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Sample records for intense terahertz radiation

  1. Intense terahertz radiation and their applications

    NASA Astrophysics Data System (ADS)

    Hafez, H. A.; Chai, X.; Ibrahim, A.; Mondal, S.; Férachou, D.; Ropagnol, X.; Ozaki, T.

    2016-09-01

    In this paper, we will review both past and recent progresses in the generation, detection and application of intense terahertz (THz) radiation. We will restrict the review to laser based intense few-cycle THz sources, and thus will not include sources such as synchrotron-based or narrowband sources. We will first review the various methods used for generating intense THz radiation, including photoconductive antennas (PCAs), optical rectification sources (especially the tilted-pulse-front lithium niobate source and the DAST source, but also those using other crystals), air plasma THz sources and relativistic laser–plasma sources. Next, we will give a brief introduction on the common methods for coherent THz detection techniques (namely the PCA technique and the electro-optic sampling), and point out the limitations of these techniques for measuring intense THz radiation. We will then review three techniques that are highly suited for detecting intense THz radiation, namely the air breakdown coherent detection technique, various single-shot THz detection techniques, and the spectral-domain interferometry technique. Finally, we will give an overview of the various applications that have been made possible with such intense THz sources, including nonlinear THz spectroscopy of condensed matter (optical-pump/THz-probe, THz-pump/THz-probe, THz-pump/optical-probe), nonlinear THz optics, resonant and non-resonant control of material (such as switching of superconductivity, magnetic and polarization switching) and controlling the nonlinear response of metamaterials. We will also provide a short perspective on the future of intense THz sources and their applications.

  2. Intense terahertz radiation and their applications

    NASA Astrophysics Data System (ADS)

    Hafez, H. A.; Chai, X.; Ibrahim, A.; Mondal, S.; Férachou, D.; Ropagnol, X.; Ozaki, T.

    2016-09-01

    In this paper, we will review both past and recent progresses in the generation, detection and application of intense terahertz (THz) radiation. We will restrict the review to laser based intense few-cycle THz sources, and thus will not include sources such as synchrotron-based or narrowband sources. We will first review the various methods used for generating intense THz radiation, including photoconductive antennas (PCAs), optical rectification sources (especially the tilted-pulse-front lithium niobate source and the DAST source, but also those using other crystals), air plasma THz sources and relativistic laser-plasma sources. Next, we will give a brief introduction on the common methods for coherent THz detection techniques (namely the PCA technique and the electro-optic sampling), and point out the limitations of these techniques for measuring intense THz radiation. We will then review three techniques that are highly suited for detecting intense THz radiation, namely the air breakdown coherent detection technique, various single-shot THz detection techniques, and the spectral-domain interferometry technique. Finally, we will give an overview of the various applications that have been made possible with such intense THz sources, including nonlinear THz spectroscopy of condensed matter (optical-pump/THz-probe, THz-pump/THz-probe, THz-pump/optical-probe), nonlinear THz optics, resonant and non-resonant control of material (such as switching of superconductivity, magnetic and polarization switching) and controlling the nonlinear response of metamaterials. We will also provide a short perspective on the future of intense THz sources and their applications.

  3. Investigation of the Frohlich hypothesis with high intensity terahertz radiation

    NASA Astrophysics Data System (ADS)

    Weightman, Peter

    2014-03-01

    This article provides an update to recent reviews of the Frohlich hypothesis that biological organisation is facilitated by the creation of coherent excited states driven by a flow of free energy provided by metabolic processes and mediated by molecular motions in the terahertz range. Sources of intense terahertz radiation have the potential to test this hypothesis since if it is true the growth and development of sensitive systems such as stem cells should be influenced by irradiation with intense terahertz radiation. A brief survey of recent work shows that it is not yet possible to make an assessment of the validity of the Frohlich hypothesis. Under some conditions a variety of cell types respond to irradiation with intense THz radiation in ways that involve changes in the activity of their DNA. In other experiments very intense and prolonged THz radiation has no measureable effect on the behavior of very sensitive systems such as stem cells. The wide variation in experimental conditions makes it impossible to draw any conclusions as to characteristics of THz radiation that will induce a response in living cells. It is possible that in environments suitable for their maintenance and growth cells are capable of compensating for any effects caused by exposure to THz radiation up to some currently unknown level of THz peak power.

  4. Terahertz radiation from a wire target irradiated by an ultra-intense laser pulse

    SciTech Connect

    Li Zhichao; Zheng Jian

    2007-05-15

    When an ultra-intense laser pulse impacts the tip of a wire whose other end is grounded, a strong return current can be driven along the wire because some energetic electrons generated in ultra-intense laser matter interaction can escape from the target and an electric field builds up. The wire then behaves like a current-carrying antenna that can emit electromagnetic radiations. If the duration of the driving pulse is several tens of femtoseconds, the radiation spectrum reaches a maximum at terahertz region, and the radiation power per solid angle could be as high as 10{sup 9} W/rad.

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

    SciTech Connect

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

    2015-09-28

    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.

  6. Intense terahertz pulses from SLAC electron beams using coherent transition radiation

    SciTech Connect

    Wu Ziran; Fisher, Alan S.; Hogan, Mark; Loos, Henrik; Goodfellow, John; Fuchs, Matthias; Daranciang, Dan; Lindenberg, Aaron

    2013-02-15

    SLAC has two electron accelerators, the Linac Coherent Light Source (LCLS) and the Facility for Advanced Accelerator Experimental Tests (FACET), providing high-charge, high-peak-current, femtosecond electron bunches. These characteristics are ideal for generating intense broadband terahertz (THz) pulses via coherent transition radiation. For LCLS and FACET respectively, the THz pulse duration is typically 20 and 80 fs RMS and can be tuned via the electron bunch duration; emission spectra span 3-30 THz and 0.5 THz-5 THz; and the energy in a quasi-half-cycle THz pulse is 0.2 and 0.6 mJ. The peak electric field at a THz focus has reached 4.4 GV/m (0.44 V/A) at LCLS. This paper presents measurements of the terahertz pulses and preliminary observations of nonlinear materials response.

  7. Generation of Intense Narrow-Band Tunable Terahertz Radiation from Highly Bunched Electron Pulse Train

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

    We present the analysis and start-to-end simulation of an intense narrow-band terahertz (THz) source with a broad tuning range of radiation frequency, using a single-pass free electron laser (FEL) driven by a THz-pulse-train photoinjector. The fundamental radiation frequency, corresponding to the spacing between the electron microbunches, can be easily tuned by varying the spacing time between the laser micropulses. Since the prebunched electron beam is highly bunched at the first several harmonics, with the harmonic generation technique, the radiation frequency range can be further enlarged by several times. The start-to-end simulation results show that this FEL is capable of generating a few tens megawatts power, several tens micro-joules pulse energy, and a few percent bandwidth at the frequencies of 0.5-5 THz. In addition, several practical issues are considered.

  8. Observation of intense terahertz-wave coherent synchrotron radiation at LEBRA

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

    We observed intense coherent synchrotron radiation (CSR) in the terahertz region using an S-band linac at the Laboratory for Electron Beam Research and Application at Nihon University. The evolution of the CSR power was measured, and the CSR reflected in the vacuum chamber of the bending magnet could be extracted through the quartz window for a few tens of picoseconds. The long wave packet of the delayed CSR in the autocorrelation suggests that the delayed CSR was the non-resonant ring-down of the vacuum chamber of the bending magnet. To design a high-energy accelerator, it is necessary to decrease high-energy photons resulting from Compton backscattering with intense CSR.

  9. Electronic response of graphene to an ultrashort intense terahertz radiation pulse

    NASA Astrophysics Data System (ADS)

    Ishikawa, Kenichi L.

    2013-05-01

    We have recently reported a study (Ishikawa 2010 Phys. Rev. B 82 201402) on a nonlinear optical response of graphene to a normally incident terahertz radiation pulse within the massless Dirac fermion (MDF) picture, where we have derived physically transparent graphene Bloch equations (GBE). Here we extend it to the tight-binding (TB) model and oblique incidence. The derived equations indicate that interband transitions are governed by the temporal variation of the spinor phase along the electron path in the momentum space and predominantly take place when the electron passes near the Dirac point. At normal incidence, the equations for electron dynamics within the TB model can be cast into the same form of GBE as for the MDF model. At oblique incidence, the equations automatically incorporate photon drag and satisfy the continuity equation for electron density. Single-electron dynamics strongly depend on the model and pulse parameters, but the rapid variations are averaged out after momentum-space integration. Direct current remaining after the pulse is generated in graphene irradiated by an intense monocycle terahertz pulse, even if it is linearly polarized and normally incident. The generated current depends on the carrier-envelope phase, pulse intensity and Fermi energy in a complex manner.

  10. A self-consistent regime of generation of terahertz radiation by an optical pulse with a tilted intensity front

    SciTech Connect

    Bugai, A N; Sazonov, S V; Shashkov, Andrei Yu

    2012-11-30

    We derived a self-consistent system of nonlinear wave equations describing the terahertz generation in dielectric uniaxial crystals by optical pulsed radiation with a tilted wavefront. The numerical analysis of the system of equations showed that the generation of a broadband one-period terahertz signal is accompanied by a red shift of the carrier frequency of the optical pulse, the magnitude of the shift being proportional to the pulse intensity. The generation efficiency with respect to energy reached a maximum at a certain distance of propagation in the crystal, after which the efficiency decreased. A satisfactory agreement was obtained between theoretical calculations and experimental data of other investigations. (generation of terahertz radiation)

  11. Nonlinear radiation response of n-doped indium antimonide and indium arsenide in intense terahertz field

    NASA Astrophysics Data System (ADS)

    Gong, Jiao-Li; Liu, Jin-Song; Chu, Zheng; Yang, Zhen-Gang; Wang, Ke-Jia; Yao, Jian-Quan

    2016-10-01

    The nonlinear radiation responses of two different n-doped bulk semiconductors: indium antimonide (InSb) and indium arsenide (InAs) in an intense terahertz (THz) field are studied by using the method of ensemble Monte Carlo (EMC) at room temperature. The results show that the radiations of two materials generate about 2-THz periodic regular spectrum distributions under a high field of 100 kV/cm at 1-THz center frequency. The center frequencies are enhanced to about 7 THz in InSb, and only 5 THz in InAs, respectively. The electron valley occupancy and the percentage of new electrons excited by impact ionization are also calculated. We find that the band nonparabolicity and impact ionization promote the generation of nonlinear high frequency radiation, while intervalley scattering has the opposite effect. Moreover, the impact ionization dominates in InSb, while impact ionization and intervalley scattering work together in InAs. These characteristics have potential applications in up-convension of THz wave and THz nonlinear frequency multiplication field. Project supported by the National Natural Science Foundation of China (Grant Nos. 11574105 and 61177095), the Natural Science Foundation of Hubei Province, China (Grant Nos. 2012FFA074 and 2013BAA002), the Wuhan Municipal Applied Basic Research Project, China (Grant No. 20140101010009), and the Fundamental Research Funds for the Central Universities, China (Grant Nos. 2013KXYQ004 and 2014ZZGH021).

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

    NASA Astrophysics Data System (ADS)

    Sei, Norihiro; Zen, Heishun; Ohgaki, Hideaki

    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.

  13. Electron beam requirements for a three-dimensional Smith-Purcell backward-wave oscillator for intense terahertz radiation.

    SciTech Connect

    Kim, K.-J.; Kumar, V.; Accelerator Systems Division; Raja Ramanna Center for Advanced Tech.

    2007-08-01

    A Smith-Purcell device can operate as a backward-wave oscillator for intense, narrow-bandwidth, continuous wave radiation at terahertz wavelengths. We determine the requirements on electron beam current and emittance for the system to oscillate based on a three-dimensional extension of our previous two-dimensional analysis. It is found that specially designed electron beams are required with a current that exceeds a certain threshold value and a flat transverse profile that allows the beam to travel very close to the grating surface. Two methods for producing electron beams with the required characteristics are discussed.

  14. Effects of nuclear motion on the ionization-induced terahertz radiation of H2+ in intense few-cycle laser pulses

    NASA Astrophysics Data System (ADS)

    Xue, Shan; Du, Hongchuan; Xia, Yue; Hu, Bitao

    2015-07-01

    We examine the residual current to investigate the conversion efficiency from the few-cycle laser pulse into the terahertz radiation of H2+ by solving the time-dependent Schrödinger equation in the non-Born-Oppenheimer approach. It is found that the nuclear motion and high vibrational states will improve the optical-to-terahertz conversion efficiency significantly, while with the increasing of the laser intensity, ionization saturation will suppress the effects of moving nuclei. Moreover, based on the dependence of the residual current on the delay time of the nuclear vibration, we conclude that the terahertz signal may serve as a tool to probe the nuclear dynamics.

  15. Terahertz radiation mixer

    DOEpatents

    Wanke, Michael C.; Allen, S. James; Lee, Mark

    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.

  16. Emission of terahertz radiations from fractal antennas

    NASA Astrophysics Data System (ADS)

    Miyamaru, F.; Saito, Y.; Takeda, M. W.; Liu, L.; Hou, B.; Wen, W.; Sheng, Ping

    2009-11-01

    We investigate the emission of terahertz radiation from a photoconductive fractal antenna fabricated on a semi-insulating gallium arsenide substrate. Owing to the self-similarity of fractal structures, our fractal antenna shows a multiband emission of terahertz radiation. The emission intensity at peak frequency is about twice that from a bow-tie antenna. We also investigate the mechanism of the multiband emission by using the finite-difference time-domain calculation.

  17. Effects of laser-plasma interactions on terahertz radiation from solid targets irradiated by ultrashort intense laser pulses

    SciTech Connect

    Li Chun; Zhou Mulin; Ding Wenjun; Du Fei; Liu Feng; Li Yutong; Wang Weimin; Ma Jinglong; Chen Liming; Lu Xin; Dong Quanli; Wang Zhaohua; Wei Zhiyi; Sheng Zhengming; Zhang Jie; Lou Zheng; Shi Shengcai

    2011-09-15

    Interactions of 100-fs laser pulses with solid targets at intensities of 10{sup 18} W/cm{sup 2} and resultant terahertz (THz) radiation are studied under different laser contrast ratio conditions. THz emission is measured in the specular reflection direction, which appears to decrease as the laser contrast ratio varies from 10{sup -8} to 10{sup -6}. Correspondingly, the frequency spectra of the reflected light are observed changing from second harmonic dominant, three-halves harmonic dominant, to vanishing of both harmonics. Two-dimensional particle-in-cell simulation also suggests that this observation is correlated with the plasma density scale length change. The results demonstrate that the THz emission is closely related to the laser-plasma interaction processes. The emission is strong when resonance absorption is a key feature of the interaction, and becomes much weaker when parametric instabilities dominate.

  18. Absorber for terahertz radiation management

    DOEpatents

    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.

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

    SciTech Connect

    Gayduchenko, I. E-mail: gefedorov@mail.ru; Kardakova, A.; Voronov, B.; Finkel, M.; Fedorov, G. E-mail: gefedorov@mail.ru; Jiménez, D.; Morozov, S.; Presniakov, M.; Goltsman, G.

    2015-11-21

    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.

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

    NASA Astrophysics Data System (ADS)

    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

    2013-01-01

    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.

  1. Terahertz radiation from a laser plasma filament

    SciTech Connect

    Wu, H.-C.; Meyer-ter-Vehn, J.; Ruhl, H.; Sheng, Z.-M.

    2011-03-15

    By the use of two-dimensional particle-in-cell simulations, we clarify the terahertz (THz) radiation mechanism from a plasma filament formed by an intense femtosecond laser pulse. The nonuniform plasma density of the filament leads to a net radiating current for THz radiation. This current is mainly located within the pulse and the first cycle of the wakefield. As the laser pulse propagates, a single-cycle and radially polarized THz pulse is constructively built up forward. The single-cycle shape is mainly due to radiation damping effect.

  2. Excitation of coherent terahertz radiation by stimulated Raman scatterings

    SciTech Connect

    Liu, Z. J.; He, X. T.; Zheng, C. Y.; Zhu Shaoping; Cao, L. H.; Wang Yugang

    2010-02-15

    The excitation of terahertz radiation by stimulated Raman scattering is considered. Vlasov-Maxwell numerical simulations show that powerful terahertz radiation can be produced by cascade Raman scatterings.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    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.

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

    PubMed

    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 >10(15) W/cm(2). We demonstrate the following. (i) With two-color pulses, photoionization prevails in the generation of GV/m THz fields up to 10(17) W/cm(2) 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

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

    PubMed Central

    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

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

    PubMed

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

    2016-06-03

    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 >10(15) W/cm(2). We demonstrate the following. (i) With two-color pulses, photoionization prevails in the generation of GV/m THz fields up to 10(17) W/cm(2) 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.

  7. Plasmonic terahertz detector response at high intensities

    NASA Astrophysics Data System (ADS)

    Gutin, A.; Kachorovskii, V.; Muraviev, A.; Shur, M.

    2012-07-01

    Recent work on plasmonic terahertz detection using field effect transistors (FETs) has yielded detectors with high responsivity. Therefore, deviation from small signal mode of operation, when the detector signal is simply proportional to the THz intensity, must be considered. This work presents a new analytical model to predict terahertz response in a FET at arbitrary intensity levels. The proposed analytical model was experimentally validated using a 0.13 μm InGaAs high electron mobility transistor and optically pumped CO2 gas laser operating at 1.63 THz of varying output intensities. The model is suitable for implementation in circuit simulators and might be used for device optimization and THz circuit design.

  8. Direct detector for terahertz radiation

    DOEpatents

    Wanke, Michael C.; Lee, Mark; Shaner, Eric A.; Allen, S. James

    2008-09-02

    A direct detector for terahertz radiation comprises a grating-gated field-effect transistor with one or more quantum wells that provide a two-dimensional electron gas in the channel region. The grating gate can be a split-grating gate having at least one finger that can be individually biased. Biasing an individual finger of the split-grating gate to near pinch-off greatly increases the detector's resonant response magnitude over prior QW FET detectors while maintaining frequency selectivity. The split-grating-gated QW FET shows a tunable resonant plasmon response to FIR radiation that makes possible an electrically sweepable spectrometer-on-a-chip with no moving mechanical optical parts. Further, the narrow spectral response and signal-to-noise are adequate for use of the split-grating-gated QW FET in a passive, multispectral terahertz imaging system. The detector can be operated in a photoconductive or a photovoltaic mode. Other embodiments include uniform front and back gates to independently vary the carrier densities in the channel region, a thinned substrate to increase bolometric responsivity, and a resistive shunt to connect the fingers of the grating gate in parallel and provide a uniform gate-channel voltage along the length of the channel to increase the responsivity and improve the spectral resolution.

  9. Overview of terahertz radiation sources.

    SciTech Connect

    Gallerano, G. P.; Biedron, S. G.; Energy Systems; ENEA

    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.

  10. Coherent and tunable terahertz radiation from graphene surface plasmon polaritons excited by an electron beam

    SciTech Connect

    Liu, Shenggang Hu, Min; Chen, Xiaoxing; Zhang, Ping; Gong, Sen; Zhao, Tao; Zhong, Renbin; Zhang, Chao

    2014-05-19

    Although surface plasmon polaritons (SPPs) resonance in graphene can be tuned in the terahertz regime, transforming such SPPs into coherent terahertz radiation has not been achieved. Here, we propose a graphene-based coherent terahertz radiation source with greatly enhanced intensity. The radiation works at room temperature, it is tunable and can cover the whole terahertz regime. The radiation intensity generated with this method is 400 times stronger than that from SPPs at a conventional dielectric or semiconducting surface and is comparable to that from the most advanced photonics source such as a quantum cascade laser. The physical mechanism for this strong radiation is presented. The phase diagrams defining the parameters range for the occurrence of radiation is also shown.

  11. Impact of terahertz radiation on the epithelialization rate of scarified cornea

    NASA Astrophysics Data System (ADS)

    Geyko, I. A.; Smolyanskaya, O. A.; Sulatsky, M. I.; Parakhuda, S. E.; Sedykh, E. A.; Odlyanitskiy, E. L.; Khodzitsky, M. K.; Zabolotniy, A. G.

    2015-07-01

    We revealed that after exposure of scarified cornea of rabbits to low-intensity pulsed terahertz radiation 0.1 to 1.8 THz a positive effect on epithelization triggered within the first hours was higher compared to non-irradiated cornea. However, while elevating power of terahertz radiation up to 60.8 nW it resulted in retarding epithelialization process. At that, irradiation did not affect timeframe of complete corneal epithelialization. During experiments it was found that terahertz radiation was well tolerated, exhibited no toxic and allergic reactions or resulted in pathohistological changes in the eye tissues. Also, low-intensity terahertz radiation did not affect normal physiological functions of the eyes and facilitated to re-epithelialization of scarified eyes in rabbits.

  12. Quadrupole radiation from terahertz dipole antennas.

    PubMed

    Rudd, J V; Johnson, J L; Mittleman, D M

    2000-10-15

    We report what is to our knowledge the first detailed investigation of the polarization state of radiation from lens-coupled terahertz dipole antennas. The radiation exhibits a weak but measurable component that is polarized orthogonally to the orientation of the emitter dipole. The angular radiation pattern of this cross-polarized emission reveals that it is quadrupolar, rather than dipolar, in nature. One can understand this result by taking into account the photocurrent flowing in the strip lines that feed the dipole antenna. A Fresnel-Kirchhoff scalar diffraction calculation is used for calculating the frequency-dependent angular distribution of the radiation pattern, providing satisfactory agreement with the measurements. PMID:18066277

  13. Sources of Coherent Terahertz Radiation

    NASA Astrophysics Data System (ADS)

    Bratman, Vladimir L.; Bandurkin, Ilya V.; Dumesh, Boris S.; Fedotov, Alexei E.; Kalynov, Yury K.; Kolganov, Nikolay G.; Manuilov, Vladimir N.; Rusin, Fedor S.; Samsonov, Sergey V.; Savilov, Andrey V.

    2006-01-01

    New results in the field of high-frequency gyrotrons, gyro-multipliers and orotrons allow one to consider these electron devices as promising candidates for the realization of powerful and available sources in Terahertz range. Electron beams with a very high compression of up to a factor of 4,400 have been obtained and selective generation at the 1st-5th cyclotron harmonics have been demonstrated in Large Orbit Gyrotrons (LOGs) at millimeter and submillimeter wavelengths at operating voltages from 50 to 250 kV. When operating at the third cyclotron harmonic (TE3,8 and TE3,9 modes in the first oscillator; TE3,5 mode in the second oscillator) output power levels of 10-20 kW have been obtained in the frequency range of 0.37-0.41 THz. Gyro-multipliers with self-exciting low-frequency sections are proposed and studied theoretically. Low-voltage orotrons have been demonstrated in the frequency range of 0.1-0.4 THz with output powers of 1.0-0.1 W and typical electrical-mechanical frequency tunability within an octave range. Using the same voltage, orotrons can achieve higher power and frequency stability within the entire Terahertz range compared with BWOs that are the most widespread devices at these frequencies.

  14. Strong emission of terahertz radiation from nanostructured Ge surfaces

    SciTech Connect

    Kang, Chul; Maeng, Inhee; Kee, Chul-Sik; Leem, Jung Woo; Yu, Jae Su; Kim, Tae Heon; Lee, Jong Seok

    2015-06-29

    Indirect band gap semiconductors are not efficient emitters of terahertz radiation. Here, we report strong emission of terahertz radiation from germanium wafers with nanostructured surfaces. The amplitude of THz radiation from an array of nano-bullets (nano-cones) is more than five (three) times larger than that from a bare-Ge wafer. The power of the terahertz radiation from a Ge wafer with an array of nano-bullets is comparable to that from n-GaAs wafers, which have been widely used as a terahertz source. We find that the THz radiation from Ge wafers with the nano-bullets is even more powerful than that from n-GaAs for frequencies below 0.6 THz. Our results suggest that introducing properly designed nanostructures on indirect band gap semiconductor wafers is a simple and cheap method to improve the terahertz emission efficiency of the wafers significantly.

  15. Generation of coherent terahertz radiation in ultrafast laser-gas interactions

    SciTech Connect

    Kim, Ki-Yong

    2009-05-15

    The generation of intense terahertz radiation in ultrafast laser-gas interactions is studied on a basis of transient electron current model. When an ultrashort pulse laser's fundamental and its second harmonic fields are mixed to ionize a gas, a nonvanishing, directional photoelectron current can be produced, which simultaneously emits terahertz radiation in the far field. Here, the generation mechanism is examined with an analytic derivation and numerical simulations, in which tunneling ionization and subsequent electron motion in the combined laser field play a key role. In the simulations, three types of laser-gas interactions are considered: (i) mixing the fundamental and its second harmonic fields, (ii) mixing nonharmonic, two-color fields, and (iii) focusing single-color, few-cycle pulses. In these interactions, terahertz generation and other nonlinear effects driven by the transient current are investigated. In particular, anticorrelation between terahertz and second (or third) harmonic generation is observed and analyzed.

  16. Direct acoustic phonon excitation by intense and ultrashort terahertz pulses

    NASA Astrophysics Data System (ADS)

    Manceau, J.-M.; Loukakos, P. A.; Tzortzakis, S.

    2010-12-01

    We report on the direct and resonant excitation of acoustic phonons in an AlGaAs intrinsic semiconductor using intense coherent and single cycle terahertz pulses created by two-color femtosecond laser pulse filamentation in air. While the electrons are left unperturbed, we follow the lattice dynamics with time-delayed optical photons tuned to the interband transition.

  17. Propagation of Terahertz Radiation in Porous Polymer and Ceramic Materials

    NASA Astrophysics Data System (ADS)

    Dodson, Caroline; Spicer, James; Fitch, Michael; Schuster, Paul; Osiander, Robert

    2005-04-01

    In this work we investigate the propagation of terahertz radiation through polyurethane foam and porous alumina ceramics to understand the effects of structure on the optical properties of these materials at terahertz frequencies. A terahertz time domain system with a GaAs photoconductive emitter and a ZnTe electro-optic crystal was used to generate and detect the transmitted terahertz signal. Using the amplitude and phase characteristics of these signals, the thickness, index of refraction, and other physical and optical properties of the materials were determined.

  18. Elliptically polarized terahertz radiation from a chiral oxide

    SciTech Connect

    Takeda, R.; Kida, N. Sotome, M.; Okamoto, H.

    2015-09-28

    Polarization control of terahertz wave is a challenging subject in terahertz science and technology. Here, we report a simple method to control polarization state of the terahertz wave in terahertz generation process. At room temperature, terahertz radiation from a noncentrosymmetric and chiral oxide, sillenite Bi{sub 12}GeO{sub 20}, is observed by the irradiation of linearly polarized femtosecond laser pulses at 800 nm. The polarization state of the emitted terahertz wave is found to be elliptic with an ellipticity of ∼0.37 ± 0.10. Furthermore, the ellipticity was altered to a nearly zero (∼0.01 ± 0.01) by changing the polarization of the incident linearly polarized femtosecond laser pulses. Such a terahertz radiation characteristic is attributable to variation of the polarization state of the emitted terahertz waves, which is induced by retardation due to the velocity mismatch between the incident femtosecond laser pulse and generated terahertz wave and by the polarization tilting due to the optical activity at 800 nm.

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

    NASA Astrophysics Data System (ADS)

    Angeluts, A. A.; Gapeyev, A. B.; Esaulkov, M. N.; Kosareva, O. G.; Matyunin, S. N.; Nazarov, M. M.; Pashovkin, T. N.; Solyankin, P. M.; Cherkasova, O. P.; Shkurinov, A. P.

    2014-03-01

    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-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.

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

    SciTech Connect

    Angeluts, A A; Esaulkov, M N; Kosareva, O G; Solyankin, P M; Shkurinov, A P; Gapeyev, A B; Pashovkin, T N; Matyunin, S N; Nazarov, M M; Cherkasova, O P

    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)

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

    PubMed

    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.

  2. Laser beat wave excitation of terahertz radiation in a plasma slab

    SciTech Connect

    Chauhan, Santosh; Parashar, Jetendra

    2014-10-15

    Terahertz (THz) radiation generation by nonlinear mixing of lasers, obliquely incident on a plasma slab is investigated. Two cases are considered: (i) electron density profile is parabolic but density peak is below the critical density corresponding to the beat frequency, (ii) plasma boundaries are sharp and density is uniform. In both cases, nonlinearity arises through the ponderomotive force that gives rise to electron drift at the beat frequency. In the case of inhomogeneous plasma, non zero curl of the nonlinear current density gives rise to electromagnetic THz generation. In case of uniform plasma, the sharp density variation at the plasma boundaries leads to radiation generation. In a slab width of less than a terahertz wavelength, plasma density one fourth of terahertz critical density, laser intensities ∼10{sup 17 }W/cm{sup 2} at 1 μm, one obtains the THz intensity ∼1 GW/cm{sup 2} at 3 THz radiation frequency.

  3. High-intensity terahertz pulses and their applications

    NASA Astrophysics Data System (ADS)

    Budiarto, Edward Wibowo

    1997-09-01

    A large aperture transmitter based on an electrically biased photoconductor has been constructed, which is capable of generating ultrashort high-intensity pulses operating in the far-infrared (terahertz) frequency regime. The terahertz pulse is a single-cycle freely propagating electrical pulse with a 600 femtosecond pulse duration and a pulse energy close to 200 nanojoules. A complete characterization of the transmitter and its output pulse has been conducted, resulting in new understandings of the pulse generation mechanism and propagation behavior. More specifically, it was revealed for the first time that near-field diffraction plays a significant role in the propagation behavior of the terahertz pulse from the large aperture transmitter. The pulse alters its temporal shape significantly as it travels away from the transmitter, especially when it is focused by a parabolic mirror. The high-intensity pulse is intended to be utilized as a probe of high-field transport properties of free carriers in semiconductors and superconductors. The transient dynamics of hot-electrons in silicon and gallium arsenide are of particular interest, as they relate to current issues in modern electronic devices. A simulation model has been developed which predicts a nonlinear absorption of the terahertz pulses by free-electrons in the semiconductors due to velocity saturation effects. The high-intensity terahertz pulse has also been used to probe the nonlinear electrodynamics of high-T c superconductors. The results confirm the ability of the pulse to break pairs of superconducting electrons and convert them to normal state electrons. This will allow further studies to be conducted to resolve the exact pair-breaking mechanism, which is ultimately linked to a better understanding of some of the failure mechanisms in today's superconducting microwave devices.

  4. Binding Energies of Hydrogen-Like Impurities in a Semiconductor in Intense Terahertz Laser Fields

    NASA Astrophysics Data System (ADS)

    Nie, J. L.; Xu, W.; Lin, L. B.

    We present a detailed theoretical study of the influence of linearly polarized intense terahertz (THz) laser radiation on energy states of hydrogen-like impurities in semiconductors. The dependence of the binding energy for ground (1s) and first excited (2s) states, E1s and E2s, on the intensity and the frequency of the THz radiation has been examined for a GaAs-based system. It is found that E1s, E2s and E2s-E1s decrease with increasing radiation intensity or with decreasing radiation frequency, which implies that an intense THz field can enhance ionization of dopants in semiconductors. Our analytical and numerical results show that one of the most important results obtained by A. L. A. Fonseca et al. [Phys. Stat. Sol. (b) 186, K57 (1994)] is incorrect.

  5. Terahertz plasmonic laser radiating in an ultra-narrow beam

    DOE PAGES

    Wu, Chongzhao; Khanal, Sudeep; Reno, John L.; Kumar, Sushil

    2016-07-07

    Plasmonic lasers (spasers) generate coherent surface plasmon polaritons (SPPs) and could be realized at subwavelength dimensions in metallic cavities for applications in nanoscale optics. Plasmonic cavities are also utilized for terahertz quantum-cascade lasers (QCLs), which are the brightest available solid-state sources of terahertz radiation. A long standing challenge for spasers that are utilized as nanoscale sources of radiation, is their poor coupling to the far-field radiation. Unlike conventional lasers that could produce directional beams, spasers have highly divergent radiation patterns due to their subwavelength apertures. Here, we theoretically and experimentally demonstrate a new technique for implementing distributed feedback (DFB) thatmore » is distinct from any other previously utilized DFB schemes for semiconductor lasers. The so-termed antenna-feedback scheme leads to single-mode operation in plasmonic lasers, couples the resonant SPP mode to a highly directional far-field radiation pattern, and integrates hybrid SPPs in surrounding medium into the operation of the DFB lasers. Experimentally, the antenna-feedback method, which does not require the phase matching to a well-defined effective index, is implemented for terahertz QCLs, and single-mode terahertz QCLs with a beam divergence as small as 4°×4° are demonstrated, which is the narrowest beam reported for any terahertz QCL to date. Moreover, in contrast to a negligible radiative field in conventional photonic band-edge lasers, in which the periodicity follows the integer multiple of half-wavelengths inside the active medium, antenna-feedback breaks this integer limit for the first time and enhances the radiative field of the lasing mode. Terahertz lasers with narrow-beam emission will find applications for integrated as well as standoff terahertz spectroscopy and sensing. Furthermore, the antenna-feedback scheme is generally applicable to any plasmonic laser with a Fabry–Perot cavity

  6. Radiation from laser accelerated electron bunches: Coherent terahertz and femtosecond X-rays

    SciTech Connect

    Leemans, W.P.; Esarey, E.; van Tilborg, J.; Michel, P.A.; Schroeder, C.B.; Toth, Cs.; Geddes, C.G.R.; Shadwick, B.A.

    2004-10-01

    Electron beam based radiation sources provide electromagnetic radiation for countless applications. The properties of the radiation are primarily determined by the properties of the electron beam. Compact laser driven accelerators are being developed that can provide ultra-short electron bunches (femtosecond duration) with relativistic energies reaching towards a GeV. The electron bunches are produced when an intense laser interacts with a dense plasma and excites a large amplitude plasma density modulation (wakefield) that can trap background electrons and accelerate them to high energies. The short pulse nature of the accelerated bunches and high particle energy offer the possibility of generating radiation from one compact source that ranges from coherent terahertz to gamma rays. The intrinsic synchronization to a laser pulse and unique character of the radiation offers a wide range of possibilities for scientific applications. Two particular radiation source regimes are discussed: Coherent terahertz emission and x-ray emission based on betatron oscillations and Thomson scattering.

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

    PubMed

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

    2015-07-20

    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.

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

    PubMed Central

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

    2015-01-01

    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. PMID:26190043

  9. Dependence of terahertz power from laser-produced plasma on laser intensity

    NASA Astrophysics Data System (ADS)

    Shin, J.-H.; Zhidkov, A.; Jin, Z.; Hosokai, T.; Kodama, R.

    2012-07-01

    Power of terahertz radiation from plasma which is generated from air irradiated by coupled (ω, 2ω) femtosecond laser pulses is analyzed for high laser intensities, for which non-linear plasma effects on the pulse propagation become essential, with multidimensional particle-in-cell simulations including the self-consistent plasma kinetics. The growth rate of THz power becomes slower as the laser intensity increases. A reason of such a lowering of efficiency in THz emission is found to be ionization of air by the laser pulse, which results in poor focusing of laser pulses.

  10. Temperature-dependent terahertz magnetic dipole radiation from antiferromagnetic GdFeO{sub 3} ceramics

    SciTech Connect

    Fu, Xiaojian; Xi, Xiaoqing; Bi, Ke; Zhou, Ji

    2013-11-18

    Temperature-dependent terahertz magnetic dipole radiation in antiferromagnetic GdFeO{sub 3} ceramic is investigated both theoretically and experimentally in this work. A two-level quantum transition mechanism is introduced to describe the excitation-radiation process, and radiative lifetime is derived analytically from the change of spin state density during this process. Terahertz spectral measurements demonstrate that the radiative frequency exhibits a red-shift and lifetime shortens as temperature increases, which is in good agreement with theoretical predictions. The temperature-sensitive radiative frequency and excellent terahertz emission mean that the antiferromagnetic ceramics show potential for application in terahertz sensors and frequency-tunable terahertz lasers.

  11. Terahertz radiation generation by nonlinear mixing of two laser beams over a thin foil

    SciTech Connect

    Chauhan, Santosh; Parashar, J.

    2015-07-31

    Terahertz radiation generation via nonlinear mixing of two laser beams incident over a thin metal foil is explored. The lasers exert a ponderomotive force on the electrons of metal foil at beat frequency which lies in the terahertz range. The metal foil acts as antenna, producing terahertz radiations, highly directional in nature.

  12. Resonant terahertz radiation from warm collisional inhomogeneous plasma irradiated by two Gaussian laser beams

    NASA Astrophysics Data System (ADS)

    Niknam, A. R.; Banjafar, M. R.; Jahangiri, F.; Barzegar, S.; Massudi, R.

    2016-05-01

    Terahertz (THz) radiation generation by the interaction of two co-propagating high intensity laser beams with a warm collisional inhomogeneous plasma is analytically investigated. By presenting the dielectric permittivity of plasma and taking into account the ponderomotive force, the nonlinear current at THz frequency is obtained. A secondary resonant enhancement of THz radiation is observed, in addition to that occurs at the plasma frequency, which can be tuned by plasma density and temperature. Moreover, we show that for each beat frequency, there exists an optimum temperature at which THz radiation is maximized. It is also shown that the power and efficiency of THz radiation decrease by increasing the collision frequency.

  13. Intense tera-hertz laser driven proton acceleration in plasmas

    NASA Astrophysics Data System (ADS)

    Sharma, A.; Tibai, Z.; Hebling, J.

    2016-06-01

    We investigate the acceleration of a proton beam driven by intense tera-hertz (THz) laser field from a near critical density hydrogen plasma. Two-dimension-in-space and three-dimension-in-velocity particle-in-cell simulation results show that a relatively long wavelength and an intense THz laser can be employed for proton acceleration to high energies from near critical density plasmas. We adopt here the electromagnetic field in a long wavelength (0.33 THz) regime in contrast to the optical and/or near infrared wavelength regime, which offers distinct advantages due to their long wavelength ( λ = 350 μ m ), such as the λ 2 scaling of the electron ponderomotive energy. Simulation study delineates the evolution of THz laser field in a near critical plasma reflecting the enhancement in the electric field of laser, which can be of high relevance for staged or post ion acceleration.

  14. Nonlinear photoresponse of field effect transistors terahertz detectors at high irradiation intensities

    SciTech Connect

    But, D. B.; Drexler, C.; Ganichev, S. D.; Sakhno, M. V.; Sizov, F. F.; Dyakonova, N.; Drachenko, O.; Gutin, A.; Knap, W.

    2014-04-28

    Terahertz power dependence of the photoresponse of field effect transistors, operating at frequencies from 0.1 to 3 THz for incident radiation power density up to 100 kW/cm{sup 2} was studied for Si metal–oxide–semiconductor field-effect transistors and InGaAs high electron mobility transistors. The photoresponse increased linearly with increasing radiation intensity up to the kW/cm{sup 2} range. Nonlinearity followed by saturation of the photoresponse was observed for all investigated field effect transistors for intensities above several kW/cm{sup 2}. The observed photoresponse nonlinearity is explained by nonlinearity and saturation of the transistor channel current. A theoretical model of terahertz field effect transistor photoresponse at high intensity was developed. The model explains quantitative experimental data both in linear and nonlinear regions. Our results show that dynamic range of field effect transistors is very high and can extend over more than six orders of magnitudes of power densities (from ∼0.5 mW/cm{sup 2} to ∼5 kW/cm{sup 2})

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

    PubMed Central

    2016-01-01

    Summary 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. PMID:27547615

  16. Generation of terahertz radiation by hot electrons in carbon nanotubes.

    PubMed

    Kibis, O V; da Costa, M Rosenau; Portnoi, M E

    2007-11-01

    We demonstrate theoretically that quasi-metallic carbon nanotubes emit terahertz radiation induced by an applied voltage. It is shown that in the ballistic transport regime their spontaneous emission spectra have a universal frequency and bias voltage dependence, which raises the possibility of utilizing this effect for high-frequency nanoelectronic devices.

  17. Terahertz radiation in alkali vapor plasmas

    SciTech Connect

    Sun, Xuan; Zhang, X.-C.

    2014-05-12

    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.

  18. An introduction to medical imaging with coherent terahertz frequency radiation.

    PubMed

    Fitzgerald, A J; Berry, E; Zinovev, N N; Walker, G C; Smith, M A; Chamberlain, J M

    2002-04-01

    Methods have recently been developed that make use of electromagnetic radiation at terahertz (THz) frequencies, the region of the spectrum between millimetre wavelengths and the infrared, for imaging purposes. Radiation at these wavelengths is non-ionizing and subject to far less Rayleigh scatter than visible or infrared wavelengths, making it suitable for medical applications. This paper introduces THz pulsed imaging and discusses its potential for in vivo medical applications in comparison with existing modalities.

  19. Enhance the terahertz Smith-Purcell superradiant radiation by using dielectric loaded grating

    SciTech Connect

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

    2015-08-15

    A dielectric loaded grating (DLG) for terahertz Smith-Purcell (SP) device is proposed to enhance the radiation intensity. By using the theoretical analysis and particle-in-cell simulations, the dispersion characteristics and SP superradiant radiation are investigated. Compared with the general metal grating, the usage of DLG can improve the magnitude of electric field and, consequently, strengthen the interaction of the evanescent wave with electron beam, which can improve the growth rate, enhance the SP superradiant radiation, and lower the start current for the operation of SP free-electron laser.

  20. Study of terahertz intensity dependence on time resolved dynamic fringes in the interferometric autocorrelation setup

    NASA Astrophysics Data System (ADS)

    Venkatesh, M.; Chaudhary, A. K.

    2014-10-01

    Terahertz signal is generated from Low temperature gallium arsenide photoconductive dipole antennas (gap = 5μm, length = 20μm) by focusing 15 fs laser pulses and applying 12V DC across it. Terahertz intensity is detected by Pyroelectric detector (THZ1.5MB-USB). The collinear autocorrelation arrangement provides dynamic fringes which are allowed to be incident on photoconductive antennas to study the variation in terahertz intensity with respect to delay between laser pulses. Interestingly, the profile of THz intensity variation was similar to interferometric autocorrelation signal of laser pulses. The THz power attenuation with its propagation distance in atmosphere was measured.

  1. Higgs mode excitation in superconductors by intense terahertz pulse

    NASA Astrophysics Data System (ADS)

    Matsunaga, Ryusuke; Shimano, Ryo

    2016-05-01

    Recent development of intense terahertz (THz) pulse generation technique has offered novel opportunities to reveal ultrafast phenomena in a variety of materials on tabletop experiments and provided a new pathway toward ultrafast control of quantum phases. Here we present our recent study of nonequilibrium dynamics in metallic superconductors NbN excited by intense THz pulse. Since the superconducting gap energy is located in the THz frequency range, the intense THz pulse excitation makes it possible to instantaneously excite high-density quasiparticles at the gap edge without injecting excess energies. It has also become possible to coherently drive the superconducting ground state without exciting incoherent quasiparticles by tuning the pump frequency below the gap energy. The ultrafast dynamics of the order parameter induced by such an intense low energy excitation is directly probed, and the nature of a collective excitation, namely the Higgs amplitude mode, is revealed. Efficient THz higher-harmonic generation from a superconductor is discovered, manifesting the nonlinear coupling between the THz wave and the Higgs mode. We also report the experimental results in a multi-gap superconductor MgB2.

  2. [Terahertz radiations application of nitrogen oxide frequencies for correction of antioxidant properties of blood and lipid peroxidation in the conditions of stress].

    PubMed

    Kirichuk, B F; Tsymbal, A A

    2010-02-01

    The effect of terahertz radiations of oxide nitrogen 150.176-150.664 GHz frequencies on intensity of lipid peroxidation processes and antioxidant properties of the white rat blood in stress condition was studied. It was shown that under terahertz radiations 150.176-150.664 GHz its effect in the form of full normalization of the lipid peroxidation processes flow and functional activity of antioxidants against a background of stress in white rats was observed. PMID:20432719

  3. Field Intensity Detection of Individual Terahertz Pulses at 80 MHz Repetition Rate

    NASA Astrophysics Data System (ADS)

    Rettich, F.; Vieweg, N.; Cojocari, O.; Deninger, A.

    2015-07-01

    We present a new approach to detect the intensity of individual terahertz pulses at repetition rates as high as 80 MHz. Our setup comprises a femtosecond fiber laser, an InGaAs-based terahertz emitter, a zero-bias Schottky detector, and a high-speed data acquisition unit. The detected pulses consist of two lobes with half-widths of 1-2 ns, which is much shorter than the inverse repetition rate of the laser. The system lends itself for high-speed terahertz transmission measurements, e.g., to study wetting dynamics in real time.

  4. Heat Induced Damage Detection by Terahertz (THz) Radiation

    NASA Astrophysics Data System (ADS)

    Rahani, Ehsan Kabiri; Kundu, Tribikram; Wu, Ziran; Xin, Hao

    2011-06-01

    Terahertz (THz) and sub-terahertz imaging and spectroscopy are becoming increasingly popular nondestructive evaluation techniques for damage detection and characterization of materials. THz radiation is being used for inspecting ceramic foam tiles used in TPS (Thermal Protection System), thick polymer composites and polymer tiles that are not good conductors of ultrasonic waves. Capability of THz electromagnetic waves in detecting heat induced damage in porous materials is investigated in this paper. Porous pumice stone blocks are subjected to long time heat exposures to produce heat induced damage in the block. The dielectric properties extracted from THz TDS (Time Domain Spectroscopy) measurements are compared for different levels of heat exposure. Experimental results show noticeable and consistent change in dielectric properties with increasing levels of heat exposure, well before its melting point.

  5. Numerical and simulation study of terahertz radiation generation by laser pulses propagating in the extraordinary mode in magnetized plasma

    SciTech Connect

    Jha, Pallavi; Kumar Verma, Nirmal

    2014-06-15

    A one-dimensional numerical model for studying terahertz radiation generation by intense laser pulses propagating, in the extraordinary mode, through magnetized plasma has been presented. The direction of the static external magnetic field is perpendicular to the polarization as well as propagation direction of the laser pulse. A transverse electromagnetic wave with frequency in the terahertz range is generated due to the presence of the magnetic field. Further, two-dimensional simulations using XOOPIC code show that the THz fields generated in plasma are transmitted into vacuum. The fields obtained via simulation study are found to be compatible with those obtained from the numerical model.

  6. Electrical Switching of Terahertz Radiation on Vanadium Dioxide Thin Film Fabricated with Nano Antennas

    NASA Astrophysics Data System (ADS)

    Jeong, Y. G.; Bernien, H.; Kyoung, J. S.; Kim, H. S.; Park, H. R.; Kim, B. J.; Kim, T.; Kim, D. S.

    2011-12-01

    Electrical switching of terahertz radiation through nano antennas on VO2 thin film is demonstrated and is compared with bare VO2. Rectangular apertures act as slot antennas which attract terahertz radiation when VO2 is in semi-conducting state. These antennas are turned-off when VO2 becomes metallic by bias, giving an enhanced control of transmission.

  7. Generation of terahertz radiation by focusing femtosecond bichromatic laser pulses in a gas or plasma

    SciTech Connect

    Chizhov, P A; Volkov, Roman V; Bukin, V V; Ushakov, A A; Garnov, Sergei V; Savel'ev-Trofimov, Andrei B

    2013-04-30

    The generation of terahertz radiation by focusing two-frequency femtosecond laser pulses is studied. Focusing is carried out both in an undisturbed gas and in a pre-formed plasma. The energy of the terahertz radiation pulses is shown to reduce significantly in the case of focusing in a plasma. (extreme light fields and their applications)

  8. Bursts of Terahertz Radiation from Large-Scale Plasmas Irradiated by Relativistic Picosecond Laser Pulses

    NASA Astrophysics Data System (ADS)

    Liao, G. Q.; Li, Y. T.; Li, C.; Su, L. N.; Zheng, Y.; Liu, M.; Wang, W. M.; Hu, Z. D.; Yan, W. C.; Dunn, J.; Nilsen, J.; Hunter, J.; Liu, Y.; Wang, X.; Chen, L. M.; Ma, J. L.; Lu, X.; Jin, Z.; Kodama, R.; Sheng, Z. M.; Zhang, J.

    2015-06-01

    Powerful terahertz (THz) radiation is observed from large-scale underdense preplasmas in front of a solid target irradiated obliquely with picosecond relativistic intense laser pulses. The radiation covers an extremely broad spectrum with about 70% of its energy located in the high frequency regime over 10 THz. The pulse energy of the radiation is found to be above 1 0 0 μ J per steradian in the laser specular direction at an optimal preplasma scale length around 40 - 50 μ m . Particle-in-cell simulations indicate that the radiation is mainly produced by linear mode conversion from electron plasma waves, which are excited successively via stimulated Raman scattering instability and self-modulated laser wakefields during the laser propagation in the preplasma. This radiation can be used not only as a powerful source for applications, but also as a unique diagnostic of parametric instabilities of laser propagation in plasmas.

  9. Tunable Circularly Polarized Terahertz Radiation from Magnetized Gas Plasma.

    PubMed

    Wang, W-M; Gibbon, P; Sheng, Z-M; Li, Y-T

    2015-06-26

    It is shown, by simulation and theory, that circularly or elliptically polarized terahertz radiation can be generated when a static magnetic (B) field is imposed on a gas target along the propagation direction of a two-color laser driver. The radiation frequency is determined by √[ω(p)(2)+ω(c)(2)/4]+ω(c)/2, where ω(p) is the plasma frequency and ω(c) is the electron cyclotron frequency. With the increase of the B field, the radiation changes from a single-cycle broadband waveform to a continuous narrow-band emission. In high-B-field cases, the radiation strength is proportional to ω(p)(2)/ω(c). The B field provides a tunability in the radiation frequency, spectrum width, and field strength.

  10. Distinguishing of different kinds of gunpowder using various methods based on terahertz radiation

    NASA Astrophysics Data System (ADS)

    Gavenda, Tomáš; Křesálek, Vojtěch

    2014-10-01

    This article provides information about using terahertz radiation based methods such as time-domain spectroscopy, ATR spectroscopy and terahertz reflection imaging for distinguishing of different kinds of gunpowder. The findings in this article prove that gunpowder does not have any sharp peaks in terahertz region of electromagnetic spectrum up to 2.5 THz, but also prove that distinguishing of different kinds of gunpowder is possible using different methods based on terahertz radiation. All presented results are connected to absorbance of gunpowder and other measured materials, because comparison of absorbance analysis is essential for distinguishing of gunpowder samples.

  11. Gamma radiation field intensity meter

    DOEpatents

    Thacker, L.H.

    1994-08-16

    A gamma radiation intensity meter measures dose rate of a radiation field. The gamma radiation intensity meter includes a tritium battery emitting beta rays generating a current which is essentially constant. Dose rate is correlated to an amount of movement of an electroscope element charged by the tritium battery. Ionizing radiation decreases the voltage at the element and causes movement. A bleed resistor is coupled between the electroscope support element or electrode and the ionization chamber wall electrode. 4 figs.

  12. Gamma radiation field intensity meter

    DOEpatents

    Thacker, Louis H.

    1994-01-01

    A gamma radiation intensity meter measures dose rate of a radiation field. The gamma radiation intensity meter includes a tritium battery emitting beta rays generating a current which is essentially constant. Dose rate is correlated to an amount of movement of an electroscope element charged by the tritium battery. Ionizing radiation decreases the voltage at the element and causes movement. A bleed resistor is coupled between the electroscope support element or electrode and the ionization chamber wall electrode.

  13. Gamma radiation field intensity meter

    DOEpatents

    Thacker, Louis H.

    1995-01-01

    A gamma radiation intensity meter measures dose rate of a radiation field. The gamma radiation intensity meter includes a tritium battery emitting beta rays generating a current which is essentially constant. Dose rate is correlated to an amount of movement of an electroscope element charged by the tritium battery. Ionizing radiation decreases the voltage at the element and causes movement. A bleed resistor is coupled between the electroscope support element or electrode and the ionization chamber wall electrode.

  14. Gamma radiation field intensity meter

    DOEpatents

    Thacker, L.H.

