CNT) based devices to sub-terahertz and terahertz radiation. Our structures are formed with CNT networks instead of individual CNTs so that effects probed are more generic and not caused by peculiarities of an individual nanoscale object. We conclude that the DC voltage response observed in our structures is not only thermal in origin. So called diode-type response caused by asymmetry of the device IV characteristic turns out to be dominant at room temperature. Quantitative analysis provides further routes for the optimization of the device configuration, which may result in appearance of novel terahertz radiation detectors

  18. Broadband terahertz generation using the semiconductor-metal transition in VO2

    Directory of Open Access Journals (Sweden)

    Nicholas A. Charipar

    2016-01-01

    Full Text Available We report the design, fabrication, and characterization of broadband terahertz emitters based on the semiconductor-metal transition in thin film VO2 (vanadium dioxide. With the appropriate geometry, picosecond electrical pulses are generated by illuminating 120 nm thick VO2 with 280 fs pulses from a femtosecond laser. These ultrafast electrical pulses are used to drive a simple dipole antenna, generating broadband terahertz radiation.

  19. Modulation of terahertz generation in dual-color filaments by an external electric field and preformed plasma

    International Nuclear Information System (INIS)

    Li Min; Li An-Yuan; Yuan Shuai; Zeng He-Ping; He Bo-Qu

    2016-01-01

    Terahertz generation driven by dual-color filaments in air is demonstrated to be remarkably enhanced by applying an external electric field to the filaments. As terahertz generation is sensitive to the dual-color phase difference, a preformed plasma is verified efficiently in modulating terahertz radiation from linear to elliptical polarization. In the presence of preformed plasma, a dual-color filament generates terahertz pulses of elliptical polarization and the corresponding ellipse rotates regularly with the change of the preformed plasma density. The observed terahertz modulation with the external electric field and the preformed plasma provides a simple way to estimate the plasma density and evaluate the photocurrent dynamics of the dual-color filaments. It provides further experimental evidence of the photo-current model in governing the dual-color filament driven terahertz generation processes. (paper)

  20. Continuous terahertz-wave generation using a monolithically integrated horn antenna

    Science.gov (United States)

    Peytavit, E.; Beck, A.; Akalin, T.; Lampin, J.-F.; Hindle, F.; Yang, C.; Mouret, G.

    2008-09-01

    A transverse electromagnetic horn antenna is monolithically integrated with a standard ultrafast interdigitated electrode photodetector on low-temperature-grown GaAs. Continuous-wave terahertz radiation is generated at frequencies up to 2 THz with a maximum power of approximately 1 μW at 780 GHz. Experimental variations in the terahertz power as function of the frequency are explained by means of electromagnetic simulations of the antenna and the photomixer vicinity.

  1. Absorption-reduced waveguide structure for efficient terahertz generation

    Energy Technology Data Exchange (ETDEWEB)

    Pálfalvi, L., E-mail: palfalvi@fizika.ttk.pte.hu [Institute of Physics, University of Pécs, Ifjúság ú. 6, 7624 Pécs (Hungary); Fülöp, J. A. [MTA-PTE High-Field Terahertz Research Group, Ifjúság ú. 6, 7624 Pécs (Hungary); Szentágothai Research Centre, University of Pécs, Ifjúság ú. 20, 7624 Pécs (Hungary); Hebling, J. [Institute of Physics, University of Pécs, Ifjúság ú. 6, 7624 Pécs (Hungary); MTA-PTE High-Field Terahertz Research Group, Ifjúság ú. 6, 7624 Pécs (Hungary); Szentágothai Research Centre, University of Pécs, Ifjúság ú. 20, 7624 Pécs (Hungary)

    2015-12-07

    An absorption-reduced planar waveguide structure is proposed for increasing the efficiency of terahertz (THz) pulse generation by optical rectification of femtosecond laser pulses with tilted-pulse-front in highly nonlinear materials with large absorption coefficient. The structure functions as waveguide both for the optical pump and the generated THz radiation. Most of the THz power propagates inside the cladding with low THz absorption, thereby reducing losses and leading to the enhancement of the THz generation efficiency by up to more than one order of magnitude, as compared with a bulk medium. Such a source can be suitable for highly efficient THz pulse generation pumped by low-energy (nJ-μJ) pulses at high (MHz) repetition rates delivered by compact fiber lasers.

  2. High-resolution broadband terahertz spectroscopy via electronic heterodyne detection of photonically generated terahertz frequency comb.

    Science.gov (United States)

    Pavelyev, D G; Skryl, A S; Bakunov, M I

    2014-10-01

    We report an alternative approach to the terahertz frequency-comb spectroscopy (TFCS) based on nonlinear mixing of a photonically generated terahertz pulse train with a continuous wave signal from an electronic synthesizer. A superlattice is used as a nonlinear mixer. Unlike the standard TFCS technique, this approach does not require a complex double-laser system but retains the advantages of TFCS-high spectral resolution and wide bandwidth.

  3. Simulation of photoconductive antennas for terahertz radiation

    Directory of Open Access Journals (Sweden)

    Carlos Criollo

    2015-01-01

    Full Text Available Simulation of terahertz (THz emission based on PC antennas imposes a challenge to couple the semiconductor carrier phenomena, optical transport and the THz energy transport. In this paper a Multi-physics simulation for coupling these phenomena using COMSOL Multi-physics 4.3b is introduced. The main parameters of THz photoconductive (PC antenna as THz emitter have been reviewed and discussed. The results indicate the role of each parameter in the resulting photocurrent waveform and THz frequency: The radiated THz photocurrent waveform is determined by the photoconductive gap (the separation between the metallic electrodes, the incident laser illumination and the DC excitation voltage; while the THz frequency depends on the dipole length. The optimization of these parameters could enhance the emission. The simulations extend the advance of compact and cost-effective THz emitters.

  4. Terahertz generation via laser coupling to anharmonic carbon nanotube array

    Science.gov (United States)

    Sharma, Soni; Vijay, A.

    2018-02-01

    A scheme of terahertz radiation generation employing a matrix of anharmonic carbon nanotubes (CNTs) embedded in silica is proposed. The matrix is irradiated by two collinear laser beams that induce large excursions on CNT electrons and exert a nonlinear force at the beat frequency ω = ω1-ω2. The force derives a nonlinear current producing THz radiation. The THz field is resonantly enhanced at the plasmon resource, ω = ω p ( 1 + β ) / √{ 2 } , where ωp is the plasma frequency and β is a characteristic parameter. Collisions are a limiting factor, suppressing the plasmon resonance. For typical values of plasma parameters, we obtain power conversion efficiency of the order of 10-6.

  5. Terahertz wave generation in coupled quantum dots

    International Nuclear Information System (INIS)

    Ma Yu-Rong; Guo Shi-Fang; Duan Su-Qing

    2012-01-01

    Based on coupled quantum dots, we present an interesting optical effect in a four-level loop coupled system. Both the two upper levels and the two lower levels are designed to be almost degenerate, which induces a considerable dipole moment. The terahertz wave is obtained from the low-frequency component of the photon emission spectrum. The frequency of the terahertz wave can be controlled by tuning the energy levels via designing the nanostructure appropriately or tuning the driving laser field. A terahertz wave with adjustable frequency and considerable intensity (100 times higher than that of the Rayleigh line) can be obtained. It provides an effective scheme for a terahertz source. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  6. Continuous wave terahertz radiation from an InAs/GaAs quantum-dot photomixer device

    Science.gov (United States)

    Kruczek, T.; Leyman, R.; Carnegie, D.; Bazieva, N.; Erbert, G.; Schulz, S.; Reardon, C.; Reynolds, S.; Rafailov, E. U.

    2012-08-01

    Generation of continuous wave radiation at terahertz (THz) frequencies from a heterodyne source based on quantum-dot (QD) semiconductor materials is reported. The source comprises an active region characterised by multiple alternating photoconductive and QD carrier trapping layers and is pumped by two infrared optical signals with slightly offset wavelengths, allowing photoconductive device switching at the signals' difference frequency ˜1 THz.

  7. Invited Review Terahertz Transmission, Scattering, Reflection, and Absorption—the Interaction of THz Radiation with Soils

    Science.gov (United States)

    Lewis, R. A.

    2017-07-01

    Terahertz radiation has been proposed as a useful tool in the study of soils and related materials from such diverse perspectives as detection of non-metallic landmines to improving soil fertility by agricultural charcoals produced by pyrolysis of organic material. The main barrier to such applications is that soils are rather opaque at terahertz frequencies. In this article, the main findings to date on the interaction of terahertz radiation with soils are reviewed, organized around the four phenomena of terahertz: transmission, scattering, reflection, and absorption. Terahertz transmission through soils is generally low and decreases with frequency. Terahertz scattering is evident in many THz-soil interactions, as the wavelength of the radiation is of the order of the particle size. Terahertz reflection is important to communications as these develop from the GHz into the THz band. Terahertz absorption on diluted soil samples has been demonstrated to be effective in identifying soil constituents, such as aromatic compounds, and soil contaminants, such as pesticides.

  8. Harmonics radiation of graphene surface plasmon polaritons in terahertz regime

    Energy Technology Data Exchange (ETDEWEB)

    Li, D., E-mail: dazhi_li@hotmail.com [Institute for Laser Technology, Suita, Osaka 565-0871 (Japan); Wang, Y. [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Nakajima, M. [Institute of Laser Engineering, Osaka University, Suita, Osaka 565-0871 (Japan); Hashida, M. [Advanced Research Center for Beam Science, ICR, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Wei, Y. [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Miyamoto, S. [Laboratory of Advanced Science and Technology for Industry, University of Hyogo, Ako, Hyogo 678-1205 (Japan)

    2016-06-03

    This letter presents an approach to extract terahertz radiation from surface plasmon polaritons excited in the surface of a uniform graphene structure by an electron beam. A sidewall configuration is proposed to lift the surface plasmon mode to be close to the light line, so that some of its harmonics have chances to go above the light line and become radiative. The harmonics are considered to be excited by a train of periodic electron bunches. The physical mechanism in this scheme is analyzed with three-dimensional theory, and the harmonics excitation and radiation are demonstrated through numerical calculations. The results show that this technique could be an alternative to transform the surface plasmon polaritons into radiation. - Highlights: • An approach to extract terahertz radiation from graphene surface plasmon polaritons is presented. • A sidewall configuration is proposed to lift the surface plasmon mode. • Harmonics of surface plasmon polaritons are possible to radiate.

  9. Terahertz radiation by subpicosecond spin-polarized photocurrent originating from Dirac electrons in a Rashba-type polar semiconductor

    Science.gov (United States)

    Kinoshita, Yuto; Kida, Noriaki; Miyamoto, Tatsuya; Kanou, Manabu; Sasagawa, Takao; Okamoto, Hiroshi

    2018-04-01

    The spin-splitting energy bands induced by the relativistic spin-orbit interaction in solids provide a new opportunity to manipulate the spin-polarized electrons on the subpicosecond timescale. Here, we report one such example in a bulk Rashba-type polar semiconductor BiTeBr. Strong terahertz electromagnetic waves are emitted after the resonant excitation of the interband transition between the Rashba-type spin-splitting energy bands with a femtosecond laser pulse circularly polarized. The phase of the emitted terahertz waves is reversed by switching the circular polarization. This suggests that the observed terahertz radiation originates from the subpicosecond spin-polarized photocurrents, which are generated by the asymmetric depopulation of the Dirac state. Our result provides a way for the current-induced terahertz radiation and its phase control by the circular polarization of incident light without external electric fields.

  10. Influence of the electron density on the characteristics of terahertz waves generated under laser–cluster interaction

    Energy Technology Data Exchange (ETDEWEB)

    Frolov, A. A., E-mail: frolov@ihed.ras.ru [Russian Academy of Sciences, Joint Institute for High Temperatures (Russian Federation)

    2016-12-15

    A theory of generation of terahertz radiation under laser–cluster interaction, developed earlier for an overdense cluster plasma [A. A. Frolov, Plasma Phys. Rep. 42. 637 (2016)], is generalized for the case of arbitrary electron density. The spectral composition of radiation is shown to substantially depend on the density of free electrons in the cluster. For an underdense cluster plasma, there is a sharp peak in the terahertz spectrum at the frequency of the quadrupole mode of a plasma sphere. As the electron density increases to supercritical values, this spectral line vanishes and a broad maximum at the frequency comparable with the reciprocal of the laser pulse duration appears in the spectrum. The dependence of the total energy of terahertz radiation on the density of free electrons is analyzed. The radiation yield is shown to increase significantly under resonance conditions, when the laser frequency is close to the eigenfrequency of the dipole or quadrupole mode of a plasma sphere.

  11. IKNO, a user facility for coherent terahertz and UV synchrotron radiation

    International Nuclear Information System (INIS)

    Sannibale, Fernando; Marcelli, Augusto; Innocenzi, Plinio

    2008-01-01

    IKNO (Innovation and KNOwledge) is a proposal for a multi-user facility based on an electron storage ring optimized for the generation of coherent synchrotron radiation (CSR) in the terahertz frequency range, and of broadband incoherent synchrotron radiation (SR) ranging from the IR to the VUV. IKNO can be operated in an ultra-stable CSR mode with photon flux in the terahertz frequency region up to nine orders of magnitude higher than in existing 3rd generation light sources. Simultaneously to the CSR operation, broadband incoherent SR up to VUV frequencies is available at the beamline ports. The main characteristics of the IKNO storage and its performance in terms of CSR and incoherent SR are described in this paper. The proposed location for the infrastructure facility is in Sardinia, Italy

  12. A simple system for 160GHz optical terahertz wave generation and data modulation

    Science.gov (United States)

    Li, Yihan; He, Jingsuo; Sun, Xueming; Shi, Zexia; Wang, Ruike; Cui, Hailin; Su, Bo; Zhang, Cunlin

    2018-01-01

    A simple system based on two cascaded Mach-Zehnder modulators, which can generate 160GHz optical terahertz waves from 40GHz microwave sources, is simulated and tested in this paper. Fiber grating filter is used in the system to filter out optical carrier. By properly adjusting the modulator DC bias voltages and the signal voltages and phases, 4-tupling optical terahertz wave can be generated with fiber grating. This notch fiber grating filter is greatly suitable for terahertz over fiber (TOF) communication system. This scheme greatly reduces the cost of long-distance terahertz communication. Furthermore, 10Gbps digital signal is modulated in the 160GHz optical terahertz wave.

  13. Efficient terahertz wave generation from GaP crystals pumped by chirp-controlled pulses from femtosecond photonic crystal fiber amplifier

    International Nuclear Information System (INIS)

    Li, Jiang; Shi, Junkai; Xu, Baozhong; Xing, Qirong; Wang, Chingyue; Chai, Lu; Liu, Bowen; Hu, Minglie; Li, Yanfeng; Fedotov, Andrey B.; Zheltikov, Aleksei M.

    2014-01-01

    A chirp-tunable femtosecond 10 W, 42 MHz photonic-crystal-fiber oscillator-amplifier system that is capable of delivering sub-60 fs light pulses at 1040 nm is used to demonstrate high-efficiency terahertz radiation generation via optical rectification in GaP crystals only a few millimeters in length. The optimization of the chirp of the fiber-laser pulses is shown to radically enhance the terahertz output, indicating one possible way to more efficiently use these extended nonlinear crystals in compact fiber-pumped terahertz radiation sources

  14. Terahertz-Radiation-Enhanced Emission of Fluorescence from Gas Plasma

    International Nuclear Information System (INIS)

    Liu Jingle; Zhang, X.-C.

    2009-01-01

    We report the study of femtosecond laser-induced air plasma fluorescence under the illumination of terahertz (THz) pulses. Semiclassical modeling and experimental verification indicate that time-resolved THz radiation-enhanced emission of fluorescence is dominated by the electron kinetics and the electron-impact excitation of gas molecules or ions. We demonstrate that the temporal waveform of the THz field could be retrieved from the transient enhanced fluorescence, making omnidirectional, coherent detection available for THz time-domain spectroscopy.

  15. Plasma wave instability and amplification of terahertz radiation in field-effect-transistor arrays

    International Nuclear Information System (INIS)

    Popov, V V; Tsymbalov, G M; Shur, M S

    2008-01-01

    We show that the strong amplification of terahertz radiation takes place in an array of field-effect transistors at small DC drain currents due to hydrodynamic plasmon instability of the collective plasmon mode. Planar designs compatible with standard integrated circuit fabrication processes and strong coupling of terahertz radiation to plasmon modes in FET arrays make such arrays very attractive for potential applications in solid-state terahertz amplifiers and emitters

  16. Terahertz Coherent Synchrotron Radiation in the MIT-Bates South Hall Ring

    CERN Document Server

    Wang, Fuhua; Cheever, Dan; Farkhondeh, Manouchehr; Franklin, Wilbur; Graves, William; Ihloff, Ernie; Podobedov, Boris; Sannibale, Fernando; Tschalär, C; Wang, Defa; Wang, Dong; Zwart, Townsend; van der Laan, Jan

    2005-01-01

    We investigate the terahertz coherent synchrotron radiation (CSR) potential of the South Hall Ring (SHR) at MIT-Bates Linear Accelerator Center. The SHR is equipped with a unique single cavity, 2.856 GHz RF system. The high RF frequency is advantageous for producing short bunch length and for having higher bunch current threshold to generate stable CSR. Combining with other techniques such as external pulse stacking cavity, femtosecond laser slicing, the potential for generating ultra-stable, high power, broadband terahertz CSR is very attractive. Beam dynamics issues related to short bunch length operation, and may associated with the high frequency RF system, such as multi-bunch instability are concerned. They could affect bunch length, bunch intensity and beam stability. The SHR is ideal for experimental exploration of these problems. Results of initial test of low momentum compaction lattice and bunch length measurements are presented and compared to expectations.

  17. NATO Advanced Research Workshop on Terahertz and Mid Infrared Radiation

    CERN Document Server

    Pereira, Mauro F; Terahertz and Mid Infrared Radiation

    2011-01-01

    Terahertz (THz) and Mid-Infrared (MIR) radiation  (TERA-MIR) can be transmitted through nearly any material without causing biological harm. Novel and rapid methods of detection can be created with devices operation in these spectral ranges allowing scanning for weapons, detecting hidden explosives (including plastic landmines), controlling the quality of food and a host of other exciting applications.  This book focuses on mathematical and physical aspects of the field, on unifying these two spectral domains (THz and MIR) with regard to common sources, detectors, materials and applications, and on key interdisciplinary topics. The main THz and MIR source is the quantum cascade laser (QCL). Thus significant attention is paid to the challenge of turning this advanced technology into affordable commercial devices so as to exploit its enormous potential. However other alternatives to THz QCLs are also presented, e.g.  sub-terahertz imaging from avalanching GaAs bipolar transistors, Josephson junctions as THz ...

  18. Percolation-enhanced generation of terahertz pulses by optical rectification on ultrathin gold films

    NARCIS (Netherlands)

    Ramakrishnan, G.; Planken, P.C.M.

    2011-01-01

    Emission of pulses of electromagnetic radiation in the terahertz range is observed when ultrathin gold films on glass are illuminated with femtosecond near-IR laser pulses. A distinct maximum is observed in the emitted terahertz amplitude from films of average thickness just above the percolation

  19. Experimental study of intense radiation in terahertz region based on cylindrical surface wave resonator

    International Nuclear Information System (INIS)

    Gong, Shaoyan; Ogura, Kazuo; Yambe, Kiyoyuki; Nomizu, Shintaro; Shirai, Akihiro; Yamazaki, Kosuke; Kawamura, Jun; Miura, Takuro; Takanashi, Sho; San, Min Thu

    2015-01-01

    Periodical corrugations structured on a cylindrical conductor have cylindrical surface waves (CSWs), which are reflected at the corrugation ends and form a CSW-resonator. In this paper, intense radiations in terahertz region based on the CSW-resonator are reported. The CSW-resonators with upper cut off frequencies in the modern IEEE G-band (110–300 GHz) are excited by a coaxially injected annular beam in a weakly relativistic region less than 100 kV. It is shown that there exists an oscillation starting energy for the CSW-resonator. Above the starting energy, very intense terahertz radiations on the order of kW are obtained. The operation frequencies in the range of 166–173 GHz and 182–200 GHz are obtained using two types of CSW-resonator with the different corrugation amplitude. Electromagnetic properties of the CSW-resonator can be controlled by the artificial structure and may play an important role in high-intensity terahertz generations and applications

  20. Pulsed CH3OH terahertz laser radiation pumped by 9P(36) CO2 lasers

    International Nuclear Information System (INIS)

    Jiu Zhixian; Zuo Duluo; Miao Liang; Cheng Zuhai

    2011-01-01

    An efficient pulsed CH 3 OH terahertz (THz) laser pumped by a TEA CO 2 laser was investigated experimentally. A simple terahertz cavity and a TEA CO 2 laser for the optically pumped THz radiation were studied experimentally. To improve THz laser energy and photon conversion efficiency, two different TEA CO 2 lasers were developed to pump CH 3 OH. When CH 3 OH was pumped by the 9P(36) line with different powers of the CO 2 laser, the generation of terahertz radiation with energy as high as 0.307mJ and 23.75mJ were obtained, respectively. The corresponding photon conversion efficiencies were 0.29% and 2.4%. The photon conversion efficiency increases by a factor of about 8. Meanwhile, higher peak power of pump laser effectively improves the photon conversion efficiency. And the optimum THz laser pressure increases with narrower pulse width of pump laser because of increasing absorptive gases molecules of CH 3 OH with higher peak power of pump laser.

  1. Advances in the biological effects of terahertz wave radiation.

    Science.gov (United States)

    Zhao, Li; Hao, Yan-Hui; Peng, Rui-Yun

    2014-01-01

    The terahertz (THz) band lies between microwave and infrared rays in wavelength and consists of non-ionizing radiation. Both domestic and foreign research institutions, including the army, have attached considerable importance to the research and development of THz technology because this radiation exhibits both photon-like and electron-like properties, which grant it considerable application value and potential. With the rapid development of THz technology and related applications, studies of the biological effects of THz radiation have become a major focus in the field of life sciences. Research in this field has only just begun, both at home and abroad. In this paper, research progress with respect to THz radiation, including its biological effects, mechanisms and methods of protection, will be reviewed.

  2. Terahertz Generation in an Electrically Biased Optical Fiber: A Theoretical Investigation

    Directory of Open Access Journals (Sweden)

    Montasir Qasymeh

    2012-01-01

    Full Text Available We propose and theoretically investigate a novel approach for generating terahertz (THz radiation in a standard single-mode fiber. The optical fiber is mediated by an electrostatic field, which induces an effective second-order nonlinear susceptibility via the Kerr effect. The THz generation is based on difference frequency generation (DFG. A dispersive fiber Bragg grating (FBG is utilized to phase match the two interacting optical carriers. A ring resonator is utilized to boost the optical intensities in the biased optical fiber. A mathematical model is developed which is supported by a numerical analysis and simulations. It is shown that a wide spectrum of a tunable THz radiation can be generated, providing a proper design of the FBG and the optical carriers.

  3. Proposal of coherent Cherenkov radiation matched to circular plane wave for intense terahertz light source

    International Nuclear Information System (INIS)

    Sei, Norihiro; Sakai, Takeshi; Hayakawa, Ken; Tanaka, Toshinari; Hayakawa, Yasushi; Nakao, Keisuke; Nogami, Kyoko; Inagaki, Manabu

    2015-01-01

    Highlights: • We proposed a new intense terahertz-wave source based on coherent Cherenkov radiation (CCR). • A hollow conical dielectric is used to generate the CCR beam. • The wave front of the CCR beam can be matched to the basal plane. • The peak-power of the CCR beam is above 1 MW per micropulse with a short interval of 350 ps. - Abstract: We propose a high-peak-power terahertz-wave source based on an electron accelerator. By passing an electron beam through a hollow conical dielectric with apex facing the incident electron beam, the wave front of coherent Cherenkov radiation generated on the inner surface of the hollow conical dielectric matches the basal plane. Using the electron beam generated at the Laboratory for Electron Beam Research and Application at Nihon University, the calculated power of coherent Cherenkov radiation that matched the circular plane (CCR-MCP) was above 1 MW per micropulse with a short interval of 350 ps, for wavelengths ranging from 0.5 to 5 mm. The electron beam is not lost for generating the CCR-MCP beam by using the hollow conical dielectric. It is possible to combine the CCR-MCP beams with other light sources based on an accelerator

  4. Terahertz waves radiated from two noncollinear femtosecond plasma filaments

    Energy Technology Data Exchange (ETDEWEB)

    Du, Hai-Wei; Hoshina, Hiromichi; Otani, Chiko, E-mail: otani@riken.jp [Terahertz Sensing and Imaging Research Team, RIKEN Center for Advanced Photonics, RIKEN, Sendai, Miyagi 980-0845 (Japan); Midorikawa, Katsumi [Attosecond Science Research Team, RIKEN Center for Advanced Photonics, RIKEN, Wako, Saitama 351-0198 (Japan)

    2015-11-23

    Terahertz (THz) waves radiated from two noncollinear femtosecond plasma filaments with a crossing angle of 25° are investigated. The irradiated THz waves from the crossing filaments show a small THz pulse after the main THz pulse, which was not observed in those from single-filament scheme. Since the position of the small THz pulse changes with the time-delay of two filaments, this phenomenon can be explained by a model in which the small THz pulse is from the second filament. The denser plasma in the overlap region of the filaments changes the movement of space charges in the plasma, thereby changing the angular distribution of THz radiation. As a result, this schematic induces some THz wave from the second filament to propagate along the path of the THz wave from the first filament. Thus, this schematic alters the direction of the THz radiation from the filamentation, which can be used in THz wave remote sensing.

  5. Compact high-power terahertz radiation source

    Directory of Open Access Journals (Sweden)

    G. A. Krafft

    2004-06-01

    Full Text Available In this paper a new type of THz radiation source, based on recirculating an electron beam through a high gradient superconducting radio frequency cavity, and using this beam to drive a standard electromagnetic undulator on the return leg, is discussed. Because the beam is recirculated and not stored, short bunches may be produced that radiate coherently in the undulator, yielding exceptionally high average THz power for relatively low average beam power. Deceleration from the coherent emission, and the detuning it causes, limits the charge-per-bunch possible in such a device.

  6. Single attosecond pulse from terahertz-assisted high-order harmonic generation

    Science.gov (United States)

    Balogh, Emeric; Kovacs, Katalin; Dombi, Peter; Fulop, Jozsef A.; Farkas, Gyozo; Hebling, Janos; Tosa, Valer; Varju, Katalin

    2011-08-01

    High-order harmonic generation by few-cycle 800 nm laser pulses in neon gas in the presence of a strong terahertz (THz) field is investigated numerically with propagation effects taken into account. Our calculations show that the combination of THz fields with up to 12 fs laser pulses can be an effective gating technique to generate single attosecond pulses. We show that in the presence of the strong THz field only a single attosecond burst can be phase matched, whereas radiation emitted during other half cycles disappears during propagation. The cutoff is extended and a wide supercontinuum appears in the near-field spectra, extending the available spectral width for isolated attosecond pulse generation from 23 to 93 eV. We demonstrate that phase-matching effects are responsible for the generation of isolated attosecond pulses, even in conditions when single-atom response yields an attosecond pulse train.

  7. Single attosecond pulse from terahertz-assisted high-order harmonic generation

    International Nuclear Information System (INIS)

    Balogh, Emeric; Kovacs, Katalin; Dombi, Peter; Farkas, Gyozo; Fulop, Jozsef A.; Hebling, Janos; Tosa, Valer; Varju, Katalin

    2011-01-01

    High-order harmonic generation by few-cycle 800 nm laser pulses in neon gas in the presence of a strong terahertz (THz) field is investigated numerically with propagation effects taken into account. Our calculations show that the combination of THz fields with up to 12 fs laser pulses can be an effective gating technique to generate single attosecond pulses. We show that in the presence of the strong THz field only a single attosecond burst can be phase matched, whereas radiation emitted during other half cycles disappears during propagation. The cutoff is extended and a wide supercontinuum appears in the near-field spectra, extending the available spectral width for isolated attosecond pulse generation from 23 to 93 eV. We demonstrate that phase-matching effects are responsible for the generation of isolated attosecond pulses, even in conditions when single-atom response yields an attosecond pulse train.

  8. Single attosecond pulse from terahertz-assisted high-order harmonic generation

    Energy Technology Data Exchange (ETDEWEB)

    Balogh, Emeric [Department of Optics and Quantum Electronics, University of Szeged, H-6701 Szeged (Hungary); Kovacs, Katalin [Department of Optics and Quantum Electronics, University of Szeged, H-6701 Szeged (Hungary); National Institute for R and D of Isotopic and Molecular Technologies, RO-400293 Cluj-Napoca (Romania); Dombi, Peter; Farkas, Gyozo [Research Institute for Solid State Physics and Optics, H-1525 Budapest (Hungary); Fulop, Jozsef A.; Hebling, Janos [Department of Experimental Physics, University of Pecs, H-7624 Pecs (Hungary); Tosa, Valer [National Institute for R and D of Isotopic and Molecular Technologies, RO-400293 Cluj-Napoca (Romania); Varju, Katalin [HAS Research Group on Laser Physics, University of Szeged, H-6701 Szeged (Hungary)

    2011-08-15

    High-order harmonic generation by few-cycle 800 nm laser pulses in neon gas in the presence of a strong terahertz (THz) field is investigated numerically with propagation effects taken into account. Our calculations show that the combination of THz fields with up to 12 fs laser pulses can be an effective gating technique to generate single attosecond pulses. We show that in the presence of the strong THz field only a single attosecond burst can be phase matched, whereas radiation emitted during other half cycles disappears during propagation. The cutoff is extended and a wide supercontinuum appears in the near-field spectra, extending the available spectral width for isolated attosecond pulse generation from 23 to 93 eV. We demonstrate that phase-matching effects are responsible for the generation of isolated attosecond pulses, even in conditions when single-atom response yields an attosecond pulse train.

  9. In vivo study of human skin using pulsed terahertz radiation

    International Nuclear Information System (INIS)

    Pickwell, E; Cole, B E; Fitzgerald, A J; Pepper, M; Wallace, V P

    2004-01-01

    Studies in terahertz (THz) imaging have revealed a significant difference between skin cancer (basal cell carcinoma) and healthy tissue. Since water has strong absorptions at THz frequencies and tumours tend to have different water content from normal tissue, a likely contrast mechanism is variation in water content. Thus, we have previously devised a finite difference time-domain (FDTD) model which is able to closely simulate the interaction of THz radiation with water. In this work we investigate the interaction of THz radiation with normal human skin on the forearm and palm of the hand in vivo. We conduct the first ever systematic in vivo study of the response of THz radiation to normal skin. We take in vivo reflection measurements of normal skin on the forearm and palm of the hand of 20 volunteers. We compare individual examples of THz responses with the mean response for the areas of skin under investigation. Using the in vivo data, we demonstrate that the FDTD model can be applied to biological tissue. In particular, we successfully simulate the interaction of THz radiation with the volar forearm. Understanding the interaction of THz radiation with normal skin will form a step towards developing improved imaging algorithms for diagnostic detection of skin cancer and other tissue disorders using THz radiation

  10. In vivo study of human skin using pulsed terahertz radiation

    Energy Technology Data Exchange (ETDEWEB)

    Pickwell, E [Semiconductor Physics Group, Cavendish Laboratory, Cambridge University, Madingley Road, Cambridge CB3 0HE (United Kingdom); Cole, B E [TeraView Ltd, Unit 302/4 Cambridge Science Park, Cambridge CB4 0WG (United Kingdom); Fitzgerald, A J [TeraView Ltd, Unit 302/4 Cambridge Science Park, Cambridge CB4 0WG (United Kingdom); Pepper, M [Semiconductor Physics Group, Cavendish Laboratory, Cambridge University, Madingley Road, Cambridge CB3 0HE (United Kingdom); Wallace, V P [TeraView Ltd, Unit 302/4 Cambridge Science Park, Cambridge CB4 0WG (United Kingdom)

    2004-05-07

    Studies in terahertz (THz) imaging have revealed a significant difference between skin cancer (basal cell carcinoma) and healthy tissue. Since water has strong absorptions at THz frequencies and tumours tend to have different water content from normal tissue, a likely contrast mechanism is variation in water content. Thus, we have previously devised a finite difference time-domain (FDTD) model which is able to closely simulate the interaction of THz radiation with water. In this work we investigate the interaction of THz radiation with normal human skin on the forearm and palm of the hand in vivo. We conduct the first ever systematic in vivo study of the response of THz radiation to normal skin. We take in vivo reflection measurements of normal skin on the forearm and palm of the hand of 20 volunteers. We compare individual examples of THz responses with the mean response for the areas of skin under investigation. Using the in vivo data, we demonstrate that the FDTD model can be applied to biological tissue. In particular, we successfully simulate the interaction of THz radiation with the volar forearm. Understanding the interaction of THz radiation with normal skin will form a step towards developing improved imaging algorithms for diagnostic detection of skin cancer and other tissue disorders using THz radiation.

  11. Terahertz Coherent Synchrotron Radiation from Femtosecond Laser Modulation of the Electron Beam at the Advanced Light Source

    CERN Document Server

    Byrd, John; Martin, Michael C; Robin, David; Sannibale, Fernando; Schönlein, Robert W; Zholents, Alexander; Zolotorev, Max S

    2005-01-01

    At the Advanced Light Source (ALS), the "femtoslicing" beamline is in operation since 1999 for the production of x-ray synchrotron radiation pulses with femtosecond duration. The mechanism used for generating the short x-ray pulses induces at the same time temporary structures in the electron bunch longitudinal distribution with very short characteristic length. Such structures emit intense coherent synchrotron radiation (CSR) in the terahertz frequency range. This CSR, whose measured intensity is routinely used as a diagnostics for the tune-up of the femtoslicing experiments, represents a potential source of terahertz radiation with very interesting features. Several measurements have been performed for its characterization and in this paper an updated description of the experimental results and of their interpretation is presented.

  12. High density terahertz frequency comb produced by coherent synchrotron radiation

    Science.gov (United States)

    Tammaro, S.; Pirali, O.; Roy, P.; Lampin, J.-F.; Ducournau, G.; Cuisset, A.; Hindle, F.; Mouret, G.

    2015-07-01

    Frequency combs have enabled significant progress in frequency metrology and high-resolution spectroscopy extending the achievable resolution while increasing the signal-to-noise ratio. In its coherent mode, synchrotron radiation is accepted to provide an intense terahertz continuum covering a wide spectral range from about 0.1 to 1 THz. Using a dedicated heterodyne receiver, we reveal the purely discrete nature of this emission. A phase relationship between the light pulses leads to a powerful frequency comb spanning over one decade in frequency. The comb has a mode spacing of 846 kHz, a linewidth of about 200 Hz, a fractional precision of about 2 × 10-10 and no frequency offset. The unprecedented potential of the comb for high-resolution spectroscopy is demonstrated by the accurate determination of pure rotation transitions of acetonitrile.

  13. Spatial properties of a terahertz beam generated from a two-color air plasma

    DEFF Research Database (Denmark)

    Pedersen, Pernille Klarskov; Wang, Tianwu; Buron, Jonas Christian Due

    2013-01-01

    We present a spatial characterization of terahertz (THz) beams generated from a two-color air plasma under different conditions by measuring full 3D beam profiles using a commercial THz camera. We compare two THz beam profiles emitted from plasmas generated by 35 fs and 100 fs laser pulses...... that this reduces the beam waist, and that the beam spot shape changes from Lorentzian to Gaussian. Finally, we observe a forward-propagating Gaussian THz beam by spatially filtering away the conical off-axis radiation with a 1 cm aperture......., and show that the spatial properties of the two THz beams do not change significantly. For the THz beam profile generated by the 35 fs pulse, the spatial effect of eliminating the lower frequencies is investigated by implementing two crossed polarizers working as a high-pass filter. We show...

  14. Generation of longitudinally polarized terahertz pulses with field amplitudes exceeding 2 kV/cm

    Energy Technology Data Exchange (ETDEWEB)

    Cliffe, M. J., E-mail: Matthew.Cliffe@manchester.ac.uk; Rodak, A.; Graham, D. M. [School of Physics and Astronomy and the Photon Science Institute, The University of Manchester, Manchester M13 9PL (United Kingdom); The Cockcroft Institute, Sci-Tech Daresbury, Keckwick Lane, Daresbury, Warrington WA4 4AD (United Kingdom); Jamison, S. P. [The Cockcroft Institute, Sci-Tech Daresbury, Keckwick Lane, Daresbury, Warrington WA4 4AD (United Kingdom); Accelerator Science and Technology Centre, Science and Technology Facilities Council, Darebsury Laboratory, Keckwick Lane, Daresbury, Warrington WA4 4AD (United Kingdom)

    2014-11-10

    We demonstrate the generation of near-single cycle longitudinally polarized terahertz radiation using a large-area radially biased photoconductive antenna with a longitudinal field amplitude in excess of 2 kV/cm. The 76 mm diameter antenna was photo-excited by a 0.5 mJ amplified near-infrared femtosecond laser system and biased with a voltage of up to 100 kV applied over concentric electrodes. Amplitudes for both the transverse and longitudinal field components of the source were measured using a calibrated electro-optic detection scheme. By tightly focusing the radiation emitted from the photoconductive antenna, we obtained a maximum longitudinal field amplitude of 2.22 kV/cm with an applied bias field of 38.5 kV/cm.

  15. Generation of longitudinally polarized terahertz pulses with field amplitudes exceeding 2 kV/cm

    Science.gov (United States)

    Cliffe, M. J.; Rodak, A.; Graham, D. M.; Jamison, S. P.

    2014-11-01

    We demonstrate the generation of near-single cycle longitudinally polarized terahertz radiation using a large-area radially biased photoconductive antenna with a longitudinal field amplitude in excess of 2 kV/cm. The 76 mm diameter antenna was photo-excited by a 0.5 mJ amplified near-infrared femtosecond laser system and biased with a voltage of up to 100 kV applied over concentric electrodes. Amplitudes for both the transverse and longitudinal field components of the source were measured using a calibrated electro-optic detection scheme. By tightly focusing the radiation emitted from the photoconductive antenna, we obtained a maximum longitudinal field amplitude of 2.22 kV/cm with an applied bias field of 38.5 kV/cm.

  16. Generation of longitudinally polarized terahertz pulses with field amplitudes exceeding 2 kV/cm

    International Nuclear Information System (INIS)

    Cliffe, M. J.; Rodak, A.; Graham, D. M.; Jamison, S. P.

    2014-01-01

    We demonstrate the generation of near-single cycle longitudinally polarized terahertz radiation using a large-area radially biased photoconductive antenna with a longitudinal field amplitude in excess of 2 kV/cm. The 76 mm diameter antenna was photo-excited by a 0.5 mJ amplified near-infrared femtosecond laser system and biased with a voltage of up to 100 kV applied over concentric electrodes. Amplitudes for both the transverse and longitudinal field components of the source were measured using a calibrated electro-optic detection scheme. By tightly focusing the radiation emitted from the photoconductive antenna, we obtained a maximum longitudinal field amplitude of 2.22 kV/cm with an applied bias field of 38.5 kV/cm

  17. Terahertz radiation induced chaotic electron transport in semiconductor superlattices with a tilted magnetic field

    International Nuclear Information System (INIS)

    Wang, C.; Wang, F.; Cao, J. C.

    2014-01-01

    Chaotic electron transport in semiconductor superlattice induced by terahertz electric field that is superimposed on a dc electric field along the superlattice axis are studied using the semiclassical motion equations including the effect of dissipation. A magnetic field that is tilted relative to the superlattice axis is also applied to the system. Numerical simulation shows that electrons in superlattice miniband exhibit complicate nonlinear oscillating modes with the influence of terahertz radiation. Transitions between frequency-locking and chaos via pattern forming bifurcations are observed with the varying of terahertz amplitude. It is found that the chaotic regions gradually contract as the dissipation increases. We attribute the appearance of complicate nonlinear oscillation in superlattice to the interaction between terahertz radiation and internal cooperative oscillating mode relative to Bloch oscillation and cyclotron oscillation

  18. Terahertz radiation induced chaotic electron transport in semiconductor superlattices with a tilted magnetic field.

    Science.gov (United States)

    Wang, C; Wang, F; Cao, J C

    2014-09-01

    Chaotic electron transport in semiconductor superlattice induced by terahertz electric field that is superimposed on a dc electric field along the superlattice axis are studied using the semiclassical motion equations including the effect of dissipation. A magnetic field that is tilted relative to the superlattice axis is also applied to the system. Numerical simulation shows that electrons in superlattice miniband exhibit complicate nonlinear oscillating modes with the influence of terahertz radiation. Transitions between frequency-locking and chaos via pattern forming bifurcations are observed with the varying of terahertz amplitude. It is found that the chaotic regions gradually contract as the dissipation increases. We attribute the appearance of complicate nonlinear oscillation in superlattice to the interaction between terahertz radiation and internal cooperative oscillating mode relative to Bloch oscillation and cyclotron oscillation.

  19. Terahertz radiation induced chaotic electron transport in semiconductor superlattices with a tilted magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Wang, C., E-mail: cwang@mail.sim.ac.cn; Wang, F.; Cao, J. C., E-mail: jccao@mail.sim.ac.cn [Key Laboratory of Terahertz Solid-State Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 865 Changning Road, Shanghai 200050 (China)

    2014-09-01

    Chaotic electron transport in semiconductor superlattice induced by terahertz electric field that is superimposed on a dc electric field along the superlattice axis are studied using the semiclassical motion equations including the effect of dissipation. A magnetic field that is tilted relative to the superlattice axis is also applied to the system. Numerical simulation shows that electrons in superlattice miniband exhibit complicate nonlinear oscillating modes with the influence of terahertz radiation. Transitions between frequency-locking and chaos via pattern forming bifurcations are observed with the varying of terahertz amplitude. It is found that the chaotic regions gradually contract as the dissipation increases. We attribute the appearance of complicate nonlinear oscillation in superlattice to the interaction between terahertz radiation and internal cooperative oscillating mode relative to Bloch oscillation and cyclotron oscillation.

  20. Generation of Elliptically Polarized Terahertz Waves from Antiferromagnetic Sandwiched Structure.

    Science.gov (United States)

    Zhou, Sheng; Zhang, Qiang; Fu, Shu-Fang; Wang, Xuan-Zhang; Song, Yu-Ling; Wang, Xiang-Guang; Qu, Xiu-Rong

    2018-04-01

    The generation of elliptically polarized electromagnetic wave of an antiferromagnetic (AF)/dielectric sandwiched structure in the terahertz range is studied. The frequency and external magnetic field can change the AF optical response, resulting in the generation of elliptical polarization. An especially useful geometry with high levels of the generation of elliptical polarization is found in the case where an incident electromagnetic wave perpendicularly illuminates the sandwiched structure, the AF anisotropy axis is vertical to the wave-vector and the external magnetic field is pointed along the wave-vector. In numerical calculations, the AF layer is FeF2 and the dielectric layers are ZnF2. Although the effect originates from the AF layer, it can be also influenced by the sandwiched structure. We found that the ZnF2/FeF2/ZnF2 structure possesses optimal rotation of the principal axis and ellipticity, which can reach up to about thrice that of a single FeF2 layer.

  1. Modeling of terahertz radiation emission from a free-electron laser

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Suresh C.; Panwar, Jyotsna; Sharma, Rinku [Department of Applied Physics, Delhi Technological University, Delhi (India)

    2017-05-15

    In this article, we report the generation of terahertz (THz) radiation using the interaction of a laser-modulated relativistic electron beam (REB) with a surface plasma wave. Two laser beams propagating through the modulator interact with the REB, leading to velocity modulation of the beam. This results in pre-bunching of the REB. The pre-bunched beam travels through the drift space, where the velocity modulation translates into density modulation. The density-modulated beam, on interacting with the surface plasma pump wave, acquires an oscillatory velocity that couples with the modulated beam density to give rise to a nonlinear current density which acts as an antenna to give THz radiation. By optimizing the parameters of the beam and the wiggler, we obtain power of the order of 10{sup -4} using the current scheme. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Prism-coupled Cherenkov phase-matched terahertz wave generation using a DAST crystal.

    Science.gov (United States)

    Suizu, Koji; Shibuya, Takayuki; Uchida, Hirohisa; Kawase, Kodo

    2010-02-15

    Terahertz (THz) wave generation based on nonlinear frequency conversion is a promising method for realizing a tunable monochromatic high-power THz-wave source. Unfortunately, many nonlinear crystals have strong absorption in the THz frequency region. This limits efficient and widely tunable THz-wave generation. The Cherenkov phase-matching method is one of the most promising techniques for overcoming these problems. Here, we propose a prism-coupled Cherenkov phase-matching (PCC-PM) method, in which a prism with a suitable refractive index at THz frequencies is coupled to a nonlinear crystal. This has the following advantages. Many crystals can be used as THz-wave emitters; the phase-matching condition inside the crystal does not have to be observed; the absorption of the crystal does not prevent efficient generation of radiation; and pump sources with arbitrary wavelengths can be employed. Here we demonstrate PCC-PM THz-wave generation using the organic crystal 4-dimethylamino-N-metyl-4-stilbazolium tosylate (DAST) and a Si prism coupler. We obtain THz-wave radiation with tunability of approximately 0.1 to 10 THz and with no deep absorption features resulting from the absorption spectrum of the crystal. The obtained spectra did not depend on the pump wavelength in the range 1300 to 1450 nm. This simple technique shows promise for generating THz radiation using a wide variety of nonlinear crystals.

  3. High-energy coherent terahertz radiation emitted by wide-angle electron beams from a laser-wakefield accelerator

    Science.gov (United States)

    Yang, Xue; Brunetti, Enrico; Jaroszynski, Dino A.

    2018-04-01

    High-charge electron beams produced by laser-wakefield accelerators are potentially novel, scalable sources of high-power terahertz radiation suitable for applications requiring high-intensity fields. When an intense laser pulse propagates in underdense plasma, it can generate femtosecond duration, self-injected picocoulomb electron bunches that accelerate on-axis to energies from 10s of MeV to several GeV, depending on laser intensity and plasma density. The process leading to the formation of the accelerating structure also generates non-injected, sub-picosecond duration, 1–2 MeV nanocoulomb electron beams emitted obliquely into a hollow cone around the laser propagation axis. These wide-angle beams are stable and depend weakly on laser and plasma parameters. Here we perform simulations to characterise the coherent transition radiation emitted by these beams if passed through a thin metal foil, or directly at the plasma–vacuum interface, showing that coherent terahertz radiation with 10s μJ to mJ-level energy can be produced with an optical to terahertz conversion efficiency up to 10‑4–10‑3.

  4. Studies on the first-order hyperpolarizability and terahertz generation in 3-nitroaniline

    International Nuclear Information System (INIS)

    Krishnakumar, V.; Nagalakshmi, R.

    2008-01-01

    Single crystals of 3-nitroaniline (C 6 H 6 N 2 O 2 ) also called as m-nitroaniline (m-NA) have been grown by adopting slow evaporation solution growth technique at room temperature using methanol as a solvent. To reveal the microscopic nonlinear optical properties, the first-order hyperpolarizability (β) was evaluated by using the density functional theory (DFT) quantum chemical calculations at B3LYP/3-21 G (d,p) level. According to the results of DFT calculations, the grown crystals exhibit non-zero β values and it might have microscopic nonlinear optical behavior which is seven times more than that of urea. Terahertz (1 THz=10 12 Hz) radiation was also generated in the title organic nonlinear optical crystal using ultra short femtosecond laser

  5. Study of terahertz-radiation-induced DNA damage in human blood leukocytes

    Energy Technology Data Exchange (ETDEWEB)

    Angeluts, A A; Esaulkov, M N; Kosareva, O G; Solyankin, P M; Shkurinov, A P [International Laser Center, M. V. Lomonosov Moscow State University, Moscow (Russian Federation); Gapeyev, A B; Pashovkin, T N [Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region (Russian Federation); Matyunin, S N [Section of Applied Problems at the Presidium of the Russian Academy of Sciences, Moscow (Russian Federation); Nazarov, M M [Institute on Laser and Information Technologies, Russian Academy of Sciences, Shatura, Moscow Region (Russian Federation); Cherkasova, O P [Institute of Laser Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk (Russian Federation)

    2014-03-28

    We have carried out the studies aimed at assessing the effect of terahertz radiation on DNA molecules in human blood leukocytes. Genotoxic testing of terahertz radiation was performed in three different oscillation regimes, the blood leukocytes from healthy donors being irradiated for 20 minutes with the mean intensity of 8 – 200 μW cm{sup -2} within the frequency range of 0.1 – 6.5 THz. Using the comet assay it is shown that in the selected regimes such radiation does not induce a direct DNA damage in viable human blood leukocytes. (biophotonics)

  6. Application of Terahertz Radiation to Soil Measurements: Initial Results

    Science.gov (United States)

    Dworak, Volker; Augustin, Sven; Gebbers, Robin

    2011-01-01

    Developing soil sensors with the possibility of continuous online measurement is a major challenge in soil science. Terahertz (THz) electromagnetic radiation may provide the opportunity for the measurement of organic material density, water content and other soil parameters at different soil depths. Penetration depth and information content is important for a functional soil sensor. Therefore, we present initial research on the analysis of absorption coefficients of four different soil samples by means of THz transmission measurements. An optimized soil sample holder to determine absorption coefficients was used. This setup improves data acquisition because interface reflections can be neglected. Frequencies of 340 GHz to 360 GHz and 1.627 THz to 2.523 THz provided information about an existing frequency dependency. The results demonstrate the potential of this THz approach for both soil analysis and imaging of buried objects. Therefore, the THz approach allows different soil samples to be distinguished according to their different absorption properties so that relations among soil parameters may be established in future. PMID:22163737

  7. Terahertz radiation from accelerating charge carriers in graphene under ultrafast photoexcitation

    Science.gov (United States)

    Rustagi, Avinash; Stanton, C. J.

    2016-11-01

    We study the generation of terahertz (THz) radiation from the acceleration of ultrafast photoexcited charge carriers in graphene in the presence of a dc electric field. Our model is based on calculating the transient current density from the time-dependent distribution function which is determined using the Boltzmann transport equation (BTE) within a relaxation time approximation. We include the time-dependent generation of carriers by the pump pulse by solving for the carrier generation rate using the optical Bloch equations in the rotating wave approximation (RWA). The linearly polarized pump pulse generates an anisotropic distribution of photoexcited carriers in the kx-ky plane. The collision integral in the Boltzmann equation includes a term that leads to the thermalization of carriers via carrier-carrier scattering to an effective temperature above the lattice temperature, as well as a cooling term, which leads to energy relaxation via inelastic carrier-phonon scattering. The radiated signal is proportional to the time derivative of the transient current density. In spite of the fact that the magnitude of the velocity is the same for all the carriers in graphene, there is still emitted radiation from the photoexcited charge carriers with frequency components in the THz range due to a change in the direction of velocity of the photoexcited carriers in the external electric field as well as cooling of the photoexcited carriers on a subpicosecond time scale.

  8. Electrical Versus Optical: Comparing Methods for Detecting Terahertz Radiation Using Neon Lamps

    Science.gov (United States)

    Slocombe, L. L.; Lewis, R. A.

    2018-05-01

    Terahertz radiation impinging on a lit neon tube causes additional ionization of the encapsulated gas. As a result, the electrical current flowing between the electrodes increases and the glow discharge in the tube brightens. These dual phenomena suggest two distinct modes of terahertz sensing. The electrical mode simply involves measuring the electrical current. The optical mode involves monitoring the brightness of the weakly ionized plasma glow discharge. Here, we directly compare the two detection modes under identical experimental conditions. We measure 0.1-THz radiation modulated at frequencies in the range 0.1-10 kHz, for lamp currents in the range 1-10 mA. We find that electrical detection provides a superior signal-to-noise ratio while optical detection has a faster response. Either method serves as the basis of a compact, robust, and inexpensive room-temperature detector of terahertz radiation.

  9. Subluminal and superluminal terahertz radiation in metamaterials with electromagnetically induced transparency.

    Science.gov (United States)

    Bai, Zhengyang; Hang, Chao; Huang, Guoxiang

    2013-07-29

    We propose a scheme to design a new type of optical metamaterial that can mimic the functionality of four-state atomic systems of N-type energy-level configuration with electromagnetically induced transparency (EIT). We show that in such metamaterial a transition from a single EIT to a double EIT of terahertz radiation may be easily achieved by actively tuning the intensity of the infrared pump field or passively tuning the geometrical parameters of resonator structures. In addition, the group velocity of the terahertz radiation can be varied from subluminal to superluminal by changing the pump field intensity. The scheme suggested here may be used to construct chip-scale slow and fast light devices and to realize rapidly responded switching of terahertz radiation at room temperature.

  10. Widely tunable narrow-band coherent Terahertz radiation from an undulator at THU

    Science.gov (United States)

    Su, X.; Wang, D.; Tian, Q.; Liang, Y.; Niu, L.; Yan, L.; Du, Y.; Huang, W.; Tang, C.

    2018-01-01

    There is anxious demand for intense widely tunable narrow-band Terahertz (THz) radiation in scientific research, which is regarded as a powerful tool for the coherent control of matter. We report the generation of widely tunable THz radiation from a planar permanent magnet undulator at Tsinghua University (THU). A relativistic electron beam is compressed by a magnetic chicane into sub-ps bunch length to excite THz radiation in the undulator coherently. The THz frequency can be tuned from 0.4 THz to 10 THz continuously with narrow-band spectrums when the undulator gap ranges from 23 mm to 75 mm. The measured pulse THz radiation energy from 220 pC bunch is 3.5 μJ at 1 THz and tens of μJ pulse energy (corresponding peak power of 10 MW) can be obtained when excited by 1 nC beam extrapolated from the property of coherent radiation. The experimental results agree well with theoretical predictions, which demonstrates a suitable THz source for the many applications that require intense and widely tunable THz sources.

  11. Mobile charge generation dynamics in P3HT: PCBM observed by time-resolved terahertz spectroscopy

    DEFF Research Database (Denmark)

    Cooke, D. G.; Krebs, Frederik C; Jepsen, Peter Uhd

    2012-01-01

    Ultra-broadband time-resolved terahertz spectroscopy is used to examine the sub-ps conductivity dynamics of a conjugated polymer bulk heterojunction film P3HT:PCBM. We directly observe mobile charge generation dynamics on a sub-100 fs time scale.......Ultra-broadband time-resolved terahertz spectroscopy is used to examine the sub-ps conductivity dynamics of a conjugated polymer bulk heterojunction film P3HT:PCBM. We directly observe mobile charge generation dynamics on a sub-100 fs time scale....

  12. On-chip photonic integrated circuit structures for millimeter and terahertz wave signal generation

    NARCIS (Netherlands)

    Gordón, C.; Guzmán, R. C.; Corral, V.; Carpintero, G.; Leijtens, X.

    2015-01-01

    We present two different on-chip photonic integrated circuit (PIC) structures for continuous-wave generation of millimeter and terahertz waves, each one using a different approach. One approach is the optical heterodyne method, using an on-chip arrayed waveguide grating laser (OC-AWGL) which is

  13. Mode coupling in terahertz metamaterials using sub-radiative and super-radiative resonators

    International Nuclear Information System (INIS)

    Qiao, Shen; Zhang, Yaxin; Zhao, Yuncheng; Xu, Gaiqi; Sun, Han; Yang, Ziqiang; Liang, Shixiong

    2015-01-01

    We theoretically and experimentally explored the electromagnetically induced transparency (EIT) mode-coupling in terahertz (THz) metamaterial resonators, in which a dipole resonator with a super-radiative mode is coupled to an inductance-capacitance resonator with a sub-radiative mode. The interference between these two resonators depends on the relative spacing between them, resulting in a tunable transparency window in the absorption spectrum. Mode coupling was experimentally demonstrated for three spacing dependent EIT metamaterials. Transmittance of the transparency windows could be either enhanced or suppressed, producing different spectral linewidths. These spacing dependent mode-coupling metamaterials provide alternative ways to create THz devices, such as filters, absorbers, modulators, sensors, and slow-light devices

  14. A MODEL FOR PRODUCING STABLE, BROADBAND TERAHERTZ COHERENT SYNCHROTRON RADIATION IN STORAGE RINGS

    International Nuclear Information System (INIS)

    Sannibale, Fernando; Byrd, John M.; Loftsdottir, Agusta; Martin, MichaelC.; Venturini, Marco

    2003-01-01

    We present a model for producing stable broadband coherent synchrotron radiation (CSR) in the terahertz frequency region in an electron storage ring. The model includes distortion of bunch shape from the synchrotron radiation (SR), enhancing higher frequency coherent emission and limits to stable emission due to a microbunching instability excited by the SR. We use this model to optimize the performance of a source for CSR emission

  15. Bridging the terahertz gap

    International Nuclear Information System (INIS)

    Davies, Giles; Linfield, Edmund

    2004-01-01

    Over the last century or so, physicists and engineers have progressively explored and conquered the electromagnetic spectrum. Starting with visible light, we have encroached outwards, developing techniques for generating and detecting radiation at both higher and lower frequencies. And as each successive region of the spectrum has been colonized, we have developed technology to exploit the radiation found there. X-rays, for example, are routinely used to image hidden objects. Near-infrared radiation is used in fibre-optic communications and in compact-disc players, while microwaves are used to transmit signals from your mobile phone. But there is one part of the electromagnetic spectrum that has steadfastly resisted our advances. This is the terahertz region, which ranges from frequencies of about 300 GHz to 10 THz (10 x 10 sup 1 sup 2 Hz). This corresponds to wavelengths of between about 1 and 0.03 mm, and lies between the microwave and infrared regions of the spectrum. However, the difficulties involved in making suitably compact terahertz sources and detectors has meant that this region of the spectrum has only begun to be explored thoroughly over the last decade. A particularly intriguing feature of terahertz radiation is that the semiconductor devices that generate radiation at frequencies above and below this range operate in completely different ways. At lower frequencies, microwaves and millimetre- waves can be generated by 'electronic' devices such as those found in mobile phones. At higher frequencies, near-infrared and visible light are generated by 'optical' devices such as semiconductor laser diodes, in which electrons emit light when they jump across the semiconductor band gap. Unfortunately, neither electronic nor optical devices can conveniently be made to work in the terahertz region because the terahertz frequency range sits between the electronic and optical regions of the electromagnetic spectrum. Developing a terahertz source is therefore a

  16. Ultrabroadband terahertz source and beamline based on coherent transition radiation

    Directory of Open Access Journals (Sweden)

    S. Casalbuoni

    2009-03-01

    Full Text Available Coherent transition radiation (CTR in the THz regime is an important diagnostic tool for analyzing the temporal structure of the ultrashort electron bunches needed in ultraviolet and x-ray free-electron lasers. It is also a powerful source of such radiation, covering an exceptionally broad frequency range from about 200 GHz to 100 THz. At the soft x-ray free-electron laser FLASH we have installed a beam transport channel for transition radiation (TR with the intention to guide a large fraction of the radiation to a laboratory outside the accelerator tunnel. The radiation is produced on a screen inside the ultrahigh vacuum beam pipe of the linac, coupled out through a diamond window and transported to the laboratory through an evacuated tube equipped with five focusing and four plane mirrors. The design of the beamline has been based on a thorough analysis of the generation of TR on metallic screens of limited size. The optical propagation of the radiation has been computed taking into account the effects of near-field (Fresnel diffraction. The theoretical description of the TR source is presented in the first part of the paper, while the design principles and the technical layout of the beamline are described in the second part. First experimental results demonstrate that the CTR beamline covers the specified frequency range and preserves the narrow time structure of CTR pulses emitted by short electron bunches.