    1995-10-17

    A gamma radiation intensity meter measures dose rate of a radiation field. The gamma radiation intensity meter includes a tritium battery emitting beta rays generating a current which is essentially constant. Dose rate is correlated to an amount of movement of an electroscope element charged by the tritium battery. Ionizing radiation decreases the voltage at the element and causes movement. A bleed resistor is coupled between the electroscope support element or electrode and the ionization chamber wall electrode. 4 figs.

  15. Interaction of Terahertz Radiation with Ferroelectrics

    NASA Astrophysics Data System (ADS)

    Nelson, Keith

    2007-03-01

    Ferroelectric crystals have long been used as acoustic transducers and receivers. An extensive toolset has been developed for MHz-frequency acoustic wave generation, control, guidance, and readout. In recent years, an analogous toolset has been developed for terahertz wave transduction and detection. Femtosecond optical pulses irradiate ferroelectric crystals to generate responses in the 0.1-5 THz frequency range that are admixtures of electromagnetic and polar lattice vibrational excitations called phonon-polaritons. Spatiotemporal femtosecond pulse shaping may be used to generate additional optical pulses that arrive at specified times and sample locations for control and manipulation of the THz waves. Femtosecond laser machining may be used for fabrication of waveguides, resonators, and other structures that are integrated into the ferroelectric host crystal. Finally, real-space imaging of the THz fields can be executed with variably delayed femtosecond probe pulses, permitting direct visualization of THz wave spatial and temporal evolution. This ``polaritonics'' toolset enables multiplexed generation of arbitrary THz waveforms and use of the waveforms within the ferroelectric host crystal or after projection into free space or an adjacent medium. The polaritonics platform will be reviewed and several new developments and applications will be presented. These include spectroscopy of relaxor ferroelectrics, whose temperature-dependent dielectric responses in the GHz-THz regime reveal complex polarization dynamics on well separated fast and slow time scales; direct measurement of phonon-polariton lattice vibrational displacements through femtosecond time-resolved x-ray diffraction; generation of high polariton field amplitudes and pulse energies; use of large-amplitude polariton waves to drive nonlinear lattice vibrational responses; and enhancement of optical-to-THz conversion efficiency through a pseudo-phase-matching approach that circumvents the very large

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

    PubMed

    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.

  17. Optically- and Electrically-Stimulated Terahertz Radiation Emission from Indium Nitride

    NASA Astrophysics Data System (ADS)

    Wilke, Ingrid; Ding, Yujie J.; Shubina, Tatiana V.

    2012-06-01

    Indium nitride is a novel narrow band gap semiconductor. The material is a potential strong source of terahertz frequency electromagnetic radiation with applications in time-domain terahertz spectroscopy and imaging systems. This article reviews recent experimental research on terahertz emission from the binary compound semiconductor indium nitride excited by near-infrared laser beams or microseconds electrical pulses. Advantages of indium nitride as terahertz radiation source material are discussed. It is demonstrated that different mechanisms contribute to the emission of terahertz radiation from indium nitride. The emission of up to 2.4 μW of THz radiation power is observed when InN is excited with near-infrared femtosecond laser pulses at an average power of 1 W.

  18. Multimode terahertz-wave generation using coherent Cherenkov radiation

    SciTech Connect

    Kan, K.; Yang, J.; Ogata, A.; Kondoh, T.; Norizawa, K.; Yoshida, Y.

    2011-12-05

    Multimode terahertz(THz)-wave generation using coherent Cherenkov radiation (CCR) was investigated. The frequency spectra of CCR, which utilized a metal-wrapped hollow dielectric tube of 7 mm outer radius and a picosecond electron bunch of 27 MeV beam energy, were measured by a Michelson interferometer with a 4.2 K silicon bolometer. In this study, discrete spectral components at frequencies of 0.09, 0.14, and 0.36 THz were observed experimentally and explained as transverse magnetic (TM) modes of TM{sub 03}, TM{sub 04}, and TM{sub 09}, respectively, according to a theoretical calculation for the tube.

  19. Photocurrent-based detection of terahertz radiation in graphene

    SciTech Connect

    Tomadin, Andrea Tredicucci, Alessandro; Vitiello, Miriam S.; Polini, Marco; Pellegrini, Vittorio

    2013-11-18

    Graphene is a promising candidate for the development of detectors of Terahertz (THz) radiation. A well-known detection scheme due to Dyakonov and Shur exploits plasma waves in a field-effect transistor (FET), whereby a dc photovoltage is generated in response to a THz field. In the quest for devices with a better signal-to-noise ratio, we theoretically investigate a plasma-wave photodetector in which a dc photocurrent is generated in a graphene FET. The noise equivalent power of our device is shown to be much smaller than that of a Dyakonov-Shur detector in a wide spectral range.

  20. Metamaterial radiation from attenuated total reflection at terahertz frequencies

    NASA Astrophysics Data System (ADS)

    Ramani, Suchitra

    The focus of this research was to explore the behavior of two-dimensional planar metamaterials or metafilms and understand the various excitation schemes for application of metafilms to Terahertz-Attenuated Total Reflection spectroscopy (THz-ATR). A standard THz time domain spectroscopy system based on photoconductive switches was modified to implement the ATR technique. Finite metamaterial arrays with varying singly- split ring resonator sizes were excited in the Kretschmann ATR configuration using finite sized terahertz beams. Numerical approaches using commercial software were looked into to explain the experimental observations. Various theoretical models were used to explain the observed phenomena. The ATR measurements showed an unexpected strengthening of the resonance when the metafilm sample was illuminated near the edge. This phenomenon referred to in this study as "the anomalous edge enhancement" was observed strongly in metafilms with closely spaced rings. A re-radiation signal was observed across the total internal reflection barrier where no signal is expected. It consisted of two peaks one at the fundamental metamaterial resonance and the second peak was due to the periodicity of the metafilm array. The anomalous behavior seen in the ATR measurements is attributed to the edge currents at the boundary of the metafilm array giving rise to this re-radiation signal. Results from analytic treatments based on Floquet method and method of moments were able to qualitatively model the measurements. The observed re-radiation signal is a potential loss mechanism that could impact observations from commonly used transmission measurements on metamaterials.

  1. Theoretical foundations of detection of terahertz radiation in laser-plasma interactions

    SciTech Connect

    Frolov, A. A.

    2013-02-15

    A theory is developed enabling one to calculate the temporal profile and spectrum of a terahertz wave packet from the energy of the second harmonic of optical radiation generated during the nonlinear interaction between terahertz and circularly polarized laser pulses in the skin layer of an overdense plasma. It is shown that the spectral and temporal characteristics of the envelope of the second harmonic of optical radiation coincide with those of the terahertz pulse only at small durations of the detecting laser radiation. For long laser pulses, the temporal profile and spectrum of the second harmonic are mainly determined by the characteristics of optical radiation at the carrier frequency.

  2. Terahertz waves radiated from two noncollinear femtosecond plasma filaments

    SciTech Connect

    Du, Hai-Wei; Hoshina, Hiromichi; Otani, Chiko; Midorikawa, Katsumi

    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.

  3. Theory of a laser-plasma method for detecting terahertz radiation

    SciTech Connect

    Frolov, A. A.; Borodin, A. V.; Esaulkov, M. N.; Kuritsyn, I. I.; Shkurinov, A. P.

    2012-06-15

    A theory is developed for calculating the spectrum and the shape of a terahertz wave packet from the temporal profile of the energy of the second harmonic of the laser field generated during nonlinear interaction of laser and terahertz pulses in an optical-breakdown plasma. The spectral and temporal characteristics of the second-harmonic envelope and a terahertz pulse are shown to coincide only for short laser pulses. For long laser pulses, the second-harmonic spectral line shifts to the red and its temporal profile is determined by the time integral of the electric field of terahertz radiation.

  4. Advantage of terahertz radiation versus X-ray to detect hidden organic materials in sealed vessels

    NASA Astrophysics Data System (ADS)

    Bessou, Maryelle; Duday, Henri; Caumes, Jean-Pascal; Salort, Simon; Chassagne, Bruno; Dautant, Alain; Ziéglé, Anne; Abraham, Emmanuel

    2012-10-01

    Terahertz imaging and conventional X-ray have been used to investigate a sealed Ancient Egyptian jar preserved at the Museum of Aquitaine (France). Terahertz radiation revealed an unknown content that could not have been visualized by X-ray. By comparison with a model object, we concluded that this content was composed of organic materials explaining their relative radiolucency.

  5. Principle of Terahertz Radiation Using Electron Beams

    NASA Astrophysics Data System (ADS)

    Shin, Young-Min; Choi, Eun-Mi; Park, Gun-Sik

    This part introduces high power THz coherent radiation sources that take advantage of free electron beams. Following a description of characteristics on vacuum electron devices (VEDs), fundamental radiation principle of beam-wave interaction is explained with specifying their types and applications. Conventional high power microwave VEDs such as klystrons, TWTs, gyrotrons, and FELs are described in their technical perspectives with brief overview of device characteristics. Addressing technical challenges on up-conversion-to-THz of conventional approach, this part explores the state-of-the-art micro-VEDs considered for modern THz applications such as communication, imaging, sensing, spectroscopy, and so on, which are combined with modern microfabrication technologies. Novel MEMS techniques to microminiaturize RF components such as electron gun and RF interaction circuits are also presented.

  6. Highly efficient terahertz radiation from a thin foil irradiated by a high-contrast laser pulse

    NASA Astrophysics Data System (ADS)

    Jin, Z.; Zhuo, H. B.; Nakazawa, T.; Shin, J. H.; Wakamatsu, S.; Yugami, N.; Hosokai, T.; Zou, D. B.; Yu, M. Y.; Sheng, Z. M.; Kodama, R.

    2016-09-01

    Radially polarized intense terahertz (THz) radiation behind a thin foil irradiated by ultrahigh-contrast ultrashort relativistic laser pulse is recorded by a single-shot THz time-domain spectroscopy system. As the thickness of the target is reduced from 30 to 2 µm, the duration of the THz emission increases from 5 to over 20 ps and the radiation energy increases dramatically, reaching ˜10.5 mJ per pulse, corresponding to a laser-to-THz radiation energy conversion efficiency of 1.7 % . The efficient THz emission can be attributed to reflection (deceleration and acceleration) of the laser-driven hot electrons by the target-rear sheath electric field. The experimental results are consistent with that of a simple model as well as particle-in-cell simulation.

  7. Terahertz radiation from a laser bunched relativistic electron beam in a magnetic wiggler

    SciTech Connect

    Kumar, Manoj; Tripathi, V. K.

    2012-07-15

    We develop a formalism for tunable coherent terahertz radiation generation from a relativistic electron beam, modulated by two laser beams, as it passes through a magnetic wiggler of wave vector k{sub w}z-caret. The lasers exert a beat frequency ponderomotive force on beam electrons, and modulate their velocity. In the drift space, velocity modulation translates into density modulation. As the beam bunches pass through the wiggler, they acquire a transverse velocity, constituting a transverse current that acts as an antenna to produce coherent THz radiation, when {omega}{sub 1}-{omega}{sub 2}=k{sub w}c/(cos{theta}-v{sub 0b}/c), where {omega}{sub 1}, {omega}{sub 2} are the frequencies of the lasers, v{sub 0b}z-caret is the beam velocity, and {theta} is the direction of maximum radiated intensity with respect to the direction of propagation of the beam.

  8. Air nonlinear dynamics initiated by ultra-intense lambda-cubic terahertz pulses

    SciTech Connect

    Shalaby, Mostafa E-mail: christoph.hauri@psi.ch; Hauri, Christoph P. E-mail: christoph.hauri@psi.ch

    2015-05-04

    We report on the measurement of the instantaneous Kerr nonlinearity and the retarded alignment of air molecules CO{sub 2}, N{sub 2}, and O{sub 2} triggered by an intense, lambda-cubic terahertz pulse, a diffraction- and transform-limited single-cycle pulse. The strong-field, impulsive low-frequency excitation (3.9 THz) leads to field-free alignment dynamics of these molecules thanks to the terahertz-induced transient dipole moments in the otherwise non-polar molecules. The strong coupling to the terahertz electric transient results in the excitation of coherent large amplitude long-living rotational states at room temperature and ambient pressure. Beyond fundamental investigations of nonlinear properties in gases, our results suggest a route towards field-free molecular alignment at laser intensity well below the ionization threshold.

  9. Terahertz Radiation from a Pipe with Small Corrugations

    SciTech Connect

    Bane, K.L.F.; Stupakov, G.; /SLAC

    2012-01-26

    We have studied through analytical and numerical methods the use of a relativistic electron bunch to drive a metallic beam pipe with small corrugations for the purpose of generating terahertz radiation. For the case of a pipe with dimensions that do not change along its length, we have shown that - with reasonable parameters - one can generate a narrow-band radiation pulse with frequency {approx}1 THz, and total energy of a few milli-Joules. The pulse length tends to be on the order of tens of picoseconds. We have also shown that, if the pipe radius is tapered along its length, the generated pulse will end up with a frequency chirp; if the pulse is then made to pass through a compressor, its final length can be reduced to a few picoseconds and its peak power increased to 1 GW. We have also shown that wall losses tend to be significant and need to be included in the structure design.

  10. High-performing nonlinear visualization of terahertz radiation on a silicon charge-coupled device

    PubMed Central

    Shalaby, Mostafa; Vicario, Carlo; Hauri, Christoph P.

    2015-01-01

    Photoinduced electron transitions can lead to significant changes of the macroscopic electronic properties in semiconductors. This principle is responsible for the detection of light with charge-coupled devices. Their spectral sensitivity is limited by the semiconductor bandgap which has restricted their visualization capabilities to the optical, ultraviolet, and X-ray regimes. The absence of an imaging device in the low frequency terahertz range has severely hampered the advance of terahertz imaging applications in the past. Here we introduce a high-performing imaging concept to the terahertz range. On the basis of a silicon charge-coupled device we visualize 5–13 THz radiation with photon energy under 2% of the sensor's band-gap energy. The unprecedented small pitch and large number of pixels allow the visualization of complex terahertz radiation patterns in real time and with high spatial detail. This advance will have a great impact on a wide range of terahertz imaging disciplines. PMID:26496973

  11. Electro-optic time lensing with an intense single-cycle terahertz pulse

    SciTech Connect

    Shen Yuzhen; Carr, G. L.; Murphy, James B.; Wang Xijie; Yang Xi; Tsang, Thomas Y.

    2010-05-15

    We demonstrate that an intense single-cycle terahertz (THz) pulse can act as a time lens to phase modulate and compress a copropagating ultrashort laser pulse. By using the THz-induced phase modulation as a time lens and a glass plate as a group velocity dispersive element, we have compressed an unchirped {approx} 165 fs laser pulse to {approx} 45 fs.

  12. Electro-optic time lensing with an intense single-cycle terahertz pulse

    SciTech Connect

    Shen, Y.; Carr, G.L.; Murphy, J.B.; Tsang, T. Y.; Wang, X.; Yang, X.

    2010-05-18

    We demonstrate that an intense single-cycle terahertz (THz) pulse can act as a time lens to phase modulate and compress a copropagating ultrashort laser pulse. By using the THz-induced phase modulation as a time lens and a glass plate as a group velocity dispersive element, we have compressed an unchirped {approx}165 fs laser pulse to {approx}45 fs.

  13. The interaction between Terahertz radiation and biological tissue.

    PubMed

    Smye, S W; Chamberlain, J M; Fitzgerald, A J; Berry, E

    2001-09-01

    Terahertz (THz) radiation occupies that region of the electromagnetic (EM) spectrum between approximately 0.3 and 20 THz. Recent advances in methods of producing THz radiation have stimulated interest in studying the interaction between radiation and biological molecules and tissue. Given that the photon energies associated with this region of the spectrum are 2.0 x 10(-22) to 1.3 x 10(-20) J, an analysis of the interactions requires an understanding of the permittivity and conductivity of the medium (which describe the bulk motions of the molecules) and the possible transitions between the molecular energy levels. This paper reviews current understanding of the interactions between THz radiation and biological molecules, cells and tissues. At frequencies below approximately 6 THz. the interaction may be understood as a classical EM wave interaction (using the parameters of permittivity and conductivity), whereas at higher frequencies. transitions between different molecular vibrational and rotational energy levels become increasingly important and are more readily understood using a quantum-mechanical framework. The latter is of particular interest in using THz to probe transitions between different vibrational modes of deoxyribonucleic acid. Much additional experimental work is required in order to fully understand the interactions between THz radiation and biological molecules and tissue.

  14. Focused terahertz radiation formed by coherently scattered surface plasmon polaritons from partially uncorrugated metal surfaces

    NASA Astrophysics Data System (ADS)

    Monnai, Y.; Shinoda, H.; Hillmer, H.

    2011-09-01

    We present that a focus of terahertz radiation can be tailored based on coherent scattering of surface plasmon polaritons (SPPs) from a partially defected metal corrugation based on numerical simulations. The introduction of teeth defects in the corrugation allows coupling of the guided SPPs with the radiation and the far-field behavior is tailored by the spatial arrangement of such defects. The proposed structures serve as a kind of planar lenses which are quite thin and inexpensive. Promising applications include interfacing lens antennas between terahertz plasmonic integrated circuits and the external free space, which make terahertz systems very compact and low-cost.

  15. Electro-optic crystal mosaics for the generation of terahertz radiation

    DOEpatents

    Carrig, T.J.; Taylor, A.J.; Stewart, K.R.

    1996-08-06

    Apparatus for the generation of high energy terahertz radiation is presented and comprises laser means effective to produce subpicosecond optical pulses and a mosaic comprising a plurality of planar electro-optic crystals fastened together edge to edge in the form of a grid. The electro-optic crystals are in optical communication with the subpicosecond optical pulses, and behave as a single large electro-optic crystal, producing high energy terahertz radiation by way of optical rectification. 5 figs.

  16. Electro-optic crystal mosaics for the generation of terahertz radiation

    DOEpatents

    Carrig, Timothy J.; Taylor, Antoinette J.; Stewart, Kevin R.

    1996-01-01

    Apparatus for the generation of high energy terahertz radiation is presented and comprises laser means effective to produce subpicosecond optical pulses and a mosaic comprising a plurality of planar electro-optic crystals fastened together edge to edge in the form of a grid. The electro-optic crystals are in optical communication with the subpicosecond optical pulses, and behave as a single large electro-optic crystal, producing high energy terahertz radiation by way of optical rectification.

  17. Coherent and Tunable Terahertz Radiation from Graphene Surface Plasmon Polarirons Excited by Cyclotron Electron Beam.

    PubMed

    Zhao, Tao; Gong, Sen; Hu, Min; Zhong, Renbin; Liu, Diwei; Chen, Xiaoxing; Zhang, Ping; Wang, Xinran; Zhang, Chao; Wu, Peiheng; Liu, Shenggang

    2015-01-01

    Terahertz (THz) radiation can revolutionize modern science and technology. To this date, it remains big challenges to develop intense, coherent and tunable THz radiation sources that can cover the whole THz frequency region either by means of only electronics (both vacuum electronics and semiconductor electronics) or of only photonics (lasers, for example, quantum cascade laser). Here we present a mechanism which can overcome these difficulties in THz radiation generation. Due to the natural periodicity of 2π of both the circular cylindrical graphene structure and cyclotron electron beam (CEB), the surface plasmon polaritions (SPPs) dispersion can cross the light line of dielectric, making transformation of SPPs into radiation immediately possible. The dual natural periodicity also brings significant excellences to the excitation and the transformation. The fundamental and hybrid SPPs modes can be excited and transformed into radiation. The excited SPPs propagate along the cyclotron trajectory together with the beam and gain energy from the beam continuously. The radiation density is enhanced over 300 times, up to 10(5) W/cm(2). The radiation frequency can be widely tuned by adjusting the beam energy or chemical potential. This mechanism opens a way for developing desired THz radiation sources to cover the whole THz frequency regime. PMID:26525516

  18. Coherent and Tunable Terahertz Radiation from Graphene Surface Plasmon Polarirons Excited by Cyclotron Electron Beam

    PubMed Central

    Zhao, Tao; Gong, Sen; Hu, Min; Zhong, Renbin; Liu, Diwei; Chen, Xiaoxing; Zhang, Ping; Wang, Xinran; Zhang, Chao; Wu, Peiheng; Liu, Shenggang

    2015-01-01

    Terahertz (THz) radiation can revolutionize modern science and technology. To this date, it remains big challenges to develop intense, coherent and tunable THz radiation sources that can cover the whole THz frequency region either by means of only electronics (both vacuum electronics and semiconductor electronics) or of only photonics (lasers, for example, quantum cascade laser). Here we present a mechanism which can overcome these difficulties in THz radiation generation. Due to the natural periodicity of 2π of both the circular cylindrical graphene structure and cyclotron electron beam (CEB), the surface plasmon polaritions (SPPs) dispersion can cross the light line of dielectric, making transformation of SPPs into radiation immediately possible. The dual natural periodicity also brings significant excellences to the excitation and the transformation. The fundamental and hybrid SPPs modes can be excited and transformed into radiation. The excited SPPs propagate along the cyclotron trajectory together with the beam and gain energy from the beam continuously. The radiation density is enhanced over 300 times, up to 105 W/cm2. The radiation frequency can be widely tuned by adjusting the beam energy or chemical potential. This mechanism opens a way for developing desired THz radiation sources to cover the whole THz frequency regime. PMID:26525516

  19. Coherent and Tunable Terahertz Radiation from Graphene Surface Plasmon Polarirons Excited by Cyclotron Electron Beam.

    PubMed

    Zhao, Tao; Gong, Sen; Hu, Min; Zhong, Renbin; Liu, Diwei; Chen, Xiaoxing; Zhang, Ping; Wang, Xinran; Zhang, Chao; Wu, Peiheng; Liu, Shenggang

    2015-11-03

    Terahertz (THz) radiation can revolutionize modern science and technology. To this date, it remains big challenges to develop intense, coherent and tunable THz radiation sources that can cover the whole THz frequency region either by means of only electronics (both vacuum electronics and semiconductor electronics) or of only photonics (lasers, for example, quantum cascade laser). Here we present a mechanism which can overcome these difficulties in THz radiation generation. Due to the natural periodicity of 2π of both the circular cylindrical graphene structure and cyclotron electron beam (CEB), the surface plasmon polaritions (SPPs) dispersion can cross the light line of dielectric, making transformation of SPPs into radiation immediately possible. The dual natural periodicity also brings significant excellences to the excitation and the transformation. The fundamental and hybrid SPPs modes can be excited and transformed into radiation. The excited SPPs propagate along the cyclotron trajectory together with the beam and gain energy from the beam continuously. The radiation density is enhanced over 300 times, up to 10(5) W/cm(2). The radiation frequency can be widely tuned by adjusting the beam energy or chemical potential. This mechanism opens a way for developing desired THz radiation sources to cover the whole THz frequency regime.

  20. High effective terahertz radiation from semi-insulating-GaAs photoconductive antennas with ohmic contact electrodes

    NASA Astrophysics Data System (ADS)

    Shi, Wei; Hou, Lei; Wang, Xinmei

    2011-07-01

    Terahertz (THz) radiation efficiency of a photoconductive antenna with Schottky contact electrodes is low because the electrical field is limited to a narrow region close to the anode. However, the electrical field in the gap of an antenna with ohmic contact electrodes is more uniform, which contributes to improving THz generation efficiency. In this paper, the semi-insulating (SI)-GaAs antennas with ohmic contact electrodes and SI-GaAs antennas with Schottky contact electrodes were fabricated by using AuGeNi alloy electrodes and Ti/Au electrodes, respectively. The voltage-ampere characteristic and the distribution of electrical field of the two kinds of antennas were tested. At the same condition, the THz intensity from the antenna with ohmic contact electrodes was 3-8 times higher than that from the antenna with Schottky contact electrodes, and the larger gap antennas with ohmic contact electrodes have higher optical and electrical energy to THz intensity conversion efficiency.

  1. Design of an electron gun for terahertz radiation source

    NASA Astrophysics Data System (ADS)

    Li, Ji; Pei, Yuan-Ji; Hu, Tong-Ning; Chen, Qu-Shan; Feng, Guang-Yao; Shang, Lei; Li, Cheng-Long

    2014-04-01

    An EC-ITC (External-Cathode Independently Tunable Cells) RF gun was employed with the aim of obtaining short-pulse bunches with high peak current for a terahertz radiation source. A gridded DC gun plays a key role as the external injecting electron source of the ITC RF gun, the performance of which determines the beam quality in the injector and transport line. In order to make the beam well compressed in the ITC RF gun, the energy of the electrons acquired from the gridded DC gun should be 15 keV at most. A proper structure of the gridded gun with double-anode is shown to overcome the strong space- charge force on the cathode, which is able to generate 6 μs beam with 4.5 A current successfully.

  2. Negative differential resistance devices for generation of terahertz radiation

    NASA Astrophysics Data System (ADS)

    Eisele, H.

    2015-08-01

    This paper discusses the principles of operation, state of the art, and future potential of active two-terminal devices for generation of low-noise, continuous-wave terahertz radiation. These devices use transit-time, transferred-electron, and quantum-mechanical effects (or a combination of them) to create a negative differential resistance (NDR) at the frequency of interest. Many different types of NDR devices have been proposed since the earliest days of semiconductor devices and studied in detailed simulations for their power generation potential, but have yet to be demonstrated experimentally. The paper focuses on NDR devices that not only yielded significant output powers at millimeter waves frequencies and higher, but also have the strong potential of generating radiation at terahertz frequencies. Examples of such NDR devices are resonant tunneling diodes (RTDs), superlattice electronic devices (SLEDs), and InP Gunn devices. Examples of their state-of-the-art results are output powers of 0.2 mW at 443 GHz and 5 μW at 1.53 THz from InGaAs/AlAs double barrier RTDs on InP substrate; 5.0 mW at 123.3 GHz, 1.1 mW at 155.1 GHz, and 0.52 mW at 252.8 GHz from GaAs/AlAs superlattice electronic devices on GaAs substrate; and 330 μW at 412 GHz, 86 μW at 479 GHz, and 18 μW at 502 GHz from InP Gunn devices.

  3. Enhancement mechanism of terahertz radiation from coherent longitudinal optical phonons in undoped GaAs/n-type GaAs epitaxial structures

    NASA Astrophysics Data System (ADS)

    Tsuruta, Shuichi; Takeuchi, Hideo; Yamada, Hisashi; Hata, Masahiko; Nakayama, Masaaki

    2013-04-01

    We have investigated the characteristics of monochromatic terahertz electromagnetic waves emitted from coherent longitudinal optical (LO) phonons in undoped GaAs/n-type GaAs epitaxial structures with various thicknesses, which range from 200 nm to 1200 nm, of the undoped GaAs layer. The terahertz waves were measured at room temperature using an optical gating method with a photoconductive dipole antenna. It was found that the intensity of the terahertz waves markedly depends on the thickness of the undoped GaAs layer. The analysis of Franz-Keldysh oscillations observed with photoreflectance spectroscopy demonstrates that the built-in electric field strength in the undoped GaAs layer, which results from the Fermi-level pinning at the surface, increases from 6.1 kV/cm to 28.4 kV/cm with a decrease in the thickness. It was revealed that the amplitude of the terahertz wave is proportional to the electric field strength in the undoped GaAs layer. This fact indicates that the efficiency of the terahertz radiation is dominated by the initial polarization of the LO phonons induced by the built-in electric field, which provides us a simple strategy for the enhancement of the terahertz radiation from the coherent LO phonons.

  4. A multimode terahertz-Orotron with the special Smith-Purcell radiation

    NASA Astrophysics Data System (ADS)

    Liu, Weihao; Lu, Yalin; Wang, Lin; Jia, Qika

    2016-05-01

    We proposed and investigated a terahertz Orotron, which is based on the recently revealed special Smith-Purcell radiation. It overcomes the main obstacles of the traditional Orotron in the terahertz region—unreachable high starting-current-density and low radiation power. With the experimentally available electron beam and facilities, its average output power can reach hundreds of milliwatts and even several watts in terahertz region, which is many orders of magnitude higher than that of the traditional Orotron. Additionally, it can be controlled to operate in ether the first or the second order mode, and the radiation frequency can extend from 0.1 THz to 1 THz. These remarkable advantages make it a promising terahertz source for practical applications.

  5. [Life Span of F1 Progeny of Female Drosophila Exposed to Low Intensity Terahertz Irradiation].

    PubMed

    Fedorov, V I; Weisman, N Ya

    2015-01-01

    Virgin female fruit flies were stressed by placement into a confined space without food for 3 hours. Some flies were subjected to terahertz irradiation (0,1-2,2 THz) for the last 30 min. Irradiated and nonirradiated females were then copulated with males. We investigated the F1 progeny of fruit flies with mature and immature oocytes at the moment of irradiation (days of oviposition: 1-2 and 9-10 after irradiation). Life span of individual flies was evaluated. It was demonstrated that terahertz radiation does not influence the absolute and average lifespan of the F1 progeny in both sexes. In response to terahertz irradiation the sexual dimorphism was detected. Survival curves of males, developed from mature and immature oocytes at the time of irradiation, differ significantly from the appropriate control, whereas in the case of females the survival curves are similar to the control. It is concluded that terahertz radiation has a remote effect on a survival of the F1 male progeny.

  6. Noninvasive detection of weapons of mass destruction using terahertz radiation

    NASA Astrophysics Data System (ADS)

    Campbell, Matthew B.; Heilweil, Edwin J.

    2003-08-01

    The growing and immediate threat of biological and chemical weapons has placed urgency on the development of chemical and biological warfare agent (CWA/BWA) screening devices. Specifically, the ability to detect CWA/BWA prior to deployment is paramount to mitigating the threat without exposing individuals to its effects. SPARTA, Inc. and NIST are currently investigating the feasibility of using far-infrared radiation, or terahertz (THz, 1 THz = 1012 Hz) radiation, to non-invasively detect biological and chemical agents, explosives and drugs/narcotics inside sealed containers. Small-to-medium sized molecules (3-100 atoms) in gas, liquid and solid phases consistently exhibit identifiable spectral features in the far-IR portion of the spectrum. Many compounds associated with weapons of mass destruction are made up of molecules of this size. The THz portion of the spectrum lies between visible light and radio waves, allowing for partial transmission of 0.3-10.0 THz (30-1000 μm, 10-330 cm-1) light through most common materials. Therefore, transmission measurements of THz light can potentially be used to non-invasively detect the presence of CWA/BWA, explosives and drugs in the pathway of a THz radiation beam.

  7. Nonlinear transmission of an intense terahertz field through monolayer graphene

    SciTech Connect

    Hafez, H. A.; Ibrahim, A.; Ozaki, T.; Al-Naib, I.; Dignam, M. M.; Oguri, K.; Sekine, Y.; Hibino, H.; Cooke, D. G.; Tanaka, S.; Komori, F.

    2014-11-15

    We report nonlinear terahertz (THz) effects in monolayer graphene, giving rise to transmission enhancement of a single-cycle THz pulse when the incident THz peak electric field is increased. This transmission enhancement is attributed to reduced photoconductivity, due to saturation effects in the field-induced current and increased intraband scattering rates arising from transient heating of electrons. We have developed a tight-binding model of the response using the length gauge interaction Hamiltonian that provides good qualitative agreement. The model fully accounts for the nonlinear response arising from the linear dispersion energy spectrum in graphene. The results reveal a strong dependence of the scattering time on the THz field, which is at the heart of the observed nonlinear response.

  8. Coherent Cherenkov radiation as an intense THz source

    NASA Astrophysics Data System (ADS)

    Bleko, V.; Karataev, P.; Konkov, A.; Kruchinin, K.; Naumenko, G.; Potylitsyn, A.; Vaughan, T.

    2016-07-01

    Diffraction and Cherenkov radiation of relativistic electrons from a dielectric target has been proposed as mechanism for production of intense terahertz (THz) radiation. The use of an extremely short high-energy electron beam of a 4th generation light source (X-ray free electron laser) appears to be very promising. A moderate power from the electron beam can be extracted and converted into THz radiation with nearly zero absorption losses. The initial experiment on THz observation will be performed at CLARA/VELA FEL test facility in the UK to demonstrate the principle to a wider community and to develop the radiator prototype. In this paper, we present our theoretical predictions (based on the approach of polarization currents), which provides the basis for interpreting the future experimental measurements. We will also present our hardware design and discuss a plan of the future experiment.

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

    PubMed

    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. PMID:25273189

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

    SciTech Connect

    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.

  11. The role of optical rectification in the generation of terahertz radiation from GaBiAs

    SciTech Connect

    Radhanpura, K.; Hargreaves, S.; Lewis, R. A.; Henini, M.

    2009-06-22

    We report on a detailed study of the emission of terahertz-frequency electromagnetic radiation from layers of GaBi{sub y}As{sub 1-y} (0{<=}y<0.04) grown by molecular beam epitaxy on (311)B and (001) GaAs substrates. We measure two orthogonally polarized components of the terahertz radiation emitted under excitation by ultrashort near-infrared laser pulses in both transmission and reflection geometries as a function of the crystal rotation about its surface normal as well as the effect of in-plane magnetic field and pump fluence on the terahertz emission. We conclude that the principal mechanism for terahertz generation is via optical rectification rather than transient currents.

  12. Room temperature broadband terahertz gains in graphene heterostructures based on inter-layer radiative transitions

    SciTech Connect

    Tang, Linlong; Du, Jinglei; Shi, Haofei Wei, Dongshan; Du, Chunlei

    2014-10-15

    We exploit inter-layer radiative transitions to provide gains to amplify terahertz waves in graphene heterostructures. This is achieved by properly doping graphene sheets and aligning their energy bands so that the processes of stimulated emissions can overwhelm absorptions. We derive an expression for the gain estimation and show the gain is insensitive to temperature variation. Moreover, the gain is broadband and can be strong enough to compensate the free carrier loss, indicating graphene based room temperature terahertz lasers are feasible.

  13. Magnetic mirror cavities as terahertz radiation sources and a means of quantifying radiation friction

    SciTech Connect

    Holkundkar, Amol R. E-mail: amol.holkundkar@gmail.com; Harvey, Chris

    2014-10-15

    We propose a radiation source based on a magnetic mirror cavity. Relativistic electrons are simulated entering the cavity and their trajectories and resulting emission spectra are calculated. The uniformity of the particle orbits is found to result in a frequency comb in terahertz range, the precise energies of which are tunable by varying the electron's γ-factor. For very high energy particles, radiation friction causes the spectral harmonics to broaden and we suggest this as a possible way to verify competing classical equations of motion.

  14. Generation of terahertz radiation in the reflection of a laser pulse from a dense plasma

    SciTech Connect

    Frolov, A. A.

    2007-12-15

    The generation of low-frequency (terahertz) electromagnetic radiation in the reflection of a laser pulse from the boundary of a dense plasma is considered. Low-frequency wave electromagnetic fields in vacuum are excited by a vortex electric current that is induced at the plasma boundary by the ponderomotive force of the laser pulse. The spectral, angular, and energy parameters of the low-frequency radiation, as well as the spatiotemporal structure of the emitted waves, are investigated. It is shown that for typical parameters of present-day laser plasma experiments, the power of terahertz radiation can amount to tens of megawatts.

  15. [Use of terahertz electromagnetic radiation at nitric oxide frequencies for the correction of thyroid functional state during stress].

    PubMed

    Kirichuk, V F; Tsymbal, A A

    2010-01-01

    The influence of terahertz electromagnetic radiation at nitric oxide frequencies (150.176-150.664 Ghz) on the functional activity of rat thyroid gland subjected to acute immobilization stress has been studied. It is shown that terahertz radiation totally normalizes thyroid activity in stressed animals within 30 min after application. PMID:20540354

  16. [Use of terahertz electromagnetic radiation at nitric oxide frequencies for the correction of thyroid functional state during stress].

    PubMed

    Kirichuk, V F; Tsymbal, A A

    2010-01-01

    The influence of terahertz electromagnetic radiation at nitric oxide frequencies (150.176-150.664 Ghz) on the functional activity of rat thyroid gland subjected to acute immobilization stress has been studied. It is shown that terahertz radiation totally normalizes thyroid activity in stressed animals within 30 min after application.

  17. A Voltage-Tunable Quantum Well Detector for Terahertz Radiation

    NASA Astrophysics Data System (ADS)

    Briceño, G.; Williams, J. B.; Sherwin, M. S.; Campman, K.; Gossard, A. C.

    1997-03-01

    Intersubband transitions in quantum wells have enabled the development of sensitive quantum well infrared photoconductors (QWIP) at wavelengths shorter than 20 microns. The potential of quantum well-based detectors at wavelengths of order 100 microns (3 Terahertz (THz)) has not been realized. We propose a novel antenna-coupled intersubband detector for THz frequencies. The detector is predicted to be sensitive only in a narrow band of frequencies which can be tuned by a factor of order two by applying dc voltages of order 1V. The speed of the detector is predicted to be limited by the intersubband relaxation rate (1 ns at T=10K)(J. N. Heyman et. al., Phys. Rev. Lett. 74), 2682 (1995). Prototype detectors have been constructed. The structure, dc transport characteristics and response of these devices to THz radiation will be discussed. Supported by the NSF Science and Technology Center for Quantized Electronic Structures DMR 91-20007, NSF DMR 9623874, AFOSR F-49620-94-1-0158, and the Ford Foundation (GB).

  18. Quantitative investigation of the bioeffects associated with terahertz radiation

    NASA Astrophysics Data System (ADS)

    Wilmink, Gerald J.; Rivest, Benjamin D.; Ibey, Bennett L.; Roth, Caleb L.; Bernhard, Joshua; Roach, William P.

    2010-02-01

    The biological effects associated with Terahertz (THz) radiation are not well characterized. In this study, we investigated the cellular response of human dermal fibroblasts exposed to an optically-pumped molecular gas THz laser (υ = 2.52 THz, irradiance = 84.8 mW/cm2, exposure duration = 5 to 80 minutes). Computational dosimetry was conducted using finite-difference time-domain (FDTD) modeling techniques. Empirical dosimetry was conducted using infrared cameras and thermocouples. Cellular viability was assessed 24 h post-exposure using MTT calorimetric assays. Quantitative PCR was performed 4 h post-exposure to evaluate the transcriptional activation of genes involved in protein and DNA damage pathways. Comparable analyses were also performed for hyperthermic and genotoxic positive control samples. For all of the exposure durations tested, we found that greater than 95% of the cells were viable post-exposure. In addition, the exposed cells showed only minor increases (~3.5-fold) in heat shock protein expression. The empirical dosimetric data showed that the temperature of the cells increased by ~3 °C during exposure. This value was consistent with that predicted by the computational models. Interestingly, although the THz-exposed cells exhibited increases in heat shock protein expression, the magnitude of these increases was comparable to those observed in hyperthermic controls. In addition, none of the DNA repair genes tested were up-regulated in the THz-exposed cells, whereas 40-fold increases were observed in the genotoxic control cells. These results suggest that the biological effects imposed by THz radiation appear to be primarily photothermal in nature.

  19. Analog of microwave-induced resistance oscillations induced in GaAs heterostructures by terahertz radiation

    NASA Astrophysics Data System (ADS)

    Herrmann, T.; Dmitriev, I. A.; Kozlov, D. A.; Schneider, M.; Jentzsch, B.; Kvon, Z. D.; Olbrich, P.; Bel'kov, V. V.; Bayer, A.; Schuh, D.; Bougeard, D.; Kuczmik, T.; Oltscher, M.; Weiss, D.; Ganichev, S. D.

    2016-08-01

    We report on the study of terahertz radiation-induced MIRO-like oscillations of magnetoresistivity in GaAs heterostructures. Our experiments provide an answer on two most intriguing questions—effect of radiation helicity and the role of the edges—yielding crucial information for an understanding of the MIRO (microwave-induced resistance oscillations) origin. Moreover, we demonstrate that the range of materials exhibiting radiation-induced magneto-oscillations can be largely extended by using high-frequency radiation.

  20. Intensity-Modulated Radiation Therapy (IMRT)

    MedlinePlus

    ... modulating—or controlling—the intensity of the radiation beam in multiple small volumes. IMRT also allows higher ... of multiple intensity-modulated fields coming from different beam directions produce a custom tailored radiation dose that ...

  1. Intense terahertz-pulse generation by four-wave mixing process in induced gas plasma

    NASA Astrophysics Data System (ADS)

    Wicharn, S.; Buranasiri, P.

    2015-08-01

    In this article, we have numerically investigated an intense terahertz (THz) pulses generation in gaseous plasma based on the third-order nonlinear effect, four-wave mixing rectification (FWMR). We have proposed that the fundamental fields and second-harmonic field of ultra-short pulse lasers are combined and focused into a very small gas chamber to induce a gaseous plasma, which intense THz pulse is produced. To understand the THz generation process, the first-order multiple-scale perturbation method (MSPM) has been utilized to derive a set of nonlinear coupled-mode equations for interacting fields such as two fundamental fields, a second-harmonic field, and a THz field. Then, we have simulate the intense THz-pulse generation by using split step-beam propagation method (SS-BPM) and calculated output THz intensities. Finally, the output THz intensities generated from induced air, nitrogen, and argon plasma have been compared.

  2. Speckle pattern of the images of objects exposed to monochromatic coherent terahertz radiation

    SciTech Connect

    Vinokurov, Nikolai A; Knyazev, Boris A; Kulipanov, Gennadii N; Dem'yanenko, M A; Esaev, D G; Chashchina, O I; Cherkasskii, Valerii S

    2009-05-31

    By using a free electron laser and a microbolometer array, real-time images are recorded for the first time in the terahertz range at the rate of up to 90 frames per second. In the case of diffusive illumination of objects by coherent monochromatic radiation, the images consist of speckles. The study of the statistical properties of speckle patterns shows that they are quite accurately described by the theory developed for speckles in the visible range. By averaging a set of images with the help of a rotating scatterer during the exposure time of a frame (20 ms) and by summing statistically independent speckle patterns of many frames, images of the acceptable quality are obtained. The possibilities of terahertz speckle photography and speckle interferometry are discussed. (terahertz radiation)

  3. Efficient Cherenkov emission of broadband terahertz radiation from an ultrashort laser pulse in a sandwich structure with nonlinear core

    SciTech Connect

    Bodrov, S. B.; Bakunov, M. I.; Hangyo, M.

    2008-11-01

    A scheme for efficient generation of broadband terahertz radiation by a femtosecond laser pulse propagating in a planar sandwichlike structure is proposed. The structure consists of a thin nonlinear core cladded with prisms made of a material with low terahertz absorption. The focused into a line laser pulse propagates in the core as a leaky or waveguide mode 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 developed theory predicts the conversion efficiency of up to several percent in a 1 cm long and 1 cm wide Si-LiNbO{sub 3}-Si sandwich structure with a 20 {mu}m thick nonlinear layer pumped by 8.5 {mu}J Ti:sapphire laser with pulse duration of 100 fs.

  4. Terahertz twisted beams generation in plasma

    NASA Astrophysics Data System (ADS)

    Sobhani, Hassan; Vaziri (Khamedi), Mohammad; Rooholamininejad, Hossien; Bahrampour, Alireza

    2016-08-01

    The resonant vortex terahertz beam generation by the cross-focusing of two twisted coaxial laser beams is investigated. For the resonant excitation of terahertz radiation, the rippled density in plasma and the ripple wave number is suitably chosen to satisfy the phase matching condition. The nonlinear current density at terahertz frequency arises due to the spatial variation of two Laguerre-Gaussian coupled field. The terahertz intensity scales as the ponderomotive force of laser beams which imparts an oscillatory velocity to the electrons and, in fact, input Laguerre-Gaussian laser beams properties such as vortex charge number and beam waist. Various laser and plasma parameters are employed to yield vortex terahertz radiation with higher efficiency. Also, it is shown that when the beating frequency approaches plasma frequency, the amplitude of THz radiation increases.

  5. Terahertz spectroscopy with a holographic Fourier transform spectrometer plus array detector using coherent synchrotron radiation

    SciTech Connect

    Nikolay I. Agladz, John Klopf, Gwyn Williams, Albert J. Sievers

    2010-06-01

    By use of coherent terahertz synchrotron radiation, we experimentally tested a holographic Fourier transform spectrometer coupled to an array detector to determine its viability as a spectral device. Somewhat surprisingly, the overall performance strongly depends on the absorptivity of the birefringent lithium tantalate pixels in the array detector.

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

    SciTech Connect

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

    2015-11-21

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    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.

  8. Generation of high-power tunable terahertz-radiation by nonrelativistic beam-echo harmonic effect

    NASA Astrophysics Data System (ADS)

    Gong, Huarong; Travish, Gil; Xu, Jin; Wei, Yanyu; Feng, Jinjun; Gong, Yubin

    2013-01-01

    A new type of terahertz radiation source based on the nonrelativistic electron beam-wave interaction is proposed. Here, the beam echo harmonic effect is applied to a traveling wave tube like device. The scheme is configured as a combination of a frequency multiplier and amplifier with, for instance, W-band (millimeter wave) input signals and terahertz output power. A one-dimensional model of this device shows that a 10th order harmonic-wave can be generated while other harmonic waves are suppressed. The device only requires a readily available input source (W-band), and the output frequency can be tuned continuously over a wide band.

  9. Application of Terahertz Radiation to the Detection of Corrosion under the Shuttle's Thermal Protection System

    NASA Technical Reports Server (NTRS)

    Madaras, Eric I.; Anastasi, Robert F.; Smith, Stephen W.; Seebo, Jeffrey P.; Walker, James L.; Lomness, Janice K.; Hintze, Paul E.; Kammerer, Catherine C.; Winfree, William P.; Russell, Richard W.

    2007-01-01

    There is currently no method for detecting corrosion under Shuttle tiles except for the expensive process of tile removal and replacement; hence NASA is investigating new NDE methods for detecting hidden corrosion. Time domain terahertz radiation has been applied to corrosion detection under tiles in samples ranging from small lab samples to a Shuttle with positive results. Terahertz imaging methods have been able to detect corrosion at thicknesses of 5 mils or greater under 1" thick Shuttle tiles and 7-12 mils or greater under 2" thick Shuttle tiles.

  10. Generation of high-power tunable terahertz-radiation by nonrelativistic beam-echo harmonic effect

    SciTech Connect

    Gong Huarong; Xu Jin; Wei Yanyu; Gong Yubin; Travish, Gil; Feng Jinjun

    2013-01-15

    A new type of terahertz radiation source based on the nonrelativistic electron beam-wave interaction is proposed. Here, the beam echo harmonic effect is applied to a traveling wave tube like device. The scheme is configured as a combination of a frequency multiplier and amplifier with, for instance, W-band (millimeter wave) input signals and terahertz output power. A one-dimensional model of this device shows that a 10th order harmonic-wave can be generated while other harmonic waves are suppressed. The device only requires a readily available input source (W-band), and the output frequency can be tuned continuously over a wide band.

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

    PubMed

    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

    2015-01-01

    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. PMID:25998840

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

    NASA Astrophysics Data System (ADS)

    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

    2015-05-01

    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.

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

    PubMed Central

    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

    2015-01-01

    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. PMID:25998840

  14. Theoretical investigation on generating terahertz radiation from gas plasma induced by three-color ultrashort lasers

    NASA Astrophysics Data System (ADS)

    Wang, Cheng-Liang; Yang, Zhen-Gang; Liu, Jin-Song; Wang, Sheng-Lie; Wang, Ke-Jia

    2015-08-01

    Generation of intense broadband terahertz (THz) waves from gas plasma induced by tri-color ultrashort (fundamental (ω), second harmonic (2ω), and third harmonic (3ω)) laser pulses is theoretically investigated. Simulation results show that the 3ω laser pulse can greatly enhance or suppress the generation of THz wave at different values of relative phase (θ 3) between the 3ω and ω fields. Moreover, the polarities of the generated THz waves can be controlled by changing θ 3, with the relative phase θ 2 (between the 2ω and ω fields) fixed to be a certain value. All of our results show that θ 3 plays a key role in the generation process, which promises to control the intensity as well as the polarity of gas plasma-induced THz radiation. Project supported by the Wuhan Applied Basic Research Project, China (Grant No. 20140101010009), the National Natural Science Foundation of China (Grant Nos. 61177095, 61475054, and 61405063), the Natural Science Foundation of Hubei Province, China (Grant Nos. 2012FFA074 and 2013BAA002), the Fundamental Research Funds for the Central Universities, China (Grant Nos. 2013KXYQ004, 2014ZZGH021, and 2014QN023), and the Technology Innovation Foundation from Innovation Institute of Huazhong University of Science and Technology, China (Grant No. CXY13Q015).

  15. Terahertz metamaterials

    DOEpatents

    Peralta, Xomalin Guaiuli; Brener, Igal; O'Hara, John; Azad, Abul; Smirnova, Evgenya; Williams, John D.; Averitt, Richard D.

    2014-08-12

    Terahertz metamaterials comprise a periodic array of resonator elements disposed on a dielectric substrate or thin membrane, wherein the resonator elements have a structure that provides a tunable magnetic permeability or a tunable electric permittivity for incident electromagnetic radiation at a frequency greater than about 100 GHz and the periodic array has a lattice constant that is smaller than the wavelength of the incident electromagnetic radiation. Microfabricated metamaterials exhibit lower losses and can be assembled into three-dimensional structures that enable full coupling of incident electromagnetic terahertz radiation in two or three orthogonal directions. Furthermore, polarization sensitive and insensitive metamaterials at terahertz frequencies can enable new devices and applications.

  16. Nonlinear electron dynamics of gold ultrathin films induced by intense terahertz waves

    SciTech Connect

    Minami, Yasuo Takeda, Jun; Katayama, Ikufumi; Dao, Thang Duy; Nagao, Tadaaki; Kitajima, Masahiro

    2014-12-15

    Linear and nonlinear electron dynamics of polycrystalline gold (Au) ultrathin films with thicknesses ranging from 1.4 to 5.8 nm were investigated via transmittance terahertz (THz) spectroscopy with intense electric field transients. We prepared ultrathin films with low surface roughness formed on a Si–(7 × 7) reconstructed surface, leading to the observation of monotonic decrease in THz transmittance with respect to film thickness. Furthermore, at all tested thicknesses, the transmittance decreased nonlinearly by 10%–30% with the application if high-intensity THz electric fields. Based on a Drude-model analysis, we found a significant decrease in the damping constant induced by the THz electric field, indicating that electrons are driven beyond the polycrystalline grain boundaries in Au thin films, and consequently leading to the suppression of the electron–boundary scattering rate.

  17. Record High Power Terahertz Radiation from Relativistic Electrons

    SciTech Connect

    G.L. Carr; Michael C. Martin; Wayne R. McKinney; Kevin Jordan; George R. Neil; Gwyn P. Williams

    2002-03-01

    Calculations and measurements confirm the production of coherent broadband THz radiation from relativistic electrons with an average power of nearly 20 watts. The radiation has qualities closely analogous to the THz radiation produced by ultrafast laser techniques (spatially coherent, short duration pulses with transform-limited spectral content). But in contrast to conventional THz radiation, the intensity is many orders of magnitude greater due to a relativistic enhancement. The absorption and dispersive properties of materials in this spectral range provide contrast for a unique type of imaging [1,2]. The striking improvement in power reported here could revolutionize this application by allowing full-field, real-time image capture. High peak and average power THz sources are also critical in driving new non-linear phenomena with excellent signal to noise, and for pump-probe studies of dynamical properties of novel materials, both of which are central to future high-speed electronic devices [3,4]. It should also be useful for studies of molecular vibrations and rotations, low frequency protein motions, phonons, superconductor bandgaps, electronic scattering and collective electronic excitations (e.g., charge density waves).

  18. Generation of coherent terahertz radiation by polarized electron-hole pairs in GaAs/AlGaAs quantum wells

    SciTech Connect

    Andrianov, A. V. Alekseev, P. S.; Klimko, G. V.; Ivanov, S. V.; Shcheglov, V. L.; Sedova, M. A.; Zakhar'in, A. O.

    2013-11-15

    The generation of coherent terahertz radiation upon the band-to-band femtosecond laser photoexcitation of GaAs/AlGaAs multiple-quantum-well structures in a transverse electric field at room temperature is investigated. The properties of the observed terahertz radiation suggest that it is generated on account of the excitation of a time-dependent dipole moment as a result of the polarization of nonequilibrium electron-hole pairs in quantum wells by the electric field. The proposed theoretical model taking into account the dynamic screening of the electric field in the quantum wells by nonequilibrium charge carriers describes the properties of the observed terahertz signal.

  19. Influences of different gases on the terahertz radiation based on the application of two-color laser pulses

    SciTech Connect

    Moradi, S.; Ganjovi, A.; Shojaei, F.; Saeed, M.

    2015-10-15

    In this work, using a two-dimensional Particle In Cell-Monte Carlo Collision simulation method, a comparative study is performed on the influences of different types of atomic and molecular gases at various background gas pressures on the generation of broadband and intense Terahertz (THz) radiation via the application of two-color laser pulses. These two modes are focused into Argon (Ar), Xenon (Xe), Nitrogen (N{sub 2}), Oxygen (O{sub 2}), and air as the background gaseous media and the plasma channel is created. It is observed that the THz radiation emission dramatically changes due to the propagation effects. A wider THz pulse is emitted from the formed plasma channel at the higher gas pressures. The significant effects of the propagation features of the emitted THz pulse on its energy at the longer lengths of the plasma channel are observed.

  20. Effects of two-photon absorption on terahertz radiation generated by femtosecond-laser excited photoconductive antennas.

    PubMed

    Lee, Chao-Kuei; Yang, Chan-Shan; Lin, Sung-Hui; Huang, Shiuan-Hua; Wada, Osamu; Pan, Ci-Ling

    2011-11-21

    Terahertz (THz) radiation can be generated more efficiently from a low-temperature-grown GaAs (LT-GaAs) photoconductive (PC) antenna by considering the two-photon absorption (TPA) induced photo-carrier in the photoconductor. A rate-equation-based approach using the Drude-Lorentz model taking into account the band-diagram of LT-GaAs is used for the theoretical analysis. The use of transform-limited pulses at the PC antenna is critical experimentally. Previously unnoticed THz pulse features and anomalously increasing THz radiation power rather than saturation were observed. These are in good agreement with the theoretical predictions. The interplay of intensity dependence and dynamics of generation of photoexcited carriers by single-photon absorption and TPA for THz emission is discussed. PMID:22109395

  1. Influences of different gases on the terahertz radiation based on the application of two-color laser pulses

    NASA Astrophysics Data System (ADS)

    Moradi, S.; Ganjovi, A.; Shojaei, F.; Saeed, M.

    2015-10-01

    In this work, using a two-dimensional Particle In Cell-Monte Carlo Collision simulation method, a comparative study is performed on the influences of different types of atomic and molecular gases at various background gas pressures on the generation of broadband and intense Terahertz (THz) radiation via the application of two-color laser pulses. These two modes are focused into Argon (Ar), Xenon (Xe), Nitrogen (N2), Oxygen (O2), and air as the background gaseous media and the plasma channel is created. It is observed that the THz radiation emission dramatically changes due to the propagation effects. A wider THz pulse is emitted from the formed plasma channel at the higher gas pressures. The significant effects of the propagation features of the emitted THz pulse on its energy at the longer lengths of the plasma channel are observed.

  2. Propagation of terahertz radiation through random structures: An alternative theoretical approach and experimental validation

    NASA Astrophysics Data System (ADS)

    Fletcher, J. R.; Swift, G. P.; Dai, De Chang; Levitt, J. A.; Chamberlain, J. M.

    2007-01-01

    A model describing the propagation of terahertz frequency radiation through inhomogeneous materials is proposed. In such materials (e.g., powders or clothing), the size of the scattering centers, their separation, and the wavelength of the radiation are all commensurate. A phase distribution function is used to model the optical properties of a randomly structured transmitting layer. The predictions of the model are compared with exact (Mie) theory for isolated spherical scatterers and with previously published experimental data. Measurements of the transmission of terahertz radiation through a variety of samples in order to validate the present model are also reported. These include arrays of cylinders, textiles, powders, and glass balls. Overall, satisfactory agreement between the experimental data and theoretical predictions is obtained.

  3. Measurement of coherent terahertz radiation for time-domain spectroscopy and imaging

    NASA Astrophysics Data System (ADS)

    Kuroda, R.; Yasumoto, M.; Sei, N.; Toyokawa, H.; Ikeura-Sekiguchi, H.; Ogawa, H.; Koike, M.; Yamada, K.

    2009-12-01

    A high-power terahertz (THz) source for THz time-domain spectroscopy (THz-TDS) and THz imaging has been developed based on an S-band compact electron linac at the National Institute of Advanced Industrial Science and Technology (AIST). A THz pulse was generated as coherent synchrotron radiation (CSR) from an ultra-short electron bunch and expected to have peak power of kW-order with frequency range of 0.1-2 THz. The electro-optic (EO) sampling method with a ZnTe crystal for the THz pulse measurement has been prepared for THz-TDS system. The timing measurement between the THz pulse and a probe laser was carried out. A preliminary experiment of THz transmission imaging of an integrated circuit (IC) card has been successfully demonstrated using the THz CSR pulse and a W-band rf detector. The imaging result was experimentally compared with a result of X-ray imaging. It is confirmed that its intensity and stability are enough to perform for the THz applications.

  4. Incoherent sub-terahertz radiation source with a photomixer array for active imaging in smoky environments

    NASA Astrophysics Data System (ADS)

    Shimizu, Naofumi; Matsuyama, Ken; Uchida, Hidetake

    2015-03-01

    We propose a sub-terahertz (THz) illuminator suitable for use with a THz camera when exploring objects within and behind smoke at the scene of a fire. The illuminator contains a photomixer array and each photomixer generates incoherent sub-THz waves from a single-mode laser light and optical noise using photomixing. The incoherency of the generated sub-THz waves enables us to raise their intensity by increasing the number of photomixers in operation, which makes it possible to realize very bright sub-THz illumination. Consequently, objects being under searched for within or behind smoke can be clearly illuminated using the illuminator and visualized by the THz camera even though they are surrounded by thick and/or high-temperature smoke. To verify our concept, we conducted active imaging with coherent and incoherent sub-THz radiation from a photomixer array utilizing reflection geometry. Although the contrast of the image was improved by increasing number of photomixers in operation on the imaging with coherent radiation, the shape of the target was degraded by the interference pattern of the illuminated sub-THz waves. The contrast of the image when using incoherent radiation was improved without obscuring the shape of the target by increasing the number of photomixers. We also confirmed that there was good visibility for active imaging using incoherent sub-THz illumination even though thick smoke was presented. These results indicate that the use of incoherent sub-THz waves and an array of photomixers should enable a sub-THz illuminator with a high level of brightness to be used for active imaging

  5. Effects of terahertz irradiation at nitric oxide frequencies on intensity of lipoperoxidation and antioxidant properties of the blood under stress conditions.

    PubMed

    Kirichuk, V F; Tsymbal, A A

    2009-08-01

    The effects of terahertz irradiation at the nitric oxide frequencies (150.176-150.664 GHz) on the intensity of lipoperoxidation and antioxidant properties of the blood were examined on albino rats subjected to immobilization stress. This terahertz irradiation completely normalized LPO processes and functional activity of antioxidants in stressed rats. PMID:20027328

  6. One-dimensional carbon nanostructures for terahertz electron-beam radiation

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    One-dimensional carbon nanostructures such as nanotubes and nanoribbons can feature near-ballistic electronic transport over micron-scale distances even at room temperature. As a result, these materials provide a uniquely suited solid-state platform for radiation mechanisms that so far have been the exclusive domain of electron beams in vacuum. Here we consider the generation of terahertz light based on two such mechanisms, namely, the emission of cyclotronlike radiation in a sinusoidally corrugated nanowire (where periodic angular motion is produced by the mechanical corrugation rather than an externally applied magnetic field), and the Smith-Purcell effect in a rectilinear nanowire over a dielectric grating. In both cases, the radiation properties of the individual charge carriers are investigated via full-wave electrodynamic simulations, including dephasing effects caused by carrier collisions. The overall light output is then computed with a standard model of charge transport for two particularly suitable types of carbon nanostructures, i.e., zigzag graphene nanoribbons and armchair single-wall nanotubes. Relatively sharp emission peaks at geometrically tunable terahertz frequencies are obtained in each case. The corresponding output powers are experimentally accessible even with individual nanowires, and can be scaled to technologically significant levels using array configurations. These radiation mechanisms therefore represent a promising paradigm for light emission in condensed matter, which may find important applications in nanoelectronics and terahertz photonics.

  7. Intense terahertz emission from molecular beam epitaxy-grown GaAs/GaSb(001)

    SciTech Connect

    Sadia, Cyril P.; Laganapan, Aleena Maria; Agatha Tumanguil, Mae; Estacio, Elmer; Somintac, Armando; Salvador, Arnel; Que, Christopher T.; Yamamoto, Kohji; Tani, Masahiko

    2012-12-15

    Intense terahertz (THz) electromagnetic wave emission was observed in undoped GaAs thin films deposited on (100) n-GaSb substrates via molecular beam epitaxy. GaAs/n-GaSb heterostructures were found to be viable THz sources having signal amplitude 75% that of bulk p-InAs. The GaAs films were grown by interruption method during the growth initiation and using various metamorphic buffer layers. Reciprocal space maps revealed that the GaAs epilayers are tensile relaxed. Defects at the i-GaAs/n-GaSb interface were confirmed by scanning electron microscope images. Band calculations were performed to infer the depletion region and electric field at the i-GaAs/n-GaSb and the air-GaAs interfaces. However, the resulting band calculations were found to be insufficient to explain the THz emission. The enhanced THz emission is currently attributed to a piezoelectric field induced by incoherent strain and defects.

  8. Edge effects in propagation of terahertz radiation in subwavelength periodic structures

    SciTech Connect

    Gelmont, B. Parthasarathy, R.; Globus, T.

    2008-08-15

    Improving detection sensitivity of biological molecules with low absorption characteristics in the terahertz gap still remains an important issue in terahertz vibrational resonance spectroscopy. One possible way to increase coupling of incident terahertz radiation to molecules is to exploit local enhancement of electromagnetic field in periodic slot arrays. In this work, we show that periodic arrays of rectangular slots with subwavelength widths provide for local electromagnetic field enhancements due to edge effects in our low frequency range of interest, 10-25 cm{sup -1}. Periodic structures of Au doped Si and InSb were studied. The half power enhancement width is {approx}500 nm or less around the slot, edges in all cases, thereby possibly bringing terahertz sensing to the nanoscale. InSb is confirmed to offer the highest results with local power enhancements on the order of 1100 at frequency 14 cm{sup -1}. InSb and Si have large skin depths in our frequency range of interest and so the analysis of their structures was done through the Fourier expansion method of field diffracted from gratings. Surface impedance boundary conditions were employed to model the Au structure. The applications possibly include development of novel biosensors, and monitoring biophysical processes such as DNA denaturation.

  9. Visualization of ferroelectric domains in a hydrogen-bonded molecular crystal using emission of terahertz radiation

    SciTech Connect

    Sotome, M.; Kida, N. Okamoto, H.; Horiuchi, S.

    2014-07-28

    Using a terahertz-radiation imaging, visualizations of ferroelectric domains were made in a room-temperature organic ferroelectric, croconic acid. In as-grown crystals, observed are ferroelectric domains with sizes larger than 50-μm square, which are separated by both 180° and tail-to-tail domain walls (DWs). By applying an electric field along c axis (the polarization direction), a pair of 180° DWs is generated and an each 180° DW oppositely propagates along a axis, resulting in a single domain. By cyclic applications of electric fields, a pair of 180° DWs repeatedly emerges, while no tail-to-tail DWs appear. We discuss the usefulness of the terahertz-radiation imaging as well as the observed unique DW dynamics.

  10. Antenna-boosted mixing of terahertz and near-infrared radiation

    SciTech Connect

    Banks, Hunter B.; Sherwin, Mark S.; Hofmann, Andrea; Mack, Shawn; Gossard, Arthur C.

    2014-09-01

    Using moderate terahertz intensities of approximately 20 kW/cm{sup 2} near 0.6 THz, together with simple antennas, we have observed up to 12 sidebands on a near IR laser. The high-order sidebands were generated at room temperature in a membrane containing GaAs/AlGaAs quantum wells. The antennas were rectangular apertures ∼0.2 mm long in a gold film evaporated onto the membrane. Comparing the intensities required to generate comparable sideband spectra with and without antennas, we estimate the local terahertz field was enhanced by a factor of 5 ± 1, in agreement with finite difference time domain calculations.

  11. Terahertz coherent transition radiation based on an ultrashort electron bunching beam

    NASA Astrophysics Data System (ADS)

    Liu, Wen-Xin; Huang, Wen-Hui; Du, Ying-Chao; Yan, Li-Xin; Wu, Dai; Tang, Chuan-Xiang

    2011-07-01

    The experimental result of terahertz (THz) coherent transition radiation generated from an ultrashort electron bunching beam is reported. During this experiment, the window for THz transmission from ultrahigh vacuum to free air is tested. The compact measurement system which can simultaneously test the THz wave power and frequency is built and proofed. With the help of improved Martin—Puplett interferometer and Kramers—Krong transform, the longitudinal bunch length is measured. The results show that the peak power of THz radiation wave is more than 80 kW, and its radiation frequency is from 0.1 THz to 1.5 THz.

  12. Superradiant amplification of terahertz radiation by plasmons in inverted graphene with a planar distributed Bragg resonator

    SciTech Connect

    Polischuk, O. V. Popov, V. V.; Otsuji, T.

    2015-11-15

    It is shown theoretically that stimulated generation of terahertz radiation by plasmons in graphene with a planar distributed Bragg resonator is possible at two different frequencies for each plasmon mode. This behavior may be attributed to the superradiance of the collective plasmon mode, which is associated with superlinear increase in the radiative damping of the plasmons with increase in pumping power. As a result, the curves of the radiative damping and the plasmon gain as a function of the pumping power intersect at two points corresponding to different generation conditions.

  13. Double negative-metamaterial based Terahertz radiation excited by a sheet beam bunch

    SciTech Connect

    Duan, Zhaoyun; Guo, Chen; Guo, Xin; Chen, Min

    2013-09-15

    We describe a new method to generate enhanced terahertz (THz) surface wave (SW) via its coupling with reversed Cherenkov radiation (RCR), excited by a sheet beam bunch which travels in a vacuum above an isotropic double negative metamaterial (DNM). The physical mechanism for the enhancement is that the DNM can support a RCR which can resonantly interact with a sheet electron beam bunch, resulting in an enhanced SW due to its coupling with the enhanced RCR. Numerical results show strong enhancement effect for the SW and RCR in the THz band. This enhanced THz radiation has potential applications to high-power THz radiation sources and Cherenkov detectors which require large signals.

  14. Quantum Well Intrasubband Photodetector for Far Infared and Terahertz Radiation Detection

    NASA Technical Reports Server (NTRS)

    Ting, David Z. -Y.; Chang, Yia-Chung; Bandara, Sumith V.; Gunapala, Sarath D.

    2007-01-01

    The authors present a theoretical analysis on the possibility of using the dopant-assisted intrasubband absorption mechanism in quantum wells for normal-incidence far infrared/terahertz radiation detection. The authors describe the proposed concept of the quantum well intrasubband photodetector (QWISP), which is a compact semiconductor heterostructure device compatible with existing GaAs focal-plane array technology, and present theoretical results demonstrating strong normal-incidence absorption and responsivity in the QWISP.

  15. Design of Terahertz-Wave Spectrophotometry by Compton Backscattering Using Relativistic Electron Bunches and their Coherent Synchrotron Radiations

    NASA Astrophysics Data System (ADS)

    Sei, Norihiro; Kuroda, Ryunosuke; Ogawa, Hiroshi

    2008-08-01

    We propose a new terahertz-wave spectrophotometry by Compton backscattering using relativistic electron bunches and coherent radiations generated by them. The terahertz-wave spectrophotometry can be realized simultaneously with Compton backscattering, where the characteristics in the terahertz-wave region are converted to those in the visible and ultraviolet regions. The number of Compton backscattered photons is estimated to be more than 100 counts per second with a wavelength divergence of 5% in the visible and ultraviolet regions using the compact S-band linac at National Institute of Advanced Industrial Science and Technology. This spectrophotometry becomes significant in energy recovery linacs.

  16. Terahertz radiation from bismuth surface induced by femtosecond laser pulses.

    PubMed

    Ilyakov, I E; Shishkin, B V; Fadeev, D A; Oladyshkin, I V; Chernov, V V; Okhapkin, A I; Yunin, P A; Mironov, V A; Akhmedzhanov, R A

    2016-09-15

    We report on the first experimental observation of terahertz (THz) wave generation from bismuth mono- and polycrystalline samples irradiated by femtosecond laser pulses. Dependencies of the THz signal on the crystal orientation, optical pulse energy, incidence angle, and polarization are presented and discussed together with features of the sample surfaces. The optical-to-THz conversion efficiency was up to two orders of magnitude higher than for metal at a moderate fluence of ∼1  mJ/cm2. We also found nonlinear effects not previously observed using other metal and semiconductor materials: (a) asymmetry of THz response with respect to a half-turn of a sample around its normal, (b) THz polarization control by orientation of the sample surface, and PMID:27628379

  17. Quasilinear theory of terahertz free-electron lasers based on Compton scattering of incoherent pump wave by intense relativistic electron beam

    NASA Astrophysics Data System (ADS)

    Ginzburg, N. S.; Kocharovskaya, E. R.

    2016-08-01

    The use of incoherent broadband pump radiation for improving the electron efficiency in the free-electron lasers (FEL) based on stimulated backscattering is considered. On the basis of a quasilinear approach, it is shown that the efficiency increases in proportion to the width of the pump spectrum. The effect is owing to a broadening of the spectrum of synchronous combination waves and realization of a mechanism of stochastic particle deceleration. The injection of a monochromatic seed signal in a single pass FEL amplifier or the implementation of a selective high-Q resonator in an FEL oscillator makes the high-frequency scattered radiation be monochromatic in spite of an incoherent pumping. In the regime of stochastic particle deceleration, the efficiency only slightly depends on the spread of the beam parameters, which is beneficial for a terahertz FEL powered by intense relativistic electron beams.

  18. Electromagnetic crystal based terahertz thermal radiators and components

    NASA Astrophysics Data System (ADS)

    Wu, Ziran

    This dissertation presents the investigation of thermal radiation from three-dimensional electromagnetic crystals (EMXT), as well as the development of a THz rapid prototyping fabrication technique and its application in THz EMXT components and micro-system fabrication and integration. First, it is proposed that thermal radiation from a 3-D EMXT would be greatly enhanced at the band gap edge frequency due to the redistribution of photon density of states (DOS) within the crystal. A THz thermal radiator could thus be built upon a THz EMXT by utilizing the exceptional emission peak(s) around its band gap frequency. The thermal radiation enhancement effects of various THz EMXT including both silicon and tungsten woodpile structures (WPS) and cubic photonic cavity (CPC) array are explored. The DOS of all three structures are calculated, and their thermal radiation intensities are predicted using Planck's Equation. These calculations show that the DOS of the silicon and tungsten WPS can be enhanced by a factor of 11.8 around 364 GHz and 2.6 around 406 GHz respectively, in comparison to the normal blackbody radiation at same frequencies. An enhancement factor of more than 100 is obtained in calculation from the CPC array. A silicon WPS with a band gap around 200 GHz has been designed and fabricated. Thermal emissivity of the silicon WPS sample is measured with a control blackbody as reference. And enhancements of the emission from the WPS over the control blackbody are observed at several frequencies quite consistent with the theoretical predictions. Second, the practical challenge of THz EMXT component and system fabrication is met by a THz rapid prototyping technique developed by us. Using this technique, the fabrications of several EMXTs with 3D electromagnetic band gaps in the 100-400 GHz range are demonstrated. Characterization of the samples via THz Time-domain Spectroscopy (THz-TDS) shows very good agreement with simulation, confirming the build accuracy of this

  19. Current-driven detection of terahertz radiation using a dual-grating-gate plasmonic detector

    SciTech Connect

    Boubanga-Tombet, S. Tanimoto, Y.; Satou, A.; Suemitsu, T.; Otsuji, T.; Wang, Y.; Minamide, H.; Ito, H.; Fateev, D. V.; Popov, V. V.

    2014-06-30

    We report on the detection of terahertz radiation by an on-chip planar asymmetric plasmonic structure in the frequency region above one terahertz. The detector is based on a field-effect transistor that has a dual grating gate structure with an asymmetric unit cell, which provides a geometrical asymmetry within the structure. Biasing the detector with a dc source-to-drain current in the linear region of the current-voltage characteristic introduces an additional asymmetry (electrical asymmetry) that enhances the detector responsivity by more than one order of magnitude (by a factor of 20) as compared with the unbiased case due to the cooperative effect of the geometrical and electrical asymmetries. In addition to the responsivity enhancement, we report a relatively low noise equivalent power and a peculiar non-monotonic dependence of the responsivity on the frequency, which results from the multi-plasmonic-cavity structure of the device.

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

    NASA Astrophysics Data System (ADS)

    Pohl, A.; Semenov, A.; Hübers, H.-W.; Hoehl, A.; Ries, M.; Wüstefeld, G.; Ulm, G.; Ilin, K.; Thoma, P.; Siegel, M.

    2016-03-01

    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.

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

    SciTech Connect

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

    2014-02-03

    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.

  2. Terahertz radiation from Cd{sub x}Hg{sub 1-x}Te photoexcited by femtosecond laser pulses

    SciTech Connect

    Krotkus, A.; Adomavicius, R.; Molis, G.; Urbanowicz, A.; Eusebe, H.

    2004-10-01

    Terahertz radiation from Cd{sub x}Hg{sub 1-x}Te samples excited by femtosecond Ti:sapphire laser pulses were measured by using an ultrafast photoconductive antenna manufactured from low-temperature grown GaAs. Terahertz fields radiated by the samples of all three investigated alloy compositions with x=0, 0.2, and 0.3 were of the same order of magnitude. No azimuthal angle dependence of the radiated signal was detected, which evidences that linear current surge effect is dominating over nonlinear optical rectification.

  3. Demonstration of Coherent Terahertz Transition Radiation from Relativistic Laser-Solid Interactions

    NASA Astrophysics Data System (ADS)

    Liao, Guo-Qian; Li, Yu-Tong; Zhang, Yi-Hang; Liu, Hao; Ge, Xu-Lei; Yang, Su; Wei, Wen-Qing; Yuan, Xiao-Hui; Deng, Yan-Qing; Zhu, Bao-Jun; Zhang, Zhe; Wang, Wei-Min; Sheng, Zheng-Ming; Chen, Li-Ming; Lu, Xin; Ma, Jing-Long; Wang, Xuan; Zhang, Jie

    2016-05-01

    Coherent transition radiation in the terahertz (THz) region with energies of sub-mJ/pulse has been demonstrated by relativistic laser-driven electron beams crossing the solid-vacuum boundary. Targets including mass-limited foils and layered metal-plastic targets are used to verify the radiation mechanism and characterize the radiation properties. Observations of THz emissions as a function of target parameters agree well with the formation-zone and diffraction model of transition radiation. Particle-in-cell simulations also well reproduce the observed characteristics of THz emissions. The present THz transition radiation enables not only a potential tabletop brilliant THz source, but also a novel noninvasive diagnostic for fast electron generation and transport in laser-plasma interactions.

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

    PubMed

    Vinokurov, Nikolay A; Jeong, Young Uk

    2013-02-01

    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.

  5. Non-thermal effects of terahertz radiation on gene expression in mouse stem cells

    PubMed Central

    Alexandrov, Boian S.; Rasmussen, Kim Ø.; Bishop, Alan R.; Usheva, Anny; Alexandrov, Ludmil B.; Chong, Shou; Dagon, Yossi; Booshehri, Layla G.; Mielke, Charles H.; Phipps, M. Lisa; Martinez, Jennifer S.; Chen, Hou-Tong; Rodriguez, George

    2011-01-01

    Abstract In recent years, terahertz radiation sources are increasingly being exploited in military and civil applications. However, only a few studies have so far been conducted to examine the biological effects associated with terahertz radiation. In this study, we evaluated the cellular response of mesenchymal mouse stem cells exposed to THz radiation. We apply low-power radiation from both a pulsed broad-band (centered at 10 THz) source and from a CW laser (2.52 THz) source. Modeling, empirical characterization, and monitoring techniques were applied to minimize the impact of radiation-induced increases in temperature. qRT-PCR was used to evaluate changes in the transcriptional activity of selected hyperthermic genes. We found that temperature increases were minimal, and that the differential expression of the investigated heat shock proteins (HSP105, HSP90, and CPR) was unaffected, while the expression of certain other genes (Adiponectin, GLUT4, and PPARG) showed clear effects of the THz irradiation after prolonged, broad-band exposure. PMID:21991556

  6. Parametric analysis of transient skin heating induced by terahertz radiation.

    PubMed

    Zilberti, Luca; Arduino, Alessandro; Bottauscio, Oriano; Chiampi, Mario

    2014-07-01

    This paper investigates the effect of relevant physical parameters on transient temperature elevation induced in human tissues by electromagnetic waves in the terahertz (THz) band. The problem is defined by assuming a plane wave, which, during a limited time interval, normally impinges on the surface of a 3-layer model of the human body, causing a thermal transient. The electromagnetic equations are solved analytically, while the thermal ones are handled according to the finite element method. A parametric analysis is performed with the aim of identifying the contribution of each parameter, showing that the properties of the first skin layer (except blood flow) play a major role in the computation of the maximum temperature rise for the considered exposure situation. Final results, obtained by combining all relevant parameters together, show that the deviation from the reference solution of the maximum temperature elevation in skin is included in the coverage intervals from -30% to +10% at 0.1 THz and from -33% to +18% at 1 THz (with 95% confidence level). These data allow bounding the possible temperature increase against the spread of tissue properties that could be reasonably used for dosimetric simulations. PMID:24510310

  7. Radiative trapping in intense laser beams

    NASA Astrophysics Data System (ADS)

    Kirk, J. G.

    2016-08-01

    The dynamics of electrons in counter-propagating, circularly polarized laser beams are shown to exhibit attractors whose ability to trap particles depends on the ratio of the beam intensities and a single parameter describing radiation reaction. Analytical expressions are found for the underlying limit cycles and the parameter range in which they are stable. In high-intensity optical pulses, where radiation reaction strongly modifies the trajectories, the production of collimated gamma-rays and the initiation of non-linear cascades of electron-positron pairs can be optimized by a suitable choice of the intensity ratio.

  8. Radiative trapping in intense laser beams

    NASA Astrophysics Data System (ADS)

    Kirk, J. G.

    2016-08-01

    The dynamics of electrons in counter-propagating, circularly polarized laser beams are shown to exhibit attractors whose ability to trap particles depends on the ratio of the beam intensities and a single parameter describing radiation reaction. Analytical expressions are found for the underlying limit cycles and the parameter range in which they are stable. In high-intensity optical pulses, where radiation reaction strongly modifies the trajectories, the production of collimated gamma-rays and the initiation of non-linear cascades of electron–positron pairs can be optimized by a suitable choice of the intensity ratio.

  9. Terahertz radiation from bacteriorhodopsin reveals correlated primary electron and proton transfer processes

    PubMed Central

    Groma, G. I.; Hebling, J.; Kozma, I. Z.; Váró, G.; Hauer, J.; Kuhl, J.; Riedle, E.

    2008-01-01

    The kinetics of electrogenic events associated with the different steps of the light-induced proton pump of bacteriorhodopsin is well studied in a wide range of time scales by direct electric methods. However, the investigation of the fundamental primary charge translocation phenomena taking place in the functional energy conversion process of this protein, and in other biomolecular assemblies using light energy, has remained experimentally unfeasible because of the lack of proper detection technique operating in the 0.1- to 20-THz region. Here, we show that extending the concept of the familiar Hertzian dipole emission into the extreme spatial and temporal range of intramolecular polarization processes provides an alternative way to study ultrafast electrogenic events on naturally ordered biological systems. Applying a relatively simple experimental arrangement based on this idea, we were able to observe light-induced coherent terahertz radiation from bacteriorhodopsin with femtosecond time resolution. The detected terahertz signal was analyzed by numerical simulation in the framework of different models for the elementary polarization processes. It was found that the principal component of the terahertz emission can be well described by excited-state intramolecular electron transfer within the retinal chromophore. An additional slower process is attributed to the earliest phase of the proton pump, probably occurring by the redistribution of a H bond near the retinal. The correlated electron and proton translocation supports the concept, assigning a functional role to the light-induced sudden polarization in retinal proteins. PMID:18456840

  10. Smith-Purcell terahertz radiation from laser modulated electron beam over a metallic grating

    NASA Astrophysics Data System (ADS)

    Kumar, Pawan; Bhasin, Lalita; Tripathi, V. K.; Kumar, Ashok; Kumar, Manoj

    2016-09-01

    We propose a novel scheme of terahertz (THz) radiation generation from the beat frequency modulation of an electron beam by two co-propagating lasers and the generation of terahertz radiation by the modulated beam passing over a periodic metallic grating. The lasers cause velocity modulation of the beam by exerting a longitudinal ponderomotive force on it. In the drift space between the modulator and metallic grating, the velocity modulation translates into density and current modulation. The modulated beam, propagating over the grating of specific wave number, induces space periodic image current in the conductor that emits beat frequency Smith-Purcell radiation. With 1 μm, 4 × 1016 W/cm2 lasers, beam current modulation of the order of 50% can be achieved at optimum lengths of the modulator and drift space. Employing 10 mA, 0.5 MeV short-period electron beam, propagating at a height of 50 μ m above the grating of period 150 μm, one may obtain THz radiated power of the order of 6 mW at 10 THz.

  11. Improvement in thermal barriers to intense terahertz generation from photoconductive antennas

    SciTech Connect

    Ropagnol, X.; Bouvier, Marcel; Reid, M.; Ozaki, T.

    2014-07-28

    We study the generation of free-space terahertz (THz) pulses at low THz frequencies using 6H-SiC and 4H-SiC photoconductive antennas. We investigate the dependence of the THz electric field radiated from the biased SiC emitters on the applied bias field and on the incident optical fluence. In this work, bias fields as high as 32 kV/cm, and optical fluences up to 2.5 mJ/cm{sup 2} (for the 400 nm laser), and 7.5 mJ/cm{sup 2} (for the 800 nm laser) were used. THz generation with back- and front-side illumination of the antennas is also examined. It is found that the SiC antenna, when illuminated from the backside, generates higher THz electric fields. The performance of 6H-SiC and ZnSe photoconductive antennas are compared. We show that, taking advantage of the superior thermal properties of SiC compare with ZnSe, the THz output power generated with the 6H-SiC photoconductive antenna under optimum conditions is 2.3 times larger that with a ZnSe photoconductive antenna.

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    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.

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

    SciTech Connect

    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.

    2014-11-10

    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.

  14. Producing terahertz coherent synchrotron radiation at the Hefei Light Source

    NASA Astrophysics Data System (ADS)

    Xu, De-Rong; Xu, Hong-Liang; Shao, Yan

    2015-07-01

    This paper theoretically proves that an electron storage ring can generate coherent radiation in the THz region using a quick kicker magnet and an AC sextupole magnet. When the vertical chromaticity is modulated by the AC sextupole magnet, the vertical beam collective motion excited by the kicker produces a wavy spatial structure after a number of longitudinal oscillation periods. The radiation spectral distribution was calculated from the wavy bunch parameters at the Hefei Light Source (HLS). When the electron energy is reduced to 400 MeV, extremely strong coherent synchrotron radiation (CSR) at 0.115 THz should be produced. Supported by National Natural Science Foundation of China (11375176)

  15. Intensive terahertz emission from GaSe0.91S0.09 under collinear difference frequency generation

    NASA Astrophysics Data System (ADS)

    Huang, Jingguo; Huang, Zhiming; Tong, Jingchao; Ouyang, Cheng; Chu, Junhao; Andreev, Yury; Kokh, Konstantin; Lanskii, Grigory; Shaiduko, Anna

    2013-08-01

    An intensive, broad tunable monochromatic Terahertz (THz) emission is generated from S-doped (2 wt. %) GaSe (solid solution GaSe0.91S0.09) crystals by collinear difference frequency generation method. The generated THz signal of 3.8 ns covers the spectral range of 0.57-3.57 THz (84.0-528.0 μm), with a maximal THz output peak power of 21.8 W at 1.62 THz. The THz power conversion efficiency is of 45% higher than that of undoped GaSe, which is mainly contributed to the improved optical properties. The terahertz source is of great potential to be exploited for the out-of-door applications due to the increased crystal hardness.

  16. Plasmonics enhanced photomixing for generating quasi-continuous-wave frequency-tunable terahertz radiation.

    PubMed

    Berry, Christopher W; Hashemi, Mohammad R; Preu, Sascha; Lu, Hong; Gossard, Arthur C; Jarrahi, Mona

    2014-08-01

    We experimentally demonstrate an order of magnitude enhancement in the quasi-continuous-wave radiated power from a photomixer with plasmonic contact electrodes in comparison with an analogous conventional photomixer without plasmonic contact electrodes in the 0.25-2.5 THz frequency range when pumped at an optical wavelength of 1550 nm. The significant efficiency enhancement results from the unique capability of the plasmonic contact electrodes to reduce the average transport path of photocarriers to the device contact electrodes, increasing the ultrafast photocurrent that drives the terahertz antenna.

  17. Graphene-based van der Waals heterostructures for emission and detection of terahertz radiation

    NASA Astrophysics Data System (ADS)

    Otsuji, Taiichi; Dubinov, Alexander; Aleshkin, Vladimir Y.; Svintsov, Dmitry; Ryzhii, Maxim; Boubanga Tombet, Stephane; Yadav, Deepika; Satou, Akira; Mitin, Vladimir; Shur, Michael S.; Ryzhii, Victor

    2016-04-01

    This paper reviews recent advances in the research of graphene-based van der Waals heterostructures for emission and detection of terahertz radiation. A gated double-graphene-layer (DGL) nanocapacitor is the core shell under consideration, in which a thin tunnel barrier layer is sandwiched by outer graphene layers at both sides. The DGL can support symmetric optical and anti-symmetric acoustic coupled plasmon modes in the GLs. The latter mode can modulate the band-offset between the GL, giving rise to modulation of the inter-GL-layer resonant tunneling. This can dramatically enhance the THz gain or responsivity via plasmon-assisted inter-GL resonant tunneling.

  18. Giant cross-polarization conversion of terahertz radiation by plasmons in an active graphene metasurface

    NASA Astrophysics Data System (ADS)

    Polischuk, O. V.; Melnikova, V. S.; Popov, V. V.

    2016-09-01

    Results of theoretical investigation of the cross-polarization conversion of terahertz (THz) radiation by the graphene metasurface formed by a periodic array of graphene nanoribbons located at the surface of a high-refractive-index dielectric substrate are presented. Giant polarization conversion at the plasmon resonance frequencies takes place without applying external DC magnetic field. Pumping graphene by its direct optical illumination or diffusion pumping allows for compensating the Drude losses in graphene and leads to further enhancement of the polarization conversion. It is shown that the total polarization conversion can be achieved in the total internal reflection regime of THz wave from the graphene metasurface at room temperature.

  19. Interactions of intense laser radiation with plasma

    NASA Astrophysics Data System (ADS)

    Key, M. H.

    1981-04-01

    The dominant physical processes involved in the interaction of intense laser radiation with plasma are discussed with emphasis on their dependence on the wavelength of the laser radiation. Hydrodynamic pressure resulting from these interactions, acceleration of spherical shell targets, and fluid instability associated with the acceleration are discussed with reference to compression of plasma in laser driven implosions. Experimental data are presented to illustrate the various phenomena.

  20. Generation of high power pulsed terahertz radiation using a plasmonic photoconductive emitter array with logarithmic spiral antennas

    SciTech Connect

    Berry, Christopher W.; Hashemi, Mohammad R.; Jarrahi, Mona

    2014-02-24

    An array of 3 × 3 plasmonic photoconductive terahertz emitters with logarithmic spiral antennas is fabricated on a low temperature (LT) grown GaAs substrate and characterized in response to a 200 fs optical pump from a Ti:sapphire mode-locked laser at 800 nm wavelength. A microlens array is used to split and focus the optical pump beam onto the active area of each plasmonic photoconductive emitter element. Pulsed terahertz radiation with record high power levels up to 1.9 mW in the 0.1–2 THz frequency range is measured at an optical pump power of 320 mW. The record high power pulsed terahertz radiation is enabled by the use of plasmonic contact electrodes, enhancing the photoconductor quantum efficiencies, and by increasing the overall device active area, mitigating the carrier screening effect and thermal breakdown at high optical pump power levels.

  1. Radiative Characteristics of On-Chip Terahertz (THz) Structures

    SciTech Connect

    Hussein, Yasser A.; Spencer, James E.; /SLAC

    2005-06-07

    Previously, we explored possibilities for producing narrow-band THz radiation using either free or bound electrons (solid state) in micro-undulatory configurations [1] because integrated circuit technology appeared well matched to this region extending from about 300 GHz to 30 THz. This range [2]-[3] has largely been neglected until recently because it runs from the limit of WR-3 waveguide around 300 GHz up to CO{sub 2} lasers where the laser regime becomes dominant. There are mainly two approaches for generating THz radiation, i.e. through free or bound electron (BE) implementations. In this paper, emphasis is on producing this radiation using bound electrons via IC technology but in close analogy to free electron lasers (FELs) that are comparatively immense, expensive, need high power and have low efficiencies [4].

  2. Terahertz radiation from magnetic excitations in diluted magnetic semiconductors.

    PubMed

    Rungsawang, R; Perez, F; Oustinov, D; Gómez, J; Kolkovsky, V; Karczewski, G; Wojtowicz, T; Madéo, J; Jukam, N; Dhillon, S; Tignon, J

    2013-04-26

    We probed, in the time domain, the THz electromagnetic radiation originating from spins in CdMnTe diluted magnetic semiconductor quantum wells containing high-mobility electron gas. Taking advantage of the efficient Raman generation process, the spin precession was induced by low power near-infrared pulses. We provide a full theoretical first-principles description of spin-wave generation, spin precession, and of emission of THz radiation. Our results open new perspectives for improved control of the direct coupling between spin and an electromagnetic field, e.g., by using semiconductor technology to insert the THz sources in cavities or pillars.

  3. Enhanced thermal radiation in terahertz and far-infrared regime by hot phonon excitation in a field effect transistor

    SciTech Connect

    Chung, Pei-Kang; Yen, Shun-Tung

    2014-11-14

    We demonstrate the hot phonon effect on thermal radiation in the terahertz and far-infrared regime. A pseudomorphic high electron mobility transistor is used for efficiently exciting hot phonons. Boosting the hot phonon population can enhance the efficiency of thermal radiation. The transistor can yield at least a radiation power of 13 μW and a power conversion efficiency higher than a resistor by more than 20%.

  4. Peculiarities of the effect of terahertz radiation at nitric oxide frequencies on gaseous and electrolyte composition of the blood in different types of stress.

    PubMed

    Kirichuk, V F; Tsymbal, A A

    2010-12-01

    We studied the effect of terahertz radiation at NO frequencies 150.176-150.664 GHz on gaseous and electrolyte composition of the blood in albino rats during stress. Partial or complete recovery of the studied parameters of blood gases and electrolytes in stressed animals was observed after 15- and 30-min terahertz irradiation at NO frequencies, respectively. PMID:21240370

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

    DOEpatents

    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. Calculations for Tera-Hertz (THZ) Radiation Sources

    SciTech Connect

    Hussein, Yasser A.; Spencer, James E.; /SLAC

    2005-06-07

    We explore possibilities for THz sources from 0.3-30 THz. While still inaccessible, this broad gap is even wider for advanced acceleration schemes extending from X or, at most, W band RF at the low end up to CO{sub 2} lasers. While the physical implementations of these two approaches are quite different, both are proving difficult to develop so that lower frequency, superconducting RF is currently preferred. Similarly, the validity of modeling techniques varies greatly over this range of frequencies but generally mandates coupling Maxwell's equations to the appropriate device transport physics for which there are many options. Here we study radiation from undulatory-shaped transmission lines using finite-difference, time-domain (FDTD) simulations. Also, we present Monte-Carlo techniques for pulse generation. Examples of THz sources demonstrating coherence are shown with the goal of optimizing on-chip THz radiators for applications that may lead to accelerators.

  7. Physics of intense, high energy radiation effects.

    SciTech Connect

    Hjalmarson, Harold Paul; Hartman, E. Frederick; Magyar, Rudolph J.; Crozier, Paul Stewart

    2011-02-01

    This document summarizes the work done in our three-year LDRD project titled 'Physics of Intense, High Energy Radiation Effects.' This LDRD is focused on electrical effects of ionizing radiation at high dose-rates. One major thrust throughout the project has been the radiation-induced conductivity (RIC) produced by the ionizing radiation. Another important consideration has been the electrical effect of dose-enhanced radiation. This transient effect can produce an electromagnetic pulse (EMP). The unifying theme of the project has been the dielectric function. This quantity contains much of the physics covered in this project. For example, the work on transient electrical effects in radiation-induced conductivity (RIC) has been a key focus for the work on the EMP effects. This physics in contained in the dielectric function, which can also be expressed as a conductivity. The transient defects created during a radiation event are also contained, in principle. The energy loss lead the hot electrons and holes is given by the stopping power of ionizing radiation. This information is given by the inverse dielectric function. Finally, the short time atomistic phenomena caused by ionizing radiation can also be considered to be contained within the dielectric function. During the LDRD, meetings about the work were held every week. These discussions involved theorists, experimentalists and engineers. These discussions branched out into the work done in other projects. For example, the work on EMP effects had influence on another project focused on such phenomena in gases. Furthermore, the physics of radiation detectors and radiation dosimeters was often discussed, and these discussions had impact on related projects. Some LDRD-related documents are now stored on a sharepoint site (https://sharepoint.sandia.gov/sites/LDRD-REMS/default.aspx). In the remainder of this document the work is described in catergories but there is much overlap between the atomistic calculations, the

  8. Helicity sensitive terahertz radiation detection by dual-grating-gate high electron mobility transistors

    SciTech Connect

    Faltermeier, P.; Olbrich, P.; Probst, W.; Schell, L.; Ganichev, S. D.; Watanabe, T.; Boubanga-Tombet, S. A.; Otsuji, T.

    2015-08-28

    We report on the observation of a radiation helicity sensitive photocurrent excited by terahertz (THz) radiation in dual-grating-gate (DGG) InAlAs/InGaAs/InAlAs/InP high electron mobility transistors (HEMT). For a circular polarization, the current measured between source and drain contacts changes its sign with the inversion of the radiation helicity. For elliptically polarized radiation, the total current is described by superposition of the Stokes parameters with different weights. Moreover, by variation of gate voltages applied to individual gratings, the photocurrent can be defined either by the Stokes parameter defining the radiation helicity or those for linear polarization. We show that artificial non-centrosymmetric microperiodic structures with a two-dimensional electron system excited by THz radiation exhibit a dc photocurrent caused by the combined action of a spatially periodic in-plane potential and spatially modulated light. The results provide a proof of principle for the application of DGG HEMT for all-electric detection of the radiation's polarization state.

  9. Parametric study of broadband terahertz radiation generation based on interaction of two-color ultra-short laser pulses

    SciTech Connect

    Moradi, S.; Ganjovi, A.; Shojaei, F.; Saeed, M.

    2015-04-15

    In this work, using a two-dimensional kinetic model based on particle in cell-Monte Carlo collision simulation method, the influence of different parameters on the broadband intense Terahertz (THz) radiation generation via application of two-color laser fields, i.e., the fundamental and second harmonic modes, is studied. These two modes are focused into the molecular oxygen (O{sub 2}) with uniform density background gaseous media and the plasma channels are created. Thus, a broadband THz pulse that is around the plasma frequency is emitted from the formed plasma channel and co-propagates with the laser pulse. For different laser pulse shapes, the THz electric field and its spectrum are both calculated. The effects of laser pulse and medium parameters, i.e., positive and negative chirp pulse, number of laser cycles in the pulse, laser pulse shape, background gas pressure, and exerted DC electric field on THz spectrum are verified. Application of a negatively chirped femtosecond (40 fs) laser pulse results in four times enhancement of the THz pulse energy (2 times in THz electric field). The emission of THz radiation is mostly observed in the forward direction.

  10. Parametric study of broadband terahertz radiation generation based on interaction of two-color ultra-short laser pulses

    NASA Astrophysics Data System (ADS)

    Moradi, S.; Ganjovi, A.; Shojaei, F.; Saeed, M.

    2015-04-01

    In this work, using a two-dimensional kinetic model based on particle in cell-Monte Carlo collision simulation method, the influence of different parameters on the broadband intense Terahertz (THz) radiation generation via application of two-color laser fields, i.e., the fundamental and second harmonic modes, is studied. These two modes are focused into the molecular oxygen (O2) with uniform density background gaseous media and the plasma channels are created. Thus, a broadband THz pulse that is around the plasma frequency is emitted from the formed plasma channel and co-propagates with the laser pulse. For different laser pulse shapes, the THz electric field and its spectrum are both calculated. The effects of laser pulse and medium parameters, i.e., positive and negative chirp pulse, number of laser cycles in the pulse, laser pulse shape, background gas pressure, and exerted DC electric field on THz spectrum are verified. Application of a negatively chirped femtosecond (40 fs) laser pulse results in four times enhancement of the THz pulse energy (2 times in THz electric field). The emission of THz radiation is mostly observed in the forward direction.

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

    SciTech Connect

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

    2015-03-15

    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.

  12. Manifestation of topological surface electron states in the photoelectromagnetic effect induced by terahertz laser radiation

    NASA Astrophysics Data System (ADS)

    Galeeva, A. V.; Egorova, S. G.; Chernichkin, V. I.; Tamm, M. E.; Yashina, L. V.; Rumyantsev, V. V.; Morozov, S. V.; Plank, H.; Danilov, S. N.; Ryabova, L. I.; Khokhlov, D. R.

    2016-09-01

    We demonstrate that measurements of the photoelectromagnetic effect using terahertz laser radiation may provide a unique opportunity to discriminate between the topological surface states and other highly conductive surface electron states. We performed a case study of mixed (Bi{}1-xIn x )2Se3 crystals undergoing a topological phase transformation due to the transition from the inverse to the direct electron energy spectrum in the crystal bulk at variation of the composition x. We show that for the topological insulator phase, the photoelectromagnetic effect amplitude is defined by the number of incident radiation quanta, whereas for the trivial insulator phase, it depends on the power in a laser pulse irrespective of its wavelength. We assume that such behavior is attributed to a strong damping of the electron-electron interaction in the topological insulator phase compared to the trivial insulator.

  13. Observation of Narrow-Band Terahertz Coherent Cherenkov Radiation from a Cylindrical Dielectric-Lined Waveguide

    NASA Astrophysics Data System (ADS)

    Cook, A. M.; Tikhoplav, R.; Tochitsky, S. Y.; Travish, G.; Williams, O. B.; Rosenzweig, J. B.

    2009-08-01

    We report experimental observation of narrow-band coherent Cherenkov radiation driven by a subpicosecond electron bunch traveling along the axis of a hollow cylindrical dielectric-lined waveguide. For an appropriate choice of dielectric wall thickness, a short-pulse beam current profile excites only the fundamental mode of the structure, producing energetic pulses in the terahertz range. We present detailed measurements showing a narrow emission spectrum peaked at 367±3GHz from a 1 cm long fused silica capillary tube with submillimeter transverse dimensions, closely matching predictions. We demonstrate a 100 GHz shift in the emitted central frequency when the tube wall thickness is changed by 50μm. Calibrated measurements of the radiated energy indicate up to 10μJ per 60 ps pulse for an incident beam charge of 200 pC, corresponding to a peak power of approximately 150 kW.

  14. Manifestation of topological surface electron states in the photoelectromagnetic effect induced by terahertz laser radiation

    NASA Astrophysics Data System (ADS)

    Galeeva, A. V.; Egorova, S. G.; Chernichkin, V. I.; Tamm, M. E.; Yashina, L. V.; Rumyantsev, V. V.; Morozov, S. V.; Plank, H.; Danilov, S. N.; Ryabova, L. I.; Khokhlov, D. R.

    2016-09-01

    We demonstrate that measurements of the photoelectromagnetic effect using terahertz laser radiation may provide a unique opportunity to discriminate between the topological surface states and other highly conductive surface electron states. We performed a case study of mixed (Bi{}1-xIn x )2Se3 crystals undergoing a topological phase transformation due to the transition from the inverse to the direct electron energy spectrum in the crystal bulk at variation of the composition x. We show that for the topological insulator phase, the photoelectromagnetic effect amplitude is defined by the number of incident radiation quanta, whereas for the trivial insulator phase, it depends on the power in a laser pulse irrespective of its wavelength. We assume that such behavior is attributed to a strong damping of the electron–electron interaction in the topological insulator phase compared to the trivial insulator.

  15. Improvement of terahertz field effect transistor detectors by substrate thinning and radiation losses reduction.

    PubMed

    Coquillat, Dominique; Marczewski, Jacek; Kopyt, Pawel; Dyakonova, Nina; Giffard, Benoit; Knap, Wojciech

    2016-01-11

    Phenomena of the radiation coupling to the field effect transistors based terahertz (THz) detectors are studied. We show that in the case of planar metal antennas a significant portion of incoming radiation, instead of being coupled to the transistors, is coupled to an antenna substrate leading to responsivity losses and/or cross-talk effects in the field effect based THz detector arrays. Experimental and theoretical investigations of the responsivity versus substrate thickness are performed. They clearly show how to minimize the losses by the detector/ array substrate thinning. In conclusion simple quantitative rules of losses minimization by choosing a proper substrate thickness of field effect transistor THz detectors are presented for common materials (Si, GaAs, InP, GaN) used in semiconductor technologies. PMID:26832258

  16. Terahertz Spectroscopy of Biomolecules

    NASA Astrophysics Data System (ADS)

    Korter, Timothy; Plusquellic, David; Hight Walker, Angela; Heilweil, Edwin

    2002-03-01

    A novel, continuous-wave (CW) terahertz spectrometer has been constructed to investigate the flexibility and dynamics of small biological molecules. Hydrogen bonding interactions, torsional vibrations, and conformational changes are expressed in this far-infrared region of the spectrum. Terahertz (THz) radiation (0 - 4 THz or 0 - 133 wavenumber) is generated at the difference frequency of two near-infrared pump lasers by optical heterodyne mixing at the surface of a solid-state photomixer. This spectrometer has been used to probe the low-frequency vibrational modes of several members of the vitamin B-complex including riboflavin, pantothenic acid, and biotin. Interpretation of these unique THz spectra has been aided by low-frequency Raman experiments as well as ab initio predictions for normal mode frequencies and intensities. Instrumental details, vitamin B-complex analyses, and preliminary results for myoglobin and other large biomolecules will be presented.

  17. Studies of the critical electric field and L valley offset of a semiconductor characterized by terahertz radiation

    NASA Astrophysics Data System (ADS)

    Hwang, J. S.; Lin, H. C.; Chang, C. K.; Wang, T. S.; Lin, K. I.; Chang, L. S.; Lu, Y. T.

    2007-02-01

    The amplitudes of terahertz radiation are measured for a series of GaAs surface intrinsic-n + (SIN +) structures with various built-in surface electric fields as the bias. As the surface field is lower than the so-called "critical electric field" related with the energy difference between the Γ to L valley of the semiconductor, the amplitude is proportional to the product of the surface field and the number of photo-excited carriers. As the intensity of surface field exceeds the critical field, the THz amplitude is independent of the surface field but proportional the number of the photo-excited carriers. Our study proposed two optimal conditions for an SIN + structure to serve as a THz emitter: the width of its intrinsic layer is nearly equal to the penetration depth of the pump beam, and the intensity of built-in electric field is nearly equal to the critical electric field. Notably, the critical field determined from the THz amplitude under various electric fields provides one way to estimate the Γ to L valley splitting in semiconductors.