  17. Observation of terahertz-radiation-induced ionization in a single nano island.

    Science.gov (United States)

    Seo, Minah; Kang, Ji-Hun; Kim, Hyo-Suk; Hyong Cho, Joon; Choi, Jaebin; Min Jhon, Young; Lee, Seok; Hun Kim, Jae; Lee, Taikjin; Park, Q-Han; Kim, Chulki

    2015-05-22

    Terahertz (THz) electromagnetic wave has been widely used as a spectroscopic probe to detect the collective vibrational mode in vast molecular systems and investigate dielectric properties of various materials. Recent technological advances in generating intense THz radiation and the emergence of THz plasmonics operating with nanoscale structures have opened up new pathways toward THz applications. Here, we present a new opportunity in engineering the state of matter at the atomic scale using THz wave and a metallic nanostructure. We show that a medium strength THz radiation of 22 kV/cm can induce ionization of ambient carbon atoms through interaction with a metallic nanostructure. The prepared structure, made of a nano slot antenna and a nano island located at the center, acts as a nanogap capacitor and enhances the local electric field by two orders of magnitudes thereby causing the ionization of ambient carbon atoms. Ionization and accumulation of carbon atoms are also observed through the change of the resonant condition of the nano slot antenna and the shift of the characteristic mode in the spectrum of the transmitted THz waves.

  18. Terahertz Coherent Synchrotron Radiation from Femtosecond Laser Modulation of the Electron Beam at the Advanced Light Source

    International Nuclear Information System (INIS)

    Byrd, John M.; Hao, Zhao; Martin, Michael C.; Robin, David S.; Sannibale, Fernando; Schoenlein, Robert W.; Zholents, Alexander A.; Zolotorev, Max S.

    2005-01-01

    At the Advanced Light Source (ALS), the ''femtoslicing'' beamline is in operation since 1999 for the production of x-ray synchrotron radiation pulses with femtosecond duration. The mechanism used for generating the short x-ray pulses induces at the same time temporary structures in the electron bunch longitudinal distribution with very short characteristic length. Such structures emit intense coherent synchrotron radiation (CSR) in the terahertz frequency range. These CSR pulses were first observed at the ALS, and the measurement of their intensity is now routinely used as a diagnostics for the tune-up of the femtoslicing x-ray experiments. At the same time, these CSR pulses synchronous with the modulating laser, represent a potential source of terahertz radiation with very interesting features. Several measurements have been performed for their characterization and in this paper we present an updated description of the experimental results and of their interpretation. In particular, we include more data on the interesting interaction, previously observed at the ALS, between the slicing and the microbunching instability (MBI), where under particular circumstances, the slicing seems to trigger the onset of the instability

  19. Rectification of terahertz radiation in semiconductor superlattices in the absence of domains

    International Nuclear Information System (INIS)

    Isohätälä, J; Alekseev, K N

    2012-01-01

    We study theoretically the dynamical rectification of a terahertz AC electric field, i.e. the DC current and voltage response to the incident radiation, in strongly coupled semiconductor superlattices. We address the problem of stability against electric field domains: a spontaneous DC voltage is known to appear exactly for parameters for which a spatially homogeneous electron distribution is unstable. We show that by applying a weak direct current bias the rectifier can be switched from a state with zero DC voltage to one with a finite voltage in full absence of domains. The switching occurs near the conditions of dynamical symmetry breaking of an unbiased semiconductor superlattice. Therefore our scheme allows for the generation of DC voltages that would otherwise be unreachable due to domain instabilities. Furthermore, for realistic, highly doped wide miniband superlattices at room temperature, the generated DC field can be nearly quantized, that is, be approximately proportional to an integer multiple of ħω/ea where a is the superlattice period and ω is the AC field frequency. (paper)

  20. Spectral distribution of the efficiency of terahertz difference frequency generation upon collinear propagation of interacting waves in semiconductor crystals

    International Nuclear Information System (INIS)

    Orlov, Sergei N; Polivanov, Yurii N

    2007-01-01

    Dispersion phase matching curves and spectral distributions of the efficiency of difference frequency generation in the terahertz range are calculated for collinear propagation of interacting waves in zinc blende semiconductor crystals (ZnTe, CdTe, GaP, GaAs). The effect of the pump wavelength, the nonlinear crystal length and absorption in the terahertz range on the spectral distribution of the efficiency of difference frequency generation is analysed. (nonlinear optical phenomena)

  1. Analysis of the hydration water around bovine serum albumin using terahertz coherent synchrotron radiation.

    Science.gov (United States)

    Bye, Jordan W; Meliga, Stefano; Ferachou, Denis; Cinque, Gianfelice; Zeitler, J Axel; Falconer, Robert J

    2014-01-09

    Terahertz spectroscopy was used to study the absorption of bovine serum albumin (BSA) in water. The Diamond Light Source operating in a low alpha mode generated coherent synchrotron radiation that covered a useable spectral bandwidth of 0.3-3.3 THz (10-110 cm(-1)). As the BSA concentration was raised, there was a nonlinear change in absorption inconsistent with Beer's law. At low BSA concentrations (0-1 mM), the absorption remained constant or rose slightly. Above a concentration of 1 mM BSA, a steady decrease in absorption was observed, which was followed by a plateau that started at 2.5 mM. Using a overlapping hydration layer model, the hydration layer was estimated to extend 15 Å from the protein. Calculation of the corrected absorption coefficient (αcorr) for the water around BSA by subtracting the excluded volume of the protein provides an alternative approach to studying the hydration layer that provides evidence for complexity in the population of water around BSA.

  2. The spectral analysis of fuel oils using terahertz radiation and chemometric methods

    Science.gov (United States)

    Zhan, Honglei; Zhao, Kun; Zhao, Hui; Li, Qian; Zhu, Shouming; Xiao, Lizhi

    2016-10-01

    The combustion characteristics of fuel oils are closely related to both engine efficiency and pollutant emissions, and the analysis of oils and their additives is thus important. These oils and additives have been found to generate distinct responses to terahertz (THz) radiation as the result of various molecular vibrational modes. In the present work, THz spectroscopy was employed to identify a number of oils, including lubricants, gasoline and diesel, with different additives. The identities of dozens of these oils could be readily established using statistical models based on principal component analysis. The THz spectra of gasoline, diesel, sulfur and methyl methacrylate (MMA) were acquired and linear fittings were obtained. By using chemometric methods, including back propagation, artificial neural network and support vector machine techniques, typical concentrations of sulfur in gasoline (ppm-grade) could be detected, together with MMA in diesel below 0.5%. The absorption characteristics of the oil additives were also assessed using 2D correlation spectroscopy, and several hidden absorption peaks were discovered. The technique discussed herein should provide a useful new means of analyzing fuel oils with various additives and impurities in a non-destructive manner and therefore will be of benefit to the field of chemical detection and identification.

  3. The spectral analysis of fuel oils using terahertz radiation and chemometric methods

    International Nuclear Information System (INIS)

    Zhan, Honglei; Zhao, Kun; Xiao, Lizhi; Zhao, Hui; Li, Qian; Zhu, Shouming

    2016-01-01

    The combustion characteristics of fuel oils are closely related to both engine efficiency and pollutant emissions, and the analysis of oils and their additives is thus important. These oils and additives have been found to generate distinct responses to terahertz (THz) radiation as the result of various molecular vibrational modes. In the present work, THz spectroscopy was employed to identify a number of oils, including lubricants, gasoline and diesel, with different additives. The identities of dozens of these oils could be readily established using statistical models based on principal component analysis. The THz spectra of gasoline, diesel, sulfur and methyl methacrylate (MMA) were acquired and linear fittings were obtained. By using chemometric methods, including back propagation, artificial neural network and support vector machine techniques, typical concentrations of sulfur in gasoline (ppm-grade) could be detected, together with MMA in diesel below 0.5%. The absorption characteristics of the oil additives were also assessed using 2D correlation spectroscopy, and several hidden absorption peaks were discovered. The technique discussed herein should provide a useful new means of analyzing fuel oils with various additives and impurities in a non-destructive manner and therefore will be of benefit to the field of chemical detection and identification. (paper)

  4. Towards terahertz detection and calibration through spontaneous parametric down-conversion in the terahertz idler-frequency range generated by a 795 nm diode laser system

    Directory of Open Access Journals (Sweden)

    Vladimir V. Kornienko

    2018-05-01

    Full Text Available We study a calibration scheme for terahertz wave nonlinear-optical detectors based on spontaneous parametric down-conversion. Contrary to the usual low wavelength pump in the green, we report here on the observation of spontaneous parametric down-conversion originating from an in-growth poled lithium niobate crystal pumped with a continuous wave 50 mW, 795 nm diode laser system, phase-matched to a terahertz frequency idler wave. Such a system is more compact and allows for longer poling periods as well as lower losses in the crystal. Filtering the pump radiation by a rubidium-87 vapor cell allowed the frequency-angular spectra to be obtained down to ∼0.5 THz or ∼1 nm shift from the pump radiation line. The presence of an amplified spontaneous emission “pedestal” in the diode laser radiation spectrum significantly hampers the observation of spontaneous parametric down-conversion spectra, in contrast to conventional narrowband gas lasers. Benefits of switching to longer pump wavelengths are pointed out, such as collinear optical-terahertz phase-matching in bulk crystals.

  5. Towards terahertz detection and calibration through spontaneous parametric down-conversion in the terahertz idler-frequency range generated by a 795 nm diode laser system

    Science.gov (United States)

    Kornienko, Vladimir V.; Kitaeva, Galiya Kh.; Sedlmeir, Florian; Leuchs, Gerd; Schwefel, Harald G. L.

    2018-05-01

    We study a calibration scheme for terahertz wave nonlinear-optical detectors based on spontaneous parametric down-conversion. Contrary to the usual low wavelength pump in the green, we report here on the observation of spontaneous parametric down-conversion originating from an in-growth poled lithium niobate crystal pumped with a continuous wave 50 mW, 795 nm diode laser system, phase-matched to a terahertz frequency idler wave. Such a system is more compact and allows for longer poling periods as well as lower losses in the crystal. Filtering the pump radiation by a rubidium-87 vapor cell allowed the frequency-angular spectra to be obtained down to ˜0.5 THz or ˜1 nm shift from the pump radiation line. The presence of an amplified spontaneous emission "pedestal" in the diode laser radiation spectrum significantly hampers the observation of spontaneous parametric down-conversion spectra, in contrast to conventional narrowband gas lasers. Benefits of switching to longer pump wavelengths are pointed out, such as collinear optical-terahertz phase-matching in bulk crystals.

  6. Field transients of coherent terahertz synchrotron radiation accessed via time-resolving and correlation techniques

    Energy Technology Data Exchange (ETDEWEB)

    Pohl, A.; Hübers, H.-W. [Humboldt-Universität zu Berlin, Institute of Physics, Newtonstraße 15, 12489 Berlin (Germany); Institute of Optical Sensor Systems, German Aerospace Center (DLR), Rutherfordstrasse 29, 12489 Berlin (Germany); Semenov, A. [Institute of Optical Sensor Systems, German Aerospace Center (DLR), Rutherfordstrasse 29, 12489 Berlin (Germany); Hoehl, A.; Ulm, G. [Physikalisch-Technische Bundesanstalt (PTB), Abbestraße 2-12, 10587 Berlin (Germany); Ries, M.; Wüstefeld, G. [Helmholz-Zentrum Berlin, Albert-Einstein-Str. 15, 12489 Berlin (Germany); Ilin, K.; Thoma, P.; Siegel, M. [Institute of Micro- and Nanoelectronic Systems, Karlsruhe Institute of Technology (KIT), Hertzstrasse 16, 76187 Karlsruhe (Germany)

    2016-03-21

    Decaying oscillations of the electric field in repetitive pulses of coherent synchrotron radiation in the terahertz frequency range was evaluated by means of time-resolving and correlation techniques. Comparative analysis of real-time voltage transients of the electrical response and interferograms, which were obtained with an ultrafast zero-bias Schottky diode detector and a Martin-Puplett interferometer, delivers close values of the pulse duration. Consistent results were obtained via the correlation technique with a pair of Golay Cell detectors and a pair of resonant polarisation-sensitive superconducting detectors integrated on one chip. The duration of terahertz synchrotron pulses does not closely correlate with the duration of single-cycle electric field expected for the varying size of electron bunches. We largely attribute the difference to the charge density oscillations in electron bunches and to the low-frequency spectral cut-off imposed by both the synchrotron beamline and the coupling optics of our detectors.

  7. Handbook of terahertz technologies devices and applications

    CERN Document Server

    Song, Ho-Jin

    2015-01-01

    Terahertz waves, which lie in the frequency range of 0.1-10 THz, have long been investigated in a few limited fields, such as astronomy, because of a lack of devices for their generation and detection. Several technical breakthroughs made over the last couple of decades now allow us to radiate and detect terahertz waves more easily, which has triggered the search for new uses of terahertz waves in many fields, such as bioscience, security, and information and communications technology. The book covers some of the technical breakthroughs in terms of device technologies. It discusses not only th

  8. Antenna-coupled terahertz radiation from joule-heated single-wall carbon nanotubes

    Directory of Open Access Journals (Sweden)

    M. Muthee

    2011-12-01

    Full Text Available In this letter an experimental method is introduced that allows detection of terahertz (THz radiation from arrays of joule-heated Single-Walled Carbon Nanotubes (SWCNTs, by coupling this radiation through integrated antennas and a silicon lens. The radiation forms a diffraction-limited beam with a total maximum radiated power of 450 nW, significantly greater than the power estimated from Nyquist thermal noise (8 nW. The physical radiation process is unknown at this stage, but possible explanations for the high radiated power are discussed briefly. The emission has a typical bandwidth of 1.2 THz and can be tuned to different frequencies by changing the dimensions of the antennas. Arrays of the devices could be integrated in CMOS integrated circuits, and find application in THz systems, such as in near-range medical imaging.

  9. Non-uniform absorption of terahertz radiation on superconducting hot electron bolometer microbridges

    International Nuclear Information System (INIS)

    Miao, W.; Zhang, W.; Zhong, J. Q.; Shi, S. C.; Delorme, Y.; Lefevre, R.; Feret, A.; Vacelet, T.

    2014-01-01

    We interpret the experimental observation of a frequency-dependence of superconducting hot electron bolometer (HEB) mixers by taking into account the non-uniform absorption of the terahertz radiation on the superconducting HEB microbridge. The radiation absorption is assumed to be proportional to the local surface resistance of the HEB microbridge, which is computed using the Mattis-Bardeen theory. With this assumption the dc and mixing characteristics of a superconducting niobium-nitride (NbN) HEB device have been modeled at frequencies below and above the equilibrium gap frequency of the NbN film

  10. Frequency-tunable terahertz wave generation via excitation of phonon-polaritons in GaP

    CERN Document Server

    Tanabé, T; Nishizawa, J I; Saitô, K; Kimura, T

    2003-01-01

    High-power, wide-frequency-tunable terahertz waves were generated based on difference-frequency generation in GaP crystals with small-angle noncollinear phase matching. The tunable frequency range was as wide as 0.5-7 THz, and the peak power remained high, near 100 mW, over most of the frequency region. The tuning properties were well described by the dispersion relationship for the phonon-polariton mode of GaP up to 6 THz. We measured the spectra of crystal polyethylene and crystal quartz with high resolution using this THz-wave source.

  11. Frequency-tunable terahertz wave generation via excitation of phonon-polaritons in GaP

    International Nuclear Information System (INIS)

    Tanabe, Tadao; Suto, Ken; Nishizawa, Jun-ichi; Saito, Kyosuke; Kimura, Tomoyuki

    2003-01-01

    High-power, wide-frequency-tunable terahertz waves were generated based on difference-frequency generation in GaP crystals with small-angle noncollinear phase matching. The tunable frequency range was as wide as 0.5-7 THz, and the peak power remained high, near 100 mW, over most of the frequency region. The tuning properties were well described by the dispersion relationship for the phonon-polariton mode of GaP up to 6 THz. We measured the spectra of crystal polyethylene and crystal quartz with high resolution using this THz-wave source

  12. On the generation of electromagnetic waves in the terahertz frequency range

    International Nuclear Information System (INIS)

    Namiot, V.A.; Shchurova, L.Yu.

    2011-01-01

    It is shown that a thin dielectric plate, which can act as an open dielectric waveguide, it is possible to produce amplification and generation of electromagnetic waves with frequencies in the terahertz range. For this purpose, we propose using a dielectric plate with a corrugated surface, in which case the electric field of the transverse electromagnetic wave in the waveguide has a periodic spatial structure in the local area near to the corrugation. Terahertz electromagnetic waves are excited by a beam of electrons moving in vacuum along the dielectric plate at a small distance from its corrugated surface. Corrugation period is chosen in order to ensure the most effective interaction of the electron beam with the first harmonic of the electric field induced by the corrugation. Amplification and generation of electromagnetic waves propagating in a dielectric waveguide is realized as a result of deceleration of the electron beam by a wave electric field induced by a corrugated dielectric surface in the zone near the corrugation. We discuss possible ways to create electron beams with the desired characteristics. We offer a way to stabilize the beam position above the plate, avoiding the bombardment of the plate by electrons. It is shown that it is possible to significantly increase the efficiency of the device through the recovery of energy that remains in the electrons after their interaction with the wave. -- Highlights: → We propose a scheme of a generator of radio waves in the terahertz range. → This scheme includes a corrugated dielectric plate, which can act as an open waveguide. → A strip electron beam is in vacuum near the dielectric corrugated surface. → Generation is achieved by converting electrons' energy into electromagnetic energy. → The waveguide wave extends perpendicularly to electron motion.

  13. Harmonics generation of a terahertz wakefield free-electron laser from a dielectric loaded waveguide excited by a direct current electron beam.

    Science.gov (United States)

    Li, Weiwei; Lu, Yalin; He, Zhigang; Jia, Qika; Wang, Lin

    2016-06-01

    We propose to generate high-power terahertz (THz) radiation from a cylindrical dielectric loaded waveguide (DLW) excited by a direct-current electron beam with the harmonics generation method. The DLW supports a discrete set of modes that can be excited by an electron beam passing through the structure. The interaction of these modes with the co-propagating electron beam results in micro-bunching and the coherent enhancement of the wakefield radiation, which is dominated by the fundamental mode. By properly choosing the parameters of DLW and beam energy, the high order modes can be the harmonics of the fundamental one; thus, high frequency radiation corresponding to the high order modes will benefit from the dominating bunching process at the fundamental eigenfrequency and can also be coherently excited. With the proposed method, high power THz radiation can be obtained with an easily achievable electron beam and a large DLW structure.

  14. Generator for ionizing radiation

    International Nuclear Information System (INIS)

    Romanovskij, V.F.; Panasjuk, V.S.; Stepanov, B.M.; Ovtscharov, A.M.; Akimov, J.A.

    1979-01-01

    The X-ray, electron, or neutron generator contains a radiation source with an accelerating tube, whose shell encloses a resonance transformer, a subdivided tube insulator and a high-tension electrode for the accelerating tube. The accelerating tube can be evacuated. The high-tension winding of the resonance transformer lies within the tube insulator of the accelerating tube and the evacuated space between resonance transformer and tube insulator. The generator may be applied in medicine, in geophysical research or for activation analysis of materials. (DG) 891 HP/DG 892 BRE [de

  15. Enhanced transmission of terahertz radiation through a periodically modulated slab of layered superconductor

    International Nuclear Information System (INIS)

    Kadygrob, D V; Slipchenko, T M; Yampol'skii, V A; Makarov, N M; Pérez-Rodríguez, F

    2013-01-01

    We predict the enhanced transparency of a modulated slab of layered superconductor for terahertz radiation due to the diffraction of an incident wave and the resonance excitation of eigenmodes. The electromagnetic field is transferred from the irradiated side of the slab to the other by excited waveguide modes (WGMs) which do not decay in layered superconductors, in contrast to metals, where the enhanced light transmission is caused by the excitation of evanescent surface waves. We show that a series of resonance peaks can be observed in the dependence of transmittance on the incidence angle when the dispersion curve of the diffracted wave crosses successive dispersion curves for the WGMs. (paper)

  16. Asymmetric devices based on carbon nanotubes for terahertz-range radiation detection

    Energy Technology Data Exchange (ETDEWEB)

    Fedorov, G. E., E-mail: gefedorov@mail.ru; Stepanova, T. S.; Gazaliev, A. Sh.; Gaiduchenko, I. A.; Kaurova, N. S.; Voronov, B. M.; Goltzman, G. N. [Moscow State Pedagogical University (Russian Federation)

    2016-12-15

    Various asymmetric detecting devices based on carbon nanotubes (CNTs) are studied. The asymmetry is understood as inhomogeneous properties along the conducting channel. In the first type of devices, an inhomogeneous morphology of the CNT grid is used. In the second type of devices, metals with highly varying work functions are used as the contact material. The relation between the sensitivity and detector configuration is analyzed. Based on the data obtained, approaches to the development of an efficient detector of terahertz radiation, based on carbon nanotubes are proposed.

  17. Anomalous response of superconducting titanium nitride resonators to terahertz radiation

    International Nuclear Information System (INIS)

    Bueno, J.; Baselmans, J. J. A; Coumou, P. C. J. J.; Zheng, G.; Visser, P. J. de; Klapwijk, T. M.; Driessen, E. F. C.; Doyle, S.

    2014-01-01

    We present an experimental study of kinetic inductance detectors (KIDs) fabricated of atomic layer deposited TiN films and characterized at radiation frequencies of 350 GHz. The responsivity to radiation is measured and found to increase with the increase in radiation powers, opposite to what is expected from theory and observed for hybrid niobium titanium nitride/aluminium (NbTiN/Al) and all-aluminium (all-Al) KIDs. The noise is found to be independent of the level of the radiation power. The noise equivalent power improves with higher radiation powers, also opposite to what is observed and well understood for hybrid NbTiN/Al and all-Al KIDs. We suggest that an inhomogeneous state of these disordered superconductors should be used to explain these observations

  18. Anomalous response of superconducting titanium nitride resonators to terahertz radiation

    Energy Technology Data Exchange (ETDEWEB)

    Bueno, J., E-mail: j.bueno@sron.nl; Baselmans, J. J. A [SRON, Netherlands Institute of Space Research, Utrecht (Netherlands); Coumou, P. C. J. J.; Zheng, G. [Kavli Institute of Nanoscience, Delft University of Technology, Delft (Netherlands); Visser, P. J. de [SRON, Netherlands Institute of Space Research, Utrecht (Netherlands); Kavli Institute of Nanoscience, Delft University of Technology, Delft (Netherlands); Klapwijk, T. M. [Kavli Institute of Nanoscience, Delft University of Technology, Delft (Netherlands); Physics Department, Moscow State Pedagogical University, 119991 Moscow (Russian Federation); Driessen, E. F. C. [Université Grenoble Alpes, INAC-SPSMS, F-38000 Grenoble (France); CEA, INAC-SPSMS, F-38000 Grenoble (France); Doyle, S. [Cardiff University, School of Physics and Astronomy, Queens Buildings, Cardiff CF24 3AA (United Kingdom)

    2014-11-10

    We present an experimental study of kinetic inductance detectors (KIDs) fabricated of atomic layer deposited TiN films and characterized at radiation frequencies of 350 GHz. The responsivity to radiation is measured and found to increase with the increase in radiation powers, opposite to what is expected from theory and observed for hybrid niobium titanium nitride/aluminium (NbTiN/Al) and all-aluminium (all-Al) KIDs. The noise is found to be independent of the level of the radiation power. The noise equivalent power improves with higher radiation powers, also opposite to what is observed and well understood for hybrid NbTiN/Al and all-Al KIDs. We suggest that an inhomogeneous state of these disordered superconductors should be used to explain these observations.

  19. EDITORIAL: Terahertz nanotechnology Terahertz nanotechnology

    Science.gov (United States)

    Demming, Anna; Tonouchi, Masayoshi; Reno, John L.

    2013-05-01

    A useful synergy is being established between terahertz research and nanotechnology. High power sources [1-3] and detectors [4] in what was once considered the terahertz 'frequency gap' [5] in the electromagnetic spectrum have stimulated research with huge potential benefits in a range of industries including food, medicine and security, as well as fundamental physics and astrophysics. This special section, with guest editors Masayoshi Tonouchi and John Reno, gives a glimpse of the new horizons nanotechnology is broaching in terahertz research. While the wavelengths relevant to the terahertz domain range from hundreds of micrometres to millimetres, structures at the nanoscale reveal interesting low energy dynamics in this region. As a result terahertz spectroscopy techniques are becoming increasingly important in nanomaterial characterization, as demonstrated in this special section by colleagues at the University of Oxford in the UK and the Australian National University. They use terahertz spectroscopy to identify the best nanostructure parameters for specific applications [6]. The low energy dynamics in nanostructures also makes them valuable tools for terahertz detection [7]. In addition the much sought after terahertz detection over broadband frequency ranges has been demonstrated, providing versatility that has been greatly in demand, particularly in spectroscopy applications [8, 9]. Also in this special section, researchers in Germany and China tackle some of the coupling issues in terahertz time domain spectroscopy with an emitter specifically well suited for systems operated with an amplified fibre [3]. 'In medical imaging, the advantage of THz radiation is safety, because its energy is much lower than the ionization energy of biological molecules, in contrast to hazardous x-ray radiation,' explains Joo-Hiuk Son from the University of Seoul in Korea in his review [10]. As he also points out, the rotational and vibrational energies of water molecules are

  20. Mobile Charge Generation Dynamics in P3HT:PCBM Observed by Time-Resolved Terahertz Spectroscopy

    DEFF Research Database (Denmark)

    Cooke, D. G.; Krebs, Frederik C; Jepsen, Peter Uhd

    2012-01-01

    Ultra-broadband time-resolved terahertz spectroscopy is used to examine the sub-ps conductivity dynamics of a conjugated polymer bulk heterojunction film P3HT:PCBM. We directly observe mobile charge generation dynamics on a sub-100 fs time scale.......Ultra-broadband time-resolved terahertz spectroscopy is used to examine the sub-ps conductivity dynamics of a conjugated polymer bulk heterojunction film P3HT:PCBM. We directly observe mobile charge generation dynamics on a sub-100 fs time scale....

  1. Generator for ionising radiation

    International Nuclear Information System (INIS)

    Romanovsky, V.F.; Panasjuk, V.S.; Stepanov, B.M.; Ovcharov, A.M.; Akimov, J.A.

    1979-01-01

    The generator for ionising radiation wherein a transmitter for ionising radiation contains a resonance transformer wherein the field coil is composed of a low voltage outside portion and a transformer coil, electrically connected with an electrically conducting housing of the resonance transformer, and an acclerating tube wherein the high voltage electrode is coupled with the high voltage end of the transformer coil of the resonance transformer and fixed to one of the ends of the tubular insulator of the accelerator tube, wherein the low voltage electrode is electrically connected with the housing of the resonance transformer and a source of charged particles is introduced into the evacuated inner space of the acceleration tube and electrically connected with one of the electrodes thereof, is described. (G.C.)

  2. Generating, Separating and Polarizing Terahertz Vortex Beams via Liquid Crystals with Gradient-Rotation Directors

    Directory of Open Access Journals (Sweden)

    Shi-Jun Ge

    2017-10-01

    Full Text Available Liquid crystal (LC is a promising candidate for terahertz (THz devices. Recently, LC has been introduced to generate THz vortex beams. However, the efficiency is intensely dependent on the incident wavelength, and the transformed THz vortex beam is usually mixed with the residual component. Thus, a separating process is indispensable. Here, we introduce a gradient blazed phase, and propose a THz LC forked polarization grating that can simultaneously generate and separate pure THz vortices with opposite circular polarization. The specific LC gradient-rotation directors are implemented by a photoalignment technique. The generated THz vortex beams are characterized with a THz imaging system, verifying features of polarization controllability. This work may pave a practical road towards generating, separating and polarizing THz vortex beams, and may prompt applications in THz communications, sensing and imaging.

  3. Single-Cycle Terahertz Pulse Generation from OH1 Crystal via Cherenkov Phase Matching

    Science.gov (United States)

    Uchida, Hirohisa; Oota, Kengo; Okimura, Koutarou; Kawase, Kodo; Takeya, Kei

    2018-06-01

    OH1 crystal is an organic nonlinear optical crystal with a large nonlinear optical constant. However, it has dispersion of refractive indices in the terahertz (THz) frequency. This limits the frequencies that satisfy the phase matching conditions for THz wave generation. In this study, we addressed the phase matching conditions for THz wave generation by combining an OH1 crystal with prism-coupled Cherenkov phase matching. We observed the generation of single-cycle THz pulses with a spectrum covering a frequency range of 3 THz. These results prove that combining prism-coupled Cherenkov phase matching with nonlinear optical crystals yields a THz wave generation method that is insusceptible to crystal dispersion.

  4. Investigation of radiant millimeter wave/terahertz radiation from low-infrared signature targets

    Science.gov (United States)

    Aytaç, B.; Alkuş, Ü.; Sivaslıgil, M.; Şahin, A. B.; Altan, H.

    2017-10-01

    Millimeter (mm) and sub-mm wave radiation is increasingly becoming a region of interest as better methods are developed to detect in this wavelength range. The development of sensitive focal plane array (FPA) architectures as well as single pixel scanners has opened up a new field of passive detection and imaging. Spectral signatures of objects, a long standing area of interest in the Short Wave Infrared (SWIR), Mid-Wave (MWIR) and Long Wave-IR (LWIR) bands can now be assessed in the mm-wave/terahertz (THz) region. The advantage is that this form of radiation is not as adversely affected by poor atmospheric conditions compared to other bands. In this study, a preliminary experiment in a laboratory environment is performed to assess the radiance from targets with low infrared signatures in the millimeter wave/terahertz (THz) band (<1 THz). The goal of this approach is to be able to model the experimental results to better understand the mm-wave/THz signature of targets with low observability in the IR bands.

  5. Energy harvesting devices for harvesting energy from terahertz electromagnetic radiation

    Science.gov (United States)

    Novack, Steven D.; Kotter, Dale K.; Pinhero, Patrick J.

    2012-10-09

    Methods, devices and systems for harvesting energy from electromagnetic radiation are provided including harvesting energy from electromagnetic radiation. In one embodiment, a device includes a substrate and one or more resonance elements disposed in or on the substrate. The resonance elements are configured to have a resonant frequency, for example, in at least one of the infrared, near-infrared and visible light spectra. A layer of conductive material may be disposed over a portion of the substrate to form a ground plane. An optical resonance gap or stand-off layer may be formed between the resonance elements and the ground plane. The optical resonance gap extends a distance between the resonance elements and the layer of conductive material approximately one-quarter wavelength of a wavelength of the at least one resonance element's resonant frequency. At least one energy transfer element may be associated with the at least one resonance element.

  6. Dispersion characteristics of planar grating with arbitrary grooves for terahertz Smith-Purcell radiation

    International Nuclear Information System (INIS)

    Cao, Miaomiao; Li, Ke; Liu, Wenxin; Wang, Yong

    2015-01-01

    In this paper, a novel method of getting the dispersion relations in planar grating with arbitrary grooves for terahertz Smith-Purcell radiation is investigated analytically. The continuous profile of the groove is approximately replaced by a series of rectangular steps. By making use of field matches method and the continuity of transverse admittance, the universal dispersion equation for grating with arbitrarily shaped grooves is derived. By solving the dispersion equation in presence of electron beam, the growth rate is obtained directly and the dependence on beam parameters is analyzed. Comparisons of the dispersion characteristics among some special groove shapes have been made by numerical calculation. The results show that the rectangular-step approximation method provides a novel approach to obtain the universal dispersion relation for grating with arbitrary grooves for Smith-Purcell radiation

  7. Terahertz-wave surface-emitted difference-frequency generation without quasi-phase-matching technique.

    Science.gov (United States)

    Avetisyan, Yuri H

    2010-08-01

    A scheme of terahertz (THz)-wave surface-emitted difference-frequency generation (SEDFG), which lacks the drawbacks associated with the usage of periodically orientation-inverted structures, is proposed. It is shown that both material birefringence of the bulk LiNbO(3) crystal and modal birefringence of GaAs/AlAs waveguide are sufficient to obtain SEDFG up to a frequency of approximately 3THz. The simplicity of the proposed scheme, along with the fact that there is a much smaller THz-wave decay in nonlinear crystal, makes it a good candidate for the practical realization of efficient THz generation. The use of a GaAs waveguide with an oxidized AlAs layer is proposed for enhanced THz-wave SEDFG in the vicinity of the GaAs polariton resonance at 8THz.

  8. Transmission of terahertz radiation by anisotropic MWCNT/polystyrene composite films

    Energy Technology Data Exchange (ETDEWEB)

    Okotrub, A.V.; Bulusheva, L.G. [Nikolaev Institute of Inorganic Chemistry, SB RAS, 3 Acad. Lavrentiev Ave., 630090 Novosibirsk (Russian Federation); Novosibirsk State Technical University, 20 Karl Marx Ave., 630092 Novosibirsk (Russian Federation); Kubarev, V.V. [Budker Institute of Nuclear Physics, SB RAS, 11 Acad. Lavrentiev Ave., 630090 Novosibirsk (Russian Federation); Novosibirsk State University, 2 Pirogova st., 630090 Novosibirsk (Russian Federation); Kanygin, M.A.; Sedelnikova, O.V. [Nikolaev Institute of Inorganic Chemistry, SB RAS, 3 Acad. Lavrentiev Ave., 630090 Novosibirsk (Russian Federation)

    2011-11-15

    Anisotropic composite materials have been prepared by repeated forge rolling of polystyrene and carbon nanotubes (CNTs) with length of {proportional_to}65 {mu}m. Transmission spectra of the composites were recorded for two different polarizations of the electric field. Obtained data indicated that the forge rolling resulted in a predominant orientation of CNTs in polymer matrix. Anisotropic response of the composites was measured at 130 {mu}m wavelength on the Novosibirsk terahertz free electron laser and angular dependence of the transmitted light was determined. Absorption spectrum showed no strong resonance features and it was interpreted by CNTs breaking and agglomeration of CNT fragments during the composite fabrication procedure. Based on classical theory of scattering, considered the scatters as electromagnetic antennas, the size distribution of CNTs in composites was found. Anisotropy of terahertz radiation transmitted from MWCNT/polystyrene composite film on the Novosibirsk free electron laser at 130 {mu}m wavelength. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Modelling the propagation of terahertz radiation through a tissue simulating phantom

    International Nuclear Information System (INIS)

    Walker, Gillian C; Berry, Elizabeth; Smye, Stephen W; Zinov'ev, Nick N; Fitzgerald, Anthony J; Miles, Robert E; Chamberlain, Martyn; Smith, Michael A

    2004-01-01

    Terahertz (THz) frequency radiation, 0.1 THz to 20 THz, is being investigated for biomedical imaging applications following the introduction of pulsed THz sources that produce picosecond pulses and function at room temperature. Owing to the broadband nature of the radiation, spectral and temporal information is available from radiation that has interacted with a sample; this information is exploited in the development of biomedical imaging tools and sensors. In this work, models to aid interpretation of broadband THz spectra were developed and evaluated. THz radiation lies on the boundary between regions best considered using a deterministic electromagnetic approach and those better analysed using a stochastic approach incorporating quantum mechanical effects, so two computational models to simulate the propagation of THz radiation in an absorbing medium were compared. The first was a thin film analysis and the second a stochastic Monte Carlo model. The Cole-Cole model was used to predict the variation with frequency of the physical properties of the sample and scattering was neglected. The two models were compared with measurements from a highly absorbing water-based phantom. The Monte Carlo model gave a prediction closer to experiment over 0.1 to 3 THz. Knowledge of the frequency-dependent physical properties, including the scattering characteristics, of the absorbing media is necessary. The thin film model is computationally simple to implement but is restricted by the geometry of the sample it can describe. The Monte Carlo framework, despite being initially more complex, provides greater flexibility to investigate more complicated sample geometries

  10. High-order sideband generation in a semiconductor quantum well driven by two orthogonal terahertz fields

    Science.gov (United States)

    Yan, Jie-Yun

    2017-08-01

    The theory of excitonic high-order sideband generation (HSG) in a semiconductor quantum well irradiated by two orthogonal terahertz (THz) fields (one frequency is an integral multiple of the other) is presented. The exact analytical solution to the sideband spectrum is given with the help of the generalized Bessel functions. As a special case, the HSG when the frequencies of these two THz fields are the same is derived and its dependence on the ellipticity of the THz field is discussed. The theory could explain the experiments, especially concerning the sensitive dependence of HSG signals on the ellipticity of the THz field: the signals are strong when the THz field has a linear polarization and totally vanish in case of a circular polarization. More interestingly, it was found that the strongest signal is not produced in the case of linear polarization for some sidebands. The theory is supported by numerical calculations.

  11. Terahertz Radiation Heterodyne Detector Using Two-Dimensional Electron Gas in a GaN Heterostructure

    Science.gov (United States)

    Karasik, Boris S.; Gill, John J.; Mehdi, Imran; Crawford, Timothy J.; Sergeev, Andrei V.; Mitin, Vladimir V.

    2012-01-01

    High-resolution submillimeter/terahertz spectroscopy is important for studying atmospheric and interstellar molecular gaseous species. It typically uses heterodyne receivers where an unknown (weak) signal is mixed with a strong signal from the local oscillator (LO) operating at a slightly different frequency. The non-linear mixer devices for this frequency range are unique and are not off-the-shelf commercial products. Three types of THz mixers are commonly used: Schottky diode, superconducting hot-electron bolometer (HEB), and superconductor-insulation-superconductor (SIS) junction. A HEB mixer based on the two-dimensional electron gas (2DEG) formed at the interface of two slightly dissimilar semiconductors was developed. This mixer can operate at temperatures between 100 and 300 K, and thus can be used with just passive radiative cooling available even on small spacecraft.

  12. Theoretical Investigation of Current Instabilities and Terahertz Oscillations in a Two-Dimensional Electron Fluid

    National Research Council Canada - National Science Library

    Dyakonov, M

    1997-01-01

    The purpose of this work is to develop further the theory of novel mechanisms for generation and detection of electromagnetic radiation in the terahertz range using the plasma oscillations of the two...

  13. Terahertz ptychography.

    Science.gov (United States)

    Valzania, Lorenzo; Feurer, Thomas; Zolliker, Peter; Hack, Erwin

    2018-02-01

    We realized a phase retrieval technique using terahertz (THz) radiation as an alternative to THz digital holography, named THz ptychography. Ptychography has been used in x-ray imaging as a groundbreaking improvement of conventional coherent diffraction imaging. Here we show that ptychography can be performed at THz frequencies too. We reconstructed an amplitude and a phase object with both simulated and real data. Lateral resolution accounts to <2λ, while depth variations as low as λ/30 can be assessed.

  14. Enhanced plasma wave detection of terahertz radiation using multiple high electron-mobility transistors connected in series

    KAUST Repository

    Elkhatib, Tamer A.; Kachorovskiǐ, Valentin Yu; Stillman, William J.; Veksler, Dmitry B.; Salama, Khaled N.; Zhang, Xicheng; Shur, Michael S.

    2010-01-01

    We report on enhanced room-temperature detection of terahertz radiation by several connected field-effect transistors. For this enhanced nonresonant detection, we have designed, fabricated, and tested plasmonic structures consisting of multiple InGaAs/GaAs pseudomorphic high electron-mobility transistors connected in series. Results show a 1.63-THz response that is directly proportional to the number of detecting transistors biased by a direct drain current at the same gate-to-source bias voltages. The responsivity in the saturation regime was found to be 170 V/W with the noise equivalent power in the range of 10-7 W/Hz0.5. The experimental data are in agreement with the detection mechanism based on the rectification of overdamped plasma waves excited by terahertz radiation in the transistor channel. © 2010 IEEE.

  15. Enhanced plasma wave detection of terahertz radiation using multiple high electron-mobility transistors connected in series

    KAUST Repository

    Elkhatib, Tamer A.

    2010-02-01

    We report on enhanced room-temperature detection of terahertz radiation by several connected field-effect transistors. For this enhanced nonresonant detection, we have designed, fabricated, and tested plasmonic structures consisting of multiple InGaAs/GaAs pseudomorphic high electron-mobility transistors connected in series. Results show a 1.63-THz response that is directly proportional to the number of detecting transistors biased by a direct drain current at the same gate-to-source bias voltages. The responsivity in the saturation regime was found to be 170 V/W with the noise equivalent power in the range of 10-7 W/Hz0.5. The experimental data are in agreement with the detection mechanism based on the rectification of overdamped plasma waves excited by terahertz radiation in the transistor channel. © 2010 IEEE.

  16. Generation of high-field terahertz pulses in an HMQ-TMS organic crystal pumped by an ytterbium laser at 1030 nm.

    Science.gov (United States)

    Rovere, Andrea; Jeong, Young-Gyun; Piccoli, Riccardo; Lee, Seung-Heon; Lee, Seung-Chul; Kwon, O-Pil; Jazbinsek, Mojca; Morandotti, Roberto; Razzari, Luca

    2018-02-05

    We present the generation of high-peak-electric-field terahertz pulses via collinear optical rectification in a 2-(4-hydroxy-3-methoxystyryl)-1-methilquinolinium-2,4,6-trimethylbenzenesulfonate (HMQ-TMS) organic crystal. The crystal is pumped by an amplified ytterbium laser system, emitting 170-fs-long pulses centered at 1030 nm. A terahertz peak electric field greater than 200 kV/cm is obtained for 420 µJ of optical pump energy, with an energy conversion efficiency of 0.26% - about two orders of magnitude higher than in common inorganic crystals collinearly pumped by amplified femtosecond lasers. An open-aperture Z-scan measurement performed on an n-doped InGaAs thin film using such terahertz source shows a nonlinear increase in the terahertz transmission of about 2.2 times. Our findings demonstrate the potential of this terahertz generation scheme, based on ytterbium laser technology, as a simple and efficient alternative to the existing intense table-top terahertz sources. In particular, we show that it can be readily used to explore nonlinear effects at terahertz frequencies.

  17. Coherent emission of terahertz radiation from intrinsic Josephson junctions in Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}

    Energy Technology Data Exchange (ETDEWEB)

    Rudau, Fabian; Wieland, Raphael; Koelle, Dieter; Kleiner, Reinhold [Physikalisches Institut and Center for Quantum Science (CQ) in LISA+, Universitaet Tuebingen (Germany); Zhou, Xianjing; Ji, Min; Hao, Luyao; Huang, Ya; Wang, Huabing [Research Institute of Superconductor Electronics, Nanjing University (China); National Institute for Materials Science, Tsukuba (Japan); Kinev, Nickolay; Koshelets, Valery [Kotel' nikov Institute of Radio Engineering and Electronics, Moscow (Russian Federation); Li, Jun; Wu, Peiheng [Research Institute of Superconductor Electronics, Nanjing University (China); Hatano, Takeshi [National Institute for Materials Science, Tsukuba (Japan)

    2016-07-01

    Stacks of intrinsic Josephson junctions, made of the high-T{sub c} superconductor Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}, can be used as emitters of electromagnetic waves at terahertz frequencies. Coherent emission from 0.3 to 2.4 THz was detected from large, rectangular or disc-shaped mesa structures. Having a linewidth of only a few MHz, emission powers of several tens of microwatt can be produced for single stacks and up to 0.61 mW for an array of mesas. Since the mechanisms of synchronizing all the junctions in the stack is still not fully understood, we investigated the temperature distribution and electromagnetic standing waves in such stacks, as well as the generation of terahertz radiation, using a combination of electric transport measurements, direct radiation detection and low temperature scanning laser microscopy. Recent experimental results from our collaboration will be presented and compared to numerical simulations.

  18. Enhancement of terahertz radiation in a Smith-Purcell backward-wave oscillator by an inverse wet-etched grating

    International Nuclear Information System (INIS)

    Kim, Jung-Il; Jeon, Seok-Gy; Kim, Geun-Ju; Kim, Jaehong

    2011-01-01

    A terahertz (THz) Smith-Purcell (SP) backward-wave oscillator with an inverse wet-etched grating based on silicon has been proposed to enhance radiation intensity. This grating strengthens the interactions between an electron beam and the evanescent wave due to the adjacent surface structure between gratings that improves the magnitude of the electric field up to 1.7 times compared to the conventional rectangular gratings. A two-dimensional particle-in-cell (PIC) simulation shows that the radiated power is increased up to 2.3 times higher at the radiated frequency of 0.66 THz for an electron-beam energy of 30 keV.

  19. Terahertz Spectroscopy and Imaging

    CERN Document Server

    Zeitler, Axel; Kuwata-Gonokami, Makoto

    2013-01-01

    "This book presents the current state of knowledge in the field of terahertz spectroscopy, providing a comprehensive source of information for beginners and experienced researchers alike whose interests lie in this area. The book aims to explain the fundamental physics that underpins terahertz  technology and to describe its key applications. Highlights of scientific research in the field of terahertz science are also outlined in some chapters, providing an overview as well as giving an insight into future directions for research.  Over the past decade terahertz spectroscopy has developed into one of the most rapidly growing areas of its kind, gaining an important impact across a wide range of scientific disciplines. Due to substantial advances in femtosecond laser technology, terahertz time-domain spectroscopy (THz-TDS) has established itself as the dominant spectroscopic technique for experimental scientists interested in measurements at this frequency range. In solids and liquids THz radiation is in reso...

  20. Development of intense terahertz coherent synchrotron radiation at KU-FEL

    Energy Technology Data Exchange (ETDEWEB)

    Sei, Norihiro, E-mail: sei.n@aist.go.jp [Research Institute for Measurement and Analytical Instrumentation, National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Umezono, Tsukuba, Ibaraki 305-8568 (Japan); Zen, Heishun; Ohgaki, Hideaki [Institute for Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)

    2016-10-01

    We produced intense coherent synchrotron radiation (CSR) in the terahertz (THz) region using an S-band linac at the Kyoto University Free Electron Laser (KU-FEL), which is a mid-infrared free-electron laser facility. The CSR beam was emitted from short-pulse electron bunches compressed by a 180° arc, and was transferred to air at a large solid angle of 0.10 rad. The measured CSR energy was 55 μJ per 7 μs macropulse, and KU-FEL was one of the most powerful CSR sources in normal conducting linear accelerator facilities. The CSR spectra were measured using an uncooled pyroelectric detector and a Michelson-type interferometer designed specifically for the KU-FEL electron beam, and had a maximum at a frequency of 0.11 THz. We found that adjusting the energy slit enhanced the CSR energy and shortened the electron beam bunch length in the CSR spectra measurements. Our results demonstrated that the efficient use of the energy slit can help improve the characteristics of CSR. - Highlights: • We have developed intense coherent synchrotron radiation (CSR) at KU-FEL. • The elevation angle of the CSR was correctly measured by a new technique. • The CSR power extracted to the air was 55 μJ per 7 μs macropulse. • It was demonstrated that an energy slit was effective to improve the CSR properties.

  1. Suggested design of gold-nanoobjects-based terahertz radiation source for biomedical research.

    Science.gov (United States)

    Postnikov, Andrei; Moldosanov, Kamil

    2018-04-18

    Gold nanoparticles (GNPs) may serve as "devices" to emit electromagnetic radiation in the terahertz (THz) range, whereby the energy is delivered by radio frequency or microwave photons which won't by themselves induce transitions between sparse confinement-shaped electron levels of a GNP, but may borrow the energy from longitudinal acoustic phonons to overcome the confinement gap. Upon excitation, the Fermi electron cannot relax otherwise than via emitting a THz photon, the other relaxation channels being blocked by force of shape and size considerations. Within this general scope that has been already outlined earlier, the present work specifically discusses two-phonon processes, namely (i) a combined absorption-emission of two phonons from the top of the longitudinal acoustic branch, and (ii) an absorption of two such phonons with nearly identical wavevectors. The case (i) may serve as a source of "soft" THz radiation (at ≃0.54 THz), the case (ii) the "hard" THz radia- tion at 8.7 THz. Numerical estimates are done for crystalline particles in the shape of rhombicuboctahedra, of 5 - 7 nm "diameter". A technical realisation of this idea is briefly discussed, assuming the deposition of GNPs onto / within the substrate of Teflon, the material sustaining high temperatures and transparent in the THz range. © 2018 IOP Publishing Ltd.

  2. The effectiveness of electromagnetic terahertz radiation use in the treatment of patients with rapidly progressive periodontitis

    Directory of Open Access Journals (Sweden)

    Zelenova A.V.

    2015-12-01

    Full Text Available The aim: to increase the efficiency of treatment of patients with rapidly progressive periodontitis (RPP using electromagnetic radiation at terahertz frequencies of molecular spectrum of radiation and absorption of nitric oxide 150,176-150,664 GHz. Material and methods. The study involved 50 patients with RPP, which according to the method of therapy were divided into 2 groups: group 1 included patients receiving conventional therapy, group 2 consisted of patients who, along with traditional therapy received EHF-therapy device "Orbit" YAKUL.941526.001. The control group consisted of 20 healthy subjects with intact periodontium. For the non-invasive study of tissue blood flow in the periodontal tissue Doppler ultrasound was used MiniMax-Doppler-Phono. The study of the microvasculature of periodontitis has been conducted. To determine the reactivity of microvascular periodontal tissue reflex functional tests on the indirect effect of the cold were performed. Results. Reductions achieved values of periodontal indices, especially important index PMA, a significant increase in the linear blood flow indices, decreased pulse pressure gradient and the index followed appropriate reduction to their cold test. Conclusion. The proposed complex therapy can accelerate the relief of inflammation in the periodontal tissues of the complex, to improve the elastic properties of blood vessels, reduce their tone and restore microcirculation in periodontal tissues.

  3. Development of intense terahertz coherent synchrotron radiation at KU-FEL

    International Nuclear Information System (INIS)

    Sei, Norihiro; Zen, Heishun; Ohgaki, Hideaki

    2016-01-01

    We produced intense coherent synchrotron radiation (CSR) in the terahertz (THz) region using an S-band linac at the Kyoto University Free Electron Laser (KU-FEL), which is a mid-infrared free-electron laser facility. The CSR beam was emitted from short-pulse electron bunches compressed by a 180° arc, and was transferred to air at a large solid angle of 0.10 rad. The measured CSR energy was 55 μJ per 7 μs macropulse, and KU-FEL was one of the most powerful CSR sources in normal conducting linear accelerator facilities. The CSR spectra were measured using an uncooled pyroelectric detector and a Michelson-type interferometer designed specifically for the KU-FEL electron beam, and had a maximum at a frequency of 0.11 THz. We found that adjusting the energy slit enhanced the CSR energy and shortened the electron beam bunch length in the CSR spectra measurements. Our results demonstrated that the efficient use of the energy slit can help improve the characteristics of CSR. - Highlights: • We have developed intense coherent synchrotron radiation (CSR) at KU-FEL. • The elevation angle of the CSR was correctly measured by a new technique. • The CSR power extracted to the air was 55 μJ per 7 μs macropulse. • It was demonstrated that an energy slit was effective to improve the CSR properties.

  4. Electricity generation using electromagnetic radiation

    Science.gov (United States)

    Halas, Nancy J.; Nordlander, Peter; Neumann, Oara

    2017-08-22

    In general, in one aspect, the invention relates to a system to create vapor for generating electric power. The system includes a vessel comprising a fluid and a complex and a turbine. The vessel of the system is configured to concentrate EM radiation received from an EM radiation source. The vessel of the system is further configured to apply the EM radiation to the complex, where the complex absorbs the EM radiation to generate heat. The vessel of the system is also configured to transform, using the heat generated by the complex, the fluid to vapor. The vessel of the system is further configured to sending the vapor to a turbine. The turbine of the system is configured to receive, from the vessel, the vapor used to generate the electric power.

  5. Mode-locked thin-disk lasers and their potential application for high-power terahertz generation

    Science.gov (United States)

    Saraceno, Clara J.

    2018-04-01

    The progress achieved in the last few decades in the performance of ultrafast laser systems with high average power has been tremendous, and continues to provide momentum to new exciting applications, both in scientific research and technology. Among the various technological advances that have shaped this progress, mode-locked thin-disk oscillators have attracted significant attention as a unique technology capable of providing ultrashort pulses with high energy (tens to hundreds of microjoules) and at very high repetition rates (in the megahertz regime) from a single table-top oscillator. This technology opens the door to compact high repetition rate ultrafast sources spanning the entire electromagnetic spectrum from the XUV to the terahertz regime, opening various new application fields. In this article, we focus on their unexplored potential as compact driving sources for high average power terahertz generation.

  6. Imaginary geometric phases of quantum trajectories in high-order terahertz sideband generation

    Science.gov (United States)

    Yang, Fan; Liu, Ren-Bao

    2014-03-01

    Quantum evolution of particles under strong fields can be described by a small number of quantum trajectories that satisfy the stationary phase condition in the Dirac-Feynmann path integral. The quantum trajectories are the key concept to understand the high-order terahertz siedeband generation (HSG) in semiconductors. Due to the nontrivial ``vacuum'' states of band materials, the quantum trajectories of optically excited electron-hole pairs in semiconductors can accumulate geometric phases under the driving of an elliptically polarized THz field. We find that the geometric phase of the stationary trajectory is generally complex with both real and imaginary parts. In monolayer MoS2, the imaginary parts of the geometric phase leads to a changing of the polarization ellipticity of the sideband. We further show that the imaginary part originates from the quantum interference of many trajectories with different phases. Thus the observation of the polarization ellipticity of the sideband shall be a good indication of the quantum nature of the stationary trajectory. This work is supported by Hong Kong RGC/GRF 401512 and the CUHK Focused Investments Scheme.

  7. Charge generation in organic solar cell materials studied by terahertz spectroscopy

    KAUST Repository

    Scarongella, M.

    2015-09-09

    We have investigated the photophysics in neat films of conjugated polymer PBDTTPD and its blend with PCBM using terahertz time-domain spectroscopy. This material has very high efficiency when used in organic solar cells. We were able to identify a THz signature for bound excitons in neat PBDTTPD films, pointing to important delocalization in those excitons. Then, we investigated the nature and local mobility (orders of magnitude higher than bulk mobility) of charges in the PBDTTPPD:PCBM blend as a function of excitation wavelength, fluence and pump-probe time delay. At low pump fluence (no bimolecular recombination phenomena), we were able to observe prompt and delayed charge generation components, the latter originating from excitons created in neat polymer domains which, thanks to delocalization, could reach the PCBM interface and dissociate to charges on a time scale of 1 ps. The nature of the photogenerated charges did not change between 0.5 ps and 800 ps after photo-excitation, which indicated that the excitons split directly into relatively free charges on an ultrafast time scale. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

  8. Convergence of Terahertz Sciences in Biomedical Systems

    CERN Document Server

    Kim, Yong; Han, Haewook; Han, Joon; Ahn, Jaewook; Son, Joo-Hiuk; Park, Woong-Yang; Jeong, Young

    2012-01-01

    Recent technological breakthrough in the field of Terahertz radiation has triggered new applications in biology and biomedicine. Particularly, biological applications are based on the specific spectroscopic fingerprints of biological matter in this spectral region. Historically with the discovery of new electromagnetic wave spectrum, we have always discovered new medical diagnostic imaging systems. The use of terahertz wave was not realized due to the absence of useful terahertz sources. Now after successful generation of THz waves, it is reported that a great potential for THz wave exists for its resonance with bio-molecules. There are many challenging issues such as development of THz passive and active instrumentations, understanding of THz-Bio interaction for THz spectroscopy, THz-Bio nonlinear phenomena and safety guideline, and THz imaging systems. Eventually the deeper understanding of THz-Bio interaction and novel THz systems enable us to develop powerful THz biomedical imaging systems which can contr...