  18. Nonlinear magnetization dynamics of antiferromagnetic spin resonance induced by intense terahertz magnetic field

    NASA Astrophysics Data System (ADS)

    Mukai, Y.; Hirori, H.; Yamamoto, T.; Kageyama, H.; Tanaka, K.

    2016-01-01

    We report on the nonlinear magnetization dynamics of a HoFeO3 crystal induced by a strong terahertz magnetic field resonantly enhanced with a split ring resonator and measured with magneto-optical Kerr effect microscopy. The terahertz magnetic field induces a large change (˜40%) in the spontaneous magnetization. The frequency of the antiferromagnetic resonance decreases in proportion to the square of the magnetization change. A modified Landau-Lifshitz-Gilbert equation with a phenomenological nonlinear damping term quantitatively reproduced the nonlinear dynamics.

  19. Time-resolved intensity and spectral changes in a wide-ridge terahertz quantum cascade laser by optical pulse injection

    NASA Astrophysics Data System (ADS)

    Sakasegawa, Yohei; Saito, Shingo; Sekine, Norihiko; Kasamatsu, Akifumi; Ashida, Masaaki; Hosako, Iwao

    2016-10-01

    We report the intensity and spectral changes in a multi-mode terahertz quantum cascade laser induced by injecting λ = 800 nm optical pulses through a cavity facet. We find that photogenerated carriers, via modulation of the intersubband gain, increase the threshold current by up to 0.2 A and cause spectral changes such that the individual peaks of the multi-lateral-mode spectra are varied in amplitude with different ratios. It is found that the indirect recombination of electron-hole pairs and thermal relaxation on timescales of ˜700 ns and ˜10 µs, respectively, are involved in the recovery kinetics.

  20. Terahertz radiation source based on self-wake beam bunching

    SciTech Connect

    Antipov, Sergey; Jing Chunguang; Schoessow, Paul; Kanareykin, Alexei; Jiang Bo; Yakimenko, Vitaly; Zholents, Alexander; Gai Wei

    2012-12-21

    A table top device for producing high power T-ray beams is described. A rectangular electron beam that can be produced out of a photoinjector via stacking of the laser pulse, and running off-crest of the photoinjector rf is sent through a dielectric loaded waveguide. Due to the beam's self-wake its energy becomes modulated. In the chicane beamline following the dielectric energy-bunching section this energy modulation is converted to a density modulation-a bunch train. The density modulated beam can be sent through a power extraction section, like a dielectric loaded accelerating structure, or simply can intercept a foil target, producing THz radiation of various bandwidths and power levels.

  1. Three-dimensional numerical analysis of terahertz radiation emitted from intrinsic Josephson junctions with hot spots

    NASA Astrophysics Data System (ADS)

    Asai, Hidehiro; Tachiki, Masashi; Kadowaki, Kazuo

    2012-02-01

    In this study, we numerically investigate the terahertz radiation from mesa-structured intrinsic Josephson junctions (IJJs) using a three-dimensional calculation model. We assume an in-phase mode of the phase differences and calculate electromagnetic fields inside and outside of the IJJs simultaneously. We consider the appearance of a hot spot in the mesa where jc locally decreases and investigate the change of the radiation power with varying hot-spot positions. The radiation powers for three different hot-spot positions are calculated as functions of voltage. We observe strong radiation when the ac Josephson frequency satisfies the cavity resonance condition. Transverse-magnetic modes TMm,n whose indices m and n are even appear regardless of the positions of hot spots. Meanwhile, the TMm,n cavity modes whose m or n are odd appear only when the hot spots break the reflectional symmetry of the mesa structure. Moreover, we calculate the radiation patterns emitted by the IJJs at these cavity resonance conditions. The radiation patterns reflect the existence of two types of internal modes, that is, a uniform background mode and a cavity resonance mode.

  2. Generation of Widely Tunable Fourier-Transform Pulsed Terahertz Radiation Using Narrowband Near-Infrared Laser Radiation

    NASA Astrophysics Data System (ADS)

    Liu, Jinjun; Haase, Christa; Merkt, Frédéric

    2009-06-01

    Widely tunable, Fourier-transform-limited pulses of terahertz (THz) radiation have been generated by optical frequency deference using (i) crystals of the highly nonlinear organic salt 4-N,N-dimethylamino-4^'-N^'-methyl stilbazolium tosylate (DAST), (ii) zinc telluride (ZnTe) crystals, and (iii) gallium phosphide (GaP) crystals. Outputs from two narrowband (Δν<1 MHz, λ˜800 nm) cw titanium-doped sapphire (Ti:Sa) ring lasers with a well-controlled frequency difference were shaped into pulses using acousto-optic modulators, coupled into an optical fiber, pulse amplified in Nd:YAG-pumped Ti:Sa crystals and used as optical sources to pump the THz nonlinear crystals. The THz radiation was detected over a broad frequency range and its bandwidth was determined to be ˜10 MHz. Absorption spectra of gas phase molecules including HF and OCS using the THz source will be presented.

  3. Real-Time Determination of Absolute Frequency in Continuous-Wave Terahertz Radiation with a Photocarrier Terahertz Frequency Comb Induced by an Unstabilized Femtosecond Laser

    NASA Astrophysics Data System (ADS)

    Minamikawa, Takeo; Hayashi, Kenta; Mizuguchi, Tatsuya; Hsieh, Yi-Da; Abdelsalam, Dahi Ghareab; Mizutani, Yasuhiro; Yamamoto, Hirotsugu; Iwata, Tetsuo; Yasui, Takeshi

    2016-05-01

    A practical method for the absolute frequency measurement of continuous-wave terahertz (CW-THz) radiation uses a photocarrier terahertz frequency comb (PC-THz comb) because of its ability to realize real-time, precise measurement without the need for cryogenic cooling. However, the requirement for precise stabilization of the repetition frequency ( f rep) and/or use of dual femtosecond lasers hinders its practical use. In this article, based on the fact that an equal interval between PC-THz comb modes is always maintained regardless of the fluctuation in f rep, the PC-THz comb induced by an unstabilized laser was used to determine the absolute frequency f THz of CW-THz radiation. Using an f rep-free-running PC-THz comb, the f THz of the frequency-fixed or frequency-fluctuated active frequency multiplier chain CW-THz source was determined at a measurement rate of 10 Hz with a relative accuracy of 8.2 × 10-13 and a relative precision of 8.8 × 10-12 to a rubidium frequency standard. Furthermore, f THz was correctly determined even when fluctuating over a range of 20 GHz. The proposed method enables the use of any commercial femtosecond laser for the absolute frequency measurement of CW-THz radiation.

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

    PubMed

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

    2004-05-21

    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.

  5. EDITORIAL: Terahertz nanotechnology Terahertz nanotechnology

    NASA Astrophysics Data System (ADS)

    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

  6. EDITORIAL: Terahertz nanotechnology Terahertz nanotechnology

    NASA Astrophysics Data System (ADS)

    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

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

    NASA Technical Reports Server (NTRS)

    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.

  8. Terahertz radiation associated with the impurity electron transition in quantum wells upon optical and electrical pumping

    SciTech Connect

    Firsov, D. A. Vorobjev, L. E.; Panevin, V. Yu.; Sofronov, A. N.; Balagula, R. M.; Makhov, I. S.; Kozlov, D. V.; Vasil’ev, A. P.

    2015-01-15

    Radiation in the terahertz (THz) spectral range from structures with GaAs/AlGaAs doped quantum wells is investigated under conditions of the interband optical excitation of electron-hole pairs in n-type structures and impurity breakdown in a longitudinal electric field in p-type structures. The emission spectra are obtained. Emission is observed at low temperatures and shown to be determined by optical transitions between impurity states and transitions between the band and impurity states. Upon optical interband pumping, the impurity states are depopulated due to the recombination of electron-hole pairs with the involvement of impurities, while, in an electric field, the impurity states are depopulated due to impact ionization.

  9. Film Dosimetry for Intensity Modulated Radiation Therapy

    NASA Astrophysics Data System (ADS)

    Benites-Rengifo, J.; Martínez-Dávalos, A.; Celis, M.; Lárraga, J.

    2004-09-01

    Intensity Modulated Radiation Therapy (IMRT) is an oncology treatment technique that employs non-uniform beam intensities to deliver highly conformal radiation to the targets while minimizing doses to normal tissues and critical organs. A key element for a successful clinical implementation of IMRT is establishing a dosimetric verification process that can ensure that delivered doses are consistent with calculated ones for each patient. To this end we are developing a fast quality control procedure, based on film dosimetry techniques, to be applied to the 6 MV Novalis linear accelerator for IMRT of the Instituto Nacional de Neurología y Neurocirugía (INNN) in Mexico City. The procedure includes measurements of individual fluence maps for a limited number of fields and dose distributions in 3D using extended dose-range radiographic film. However, the film response to radiation might depend on depth, energy and field size, and therefore compromise the accuracy of measurements. In this work we present a study of the dependence of Kodak EDR2 film's response on the depth, field size and energy, compared with those of Kodak XV2 film. The first aim is to devise a fast and accurate method to determine the calibration curve of film (optical density vs. doses) commonly called a sensitometric curve. This was accomplished by using three types of irradiation techniques: Step-and-shoot, dynamic and static fields.

  10. Polarization-tunable terahertz radiation in the high-field regime.

    PubMed

    Chen, Zi-Yu; Pukhov, Alexander

    2016-06-01

    Polarization control of terahertz (THz) pulses in the high-field regime is a challenging subject. Here we propose and numerically demonstrate an all-optical scheme to generate a polarization-tunable high-field THz source based on relativistic laser plasma interactions. By adjusting the polarization state of the driving laser, collective oscillation of the plasmas can be steered. Phase difference between the laser field components is inherited in the plasma dynamics, as well as in the resulting THz generation process. Single-cycle extremely intense THz pulses with field strength ∼  GV/cm can be generated. The THz polarization state can be tuned from linear through elliptical to circular by changing the polarization state of the driving laser. PMID:27244439

  11. A Micro-Cantilever Based Photoacoustic Detector of Terahertz Radiation for Chemical Sensing

    NASA Astrophysics Data System (ADS)

    Glauvitz, Nathan E.; Coutu, Ronald A. Coutu, Jr.; Kistler, Michael N.; Hamilton, Ryan F.; Petkie, Douglas T.; Medvedev, Ivan R.

    2013-06-01

    In this paper we describe a novel photoacoustic detector that can detect radiation in the Terahertz/sub-millimeter (THz/smm) spectral range, is immune to the effect of standing waves, and potentially can have spectral response that is independent of the absorption path length, thus offering crucial advantages for acquisition of THz/smm molecular spectra. The photoacoustic effect occurs when the energy from electromagnetic waves is absorbed by molecules and collisionally transferred into translational energy, thus resulting in local heating induced by the radiation. If radiation produced by the source is modulated, an acoustic wave results which can be detected by a pressure sensitive device such as a microphone or a cantilever. This transduction of the THz signal into a photoacoustic wave is what makes this approach insensitive to the detrimental standing waves associated with traditional THz sensors and allows for a significant reduction in the size of the absorption cell. A Microelectromechanical system (MEMS) cantilever pressure sensor was designed, modeled, fabricated, and tested for sensing the photoacoustic response of gases to THz/smm radiation. Here we present our manufacturing, experimental set-up and most recent spectroscopic results, which demonstrate the capabilities of this spectroscopic technique.

  12. An ultrafast carbon nanotube terahertz polarisation modulator

    SciTech Connect

    Docherty, Callum J.; Stranks, Samuel D.; Habisreutinger, Severin N.; Joyce, Hannah J.; Herz, Laura M.; Nicholas, Robin J.; Johnston, Michael B.

    2014-05-28

    We demonstrate ultrafast modulation of terahertz radiation by unaligned optically pumped single-walled carbon nanotubes. Photoexcitation by an ultrafast optical pump pulse induces transient terahertz absorption in nanowires aligned parallel to the optical pump. By controlling the polarisation of the optical pump, we show that terahertz polarisation and modulation can be tuned, allowing sub-picosecond modulation of terahertz radiation. Such speeds suggest potential for semiconductor nanowire devices in terahertz communication technologies.

  13. Strong sub-terahertz surface waves generated on a metal wire by high-intensity laser pulses

    PubMed Central

    Tokita, Shigeki; Sakabe, Shuji; Nagashima, Takeshi; Hashida, Masaki; Inoue, Shunsuke

    2015-01-01

    Terahertz pulses trapped as surface waves on a wire waveguide can be flexibly transmitted and focused to sub-wavelength dimensions by using, for example, a tapered tip. This is particularly useful for applications that require high-field pulses. However, the generation of strong terahertz surface waves on a wire waveguide remains a challenge. Here, ultrafast field propagation along a metal wire driven by a femtosecond laser pulse with an intensity of 1018 W/cm2 is characterized by femtosecond electron deflectometry. From experimental and numerical results, we conclude that the field propagating at the speed of light is a half-cycle transverse-magnetic surface wave excited on the wire and a considerable portion of the kinetic energy of laser-produced fast electrons can be transferred to the sub-surface wave. The peak electric field strength of the surface wave and the pulse duration are estimated to be 200 MV/m and 7 ps, respectively. PMID:25652694

  14. Strong sub-terahertz surface waves generated on a metal wire by high-intensity laser pulses.

    PubMed

    Tokita, Shigeki; Sakabe, Shuji; Nagashima, Takeshi; Hashida, Masaki; Inoue, Shunsuke

    2015-02-05

    Terahertz pulses trapped as surface waves on a wire waveguide can be flexibly transmitted and focused to sub-wavelength dimensions by using, for example, a tapered tip. This is particularly useful for applications that require high-field pulses. However, the generation of strong terahertz surface waves on a wire waveguide remains a challenge. Here, ultrafast field propagation along a metal wire driven by a femtosecond laser pulse with an intensity of 10(18) W/cm(2) is characterized by femtosecond electron deflectometry. From experimental and numerical results, we conclude that the field propagating at the speed of light is a half-cycle transverse-magnetic surface wave excited on the wire and a considerable portion of the kinetic energy of laser-produced fast electrons can be transferred to the sub-surface wave. The peak electric field strength of the surface wave and the pulse duration are estimated to be 200 MV/m and 7 ps, respectively.

  15. Strong sub-terahertz surface waves generated on a metal wire by high-intensity laser pulses.

    PubMed

    Tokita, Shigeki; Sakabe, Shuji; Nagashima, Takeshi; Hashida, Masaki; Inoue, Shunsuke

    2015-01-01

    Terahertz pulses trapped as surface waves on a wire waveguide can be flexibly transmitted and focused to sub-wavelength dimensions by using, for example, a tapered tip. This is particularly useful for applications that require high-field pulses. However, the generation of strong terahertz surface waves on a wire waveguide remains a challenge. Here, ultrafast field propagation along a metal wire driven by a femtosecond laser pulse with an intensity of 10(18) W/cm(2) is characterized by femtosecond electron deflectometry. From experimental and numerical results, we conclude that the field propagating at the speed of light is a half-cycle transverse-magnetic surface wave excited on the wire and a considerable portion of the kinetic energy of laser-produced fast electrons can be transferred to the sub-surface wave. The peak electric field strength of the surface wave and the pulse duration are estimated to be 200 MV/m and 7 ps, respectively. PMID:25652694

  16. Generation of scalable terahertz radiation from cylindrically focused laser pulses in air

    NASA Astrophysics Data System (ADS)

    Kuk, Donghoon; Yoo, Yungjun; Rosenthal, Eric; Jhajj, Nihal; Milchberg, Howard; Kim, Ki-Yong

    We have demonstrated scalable terahertz (THz) generation via cylindrical focusing of two-color laser pulses in air. In this experiment, we have used a terawatt (TW) laser system which can deliver >50 mJ, 800 nm, 50 fs pulses at a 10 Hz repetition rate. A 800 nm pulse passing through a nonlinear crystal (BBO) generates its second harmonic pulse (400 nm). Both pulses pass through a cylindrical lens and are focused together to generate a 2-dimensional plasma sheet in air. This yields two diverging THz lobes, characterized by an uncooled microbolometer. This observed radiation angle and pattern is explained by the optical-Cherenkov radiation theory. The diverging THz radiation is re-focused to yield strong THz field strengths (>20 MV/cm) at the focus. At laser energy of 40 mJ, cylindrical focusing provides THz energy of >30 microjoules, far exceeding the output produced by spherical focusing. This shows that cylindrical focusing can effectively minimize ionization-induced defocusing, previously observed in spherical focusing, and can allow scalable THz generation with relatively high laser energies (>20 mJ). Work supported by DOE, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award No. 014216-001.

  17. Gene expression profile of Jurkat cells exposed to high power terahertz radiation

    NASA Astrophysics Data System (ADS)

    Grundt, Jessica E.; Roth, Caleb C.; Rivest, Benjamin D.; Doroski, Michael L.; Payne, Jason; Ibey, Bennett L.; Wilmink, Gerald J.

    2011-03-01

    Terahertz (THz) radiation sources are now being used in a host of military, defense, and medical applications. Widespread employment of these applications has prompted concerns regarding the health effects associated with THz radiation. In this study, we examined the gene expression profile of mammalian cells exposed to THz radiation. We hypothesized that if THz radiation couples directly to cellular constituents, then exposed cells may express a specific gene expression profile indicative of ensuing damage. To test this hypothesis, Jurkat cells were irradiated with a molecular gas THz laser (2.52 THz, 636 mWcm-2, durations: 5, 10, 20, 30, 40, or 50 minutes). Viability was assessed 24 h post-exposure using MTT assays, and gene expression profiles were evaluated 4 h post-exposure using mRNA microarrays. Comparable analyses were also performed for hyperthermic positive controls (44°C for 40 minutes). We found that cellular temperatures increased by ~6 °C during THz exposures. We also found that cell death increased with exposure duration, and the median lethal dose (LD50) was calculated to be ~44 minutes. The microarray data showed that THz radiation induced the transcriptional activation of genes associated with cellular proliferation, differentiation, transcriptional activation, chaperone protein stabilization, and apoptosis. For most genes, we found that the magnitude of differential expression was comparable for both the THz and thermal exposure groups; however, several genes were specifically activated by the THz exposure. These results suggest that THz radiation may elicit effects that are not exclusively due to the temperature rise created during THz exposures (i.e. thermal effects). In future work, we plan to verify the results of our microarray experiments using qPCR techniques.

  18. Modeling of ultrasonic and terahertz radiations in defective tiles for condition monitoring of thermal protection systems

    NASA Astrophysics Data System (ADS)

    Kabiri Rahani, Ehsan

    Condition based monitoring of Thermal Protection Systems (TPS) is necessary for safe operations of space shuttles when quick turn-around time is desired. In the current research Terahertz radiation (T-ray) has been used to detect mechanical and heat induced damages in TPS tiles. Voids and cracks inside the foam tile are denoted as mechanical damage while property changes due to long and short term exposures of tiles to high heat are denoted as heat induced damage. Ultrasonic waves cannot detect cracks and voids inside the tile because the tile material (silica foam) has high attenuation for ultrasonic energy. Instead, electromagnetic terahertz radiation can easily penetrate into the foam material and detect the internal voids although this electromagnetic radiation finds it difficult to detect delaminations between the foam tile and the substrate plate. Thus these two technologies are complementary to each other for TPS inspection. Ultrasonic and T-ray field modeling in free and mounted tiles with different types of mechanical and thermal damages has been the focus of this research. Shortcomings and limitations of FEM method in modeling 3D problems especially at high-frequencies has been discussed and a newly developed semi-analytical technique called Distributed Point Source Method (DPSM) has been used for this purpose. A FORTRAN code called DPSM3D has been developed to model both ultrasonic and electromagnetic problems using the conventional DPSM method. This code is designed in a general form capable of modeling a variety of geometries. DPSM has been extended from ultrasonic applications to electromagnetic to model THz Gaussian beams, multilayered dielectrics and Gaussian beam-scatterer interaction problems. Since the conventional DPSM has some drawbacks, to overcome it two modification methods called G-DPSM and ESM have been proposed. The conventional DPSM in the past was only capable of solving time harmonic (frequency domain) problems. Time history was

  19. Study on applications of terahertz technology

    NASA Astrophysics Data System (ADS)

    Luo, Ji-jun; Hou, Su-xia; Xu, Jun; Li, Juan-juan

    2008-03-01

    Terahertz (THz) technology, as new research topic and technology field which is paid more and more attention by the researchers and governments, has some unique properties which is different from other electromagnetic wave. THz wave is regarded to have potential application in many fields. Existing and emerging applications of terahertz technology in imaging, medicine, biology, space exploration, covert communications, compact radar ranges, industrial controls, terahertz microscopy, terahertz tomography, and homeland security have stimulated intensive research effort in photonics and electronics technologies bracketing the famous terahertz gap from the high and low frequency sides, respectively. Cutoff frequencies and maximum frequencies of operation of InGaAs-based Heterostructure Bipolar Transistors and High Electron Mobility Transistors are now approaching or even exceeding 600 GHz. New ideas of using plasma resonances of two-dimensional electrons for tunable detection and emission of terahertz radiation are being explored and proven experimentally. Plasma effects in polarization-induced electrons and holes in granular pyroelectric/semiconductor heterostructures hold promise of an active THz medium tunable by external electric field or light.

  20. [A Compact Source of Terahertz Radiation Based on Interaction of Electrons in à Quantum Well with an Electromagnetic Wave of a Corrugated Waveguide].

    PubMed

    Shchurova, L Yu; Namiot, V A; Sarkisyan, D R

    2015-01-01

    Coherent sources of electromagnetic waves in the terahertz frequency range are very promising for various applications, including biology and medicine. In this paper we propose a scheme of a compact terahertz source, in which terahertz radiation is generated due to effective interaction of electrons in a quantum well with an electromagnetic wave of a corrugated waveguide. We have shown that the generation of electromagnetic waves with a frequency of 1012 sec(-1) and an output power of up to 25. mW is possible in the proposed scheme.

  1. The intensive terahertz electroluminescence induced by Bloch oscillations in SiC natural superlattices.

    PubMed

    Sankin, Vladimir; Andrianov, Alexandr; Petrov, Alexey; Zakhar'in, Alexey; Lepneva, Ala; Shkrebiy, Pavel

    2012-10-09

    : We report on efficient terahertz (THz) emission from high-electric-field-biased SiC structures with a natural superlattice at liquid helium temperatures. The emission spectrum demonstrates a single line, the maximum of which shifts linearly with increases in bias field. We attribute this emission to steady-state Bloch oscillations of electrons in the SiC natural superlattice. The properties of the THz emission agree fairly with the parameters of the Bloch oscillator regime, which have been proven by high-field electron transport studies of SiC structures with natural superlattices.

  2. The intensive terahertz electroluminescence induced by Bloch oscillations in SiC natural superlattices

    PubMed Central

    2012-01-01

    We report on efficient terahertz (THz) emission from high-electric-field-biased SiC structures with a natural superlattice at liquid helium temperatures. The emission spectrum demonstrates a single line, the maximum of which shifts linearly with increases in bias field. We attribute this emission to steady-state Bloch oscillations of electrons in the SiC natural superlattice. The properties of the THz emission agree fairly with the parameters of the Bloch oscillator regime, which have been proven by high-field electron transport studies of SiC structures with natural superlattices. PMID:23043773

  3. Colloquium: Nanoplasmas generated by intense radiation

    NASA Astrophysics Data System (ADS)

    Ostrikov, Kostya Ken; Beg, Farhat; Ng, Andrew

    2016-01-01

    Solid, liquid, and gaseous states of matter can exist and acquire unique properties when reduced in size into a nanometer domain. This Colloquium explores the approaches to produce plasmas with nanometer dimensions and the arising physical phenomena and properties associated with this extreme, nonequilibrium state of matter. Analysis of the spatial confinement, coupling, ideality, and degeneracy criteria lead to the possibilities to produce transient nanoplasma states near, in, and from solids by using ultrafast photoexcitation. These states arise through the interplay of nonequilibrium, many-body Coulomb interactions, thermal, and nonthermal effects. Examples include photoexcited electron-hole plasmas in semiconductors, transient solid-to-plasma states including warm dense matter, nanoplasmas produced by interaction of nanoclusters and nanoparticles with intense radiation, nanoplasmas in high-energy ion tracks within solids, nanoplasmas in relativistic regime, and others. Physical phenomena arising due to the localization of high-energy densities to microscales and nanoscales and their potential applications are discussed.

  4. Influence of terahertz laser radiation on the spectral characteristics and functional properties of albumin

    NASA Astrophysics Data System (ADS)

    Cherkasova, O. P.; Fedorov, V. I.; Nemova, E. F.; Pogodin, A. S.

    2009-10-01

    The exposure of albumin (transport protein of blood serum) to laser radiation with a frequency of 3.6 THz resulted in a change in the intensity of characteristic bands in UV absorption spectra and in circular dichroism spectra. These changes depend on the exposure duration and the laser radiation power and indicate conformational changes in protein molecules.

  5. On the transmission of terahertz radiation through silicon-based structures

    SciTech Connect

    Persano, Anna Francioso, Luca; Cola, Adriano; Torres, Jérémie; Nouvel, Philippe; Varani, Luca; Korotyeyev, Vadym V.; Lyaschuk, Yu M.

    2014-07-28

    We report on the transmission of a terahertz (THz) radiation through prototype structures based on a p-type silicon substrate. In particular, the bare substrate and progressively more complicated multilayer structures were investigated, allowing to address the effect on the transmission of different factors, such as the orientation of interdigitated contacts with respect to the polarized beam, the temperature, and the current flowing through a conductive SnO{sub 2} nanorods layer. A suitable experimental set-up was developed for the direct spectral measurement of transmission in the range of 0.75–1.1 THz at room and low temperatures. A simple Drude-Lorentz model was formulated, finding a quantitative agreement with the experimental transmission spectrum of the bare substrate at room temperature. For the multilayer structures, the spectra variations observed with temperature are well accounted by the corresponding change of the mobility of holes in the silicon p-type substrate. The influence of the contact orientation is consistent with that of a polarizing metallic grating. Finally, Joule heating effects are observed in the spectra performed as a function of the current flowing through the SnO{sub 2} nanorods layer. The experimental results shown here, together with their theoretical interpretation, provide insights for the development of devices fabricated on conductive substrates aimed to absorb/modulate radiation in the THz range.

  6. Measurement and Characterization of Terahertz Radiation Propagating Through a Parallel Plate Waveguide

    NASA Astrophysics Data System (ADS)

    Wachsmuth, Matthew George

    As the amount of study into the terahertz (THz) region of the electromagnetic spectrum steadily increases, the parallel plate waveguide has emerged as a simple and effective fixture to perform many experiments. The ability to concentrate THz radiation into a small area or volume enables us to analyze smaller samples and perform more repeatable measurements, which is essential for future research. While the fundamental physics of PPW transmission are understood mathematically, the practical knowledge of building such a fixture for the THz domain and taking measurements on it with a real system needs to be built up through experience. In this thesis, multiple PPW configurations are built and tested. These include waveguides of different lengths and opening heights, using lenses and antennas to focus and collect radiation from the input and output, and different amounts of polish on the waveguide surface. A basic resonator structure is also built and measured as a proof of concept for future research. The two most useful propagation modes through the waveguide, the lowest order transverse magnetic (TEM) and transverse electric (TE) modes, were characterized on all of the setups. Additionally, a flexible fixture was designed and measured which will allow future work in the THz field to be much more reliable and repeatable.

  7. Dielectric Wakefield Accelerating Structure as a Source of Terahertz Coherent Cerenkov Radiation

    SciTech Connect

    Cook, A. M.; Rosenzweig, J. B.; Badakov, H.; Travish, G.; Tikhoplav, R.; Williams, O. B.; England, R. J.; Thompson, M. C.

    2006-11-27

    We discuss future experimental work proposed to study the performance of a cylindrical dielectric wakefield accelerating structure as a coherent Cerenkov radiation source at the Neptune laboratory at UCLA. The Cerenkov wakefield acceleration experiment carried out recently by UCLA/SLAC/USC, using the ultrashort and high charge beam (Q = 3 nC, {sigma}z = 20 micron) at the SLAC FFTB, demonstrated electromagnetic wakes at the few GV/m level. The motivation of our prospective experiment is to investigate the operation of a similar scenario using the comparatively long pulse, low charge beam (Q = 0.5 nC, {sigma}z = 200 micron) at UCLA Neptune. The field amplitude produced in this setup would be one to two orders of magnitude lower, at the few tens to few 100 MV/m level. Such a decelerating field would extract a significant amount of energy from a low-energy beam in a distance on the order of a few centimeters, allowing the use of short dielectric structures. We discuss details of the geometry and composition of the structures to be used in the experiment. We also examine the possibility of a future dedicated facility at UCLA Neptune based on a hybrid photoinjector currently in development. The intrinsic bunch compression capabilities and improved beam parameters ({sigma}z = 100 micron, Q = 1 nC) of the photoinjector would allow the creation of a high power radiation source in the terahertz regime.

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

    NASA Astrophysics Data System (ADS)

    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).

  9. Note: Single-shot time-domain spectroscopy and spatial profiling of terahertz pulses from intense laser systems.

    PubMed

    Zhang, T J; Jin, Z; Wakamatsu, S; Hosokai, T; Yugami, N; Kodama, R

    2016-06-01

    Single-shot terahertz time-domain spectroscopy is presented with directly encoded spatial resolution. A single reflective echelon and multiple semi-cylindrical lenses are used to obtain both the temporal waveform and the spatial distribution of the terahertz field. This system can be used to rapidly characterize terahertz pulses generated by high power pulsed laser systems, which themselves suffer from large pulse energy and spectrum fluctuations. PMID:27370502

  10. Remote Detection of Concealed Radioactive Materials by Using Focused Powerful Terahertz Radiation

    NASA Astrophysics Data System (ADS)

    Nusinovich, Gregory S.

    2016-06-01

    This review paper summarizes the results of studies of a novel concept of the remote detection of concealed radioactive materials by using focused high-power terahertz (THz) radiation. The concept is based on the known fact that the ambient electron density in air is low (one to three free electrons per cubic centimeter). These electrons can serve as seed electrons from which an avalanche breakdown in strong electromagnetic fields starts. When a powerful THz radiation is focused in a small spot, the breakdown-prone volume can be much smaller than a cubic centimeter. So, the probability of having some free electrons in this volume and, hence, the probability of breakdown are low in the absence of additional sources of air ionization. However, in the vicinity of radioactive materials (10-20 m), the electron density can be higher, and, hence, there are always some seed free electrons from which the avalanche ionization will start. Thus, the breakdown rate in this case can be close to 100 %. Realization of this concept requires studies of various physical and technical issues. First, it is necessary to develop a high-power source of (sub-) THz radiation whose power, frequency, and pulse duration are sufficient for realizing this goal. Second, it is necessary to analyze numerous issues important for realizing this concept. Among these issues are (a) enhancement of the ionization level of air molecules in the presence of hidden radioactive materials, (b) estimating the minimum detectable mass of radioactive material, (c) formation of breakdown-prone volumes in focused THz wave beams, and (d) effect of atmospheric conditions on the propagation and focusing of THz wave beams and on the optimal location of the breakdown-prone volume between a container with hidden radioactive material and a THz antenna. The results of these studies are described below.

  11. Coherent terahertz radiation from high-harmonic component of modulated free-electron beam in a tapered two-asymmetric grating structure

    SciTech Connect

    Zhang Yaxin; Zhou Yucong; Dong Liang; Liu Shenggang

    2012-09-17

    Based on the mechanism of incoherent diffraction radiation excited by an electron bunch in a waveguide with periodic structure, this paper presents the concept of coherent terahertz (THz) radiation from the high-harmonic component of a modulated free-electron beam in a tapered two-asymmetric grating structure. The results show that in this mechanism 0.43 THz radiation can be generated with 10 A/cm{sup 2} current density, and the efficiency can reach 0.5%. Because of the low required current density and relative high efficiency, this concept shows the application potential for electron-beam-driven terahertz sources.

  12. Specificity and Heterogeneity of Terahertz Radiation Effect on Gene Expression in Mouse Mesenchymal Stem Cells

    DOE PAGES

    Alexandrov, Boian S.; Phipps, M. Lisa; Alexandrov, Ludmil B.; Booshehri, Layla G.; Erat, Anna; Zabolotny, Janice; Mielke, Charles H.; Chen, Hou-Tong; Rodriguez, George; Rasmussen, Kim O.; et al

    2013-01-31

    In this paper, we report that terahertz (THz) irradiation of mouse mesenchymal stem cells (mMSCs) with a single-frequency (SF) 2.52 THz laser or pulsed broadband (centered at 10 THz) source results in irradiation specific heterogenic changes in gene expression. The THz effect depends on irradiation parameters such as the duration and type of THz source, and on the degree of stem cell differentiation. Our microarray survey and RT-PCR experiments demonstrate that prolonged broadband THz irradiation drives mMSCs toward differentiation, while 2-hour irradiation (regardless of THz sources) affects genes transcriptionally active in pluripotent stem cells. The strictly controlled experimental environment indicatesmore » minimal temperature changes and the absence of any discernable response to heat shock and cellular stress genes imply a non-thermal response. Computer simulations of the core promoters of two pluripotency markers reveal association between gene upregulation and propensity for DNA breathing. Finally, we propose that THz radiation has potential for non-contact control of cellular gene expression.« less

  13. Specificity and Heterogeneity of Terahertz Radiation Effect on Gene Expression in Mouse Mesenchymal Stem Cells

    SciTech Connect

    Alexandrov, Boian S.; Phipps, M. Lisa; Alexandrov, Ludmil B.; Booshehri, Layla G.; Erat, Anna; Zabolotny, Janice; Mielke, Charles H.; Chen, Hou-Tong; Rodriguez, George; Rasmussen, Kim O.; Martinez, Jennifer S.; Bishop, Alan R.; Usheva, Anny

    2013-01-31

    In this paper, we report that terahertz (THz) irradiation of mouse mesenchymal stem cells (mMSCs) with a single-frequency (SF) 2.52 THz laser or pulsed broadband (centered at 10 THz) source results in irradiation specific heterogenic changes in gene expression. The THz effect depends on irradiation parameters such as the duration and type of THz source, and on the degree of stem cell differentiation. Our microarray survey and RT-PCR experiments demonstrate that prolonged broadband THz irradiation drives mMSCs toward differentiation, while 2-hour irradiation (regardless of THz sources) affects genes transcriptionally active in pluripotent stem cells. The strictly controlled experimental environment indicates minimal temperature changes and the absence of any discernable response to heat shock and cellular stress genes imply a non-thermal response. Computer simulations of the core promoters of two pluripotency markers reveal association between gene upregulation and propensity for DNA breathing. Finally, we propose that THz radiation has potential for non-contact control of cellular gene expression.

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

    SciTech Connect

    Balal, N.; Magory, E.; Bandurkin, I. V.; Bratman, V. L.; Savilov, A. V.

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  16. Specificity and Heterogeneity of Terahertz Radiation Effect on Gene Expression in Mouse Mesenchymal Stem Cells

    NASA Astrophysics Data System (ADS)

    Alexandrov, Boian S.; Phipps, M. Lisa; Alexandrov, Ludmil B.; Booshehri, Layla G.; Erat, Anna; Zabolotny, Janice; Mielke, Charles H.; Chen, Hou-Tong; Rodriguez, George; Rasmussen, Kim Ø.; Martinez, Jennifer S.; Bishop, Alan R.; Usheva, Anny

    2013-01-01

    We report that terahertz (THz) irradiation of mouse mesenchymal stem cells (mMSCs) with a single-frequency (SF) 2.52 THz laser or pulsed broadband (centered at 10 THz) source results in irradiation specific heterogenic changes in gene expression. The THz effect depends on irradiation parameters such as the duration and type of THz source, and on the degree of stem cell differentiation. Our microarray survey and RT-PCR experiments demonstrate that prolonged broadband THz irradiation drives mMSCs toward differentiation, while 2-hour irradiation (regardless of THz sources) affects genes transcriptionally active in pluripotent stem cells. The strictly controlled experimental environment indicates minimal temperature changes and the absence of any discernable response to heat shock and cellular stress genes imply a non-thermal response. Computer simulations of the core promoters of two pluripotency markers reveal association between gene upregulation and propensity for DNA breathing. We propose that THz radiation has potential for non-contact control of cellular gene expression.

  17. An ultra-fast data acquisition system for coherent synchrotron radiation with terahertz detectors

    NASA Astrophysics Data System (ADS)

    Caselle, M.; Balzer, M.; Chilingaryan, S.; Hofherr, M.; Judin, V.; Kopmann, A.; Smale, N. J.; Thoma, P.; Wuensch, S.; Müller, A.-S.; Siegel, M.; Weber, M.

    2014-01-01

    The recording of coherent synchrotron radiation requires data acquisition systems with a temporal resolution of tens of picosecond. This paper describes a new real-time and high-accuracy data acquisition system suitable for recording individual ultra-short pulses generated by a fast terahertz (THz) detector (e.g. YBCO, NbN, Zero Biased Schottky Diode). The system consists of a fast sampling board combined with a high data throughput readout. The first board is designed for sampling the fast pulse signals with a full width half maximum (FWHM) between a few tens to one hundred picoseconds with a minimum sampling time of 3 ps. The high data throughput board consists of a PCIe-Bus Master DMA architecture used for fast data transfer up to 3 GByte/s. The full readout chain with fast THz detectors and the acquisition system has been successfully tested at the synchrotron ANKA. An overview of the electronics system and preliminary results with multi-bunch filling pattern will be presented.

  18. Ultrabright continuously tunable terahertz-wave generation at room temperature

    NASA Astrophysics Data System (ADS)

    Hayashi, Shin'ichiro; Nawata, Kouji; Taira, Takunori; Shikata, Jun-Ichi; Kawase, Kodo; Minamide, Hiroaki

    2014-06-01

    The hottest frequency region in terms of research currently lies in the `frequency gap' region between microwaves and infrared: terahertz waves. Although new methods for generating terahertz radiation have been developed, most sources cannot generate high-brightness terahertz beams. Here we demonstrate the generation of ultrabright terahertz waves (brightness ~0.2 GW/sr.cm2, brightness temperature of ~1018 K, peak power of >50 kW) using parametric wavelength conversion in a nonlinear crystal; this is brighter than many specialized sources such as far-infrared free-electron lasers (~1016 K, ~2 kW). We revealed novel parametric wavelength conversion using stimulated Raman scattering in LiNbO3 without stimulated Brillouin scattering using recently-developed microchip laser. Furthermore, nonlinear up-conversion techniques allow the intense terahertz waves to be visualized and their frequency determined. These results are very promising for extending applied research into the terahertz region, and we expect that this source will open up new research fields such as nonlinear optics in the terahertz region.

  19. Ultrabright continuously tunable terahertz-wave generation at room temperature

    PubMed Central

    Hayashi, Shin'ichiro; Nawata, Kouji; Taira, Takunori; Shikata, Jun-ichi; Kawase, Kodo; Minamide, Hiroaki

    2014-01-01

    The hottest frequency region in terms of research currently lies in the ‘frequency gap' region between microwaves and infrared: terahertz waves. Although new methods for generating terahertz radiation have been developed, most sources cannot generate high-brightness terahertz beams. Here we demonstrate the generation of ultrabright terahertz waves (brightness ~0.2 GW/sr·cm2, brightness temperature of ~1018 K, peak power of >50 kW) using parametric wavelength conversion in a nonlinear crystal; this is brighter than many specialized sources such as far-infrared free-electron lasers (~1016 K, ~2 kW). We revealed novel parametric wavelength conversion using stimulated Raman scattering in LiNbO3 without stimulated Brillouin scattering using recently-developed microchip laser. Furthermore, nonlinear up-conversion techniques allow the intense terahertz waves to be visualized and their frequency determined. These results are very promising for extending applied research into the terahertz region, and we expect that this source will open up new research fields such as nonlinear optics in the terahertz region. PMID:24898269

  20. Calorimetric detection of the conical terahertz radiation from femtosecond laser filaments in air

    NASA Astrophysics Data System (ADS)

    Houard, Aurélien; Liu, Yi; Mysyrowicz, André; Leriche, Bernadette

    2007-12-01

    The spectral distribution of the conical terahertz emission from a femtosecond laser filament in air is measured with a bolometric detector and a set of filters, confirming that the main part of the emission lies between 0.5 and 3THz. The efficiency of this terahertz emission is compared with that obtained in air via four wave mixing of femtosecond laser pulses at ω and 2ω in the presence of a plasma.

  1. Generation of terahertz radiation by a surface ballistic photocurrent in semiconductors under subpicosecond laser excitation

    SciTech Connect

    Ziaziulia, P. A.; Malevich, V. L.; Manak, I. S.; Krotkus, A.

    2012-02-15

    An analytical model describing the onset of a surface ballistic photocurrent in cubic semiconductors under femtosecond laser excitation is proposed. It is shown that the contribution of the photocurrent component parallel to the surface to the generation of terahertz pulses may be comparable to the contribution of the perpendicular component. Consideration of the cubic symmetry of a semiconductor leads to the azimuthal anisotropy of terahertz generation.

  2. Radiation of terahertz electromagnetic waves from build-in nano Josephson junctions of cuprate high-T(c) superconductors.

    PubMed

    Lin, Shi-Zeng; Hu, Xiao

    2011-04-01

    The nano-scale intrinsic Josephson junctions in highly anisotropic cuprate superconductors have potential for generation of terahertz electromagnetic waves. When the thickness of a superconductor sample is much smaller than the wavelength of electromagnetic waves in vacuum, the superconductor renders itself as a cavity. Unlike conventional lasers, the presence of the cavity does not guarantee a coherent emission because of the internal degree of freedom of the superconductivity phase in long junctions. We study the excitation of terahertz wave by solitons in a stack of intrinsic Josephson junctions, especially for relatively short junctions. Coherent emission requires a rectangular configuration of solitons. However such a configuration is unstable against weak fluctuations, contrarily solitons favor a triangular lattice corresponding to an out-phase oscillation of electromagnetic waves. To utilize the cavity, we propose to use an array of stacks of short intrinsic Josephson junctions to generate powerful terahertz electromagnetic waves. The cavity synchronizes the plasma oscillation in different stacks and the emission intensity is predicted to be proportional to the number of stacks squared.

  3. Quantum computing Hyper Terahertz Facility opens

    NASA Astrophysics Data System (ADS)

    Singh Chadha, Kulvinder

    2016-01-01

    A new facility has opened at the University of Surrey to use terahertz radiation for quantum computing. The Hyper Terahertz Facility (HTF) is a joint collaboration between the University of Surrey and the National Physical Laboratory (NPL).

  4. Terahertz electromagnetic radiation from Bi2Sr2CaCu2Oy intrinsic Josephson junction stack

    NASA Astrophysics Data System (ADS)

    Oikawa, Dai; Irie, Akinobu; Yamaki, Kazuhiro; Oya, Gin-ichiro

    We have observed terahertz (THz) electromagnetic wave radiation from Bi2Sr2CaCu2Oy intrinsic Josephson junction (IJJ) stacks using high sensitive detector made of a small IJJ mesa. In this study, we focused on the THz radiation from a few hundred IJJs. We fabricated the IJJ oscillator and detector. The oscillators consist of 55 ∼ 300 IJJs with the lateral dimensions of 290 ¥ 50 μm2. The current-voltage characteristics of the IJJ oscillators showed a negative resistance accompanied with large hysteresis. The THz radiation was observed for several samples when the oscillator was biased at some current in the negative resistance region. We attribute the observed radiation to synchronized emission from many IJJs in the stack and find the emission frequency corresponds to the in-phase cavity resonance frequency.

  5. Competition between linear and nonlinear processes during generation of pulsed terahertz radiation in a ZnTe crystal

    SciTech Connect

    Gaivoronsky, Vladimir Ya; Shepelyavyi, Yevgenii V; Nazarov, Maksim M; Sapozhnikov, Dmitrii A; Shkel'nyuk, Svetlana A; Shkurinov, A P; Shuvaev, Aleksandr V

    2005-05-31

    The generation of terahertz (THz) pulses by the optical rectification of femtosecond laser pulses in a ZnTe crystal is studied. A substantial decrease in the THz radiation power was observed upon tight focusing of laser radiation into the crystal. It is shown that the consideration of competing two-photon absorption and second-harmonic generation processes proceeding simultaneously with optical rectification cannot explain this effect even qualitatively. It is assumed that the observed decrease in the THz radiation power is caused by a decrease in the size of a source of nonlinear polarisation. The conditions are found for the most efficient generation of THz radiation in the ZnTe crystal. (nonlinear optical phenomena)

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

    NASA Astrophysics Data System (ADS)

    Duka, M. V.; Dvoretskaya, L. N.; Babelkin, N. S.; Khodzitskii, M. K.; Chivilikhin, S. A.; Smolyanskaya, O. A.

    2014-08-01

    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.

  7. The polarization trajectory of terahertz magnetic dipole radiation in (110)-oriented PrFeO{sub 3} single crystal

    SciTech Connect

    Song, Gaibei; Jin, Zuanming; Lin, Xian; Jiang, Junjie; Wang, Xinyan; Wu, Hailong; Ma, Guohong E-mail: sxcao@shu.edu.cn; Cao, Shixun E-mail: sxcao@shu.edu.cn

    2014-04-28

    By using the polarized terahertz (THz) time-domain spectroscopy, the macro-magnetization motion in (110)-oriented PrFeO{sub 3} single crystal was constructed. We emphasize that the trajectory of the emitted THz waveforms relies on not only the motion of macroscopic magnetization vector, but also the spin configuration in the ground state and the propagation of THz pulse. The azimuthal angle (the incident THz pulse polarization with respect to the crystal axes) enables us to control the polarization trajectories of the quasiferromagnetic and quasiantiferromagnetic mode radiations that can lead to further applications on multiple information storing and quantum processing.

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

    SciTech Connect

    Duka, M V; Dvoretskaya, L N; Babelkin, N S; Khodzitskii, M K; Chivilikhin, S A; Smolyanskaya, O A

    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)

  9. No DNA damage response and negligible genome-wide transcriptional changes in human embryonic stem cells exposed to terahertz radiation.

    PubMed

    Bogomazova, A N; Vassina, E M; Goryachkovskaya, T N; Popik, V M; Sokolov, A S; Kolchanov, N A; Lagarkova, M A; Kiselev, S L; Peltek, S E

    2015-01-01

    Terahertz (THz) radiation was proposed recently for use in various applications, including medical imaging and security scanners. However, there are concerns regarding the possible biological effects of non-ionising electromagnetic radiation in the THz range on cells. Human embryonic stem cells (hESCs) are extremely sensitive to environmental stimuli, and we therefore utilised this cell model to investigate the non-thermal effects of THz irradiation. We studied DNA damage and transcriptome responses in hESCs exposed to narrow-band THz radiation (2.3 THz) under strict temperature control. The transcription of approximately 1% of genes was subtly increased following THz irradiation. Functional annotation enrichment analysis of differentially expressed genes revealed 15 functional classes, which were mostly related to mitochondria. Terahertz irradiation did not induce the formation of γH2AX foci or structural chromosomal aberrations in hESCs. We did not observe any effect on the mitotic index or morphology of the hESCs following THz exposure. PMID:25582954

  10. No DNA damage response and negligible genome-wide transcriptional changes in human embryonic stem cells exposed to terahertz radiation.

    PubMed

    Bogomazova, A N; Vassina, E M; Goryachkovskaya, T N; Popik, V M; Sokolov, A S; Kolchanov, N A; Lagarkova, M A; Kiselev, S L; Peltek, S E

    2015-01-13

    Terahertz (THz) radiation was proposed recently for use in various applications, including medical imaging and security scanners. However, there are concerns regarding the possible biological effects of non-ionising electromagnetic radiation in the THz range on cells. Human embryonic stem cells (hESCs) are extremely sensitive to environmental stimuli, and we therefore utilised this cell model to investigate the non-thermal effects of THz irradiation. We studied DNA damage and transcriptome responses in hESCs exposed to narrow-band THz radiation (2.3 THz) under strict temperature control. The transcription of approximately 1% of genes was subtly increased following THz irradiation. Functional annotation enrichment analysis of differentially expressed genes revealed 15 functional classes, which were mostly related to mitochondria. Terahertz irradiation did not induce the formation of γH2AX foci or structural chromosomal aberrations in hESCs. We did not observe any effect on the mitotic index or morphology of the hESCs following THz exposure.

  11. Improvement of Terahertz Wave Radiation for InAs Nanowires by Simple Dipping into Tap Water

    PubMed Central

    Park, Dong Woo; Bin Ji, Young; Hwang, Jehwan; Lee, Cheul-Ro; Lee, Sang Jun; Kim, Jun Oh; Noh, Sam Kyu; Oh, Seung Jae; Kim, Sang-Hoon; Jeon, Tae-In; Jeong, Kwang-Un; Kim, Jin Soo

    2016-01-01

    We report improvement of terahertz (THz) wave radiation for Si-based catalyst-free InAs nanowires (NWs) by simple dipping into tap water (DTW). In addition, the possibility of using InAs NWs as a cost-effective method for biomedical applications is discussed by comparison to bulk InAs. The peak-to-peak current signals (PPCSs) of InAs NWs measured from THz time-domain spectroscopy increased with increasing NW height. For example, the PPCS of 10 μm-long InAs NWs was 2.86 times stronger than that of 2.1 μm-long NWs. The THz spectra of the InAs NWs obtained by applying a fast Fourier transformation to the current signals showed a main frequency of 0.5 THz, which can be applied to a variety of medical imaging systems. After the DTW process, structural variation was not observed for 2.1 μm-long InAs NWs. However, the top region of several InAs NWs with heights of 4.6 and 5.8 μm merged into a conical structure. InAs NWs with a height of 10 μm resulted in a bundle feature forming above the conical shape, where the length of bundle region was 4 μm. After the DTW process, the PPCS for 10 μm-long InAs NWs increased by 15 percent compared to that of the as-grown case. PMID:27782220

  12. Experimental research on spectrum and imaging of continuous-wave terahertz radiation based on interferometry

    NASA Astrophysics Data System (ADS)

    Lu, Tie-Lin; Yuan, Hui; Kong, Ling-Qin; Zhao, Yue-Jin; Zhang, Liang-Liang; Zhang, Cun-Lin

    2016-08-01

    A system for measuring terahertz spectrum is proposed based on optical interferometer theory, and is experimentally demonstrated by using a backward-wave oscillator as the terahertz source. A high-resolution, high-precision interferometer is constructed by using a pyroelectric detector and a chopper. The results show that the spectral resolution is better than 1 GHz and the relative error of frequency is less than 3%. The terahertz energy density distribution is calculated by an inverse Fourier transform and tested to verify the feasibility of the interferometric approach. Two kinds of carbon-fiber composites are imaged. The results confirm that the interferometer is useful for transmission imaging of materials with different thickness values. Project supported by the National Natural Science Foundation of China (Grant Nos. 61377109 and 11374007).

  13. Experimental research on spectrum and imaging of continuous-wave terahertz radiation based on interferometry

    NASA Astrophysics Data System (ADS)

    Lu, Tie-Lin; Yuan, Hui; Kong, Ling-Qin; Zhao, Yue-Jin; Zhang, Liang-Liang; Zhang, Cun-Lin

    2016-08-01

    A system for measuring terahertz spectrum is proposed based on optical interferometer theory, and is experimentally demonstrated by using a backward-wave oscillator as the terahertz source. A high-resolution, high-precision interferometer is constructed by using a pyroelectric detector and a chopper. The results show that the spectral resolution is better than 1 GHz and the relative error of frequency is less than 3%. The terahertz energy density distribution is calculated by an inverse Fourier transform and tested to verify the feasibility of the interferometric approach. Two kinds of carbon-fiber composites are imaged. The results confirm that the interferometer is useful for transmission imaging of materials with different thickness values. Project supported by the National Natural Science Foundation of China (Grant Nos. 61377109 and 11374007).

  14. Sensor structure concepts for the analysis or local radiation exposure of biological samples at terahertz and millimeter wave frequencies

    NASA Astrophysics Data System (ADS)

    Dornuf, Fabian; Dörr, Roland; Lämmle, David; Schlaak, Helmut F.; Krozer, Viktor

    2016-03-01

    We have studied several sensor concepts for biomedical applications operating in the millimeter wave and terahertz range. On one hand, rectangular waveguide structure were designed and extended with microfluidic channels. In this way a simple analysis of aqueous solutions at various waveguide bands is possible. In our case, we focused on the frequency range between 75 GHz and 110 GHz. On the other hand, planar sensor structures for aqueous solutions have been developed based on coplanar waveguides. With these planar sensors it is possible to concentrate the interaction volume on small sensor areas, which achieve a local exposure of the radiation to the sample. When equipping the sensor with microfluidic structures the sample volume could be reduced significantly and enabled a localized interaction with the sensor areas. The sensors are designed to exhibit a broadband behavior up to 300 GHz. Narrow-band operation can also be achieved for potentially increased sensitivity by using resonant structures. Several tests with Glucose dissolved in water show promising results for the distinction of different glucose levels at millimeter wave frequencies. The planar structures can also be used for the exposure of biological cells or cell model systems like liposomes with electromagnetic radiation. Several studies are planned to distinguish on one hand the influence of millimeter wave exposure on biological systems and also to have a spectroscopic method which enables the analysis of cell processes, like membrane transport processes, with millimeter wave and terahertz frequencies by focusing the electric field directly on the analyzing sample.

  15. Terahertz calorimetry: an absolute power meter for terahertz radiation and the absorptivity of the Herschel Space Observatory telescope mirror coating

    NASA Astrophysics Data System (ADS)

    Klaassen, Tjeerd O.; Hovenier, J. Niels; Fischer, Jacqueline; Jakob, Gerd; Poglitsch, Albrecht; Sternberg, Oren

    2004-04-01

    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 based on the calorimetric method: in order to determine the power of a beam of THz radiation, the beam is used to illuminate a highly absorbing surface with known BRDF characteristics until a stable temperature is reached. The power in the incident beam can then be determined by measuring the electric power needed to cause the sample temperature rise. The new power meter was used with laser calorimetry to measure the absorptivity, and thus the emissivity, of aluminum-coated silicon carbide mirror samples produced during the coating qualification run of the Herschel Space Observatory telescope to be launched by the European Space Agency in 2007. The samples were measured at 77 Kelvin to simulate the operating temperature of the telescope in its planned orbit around the second Lagrangian point, L2, of the Earth-Sun system. The absorptivity of both clean and dust-contaminated samples was measured at 70, 118, 184 and 496 mm and found to be in the range 0.2 - 0.8%.

  16. Transformation of surface plasmon polaritons to radiation in graphene in terahertz regime

    NASA Astrophysics Data System (ADS)

    Gong, Sen; Zhao, Tao; Sanderson, Matthew; Hu, Min; Zhong, Renbin; Chen, Xiaoxing; Zhang, Ping; Zhang, Chao; Liu, Shenggang

    2015-06-01

    We demonstrate a concept that allows direct excitation of surface plasmon polaritons (SPPs) by a moving electron bunch above a single layer graphene sheet deposited on a dielectric substrate without any additional coupling requirements. We show that if the two-dimensional current in the graphene is dominated by the third order nonlinear effect when the surface electric field exceeds a moderate strength of ˜5 kV/cm, the SPP mode can cross the light line although the group velocity remains much smaller than the speed of light. This effect gives rise to direct transformation of SPPs into radiation. The underlying mechanism of the crossing of the SPP dispersion into the light line is the energy shift of charged particles in the nonlinear regime and the finite transport scattering time in graphene. Both the energy and lifetime of the SPPs increase with the field intensity. The radiation intensity and frequency can be tuned with an AC bias.

  17. Transformation of surface plasmon polaritons to radiation in graphene in terahertz regime

    SciTech Connect

    Gong, Sen; Zhao, Tao; Hu, Min; Zhong, Renbin; Chen, Xiaoxing; Zhang, Ping; Liu, Shenggang; Sanderson, Matthew; Zhang, Chao

    2015-06-01

    We demonstrate a concept that allows direct excitation of surface plasmon polaritons (SPPs) by a moving electron bunch above a single layer graphene sheet deposited on a dielectric substrate without any additional coupling requirements. We show that if the two-dimensional current in the graphene is dominated by the third order nonlinear effect when the surface electric field exceeds a moderate strength of ∼5 kV/cm, the SPP mode can cross the light line although the group velocity remains much smaller than the speed of light. This effect gives rise to direct transformation of SPPs into radiation. The underlying mechanism of the crossing of the SPP dispersion into the light line is the energy shift of charged particles in the nonlinear regime and the finite transport scattering time in graphene. Both the energy and lifetime of the SPPs increase with the field intensity. The radiation intensity and frequency can be tuned with an AC bias.

  18. Supersonic intensity and non-negative intensity for prediction of radiated sound.

    PubMed

    Liu, Daipei; Peters, Herwig; Marburg, Steffen; Kessissoglou, Nicole

    2016-05-01

    Two numerical methods to identify the surface areas of a vibrating structure that radiate sound are presented. The supersonic intensity identifies only the supersonic wave components of the sound field contributing to far-field radiated sound. The supersonic intensity is calculated using a two-dimensional convolution between a spatial radiation filter and the sound field. To compute the spatial radiation filter, the shortest surface distance between two points on the structure is calculated using the geodesic distance method. The non-negative intensity is based on acoustic radiation modes and identifies the radiated sound power from a vibrating structure. Numerical models of a baffled plate, a cylinder and an engine crankcase are presented. The supersonic intensity is shown to be difficult to implement at low frequencies due to the size of the spatial radiation filter and accuracy of the surface distances. A cut-off coefficient associated with the acoustic wavenumber of the spatial radiation filter is used to reduce the aperture error. A comparison of the two intensity-based techniques both in terms of a sound power ratio and the modal assurance criterion is introduced to identify the optimal values of the cut-off coefficients that result in better convergence between the intensity techniques.

  19. Supersonic intensity and non-negative intensity for prediction of radiated sound.

    PubMed

    Liu, Daipei; Peters, Herwig; Marburg, Steffen; Kessissoglou, Nicole

    2016-05-01

    Two numerical methods to identify the surface areas of a vibrating structure that radiate sound are presented. The supersonic intensity identifies only the supersonic wave components of the sound field contributing to far-field radiated sound. The supersonic intensity is calculated using a two-dimensional convolution between a spatial radiation filter and the sound field. To compute the spatial radiation filter, the shortest surface distance between two points on the structure is calculated using the geodesic distance method. The non-negative intensity is based on acoustic radiation modes and identifies the radiated sound power from a vibrating structure. Numerical models of a baffled plate, a cylinder and an engine crankcase are presented. The supersonic intensity is shown to be difficult to implement at low frequencies due to the size of the spatial radiation filter and accuracy of the surface distances. A cut-off coefficient associated with the acoustic wavenumber of the spatial radiation filter is used to reduce the aperture error. A comparison of the two intensity-based techniques both in terms of a sound power ratio and the modal assurance criterion is introduced to identify the optimal values of the cut-off coefficients that result in better convergence between the intensity techniques. PMID:27250172

  20. Use of terahertz electromagnetic radiation for correction of blood rheology parameters in patients with unstable angina under conditions of treatment with isoket, an NO donor.

    PubMed

    Kirichuk, V F; Andronov, E V; Mamontova, N V; Tupicin, V D; Mayborodin, A V

    2008-09-01

    The effect of terahertz electromagnetic radiation at the emission and absorption frequencies of NO molecular spectrum on blood rheology were studied in vitro in patients with unstable angina treated with isoket (NO donor). Irradiated NO donor isoket produced better normalizing effect on blood viscosity and erythrocyte deformability in patients with unstable angina.

  1. [Changes gas and electrolyte structure of blood under influence terahertz radiations on frequencies nitrogen oxide 150,176-150,664 GHz in the conditions of stress].

    PubMed

    Tsymbal, A A; Kirichuk, V F

    2011-01-01

    Influence terahertz radiations nitrogen oxide frequencies of 150,176 - 150,664 GHz on gas and electrolyte structure of blood of white rats being in condition of sharp stress. It is shown that at 15 minute mode of influence terahertz waves on frequencies nitrogen oxide observe partial restoration of studied indicators gas and electrolyte structure of blood at stress animals. At 30 minute mode of influence the specified waves observe complete recovery of the broken indicators gas and electrolyte blood structure. PMID:21688667

  2. Terahertz photoluminescence from S.I.-GaAs by below gap excitation via EL2 level

    SciTech Connect

    Oyama, Yutaka Dezaki, Hikari; Shimizu, Yusaku; Maeda, Kensaku

    2015-01-12

    Terahertz emission by radiative transitions in semi-conductors via shallow impurity states is investigated. We report on the observation of terahertz photoluminescence from S.I.-GaAs by below gap excitation via EL2 level which is located at the center of band gap. In order to investigate the terahertz wave emission mechanisms, the emission spectra and temperature dependence of the emission intensity are evaluated. It is shown that intense terahertz emission from S.I.-GaAs over 120 K is observed due to the thermal recovery of photo-quenched EL2 meta-stable state, and that the emission peak frequency looks to be attributed to the shallow level energy in GaAs.

  3. Terahertz radiation from carbon nanorings in external collinear constant and varying electric fields

    NASA Astrophysics Data System (ADS)

    Fedorov, E. G.; Yanyushkina, N. N.; Belonenko, M. B.

    2013-04-01

    We consider the response of a quasi-one-dimensional ballistic carbon ring to the field of an electromagnetic wave propagating along the normal to the ring plane in the presence of a constant electric field collinear to the field of the wave. The dipole moment and the radiation intensity of the ring are calculated for the ballistic motion of a conduction electron. The possibility of implementation of regular periodic and chaotic regimes of ring emission under the action of external fields is demonstrated. The radiation spectrum of the ring is analyzed, and the dependence of the scattering cross section for an electromagnetic wave incident on the ring on its frequency and amplitude is calculated.

  4. Terahertz wave spectrum analysis of microstrip structure

    NASA Astrophysics Data System (ADS)

    Song, Mei-jing; Li, Jiu-sheng

    2011-11-01

    Terahertz wave is a kind of electromagnetic wave ranging from 0.1~10THz, between microwave and infrared, which occupies a special place in the electromagnetic spectrum. Terahertz radiation has a strong penetration for many media materials and nonpolar substance, for example, dielectric material, plastic, paper carton and cloth. In recent years, researchers around the world have paid great attention on terahertz technology, such as safety inspection, chemical biology, medical diagnosis and terahertz wave imaging, etc. Transmission properties of two-dimensional metal microstrip structures in the terahertz regime are presented and tested. Resonant terahertz transmission was demonstrated in four different arrays of subwavelength microstrip structure patterned on semiconductor. The effects of microstrip microstrip structure shape were investigated by using terahertz time-domain spectroscopy system. The resonant terahertz transmission has center frequency of 2.05 THz, transmission of 70%.

  5. Terahertz wave spectrum analysis of microstrip structure

    NASA Astrophysics Data System (ADS)

    Song, Mei-jing; Li, Jiu-sheng

    2012-03-01

    Terahertz wave is a kind of electromagnetic wave ranging from 0.1~10THz, between microwave and infrared, which occupies a special place in the electromagnetic spectrum. Terahertz radiation has a strong penetration for many media materials and nonpolar substance, for example, dielectric material, plastic, paper carton and cloth. In recent years, researchers around the world have paid great attention on terahertz technology, such as safety inspection, chemical biology, medical diagnosis and terahertz wave imaging, etc. Transmission properties of two-dimensional metal microstrip structures in the terahertz regime are presented and tested. Resonant terahertz transmission was demonstrated in four different arrays of subwavelength microstrip structure patterned on semiconductor. The effects of microstrip microstrip structure shape were investigated by using terahertz time-domain spectroscopy system. The resonant terahertz transmission has center frequency of 2.05 THz, transmission of 70%.

  6. Terahertz emission upon the band-to-band excitation of Group-IV semiconductors at room temperature

    SciTech Connect

    Zakhar’in, A. O.; Bobylev, A. V.; Egorov, S. V.; Andrianov, A. V.

    2015-03-15

    Terahertz emission upon the band-to-band excitation of Group-IV semiconductors (Si:B and Ge:Ga) at room temperature by a semiconductor laser emitting in the visible range (660 nm) is observed and investigated. It is established that, as the crystal temperature is elevated above room temperature, the emission intensity increases considerably, while the emission spectrum shifts to higher frequencies. The terahertz-emission spectra of germanium and silicon are quite similar to each other. The pump-intensity dependence of the terahertz-emission intensity is nearly linear. The above features make it possible to attribute the observed terahertz emission to the effect of crystal heating by absorbed pump radiation.

  7. Ray tracing method with Fresnel's transmission to calculate polarized radiation power distribution focused by a terahertz Silicon lens antenna

    NASA Astrophysics Data System (ADS)

    Apriono, Catur; Rahardjo, Eko Tjipto; Hiromoto, Norihisa

    2015-03-01

    We study a method for simulating a power-flow density distribution of terahertz-wave focused by a hemispherical Silicon lens antenna. A regular ray-tracing method is not enough to evaluate a correct radiation power-flow because it does not take into account transmittances dependent on angles of incidence at different positions on the spherical boundary of the Si-lens. In this study, we propose a ray-tracing method including Fresnel's transmission coefficients on the surface of a Si-lens for incoming polarized rays. The power-flow-density distribution calculated by the proposed method has a good agreement except for interference and diffraction with the result obtained by an electromagnetic wave simulator. Our method is so simple and reliable that it is useful for designing and evaluating THz optical systems using dielectric lens antennas.

  8. Terahertz radiation generation by beating of two super Gaussian lasers in plasma having static dc electric field

    NASA Astrophysics Data System (ADS)

    Hussain, Saba; Singh, Ram Kishor; Sharma, R. P.

    2016-07-01

    This paper presents a scheme for the generation of high power terahertz radiation by the beating of two femtosecond super Gaussian lasers in plasma having dc electric field in the transverse direction. In this mechanism, a strong nonlinear ponderomotive force acts on the plasma electrons at the frequency difference of the two lasers ( ω 1 - ω 2 ) that imparts a nonlinear oscillatory velocity to plasma electrons which further result in the generation of a nonlinear current at this difference frequency (lying in THz domain). The dynamical equations governing the generation of THz waves have been solved semi-analytically; the result shows that the amplitude of the generated waves is considerably enhanced in the presence of dc electric field, and the index of super Gaussian beams also plays a keen role in governing the yield of THz waves.

  9. Superimposed coherent terahertz wave radiation from mono-energetically bunched multi-beam

    SciTech Connect

    Shin, Young -Min

    2012-06-27

    Intense coherent radiation is obtained from multiple electron beams monochromatically bunched over the wide higher-order-mode (HOM) spectral band in the THz regime. The overmoded waveguide corrugated by dielectric-implanted staggered gratings superimposes evanescent waves emitted from the low energy electron beams. The dispersion and transmission simulations of the three-beam slow wave structure show that the first two fundamental modes ($TE_{10}$ and $TE_{20}$) are considerably suppressed ($\\sim-50$ dB) below the multi-beam resonating mode ($TE_{30}$) at the THz regime (0.8–1.24 THz). The theoretical calculations and particle-in-cell simulations show that with significantly higher interaction impedance and power growth rate radiation of the $TE_{30}$ mode is $\\sim$23 dBm and $\\sim$50 dBm stronger than the $TE_{10}$ and $TE_{20}$ modes around 1 THz, respectively. As a result, this highly selective HOM multi-beam interaction has potential applications for power THz sources and high intensity accelerators.

  10. Superimposed coherent terahertz wave radiation from mono-energetically bunched multi-beam

    DOE PAGES

    Shin, Young -Min; Fermi National Accelerator Lab.

    2012-06-27

    Intense coherent radiation is obtained from multiple electron beams monochromatically bunched over the wide higher-order-mode (HOM) spectral band in the THz regime. The overmoded waveguide corrugated by dielectric-implanted staggered gratings superimposes evanescent waves emitted from the low energy electron beams. The dispersion and transmission simulations of the three-beam slow wave structure show that the first two fundamental modes (more » $$TE_{10}$$ and $$TE_{20}$$) are considerably suppressed ($$\\sim-50$$ dB) below the multi-beam resonating mode ($$TE_{30}$$) at the THz regime (0.8–1.24 THz). The theoretical calculations and particle-in-cell simulations show that with significantly higher interaction impedance and power growth rate radiation of the $$TE_{30}$$ mode is $$\\sim$$23 dBm and $$\\sim$$50 dBm stronger than the $$TE_{10}$$ and $$TE_{20}$$ modes around 1 THz, respectively. As a result, this highly selective HOM multi-beam interaction has potential applications for power THz sources and high intensity accelerators.« less

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    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.

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

    SciTech Connect

    Zhang, Jingdi; Averitt, Richard D. E-mail: raveritt@ucsd.edu; Zhao, Xiaoguang; Fan, Kebin; Wang, Xiaoning; Zhang, Xin E-mail: raveritt@ucsd.edu; Zhang, Gu-Feng; Geng, Kun

    2015-12-07

    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{sup −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.

  13. A terahertz confocal microscope for far-field thermal radiation detection and near-field sub-wavelength imaging

    NASA Astrophysics Data System (ADS)

    Weng, Qianchun; Yang, Le; Xu, Jie; Qian, Qingbai; Yu, Haochi; Zhang, Bo; An, Zhenghua; Zhu, Ziqiang; Lu, Wei

    2015-11-01

    We present a novel scattering-type scanning near-field optical microscope (s-SNOM) operating in the terahertz (THz) wavelength. A home-made ultra-high sensitive detector named charge sensitive infrared phototransistor (CSIP, detection wavelength ~15 μm) is equipped for spontaneous thermal radiation detection (external illumination should be avoided). Thermal emission from room-temperature objects is collected by a cassegrain objective lens placed above the sample, and focused to a pinhole (d=250 μm) which is kept in liquid-helium (LHe) temperature(4.2 K). With the background radiation from environment efficiently blocked by the low-temperature pinhole, the detector is only sensitive to the THz radiation from a small spot (~λ) on sample surface (the confocal point). As a result, thermal radiation spontaneously emitted by object itself is measured with an excellent spatial resolution of ~14 μm (diffraction-limit). For overcoming the diffraction limit by detecting the near-field evanescent waves, this THz microscope is combined with a home-built atomic-force microscope (AFM). With sharp AFM tip (<100 nm) scattering the evanescent waves with an improved tip-modulation method, we successfully obtained thermal near-field images with a spatial resolution of ~100 nm, which is already less than 1% of the detection wavelength (15 μm). This THz s-SNOM should be a powerful tool for various material research down to the nanometer scale.

  14. A Device for Search of Gamma-Radiation Intensive Sources at the Radiation Accident Condition

    SciTech Connect

    Batiy, Valeriy; Klyuchnykov, A; Kochnev, N; Rudko, Vladimir; shcherbin, vladimir; Yegorov, V; Schmieman, Eric A.

    2005-08-08

    The procedure designed for measuring angular distributions of gamma radiation and for search of gamma radiation intensive sources is described. It is based on application of the original multidetector device ShD-1, for measuring an angular distribution in a complete solid angle (4 pi). The calibration results and data on the angular distributions of intensity of gamma radiation at the roof of Chornobyl NPP ''Shelter'' are presented.

  15. A capillary discharge plasma source of intense VUV radiation

    SciTech Connect

    Sobel'man, Igor I; Shevelko, A P; Yakushev, O F; Knight, L V; Turley, R S

    2003-01-31

    The results of investigation of a capillary discharge plasma, used as a source of intense VUV radiation and soft X-rays, are presented. The plasma was generated during the discharge of low-inductance condensers in a gas-filled ceramic capillary. Intense line radiation was observed in a broad spectral range (30-400 A) in various gases (CO{sub 2}, Ne, Ar, Kr, Xe). The absolute radiation yield for the xenon discharge was {approx}5 mJ (2{pi} sr){sup -1} pulse{sup -1} within a spectral band of width 9 A at 135 A. Such a radiation source can be used for various practical applications, such as EUV projection lithography, microscopy of biological objects in a 'water window', reflectometry, etc. (special issue devoted to the 80th anniversary of academician n g basov's birth)

  16. Sensitivity of a vanadium oxide uncooled microbolometer array for terahertz imaging

    NASA Astrophysics Data System (ADS)

    Coppinger, Matthew J.; Sustersic, Nathan A.; Kolodzey, James; Allik, Toomas H.

    2011-05-01

    The broadband imaging capabilities of a vanadium oxide microbolometer camera were investigated in the far-infrared for applications in real-time terahertz imaging and analysis. To accomplish this, we used an optical configuration consisting of a broadband terahertz source, terahertz filtering optics, and a modified commercial broadband microbolometer camera. A blackbody radiator was employed as the broadband terahertz source to illuminate the microbolometer array with all components in a nitrogen purged enclosure. Data was taken using several different levels of radiant flux intensity. Optical filtering were necessary to isolate incident radiation frequencies into a band from 1.5 to 7.5 THz. Fourier transform infrared spectroscopy was used to characterize the transmission properties of each optical component. The noise equivalent differential temperature (NEDT) and the noise equivalent power (NEP) were recorded over a range of blackbody intensities. We discuss the relative utility of these two figures of merit for terahertz imaging. For example, at a blackbody temperature of 925°C the NEDT was recorded below 800 mK, and the NEP was calculated to be 136 pW/√Hz. This study provides a complete analysis of a microbolometer as the detector component of a terahertz imaging system in a broadband imaging configuration.

  17. Scatter radiation intensities around full-field digital mammography units.

    PubMed

    Judge, M A; Keavey, E; Phelan, N

    2013-01-01

    The aim of this study was to investigate the scatter radiation intensity around digital mammography systems and apply these data to standard shielding calculations to reveal whether shielding design of existing breast screening rooms is adequate for the use of digital mammography systems. Three digital mammography systems from GE Healthcare, Hologic and Philips were employed in the study. A breast-equivalent phantom was imaged under clinical workload conditions and scatter radiation intensities around the digital mammography systems were measured for a range of angles in three planes using an ionisation chamber. The results were compared with those from previous studies of film-screen systems. It may be deduced from the results that scattering in the backward direction is significant for all three systems, while scattering in the forward direction can be significant for some planes around the GE and Hologic systems. Measurements at typical clinical settings on each system revealed the Philips system to have markedly lower scatter radiation intensities than the other systems. Substituting the measured scattered radiation intensity into shielding calculations yielded barrier requirements similar to those already in place at the screening centres operating these systems. Current radiation protection requirements based on film-screen technology remain sufficient when applied to rooms with digital mammography installations and no alteration is required to the structural shielding.

  18. Testing Unruh Radiation with Ultra-Intense Lasers

    NASA Astrophysics Data System (ADS)

    Chen, Pisin; Tajima, Toshiki

    1997-04-01

    We point of that using the state-of-the-art (or soon to be) intense ultrafast laser technology, violent acceleration of electrons that may be suitable for testing general relativistic effects can be realized in the laboratory settings. In particular we demonstrate that the Unruh radiation is detectable, in principle, beyond the conventional radiation (most notably the Larmor radiation) background noise, by taking the advantages of their specific dependences on the laser power, their different characters in spectral-angular distributions, and the time structure of the signals.

  19. Terahertz technology: Mind the gap

    NASA Astrophysics Data System (ADS)

    Martin-Moreno, Luis

    2009-03-01

    Researchers in South Korea and the Netherlands have demonstrated that the enhancement of the electric field of terahertz radiation inside a nano-slit continues to grow, even when the slit becomes narrower than the skin depth of the material.

  20. Application of Terahertz Field Enhancement Effect in Metal Microstructures

    NASA Astrophysics Data System (ADS)

    Nakajima, M.; Kurihara, T.; Tadokoro, Y.; Kang, B.; Takano, K.; Yamaguchi, K.; Watanabe, H.; Oto, K.; Suemoto, T.; Hangyo, M.

    2016-10-01

    Applications of high-field terahertz pulses are attractive in physics and terahertz technology. In this study, two applications related to high-intensity terahertz pulses are demonstrated. The field enhancement effect by subwavelength metallic microstructures is utilized for terahertz excitation measurement. The spin precession dynamics in magnetic materials was induced by a terahertz magnetic field. Spin precession was amplified by one order of magnitude in amplitude by the enhanced magnetic terahertz field in orthoferrite ErFeO3 with metal microstructures. The induced spin dynamics was analyzed and explained by LLG-LCR model. Moreover, a detection method for terahertz pulses was developed using a cholesteric liquid crystal at room temperature without any electronic devices. The beam profile of terahertz pulses was visualized and compared to other methods such as the knife edge method using pyroelectric detector and micro-bolometer array. The liquid crystal terahertz imager is very simple and has good applicability as a portable terahertz-sensing card.

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

    PubMed Central

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

    2015-01-01

    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. PMID:26798828

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

    PubMed

    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.

  3. Response of two-phase droplets to intense electromagnetic radiation

    NASA Technical Reports Server (NTRS)

    Spann, James F.; Maloney, Daniel J.; Lawson, William F.; Casleton, Kent H.

    1993-01-01

    The behavior of two-phase droplets subjected to high intensity radiation pulses is studied. Droplets are highly absorbing solids in weakly absorbing liquid medium. The objective of the study was to define heating thresholds required for causing explosive boiling and secondary atomization of the fuel droplet. The results point to mechanisms for energy storage and transport in two-phase systems.

  4. Note: Recent achievements at the 60-MeV Linac for sub-picosecond terahertz radiation at the Pohang Accelerator Laboratory

    SciTech Connect

    Yim, Changmook; Hong, Juho; Parc, Yongwoon; Ko, In Soo; Jung, Seonghoon; Park, Jaehun; Kang, Heung-Sik; Han, Daehun; Ryu, Jaehyun

    2011-10-15

    A femtosecond (fs) terahertz (THz) linac has been constructed to generate fs-THz radiation by using ultrashort electron beam at the Pohang Accelerator Laboratory. To generate an ultrashort electron beam with 60-MeV energy, a chicane bunch compressor has been adopted. Simulation studies have been conducted to design the linac. In this note, recent achievements at 60-MeV linac are presented.

  5. Observation of a cascaded process in intracavity terahertz optical parametric oscillators based on lithium niobate.

    PubMed

    Thomson, C L; Dunn, M H

    2013-07-29

    Cascaded difference frequency generation has been observed in intracavity optical parametric oscillators based on bulk lithium niobate and producing nanosecond pulses of terahertz radiation. Two idler waves are generated, namely: the primary idler wave associated with the parametric down conversion process itself; and a secondary idler wave, due to difference frequency generation. Experimental investigations of the frequency, temporal evolution, propagation direction, intensity, phase matching and oscillation threshold of the generated down-converted waves are reported. The overall generation efficiency for the terahertz radiation is enhanced, thereby overcoming the Manley-Rowe limit. Advantages of the present approach over schemes based on periodically poled lithium niobate are identified.

  6. Measurement of natural background radiation intensity on a train.

    PubMed

    Chen, Yen-Fu; Lin, Jeng-Wei; Sheu, Rong-Jiun; Lin, Uei-Tyng; Jiang, Shiang-Huei

    2011-03-01

    This work aims to measure different components of natural background radiation on a train. A radiation measurement system consisting of four types of radiation detectors, namely, a Berkeley Lab cosmic-ray detector, moderated (3)He detector, high-pressure ionisation chamber and NaI(Tl) spectrometer, associated with a global positioning system unit was established for this purpose. For the commissioning of the system, a test measurement on a train along the railway around the northern Taiwan coast from Hsinchu to Hualien with a distance of ∼ 275 km was carried out. No significant variation of the intensities of the different components of natural background radiation was observed, except when the train went underground or in the tunnels. The average external dose rate received by the crew of the train was estimated to be 62 nSv h(-1).

  7. Modal analysis and intensity of acoustic radiation of the kettledrum.

    PubMed

    Tronchin, Lamberto

    2005-02-01

    The acoustical features of kettledrums have been analyzed by means of modal analysis and acoustic radiation (p/v ratio) measurements. Modal analysis of two different kettledrums was undertaken, exciting the system both by a hammer and a shaker. Up to 15 vibrational modes were clearly identified. Acoustic radiation was studied using two ways. Based on previous experiments of other researchers, a new parameter, called intensity of acoustic radiation (IAR), has been defined and measured. Results show a strict relationship between IAR and the frequency response function (FRF, which is the v/F ratio), and IAR also strongly relates the modal pattern to acoustic radiation. Finally, IAR is proposed for vibro-acoustical characterization of kettledrums and other musical instruments such as strings, pianos, and harpsichords. PMID:15759711

  8. Monopolar photoelectromagnetic effect in Pb1-xSnxTe(In) under terahertz laser radiation

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

    We report on the observation of a new effect—the appearance of a galvanic signal in the narrow-gap semiconductor Pb1-xSnxTe(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.

  9. Controlling terahertz radiation with nanoscale metal barriers embedded in nano slot antennas.

    PubMed

    Park, Hyeong-Ryeol; Bahk, Young-Mi; Ahn, Kwang Jun; Park, Q-Han; Kim, Dai-Sik; Martín-Moreno, Luis; García-Vidal, Francisco J; Bravo-Abad, Jorge

    2011-10-25

    Nanoscale metallic barriers embedded in terahertz (THz) slot antennas are shown to provide unprecedented control of the transition state arising at the crossover between the full- and half-wavelength resonant modes of such antennas. We demonstrate strong near-field coupling between two paired THz slot antennas separated by a 5 nm wide nanobarrier, almost fully inducing the shift to the resonance of the double-length slot antenna. This increases by a factor of 50 the length-scale needed to observe similar coupling strengths in conventional air-gap antennas (around 0.1 nm), making the transition state readily accessible to experiment. Our measurements are in good agreement with a quantitative theoretical modeling, which also provides a simple physical picture of our observations.

  10. Controlling terahertz radiation with nanoscale metal barriers embedded in nano slot antennas.

    PubMed

    Park, Hyeong-Ryeol; Bahk, Young-Mi; Ahn, Kwang Jun; Park, Q-Han; Kim, Dai-Sik; Martín-Moreno, Luis; García-Vidal, Francisco J; Bravo-Abad, Jorge

    2011-10-25

    Nanoscale metallic barriers embedded in terahertz (THz) slot antennas are shown to provide unprecedented control of the transition state arising at the crossover between the full- and half-wavelength resonant modes of such antennas. We demonstrate strong near-field coupling between two paired THz slot antennas separated by a 5 nm wide nanobarrier, almost fully inducing the shift to the resonance of the double-length slot antenna. This increases by a factor of 50 the length-scale needed to observe similar coupling strengths in conventional air-gap antennas (around 0.1 nm), making the transition state readily accessible to experiment. Our measurements are in good agreement with a quantitative theoretical modeling, which also provides a simple physical picture of our observations. PMID:21961910

  11. Mode Content Determination of Terahertz Corrugated Waveguides Using Experimentally Measured Radiated Field Patterns

    PubMed Central

    Jawla, Sudheer K.; Nanni, Emilio A.; Shapiro, Michael A.; Woskov, Paul P.; Temkin, Richard J.

    2012-01-01

    This work focuses on the accuracy of the mode content measurements in an overmoded corrugated waveguide using measured radiated field patterns. Experimental results were obtained at 250 GHz using a vector network analyzer with over 70 dB of dynamic range. The intensity and phase profiles of the fields radiated from the end of the 19 mm diameter helically tapped brass waveguide were measured on planes at 7, 10, and 13 cm from the waveguide end. The measured fields were back propagated to the waveguide aperture to provide three independent estimates of the field at the waveguide exit aperture. Projecting that field onto the modes of the guide determined the waveguide mode content. The three independent mode content estimates were found to agree with one another to an accuracy of better than ±0.3%. These direct determinations of the mode content were compared with indirect measurements using the experimentally measured amplitude in three planes, with the phase determined by a phase retrieval algorithm. The phase retrieval technique using the planes at 7, 10, and 13 cm yielded a mode content estimate in excellent agreement, within 0.3%, of the direct measurements. Phase retrieval results using planes at 10, 20, and 30 cm were less accurate due to truncation of the measurement in the transverse plane. The reported measurements benefited greatly from a precise mechanical alignment of the scanner with respect to the waveguide axis. These results will help to understand the accuracy of mode content measurements made directly in cold test and indirectly in hot test using the phase retrieval technique. PMID:25264391

  12. INTERPRETING THE UNRESOLVED INTENSITY OF COSMOLOGICALLY REDSHIFTED LINE RADIATION

    SciTech Connect

    Switzer, E. R.; Chang, T.-C.; Pen, U.-L.; Voytek, T. C.

    2015-12-10

    Intensity mapping experiments survey the spectrum of diffuse line radiation rather than detect individual objects at high signal-to-noise ratio. Spectral maps of unresolved atomic and molecular line radiation contain three-dimensional information about the density and environments of emitting gas and efficiently probe cosmological volumes out to high redshift. Intensity mapping survey volumes also contain all other sources of radiation at the frequencies of interest. Continuum foregrounds are typically ∼10{sup 2}–10{sup 3} times brighter than the cosmological signal. The instrumental response to bright foregrounds will produce new spectral degrees of freedom that are not known in advance, nor necessarily spectrally smooth. The intrinsic spectra of foregrounds may also not be well known in advance. We describe a general class of quadratic estimators to analyze data from single-dish intensity mapping experiments and determine contaminated spectral modes from the data themselves. The key attribute of foregrounds is not that they are spectrally smooth, but instead that they have fewer bright spectral degrees of freedom than the cosmological signal. Spurious correlations between the signal and foregrounds produce additional bias. Compensation for signal attenuation must estimate and correct this bias. A successful intensity mapping experiment will control instrumental systematics that spread variance into new modes, and it must observe a large enough volume that contaminant modes can be determined independently from the signal on scales of interest.

  13. Interpreting The Unresolved Intensity Of Cosmologically Redshifted Line Radiation

    NASA Technical Reports Server (NTRS)

    Switzer, E. R.; Chang, T.-C.; Masui, K. W.; Pen, U.-L.; Voytek, T. C.

    2016-01-01

    Intensity mapping experiments survey the spectrum of diffuse line radiation rather than detect individual objects at high signal-to-noise ratio. Spectral maps of unresolved atomic and molecular line radiation contain three-dimensional information about the density and environments of emitting gas and efficiently probe cosmological volumes out to high redshift. Intensity mapping survey volumes also contain all other sources of radiation at the frequencies of interest. Continuum foregrounds are typically approximately 10(sup 2)-10(Sup 3) times brighter than the cosmological signal. The instrumental response to bright foregrounds will produce new spectral degrees of freedom that are not known in advance, nor necessarily spectrally smooth. The intrinsic spectra of fore-grounds may also not be well known in advance. We describe a general class of quadratic estimators to analyze data from single-dish intensity mapping experiments and determine contaminated spectral modes from the data themselves. The key attribute of foregrounds is not that they are spectrally smooth, but instead that they have fewer bright spectral degrees of freedom than the cosmological signal. Spurious correlations between the signal and foregrounds produce additional bias. Compensation for signal attenuation must estimate and correct this bias. A successful intensity mapping experiment will control instrumental systematics that spread variance into new modes, and it must observe a large enough volume that contaminant modes can be determined independently from the signal on scales of interest.

  14. Intense monochromatic terahertz electromagnetic waves from coherent GaAs-like longitudinal optical phonons in (11n)-oriented GaAs/In0.1Al0.9As strained multiple quantum wells

    NASA Astrophysics Data System (ADS)

    Takeuchi, Hideo; Asai, Souta; Tsuruta, Syuichi; Nakayama, Masaaki

    2012-06-01

    We demonstrate that, in (11n)-oriented GaAs/In0.1Al0.9As strained multiple quantum wells, the terahertz electromagnetic wave from the coherent GaAs-like longitudinal optical (LO) phonon is enhanced by a piezoelectric field originating from a tensile strain in the GaAs layer. The presence of the tensile strain is confirmed using Raman scattering spectroscopy. The Fourier power spectrum of the terahertz waveform shows that the intensity of the terahertz band of the coherent GaAs-like LO phonon increases as the index n approaches 1. The amplitude of the GaAs-like LO phonon is proportional to the piezoelectric field in the strained GaAs layer.

  15. Intensity modulating and other radiation therapy devices for dose painting.

    PubMed

    Galvin, James M; De Neve, Wilfried

    2007-03-10

    The introduction of intensity-modulated radiation therapy (IMRT) in the early 1990s created the possibility of generating dramatically improved dose distributions that could be tailored to fit a complex geometric arrangement of targets that push against or even surround healthy critical structures. IMRT is a new treatment paradigm that goes beyond the capabilities of the earlier technology called three-dimensional radiation therapy (3DCRT). IMRT took the older approach of using fields that conformed to the silhouette of the target to deliver a relatively homogeneous intensity of radiation and separated the conformal fields into many subfields so that intensity could be varied to better control the final dose distribution. This technique makes it possible to generate radiation dose clouds that have indentations in their surface. Initially, this technology was mainly used to avoid and thus control the dose delivered to critical structures so that they are not seriously damaged in the process of irradiating nearby targets to an appropriately high dose. Avoidance of critical structures allowed homogeneous dose escalation that led to improved local control for small tumors. However, the normal tissue component of large tumors often prohibits homogeneous dose escalation. A newer concept of dose-painting IMRT is aimed at exploiting inhomogeneous dose distributions adapted to tumor heterogeneity. Tumor regions of increased radiation resistance receive escalated dose levels, whereas radiation-sensitive regions receive conventional or even de-escalated dose levels. Dose painting relies on biologic imaging such as positron emission tomography, functional magnetic resonance imaging, and magnetic resonance spectroscopy. This review will describe the competing techologies for dose painting with an emphasis on their commonalities.

  16. Quantum path control of H2 + during a high-order harmonic generation process by adjusting the laser intensity of a terahertz assisted field

    NASA Astrophysics Data System (ADS)

    Ge, Xin-Lei

    2016-06-01

    We investigate high-harmonic generation (HHG) for the \\text{H}2+ molecular ion by solving a two-dimensional time-dependent Schrödinger equation in the combination of a circularly polarized laser pulse and a terahertz (THz) field. The results published recently by Ge et al (Opt. Express 23 8837-44) show that the harmonic intensity can be greatly enhanced when a THz field is added. Our work is an extension of Ge et al’s. We focus on considering the influence of THz field with different peak intensity, which shows that, with the increasing peak intensity of THz field, the cutoff of the harmonics can be remarkably extended, and the harmonic spectrum presents a two-plateau structure. The time-frequency analysis shows that the long trajectory makes a contribution to HHG when the intensity of THz field is low. With the increase of peak intensity of THz field, the long trajectory gradually disappears and the short trajectory makes the main contribution to HHG. We present the classical trajectory of the electron and the temporal evolution of the probability density of the electron wave packet to further understand the electron motion and the physical insight into HHG.

  17. Identification of patterns in diffraction intensities affected by radiation exposure.

    PubMed

    Borek, Dominika; Dauter, Zbigniew; Otwinowski, Zbyszek

    2013-01-01

    In an X-ray diffraction experiment, the structure of molecules and the crystal lattice changes owing to chemical reactions and physical processes induced by the absorption of X-ray photons. These structural changes alter structure factors, affecting the scaling and merging of data collected at different absorbed doses. Many crystallographic procedures rely on the analysis of consistency between symmetry-equivalent reflections, so failure to account for the drift of their intensities hinders the structure solution and the interpretation of structural results. The building of a conceptual model of radiation-induced changes in macromolecular crystals is the first step in the process of correcting for radiation-induced inconsistencies in diffraction data. Here the complexity of radiation-induced changes in real and reciprocal space is analysed using matrix singular value decomposition applied to multiple complete datasets obtained from single crystals. The model consists of a resolution-dependent decay correction and a uniform-per-unique-reflection term modelling specific radiation-induced changes. This model is typically sufficient to explain radiation-induced effects observed in diffraction intensities. This analysis will guide the parameterization of the model, enabling its use in subsequent crystallographic calculations.

  18. Fire Intensity Data for Validation of the Radiative Transfer Equation

    SciTech Connect

    Blanchat, Thomas K.; Jernigan, Dann A.

    2016-01-01

    A set of experiments and test data are outlined in this report that provides radiation intensity data for the validation of models for the radiative transfer equation. The experiments were performed with lightly-sooting liquid hydrocarbon fuels that yielded fully turbulent fires 2 m diameter). In addition, supplemental measurements of air flow and temperature, fuel temperature and burn rate, and flame surface emissive power, wall heat, and flame height and width provide a complete set of boundary condition data needed for validation of models used in fire simulations.

  19. Absolute intensity of radiation emitted by uranium plasmas

    NASA Technical Reports Server (NTRS)

    Jalufka, N. W.; Lee, J. H.; Mcfarland, D. R.

    1975-01-01

    The absolute intensity of radiation emitted by fissioning and nonfissioning uranium plasmas in the spectral range from 350 nm to 1000 nm was measured. The plasma was produced in a plasma-focus apparatus and the plasma properties are simular to those anticipated for plasma-core nuclear reactors. The results are expected to contribute to the establishment of design criteria for the development of plasma-core reactors.

  20. The Effect of Intense Laser Radiation on Atomic Collisions

    NASA Astrophysics Data System (ADS)

    Young, Stephen Michael Radley

    1991-02-01

    Available from UMI in association with The British Library. Requires signed TDF. We have carried out theoretical and experimental studies into the effect of intense laser radiation on atomic collisions. The first experiment used neon. Excitation by electron impact in a gas discharge demanded a pressure of at least 0.075 Torr. Measurement of the intensity of 3^1S_0to 3^1P_1 fluorescence has been made for the case where high intensity ASE wings in the laser profile and background laser scatter are unimportant, with the laser tuned to resonance. The field intensity required to produce strong field fluorescence (exemplified by the Mollow triplet) was found to give rise to complications capable of screening the effects sought. Our theoretical model has suggested that at finite detunings, line-centre fluorescence will dominate Rayleigh scatter and omega_3 fluorescence. Our measurements provide information on the saturation of neon fluorescence but not of the variation of the intense field collision rate. Absorption of weak field 253.7 nm laser photons by ground state mercury atoms yielded a high 6 ^3P_1 population at a lower pressure of 0.02 Torr. The Mollow triplet has been observed in the self-broadened mercury system. Dressing of the upper transition (6^3P_1rightarrow 7^3S_1) by an intense laser close to 435.8 nm yielded the strong field signal. Polarisation studies were made possible by the 3-level mercury system (radiation trapping in a 2-level system would depolarise fluorescence) perturbed by argon. The studies yielded results that were explainable in terms of the selective population of Stark shifted dressed states by a detuned, weak probe field. Use has been made of the electric-dipole radiation selection rule m_{J}=0 rightarrow m_{J^' } = 0 unless J=J^' to devise a 'Stark shift collision switch'. The competition between collision and radiation induced transitions within the mercury atom has then been studied. The resonant, strong lambda 435.8 nm field was used

  1. Effects of terahertz radiation at atmospheric oxygen frequency of 129 GHz on blood nitrite concentrations under conditions of different types of stress against the background of administration of nonselective inhibitor of constitutive NO-synthases.

    PubMed

    Kirichuk, V F; Tsymbal, A A

    2012-02-01

    We studied the effect of terahertz radiation at atmospheric oxygen frequency 129 GHz on blood nitrite concentration in different types of experimental stress against the background of administration of nonselective inhibitor of constitutive NO-synthases. Normalizing effects of radiation on blood nitrite dynamics in animals with acute stress was shown after 15-min exposure and in animals with chronic stress after 30-min exposure. No positive effect of terahertz radiation was observed on altered blood nitrite concentration in male rats after preliminary administration of nonselective constitutive NO-synthase isoform inhibitor L-NAME.

  2. Effects of terahertz radiation at atmospheric oxygen frequency of 129 GHz on blood nitrite concentrations under conditions of different types of stress against the background of administration of nonselective inhibitor of constitutive NO-synthases.

    PubMed

    Kirichuk, V F; Tsymbal, A A

    2012-02-01

    We studied the effect of terahertz radiation at atmospheric oxygen frequency 129 GHz on blood nitrite concentration in different types of experimental stress against the background of administration of nonselective inhibitor of constitutive NO-synthases. Normalizing effects of radiation on blood nitrite dynamics in animals with acute stress was shown after 15-min exposure and in animals with chronic stress after 30-min exposure. No positive effect of terahertz radiation was observed on altered blood nitrite concentration in male rats after preliminary administration of nonselective constitutive NO-synthase isoform inhibitor L-NAME. PMID:22803105

  3. Diffraction mode terahertz tomography

    DOEpatents

    Ferguson, Bradley; Wang, Shaohong; Zhang, Xi-Cheng

    2006-10-31

    A method of obtaining a series of images of a three-dimensional object. The method includes the steps of transmitting pulsed terahertz (THz) radiation through the entire object from a plurality of angles, optically detecting changes in the transmitted THz radiation using pulsed laser radiation, and constructing a plurality of imaged slices of the three-dimensional object using the detected changes in the transmitted THz radiation. The THz radiation is transmitted through the object as a two-dimensional array of parallel rays. The optical detection is an array of detectors such as a CCD sensor.

  4. Superlattice conductivity sign change induced by intense electromagnetic radiation

    NASA Astrophysics Data System (ADS)

    Kryuchkov, S. V.; Kukhar', E. I.; Ionkina, E. S.

    2016-07-01

    The current density in a superlattice exposed to a quantizing electric field and the terahertz field has been calculated. The calculations have been carried out taking into account inelastic scattering of charge carriers by phonons. The possibility of an absolute negative conductivity, i.e., the emergence of electric current opposing the direction of the quantizing electric field, has been demonstrated.

  5. Radiative decay effects influence the local electromagnetic response of the monolayer graphene with surface corrugations in terahertz range

    NASA Astrophysics Data System (ADS)

    Firsov, Yu. A.; Firsova, N. E.

    2015-07-01

    We continue the study of surface corrugations influence on the monolayer graphene local electromagnetic response in terahertz range we started earlier. The effects of radiative decay, double-valley structure of charge carriers spectrum in graphene and the "breathing" corrugated surface form induced synthetic electric fields are taken into account. To fulfill this program the generalized nonlinear self-consistent-field equation is obtained. In case of weak external alternating electric field E→ext (t) =E→0 cos ωt for the obtained equation in linear approximation on the external electric field the exact solution is found. It shows that in this case we get local induced current paths depending on the surface form z = h (x , y) . This theoretical result qualitatively explains the corresponding experiments with local current patterns depending on the point by corrugations influence. The induced currents formula was obtained without using fully quantum approach which is necessary for theoretical description of such phenomenon in graphene nanoribbons. Besides the formulae obtained in the present paper could become the basis of the new method of the imaging of surface corrugations form for given experimental picture of local current paths.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    We use intense terahertz pulses to excite the resonant mode (0.6THz) 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 MVcm-1, THz-induced field electron emission is observed (TIFEE) 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. (arXiv: 1508.04737) We acknowledge support from DOE-BES No. DE-FG02-09ER46643 and NSF No. ECCS-1309835.

  8. Invited Review Article: Current State of Research on Biological Effects of Terahertz Radiation

    NASA Astrophysics Data System (ADS)

    Wilmink, Gerald J.; Grundt, Jessica E.

    2011-10-01

    Terahertz (THz) imaging and sensing technologies are increasingly being used in a host of medical, military, and security applications. For example, THz systems are now being tested at international airports for security screening purposes, at major medical centers for cancer and burn diagnosis, and at border patrol checkpoints for identification of concealed explosives, drugs, and weapons. Recent advances in THz applications have stimulated renewed interest regarding the biological effects associated with this frequency range. Biological effects studies are a valuable type of basic science research because they serve to enhance our fundamental understanding of the mechanisms that govern THz interactions with biological systems. Such studies are also important because they often times lay the foundation for the development of future applications. In addition, from a practical standpoint, THz biological effects research is also necessary for accurate health hazard evaluation, the development of empirically-based safety standards, and for the safe use of THz systems. Given the importance and timeliness of THz bioeffects data, the purpose of this review is twofold. First, to provide readers with a common reference, which contains the necessary background concepts in biophysics and THz technology, that are required to both conduct and evaluate THz biological research. Second, to provide a critical review of the scientific literature.

  9. CMOS-Compatible Room-Temperature Rectifier Toward Terahertz Radiation Detection

    NASA Astrophysics Data System (ADS)

    Varlamava, Volha; De Amicis, Giovanni; Del Monte, Andrea; Perticaroli, Stefano; Rao, Rosario; Palma, Fabrizio

    2016-08-01

    In this paper, we present a new rectifying device, compatible with the technology of CMOS image sensors, suitable for implementing a direct-conversion detector operating at room temperature for operation at up to terahertz frequencies. The rectifying device can be obtained by introducing some simple modifications of the charge-storage well in conventional CMOS integrated circuits, making the proposed solution easy to integrate with the existing imaging systems. The rectifying device is combined with the different elements of the detector, composed of a 3D high-performance antenna and a charge-storage well. In particular, its position just below the edge of the 3D antenna takes maximum advantage of the high electric field concentrated by the antenna itself. In addition, the proposed structure ensures the integrity of the charge-storage well of the detector. In the structure, it is not necessary to use very scaled and costly technological nodes, since the CMOS transistor only provides the necessary integrated readout electronics. On-wafer measurements of RF characteristics of the designed junction are reported and discussed. The overall performances of the entire detector in terms of noise equivalent power (NEP) are evaluated by combining low-frequency measurements of the rectifier with numerical simulations of the 3D antenna and the semiconductor structure at 1 THz, allowing prediction of the achievable NEP.

  10. Broadband ultra-high transmission of terahertz radiation through monolayer MoS{sub 2}

    SciTech Connect

    Deng, Xue-Yong; Deng, Xin-Hua; Su, Fu-Hai; Liu, Nian-Hua; Liu, Jiang-Tao

    2015-12-14

    In this study, the terahertz (THz) absorption and transmission of monolayer MoS{sub 2} with different carrier concentrations were investigated theoretically. The calculation shows that the THz absorption of monolayer MoS{sub 2} is very low even under high carrier concentrations and large incident angles. The sum of reflection and absorption losses of monolayer MoS{sub 2} is lower than that of graphene by one to three orders of magnitude. The transmission of monolayer MoS{sub 2} is higher than that of two-dimensional electron gases in traditional GaAs and InAs. The field-effect tube structure formed by monolayer MoS{sub 2}-insulation-layer-graphene is also studied. The THz absorption of graphene can reach saturation under low voltage by tuning the voltage between MoS{sub 2} and graphene layers in the structure. The maximum THz absorption of monolayer MoS{sub 2} is approximately 5%. Thus, monolayer MoS{sub 2} is a promising candidate for THz transparent electrodes.

  11. Approaching Oxygen-Guided Intensity-Modulated Radiation Therapy.

    PubMed

    Epel, Boris; Redler, Gage; Pelizzari, Charles; Tormyshev, Victor M; Halpern, Howard J

    2016-01-01

    The outcome of cancer radiation treatment is strongly correlated with tumor oxygenation. The aim of this study is to use oxygen tension distributions in tumors obtained using Electron Paramagnetic Resonance (EPR) imaging to devise better tumor radiation treatment. The proposed radiation plan is delivered in two steps. In the first step, a uniform 50% tumor control dose (TCD50) is delivered to the whole tumor. For the second step an additional dose boost is delivered to radioresistant, hypoxic tumor regions. FSa fibrosarcomas grown in the gastrocnemius of the legs of C3H mice were used. Oxygen tension images were obtained using a 250 MHz pulse imager and injectable partially deuterated trityl OX63 (OX71) spin probe. Radiation was delivered with a novel animal intensity modulated radiation therapy (IMRT) XRAD225Cx microCT/radiation therapy delivery system. In a simplified scheme for boost dose delivery, the boost area is approximated by a sphere, whose radius and position are determined using an EPR O2 image. The sphere that irradiates the largest fraction of hypoxic voxels in the tumor was chosen using an algorithm based on Receiver Operator Characteristic (ROC) analysis. We used the fraction of irradiated hypoxic volume as the true positive determinant and the fraction of irradiated normoxic volume as the false positive determinant in the terms of that analysis. The most efficient treatment is the one that demonstrates the shortest distance from the ROC curve to the upper left corner of the ROC plot. The boost dose corresponds to the difference between TCD90 and TCD50 values. For the control experiment an identical radiation dose to the normoxic tumor area is delivered.