  9. Negative-mass mitigation of Coulomb repulsion for terahertz undulator radiation of electron bunches

    Energy Technology Data Exchange (ETDEWEB)

    Balal, N.; Magory, E. [Ariel University, Ariel 40700 (Israel); Bandurkin, I. V. [Institute of Applied Physics, Russian Academy of Sciences, 46 Ulyanov St., Nizhny Novgorod 603950 (Russian Federation); Bratman, V. L. [Ariel University, Ariel 40700 (Israel); Institute of Applied Physics, Russian Academy of Sciences, 46 Ulyanov St., Nizhny Novgorod 603950 (Russian Federation); Savilov, A. V. [Institute of Applied Physics, Russian Academy of Sciences, 46 Ulyanov St., Nizhny Novgorod 603950 (Russian Federation); Lobachevsky State University of Nizhny Novgorod, 23 Gagarin Avenue, Nizhny Novgorod 603950 (Russian Federation)

    2015-10-19

    It is proposed to utilize the effect of negative mass for stabilization of the effective axial size of very dense and short electron bunches produced by photo-injector guns by using combined undulator and strong uniform magnetic fields. It has been shown that in the “abnormal” regime, an increase in the electron energy leads to a decrease in the axial velocity of the electron; due to the negative-mass effect, the Coulomb repulsion of electrons leads to their attraction and formation of a fairly stable and compact bunch “nucleus.” An undulator with a strong uniform magnetic field providing the negative-mass effect is designed for an experimental source of terahertz radiation. The use of the negative-mass regime in this experiment should result in a long-pulse coherent spontaneous undulator emission from a short dense moderately relativistic (5.5 MeV) photo-injector electron bunch with a high (up to 20%) efficiency and a narrow frequency spectrum.

  10. Squeezing terahertz light into nanovolumes: Nanoantenna enhanced terahertz spectroscopy (NETS) of semiconductor quantum dots

    KAUST Repository

    Toma, Andrea; Tuccio, Salvatore; Prato, Mirko; De Donato, Francesco; Perucchi, Andrea; Di Pietro, Paola; Marras, Sergio; Liberale, Carlo; Proietti Zaccaria, Remo; De Angelis, Francesco De; Manna, Liberato; Lupi, Stefano; Di Fabrizio, Enzo M.; Razzari, Luca

    2015-01-01

    Terahertz spectroscopy has vast potentialities in sensing a broad range of elementary excitations (e.g., collective vibrations of molecules, phonons, excitons, etc.). However, the large wavelength associated with terahertz radiation (about 300 μm

  11. Manifestation of plasmonic response in the detection of sub-terahertz radiation by graphene-based devices

    Science.gov (United States)

    Gayduchenko, I. A.; Fedorov, G. E.; Moskotin, M. V.; Yagodkin, D. I.; Seliverstov, S. V.; Goltsman, G. N.; Kuntsevich, A. Yu; Rybin, M. G.; Obraztsova, E. D.; Leiman, V. G.; Shur, M. S.; Otsuji, T.; Ryzhii, V. I.

    2018-06-01

    We report on the sub-terahertz (THz) (129–450 GHz) photoresponse of devices based on single layer graphene and graphene nanoribbons with asymmetric source and drain (vanadium and gold) contacts. Vanadium forms a barrier at the graphene interface, while gold forms an Ohmic contact. We find that at low temperatures (77 K) the detector responsivity rises with the increasing frequency of the incident sub-THz radiation. We interpret this result as a manifestation of a plasmonic effect in the devices with the relatively long plasmonic wavelengths. Graphene nanoribbon devices display a similar pattern, albeit with a lower responsivity.

  12. Numerical and experimental studies of mechanisms underlying the effect of pulsed broadband terahertz radiation on nerve cells

    Energy Technology Data Exchange (ETDEWEB)

    Duka, M V; Dvoretskaya, L N; Babelkin, N S; Khodzitskii, M K; Chivilikhin, S A; Smolyanskaya, O A [St. Petersburg National Research University of Information Technologies, Mechanics and Optics, St. Petersburg (Russian Federation)

    2014-08-31

    We have studied the mechanisms underlying the effect of pulsed broadband terahertz radiation on the growth of neurites of sensory ganglia using a comparative analysis of measured reflection spectra of ganglion neurites (in the frequency range 0.1 – 2.0 THz) and spectra obtained by numerical simulation with CST Microwave Studio. The observed changes are shown to be mainly due to pulse energy absorption in the ganglion neurites. Of particular interest are the observed single resonance frequencies related to resonance size effects, which can be used to irradiate ganglia in order to activate their growth. (laser biophotonics)

  13. Ultra-short coherent terahertz radiation from ultra-short dips in electron bunches circulating in a storage ring

    International Nuclear Information System (INIS)

    Yamamoto, N.; Shimada, M.; Adachi, M.; Zen, H.; Tanikawa, T.; Taira, Y.; Kimura, S.; Hosaka, M.; Takashima, Y.; Takahashi, T.; Katoh, M.

    2011-01-01

    Terahertz (THz) coherent synchrotron radiation (CSR) is emitted not only from ultra-short electron bunches, but also from electron bunches with micro-structures. Formation of micro-structures at the sub-picosecond scale in electron bunches by a laser slicing technique is experimentally studied through observation of the THz CSR. The THz CSR spectrum was found to depend strongly on the intensity and the pulse width of the laser. The results agreed qualitatively with a numerical simulation. It was suggested that the evolution of the micro-structure during CSR emission is important under some experimental conditions.

  14. Characteristic responses of biological and nanoscale systems in the terahertz frequency range

    Energy Technology Data Exchange (ETDEWEB)

    Angeluts, A A; Balakin, A V; Evdokimov, M G; Ozheredov, I A; Sapozhnikov, D A; Solyankin, P M; Shkurinov, A P [International Laser Center, M. V. Lomonosov Moscow State University, Moscow (Russian Federation); Esaulkov, M N; Nazarov, M M [Institute on Laser and Information Technologies, Russian Academy of Sciences, Shatura, Moscow Region (Russian Federation); Cherkasova, O P [Institute of Laser Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk (Russian Federation)

    2014-07-31

    This paper briefly examines methods for the generation of pulsed terahertz radiation and principles of pulsed terahertz spectroscopy, an advanced informative method for studies of complex biological and nanostructured systems. Some of its practical applications are described. Using a number of steroid hormones as examples, we demonstrate that terahertz spectroscopy in combination with molecular dynamics methods and computer simulation allows one to gain information about the structure of molecules in crystals. A 'terahertz colour vision' method is proposed for analysis of pulsed terahertz signals reflected from biological tissues and it is shown that this method can be effectively used to analyse the properties of biological tissues and for early skin cancer diagnosis. (laser biophotonics)

  15. Terahertz plasmonic Bessel beamformer

    International Nuclear Information System (INIS)

    Monnai, Yasuaki; Shinoda, Hiroyuki; Jahn, David; Koch, Martin; Withayachumnankul, Withawat

    2015-01-01

    We experimentally demonstrate terahertz Bessel beamforming based on the concept of plasmonics. The proposed planar structure is made of concentric metallic grooves with a subwavelength spacing that couple to a point source to create tightly confined surface waves or spoof surface plasmon polaritons. Concentric scatterers periodically incorporated at a wavelength scale allow for launching the surface waves into free space to define a Bessel beam. The Bessel beam defined at 0.29 THz has been characterized through terahertz time-domain spectroscopy. This approach is capable of generating Bessel beams with planar structures as opposed to bulky axicon lenses and can be readily integrated with solid-state terahertz sources

  16. Computed tomography image using sub-terahertz waves generated from a high-Tc superconducting intrinsic Josephson junction oscillator

    International Nuclear Information System (INIS)

    Kashiwagi, T.; Minami, H.; Kadowaki, K.; Nakade, K.; Saiwai, Y.; Kitamura, T.; Watanabe, C.; Ishida, K.; Sekimoto, S.; Asanuma, K.; Yasui, T.; Shibano, Y.; Tsujimoto, M.; Yamamoto, T.; Marković, B.; Mirković, J.; Klemm, R. A.

    2014-01-01

    A computed tomography (CT) imaging system using monochromatic sub-terahertz coherent electromagnetic waves generated from a device constructed from the intrinsic Josephson junctions in a single crystalline mesa structure of the high-T c superconductor Bi 2 Sr 2 CaCu 2 O 8+δ was developed and tested on three samples: Standing metallic rods supported by styrofoam, a dried plant (heart pea) containing seeds, and a plastic doll inside an egg shell. The images obtained strongly suggest that this CT imaging system may be useful for a variety of practical applications

  17. Expansion of the tuning range of injection-seeded terahertz-wave parametric generator up to 5 THz

    OpenAIRE

    Murate, Kosuke; Hayashi, Shin'ichiro; Kawase, Kodo

    2016-01-01

    In this paper, we report the improvement of the frequency tuning range of an injection-seeded terahertz (THz)-wave parametric generator (is-TPG). A significant previous limitation was the high absorption coefficient in the higher-frequency region of a MgO:LiNbO3 crystal. Here, we inclined the crystal slightly, so that a fraction of the pump beam was internally reflected at the THz-wave exit surface of the crystal. In this configuration, it was easier for a higher-frequency THz wave to reach t...

  18. The effect of terahertz electromagnetic radiation on cardiovascular system and orbital vessels in age-related macular degeneration

    Directory of Open Access Journals (Sweden)

    K. U. Eremenko

    2014-07-01

    Full Text Available Aim.To study the effect of terahertz (THz radiation at atmospheric oxygen frequency (129 GHz on cardiovascular and hemodynamic parameters of orbital arteries following the irradiation of bioactive points in healthy volunteers and age-related macular degeneration (AMD patients.Materials and methods. 18 healthy volunteers (36 eyes and 20 AMD patients (34 eyes were examined. Blood pressure (BP, heart rate (HR, systolic and diastolic blood flow velocities, resistance index (RI in orbital arteries before and following THz radiation of two bioactive points VB1 and TR23 at atmospheric oxygen frequency 129 GHz in continuouswave generation mode were measured.Results. First data on the effect of THz waves at atmospheric oxygen irradiation and absorption molecular spectrum frequency (129 GHz in continuous wave generation mode on ocular hemodynamics in healthy persons and AMD patients are presented. Following THz irradiation at atmospheric oxygen frequency (129 GHz, common hemodynamicparameters (BP, HR decreased. In healthy volunteers, systolic and diastolic BP reduced by 22.83±4.09 and 8.82±0.98 mm Hg, respectively (р<0.05, HR reduced by 6.11±0.15 bpm (р<0.05. In AMD patients, systolic and diastolic BP significantly decreased by 45.55±0.43 and 9.56±1.42 mm Hg, respectively (р<0.05, HR decreased by 6.15±1.1 bpm (р<0.05. In AMD patients, systolic blood flow velocity significantly reduced by 2.89±0.1 cm / sec in central retinal artery and increased by0.9‑5.97 cm / sec in short posterior ciliary arteries and ophthalmic artery. RI in these vessels decreased by 0.13, 0.11, 0.13 and 0.12, respectively.Conclusion. THz waves at atmospheric oxygen irradiation and absorption molecular spectrum frequency (129 GHz are safe and cause no side effects on general health of healthy volunteers and AMD patients. Besides, this method improves ocular hemodynamics.

  19. A Josephson radiation comb generator.

    Science.gov (United States)

    Solinas, P; Gasparinetti, S; Golubev, D; Giazotto, F

    2015-07-20

    We propose the implementation of a Josephson Radiation Comb Generator (JRCG) based on a dc superconducting quantum interference device (SQUID) driven by an external magnetic field. When the magnetic flux crosses a diffraction node of the critical current interference pattern, the superconducting phase undergoes a jump of π and a voltage pulse is generated at the extremes of the SQUID. Under periodic drive this allows one to generate a sequence of sharp, evenly spaced voltage pulses. In the frequency domain, this corresponds to a comb-like structure similar to the one exploited in optics and metrology. With this device it is possible to generate up to several hundreds of harmonics of the driving frequency. For example, a chain of 50 identical high-critical-temperature SQUIDs driven at 1 GHz can deliver up to a 0.5 nW at 200 GHz. The availability of a fully solid-state radiation comb generator such as the JRCG, easily integrable on chip, may pave the way to a number of technological applications, from metrology to sub-millimeter wave generation.

  20. Enhancement of spatial resolution of terahertz imaging systems based on terajet generation by dielectric cube

    Directory of Open Access Journals (Sweden)

    Hai Huy Nguyen Pham

    2017-05-01

    Full Text Available The terahertz (THz, 0.1–10 THz region has been attracting tremendous research interest owing to its potential in practical applications such as biomedical, material inspection, and nondestructive imaging. Those applications require enhancing the spatial resolution at a specific frequency of interest. A variety of resolution-enhancement techniques have been proposed, such as near-field scanning probes, surface plasmons, and aspheric lenses. Here, we demonstrate for the first time that a mesoscale dielectric cube can be exploited as a novel resolution enhancer by simply placing it at the focused imaging point of a continuous wave THz imaging system. The operating principle of this enhancer is based on the generation—by the dielectric cuboid—of the so-called terajet, a photonic jet in the THz region. A subwavelength hotspot is obtained by placing a Teflon cube, with a 1.46 refractive index, at the imaging point of the imaging system, regardless of the numerical aperture (NA. The generated terajet at 125 GHz is experimentally characterized, using our unique THz-wave visualization system. The full width at half maximum (FWHM of the hotspot obtained by placing the enhancer at the focal point of a mirror with a measured NA of 0.55 is approximately 0.55λ, which is even better than the FWHM obtained by a conventional focusing device with the ideal maximum numerical aperture (NA = 1 in air. Nondestructive subwavelength-resolution imaging demonstrations of a Suica integrated circuit card, which is used as a common fare card for trains in Japan, and an aluminum plate with 0.63λ trenches are presented. The amplitude and phase images obtained with the enhancer at 125 GHz can clearly resolve both the air-trenches on the aluminum plate and the card’s inner electronic circuitry, whereas the images obtained without the enhancer are blurred because of insufficient resolution. An increase of the image contrast by a factor of 4.4 was also obtained using

  1. Photoacoustic Detection of Terahertz Radiation for Chemical Sensing and Imaging Applications

    Science.gov (United States)

    2013-03-01

    ISSN 2229-5518 [39] Jingle Liu, Benjamin Clough, and X. C. Zhang, “Enhancement of photoacoustic emission through terahertz-field driven electron...materials,” Journal of Electroceramics, vol. 2: p. 257-272, 2009. [47] Jingle Liu, Benjamin Clough, and X. C. Zhang, “Enhancement of photoacoustic

  2. Optimization of radiation sensors for a passive terahertz video camera for security applications

    NARCIS (Netherlands)

    Zieger, G.J.M.

    2014-01-01

    A passive terahertz video camera allows for fast security screenings from distances of several meters. It avoids irradiation or the impressions of nakedness, which oftentimes cause embarrassment and trepidation of the concerned persons. This work describes the optimization of highly sensitive

  3. Enhanced Cherenkov phase matching terahertz wave generation via a magnesium oxide doped lithium niobate ridged waveguide crystal

    Directory of Open Access Journals (Sweden)

    K. Takeya

    2017-01-01

    Full Text Available When combined with a nonlinear waveguide crystal, Cherenkov phase matching allows for highly effective generation of high power and broadband terahertz (THz waves. Using a ridged Lithium Niobate (LiNbO3 waveguide coupled with a specially designed silicon lens, we successfully generated THz waves with intensity of approximately three orders of magnitude stronger than those from conventional photoconductive antenna. The broadband spectrum was from 0.1 THz to 7 THz with a maximum dynamic range of 80 dB. The temporal shape of time domain pulse is a regular single cycle which could be used for high depth resolution time of flight tomography. The generated THz wave can also be easily monitored by compact room-temperature THz camera, enabling us to determine the spatial characteristics of the THz propagation.

  4. Highly nonlinear organic crystal OHQ-T for efficient ultra-broadband terahertz wave generation beyond 10 THz.

    Science.gov (United States)

    Kang, Bong Joo; Baek, In Hyung; Lee, Seung-Heon; Kim, Won Tae; Lee, Seung-Jun; Jeong, Young Uk; Kwon, O-Pil; Rotermund, Fabian

    2016-05-16

    We report on efficient generation of ultra-broadband terahertz (THz) waves via optical rectification in a novel nonlinear organic crystal with acentric core structure, i.e. 2-(4-hydroxystyryl)-1-methylquinolinium 4-methylbenzenesulfonate (OHQ-T), which possesses an ideal molecular structure leading to a maximized nonlinear optical response for near-infrared-pumped THz wave generation. By systematic studies on wavelength-dependent phase-matching conditions in OHQ-T crystals of different thicknesses we are able to generate coherent THz waves with a high peak-to-peak electric field amplitude of up to 650 kV/cm and an upper cut-off frequency beyond 10 THz. High optical-to-THz conversion efficiency of 0.31% is achieved by efficient index matching with a selective pumping at 1300 nm.

  5. Generation of auroral kilometric radiation

    International Nuclear Information System (INIS)

    Green, J.L.

    1979-01-01

    Simultaneous observations between the Hawkeye spacecraft in the AKR emission cone and the low altitude polar orbiting spacecraft Triad and AE-D reveal that auroral kilometric radiation (AKR) is correlated with a variety of auroral particle precipitation in the evening to midnight local time sector. It is found that as the AKR intensity increases so does the integrated current sheet intensity of auroral zone field aligned currents observed by Triad of 257 simultaneous observations. Statistically, the linear correlation coefficient between the log of the AKR power flux and the log of the current sheet intensity is 0.57. Auroral kilometric radiation observations from Hawkeye during low altitude (2.0 to 2.5 R/sub E/) auroral zone passes reveal that intense AKR has a low frequency cutoff near the local electron gyrofrequency (f/sub g/ - ) with maximum electric field strengths as large as 12 mV/m. The large electric fields observed near f/sub g/ - are consistent with high altitude observations of AKR using a simple 1/R 2 scaling indicating that the kilometric radiation in or near the average source region is almost completely electromagnetic. The results presented in this study indicate that kilometric radiation is generated by inverted-V electron distribution functions in a direct coupling mechanism between particle energy and R-X mode electromagnetic waves in the region of the auroral zone where f/sub g/ - >> f/sub p/ -

  6. Terahertz Quantum Cascade Laser With Efficient Coupling and Beam Profile

    Science.gov (United States)

    Chattopadhyay, Goutam; Kawamura, Jonathan H.; Lin, Robert H.; Williams, Benjamin

    2012-01-01

    Quantum cascade lasers (QCLs) are unipolar semiconductor lasers, where the wavelength of emitted radiation is determined by the engineering of quantum states within the conduction band in coupled multiple-quantum-well heterostructures to have the desired energy separation. The recent development of terahertz QCLs has provided a new generation of solid-state sources for radiation in the terahertz frequency range. Terahertz QCLs have been demonstrated from 0.84 to 5.0 THz both in pulsed mode and continuous wave mode (CW mode). The approach employs a resonant-phonon depopulation concept. The metal-metal (MM) waveguide fabrication is performed using Cu-Cu thermo-compression bonding to bond the GaAs/AlGaAs epitaxial layer to a GaAs receptor wafer.

  7. Spectral purity and tunability of terahertz quantum cascade laser sources based on intracavity difference-frequency generation.

    Science.gov (United States)

    Consolino, Luigi; Jung, Seungyong; Campa, Annamaria; De Regis, Michele; Pal, Shovon; Kim, Jae Hyun; Fujita, Kazuue; Ito, Akio; Hitaka, Masahiro; Bartalini, Saverio; De Natale, Paolo; Belkin, Mikhail A; Vitiello, Miriam Serena

    2017-09-01

    Terahertz sources based on intracavity difference-frequency generation in mid-infrared quantum cascade lasers (THz DFG-QCLs) have recently emerged as the first monolithic electrically pumped semiconductor sources capable of operating at room temperature across the 1- to 6-THz range. Despite tremendous progress in power output, which now exceeds 1 mW in pulsed and 10 μW in continuous-wave regimes at room temperature, knowledge of the major figure of merits of these devices for high-precision spectroscopy, such as spectral purity and absolute frequency tunability, is still lacking. By exploiting a metrological grade system comprising a terahertz frequency comb synthesizer, we measure, for the first time, the free-running emission linewidth (LW), the tuning characteristics, and the absolute center frequency of individual emission lines of these sources with an uncertainty of 4 × 10 -10 . The unveiled emission LW (400 kHz at 1-ms integration time) indicates that DFG-QCLs are well suited to operate as local oscillators and to be used for a variety of metrological, spectroscopic, communication, and imaging applications that require narrow-LW THz sources.

  8. Real-Time, Single-Shot Temporal Measurements of Short Electron Bunches, Terahertz CSR and FEL Radiation

    CERN Document Server

    Berden, G; Van der Meer, A F G

    2005-01-01

    Electro-optic detection of the Coulomb field of electron bunches is a promising technique for single-shot measurements of the bunch length and shape in the sub-picosecond time domain. This technique has been applied to the measurement of 50 MeV electron bunches in the FELIX free electron laser, showing the longitudinal profile of single bunches of around 650 fs FWHM [Phys. Rev. Lett. 93, 114802 (2004)]. The method is non-destructive and real-time, and therefore ideal for online monitoring of the longitudinal shape of single electron bunches. At FELIX we have used it for real-time optimization of sub-picosecond electron bunches. Electro-optic detection has also been used to measure the electric field profiles of far-infrared (or terahertz) optical pulses generated by the relativistic electrons. We have characterised the far-infrared output of the free electron laser, and more recently, we have measured the temporal profile of terahertz optical pulses generated at one of the bending magnets.

  9. High-power terahertz optical pulse generation with a dual-wavelength harmonically mode-locked Yb:YAG laser

    International Nuclear Information System (INIS)

    Zhuang, W Z; Chang, M T; Su, K W; Huang, K F; Chen, Y F

    2013-01-01

    We report on high-power terahertz optical pulse generation with a dual-wavelength harmonically mode-locked Yb:YAG laser. A semiconductor saturable absorber mirror is developed to achieve synchronously mode-locked operation at two spectral bands centered at 1031.67 and 1049.42 nm with a pulse duration of 1.54 ps and a pulse repetition rate of 80.3 GHz. With a diamond heat spreader to improve the heat removal efficiency, the average output power can be up to 1.1 W at an absorbed pump power of 5.18 W. The autocorrelation traces reveal that the mode-locked pulse is modulated with a beat frequency of 4.92 THz and displays a modulation depth to be greater than 80%. (paper)

  10. Design of a GaP/Si composite waveguide for CW terahertz wave generation via difference frequency mixing.

    Science.gov (United States)

    Saito, Kyosuke; Tanabe, Tadao; Oyama, Yutaka

    2014-06-10

    We design a GaP/Si composite waveguide to achieve efficient terahertz (THz) wave generation under collinear phase-matched difference frequency mixing (DFM) between near-infrared light sources. This waveguide structure provides a strong mode confinement of both near-infrared sources and THz wave, resulting in an efficient mode overlapping. The numerical results show that the waveguide can produce guided THz wave (5.93 THz) with a power conversion efficiency of 6.6×10(-4)  W(-1). This value is larger than previously obtained with the bulk GaP crystal: 0.5×10(-9)  W(-1) [J. Lightwave Technol.27, 3057 (2009)]. Our proposed composite waveguide can be achieved by bridging the telecom wavelength and THz frequency region.

  11. Ultrashort Generation Regimes in the All-Fiber Kerr Mode-Locked Erbium-Doped Fiber Ring Laser for Terahertz Pulsed Spectroscopy

    Directory of Open Access Journals (Sweden)

    V. S. Voropaev

    2015-01-01

    Full Text Available Many femtosecond engineering applications require for a stable generation of ultrashort pulses. Thus, in the terahertz pulsed spectroscopy a measurement error in the refractive index is strongly dependent on the pulse duration stability with allowable variation of few femtoseconds. The aim of this work is to study the ultrashort pulses (USP regimes stability in the all – fiber erbium doped ring laser with Kerr mode-locking. The study was conducted at several different values of the total resonator intra-cavity dispersion. Three laser schemes with the intra-cavity dispersion values from -1.232 ps2 to +0.008 ps2 have been studied. In the experiment there were two regimes of generation observed: the stretched pulse generation and ordinary soliton generation. Main attention is focused on the stability of regimes under study. The most stable regime was that of the stretched pulse generation with a spectrum form of sech2 , possible pulse duration of 490 fs at least, repetition rate of 2.9 MHz, and average output power of 17 mW. It is worth noting, that obtained regimes had characteristics suitable for the successful use in the terahertz pulsed spectroscopy. The results may be useful in the following areas of science and technology: a high-precision spectroscopy, optical frequency standards, super-continuum generation, and terahertz pulsed spectroscopy. The future system development is expected to stabilize duration and repetition rate of the obtained regime of ultra-short pulse generation.

  12. Intense Plasma Waveguide Terahertz Sources for High-Field THz Probe Science with Ultrafast Lasers for Solid State Physics

    Science.gov (United States)

    2016-08-25

    Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a...Summary 2 1. Introduction 2. Two colour excitation of intense terahertz radiation in MOFs 2 3. Terahertz optical nonlinearities in...of 2- colour THz generation and propagation in waveguides that we have developed to evaluate fibre designs before fabrication is only one

  13. Generation, transmission, and detection of terahertz photons on an electrically driven single chip

    Energy Technology Data Exchange (ETDEWEB)

    Ikushima, Kenji; Ito, Atsushi; Okano, Shun [Department of Applied Physics, Tokyo University of Agriculture and Technology, 2-24-16 Nakacho, Koganei, Tokyo 184-8588 (Japan)

    2014-02-03

    We demonstrate single photon counting of terahertz (THz) waves transmitted from a local THz point source through a coplanar two-wire waveguide on a GaAs/AlGaAs single heterostructure crystal. In the electrically driven all-in-one chip, quantum Hall edge transport is used to achieve a noiseless injection current for a monochromatic point source of THz fields. The local THz fields are coupled to a coplanar two-wire metal waveguide and transmitted over a macroscopic scale greater than the wavelength (38 μm in GaAs). THz waves propagating on the waveguide are counted as individual photons by a quantum-dot single-electron transistor on the same chip. Photon counting on integrated high-frequency circuits will open the possibilities for on-chip quantum optical experiments.

  14. Spatial Terahertz Modulator

    Science.gov (United States)

    Xie, Zhenwei; Wang, Xinke; Ye, Jiasheng; Feng, Shengfei; Sun, Wenfeng; Akalin, Tahsin; Zhang, Yan

    2013-11-01

    Terahertz (THz) technology is a developing and promising candidate for biological imaging, security inspection and communications, due to the low photon energy, the high transparency and the broad band properties of the THz radiation. However, a major encountered bottleneck is lack of efficient devices to manipulate the THz wave, especially to modulate the THz wave front. A wave front modulator should allow the optical or electrical control of the spatial transmission (or reflection) of an input THz wave and hence the ability to encode the information in a wave front. Here we propose a spatial THz modulator (STM) to dynamically control the THz wave front with photo-generated carriers. A computer generated THz hologram is projected onto a silicon wafer by a conventional spatial light modulator (SLM). The corresponding photo-generated carrier spatial distribution will be induced, which forms an amplitude hologram to modulate the wave front of the input THz beam. Some special intensity patterns and vortex beams are generated by using this method. This all-optical controllable STM is structure free, high resolution and broadband. It is expected to be widely used in future THz imaging and communication systems.

  15. Terahertz radiation induces non-thermal structural changes associated with Fröhlich condensation in a protein crystal.

    Science.gov (United States)

    Lundholm, Ida V; Rodilla, Helena; Wahlgren, Weixiao Y; Duelli, Annette; Bourenkov, Gleb; Vukusic, Josip; Friedman, Ran; Stake, Jan; Schneider, Thomas; Katona, Gergely

    2015-09-01

    Whether long-range quantum coherent states could exist in biological systems, and beyond low-temperature regimes where quantum physics is known to be applicable, has been the subject to debate for decades. It was proposed by Fröhlich that vibrational modes within protein molecules can order and condense into a lowest-frequency vibrational mode in a process similar to Bose-Einstein condensation, and thus that macroscopic coherence could potentially be observed in biological systems. Despite the prediction of these so-called Fröhlich condensates almost five decades ago, experimental evidence thereof has been lacking. Here, we present the first experimental observation of Fröhlich condensation in a protein structure. To that end, and to overcome the challenges associated with probing low-frequency molecular vibrations in proteins (which has hampered understanding of their role in proteins' function), we combined terahertz techniques with a highly sensitive X-ray crystallographic method to visualize low-frequency vibrational modes in the protein structure of hen-egg white lysozyme. We found that 0.4 THz electromagnetic radiation induces non-thermal changes in electron density. In particular, we observed a local increase of electron density in a long α-helix motif consistent with a subtle longitudinal compression of the helix. These observed electron density changes occur at a low absorption rate indicating that thermalization of terahertz photons happens on a micro- to milli-second time scale, which is much slower than the expected nanosecond time scale due to damping of delocalized low frequency vibrations. Our analyses show that the micro- to milli-second lifetime of the vibration can only be explained by Fröhlich condensation, a phenomenon predicted almost half a century ago, yet never experimentally confirmed.

  16. Continuous-wave terahertz light from optical parametric oscillators

    Energy Technology Data Exchange (ETDEWEB)

    Sowade, Rosita

    2010-12-15

    Continuous-wave (cw) optical parametric oscillators (OPOs) are working horses for spectroscopy in the near and mid infrared. However, in the terahertz frequency range (0.1 to 10 THz), the pump threshold is more than 100 W due to the high absorption in nonlinear crystals and thus exceeds the power of standard cw single-frequency pump sources. In this thesis the first cw OPO capable of generating terahertz radiation is demonstrated. To overcome the high threshold, the signal wave of a primary infrared process is resonantly enhanced to serve as the pump wave for a cascaded parametric process with one wave being at the terahertz frequency level. A terahertz output power of more than two microwatts is measured and tuning is achieved from 1.3 to 1.7 THz. This terahertz source emits a narrow-band, diffraction-limited beam which remains mode-hop free over more than one hour. Such a device inhibits high potential for applications in areas like astronomy, telecommunications or high-resolution spectroscopy. (orig.)

  17. Continuous-wave terahertz light from optical parametric oscillators

    International Nuclear Information System (INIS)

    Sowade, Rosita

    2010-12-01

    Continuous-wave (cw) optical parametric oscillators (OPOs) are working horses for spectroscopy in the near and mid infrared. However, in the terahertz frequency range (0.1 to 10 THz), the pump threshold is more than 100 W due to the high absorption in nonlinear crystals and thus exceeds the power of standard cw single-frequency pump sources. In this thesis the first cw OPO capable of generating terahertz radiation is demonstrated. To overcome the high threshold, the signal wave of a primary infrared process is resonantly enhanced to serve as the pump wave for a cascaded parametric process with one wave being at the terahertz frequency level. A terahertz output power of more than two microwatts is measured and tuning is achieved from 1.3 to 1.7 THz. This terahertz source emits a narrow-band, diffraction-limited beam which remains mode-hop free over more than one hour. Such a device inhibits high potential for applications in areas like astronomy, telecommunications or high-resolution spectroscopy. (orig.)

  18. Wireless Data Transmission at Terahertz Carrier Waves Generated from a Hybrid InP-Polymer Dual Tunable DBR Laser Photonic Integrated Circuit.

    Science.gov (United States)

    Carpintero, Guillermo; Hisatake, Shintaro; de Felipe, David; Guzman, Robinson; Nagatsuma, Tadao; Keil, Norbert

    2018-02-14

    We report for the first time the successful wavelength stabilization of two hybrid integrated InP/Polymer DBR lasers through optical injection. The two InP/Polymer DBR lasers are integrated into a photonic integrated circuit, providing an ideal source for millimeter and Terahertz wave generation by optical heterodyne technique. These lasers offer the widest tuning range of the carrier wave demonstrated to date up into the Terahertz range, about 20 nm (2.5 THz) on a single photonic integrated circuit. We demonstrate the application of this source to generate a carrier wave at 330 GHz to establish a wireless data transmission link at a data rate up to 18 Gbit/s. Using a coherent detection scheme we increase the sensitivity by more than 10 dB over direct detection.

  19. Measurement of optical-beat frequency in a photoconductive terahertz-wave generator using microwave higher harmonics.

    Science.gov (United States)

    Murasawa, Kengo; Sato, Koki; Hidaka, Takehiko

    2011-05-01

    A new method for measuring optical-beat frequencies in the terahertz (THz) region using microwave higher harmonics is presented. A microwave signal was applied to the antenna gap of a photoconductive (PC) device emitting a continuous electromagnetic wave at about 1 THz by the photomixing technique. The microwave higher harmonics with THz frequencies are generated in the PC device owing to the nonlinearity of the biased photoconductance, which is briefly described in this article. Thirteen nearly periodic peaks in the photocurrent were observed when the microwave was swept from 16 to 20 GHz at a power of -48 dBm. The nearly periodic peaks are generated by the homodyne detection of the optical beat with the microwave higher harmonics when the frequency of the harmonics coincides with the optical-beat frequency. Each peak frequency and its peak width were determined by fitting a Gaussian function, and the order of microwave harmonics was determined using a coarse (i.e., lower resolution) measurement of the optical-beat frequency. By applying the Kalman algorithm to the peak frequencies of the higher harmonics and their standard deviations, the optical-beat frequency near 1 THz was estimated to be 1029.81 GHz with the standard deviation of 0.82 GHz. The proposed method is applicable to a conventional THz-wave generator with a photomixer.

  20. Monopolar photoelectromagnetic effect in Pb1−xSnxTe(In) under terahertz laser radiation

    International Nuclear Information System (INIS)

    Chernichkin, V I; Ryabova, L I; Khokhlov, D R; Nicorici, A V

    2012-01-01

    We report on the observation of a new effect—the appearance of a galvanic signal in the narrow-gap semiconductor Pb 1-x Sn x Te(In) in the magnetic field under the action of strong 100 ns-long terahertz laser pulses. The signal changes its sign and kinetics as the temperature increases from 4.2 K to 25 K. This semiconductor possesses inversion symmetry of the crystalline lattice making impossible the observation of the magnetophotogalvanic effect which looks similar in its experimental manifestation. On the other hand, the laser quantum energy is much less than the bandgap of the semiconductor making the effect considerably different from the conventional Kikoin–Noskov photoelectromagnetic effect. Possible mechanisms responsible for the appearance of the effect are discussed. (paper)

  1. Numerical Investigation of Terahertz Emission Properties of Microring Difference-Frequency Resonators

    DEFF Research Database (Denmark)

    Iwaszczuk, Krzysztof; Bisgaard, Christer Zoffmann; Andronico, Alessio

    2013-01-01

    We investigate the electromagnetic design of whispering gallery mode (WGM) terahertz (THz) resonators. Terahertz radiation is generated by difference-frequency mixing of two electrically pumped high-order near-infrared laser WGM's at room temperature in the active cavity. Due to the leaky nature...... this symmetry by modification of the dielectric environment of the resonator, and demonstrate a fabrication-optimized structure based on a concentric grating design which efficiently couples the emitted radiation into a narrow, near-gaussian forward-propagating cone of well-defined linear or circular...

  2. Ultrafast photocurrents and terahertz radiation in gallium arsenide and carbon based nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Prechtel, Hans Leonhard

    2011-08-15

    In this thesis we developed a measurement technique based on a common pump-probe scheme and coplanar stripline circuits that enables time-resolved photocurrent measurements of contacted nanosystems with a micrometer spatial and a picosecond time resolution. The measurement technique was applied to lowtemperature grown gallium arsenide (LT-GaAs), carbon nanotubes (CNTs), graphene, and p-doped gallium arsenide (GaAs) nanowires. The various mechanisms responsible for the generation of current pulses by pulsed laser excitation were reviewed. Furthermore the propagation of the resulting electromagnetic radiation along a coplanar stripline circuit was theoretically and numerically treated. The ultrafast photocurrent response of low-temperature grown GaAs was investigated. We found two photocurrent pulses in the time-resolved response. We showed that the first pulse is consistent with a displacement current pulse. We interpreted the second pulse to result from a transport current process. We further determined the velocity of the photo-generated charge carriers to exceed the drift, thermal and quantum velocities of single charge carriers. Hereby, we interpreted the transport current pulse to stem from an electron-hole plasma excitation. We demonstrated that the photocurrent response of CNTs comprises an ultrafast displacement current and a transport current. The data suggested that the photocurrent is finally terminated by the recombination lifetime of the charge carriers. To the best of our knowledge, we presented in this thesis the first recombination lifetime measurements of contacted, suspended, CVD grown CNT networks. In addition, we studied the ultrafast photocurrent dynamics of freely suspended graphene contacted by metal electrodes. At the graphene-metal interface, we demonstrated that built-in electric fields give rise to a photocurrent with a full-width-half-maximum of a few picoseconds and that a photo-thermoelectric effect generates a current with a decay time

  3. Strain Imaging Using Terahertz Waves and Metamaterials

    Science.gov (United States)

    2016-11-01

    predictions. 14. SUBJECT TERMS Birefringence, Terahertz Waves, Metamaterials 15. NUMBER OF PAGES 16 16. PRICE CODE 17. SECURITY...opaque objects by using the principles of strain-induced birefringence. 4 III. CONCEPT To overcome the inability of visual light to penetrate ...opaque objects, terahertz radiation was investigated. Longer wavelength EM waves, such as radio waves, have excellent penetration ability but low image

  4. Pulse generator circuit triggerable by nuclear radiation

    International Nuclear Information System (INIS)

    Fredrickson, P.B.

    1980-01-01

    A pulse generator circuit triggerable by a pulse of nuclear radiation is described. The pulse generator circuit includes a pair of transistors arranged, together with other electrical components, in the topology of a standard monostable multivibrator circuit. The circuit differs most significantly from a standard monostable multivibrator circuit in that the circuit is adapted to be triggered by a pulse of nuclear radiation rather than electrically and the transistors have substantially different sensitivities to radiation, due to different physical and electrical characteristics and parameters. One of the transistors is employed principally as a radiation detector and is in a normally non-conducting state and the other transistor is normally in a conducting state. When the circuit is exposed to a pulse of nuclear radiation, currents are induced in the collector-base junctions of both transistors but, due to the different radiation sensitivities of the transistors, the current induced in the collector-base junction of the radiation-detecting transistor is substantially greater than that induced in the collector-base junction of the other transistor. The pulse of radiation causes the radiation-detecting transistor to operate in its conducting state, causing the other transistor to operate in its non-conducting state. As the radiation-detecting transistor operates in its conducting state, an output signal is produced at an output terminal connected to the radiation-detecting transistor indicating the presence of a predetermined intensity of nuclear radiation

  5. Two-dimensional plasmons in lateral carbon nanotube network structures and their effect on the terahertz radiation detection

    International Nuclear Information System (INIS)

    Ryzhii, V.; Otsuji, T.; Ryzhii, M.; Leiman, V. G.; Fedorov, G.; Goltzman, G. N.; Titova, N.; Gayduchenko, I. A.; Coquillat, D.; But, D.; Knap, W.; Mitin, V.; Shur, M. S.

    2016-01-01

    We consider the carrier transport and plasmonic phenomena in the lateral carbon nanotube (CNT) networks forming the device channel with asymmetric electrodes. One electrode is the Ohmic contact to the CNT network and the other contact is the Schottky contact. These structures can serve as detectors of the terahertz (THz) radiation. We develop the device model for collective response of the lateral CNT networks which comprise a mixture of randomly oriented semiconductor CNTs (s-CNTs) and quasi-metal CNTs (m-CNTs). The proposed model includes the concept of the collective two-dimensional (2D) plasmons in relatively dense networks of randomly oriented CNTs (CNT “felt”) and predicts the detector responsivity spectral characteristics exhibiting sharp resonant peaks at the signal frequencies corresponding to the 2D plasmonic resonances. The detection mechanism is the rectification of the ac current due the nonlinearity of the Schottky contact current-voltage characteristics under the conditions of a strong enhancement of the potential drop at this contact associated with the plasmon excitation. The detector responsivity depends on the fractions of the s- and m-CNTs. The burning of the near-contact regions of the m-CNTs or destruction of these CNTs leads to a marked increase in the responsivity in agreement with our experimental data. The resonant THz detectors with sufficiently dense lateral CNT networks can compete and surpass other THz detectors using plasmonic effects at room temperatures.

  6. Two-dimensional plasmons in lateral carbon nanotube network structures and their effect on the terahertz radiation detection

    Energy Technology Data Exchange (ETDEWEB)

    Ryzhii, V. [Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577 (Japan); Institute of Ultra High Frequency Semiconductor Electronics of RAS, Moscow 117105 (Russian Federation); Center for Photonics and Infrared Engineering, Bauman Moscow State Technical University, Moscow 111005 (Russian Federation); Otsuji, T. [Research Institute of Electrical Communication, Tohoku University, Sendai 980-8577 (Japan); Ryzhii, M. [Department of Computer Science and Engineering, University of Aizu, Aizu-Wakamatsu 965-8580 (Japan); Leiman, V. G. [Department of General Physics, Moscow Institute of Physics and Technology, Dolgoprudny, 147100 (Russian Federation); Fedorov, G. [Department of General Physics, Moscow Institute of Physics and Technology, Dolgoprudny, 147100 (Russian Federation); Physics Department, Moscow State Pedagogical University, Moscow 119991 (Russian Federation); Goltzman, G. N.; Titova, N. [Physics Department, Moscow State Pedagogical University, Moscow 119991 (Russian Federation); Gayduchenko, I. A. [Physics Department, Moscow State Pedagogical University, Moscow 119991 (Russian Federation); National Research Center “Kurchatov Institute,” Moscow 123182 (Russian Federation); Coquillat, D.; But, D.; Knap, W. [Laboratoire Charles Coulomb UMR 5221, Universite Montpellier 2 and CNRS, F-34095, Montpellier (France); Mitin, V. [Department of Electrical Engineering, University at Buffalo, Buffalo, New York 1460-1920 (United States); Shur, M. S. [Departments of Electrical, Computer, and Systems Engineering and Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

    2016-07-28

    We consider the carrier transport and plasmonic phenomena in the lateral carbon nanotube (CNT) networks forming the device channel with asymmetric electrodes. One electrode is the Ohmic contact to the CNT network and the other contact is the Schottky contact. These structures can serve as detectors of the terahertz (THz) radiation. We develop the device model for collective response of the lateral CNT networks which comprise a mixture of randomly oriented semiconductor CNTs (s-CNTs) and quasi-metal CNTs (m-CNTs). The proposed model includes the concept of the collective two-dimensional (2D) plasmons in relatively dense networks of randomly oriented CNTs (CNT “felt”) and predicts the detector responsivity spectral characteristics exhibiting sharp resonant peaks at the signal frequencies corresponding to the 2D plasmonic resonances. The detection mechanism is the rectification of the ac current due the nonlinearity of the Schottky contact current-voltage characteristics under the conditions of a strong enhancement of the potential drop at this contact associated with the plasmon excitation. The detector responsivity depends on the fractions of the s- and m-CNTs. The burning of the near-contact regions of the m-CNTs or destruction of these CNTs leads to a marked increase in the responsivity in agreement with our experimental data. The resonant THz detectors with sufficiently dense lateral CNT networks can compete and surpass other THz detectors using plasmonic effects at room temperatures.

  7. Terahertz radiation driven by two-color laser pulses at near-relativistic intensities: Competition between photoionization and wakefield effects

    Science.gov (United States)

    González de Alaiza Martínez, P.; Davoine, X.; Debayle, A.; Gremillet, L.; Bergé, L.

    2016-01-01

    We numerically investigate terahertz (THz) pulse generation by linearly-polarized, two-color femtosecond laser pulses in highly-ionized argon. Major processes consist of tunneling photoionization and ponderomotive forces associated with transverse and longitudinal field excitations. By means of two-dimensional particle-in-cell (PIC) simulations, we reveal the importance of photocurrent mechanisms besides transverse and longitudinal plasma waves for laser intensities >1015 W/cm2. We demonstrate the following. (i) With two-color pulses, photoionization prevails in the generation of GV/m THz fields up to 1017 W/cm2 laser intensities and suddenly loses efficiency near the relativistic threshold, as the outermost electron shell of ionized Ar atoms has been fully depleted. (ii) PIC results can be explained by a one-dimensional Maxwell-fluid model and its semi-analytical solutions, offering the first unified description of the main THz sources created in plasmas. (iii) The THz power emitted outside the plasma channel mostly originates from the transverse currents. PMID:27255689

  8. Anisotropic effects of terahertz emission from laser sparks in air

    International Nuclear Information System (INIS)

    Zharova, N. A.; Mironov, V. A.; Fadeev, D. A.

    2010-01-01

    Strong terahertz (THz) radiation can be generated by intense femtosecond laser pulses propagating in air. The excitation of transient current induced in the wake just behind the laser pulse is studied in detail using numerical simulations on the basis of Maxwell's equations for THz-band fields and hydrodynamic model for the plasma motion. It is shown that the thermal effects, anisotropic in character in the case of linear polarized laser field, can explain observed quadrupole-type THz radiation pattern in the experiment performed by Akhmedzhanov et al. [Radiophys. Quantum Electron. 52, 482 (2009)]. Taking into account the transverse structure of the plasma filament, our numerical code enables us to calculate the spatial distribution and temporal evolution of terahertz electron current, its spectrum, and angular emission pattern. It is shown that an expansion of full fields in terms of azimuthal modes is a useful tool for research of THz generation in many situations of practical interest.

  9. Wide-band continuous-wave terahertz source with a vertically integrated photomixer

    Science.gov (United States)

    Peytavit, E.; Lampin, J.-F.; Hindle, F.; Yang, C.; Mouret, G.

    2009-10-01

    A transverse electromagnetic horn antenna is monolithically integrated with a low temperature grown GaAs vertical photodetector on a silicon substrate forming a vertically integrated photomixer. Continuous-wave terahertz radiation is generated at frequencies up to 3.5 THz with a power level reaching 20 nW around 3 THz. Microwave and material concepts allow both qualitative and quantitative explanations of the experimental results. The thin film microstrip line topology has been adapted for active devices by an Au-Au thermocompression layer transfer technique and seems to be a promising generic tool for a new generation of efficient terahertz devices.

  10. Generation and propagation of synchro - Cherenkov radiation

    International Nuclear Information System (INIS)

    Heintzmann, H.; Novello, M.; Schruefer, E.

    1981-01-01

    Particles moving along the magnetic field lines emit under favorable conditions Cherenkov radiation in a cold, rarefied plasma. A peculiar phenomenon occurs for curved magnetic fields: in for example a toroidal magnetic field the radiation spirals inward and approaches a resonance. Both the generation and the study of the propagation of these Cherenkov modes appear to be within reach of present technology. (Author) [pt

  11. Photomlxer for terahertz electromagnetic wave emission comprising quantum dots in a laser cavity

    DEFF Research Database (Denmark)

    2013-01-01

    The present invention relates to a photomixer for generating terahertz electromagnetic radiation in response to illumination by a time-modulated optical signal. The photomixer (300) comprises a carrier substrate (310) with a plurality of quantum dots arranged in an emission region (308) thereof...

  12. High-sweeping-speed optically synchronized dual-channel terahertz-signal generator for driving a superconducting tunneling mixer and its application to active gas sensing.

    Science.gov (United States)

    Oh, Kyoung-Hwan; Shimizu, Naofumi; Kohjiro, Satoshi; Kikuchi, Ken'ichi; Wakatsuki, Atsushi; Kukutsu, Naoya; Kado, Yuichi

    2009-10-12

    We propose a high-sweeping-speed optically synchronized dual-channel terahertz (THz) signal generator for an active gas-sensing system with a superconductor-insulator-superconductor (SIS) mixer. The generator can sweep a frequency range from 200 to 500 GHz at a speed of 375 GHz/s and a frequency resolution of 500 MHz. With the developed gas-sensing system, a gas-absorption-line measurement was successfully carried out with N(2)O gas in that frequency range.

  13. A new-generation radiation monitoring vehicle

    International Nuclear Information System (INIS)

    Gryc, Lubomir; Cespirova, Irena; Sury, Jan; Hanak, Vitezslav; Sladek, Petr

    2015-01-01

    A new radiation monitoring vehicle has been developed within the MOSTAR (Mobile and Stationary Radiation monitoring systems for a new generation of radiation monitoring network) Security Research project. The vehicle accommodates a system for radiation survey using scintillation detectors. Basic spectroscopy is performed with a sodium iodine crystal system, directional measurement is based on two side-mounted plastic detectors, logging dose rates, GPS coordinates and displaying results in a map. A semiconductor spectrometric chain for rapid qualitative and quantitative evaluation of environmental samples is also included. (orig.)

  14. The influence of high intensity terahertz radiation on mammalian cell adhesion, proliferation and differentiation.

    Science.gov (United States)

    Williams, Rachel; Schofield, Amy; Holder, Gareth; Downes, Joan; Edgar, David; Harrison, Paul; Siggel-King, Michele; Surman, Mark; Dunning, David; Hill, Stephen; Holder, David; Jackson, Frank; Jones, James; McKenzie, Julian; Saveliev, Yuri; Thomsen, Neil; Williams, Peter; Weightman, Peter

    2013-01-21

    Understanding the influence of exposure of biological systems to THz radiation is becoming increasingly important. There is some evidence to suggest that THz radiation can influence important activities within mammalian cells. This study evaluated the influence of the high peak power, low average power THz radiation produced by the ALICE (Daresbury Laboratory, UK) synchrotron source on human epithelial and embryonic stem cells. The cells were maintained under standard tissue culture conditions, during which the THz radiation was delivered directly into the incubator for various exposure times. The influence of the THz radiation on cell morphology, attachment, proliferation and differentiation was evaluated. The study demonstrated that there was no difference in any of these parameters between irradiated and control cell cultures. It is suggested that under these conditions the cells are capable of compensating for any effects caused by exposure to THz radiation with the peak powers levels employed in these studies.

  15. Polarization-stable dual-color DFB fibre laser system for CW terahertz generation

    DEFF Research Database (Denmark)

    Eichhorn, Finn; Petersen, Jens Engholm; Jepsen, Peter Uhd

    , and crystalline materials such as explosives, illicit drugs, and pharmaceutical products. At the same time, the long wavelength of the radiation (1 THz corresponds to a wavelength of 300 µm) guarantees little scattering in most packing materials and textiles. This combination allows THz sensors to “look through...

  16. Modelling terahertz radiation absorption and reflection with computational phantoms of skin and associated appendages

    Science.gov (United States)

    Vilagosh, Zoltan; Lajevardipour, Alireza; Wood, Andrew

    2018-01-01

    Finite-difference time-domain (FDTD) computational phantoms aid the analysis of THz radiation interaction with human skin. The presented computational phantoms have accurate anatomical layering and electromagnetic properties. A novel "large sheet" simulation technique is used allowing for a realistic representation of lateral absorption and reflection of in-vivo measurements. Simulations carried out to date have indicated that hair follicles act as THz propagation channels and confirms the possible role of melanin, both in nevi and skin pigmentation, to act as a significant absorber of THz radiation. A novel freezing technique has promise in increasing the depth of skin penetration of THz radiation to aid diagnostic imaging.

  17. Computed tomography image using sub-terahertz waves generated from a high-T{sub c} superconducting intrinsic Josephson junction oscillator

    Energy Technology Data Exchange (ETDEWEB)

    Kashiwagi, T., E-mail: kashiwagi@ims.tsukuba.ac.jp; Minami, H.; Kadowaki, K. [Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba (Japan); Division of Materials Science, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1, Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); Nakade, K.; Saiwai, Y.; Kitamura, T.; Watanabe, C.; Ishida, K.; Sekimoto, S.; Asanuma, K.; Yasui, T.; Shibano, Y. [Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba (Japan); Tsujimoto, M. [Department of Electronic Science and Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan); Yamamoto, T. [Wide Bandgap Materials Group, Optical and Electronic Materials Unit, Environment and Energy Materials Division, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Marković, B. [Faculty of Sciences, University of Montenegro, George Washington Str., 81000 Podgorica (Montenegro); Mirković, J. [Faculty of Science, University of Montenegro, and CETI, Put Radomira Ivanovica, 81000 Podgorica (Montenegro); Klemm, R. A. [Department of Physics, University of Central Florida, 4000 Central Florida Blvd., Orlando, Florida 32816-2385 (United States)

    2014-02-24

    A computed tomography (CT) imaging system using monochromatic sub-terahertz coherent electromagnetic waves generated from a device constructed from the intrinsic Josephson junctions in a single crystalline mesa structure of the high-T{sub c} superconductor Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+δ} was developed and tested on three samples: Standing metallic rods supported by styrofoam, a dried plant (heart pea) containing seeds, and a plastic doll inside an egg shell. The images obtained strongly suggest that this CT imaging system may be useful for a variety of practical applications.

  18. Towards the generation of random bits at terahertz rates based on a chaotic semiconductor laser

    International Nuclear Information System (INIS)

    Kanter, Ido; Aviad, Yaara; Reidler, Igor; Cohen, Elad; Rosenbluh, Michael

    2010-01-01

    Random bit generators (RBGs) are important in many aspects of statistical physics and crucial in Monte-Carlo simulations, stochastic modeling and quantum cryptography. The quality of a RBG is measured by the unpredictability of the bit string it produces and the speed at which the truly random bits can be generated. Deterministic algorithms generate pseudo-random numbers at high data rates as they are only limited by electronic hardware speed, but their unpredictability is limited by the very nature of their deterministic origin. It is widely accepted that the core of any true RBG must be an intrinsically non-deterministic physical process, e.g. measuring thermal noise from a resistor. Owing to low signal levels, such systems are highly susceptible to bias, introduced by amplification, and to small nonrandom external perturbations resulting in a limited generation rate, typically less than 100M bit/s. We present a physical random bit generator, based on a chaotic semiconductor laser, having delayed optical feedback, which operates reliably at rates up to 300Gbit/s. The method uses a high derivative of the digitized chaotic laser intensity and generates the random sequence by retaining a number of the least significant bits of the high derivative value. The method is insensitive to laser operational parameters and eliminates the necessity for all external constraints such as incommensurate sampling rates and laser external cavity round trip time. The randomness of long bit strings is verified by standard statistical tests.

  19. Towards the generation of random bits at terahertz rates based on a chaotic semiconductor laser

    Science.gov (United States)

    Kanter, Ido; Aviad, Yaara; Reidler, Igor; Cohen, Elad; Rosenbluh, Michael

    2010-06-01

    Random bit generators (RBGs) are important in many aspects of statistical physics and crucial in Monte-Carlo simulations, stochastic modeling and quantum cryptography. The quality of a RBG is measured by the unpredictability of the bit string it produces and the speed at which the truly random bits can be generated. Deterministic algorithms generate pseudo-random numbers at high data rates as they are only limited by electronic hardware speed, but their unpredictability is limited by the very nature of their deterministic origin. It is widely accepted that the core of any true RBG must be an intrinsically non-deterministic physical process, e.g. measuring thermal noise from a resistor. Owing to low signal levels, such systems are highly susceptible to bias, introduced by amplification, and to small nonrandom external perturbations resulting in a limited generation rate, typically less than 100M bit/s. We present a physical random bit generator, based on a chaotic semiconductor laser, having delayed optical feedback, which operates reliably at rates up to 300Gbit/s. The method uses a high derivative of the digitized chaotic laser intensity and generates the random sequence by retaining a number of the least significant bits of the high derivative value. The method is insensitive to laser operational parameters and eliminates the necessity for all external constraints such as incommensurate sampling rates and laser external cavity round trip time. The randomness of long bit strings is verified by standard statistical tests.

  20. Terahertz radiation on the base of accelerated charge carriers in GaAs; Terahertz-Strahlung auf der Basis beschleunigter Ladungstraeger in GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Dreyhaupt, Andre

    2008-07-01

    Electromagnetic radiation in the frequency range between about 100 GHz and 5 THz can be used for spectroscopy and microscopy, but it is also promising for security screening and even wireless communication. In the present thesis a planar photoconducting large-area THz radiation source is presented. The device exhibits outstanding properties, in particular high THz field strength and generation efficiency and large spectral bandwidth with short THz pulse length. The THz emission is based on acceleration and deceleration of photoexcited carriers in semiconductor substrates. A metallic interdigitated structure at the surface of semi-insulating GaAs provides the electrodes of an Auston switch. In a biased structure photoexcited charge carriers are accelerated. Hence electromagnetic waves are emitted. An appropriately structured second metallization, electrically isolated from the electrodes, prevents destructive interference of the emitted waves. The structure investigated here combines several advantages of different conventional photoconducting THz sources. First, it provides high electric acceleration fields at moderate voltages owing to the small electrode separation. Second, the large active area in the mm2 range allows excitation by large optical powers of some mW. Optical excitation with near-infrared femtosecond lasers is possible with repetition rates in the GHz range. The presented results point out the excellent characteristics regarding the emitted THz field strength, average power, spectral properties, and easy handling of the interdigitated structure in comparison to various conventional emitter structures. Various modifications of the semiconductor substrate and the optimum excitation conditions were investigated. In the second part of this thesis the dynamic conductivity of GaAs/Al{sub x}Ga{sub 1-x}As superlattices in an applied static electric field was investigated with time-resolved THz spectroscopy. The original goal was to explore whether the

  1. Optimization of a coherent synchrotron radiation source in the Tera-hertz range for high-resolution spectroscopy of molecules of astrophysical interest

    International Nuclear Information System (INIS)

    Barros, J.

    2012-01-01

    Fourier Transform spectroscopy is the most used multiplex tool for high-resolution measurements in the infrared range. Its extension to the Tera-hertz domain is of great interest for spectroscopic studies of interstellar molecules. This application is however hampered by the lack of dedicated, broadband sources with a sufficient intensity and stability. In this work, Coherent Synchrotron Radiation (CSR) was used as a source for molecular spectroscopy at high resolution on the AILES infrared and Tera-hertz beamline of SOLEIL synchrotron. The beamline being optimized for far-infrared, we could characterize the properties of CSR and compare them to the incoherent synchrotron radiation. A double detection system allowed to correct the effect of the source-related instabilities, hence to significantly increase the signal-to-noise ratio. Pure rotational spectra were measured using these developments. The case of the propynal molecule, for which a refined set of rotational and centrifugal distortion constants was calculated, proves the complementarity between CSR and the classical microwave or infrared sources. (author)

  2. Domain-Reversed Lithium Niobate Single-Crystal Fibers are Potentially for Efficient Terahertz Wave Generation

    Directory of Open Access Journals (Sweden)

    Yalin Lu

    2008-01-01

    Full Text Available Nonlinear frequency conversion remains one of the dominant approaches to efficiently generate THz waves. Significant material absorption in the THz range is the main factor impeding the progress towards this direction. In this research, a new multicladding nonlinear fiber design was proposed to solve this problem, and as the major experimental effort, periodic domain structure was introduced into lithium niobate single-crystal fibers by electrical poling. The introduced periodic domain structures were nondestructively revealed using a crossly polarized optical microscope and a confocal scanning optical microscope for quality assurance.

  3. Time-domain electric field enhancement on micrometer scale in coupled split ring resonator upon terahertz radiation

    DEFF Research Database (Denmark)

    Lange, Simon Lehnskov; Iwaszczuk, Krzysztof; Hoffmann, Matthias

    2016-01-01

    We present here a novel design for a coupled split ring resonator antenna optimized for time-domain electric field enhancement in the 0.1 to 1 terahertz (THz) range. The antenna is designed to be sensitive to the incident field polarization and seeks to avoid metal damage due to electron bombardm...

  4. Molecular spectrum of laterally coupled quantum rings under intense terahertz radiation.

    Science.gov (United States)

    Baghramyan, Henrikh M; Barseghyan, Manuk G; Laroze, David

    2017-09-05

    We study the influence of intense THz laser radiation and electric field on molecular states of laterally coupled quantum rings. Laser radiation shows the capability to dissociate quantum ring molecule and add 2-fold degeneracy to the molecular states at the fixed value of the overlapping size between rings. It is shown that coupled to decoupled molecular states phase transition points form almost a straight line with a slope equal to two. In addition, the electric field direction dependent energy spectrum shows unexpected oscillations, demonstrating strong coupling between molecular states. Besides, intraband absorption is considered, showing both blue and redshifts in its spectrum. The obtained results can be useful for the controlling of degeneracy of the discrete energy spectrum of nanoscale structures and in the tunneling effects therein.

  5. Observation of coherently enhanced tunable narrow-band terahertz transition radiation from a relativistic sub-picosecond electron bunch train

    International Nuclear Information System (INIS)

    Piot, P.; Maxwell, T. J.; Sun, Y.-E; Ruan, J.; Lumpkin, A. H.; Thurman-Keup, R.; Rihaoui, M. M.

    2011-01-01

    We experimentally demonstrate the production of narrow-band (δf/f≅20% at f≅0.5THz) transition radiation with tunable frequency over [0.37, 0.86] THz. The radiation is produced as a train of sub-picosecond relativistic electron bunches transits at the vacuum-aluminum interface of an aluminum converter screen. The bunch train is generated via a transverse-to-longitudinal phase space exchange technique. We also show a possible application of modulated beams to extend the dynamical range of a popular bunch length diagnostic technique based on the spectral analysis of coherent radiation.

  6. Graphene based terahertz phase modulators

    Science.gov (United States)

    Kakenov, N.; Ergoktas, M. S.; Balci, O.; Kocabas, C.

    2018-07-01

    Electrical control of amplitude and phase of terahertz radiation (THz) is the key technological challenge for high resolution and noninvasive THz imaging. The lack of active materials and devices hinders the realization of these imaging systems. Here, we demonstrate an efficient terahertz phase and amplitude modulation using electrically tunable graphene devices. Our device structure consists of electrolyte-gated graphene placed at quarter wavelength distance from a reflecting metallic surface. In this geometry, graphene operates as a tunable impedance surface which yields electrically controlled reflection phase. Terahertz time domain reflection spectroscopy reveals the voltage controlled phase modulation of π and the reflection modulation of 50 dB. To show the promises of our approach, we demonstrate a multipixel phase modulator array which operates as a gradient impedance surface.

  7. Terahertz Technology: A Boon to Tablet Analysis

    Science.gov (United States)

    Wagh, M. P.; Sonawane, Y. H.; Joshi, O. U.

    2009-01-01

    The terahertz gap has a frequency ranges from ∼0.3 THz to ∼10 THz in the electromagnetic spectrum which is in between microwave and infrared. The terahertz radiations are invisible to naked eye. In comparison with x-ray they are intrinsically safe, non-destructive and non-invasive. Terahertz spectroscopy enables 3D imaging of structures and materials, and the measurement of the unique spectral fingerprints of chemical and physical forms. Terahertz radiations are produced by a dendrimer based high power terahertz source and spectroscopy technologies. It resolves many of the questions left unanswered by complementary techniques, such as optical imaging, Raman and infrared spectra. In the pharmaceutical industries it enables nondestructive, internal, chemical analysis of tablets, capsules, and other dosage forms. Tablet coatings are a major factor in drug bioavailability. Therefore tablet coatings integrity and uniformity are of crucial importance to quality. Terahertz imaging gives an unparalleled certainty about the integrity of tablet coatings and the matrix performance of tablet cores. This article demonstrates the potential of terahertz pulse imaging for the analysis of tablet coating thickness by illustrating the technique on tablets. PMID:20490288

  8. Terahertz Imaging for Biomedical Applications Pattern Recognition and Tomographic Reconstruction

    CERN Document Server

    Yin, Xiaoxia; Abbott, Derek

    2012-01-01

    Terahertz Imaging for Biomedical Applications: Pattern Recognition and Tomographic Reconstruction presents the necessary algorithms needed to assist screening, diagnosis, and treatment, and these algorithms will play a critical role in the accurate detection of abnormalities present in biomedical imaging. Terahertz biomedical imaging has become an area of interest due to its ability to simultaneously acquire both image and spectral information. Terahertz imaging systems are being commercialized with an increasing number of trials performed in a biomedical setting. Terahertz tomographic imaging and detection technology contributes to the ability to identify opaque objects with clear boundaries,and would be useful to both in vivo and ex vivo environments. This book also: Introduces terahertz radiation techniques and provides a number of topical examples of signal and image processing, as well as machine learning Presents the most recent developments in an emerging field, terahertz radiation Utilizes new methods...

  9. Resonant Excitation of Terahertz Surface Plasmons in Subwavelength Metal Holes

    Directory of Open Access Journals (Sweden)

    Weili Zhang

    2007-01-01

    Full Text Available We present a review of experimental studies of resonant excitation of terahertz surface plasmons in two-dimensional arrays of subwavelength metal holes. Resonant transmission efficiency higher than unity was recently achieved when normalized to the area occupied by the holes. The effects of hole shape, hole dimensions, dielectric function of metals, polarization dependence, and array film thickness on resonant terahertz transmission in metal arrays were investigated by the state-of-the-art terahertz time-domain spectroscopy. In particular, extraordinary terahertz transmission was demonstrated in arrays of subwavelength holes made even from Pb, a generally poor metal, and having thickness of only one-third of skin depth. Terahertz surface plasmons have potential applications in terahertz imaging, biosensing, interconnects, and development of integrated plasmonic components for terahertz generation and detection.

  10. Synchronous dual-wavelength pulse generation in coaxial pumping scheme and its application in terahertz difference frequency generation

    Science.gov (United States)

    Liu, Yang; Zhong, Kai; Mei, Jialin; Jin, Shuo; Ge, Meng; Xu, Degang; Yao, Jianquan

    2018-02-01

    A compact and flexible dual-wavelength laser with combined two laser crystals (a-cut and c-cut Nd:YLF) as the gain media under coaxially laser-diode (LD) end-pumping configuration was demonstrated and μW-level THz wave was generated based on difference frequency generation (DFG) in a GaSe crystal. The dynamics of coaxial pumping dualwavelength laser was theoretically investigated, showing that the power ratio and pulse interval for both wavelengths could be tuned by balancing the gains at both wavelengths via tuning pump focal position. Synchronized orthogonal 1047/1053 nm laser pulses were obtained and optimal power ratio was realized with the total output power of 2.92W at 5 kHz pumped by 10-W LD power. With an 8-mm-long GaSe crystal, 0.93 μW THz wave at 1.64 THz (182 μm) was generated. Such coaxially LD end-pumped lasers can be extended to various combinations of neodymium doped laser media to produce different THz wavelengths for costless and portable applications.

  11. Terahertz and infrared Smith-Purcell radiation from Babinet metasurfaces: Loss and efficiency

    Science.gov (United States)

    Liu, Liu; Chang, Huiting; Zhang, Chi; Song, Yanan; Hu, Xinhua

    2017-10-01

    When a charged particle moves close and parallel to the surface of a Babinet metasurface composed of metallic C -aperture resonators, strong electromagnetic radiation arises at resonant frequency. Here we systematically study the Smith-Purcell effects in Babinet metasurfaces with different periods. By tuning the period, the resonant (or working) frequency of the metasurface can vary from GHz to THz and infrared ranges. It is found that for working frequencies lower than 10 GHz, the ratio of absorption loss to input power is about 3.7%. Although the loss ratio increases with increasing working frequency, it remains as low as 11% (29%) at a working frequency of 10 THz (224 THz). Due to the existence of loss, a nonlinear relationship is also found between resonant frequency and the reciprocal of period. Our results suggest that Babinet metasurfaces could be a good candidate for fabricating efficient, compact THz and infrared free-electron light sources.

  12. Radiative generation of the Higgs potential

    International Nuclear Information System (INIS)

    Chun, Eung Jin; Jung, Sunghoon; Lee, Hyun Min

    2013-01-01

    We consider the minimal extension of the Standard Model with U(1) B−L gauge symmetry for generating the Higgs potential radiatively. Assuming that the full scalar potential vanishes at the vacuum instability scale, we achieve the goal in terms of two free parameters, the B−L gauge coupling and the right-handed neutrino Yukawa coupling. The B−L gauge symmetry is broken spontaneously by the Coleman–Weinberg mechanism while the scale symmetry breakdown induces electroweak symmetry breaking through the radiative generation of appropriate scalar quartic couplings. We show that there is a reasonable parameter space that is consistent with a correct electroweak symmetry breaking and the observed Higgs mass

  13. Terahertz electric field driven electric currents and ratchet effects in graphene

    Energy Technology Data Exchange (ETDEWEB)

    Ganichev, Sergey D.; Weiss, Dieter; Eroms, Jonathan [Terahertz Center, University of Regensburg (Germany)

    2017-11-15

    Terahertz field induced photocurrents in graphene were studied experimentally and by microscopic modeling. Currents were generated by cw and pulsed laser radiation in large area as well as small-size exfoliated graphene samples. We review general symmetry considerations leading to photocurrents depending on linear and circular polarized radiation and then present a number of situations where photocurrents were detected. Starting with the photon drag effect under oblique incidence, we proceed to the photogalvanic effect enhancement in the reststrahlen band of SiC and edge-generated currents in graphene. Ratchet effects were considered for in-plane magnetic fields and a structure inversion asymmetry as well as for graphene with non-symmetric patterned top gates. Lastly, we demonstrate that graphene can be used as a fast, broadband detector of terahertz radiation. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Scanning Terahertz Heterodyne Imaging Systems

    Science.gov (United States)

    Siegel, Peter; Dengler, Robert

    2007-01-01

    Scanning terahertz heterodyne imaging systems are now at an early stage of development. In a basic scanning terahertz heterodyne imaging system, (see Figure 1) two far-infrared lasers generate beams denoted the local-oscillator (LO) and signal that differ in frequency by an amount, denoted the intermediate frequency (IF), chosen to suit the application. The LO beam is sent directly to a mixer as one of two inputs. The signal beam is focused to a spot on or in the specimen. After transmission through or reflection from the specimen, the beams are focused to a spot on a terahertz mixer, which extracts the IF outputs. The specimen is mounted on a translation stage, by means of which the focal spot is scanned across the specimen to build up an image.

  15. Terahertz radar cross section measurements.

    Science.gov (United States)

    Iwaszczuk, Krzysztof; Heiselberg, Henning; Jepsen, Peter Uhd

    2010-12-06

    We perform angle- and frequency-resolved radar cross section (RCS) measurements on objects at terahertz frequencies. Our RCS measurements are performed on a scale model aircraft of size 5-10 cm in polar and azimuthal configurations, and correspond closely to RCS measurements with conventional radar on full-size objects. The measurements are performed in a terahertz time-domain system with freely propagating terahertz pulses generated by tilted pulse front excitation of lithium niobate crystals and measured with sub-picosecond time resolution. The application of a time domain system provides ranging information and also allows for identification of scattering points such as weaponry attached to the aircraft. The shapes of the models and positions of reflecting parts are retrieved by the filtered back projection algorithm.

  16. Ionising radiation and trans-generational instability

    International Nuclear Information System (INIS)

    Vrhovac, I.; Niksic, G.

    2007-01-01

    Indirect monitoring of the impact posed by ionising radiation to the genome instability of the descendants, consequent to the irradiation of one of their parents, boils down to the investigation of changes occurring exclusively in the mini-satellite loci of the cells constituting the gametal developmental line. The resultant mini-satellite mutations are expressed in their percentages, and equal to the ratio of the number of mutated alleles in that particular generation over the total number of alleles present. The impact of ionising radiation to the irradiated parent's offspring was first noticed on haematopoietic mouse stem-cells. Even though an irradiated cell of a female parent lacks any mutations whatsoever, daughter cells present with the increased mutation rates. The observed phenomenon of the so called trans-generational instability has been defined as the occurrence of mutations in the genome of individuals originating from the irradiated ancestors. Due to the aforementioned, one can conclude that these mutations need not be present in the irradiated parental cells, and do not necessarily vanish in the next few generations, but may result in the increase in mutation rates observed in the latter. The results of the investigations performed on the animal model, as well as of those carried out in human population, point to the occurrence of significant changes to be found on mini-satellite loci of the descending generation, while the mechanism underlying those changes hasn't been completely clarified yet, and, therefore, calls for the further investigation. (author)

  17. Radar cross section measurements using terahertz waves

    DEFF Research Database (Denmark)

    Iwaszczuk, Krzysztof; Heiselberg, Henning; Jepsen, Peter Uhd

    2010-01-01

    Radar cross sections at terahertz frequencies are measured on scale models of aircrafts. A time domain broadband THz system generates freely propagating THz pulses measured with sub-picosecond time resolution. The THz radiation is generated using fs laser pulses by optical rectification...... in order to measure realistic radar cross sections. RCS polar and azimuthal angle plots of F-16 and F-35 are presented....... in a lithium niobate crystal with application of the tilted wave front method, resulting in high electric field THz pulses with a broad band spectrum from 100 GHz up to 4 THz. The corresponding wave lengths are two orders of magnitude smaller than normal radars and we therefore use scale models of size 5-10 cm...

  18. Surface and interface states of Bi{sub 2}Se{sub 3} thin films investigated by optical second-harmonic generation and terahertz emission

    Energy Technology Data Exchange (ETDEWEB)

    Hamh, S. Y.; Park, S.-H.; Lee, J. S., E-mail: jsl@gist.ac.kr [Department of Physics and Photon Science, School of Physics and Chemistry, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Jerng, S.-K.; Jeon, J. H.; Chun, S. H. [Department of Physics and Graphene Research Institute, Sejong University, Seoul 143-747 (Korea, Republic of); Jeon, J. H.; Kahng, S. J. [Department of Physics, Korea University, Seoul 136-701 (Korea, Republic of); Yu, K.; Choi, E. J. [Department of Physics, University or Seoul, Seoul 130-743 (Korea, Republic of); Kim, S.; Choi, S.-H. [Department of Applied Physics, College of Applied Science, Kyung Hee University, Yongin 446-701 (Korea, Republic of); Bansal, N. [Department of Electrical and Computer Engineering, Rutgers, The state University of New Jersey, Piscataway, New Jersey 08854 (United States); Oh, S. [Department of Physics and Astronomy, Rutgers, The state University of New Jersey, Piscataway, New Jersey 08854 (United States); Park, Joonbum; Kho, Byung-Woo; Kim, Jun Sung [Department of Physics, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of)

    2016-02-01

    We investigate the surface and interface states of Bi{sub 2}Se{sub 3} thin films by using the second-harmonic generation technique. Distinct from the surface of bulk crystals, the film surface and interface show the isotropic azimuth dependence of second-harmonic intensity, which is attributed to the formation of randomly oriented domains on the in-plane. Based on the nonlinear susceptibility deduced from the model fitting, we determine that the surface band bending induced in a space charge region occurs more strongly at the film interface facing the Al{sub 2}O{sub 3} substrate or capping layer compared with the interface facing the air. We demonstrate that distinct behavior of the terahertz electric field emitted from the samples can provide further information about the surface electronic state of Bi{sub 2}Se{sub 3}.

  19. Terahertz wave manipulation based on multi-bit coding artificial electromagnetic surfaces

    Science.gov (United States)

    Li, Jiu-Sheng; Zhao, Ze-Jiang; Yao, Jian-Quan

    2018-05-01

    A polarization insensitive multi-bit coding artificial electromagnetic surface is proposed for terahertz wave manipulation. The coding artificial electromagnetic surfaces composed of four-arrow-shaped particles with certain coding sequences can generate multi-bit coding in the terahertz frequencies and manipulate the reflected terahertz waves to the numerous directions by using of different coding distributions. Furthermore, we demonstrate that our coding artificial electromagnetic surfaces have strong abilities to reduce the radar cross section with polarization insensitive for TE and TM incident terahertz waves as well as linear-polarized and circular-polarized terahertz waves. This work offers an effectively strategy to realize more powerful manipulation of terahertz wave.

  20. Nanometer size field effect transistors for terahertz detectors

    International Nuclear Information System (INIS)

    Knap, W; Rumyantsev, S; Coquillat, D; Dyakonova, N; Teppe, F; Vitiello, M S; Tredicucci, A; Blin, S; Shur, M; Nagatsuma, T

    2013-01-01

    Nanometer size field effect transistors can operate as efficient resonant or broadband terahertz detectors, mixers, phase shifters and frequency multipliers at frequencies far beyond their fundamental cut-off frequency. This work is an overview of some recent results concerning the application of nanometer scale field effect transistors for the detection of terahertz radiation. (paper)

  1. Semiconductor terahertz technology devices and systems at room temperature operation

    CERN Document Server

    Carpintero, G; Hartnagel, H; Preu, S; Raisanen, A

    2015-01-01

    Key advances in Semiconductor Terahertz (THz) Technology now promises important new applications enabling scientists and engineers to overcome the challenges of accessing the so-called "terahertz gap".  This pioneering reference explains the fundamental methods and surveys innovative techniques in the generation, detection and processing of THz waves with solid-state devices, as well as illustrating their potential applications in security and telecommunications, among other fields. With contributions from leading experts, Semiconductor Terahertz Technology: Devices and Systems at Room Tempe

  2. Terahertz metamaterials

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Hou-tong [Los Alamos National Laboratory; Taylor, Antoineete J [Los Alamos National Laboratory; Azad, Abul K [Los Alamos National Laboratory; O' Hara, John F [Los Alamos National Laboratory

    2009-01-01

    In this paper we present our recent developments in terahertz (THz) metamaterials and devices. Planar THz metamaterials and their complementary structures fabricated on suitable substrates have shown electric resonant response, which causes the band-pass or band-stop property in THz transmission and reflection. The operational frequency can be further tuned up to 20% upon photoexcitation of an integrated semiconductor region in the splitring resonators as the metamaterial elements. On the other hand, the use of semiconductors as metamaterial substrates enables dynamical control of metamaterial resonances through photoexcitation, and reducing the substrate carrier lifetime further enables an ultrafast switching recovery. The metamaterial resonances can also be actively controlled by application of a voltage bias when they are fabricated on semiconductor substrates with appropriate doping concentration and thickness. Using this electrically driven approach, THz modulation depth up to 80% and modulation speed of 2 MHz at room temperature have been demonstrated, which suggests practical THz applications.

  3. Broadband terahertz spectroscopy: principles, fundamental research and potential for industrial applications

    International Nuclear Information System (INIS)

    Zouaghi, W; Thomson, M D; Rabia, K; Hahn, R; Blank, V; Roskos, H G

    2013-01-01

    Terahertz radiation (also called T-rays) can be employed for spectroscopy and imaging, from the laboratory to industrial applications. In this paper we give an overview of how broadband optoelectronic THz techniques (i.e. using optical lasers to achieve THz generation and detection) can be implemented, and give examples of their unique use in solid-state physics, and in biological and industrial applications. (paper)

  4. Berkeley Lab's ALS generates femtosecond synchrotron radiation

    CERN Document Server

    Robinson, A L

    2000-01-01

    A team at Berkeley's Advanced Light Source has shown how a laser time-slicing technique provides a path to experiments with ultrafast time resolution. A Lawrence Berkeley National Laboratory team has succeeded in generating 300 fs pulses of synchrotron radiation at the ALS synchrotron radiation machine. The team's members come from the Materials Sciences Division (MSD), the Center for Beam Physics in the Accelerator and Fusion Research Division and the Advanced Light Source (ALS). Although this proof-of principle experiment made use of visible light on a borrowed beamline, the laser "time-slicing" technique at the heart of the demonstration will soon be applied in a new bend magnet beamline that was designed specially for the production of femtosecond pulses of X-rays to study long-range and local order in condensed matter with ultrafast time resolution. An undulator beamline based on the same technique has been proposed that will dramatically increase the flux and brightness. The use of X-rays to study the c...

  5. Terahertz radiation in In{sub 0.38}Ga{sub 0.62}As grown on a GaAs wafer with a metamorphic buffer layer under femtosecond laser excitation

    Energy Technology Data Exchange (ETDEWEB)

    Ponomarev, D. S., E-mail: ponomarev-dmitr@mail.ru; Khabibullin, R. A.; Yachmenev, A. E.; Maltsev, P. P. [Russian Academy of Sciences, Institute of Ultrahigh Frequency Semiconductor Electronics (Russian Federation); Grekhov, M. M. [National Research Nuclear University “MEPhI” (Russian Federation); Ilyakov, I. E.; Shishkin, B. V.; Akhmedzhanov, R. A. [Russian Academy of Sciences, Institute of Applied Physics (Russian Federation)

    2017-04-15

    The results of time-domain spectroscopy of the terahertz (THz) generation in a structure with an In{sub 0.38}Ga{sub 0.62}As photoconductive layer are presented. This structure grown by molecular-beam epitaxy on a GaAs substrate using a metamorphic buffer layer allows THz generation with a wide frequency spectrum (to 6 THz). This is due to the additional contribution of the photo-Dember effect to THz generation. The measured optical-to-terahertz conversion efficiency in this structure is 10{sup –5} at a rather low optical fluence of ~40 μJ/cm{sup 2}, which is higher than that in low-temperature grown GaAs by almost two orders of magnitude.

  6. Plasmon-enhanced terahertz emission in self-assembled quantum dots by femtosecond pulses

    Energy Technology Data Exchange (ETDEWEB)

    Carreño, F., E-mail: ferpo@fis.ucm.es; Antón, M. A., E-mail: antonm@fis.ucm.es; Melle, Sonia, E-mail: smelle@fis.ucm.es; Calderón, Oscar G., E-mail: oscargc@fis.ucm.es; Cabrera-Granado, E., E-mail: ecabrera@fis.ucm.es [Facultad de Óptica y Optometría, Universidad Complutense de Madrid, C/ Arcos de Jalón 118, 28037 Madrid (Spain); Cox, Joel, E-mail: jcox27@uwo.ca; Singh, Mahi R., E-mail: msingh@uwo.ca [Department of Physics and Astronomy, The University of Western Ontario, London N6A 3K7 (Canada); Egatz-Gómez, A., E-mail: Ana.Egatz-Gomez.1@nd.edu [Department of Chemical and Biomolecular Engineering, University of Notre Dame, South Bend, Indiana 46556 (United States)

    2014-02-14

    A scheme for terahertz (THz) generation from intraband transition in a self-assembled quantum dot (QD) molecule coupled to a metallic nanoparticle (MNP) is analyzed. The QD structure is described as a three-level atom-like system using the density matrix formalism. The MNP with spherical geometry is considered in the quasistatic approximation. A femtosecond laser pulse creates a coherent superposition of two subbands in the quantum dots and produces localized surface plasmons in the nanoparticle which act back upon the QD molecule via dipole-dipole interaction. As a result, coherent THz radiation with a frequency corresponding to the interlevel spacing can be obtained, which is strongly modified by the presence of the MNP. The peak value of the terahertz signal is analyzed as a function of nanoparticle's size, the MNP to QD distance, and the area of the applied laser field. In addition, we theoretically demonstrate that the terahertz pulse generation can be effectively controlled by making use of a train of femtosecond laser pulses. We show that by a proper choice of the parameters characterizing the pulse train a huge enhancement of the terahertz signal is obtained.

  7. Terahertz radiation-induced sub-cycle field electron emission across a split-gap dipole antenna

    International Nuclear Information System (INIS)

    Zhang, Jingdi; Averitt, Richard D.; Zhao, Xiaoguang; Fan, Kebin; Wang, Xiaoning; Zhang, Xin; Zhang, Gu-Feng; Geng, Kun

    2015-01-01

    We use intense terahertz pulses to excite the resonant mode (0.6 THz) of a micro-fabricated dipole antenna with a vacuum gap. The dipole antenna structure enhances the peak amplitude of the in-gap THz electric field by a factor of ∼170. Above an in-gap E-field threshold amplitude of ∼10 MV/cm −1 , THz-induced field electron emission is observed as indicated by the field-induced electric current across the dipole antenna gap. Field emission occurs within a fraction of the driving THz period. Our analysis of the current (I) and incident electric field (E) is in agreement with a Millikan-Lauritsen analysis where log (I) exhibits a linear dependence on 1/E. Numerical estimates indicate that the electrons are accelerated to a value of approximately one tenth of the speed of light

  8. Terahertz optoelectronics in graphene

    International Nuclear Information System (INIS)

    Otsuji, Taiichi

    2016-01-01

    Graphene has attracted considerable attention due to its extraordinary carrier transport, optoelectronic, and plasmonic properties originated from its gapless and linear energy spectra enabling various functionalities with extremely high quantum efficiencies that could never be obtained in any existing materials. This paper reviews recent advances in graphene optoelectronics particularly focused on the physics and device functionalities in the terahertz (THz) electromagnetic spectral range. Optical response of graphene is characterized by its optical conductivity and nonequilibrium carrier energy relaxation dynamics, enabling amplification of THz radiation when it is optically or electrically pumped. Current-injection THz lasing has been realized very recently. Graphene plasmon polaritons can greatly enhance the THz light and graphene matter interaction, enabling giant enhancement in detector responsivity as well as amplifier/laser gain. Graphene-based van der Waals heterostructures could give more interesting and energy-efficient functionalities. (author)

  9. Compact Tunable Narrowband Terahertz-Wave Source Based on Difference Frequency Generation Pumped by Dual Fiber Lasers in MgO:LiNbO3

    Science.gov (United States)

    Wada, Yoshio; Satoh, Takumi; Higashi, Yasuhiro; Urata, Yoshiharu

    2017-12-01

    We demonstrate a high-average-power, single longitudinal-mode, and tunable terahertz (THz)-wave source based on difference frequency generation (DFG) in a MgO:LiNbO3 (MgO:LN) crystal. The waves for DFG are generated using a pair of Yb-doped pulsed fiber lasers with a master oscillator power fiber amplifier configuration. The average power of the THz-wave output reaches 450 μW at 1.07 THz (280 μm) at a linewidth of 7.2 GHz, and the tunability ranges from 0.35 to 1.07 THz under the pulse repetition frequency of 500 kHz. A short burn-in test of the THz wave is also carried out, and the output power stability is within ± 5% of the averaged power without any active stabilizing technique. The combination of MgO:LN-DFG and stable and robust fiber laser sources is highly promising for the development of high-average-power THz-wave sources, particularly in the high transmission sub-THz region. This approach may enable new applications of THz-wave spectroscopy in imaging and remote sensing.

  10. Nano-Antenna For Terahertz (THz) Medical Imaging Applications

    Data.gov (United States)

    National Aeronautics and Space Administration — As a result of technological breakthroughs, research and applications in the Terahertz (THz) radiation system are experiencing explosive growth. The non-ionizing and...

  11. High efficiency optoelectronic terahertz sources

    Science.gov (United States)

    Lampin, Jean-François; Peytavit, Emilien; Akalin, Tahsin; Ducournau, G.; Hindle, Francis; Mouret, Gael

    2010-08-01

    We have developed a new generation of optoelectronic large bandwidth terahertz sources based on TEM horn antennas monolithically integrated with several types of photodetectors: low-temperature grown GaAs (LTG-GaAs) planar photoconductors, vertically integrated LTG-GaAs photoconductors on silicon substrate and uni-travelling-carrier photodiodes. Results of pulsed (time-domain) and photomixing (CW, frequency domain) experiments are presented.

  12. Terahertz pulsed imaging study of dental caries

    Science.gov (United States)

    Karagoz, Burcu; Altan, Hakan; Kamburoglu, Kıvanç

    2015-07-01

    Current diagnostic techniques in dentistry rely predominantly on X-rays to monitor dental caries. Terahertz Pulsed Imaging (TPI) has great potential for medical applications since it is a nondestructive imaging method. It does not cause any ionization hazard on biological samples due to low energy of THz radiation. Even though it is strongly absorbed by water which exhibits very unique chemical and physical properties that contribute to strong interaction with THz radiation, teeth can still be investigated in three dimensions. Recent investigations suggest that this method can be used in the early identification of dental diseases and imperfections in the tooth structure without the hazards of using techniques which rely on x-rays. We constructed a continuous wave (CW) and time-domain reflection mode raster scan THz imaging system that enables us to investigate various teeth samples in two or three dimensions. The samples comprised of either slices of individual tooth samples or rows of teeth embedded in wax, and the imaging was done by scanning the sample across the focus of the THz beam. 2D images were generated by acquiring the intensity of the THz radiation at each pixel, while 3D images were generated by collecting the amplitude of the reflected signal at each pixel. After analyzing the measurements in both the spatial and frequency domains, the results suggest that the THz pulse is sensitive to variations in the structure of the samples that suggest that this method can be useful in detecting the presence of caries.

  13. Theory of coherent transition radiation generated by ellipsoidal electron bunches

    NARCIS (Netherlands)

    Root, op 't W.P.E.M.; Smorenburg, P.W.; Oudheusden, van T.; Wiel, van der M.J.; Luiten, O.J.

    2007-01-01

    We present the theory of coherent transition radiation (CTR) generated by ellipsoidal electron bunches. We calculate analytical expressions for the electric field spectrum, the power spectrum, and the temporal electric field of CTR, generated by cylindrically symmetric ellipsoidal electron bunches

  14. Integrated heterodyne terahertz transceiver

    Science.gov (United States)

    Wanke, Michael C [Albuquerque, NM; Lee, Mark [Albuquerque, NM; Nordquist, Christopher D [Albuquerque, NM; Cich, Michael J [Albuquerque, NM

    2012-09-25

    A heterodyne terahertz transceiver comprises a quantum cascade laser that is integrated on-chip with a Schottky diode mixer. A terahertz signal can be received by an antenna connected to the mixer, an end facet or sidewall of the laser, or through a separate active section that can amplify the incident signal. The quantum cascade laser couples terahertz local oscillator power to the Schottky diode to mix with the received terahertz signal to provide an intermediate frequency output signal. The fully integrated transceiver optimizes power efficiency, sensitivity, compactness, and reliability. The transceiver can be used in compact, fieldable systems covering a wide variety of deployable applications not possible with existing technology.

  15. Integrated heterodyne terahertz transceiver

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Mark [Albuquerque, NM; Wanke, Michael C [Albuquerque, NM

    2009-06-23

    A heterodyne terahertz transceiver comprises a quantum cascade laser that is integrated on-chip with a Schottky diode mixer. An antenna connected to the Schottky diode receives a terahertz signal. The quantum cascade laser couples terahertz local oscillator power to the Schottky diode to mix with the received terahertz signal to provide an intermediate frequency output signal. The fully integrated transceiver optimizes power efficiency, sensitivity, compactness, and reliability. The transceiver can be used in compact, fieldable systems covering a wide variety of deployable applications not possible with existing technology.

  16. Terahertz transmission properties of silicon wafers using continuous-wave terahertz spectroscopy

    Science.gov (United States)

    Kim, Chihoon; Ahn, Jae Sung; Ji, Taeksoo; Eom, Joo Beom

    2017-04-01

    We present the spectral properties of Si wafers using continuous-wave terahertz (CW-THz) spectroscopy. By using a tunable laser source and a fixed distributed-feedback laser diode (DFB-LD), a stably tunable beat source for CW-THz spectroscopy system can be implemented. THz radiation is generated in the frequency range of 100 GHz-800 GHz by photomixing in a photoconductive antenna. We also measured CW-THz waveforms by changing the beat frequency and confirmed repeatability through repeated measurement. We calculated the peaks of the THz frequency by taking fast Fourier transforms (FFTs) of measured THz waveforms. The feasibility of CW-THz spectroscopy is demonstrated by the THz spectra of Si wafers with different resistivities, mobilities, and carrier concentrations. The results show that Si wafers with a lower resistivity absorb more THz waves. Thus, we expect our CW-THz system to have the advantage of being able to perform fast non-destructive analysis.

  17. Terahertz transmission properties of silicon wafers using continuous-wave terahertz spectroscopy

    International Nuclear Information System (INIS)

    Kim, Chihoon; Ahn, Jae Sung; Eom, Joo Beom; Ji, Taeksoo

    2017-01-01

    We present the spectral properties of Si wafers using continuous-wave terahertz (CW-THz) spectroscopy. By using a tunable laser source and a fixed distributed-feedback laser diode (DFB-LD), a stably tunable beat source for CW-THz spectroscopy system can be implemented. THz radiation is generated in the frequency range of 100 GHz–800 GHz by photomixing in a photoconductive antenna. We also measured CW-THz waveforms by changing the beat frequency and confirmed repeatability through repeated measurement. We calculated the peaks of the THz frequency by taking fast Fourier transforms (FFTs) of measured THz waveforms. The feasibility of CW-THz spectroscopy is demonstrated by the THz spectra of Si wafers with different resistivities, mobilities, and carrier concentrations. The results show that Si wafers with a lower resistivity absorb more THz waves. Thus, we expect our CW-THz system to have the advantage of being able to perform fast non-destructive analysis. (paper)

  18. Terahertz transport dynamics of graphene charge carriers

    DEFF Research Database (Denmark)

    Buron, Jonas Christian Due

    The electronic transport dynamics of graphene charge carriers at femtosecond (10-15 s) to picosecond (10-12 s) time scales are investigated using terahertz (1012 Hz) time-domain spectroscopy (THz-TDS). The technique uses sub-picosecond pulses of electromagnetic radiation to gauge the electrodynamic...... response of thin conducting films at up to multi-terahertz frequencies. In this thesis THz-TDS is applied towards two main goals; (1) investigation of the fundamental carrier transport dynamics in graphene at femtosecond to picosecond timescales and (2) application of terahertz time-domain spectroscopy...... to rapid and non-contact electrical characterization of large-area graphene, relevant for industrial integration. We show that THz-TDS is an accurate and reliable probe of graphene sheet conductance, and that the technique provides insight into fundamental aspects of the nanoscopic nature of conduction...

  19. Spectral investigation of hot-spot and cavity resonance effects on the terahertz radiation emitted from high-Tc superconducting Bi2Sr2CaCu2O8+δ single crystal mesa structures

    Science.gov (United States)

    Kadowaki, Kazuo; Watanabe, Chiharu; Minami, Hidetoshi; Yamamoto, Takashi; Kashiwagi, Takanari; Klemm, Richard

    2014-03-01

    Terahertz (THz) electromagnetic radiation emitted from high-Tc superconducting Bi2Sr2CaCu2O8+δ mesa structures in the case of single mesa and series-connected mesas is investigated by the FTIR spectroscopic technique while observing its temperature distribution simultaneously by a SiC photoluminescence technique. Changing the bias level, sudden jumps of the hot-spot position were clearly observed. Although the radiation intensity changes drastically associated with the jump of the hot spot position, the frequency is unaffected as long as the voltage per junction is kept constant. Since the frequency of the intense radiation satisfies the cavity resonance condition, we confirmed that the cavity resonance is of primarily importance for the synchronization of whole intrinsic Josephson junctions in the mesa for high power radiation. This work was supported in part by the Grant-in-Aid for challenging Exploratory Research, the Ministry of Education, Culture, Sports, Science & Technology (MEXT).

  20. Generation of terrestrial radiation database in the Larsemann Hills, Antarctica

    International Nuclear Information System (INIS)

    Pal, Rupali; Dhabekar, Bhushan; Jose, Jis Romal; Chinnaesakki, S.; Bakshi, A.K.; Datta, D.; Pradeepkumar, K.S.

    2018-01-01

    Natural background radiation in the environment includes terrestrial radiation, cosmic radiation from space and air activity due to radon/thoron. It is known that cosmic contribution increases near the poles. The terrestrial component is largely due to 232 Th and 238 U series and 40 K. BARC under the cosmic ray dosimetry project with National Centre for Antarctic and Ocean Research (NCAOR) has taken up measurement of natural background radiation at Larsemann Hills, Antarctica. The project includes generation of baseline data on terrestrial radioactivity in water, soil and rock and estimation of cosmic ray doses. Extensive radiation surveys were carried out by the BARC team in the 35 th and 36 th expedition in and around Larsemann hills in East Antarctica where the third Indian station 'Bharati' is situated. This paper presents mapping of terrestrial radiation levels in Antarctica which will help in strengthening the background radiation database and develop a Radiation Informatics System (RIS)

  1. A tunable dual-wavelength pump source based on simulated polariton scattering for terahertz-wave generation

    International Nuclear Information System (INIS)

    Sun, Bo; Liu, Jinsong; Yao, Jianquan; Li, Enbang

    2013-01-01

    We propose a dual-wavelength pump source by utilizing stimulated polariton scattering in a LiNbO 3 crystal. The residual pump and the generated tunable Stokes waves can be combined to generate THz-wave generation via difference frequency generation (DFG). With a pump energy of 49 mJ, Stokes waves with a tuning range from 1067.8 to 1074 nm have been generated, and an output energy of up to 14.9 mJ at 1070 nm has been achieved with a conversion efficiency of 21.7%. A sum frequency generation experiment was carried out to demonstrate the feasibility of the proposed scheme for THz-wave DFG. (paper)

  2. Aspheric lenses for terahertz imaging.

    Science.gov (United States)

    Lo, Yat Hei; Leonhardt, Rainer

    2008-09-29

    We present novel designs for aspheric lenses used in terahertz (THz) imaging. As different surfaces result in different beam shaping properties and in different losses from reflection and absorption, the resultant imaging resolution (i.e. the focal spot size) depends critically on the design approach. We evaluate the different lens designs using Kirchhoff's scalar diffraction theory, and test the predictions experimentally. We also show that our lenses can achieve sub-wavelength resolution. While our lens designs are tested with THz radiation, the design considerations are applicable also to other regions of the electro-magnetic spectrum.

  3. Apparatus and method for inhibiting the generation of excessive radiation

    International Nuclear Information System (INIS)

    Hernandez, F.; Chamberlain, J.

    1991-01-01

    This patent describes an apparatus for generating electron radiation or X-ray radiation. It comprises accelerator means for generating and accelerating electrons to form an electron beam which has a predetermined low intensity level for the generation of the electron radiation or a predetermined high intensity level for the generation of the X-ray radiation; supporting means for supporting a scattering foil and a target and for selectively moving either the foil into the trajectory of the electron beam having the low intensity level for generating the electron radiation upon impingement of the electrons there or on the target into the trajectory of the electron beam having the high intensity level for generating the X-ray radiation upon impingement of the electrons thereon; detecting means operable by the supporting means for sensing the position of the target relative to the trajectory of the electron beam; and inhibiting means coupled to the accelerator means and to the detecting means for preventing the generation of an electron beam having the high intensity level if the foil and not the target is positioned in the trajectory of the electron beam

  4. Graphene-based magnetless converter of terahertz wave polarization

    Science.gov (United States)

    Melnikova, Veronica S.; Polischuk, Olga V.; Popov, Vyacheslav V.

    2016-04-01

    The polarization conversion of terahertz radiation by the periodic array of graphene nanoribbons located at the surface of a high-refractive-index dielectric substrate (terahertz prism) is studied theoretically. Giant polarization conversion at the plasmon resonance frequencies takes place without applying external DC magnetic field. It is shown that the total polarization conversion can be reached at the total internal reflection of THz wave from the periodic array of graphene nanoribbons even at room temperature.

  5. Optically pumped terahertz sources

    Institute of Scientific and Technical Information of China (English)

    ZHONG Kai; SHI Wei; XU DeGang; LIU PengXiang; WANG YuYe; MEI JiaLin; YAN Chao; FU ShiJie; YAO JianQuan

    2017-01-01

    High-power terahertz (THz) generation in the frequency range of0.1-10 THz has been a fast-developing research area ever since the beginning of the THz boom two decades ago,enabling new technological breakthroughs in spectroscopy,communication,imaging,etc.By using optical (laser) pumping methods with near-or mid-infrared (IR) lasers,flexible and practical THz sources covering the whole THz range can be realized to overcome the shortage of electronic THz sources and now they are playing important roles in THz science and technology.This paper overviews various optically pumped THz sources,including femtosecond laser based ultrafast broadband THz generation,monochromatic widely tunable THz generation,single-mode on-chip THz source from photomixing,and the traditional powerful THz gas lasers.Full descriptions from basic principles to the latest progress are presented and their advantages and disadvantages are discussed as well.It is expected that this review gives a comprehensive reference to researchers in this area and additionally helps newcomers to quickly gain understanding of optically pumped THz sources.

  6. Miniature field deployable terahertz source

    Science.gov (United States)

    Mayes, Mark G.

    2006-05-01

    Developments in terahertz sources include compacted electron beam systems, optical mixing techniques, and multiplication of microwave frequencies. Although significant advances in THz science have been achieved, efforts continue to obtain source technologies that are more mobile and suitable for field deployment. Strategies in source development have approached generation from either end of the THz spectrum, from up-conversion of high-frequency microwave to down-conversion of optical frequencies. In this paper, we present the design of a THz source which employs an up-conversion method in an assembly that integrates power supply, electronics, and radiative component into a man-portable unit for situations in which a lab system is not feasible. This unit will ultimately evolve into a ruggedized package suitable for use in extreme conditions, e.g. temporary security check points or emergency response teams, in conditions where THz diagnostics are needed with minimal planning or logistical support. In order to meet design goals of reduced size and complexity, the inner workings of the unit ideally would be condensed into a monolithic active element, with ancillary systems, e.g. user interface and power, coupled to the element. To attain these goals, the fundamental component of our design is a THz source and lens array that may be fabricated with either printed circuit board or wafer substrate. To reduce the volume occupied by the source array, the design employs a metamaterial composed of a periodic lattice of resonant elements. Each resonant element is an LC oscillator, or tank circuit, with inductance, capacitance, and center frequency determined by dimensioning and material parameters. The source array and supporting electronics are designed so that the radiative elements are driven in-phase to yield THz radiation with a high degree of partial coherence. Simulation indicates that the spectral width of operation may be controlled by detuning of critical dimensions

  7. Third generation synchrotron radiation applied to materials science

    International Nuclear Information System (INIS)

    Kaufmann, E.N.; Yun, W.

    1993-01-01

    Utility of synchrotron radiation for characterization of materials and ramifications of availability of new third-generation, high-energy, high-intensity sources of synchrotron radiation are discussed. Examples are given of power of x-ray analysis techniques to be expected with these new machines

  8. Entropy flow and generation in radiative transfer between surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Z.M.; Basu, S. [Georgia Institute of Technolgy, Atlanta, GA (United States). George W. Woodruff School of Mechanical Engineering

    2007-02-15

    Entropy of radiation has been used to derive the laws of blackbody radiation and determine the maximum efficiency of solar energy conversion. Along with the advancement in thermophotovoltaic technologies and nanoscale heat radiation, there is an urgent need to determine the entropy flow and generation in radiative transfer between nonideal surfaces when multiple reflections are significant. This paper investigates entropy flow and generation when incoherent multiple reflections are included, without considering the effects of interference and photon tunneling. The concept of partial equilibrium is applied to interpret the monochromatic radiation temperature of thermal radiation, T{sub l}(l,{omega}), which is dependent on both wavelength l and direction {omega}. The entropy flux and generation can thus be evaluated for nonideal surfaces. It is shown that several approximate expressions found in the literature can result in significant errors in entropy analysis even for diffuse-gray surfaces. The present study advances the thermodynamics of nonequilibrium thermal radiation and will have a significant impact on the future development of thermophotovoltaic and other radiative energy conversion devices. (author)

  9. Coherent terahertz emission from Bi2Sr2CaCu2O8+δ intrinsic Josephson junction stacks

    International Nuclear Information System (INIS)

    Gross, Boris Andre

    2013-01-01

    In recent years, terahertz technology has become a rapidly growing sector, driven by the demands of a vast range of (potential) applications. The terahertz spectral range roughly spans from 300 GHz to 30 THz. In the low terahertz range, there is a lack of good and compact devices, that emit electromagnetic waves. Particularly, coherent, narrow-band and continuous-wave sources are lacking, and researchers are following many different approaches to fill this gap. The thesis at hand contributes to the exploration of one of those sources: Operating intrinsic Josephson junctions as emitters in the terahertz spectral range. Josephson junctions (JJs) work as direct current (dc) voltage to frequency converters, if operated in the resistive state. 1 mV voltage drop generates a frequency of about 484 GHz. Intrinsic Josephson junctions (IJJs) in the high temperature superconductor Bi 2 Sr 2 CaCu 2 O 8+δ (BSCCO) are adequate candidates for emitting devices; the layered structure of the material intrinsically provides stacks consisting of 1.5 nm thick, nearly perfectly equal JJs. The fabrication of a series of hundreds of JJs in a stack of micrometer thickness is easily feasible, which is essential for high power frequency generation. Further, the energy gap of BSCCO is in principle large enough to allow for frequencies up to more than 10 THz. The key challenge is the synchronization of all IJJs in order to produce coherent radiation. In 2007, a research team from Argonne National Laboratories succeeded in detecting coherent terahertz radiation from more than 500 synchronized IJJs in a mesa structure. The frequencies ranged from 350 to 850 GHz with output powers up to 0.5 μW. They proposed the formation of electromagnetic standing waves in the cavity of the mesa as synchronization mechanism. Coming from the fully resistive state (nonzero voltage across all junctions), the radiation occurred in the bias regime, where groups of junctions switch back to the zero voltage state

  10. Nanoscale Terahertz Emission Spectroscopy

    DEFF Research Database (Denmark)

    Pedersen, Pernille Klarskov; Kim, Hyewon; Colvin, Vicki L.

    By utilizing plasmonic coupling to an AFM probe, we demonstrate Laser Terahertz Emission Nanoscopy (LTEN) with sub-20 nm resolution. We demonstrate the resolution by imaging a single gold nanorod on an InAs substrate....

  11. Squeezing terahertz light into nanovolumes: Nanoantenna enhanced terahertz spectroscopy (NETS) of semiconductor quantum dots

    KAUST Repository

    Toma, Andrea

    2015-01-14

    Terahertz spectroscopy has vast potentialities in sensing a broad range of elementary excitations (e.g., collective vibrations of molecules, phonons, excitons, etc.). However, the large wavelength associated with terahertz radiation (about 300 μm at 1 THz) severely hinders its interaction with nano-objects, such as nanoparticles, nanorods, nanotubes, and large molecules of biological relevance, practically limiting terahertz studies to macroscopic ensembles of these compounds, in the form of thick pellets of crystallized molecules or highly concentrated solutions of nanomaterials. Here we show that chains of terahertz dipole nanoantennas spaced by nanogaps of 20 nm allow retrieving the spectroscopic signature of a monolayer of cadmium selenide quantum dots, a significant portion of the signal arising from the dots located within the antenna nanocavities. A Fano-like interference between the fundamental antenna mode and the phonon resonance of the quantum dots is observed, accompanied by an absorption enhancement factor greater than one million. NETS can find immediate applications in terahertz spectroscopic studies of nanocrystals and molecules at extremely low concentrations. Furthermore, it shows a practicable route toward the characterization of individual nano-objects at these frequencies.

  12. Terahertz pulse imaging in reflection geometry of human skin cancer and skin tissue

    International Nuclear Information System (INIS)

    Woodward, Ruth M; Cole, Bryan E; Wallace, Vincent P; Pye, Richard J; Arnone, Donald D; Linfield, Edmund H; Pepper, Michael

    2002-01-01

    We demonstrate the application of terahertz pulse imaging (TPI) in reflection geometry for the study of skin tissue and related cancers both in vitro and in vivo. The sensitivity of terahertz radiation to polar molecules, such as water, makes TPI suitable for studying the hydration levels in the skin and the determination of the lateral spread of skin cancer pre-operatively. By studying the terahertz pulse shape in the time domain we have been able to differentiate between diseased and normal tissue for the study of basal cell carcinoma (BCC). Basal cell carcinoma has shown a positive terahertz contrast, and inflammation and scar tissue a negative terahertz contrast compared to normal tissue. In vivo measurements on the stratum corneum have enabled visualization of the stratum corneum-epidermis interface and the study of skin hydration levels. These results demonstrate the potential of terahertz pulse imaging for the study of skin tissue and its related disorders, both in vitro and in vivo

  13. Heavy quark radiation in NLO+PS POWHEG generators

    Energy Technology Data Exchange (ETDEWEB)

    Buonocore, Luca; Tramontano, Francesco [Universita di Napoli ' ' Federico II' ' , Napoli (Italy); INFN, Sezione di Napoli, Napoli (Italy); Nason, Paolo [CERN, Theoretical Physics Department, Geneve (Switzerland); INFN, Sezione di Milano-Bicocca, Milano (Italy)

    2018-02-15

    In this paper we deal with radiation from heavy quarks in the context of next-to-leading order calculations matched to parton shower generators. A new algorithm for radiation from massive quarks is presented that has considerable advantages over the one previously employed. We implement the algorithm in the framework of the POWHEG-BOX, and compare it with the previous one in the case of the hvq generator for bottom production in hadronic collisions, and in the case of the bb4l generator for top production and decay. (orig.)

  14. A Thermoelectric Generator Replacing Radiator for Internal Combustion Engine Vehicles

    Directory of Open Access Journals (Sweden)

    Shiho Kim

    2011-12-01

    Full Text Available We have proposed and developed a low temperature thermoelectric generator (TEG using engine water coolant of light-duty vehicles. Experimental results from test vehicle, of which engine size is about 2.0 liters, show that fabricated prototype Thermoelectric Generator generates more than 75W for driving condition of 80 km/hour, and output power is about 28W during idle condition. The proposed TEG can replace conventional radiator without additional water pumps or mechanical devices except for basic components of legacy water cooling system of radiator.

  15. Quasioptische Terahertz-Bauelemente

    OpenAIRE

    Busch, Stefan Frederik (M. Sc.)

    2016-01-01

    Die Dissertation „Quasioptische Terahertz-Bauelemente“ beschäftigt sich mit der Frage, in wieweit sich das 3D-Druck-Verfahren Fused Deposition Modeling (FDM) für die Herstellung von quasioptischen Komponenten für Terahertz-Strahlung eignet. Neben der grundlegenden Validierung des Verfahrens werden verschiedenste 3D-gedruckte Bauelemente vorgestellt. Der Fokus liegt hierbei auf innovativen und neuartigen Quasioptiken, wie Alvarez-Optiken, Axicons, variablen Beugungsgittern und Diffractive Opti...

  16. Milliwatt-level output power in the sub-terahertz range generated by photomixing in a GaAs photoconductor

    Science.gov (United States)

    Peytavit, E.; Lepilliet, S.; Hindle, F.; Coinon, C.; Akalin, T.; Ducournau, G.; Mouret, G.; Lampin, J.-F.

    2011-11-01

    It is shown from accurate on-wafer measurement that continuous wave output powers of 1.2 mW at 50 GHz and 0.35 mW at 305 GHz can be generated by photomixing in a low temperature grown GaAs photoconductor using a metallic mirror Fabry-Pérot cavity. The output power is improved by a factor of about 100 as compared to the previous works on GaAs photomixers. A satisfactory agreement between the theory and the experiment is obtained in considering both the contribution of the holes and the electrons to the total photocurrent.

  17. New generation low power radiation survey instruments

    International Nuclear Information System (INIS)

    Waechter, D.A.; Bjarke, G.O.; Trujillo, F.; Umbarger, C.J.; Wolf, M.A.

    1984-01-01

    A number of new, ultra-low-powered radiation instruments have recently been developed at Los Alamos. Among these are two instruments which use a novel power source to eliminate costly batteries. The newly developed gamma detecting radiac, nicknamed the Firefly, and the alpha particle detecting instrument, called the Simple Cordless Alpha Monitor, both use recent advances in miniaturization and powersaving electronics to yield devices which are small, rugged, and very power-frugal. The two instruments consume so little power that the need for batteries to run them is eliminated. They are, instead, powered by a charged capacitor which will operate the instruments for an hour or more. Use of a capacitor as a power source eliminates many problems commonly associated with battery-operated instruments, such as having to open the case to change batteries, battery storage life, availability of batteries in the field, and some savings in weight. Both line power and mechanical sources are used to charge the storage capacitors which power the instruments

  18. Drug detection by terahertz time-domain spectroscopy

    International Nuclear Information System (INIS)

    Duan Ruixin; Zhu Yiming; Zhao Hongwei

    2013-01-01

    Due to unique spectral region, functional imaging ability, excellent penetration and safety characteristics of terahertz radiation, the terahertz technology rapidly becomes a vital method to detect and analyze drugs. In this paper, firstly, we identify the functional groups of anti-diabetic drugs by density functional theory (DFT), HIPHOP models and experimental results from terahertz time-domain spectroscopy measurements. Secondly, we identify four kinds of herbs of radix curcumae by using the support vector machine (SVM) analysis. Besides, we analyze the absorption of anhydrous and hydrous glucose, and determine the state of water in the crystalized D-glucose·H 2 O through the results of differential scanning calorimetry measurement. Finally, we summarize the advantages and disadvantages of terahertz time-domain spectroscopy method in drug detection and analyzing. (authors)

  19. Terahertz spectroscopy of two-dimensional subwavelength plasmonic structures

    Energy Technology Data Exchange (ETDEWEB)

    Azad, Abul K [Los Alamos National Laboratory; Chen, Houtong [Los Alamos National Laboratory; Taylor, Antoinette [Los Alamos National Laboratory; O' Hara, John F [Los Alamos National Laboratory; Han, Jiaguang [OSU; Lu, Xinchao [OSU; Zhang, Weili [OSU

    2009-01-01

    The fascinating properties of plasmonic structures have had significant impact on the development of next generation ultracompact photonic and optoelectronic components. We study two-dimensional plasmonic structures functioning at terahertz frequencies. Resonant terahertz response due to surface plasmons and dipole localized surface plasmons were investigated by the state-of-the-art terahertz time domain spectroscopy (THz-TDS) using both transmission and reflection configurations. Extraordinary terahertz transmission was demonstrated through the subwavelength metallic hole arrays made from good conducting metals as well as poor metals. Metallic arrays m!lde from Pb, generally a poor metal, and having optically thin thicknesses less than one-third of a skin depth also contributed in enhanced THz transmission. A direct transition of a surface plasmon resonance from a photonic crystal minimum was observed in a photo-doped semiconductor array. Electrical controls of the surface plasmon resonances by hybridization of the Schottkey diode between the metallic grating and the semiconductor substrate are investigated as a function of the applied reverse bias. In addition, we have demonstrated photo-induced creation and annihilation of surface plasmons with appropriate semiconductors at room temperature. According to the Fano model, the transmission properties are characterized by two essential contributions: resonant excitation of surface plasmons and nonresonant direct transmission. Such plasmonic structures may find fascinating applications in terahertz imaging, biomedical sensing, subwavelength terahertz spectroscopy, tunable filters, and integrated terahertz devices.

  20. EDITORIAL: Photonic terahertz technology

    Science.gov (United States)

    Lisauskas, Alvydas; Löffler, Torsten; Roskos, Hartmut G.

    2005-07-01

    In recent years, when reading newspapers and journals or watching TV, one has been able to find feature presentations dealing with the prospects of terahertz (THz) technology and its potential impact on market applications. THz technology aims to fill the THz gap in the electro-magnetic spectrum in order to make the THz frequency regime, which spans the two orders of magnitude from 100 GHz to 10 THz, accessible for applications. From the lower-frequency side, electronics keeps pushing upwards, while photonic approaches gradually improve our technological options at higher frequencies. The popular interest reflects the considerable advances in research in the THz field, and it is mainly advances in the photonic branch, with the highlight being the development of the THz quantum cascade laser, which in recent years have caught the imagination of the public, and of potential users and investors. This special issue of Semiconductor Science and Technology provides an overview of key scientific developments which currently represent the cutting edge of THz photonic technology. In order to be clear about the implications, we should define exactly what we mean by 'THz photonic technology', or synonymously 'THz photonics'. It is characterized by the way in which THz radiation (or a guided THz wave) is generated, namely by the use of lasers. This may be done in one of two fundamentally different schemes: (i) by laser action in the terahertz frequency range itself (THz lasers), or (ii) by down-conversion processes (photomixing) involving the radiation of lasers which operate in the visible, near-infrared or infrared spectral ranges, either in pulsed or continuous-wave mode. The field of THz photonics has grown so considerably that it is out of the question to cover all its aspects in a single special issue of a journal. We have elected, instead, to focus our attention on two types of development with a potentially strong impact on the THz field: first, on significant advances

  1. Enhanced THz radiation generation by photo-mixing of tophat lasers in rippled density plasma with a planar magnetostatic wiggler and s-parameter

    Science.gov (United States)

    Abedi-Varaki, M.