  12. Correlations between solar wind parameters and auroral kilometric radiation intensity

    NASA Technical Reports Server (NTRS)

    Gallagher, D. L.; Dangelo, N.

    1981-01-01

    The relationship between solar wind properties and the influx of energy into the nightside auroral region as indicated by the intensity of auroral kilometric radiation is investigated. Smoothed Hawkeye satellite observations of auroral radiation at 178, 100 and 56.2 kHz for days 160 through 365 of 1974 are compared with solar wind data from the composite Solar Wind Plasma Data Set, most of which was supplied by the IMP-8 spacecraft. Correlations are made between smoothed daily averages of solar wind ion density, bulk flow speed, total IMF strength, electric field, solar wind speed in the southward direction, solar wind speed multiplied by total IMF strength, the substorm parameter epsilon and the Kp index. The greatest correlation is found between solar wind bulk flow speed and auroral radiation intensity, with a linear correlation coefficient of 0.78 for the 203 daily averages examined. A possible mechanism for the relationship may be related to the propagation into the nightside magnetosphere of low-frequency long-wavelength electrostatic waves produced in the magnetosheath by the solar wind.

  13. THz electromagnetic radiation driven by intense relativistic electron beam based on ion focus regime

    NASA Astrophysics Data System (ADS)

    Zhou, Qing; Yang, Shengpeng; Xu, Jin; Zhang, Wenchao; Tang, Changjian; Duan, Zhaoyun; Gong, Yubin

    2016-06-01

    The simulation study finds that the relativistic electron beam propagating through the plasma background can produce electromagnetic (EM) radiation. With the propagation of the electron beam, the oscillations of the beam electrons in transverse and longitudinal directions have been observed simultaneously, which provides the basis for the electromagnetic radiation. The simulation results clearly show that the electromagnetic radiation frequency can reach up to terahertz (THz) wave band which may result from the filter-like property of plasma background, and the electromagnetic radiation frequency closely depends on the plasma density. To understand the above simulation results physically, the dispersion relation of the beam-plasma system has been derived using the field-matching method, and the dispersion curves show that the slow wave modes can couple with the electron beam effectively in THz wave band, which is an important theoretical evidence of the EM radiation.

  14. The radiation techniques of tomotherapy & intensity-modulated radiation therapy applied to lung cancer

    PubMed Central

    Zhu, Zhengfei

    2015-01-01

    Radiotherapy (RT) plays an important role in the management of lung cancer. Development of radiation techniques is a possible way to improve the effect of RT by reducing toxicities through better sparing the surrounding normal tissues. This article will review the application of two forms of intensity-modulated radiation therapy (IMRT), fixed-field IMRT and helical tomotherapy (HT) in lung cancer, including dosimetric and clinical studies. The advantages and potential disadvantages of these two techniques are also discussed. PMID:26207214

  15. [Changes in cortikosteron concentration--a marker of stress-response under the influence of terahertz radiations at nitrogen oxide frequencies of 150, 176-150, 664 GHz].

    PubMed

    Kirichuk, V F; Tsymbal, A A; Antipova, O N; Krenitskiĭ, A P; Maĭborodin, A V

    2008-11-01

    Influence of electromagnetic radiation ofterahertz frequencies of molecular spectrum of radiation and absorption oxide nitrogen of 150, 176-150, 664 GHz by means of device KVCH-NO forming specified spectra, on concentration at stress-realizing hormone cortikosteron in conditions of sharp and chronic stress was is studied. It is shown that preliminary continuous 15-minute influence by electromagnetic radiation of terahertz range at frequencies of oxide nitrogen 150, 176-150, 664 GHz limits development of stress-reaction due to reduction of allocation by a of adrenal glands of glucocorticoids, in particular cortikosteron, that led restriction of excessive activation of stress-realizing system. The given fact serves as the proof of stress-limiting function of electromagnetic radiation at the given range. PMID:19140305

  16. A Terahertz Blackbody Radiation Standard Based on Emissivity Measurements and a Monte-Carlo Simulation

    NASA Astrophysics Data System (ADS)

    Monte, C.; Gutschwager, B.; Adibekyan, A.; Hollandt, J.

    2014-08-01

    Blackbody radiators are commonly used metrological standards of spectral radiance and radiation temperature according to Planck's law of thermal radiation. In a well defined geometry of observation they also provide calculable irradiance for the calibration of radiation detectors. Here we describe the metrological characterization of a vacuum variable-temperature blackbody to serve as a source standard for FIR- and THz radiation from 5 μm to 200 μm (60 THz to 1.5 THz). The key quantity of the characterization is the effective spectral emissivity of its cavity. This is determined by angular resolved directional spectral emissivity and directional spectral reflectivity measurements of its wall coating, Aeroglaze Z306. From the reflectivity measurements the diffusity is determined. Spectral emissivity and diffusity in combination with the well known cavity geometry allow the determination of the effective spectral cavity emissivity via a Monte-Carlo ray tracing simulation.

  17. Nanoscale shift of the intensity distribution of dipole radiation.

    PubMed

    Shu, Jie; Li, Xin; Arnoldus, Henk F

    2009-02-01

    The energy flow lines (field lines of the Poynting vector) for radiation emitted by a dipole are in general curves, rather than straight lines. For a linear dipole the field lines are straight, but when the dipole moment of a source rotates, the field lines wind numerous times around an axis, which is perpendicular to the plane of rotation, before asymptotically approaching a straight line. We consider an elliptical dipole moment, representing the most general state of oscillation, and this includes the linear dipole as a special case. Due to the spiraling near the source, for the case of a rotating dipole moment, the field lines in the far field are displaced with respect to the outward radial direction, and this leads to a shift of the intensity distribution of the radiation in the far field. This shift is shown to be independent of the distance to the source and, although of nanoscale dimension, should be experimentally observable.

  18. A Novel Microsensor for Measuring Angular Distribution of Radiative Intensity.

    PubMed

    Murphy, Thomas E; Pilorz, Stuart; Prufert-Bebout, Leslie; Bebout, Brad

    2015-01-01

    This article presents the design, construction and characterization of a novel type of light probe for measuring the angular radiance distribution of light fields. The differential acceptance angle (DAA) probe can resolve the directionality of a light field in environments with steep light gradients, such as microbial mats, without the need to remove, reorient, and reinsert the probe, a clear advantage over prior techniques. The probe consists of an inner irradiance sensor inside a concentric, moveable light-absorbing sheath. The radiative intensity in a specific zenith direction can be calculated by comparing the irradiance onto the sensor at different acceptance angles. We used this probe to measure the angular radiance distribution of two sample light fields, and observed good agreement with a conventional radiance probe. The DAA probe will aid researchers in understanding light transfer physics in dense microbial communities and expedite validation of numerical radiative transfer models for these environments. PMID:25763775

  19. Direct Radiative Effect of Intense Dust Outbreaks in the Mediterranean

    NASA Astrophysics Data System (ADS)

    Gkikas, A.; Obiso, V.; Basart, S.; Jorba, O.; Pérez García-Pando, C.; Hatzianastassiou, N.; Gassó, S.; Baldasano, J. M.

    2015-12-01

    The broader Mediterranean basin is affected by intense desert dust outbreaks in spring. In the present study, we make use of satellite observations and modelling to investigate dust radiative impacts during three consecutive dust outbreaks occurred over the Mediterranean in the period 9/4-15/4/2008. The direct radiative effect (DRE) is estimated by using two simulations run with the NMMB/BSC-Dust model, where the interaction between dust aerosols and radiation is activated and deactivated, respectively. The simulation domain covers the North Africa, the Middle East and Europe at 0.25ºx0.25° and 40σ-layers. The first outbreak took place over the central and eastern Mediterranean on the 9th reaching aerosol optical depths (AODs) close to 1. The second one, with AODs up to 2, lasted from 10th to 14th affecting mainly the central Mediterranean. The third one, with AODs up to 5, affected the Iberian Peninsula on the 15th. DREs are computed for the outgoing radiation at the top of the atmosphere (TOA), the absorbed radiation into the atmosphere (ATMAB), for the downwelling (SURF) and the absorbed (NETSURF) radiation at surface, for the shortwave (SW), longwave (LW) and NET (SW+LW) radiation. According to our results, it is evident that DREs' spatial patterns are driven by those of AOD. Negative (cooling) instantaneous DRETOA, DRESURF and DRENETSURF values up to -500W/m2, -700W/m2 and -600W/m2, respectively, and positive (warming) instantaneous DREATMAB up to 340W/m2 are found for the SW spectrum, during daytime. Opposite but less pronounced effects are encountered for the LW radiation and during nightime. Due to these perturbations on the radiation field, the surface temperature is reduced locally by up to 8°C during daytime and increased by up to 4°C during nightime. It is found that the regional average NET DREs can be as large as -12W/m2, -45W/m2, -30W/m2 and 27W/m2 for TOA, SURF, NETSURF and ATMAB, respectively. Impacts on atmospheric stability and dust

  20. Spatial Terahertz Modulator

    NASA Astrophysics Data System (ADS)

    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.

  1. Radiation control in the intensive care unit for high intensity iridium-192 brain implants

    SciTech Connect

    Sewchand, W.; Drzymala, R.E.; Amin, P.P.; Salcman, M.; Salazar, O.M.

    1987-04-01

    A bedside lead cubicle was designed to minimize the radiation exposure of intensive care unit staff during routine interstitial brain irradiation by removable, high intensity iridium-192. The cubicle shields the patient without restricting intensive care routines. The design specifications were confirmed by exposure measurements around the shield with an implanted anthropomorphic phantom simulating the patient situation. The cubicle reduces the exposure rate around an implant patient by as much as 90%, with the exposure level not exceeding 0.1 mR/hour/mg of radium-equivalent /sup 192/Ir. Evaluation of data accumulated for the past 3 years has shown that the exposure levels of individual attending nurses are 0.12 to 0.36 mR/mg of radium-equivalent /sup 192/Ir per 12-hour shift. The corresponding range for entire nursing teams varies between 0.18 and 0.26. A radiation control index (exposure per mg of radium-equivalent /sup 192/Ir per nurse-hour) is thus defined for individual nurses and nursing teams; this index is a significant guide to the planning of nurse rotations for brain implant patients with various /sup 192/Ir loads. The bedside shield reduces exposure from /sup 192/Ir implants by a factor of about 20, as expected, and the exposure from the lower energy radioisotope iodine-125 is barely detectable.

  2. Radiation control in the intensive care unit for high intensity iridium-192 brain implants.

    PubMed

    Sewchand, W; Drzymala, R E; Amin, P P; Salcman, M; Salazar, O M

    1987-04-01

    A bedside lead cubicle was designed to minimize the radiation exposure of intensive care unit staff during routine interstitial brain irradiation by removable, high intensity iridium-192. The cubicle shields the patient without restricting intensive care routines. The design specifications were confirmed by exposure measurements around the shield with an implanted anthropomorphic phantom simulating the patient situation. The cubicle reduces the exposure rate around an implant patient by as much as 90%, with the exposure level not exceeding 0.1 mR/hour/mg of radium-equivalent 192Ir. Evaluation of data accumulated for the past 3 years has shown that the exposure levels of individual attending nurses are 0.12 to 0.36 mR/mg of radium-equivalent 192Ir per 12-hour shift. The corresponding range for entire nursing teams varies between 0.18 and 0.26. A radiation control index (exposure per mg of radium-equivalent 192Ir per nurse-hour) is thus defined for individual nurses and nursing teams; this index is a significant guide to the planning of nurse rotations for brain implant patients with various 192Ir loads. The bedside shield reduces exposure from 192Ir implants by a factor of about 20, as expected, and the exposure from the lower energy radioisotope iodine-125 is barely detectable.

  3. Graphene-Based Waveguide Terahertz Wave Attenuator

    NASA Astrophysics Data System (ADS)

    Jian-rong, Hu; Jiu-sheng, Li; Guo-hua, Qiu

    2016-07-01

    We design an electrically controllable terahertz wave attenuator by using graphene. We show that terahertz wave can be confined and propagate on S-shaped graphene waveguide with little radiation losses, and the confined terahertz wave is further manipulated and controlled via external applied voltage bias. The simulated results show that, when chemical potential changes from 0.03 into 0.05 eV, the extinction ratio of the terahertz wave attenuator can be tuned from 1.28 to 39.42 dB. Besides the simplicity, this novel terahertz wave attenuator has advantages of small size (24 × 30 μm2), a low insertion loss, and good controllability. It has a potential application for forthcoming planar terahertz wave integrated circuit fields.

  4. Coherent Nonlinear Terahertz Spectroscopy of Halomethane Liquids

    NASA Astrophysics Data System (ADS)

    Finneran, Ian A.; Welsch, Ralph; Allodi, Marco A.; Miller, Thomas F., III; Blake, Geoffrey

    2016-06-01

    The low-energy terahertz motions of liquids greatly influence their behavior, but are not fully understood. Here, we present results from a recently developed heterodyne-detected Terahertz Kerr Effect (TKE) spectrometer, using an intense picosecond terahertz pump pulse, followed by a weak near-infrared femtosecond probe pulse. In the responses of several halomethane liquids, we find evidence for terahertz intramolecular vibrational coupling and the excitation of intermolecular motions. The experimental results are further supported by reduced density matrix and molecular dynamics simulations. With modest improvements in sensitivity, we expect this technique to be applicable to hydrogen-bonded liquids and amorphous solids.

  5. Measurement of submilliwatt, picosecond terahertz emission from a femtosecond-laser-pumped solid-state dc to ac radiation converter based on a ZnSe crystal

    SciTech Connect

    Yugami, Noboru; Ohata, Nobuo; Yaegashi, Kenta; Kawanago, Hiroshi

    2006-11-15

    We measured the terahertz pulse emission from a femtosecond-laser-pumped solid-state dc to ac radiation converter using a 150 fs Ti:sapphire laser pulse for dense plasma diagnostics. The laser-produced ionization front was directly modulated from a periodic electrostatic field to pulsed emission. The central frequency of the emission was measured to be 0.13 THz having a bandwidth of 0.1 THz and a peak power of 0.2 mW. This emission source is suitable for use in various novel diagnostic techniques, such as dense plasma diagnostics.

  6. Terahertz homodyne self-mixing transmission spectroscopy

    SciTech Connect

    Mohr, Till Breuer, Stefan; Blömer, Dominik; Patel, Sanketkumar; Schlosser, Malte; Birkl, Gerhard; Elsäßer, Wolfgang; Simonetta, Marcello; Deninger, Anselm; Giuliani, Guido

    2015-02-09

    A compact homodyne self-mixing terahertz spectroscopy concept is experimentally investigated and confirmed by calculations. This method provides amplitude and phase information of the terahertz radiation emitted by a photoconductive antenna in a transmission experiment where a rotating chopper wheel serves as a feedback mirror. As a proof-of-principle experiment the frequency-dependent refractive index of Teflon is measured.

  7. Compliance with High-Intensity Radiated Fields Regulations - Emitter's Perspective

    NASA Technical Reports Server (NTRS)

    Statman, Joseph; Jamnejad, Vahraz; Nguyen, Lee

    2012-01-01

    NASA's Deep Space Network (DSN) uses high-power transmitters on its large antennas to communicate with spacecraft of NASA and its partner agencies. The prime reflectors of the DSN antennas are parabolic, at 34m and 70m in diameter. The DSN transmitters radiate Continuous Wave (CW) signals at 20 kW - 500 kW at X-band and S-band frequencies. The combination of antenna reflector size and high frequency results in a very narrow beam with extensive oscillating near-field pattern. Another unique feature of the DSN antennas is that they (and the radiated beam) move mostly at very slow sidereal rate, essentially identical in magnitude and at the opposite direction of Earth rotation.The DSN is in the process of revamping its documentation to provide analysis of the High Intensity Radiation Fields (HIRF) environment resulting from radio frequency radiation from DSN antennas for comparison to FAA regulations regarding certification of HIRF protection as outlined in the FAA regulations on HIRF protection for aircraft electrical and electronic systems (Title 14, Code of Federal Regulations (14 CFR) [section sign][section sign] 23.1308, 25.1317, 27.1317, and 29.1317).This paper presents work done at JPL, in consultation with the FAA. The work includes analysis of the radiated field structure created by the unique DSN emitters (combination of transmitters and antennas) and comparing it to the fields defined in the environments in the FAA regulations. The paper identifies areas that required special attention, including the implications of the very narrow beam of the DSN emitters and the sidereal rate motion. The paper derives the maximum emitter power allowed without mitigation and the mitigation zones, where required.Finally, the paper presents summary of the results of the analyses of the DSN emitters and the resulting DSN process documentation.

  8. Intense, carrier frequency and bandwidth tunable quasi single-cycle pulses from an organic emitter covering the Terahertz frequency gap

    NASA Astrophysics Data System (ADS)

    Vicario, C.; Monoszlai, B.; Jazbinsek, M.; Lee, S.-H.; Kwon, O.-P.; Hauri, C. P.

    2015-09-01

    In Terahertz (THz) science, one of the long-standing challenges has been the formation of spectrally dense, single-cycle pulses with tunable duration and spectrum across the frequency range of 0.1-15 THz (THz gap). This frequency band, lying between the electronically and optically accessible spectra hosts important molecular fingerprints and collective modes which cannot be fully controlled by present strong-field THz sources. We present a method that provides powerful single-cycle THz pulses in the THz gap with a stable absolute phase whose duration can be continuously selected between 68 fs and 1100 fs. The loss-free and chirp-free technique is based on optical rectification of a wavelength-tunable pump pulse in the organic emitter HMQ-TMS that allows for tuning of the spectral bandwidth from 1 to more than 7 octaves over the entire THz gap. The presented source tunability of the temporal carrier frequency and spectrum expands the scope of spectrally dense THz sources to time-resolved nonlinear THz spectroscopy in the entire THz gap. This opens new opportunities towards ultrafast coherent control over matter and light.

  9. Intense, carrier frequency and bandwidth tunable quasi single-cycle pulses from an organic emitter covering the Terahertz frequency gap

    PubMed Central

    Vicario, C.; Monoszlai, B.; Jazbinsek, M.; Lee, S. -H.; Kwon, O. -P.; Hauri, C. P.

    2015-01-01

    In Terahertz (THz) science, one of the long-standing challenges has been the formation of spectrally dense, single-cycle pulses with tunable duration and spectrum across the frequency range of 0.1–15 THz (THz gap). This frequency band, lying between the electronically and optically accessible spectra hosts important molecular fingerprints and collective modes which cannot be fully controlled by present strong-field THz sources. We present a method that provides powerful single-cycle THz pulses in the THz gap with a stable absolute phase whose duration can be continuously selected between 68 fs and 1100 fs. The loss-free and chirp-free technique is based on optical rectification of a wavelength-tunable pump pulse in the organic emitter HMQ-TMS that allows for tuning of the spectral bandwidth from 1 to more than 7 octaves over the entire THz gap. The presented source tunability of the temporal carrier frequency and spectrum expands the scope of spectrally dense THz sources to time-resolved nonlinear THz spectroscopy in the entire THz gap. This opens new opportunities towards ultrafast coherent control over matter and light. PMID:26400005

  10. Prone Breast Intensity Modulated Radiation Therapy: 5-Year Results

    SciTech Connect

    Osa, Etin-Osa O.; DeWyngaert, Keith; Roses, Daniel; Speyer, James; Guth, Amber; Axelrod, Deborah; Fenton Kerimian, Maria; Goldberg, Judith D.; Formenti, Silvia C.

    2014-07-15

    Purpose: To report the 5-year results of a technique of prone breast radiation therapy delivered by a regimen of accelerated intensity modulated radiation therapy with a concurrent boost to the tumor bed. Methods and Materials: Between 2003 and 2006, 404 patients with stage I-II breast cancer were prospectively enrolled into 2 consecutive protocols, institutional trials 03-30 and 05-181, that used the same regimen of 40.5 Gy/15 fractions delivered to the index breast over 3 weeks, with a concomitant daily boost to the tumor bed of 0.5 Gy (total dose 48 Gy). All patients were treated after segmental mastectomy and had negative margins and nodal assessment. Patients were set up prone: only if lung or heart volumes were in the field was a supine setup attempted and chosen if found to better spare these organs. Results: Ninety-two percent of patients were treated prone, 8% supine. Seventy-two percent had stage I, 28% stage II invasive breast cancer. In-field lung volume ranged from 0 to 228.27 cm{sup 3}, mean 19.65 cm{sup 3}. In-field heart volume for left breast cancer patients ranged from 0 to 21.24 cm{sup 3}, mean 1.59 cm{sup 3}. There was no heart in the field for right breast cancer patients. At a median follow-up of 5 years, the 5-year cumulative incidence of isolated ipsilateral breast tumor recurrence was 0.82% (95% confidence interval [CI] 0.65%-1.04%). The 5-year cumulative incidence of regional recurrence was 0.53% (95% CI 0.41%-0.69%), and the 5-year overall cumulative death rate was 1.28% (95% CI 0.48%-3.38%). Eighty-two percent (95% CI 77%-85%) of patients judged their final cosmetic result as excellent/good. Conclusions: Prone accelerated intensity modulated radiation therapy with a concomitant boost results in excellent local control and optimal sparing of heart and lung, with good cosmesis. Radiation Therapy Oncology Group protocol 1005, a phase 3, multi-institutional, randomized trial is ongoing and is evaluating the equivalence of a similar dose and

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

    SciTech Connect

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

    2014-12-15

    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.

  12. Survey of resident education in intensity-modulated radiation therapy.

    PubMed

    Malik, Renuka; Oh, Julia L; Roeske, John C; Mundt, Arno J

    2005-06-01

    Intensity-modulated radiation therapy (IMRT) has been gaining increasing popularity among practicing physicians in the U.S., but the extent to which radiation oncology residents are taught the principles of this technology and are trained to use IMRT remains unknown. In this paper, we assessed the current level of resident education in IMRT in the United States. Chief residents at all 77 accredited radiation oncology programs were sent a 13-question survey addressing formal didactics and hands-on experience in IMRT. The survey assessed the frequency, subject, and format of IMRT didactics. Questions also addressed the number of IMRT patients and anatomical sites treated, resident involvement in the IMRT process, and the intent of IMRT use. Finally, residents were asked for their opinions on their IMRT education. Sixty-one surveys (79%) were completed. Overall, forty-three respondents (71%) reported receiving formal IMRT didactics, with nearly one-third reporting extensive didactics (> or = 3 lectures/seminars et cetera per year). The most common didactic formats were lectures (95%) and journal clubs (63%), most commonly supervised by physicists (98%). Involvement by physicians and radiobiologists were reported by 63% and 7% of respondents, respectively. Overall, 87% of respondents had hands-on IMRT training, with nearly one-half having treated > 25 patients. The most common sites treated were head and neck (94%) and prostate (81%). Involvement in all aspects of the IMRT process was common, particularly target and tissue delineation (98%) and plan evaluation (93%). Most respondents (79%) with hands-on experience reported receiving formal didactics. However, nearly one-third received no or only minimal formal didactics. The percentage of respondents desiring increased IMRT didactics and hands-on experience were 70% and 47%, respectively. Our results suggest that the great majority of radiation oncology residents in the United States are currently exposed to didactics

  13. Generation of terahertz radiation in ordered arrays of GaAs nanowires

    SciTech Connect

    Trukhin, V. N.; Mustafin, I. A.; Bouravleuv, A. D.; Cirlin, G. E.; Kakko, J. P.; Huhtio, T.; Lipsanen, H.

    2015-06-22

    THz generation under excitation by ultrashort optical pulses in ordered arrays of GaAs nanowires is reported. It was found that the efficiency of THz radiation generation increases due to the resonant leaky mode excitation in nanowires. The maximum value of the THz field is achieved when the distance between the nanowires is of the order of the wavelength of exciting light.

  14. Nonlinear vacuum polarization in intense blackbody radiation and its effects on the radiation spectrum

    NASA Astrophysics Data System (ADS)

    Wu, Sheldon; Hartemann, Frederic; Siders, Craig; Barty, Christopher

    2009-11-01

    A study of thermally induced vacuum polarization stemming from the Euler-Heisenberg radiation correction to Maxwell equations is conducted. While nonlinear effects associated with interactions of electromagnetic pulse with a background photon gas had been previously calculated, we examine the possibility of nonlinear corrective terms to the blackbody radiation spectrum. Suitable conditions can be found in both astrophysical and laboratory environments. Inertial confined, ignited thermonuclear plasmas will produce intense blackbody radiation at temperatures in excess of 20 keV. In this theoretical investigation, our analysis shows that in an ideal incoherent blackbody the radiation spectrum is unaffected in the regime studied. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  15. Intensity-modulated radiation therapy: supportive data for prostate cancer.

    PubMed

    Cahlon, Oren; Hunt, Margie; Zelefsky, Michael J

    2008-01-01

    Since its introduction into clinical use in the mid-1990s, intensity-modulated radiation therapy (IMRT) has emerged as the most effective and widely used form of external-beam radiotherapy for localized prostate cancer. Multiple studies have confirmed the importance of delivering sufficiently high doses to the prostate to achieve cure. The dosimetric superiority of IMRT over conventional techniques to produce conformal dose distributions that allow for organ sparing has been shown. A growing number of reports have confirmed that IMRT is the safest way to deliver high doses of external-beam irradiation to the prostate and the regional lymph nodes. Advances in imaging and onboard verification systems continue to advance the capabilities of IMRT and have potential implications with regards to further dose escalation and hypofractionated regimens. The clinical data in support of IMRT and the associated technical aspects of IMRT treatment planning and implementation are highlighted in this review.

  16. Interaction of surface plasmon polaritons in heavily doped GaN microstructures with terahertz radiation

    NASA Astrophysics Data System (ADS)

    Melentev, G. A.; Shalygin, V. A.; Vorobjev, L. E.; Panevin, V. Yu.; Firsov, D. A.; Riuttanen, L.; Suihkonen, S.; Korotyeyev, V. V.; Lyaschuk, Yu. M.; Kochelap, V. A.; Poroshin, V. N.

    2016-03-01

    We present the results of experimental and theoretical studies of the surface plasmon polariton excitations in heavily doped GaN epitaxial layers. Reflection and emission of radiation in the frequency range of 2-20 THz including the Reststrahlen band were investigated for samples with grating etched on the sample surface, as well as for samples with flat surface. The reflectivity spectrum for p-polarized radiation measured for the sample with the surface-relief grating demonstrates a set of resonances associated with excitations of different surface plasmon polariton modes. Spectral peculiarities due to the diffraction effect have been also revealed. The characteristic features of the reflectivity spectrum, namely, frequencies, amplitudes, and widths of the resonance dips, are well described theoretically by a modified technique of rigorous coupled-wave analysis of Maxwell equations. The emissivity spectra of the samples were measured under epilayer temperature modulation by pulsed electric field. The emissivity spectrum of the sample with surface-relief grating shows emission peaks in the frequency ranges corresponding to the decay of the surface plasmon polariton modes. Theoretical analysis based on the blackbody-like radiation theory well describes the main peculiarities of the observed THz emission.

  17. Intensity-modulated radiation therapy for head and neck carcinoma.

    PubMed

    Grégoire, Vincent; De Neve, Wilfried; Eisbruch, Avraham; Lee, Nancy; Van den Weyngaert, Danielle; Van Gestel, Dirk

    2007-05-01

    Intensity-modulated radiation therapy (IMRT) for head and neck tumors refers to a new approach that aims at increasing the radiation dose gradient between the target tissues and the surrounding normal tissues at risk, thus offering the prospect of increasing the locoregional control probability while decreasing the complication rate. As a prerequisite, IMRT requires a proper selection and delineation of target volumes. For the latter, recent data indicate the potential of functional imaging to complement anatomic imaging modalities. Nonrandomized clinical series in paranasal sinuses and pharyngolaryngeal carcinoma have shown that IMRT was able to achieve a very high rate of locoregional control with less morbidity, such as dry-eye syndrome, xerostomia, and swallowing dysfunction. The promising results of IMRT are likely to be achieved when many treatment conditions are met, for example, optimal selection and delineation of the target volumes and organs at risk, appropriate physical quality control of the irradiation, and accurate patient setup with the use of onboard imaging. Because of the complexity of the various tasks, it is thus likely that these conditions will only be met in institutions having large patient throughput and experience with IMRT. Therefore, patient referral to those institutions is recommended.

  18. Rock Burst Intensity Classification Based on the Radiated Energy with Damage Intensity at Jinping II Hydropower Station, China

    NASA Astrophysics Data System (ADS)

    Chen, Bing-Rui; Feng, Xia-Ting; Li, Qing-Peng; Luo, Ru-Zhou; Li, Shaojun

    2015-01-01

    Based on the radiated energy of 133 rock bursts monitored by a microseismic technique at the Jinping II hydropower station, in Sichuan province, China, we analyzed the advantages and disadvantages of qualitative classification methods for the rock burst intensity. Then, we investigated the characteristics, magnitude, and laws of the radiated energy, as well as the relationship between the rock burst radiated energy and intensity. Then, we selected the energy as an evaluation index for the rock burst intensity classification, and proposed a new rock burst intensity quantitative classification method, which utilized the hierarchical clustering analysis technique with the complete-linkage method. Next, we created a new set of criteria for the quantitative classification of the rock burst intensity based on radiated energy and surrounding rock damage severity. The new criteria classified the rock burst intensity into five levels: extremely intense, intense, moderate, weak, and none, and the common logarithms of the radiated energy of each level were >7 lg( E/J), >4 lg( E/J) and <7 lg( E/J), >2 lg( E/J) and <4 lg( E/J), >1 lg( E/J) and <2 lg( E/J), and <1 lg( E/J), respectively. Finally, we investigated the factors influencing the classification, and verified its feasibility and applicability via several practical rock burst examples.

  19. Terahertz radiation as a bunch diagnostic for laser-wakefield-accelerated electron bunches

    SciTech Connect

    van Tilborg, Jeroen; Schroeder, Carl; Filip, Catalin; Toth, Csaba; Geddes, Cameron; Fubiani, Gwenael; Esarey, Eric; Leemans, Wim

    2011-06-17

    Experimental results are reported from two measurement techniques (semiconductor switching and electro-optic sampling) that allow temporal characterization of electron bunches produced by a laser-driven plasma-based accelerator. As femtosecond electron bunches exit the plasma-vacuum interface, coherent transition radiation (at THz frequencies) is emitted. Measuring the properties of this radiation allows characterization of the electron bunches. Theoretical work on the emission mechanism is presented, including a model that calculates the THz wave form from a given bunch profile. It is found that the spectrum of the THz pulse is coherent up to the 200 {micro}m thick crystal (ZnTe) detection limit of 4 THz, which corresponds to the production of sub-50 fs (rms) electron bunch structure. The measurements demonstrate both the shot-to-shot stability of bunch parameters that are critical to THz emission (such as total charge and bunch length), as well as femtosecond synchronization among bunch, THz pulse, and laser beam.

  20. Origins of Terahertz Difference Frequency Susceptibility in Midinfrared Quantum Cascade Lasers

    NASA Astrophysics Data System (ADS)

    Burnett, Benjamin A.; Williams, Benjamin S.

    2016-03-01

    We present a density-matrix-based transport model applicable to quantum cascade lasers which computes both linear and nonlinear optical properties coherently and nonperturbatively. The model is applied to a dual-active-region midinfrared quantum cascade laser which generates terahertz radiation at the difference frequency between two midinfrared pumps. A new mechanism for terahertz generation is identified as self-detection, ascribed to the beating of current flow following the intensity, associated with stimulated emission. This mechanism peaks at optical rectification but exhibits a bandwidth reaching significantly into the terahertz range, which is primarily limited by the subpicosecond intersubband lifetimes. A metric is derived to assess the strength of self-detection in candidate active regions through experiment alone, and suggestions are made for improvement of the performance at frequencies below 2 THz.

  1. Frequency locking and monitoring based on Bi-directional terahertz radiation of a 3rd-order distributed feedback quantum cascade laser

    SciTech Connect

    van Marrewijk, N.; Mirzaei, B.; Hayton, D.; Gao, J. R.; Kao, T. Y.; Hu, Q.; Reno, J. L.

    2015-10-07

    In this study, we have performed frequency locking of a dual, forward reverse emitting third-order distributed feedback quantum cascade laser (QCL) at 3.5 THz. By using both directions of THz emission in combination with two gas cells and two power detectors, we can for the first time perform frequency stabilization, while monitor the frequency locking quality independently. We also characterize how the use of a less sensitive pyroelectric detector can influence the quality of frequency locking, illustrating experimentally that the sensitivity of the detectors is crucial. Using both directions of terahertz (THz) radiation has a particular advantage for the application of a QCL as a local oscillator, where radiation from one side can be used for frequency/phase stabilization, leaving the other side to be fully utilized as a local oscillator to pump a mixer.

  2. Frequency locking and monitoring based on Bi-directional terahertz radiation of a 3rd-order distributed feedback quantum cascade laser

    DOE PAGES

    van Marrewijk, N.; Mirzaei, B.; Hayton, D.; Gao, J. R.; Kao, T. Y.; Hu, Q.; Reno, J. L.

    2015-10-07

    In this study, we have performed frequency locking of a dual, forward reverse emitting third-order distributed feedback quantum cascade laser (QCL) at 3.5 THz. By using both directions of THz emission in combination with two gas cells and two power detectors, we can for the first time perform frequency stabilization, while monitor the frequency locking quality independently. We also characterize how the use of a less sensitive pyroelectric detector can influence the quality of frequency locking, illustrating experimentally that the sensitivity of the detectors is crucial. Using both directions of terahertz (THz) radiation has a particular advantage for the applicationmore » of a QCL as a local oscillator, where radiation from one side can be used for frequency/phase stabilization, leaving the other side to be fully utilized as a local oscillator to pump a mixer.« less

  3. Frequency Locking and Monitoring Based on Bi-directional Terahertz Radiation of a 3rd-Order Distributed Feedback Quantum Cascade Laser

    NASA Astrophysics Data System (ADS)

    van Marrewijk, N.; Mirzaei, B.; Hayton, D.; Gao, J. R.; Kao, T. Y.; Hu, Q.; Reno, J. L.

    2015-12-01

    We have performed frequency locking of a dual, forward reverse emitting third-order distributed feedback quantum cascade laser (QCL) at 3.5 THz. By using both directions of THz emission in combination with two gas cells and two power detectors, we can for the first time perform frequency stabilization, while monitor the frequency locking quality independently. We also characterize how the use of a less sensitive pyroelectric detector can influence the quality of frequency locking, illustrating experimentally that the sensitivity of the detectors is crucial. Using both directions of terahertz (THz) radiation has a particular advantage for the application of a QCL as a local oscillator, where radiation from one side can be used for frequency/phase stabilization, leaving the other side to be fully utilized as a local oscillator to pump a mixer.

  4. Generation of continuous wave terahertz frequency radiation from metal-organic chemical vapour deposition grown Fe-doped InGaAs and InGaAsP

    NASA Astrophysics Data System (ADS)

    Mohandas, Reshma A.; Freeman, Joshua R.; Rosamond, Mark C.; Hatem, Osama; Chowdhury, Siddhant; Ponnampalam, Lalitha; Fice, Martyn; Seeds, Alwyn J.; Cannard, Paul J.; Robertson, Michael J.; Moodie, David G.; Cunningham, John E.; Davies, A. Giles; Linfield, Edmund H.; Dean, Paul

    2016-04-01

    We demonstrate the generation of continuous wave terahertz (THz) frequency radiation from photomixers fabricated on both Fe-doped InGaAs and Fe-doped InGaAsP, grown by metal-organic chemical vapor deposition. The photomixers were excited using a pair of distributed Bragg reflector lasers with emission around 1550 nm, and THz radiation was emitted over a bandwidth of greater than 2.4 THz. Two InGaAs and four InGaAsP wafers with different Fe doping concentrations were investigated, with the InGaAs material found to outperform the InGaAsP in terms of emitted THz power. The dependencies of the emitted power on the photomixer applied bias, incident laser power, and material doping level were also studied.

  5. Survey of resident education in intensity-modulated radiation therapy.

    PubMed

    Malik, Renuka; Oh, Julia L; Roeske, John C; Mundt, Arno J

    2005-06-01

    Intensity-modulated radiation therapy (IMRT) has been gaining increasing popularity among practicing physicians in the U.S., but the extent to which radiation oncology residents are taught the principles of this technology and are trained to use IMRT remains unknown. In this paper, we assessed the current level of resident education in IMRT in the United States. Chief residents at all 77 accredited radiation oncology programs were sent a 13-question survey addressing formal didactics and hands-on experience in IMRT. The survey assessed the frequency, subject, and format of IMRT didactics. Questions also addressed the number of IMRT patients and anatomical sites treated, resident involvement in the IMRT process, and the intent of IMRT use. Finally, residents were asked for their opinions on their IMRT education. Sixty-one surveys (79%) were completed. Overall, forty-three respondents (71%) reported receiving formal IMRT didactics, with nearly one-third reporting extensive didactics (> or = 3 lectures/seminars et cetera per year). The most common didactic formats were lectures (95%) and journal clubs (63%), most commonly supervised by physicists (98%). Involvement by physicians and radiobiologists were reported by 63% and 7% of respondents, respectively. Overall, 87% of respondents had hands-on IMRT training, with nearly one-half having treated > 25 patients. The most common sites treated were head and neck (94%) and prostate (81%). Involvement in all aspects of the IMRT process was common, particularly target and tissue delineation (98%) and plan evaluation (93%). Most respondents (79%) with hands-on experience reported receiving formal didactics. However, nearly one-third received no or only minimal formal didactics. The percentage of respondents desiring increased IMRT didactics and hands-on experience were 70% and 47%, respectively. Our results suggest that the great majority of radiation oncology residents in the United States are currently exposed to didactics

  6. Terahertz time-domain transmission of superconductors

    SciTech Connect

    Nuss, M.C.; Manklewich, P.M.; O'Malley, M.; Gossen, K.W.; Roskos, H.

    1992-05-22

    The conductivity of superconducting films is studied with collimated terahertz radiation from photoconductive dipole antennas. We measure both real and imaginary part of the conductivity directly without using the Kramers-Kronig relations.

  7. Comparison of an electro-optical system and photo-conducting antenna employed as detectors of pulsed terahertz radiation by means of a new method for measuring spectral width

    SciTech Connect

    Grachev, Ya V; Osipova, M O; Bespalov, V G

    2014-12-31

    Two detection systems, electro-optical system and photoconducting system, are tested by the method suggested previously for determining the boundaries of broadband terahertz radiation in time-domain spectroscopy. From a series of measurements the error in determining the operation ranges is calculated. The terahertz spectrometer with an electro-optical detector based on a ZnTe (110) crystal of thickness 2 mm has the operation spectral range of 0.059 – 1.092 THz. The detector utilizing an iPCA-21-05-1000-800-h photo-conducting antenna with the same source of signal demonstrates a wider operation band ranging from 0.017 to 1.6 THz. The method developed makes it possible to experimentally compare the parameters of the considered terahertz spectrometers obtained under the same quality of adjustment. (laser applications and other topics in quantum electronics)

  8. The SPARC linear accelerator based terahertz source

    SciTech Connect

    Chiadroni, E.; Bacci, A.; Bellaveglia, M.; Boscolo, M.; Castellano, M.; Cultrera, L.; Di Pirro, G.; Ferrario, M.; Ficcadenti, L.; Filippetto, D.; Gatti, G.; Pace, E.; Rossi, A. R.; Vaccarezza, C.; Catani, L.; Cianchi, A.; Marchetti, B.; Mostacci, A.; Palumbo, L.; Ronsivalle, C.; and others

    2013-03-04

    Ultra-short electron beams, produced through the velocity bunching compression technique, are used to drive the SPARC linear accelerator based source, which relies on the emission of coherent transition radiation in the terahertz range. This paper reports on the main features of this radiation, as terahertz source, with spectral coverage up to 5 THz and pulse duration down to 200 fs, with an energy per pulse of the order of several micro-joule, and as electron beam longitudinal diagnostics.

  9. Coupled cavity terahertz quantum cascade lasers with integrated emission monitoring.

    PubMed

    Krall, Michael; Martl, Michael; Bachmann, Dominic; Deutsch, Christoph; Andrews, Aaron M; Schrenk, Werner; Strasser, Gottfried; Unterrainer, Karl

    2015-02-01

    We demonstrate the on-chip generation and detection of terahertz radiation in coupled cavity systems using a single semiconductor heterostructure. Multiple sections of a terahertz quantum cascade laser structure in a double-metal waveguide are optically coupled and operate either as a laser or an integrated emission monitor. A detailed analysis of the photon-assisted carrier transport in the active region below threshold reveals the detection mechanism for photons emitted by the very same structure above threshold. Configurations with a single laser cavity and two coupled laser cavities are studied. It is shown that the integrated detector can be used for spatial sensing of the light intensity within a coupled cavity.

  10. Ultrasound-based guidance of intensity-modulated radiation therapy.

    PubMed

    Fung, Albert Y C; Ayyangar, Komanduri M; Djajaputra, David; Nehru, Ramasamy M; Enke, Charles A

    2006-01-01

    In ultrasound-guided intensity-modulated radiation therapy (IMRT) of prostate cancer, ultrasound imaging ascertains the anatomical position of patients during x-ray therapy delivery. The ultrasound transducers are made of piezoelectric ceramics. The same crystal is used for both ultrasound production and reception. Three-dimensional (3D) ultrasound devices capture and correlate series of 2-dimensional (2D) B-mode images. The transducers are often arranged in a convex array for focusing. Lower frequency reaches greater depth, but results in low resolution. For clear image, some gel is usually applied between the probe and the skin contact surface. For prostate positioning, axial and sagittal scans are performed, and the volume contours from computed tomography (CT) planning are superimposed on the ultrasound images obtained before radiation delivery at the linear accelerator. The planning volumes are then overlaid on the ultrasound images and adjusted until they match. The computer automatically deduces the offset necessary to move the patient so that the treatment area is in the correct location. The couch is translated as needed. The currently available commercial equipment can attain a positional accuracy of 1-2 mm. Commercial manufacturer designs differ in the detection of probe coordinates relative to the isocenter. Some use a position-sensing robotic arm, while others have infrared light-emitting diodes or pattern-recognition software with charge-couple-device cameras. Commissioning includes testing of image quality and positional accuracy. Ultrasound is mainly used in prostate positioning. Data for 7825 daily fractions of 234 prostate patients indicated average 3D inter-fractional displacement of about 7.8 mm. There was no perceivable trend of shift over time. Scatter plots showed slight prevalence toward superior-posterior directions. Uncertainties of ultrasound guidance included tissue inhomogeneities, speckle noise, probe pressure, and inter

  11. Ultrasound-based guidance of intensity-modulated radiation therapy

    SciTech Connect

    Fung, Albert Y.C. . E-mail: afung@unmc.edu; Ayyangar, Komanduri M.; Djajaputra, David; Nehru, Ramasamy M.; Enke, Charles A.

    2006-04-01

    In ultrasound-guided intensity-modulated radiation therapy (IMRT) of prostate cancer, ultrasound imaging ascertains the anatomical position of patients during x-ray therapy delivery. The ultrasound transducers are made of piezoelectric ceramics. The same crystal is used for both ultrasound production and reception. Three-dimensional (3D) ultrasound devices capture and correlate series of 2-dimensional (2D) B-mode images. The transducers are often arranged in a convex array for focusing. Lower frequency reaches greater depth, but results in low resolution. For clear image, some gel is usually applied between the probe and the skin contact surface. For prostate positioning, axial and sagittal scans are performed, and the volume contours from computed tomography (CT) planning are superimposed on the ultrasound images obtained before radiation delivery at the linear accelerator. The planning volumes are then overlaid on the ultrasound images and adjusted until they match. The computer automatically deduces the offset necessary to move the patient so that the treatment area is in the correct location. The couch is translated as needed. The currently available commercial equipment can attain a positional accuracy of 1-2 mm. Commercial manufacturer designs differ in the detection of probe coordinates relative to the isocenter. Some use a position-sensing robotic arm, while others have infrared light-emitting diodes or pattern-recognition software with charge-couple-device cameras. Commissioning includes testing of image quality and positional accuracy. Ultrasound is mainly used in prostate positioning. Data for 7825 daily fractions of 234 prostate patients indicated average 3D inter-fractional displacement of about 7.8 mm. There was no perceivable trend of shift over time. Scatter plots showed slight prevalence toward superior-posterior directions. Uncertainties of ultrasound guidance included tissue inhomogeneities, speckle noise, probe pressure, and inter

  12. Dosimetrically Triggered Adaptive Intensity Modulated Radiation Therapy for Cervical Cancer

    SciTech Connect

    Lim, Karen; Stewart, James; Kelly, Valerie; Xie, Jason; Brock, Kristy K.; Moseley, Joanne; Cho, Young-Bin; Fyles, Anthony; Lundin, Anna; Rehbinder, Henrik; Löf, Johan; Jaffray, David A.; Milosevic, Michael

    2014-09-01

    Purpose: The widespread use of intensity modulated radiation therapy (IMRT) for cervical cancer has been limited by internal target and normal tissue motion. Such motion increases the risk of underdosing the target, especially as planning margins are reduced in an effort to reduce toxicity. This study explored 2 adaptive strategies to mitigate this risk and proposes a new, automated method that minimizes replanning workload. Methods and Materials: Thirty patients with cervical cancer participated in a prospective clinical study and underwent pretreatment and weekly magnetic resonance (MR) scans over a 5-week course of daily external beam radiation therapy. Target volumes and organs at risk (OARs) were contoured on each of the scans. Deformable image registration was used to model the accumulated dose (the real dose delivered to the target and OARs) for 2 adaptive replanning scenarios that assumed a very small PTV margin of only 3 mm to account for setup and internal interfractional motion: (1) a preprogrammed, anatomy-driven midtreatment replan (A-IMRT); and (2) a dosimetry-triggered replan driven by target dose accumulation over time (D-IMRT). Results: Across all 30 patients, clinically relevant target dose thresholds failed for 8 patients (27%) if 3-mm margins were used without replanning. A-IMRT failed in only 3 patients and also yielded an additional small reduction in OAR doses at the cost of 30 replans. D-IMRT assured adequate target coverage in all patients, with only 23 replans in 16 patients. Conclusions: A novel, dosimetry-triggered adaptive IMRT strategy for patients with cervical cancer can minimize the risk of target underdosing in the setting of very small margins and substantial interfractional motion while minimizing programmatic workload and cost.

  13. Mapping of laser diode radiation intensity by atomic-force microscopy

    NASA Astrophysics Data System (ADS)

    Alekseev, P. A.; Dunaevskii, M. S.; Slipchenko, S. O.; Podoskin, A. A.; Tarasov, I. S.

    2015-09-01

    The distribution of the intensity of laser diode radiation has been studied using an original method based on atomic-force microscopy (AFM). It is shown that the laser radiation intensity in both the near field and transition zone of a high-power semiconductor laser under room-temperature conditions can be mapped by AFM at a subwavelength resolution. The obtained patterns of radiation intensity distribution agree with the data of modeling and the results of near-field optical microscopy measurements.

  14. Intensity-Modulated Radiation Therapy in Childhood Ependymoma

    SciTech Connect

    Schroeder, Thomas M.; Chintagumpala, Murali; Okcu, M. Fatih; Chiu, J. Kam; Teh, Bin S.; Woo, Shiao Y.; Paulino, Arnold C.

    2008-07-15

    Purpose: To determine the patterns of failure after intensity-modulated radiation therapy (IMRT) for localized intracranial ependymoma. Methods and Materials: From 1994 to 2005, 22 children with pathologically proven, localized, intracranial ependymoma were treated with adjuvant IMRT. Of the patients, 12 (55%) had an infratentorial tumor and 14 (64%) had anaplastic histology. Five patients had a subtotal resection (STR), as evidenced by postoperative magnetic resonance imaging. The clinical target volume encompassed the tumor bed and any residual disease plus margin (median dose 54 Gy). Median follow-up for surviving patients was 39.8 months. Results: The 3-year overall survival rate was 87% {+-} 9%. The 3-year local control rate was 68% {+-} 12%. There were six local recurrences, all in the high-dose region of the treatment field. Median time to recurrence was 21.7 months. Of the 5 STR patients, 4 experienced recurrence and 3 died. Patients with a gross total resection had significantly better local control (p = 0.024) and overall survival (p = 0.008) than those with an STR. At last follow-up, no patient had developed visual loss, brain necrosis, myelitis, or a second malignancy. Conclusions: Treatment with IMRT provides local control and survival rates comparable with those in historic publications using larger treatment volumes. All failures were within the high-dose region, suggesting that IMRT does not diminish local control. The degree of surgical resection was shown to be significant for local control and survival.

  15. Generation of terahertz radiation via an electromagnetically induced transparency at ion acoustic frequency region in laser-produced dense plasmas.

    PubMed

    Nakagawa, Makoto; Kodama, Ryosuke; Higashiguchi, Takeshi; Yugami, Noboru

    2009-08-01

    Electromagnetically induced transparency is a well-known quantum phenomena that electromagnetic wave controls the refractive index of medium. It enables us to create a passband for low-frequency electromagnetic wave in a dense plasma even if the plasma is opaque for the electromagnetic wave. This technique can be used to prove the ion acoustic wave because the ion acoustic frequency is lower than the plasma frequency. We have investigated a feasibility of electromagnetic radiation at THz region corresponding to the ion acoustic frequency from a dense plasma. We confirmed that the passband is created at about 7.5 THz corresponding to the ion acoustic frequency in the electron plasma density of 10(21) cm(-3) with a Ti:Sapphire laser with the wavelength of 800 nm and the laser intensity of 10(17) W/cm(2). The estimated radiation power is around 1 MW, which is expected to be useful for nonlinear THz science and applications.

  16. Continuous wave terahertz radiation from antennas fabricated on C¹²-irradiated semi-insulating GaAs.

    PubMed

    Deshmukh, Prathmesh; Mendez-Aller, M; Singh, Abhishek; Pal, Sanjoy; Prabhu, S S; Nanal, Vandana; Pillay, R G; Döhler, G H; Preu, S

    2015-10-01

    We demonstrate continuous wave (CW) terahertz generation from antennas fabricated on C12-irradiated semi-insulating (SI) GaAs substrates. The dark current drawn by the antennas fabricated on irradiated substrates is ∼3 to 4 orders of magnitude lower compared to antennas fabricated on un-irradiated substrates, while the photocurrents decrease by only ∼1.5 orders of magnitude. This can be attributed to the strong reduction of the carrier lifetime that is 2.5 orders of magnitude, with values around τ(rec)=0.2  ps. Reduced thermal heating allows for higher bias voltages to the irradiated antenna devices resulting in higher CW terahertz power, just slightly lower than that of low-temperature grown GaAs (LT GaAs)at similar excitation conditions.

  17. Continuous wave terahertz radiation from antennas fabricated on C¹²-irradiated semi-insulating GaAs.

    PubMed

    Deshmukh, Prathmesh; Mendez-Aller, M; Singh, Abhishek; Pal, Sanjoy; Prabhu, S S; Nanal, Vandana; Pillay, R G; Döhler, G H; Preu, S

    2015-10-01

    We demonstrate continuous wave (CW) terahertz generation from antennas fabricated on C12-irradiated semi-insulating (SI) GaAs substrates. The dark current drawn by the antennas fabricated on irradiated substrates is ∼3 to 4 orders of magnitude lower compared to antennas fabricated on un-irradiated substrates, while the photocurrents decrease by only ∼1.5 orders of magnitude. This can be attributed to the strong reduction of the carrier lifetime that is 2.5 orders of magnitude, with values around τ(rec)=0.2  ps. Reduced thermal heating allows for higher bias voltages to the irradiated antenna devices resulting in higher CW terahertz power, just slightly lower than that of low-temperature grown GaAs (LT GaAs)at similar excitation conditions. PMID:26421576

  18. Radiation efficacy and biological risk from whole-breast irradiation via intensity modulated radiation therapy (IMRT)

    NASA Astrophysics Data System (ADS)

    Desantis, David M.