    2018-02-01

    In this paper, the effects of planar magnetostatic wiggler and s-parameter on the terahertz (THz) radiation generation through rippled plasma have been investigated. Efficient THz radiation generation by photo-mixing of tophat lasers for rippled density plasma in the presence of the wiggler field has been presented. Fundamental equations for the analysis of the non-linear current density and THz radiation generation by wiggler magnetostatic field have been derived. It is shown that for the higher order of the tophat lasers, the values of THz amplitude are greater. In fact, the higher order of the tophat lasers has a sharp gradient in the intensity of lasers, which leads to a stronger nonlinear ponderomotive force and, consequently, a stronger current density. In addition, it is seen that by increasing s-parameter, the normalized transverse profile becomes more focused near the axis of y. Furthermore, it is observed that the normalized laser efficiency has a decreasing trend with increasing normalized THz frequency for different values of the wiggler field. Also, it is shown that by employing a greater order of the tophat lasers and a stronger wiggler field, the efficiency of order of 30% can be achieved. Moreover, it is found that we can control focus and intensity of THz radiation emitted in rippled plasma by choosing the appropriate order of the tophat lasers and tuning of the wiggler field.

  2. Generation of radiation by intense plasma and electromagnetic undulators

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, C.

    1991-10-01

    We examine the characteristics of the classical radiation emission resulting from the interaction of a relativistic electron beam that propagates perpendicularly through a large amplitude relativistic plasma wave. Such a study is useful for evaluating the feasibility of using relativistic plasma waves as extremely short wavelength undulators for generating short wavelength radiation. The electron trajectories in a plasma wave undulator and in an ac FEL undulator are obtained using perturbation techniques. The spontaneous radiation frequency spectrum and angular distribution emitted by a single electron oscillating in these two undulators are then calculated. The radiation gain of a copropagating electromagnetic wave is calculated. The approximate analytic results for the trajectories, spontaneous radiation and gain are compared with 3-D simulation results. The characteristics of the plasma wave undulator are compared with the ac FEL undulator and linearly polarized magnetic undulator. 50 refs., 26 figs., 3 tabs.

  3. Generation of radiation by intense plasma and electromagnetic undulators

    International Nuclear Information System (INIS)

    Joshi, C.

    1991-10-01

    We examine the characteristics of the classical radiation emission resulting from the interaction of a relativistic electron beam that propagates perpendicularly through a large amplitude relativistic plasma wave. Such a study is useful for evaluating the feasibility of using relativistic plasma waves as extremely short wavelength undulators for generating short wavelength radiation. The electron trajectories in a plasma wave undulator and in an ac FEL undulator are obtained using perturbation techniques. The spontaneous radiation frequency spectrum and angular distribution emitted by a single electron oscillating in these two undulators are then calculated. The radiation gain of a copropagating electromagnetic wave is calculated. The approximate analytic results for the trajectories, spontaneous radiation and gain are compared with 3-D simulation results. The characteristics of the plasma wave undulator are compared with the ac FEL undulator and linearly polarized magnetic undulator. 50 refs., 26 figs., 3 tabs

  4. Laser-based terahertz-field-driven streak camera for the temporal characterization of ultrashort processes

    International Nuclear Information System (INIS)

    Schuette, Bernd

    2011-09-01

    In this work, a novel laser-based terahertz-field-driven streak camera is presented. It allows for a pulse length characterization of femtosecond (fs) extreme ultraviolet (XUV) pulses by a cross-correlation with terahertz (THz) pulses generated with a Ti:sapphire laser. The XUV pulses are emitted by a source of high-order harmonic generation (HHG) in which an intense near-infrared (NIR) fs laser pulse is focused into a gaseous medium. The design and characterization of a high-intensity THz source needed for the streak camera is also part of this thesis. The source is based on optical rectification of the same NIR laser pulse in a lithium niobate crystal. For this purpose, the pulse front of the NIR beam is tilted via a diffraction grating to achieve velocity matching between NIR and THz beams within the crystal. For the temporal characterization of the XUV pulses, both HHG and THz beams are focused onto a gas target. The harmonic radiation creates photoelectron wavepackets which are then accelerated by the THz field depending on its phase at the time of ionization. This principle adopted from a conventional streak camera and now widely used in attosecond metrology. The streak camera presented here is an advancement of a terahertz-field-driven streak camera implemented at the Free Electron Laser in Hamburg (FLASH). The advantages of the laser-based streak camera lie in its compactness, cost efficiency and accessibility, while providing the same good quality of measurements as obtained at FLASH. In addition, its flexibility allows for a systematic investigation of streaked Auger spectra which is presented in this thesis. With its fs time resolution, the terahertz-field-driven streak camera thereby bridges the gap between attosecond and conventional cameras. (orig.)

  5. Laser-based terahertz-field-driven streak camera for the temporal characterization of ultrashort processes

    Energy Technology Data Exchange (ETDEWEB)

    Schuette, Bernd

    2011-09-15

    In this work, a novel laser-based terahertz-field-driven streak camera is presented. It allows for a pulse length characterization of femtosecond (fs) extreme ultraviolet (XUV) pulses by a cross-correlation with terahertz (THz) pulses generated with a Ti:sapphire laser. The XUV pulses are emitted by a source of high-order harmonic generation (HHG) in which an intense near-infrared (NIR) fs laser pulse is focused into a gaseous medium. The design and characterization of a high-intensity THz source needed for the streak camera is also part of this thesis. The source is based on optical rectification of the same NIR laser pulse in a lithium niobate crystal. For this purpose, the pulse front of the NIR beam is tilted via a diffraction grating to achieve velocity matching between NIR and THz beams within the crystal. For the temporal characterization of the XUV pulses, both HHG and THz beams are focused onto a gas target. The harmonic radiation creates photoelectron wavepackets which are then accelerated by the THz field depending on its phase at the time of ionization. This principle adopted from a conventional streak camera and now widely used in attosecond metrology. The streak camera presented here is an advancement of a terahertz-field-driven streak camera implemented at the Free Electron Laser in Hamburg (FLASH). The advantages of the laser-based streak camera lie in its compactness, cost efficiency and accessibility, while providing the same good quality of measurements as obtained at FLASH. In addition, its flexibility allows for a systematic investigation of streaked Auger spectra which is presented in this thesis. With its fs time resolution, the terahertz-field-driven streak camera thereby bridges the gap between attosecond and conventional cameras. (orig.)

  6. Coherent terahertz emission from Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} intrinsic Josephson junction stacks

    Energy Technology Data Exchange (ETDEWEB)

    Rudau, Fabian; Gross, Boris; Wieland, Raphael; Judd, Thomas; Koelle, Dieter; Kleiner, Reinhold [Physikalisches Institut and Center for Collective Quantum Phenomena in LISA" +, Universitaet Tuebingen, Tuebingen (Germany); Kinev, Nickolay; Koshelets, Valery [Kotel' nikov Institute of Radio Engineering and Electronics, Moscow (Russian Federation); Tsujimoto, Manabu [Kyoto University, Kyoto (Japan); Ji, Min; Huang, Ya; Zhou, Xianjing; An, Deyue; Wang, Huabing [National Institute for Materials Science, Tsukuba (Japan); Research Institute of Superconductor Electronics, Nanjing University, Nanjing (China); Wu, Peiheng [Research Institute of Superconductor Electronics, Nanjing University, Nanjing (China); Hatano, Takeshi [National Institute for Materials Science, Tsukuba (Japan)

    2015-07-01

    Stacks of intrinsic Josephson junctions, made of the high temperature superconductor Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}, are promising candidates to be used as generators of electromagnetic waves in the terahertz regime, in principle allowing frequencies up to ∝10 THz. Ranging from 0.4 to 1 THz, coherent emission was detected from large, rectangular stacks, producing several tens of microwatt in power. Despite of several years of research, the mechanism of synchronizing all the junctions in the stack is still not fully understood. We investigated the heat distribution and electromagnetic standing waves in such stacks, as well as the generation of terahertz radiation, using a combination of electric transport measurements, direct radiation detection and low temperature scanning laser microscopy. Recent experimental results from our collaboration will be presented and compared to numerical simulations.

  7. Nonlinear Optical Terahertz Technology

    Data.gov (United States)

    National Aeronautics and Space Administration — We develop a new approach to generation of THz radiation. Our method relies on mixing two optical frequency beams in a nonlinear crystalline Whispering Gallery Mode...

  8. Generation of polypeptide-templated gold nanoparticles using ionizing radiation.

    Science.gov (United States)

    Walker, Candace Rae; Pushpavanam, Karthik; Nair, Divya Geetha; Potta, Thrimoorthy; Sutiyoso, Caesario; Kodibagkar, Vikram D; Sapareto, Stephen; Chang, John; Rege, Kaushal

    2013-08-13

    Ionizing radiation, including γ rays and X-rays, are high-energy electromagnetic radiation with diverse applications in nuclear energy, astrophysics, and medicine. In this work, we describe the use of ionizing radiation and cysteine-containing elastin-like polypeptides (C(n)ELPs, where n = 2 or 12 cysteines in the polypeptide sequence) for the generation of gold nanoparticles. In the presence of C(n)ELPs, ionizing radiation doses higher than 175 Gy resulted in the formation of maroon-colored gold nanoparticle dispersions, with maximal absorbance at 520 nm, from colorless metal salts. Visible color changes were not observed in any of the control systems, indicating that ionizing radiation, gold salt solution, and C(n)ELPs were all required for nanoparticle formation. The hydrodynamic diameters of nanoparticles, determined using dynamic light scattering, were in the range of 80-150 nm, while TEM imaging indicated the formation of gold cores 10-20 nm in diameter. Interestingly, C2ELPs formed 1-2 nm diameter gold nanoparticles in the absence of radiation. Our results describe a facile method of nanoparticle formation in which nanoparticle size can be tailored based on radiation dose and C(n)ELP type. Further improvements in these polypeptide-based systems can lead to colorimetric detection of ionizing radiation in a variety of applications.

  9. LDRD final report on continuous wave intersubband terahertz sources.

    Energy Technology Data Exchange (ETDEWEB)

    Samora, Sally; Mangan, Michael A.; Foltynowicz, Robert J.; Young, Erik W.; Fuller, Charles T.; Stephenson, Larry L.; Reno, John Louis; Wanke, Michael Clement; Hudgens, James J.

    2005-02-01

    There is a general lack of compact electromagnetic radiation sources between 1 and 10 terahertz (THz). This a challenging spectral region lying between optical devices at high frequencies and electronic devices at low frequencies. While technologically very underdeveloped the THz region has the promise to be of significant technological importance, yet demonstrating its relevance has proven difficult due to the immaturity of the area. While the last decade has seen much experimental work in ultra-short pulsed terahertz sources, many applications will require continuous wave (cw) sources, which are just beginning to demonstrate adequate performance for application use. In this project, we proposed examination of two potential THz sources based on intersubband semiconductor transitions, which were as yet unproven. In particular we wished to explore quantum cascade lasers based sources and electronic based harmonic generators. Shortly after the beginning of the project, we shifted our emphasis to the quantum cascade lasers due to two events; the publication of the first THz quantum cascade laser by another group thereby proving feasibility, and the temporary shut down of the UC Santa Barbara free-electron lasers which were to be used as the pump source for the harmonic generation. The development efforts focused on two separate cascade laser thrusts. The ultimate goal of the first thrust was for a quantum cascade laser to simultaneously emit two mid-infrared frequencies differing by a few THz and to use these to pump a non-linear optical material to generate THz radiation via parametric interactions in a specifically engineered intersubband transition. While the final goal was not realized by the end of the project, many of the completed steps leading to the goal will be described in the report. The second thrust was to develop direct THz QC lasers operating at terahertz frequencies. This is simpler than a mixing approach, and has now been demonstrated by a few groups

  10. Radiation pressure induced difference-sideband generation beyond linearized description

    OpenAIRE

    Xiong, Hao; Fan, Y. W.; Yang, X.; Wu, Y.

    2016-01-01

    We investigate radiation-pressure induced generation of the frequency components at the difference-sideband in an optomechanical system, which beyond the conventional linearized description of optomechanical interactions between cavity fields and the mechanical oscillation. We analytically calculate amplitudes of these signals, and identify a simple square-root law for both the upper and lower difference-sideband generation which can describe the dependence of the intensities of these signals...

  11. Electromagnetic Radiation from Vortex Flow in Type-II Superconductors

    International Nuclear Information System (INIS)

    Bulaevskii, L. N.; Chudnovsky, E. M.

    2006-01-01

    We show that a moving vortex lattice, as it comes to a crystal edge, radiates into a free space the harmonics of the washboard frequency, ω 0 =2πv/a, up to a superconducting gap, Δ/(ℎ/2π). Here v is the velocity of the vortex lattice and a is the intervortex spacing. We compute radiation power and show that this effect can be used for the generation of terahertz radiation and for characterization of moving vortex lattices

  12. Electromagnetic radiation from vortex flow in type-II superconductors

    OpenAIRE

    Bulaevskii, L. N.; Chudnovsky, E. M.

    2006-01-01

    We show that a moving vortex lattice, as it comes to a crystal edge, radiates into a free space the harmonics of the washboard frequency, $\\omega_0=2\\pi v/a$, up to a superconducting gap, $\\Delta/\\hbar$. Here $v$ is the velocity of the vortex lattice and $a$ is the intervortex spacing. We compute radiation power and show that this effect can be used for generation of terahertz radiation and for characterization of moving vortex lattices.

  13. Technological challenges of third generation synchrotron radiation sources

    International Nuclear Information System (INIS)

    Cornacchia, M.; Winick, H.

    1990-01-01

    New ''third generation'' synchrotron radiation research facilities are now in construction in France, Italy, Japan, Taiwan and the USA. Designs for such facilities are being developed in several other countries. Third generation facilities are based on storage rings with low electron beam emittance and space for many undulator magnets to produce radiation with extremely high brightness and coherent power. Photon beam from these rings will greatly extend present research capabilities and open up new opportunities in imaging, spectroscopy, structural and dynamic studies and other applications. The technological problems of the third generation of synchrotron radiation facilities are reviewed. These machines are designed to emit radiation of very high intensity, extreme brightness, very short pulses, and partial coherence. These performance goals put severe requirements on the quality of the electron or positron beams. Phenomena affecting the injection process and the beam lifetime are discussed. Gas desorption by synchrotron radiation and collective effects play an important role. Low emittance lattices are more sensitive to quadrupole movements and at the same time, in order not to lose the benefits of high brilliance, require tighter tolerances on the allowed movement of the photon beam source. We discuss some of the ways that should be considered to extend the performance capabilities of the facilities in the future. 14 refs., 1 fig

  14. RADGEN: A radiation exchange factor generator for rod bundles

    International Nuclear Information System (INIS)

    Rector, D.R.

    1987-10-01

    The RADGEN computer program has been developed at Pacific Northwest Laboratory (PNL) to generate input required for the thermal radiation models used in the COBRA-SFS (Spent Fuel Storage) computer program. The COBRA-SFS program uses radiation exchange factors to describe the net amount of energy transferred from each surface to every other surface in an enclosure. The RADGEN program generates radiation exchange factors for arrays of rods on a square or triangular pitch as well as open channel geometries. This report describes the input requirements for the RADGEN code, which may be executed in a batch or interactive mode, and outlines the solution procedure used to obtain the exchange factors. 4 refs., 25 figs., 13 tabs

  15. Terahertz instability of surface optical-phonon polaritons that interact with surface plasmon polaritons in the presence of electron drift

    International Nuclear Information System (INIS)

    Sydoruk, O.; Solymar, L.; Shamonina, E.; Kalinin, V.

    2010-01-01

    Traveling-wave interaction between optical phonons and electrons drifting in diatomic semiconductors has potential for amplification and generation of terahertz radiation. Existing models of this interaction were developed for infinite materials. As a more practically relevant configuration, we studied theoretically a finite semiconductor slab surrounded by a dielectric. This paper analyzes the optical-phonon instability in the slab including the Lorentz force and compares it to the instability in an infinite material. As the analysis shows, the slab instability occurs because of the interaction of surface optical-phonon polaritons with surface plasmon polaritons in the presence of electron drift. The properties of the instability depend on the slab thickness when the thickness is comparable to the wavelength. For large slab thicknesses, however, the dispersion relation of the slab is similar to that of an infinite material, although the coupling is weaker. The results could be used for the design of practical terahertz traveling-wave oscillators and amplifiers.

  16. Asymmetric planar terahertz metamaterials

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Ramjan [Los Alamos National Laboratory; Al - Naib, Ibraheem A. I. [PHILIPPS UNIV; Koch, Martin [PHILIPPS UNIV; Zhang, Weili [OKLAHOMA STATE UNIV

    2010-01-01

    Using terahertz time-domain spectroscopy, we report an experimental observation of three distinct resonances in split ring resonators (SRRs) for both vertical and horizontal electric field polarizations at normal incidence. Breaking the symmetry in SRRs by gradually displacing the capacitive gap from the centre towards the comer of the ring allows for an 85% modulation of the fundamental inductive-capacitive (LC) resonance. Increasing asymmetry leads to the evolution of an otherwise inaccessible high quality factor electric quadrupole resonance that can be exploited for bio-sensing applications in the terahertz region.

  17. Graphene geometric diodes for terahertz rectennas

    International Nuclear Information System (INIS)

    Zhu Zixu; Joshi, Saumil; Grover, Sachit; Moddel, Garret

    2013-01-01

    We demonstrate a new thin-film graphene diode called a geometric diode that relies on geometric asymmetry to provide rectification at 28 THz. The geometric diode is coupled to an optical antenna to form a rectenna that rectifies incoming radiation. This is the first reported graphene-based antenna-coupled diode working at 28 THz, and potentially at optical frequencies. The planar structure of the geometric diode provides a low RC time constant, on the order of 10 −15 s, required for operation at optical frequencies, and a low impedance for efficient power transfer from the antenna. Fabricated geometric diodes show asymmetric current–voltage characteristics consistent with Monte Carlo simulations for the devices. Rectennas employing the geometric diode coupled to metal and graphene antennas rectify 10.6 µm radiation, corresponding to an operating frequency of 28 THz. The graphene bowtie antenna is the first demonstrated functional antenna made using graphene. Its response indicates that graphene is a suitable terahertz resonator material. Applications for this terahertz diode include terahertz-wave and optical detection, ultra-high-speed electronics and optical power conversion. (paper)

  18. The effect of turbulence-radiation interaction on radiative entropy generation and heat transfer

    International Nuclear Information System (INIS)

    Caldas, Miguel; Semiao, Viriato

    2007-01-01

    The analysis under the second law of thermodynamics is the gateway for optimisation in thermal equipments and systems. Through entropy minimisation techniques it is possible to increase the efficiency and overall performance of all kinds of thermal systems. Radiation, being the dominant mechanism of heat transfer in high-temperature systems, plays a determinant role in entropy generation within such equipments. Turbulence is also known to be a major player in the phenomenon of entropy generation. Therefore, turbulence-radiation interaction is expected to have a determinant effect on entropy generation. However, this is a subject that has not been dealt with so far, at least to the extent of the authors' knowledge. The present work attempts to fill that void, by studying the effect of turbulence-radiation interaction on entropy generation. All calculations are approached in such a way as to make them totally compatible with standard engineering methods for radiative heat transfer, namely the discrete ordinates method. It was found that turbulence-radiation interaction does not significantly change the spatial pattern of entropy generation, or heat transfer, but does change significantly their magnitude, in a way approximately proportional to the square of the intensity of turbulence

  19. A polarization-insensitive plasmonic photoconductive terahertz emitter

    KAUST Repository

    Li, Xurong

    2017-11-16

    We present a polarization-insensitive plasmonic photoconductive terahertz emitter that uses a two-dimensional array of nanoscale cross-shaped apertures as the plasmonic contact electrodes. The geometry of the cross-shaped apertures is set to maximize optical pump absorption in close proximity to the contact electrodes. The two-dimensional symmetry of the cross-shaped apertures offers a polarization-insensitive interaction between the plasmonic contact electrodes and optical pump beam. We experimentally demonstrate a polarization-insensitive terahertz radiation from the presented emitter in response to a femtosecond optical pump beam and similar terahertz radiation powers compared to previously demonstrated polarization-sensitive photoconductive emitters with plasmonic contact electrode gratings at the optimum optical pump polarization.

  20. Terahertz Radome Inspection

    Directory of Open Access Journals (Sweden)

    Fabian Friederich

    2018-01-01

    Full Text Available Radomes protecting sensitive radar, navigational, and communications equipment of, e.g., aircraft, are strongly exposed to the environment and have to withstand harsh weather conditions and potential impacts. Besides their significance to the structural integrity of the radomes, it is often crucial to optimize the composite structures for best possible radio performance. Hence, there exists a significant interest in non-destructive testing techniques, which can be used for defect inspection of radomes in field use as well as for quality inspection during the manufacturing process. Contactless millimeter-wave and terahertz imaging techniques provide millimeter resolution and have the potential to address both application scenarios. We report on our development of a three-dimensional (3D terahertz imaging system for radome inspection during industrial manufacturing processes. The system was designed for operation within a machining center for radome manufacturing. It simultaneously gathers terahertz depth information in adjacent frequency ranges, from 70 to 110 GHz and from 110 to 170 GHz by combining two frequency modulated continuous-wave terahertz sensing units into a single measurement device. Results from spiraliform image acquisition of a radome test sample demonstrate the successful integration of the measurement system.

  1. Challenging Aspects of Terahertz Terabit Wireless Communications

    DEFF Research Database (Denmark)

    Yu, Xianbin; Galili, Michael; Jepsen, Peter Uhd

    The increasing demand on fast wireless communications, e.g. huge data file transferring and mobile broadband access, has driven wireless communication systems into a path towards Terabit era. Terahertz (THz) technology is promising due to its unique features, such as unlimited bandwidth available......, in terms of THz generation and link power budget. The THz atmospheric absorption is another critical issue to limit wireless communication range....

  2. Design of Integrated Circuits Approaching Terahertz Frequencies

    OpenAIRE

    Yan, Lei; Johansen, Tom Keinicke

    2013-01-01

    In this thesis, monolithic microwave integrated circuits(MMICs) are presented for millimeter-wave and submillimeter-wave or terahertz(THz) applications. Millimeter-wave power generation from solid state devices is not only crucial for the emerging high data rate wireless communications but also important for driving THz signal sources. To meet the requirement of high output power, amplifiers based on InP double heterojunction bipolar transistor (DHBT) devices from the III-V Lab in Marcoussic,...

  3. Reducing waste generation and radiation exposure by analytical method modification

    International Nuclear Information System (INIS)

    Ekechukwu, A.A.

    1996-01-01

    The primary goal of an analytical support laboratory has traditionally been to provide accurate data in a timely and cost effective fashion. Added to this goal is now the need to provide the same high quality data while generating as little waste as possible. At the Savannah River Technology Center (SRTC), we have modified and reengineered several methods to decrease generated waste and hence reduce radiation exposure. These method changes involved improving detection limits (which decreased the amount of sample required for analysis), decreasing reaction and analysis time, decreasing the size of experimental set-ups, recycling spent solvent and reagents, and replacing some methods. These changes had the additional benefits of reducing employee radiation exposure and exposure to hazardous chemicals. In all cases, the precision, accuracy, and detection limits were equal to or better than the replaced method. Most of the changes required little or no expenditure of funds. This paper describes these changes and discusses some of their applications

  4. Observations pertaining to the generation of auroral kilometric radiation

    International Nuclear Information System (INIS)

    Green, J.L.

    1981-01-01

    Auroral kilometric radiation (AKR) observations that have determined the propagation mode or polarization of the radiation and the detailed intensity distribution of the AKR emission cone are discussed. Attention is also given to correlations between AKR with discrete field-aligned currents. It is noted that these observations have helped to identify the auroral particle population most likely responsible for the generation of AKR and the possible sources of the free energy that drives the instability. Thus far, AKR has not been observed simultaneously with large electrostatic waves. Auroral zone current systems are thought to be intimately involved in the generation of AKR. In particular, the most probable source of energy for AKR is the precipitating inverted-V auroral electron distribution

  5. Radiation pressure induced difference-sideband generation beyond linearized description

    Energy Technology Data Exchange (ETDEWEB)

    Xiong, Hao, E-mail: haoxiong1217@gmail.com; Fan, Yu-Wan; Yang, Xiaoxue; Wu, Ying, E-mail: yingwu2@126.com [School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2016-08-08

    We investigate radiation-pressure induced generation of the frequency components at the difference-sideband in an optomechanical system, which beyond the conventional linearized description of optomechanical interactions between cavity fields and the mechanical oscillation. We analytically calculate amplitudes of these signals, and identify a simple square-root law for both the upper and lower difference-sideband generation which can describe the dependence of the intensities of these signals on the pump power. Further calculation shows that difference-sideband generation can be greatly enhanced via achieving the matching conditions. The effect of difference-sideband generation, which may have potential application for manipulation of light, is especially suited for on-chip optomechanical devices, where nonlinear optomechanical interaction in the weak coupling regime is within current experimental reach.

  6. Optical Cherenkov radiation in ultrafast cascaded second-harmonic generation

    DEFF Research Database (Denmark)

    Bache, Morten; Bang, Ole; Zhou, Binbin

    2010-01-01

    -matching point is located in the absorption region of the crystal, effectively absorbing the generated dispersive wave. By calculating the phase-matching curves for typically used frequency conversion crystals, we point out that the mid-IR absorption in the crystal in many cases automatically will filter away....... The beating between the dispersive wave and the soliton generates trailing temporal oscillations on the compressed soliton. Insertion of a simple short-wave pass filter after the crystal can restore a clean soliton. On the other hand, bandpass filtering around the dispersive wave peak results in near......We show through theory and numerics that when few-cycle femtosecond solitons are generated through cascaded (phase-mismatched) second-harmonic generation, these broadband solitons can emit optical Cherenkov radiation in the form of linear dispersive waves located in the red part of the spectrum...

  7. Study Regarding Electromagnetic Radiation Exposure Generated By Mobile Phone

    Science.gov (United States)

    Marica, Lucia; Moraru, Luminita

    2011-12-01

    Number of mobile phone users reached to 5 billion subscribers in 2010 [ABI Research, 2010]. A large number of studies illustrated the public concern about adverse effects of mobile phone radiation and possible health hazards. Position of mobile phone use in close proximity to the head leads the main radiation between the hand and the head. Many investigations studying the possible effects of mobile phone exposure, founded no measurable effects of short-term mobile phone radiation, and there was no evidence for the ability to perceive mobile phone EMF in the general population. In this study, field radiation measurements were performed on different brand and different models of mobile phones in active mode, using an EMF RF Radiation Field Strength Power Meter 1 MHz-8 GHz. The study was effectuated on both the 2G and 3G generations phones connected to the providers operating in the frequency range 450 MHz-1800 MHz. There were recorded values in outgoing call and SMS mode, incoming call and SMS mode. Results were compared with ICNIRP guidelines for exposure to general public.

  8. Study Regarding Electromagnetic Radiation Exposure Generated By Mobile Phone

    International Nuclear Information System (INIS)

    Marica, Lucia; Moraru, Luminita

    2011-01-01

    Number of mobile phone users reached to 5 billion subscribers in 2010 [ABI Research, 2010]. A large number of studies illustrated the public concern about adverse effects of mobile phone radiation and possible health hazards. Position of mobile phone use in close proximity to the head leads the main radiation between the hand and the head. Many investigations studying the possible effects of mobile phone exposure, founded no measurable effects of short-term mobile phone radiation, and there was no evidence for the ability to perceive mobile phone EMF in the general population. In this study, field radiation measurements were performed on different brand and different models of mobile phones in active mode, using an EMF RF Radiation Field Strength Power Meter 1 MHz-8 GHz. The study was effectuated on both the 2G and 3G generations phones connected to the providers operating in the frequency range 450 MHz-1800 MHz. There were recorded values in outgoing call and SMS mode, incoming call and SMS mode. Results were compared with ICNIRP guidelines for exposure to general public.

  9. Examination of spent fuel radiation energy conversion for electricity generation

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Haneol; Yim, Man-Sung, E-mail: msyim@kaist.ac.kr

    2016-04-15

    Highlights: • Utilizing conversion of radiation energy of spent fuel to electric energy. • MCNPX modeling and experiment were used to estimate energy conversion. • The converted energy may be useful for nuclear security applications. • The converted energy may be utilized for safety applications through energy storage. - Abstract: Supply of electricity inside nuclear power plant is one of the most important considerations for nuclear safety and security. In this study, generation of electric energy by converting radiation energy of spent nuclear fuel was investigated. Computational modeling work by using MCNPX 2.7.0 code along with experiment was performed to estimate the amount of electric energy generation. The calculation using the developed modeling work was validated through comparison with an integrated experiment. The amount of electric energy generation based on a conceptual design of an energy conversion module was estimated to be low. But the amount may be useful for nuclear security applications. An alternative way of utilizing the produced electric energy could be considered for nuclear safety application through energy storage. Further studies are needed to improve the efficiency of the proposed energy conversion concept and to examine the issue of radiation damage and economic feasibility.

  10. Generation of ionizing radiation from lithium niobate crystals

    Science.gov (United States)

    Orlikov, L. N.; Orlikov, N. L.; Arestov, S. I.; Mambetova, K. M.; Shandarov, S. M.

    2017-01-01

    The work done experimentally explores generation of electron and x-ray radiation in the process of heating and cooling monolithic and iron-doped crystals of lithium niobate. Iron doping to the concentrations in the range of 1023 m3 was carried out by adding ferric oxide into the melt during the process of crystal growth. The research into radiation generation was performed at 1-10 Pa. The speed of heating from -10 to 1070 C was 10-20 degrees a minute. Current pulses appeared at 17, 38, 56, 94, 98, 100, 105, 106, 1070 C with the interval of 1-3 minutes. The obtained electron current increased in direct proportion to the crystal surface area. The maximum current was 3mA at the design voltage 11 kV on the crystal with 14,5x10,5x10 mm3 surface area. The article describes the possibility to control the start of generation by introducing priming pulse. The results achieved are explained by the domain repolarization while heating the crystal and the appearance of electric field local strength. Bias and overcharge currents contribute to the appearance of electric strength, which stimulates breakdown and plasma formation. X-ray radiation appears both at the stage of discharge formation and during electron deceleration on gas and target material.

  11. Terahertz-Frequency Spin Hall Auto-oscillator Based on a Canted Antiferromagnet

    Science.gov (United States)

    Sulymenko, O. R.; Prokopenko, O. V.; Tiberkevich, V. S.; Slavin, A. N.; Ivanov, B. A.; Khymyn, R. S.

    2017-12-01

    We propose a design of a terahertz-frequency signal generator based on a layered structure consisting of a current-driven platinum (Pt) layer and a layer of an antiferromagnet (AFM) with easy-plane anisotropy, where the magnetization vectors of the AFM sublattices are canted inside the easy plane by the Dzyaloshinskii-Moriya interaction (DMI). The dc electric current flowing in the Pt layer creates due to the spin Hall effect, a perpendicular spin current that, being injected in the AFM layer, tilts the DMI-canted AFM sublattices out of the easy plane, thus exposing them to the action of a strong internal exchange magnetic field of the AFM. The sublattice magnetizations, along with the small net magnetization vector mDMI of the canted AFM, start to rotate about the hard anisotropy axis of the AFM with the terahertz frequency proportional to the injected spin current and the AFM exchange field. The rotation of the small net magnetization mDMI results in the terahertz-frequency dipolar radiation that can be directly received by an adjacent (e.g., dielectric) resonator. We demonstrate theoretically that the radiation frequencies in the range f =0.05 - 2 THz are possible at the experimentally reachable magnitudes of the driving current density, and we evaluate the power of the signal radiated into different types of resonators. This power increases with the increase of frequency f , and it can exceed 1 μ W at f ˜0.5 THz for a typical dielectric resonator of the electric permittivity ɛ ˜10 and a quality factor Q ˜750 .

  12. Terahertz imaging and spectroscopy based on hot electron bolometer (HEB) heterodyne detection

    Science.gov (United States)

    Gerecht, Eyal; You, Lixing

    2008-02-01

    Imaging and spectroscopy at terahertz frequencies have great potential for healthcare, plasma diagnostics, and homeland security applications. Terahertz frequencies correspond to energy level transitions of important molecules in biology and astrophysics. Terahertz radiation (T-rays) can penetrate clothing and, to some extent, can also penetrate biological materials. Because of their shorter wavelengths, they offer higher spatial resolution than do microwaves or millimeter waves. We are developing hot electron bolometer (HEB) mixer receivers for heterodyne detection at terahertz frequencies. HEB detectors provide unprecedented sensitivity and spectral resolution at terahertz frequencies. We describe the development of a two-pixel focal plane array (FPA) based on HEB technology. Furthermore, we have demonstrated a fully automated, two-dimensional scanning, passive imaging system based on our HEB technology operating at 0.85 THz. Our high spectral resolution terahertz imager has a total system noise equivalent temperature difference (NEΔT) value of better than 0.5 K and a spatial resolution of a few millimeters. HEB technology is becoming the basis for advanced terahertz imaging and spectroscopic technologies for the study of biological and chemical agents over the entire terahertz spectrum.

  13. Reversed Cherenkov emission of terahertz waves from an ultrashort laser pulse in a sandwich structure with nonlinear core and left-handed cladding.

    Science.gov (United States)

    Bakunov, M I; Mikhaylovskiy, R V; Bodrov, S B; Luk'yanchuk, B S

    2010-01-18

    We propose a scheme for an experimental verification of the reversed Cherenkov effect in left-handed media. The scheme uses optical-to-terahertz conversion in a planar sandwichlike structure that consists of a nonlinear core cladded with a material that exhibits left-handedness at terahertz frequencies. The focused into a line femtosecond laser pulse propagates in the core and emits Cherenkov wedge of terahertz waves in the cladding. We developed a theory that describes terahertz generation in such a structure and calculated spatial distribution of the generated terahertz field, its energy spectrum, and optical-to-terahertz conversion efficiency. The proposed structure can be a useful tool for characterization of the electromagnetic properties of metamaterials in the terahertz frequency range.

  14. Determination of circumsolar radiation from Meteosat Second Generation

    Science.gov (United States)

    Reinhardt, B.; Buras, R.; Bugliaro, L.; Wilbert, S.; Mayer, B.

    2014-03-01

    Reliable data on circumsolar radiation, which is caused by scattering of sunlight by cloud or aerosol particles, is becoming more and more important for the resource assessment and design of concentrating solar technologies (CSTs). However, measuring circumsolar radiation is demanding and only very limited data sets are available. As a step to bridge this gap, a method was developed which allows for determination of circumsolar radiation from cirrus cloud properties retrieved by the geostationary satellites of the Meteosat Second Generation (MSG) family. The method takes output from the COCS algorithm to generate a cirrus mask from MSG data and then uses the retrieval algorithm APICS to obtain the optical thickness and the effective radius of the detected cirrus, which in turn are used to determine the circumsolar radiation from a pre-calculated look-up table. The look-up table was generated from extensive calculations using a specifically adjusted version of the Monte Carlo radiative transfer model MYSTIC and by developing a fast yet precise parameterization. APICS was also improved such that it determines the surface albedo, which is needed for the cloud property retrieval, in a self-consistent way instead of using external data. Furthermore, it was extended to consider new ice particle shapes to allow for an uncertainty analysis concerning this parameter. We found that the nescience of the ice particle shape leads to an uncertainty of up to 50%. A validation with 1 yr of ground-based measurements shows, however, that the frequency distribution of the circumsolar radiation can be well characterized with typical ice particle shape mixtures, which feature either smooth or severely roughened particle surfaces. However, when comparing instantaneous values, timing and amplitude errors become evident. For the circumsolar ratio (CSR) this is reflected in a mean absolute deviation (MAD) of 0.11 for both employed particle shape mixtures, and a bias of 4 and 11%, for the

  15. Terahertz reflection spectroscopy of Debye relaxation in polar liquids

    DEFF Research Database (Denmark)

    Møller, Uffe; Cooke, David; Tanaka, Koichiro

    2009-01-01

    Terahertz (THz) radiation interacts strongly with the intermolecular hydrogen-bond network in aqueous liquids. The dielectric properties of liquid water and aqueous solutions in the THz spectral region are closely linked to the microscopic dynamics of the liquid solution, and hence THz spectrosco...

  16. Terahertz Fibres and Functional FibreI-Based Devices

    DEFF Research Database (Denmark)

    Bao, Hualong

    The area of Terahertz (THz) radiation has been proved to be a very promising utility for a wide range of applications. However, since current THz systems predominantly utilize freespace propagation, the large size and requirement of careful alignment thus increasing the complexity are the drawbacks...

  17. Terahertz-field-induced photoluminescence of nanostructured gold films

    DEFF Research Database (Denmark)

    Iwaszczuk, Krzysztof; Malureanu, Radu; Zalkovskij, Maksim

    2013-01-01

    We experimentally demonstrate photoluminescence from nanostructured ultrathin gold films subjected to strong single-cycle terahertz transients with peak electric field over 300 kV/cm. We show that UV-Vis-NIR light is being generated and the efficiency of the process is strongly enhanced at the pe......We experimentally demonstrate photoluminescence from nanostructured ultrathin gold films subjected to strong single-cycle terahertz transients with peak electric field over 300 kV/cm. We show that UV-Vis-NIR light is being generated and the efficiency of the process is strongly enhanced...

  18. Nonlinear generation of the fundamental radiation in plasmas

    International Nuclear Information System (INIS)

    Chian, A.C.L.; Rizzato, F.B.

    1993-01-01

    Nonlinear generation of coherent electromagnetic radiation by intense Langmuir waves in the vicinity of the fundamental plasma frequency f p is of current interest in space and laboratory plasmas. In a pioneer work, Lashmore-Davies demonstrated that an efficient process for converting intense Langmuir waves into f p electromagnetic radiation can be achieved by two counterstreaming Langmuir pump waves through an electromagnetic oscillating two-stream instability. Recently Chian and Alves, Akimoto and Rizzato and Chian extended the formalism of Lashmore-Davies in order to include mixed processes with induced modes which are purely electrostatic or electromagnetic. In this paper we extend our previous analysis, in order to study the nonlinear interaction involving travelling electromagnetic pumps, low-frequency density fluctuations and high-frequency f p modes which can be electrostatic-electromagnetic hybrids. (author) 5 refs., 2 figs

  19. Radiatively generated hierarchy of lepton and quark masses

    Energy Technology Data Exchange (ETDEWEB)

    Hernández, A.E. Cárcamo; Kovalenko, Sergey; Schmidt, Ivan [Centro Científico Tecnológico de Valparaíso-CCTVal, Universidad Técnica Federico Santa María,Casilla 110-V, Valparaíso (Chile)

    2017-02-24

    We propose a model for radiatively generating the hierarchy of the Standard Model (SM) fermion masses: tree-level top quark mass; 1-loop bottom, charm, tau and muon masses; 2-loop masses for the light up, down and strange quarks as well as for the electron; and 4-loop masses for the light active neutrinos. Our model is based on a softly-broken S{sub 3}×Z{sub 2} discrete symmetry. Its scalar sector consists only of one SM Higgs doublet and three electrically neutral SM-singlet scalars. We do not need to invoke either electrically charged scalar fields, or an extra SU{sub 2L} scalar doublet, or the spontaneous breaking of the discrete group, which are typical for other radiative models in the literature. The model features a viable scalar dark matter candidate.

  20. Radiofrequency radiation exposure from RF-generating plant

    International Nuclear Information System (INIS)

    Wright, J.M.; Bell, K.M.

    2000-01-01

    As part of an intervention to assist industry improve the control of risks associated with the use of RF-generating plant, exposure to radiofrequency radiation (RFR) was assessed in 30 workplaces. Information about the workplace, work practices and knowledge about RFR and its control was also collected. The study found that: 1. For 72% of operators and 35% of bystanders, the spatially averaged exposure exceeded the exposure limits. These figures approximately halved when the duty cycle was applied; 2. Assessment of RFR levels was not common; 3. Task rotation was used to limit exposure of operators; 4. Access was not controlled to areas where RFR sources were used; 5. There was lack of knowledge about RF shielding practices in industry; 6. Nearly 50% of workplaces did not maintain the plant regularly; and 7. There had been no health surveillance on any plant operators in any of the workplaces in the study. Copyright (2000) Australasian Radiation Protection Society Inc

  1. TERAHERTZ REFLECTANCE SPECTRA OF SKIN DERMATITIS AND MORPHOLOGICAL CHANGES

    Directory of Open Access Journals (Sweden)

    E. A. Strepitov

    2013-05-01

    Full Text Available The article deals withthe diagnostics possibility of dermatitis and morphological changes of human skin using terahertz frequency range equal to 2,0¸0,05 THz. Features of different types of human skin diseases occur in vivo over the entire frequency range, especially in the field of vibration: 2,0¸1,5 THz. They were caused by the backscattering on skin new formations in its upper layers. In terahertz reflection spectra spectral lines of different dermatitis, age spots, haematoma are well distinguishable. Terahertz radiation penetrates well through the medical bandages. At the same time in a single scan, lasting about one minute, the spectrum is processed not only of the bandages, but of different skin layers.

  2. Spatial-temporal dynamics of broadband terahertz Bessel beam propagation

    International Nuclear Information System (INIS)

    Semenova, V A; Kulya, M S; Bespalov, V G

    2016-01-01

    The unique properties of narrowband and broadband terahertz Bessel beams have led to a number of their applications in different fields, for example, for the depth of focusing and resolution enhancement in terahertz imaging. However, broadband terahertz Bessel beams can probably be also used for the diffraction minimization in the short-range broadband terahertz communications. For this purpose, the study of spatial-temporal dynamics of the broadband terahertz Bessel beams is needed. Here we present a simulation-based study of the propagating in non-dispersive medium broadband Bessel beams generated by a conical axicon lens. The algorithm based on scalar diffraction theory was used to obtain the spatial amplitude and phase distributions of the Bessel beam in the frequency range from 0.1 to 3 THz at the distances 10-200 mm from the axicon. Bessel beam field is studied for the different spectral components of the initial pulse. The simulation results show that for the given parameters of the axicon lens one can obtain the Gauss-Bessel beam generation in the spectral range from 0.1 to 3 THz. The length of non-diffraction propagation for a different spectral components was measured, and it was shown that for all spectral components of the initial pulse this length is about 130 mm. (paper)

  3. Nonlinear radiation generation processes in the auroral acceleration region

    Directory of Open Access Journals (Sweden)

    R. Pottelette

    2017-11-01

    Full Text Available It is known from laboratory plasma experiments that double layers (DLs radiate in the electromagnetic spectrum; but this is only known qualitatively. In these experiments, it was shown that the electron beam created on the high-potential side of a DL generates nonlinear structures which couple to electromagnetic waves and act as a sender antenna. In the Earth auroral region, observations performed by auroral spacecraft have shown that DLs occur naturally in the source region of intense radio emissions called auroral kilometric radiation (AKR. Very high time-, spatial-, and temporal-resolution measurements are needed in order to characterize waves and particle distributions in the vicinity of DLs, which are moving transient structures. We report observations from the FAST satellite of a localized large-amplitude parallel electric field (∼ 300 mV m−1 recorded at the edges of the auroral density cavity. In agreement with laboratory experiments, on the high-potential side of the DL, elementary radiation events are detected. They occur substantially above the local electron gyrofrequency and are associated with the presence of electron holes. The velocity of these nonlinear structures can be derived from the measurement of the Doppler-shifted AKR frequency spectrum above the electron gyrofrequency. The generated electron holes appear as the nonlinear evolution of electrostatic waves generated by the electron–electron two-stream instability because they propagate at about half the beam velocity. It is pointed out that, in the vicinity of a DL, the shape of the electron distribution gives rise to a significant power recorded in the left-hand polarized ordinary (LO mode.

  4. FDTD-based quantitative analysis of terahertz wave detection for multilayered structures.

    Science.gov (United States)

    Tu, Wanli; Zhong, Shuncong; Shen, Yaochun; Zhou, Qing; Yao, Ligang

    2014-10-01

    Experimental investigations have shown that terahertz pulsed imaging (TPI) is able to quantitatively characterize a range of multilayered media (e.g., biological issues, pharmaceutical tablet coatings, layered polymer composites, etc.). Advanced modeling of the interaction of terahertz radiation with a multilayered medium is required to enable the wide application of terahertz technology in a number of emerging fields, including nondestructive testing. Indeed, there have already been many theoretical analyses performed on the propagation of terahertz radiation in various multilayered media. However, to date, most of these studies used 1D or 2D models, and the dispersive nature of the dielectric layers was not considered or was simplified. In the present work, the theoretical framework of using terahertz waves for the quantitative characterization of multilayered media was established. A 3D model based on the finite difference time domain (FDTD) method is proposed. A batch of pharmaceutical tablets with a single coating layer of different coating thicknesses and different refractive indices was modeled. The reflected terahertz wave from such a sample was computed using the FDTD method, assuming that the incident terahertz wave is broadband, covering a frequency range up to 3.5 THz. The simulated results for all of the pharmaceutical-coated tablets considered were found to be in good agreement with the experimental results obtained using a commercial TPI system. In addition, we studied a three-layered medium to mimic the occurrence of defects in the sample.

  5. Seeded free-electron and inverse free-electron laser techniques for radiation amplification and electron microbunching in the terahertz range

    Directory of Open Access Journals (Sweden)

    C. Sung

    2006-12-01

    Full Text Available A comprehensive analysis is presented that describes amplification of a seed THz pulse in a single-pass free-electron laser (FEL driven by a photoinjector. The dynamics of the radiation pulse and the modulated electron beam are modeled using the time-dependent FEL code, GENESIS 1.3. A 10-ps (FWHM electron beam with a peak current of 50–100 A allows amplification of a ∼1  kW seed pulse in the frequency range 0.5–3 THz up to 10–100 MW power in a relatively compact 2-m long planar undulator. The electron beam driving the FEL is strongly modulated, with some inhomogeneity due to the slippage effect. It is shown that THz microbunching of the electron beam is homogeneous over the entire electron pulse when saturated FEL amplification is utilized at the very entrance of an undulator. This requires seeding of a 30-cm long undulator buncher with a 1–3 MW of pump power with radiation at the resonant frequency. A narrow-band seed pulse in the THz range needed for these experiments can be generated by frequency mixing of CO_{2} laser lines in a GaAs nonlinear crystal. Two schemes for producing MW power pulses in seeded FELs are considered in some detail for the beam parameters achievable at the Neptune Laboratory at UCLA: the first uses a waveguide to transport radiation in the 0.5–3 THz range through a 2-m long FEL amplifier and the second employs high-gain third harmonic generation using the FEL process at 3–9 THz.

  6. A radiative corrections scheme for generation of the lepton masses

    International Nuclear Information System (INIS)

    Pisano, F.; Pleitez, V.; Tonasse, M.D.

    1994-01-01

    We consider in the context of 331 model of the electroweak interactions the generation of the lepton masses by introducing a single neutral right-handed singlet in a radiatively corrections scheme. By adding a lepton-baryon number violating term in the Higgs potential, we show that one can have the right mass spectrum for the leptons without introducing a sextet of Higgs fields which is present in the original model. (author) of Higgs fields which is present in the original model. (author)

  7. Generating Far-Infrared Radiation By Two-Wave Mixing

    Science.gov (United States)

    Borenstain, Shmuel

    1992-01-01

    Far-infrared radiation 1 to 6 GHz generated by two-wave mixing in asymmetrically grown GaAs/AlxGa1-xAs multiple-quantum-well devices. Two near-infrared semiconductor diode lasers phase-locked. Outputs amplified, then combined in semiconductor nonlinear multiple-quantum-well planar waveguide. Necessary to optimize design of device with respect to three factors: high degree of confinement of electromagnetic field in nonlinear medium to maximize power density, phase matching to extend length of zone of interaction between laser beams in non-linear medium, and nonlinear susceptibility. Devices used as tunable local oscillators in heterodyne-detection radiometers.

  8. Generation of electromagnetic radiation in laser action with solids

    International Nuclear Information System (INIS)

    Aref'ev, K.P.; Vorob'ev, S.A.; Kuznetsov, M.F.; Mastov, Sh.R.; Pogrebnyak, A.D.

    1984-01-01

    A new effect of electromagnetic pulse generation in solids, exposed to laser irradiation was revealed experimentally. The ruby laser with 694.36 nm wave length was used in the experiments. Monocrystals of Si, GaAs, KCl, LiF, polycrystals of Cu, Al, metals, the rocks-calcite, marble, natural quartz, feldspar - were used as samples. The effect of electromagnetic pulse generation, which is characterized by sharp threshold dependence on the density of laser radiation power, as well as on the type of material and its characteristics was observed for each material. The possibility of using the method of electromagnetic pulse detection during laser irradiation for evaluation of defectiveness degree and strength characteristics of investigated materials was shown

  9. Generation of radiation by intense plasma and electromagnetic undulators

    International Nuclear Information System (INIS)

    Joshi, C.

    1989-01-01

    This is a second year progress report which details the work on the generation of radiation by intense plasma and electromagnetic undulators being carried out at UCLA. The status of the experimental work is described and the future directions are outlined. We have completed the first phase of experiments on the plasma wiggler generation and characterization. Suitability of a null-pinch as a plasma source was investigated in great detail. It is found that a w of a few percent can be excited but there are trapped magnetic fields within null-pinch plasma which hinder the injection of the electrons. A new more uniform and field-free plasma source is now being characterized

  10. Generation of radiation by intense plasma and electromagnetic undulators

    International Nuclear Information System (INIS)

    Joshi, C.

    1989-01-01

    This is a second year progress report which details the work on the generation of radiation by intense plasma and electromagnetic undulators being carried out at UCLA. The status of the experimental work is described and the future directions are outlined. We have completed the first phase of experiments on the plasma wiggler generation and characterization. Suitability of a θ-pinch as a plasma source was investigated in great detail. It is found that a w of a few percent can be excited but there are trapped magnetic fields within θ-pinch plasma which hinder the injection of the electrons. A few more uniform and field-free plasma source is now being characterized. 8 refs., 5 figs

  11. Power-scalable, polarization-stable, dual-colour DFB fibre laser system for CW terahertz imaging

    DEFF Research Database (Denmark)

    Eichhorn, Finn; Pedersen, Jens Engholm; Jepsen, Peter Uhd

    Imaging with electromagnetic radiation in the terahertz (THz) range has received a large amount of attention during recent years. THz imaging systems have diverse potential application areas such as security screening, medical diagnostics and non-destructive testing. We will discuss a power......-scalable, dual-colour, polarization-maintaining distributed feedback (DFB) fibre laser system with an inherent narrow linewidth from the DFB fibre laser oscillators. The laser system can be used as source in CW THz systems employing photomixing (optical heterodyning) for generation and detection...

  12. In vitro terahertz monitoring of muscle tissue dehydration under the action of hyperosmotic agents

    Energy Technology Data Exchange (ETDEWEB)

    Kolesnikov, A S; Kolesnikova, E A; Popov, A P; Tuchin, V V [N.G. Chernyshevsky Saratov State University, Saratov (Russian Federation); Nazarov, M M [Institute on Laser and Information Technologies, Russian Academy of Sciences, Shatura, Moscow Region (Russian Federation); Shkurinov, A P [International Laser Center, M. V. Lomonosov Moscow State University, Moscow (Russian Federation)

    2014-07-31

    Dehydration of muscle tissue in vitro under the action of biologically compatible hyperosmotic agents is studied using a laser terahertz spectrometer in the frequency range from 0.25 to 2.5 THz. Broadband terahertz absorption and reflection spectra of the bovine skeletal muscle tissue were obtained under the action of glycerol, polyethylene glycol with the molecular weight 600 (PEG-600), and propylene glycol. The presented results are proposed for application in developing the methods of image contrast enhancement and increasing the depth of biological tissue probing with terahertz radiation. (laser biophotonics)

  13. Phase-locking to a free-space terahertz comb for metrological-grade terahertz lasers.

    Science.gov (United States)

    Consolino, L; Taschin, A; Bartolini, P; Bartalini, S; Cancio, P; Tredicucci, A; Beere, H E; Ritchie, D A; Torre, R; Vitiello, M S; De Natale, P

    2012-01-01

    Optical frequency comb synthesizers have represented a revolutionary approach to frequency metrology, providing a grid of frequency references for any laser emitting within their spectral coverage. Extending the metrological features of optical frequency comb synthesizers to the terahertz domain would be a major breakthrough, due to the widespread range of accessible strategic applications and the availability of stable, high-power and widely tunable sources such as quantum cascade lasers. Here we demonstrate phase-locking of a 2.5 THz quantum cascade laser to a free-space comb, generated in a LiNbO(3) waveguide and covering the 0.1-6 THz frequency range. We show that even a small fraction (quantum cascade laser is sufficient to generate a beat note suitable for phase-locking to the comb, paving the way to novel metrological-grade terahertz applications, including high-resolution spectroscopy, manipulation of cold molecules, astronomy and telecommunications.

  14. Electromagnetic radiation generated by arcing in low density plasma

    Science.gov (United States)

    Vayner, Boris V.; Ferguson, Dale C.; Snyder, David B.; Doreswamy, C. V.

    1996-01-01

    An unavoidable step in the process of space exploration is to use high-power, very large spacecraft launched into Earth orbit. Obviously, the spacecraft will need powerful energy sources. Previous experience has shown that electrical discharges occur on the surfaces of a high-voltage array, and these discharges (arcs) are undesirable in many respects. Moreover, any high voltage conductor will interact with the surrounding plasma, and that interaction may result in electrical discharges between the conductor and plasma (or between two conductors with different potentials, for example, during docking and extravehicular activity). One very important aspect is the generation of electromagnetic radiation by arcing. To prevent the negative influence of electromagnetic noise on the operation of spacecraft systems, it seems necessary to determine the spectra and absolute levels of the radiation, and to determine limitations on the solar array bias voltage that depend on the parameters of LEO plasma and the technical requirements of the spacecraft equipment. This report describes the results of an experimental study and computer simulation of the electromagnetic radiation generated by arcing on spacecraft surfaces. A large set of high quality data was obtained during the Solar Array Module Plasma Interaction Experiment (SAMPIE, flight STS-62) and ground test. These data include the amplitudes of current, pulse forms, duration of each arc, and spectra of plasma waves. A theoretical explanation of the observed features is presented in this report too. The elaborated model allows us to determine the parameters of the electromagnetic noise for different frequency ranges, distances from the arcing site, and distinct kinds of plasma waves.

  15. Superiority of terahertz over infrared transmission through bandages and burn wound ointments

    International Nuclear Information System (INIS)

    Suen, Jonathan Y.; Padilla, Willie J.

    2016-01-01

    Terahertz electromagnetic waves have long been proposed to be ideal for spectroscopy and imaging through non-polar dielectric materials that contain no water. Terahertz radiation may thus be useful for monitoring burn and wound injury recovery, as common care treatments involve application of both a clinical dressing and topical ointment. Here, we investigate the optical properties of typical care treatments in the millimeter wave (150–300 GHz), terahertz (0.3–3 THz), and infrared (14.5–0.67 μm) ranges of the electromagnetic spectrum. We find that THz radiation realizes low absorption coefficients and high levels of transmission compared to infrared wavelengths, which were strongly attenuated. Terahertz imaging can enable safe, non-ionizing, noninvasive monitoring of the healing process directly through clinical dressings and recovery ointments, minimizing the frequency of dressing changes and thus increasing the rate of the healing process.

  16. Superiority of terahertz over infrared transmission through bandages and burn wound ointments

    Energy Technology Data Exchange (ETDEWEB)

    Suen, Jonathan Y., E-mail: j.suen@duke.edu; Padilla, Willie J. [Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708 (United States)

    2016-06-06

    Terahertz electromagnetic waves have long been proposed to be ideal for spectroscopy and imaging through non-polar dielectric materials that contain no water. Terahertz radiation may thus be useful for monitoring burn and wound injury recovery, as common care treatments involve application of both a clinical dressing and topical ointment. Here, we investigate the optical properties of typical care treatments in the millimeter wave (150–300 GHz), terahertz (0.3–3 THz), and infrared (14.5–0.67 μm) ranges of the electromagnetic spectrum. We find that THz radiation realizes low absorption coefficients and high levels of transmission compared to infrared wavelengths, which were strongly attenuated. Terahertz imaging can enable safe, non-ionizing, noninvasive monitoring of the healing process directly through clinical dressings and recovery ointments, minimizing the frequency of dressing changes and thus increasing the rate of the healing process.

  17. Generating AN Optimum Treatment Plan for External Beam Radiation Therapy.

    Science.gov (United States)

    Kabus, Irwin

    1990-01-01

    The application of linear programming to the generation of an optimum external beam radiation treatment plan is investigated. MPSX, an IBM linear programming software package was used. All data originated from the CAT scan of an actual patient who was treated for a pancreatic malignant tumor before this study began. An examination of several alternatives for representing the cross section of the patient showed that it was sufficient to use a set of strategically placed points in the vital organs and tumor and a grid of points spaced about one half inch apart for the healthy tissue. Optimum treatment plans were generated from objective functions representing various treatment philosophies. The optimum plans were based on allowing for 216 external radiation beams which accounted for wedges of any size. A beam reduction scheme then reduced the number of beams in the optimum plan to a number of beams small enough for implementation. Regardless of the objective function, the linear programming treatment plan preserved about 95% of the patient's right kidney vs. 59% for the plan the hospital actually administered to the patient. The clinician, on the case, found most of the linear programming treatment plans to be superior to the hospital plan. An investigation was made, using parametric linear programming, concerning any possible benefits derived from generating treatment plans based on objective functions made up of convex combinations of two objective functions, however, this proved to have only limited value. This study also found, through dual variable analysis, that there was no benefit gained from relaxing some of the constraints on the healthy regions of the anatomy. This conclusion was supported by the clinician. Finally several schemes were found that, under certain conditions, can further reduce the number of beams in the final linear programming treatment plan.

  18. Broadband terahertz wave deflection based on C-shape complex metamaterials with phase discontinuities

    KAUST Repository

    Zhang, Xueqian; Tian, Zhen; Yue, Weisheng; Gu, Jianqiang; Zhang, Shuang; Han, Jiaguang; Zhang, Weili

    2013-01-01

    A broadband terahertz wave deflector based on metasurface induced phase discontinuities is reported. Various frequency components ranging from 0.43 to 1.0 THz with polarization orthogonal to the incidence are deflected into a broad range of angles from 25° to 84°. A Fresnel zone plate consequently developed from the beam deflector is capable of focusing a broadband terahertz radiation. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Broadband terahertz wave deflection based on C-shape complex metamaterials with phase discontinuities

    KAUST Repository

    Zhang, Xueqian

    2013-06-21

    A broadband terahertz wave deflector based on metasurface induced phase discontinuities is reported. Various frequency components ranging from 0.43 to 1.0 THz with polarization orthogonal to the incidence are deflected into a broad range of angles from 25° to 84°. A Fresnel zone plate consequently developed from the beam deflector is capable of focusing a broadband terahertz radiation. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Ginzburg's invention of undulators and their role in modern synchrotron radiation sources and free electron lasers

    International Nuclear Information System (INIS)

    Kulipanov, Gennadii N

    2007-01-01

    Undulators - periodic magnetic structures that were originally introduced by Vitalii Ginzburg in 1947 for electromagnetic radiation generation using relativistic electrons - are among the key elements of modern synchrotron radiation sources and free electron lasers (FELs). In this talk, the history of three generations of storage ring-based synchrotron X-ray sources using wigglers and undulators is briefly traced. Prospects for two types of next-generation space-coherent X-ray sources are discussed, which use long undulators and energy recovery accelerators or, alternatively, employ linear accelerator-based FELs. The recently developed Novosibirsk terahertz FEL facility, currently the world' s most powerful terahertz source, is described. It was the generation of electromagnetic radiation in this range that Ginzburg discussed in his 1947 work. (oral issue of the journal 'uspekhi fizicheskikh nauk')

  1. Terahertz wave reflective sensing and imaging

    Science.gov (United States)

    Zhong, Hua

    Sensing and imaging technologies using terahertz (THz) radiation have found diverse applications as they approach maturity. Since the burgeoning of this technique in the 1990's, many THz sensing and imaging investigations have been designed and conducted in transmission geometry, which provides sufficient phase and amplitude contrast for the study of the spectral properties of targets in the THz domain. Driven by rising expectations that THz technology will be a potential candidate in the next generation of security screening, remote sensing, biomedical imaging and non-destructive testing (NDT), most THz sensing and imaging modalities are being extended to reflection geometry, which offers unique and adaptive solutions, and multi-dimensional information in many real scenarios. This thesis takes an application-focused approach to the advancement of THz wave reflective sensing and imaging systems: The absorption signature of the explosive material hexahydro-1,3,5-trinitro-1,3,5triazine (RDX) is measured at 30 m---the longest standoff distance so far attained by THz time-domain spectroscopy (THz-TDS). The standoff distance sensing ability of THz-TDS is investigated along with discussions specifying the influences of a variety of factors such as propagation distance, water vapor absorption and collection efficiency. Highly directional THz radiation from four-wave mixing in laser-induced air plasmas is first observed and measured, which provides a potential solution for the atmospheric absorption effect in standoff THz sensing. The simulations of the beam profiles also illuminate the underlying physics behind the interaction of the optical beam with the plasma. THz wave reflective spectroscopic focal-plane imaging is realized the first time. Absorption features of some explosives and related compounds (ERCs) and biochemical materials are identified by using adaptive feature extraction method. Good classification results using multiple pattern recognition methods are

  2. Foreign Object Detection by Sub-Terahertz Quasi-Bessel Beam Imaging

    Directory of Open Access Journals (Sweden)

    Hyang Sook Chun

    2012-12-01

    Full Text Available Food quality monitoring, particularly foreign object detection, has recently become a critical issue for the food industry. In contrast to X-ray imaging, terahertz imaging can provide a safe and ionizing-radiation-free nondestructive inspection method for foreign object sensing. In this work, a quasi-Bessel beam (QBB known to be nondiffracting was generated by a conical dielectric lens to detect foreign objects in food samples. Using numerical evaluation via the finite-difference time-domain (FDTD method, the beam profiles of a QBB were evaluated and compared with the results obtained via analytical calculation and experimental characterization (knife edge method, point scanning method. The FDTD method enables a more precise estimation of the beam profile. Foreign objects in food samples, namely crickets, were then detected with the QBB, which had a deep focus and a high spatial resolution at 210 GHz. Transmitted images using a Gaussian beam obtained with a conventional lens were compared in the sub-terahertz frequency experimentally with those using a QBB generated using an axicon.

  3. Fingerprint extraction from interference destruction terahertz spectrum.

    Science.gov (United States)

    Xiong, Wei; Shen, Jingling

    2010-10-11

    In this paper, periodic peaks in a terahertz absorption spectrum are confirmed to be induced from interference effects. Theoretically, we explained the periodic peaks and calculated the locations of them. Accordingly, a technique was suggested, with which the interference peaks in a terahertz spectrum can be eliminated and therefore a real terahertz absorption spectrum can be obtained. Experimentally, a sample, Methamphetamine, was investigated and its terahertz fingerprint was successfully extracted from its interference destruction spectrum. This technique is useful in getting samples' terahertz fingerprint spectra, and furthermore provides a fast nondestructive testing method using a large size terahertz beam to identify materials.

  4. Radicals of DNA and DNA nucleotides generated by ionising radiation

    International Nuclear Information System (INIS)

    Przybytniak, G.

    2004-01-01

    A first stage of cell processes leading to DNA damage of initiated by radical reactions. In a model system such transformations were generated by ionising radiation which involves production of electron loss and electron gain centers of the substrate and radical formation. Using cryogenic ESR spectroscopy it was found that the DNA nucleotides, which convert to radical anions upon electron capture undergo the separation of unpaired spin and charge due to protonation. Circular and linear dichroism studies enabled to conclude that iron ions(III) induce strong changes in the DNA helical structure indicating their coordination with nitrogen bases. The repair of DNA radicals produced via radiolytic oxidation, i.e. the guanine radical cation and the allyl type radical of thymine, is possible at elevated temperatures due to the involvement of sulphydryl groups. The influence of the thiol charge is then limited

  5. The Third International Symposium on Space Terahertz Technology: Symposium proceedings

    Science.gov (United States)

    1992-01-01

    Papers from the symposium are presented that are relevant to the generation, detection, and use of the terahertz spectral region for space astronomy and remote sensing of the Earth's upper atmosphere. The program included thirteen sessions covering a wide variety of topics including solid-state oscillators, power-combining techniques, mixers, harmonic multipliers, antennas and antenna arrays, submillimeter receivers, and measurement techniques.

  6. Time Resolved Broadband Terahertz Relaxation Dynamics of Electron in Water

    DEFF Research Database (Denmark)

    Wang, Tianwu; Iwaszczuk, Krzysztof; Cooke, David G.

    We investigated the transient response of the solvated electron in water ejected by photodetachment from potassium ferrocyanide using time resolved terahertz spectroscopy (TSTS). Ultrabroadband THz transients are generated and detected by a two-color femtosecond-induced air plasma and air biased...

  7. Active terahertz metamaterials

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Hou-tong [Los Alamos National Laboratory; O' Hara, John F [Los Alamos National Laboratory; Taylor, Antoinette J [Los Alamos National Laboratory

    2009-01-01

    In this paper we present an overview of research in our group in terahertz (THz) metamaterials and their applications. We have developed a series of planar metamaterials operating at THz frequencies, all of which exhibit a strong resonant response. By incorporating natural materials, e.g. semiconductors, as the substrates or as critical regions of metamaterial elements, we are able to effectively control the metamaterial resonance by the application of external stimuli, e.g., photoexcitation and electrical bias. Such actively controllable metamaterials provide novel functionalities for solid-state device applications with unprecedented performance, such as THz spectroscopy, imaging, and many others.

  8. The application of terahertz spectroscopy and imaging in biomedicine

    International Nuclear Information System (INIS)

    Liu Shangjian; Yu Fei; Li Kai; Zhou Jing

    2013-01-01

    Terahertz (THz) science and technology is gaining increasing attention in the biomedical field. Compared with traditional medical diagnosis methods using infrared radiation, nuclear magnetic resonance, X-rays or ultrasound, THz radiation has low energy, high spatial resolution, a broad spectral range, and is a reliable means of imaging for the human body. Terahertz waves have strong penetration and high fingerprint specificity, so they can play an important role in drug detection and identification. This paper reviews the special techniques based on conventional THz time-domain setups in disease detection and drug identification. With regard to the biomedical fields, we focus on the application of THz radiation in studies of skin tissue, gene expression, cells, cancer imaging, the quantitative analysis of drugs, and so on. We also present an overview of the future challenges and prospects of THz research in medicine. (authors)

  9. Terahertz magnonics: Feasibility of using terahertz magnons for information processing

    Science.gov (United States)

    Zakeri, Khalil

    2018-06-01

    An immediate need of information technology is designing fast, small and low-loss devices. One of the ways to design such devices is using the bosonic quasiparticles, such as magnons, for information transfer/processing. This is the main idea behind the field of magnonics. When a magnon propagates through a magnetic medium, no electrical charge transport is involved and therefore no energy losses, creating Joule heating, occur. This is the most important advantage of using magnons for information transfer. Moreover the mutual conversion between magnons and the other carriers e.g. electrons, photons and plasmons shall open new opportunities to realize tunable multifunctional devices. Magnons cover a very wide range of frequency, from sub-gigahertz up to a few hundreds of terahertz. The magnon frequency has an important impact on the performance of magnon-based devices (the larger the excitation frequency, the faster the magnons). This means that the use of high-frequency (terahertz) magnons would provide a great opportunity for the design of ultrafast devices. However, up to now the focus in magnonics has been on the low-frequency gigahertz magnons. Here we discuss the feasibility of using terahertz magnons for application in magnonic devices. We shall bring the concept of terahertz magnonics into discussion. We discuss how the recently discovered phenomena in the field of terahertz magnons may inspire ideas for designing new magnonic devices. We further introduce methods to tune the fundamental properties of terahertz magnons, e.g. their eigenfrequency and lifetime.

  10. Neutron radiation characteristics of the IVth generation reactor spent fuel

    Science.gov (United States)

    Bedenko, Sergey; Shamanin, Igor; Grachev, Victor; Knyshev, Vladimir; Ukrainets, Olesya; Zorkin, Andrey

    2018-03-01

    Exploitation of nuclear power plants as well as construction of new generation reactors lead to great accumulation of spent fuel in interim storage facilities at nuclear power plants, and in spent fuel «wet» and «dry» long-term storages. Consequently, handling the fuel needs more attention. The paper is focused on the creation of an efficient computational model used for developing the procedures and regulations of spent nuclear fuel handling in nuclear fuel cycle of the new generation reactor. A Thorium High-temperature Gas-Cooled Reactor Unit (HGTRU, Russia) was used as an object for numerical research. Fuel isotopic composition of HGTRU was calculated using the verified code of the MCU-5 program. The analysis of alpha emitters and neutron radiation sources was made. The neutron yield resulting from (α,n)-reactions and at spontaneous fission was calculated. In this work it has been shown that contribution of (α,n)-neutrons is insignificant in case of such (Th,Pu)-fuel composition and HGTRU operation mode, and integral neutron yield can be approximated by the Watt spectral function. Spectral and standardized neutron distributions were achieved by approximation of the list of high-precision nuclear data. The distribution functions were prepared in group and continuous form for further use in calculations according to MNCP, MCU, and SCALE.

  11. Radiation protection aspects of a high flux, fast neutron generator

    International Nuclear Information System (INIS)

    DeLuca, P.M.; Torti, R.P.; Chenevert, G.M.; Tesmer, J.R.; Kelsey, C.A.

    1976-01-01

    During the development and operation of a gas target, DT neutron generator for use in cancer therapy, two radiation hazards were routinely encountered - personnel exposure to neutrons and to tritium. The principal hazard was irradiation by fast neutrons. By assembling the source below ground level, adding shielding and the use of a controlled access, key identification interlock, the neutron hazard has been reduced. With the present source strength of 2 x 10 12 n/sec, an average neutron dose rate in the control room of 20 mrem/hr was measured- a level compatible with a limited run schedule. The second hazard was exposure to tritium in both gaseous and solid forms. A target inventory of 90 Ci, and overall inventory of 500 Ci, and the need to modify and repair the generator present significant potential hazard due to tritium exposure. The use of protective gloves, wipe tests, urine assays, continuous room air monitoring, and equipment decontamination minimized personnel exposure and effectively confined contamination. The dose due to tritium has been ∼ 0.5 rem/year and negligible spread of contamination has occurred

  12. Plasma Wave Electronic Terahertz Technology

    National Research Council Canada - National Science Library

    Shur, Michael

    2003-01-01

    Plasma waves are oscillations of electron density in time and space. In deep submicron field effect transistors plasma wave frequencies lie in the terahertz range and can be tuned by applied gate bias...

  13. Terahertz composite imaging method

    Institute of Scientific and Technical Information of China (English)

    QIAO Xiaoli; REN Jiaojiao; ZHANG Dandan; CAO Guohua; LI Lijuan; ZHANG Xinming

    2017-01-01

    In order to improve the imaging quality of terahertz(THz) spectroscopy, Terahertz Composite Imaging Method(TCIM) is proposed. The traditional methods of improving THz spectroscopy image quality are mainly from the aspects of de-noising and image enhancement. TCIM breaks through this limitation. A set of images, reconstructed in a single data collection, can be utilized to construct two kinds of composite images. One algorithm, called Function Superposition Imaging Algorithm(FSIA), is to construct a new gray image utilizing multiple gray images through a certain function. The features of the Region Of Interest (ROI) are more obvious after operating, and it has capability of merging ROIs in multiple images. The other, called Multi-characteristics Pseudo-color Imaging Algorithm(McPcIA), is to construct a pseudo-color image by combining multiple reconstructed gray images in a single data collection. The features of ROI are enhanced by color differences. Two algorithms can not only improve the contrast of ROIs, but also increase the amount of information resulting in analysis convenience. The experimental results show that TCIM is a simple and effective tool for THz spectroscopy image analysis.

  14. Synchrotron radiation generation: Technological considerations, feasibility of practical realization with available way in the Country

    International Nuclear Information System (INIS)

    Moreira, A.F.O.

    1983-01-01

    Technological aspects linked to the synchrotron radiation generation in laboratory are discussed. A feasibility study for the implantation of a machine for such a radiation in a laboratory in Brazil is also discussed. (L.C.) [pt

  15. PREFACE: Acceleration and radiation generation in space and laboratory plasmas

    Science.gov (United States)

    Bingham, R.; Katsouleas, T.; Dawson, J. M.; Stenflo, L.

    1994-01-01

    Sixty-six leading researchers from ten nations gathered in the Homeric village of Kardamyli, on the southern coast of mainland Greece, from August 29-September 4, 1993 for the International Workshop on Acceleration and Radiation Generation in Space and Laboratory Plasmas. This Special Issue represents a cross-section of the presentations made at and the research stimulated by that meeting. According to the Iliad, King Agamemnon used Kardamyli as a dowry offering in order to draw a sulking Achilles into the Trojan War. 3000 years later, Kardamyli is no less seductive. Its remoteness and tranquility made it an ideal venue for promoting the free exchange of ideas between various disciplines that do not normally interact. Through invited presen tations, informal poster discussions and working group sessions, the Workshop brought together leaders from the laboratory and space/astrophysics communities working on common problems of acceleration and radiation generation in plasmas. It was clear from the presentation and discussion sessions that there is a great deal of common ground between these disciplines which is not at first obvious due to the differing terminologies and types of observations available to each community. All of the papers in this Special Issue highlight the role collective plasma processes play in accelerating particles or generating radiation. Some are state-of-the-art presentations of the latest research in a single discipline, while others investi gate the applicability of known laboratory mechanisms to explain observations in natural plasmas. Notable among the latter are the papers by Marshall et al. on kHz radiation in the magnetosphere ; Barletta et al. on collective acceleration in solar flares; and by Dendy et al. on ion cyclotron emission. The papers in this Issue are organized as follows: In Section 1 are four general papers by Dawson, Galeev, Bingham et al. and Mon which serves as an introduction to the physical mechanisms of acceleration

  16. Design of Integrated Circuits Approaching Terahertz Frequencies

    DEFF Research Database (Denmark)

    Yan, Lei

    In this thesis, monolithic microwave integrated circuits(MMICs) are presented for millimeter-wave and submillimeter-wave or terahertz(THz) applications. Millimeter-wave power generation from solid state devices is not only crucial for the emerging high data rate wireless communications but also...... heterodyne receivers with requirements of room temperature operation, low system complexity, and high sensitivity, monolithic integrated Schottky diode technology is chosen for the implementation of submillimeterwave components. The corresponding subharmonic mixer and multiplier for a THz radiometer system...

  17. Resonant metallic nanostructures for enhanced terahertz spectroscopy

    KAUST Repository

    Toma, A.

    2015-11-12

    We present our recent studies on terahertz resonant dipole nanoantennas. Exploiting the localization and enhancement capabilities of these devices, we introduce an effective method to perform terahertz spectroscopy on an extremely small number of nano-objects.

  18. Resonant metallic nanostructures for enhanced terahertz spectroscopy

    KAUST Repository

    Toma, A.; Tuccio, S.; Prato, M.; De Donato, F.; Perucchi, A.; Di Pietro, P.; Marras, S.; Liberale, Carlo; Zaccaria, R. Proietti; De Angelis, F.; Manna, L.; Lupi, S.; Di Fabrizio, Enzo M.; Razzari, L.

    2015-01-01

    We present our recent studies on terahertz resonant dipole nanoantennas. Exploiting the localization and enhancement capabilities of these devices, we introduce an effective method to perform terahertz spectroscopy on an extremely small number

  19. Losses in magnetic flux compression generators: Part 2, Radiation losses

    International Nuclear Information System (INIS)

    Fowler, C.M.

    1988-06-01

    This is the second monograph devoted to the analysis of flux losses in explosive driven magnetic flux compression generators. In the first monograph, flux losses from magnetic field penetration into conductor walls was studied by conventional diffusion theory. In the present report flux loss by radiation from the outer conductor walls is treated. Flux leakage rates through walls of finite thickness are first obtained by diffusion theory. It is shown, for normal wall thicknesses, that flux leakage is determined essentially by the wall conductance, defined as the product of wall thickness and wall conductivity. This remains true when the wall thickness is reduced to zero at unchanged conductance. In this case the wall is said to be coalesced. Solutions for a cavity bounded by a perfect conductor on one side and a coalesced wall on the other are then obtained using the complete Maxwell wave equations in both the cavity and free space beyond the coalesced wall. Several anomalies, noted earlier, that arise from diffusion analysis are resolved by the wave treatment. Conditions for the validity of the diffusion treatment are noted, and an expression is obtained within the framework of diffusion theory for energy radiated into space from the cavity walls. The free space wave equations are solved by using the method of characteristics in both the cavity and free space regions. An extension of the characteristic method to situations where the constitutive relations are non-linear is outlined in an appendix. For a special class of these relations, Riemann-like invariants are determined explicitly and used to solve a particular example

  20. Experimental Realization of an Epsilon-Near-Zero Graded-Index Metalens at Terahertz Frequencies

    Science.gov (United States)

    Pacheco-Peña, Victor; Engheta, Nader; Kuznetsov, Sergei; Gentselev, Alexandr; Beruete, Miguel

    2017-09-01

    The terahertz band has been historically hindered by the lack of efficient generators and detectors, but a series of recent breakthroughs have helped to effectively close the "terahertz gap." A rapid development of terahertz technology has been possible thanks to the translation of revolutionary concepts from other regions of the electromagnetic spectrum. Among them, metamaterials stand out for their unprecedented ability to control wave propagation and manipulate electromagnetic response of matter. They have become a workhorse in the development of terahertz devices such as lenses, polarizers, etc., with fascinating features. In particular, epsilon-near-zero (ENZ) metamaterials have attracted much attention in the past several years due to their unusual properties such as squeezing, tunneling, and supercoupling where a wave traveling inside an electrically small channel filled with an ENZ medium can be tunneled through it, reducing reflections and coupling most of its energy. Here, we design and experimentally demonstrate an ENZ graded-index (GRIN) metamaterial lens operating at terahertz with a power enhancement of 16.2 dB, using an array of narrow hollow rectangular waveguides working near their cutoff frequencies. This is a demonstration of an ENZ GRIN device at terahertz and can open the path towards other realizations of similar devices enabling full quasioptical processing of terahertz signals.

  1. Nondestructive Imaging of an Object Using the Compact Continuous-Wave Sub-Terahertz Imaging System

    Energy Technology Data Exchange (ETDEWEB)

    Jang, Jin Seok; Kwon, Il Bub; Yoon, Dong Jin; Seo, Dae Cheol [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of)

    2010-08-15

    This paper presented compact CW sub-THz imaging system using the terahertz transmitter(Tx) that generating 0.34 THz electromagnetic wave on based electronic device. Using 0.34 THz electromagnetic wave generated by Tx, we transmitted to sample by point by point scan method and measured transmitting terahertz wave magnitude and phase information respectively with terahertz receiver(Rx) based on sub harmonic mixer. This paper measured and compared images of several samples to obtain better imaging results by changing time delay and step distance of scanning stage which affect image resolution. Also, through the imaging measurement of various samples, we were able to assure possibility of application of terahertz wave

  2. Nondestructive Imaging of an Object Using the Compact Continuous-Wave Sub-Terahertz Imaging System

    International Nuclear Information System (INIS)

    Jang, Jin Seok; Kwon, Il Bub; Yoon, Dong Jin; Seo, Dae Cheol

    2010-01-01

    This paper presented compact CW sub-THz imaging system using the terahertz transmitter(Tx) that generating 0.34 THz electromagnetic wave on based electronic device. Using 0.34 THz electromagnetic wave generated by Tx, we transmitted to sample by point by point scan method and measured transmitting terahertz wave magnitude and phase information respectively with terahertz receiver(Rx) based on sub harmonic mixer. This paper measured and compared images of several samples to obtain better imaging results by changing time delay and step distance of scanning stage which affect image resolution. Also, through the imaging measurement of various samples, we were able to assure possibility of application of terahertz wave

  3. Multilayer Graphene for Waveguide Terahertz Modulator

    DEFF Research Database (Denmark)

    Khromova, I.; Andryieuski, Andrei; Lavrinenko, Andrei

    2014-01-01

    We study terahertz to infrared electromagnetic properties of multilayer graphene/dielectric artificial medium and present a novel concept of terahertz modulation at midinfrared wavelengths. This approach allows the realization of high-speed electrically controllable terahertz modulators based...... on hollow waveguide sections filled with multilayer graphene....

  4. Terahertz detectors using hot-electrons in superconducting films

    Energy Technology Data Exchange (ETDEWEB)

    Semenov, A. [DLR, Inst. of Planetary Research, Berlin (Germany)

    2007-07-01

    Recently the terahertz gap has been recognized as a prospective spectral range for radioastronomy as well as for material and security studies. Implementation of terahertz technology in these fields requires further improvement of instruments and their major subcomponents. Physical phenomena associated with the local and homogeneous non-equilibrium electron sates in thin superconducting films offer numerous possibilities for the development of terahertz and infrared detectors. Depending on the nature of the resistive state and the operation regime, a variety of detector can be realized. They are e.g. direct bolometric or kinetic inductance detectors, heterodyne mixers or photon counters. Operation principles and physical limitations of these devices will be discussed. Two examples of the detector development made in cooperation between the German Aerospace Center, the University of Karlsruhe and PTB, Berlin will be presented. The energy resolving single-photon detector with an almost fundamentally limited energy resolution of 0.6 eV at 6.5 K for photons with wavelengths from 400 nm to 2500 nm and the heterodyne mixer quasioptically coupled to radiation in the frequency range from 0.8 THz to 5 THz and providing a noise temperature of less then ten times the quantum limit. The mixers will be implemented in the terahertz radar for security screening (TERASEC) and in the heterodyne receiver of the stratospheric observatory SOFIA. (orig.)

  5. Tunable plasmonic toroidal terahertz metamodulator

    Science.gov (United States)

    Gerislioglu, Burak; Ahmadivand, Arash; Pala, Nezih

    2018-04-01

    Optical modulators are essential and strategic parts of micro- and nanophotonic circuits to encode electro-optical signals in the optical domain. Here, by using arrays of multipixel toroidal plasmonic terahertz (THz) metamolecules, we developed a functional plasmonic metamodulator with high efficiency and tunability. Technically, the dynamic toroidal dipole induces nonradiating charge-current arrangements leading to have an exquisite role in defining the inherent spectral features of various materials. By categorizing in a different family of multipoles far from the traditional electromagnetic multipoles, the toroidal dipole corresponds to poloidal currents flowing on the surface of a closed-loop torus. Utilizing the sensitivity of the optically driven toroidal momentum to the incident THz beam power and by employing both numerical tools and experimental analysis, we systematically studied the spectral response of the proposed THz plasmonic metadevice. In this Rapid Communication, we uncover a correlation between the existence and the excitation of the toroidal response and the incident beam power. This mechanism is employed to develop THz toroidal metamodulators with a strong potential to be employed for practical advanced and next-generation communication, filtering, and routing applications.

  6. THz calorimetry : An absolute power meter for TeraHertz radiation and the absorptivity of the Herschel Space Observatory telescope mirror coating

    NARCIS (Netherlands)

    Klaassen, T.O.; Hovenier, J.N.; Fischer, J.; Jakob, G.; Poglitsch, A.; Sternberg, O.

    2004-01-01

    A new calorimetric absolute power meter has been developed for THz radiation. This broad band THz power meter measures average power at ambient temperature and pressure, does not use a window, and is insensitive to polarization and time structure of THz radiation. The operation of the power meter is

  7. Ground-plane-less bidirectional terahertz absorber based on omega resonators

    NARCIS (Netherlands)

    Balmakou, Alexei; Podalov, Maxim; Khakhomov, Sergei; Stavenga, Doekele; Semchenko, Igor

    2015-01-01

    We present a new ultrathin metamaterial that acts as a frequency-selective absorber of terahertz radiation. The absorber is a square array of pairs of omega-shaped micro-resonators made of high-ohmic-loss metal. The metamaterial provides significant suppression of transmitted and reflected radiation

  8. Intraband dynamics and terahertz emission in biased semiconductor superlattices coupled to double far-infrared pulses

    International Nuclear Information System (INIS)

    Min, Li; Xian-Wu, Mi

    2009-01-01

    This paper studies both the intraband polarization and terahertz emission of a semiconductor superlattice in combined dc and ac electric fields by using the superposition of two identical time delayed and phase shifted optical pulses. By adjusting the delay between these two optical pulses, our results show that the intraband polarization is sensitive to the time delay. The peak values appear again for the terahertz emission intensity due to the superposition of two optical pulses. The emission lines of terahertz blueshift and redshift in different ac electric fields and dynamic localization appears. The emission lines of THz only appear to blueshift when the biased superlattice is driven by a single optical pulse. Due to excitonic dynamic localization, the terahertz emission intensity decays with time in different dc and ac electric fields. These are features of this superlattice which distinguish it from a superlattice generated by a single optical pulse to drive it. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  9. Nitrogen plasma formation through terahertz-induced ultrafast electron field emission

    DEFF Research Database (Denmark)

    Iwaszczuk, Krzysztof; Zalkovskij, Maksim; Strikwerda, Andrew

    2015-01-01

    Electron microscopy and electron diffraction techniques rely on electron sources. Those sources require strong electric fields to extract electrons from metals, either by the photoelectric effect, driven by multiphoton absorption of strong laser fields, or in the static field emission regime....... Terahertz (THz) radiation, commonly understood to be nonionizing due to its low photon energy, is here shown to produce electron field emission. We demonstrate that a carrier-envelope phase-stable single-cycle optical field at THz frequencies interacting with a metallic microantenna can generate...... and accelerate ultrashort and ultrabright electron bunches into free space, and we use these electrons to excite and ionize ambient nitrogen molecules near the antenna. The associated UV emission from the gas forms a novel THz wave detector, which, in contrast with conventional photon-counting or heat...

  10. High field terahertz emission from relativistic laser-driven plasma wakefields

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zi-Yu, E-mail: Ziyu.Chen@uni-duesseldorf.de [Institut für Theoretische Physik I, Heinrich-Heine-Universität Düsseldorf, Düsseldorf 40225 (Germany); LSD, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621999 (China); Pukhov, Alexander [Institut für Theoretische Physik I, Heinrich-Heine-Universität Düsseldorf, Düsseldorf 40225 (Germany)

    2015-10-15

    We propose a method to generate high field terahertz (THz) radiation with peak strength of GV/cm level in the THz frequency gap range of 1–10 THz using a relativistic laser interaction with a gaseous plasma target. Due to the effect of local pump depletion, an initially Gaussian laser pulse undergoes leading edge erosion and eventually evolves to a state with leading edge being step function. Interacting with such a pulse, electrons gain transverse residual momentum and excite net transverse currents modulated by the relativistic plasma frequency. These currents give rise to the low frequency THz emission. We demonstrate this process with one and two dimensional particle-in-cell simulations.

  11. Nanoplasmonic-gold-cylinder-array-enhanced terahertz source

    Science.gov (United States)

    Zhiguang, Ao; Jinhai, Sun; He, Cai; Guofeng, Song; Jiakun, Song; Yuzhi, Song; Yun, Xu

    2016-12-01

    Photoconductive antennas (PCAs) based on nanoplasmonic gratings contact electrodes have been proposed to satisfy the demand for high power, efficiency and responsivity terahertz (THz) sources. Reducing the average photo-generated carrier transport path to the photoconductor contact electrodes was previously considered the dominant mechanism to improve PCAs' power. However, considering the bias in a real device, the electric field between gratings is limited and the role of surface plasmonic resonance (SPR) field enhancement is more important in improving THz radiation. This paper, based on SPR, analyzes the interaction between incident light and substrate in nano cylinder array PCAs and clearly shows that the SPR can enhance the light absorption in the substrate. After the optimization of the structure size, the proposed structure can offer 87% optical transmission into GaAs substrate. Compared with conventional PCAs, the optical transmission into the substrate will increase 5.8 times and the enhancement factor of substrate absorption will reach 13.7 respectively. Project supported by the National Basic Research Program of China (Nos. 2015CB351902, 2015CB932402), the National Key Research Program of China (No. 2011ZX01015-001), and the National Natural Science Foundation of China (No. U143231).

  12. Homogeneous spectral spanning of terahertz semiconductor lasers with radio frequency modulation.

    Science.gov (United States)

    Wan, W J; Li, H; Zhou, T; Cao, J C

    2017-03-08

    Homogeneous broadband and electrically pumped semiconductor radiation sources emitting in the terahertz regime are highly desirable for various applications, including spectroscopy, chemical sensing, and gas identification. In the frequency range between 1 and 5 THz, unipolar quantum cascade lasers employing electron inter-subband transitions in multiple-quantum-well structures are the most powerful semiconductor light sources. However, these devices are normally characterized by either a narrow emission spectrum due to the narrow gain bandwidth of the inter-subband optical transitions or an inhomogeneous broad terahertz spectrum from lasers with heterogeneous stacks of active regions. Here, we report the demonstration of homogeneous spectral spanning of long-cavity terahertz semiconductor quantum cascade lasers based on a bound-to-continuum and resonant phonon design under radio frequency modulation. At a single drive current, the terahertz spectrum under radio frequency modulation continuously spans 330 GHz (~8% of the central frequency), which is the record for single plasmon waveguide terahertz lasers with a bound-to-continuum design. The homogeneous broadband terahertz sources can be used for spectroscopic applications, i.e., GaAs etalon transmission measurement and ammonia gas identification.

  13. Large static tuning of narrow-beam terahertz plasmonic lasers operating at 78K

    Directory of Open Access Journals (Sweden)

    Chongzhao Wu

    2017-02-01

    Full Text Available A new tuning mechanism is demonstrated for single-mode metal-clad plasmonic lasers, in which the refractive-index of the laser’s surrounding medium affects the resonant-cavity mode in the same vein as the refractive-index of gain medium inside the cavity. Reversible, continuous, and mode-hop-free tuning of ∼57 GHz is realized for single-mode narrow-beam terahertz plasmonic quantum-cascade lasers (QCLs, which is demonstrated at a much more practical temperature of 78 K. The tuning is based on post-process deposition/etching of a dielectric (silicon-dioxide on a QCL chip that has already been soldered and wire-bonded onto a copper mount. This is a considerably larger tuning range compared to previously reported results for terahertz QCLs with directional far-field radiation patterns. The key enabling mechanism for tuning is a recently developed antenna-feedback scheme for plasmonic lasers, which leads to the generation of hybrid surface-plasmon-polaritons propagating outside the cavity of the laser with a large spatial extent. The effect of dielectric deposition on QCL’s characteristics is investigated in detail including that on maximum operating temperature, peak output power, and far-field radiation patterns. Single-lobed beam with low divergence (<7° is maintained through the tuning range. The antenna-feedback scheme is ideally suited for modulation of plasmonic lasers and their sensing applications due to the sensitive dependence of spectral and radiative properties of the laser on its surrounding medium.

  14. Terahertz Science, Technology, and Communication

    Science.gov (United States)

    Chattopadhyay, Goutam

    2013-01-01

    The term "terahertz" has been ubiquitous in the arena of technology over the past couple of years. New applications are emerging every day which are exploiting the promises of terahertz - its small wavelength; capability of penetrating dust, clouds, and fog; and possibility of having large instantaneous bandwidth for high-speed communication channels. Until very recently, space-based instruments for astrophysics, planetary science, and Earth science missions have been the primary motivator for the development of terahertz sensors, sources, and systems. However, in recent years the emerging areas such as imaging from space platforms, surveillance of person-borne hidden weapons or contraband from a safe stand-off distance and reconnaissance, medical imaging and DNA sequencing, and in the world high speed communications have been the driving force for this area of research.

  15. Theory of terahertz electric oscillations by supercooled superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Mishonov, Todor M; Mishonov, Mihail T [Department of Theoretical Physics, Faculty of Physics, University of Sofia St Kliment Ohridski, 5 J Bourchier Boulevard, 1164 Sofia (Bulgaria); Laboratorium voor Vaste-Stoffysica en Magnetisme, Katholieke Universiteit Leuven, Celestijnenlaan 200 D B-3001 Leuven (Belgium)

    2005-11-15

    We predict that below T{sub c} a regime of negative differential conductivity (NDC) can be reached. The superconductor should be supercooled to Tgeneration of electric oscillations. Such generators can be used in the superconducting electronics as a new type THz source of radiation. Oscillations can be modulated by the change of the bias voltage, electrostatic doping by a gate electrode when the superconductor is the channel of a field effect transistor, or by light. When small amplitude oscillations are stabilized near the critical temperature T{sub c} the generator can be used as a bolometer. NDC, which is essential for the applications, is predicted on the basis of analysis of known results for fluctuation conductivity, obtained in previous papers by solving the Boltzmann kinetic equation for the Cooper pairs metastable in the normal phase. The Boltzmann equation for fluctuation Cooper pairs is a result of state-of-the-art application of the microscopic theory of superconductivity. Our theoretical conclusions are based on some approximations like time dependent Ginzburg-Landau theory initially derived for gapless superconductors, but nevertheless can reliably predict the appearance of NDC. NDC is the main ingredient of the proposed technical applications. The maximal frequency at which superconductors can operate as generators is determined by the critical temperature {Dirac_h}/2{pi}{omega}{sub max} {approx} k{sub B}T{sub c}. For high-T{sub c} superconductors this maximal frequency falls well inside the terahertz range. Technical conditions to avoid nucleation of the superconducting phase are briefly discussed. We suggest that nanostructured high-T{sub c} superconductors patterned in a single chip can

  16. Terahertz absorption and emission upon the photoionization of acceptors in uniaxially stressed silicon

    Energy Technology Data Exchange (ETDEWEB)

    Zhukavin, R. Kh., E-mail: zhur@ipmras.ru; Kovalevsky, K. A.; Orlov, M. L.; Tsyplenkov, V. V. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Hübers, H.-W. [DLR Institute of Optical Sensor Systems (Germany); Dessmann, N. [Humboldt University of Berlin, Institute of Physics (Germany); Kozlov, D. V.; Shastin, V. N. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)

    2016-11-15

    Experimental data on the spontaneous emission and absorption modulation in boron-doped silicon under CO{sub 2} laser excitation depending on the uniaxial stress applied along the [001] and [011] crystallographic directions are presented. Room-temperature radiation is used as the probe radiation. Low stress (less than 0.5 kbar) is shown to reduce losses in the terahertz region by 20%. The main contribution to absorption modulation at zero and low stress is made by A{sup +} centers. Intersubband free hole transitions additionally contribute to terahertz absorption at higher stress. These contributions can be minimized by compensation.

  17. Electrically nonconductive shield for electric equipment generating ionizing radiation

    International Nuclear Information System (INIS)

    Aitken, D.

    1979-01-01

    As a radiation protection shield there is proposed a nonconductive shield fabricated from epoxides or other plastics material and containing finely dispersed radiation absorbing metal. It is to be designed in such a way that it lies in the range of a high electric gradient in the equipment, close to the radiation-producing component. As suitable metals there are mentioned tin, tungsten, and lead resp. their oxides. As an example there is used an X-ray shielding. (RW) 891 RW/RW 892 MKO [de

  18. Nanoscale Laser Terahertz Emission Microscopy

    DEFF Research Database (Denmark)

    Klarskov, Pernille; Kim, Hyewon; Colvin, Vicki L.

    2017-01-01

    Laser terahertz emission microscopy (LTEM) has become a powerful tool for studying ultrafast dynamics and local fields in many different types of materials. This technique, which relies on acceleration of charge carriers in a material upon femtosecond excitation, can provide insight into the phys......Laser terahertz emission microscopy (LTEM) has become a powerful tool for studying ultrafast dynamics and local fields in many different types of materials. This technique, which relies on acceleration of charge carriers in a material upon femtosecond excitation, can provide insight...

  19. Radiation from communication antenna and electrical cable generator

    International Nuclear Information System (INIS)

    Rozaimah Abdul Rahim; Norzehan Ngadiron

    2009-01-01

    Lack of knowledge about radio frequency wave antenna emitter and electrical cable cause misunderstanding among public that make this technologies dangerous, thereby can harm the public hearths. Malaysian Nuclear Agency as one technical body in Malaysia that specialized in this matter had already explained it to the public about this issue long time ago. Basically, non-ionizing radiation are one of the electromagnetic radiation that can be produced naturally or artificially. It consists of two main component, electrical field and magnetic field that propagated with velocity of light. Energy for this radiation less than 12.4 eV, wave distance more than 100 nm with frequency less than 3000 THz. With low energy, this radiation cannot go to ionizing process. Exposure to this radiation also can cause biological effect, acute and chronic. For human that expose to this radiation, direct effect only involved in thermal effect which suddenly increasing of temperature in body. This can cause heat stress, heat stroke and cataract in eyes lens. For infrared, visible light, ultraviolet and laser, the critical organ are eyes and skins. In Malaysia, Telecommunication Department had already produce guideline , Regulatory Framework on the sharing communication infrastructures 1988 that mentioned about all the guideline that must be obey by all the network operator including safety aspect, especially for radio wave and micro wave with frequency from 30 MHz to 300 GHz. The other agencies that produced standards such as SIRIM specialized in level of exposure for electromagnetic radiation until 3 kHz. For the other non-ionizing radiation, guideline from ICNIRP, WHO or others will be referred. For the public the main problem for this issues are psychology problem, political influence and jealously. For Malaysian Nuclear Agency, public awareness must be proceeded in order to give knowledge and understanding about this matter so that the public will not fear in the future.

  20. Metamaterial-Enhanced Nonlinear Terahertz Spectroscopy

    Directory of Open Access Journals (Sweden)

    Zhang X.

    2013-03-01

    Full Text Available We demonstrate large nonlinear terahertz responses in the gaps of metamaterial split ring resonators in several materials and use nonlinear THz transmission and THz-pump/THz-probe spectroscopy to study the nonlinear responses and dynamics. We use the field enhancement in the SRR gaps to initiate high-field phenomena at lower incident fields. In vanadium dioxide, we drive the insulator-to-metal phase transition with high-field THz radiation. The film conductivity increases by over two orders of magnitude and the phase transition occurs on a several picosecond timescale. In gallium arsenide, we observe high-field transport phenomena, including mobility saturation and impact ionization. The carrier density increases by up to ten orders of magnitude at high fields. At the highest fields, we demonstrate THz-induced damage in both vanadium dioxide and gallium arsenide.

  1. Generating a heated fluid using an electromagnetic radiation-absorbing complex

    Science.gov (United States)

    Halas, Nancy J.; Nordlander, Peter; Neumann, Oara

    2018-01-09

    A vessel including a concentrator configured to concentrate electromagnetic (EM) radiation received from an EM radiation source and a complex configured to absorb EM radiation to generate heat. The vessel is configured to receive a cool fluid from the cool fluid source, concentrate the EM radiation using the concentrator, apply the EM radiation to the complex, and transform, using the heat generated by the complex, the cool fluid to the heated fluid. The complex is at least one of consisting of copper nanoparticles, copper oxide nanoparticles, nanoshells, nanorods, carbon moieties, encapsulated nanoshells, encapsulated nanoparticles, and branched nanostructures. Further, the EM radiation is at least one of EM radiation in an ultraviolet region of an electromagnetic spectrum, in a visible region of the electromagnetic spectrum, and in an infrared region of the electromagnetic spectrum.

  2. Theory of coherent transition radiation generated at a plasma-vacuum interface

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, Carl B.; Esarey, Eric; van Tilborg, Jeroen; Leemans, Wim P.

    2003-06-26

    Transition radiation generated by an electron beam, produced by a laser wakefield accelerator operating in the self-modulated regime, crossing the plasma-vacuum boundary is considered. The angular distributions and spectra are calculated for both the incoherent and coherent radiation. The effects of the longitudinal and transverse momentum distributions on the differential energy spectra are examined. Diffraction radiation from the finite transverse extent of the plasma is considered and shown to strongly modify the spectra and energy radiated for long wavelength radiation. This method of transition radiation generation has the capability of producing high peak power THz radiation, of order 100 (mu)J/pulse at the plasma-vacuum interface, which is several orders of magnitude beyond current state-of-the-art THz sources.

  3. High Reliability Oscillators for Terahertz Systems, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Terahertz sources based on lower frequency oscillators and amplifiers plus a chain of frequency multipliers are the workhorse technology for NASA's terahertz...

  4. Electromagnetic radiation from vortex flow in Type-II superconductors.

    Science.gov (United States)

    Bulaevskii, L N; Chudnovsky, E M

    2006-11-10

    We show that a moving vortex lattice, as it comes to a crystal edge, radiates into a free space the harmonics of the washboard frequency, omega(0)=2pi v/a, up to a superconducting gap, Delta/variant Planck's over 2pi. Here v is the velocity of the vortex lattice and a is the intervortex spacing. We compute radiation power and show that this effect can be used for the generation of terahertz radiation and for characterization of moving vortex lattices.

  5. Terahertz computed tomography in three-dimensional using a pyroelectric array detector

    Science.gov (United States)

    Li, Bin; Wang, Dayong; Zhou, Xun; Rong, Lu; Huang, Haochong; Wan, Min; Wang, Yunxin

    2017-05-01

    Terahertz frequency range spans from 0.1 to 10 THz. Terahertz radiation can penetrate nonpolar materials and nonmetallic materials, such as plastics, wood, and clothes. Then the feature makes the terahertz imaging have important research value. Terahertz computed tomography makes use of the penetrability of terahertz radiation and obtains three-dimensional object projection data. In the paper, continuous-wave terahertz computed tomography with a pyroelectric array detectoris presented. Compared with scanning terahertz computed tomography, a pyroelectric array detector can obtain a large number of projection data in a short time, as the acquisition mode of the array pyroelectric detector omit the projection process on the vertical and horizontal direction. With the two-dimensional cross-sectional images of the object are obtained by the filtered back projection algorithm. The two side distance of the straw wall account for 80 pixels, so it multiplied by the pixel size is equal to the diameter of the straw about 6.4 mm. Compared with the actual diameter of the straw, the relative error is 6%. In order to reconstruct the three-dimensional internal structure image of the straw, the y direction range from 70 to 150 are selected on the array pyroelectric detector and are reconstructed by the filtered back projection algorithm. As the pixel size is 80 μm, the height of three-dimensional internal structure image of the straw is 6.48 mm. The presented system can rapidly reconstruct the three-dimensional object by using a pyroelectric array detector and explores the feasibility of on non-destructive evaluation and security testing.

  6. Markets, Availability, Notice, and Technical Performance of Terahertz Systems: Historic Development, Present, and Trends

    Science.gov (United States)

    Hochrein, Thomas

    2015-03-01

    Although a lot of work has already been done under the older terms "far infrared" or "sub-millimeter waves", the term "terahertz" stands for a novel technique offering many potential applications. The latter term also represents a new generation of systems with the opportunity for coherent, time-resolved detection. In addition to the well-known technical opportunities, an historical examination of Internet usage, as well as the number of publications and patent applications, confirms ongoing interest in this technique. These activities' annual growth rate is between 9 % and 21 %. The geographical distribution shows the center of terahertz activities. A shift from the scientific to more application-oriented research can be observed. We present a survey among worldwide terahertz suppliers with special focus on the European region and the use of terahertz systems in the field of measurement and analytical applications. This reveals the current state of terahertz systems' commercial and geographical availability as well as their costs, target markets, and technical performance. Component cost distribution using the example of an optical pulsed time-domain terahertz system gives an impression of the prevailing cost structure. The predication regarding prospective market development, decreasing system costs and higher availability shows a convenient situation for potential users and interested customers. The causes are primarily increased competition and larger quantities in the future.

  7. Stability of heterodyne terahertz receivers

    NARCIS (Netherlands)

    Kooi, J.W.; Baselmans, J.J.A.; Baryshev, A.; Schieder, R.; Hajenius, M.; Gao, J.R.; Klapwijk, T.M.; Voronov, B.; Gol'tsman, G.

    2006-01-01

    In this paper we discuss the stability of heterodyne terahertz receivers based on small volume NbN phonon cooled hot electron bolometers (HEBs). The stability of these receivers can be broken down in two parts: the intrinsic stability of the HEB mixer and the stability of the local oscillator (LO)

  8. Terahertz radar cross section measurements

    DEFF Research Database (Denmark)

    Iwaszczuk, Krzysztof; Heiselberg, Henning; Jepsen, Peter Uhd

    2010-01-01

    We perform angle- and frequency-resolved radar cross section (RCS) measurements on objects at terahertz frequencies. Our RCS measurements are performed on a scale model aircraft of size 5-10 cm in polar and azimuthal configurations, and correspond closely to RCS measurements with conventional radar...

  9. Widely tunable quantum cascade laser-based terahertz source.

    Science.gov (United States)

    Danylov, Andriy A; Light, Alexander R; Waldman, Jerry; Erickson, Neal; Qian, Xifeng

    2014-07-10

    A compact, tunable, ultranarrowband terahertz source, Δν∼1  MHz, is demonstrated by upconversion of a 2.324 THz, free-running quantum cascade laser with a THz Schottky-diode-balanced mixer using a swept, synthesized microwave source to drive the nonlinearity. Continuously tunable radiation of 1 μW power is demonstrated in two frequency regions: ν(Laser) ± 0 to 50 GHz and ν(Laser) ± 70 to 115 GHz. The sideband spectra were characterized with a Fourier-transform spectrometer, and the radiation was tuned through CO, HDO, and D2O rotational transitions.

  10. Enhanced terahertz magnetic dipole response by subwavelength fiber

    DEFF Research Database (Denmark)

    Atakaramians, Shaghik; Shadrivov, Ilya V.; Miroshnichenko, Andrey E.

    2018-01-01

    Dielectric sub-wavelength particles have opened up a new platform for realization of magnetic light. Recently, we have demonstrated that a dipole emitter by a sub-wavelength fiber leads to an enhanced magnetic response. Here, we experimentally demonstrate an enhanced magnetic dipole source......-fiber system excited by a magnetic source. This coupled magnetic dipole and optical fiber system can be considered a unit cell of metasurfaces for manipulation of terahertz radiation and is a proof-of-concept of a possibility to achieve enhanced radiation of a dipole source in proximity of a sub...

  11. Effect of surface treatments on radiation buildup in steam generators

    International Nuclear Information System (INIS)

    Asay, R.H.; Pick, M.E.; van Melsen, C.

    1991-11-01

    Test coupons of typical PWR materials of construction were prepared using a number of pretreatments to minimize radiation buildup. The coupons were then exposed to primary coolant at the Doel-2 PWR in Belgium. The exposure periods for the coupons ranged from one to three fuel cycles. After removal from the primary system, doserate and gamma spectroscopy measurements were made to determine the radioactivity levels on the coupons. Varying levels of success were achieved for the preconditioning techniques tested. Electropolishing alone provided some degree of resistance to radiation buildup on the treated surface and electropolishing plus passivation was shown to be even better. Radiation buildup resistance of the palladium-coated coupons was poor; radiation levels on these coupons were even higher than on the untreated reference coupons. The poor performance of the palladium-coated coupons was possibly due to the method used to apply the coating. In contrast to palladium coating, very encouraging results were achieved with chromium plating plus passivation. Preliminary results show that this technique can inhibit activity deposition by as much as a factor of ten. 4 refs., 64 figs., 26 tabs

  12. Terahertz antenna technology for space applications

    CERN Document Server

    Choudhury, Balamati; Jha, Rakesh Mohan

    2016-01-01

    This book explores the terahertz antenna technology towards implementation of compact, consistent and cheap terahertz sources, as well as the high sensitivity terahertz detectors. The terahertz EM band provides a transition between the electronic and the photonic regions thus adopting important characteristics from these regimes. These characteristics, along with the progress in semiconductor technology, have enabled researchers to exploit hitherto unexplored domains including satellite communication, bio-medical imaging, and security systems. The advances in new materials and nanostructures such as graphene will be helpful in miniaturization of antenna technology while simultaneously maintaining the desired output levels. Terahertz antenna characterization of bandwidth, impedance, polarization, etc. has not yet been methodically structured and it continues to be a major research challenge. This book addresses these issues besides including the advances of terahertz technology in space applications worldwide,...

  13. Training the next generation of radiation protection professionals in canada

    International Nuclear Information System (INIS)

    Waller, Edward; Waker, Anthony

    2008-01-01

    Full text: The University of Ontario Institute of Technology (UOIT) is Canada's newest university, specializing in market-driven programs. The first class of students started in Fall of 2003. The University is located in close proximity to Pickering, Darlington and Bruce Nuclear Power Plants, the fuel manufacturer Cameco, and a number of regional health centres. As such, the initial program focus was to serve the needs of the power utilities and the health sectors. The first programs envisioned and adopted at UOIT were programs in Nuclear Engineering and Radiation Science/Health Physics. These programs are unique in Canada. The four year Bachelor of Science honours degree programs in Radiation Science curriculum includes medical, industrial, agricultural and material science applications, and emphasizes a strong mathematics and science foundation to the discipline. The four year Canadian Engineering Accreditation Board accredited Bachelor of Nuclear Engineering honours program has a strong emphasis on radiation protection, environmental effects of radioactivity, and risk assessment. Both programs have internship options, and both have 'and Management' options, requiring an additional year of study. One key aspect to the pedagogy at UOIT is web-centric learning. Each student is issued a fully equipped internet-ready laptop for use in classes, tutorials and laboratories. The professors endeavor to integrate technology wherever possible to assist the student learning process, for example with on-line testing and course-work submission. Course materials are provided via learning management system software, and instruction is provided for industry standard computational and simulation tools. For courses in radiation protection and environmental effects, there is great emphasis on 'hands on' experience and realistic field exercises. The first graduating class was in spring 2007, and the indication from industry is that the specially trained radiation protection and

  14. Thermoelectric generator hidden in a shirt with a fabric radiator

    NARCIS (Netherlands)

    Leonov, V.; Vullers, R.J.M.; Hoof, C.V.

    2012-01-01

    Integration of thermopiles in garments has been performed in this work in different ways. It is shown that textile has a minor effect on power generation, which enables completely hidden and unobtrusive energy harvester. A one-milliwatt thermoelectric generator is then integrated between two layers

  15. Terahertz inline wall thickness monitoring system for plastic pipe extrusion

    Energy Technology Data Exchange (ETDEWEB)

    Hauck, J., E-mail: j.hauck@skz.de, E-mail: d.stich@skz.de, E-mail: p.heidemeyer@skz.de, E-mail: m.bastian@skz.de, E-mail: t.hochrein@skz.de; Stich, D., E-mail: j.hauck@skz.de, E-mail: d.stich@skz.de, E-mail: p.heidemeyer@skz.de, E-mail: m.bastian@skz.de, E-mail: t.hochrein@skz.de; Heidemeyer, P., E-mail: j.hauck@skz.de, E-mail: d.stich@skz.de, E-mail: p.heidemeyer@skz.de, E-mail: m.bastian@skz.de, E-mail: t.hochrein@skz.de; Bastian, M., E-mail: j.hauck@skz.de, E-mail: d.stich@skz.de, E-mail: p.heidemeyer@skz.de, E-mail: m.bastian@skz.de, E-mail: t.hochrein@skz.de; Hochrein, T., E-mail: j.hauck@skz.de, E-mail: d.stich@skz.de, E-mail: p.heidemeyer@skz.de, E-mail: m.bastian@skz.de, E-mail: t.hochrein@skz.de [SKZ - German Plastics Center, Wuerzburg (Germany)

    2014-05-15

    Conventional and commercially available inline wall thickness monitoring systems for pipe extrusion are usually based on ultrasonic or x-ray technology. Disadvantages of ultrasonic systems are the usual need of water as a coupling media and the high damping in thick walled or foamed pipes. For x-ray systems special safety requirements have to be taken into account because of the ionizing radiation. The terahertz (THz) technology offers a novel approach to solve these problems. THz waves have many properties which are suitable for the non-destructive testing of plastics. The absorption of electrical isolators is typically very low and the radiation is non-ionizing in comparison to x-rays. Through the electromagnetic origin of the THz waves they can be used for contact free measurements. Foams show a much lower absorption in contrast to acoustic waves. The developed system uses THz pulses which are generated by stimulating photoconductive switches with femtosecond laser pulses. The time of flight of THz pulses can be determined with a resolution in the magnitude of several ten femtoseconds. Hence the thickness of an object like plastic pipes can be determined with a high accuracy by measuring the time delay between two reflections on materials interfaces e.g. at the pipe's inner and outer surface, similar to the ultrasonic technique. Knowing the refractive index of the sample the absolute layer thickness from the transit time difference can be calculated easily. This method in principle also allows the measurement of multilayer systems and the characterization of foamed pipes.

  16. Environmental impact assessment methods of the radiation generated by the runing medical linear accelerator

    International Nuclear Information System (INIS)

    Yin haihua; Yao Zhigang

    2014-01-01

    This article describes the environmental impact assessment methods of the radiation generated by the runing. medical linear accelerator. The material and thickness of shielding wall and protective doors of the linear accelerator were already knew, therefore we can evaluate the radiation by the runing. medical linear accelerator whether or not in the normal range of national standard by calculating the annual effective radiation dose of the surrounding personnel suffered. (authors)

  17. Environmental radiation monitoring data for Point Lepreau Generating Station, 1988. Annual publication

    Energy Technology Data Exchange (ETDEWEB)

    Sutherland, J K

    1989-01-01

    Annual report presenting a compilation of the 1988 environmental radiation monitoring program data from samples collected around the Point Lepreau Nuclear Generating Station (PLNGS) and at reference stations remote from PLNGS. About 1,700 analyses were made on 1,200 samples to monitor environmental radiation, including air filters, airborne water vapour, sea water, well water, milk, beach sediments, clams, fish, lobster, dulse, crabs, scallops and lichen. Background radiation is measured by thermoluminescence dosimetry.

  18. Environmental radiation monitoring data for Point Lepreau Generating Station, 1987. Annual publication

    Energy Technology Data Exchange (ETDEWEB)

    Sutherland, J K

    1988-01-01

    Annual report presenting a compilation of the 1987 environmental radiation monitoring program data from samples collected around the Point Lepreau Nuclear Generating Station (PLNGS) and at reference stations remote from PLNGS. About 1,800 analyses were made on 1,300 samples to monitor environmental radiation, including air filters, airborne water vapour, sea water, well water, milk, beach sediments, clams, fish, lobster, dulse, crabs, scallops and periwinkles. Background radiation is measured by thermoluminescence dosimetry.

  19. Nonlinear-optical generation of short-wavelength radiation controlled by laser-induced interference structures

    International Nuclear Information System (INIS)

    Popov, A K; Kimberg, V V

    1998-01-01

    A study is reported of the combined influence of laser-induced resonances in the energy continuum, of splitting of discrete resonances in the field of several strong radiations, and of absorption of the initial and generated radiations on totally resonant parametric conversion to the short-wavelength range. It is shown that the radiation power can be increased considerably by interference processes involving quantum transitions. (nonlinear optical phenomena and devices)

  20. Transverse velocity modulator and generator schemes based on non-collinear radiation and electron beams

    CERN Document Server

    Varfolomeev, A A

    2000-01-01

    New non-collinear schemes are suggested for transverse velocity modulation of electron beams and for the generation of coherent spontaneous radiation by these transversely modulated beams. It is shown that due to the non-collinearity some orders of magnitude enhancement can be achieved for the coherent spontaneous radiation (CSR) power at both the fundamental and harmonic frequencies.