    Radiotherapy is an established modality for women with breast cancer. During the delivery of external beam radiation to the breast, leakage, scattered x-rays from the patient and the linear accelerator also expose healthy tissues and organs outside of the breast, thereby increasing the patient's whole-body dose, which then increases the chance of developing a secondary, radiation-induced cancer. Generally, there are three IntensityModulated Radiotherapy (IMRT) delivery techniques from a conventional linear accelerator; forward planned (FMLC), inverse planned 'sliding window' (DMLC), and inverse planned 'step-and-shoot' (SMLC). The goal of this study was to determine which of these three techniques delivers an optimal dose to the breast with the least chance of causing a fatal, secondary, radiation-induced cancer. A conventional, non-IMRT, 'Wedge' plan also was compared. Computerized Tomography (CT) data sets for both a large and small sized patient were used in this study. With Varian's Eclipse AAA algorithm, the organ doses specified in the revised ICRP 60 publication were used to calculate the whole-body dose. Also, an anthropomorphic phantom was irradiated with thermoluminescent dosimeters (TLD) at each organ site for measured doses. The risk coefficient from the Biological Effects of Ionizing Radiation (BEIR) VII report of 4.69 x 10-2 deaths per Gy was used to convert whole-body dose to risk of a fatal, secondary, radiation-induced cancer. The FMLC IMRT delivered superior tumor coverage over the 3D conventional plan and the inverse DMLC or SMLC treatment plans delivered clinically equivalent tumor coverage. However, the FMLC plan had the least likelihood of inadvertently causing a fatal, secondary, radiation-induced cancer compared to the inverse DMLC, SMLC, and Wedge plans.

  19. Generation of Terahertz Radiation from Fe-doped InGaAsP Using 800 nm to 1550 nm Pulsed Laser Excitation

    NASA Astrophysics Data System (ADS)

    Hatem, O.; Freeman, J. R.; Cunningham, J. E.; Cannard, P. J.; Robertson, M. J.; Linfield, E. H.; Davies, A. G.; Moodie, D. G.

    2016-05-01

    We demonstrate efficient generation of terahertz (THz) frequency radiation by pulsed excitation, at wavelengths between 800 and 1550 nm, of photoconductive (PC) switches fabricated using Fe-doped InGaAsP wafers, grown by metal organic chemical vapor deposition (MOCVD). Compared to our previous studies of Fe-doped InGaAs wafers, Fe:InGaAsP wafers exhibited five times greater dark resistivity to give a value of 10 kΩ cm, and Fe:InGaAsP PC switches produced five times higher THz power emission. The effect of Fe-doping concentration (between 1E16 and 1.5E17 cm-3) on optical light absorption (between 800 and 1600 nm), on resistivity, and on THz emission is also discussed.

  20. Terahertz radiation from InAlAs and GaAs surface intrinsic-N+ structures and the critical electric fields of semiconductors

    NASA Astrophysics Data System (ADS)

    Hwang, J. S.; Lin, H. C.; Lin, K. I.; Zhang, X. C.

    2005-09-01

    This study examines terahertz radiation from a series of In0.52Al0.48As and GaAs surface-intrinsic-N+ structures (SIN+) with surface-intrinsic layers of various thicknesses. The built-in electric fields in the SIN+ structures are used as the bias. Experimental results indicate that the amplitudes of the THz emission are independent of the built-in electric fields in the emitters when the built-in electric fields exceed the corresponding critical electric fields of the semiconductors. In contrast, the amplitudes of the THz emission are proportional to the thickness of the intrinsic layer and, therefore, the number of photo-excited charged carriers.

  1. Intensity Modulated Radiation Therapy With Dose Painting to Treat Rhabdomyosarcoma

    SciTech Connect

    Yang, Joanna C.; Dharmarajan, Kavita V.; Wexler, Leonard H.; La Quaglia, Michael P.; Happersett, Laura; Wolden, Suzanne L.

    2012-11-01

    Purpose: To examine local control and patterns of failure in rhabdomyosarcoma patients treated with intensity modulated radiation therapy (RT) with dose painting (DP-IMRT). Patients and Methods: A total of 41 patients underwent DP-IMRT with chemotherapy for definitive treatment. Nineteen also underwent surgery with or without intraoperative RT. Fifty-six percent had alveolar histologic features. The median interval from beginning chemotherapy to RT was 17 weeks (range, 4-25). Very young children who underwent second-look procedures with or without intraoperative RT received reduced doses of 24-36 Gy in 1.4-1.8-Gy fractions. Young adults received 50.4 Gy to the primary tumor and lower doses of 36 Gy in 1.8-Gy fractions to at-risk lymph node chains. Results: With 22 months of median follow-up, the actuarial local control rate was 90%. Patients aged {<=}7 years who received reduced overall and fractional doses had 100% local control, and young adults had 79% (P=.07) local control. Three local failures were identified in young adults whose primary target volumes had received 50.4 Gy in 1.8-Gy fractions. Conclusions: DP-IMRT with lower fractional and cumulative doses is feasible for very young children after second-look procedures with or without intraoperative RT. DP-IMRT is also feasible in adolescents and young adults with aggressive disease who would benefit from prophylactic RT to high-risk lymph node chains, although dose escalation might be warranted for improved local control. With limited follow-up, it appears that DP-IMRT produces local control rates comparable to those of sequential IMRT in patients with rhabdomyosarcoma.

  2. Inelastic scattering in condensed matter with high intensity Moessbauer radiation

    NASA Astrophysics Data System (ADS)

    Yelon, W. B.; Schupp, G.

    1991-05-01

    We give a progress report for the work which has been carried out in the last three years with DOE support. A facility for high-intensity Moessbauer scattering is not fully operational at the University of Missouri Research Reactor (MURR) as well as a facility at Purdue, using special isotopes produced at MURR. High precision, fundamental Moessbauer effect studies have been carried out using Bragg scattering filters to suppress unwanted radiation. These have led to a Fourier transform method for describing Moessbauer effect (ME) lineshape and a direct method of fitting ME data to the convolution integral. These methods allow complete correction for source resonance self absorption and the accurate representation of interference effects that add an asymmetric component to the ME lines. We have begun applying these techniques to attenuated ME sources whose central peak has been attenuated by stationary resonant absorbers, to make a novel independent determination of interference parameters and line-shape behavior in the resonance asymptotic region. This analysis is important to both fundamental ME studies and to scattering studies for which a deconvolution is essential for extracting the correct recoilless fractions and interference parameters. A number of scattering studies have been successfully carried out including a study of the thermal diffuse scattering in Si, which led to an analysis of the resolution function for gamma-ray scattering. Also studied was the anharmonic motion in Na metal and the charge density wave satellite reflection Debye-Waller factor in TaS2, which indicate phason rather than phonon behavior. Using a specially constructed sample cell which enables us to vary temperatures from -10 C to 110 C, we have begun quasielastic diffusion studies in viscous liquids and current results are summarized. Included are the temperature and Q dependence of the scattering in pentadecane and diffusion in glycerol.

  3. 14 CFR 25.1317 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false High-intensity Radiated Fields (HIRF) Protection. 25.1317 Section 25.1317 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Equipment General § 25.1317 High-intensity Radiated Fields...

  4. 14 CFR 27.1317 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false High-intensity Radiated Fields (HIRF) Protection. 27.1317 Section 27.1317 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT Equipment General § 27.1317 High-intensity Radiated Fields...

  5. 14 CFR 27.1317 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false High-intensity Radiated Fields (HIRF) Protection. 27.1317 Section 27.1317 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL CATEGORY ROTORCRAFT Equipment General § 27.1317 High-intensity Radiated Fields...

  6. 14 CFR 25.1317 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false High-intensity Radiated Fields (HIRF) Protection. 25.1317 Section 25.1317 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Equipment General § 25.1317 High-intensity Radiated Fields...

  7. 14 CFR 29.1317 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false High-intensity Radiated Fields (HIRF) Protection. 29.1317 Section 29.1317 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Equipment General § 29.1317 High-intensity Radiated Fields...

  8. 14 CFR 29.1317 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false High-intensity Radiated Fields (HIRF) Protection. 29.1317 Section 29.1317 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Equipment General § 29.1317 High-intensity Radiated Fields...

  9. 14 CFR 23.1308 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false High-intensity Radiated Fields (HIRF) Protection. 23.1308 Section 23.1308 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF... Equipment General § 23.1308 High-intensity Radiated Fields (HIRF) Protection. (a) Except as provided...

  10. 14 CFR 25.1317 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false High-intensity Radiated Fields (HIRF) Protection. 25.1317 Section 25.1317 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF...-intensity Radiated Fields (HIRF) Protection. (a) Except as provided in paragraph (d) of this section,...

  11. 14 CFR 29.1317 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false High-intensity Radiated Fields (HIRF) Protection. 29.1317 Section 29.1317 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF...-intensity Radiated Fields (HIRF) Protection. (a) Except as provided in paragraph (d) of this section,...

  12. 14 CFR 23.1308 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false High-intensity Radiated Fields (HIRF... Equipment General § 23.1308 High-intensity Radiated Fields (HIRF) Protection. (a) Except as provided in... reduce the capability of the airplane or the ability of the flightcrew to respond to an adverse...

  13. [Modalities of breast cancer irradiation in 2016: Aims and indications of intensity modulated radiation therapy].

    PubMed

    Bourgier, C; Fenoglietto, P; Lemanski, C; Ducteil, A; Charissoux, M; Draghici, R; Azria, D

    2016-10-01

    Irradiation techniques for breast cancer (arctherapy, tomotherapy) are evolving and intensity-modulated radiation therapy is being increasingly considered for the management of these tumours. Here, we propose a review of intensity-modulated radiation therapy planning issues, clinical toxicities and indications for breast cancer. PMID:27614497

  14. Terahertz Technology: A Boon to Tablet Analysis

    PubMed Central

    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

  15. Theoretical study of terahertz generation from atoms and aligned molecules driven by two-color laser fields

    NASA Astrophysics Data System (ADS)

    Chen, Wenbo; Huang, Yindong; Meng, Chao; Liu, Jinlei; Zhou, Zhaoyan; Zhang, Dongwen; Yuan, Jianmin; Zhao, Zengxiu

    2015-09-01

    We study the generation of terahertz radiation from atoms and molecules driven by an ultrashort fundamental laser and its second-harmonic field by solving the time-dependent Schrödinger equation (TDSE). The comparisons between one-, two-, and three-dimensional TDSE numerical simulations show that the initial ionized wave packet and its subsequent acceleration in the laser field and rescattering with long-range Coulomb potential play key roles. We also present the dependence of the optimum phase delay and yield of terahertz radiation on the laser intensity, wavelength, duration, and ratio of two-color laser components. Terahertz wave generation from model hydrogen molecules is further investigated by comparing with high harmonic emission. It is found that the terahertz yield follows the alignment dependence of the ionization rate, while the optimal two-color phase delays vary by a small amount when the alignment angle changes from 0 to 90 degrees, which reflects the alignment dependence of attosecond electron dynamics. Finally, we show that terahertz emission might be used to clarify the origin of interference in high harmonic generation from aligned molecules by coincidentally measuring the alignment-dependent THz yields.

  16. [Adaptation reactions of rat blood exposed to low intensity electromagnetic radiation].

    PubMed

    Krylov, V N; Deriugina, A V

    2010-06-01

    It is carried out research of action low-intensive electromagnetic radiations--low-intensive laser radiation and radiations of the highest frequency on normal animals and at modelling the stress-reaction, caused by introduction of adrenaline. Absence of effects of system of blood is noted at action low-intensive electromagnetic radiations on normal an organism and them correction action on alteration an organism, shown in restoration of the broken parameters--leukocyte the blood count, electrophoretic mobility of erythrocytes and phospholipide's structure of their membranes.

  17. Metal wires for terahertz wave guiding.

    PubMed

    Wang, Kanglin; Mittleman, Daniel M

    2004-11-18

    Sources and systems for far-infrared or terahertz (1 THz = 10(12) Hz) radiation have received extensive attention in recent years, with applications in sensing, imaging and spectroscopy. Terahertz radiation bridges the gap between the microwave and optical regimes, and offers significant scientific and technological potential in many fields. However, waveguiding in this intermediate spectral region still remains a challenge. Neither conventional metal waveguides for microwave radiation, nor dielectric fibres for visible and near-infrared radiation can be used to guide terahertz waves over a long distance, owing to the high loss from the finite conductivity of metals or the high absorption coefficient of dielectric materials in this spectral range. Furthermore, the extensive use of broadband pulses in the terahertz regime imposes an additional constraint of low dispersion, which is necessary for compatibility with spectroscopic applications. Here we show how a simple waveguide, namely a bare metal wire, can be used to transport terahertz pulses with virtually no dispersion, low attenuation, and with remarkable structural simplicity. As an example of this new waveguiding structure, we demonstrate an endoscope for terahertz pulses.

  18. Terahertz Tools Advance Imaging for Security, Industry

    NASA Technical Reports Server (NTRS)

    2010-01-01

    Picometrix, a wholly owned subsidiary of Advanced Photonix Inc. (API), of Ann Arbor, Michigan, invented the world s first commercial terahertz system. The company improved the portability and capabilities of their systems through Small Business Innovation Research (SBIR) agreements with Langley Research Center to provide terahertz imaging capabilities for inspecting the space shuttle external tanks and orbiters. Now API s systems make use of the unique imaging capacity of terahertz radiation on manufacturing floors, for thickness measurements of coatings, pharmaceutical tablet production, and even art conservation.

  19. A Concealed Barcode Identification System Using Terahertz Time-domain Spectroscopy

    NASA Astrophysics Data System (ADS)

    Guan, Yu; Yamamoto, Manabu; Kitazawa, Toshiyuki; Tripathi, Saroj R.; Takeya, Kei; Kawase, Kodo

    2015-03-01

    We present a concealed terahertz barcode/chipless tag to achieve remote identification through an obstructing material using terahertz radiation. We show scanned terahertz reflection spectral images of barcodes concealed by a thick obstacle. A concealed and double- side printed terahertz barcode structure is proposed, and we demonstrate that our design has better performance in definition than a single-side printed barcode using terahertz time-domain spectroscopy. This technique combines the benefits of a chipless tag to read encoded information covered by an optically opaque material with low cost and a simple fabrication process. Simulations are also described, along with an explanation of the principle of the terahertz barcode identification system.

  20. Advances in three-dimensional conformal radiation therapy physics with intensity modulation.

    PubMed

    Webb, S

    2000-09-01

    Intensity-modulated radiation therapy, a specific form of conformal radiation therapy, is currently attracting a lot of attention, and there are high expectations for this class of treatment techniques. Several new technologies are in development, but physicists are still working to improve the physical basis of radiation therapy.

  1. Characterizing intra-exciton Coulomb scattering in terahertz excitations

    SciTech Connect

    Zybell, S.; Eßer, F.; Helm, M.; Bhattacharyya, J.; Winnerl, S.; Schneider, H.; Schneebeli, L.; Böttge, C. N.; Kira, M.; Koch, S. W.; Andrews, A. M.; Strasser, G.

    2014-11-17

    An intense terahertz field is applied to excite semiconductor quantum wells yielding strong non-equilibrium exciton distributions. Even though the relaxation channels involve a complicated quantum kinetics of Coulomb and phonon effects, distinct relaxation signatures of Coulomb scattering are identified within time-resolved photoluminescence by comparing the experiment with a reduced model that contains all relevant microscopic processes. The analysis uncovers a unique time scale for the Coulomb scattering directly from experiments and reveals the influence of phonon relaxation as well as radiative decay.

  2. Characterizing intra-exciton Coulomb scattering in terahertz excitations

    NASA Astrophysics Data System (ADS)

    Zybell, S.; Bhattacharyya, J.; Winnerl, S.; Eßer, F.; Helm, M.; Schneider, H.; Schneebeli, L.; Böttge, C. N.; Kira, M.; Koch, S. W.; Andrews, A. M.; Strasser, G.

    2014-11-01

    An intense terahertz field is applied to excite semiconductor quantum wells yielding strong non-equilibrium exciton distributions. Even though the relaxation channels involve a complicated quantum kinetics of Coulomb and phonon effects, distinct relaxation signatures of Coulomb scattering are identified within time-resolved photoluminescence by comparing the experiment with a reduced model that contains all relevant microscopic processes. The analysis uncovers a unique time scale for the Coulomb scattering directly from experiments and reveals the influence of phonon relaxation as well as radiative decay.

  3. Terahertz generation in multiple laser-induced air plasmas

    SciTech Connect

    Chen, M.-K.; Kim, Jae Hun; Yang, C.-E.; Yin, Stuart Shizhuo; Hui Rongqing; Ruffin, Paul

    2008-12-08

    An investigation of the terahertz wave generation in multiple laser-induced air plasmas is presented. First, it is demonstrated that the intensity of the terahertz wave increases as the number of air plasmas increases. Second, the physical mechanism of this enhancement effect of the terahertz generation is studied by quantitatively measuring the intensity of the generated terahertz wave as a function of phase difference between adjacent air plasmas. It is found out that the superposition is the main mechanism to cause this enhancement. Thus, the results obtained in this paper not only provide a technique to generate stronger terahertz wave but also enable a better understanding of the mechanism of the terahertz generation in air plasma.

  4. Inverse planning optimization method for intensity modulated radiation therapy.

    PubMed

    Lan, Yihua; Ren, Haozheng; Li, Cunhua; Min, Zhifang; Wan, Jinxin; Ma, Jianxin; Hung, Chih-Cheng

    2013-10-01

    In order to facilitate the leaf sequencing process in intensity modulated radiation therapy (IMRT), and design of a practical leaf sequencing algorithm, it is an important issue to smooth the planned fluence maps. The objective is to achieve both high-efficiency and high-precision dose delivering by considering characteristics of leaf sequencing process. The key factor which affects total number of monitor units for the leaf sequencing optimization process is the max flow value of the digraph which formulated from the fluence maps. Therefore, we believe that one strategy for compromising dose conformity and total number of monitor units in dose delivery is to balance the dose distribution function and the max flow value mentioned above. However, there are too many paths in the digraph, and we don't know the flow value of which path is the maximum. The maximum flow value among the horizontal paths was selected and used in the objective function of the fluence map optimization to formulate the model. The model is a traditional linear constrained quadratic optimization model which can be solved by interior point method easily. We believe that the smoothed maps from this model are more suitable for leaf sequencing optimization process than other smoothing models. A clinical head-neck case and a prostate case were tested and compared using our proposed model and the smoothing model which is based on the minimization of total variance. The optimization results with the same level of total number of monitor units (TNMU) show that the fluence maps obtained from our model have much better dose performance for the target/non-target region than the maps from total variance based on the smoothing model. This indicates that our model achieves better dose distribution when the algorithm suppresses the TNMU at the same level. Although we have just used the max flow value of the horizontal paths in the diagraph in the objective function, a good balance has been achieved between

  5. Detection of terahertz radiation by tightly concatenated InGaAs field-effect transistors integrated on a single chip

    SciTech Connect

    Popov, V. V.; Yermolaev, D. M.; Shapoval, S. Yu.; Maremyanin, K. V.; Gavrilenko, V. I.; Zemlyakov, V. E.; Bespalov, V. A.; Yegorkin, V. I.; Maleev, N. A.; Ustinov, V. M.

    2014-04-21

    A tightly concatenated chain of InGaAs field-effect transistors with an asymmetric T-gate in each transistor demonstrates strong terahertz photovoltaic response without using supplementary antenna elements. We obtain the responsivity above 1000 V/W and up to 2000 V/W for unbiased and drain-biased transistors in the chain, respectively, with the noise equivalent power below 10{sup −11} W/Hz{sup 0.5} in the unbiased mode of the detector operation.

  6. Stereotactic Body Radiation Therapy Versus Intensity-Modulated Radiation Therapy for Prostate Cancer: Comparison of Toxicity

    PubMed Central

    Yu, James B.; Cramer, Laura D.; Herrin, Jeph; Soulos, Pamela R.; Potosky, Arnold L.; Gross, Cary P.

    2014-01-01

    Purpose Stereotactic body radiation therapy (SBRT) is a technically demanding prostate cancer treatment that may be less expensive than intensity-modulated radiation therapy (IMRT). Because SBRT may deliver a greater biologic dose of radiation than IMRT, toxicity could be increased. Studies comparing treatment cost to the Medicare program and toxicity are needed. Methods We performed a retrospective study by using a national sample of Medicare beneficiaries age ≥ 66 years who received SBRT or IMRT as primary treatment for prostate cancer from 2008 to 2011. Each SBRT patient was matched to two IMRT patients with similar follow-up (6, 12, or 24 months). We calculated the cost of radiation therapy treatment to the Medicare program and toxicity as measured by Medicare claims; we used a random effects model to compare genitourinary (GU), GI, and other toxicity between matched patients. Results The study sample consisted of 1,335 SBRT patients matched to 2,670 IMRT patients. The mean treatment cost was $13,645 for SBRT versus $21,023 for IMRT. In the 6 months after treatment initiation, 15.6% of SBRT versus 12.6% of IMRT patients experienced GU toxicity (odds ratio [OR], 1.29; 95% CI, 1.05 to 1.53; P = .009). At 24 months after treatment initiation, 43.9% of SBRT versus 36.3% of IMRT patients had GU toxicity (OR, 1.38; 95% CI, 1.12 to 1.63; P = .001). The increase in GU toxicity was due to claims indicative of urethritis, urinary incontinence, and/or obstruction. Conclusion Although SBRT was associated with lower treatment costs, there appears to be a greater rate of GU toxicity for patients undergoing SBRT compared with IMRT, and prospective correlation with randomized trials is needed. PMID:24616315

  7. Generation of radiation by intense plasma and electromagnetic undulators

    SciTech Connect

    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.

  8. A point-like source of extreme ultraviolet radiation based on a discharge in a non-uniform gas flow, sustained by powerful gyrotron radiation of terahertz frequency band

    SciTech Connect

    Glyavin, M. Yu.; Golubev, S. V.; Izotov, I. V.; Litvak, A. G.; Luchinin, A. G.; Razin, S. V.; Sidorov, A. V.; Skalyga, V. A.; Vodopyanov, A. V.

    2014-10-27

    The possibility and prospects of extreme ultraviolet (UV) point-like source development are discussed in the present paper. The UV source is based on the discharge sustained by powerful gyrotron radiation of terahertz (THz) frequency band in non-uniform gas flow injected into vacuum volume through a nozzle with diameter less than 1 mm. Recent developments of THz-band gyrotrons with appropriate power level made such discharges possible. First experimental results on a point-like plasma creation by 100 kW radiation of 0.67 THz gyrotron are presented. The possibility of discharge localization within the area less than 1 mm is demonstrated. The discharge emission within the wavelength range from 112 nm to 650 nm was studied. The measured power of light emission in the range of 112–180 nm was measured to be up to 10 kW.

  9. Application of Histogram Analysis in Radiation Therapy (HART) in Intensity Modulation Radiation Therapy (IMRT) Treatments

    NASA Astrophysics Data System (ADS)

    Pyakuryal, Anil

    2009-03-01

    A carcinoma is a malignant cancer that emerges from epithelial cells in structures through out the body.It invades the critical organs, could metastasize or spread to lymph nodes.IMRT is an advanced mode of radiation therapy treatment for cancer. It delivers more conformal doses to malignant tumors sparing the critical organs by modulating the intensity of radiation beam.An automated software, HART (S. Jang et al.,2008,Med Phys 35,p.2812) was used for efficient analysis of dose volume histograms (DVH) for multiple targets and critical organs in four IMRT treatment plans for each patient. IMRT data for ten head and neck cancer patients were exported as AAPM/RTOG format files from a commercial treatment planning system at Northwestern Memorial Hospital (NMH).HART extracted DVH statistics were used to evaluate plan indices and to analyze dose tolerance of critical structures at prescription dose (PD) for each patient. Mean plan indices (n=10) were found to be in good agreement with published results for Linac based plans. The least irradiated volume at tolerance dose (TD50) was observed for brainstem and the highest volume for larynx in SIB treatment techniques. Thus HART, an open source platform, has extensive clinical implications in IMRT treatments.

  10. Terahertz deconvolution.

    PubMed

    Walker, Gillian C; Bowen, John W; Labaune, Julien; Jackson, J-Bianca; Hadjiloucas, Sillas; Roberts, John; Mourou, Gerard; Menu, Michel

    2012-12-01

    The ability to retrieve information from different layers within a stratified sample using terahertz pulsed reflection imaging and spectroscopy has traditionally been resolution limited by the pulse width available. In this paper, a deconvolution algorithm is presented which circumvents this resolution limit, enabling deep sub-wavelength and sub-pulse width depth resolution. The algorithm is explained through theoretical investigation, and demonstrated by reconstructing signals reflected from boundaries in stratified materials that cannot be resolved directly from the unprocessed time-domain reflection signal. Furthermore, the deconvolution technique has been used to recreate sub-surface images from a stratified sample: imaging the reverse side of a piece of paper. PMID:23262673

  11. Terahertz radiation using log-spiral-based low-temperature-grown InGaAs photoconductive antenna pumped by mode-locked Yb-doped fiber laser.

    PubMed

    Kong, Moon Sik; Kim, Ji Su; Han, Sang Pil; Kim, Namje; Moon, Kiwon; Park, Kyung Hyun; Jeon, Min Yong

    2016-04-01

    We demonstrate a terahertz (THz) radiation using log-spiral-based low-temperature-grown (LTG) InGaAs photoconductive antenna (PCA) modules and a passively mode-locked 1030 nm Yb-doped fiber laser. The passively mode-locked Yb-doped fiber laser is easily implemented with nonlinear polarization rotation in the normal dispersion using a 10-nm spectral filter. The laser generates over 250 mW of the average output power with positively chirped 1.58 ps pulses, which are dechirped to 127 fs pulses using a pulse compressor outside the laser cavity. In order to obtain THz radiation, a home-made emitter and receiver constructed from log-spiral-based LTG InGaAs PCA modules were used to generate and detect THz signals, respectively. We successfully achieved absorption lines over 1.5 THz for water vapor in free space. Therefore, we confirm that a mode-locked Yb-doped fiber laser has the potential to be used as an optical source to generate THZ waves.

  12. Absorption of terahertz radiation by plasmon modes in a grid-gated double-quantum-well field-effect transistor

    NASA Astrophysics Data System (ADS)

    Popov, V. V.; Polischuk, O. V.; Teperik, T. V.; Peralta, X. G.; Allen, S. J.; Horing, N. J. M.; Wanke, M. C.

    2003-09-01

    The terahertz absorption spectrum of plasmon modes in a grid-gated double-quantum-well (DQW) field-effect transistor structure is analyzed theoretically and numerically using a first principles electromagnetic approach and is shown to faithfully reproduce important physical features of recent experimental observations. We find that the essential character of the response—multiple resonances corresponding to spatial harmonics of standing plasmons under the metal grating—is caused by the static spatial modulation of electron density in the channel. Higher order plasmon modes become more optically active as the depth of the electron density modulation in the DQW tends towards unity. The maximum absorbance, at plasma resonance, is shown to be 1/2. Furthermore, the strongest absorption also occurs when the standing plasmon resonance coincides with the fundamental dipole mode of the ungated portion of the channel.

  13. Mechanism and modulation of terahertz generation from a semimetal - graphite

    NASA Astrophysics Data System (ADS)

    Ye, Tong; Meng, Sheng; Zhang, Jin; E, Yiwen; Yang, Yuping; Liu, Wuming; Yin, Yan; Wang, Li

    2016-03-01

    Semi-metals might offer a stronger interaction and a better confinement for terahertz wave than semiconductors, while preserve tunability. Particularly, graphene-based materials are envisioned as terahertz modulators, filters and ultra-broadband sources. However, the understanding of terahertz generation from those materials is still not clear, thus limits us recognizing the potential and improving device performances. Graphite, the mother material of graphene and a typical bulk semi-metal, is a good system to study semi-metals and graphene-based materials. Here we experimentally modulate and maximize the terahertz signal from graphite surface, thus reveal the mechanism - surface field driving photon induced carriers into transient current to radiate terahertz wave. We also discuss the differences between graphite and semiconductors; particularly graphite shows very weak temperature dependency from room temperature to 80 °C. Above knowledge will help us understand terahertz generations, achieve maximum output and electric modulation, in semi-metal or graphene based devices.

  14. A promising diagnostic method: Terahertz pulsed imaging and spectroscopy

    PubMed Central

    Sun, Yiwen; Sy, Ming Yiu; Wang, Yi-Xiang J; Ahuja, Anil T; Zhang, Yuan-Ting; Pickwell-MacPherson, Emma

    2011-01-01

    The terahertz band lies between the microwave and infrared regions of the electromagnetic spectrum. This radiation has very low photon energy and thus it does not pose any ionization hazard for biological tissues. It is strongly attenuated by water and very sensitive to water content. Unique absorption spectra due to intermolecular vibrations in this region have been found in different biological materials. These unique features make terahertz imaging very attractive for medical applications in order to provide complimentary information to existing imaging techniques. There has been an increasing interest in terahertz imaging and spectroscopy of biologically related applications within the last few years and more and more terahertz spectra are being reported. This paper introduces terahertz technology and provides a short review of recent advances in terahertz imaging and spectroscopy techniques, and a number of applications such as molecular spectroscopy, tissue characterization and skin imaging are discussed. PMID:21512652

  15. Features of electromagnetic radiation time-and-frequency fluctuation intensity distributions from human brain structures.

    PubMed

    Kublanov, V S; Gasilov, V L; Kazakov, Y E

    2000-01-01

    Time-and-frequency fluctuation intensity distributions' analysis is made of the electromagnetic radiation obtained from deep human brain structures. The role of monitoring the distribution changes due to various cerebral circulation disorders is explained.

  16. PHYSICAL BASIS OF QUANTUM ELECTRONICS: Spatial coherence and intensity of reflected laser radiation

    NASA Astrophysics Data System (ADS)

    Kozin, G. I.; Kuznetsov, A. P.

    1998-12-01

    A theoretical analysis is made of the statistical characteristics of nonspecularly reflected laser radiation in its far-field zone. No restrictions are placed on the angles of incidence and observation of light. Generalised integral relationships are derived between the distribution of the intensity of light on a reflector and the degree of the spatial coherence of the emitted light, and also between the function representing the degree of the spatial coherence on a reflector and the intensity of the emitted radiation. The shape of the surface representing the regular phase of the reflected radiation is determined. It is shown that the degree of coherence of the radiation and its intensity can be represented by a function of the angles of observation. A method is proposed for determination of the relative intensity and of the degree of the spatial coherence in images formed by paraxial optical systems subject to aperture restrictions.

  17. Sound radiation from an infinite elastic cylinder with dual-wave propagation-intensity distributions

    NASA Technical Reports Server (NTRS)

    Fuller, C. R.

    1988-01-01

    The radiation of sound from an elastic cylindrical shell filled with fluid and supporting multiwave propagation is studied analytically. Combinations of supersonic and subsonic shell waves are considered. The radiated field is mapped by using acoustic intensity vectors evaluated at various locations. Both time averaged and instantaneous intensity are investigated. The acoustic intensity is seen to vary markedly with axial distance down the cylinder. The effect is shown to be associated with cross terms in the intensity relations, and its magnitude and location to depend upon the relative phase and amplitudes of individual waves. Subsonic shell waves are demonstrated to interact strongly with supersonic shell waves to cause a large modification in the radiated intensity distributions near the shell surface.

  18. Optimizing biased semiconductor superlattices for terahertz amplification

    SciTech Connect

    Lei, Xiaoli; Wang, Dawei; Wu, Zhaoxin; Dignam, M. M.

    2014-08-11

    Over the past 15 yr or more, researchers have been trying to achieve gain for electromagnetic fields in the terahertz frequency region using biased semiconductor superlattices, but with little success. In this work, we employ our model of the excitonic states in biased GaAs/Al{sub 0.3}Ga{sub 0.7}As semiconductor superlattices to find the optimal structures for amplification of terahertz radiation. In particular, we determine the optimum well width, barrier width, and bias field for terahertz fields with frequencies ranging from 1 to 4 terahertz. We find that gain coefficients on the order of 40 cm{sup −1} should be achievable over most of this frequency range.

  19. Coherent and incoherent terahertz beams measured from a terahertz photoconductive antenna

    SciTech Connect

    Ho Wu, Dong; Graber, Benjamin; Kim, Christopher; Qadri, S. B.; Garzarella, Anthony

    2014-02-03

    We have systematically measured and analyzed the terahertz beams of a photoconductive antenna fabricated on a GaAs substrate. Our data indicate that the antenna produces both coherent and incoherent terahertz beams. The former is produced largely by the plasmon, and the latter is believed to be due to the black body radiation resulting from the thermal excitations and Joule heating by both the femto-second laser and the bias voltage, applied across the electrodes of the antenna. The terahertz-beam property is greatly affected by the operating condition of the photoconductive antenna.

  20. Strategies for quality assurance of intensity modulated radiation therapy

    NASA Astrophysics Data System (ADS)

    Benedek, Hunor; Isacsson, Ulf; Olevik-Dunder, Maria; Westermark, Mathias; Hållström, Per; Olofsson, Jörgen; Gustafsson, Magnus

    2015-01-01

    In late 2011 The Swedish Society of Radiation Physics formed a working group to concentrate on the Quality Assurance of modern radiation therapy techniques. The given task was to identify and summarise the different QA strategies in Sweden and also the international recommendations. This was used to formulate recommendations for practical guidelines within Sweden. In this paper a brief summery of the group's work is presented. All the Swedish radiation therapy centres do a pre treatment verification measurement as QA for every new IMRT and VMAT plan. Physicists do it and they believe it to be time consuming. A general standpoint from all the centres was that new guidelines and legislation is needed to allow QA that does not require a measurement. Based on various international publications and recommendations the working group has presented two strategies, one where all new plans are checked through measurement and one where no measurement is needed. The measurement- based strategy is basically the same as the one used today with an extended machine QA part. The other presented strategy is process oriented where all the different parts of the treatment chain are checked separately. The final report can be found in Swedish on http://www.radiofysik.org.

  1. Low-intensity infrared laser radiation influence on the tumor growth

    NASA Astrophysics Data System (ADS)

    Cheida, A. A.; Efimova, E. G.

    2005-08-01

    Infrared laser radiation of low intensity in exposition dose of 25-35 mJicm2 does not cause progress the tumor process. Moreover, disturbing the blood flow in the tumor due to changing synthesis of norepinephrine and histamine this radiation contributes to the damage of the tumor tissue accompanied by the beginning of adaptation reaction in the organism.

  2. Silicone rubber curing by high intensity infrared radiation

    SciTech Connect

    Huang, T.; Tsai, J.; Cherng, C.; Chen, J.

    1994-08-10

    A high-intensity (12 kW) and compact (80 cm) infrared heating oven for fast curing (12 seconds) of tube-like silicone rubber curing studies is reported. Quality inspection by DSC and DMA and results from pilot-scale curing oven all suggest that infrared heating provides a better way of vulcanization regarding to curing time, quality, cost, and spacing over conventional hot air heating. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  3. Modelling of radiation losses for ion acceleration at ultra-high laser intensities

    NASA Astrophysics Data System (ADS)

    Capdessus, Remi; d'Humières, Emmanuel; Tikhonchuk, Vladimir

    2013-11-01

    Radiation losses of charged particles can become important in ultra high intensity laser plasma interaction. This process is described by the radiation back reaction term in the electron equation of motion. This term is implemented in the relativistic particle-in-cell code by using a renormalized Lorentz-Abraham-Dirac model. In the hole boring regime case of laser ion acceleration it is shown that radiation losses results in a decrease of the piston velocity.

  4. Numerical studies of powerful terahertz pulse generation from a super-radiant surface wave oscillator

    SciTech Connect

    Zhang Hai; Wang Jianguo; Tong Changjiang; Li Xiaoze; Wang Guangqiang

    2009-12-15

    The results of theoretical and numerical studies of coherent stimulated terahertz radiation from intense, subnanosecond electron beam are presented. The mechanism of terahertz pulse generation is associated with self-bunching of the beam and slippage of the wave over the whole electron flow. This so called Cherenkov super-radiance (SR) is used to propose a compact terahertz generator with high peak power. A large cross-section (overmoded), slow wave structure is designed to support the high power handling capability, and the mode competition is avoided by operating the device in the surface wave status. With 2.5 D particle-in-cell simulation, the 'hot' characteristics of the proposed super-radiant terahertz generator are investigated, and the numerical results show that the SR peak power could be further increased by optimizing the amplitude profile of electron pulse. Under the condition of 0.5 ns pulsewidth, 500 kV voltage, and 1.5 kA current, the 110 ps, 680 MW, and 0.14 THz SR pulse is achieved with a power efficiency of 90.67% in TM{sub 01} mode.

  5. Terahertz quantum cascade VECSEL

    NASA Astrophysics Data System (ADS)

    Xu, Luyao; Curwen, Christopher A.; Hon, Philip W. C.; Itoh, Tatsuo; Williams, Benjamin S.

    2016-03-01

    Vertical-external-cavity surface-emitting lasers (VECSELs) have been successfully used in the visible and near-infrared to achieve high output power with excellent Gaussian beam quality. However, the concept of VECSEL has been impossible to implement for quantum-cascade (QC) lasers due to the "intersubband selection rule". We have recently demonstrated the first VECSEL in the terahertz range. The enabling component for the QC-VECSEL is an amplifying metasurface reflector composed of a sparse array of metallic sub-cavities, which allows the normally incident radiation to interact with the electrically pumped QC gain medium. In this work, we presented multiple design variations based on the first demonstrated THz QC-VECSEL, regarding the lasing frequencies, the output coupler and the intra-cavity aperture. Our work on THz QC-VECSEL initiates a new approach towards achieving scalable output power in combination with a diffraction-limited beam pattern for THz QC-lasers. The design variations presented in this work further demonstrate the practicality and potential of VECSEL approach to make ideal terahertz QC-laser sources.

  6. Terahertz metamaterials

    SciTech Connect

    Chen, Hou-tong; Taylor, Antoineete J; Azad, Abul K; O' Hara, John F

    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.

  7. Broadband terahertz radiation from a biased two-dimensional electron gas in an AlGaN/GaN heterostructure

    NASA Astrophysics Data System (ADS)

    Zhongxin, Zheng; Jiandong, Sun; Yu, Zhou; Zhipeng, Zhang; Hua, Qin

    2015-10-01

    The broadband terahertz (THz) emission from drifting two-dimensional electron gas (2DEG) in an AlGaN/GaN heterostructure at 6 K is reported. The devices are designed as THz plasmon emitters according to the Smith-Purcell effect and the ‘shallow water’ plasma instability mechanism in 2DEG. Plasmon excitation is excluded since no signature of electron-density dependent plasmon mode is observed. Instead, the observed THz emission is found to come from the heated lattice and/or the hot electrons. Simulated emission spectra of hot electrons taking into account the THz absorption in air and Fabry-Pérot interference agree well with the experiment. It is confirmed that a blackbody-like THz emission will inevitably be encountered in similar devices driven by a strong in-plane electric field. A conclusion is drawn that a more elaborate device design is required to achieve efficient plasmon excitation and THz emission. Project supported by the National Basic Research Program of China (No. G2009CB929303), the National Natural Science Foundation of China (No. 61271157), the China Postdoctoral Science Foundation (No. 2014M551678), and the Jiangsu Planned Projects for Postdoctoral Research Funds (No. 1301054B).

  8. Response of two-phase droplets to intense electromagnetic radiation

    NASA Technical Reports Server (NTRS)

    Spann, James F.; Maloney, Daniel J.; Lawson, William F.; Casleton, Kent H.

    1993-01-01

    The response of two-phase droplets to intense radiant heating is studied to determine the incident power that is required for causing explosive boiling in the liquid phase. The droplets studied consist of strongly absorbing coal particles dispersed in a weakly absorbing water medium. Experiments are performed by confining droplets (radii of 37, 55, and 80 microns) electrodynamically and irradiating them from two sides with pulsed laser beams. Emphasis is placed on the transition region from accelerated droplet vaporization to droplet superheating and explosive boiling. The time scale observed for explosive boiling is more than 2 orders of magnitude longer than published values for pure liquids. The delayed response is the result of energy transfer limitations between the absorbing solid phase and the surrounding liquid.

  9. Reverberation Chamber Uniformity Validation and Radiated Susceptibility Test Procedures for the NASA High Intensity Radiated Fields Laboratory

    NASA Technical Reports Server (NTRS)

    Koppen, Sandra V.; Nguyen, Truong X.; Mielnik, John J.

    2010-01-01

    The NASA Langley Research Center's High Intensity Radiated Fields Laboratory has developed a capability based on the RTCA/DO-160F Section 20 guidelines for radiated electromagnetic susceptibility testing in reverberation chambers. Phase 1 of the test procedure utilizes mode-tuned stirrer techniques and E-field probe measurements to validate chamber uniformity, determines chamber loading effects, and defines a radiated susceptibility test process. The test procedure is segmented into numbered operations that are largely software controlled. This document is intended as a laboratory test reference and includes diagrams of test setups, equipment lists, as well as test results and analysis. Phase 2 of development is discussed.

  10. Subwavelength hybrid terahertz waveguides.

    PubMed

    Nam, Sung Hyun; Taylor, Antoinette J; Efimov, Anatoly

    2009-12-01

    We introduce and present general properties of hybrid terahertz waveguides. Weakly confined Zenneck waves on a metal-dielectric interface at terahertz frequencies can be transformed to a strongly confined yet low-loss subwavelength mode through coupling with a photonic mode of a nearby high-index dielectric strip. We analyze confinement, attenuation, and dispersion properties of this mode. The proposed design is suitable for planar integration and allows easy fabrication on chip scale. The superior waveguiding properties at terahertz frequencies could enable the hybrid terahertz waveguides as building blocks for terahertz integrated circuits.

  11. Optimization of THz Radiation Generation from a Laser Wakefield Accelerator

    SciTech Connect

    Plateau, G. R.; Matlis, N. H.; Toth, C.; Geddes, C. G. R.; Schroeder, C. B.; Tilborg, J. van; Albert, O.; Esarey, E.; Leemans, W. P.

    2009-01-22

    Ultrashort terahertz pulses with energies in the {mu}J range can be generated with laser wakefield accelerators (LWFA), which are novel, compact accelerators that produce ultrashort electron bunches with energies up to 1 GeV and energy spreads of a few-percent. Laser pulses interacting with a plasma create accelerated electrons which upon exiting the plasma emit terahertz pulses via transition radiation. Because these electron bunches are ultrashort (<50 fs), they can radiate coherently (coherent transition radiation--CTR) in a wide bandwidth ({approx}1-10 THz) yielding high intensity terahertz pulses. In addition to providing a non-invasive bunch-length diagnostic and thus feedback for the LWFA, these high peak power THz pulses are suitable for high field (MV/cm) pump-probe experiments. Here we present energy-based measurements using a Golay cell and an electro-optic technique which were used to characterize these THz pulses.

  12. Cooling of relativistic electron beams in intense laser pulses: Chirps and radiation

    NASA Astrophysics Data System (ADS)

    Yoffe, S. R.; Noble, A.; Macleod, A. J.; Jaroszynski, D. A.

    2016-09-01

    Next-generation high-power laser facilities (such as the Extreme Light Infrastructure) will provide unprecedented field intensities, and will allow us to probe qualitatively new physical regimes for the first time. One of the important fundamental questions which will be addressed is particle dynamics when radiation reaction and quantum effects play a significant role. Classical theories of radiation reaction predict beam cooling in the interaction of a relativistic electron bunch and a high-intensity laser pulse, with final-state properties only dependent on the laser fluence. The observed quantum suppression of this cooling instead exhibits a dependence on the laser intensity directly. This offers the potential for final-state properties to be modified or even controlled by tailoring the intensity profile of the laser pulse. In addition to beam properties, quantum effects will be manifest in the emitted radiation spectra, which could be manipulated for use as radiation sources. We compare predictions made by classical, quasi-classical and stochastic theories of radiation reaction, and investigate the influence of chirped laser pulses on the observed radiation spectra.

  13. Inelastic scattering in condensed matter with high intensity Moessbauer radiation

    SciTech Connect

    Yelon, W.B.; Schupp, G.

    1993-02-01

    The QUEGS facility at MURR has produced a number of new results and demonstrated the range of potential applications of high resolution, high intensity Moessbauer scattering. This work has been carried out by both MU and Purdue researchers and includes published results on Na, W, pentadecane, polydimethylsiloxane and other systems, manuscripts submitted on alkali halides (Phys. Rev. B) and accurate Moessbauer lineshape measurements (Phys. Rev. C), and manuscripts in preparation on glycerol, NiAl and Moessbauer spectra obtained by modulating a scattering crystal. Recently, new collaborations have been initiated which will substantially enhance our efforts. These are with W. Steiner (Vienna), G. Coddens (Saclay), and R. D. Taylor (Los Alamos). Steiner is experienced with Fe-57 Moessbauer scattering, while Coddens specializes in quasielastic neutron scattering; both of these areas naturally complement our work. R. D. Taylor has pioneered Moessbauer spectroscopy from the time of its discovery and has already made important contributions to our study of lattice dynamics and superconductivity for lead alloyed with small quantities of tin. At the same time, a significant instrument upgrade is underway, funded in part by the DOE-URIP program.

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

    NASA Astrophysics Data System (ADS)

    Angeluts, A. A.; Balakin, A. V.; Evdokimov, M. G.; Esaulkov, M. N.; Nazarov, M. M.; Ozheredov, I. A.; Sapozhnikov, D. A.; Solyankin, P. M.; Cherkasova, O. P.; Shkurinov, A. P.

    2014-07-01

    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.

  15. Terahertz pulsed imaging study of dental caries

    NASA Astrophysics Data System (ADS)

    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.

  16. Sensing individual terahertz photons.

    PubMed

    Hashiba, Hideomi; Antonov, Vladimir; Kulik, Leonid; Tzalenchuk, Alexander; Komiyama, Susumu

    2010-04-23

    One of the promising ways to perform single-photon counting of terahertz radiation consists in sensitive probing of plasma excitation in the electron gas upon photon absorption. We demonstrate the ultimate sensor operating on this principle. It is assembled from a GaAs/AlGaAs quantum dot, electron reservoir and superconducting single-electron transistor. The quantum dot is isolated from the surrounding electron reservoir in such a way that when the excited plasma wave decays, an electron could tunnel off the dot to the reservoir. The resulting charge polarization of the dot is detected with the single-electron transistor. Such a system forms an easy-to-use sensor enabling single-photon counting in a very obscure wavelength region.

  17. Nonlinear terahertz superconducting plasmonics

    SciTech Connect

    Wu, Jingbo; Liang, Lanju; Jin, Biaobing E-mail: tonouchi@ile.osaka-u.ac.jp Kang, Lin; Xu, Weiwei; Chen, Jian; Wu, Peiheng E-mail: tonouchi@ile.osaka-u.ac.jp; Zhang, Caihong; Kawayama, Iwao; Murakami, Hironaru; Tonouchi, Masayoshi E-mail: tonouchi@ile.osaka-u.ac.jp; Wang, Huabing

    2014-10-20

    Nonlinear terahertz (THz) transmission through subwavelength hole array in superconducting niobium nitride (NbN) film is experimentally investigated using intense THz pulses. The good agreement between the measurement and numerical simulations indicates that the field strength dependent transmission mainly arises from the nonlinear properties of the superconducting film. Under weak THz pulses, the transmission peak can be tuned over a frequency range of 145 GHz which is attributed to the high kinetic inductance of 50 nm-thick NbN film. Utilizing the THz pump-THz probe spectroscopy, we study the dynamic process of transmission spectra and demonstrate that the transition time of such superconducting plasmonic device is within 5 ps.

  18. Terahertz spectroscopy: Its future role in medical diagnoses

    NASA Astrophysics Data System (ADS)

    Parrott, Edward Philip John; Sun, Yiwen; Pickwell-MacPherson, Emma

    2011-12-01

    Over the past two decades, terahertz radiation has received a lot of interest due to advances in emission and detection technologies in the late 1980s and early 1990s which allowed the construction of coherent source/detection regimes. This paper focuses on reviewing the use of terahertz radiation in the investigation and understanding of biological systems and medical diagnosis. In particular, research on terahertz spectroscopy of biomolecules, from amino acids to proteins is presented, and examples of potential medical applications are discussed.

  19. Terahertz applications: trends and challenges

    NASA Astrophysics Data System (ADS)

    Robin, Thierry; Bouye, Clementine; Cochard, Jacques

    2014-03-01

    The objective of our work [1] was to determine the opportunities and challenges for Terahertz application development for the next years with a focus on systems: for homeland security and for Non Destructive Testing (NDT). Terahertz radiation has unique abilities and has been the subject of extensive research for many years. Proven concepts have emerged for numerous applications including Industrial NDT, Security, Health, Telecommunications, etc. Nevertheless, there has been no widely deployed application and Businesses based on THz technologies are still in their infancy. Some technological, market and industrial barriers are still to be broken. We summarize the final analysis and data: study of the technology trends and major bottlenecks per application segment, main challenges to be addressed in the next years, key opportunities for THz technologies based on market needs and requirements.

  20. Terahertz laser based on dipolaritons

    NASA Astrophysics Data System (ADS)

    Kristinsson, K.; Kyriienko, O.; Shelykh, I. A.

    2014-02-01

    We develop the microscopic theory of a terahertz (THz) laser based on the effects of resonant tunneling in a double quantum well heterostructure embedded in both optical and THz cavities. In the strong-coupling regime the system hosts dipolaritons, hybrid quasiparticles formed by the direct exciton, indirect exciton, and optical photon, which possess large dipole moments in the growth direction. Their radiative coupling to the mode of a THz cavity combined with strong nonlinearities provided by exciton-exciton interactions allows for stable emission of THz radiation in the regime of the continuous optical excitation. The optimal parameters for maximizing the THz signal output power are analyzed.

  1. SU-E-J-267: Change in Mean CT Intensity of Lung Tumors During Radiation Treatment

    SciTech Connect

    Mahon, R; Tennyson, N; Weiss, E; Hugo, G

    2015-06-15

    Purpose: To evaluate CT intensity change of lung tumors during radiation therapy. Methods: Repeated 4D CT images were acquired on a CT simulator during the course of therapy for 27 lung cancer patients on IRB approved protocols. All subjects received definitive radiation treatment ± chemotherapy. CT scans were completed prior to treatment, and 2–7 times during the treatment course. Primary tumor was delineated by an experienced Radiation Oncologist. Contours were thresholded between −100 HU and 200 HU to remove airways and bone. Correlations between the change in the mean tumor intensity and initial tumor intensity, SUVmax, and tumor volume change rate were investigated. Reproducibility was assessed by evaluating the variation in mean intensity over all phases in 4DCT, for a subgroup of 19 subjects. Results: Reproducibility of tumor intensity between phases as characterized by the root mean square of standard deviation across 19 subjects was 1.8 HU. Subjects had a mean initial tumor intensity of 16.5 ± 11.6 HU and an overall reduction in HU by 10.3 ± 8.5 HU. Evaluation of the changes in tumor intensity during treatment showed a decrease of 0.3 ± 0.3 HU/day for all subjects, except three. No significant correlation was found between change in HU/day and initial HU intensity (p=0.53), initial PET SUVmax (p=0.69), or initial tumor volume (p=0.70). The rate of tumor volume change was weakly correlated (R{sup 2}=0.05) with HU change (p=0.01). Conclusion: Most lung cancer subjects showed a marked trend of decreasing mean tumor CT intensity throughout radiotherapy, including early in the treatment course. Change in HU/day is not correlated with other potential early predictors for response, such as SUV and tumor volume change. This Result supports future studies to evaluate change in tumor intensity on CT as an early predictor of response.