  1. Generation of Coherent Synchrotron Radiation from JAERI-ERL

    CERN Document Server

    Hajima, R; Kikuzawa, N; Minehara, E J; Nagai, R; Nishitani, T; Sawamura, M

    2005-01-01

    An electron beam with high-average current and short bunch length can be accelerated by energy-recovery linac. Coherent synchrotron radiation (CSR) from such an electron beam will be a useful light source around millimeter wavelength. We report results from a preliminary measurement of CSR emitted from a bending magnet of JAERI-ERL. Possible enhancement of CSR power by FEL micro-bunching is also discussed.

  2. Toward practical terahertz time-domain spectroscopy

    Science.gov (United States)

    Brigada, David J.

    Terahertz time-domain spectroscopy is a promising technology for the identification of explosive and pharmaceutical substances in adverse conditions. It interacts strongly with intermolecular vibrational and rotational modes. Terahertz also passes through many common dielectric covering materials, allowing for the identification of substances in envelopes, wrapped in opaque plastic, or otherwise hidden. However, there are several challenges preventing the adoption of terahertz spectroscopy outside the laboratory. This dissertation examines the problems preventing widespread adoption of terahertz technology and attempts to resolve them. In order to use terahertz spectroscopy to identify substances, a spectrum measured of the target sample must be compared to the spectra of various known standard samples. This dissertation examines various methods that can be employed throughout the entire process of acquiring and transforming terahertz waveforms to improve the accuracy of these comparisons. The concepts developed in this dissertation directly apply to terahertz spectroscopy, but also carry implications for other spectroscopy methods, from Raman to mass spectrometry. For example, these techniques could help to lower the rate of false positives at airport security checkpoints. This dissertation also examines the implementation of several of these methods as a way to realize a fully self-contained, handheld, battery-operated terahertz spectrometer. This device also employs techniques to allow minimally-trained operators use terahertz to detect different substances of interest. It functions as a proof-of-concept of the true benefits of the improvements that have been developed in this dissertation.

  3. Properties of solar generators with reflectors and radiators

    Science.gov (United States)

    Ebeling, W. D.; Rex, D.; Bierfischer, U.

    1980-06-01

    Radiation cooled concentrator systems using silicon and GaAs cells were studied. The principle of radiation cooling by the reflector surfaces is discussed for cylindrical parabolic reflectors (SARA), truncated hexagonal pyramids, and a small trough configuration. Beam paths, collection properties for imperfect orientation, and thermal optimization parameters were analyzed. The three concentrating systems with radiation cooling offer advantages over the plane panel and over the large trough. With silicon solar cells they exhibit considerably lower solar cell consumption per Kw and also lower mass per kW. With GaAs cells the SARA system reduces the number of solar cells needed per kW to less than 10%. Also in all other cases SARA offers the best values for alpha and F sub sol, as long as narrow angular tolerances of the panel orientation can be met. Analysis of the energy collecting properties for imperfect orientation shows the superiority of the hexagonal concentrator. This device can produce power for even large angles between the sun and the panel normal.

  4. On superfluorescent generation of coherent radiation in a paramagnet

    International Nuclear Information System (INIS)

    Turaev, M.T.; Shumovsky, A.S.

    1988-08-01

    An exact definition is given of a superradiation intensity for a free system and for a system in cavity. The superradiant generation of the Zeeman transitions in proton paramagnet is described. (author). 7 refs, 2 figs

  5. Efficient femtosecond mid-infrared pulse generation by dispersivewave radiation in bulk lithium niobate crystal

    DEFF Research Database (Denmark)

    Zhou, Binbin; Guo, Hairun; Bache, Morten

    2014-01-01

    We experimentally demonstrate efficient mid-infrared pulse generation by dispersive wave radiation in bulk lithium niobate crystal. Femtosecond mid-IR pulses centering from 2.8–2.92 µm are generated using the single pump wavelengths from 1.25–1.45 µm.......We experimentally demonstrate efficient mid-infrared pulse generation by dispersive wave radiation in bulk lithium niobate crystal. Femtosecond mid-IR pulses centering from 2.8–2.92 µm are generated using the single pump wavelengths from 1.25–1.45 µm....

  6. Progress of Terahertz Devices Based on Graphene

    Institute of Scientific and Technical Information of China (English)

    Mai-Xia Fu; Yan Zhang

    2013-01-01

    Graphene is a one-atom-thick planar sheet of sp2-hybridized orbital bonded honeycomb carbon crystal. Its gapless and linear energy spectra of electrons and holes lead to the unique carrier transport and optical properties, such as giant carrier mobility and broadband flat optical response. As a novel material, graphene has been regarded to be extremely suitable and competent for the development of terahertz (THz) optical devices. In this paper, the fundamental electronic and optic properties of graphene are described. Based on the energy band structure and light transmittance properties of graphene, many novel graphene based THz devices have been proposed, including modulator, generator, detector, and imaging device. This progress has been reviewed. Future research directions of the graphene devices for THz applications are also proposed.

  7. Terahertz Josephson spectral analysis and its applications

    Science.gov (United States)

    Snezhko, A. V.; Gundareva, I. I.; Lyatti, M. V.; Volkov, O. Y.; Pavlovskiy, V. V.; Poppe, U.; Divin, Y. Y.

    2017-04-01

    Principles of Hilbert-transform spectral analysis (HTSA) are presented and advantages of the technique in the terahertz (THz) frequency range are discussed. THz HTSA requires Josephson junctions with high values of characteristic voltages I c R n and dynamics described by a simple resistively shunted junction (RSJ) model. To meet these requirements, [001]- and [100]-tilt YBa2Cu3O7-x bicrystal junctions with deviations from the RSJ model less than 1% have been developed. Demonstrators of Hilbert-transform spectrum analyzers with various cryogenic environments, including integration into Stirling coolers, are described. Spectrum analyzers have been characterized in the spectral range from 50 GHz to 3 THz. Inside a power dynamic range of five orders, an instrumental function of the analyzers has been found to have a Lorentz form around a single frequency of 1.48 THz with a spectral resolution as low as 0.9 GHz. Spectra of THz radiation from optically pumped gas lasers and semiconductor frequency multipliers have been studied with these spectrum analyzers and the regimes of these radiation sources were optimized for a single-frequency operation. Future applications of HTSA will be related with quick and precise spectral characterization of new radiation sources and identification of substances in the THz frequency range.

  8. Feasibility study of generating ultra-high harmonic radiation with a single stage echo-enabled harmonic generation scheme

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Kaishang, E-mail: zhoukaishang@sinap.ac.cn; Feng, Chao, E-mail: fengchao@sinap.ac.cn; Wang, Dong, E-mail: wangdong@sinap.ac.cn

    2016-10-21

    The echo enabled harmonic generation (EEHG) scheme holds the ability for the generation of fully coherent soft x-ray free-electron laser (FEL) pulses directly from external UV seeding sources. In this paper, we study the feasibility of using a single stage EEHG to generate coherent radiation in the “water window” and beyond. Using the high-order operating modes of the EEHG scheme, intensive numerical simulations have been performed considering various three-dimensional effects. The simulation results demonstrated that coherent soft x-ray radiation at 150th harmonic (1.77 nm) of the seed can be produced by a single stage EEHG. The decreasing of the final bunching factor at the desired harmonic caused by intra beam scattering (IBS) effect has also been analyzed.

  9. Development of inventory database for radioisotopes and radiation generators

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Du Hui; Oh, Jin Seon; Park, Chan Geol [Green and Global RADCON Co., LTD, Taejon (Korea, Republic of)

    2000-03-15

    This project is part of the other project, building of unified information network for radiation safety regulation that national computerization agency backs up. Main objectives of this project are inventory data collection, searching for the point at issue, analysis into the issue and collection of partially initial data. The scope of this study consists of : analysis into the previous collected data, making up the investigation table, sending the table to users and gathering data, drawing up the data management plan, making up the system of national inventory control system and procedure.

  10. New generation of compact electron accelerators for radiation technologies

    International Nuclear Information System (INIS)

    Auslender, V.L.; Balakin, V.E.; Kraynov, G.S.

    1995-01-01

    Compact electron accelerators with energy range 0.25-1.0 MeV and beam power up to 32 kw are described. The feeding high voltage is formed by converter (working frequency 20 khz), coreless step-up transformer and a set of rectifying sections. The rectifying multiplier circuit used in rectifying sections permits to reach voltage gradient along accelerator's axis up to 14 kV/cm. The accelerators with vertical and horizontal position are described. The accelerators can be produced together with local radiation shielding and various underbeam transportation systems for irradiation of different products. Such version can be installed in any room facing general requirements for electric equipment

  11. All-dielectric rod antenna array for terahertz communications

    Science.gov (United States)

    Withayachumnankul, Withawat; Yamada, Ryoumei; Fujita, Masayuki; Nagatsuma, Tadao

    2018-05-01

    The terahertz band holds a potential for point-to-point short-range wireless communications at sub-terabit speed. To realize this potential, supporting antennas must have a wide bandwidth to sustain high data rate and must have high gain and low dissipation to compensate for the free space path loss that scales quadratically with frequency. Here we propose an all-dielectric rod antenna array with high radiation efficiency, high gain, and wide bandwidth. The proposed array is integral to a low-loss photonic crystal waveguide platform, and intrinsic silicon is the only constituent material for both the antenna and the feed to maintain the simplicity, compactness, and efficiency. Effective medium theory plays a key role in the antenna performance and integrability. An experimental validation with continuous-wave terahertz electronic systems confirms the minimum gain of 20 dBi across 315-390 GHz. A demonstration shows that a pair of such identical rod array antennas can handle bit-error-free transmission at the speed up to 10 Gbit/s. Further development of this antenna will build critical components for future terahertz communication systems.

  12. Terahertz (THz) Optical Parameters of Three-Dimensional (3-D) Printing Materials

    Science.gov (United States)

    2017-03-01

    Terahertz (THz), Submillimeter Wave, Imaging 15. NUMBER OF PAGES 16 16. PRICE CODE 17. SECURITY CLASSIFICATION OF REPORT UNCLASSIFIED 18...and imaging has become a topic of research as an optical technique to study these materials because THz radiation can penetrate many visibly opaque...2) Three materials, each tinted with two different colors, were measured. The materials were High Impact polystyrene (HIPS

  13. Assessing skin hydration status in haemodialysis patients using terahertz spectroscopy: a pilot / feasibility study

    Czech Academy of Sciences Publication Activity Database

    Kadlec, Filip; Berta, Milan; Kužel, Petr; Lopot, F.; Polakovič, V.

    2008-01-01

    Roč. 53, č. 24 (2008), 7063-7071 ISSN 0031-9155 R&D Projects: GA MŠk LC512 Institutional research plan: CEZ:AV0Z10100520 Keywords : terahertz radiation * haemodialysis * skin turgor * epidermis Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.784, year: 2008

  14. Two-wave generator of subnanosecond radiation pulses on an yttrium-aluminium garnet

    International Nuclear Information System (INIS)

    Babikov, Yu.I.; Ir, K.S.; Mironov, V.E.

    1988-01-01

    Great attention is paid to the electron accelerator based on the mechanism of electron accelerator in the field of plasma wave, excited by laser radiation. The laser system master generator based on serial LTIPC-8 laser is described. The system is intended for investigating the plasma excitation processes initiated by two-frequency laser radiation beats. Pulse duration is ≤1 ns at 3-4 pulse train. Radiation on 1.0615 and 1.0641 μm wave length is generated. 5 refs.; 3 figs

  15. Exposure of vitamins to UVB and UVA radiation generates singlet oxygen.

    Science.gov (United States)

    Knak, Alena; Regensburger, Johannes; Maisch, Tim; Bäumler, Wolfgang

    2014-05-01

    Deleterious effects of UV radiation in tissue are usually attributed to different mechanisms. Absorption of UVB radiation in cell constituents like DNA causes photochemical reactions. Absorption of UVA radiation in endogenous photosensitizers like vitamins generates singlet oxygen via photosensitized reactions. We investigated two further mechanisms that might be involved in UV mediated cell tissue damage. Firstly, UVB radiation and vitamins also generate singlet oxygen. Secondly, UVB radiation may change the chemical structure of vitamins that may change the role of such endogenous photosensitizers in UVA mediated mechanisms. Vitamins were irradiated in solution using monochromatic UVB (308 nm) or UVA (330, 355, or 370 nm) radiation. Singlet oxygen was directly detected and quantified by its luminescence at 1270 nm. All investigated molecules generated singlet oxygen with a quantum yield ranging from 0.007 (vitamin D3) to 0.64 (nicotinamide) independent of the excitation wavelength. Moreover, pre-irradiation of vitamins with UVB changed their absorption in the UVB and UVA spectral range. Subsequently, molecules such as vitamin E and vitamin K1, which normally exhibit no singlet oxygen generation in the UVA, now produce singlet oxygen when exposed to UVA at 355 nm. This interplay of different UV sources is inevitable when applying serial or parallel irradiation with UVA and UVB in experiments in vitro. These results should be of particular importance for parallel irradiation with UVA and UVB in vivo, e.g. when exposing the skin to solar radiation.

  16. Terahertz performance of quasioptical front-ends with a hotelectron bolometer

    International Nuclear Information System (INIS)

    Semenov, A; Richter, H; Guenther, B; Huebers, H-W; Karamarkovic, J

    2006-01-01

    We present terahertz performance of quasioptical front-ends consisting of a hotelectron bolometer imbedded in a planar feed antenna and integrated with an immersion lens. The impedance and radiation pattern of the log-spiral and double-slot planar feeds are evaluated using the method of moments; the collimating action of the lens is modelled using the physical optics. The total efficiency of the front-ends is computed taking into account frequency dependent impedance of the bolometer. Measured performance of the front-ends qualifies the simulation technique as a reliable tool for the design of terahertz receivers

  17. First indication of the coherent unipolar diffraction radiation generated by relativistic electrons

    Science.gov (United States)

    Naumenko, G.; Shevelev, M.

    2018-05-01

    As is generally known, the integral of the electric field strength over all time for usual (bipolar) radiation is zero. The first demonstration of the possibility of unipolar radiation generation has been considered theoretically by Bessonov in 1981 [E.G. Bessonov, Zh. Eksp. Teor. Fiz. 80 (1981) 852]. According to this work, the unipolar radiation (or strange electromagnetic waves) is radiation for which the integral of the electric field strength over the entire duration of a pulse differs significantly from zero. Later, several theoretical papers devoted to this phenomenon have appeared in the literature, where authors investigated mainly synchrotron radiation. However, despite the critical interest, the experimental investigations ignored this effect. In this paper we present results of the first experimental investigation of the unipolar radiation generated by a relativistic electron beam. To detect the unipolar radiation the detector that is sensitive to the selected direction of the electric field strength has been elaborated and tested. We used a designed detector to observe the coherent backward diffraction radiation appearing when a bunched electron beam travels in the vicinity of a flat conductive target. The asymmetry of the electric field strength of the coherent backward diffraction radiation has been demonstrated.

  18. Trans-generational effects induced by alpha and gamma ionizing radiations at Daphnia magna

    International Nuclear Information System (INIS)

    Parisot, Florian

    2015-01-01

    Anthropogenic activities related to the nuclear industry contribute to continuous discharges of radionuclides into terrestrial and aquatic ecosystems. Over the past decades, the ecological risk of ionizing radiation has become a growing public, regulatory and scientific concern for ecosystems protection. Until recently, only few studies focus on exposure situations at low doses of irradiation, although these situations are representative of realistic environmental conditions. Understanding how ionizing radiation affects species over several generations and at various levels of biological organization is a major research goal in radioecology. The aim of this PhD was to bring new knowledge on the effects of ionizing radiation during a multi-generational expose of the aquatic invertebrate, Daphnia magna. A two-step strategy was implemented. First, an external gamma radiation at environmentally relevant dose rates was performed on D. magna over three successive generations (F0, F1 and F2). The objective of this experiment was to examine whether low dose rates of radiation induced increasing effects on survival, growth and reproduction of daphnids over generations and to test a possible accumulation and transmission of DNA alterations from adults to offspring. Results showed an accumulation and a transmission of DNA alterations over generations, together with an increase in effect severity on growth and reproduction from generation F0 to generation F2. Transiently more efficient DNA repair leading to some recovery at the organism level was suggested in generation F1. Second, data from the external gamma irradiation and those from an earlier study of internal alpha contamination were analyzed with DEBtox models (Dynamic Energy Budget applied to toxicology), to identify and compare the causes of the trans-generational increase in effect severity between the two types of radiation. In each case, two distinct metabolic modes of action were necessary to explain effects on

  19. Generation of radiation by benzimidazoles in various aggregate states

    Energy Technology Data Exchange (ETDEWEB)

    Gruzinsky, V V; Degtyarenko, K M; Shalaev, V K; Kopylova, T N; Verkhovsky, V S; Tarasenko, V F; Melochenko, S V

    1983-04-01

    Lasing has been obtained on the solutions of new derivatives of benzimidazole (Bi): 2-phenyl-Bi (the band maximum lambda/sub r.max/ = 341/347 nm), 2-n-tolyl-Bi (344 nm) and 2-(4'-biphenilyl) Bi (366/374 nm). Compounds of this class provide a perspective basis for laser radiation covering of a wide spectrum region. Lasing has been obtained on the vapors of 2-(4'-biphenilyl)Bi (361.2 nm) and 2-(n-tolyl) Bi (336.3 nm) with pentane stabilizer of excited states. High volatility, photostability and laser-action over wide concentration ranges determine the efficiency of using the new class of compounds - chain arylbenzimitazoles - in lasers based on complex molecule vapors.

  20. New-generation low-power radiation survey instruments

    International Nuclear Information System (INIS)

    Waechter, D.A.; Bjarke, G.O.; Wolf, M.A.; Trujillo, F.; Umbarger, C.J.

    1983-01-01

    A number of new, ultra-low-powered radiation instruments have recently been developed at Los Alamos. Among these are two instruments which use a novel power source to eliminate costly batteries. The newly developed gamma detecting radiac, nicknamed the Firefly, and the alpha particle detecting instrument, called the Simple Cordless Alpha Monitor, both use recent advances in miniaturization and power-saving electronics to yield devices which are small, rugged, and very power-frugal. The two instruments consume so little power that the need for batteries to run them is eliminated. They are, instead, powered by a charged capacitor which will operate the instruments for an hour or more. Both line power and mechanical sources are used to charge the storage capacitors which power the instruments

  1. Calculation of radiation heat generation on a graphite reflector side of IAN-R1 Reactor

    International Nuclear Information System (INIS)

    Duque O, J.; Velez A, L.H.

    1987-01-01

    Calculation methods for radiation heat generation in nuclear reactor, based on the point kernel approach are revisited and applied to the graphite reflector of IAN-R1 reactor. A Fortran computer program was written for the determination of total heat generation in the reflector, taking 1155 point in it

  2. Hemodynamic changes induced by preventive exposure to terahertz radiation at a frequency range corresponding to molecular emission and absorption spectrum of nitric oxide in animals under conditions of acute stress.

    Science.gov (United States)

    Kirichuck, V F; Velikanova, T S; Ivanov, A N

    2011-06-01

    We studied the influence of preventive irradiation with terahertz electromagnetic waves at frequencies corresponding to nitric oxide emission and absorption molecular spectrum (150,176-150,664 GHz) on hemodynamic parameters in arteries of albino rats upon acute immobilization stress. We showed that exposure to the specified frequencies can produce adaptogenic effect manifesting in the absence of post-stress changes in the linear, systolic, and diastolic blood flow velocities and pressure gradient in various blood vessels of experimental animals.

  3. 36th Annual International Conference on Infrared Millimeter and Terahertz Waves

    Energy Technology Data Exchange (ETDEWEB)

    Mittleman, Daniel M. [Rice University

    2011-12-31

    The Major Topic List of the 2011 conference featured a category entitled “IR, millimeter-wave, and THz spectroscopy,” another entitled “Gyro-Oscillators and Amplifiers, Plasma Diagnostics,” and a third called “Free Electron Lasers and Synchrotron Radiation.” Topical areas of interest to meeting participants include millimeter-wave electronics, high-power sources, high-frequency communications systems, and terahertz sensing and imaging, all of which are prominent in the research portfolios of the DOE. The development and study of new materials, components, and systems for use in the IR, THz, and MMW regions of the spectrum are of significant interest as well. a series of technical sessions were organized on the following topics: terahertz metamaterials and plasmonics; imaging techniques and applications; graphene spectroscopy; waveguide concepts; gyrotron science and technology; ultrafast terahertz measurements; and quantum cascade lasers.

  4. Generation of coherent electromagnetic radiation by superconducting films at nitrogen temperatures

    CERN Document Server

    Lykov, A N

    2001-01-01

    One detected generation of coherent electromagnetic radiation by GdBa sub 2 Cu sub 3 O sub 7 sub - sub x superconducting films within 1-10 MHz range at temperature of liquid nitrogen boiling. This type generation is caused by synchronization realized due to the feedback of abrupt changes of the Abrikosov's vortices produced by the external low-frequency magnetic field. Possibility to reach more intensive radiation due to increase of the area of superconducting film, as well as, via increase of amplitude and of frequency of electromagnetic field exciting a vortex system in films is the most important advantage of the given technique of generation

  5. Nonlinear radiative heat flux and heat source/sink on entropy generation minimization rate

    Science.gov (United States)

    Hayat, T.; Khan, M. Waleed Ahmed; Khan, M. Ijaz; Alsaedi, A.

    2018-06-01

    Entropy generation minimization in nonlinear radiative mixed convective flow towards a variable thicked surface is addressed. Entropy generation for momentum and temperature is carried out. The source for this flow analysis is stretching velocity of sheet. Transformations are used to reduce system of partial differential equations into ordinary ones. Total entropy generation rate is determined. Series solutions for the zeroth and mth order deformation systems are computed. Domain of convergence for obtained solutions is identified. Velocity, temperature and concentration fields are plotted and interpreted. Entropy equation is studied through nonlinear mixed convection and radiative heat flux. Velocity and temperature gradients are discussed through graphs. Meaningful results are concluded in the final remarks.

  6. Ultrabroadband terahertz conductivity of Si nanocrystal films

    DEFF Research Database (Denmark)

    Cooke, D. G.; Meldrum, A.; Jepsen, P. Uhd

    2012-01-01

    The terahertz conductivity of silicon nanoparticles embedded in glass with varying density is studied with ultra-broadband terahertz spectroscopy on picosecond time scales following fs optical excitation. The transition from relatively isolated charge carriers to densities which allow inter...... the applicability of this simple model to the conductivity of nanoparticle ensembles over the entire THz spectral window....

  7. The random signal generator of imitated nuclear radiation pulse

    International Nuclear Information System (INIS)

    Li Dongcang; Yang Lei; Yuan Shulin; Yang Yinghui; Zang Fujia

    2007-01-01

    Based in pseudo-random uniformity number, it produces random numbers of Gaussian distribution and exponential distribution by arithmetic. The hardware is the single-chip microcomputer of 89C51. Program language makes use of Keil C. The output pulse amplitude is Gaussian distribution, exponential distribution or uniformity distribution. Likewise, it has two mode or upwards two. The time alternation of output pulse is both periodic and exponential distribution. The generator has achieved output control of multi-mode distribution, imitated random characteristic of nuclear pulse in amplitude and in time. (authors)

  8. A Fabry-Pérot interferometer with wire-grid polarizers as beamsplitters at terahertz frequencies

    Science.gov (United States)

    Harrison, H.; Lancaster, A. J.; Konoplev, I. V.; Doucas, G.; Aryshev, A.; Shevelev, M.; Terunuma, N.; Urakawa, J.; Huggard, P. G.

    2018-03-01

    The design of a compact Fabry-Pérot interferometer (FPi) and results of the experimental studies carried out using the device are presented. Our FPi uses freestanding wire-grid polarizers (WGPs) as beamsplitters and is suitable for use at terahertz (THz) frequencies. The FPi was studied at the LUCX facility, KEK, Japan, and an 8 MeV linear electron accelerator was used to generate coherent Smith-Purcell radiation. The FPi was designed to be easy to align and reposition for experiments at linear accelerator facilities. All of the components used were required to have a flat or well understood frequency response in the THz range. The performance of the FPi with WGPs was compared to that of a Michelson interferometer and the FPi is seen to perform well. The effectiveness of the beamsplitters used in the FPi is also investigated. Measurements made with the FPi using WGPs, the preferred beamsplitters, are compared to measurements made with the FPi using silicon wafers as alternative beamsplitters. The FPi performs well with both types of beamsplitter in the frequency range used (0.3-0.5 THz). The successful measurements taken with the FPi demonstrate a compact and adaptable interferometer that is capable of analyzing THz radiation over a broad frequency range. The scheme is particularly well suited for polarization studies of THz radiation produced in an accelerator environment.

  9. Radiation after-effects in daughter generations of barley grown under conditions of enhanced radioactive background

    International Nuclear Information System (INIS)

    Popova, O.N.; Shershunova, V.I.; Taskaev, A.I.

    1978-01-01

    Stimulation of growth and development was observed in the first daughter generation of barley plants grown under conditions simulating an enhanced radioactive background. The stimulatory effect was partially reproduced in the second generation, and signs of depression of initial growth of plants were found in the third generation. A great number of alterations and their regular occurrence allow to refer them to lingering modifications originating under the effect of a radiation factor on vegetating plants

  10. A comparison of different entransy flow definitions and entropy generation in thermal radiation optimization

    International Nuclear Information System (INIS)

    Zhou Bing; Cheng Xue-Tao; Liang Xin-Gang

    2013-01-01

    In thermal radiation, taking heat flow as an extensive quantity and defining the potential as temperature T or the blackbody emissive power U will lead to two different definitions of radiation entransy flow and the corresponding principles for thermal radiation optimization. The two definitions of radiation entransy flow and the corresponding optimization principles are compared in this paper. When the total heat flow is given, the optimization objectives of the extremum entransy dissipation principles (EEDPs) developed based on potentials T and U correspond to the minimum equivalent temperature difference and the minimum equivalent blackbody emissive power difference respectively. The physical meaning of the definition based on potential U is clearer than that based on potential T, but the latter one can be used for the coupled heat transfer optimization problem while the former one cannot. The extremum entropy generation principle (EEGP) for thermal radiation is also derived, which includes the minimum entropy generation principle for thermal radiation. When the radiation heat flow is prescribed, the EEGP reveals that the minimum entropy generation leads to the minimum equivalent thermodynamic potential difference, which is not the expected objective in heat transfer. Therefore, the minimum entropy generation is not always appropriate for thermal radiation optimization. Finally, three thermal radiation optimization examples are discussed, and the results show that the difference in optimization objective between the EEDPs and the EEGP leads to the difference between the optimization results. The EEDP based on potential T is more useful in practical application since its optimization objective is usually consistent with the expected one. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  11. Generation of Z mode radiation by diffuse auroral electron precipitation

    Science.gov (United States)

    Dusenbery, P. B.; Lyons, L. R.

    1985-01-01

    The generation of Z mode waves by diffuse auroral electron precipitation is investigated assuming that a loss cone exists in the upgoing portion of the distribution due to electron interactions with the atmosphere. The waves are generated at frequencies above, but very near, the local electron cyclotron frequency omega(e) and at wave normal angles larger than 90 deg. In agreement with Hewitt et al. (1983), the group velocity is directed downward in regions where the ratio of the upper hybrid frequency omega(pe) to Omega(e) is less than 0.5, so that Z mode waves excited above a satellite propagate toward it and away from the upper hybrid resonance. Z mode waves are excited in a frequency band between Omega(e) and about 1.02 Omega(e), and with maximum growth rates of about 0.001 Omega(e). The amplification length is about 100 km, which allows Z mode waves to grow to the intensities observed by high-altitude satellites.

  12. [Terahertz Spectroscopic Identification with Deep Belief Network].

    Science.gov (United States)

    Ma, Shuai; Shen, Tao; Wang, Rui-qi; Lai, Hua; Yu, Zheng-tao

    2015-12-01

    Feature extraction and classification are the key issues of terahertz spectroscopy identification. Because many materials have no apparent absorption peaks in the terahertz band, it is difficult to extract theirs terahertz spectroscopy feature and identify. To this end, a novel of identify terahertz spectroscopy approach with Deep Belief Network (DBN) was studied in this paper, which combines the advantages of DBN and K-Nearest Neighbors (KNN) classifier. Firstly, cubic spline interpolation and S-G filter were used to normalize the eight kinds of substances (ATP, Acetylcholine Bromide, Bifenthrin, Buprofezin, Carbazole, Bleomycin, Buckminster and Cylotriphosphazene) terahertz transmission spectra in the range of 0.9-6 THz. Secondly, the DBN model was built by two restricted Boltzmann machine (RBM) and then trained layer by layer using unsupervised approach. Instead of using handmade features, the DBN was employed to learn suitable features automatically with raw input data. Finally, a KNN classifier was applied to identify the terahertz spectrum. Experimental results show that using the feature learned by DBN can identify the terahertz spectrum of different substances with the recognition rate of over 90%, which demonstrates that the proposed method can automatically extract the effective features of terahertz spectrum. Furthermore, this KNN classifier was compared with others (BP neural network, SOM neural network and RBF neural network). Comparisons showed that the recognition rate of KNN classifier is better than the other three classifiers. Using the approach that automatic extract terahertz spectrum features by DBN can greatly reduce the workload of feature extraction. This proposed method shows a promising future in the application of identifying the mass terahertz spectroscopy.

  13. Terahertz spectroscopy applied to the measurement of strengths and self-broadening coefficients for high- J lines of OCS

    Science.gov (United States)

    Matton, S.; Rohart, F.; Bocquet, R.; Mouret, G.; Bigourd, D.; Cuisset, A.; Hindle, F.

    2006-10-01

    A spectrometer operating in the 100-2000 GHz range and allowing for absolute line strength measurements has been developed. The continuous wave terahertz radiation is generated by mixing two Ti:Sapphire laser beams in a vertically integrated low temperature grown GaAs (LTG-GaAs) photomixer. Pure rotational lines of 16O 12C 32S in the ground vibrational state have been considered for J values up to 90. Observed self-broadening parameters are in agreement with those deduced from infrared experiments. For the first time in the submillimeter range, absolute line strengths have been determined, allowing for a determination of the electric dipole moment in good agreement with the value previously obtained from Stark effect measurements.

  14. Radiation heat transfer within an open-cycle MHD generator channel

    Science.gov (United States)

    Delil, A. A. M.

    1983-05-01

    Radiation heat transfer in an MHD generator was modeled using the Sparrow and Cess model for radiation in an emitting, absorbing and scattering medium. The resulting general equations can be considerably reduced by introducing simplifying approximations for the channel and MHD gas properties. The simplifications lead to an engineering model, which is very useful for one-dimensional channel flow approximation. The model can estimate thermo-optical MHD gas properties, which can be substituted in the energy equation. The model considers the contribution of solid particles in the MHD gas to radiation heat transfer, considerable in coal-fired closed cycle MHD generators. The modeling is applicable also for other types of flow at elevated temperatures, where radiation heat transfer is an important quantity.

  15. High harmonic terahertz confocal gyrotron with nonuniform electron beam

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Wenjie; Guan, Xiaotong; Yan, Yang [THz Research Center, School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China)

    2016-01-15

    The harmonic confocal gyrotron with nonuniform electron beam is proposed in this paper in order to develop compact and high power terahertz radiation source. A 0.56 THz third harmonic confocal gyrotron with a dual arc section nonuniform electron beam has been designed and investigated. The studies show that confocal cavity has extremely low mode density, and has great advantage to operate at high harmonic. Nonuniform electron beam is an approach to improve output power and interaction efficiency of confocal gyrotron. A dual arc beam magnetron injection gun for designed confocal gyrotron has been developed and presented in this paper.

  16. Experimental Observation of RF Radiation Generated by an Explosively Driven Voltage Generator

    National Research Council Canada - National Science Library

    Rader, Mark S; Sullivan, Carol; Andreadis, Tim D

    2005-01-01

    .... located in Rolla, Missouri. A pulse-forming network and transmitting antenna were constructed and attached to the voltage-pulse generator, and a matched receiving antenna was located approximately 3 m from the transmitting antenna...

  17. Generation of linearly polarized resonant transition radiation X-ray beam

    International Nuclear Information System (INIS)

    Yajima, Kazuaki; Awata, Takaaki; Ikeda, Mitsuharu; Ikeda, Kenichi; Yogo, Akifumi; Itoh, Akio; Imanishi, Nobutsugu

    2000-01-01

    We have proposed a method to generate almost linearly polarized resonant transition radiation X rays by using a rectangular slit placed on an electron beam axis. Our calculation predicted that the linearity is 93.5% for the resonant transition radiation X-ray beam extracted through a slit of 0.5 mrad long and 0.2 mrad wide in case of 1-GeV electron beam irradiating a 7.5-μm thick Kapton foil stack. (author)

  18. Generation of linearly polarized resonant transition radiation X-ray beam

    Energy Technology Data Exchange (ETDEWEB)

    Yajima, Kazuaki; Awata, Takaaki; Ikeda, Mitsuharu; Ikeda, Kenichi; Yogo, Akifumi; Itoh, Akio; Imanishi, Nobutsugu [Kyoto Univ. (Japan). Dept. of Nuclear Engineering

    2000-03-01

    We have proposed a method to generate almost linearly polarized resonant transition radiation X rays by using a rectangular slit placed on an electron beam axis. Our calculation predicted that the linearity is 93.5% for the resonant transition radiation X-ray beam extracted through a slit of 0.5 mrad long and 0.2 mrad wide in case of 1-GeV electron beam irradiating a 7.5-{mu}m thick Kapton foil stack. (author)

  19. The enhancement of natural radiation dosage by coal-fired power generation in the United Kingdom

    International Nuclear Information System (INIS)

    Corbett, J.O.

    1980-02-01

    The total fuel cycle of electricity generation from coal is assessed as a source of enhanced exposure to natural radiation. The various routes by which such exposure can arise are discussed and the consequent individual and collective radiation doses in the United Kingdom are estimated on the basis of a critical review of published data augmented by the results of recent, hitherto unpublished work within the CEGB. Further work is in progress to clarify particular areas of uncertainty that have been identified. (author)

  20. Direct radiative effect due to brownness in organic carbon aerosols generated from biomass combustion

    International Nuclear Information System (INIS)

    Rathod, T.D.; Sahu, S.K.; Tiwari, M.; Pandit, G.G.

    2016-01-01

    We report the enhancement in the direct radiative effect due the presence of Brown carbon (BrC) as a part of organic carbon aerosols. The optical properties of organic carbon aerosols generated from pyrolytic combustion of mango tree wood (Magnifera Indica) and dung cake at different temperatures were considered. Mie codes were used to calculate absorption and scattering coefficients coupled with experimentally derived imaginary complex refractive index. The direct radiative effect (DRE) for sampled organic carbon aerosols was estimated using a wavelength dependent radiative transfer equation. The BrC DRE was estimated taking virtually non absorbing organic aerosols as reference. The BrC DRE from wood and dung cake was compared at different combustion temperatures and conditions. The BrC contributed positively to the direct top of the atmosphere radiative effect. Dung cake generated BrC aerosols were found to be strongly light absorbing as compared to BrC from wood combustion. It was noted that radiative effects of BrC from wood depended on its generation temperature and conditions. For BrC aerosols from dung cake such strong dependence was not observed. The average BrC aerosol DRE values were 1.53±0.76 W g"−"1 and 17.84±6.45 W g"−"1 for wood and dung cake respectively. The DRE contribution of BrC aerosols came mainly (67–90%) from visible light absorption though they exhibited strong absorption in shorter wavelengths of the UV–visible spectrum. - Highlights: • Biomass fuels (wood and dung cake) were studied for brown carbon direct radiative effects. • Model calculations predicted positive contribution of Brown carbon aerosols to organic carbon direct radiative effect. • Average direct radiative values for brown carbon from dung cake were higher compare to wood. • The visible light absorption played major role in brown carbon contribution (67–90 %) to total direct radiative effect.

  1. Fiber MOPA based tunable source for terahertz spectroscopy

    International Nuclear Information System (INIS)

    Malinowski, A; Lin, D; Alam, S U; Zhang, Z; Ibsen, M; Richardson, D J; Young, J; Wright, P; Ozanyan, K; Stringer, M; Miles, R E

    2012-01-01

    We have developed a terahertz spectrometer based on difference frequency generation of beams from an ytterbium fiber master oscillator power amplifier (MOPA) system. The spectrometer has a resolution of ∼ 2 GHz. It can be tuned rapidly over several hundred GHz, and a wider frequency range can be covered (0.7–2.5 THz demonstrated) by swapping in alternate seed lasers and adjusting the alignment of the beams into the difference frequency generation (DFG) crystal. The system was constructed entirely from commercially available fiber and fiber components. We present some demonstration data on water vapor absorption lines

  2. Generation of typical solar radiation data for different climates of China

    International Nuclear Information System (INIS)

    Zang, Haixiang; Xu, Qingshan; Bian, Haihong

    2012-01-01

    In this study, typical solar radiation data are generated from both measured data and synthetic generation for 35 stations in six different climatic zones of China. (1) By applying the measured weather data during at least 10 years from 1994 to 2009, typical meteorological years (TMYs) for 35 cities are generated using the Finkelstein–Schafer statistical method. The cumulative distribution function (CDF) of daily global solar radiation (DGSR) for each year is compared with the CDF of DGSR for the long-term years in six different climatic stations (Sanya, Shanghai, Zhengzhou, Harbin, Mohe and Lhasa). The daily global solar radiation as typical data obtained from the TMYs are presented in the Table. (2) Based on the recorded global radiation data from at least 10 years, a new daily global solar radiation model is developed with a sine and cosine wave (SCW) equation. The results of the proposed model and other empirical regression models are compared with measured data using different statistical indicators. It is found that solar radiation data, calculated by the new model, are superior to these from other empirical models at six typical climatic zones. In addition, the novel SCW model is tested and applied for 35 stations in China. -- Highlights: ► Both TMY method and synthetic generation are used to generate solar radiation data. ► The latest and accurate long term weather data in six different climates are applied. ► TMYs using new weighting factors of 8 weather indices for 35 regions are obtained. ► A new sine and cosine wave model is proposed and utilized for 35 major stations. ► Both TMY method and the proposed regression model perform well on monthly bases.

  3. Report of preliminary investigations on the next-generation large-scale synchrotron radiation facility projects

    International Nuclear Information System (INIS)

    1990-01-01

    The Special Committee for Future Project of the Japanese Society for Synchrotron Radiation Research investigated the construction-projects of the large-scaled synchrotron radiation facilities which are presently in progress in Japan. As a result, the following both projects are considered the very valuable research-project which will carry the development of Japan's next-generation synchrotron radiation science: 1. the 8 GeV synchrotron radiation facilities (SPring-8) projected to be constructed by Japan Atomic Energy Research Institute and the Institute of Physical and Chemical Research under the sponsorship of Science Technology Agency at Harima Science Park City, Hyogo Pref., Japan. 2. The project to utilize the Tristan Main Ring (MR) of the National Laboratory for High Energy Physics as the radiation source. Both projects are unique in research theme and technological approach, and complemental each other. Therefore it has been concluded that both projects should be aided and ratified by the Society. (M.T.)

  4. Radiation sensors based on the generation of mobile protons in organic dielectrics.

    Science.gov (United States)

    Kapetanakis, Eleftherios; Douvas, Antonios M; Argitis, Panagiotis; Normand, Pascal

    2013-06-26

    A sensing scheme based on mobile protons generated by radiation, including ionizing radiation (IonR), in organic gate dielectrics is investigated for the development of metal-insulator-semiconductor (MIS)-type dosimeters. Application of an electric field to the gate dielectric moves the protons and thereby alters the flat band voltage (VFB) of the MIS device. The shift in the VFB is proportional to the IonR-generated protons and, therefore, to the IonR total dose. Triphenylsulfonium nonaflate (TPSNF) photoacid generator (PAG)-containing poly(methyl methacrylate) (PMMA) polymeric films was selected as radiation-sensitive gate dielectrics. The effects of UV (249 nm) and gamma (Co-60) irradiations on the high-frequency capacitance versus the gate voltage (C-VG) curves of the MIS devices were investigated for different total dose values. Systematic improvements in sensitivity can be accomplished by increasing the concentration of the TPSNF molecules embedded in the polymeric matrix.

  5. Investigation of Electricity Generation by Using Gamma Radiation from Spent Fuels

    International Nuclear Information System (INIS)

    Lee, Haneol; Yim, Man-Sung Yim

    2015-01-01

    The purpose of this study is to investigate the electric power generation with scale spent fuel. OrigenArp has analyzed gamma radiation environment of spent fuel assembly, MCNPX has analyzed the scintillator behavior, and experimental work has analyzed the electric output of photovoltaic cell. Gamma radiation environment analysis result indicates gamma source rapidly decreases for the early storage period. Scintillator analysis result calculates the photon flux distribution which enters photovoltaic cell. Photovoltaic cell experiment calculates electric current, voltage current generation per each system unit. Generated electric power can be used to cope with existing safety system (i.e. storage monitoring system) under severe accident or to operate security system under external invasion situation (i.e. passive physical barrier system). Several researchers have shown that converting radiation energy into electric energy is possible. Karl Scharf studied the direct electric conversion of radiation energy by using photovoltaic cells. Researchers in University of Massachusetts Lowell have studied radiation-electric energy conversion by using gadolinium oxide scintillator and dye sensitized solar cell (DSSCs) and N. Horuichi et al. studied radiation-electric energy conversion by using inorganic scintillators and amorphous and crystal photovoltaic cells

  6. Environmental radiation monitoring data for Point Lepreau Generating Station, 1990. Annual publication

    Energy Technology Data Exchange (ETDEWEB)

    Sutherland, J K

    1991-01-01

    Annual report presenting a compilation of the 1990 environmental radiation monitoring program data from samples collected around the Point Lepreau Nuclear Generating Station (PLNGS) and at reference stations remote from PLNGS. About 1,500 analyses were made on 1,100 samples to monitor environmental radiation, including air particulates, airborne water vapour, carbon dioxide in air, sea water, well water, milk, beach sediments, clams, fish, lobster, dulse, crabs, scallops, periwinkles, sea plants and lichen. Background radiation is measured by thermoluminescence dosimetry. Radon is not assessed.

  7. Enhanced terahertz magnetic dipole response by subwavelength fiber

    Directory of Open Access Journals (Sweden)

    Shaghik Atakaramians

    2018-05-01

    Full Text Available Dielectric sub-wavelength particles have opened up a new platform for realization of magnetic light. Recently, we have demonstrated that a dipole emitter by a sub-wavelength fiber leads to an enhanced magnetic response. Here, we experimentally demonstrate an enhanced magnetic dipole source in the terahertz frequency range. By placing the fiber next to the hole in a metal screen, we find that the radiation power can be enhanced more than one order of magnitude. The enhancement is due to the excitation of the Mie-type resonances in the fiber. We demonstrate that such a system is equivalent to a double-fiber system excited by a magnetic source. This coupled magnetic dipole and optical fiber system can be considered a unit cell of metasurfaces for manipulation of terahertz radiation and is a proof-of-concept of a possibility to achieve enhanced radiation of a dipole source in proximity of a sub-wavelength fiber. It can also be scaled down to optical frequencies opening up promising avenues for developing integrated nanophotonic devices such as nanoantennas or lasers on fibers.

  8. Using a whole body counter to attract a younger generation to radiation and radiation protection topics

    International Nuclear Information System (INIS)

    Breustedt, B.; Mohr, U.; Bohnstedt, A.; Knebel, J.U.

    2010-01-01

    Currently there is a lack of young academics in the nuclear field especially in the field of radiation protection RP. One of the reasons is the very small number of students in the so called STEM subjects (science, technology, engineering and mathematics) which distribute among the different topics in these fields. One important task to overcome the foreseeable shortage of RP professionals is to attract pupils to this field. In routine monitoring the whole body counter of the Institute of Radiation Research (ISF) is used to identify and quantify radioactive materials that are incorporated in the human body using the technique of gamma spectroscopy. The in-vivo monitoring lab participates in activities for pupils at school level, e.g. Kinderuniversitaet, practical studies of secondary level pupils and 'Girls day'. Pupils that come to the lab are ages 14 to 18. The whole body counter is an optimal tool for these children to experience (natural) radioactivity and radiation protection issues. First pupils get a short introduction on radioactivity and gamma spectroscopy at a level adjusted to their current knowledge. After this they are measuring themselves in the whole body counter. A routine measurement of 300 s is able to show the natural occurring K-40 in their bodies. After their own measurements they do calibration measurements using a bottle phantom with a set up adjusted to their own body weights. The bottle phantom is filled with a potassium chloride (KCl) solution and contains no other radioactivity than the natural K-40 content of the KCl. Thus no further radiation protection measures need to be taken for using this phantom. A simple Excel-Sheet is then used to estimate their own K-40 activity by comparing the spectra of their measurement to the ones of the calibration measurements. This 'hands on' experience and the connection of radiation and their own bodies often is a 'eureka' effect and opens discussion on preconceptions of radiation and the need of RP

  9. High Harmonic Radiation Generation and Attosecond pulse generation from Intense Laser-Solid Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, Alexander Roy [Univ. of Michigan, Ann Arbor, MI (United States); Krushelnick, Karl [Univ. of Michigan, Ann Arbor, MI (United States)

    2016-09-08

    We have studied ion motion effects in high harmonic generation, including shifts to the harmonics which result in degradation of the attosecond pulse train, and how to mitigate them. We have examined the scaling with intensity of harmonic emission. We have also switched the geometry of the interaction to measure, for the first time, harmonics from a normal incidence interaction. This was performed by using a special parabolic reflector with an on axis hole and is to allow measurements of the attosecond pulses using standard techniques. Here is a summary of the findings: First high harmonic generation in laser-solid interactions at 1021 Wcm-2, demonstration of harmonic focusing, study of ion motion effects in high harmonic generation in laser-solid interactions, and demonstration of harmonic amplification.

  10. Tuning characteristics of narrowband THz radiation generated via optical rectification in periodically poled lithium niobate.

    Science.gov (United States)

    Weiss, C; Torosyan, G; Meyn, J P; Wallenstein, R; Beigang, R; Avetisyan, Y

    2001-04-23

    The tuning properties of pulsed narrowband THz radiation generated via optical rectification in periodically poled lithium niobate have been investigated. Using a disk-shaped periodically poled crystal tuning was easily accomplished by rotating the crystal around its axis and observing the generated THz radiation in forward direction. In this way no beam deflection during tuning was observed. The total tuning range extended from 180 GHz up to 830 GHz and was limited by the poling period of 127 microm which determines the maximum THz frequency in forward direction.

  11. Origin of interface states and oxide charges generated by ionizing radiation

    International Nuclear Information System (INIS)

    Sah, C.T.

    1976-01-01

    The randomly located trivalent silicon atoms are shown to account for the thermally generated interface states at the SiO 2 -Si interface. The interface state density is greatly reduced in water containing ambients at low temperatures (450 0 C) by forming trivalent silicon hydroxide bonds. Interface states are regenerated when the /triple bond/Si-OH bonds are broken by ionizing radiation and the OH ions are drifted away. In the bulk of the oxide film, the trivalent silicon and the interstitial oxygen donor centers are shown to be responsible for the heat and radiation generated positive space charge build-up (oxide charge) in thermally grown silicon oxide

  12. Generation of auroral kilometric radiation and the structure of auroral acceleration region

    International Nuclear Information System (INIS)

    Lee, L.C.; Kan, J.R.; Wu, C.S.

    1980-01-01

    Generation of auroral kilometric radiation (AKR) in the auroral acceleration region is studied. It is shown that auroral kilometric radiation can be generated by the backscattered electrons trapped in the acceleration region via a cyclotron maser process. The parallel electric field in the acceleration region is required to be distributed over 1-2 Rsub(E). The observed AKR frequency spectrum can be used to estimate the altitude range of the auroral acceleration region. The altitudes of the lower and upper boundaries of the acceleration region determined from the AKR data are respectively approximately 2000 and approximately 9000 km. (author)

  13. Summary Report of Working Group 5: Beam and Radiation Generation, Monitoring, and Control

    International Nuclear Information System (INIS)

    Church, Mike; Kim, Kiyong

    2010-01-01

    This paper summarizes the activities and presentations of Working Group 5 of the Advanced Accelerator Concepts Workshop held at Annapolis, Maryland in June 2010. Working Group 5 touched on a broad range of topics in the fields of beam and radiation generation and their monitoring and control. These topics were not comprehensively covered in this Workshop, but rather the Working Group concentrated on specific new developments and recent investigations. The Working Group divided its sessions into four broad categories: cathodes and electron guns, radiation generation, beam diagnostics, and beam control and dynamics. This summary is divided into the same structure.

  14. Photogalvanic effects induced by terahertz-lasers in semiconductor quantum films and applications; Terahertzlaserinduzierte photogalvanische Effekte in Halbleiter-Quantenfilmen und deren Anwendung

    Energy Technology Data Exchange (ETDEWEB)

    Weber, Wolfgang

    2008-06-16

    In this work photogalvanic effects where investigated in GaN/AlGaN heterostructures for the first time. For this purpose one of the strongest pulsed terahertz-lasers in the world was built and a computer controlled measurement system was developed. Additionally in this work an application of photogalvanic effects is presented, a pure-electric detection system, which allows to determine the polarisation state of terahertz radiation in sub-nanosecond time resolution. (orig.)

  15. High speed, High resolution terahertz spectrometers

    International Nuclear Information System (INIS)

    Kim, Youngchan; Yee, Dae Su; Yi, Miwoo; Ahn, Jaewook

    2008-01-01

    A variety of sources and methods have been developed for terahertz spectroscopy during almost two decades. Terahertz time domain spectroscopy (THz TDS)has attracted particular attention as a basic measurement method in the fields of THz science and technology. Recently, asynchronous optical sampling (AOS)THz TDS has been demonstrated, featuring rapid data acquisition and a high spectral resolution. Also, terahertz frequency comb spectroscopy (TFCS)possesses attractive features for high precision terahertz spectroscopy. In this presentation, we report on these two types of terahertz spectrometer. Our high speed, high resolution terahertz spectrometer is demonstrated using two mode locked femtosecond lasers with slightly different repetition frequencies without a mechanical delay stage. The repetition frequencies of the two femtosecond lasers are stabilized by use of two phase locked loops sharing the same reference oscillator. The time resolution of our terahertz spectrometer is measured using the cross correlation method to be 270 fs. AOS THz TDS is presented in Fig. 1, which shows a time domain waveform rapidly acquired on a 10ns time window. The inset shows a zoom into the signal with 100ps time window. The spectrum obtained by the fast Fourier Transformation (FFT)of the time domain waveform has a frequency resolution of 100MHz. The dependence of the signal to noise ratio (SNR)on the measurement time is also investigated

  16. Tutorial: Terahertz beamforming, from concepts to realizations

    Science.gov (United States)

    Headland, Daniel; Monnai, Yasuaki; Abbott, Derek; Fumeaux, Christophe; Withayachumnankul, Withawat

    2018-05-01

    The terahertz range possesses significant untapped potential for applications including high-volume wireless communications, noninvasive medical imaging, sensing, and safe security screening. However, due to the unique characteristics and constraints of terahertz waves, the vast majority of these applications are entirely dependent upon the availability of beam control techniques. Thus, the development of advanced terahertz-range beam control techniques yields a range of useful and unparalleled applications. This article provides an overview and tutorial on terahertz beam control. The underlying principles of wavefront engineering include array antenna theory and diffraction optics, which are drawn from the neighboring microwave and optical regimes, respectively. As both principles are applicable across the electromagnetic spectrum, they are reconciled in this overview. This provides a useful foundation for investigations into beam control in the terahertz range, which lies between microwaves and infrared light. Thereafter, noteworthy experimental demonstrations of beam control in the terahertz range are discussed, and these include geometric optics, phased array devices, leaky-wave antennas, reflectarrays, and transmitarrays. These techniques are compared and contrasted for their suitability in applications of terahertz waves.

  17. Macroscopic Magnetization Control by Symmetry Breaking of Photoinduced Spin Reorientation with Intense Terahertz Magnetic Near Field

    Science.gov (United States)

    Kurihara, Takayuki; Watanabe, Hiroshi; Nakajima, Makoto; Karube, Shutaro; Oto, Kenichi; Otani, YoshiChika; Suemoto, Tohru

    2018-03-01

    We exploit an intense terahertz magnetic near field combined with femtosecond laser excitation to break the symmetry of photoinduced spin reorientation paths in ErFeO3 . We succeed in aligning macroscopic magnetization reaching up to 80% of total magnetization in the sample to selectable orientations by adjusting the time delay between terahertz and optical pump pulses. The spin dynamics are well reproduced by equations of motion, including time-dependent magnetic potential. We show that the direction of the generated magnetization is determined by the transient direction of spin tilting and the magnetic field at the moment of photoexcitation.

  18. Polarised two-photon excitation of quantum well excitons for manipulation of optically pumped terahertz lasers

    Energy Technology Data Exchange (ETDEWEB)

    Slavcheva, G., E-mail: gsk23@bath.ac.uk [Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ (United Kingdom); Kavokin, A.V., E-mail: A.Kavokin@soton.ac.uk [School of Physics and Astronomy, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); Spin Optics Laboratory, St. Petersburg State University, 1, Ulyanovskaya 198504 (Russian Federation)

    2014-11-15

    Optical pumping of excited exciton states in a semiconductor quantum well embedded in a microcavity is a tool for realisation of ultra-compact terahertz (THz) lasers based on stimulated optical transition between excited (2p) and ground (1s) exciton state. We show that the probability of two-photon absorption by a 2p-exciton is strongly dependent on the polarisation of both pumping photons. Five-fold variation of the threshold power for terahertz lasing by switching from circular to co-linear pumping is predicted. We identify photon polarisation configurations for achieving maximum THz photon generation quantum efficiency.

  19. Widely tunable terahertz source based on intra-cavity frequency mixing in quantum cascade laser arrays

    International Nuclear Information System (INIS)

    Jiang, Aiting; Jung, Seungyong; Jiang, Yifan; Kim, Jae Hyun; Belkin, Mikhail A.; Vijayraghavan, Karun

    2015-01-01

    We demonstrate a compact monolithic terahertz source continuously tunable from 1.9 THz to 3.9 THz with the maximum peak power output of 106 μW at 3.46 THz at room temperature. The source consists of an array of 10 electrically tunable quantum cascade lasers with intra-cavity terahertz difference-frequency generation. To increase fabrication yield and achieve high THz peak power output in our devices, a dual-section current pumping scheme is implemented using two electrically isolated grating sections to independently control gain for the two mid-IR pumps

  20. High-Efficiency Dielectric Metasurfaces for Polarization-Dependent Terahertz Wavefront Manipulation

    KAUST Repository

    Zhang, Huifang

    2017-11-30

    Recently, metasurfaces made up of dielectric structures have drawn enormous attentions in the optical and infrared regimes due to their high efficiency and designing freedom in manipulating light propagation. Such advantages can also be introduced to terahertz frequencies where efficient functional devices are still lacking. Here, polarization-dependent all-silicon terahertz dielectric metasurfaces are proposed and experimentally demonstrated. The metasurfaces are composed of anisotropic rectangular-shaped silicon pillars on silicon substrate. Each metasurface holds dual different functions depending on the incident polarizations. Furthermore, to suppress the reflection loss and multireflection effect in practical applications, a high-performance polarization-independent antireflection silicon pillar array is also proposed, which can be patterned at the other side of the silicon substrate. Such all-silicon dielectric metasurfaces are easy to fabricate and can be very promising in developing next-generation efficient, compact, and low-cost terahertz functional devices.

  1. Terahertz lasers and amplifiers based on resonant optical phonon scattering to achieve population inversion

    Science.gov (United States)

    Williams, Benjamin S. (Inventor); Hu, Qing (Inventor)

    2009-01-01

    The present invention provides quantum cascade lasers and amplifier that operate in a frequency range of about 1 Terahertz to about 10 Terahertz. In one aspect, a quantum cascade laser of the invention includes a semiconductor heterostructure that provides a plurality of lasing modules connected in series. Each lasing module includes a plurality of quantum well structure that collectively generate at least an upper lasing state, a lower lasing state, and a relaxation state such that the upper and the lower lasing states are separated by an energy corresponding to an optical frequency in a range of about 1 to about 10 Terahertz. The lower lasing state is selectively depopulated via resonant LO-phonon scattering of electrons into the relaxation state.

  2. Frequency-dependent absorbance of broadband terahertz wave in dense plasma sheet

    Science.gov (United States)

    Peng, Yan; Qi, Binbin; Jiang, Xiankai; Zhu, Zhi; Zhao, Hongwei; Zhu, Yiming

    2018-05-01

    Due to the ability of accurate fingerprinting and low-ionization for different substances, terahertz (THz) technology has a lot of crucial applications in material analysis, information transfer, and safety inspection, etc. However, the spectral characteristic of atmospheric gas and ionized gas has not been widely investigated, which is important for the remote sensing application. Here, in this paper, we investigate the absorbance of broadband terahertz wave in dense plasma sheet generated by femtosecond laser pulses. It was found that as the terahertz wave transmits through the plasma sheet formed, respectively, in carbon dioxide, oxygen, argon and nitrogen, spectrum presents completely different and frequency-dependent absorbance. The reasons for these absorption peaks are related to the molecular polarity, electric charge, intermolecular and intramolecular interactions, and collisional absorption of gas molecules. These results have significant implications for the remote sensing of gas medium.

  3. Low-intensive proton generators for radiation testing; Nizkointensivnyj protonnyj generator dlya radiatsionnykh ispytanij

    Energy Technology Data Exchange (ETDEWEB)

    Istomin, I V; Gurbich, A F; Semenov, A V

    1994-12-31

    Experiment is conducted and calculations are performed grounding the possibility of creating a low-intensity proton generator based on nuclear reaction. The necessity in such a proton source is defined by the need of conducting long-term testings and by the absence of appropriate equipment.

  4. Radiative generation of quark masses and mixing angles in the two Higgs doublet model

    International Nuclear Information System (INIS)

    Ibarra, Alejandro; Solaguren-Beascoa, Ana

    2014-01-01

    We present a framework to generate the quark mass hierarchies and mixing angles by extending the Standard Model with one extra Higgs doublet. The charm and strange quark masses are generated by small quantum effects, thus explaining the hierarchy between the second and third generation quark masses. All the mixing angles are also generated by small quantum effects: the Cabibbo angle is generated at zeroth order in perturbation theory, while the remaining off-diagonal entries of the Cabibbo–Kobayashi–Maskawa matrix are generated at first order, hence explaining the observed hierarchy |V ub |,|V cb |≪|V us |. The values of the radiatively generated parameters depend only logarithmically on the heavy Higgs mass, therefore this framework can be reconciled with the stringent limits on flavor violation by postulating a sufficiently large new physics scale

  5. Terahertz spectroscopy and imaging for cultural heritage management: state of art and perspectives

    Science.gov (United States)

    Catapano, Ilaria; Soldovieri, Francesco

    2014-05-01

    Non-invasive diagnostic tools able to provide information on the materials and preservation state of artworks are crucial to help conservators, archaeologists and anthropologists to plan and carry out their tasks properly. In this frame, technological solutions exploiting Terahertz (THz) radiation, i.e., working at frequencies ranging from 0.1 to 10 THz, are currently deserving huge attention as complementary techniques to classical analysis methodologies based on electromagnetic radiations from X-rays to mid infrared [1]. The main advantage offered by THz spectroscopy and imaging systems is referred to their capability of providing information useful to determine the construction modality, the history life and the conservation state of artworks as well as to identify previous restoration actions [1,2]. In particular, unlike mid- and near-infrared spectroscopy, which provides fingerprint absorption spectra depending on the intramolecular behavior, THz spectroscopy is related to the structure of the molecules of the investigated object. Hence, it can discriminate, for instance, the different materials mixed in a paint [1,2]. Moreover, THz radiation is able to penetrate several materials which are opaque to both visible and infrared materials, such as varnish, paint, plaster, paper, wood, plastic, and so on. Accordingly, it is useful to detect hidden objects and characterize the inner structure of the artwork under test even in the direction of the depth, while avoiding core drillings. In this frame, THz systems allow us to discriminate different layers of materials present in artworks like paints, to obtain images providing information on the construction technique as well as to discover risk factors affecting the preservation state, such as non-visible cracks, hidden molds and air gaps between the paint layer and underlying structure. Furthermore, adopting a no-ionizing radiation, THz systems offer the not trivial benefit of negligible long term risks to the

  6. For the definition of capacity effects of electricity generation from wind power and solar radiation

    International Nuclear Information System (INIS)

    Kaltschmitt, M.

    1996-01-01

    It is the objective of this contribution to define the calculable really available output of a fluctuating electricity generation from wind energy and solar radiation. Apart from that, the methods for determining the really available output are explained, as far as they are necessary for understanding the definitions. Exemplified on a simulated large-scale regenerative electricity generation in Germany, in addition, some defined values are calculated and discussed. (orig.) [de

  7. Ultrafast electron field emission from gold resonant antennas studied by two terahertz pulse experiments

    DEFF Research Database (Denmark)

    Iwaszczuk, Krzysztof; Zalkovskij, Maksim; Strikwerda, Andrew C.

    2015-01-01

    Summary form only given. Ultrafast electron field emission from gold resonant antennas induced by strong terahertz (THz) transient is investigated using two THz pulse experiments. It is shown that UV emission from nitrogen plasma generated by liberated electrons is a good indication of the local...

  8. Stability of heterodyne terahertz receivers

    OpenAIRE

    Kooi, J. W.; Baselmans, J. J. A.; Baryshev, A.; Schieder, R.; Hajenius, M.; Gao, J. R.; Klapwijk, T. M.; Voronov, B.; Gol'tsman, G.

    2006-01-01

    In this paper we discuss the stability of heterodyne terahertz receivers based on small volume NbN phonon cooled hot electron bolometers (HEBs). The stability of these receivers can be broken down in two parts: the intrinsic stability of the HEB mixer and the stability of the local oscillator (LO) signal injection scheme. Measurements show that the HEB mixer stability is limited by gain fluctuations with a 1/f spectral distribution. In a 60 MHz noise bandwidth this results in an Allan varian...

  9. A simple model for determining photoelectron-generated radiation scaling laws

    International Nuclear Information System (INIS)

    Dipp, T.M.

    1993-12-01

    The generation of radiation via photoelectrons induced off of a conducting surface was explored using a simple model to determine fundamental scaling laws. The model is one-dimensional (small-spot) and uses monoenergetic, nonrelativistic photoelectrons emitted normal to the illuminated conducting surface. Simple steady-state radiation, frequency, and maximum orbital distance equations were derived using small-spot radiation equations, a sin 2 type modulation function, and simple photoelectron dynamics. The result is a system of equations for various scaling laws, which, along with model and user constraints, are simultaneously solved using techniques similar to linear programming. Typical conductors illuminated by low-power sources producing photons with energies less than 5.0 eV are readily modeled by this small-spot, steady-state analysis, which shows they generally produce low efficiency (η rsL -10.5 ) pure photoelectron-induced radiation. However, the small-spot theory predicts that the total conversion efficiency for incident photon power to photoelectron-induced radiated power can go higher than 10 -5.5 for typical real conductors if photons having energies of 15 eV and higher are used, and should go even higher still if the small-spot limit of this theory is exceeded as well. Overall, the simple theory equations, model constraint equations, and solution techniques presented provide a foundation for understanding, predicting, and optimizing the generated radiation, and the simple theory equations provide scaling laws to compare with computational and laboratory experimental data

  10. Precise real-time polarization measurement of terahertz electromagnetic waves by a spinning electro-optic sensor.

    Science.gov (United States)

    Yasumatsu, Naoya; Watanabe, Shinichi

    2012-02-01

    We propose and develop a method to quickly and precisely determine the polarization direction of coherent terahertz electromagnetic waves generated by femtosecond laser pulses. The measurement system consists of a conventional terahertz time-domain spectroscopy system with the electro-optic (EO) sampling method, but we add a new functionality in the EO crystal which is continuously rotating with the angular frequency ω. We find a simple yet useful formulation of the EO signal as a function of the crystal orientation, which enables a lock-in-like detection of both the electric-field amplitude and the absolute polarization direction of the terahertz waves with respect to the probe laser pulse polarization direction at the same time. The single measurement finishes around two periods of the crystal rotations (∼21 ms), and we experimentally prove that the accuracy of the polarization measurement does not suffer from the long-term amplitude fluctuation of the terahertz pulses. Distribution of the measured polarization directions by repeating the measurements is excellently fitted by a gaussian distribution function with a standard deviation of σ = 0.56°. The developed technique is useful for the fast direct determination of the polarization state of the terahertz electromagnetic waves for polarization imaging applications as well as the precise terahertz Faraday or Kerr rotation spectroscopy.

  11. Infrared radiation scene generation of stars and planets in celestial background

    Science.gov (United States)

    Guo, Feng; Hong, Yaohui; Xu, Xiaojian

    2014-10-01

    An infrared (IR) radiation generation model of stars and planets in celestial background is proposed in this paper. Cohen's spectral template1 is modified for high spectral resolution and accuracy. Based on the improved spectral template for stars and the blackbody assumption for planets, an IR radiation model is developed which is able to generate the celestial IR background for stars and planets appearing in sensor's field of view (FOV) for specified observing date and time, location, viewpoint and spectral band over 1.2μm ~ 35μm. In the current model, the initial locations of stars are calculated based on midcourse space experiment (MSX) IR astronomical catalogue (MSX-IRAC) 2 , while the initial locations of planets are calculated using secular variations of the planetary orbits (VSOP) theory. Simulation results show that the new IR radiation model has higher resolution and accuracy than common model.

  12. Enhanced possibilities of section topography at a third-generation synchrotron radiation facility

    International Nuclear Information System (INIS)

    Medrano, C.; Rejmankova, P.; Ohler, M.; Matsouli, I.

    1997-01-01

    The authors show the new possibilities of section topography techniques at a third-generation synchrotron radiation facility, taking advantage of the high performances of this machine. Examples of the 1) so-called multiple sections, 2) visibility of weakly misoriented regions, 3) study of thick samples, 4) monochromatic and 5) realtime sections are presented

  13. Radiative corrections and Monte Carlo generators for physics at flavor factories

    Directory of Open Access Journals (Sweden)

    Montagna Guido

    2016-01-01

    Full Text Available I review the state of the art of precision calculations and related Monte Carlo generators used in physics at flavor factories. The review describes the tools relevant for the measurement of the hadron production cross section (via radiative return, energy scan and in γγ scattering, luminosity monitoring, searches for new physics and physics of the τ lepton.

  14. Users manual. Pursuit program of use licenses of radioactive material or generator equipment of ionizing radiations

    International Nuclear Information System (INIS)

    Becerril M, V.M.; Villarreal, J.E.

    1992-05-01

    The objective of the program 'Databases for the pursuit of licenses of use of radioactive material', it consists on the application of a computer system carried out in dbase IV that it allows the control of the all the information related with those licenses for use, possession and storage of radioactive material or generator equipment of ionizing radiations. (Author)

  15. Process of cross section generation for radiation shielding calculations, using the NJOY code

    International Nuclear Information System (INIS)

    Ono, S.; Corcuera, R.P.

    1986-10-01

    The process of multigroup cross sections generation for radiation shielding calculations, using the NJOY code, is explained. Photon production cross sections, processed by the GROUPR module, and photon interaction cross sections processed by the GAMINR are given. These data are compared with the data produced by the AMPX system and published data. (author) [pt

  16. Generation of 13.9 µm radiation from CO2 by cascade lasing or ...

    Indian Academy of Sciences (India)

    the 1000 level is fast, and such lasers operate at low power and energies. ... CO2 laser; Q-switching; generation of 14 µm radiation from CO2; cascade lasing ... of 5% hole coupling output mirror, and a high reflectivity rotating mirror. This.

  17. Testing and analysis of tube voltage and tube current in the radiation generator for mammography

    International Nuclear Information System (INIS)

    Jung, Hong Ryang; Hong, Dong Hee; Han, Beom Hui

    2014-01-01

    Breast shooting performance management and quality control of the generator is applied to the amount of current IEC(International Electrotechnical Commission) 60601-2-45 tube voltage and tube current are based on standards that were proposed in the analysis of the test results were as follows. Tube voltage according to the value of the standard deviation by year of manufacture from 2001 to 2010 as a 42-3.15 showed the most significant, according to the year of manufacture by tube amperage value of the standard deviation to 6.38 in the pre-2000 showed the most significant , manufactured after 2011 the standard deviation of the devices, the PAE(Percent Average Error) was relatively low. This latest generation device was manufactured in the breast of the tube voltage and tube diagnosed shooting the correct amount of current to maintain the performance that can be seen. The results of this study as the basis for radiography diagnosed breast caused by using the device's performance and maintain quality control, so the current Food and Drug Administration 'about the safety of diagnostic radiation generator rule' specified in the test cycle during three years of self-inspection radiation on a radiation generating device ensure safety and performance of the device using a coherent X-ray(constancy) by two ultimately able to keep the radiation dose to the public to reduce the expected effect is expected

  18. Adaptive sampling dual terahertz comb spectroscopy using dual free-running femtosecond lasers.

    Science.gov (United States)

    Yasui, Takeshi; Ichikawa, Ryuji; Hsieh, Yi-Da; Hayashi, Kenta; Cahyadi, Harsono; Hindle, Francis; Sakaguchi, Yoshiyuki; Iwata, Tetsuo; Mizutani, Yasuhiro; Yamamoto, Hirotsugu; Minoshima, Kaoru; Inaba, Hajime

    2015-06-02

    Terahertz (THz) dual comb spectroscopy (DCS) is a promising method for high-accuracy, high-resolution, broadband THz spectroscopy because the mode-resolved THz comb spectrum includes both broadband THz radiation and narrow-line CW-THz radiation characteristics. In addition, all frequency modes of a THz comb can be phase-locked to a microwave frequency standard, providing excellent traceability. However, the need for stabilization of dual femtosecond lasers has often hindered its wide use. To overcome this limitation, here we have demonstrated adaptive-sampling THz-DCS, allowing the use of free-running femtosecond lasers. To correct the fluctuation of the time and frequency scales caused by the laser timing jitter, an adaptive sampling clock is generated by dual THz-comb-referenced spectrum analysers and is used for a timing clock signal in a data acquisition board. The results not only indicated the successful implementation of THz-DCS with free-running lasers but also showed that this configuration outperforms standard THz-DCS with stabilized lasers due to the slight jitter remained in the stabilized lasers.

  19. Generation of volatile hydrocarbons as a measure of radiation-induced lipid peroxidation in vitro

    Energy Technology Data Exchange (ETDEWEB)

    Dobbs, C R; Kumar, K S; Weiss, J F; Catravas, G N [Armed Forces Radiobiology Research Inst., Bethesda, MD (USA)

    1981-04-01

    Using gas chromatography techniques, pentane production from microsomes could be detected at gamma radiation doses as low as 50 Gy, but definite increases were observed only with the addition of the peroxidation promoter ADP-Fe. There was a small but linear increase in pentane production, and presumably lipid peroxidation, when nonirradiated microsomes alone were incubated. The addition of ADP-Fe induced a further production of pentane which was linear with incubation time. Radiation alone (700 and 2000 Gy) also induced pentane production, but the highest levels were observed with the combination of ADP-Fe and radiation. In microsomes irradiated with 700 Gy, the rate of pentane production was greatest during the first 100 min post-irradiation. In comparing radiation-induced pentane generation to the enzymatic-induced system, it was seen that pentane production was much greater in the latter system.

  20. Method to generate a pulse train of few-cycle coherent radiation

    Directory of Open Access Journals (Sweden)

    Bryant Garcia

    2016-09-01

    Full Text Available We develop a method to generate a long pulse train of few-cycle coherent radiation by modulating an electron beam with a high power laser. The large energy modulation disperses the beam in a radiating undulator and leads to the production of phase-locked few-cycle coherent radiation pulses. These pulses are produced at a high harmonic of the modulating laser, and are longitudinally separated by the modulating laser wavelength. We discuss an analytical model for this scheme and investigate the temporal and spectral properties of this radiation. This model is compared with numerical simulation results using the unaveraged code Puffin. We examine various harmful effects and how they might be avoided, as well as a possible experimental realization of this scheme.

  1. The role of molecular mobility in the transfer of charge generated by ionizing radiation in polymers

    International Nuclear Information System (INIS)

    Khatinov, S.A.; Edrisov, K.M.; Turdybekov, K.M.; Milinchuk, V.K.

    1995-01-01

    The dependence of radiation-induced electrical conductivity on the irradiation time and temperature was studied for a number of polymers. The character of variation of radiation-induced conductivity with time and temperature correlates with the physical state of a polymer. Defreezing of the segmental mobility in the region of α-relaxation transition leads to a sharp change in radiation-induced conductivity, and the appearance of peaks in the kinetic curves and break points on the Arrhenius plots in conductivity versus temperature coordinates. Molecular mobility plays a determining role in the transfer of charge carriers generated by radiation. This conclusion agrees with the data on the carrier mobility obtained by the time-of-flight methods. 24 refs., 8 figs

  2. High level harmonic radiation: atto-second impulse generation, application to coherent radiation

    International Nuclear Information System (INIS)

    Kovacev, Milutin

    2003-01-01

    The work presented in this thesis is dedicated to the characterization and optimization of the unique properties of high order harmonic generation in a rare gas: high brilliance, short pulse duration (femtosecond to atto-second, 1 as = 10"-"1"8 s and good mutual coherence. In the first part of this work, we concentrate on the exploitation of a scaling law using a high-energy laser loosely focused inside an extended gaseous medium. For the first time, the generated harmonic energy exceeds the 1 μJ level per laser pulse using the fifteenth harmonic order at a wavelength of 53 nm. The conversion efficiency reaches 4.10"-"5, which results from the combination of a strong dipolar response and a good phase matching within a generating volume that is extended by self guiding of the generating laser pulse. In the second part, our interest is devoted to the temporal profile of the harmonic emission and its atto-second structure. We first demonstrate the feasibility of a spatial/spectral selection of the contributions associated to the two main electronic trajectories, allowing thereby the generation of regular atto-second pulse trains. We then characterize such a pulse train by the measurement of the relative phases of consecutive harmonics. Finally, we describe an original technique for the temporal confinement of the harmonic emission by manipulating the ellipticity of the generating laser beam. In the third part, our interest is dedicated to the mutual coherence properties of the harmonic emission. We first demonstrate the precise control of the relative phase of the harmonic pulses by multiple beam interference in the XUV. This frequency-domain interferometry using four phase-locked temporally separated pulses shows an extreme sensitivity to the relative phase of the pulses on an atto-second time scale. We then measure the first order autocorrelation trace of the harmonic beam thanks to the generation of two harmonic sources mutually coherent and spatially separated

  3. Planning and Programming of Education and Training Courses on the Radiation Fusion Technologies for Next Generations

    International Nuclear Information System (INIS)

    Kim, Jin Kyu; Nam, Y. M.; Choi, P. H.

    2009-06-01

    In order to program education and training courses on the radiation technologies and to have the WNU RT School to be held in Korea, this project was carried out. It was also done to make a strategy for running the programmed courses, and to build and knit a global network among radiation specialists such as international advisory board, domestic advisory board and steering committee. A plan for the WNU RT School in Korea was made under this project. Curricula in all subjects related to radiation technology and the lecture materials were prepared, which are essential for education and training courses on radiation technologies for next generations. Lecturers were selected among global CEOs and professionals in radiation industries and university professors and radiation specialists. In addition, a global network among radiation specialists such as international advisory board, domestic advisory board and steering committee was built and organized. As a model for the international education and training courses in RT field as well as the other fields, it can be used for making fundamentals of technology exports and promoting Korea's national image in science and technology

  4. A model of radiative neutrino masses. Mixing and a possible fourth generation

    International Nuclear Information System (INIS)

    Babu, K.S.; Ma, E.; Pantaleone, J.

    1989-01-01

    We consider the phenomenological consequences of a recently proposed model with four lepton generations such that the three known neutrinos have radiatively induced Majorana masses. Mixing among generations in the presence of a heavy fourth neutrino necessitates a reevaluation of the usual experimental tests of the standard model. One interesting possibility is to have a τ lifetime longer than predicted by the standard three-generation model. Another is to have neutrino masses and mixing angles in the range needed for a natural explanation of the solar-neutrino puzzle in terms of the Mikheyev-Smirnov-Wolfenstein effect. (orig.)

  5. Investigating murals with terahertz reflective tomography

    Science.gov (United States)

    Yuan, Minjie; Sun, Wenfeng; Wang, Xinke; Wang, Sen; Zhang, Qunxi; Ye, Jiasheng; Zhang, Yan

    2015-08-01

    Terahertz time-domain spectroscopy (THz-TDS) imaging technology has been proposed to be used in the non-invasive detection of murals. THz-TDS images provide structural data of the sample that cannot be obtained with other complementary techniques. In this paper, two types of defects hidden in the plaster used to simulate the cases of defects in the murals, have been investigated by the terahertz reflected time domain spectroscopy imaging system. These preset defects include a leaf slice and a slit built in the plaster. With the terahertz reflective tomography, information about defects has been determined involving the thickness from the surface of sample to the built-in defect, the profile and distribution of the defect. With this THz tomography, different defects with the changes of optical thickness and their relative refractive index have been identified. The application of reflective pulsed terahertz imaging has been extended to the defect detection of the murals.

  6. Excitonic terahertz photoconductivity in intrinsic semiconductor nanowires

    Science.gov (United States)

    Yan, Jie-Yun

    2018-06-01

    Excitonic terahertz photoconductivity in intrinsic semiconductor nanowires is studied. Based on the excitonic theory, the numerical method to calculate the photoconductivity spectrum in the nanowires is developed, which can simulate optical pump terahertz-probe spectroscopy measurements on real nanowires and thereby calculate the typical photoconductivity spectrum. With the help of the energetic structure deduced from the calculated linear absorption spectrum, the numerically observed shift of the resonant peak in the photoconductivity spectrum is found to result from the dominant exciton transition between excited or continuum states to the ground state, and the quantitative analysis is in good agreement with the quantum plasmon model. Besides, the dependence of the photoconductivity on the polarization of the terahertz field is also discussed. The numerical method and supporting theoretical analysis provide a new tool for experimentalists to understand the terahertz photoconductivity in intrinsic semiconductor nanowires at low temperatures or for nanowires subjected to below bandgap photoexcitation, where excitonic effects dominate.

  7. A Report on the Workshop on the Uses and Generation of Femtosecond Radiation

    International Nuclear Information System (INIS)

    Jackson, A.

    1998-01-01

    We describe the proceedings of the Workshop on the Uses and Generation of Femtosecond Radiation, held at the E.O. Lawrence Berkeley National Laboratory (LBNL), in February 1998, and some of the ideas that were generated subsequent to the workshop. The motivation for this workshop was to bring together accelerator physicists interested in the generation of ultra-short (< 200 fs) pulses of XUV and x-ray radiation, and scientists interested in using them. The primary purpose of the workshop was to educate the accelerator physicists about the source characteristics necessary to carry out specific experiments, and to inform the user community of ideas currently being explored by the accelerator community. A second objective was to develop a set of parameters and requirements that could form the basis for a broad-based femtoscience user facility. In this paper we describe some of the ideas and techniques that accelerator physicists are pursuing to ilfill the diverse requirements of this expanding community

  8. Estimates of the generation of available potential energy by infrared radiation

    Science.gov (United States)

    Hansen, A. R.; Nagle, R. L.

    1984-01-01

    Data from the National Meteorological Center and net outgoing infrared radiation (IR) data measured by NOAA satellites for January 1977 are used to compute estimates of the spectral and spatial contributions to the net generation of available potential energy in the Northern Hemisphere due to infrared radiation. Although these estimates are necessarily crude, the results obtained indicate that IR causes destruction of both zonal and eddy available potential energy. The contributions from midlatitudes to the zonal and eddy generation are about -5.0 W/sq m and about -0.6 W/sq m, respectively. The eddy generation is due almost entirely to stationary wavenumbers one and two. Comparison with earlier studies and computation of Newtonian cooling coefficients are discussed.

  9. Effects of shutdown chemistry on steam generator radiation levels at Point Beach Unit 2. Interim report

    International Nuclear Information System (INIS)

    Kormuth, J.W.

    1982-05-01

    A refueling shutdown chemistry test was conducted at a PWR, Point Beach Unit 2. The objective was to yield reactor coolant chemistry data during the cooldown/shutdown process which might establish a relationship between shutdown chemistry and its effects on steam generator radiation fields. Of particular concern were the effects of the presence of hydrogen in the coolant as contrasted to an oxygenated coolant. Analysis of reactor coolant samples showed a rapid soluble release (spike) in Co-58, Co-60, and nickel caused by oxygenation of the coolant. The measurement of radioisotope specific activities indicates that the material undergoing dissolution during the shutdown originated from different sources which had varying histories of activation. The test program developed no data which would support theories that oxygenation of the coolant while the steam generators are full of water contributes to increased steam generator radiation levels

  10. On the evaluation of modified Bessel functions of the second kind and fractional order for synchrotron radiation calculations

    International Nuclear Information System (INIS)

    Rutt, H.N.

    2003-01-01

    The modified Bessel functions of the second kind and fractional order K 1/3 (x) and K 2/3 (x) are of importance in the calculation of the frequency spectrum of synchrotron radiation. The parameter range of interest is typically 10 -6 x10. Recently, there has been particular interest in the generation of 'terahertz' radiation, which can be coherently enhanced by many orders of magnitude when the electron bunch length is shorter than the terahertz wavelength. This requires evaluation of the Bessel functions for small values of the argument. It is shown that the series commonly used to evaluate these functions has poor convergence properties under these conditions. An alternative series is derived which has much better convergence for x1

  11. Effective thermal conductivity of a heat generating rod bundle dissipating heat by natural convection and radiation

    International Nuclear Information System (INIS)

    Senve, Vinay; Narasimham, G.S.V.L.

    2011-01-01

    Highlights: → Transport processes in isothermal hexagonal sheath with 19 heat generating rods is studied. → Correlation is given to predict the maximum temperature considering all transport processes. → Effective thermal conductivity of rod bundle can be obtained using max temperature. → Data on the critical Rayleigh numbers for p/d ratios of 1.1-2.0 is presented. → Radiative heat transfer contributes to heat dissipation of 38-65% of total heat. - Abstract: A numerical study of conjugate natural convection and surface radiation in a horizontal hexagonal sheath housing 19 solid heat generating rods with cladding and argon as the fill gas, is performed. The natural convection in the sheath is driven by the volumetric heat generation in the solid rods. The problem is solved using the FLUENT CFD code. A correlation is obtained to predict the maximum temperature in the rod bundle for different pitch-to-diameter ratios and heat generating rates. The effective thermal conductivity is related to the heat generation rate, maximum temperature and the sheath temperature. Results are presented for the dimensionless maximum temperature, Rayleigh number and the contribution of radiation with changing emissivity, total wattage and the pitch-to-diameter ratio. In the simulation of a larger system that contains a rod bundle, the effective thermal conductivity facilitates simplified modelling of the rod bundle by treating it as a solid of effective thermal conductivity. The parametric studies revealed that the contribution of radiation can be 38-65% of the total heat generation, for the parameter ranges chosen. Data for critical Rayleigh number above which natural convection comes into effect is also presented.

  12. A Statistical Model for Generating a Population of Unclassified Objects and Radiation Signatures Spanning Nuclear Threats

    International Nuclear Information System (INIS)

    Nelson, K.; Sokkappa, P.

    2008-01-01

    This report describes an approach for generating a simulated population of plausible nuclear threat radiation signatures spanning a range of variability that could be encountered by radiation detection systems. In this approach, we develop a statistical model for generating random instances of smuggled nuclear material. The model is based on physics principles and bounding cases rather than on intelligence information or actual threat device designs. For this initial stage of work, we focus on random models using fissile material and do not address scenarios using non-fissile materials. The model has several uses. It may be used as a component in a radiation detection system performance simulation to generate threat samples for injection studies. It may also be used to generate a threat population to be used for training classification algorithms. In addition, we intend to use this model to generate an unclassified 'benchmark' threat population that can be openly shared with other organizations, including vendors, for use in radiation detection systems performance studies and algorithm development and evaluation activities. We assume that a quantity of fissile material is being smuggled into the country for final assembly and that shielding may have been placed around the fissile material. In terms of radiation signature, a nuclear weapon is basically a quantity of fissile material surrounded by various layers of shielding. Thus, our model of smuggled material is expected to span the space of potential nuclear weapon signatures as well. For computational efficiency, we use a generic 1-dimensional spherical model consisting of a fissile material core surrounded by various layers of shielding. The shielding layers and their configuration are defined such that the model can represent the potential range of attenuation and scattering that might occur. The materials in each layer and the associated parameters are selected from probability distributions that span the

  13. Participation of superoxide generating system, superoxide dismutase and vitamin E in the radiation hazards

    International Nuclear Information System (INIS)

    Aono, Kaname; Yamamoto, Michio; Iida, Sosuke; Utsumi, Kozo

    1978-01-01

    In relation to the mechanism by which hemolysis was induced in radiated human erythrocytes in vitro, several inducements of membrane lipid peroxidation and protective effects of vitamin E (V.E) and superoxide dismutase (SOD) were investigated. (1) K + -release from erythrocytes was accelerated by radiation prior to hemolysis. These accelerated hemolysis and K + -release were protected remarkably by V.E and evidently by SOD. (2) Mitochondrial Fe 2+ induced and Fe 3+ -superoxide generating system -- ADP induced lipid peroxidation, and microsomal superoxide generating system -- induced lipid peroxidation were also protected by V.E and SOD. (3) Radiation of x-ray or 60 Co γ-ray accelerated lipid peroxidation of liver homogenate, microsome and liposome. Some of these accelerated lipid peroxidations were protected effectively by V.E and SOD. These results suggest that superoxide and/or OH generation by radiation induces of membrane lipid peroxidation, which leads deterioration of membrane resulting in the change of ion permeability and then hemolysis. (author)

  14. Test reference year generation from meteorological and simulated solar radiation data

    Energy Technology Data Exchange (ETDEWEB)

    Miguel, A. de; Bilbao, J. [University of Valladolid (Spain). Dept. of Applied Physics

    2005-06-01

    In this paper, a new method for generating test reference year (TRY) from the measured meteorological variables is proposed. Hourly recorded data of air temperature, relative humidity and wind velocity for two stations, Valladolid and Madrid (Spain) were selected to develop the method and a TRY was obtained. Monthly average solar radiation values were calculated taking into account the temperature and solar radiation correlations. Four different methodologies were used to evaluate hourly global solar radiation from hourly weather data of temperature and, as a consequence, four different TRYs with common data sets of temperature, relative humidity and wind velocity were generated for Valladolid and Madrid (Spain) stations. In order to evaluate the four different methodologies, TRYs data were compared with long-term measured data series using statistical estimators such as average, standard deviation, root mean square error (rmse) and mean bias error (mbe). Festa and Ratto and the TAG model, from Aguiar and Collares-Pereira, respectively, turned out to be the best methods for generating hourly solar irradiation data. The best performance was shown by the TRY0 year which was based on the solar radiation models mentioned above. The results show that the best reference year for each site varies with the season and the characteristics of the station. (author)

  15. Behavior of hybrid concentrated photovoltaic-thermoelectric generator under variable solar radiation

    DEFF Research Database (Denmark)

    Mahmoudi Nezhad, Sajjad; Rezaniakolaei, Alireza; Rosendahl, Lasse Aistrup

    2018-01-01

    diversely versus changing the solar radiation and module temperature. Moreover, the thermal response of the TEG stabilizes temperature fluctuation of the hybrid module when the solar radiation rapidly changes. In this work, impact of the thermal contact resistance on the temperature profile and system...... and solved by finite volume algorithm. In spite of temperatures profile in the hybrid CPV-TEG module, as results of variation of solar irradiation, power generation and efficiency of the CPV and TEG under the transient condition are presented. The results show that efficiency of the TEG and CPV varies...

  16. A critical experimental test of synchrotron radiation theory with 3rd generation light source

    Energy Technology Data Exchange (ETDEWEB)

    Geloni, Gianluca [European XFEL GmbH, Hamburg (Germany); Kocharyan, Vitali; Saldin, Evgeni [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2016-05-15

    A recent ''beam splitting'' experiment at LCLS apparently demonstrated that after a microbunched electron beam is kicked on a large angle compared to the divergence of the FEL radiation, the microbunching wave front is readjusted along the new direction of motion of the kicked beam. Therefore, coherent radiation from an undulator placed after the kicker is emitted along the kicked direction without suppression. This strong emission of coherent undulator radiation in the kicked direction cannot be explained in the framework of conventional synchrotron radiation theory. In a previous paper we explained this puzzle. We demonstrated that, in accelerator physics, the coupling of fields and particles is based, on the one hand, on the use of results from particle dynamics treated according to the absolute time convention and, on the other hand, on the use of Maxwell equations treated according to the standard (Einstein) synchronization convention. Here lies the misconception which led to the strong qualitative disagreement between theory and experiment. After the ''beam splitting'' experiment at LCLS, it became clear that the conventional theory of synchrotron radiation cannot ensure the correct description of coherent and spontaneous emission from a kicked electron beam, nor the emission from a beam with finite angular divergence, in an undulator or a bending magnet. However, this result requires further experimental confirmation. In this publication we propose an uncomplicated and inexpensive experiment to test synchrotron radiation theory at 3rd generation light sources.

  17. A critical experimental test of synchrotron radiation theory with 3rd generation light source

    International Nuclear Information System (INIS)

    Geloni, Gianluca; Kocharyan, Vitali; Saldin, Evgeni

    2016-05-01

    A recent ''beam splitting'' experiment at LCLS apparently demonstrated that after a microbunched electron beam is kicked on a large angle compared to the divergence of the FEL radiation, the microbunching wave front is readjusted along the new direction of motion of the kicked beam. Therefore, coherent radiation from an undulator placed after the kicker is emitted along the kicked direction without suppression. This strong emission of coherent undulator radiation in the kicked direction cannot be explained in the framework of conventional synchrotron radiation theory. In a previous paper we explained this puzzle. We demonstrated that, in accelerator physics, the coupling of fields and particles is based, on the one hand, on the use of results from particle dynamics treated according to the absolute time convention and, on the other hand, on the use of Maxwell equations treated according to the standard (Einstein) synchronization convention. Here lies the misconception which led to the strong qualitative disagreement between theory and experiment. After the ''beam splitting'' experiment at LCLS, it became clear that the conventional theory of synchrotron radiation cannot ensure the correct description of coherent and spontaneous emission from a kicked electron beam, nor the emission from a beam with finite angular divergence, in an undulator or a bending magnet. However, this result requires further experimental confirmation. In this publication we propose an uncomplicated and inexpensive experiment to test synchrotron radiation theory at 3rd generation light sources.

  18. The effect of near-infrared MLS laser radiation on cell membrane structure and radical generation.

    Science.gov (United States)

    Kujawa, Jolanta; Pasternak, Kamila; Zavodnik, Ilya; Irzmański, Robert; Wróbel, Dominika; Bryszewska, Maria

    2014-09-01

    The therapeutic effects of low-power laser radiation of different wavelengths and light doses are well known, but the biochemical mechanism of the interaction of laser light with living cells is not fully understood. We have investigated the effect of MLS (Multiwave Locked System) laser near-infrared irradiation on cell membrane structure, functional properties, and free radical generation using human red blood cells and breast cancer MCF-4 cells. The cells were irradiated with low-intensity MLS near-infrared (simultaneously 808 nm, continuous emission and 905 nm, pulse emission, pulse-wave frequency, 1,000 or 2,000 Hz) laser light at light doses from 0 to 15 J (average power density 212.5 mW/cm(2), spot size was 3.18 cm(2)) at 22 °C, the activity membrane bound acetylcholinesterase, cell stability, anti-oxidative activity, and free radical generation were the parameters used in characterizing the structural and functional changes of the cell. Near-infrared low-intensity laser radiation changed the acetylcholinesterase activity of the red blood cell membrane in a dose-dependent manner: There was a considerable increase of maximal enzymatic rate and Michaelis constant due to changes in the membrane structure. Integral parameters such as erythrocyte stability, membrane lipid peroxidation, or methemoglobin levels remained unchanged. Anti-oxidative capacity of the red blood cells increased after MLS laser irradiation. This irradiation induced a time-dependent increase in free radical generation in MCF-4 cells. Low-intensity near-infrared MLS laser radiation induces free radical generation and changes enzymatic and anti-oxidative activities of cellular components. Free radical generation may be the mechanism of the biomodulative effect of laser radiation.

  19. Radiative Effects of Aerosols Generated from Biomass Burning, Dust Storms, and Forest Fires

    Science.gov (United States)

    Christopher Sundar A.; Vulcan, Donna V.; Welch, Ronald M.

    1996-01-01

    Atmospheric aerosol particles, both natural and anthropogenic, are important to the earth's radiative balance. They scatter the incoming solar radiation and modify the shortwave reflective properties of clouds by acting as Cloud Condensation Nuclei (CCN). Although it has been recognized that aerosols exert a net cooling influence on climate (Twomey et al. 1984), this effect has received much less attention than the radiative forcings due to clouds and greenhouse gases. The radiative forcing due to aerosols is comparable in magnitude to current anthropogenic greenhouse gas forcing but opposite in sign (Houghton et al. 1990). Atmospheric aerosol particles generated from biomass burning, dust storms and forest fires are important regional climatic variables. A recent study by Penner et al. (1992) proposed that smoke particles from biomass burning may have a significant impact on the global radiation balance. They estimate that about 114 Tg of smoke is produced per year in the tropics through biomass burning. The direct and indirect effects of smoke aerosol due to biomass burning could add up globally to a cooling effect as large as 2 W/sq m. Ackerman and Chung (1992) used model calculations and the Earth Radiation Budget Experiment (ERBE) data to show that in comparison to clear days, the heavy dust loading over the Saudi Arabian peninsula can change the Top of the Atmosphere (TOA) clear sky shortwave and longwave radiant exitance by 40-90 W/sq m and 5-20 W/sq m, respectively. Large particle concentrations produced from these types of events often are found with optical thicknesses greater than one. These aerosol particles are transported across considerable distances from the source (Fraser et al. 1984). and they could perturb the radiative balance significantly. In this study, the regional radiative effects of aerosols produced from biomass burning, dust storms and forest fires are examined using the Advanced Very High Resolution Radiometer (AVHRR) Local Area

  20. A Broadband Metasurface-Based Terahertz Flat-Lens Array

    KAUST Repository

    Wang, Qiu; Zhang, Xueqian; Xu, Yuehong; Tian, Zhen; Gu, Jianqiang; Yue, Weisheng; Zhang, Shuang; Han, Jiaguang; Zhang, Weili; Zhang, Weili

    2015-01-01

    A metasurface-based terahertz flat-lens array is proposed, comprising C-shaped split-ring resonators exhibiting locally engineerable phase discontinuities. Possessing a high numerical aperture, the planar lens array is flexible, robust, and shows excellent focusing characteristics in a broadband terahertz frequency. It could be an important step towards the development of planar terahertz focusing devices for practical applications.

  1. A Broadband Metasurface-Based Terahertz Flat-Lens Array

    KAUST Repository

    Wang, Qiu

    2015-02-12

    A metasurface-based terahertz flat-lens array is proposed, comprising C-shaped split-ring resonators exhibiting locally engineerable phase discontinuities. Possessing a high numerical aperture, the planar lens array is flexible, robust, and shows excellent focusing characteristics in a broadband terahertz frequency. It could be an important step towards the development of planar terahertz focusing devices for practical applications.

  2. Metallic and 3D-printed dielectric helical terahertz waveguides.

    Science.gov (United States)

    Vogt, Dominik Walter; Anthony, Jessienta; Leonhardt, Rainer

    2015-12-28

    We investigate guidance of Terahertz (THz) radiation in metallic and 3D-printed dielectric helical waveguides in the frequency range from 0.2 to 1 THz. Our experimental results obtained from THz time-domain spectroscopy (THz-TDS) measurements are in very good agreement with finite-difference time-domain (FDTD) simulations. We observe single-mode, low loss and low dispersive propagation of THz radiation in metallic helical waveguides over a broad bandwidth. The 3D-printed dielectric helical waveguides have substantially extended the bandwidth of a low loss dielectric tube waveguide as observed from the experimental and simulation results. The high flexibility of the helical design allows an easy incorporation into bench top THz devices.

  3. Photonic quasi-crystal terahertz lasers

    Science.gov (United States)

    Vitiello, Miriam Serena; Nobile, Michele; Ronzani, Alberto; Tredicucci, Alessandro; Castellano, Fabrizio; Talora, Valerio; Li, Lianhe; Linfield, Edmund H.; Davies, A. Giles

    2014-12-01

    Quasi-crystal structures do not present a full spatial periodicity but are nevertheless constructed starting from deterministic generation rules. When made of different dielectric materials, they often possess fascinating optical properties, which lie between those of periodic photonic crystals and those of a random arrangement of scatterers. Indeed, they can support extended band-like states with pseudogaps in the energy spectrum, but lacking translational invariance, they also intrinsically feature a pattern of ‘defects’, which can give rise to critically localized modes confined in space, similar to Anderson modes in random structures. If used as laser resonators, photonic quasi-crystals open up design possibilities that are simply not possible in a conventional periodic photonic crystal. In this letter, we exploit the concept of a 2D photonic quasi crystal in an electrically injected laser; specifically, we pattern the top surface of a terahertz quantum-cascade laser with a Penrose tiling of pentagonal rotational symmetry, reaching 0.1-0.2% wall-plug efficiencies and 65 mW peak output powers with characteristic surface-emitting conical beam profiles, result of the rich quasi-crystal Fourier spectrum.

  4. A concept of a new undulator that will generate irrational higher harmonics in synchrotron radiation

    International Nuclear Information System (INIS)

    Hashimoto, Shinya; Sasaki, Shigemi

    1994-03-01

    A preliminary consideration has been made on an undulator with magnetic poles quasi-periodically aligned along the path of electron beams to discriminate the rational higher harmonics of radiation that are harmful in some synchrotron radiation experiments. The harmonics with irrational ratios in energy generated by the undulator is never simultaneously reflected by a crystal monochromator in the same orientation. A combination of the new undulator and high-resolution crystal monochromator is expected to be very useful on beamlines of high energy radiation in which X-ray mirrors are useless because of too small critical angles of total reflection. Further, a possibility of manufacturing the new undulator has been discussed. (author)

  5. Radiation field calculation in the vicinity of Russian radioisotope generator sources

    Energy Technology Data Exchange (ETDEWEB)

    Pretzsch, Gunter; Hummelsheim, Klemens; Bogorinski, Peter [Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH, Kurfuerstendamm 200, 10719 Berlin (Germany)

    2005-07-01

    Germany supports the Russian Federation in the framework of the G8 Global Partnership programme to secure nuclear and radioactive materials against misuse and proliferation. In this context, GRS, on behalf of the German Foreign Office, is coordinating activities to remove disused radioisotope thermoelectric generators (RITEG) from the Baltic Sea which serve as power supply for marine lighthouses and their replacement by alternative energy sources. Further the planned project includes transportation to an interim storage, the storage equipped with radiation monitoring and physical protection measures, later transportation for reprocessing to the Mayak Production Association, where the RITEG will be dismantled in a hot cell and encapsulated radioactive source will be vitrified and stored as radioactive waste. For the whole project safety analyses are to be performed e.g. to meet radiation protection requirements. In the present paper modelling and calculation of radiation fields in the vicinity of RITEG as a basis for safety analyses is reported. (authors)

  6. Terahertz spectroscopy of shift currents resulting from asymmetric (110)-oriented GaAs/AlGaAs quantum wells

    International Nuclear Information System (INIS)

    Priyadarshi, Shekhar; Leidinger, Markus; Pierz, Klaus; Racu, Ana M.; Siegner, Uwe; Bieler, Mark; Dawson, Philip

    2009-01-01

    We report the observation and the study of an additional shift current tensor element in (110)-oriented GaAs quantum wells, which arises from an out-of-plane asymmetry of the quantum well structure. The current resulting from this tensor element is optically induced with 150 fs laser pulses and detected by measuring the simultaneously emitted terahertz radiation. This terahertz spectroscopy of shift currents is a powerful technique for symmetry investigations, which shows, for example, that our nominally symmetric (110)-oriented GaAs/AlGaAs quantum wells grown by molecular beam epitaxy are in reality asymmetric structures with different right and left interfaces.

  7. Extreme UV harmonic production by free-electron generators of coherent radiation

    International Nuclear Information System (INIS)

    Ortega, J.M.

    1986-01-01

    The bunching phenomenon is the basic process occurring in a free-electron generator of coherent generation such as the Klystron in the mm-wave-length range or the free-electron laser (FEL) in the optical region. During interaction with the incident electromagnetic wave the electrons are progressively gathered into small packets separated by a length equal to its wavelength λ/sub L/. Once the electrons are bunched there is a given phase relationship between them and the field of any wave which wavelength is an harmonic of λ/sub L/. This is the source of the gain (electrons decelerated by the field) or of the absorption (electrons accelerated by the laser) mechanisms. In the FEL case the electrons are passing through an undulator (spatially varying periodic magnetic field). Since one uses high-energy electrons (E≅100-1000 MeV) they emit synchrotron radiation called in this case undulator radiation or spontaneous emission. This radiation coexists with the stimulated emission giving rise to the gain mechanism and to the FEL oscillation. When the electrons are bunched the spontaneous emission becomes coherent at the wavelength harmonic of λ/sub L/, and there is an increase in the emission intensity which ideally would be N/sub e/. (Number of electrons is typically ≅10/sup 10/.) Thus bursts of photons are emitted at frequencies harmonic of an incident wave which may be an external laser or the FEL itself. This is likely to extend the spectral range of the free-electron generation of coherent radiation toward the extreme UV λ<1000A). The advantages and limitations of the various solutions (linear or circular accelerator, FEL, or external laser) are discussed. The authors summarize the various experimental results obtained to date and the prospects for the synchrotron radiation dedicated ring super-ACO presently under construction at LURE at Orsay

  8. Radiation Environments and Exposure Considerations for the Multi-Mission Radioisotope Thermoelectric Generator

    International Nuclear Information System (INIS)

    Kelly, William M.; Low, Nora M.; Zillmer, Andrew; Johnson, Gregory A.; Normand, Eugene

    2006-01-01

    The Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) is the next generation (RTG) being developed by DOE to provide reliable, long-life electric power for NASA's planetary exploration programs. The MMRTG is being developed by Pratt and Whitney Rocketdyne and Teledyne Energy Systems Incorporated (TESI) for use on currently planned and projected flyby, orbital and planet landing missions. This is a significant departure from the design philosophy of the past which was to match specific mission requirements to RTG design capabilities. Undefined mission requirements provide a challenge to system designers by forcing them to put a design envelope around 'all possible missions'. These multi-mission requirements include internal and external radiation sources. Internal sources include the particles ejected by decaying Pu-238 and its daughters plus particles resulting from the interaction of these particles with other MMRTG materials. External sources include the full spectrum of charged particle radiation surrounding planets with magnetic fields and the surfaces of extraterrestrial objects not shielded by magnetic fields. The paper presents the results of investigations into the environments outlined above and the impact of radiation exposure on potential materials to be used on MMRTG and ground support personnel. Mission requirements were also reviewed to evaluate total integrated dose and to project potential shielding requirements for materials. Much of the information on mission shielding requirements was provided by NASA's Jet Propulsion Laboratory. The primary result is an ionizing radiation design curve which indicates the limits to which a particular mission can take the MMRTG in terms of ionizing radiation exposure. Estimates of personnel radiation exposure during ground handling are also provided

  9. Thermally radiative three-dimensional flow of Jeffrey nanofluid with internal heat generation and magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Shehzad, S.A., E-mail: ali_qau70@yahoo.com [Department of Mathematics, Comsats Institute of Information Technology, Sahiwal 57000 (Pakistan); Abdullah, Z. [Department of Mathematics, Comsats Institute of Information Technology, Sahiwal 57000 (Pakistan); Alsaedi, A. [Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Faculty of Science, King Abdulaziz University, P. O. Box 80257, Jeddah 21589 (Saudi Arabia); Abbasi, F.M. [Department of Mathematics, Comsats Institute of Information Technology, Islamabad 44000 (Pakistan); Hayat, T. [Nonlinear Analysis and Applied Mathematics (NAAM) Research Group, Faculty of Science, King Abdulaziz University, P. O. Box 80257, Jeddah 21589 (Saudi Arabia); Department of Mathematics, Quaid-I-Azam University 45320, Islamabad 44000 (Pakistan)

    2016-01-01

    This research work addresses the three-dimensional hydromagnetic flow of Jeffrey fluid with nanoparticles. Flow is generated by a bidirectional stretching surface. The effects of thermal radiation and internal heat generation are encountered in energy expressions. More realistic convective boundary conditions at the surface are employed instead of constant surface temperature and mass species conditions. Boundary layer assumptions lead to the governing non-linear mathematical model. Resulting equations through momentum, energy and mass species are made dimensionless using suitable variables. The solution expressions of dimensionless velocities, temperature and nanoparticle concentration have been computed for the convergent series solutions. The impacts of interesting parameters on the dimensionless quantities are displayed and interpreted. The values of physical quantities are computed and analyzed. - Highlights: • Three-dimensional hydromagnetic flow of Jeffrey nanofluid is considered. • Brownian motion and thermophoresis effects are encountered. • Heat transfer analysis is performed with thermal radiation. • Results are plotted and visualized.

  10. Charged lepton flavor violation in a class of radiative neutrino mass generation models

    Science.gov (United States)

    Chowdhury, Talal Ahmed; Nasri, Salah

    2018-04-01

    We investigate the charged lepton flavor violating processes μ →e γ , μ →e e e ¯, and μ -e conversion in nuclei for a class of three-loop radiative neutrino mass generation models with electroweak multiplets of increasing order. We find that, because of certain cancellations among various one-loop diagrams which give the dipole and nondipole contributions in an effective μ e γ vertex and a Z-penguin contribution in an effective μ e Z vertex, the flavor violating processes μ →e γ and μ -e conversion in nuclei become highly suppressed compared to μ →e e e ¯ process. Therefore, the observation of such a pattern in LFV processes may reveal the radiative mechanism behind neutrino mass generation.

  11. Experimental demonstration of ultrasensitive sensing with terahertz metamaterial absorbers: A comparison with the metasurfaces

    Energy Technology Data Exchange (ETDEWEB)

    Cong, Longqing; Singh, Ranjan, E-mail: ranjans@ntu.edu.sg [Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371 (Singapore); Centre for Disruptive Photonic Technologies, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371 (Singapore); Tan, Siyu [School of Electrical Engineering and Computer Science, Oklahoma State University, Stillwater, Oklahoma 87074 (United States); Key Lab of All Optical Network and Advanced Telecommunication Network of EMC, Institute of Lightwave Technology, Beijing Jiaotong University, Beijing 100044 (China); Yahiaoui, Riad [XLIM, Limoges University, CNRS, UMR 7252, 7 rue Jules Vallès, F-19100 Brive (France); Yan, Fengping [Key Lab of All Optical Network and Advanced Telecommunication Network of EMC, Institute of Lightwave Technology, Beijing Jiaotong University, Beijing 100044 (China); Zhang, Weili [School of Electrical Engineering and Computer Science, Oklahoma State University, Stillwater, Oklahoma 87074 (United States)

    2015-01-19

    Planar metasurfaces and plasmonic resonators have shown great promise for sensing applications across the electromagnetic domain ranging from the microwaves to the optical frequencies. However, these sensors suffer from lower figure of merit and sensitivity due to the radiative and the non-radiative loss channels in the plasmonic metamaterial systems. We demonstrate a metamaterial absorber based ultrasensitive sensing scheme at the terahertz frequencies with significantly enhanced sensitivity and an order of magnitude higher figure of merit compared to planar metasurfaces. Magnetic and electric resonant field enhancement in the impedance matched absorber cavity enables stronger interaction with the dielectric analyte. This finding opens up opportunities for perfect metamaterial absorbers to be applied as efficient sensors in the finger print region of the electromagnetic spectrum with several organic, explosive, and bio-molecules that have unique spectral signature at the terahertz frequencies.

  12. Terahertz Focusing and Polarization Control in Large-Area Bias-Free Semiconductor Emitters

    Science.gov (United States)

    Carthy, Joanna L.; Gow, Paul C.; Berry, Sam A.; Mills, Ben; Apostolopoulos, Vasilis

    2018-03-01

    We show that, when large-area multiplex terahertz semiconductor emitters, that work on diffusion currents and Schottky potentials, are illuminated by ultrashort optical pulses they can radiate a directional electromagnetic terahertz pulse which is controlled by the angular spectrum of the incident optical beam. Using the lens that focuses the incident near-infrared pulse, we have demonstrated THz emission focusing in free space, at the same point where the optical radiation would focus. We investigated the beam waist and Gouy phase shift of the THz emission as a function of frequency. We also show that the polarization profile of the emitted THz can be tailored by the metallic patterning on the semiconductor, demonstrating radial polarization when a circular emitter design is used. Our techniques can be used for fast THz beam steering and mode control for efficiently coupling to waveguides without the need for THz lenses or parabolic mirrors.

  13. The effect of therapeutic x-radiation on a sample of pacemaker generators

    International Nuclear Information System (INIS)

    Maxted, K.J.

    1984-01-01

    Tests were made on nineteen generators, comprising seventeen types from five manufacturers and including four programmable units, and x-ray energies of about 4 MeV. The bipolar generators suffered no measureable damage and radiotherapy patients using these would appear not to be exposed to any hazard. Nor were any of the generators using entirely CMOS circuitry, including the programmable types, affected. Generators using hybrid bipolar and CMOS circuitry were damaged by radiation exposure, the majority of these being Medtronic pacemakers. Transient recovery of function followed by total failure suggested that even a transient loss of function must be regarded as a precursor to permanent damage. This transient effect indicates that it is most likely the CMOS circuit element that is affected. (U.K.)

  14. New thermodynamics of entropy generation minimization with nonlinear thermal radiation and nanomaterials

    Science.gov (United States)

    Hayat, T.; Khan, M. Ijaz; Qayyum, Sumaira; Alsaedi, A.; Khan, M. Imran

    2018-03-01

    This research addressed entropy generation for MHD stagnation point flow of viscous nanofluid over a stretching surface. Characteristics of heat transport are analyzed through nonlinear radiation and heat generation/absorption. Nanoliquid features for Brownian moment and thermophoresis have been considered. Fluid in the presence of constant applied inclined magnetic field is considered. Flow problem is mathematically modeled and governing expressions are changed into nonlinear ordinary ones by utilizing appropriate transformations. The effects of pertinent variables on velocity, nanoparticle concentration and temperature are discussed graphically. Furthermore Brownian motion and thermophoresis effects on entropy generation and Bejan number have been examined. Total entropy generation is inspected through various flow variables. Consideration is mainly given to the convergence process. Velocity, temperature and mass gradients at the surface of sheet are calculated numerically.

  15. Terahertz Sensing, Imaging and Applications

    Energy Technology Data Exchange (ETDEWEB)

    Otani, C.; Hoshing, H.; Sasaki, Y.; Maki, K.; Hayashi, A. [RIKEN Advanced Science Institute, Sendai (Japan)

    2008-11-15

    Diagnosis using terahertz (THz) wave holds a great potential for various applications in various fields because of its transmittance to many soft materials with the good spatial resolution. In addition, the presence of specific spectral absorption features of crystalline materials is also important for many applications. Such features are different from material to material to material and is applicable for identifying materials inside packages that are opaque to visible light. One of the most impressive examples of such applications is the detection of illicit drugs inside envelopes. In this talk, we will present our recent topics of THz sensing, imaging and applications including this example. We will also present the cancer diagnosis, an application of the photonic crystal to high sensitivity detection, and gas spectroscopy if we have enough time. We also would like to briefly review the recent topics related to THz applications.

  16. Terahertz Sensing, Imaging and Applications

    International Nuclear Information System (INIS)

    Otani, C.; Hoshing, H.; Sasaki, Y.; Maki, K.; Hayashi, A.

    2008-01-01

    Diagnosis using terahertz (THz) wave holds a great potential for various applications in various fields because of its transmittance to many soft materials with the good spatial resolution. In addition, the presence of specific spectral absorption features of crystalline materials is also important for many applications. Such features are different from material to material to material and is applicable for identifying materials inside packages that are opaque to visible light. One of the most impressive examples of such applications is the detection of illicit drugs inside envelopes. In this talk, we will present our recent topics of THz sensing, imaging and applications including this example. We will also present the cancer diagnosis, an application of the photonic crystal to high sensitivity detection, and gas spectroscopy if we have enough time. We also would like to briefly review the recent topics related to THz applications

  17. Magnetic Field Generation through Angular Momentum Exchange between Circularly Polarized Radiation and Charged Particles

    CERN Document Server

    Shvets, G

    2002-01-01

    The interaction between circularly polarized (CP) radiation and charged particles can lead to generation of magnetic field through an inverse Faraday effect. The spin of the circularly polarized electromagnetic wave can be converted into the angular momentum of the charged particles so long as there is dissipation. We demonstrate this by considering two mechanisms of angular momentum absorption relevant for laser-plasma interactions: electron-ion collisions and ionization. The precise dissipative mechanism, however, plays a role in determining the efficiency of the magnetic field generation.

  18. Propagation and generation of Josephson radiation in superconductor/insulator superlattices

    International Nuclear Information System (INIS)

    Auvil, P.R.; Ketterson, J.B.

    1987-01-01

    The wave propagation and generation characteristics of a metal-insulator superlattice are calculated in a low-field Landau--Ginzburg model, including Josephson coupling through the insulating layers. It is shown that a significant increase in the phase velocity of the electromagnetic waves propagating in the superlattice occurs when the thickness of the superconducting layers becomes much less than the London penetration depth, suggesting that increased output of Josephson radiation may be achieved from such structures. Wave generation via the ac Josephson effect (in the presence of applied dc electric and magnetic fields) is studied for both parallel and series driven multilayer structures

  19. Design of Radiation-Tolerant Structural Alloys for Generation IV Nuclear Energy Systems

    Energy Technology Data Exchange (ETDEWEB)

    Allen, T.R.; Was, G.S.; Bruemmer, S.M.; Gan, J.; Ukai, S.

    2005-12-28

    The objective of this program is to improve the radiation tolerance of both austenitic and ferritic-martensitic (F-M) alloys projected for use in Generation IV systems. The expected materials limitations of Generation IV components include: creep strength, dimensional stability, and corrosion/stress corrosion compatibility. The material design strategies to be tested fall into three main categories: (1) engineering grain boundaries; (2) alloying, by adding oversized elements to the matrix; and (3) microstructural/nanostructural design, such as adding matrix precipitates. These three design strategies were tested across both austenitic and ferritic-martensitic alloy classes

  20. Magnetic Field Generation through Angular Momentum Exchange between Circularly Polarized Radiation and Charged Particles

    International Nuclear Information System (INIS)

    G. Shvets; N.J. Fisch; J.-M. Rax

    2002-01-01

    The interaction between circularly polarized (CP) radiation and charged particles can lead to generation of magnetic field through an inverse Faraday effect. The spin of the circularly polarized electromagnetic wave can be converted into the angular momentum of the charged particles so long as there is dissipation. We demonstrate this by considering two mechanisms of angular momentum absorption relevant for laser-plasma interactions: electron-ion collisions and ionization. The precise dissipative mechanism, however, plays a role in determining the efficiency of the magnetic field generation