  2. Non-linear plasma effects on laser-induced terahertz emission from the atmosphere

    NASA Astrophysics Data System (ADS)

    Shin, J.-H.; Zhidkov, A.; Jin, Z.; Hosokai, T.; Kodama, R.

    2012-02-01

    Power, spectral characteristics, and angle distribution of terahertz (THz) radiation from air irradiated by a single (ω) or coupled (ω, 2ω) femtosecond laser pulses are analyzed for higher intensities, for which non-linear plasma effects on the pulse propagation become essential, by means of multidimensional particle-in-cell simulations exploiting the self-consistent plasma kinetics. THz radiation is shown to be a result of beat waves generated at ionization front with fundamental and second harmonic waves. At lower intensities, the THz power growth is far faster than the linear; at pulse intensities over I > 1015 W/cm2, the power increases slower than the linear. Along with the forward emission, strong power in around 30o angles occurs at high intensities. Ionization of air results in poor focusing of laser pulses and, therefore, lower efficiency of THz emission.

  3. [Application of low-intensity and ultrahigh frequency electromagnetic radiation in modern pediatric practice].

    PubMed

    Azov, N A; Azova, E A

    2009-01-01

    The use of an Amfit-0,2/10-01 apparatus generating low-intensity ultrahigh frequency (UHF) electromagnetic radiation improved efficiency of therapy of sick children. This treatment allowed to reduce the frequency of intake of anesthetics in the post-operative period, correct metabolic disorders in children with type 1 diabetes mellitus, reduce severity of diabetic nephropathy and polyneuropathy, prevent formation of fresh foci of lipoid necrobiosis. The results of the study indicate that the use of low-intensity UHF electromagnetic radiation may be recommended for more extensive introduction into practical clinical work of pediatric endocrinologists and surgeons.

  4. Effect of low-intensity infrared and millimeter radiation on higher plants' biopotentials.

    PubMed

    Mironova, E A; Romanovskii, Y M

    2001-01-01

    This article studies the effect of local low-intensity electromagnetic radiation on the bioelectric responses of plants. In our investigation, we used thirty-three wavelengths in the visible and infrared spectrurm regions as well as three wavelengths in the millimeter spectrum region. As a result, we obtained the bioelectric responses of plants to electromagnetic radiation not only in the absorption region of cellular pigments (such as chlorophyll, flavin, and phytochrome) but also in the absorption region of water molecules.

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

    SciTech Connect

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

    2011-06-27

    We experimentally demonstrate the production of narrow-band (δf/f ~ =20% at f ~ = 0.5 THz) THz 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. In addition, we 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. Nonlinear Vacuum Polarization In Intense Blackbody Radiation And The Generation Of Cherenkov Radiation By Energetic Charged Particles

    NASA Astrophysics Data System (ADS)

    Wu, Sheldon S. Q.; Hartemann, F. V.; Barty, C. P. J.

    2010-03-01

    A study of thermally-induced vacuum polarization stemming from the Euler-Heisenberg nonlinear radiation correction to Maxwell equations is conducted. While nonlinear effects associated with photon-photon scattering in the photon gas had been previously calculated, we present an analysis in the framework of stochastic electrodynamics. To lowest order of approximation, it is shown that the phase velocity of light is reduced in the presence of intense ambient electromagnetic radiation. Therefore Cherenkov radiation can be generated when charged particles traverse a region of intense blackbody radiation. Suitable conditions may be found in astrophysical environments. Cosmic ray electrons and positrons in the GeV to TeV range meet the energy requirement for this process to occur. We present calculations of the emission characteristics and conditions under which Cherenkov radiation may be observed. This effect combined with synchrotron and inverse Compton processes may lead to a more complete understanding of cosmic ray propagation. Also of interest, the question of the linearity of the relic cosmic microwave background is under investigation using this formalism and will be discussed. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  7. Transmission mode terahertz computed tomography

    DOEpatents

    Ferguson, Bradley Stuart; Wang, Shaohong; Zhang, Xi-Cheng

    2006-10-10

    A method of obtaining a series of images of a three-dimensional object by transmitting pulsed terahertz (THz) radiation through the entire object from a plurality of angles, optically detecting changes in the transmitted THz radiation using pulsed laser radiation, and constructing a plurality of imaged slices of the three-dimensional object using the detected changes in the transmitted THz radiation. The THz radiation is transmitted through the object as a scanning spot. The object is placed within the Rayleigh range of the focused THz beam and a focusing system is used to transfer the imaging plane from adjacent the object to a desired distance away from the object. A related system is also disclosed.

  8. Transverse beam shape measurements of intense proton beams using optical transition radiation

    SciTech Connect

    Scarpine, Victor E.; /Fermilab

    2012-03-01

    A number of particle physics experiments are being proposed as part of the Department of Energy HEP Intensity Frontier. Many of these experiments will utilize megawatt level proton beams onto targets to form secondary beams of muons, kaons and neutrinos. These experiments require transverse size measurements of the incident proton beam onto target for each beam spill. Because of the high power levels, most beam intercepting profiling techniques will not work at full beam intensity. The possibility of utilizing optical transition radiation (OTR) for high intensity proton beam profiling is discussed. In addition, previous measurements of OTR beam profiles from the NuMI beamline are presented.

  9. Primary radiation damage of protein crystals by an intense synchrotron X-ray beam.

    PubMed

    Teng, T Y; Moffat, K

    2000-09-01

    X-ray radiation damage of a lysozyme single crystal by an intense monochromatic beam from a third-generation radiation source at the Advanced Photon Source has been studied. The results show that primary radiation damage is linearly dependent on the X-ray dose even when the crystal is at cryogenic temperatures. The existence of an upper limit for the primary radiation damage was observed. Above the threshold of approximately 1 x 10(7) Gy, excessive damage of the crystal develops which is interpreted as the onset of secondary and/or tertiary radiation damage. This upper limit of X-ray dose is compared with Henderson's limit [Henderson (1990). Proc. R. Soc. London, B241, 6-8], and its implication for the amount of useful X-ray diffraction data that can be obtained for crystals of a given scattering power is also discussed. PMID:16609214

  10. High-intensity coherent FIR radiation from sub-picosecond electron bunches

    SciTech Connect

    Kung, P.H.; Lihn, Hung-chi; Wiedemann, H.; Bocek, D.

    1994-01-01

    A facility to generate high-intensity, ultra-short pulses of broad-band far-infrared radiation has been assembled and tested at Stanford. The device uses sub-picosecond relativistic electron bunches to generate coherent radiation through transition or synchrotron radiation in the far-infrared (FIR) regime between millimeter waves and wavelengths of about 100 {mu}m and less. Experimental results show a peak radiation power of greater than 0.33 MW within a micro-bunch and an average FIR radiation power of 4 mW. The average bunch length of 2856 micro-bunches within a 1 {mu}sec macro-pulse is estimated to be about 480 sec. Simulations experimental setup and results will be discussed.

  11. High mobility ZnO nanowires for terahertz detection applications

    NASA Astrophysics Data System (ADS)

    Liu, Huiqiang; Peng, Rufang; Chu, Sheng; Chu, Shijin

    2014-07-01

    An oxide nanowire material was utilized for terahertz detection purpose. High quality ZnO nanowires were synthesized and field-effect transistors were fabricated. Electrical transport measurements demonstrated the nanowire with good transfer characteristics and fairly high electron mobility. It is shown that ZnO nanowires can be used as building blocks for the realization of terahertz detectors based on a one-dimensional plasmon detection configuration. Clear terahertz wave (˜0.3 THz) induced photovoltages were obtained at room temperature with varying incidence intensities. Further analysis showed that the terahertz photoresponse is closely related to the high electron mobility of the ZnO nanowire sample, which suggests that oxide nanoelectronics may find useful terahertz applications.

  12. Broadband graphene terahertz modulators enabled by intraband transitions.

    PubMed

    Sensale-Rodriguez, Berardi; Yan, Rusen; Kelly, Michelle M; Fang, Tian; Tahy, Kristof; Hwang, Wan Sik; Jena, Debdeep; Liu, Lei; Xing, Huili Grace

    2012-01-01

    Terahertz technology promises myriad applications including imaging, spectroscopy and communications. However, one major bottleneck at present for advancing this field is the lack of efficient devices to manipulate the terahertz electromagnetic waves. Here we demonstrate that exceptionally efficient broadband modulation of terahertz waves at room temperature can be realized using graphene with extremely low intrinsic signal attenuation. We experimentally achieved more than 2.5 times superior modulation than prior broadband intensity modulators, which is also the first demonstrated graphene-based device enabled solely by intraband transitions. The unique advantages of graphene in comparison to conventional semiconductors are the ease of integration and the extraordinary transport properties of holes, which are as good as those of electrons owing to the symmetric conical band structure of graphene. Given recent progress in graphene-based terahertz emitters and detectors, graphene may offer some interesting solutions for terahertz technologies. PMID:22510685

  13. Four-Week Course of Radiation for Breast Cancer Using Hypofractionated Intensity Modulated Radiation Therapy With an Incorporated Boost

    SciTech Connect

    Freedman, Gary M. . E-mail: Gary.Freedman@FCCC.edu; Anderson, Penny R.; Goldstein, Lori J.; Ma Changming; Li Jinsheng; Swaby, Ramona F.; Litwin, Samuel; Watkins-Bruner, Deborah; Sigurdson, Elin R.; Morrow, Monica

    2007-06-01

    Purpose: Standard radiation for early breast cancer requires daily treatment for 6 to 7 weeks. This is an inconvenience to many women, and for some a barrier for breast conservation. We present the acute toxicity of a 4-week course of hypofractionated radiation. Methods and Materials: A total of 75 patients completed radiation on a Phase II trial approved by the hospital institutional review board. Eligibility criteria were broad to include any patient normally eligible for standard radiation: age {>=}18 years, invasive or in situ cancer, American Joint Committee on Cancer Stage 0 to II, breast-conserving surgery, and any systemic therapy not given concurrently. The median age was 52 years (range, 31-81 years). Of the patients, 15% had ductal carcinoma in situ, 67% T1, and 19% T2; 71% were N0, 17% N1, and 12% NX. Chemotherapy was given before radiation in 44%. Using photon intensity-modulated radiation therapy and incorporated electron beam boost, the whole breast received 45 Gy and the lumpectomy bed 56 Gy in 20 treatments over 4 weeks. Results: The maximum acute skin toxicity by the end of treatment was Grade 0 in 9 patients (12%), Grade 1 in 49 (65%) and Grade 2 in 17 (23%). There was no Grade 3 or higher skin toxicity. After radiation, all Grade 2 toxicity had resolved by 6 weeks. Hematologic toxicity was Grade 0 in most patients except for Grade 1 neutropenia in 2 patients, and Grade 1 anemia in 11 patients. There were no significant differences in baseline vs. 6-week posttreatment patient-reported or physician-reported cosmetic scores. Conclusions: This 4-week course of postoperative radiation using intensity-modulated radiation therapy is feasible and is associated with acceptable acute skin toxicity and quality of life. Long-term follow-up data are needed. This radiation schedule may represent an alternative both to longer 6-week to 7-week standard whole-breast radiation and more radically shortened 1-week, partial-breast treatment schedules.

  14. Active terahertz metamaterial devices.

    PubMed

    Chen, Hou-Tong; Padilla, Willie J; Zide, Joshua M O; Gossard, Arthur C; Taylor, Antoinette J; Averitt, Richard D

    2006-11-30

    The development of artificially structured electromagnetic materials, termed metamaterials, has led to the realization of phenomena that cannot be obtained with natural materials. This is especially important for the technologically relevant terahertz (1 THz = 10(12) Hz) frequency regime; many materials inherently do not respond to THz radiation, and the tools that are necessary to construct devices operating within this range-sources, lenses, switches, modulators and detectors-largely do not exist. Considerable efforts are underway to fill this 'THz gap' in view of the useful potential applications of THz radiation. Moderate progress has been made in THz generation and detection; THz quantum cascade lasers are a recent example. However, techniques to control and manipulate THz waves are lagging behind. Here we demonstrate an active metamaterial device capable of efficient real-time control and manipulation of THz radiation. The device consists of an array of gold electric resonator elements (the metamaterial) fabricated on a semiconductor substrate. The metamaterial array and substrate together effectively form a Schottky diode, which enables modulation of THz transmission by 50 per cent, an order of magnitude improvement over existing devices. PMID:17136089

  15. 14 CFR 23.1308 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false High-intensity Radiated Fields (HIRF) Protection. 23.1308 Section 23.1308 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Equipment General §...

  16. 14 CFR 23.1308 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false High-intensity Radiated Fields (HIRF) Protection. 23.1308 Section 23.1308 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Equipment General §...

  17. 14 CFR 25.1317 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false High-intensity Radiated Fields (HIRF) Protection. 25.1317 Section 25.1317 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF... adversely affected during and after the time the airplane is exposed to HIRF environment I, as described...

  18. 14 CFR 29.1317 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false High-intensity Radiated Fields (HIRF) Protection. 29.1317 Section 29.1317 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF... adversely affected during and after the time the rotorcraft is exposed to HIRF environment I, as...

  19. 14 CFR 23.1308 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false High-intensity Radiated Fields (HIRF) Protection. 23.1308 Section 23.1308 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF... HIRF environment I, as described in appendix J to this part; (2) The system automatically...

  20. 14 CFR 27.1317 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false High-intensity Radiated Fields (HIRF) Protection. 27.1317 Section 27.1317 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF... adversely affected during and after the time the rotorcraft is exposed to HIRF environment I, as...

  1. 14 CFR 25.1317 - High-intensity Radiated Fields (HIRF) Protection.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false High-intensity Radiated Fields (HIRF... TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Equipment General § 25.1317 High... that performs a function whose failure would significantly reduce the capability of the airplane or...

  2. Emission of strong Terahertz pulses from laser wakefields in weakly coupled plasma

    NASA Astrophysics Data System (ADS)

    Singh, Divya; Malik, Hitendra K.

    2016-09-01

    The present paper discusses the laser plasma interaction for the wakefield excitation and the role of external magnetic field for the emission of Terahertz radiation in a collisional plasma. Flat top lasers are shown to be more appropriate than the conventional Gaussian lasers for the effective excitation of wakefields and hence, the generation of strong Terahertz radiation through the transverse component of wakefield.

  3. Breast Intensity-Modulated Radiation Therapy Reduces Time Spent With Acute Dermatitis for Women of All Breast Sizes During Radiation

    SciTech Connect

    Freedman, Gary M. Li Tianyu; Nicolaou, Nicos; Chen Yan; Ma, Charlie C.-M.; Anderson, Penny R.

    2009-07-01

    Purpose: To study the time spent with radiation-induced dermatitis during a course of radiation therapy for breast cancer in women treated with conventional or intensity-modulated radiation therapy (IMRT). Methods and Materials: The study population consisted of 804 consecutive women with early-stage breast cancer treated with breast-conserving surgery and radiation from 2001 to 2006. All patients were treated with whole-breast radiation followed by a boost to the tumor bed. Whole-breast radiation consisted of conventional wedged photon tangents (n = 405) earlier in the study period and mostly of photon IMRT (n = 399) in later years. All patients had acute dermatitis graded each week of treatment. Results: The breakdown of the cases of maximum acute dermatitis by grade was as follows: 3%, Grade 0; 34%, Grade 1; 61%, Grade 2; and 2%, Grade 3. The breakdown of cases of maximum toxicity by technique was as follows: 48%, Grade 0/1, and 52%, Grade 2/3, for IMRT; and 25%, Grade 0/1, and 75%, Grade 2/3, for conventional radiation therapy (p < 0.0001). The IMRT patients spent 82% of weeks during treatment with Grade 0/1 dermatitis and 18% with Grade 2/3 dermatitis, compared with 29% and 71% of patients, respectively, treated with conventional radiation (p < 0.0001). Furthermore, the time spent with Grade 2/3 toxicity was decreased in IMRT patients with small (p = 0.0015), medium (p < 0.0001), and large (p < 0.0001) breasts. Conclusions: Breast IMRT is associated with a significant decrease both in the time spent during treatment with Grade 2/3 dermatitis and in the maximum severity of dermatitis compared with that associated with conventional radiation, regardless of breast size.

  4. Integrated heterodyne terahertz transceiver

    DOEpatents

    Lee, Mark; Wanke, Michael C.

    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.

  5. Integrated heterodyne terahertz transceiver

    DOEpatents

    Wanke, Michael C.; Lee, Mark; Nordquist, Christopher D.; Cich, Michael J.

    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.

  6. Simulations of high harmonic generation from plasmonic nanoparticles in the terahertz region

    NASA Astrophysics Data System (ADS)

    Grynko, Yevgen; Zentgraf, Thomas; Meier, Torsten; Förstner, Jens

    2016-09-01

    Metallic nanostructures are known for enhancing weak nonlinear processes when a resonant and coherent excitation takes place. With proper structural design, an additional boost of particular nonlinear processes is expected to be possible. Here, we present a numerical technique that is capable of simulating high harmonic generation from resonantly excited metallic nanoparticles in the terahertz frequency range. We demonstrate our method by investigating the nonlinear emission of arrays of plasmonic split-ring resonators at the range of ten terahertzs. Our multiscale, non-perturbative, and microscopic approach is based on a self-consistent combination of a hydrodynamic model for the nonlinear electronic material response and the discontinuous Garlerkin time-domain technique for the evaluation of the propagation of the electromagnetic field. It is predicted that the electronic nonlinearities of plasmonic nanoparticles give rise to several harmonics in the light emission when excited by intense terahertz radiation. Furthermore, our analysis predicts a non-perturbative scaling of higher harmonics at high excitation intensities.

  7. Radiation Dose Measurement for High-Intensity Laser Interactions with Solid Targets at SLAC

    SciTech Connect

    Liang, Taiee

    2015-09-25

    A systematic study of photon and neutron radiation doses generated in high-intensity laser-solid interactions is underway at SLAC National Accelerator Laboratory. We found that these laser-solid experiments are being performed using a 25 TW (up to 1 J in 40 fs) femtosecond pulsed Ti:sapphire laser at the Linac Coherent Light Source’s (LCLS) Matter in Extreme Conditions (MEC) facility. Additionally, radiation measurements were performed with passive and active detectors deployed at various locations inside and outside the target chamber. Results from radiation dose measurements for laser-solid experiments at SLAC MEC in 2014 with peak intensity between 1018 to 7.1x1019 W/cm2 are presented.

  8. Miniature field deployable terahertz source

    NASA Astrophysics Data System (ADS)

    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

  9. Quantum mechanical theory of collisional ionization in the presence of intense laser radiation

    NASA Technical Reports Server (NTRS)

    Bellum, J. C.; George, T. F.

    1978-01-01

    The paper presents a quantum mechanical formalism for treating ionizing collisions occurring in the presence of an intense laser field. Both the intense laser radiation and the internal electronic continuum states associated with the emitted electrons are rigorously taken into account by combining discretization techniques with expansions in terms of electronic-field representations for the quasi-molecule-plus-photon system. The procedure leads to a coupled-channel description of the heavy-particle dynamics which involves effective electronic-field potential surfaces and continua. It is suggested that laser-influenced ionizing collisions can be studied to verify the effects of intense laser radiation on inelastic collisional processes. Calculation procedures for electronic transition dipole matrix elements between discrete and continuum electronic states are outlined.

  10. Plasmonic corrugated cylinder-cone terahertz probe.

    PubMed

    Yao, Haizi; Zhong, Shuncong

    2014-08-01

    The spoof surface plasmon polariton (SPP) effect on the electromagnetic field distribution near the tip of a periodically corrugated metal cylinder-cone probe working at the terahertz regime was studied. We found that radially polarized terahertz radiation could be coupled effectively through a spoof SPP into a surface wave and propagated along the corrugated surface, resulting in more than 20× electric field enhancement near the tip of probe. Multiple resonances caused by the antenna effect were discussed in detail by finite element computation and theoretical analysis of dispersion relation for spoof SPP modes. Moreover, the key figures of merit such as the resonance frequency of the SPP can be flexibly tuned by modifying the geometry of the probe structure, making it attractive for application in an apertureless background-free terahertz near-field microscope. PMID:25121543

  11. Strong terahertz generation by optical rectification of a super-Gaussian laser beam

    NASA Astrophysics Data System (ADS)

    Kumar, Subodh; Kishor Singh, Ram; Sharma, R. P.

    2016-06-01

    Terahertz (THz) generation by optical rectification of a laser beam having spatially super-Gaussian and temporally Gaussian intensity profile is investigated when it is propagating in a pre-formed rippled density plasma. The quasi-static ponderomotive force which is generated due to the variation in intensity of laser pulse leads to a nonlinear current density in the direction transverse to the direction of propagation which drives a radiation. The frequency of this radiation falls in the THz range if the pulse duration of the laser is chosen suitably. The density ripple provides the phase matching. The yield of generated THz has been compared when the phase matching is exact and when there is slight mismatch of phases. The variation in the intensity of the generated THz with the index of super-Gaussian pulse has also been studied.

  12. Gas-Monitor Detector for Intense and Pulsed VUV/EUV Free-Electron Laser Radiation

    NASA Astrophysics Data System (ADS)

    Sorokin, A. A.; Bobashev, S. V.; Feldhaus, J.; Gerth, Ch.; Gottwald, A.; Hahn, U.; Kroth, U.; Richter, M.; Shmaenok, L. A.; Steeg, B.; Tiedtke, K.; Treusch, R.

    2004-05-01

    In the framework of current developments of new powerful VUV and EUV radiation sources, like VUV free-electron-lasers or EUV plasma sources for 13-nm lithography, we developed a gas-monitor detector in order to measure the photon flux of highly intense and extremely pulsed VUV and EUV radiation in absolute terms. The device is based on atomic photoionization of a rare gas at low particle density. Therefore, it is free of degradation and almost transparent, which allows the detector to be used as a continuously working beam-intensity monitor. The extended dynamic range of the detector allowed its calibration with relative standard uncertainties of 4% in the Radiometry Laboratory of the Physikalisch-Technische Bundesanstalt at the electron-storage ring BESSY II in Berlin using spectrally dispersed synchrotron radiation at low photon intensities and its utilization for absolute photon flux measurements of high power sources. In the present contribution, we describe the design of the detector and its application for the characterization of VUV free-electron-laser radiation at the TESLA test facility in Hamburg. By first pulse resolved measurements, a peak power of more than 100 MW at a wavelength of 87 nm was detected.

  13. Intensity-modulated radiation therapy, protons, and the risk of second cancers

    SciTech Connect

    Hall, Eric J. . E-mail: ejh1@columbia.edu

    2006-05-01

    Intensity-modulated radiation therapy (IMRT) allows dose to be concentrated in the tumor volume while sparing normal tissues. However, the downside to IMRT is the potential to increase the number of radiation-induced second cancers. The reasons for this potential are more monitor units and, therefore, a larger total-body dose because of leakage radiation and, because IMRT involves more fields, a bigger volume of normal tissue is exposed to lower radiation doses. Intensity-modulated radiation therapy may double the incidence of solid cancers in long-term survivors. This outcome may be acceptable in older patients if balanced by an improvement in local tumor control and reduced acute toxicity. On the other hand, the incidence of second cancers is much higher in children, so that doubling it may not be acceptable. IMRT represents a special case for children for three reasons. First, children are more sensitive to radiation-induced cancer than are adults. Second, radiation scattered from the treatment volume is more important in the small body of the child. Third, the question of genetic susceptibility arises because many childhood cancers involve a germline mutation. The levels of leakage radiation in current Linacs are not inevitable. Leakage can be reduced but at substantial cost. An alternative strategy is to replace X-rays with protons. However, this change is only an advantage if the proton machine employs a pencil scanning beam. Many proton facilities use passive modulation to produce a field of sufficient size, but the use of a scattering foil produces neutrons, which results in an effective dose to the patient higher than that characteristic of IMRT. The benefit of protons is only achieved if a scanning beam is used in which the doses are 10 times lower than with IMRT.

  14. Carcinoma of the anal canal: Intensity modulated radiation therapy (IMRT) versus three-dimensional conformal radiation therapy (3DCRT)

    PubMed Central

    Sale, Charlotte; Moloney, Phillip; Mathlum, Maitham

    2013-01-01

    Introduction Patients with anal canal carcinoma treated with standard conformal radiotherapy frequently experience severe acute and late toxicity reactions to the treatment area. Roohipour et al. (Dis Colon Rectum 2008; 51: 147–53) stated a patient's tolerance of chemoradiation to be an important prediction of treatment success. A new intensity modulated radiation therapy (IMRT) technique for anal carcinoma cases has been developed at the Andrew Love Cancer Centre aimed at reducing radiation to surrounding healthy tissue. Methods A same-subject repeated measures design was used for this study, where five anal carcinoma cases at the Andrew Love Cancer Centre were selected. Conformal and IMRT plans were generated and dosimetric evaluations were performed. Each plan was prescribed a total of 54 Gray (Gy) over a course of 30 fractions to the primary site. Results The IMRT plans resulted in improved dosimetry to the planning target volume (PTV) and reduction in radiation to the critical structures (bladder, external genitalia and femoral heads). Statistically there was no difference between the IMRT and conformal plans in the dose to the small and large bowel; however, the bowel IMRT dose–volume histogram (DVH) doses were consistently lower. Conclusion The IMRT plans were superior to the conformal plans with improved dose conformity and reduced radiation to the surrounding healthy tissue. Anecdotally it was found that patients tolerated the IMRT treatment better than the three-dimensional (3D) conformal radiation therapy. This study describes and compares the planning techniques. PMID:26229623

  15. Carcinoma of the anal canal: Intensity modulated radiation therapy (IMRT) versus three-dimensional conformal radiation therapy (3DCRT)

    SciTech Connect

    Sale, Charlotte; Moloney, Phillip; Mathlum, Maitham

    2013-12-15

    Patients with anal canal carcinoma treated with standard conformal radiotherapy frequently experience severe acute and late toxicity reactions to the treatment area. Roohipour et al. (Dis Colon Rectum 2008; 51: 147–53) stated a patient's tolerance of chemoradiation to be an important prediction of treatment success. A new intensity modulated radiation therapy (IMRT) technique for anal carcinoma cases has been developed at the Andrew Love Cancer Centre aimed at reducing radiation to surrounding healthy tissue. A same-subject repeated measures design was used for this study, where five anal carcinoma cases at the Andrew Love Cancer Centre were selected. Conformal and IMRT plans were generated and dosimetric evaluations were performed. Each plan was prescribed a total of 54 Gray (Gy) over a course of 30 fractions to the primary site. The IMRT plans resulted in improved dosimetry to the planning target volume (PTV) and reduction in radiation to the critical structures (bladder, external genitalia and femoral heads). Statistically there was no difference between the IMRT and conformal plans in the dose to the small and large bowel; however, the bowel IMRT dose–volume histogram (DVH) doses were consistently lower. The IMRT plans were superior to the conformal plans with improved dose conformity and reduced radiation to the surrounding healthy tissue. Anecdotally it was found that patients tolerated the IMRT treatment better than the three-dimensional (3D) conformal radiation therapy. This study describes and compares the planning techniques.

  16. Active Terahertz Metamaterials

    NASA Astrophysics Data System (ADS)

    Taylor, Antoinette

    2011-03-01

    In recent years terahertz technology has become an optimistic candidate for numerous sensing, imaging, and diagnostic applications. Nevertheless, THz technology still suffers from a deficiency in high-power sources, efficient detectors, and other functional devices ubiquitous in neighboring microwave and infrared frequency bands, such as amplifiers, modulators, and switches. One of the greatest obstacles in this progress is the lack of materials that naturally respond well to THz radiation. The potential of metamaterials for THz applications originates from their resonant electromagnetic response, which significantly enhances their interaction with THz radiation. Thus, metamaterials offer a route towards helping to fill the so-called ``THz gap''. Here, we present a series of novel THz metamaterials. Importantly, the critical dependence of the resonant response on the supporting substrate and/or the fabricated structure enables the creation of active THz metamaterial devices. We show that the resonant response can be controlled using optical or electrical excitation and thermal tuning, enabling efficient THz devices which will be of importance for advancing numerous real world THz applications. We acknowledge contribution to this work from H. Chen, J. O'Hara, A. Azad, J. Zhou, R. Singh, M. Reiten, and D. Chowdhury of the Center for Integrated Nanotechnologies.

  17. Asymmetric devices based on carbon nanotubes as detectors of sub-THz radiation

    NASA Astrophysics Data System (ADS)

    Gayduchenko, I. A.; Fedorov, G. E.; Stepanova, T. S.; Titova, N.; Voronov, B. M.; But, D.; Coquillat, D.; Diakonova, N.; Knap, W.; Goltsman, G. N.

    2016-08-01

    Demand for efficient terahertz (THz) radiation detectors resulted in intensive study of the asymmetric carbon nanostructures as a possible solution for that problem. In this work, we systematically investigate the response of asymmetric carbon nanodevices to sub-terahertz radiation using different sensing elements: from dense carbon nanotube (CNT) network to individual CNT. We conclude that the detectors based on individual CNTs both semiconducting and quasi-metallic demonstrate much stronger response in sub-THz region than detectors based on disordered CNT networks at room temperature. We also demonstrate the possibility of using asymmetric detectors based on CNT for imaging in the THz range at room temperature. Further optimization of the device configuration may result in appearance of novel terahertz radiation detectors.

  18. Terahertz-to-infrared emission through laser excitation of surface plasmons in metal films with porous nanostructures.

    PubMed

    Zhang, Liangliang; Zhao, Ji; Wu, Tong; Zhang, Cunlin; Zhang, X-C

    2015-06-29

    We report on the investigation of terahertz-to-infrared (THz-to-IR) thermal emission that relies on the excitation of surface plasmons in metal films deposited on a substrate with randomly ordered nanoscale pore arrays. The THz-to-IR radiation was observed both in the direction of laser beam propagation and the reverse direction. The intensity ratio between backward and forward radiation is exponentially dependent on the nominal thickness of the porous metal films. The findings are discussed in view of the proposed generation mechanism based on propagating surface plasmon polaritons on both air/metal and metal/substrate interfaces.

  19. Terahertz-to-infrared emission through laser excitation of surface plasmons in metal films with porous nanostructures.

    PubMed

    Zhang, Liangliang; Zhao, Ji; Wu, Tong; Zhang, Cunlin; Zhang, X-C

    2015-06-29

    We report on the investigation of terahertz-to-infrared (THz-to-IR) thermal emission that relies on the excitation of surface plasmons in metal films deposited on a substrate with randomly ordered nanoscale pore arrays. The THz-to-IR radiation was observed both in the direction of laser beam propagation and the reverse direction. The intensity ratio between backward and forward radiation is exponentially dependent on the nominal thickness of the porous metal films. The findings are discussed in view of the proposed generation mechanism based on propagating surface plasmon polaritons on both air/metal and metal/substrate interfaces. PMID:26191727

  20. Radiation exposure among medical professionals working in the Intensive Care Unit

    PubMed Central

    Siddiqui, Suhail S.; Jha, Ashish; Konar, Nambiraj; Ranganathan, Priya; Deshpande, Deepak D.; Divatia, Jigeeshu V.

    2014-01-01

    Background and Aims: With the expanding use of diagnostic and therapeutic radiological modalities in critically ill patients, doctors working in Intensive Care Units (ICUs) are increasingly exposed to ionizing radiation. This risk of radiation exposure occurs not only during bedside radiologic procedures, but also when ICU physicians accompany patients to radiology suites. The aim of this study was to quantify levels of radiation exposure among medical professionals working in the ICU. Materials and Methods: The study was carried out prospectively over 6 months in the ICU of a tertiary-referral cancer hospital. Two teams consisting of 4 ICU resident doctors each were instructed to wear thermoluminescent dosimeters (TLDs) during their duty shifts. Standard radiation protection precautions were used throughout the study period. TLDs were also placed in selected areas of the ICU to measure the amount of scattered radiation. TLDs were analyzed at the end of every 3 months. Results: The readings recorded on TLDs placed in the ICU were almost immeasurable. The mean value of residents' radiation exposure was 0.059 mSv, though the highest individual reading approached 0.1 mSv. The projected maximum yearly radiation exposure was 0.4 mSv. Conclusions: If standard radiation safety precautions are followed, the cumulative radiation exposure to ICU resident doctors is well within permissible limits and is not a cause of concern. However, with the increasing use of radiological procedures in the management of critically ill patients, there is a need to repeat such audits periodically to monitor radiation exposure. PMID:25249743

  1. Diffuse gamma radiation. [intensity, energy spectrum and spatial distribution from SAS 2 observations

    NASA Technical Reports Server (NTRS)

    Fichtel, C. E.; Simpson, G. A.; Thompson, D. J.

    1978-01-01

    Results are reported for an investigation of the intensity, energy spectrum, and spatial distribution of the diffuse gamma radiation detected by SAS 2 away from the galactic plane in the energy range above 35 MeV. The gamma-ray data are compared with relevant data obtained at other wavelengths, including 21-cm emission, radio continuum radiation, and the limited UV and radio information on local molecular hydrogen. It is found that there are two quite distinct components to the diffuse radiation, one of which shows a good correlation with the galactic matter distribution and continuum radiation, while the other has a much steeper energy spectrum and appears to be isotropic at least on a coarse scale. The galactic component is interpreted in terms of its implications for both local and more distant regions of the Galaxy. The apparently isotropic radiation is discussed partly with regard to the constraints placed on possible models by the steep energy spectrum, the observed intensity, and an upper limit on the anisotropy.

  2. Augmentation of Radiation Intensity in Quasi-Spherical Double Liner/Dynamic Hohlraum

    NASA Astrophysics Data System (ADS)

    Zakharov, S. V.; Smirnov, V. P.

    2006-01-01

    To increase the conversion efficiency of magnetic energy to radiation in Double Liner/Dynamic-Hohlraum and to approach closer to the ignition conditions we proposed the concept of implosion of a quasi-spherical double liner. The almost spherical implosion can be realized with a special mass distribution in liners. Axial cumulating of liner kinetic energy and more efficient radiation energy confinement allow augmentation of radiation intensity on the capsule with respect to cylindrical case under the same driver conditions. A controllable mass redistribution inside the nested external liner allows significant reduction and correction of distortions produced by the Rayleigh-Taylor instability. A phenomenon of energy confinement and enhancement of radiation intensity is considered and compared with the cylindrical case. On the basis of the developed physical model of non-LTE plasma using the RMHD code ZETA the dynamics of quasi-spherical Double Liner/Dynamic-Hohlraum and generation of radiation in two-dimensional geometry is examined and liner configuration is optimized.

  3. Augmentation of Radiation Intensity in Quasi-Spherical Double Liner/Dynamic Hohlraum

    SciTech Connect

    Zakharov, S.V.; Smirnov, V.P.

    2006-01-05

    To increase the conversion efficiency of magnetic energy to radiation in Double Liner/Dynamic-Hohlraum and to approach closer to the ignition conditions we proposed the concept of implosion of a quasi-spherical double liner. The almost spherical implosion can be realized with a special mass distribution in liners. Axial cumulating of liner kinetic energy and more efficient radiation energy confinement allow augmentation of radiation intensity on the capsule with respect to cylindrical case under the same driver conditions. A controllable mass redistribution inside the nested external liner allows significant reduction and correction of distortions produced by the Rayleigh-Taylor instability. A phenomenon of energy confinement and enhancement of radiation intensity is considered and compared with the cylindrical case. On the basis of the developed physical model of non-LTE plasma using the RMHD code ZETA the dynamics of quasi-spherical Double Liner/Dynamic-Hohlraum and generation of radiation in two-dimensional geometry is examined and liner configuration is optimized.

  4. Estimation of effective day length at any light intensity using solar radiation data.

    PubMed

    Yokoya, Masana; Shimizu, Hideyasu

    2011-11-01

    The influence of day length on living creatures differs with the photosensitivity of the creature; however, the possible sunshine duration (N(0)) might be an inadequate index of the photoperiod for creatures with low light sensitivity. To address this issue, the authors tried to estimate the effective day length, i.e., the duration of the photoperiod that exceeds a certain threshold of light intensity. Continual global solar radiation observation data were gathered from the baseline surface radiation network (BSRN) of 18 sites from 2004 to 2007 and were converted to illuminance data using a luminous efficiency model. The monthly average of daily photoperiods exceeding each defined intensity (1 lx, 300 lx, … 20,000 lx) were calculated [defined as Ne(() (lux) ())]. The relationships between the monthly average of global solar radiation (Rs), N(0), and Ne(() (lux) ()) were investigated. At low light intensity (<500 lx), Ne(() (lux) ()) were almost the same as N(0). At high light intensity (>10,000 lx), Ne(() (lux) ()) and Rs showed a logarithmic relationship. Using these relationships, empirical models were derived to estimate the effective day length at different light intensities. According to the validation of the model, the effective day length for any light intensity could be estimated with an accuracy of less than 11% of the mean absolute percentage error (MAPE) in the estimation of the monthly base photoperiod. Recently, a number of studies have provided support for a link between day length and some diseases. Our results will be useful in further assessing the relationships between day length and these diseases.

  5. Terahertz sensing using ferroelectric nanowires.

    PubMed

    Herchig, R; Schultz, Kimberly; McCash, Kevin; Ponomareva, I

    2013-02-01

    Molecular dynamics simulations are used to study the interaction of ferroelectric nanowires with terahertz (THz) Gaussian-shaped pulses of electric field. The computational data indicate the existence of two interaction scenarios that are associated with 'lossless' and dissipative, or 'lossy', interaction mechanisms. A thermodynamical approach is used to analyze the computational data for a wide range of THz pulses. The analysis establishes the foundation for understanding the nanowires' response to the THz pulses and reveals the potential of ferroelectric nanowires to function as nanoscale sensors of THz radiation. Various aspects of this THz nanosensing are analyzed and discussed.

  6. Experimental demonstration of reflectarray antennas at terahertz frequencies.

    PubMed

    Niu, Tiaoming; Withayachumnankul, Withawat; Ung, Benjamin S-Y; Menekse, Hakan; Bhaskaran, Madhu; Sriram, Sharath; Fumeaux, Christophe

    2013-02-11

    Reflectarrays composed of resonant microstrip gold patches on a dielectric substrate are demonstrated for operation at terahertz frequencies. Based on the relation between the patch size and the reflection phase, a progressive phase distribution is implemented on the patch array to create a reflector able to deflect an incident beam towards a predefined angle off the specular direction. In order to confirm the validity of the design, a set of reflectarrays each with periodically distributed 360 × 360 patch elements are fabricated and measured. The experimental results obtained through terahertz time-domain spectroscopy (THz-TDS) show that up to nearly 80% of the incident amplitude is deflected into the desired direction at an operation frequency close to 1 THz. The radiation patterns of the reflectarray in TM and TE polarizations are also obtained at different frequencies. This work presents an attractive concept for developing components able to efficiently manipulate terahertz radiation for emerging terahertz communications.

  7. Experimental demonstration of reflectarray antennas at terahertz frequencies.

    PubMed

    Niu, Tiaoming; Withayachumnankul, Withawat; Ung, Benjamin S-Y; Menekse, Hakan; Bhaskaran, Madhu; Sriram, Sharath; Fumeaux, Christophe

    2013-02-11

    Reflectarrays composed of resonant microstrip gold patches on a dielectric substrate are demonstrated for operation at terahertz frequencies. Based on the relation between the patch size and the reflection phase, a progressive phase distribution is implemented on the patch array to create a reflector able to deflect an incident beam towards a predefined angle off the specular direction. In order to confirm the validity of the design, a set of reflectarrays each with periodically distributed 360 × 360 patch elements are fabricated and measured. The experimental results obtained through terahertz time-domain spectroscopy (THz-TDS) show that up to nearly 80% of the incident amplitude is deflected into the desired direction at an operation frequency close to 1 THz. The radiation patterns of the reflectarray in TM and TE polarizations are also obtained at different frequencies. This work presents an attractive concept for developing components able to efficiently manipulate terahertz radiation for emerging terahertz communications. PMID:23481746

  8. Theory of molecular rate processes in the presence of intense laser radiation

    NASA Technical Reports Server (NTRS)

    George, T. F.; Zimmerman, I. H.; Devries, P. L.; Yuan, J.-M.; Lam, K.-S.; Bellum, J. C.; Lee, H.-W.; Slutsky, M. S.; Lin, J.-T.

    1979-01-01

    The present paper deals with the influence of intense laser radiation on gas-phase molecular rate processes. Representations of the radiation field, the particle system, and the interaction involving these two entities are discussed from a general rather than abstract point of view. The theoretical methods applied are outlined, and the formalism employed is illustrated by application to a variety of specific processes. Quantum mechanical and semiclassical treatments of representative atom-atom and atom-diatom collision processes in the presence of a field are examined, and examples of bound-continuum processes and heterogeneous catalysis are discussed within the framework of both quantum-mechanical and semiclassical theories.

  9. Development of a proposed international standard for certification of aircraft to High Intensity Radiated Fields (HIRF)

    NASA Technical Reports Server (NTRS)

    Sargent, Noel B.

    1993-01-01

    Avionic systems performing critical functions in modern aircraft are potentially susceptible to the hazards of electromagnetic radiation from ground and airborne transmitters. The Federal Aviation Administration (FAA) requested that the Society of Automotive Engineers (SAE) coordinate the development of procedures and guidance material which can be used during the aircraft certification process to ensure adequate protection against high intensity radiated fields (HIRF). This paper addresses both the technical challenge of drafting a certification procedure and guidance standard as well as the management process used by the SAE subcommittee AE4R to converge a diverse range of opinions by its international membership in the shortest possible time.

  10. Experiments on the interaction of intense femtosecond radiation with dense plasmas. Final report

    SciTech Connect

    Rhodes, C.K.

    1996-01-24

    An upgraded KrF{sup {asterisk}} (248 nm) system producing a pulse energy of {approximately} 400 mJ, a pulse width of {approximately} 220 fs, and focal intensities above 10{sup 19} W/cm{sup 2}, has been constructed, tested, operated, and used in experimental studies. The spatial morphology of channeled radiation in plasmas has been measured with a spatial resolution of {approximately} 30 {mu}m and damage studies of fused silica indicate that femtosecond (200 - 300 fs) 248 nm radiation has a damage limit not exceeding {approximately} 50 GW/cm{sup 2}, an unfavorably low level. 2 figs.

  11. Dependence of injection locking of a TEA CO2 laser on intensity of injected radiation

    NASA Technical Reports Server (NTRS)

    Oppenheim, U. P.; Menzies, R. T.; Kavaya, M. J.

    1982-01-01

    The results of an experimental study to determine the minimum required injected power to control the output frequency of a TEA CO2 laser are reported. A CW CO2 waveguide laser was used as the injection oscillator. Both the power and the frequency of the injected radiation were varied, while the TEA resonator cavity length was adjusted to match the frequency of the injected signal. Single-longitudinal mode (SLM) TEA laser radiation was produced for injected power levels which are several orders of magnitude below those previously reported. The ratio of SLM output power to injection power exceeded 10 to the 12th at the lowest levels of injected intensity.

  12. High-order harmonic generation of picosecond radiation of moderate intensity in laser plasma

    SciTech Connect

    Boltaev, G S; Ganeev, Rashid A; Kulagin, I A; Satlikov, N Kh; Usmanov, T

    2012-10-31

    The results of investigations into the generation of highorder harmonics (up to the 21st order) of picosecond ({tau} = 38 ps) Nd : YAG laser radiation in the plasma produced by laser ablation of metal and carbon-containing material surfaces are presented. We demonstrate the feasibility of generating high-order harmonics in the vacuum ultraviolet spectral range (with radiation wavelengths shorter than 120 nm) in plasmas with an efficiency of {approx}0.7 Multiplication-Sign 10{sup -4}. In carbon-containing plasma, the 7th harmonic intensity exceeded that of the 5th one by a factor of seven. (nonlinear optical phenomena)

  13. High-order harmonic generation of picosecond radiation of moderate intensity in laser plasma

    NASA Astrophysics Data System (ADS)

    Boltaev, G. S.; Ganeev, Rashid A.; Kulagin, I. A.; Satlikov, N. Kh; Usmanov, T.

    2012-10-01

    The results of investigations into the generation of highorder harmonics (up to the 21st order) of picosecond (τ = 38 ps) Nd : YAG laser radiation in the plasma produced by laser ablation of metal and carbon-containing material surfaces are presented. We demonstrate the feasibility of generating high-order harmonics in the vacuum ultraviolet spectral range (with radiation wavelengths shorter than 120 nm) in plasmas with an efficiency of ~0.7 × 10-4. In carbon-containing plasma, the 7th harmonic intensity exceeded that of the 5th one by a factor of seven.

  14. Tunable Radiation Source by Coupling Laser-Plasma-Generated Electrons to a Periodic Structure

    SciTech Connect

    Jin, Z.; Chen, Z. L.; Kon, A.; Nakatsutsumi, M.; Zhuo, H. B.; Wang, H. B.; Zhang, B. H.; Gu, Y. Q.; Wu, Y. C.; Zhu, B.; Wang, L.; Yu, M. Y.; Sheng, Z. M.; Kodama, R.

    2011-12-23

    Near-infrared radiation around 1000 nm generated from the interaction of a high-density MeV electron beam, obtained by impinging an intense ultrashort laser pulse on a solid target, with a metal grating is observed experimentally. Theoretical modeling and particle-in-cell simulation suggest that the radiation is caused by the Smith-Purcell mechanism. The results here indicate that tunable terahertz radiation with tens GV/m field strength can be achieved by using appropriate grating parameters.

  15. Ablation and transmission of thin solid targets irradiated by intense extreme ultraviolet laser radiation

    NASA Astrophysics Data System (ADS)

    Aslanyan, V.; Kuznetsov, I.; Bravo, H.; Woolston, M. R.; Rossall, A. K.; Menoni, C. S.; Rocca, J. J.; Tallents, G. J.

    2016-09-01

    The interaction of an extreme ultraviolet (EUV) laser beam with a parylene foil was studied by experiments and simulation. A single EUV laser pulse of nanosecond duration focused to an intensity of 3 × 1010 W cm-2 perforated micrometer thick targets. The same laser pulse was simultaneously used to diagnose the interaction by a transmission measurement. A combination of 2-dimensional radiation-hydrodynamic and diffraction calculations was used to model the ablation, leading to good agreement with experiment. This theoretical approach allows predictive modelling of the interaction with matter of intense EUV beams over a broad range of parameters.

  16. Switchable Scattering Meta-Surfaces for Broadband Terahertz Modulation

    PubMed Central

    Unlu, M.; Hashemi, M. R.; Berry, C. W.; Li, S.; Yang, S.-H.; Jarrahi, M.

    2014-01-01

    Active tuning and switching of electromagnetic properties of materials is of great importance for controlling their interaction with electromagnetic waves. In spite of their great promise, previously demonstrated reconfigurable metamaterials are limited in their operation bandwidth due to their resonant nature. Here, we demonstrate a new class of meta-surfaces that exhibit electrically-induced switching in their scattering parameters at room temperature and over a broad range of frequencies. Structural configuration of the subwavelength meta-molecules determines their electromagnetic response to an incident electromagnetic radiation. By reconfiguration of the meta-molecule structure, the strength of the induced electric field and magnetic field in the opposite direction to the incident fields are varied and the scattering parameters of the meta-surface are altered, consequently. We demonstrate a custom-designed meta-surface with switchable scattering parameters at a broad range of terahertz frequencies, enabling terahertz intensity modulation with record high modulation depths and modulation bandwidths through a fully integrated, voltage-controlled device platform at room temperature. PMID:25028123

  17. Observation of Relativistic Electron Microbursts in Conjunction with Intense Radiation Belt Whistler-Mode Waves

    NASA Technical Reports Server (NTRS)

    Kersten, K.; Cattell, C. A.; Breneman, A.; Goetz, K.; Kellogg, P. J.; Wygant, J. R.; Wilson, L. B., III; Blake, J. B.; Looper, M. D.; Roth, I.

    2011-01-01

    We present multi-satellite observations of large amplitude radiation belt whistler-mode waves and relativistic electron precipitation. On separate occasions during the Wind petal orbits and STEREO phasing orbits, Wind and STEREO recorded intense whistler-mode waves in the outer nightside equatorial radiation belt with peak-to-peak amplitudes exceeding 300 mV/m. During these intervals of intense wave activity, SAMPEX recorded relativistic electron microbursts in near magnetic conjunction with Wind and STEREO. This evidence of microburst precipitation occurring at the same time and at nearly the same magnetic local time and L-shell with a bursty temporal structure similar to that of the observed large amplitude wave packets suggests a causal connection between the two phenomena. Simulation studies corroborate this idea, showing that nonlinear wave.particle interactions may result in rapid energization and scattering on timescales comparable to those of the impulsive relativistic electron precipitation.

  18. Higher order terms of radiative damping in extreme intense laser-matter interaction

    SciTech Connect

    Pandit, Rishi R.; Sentoku, Yasuhiko

    2012-07-15

    The higher order terms of the Lorentz-Abraham-Dirac equation have been derived, and their effects are studied via a relativistic collisional particle-in-cell simulation. The dominant group of terms up to the fourth order of the Lorentz-Abraham-Dirac equation is identified for ultra-intense laser-matter interactions. The second order terms are found to be the damping terms of the Lorentz force while the first order terms represent friction in the equation of motion. Because the second order terms restrict electron acceleration during the laser interaction, electrons/ions are prevented from over-accelerating. Radiative damping becomes highly significant when I{>=} 10{sup 22} W/cm{sup 2} while Bremsstrahlung will be saturated, thus radiative damping will be a dominant source of hard x-rays in regimes at extreme intensities.

  19. Calculation of synchrotron radiation from high intensity electron beam at eRHIC

    SciTech Connect

    Jing Y.; Chubar, O.; Litvinenko, V.

    2012-05-20

    The Electron-Relativistic Heavy Ion Collider (eRHIC) at Brookhaven National Lab is an upgrade project for the existing RHIC. A 30 GeV energy recovery linac (ERL) will provide a high charge and high quality electron beam to collide with proton and ion beams. This will improve the luminosity by at least 2 orders of magnitude. The synchrotron radiation (SR) from the bending magnets and strong quadrupoles for such an intense beam could be penetrating the vacuum chamber and producing hazards to electronic devices and undesired background for detectors. In this paper, we calculate the SR spectral intensity, power density distributions and heat load on the chamber wall. We suggest the wall thickness required to stop the SR and estimate spectral characteristics of the residual and scattered background radiation outside the chamber.

  20. [The application of low-intensity electromagnetic radiation under immobilization stress conditions (an experimental study)].

    PubMed

    Korolev, Iu N; Bobrovnitskiĭ, I P; Nikoulina, L A; Mikhaĭlik, L V; Geniatulina, M S; Bobkova, A S

    2014-01-01

    The experiments carried out on outbred male white rats with the use of optical, electron-microscopic, biochemical, and radioimmunological methods have demonstrated that the application of low-intensity electromagnetic radiation (LI-EMR) with a flow density of 1 mcW/cm2 and a frequency of around 1,000 MHz both in the primary prophylaxis regime and as the therapeuticpreventive modality arrested the development of post-stress disorders in the rat testicles, liver, and thymus; moreover, it promoted activation of the adaptive, preventive, and compensatory processes. The data obtained provide a rationale for the application of low-intensity electromagnetic radiation to protect the organism from negative effects of stressful factors.

  1. Graphene-based magnetless converter of terahertz wave polarization

    NASA Astrophysics Data System (ADS)

    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.

  2. Radiative properties of ceramic metal-halide high intensity discharge lamps containing additives in argon plasma

    NASA Astrophysics Data System (ADS)

    Cressault, Yann; Teulet, Philippe; Zissis, Georges

    2016-07-01

    The lighting represents a consumption of about 19% of the world electricity production. We are thus searching new effective and environment-friendlier light sources. The ceramic metal-halide high intensity lamps (C-MHL) are one of the options for illuminating very high area. The new C-MHL lamps contain additives species that reduce mercury inside and lead to a richer spectrum in specific spectral intervals, a better colour temperature or colour rendering index. This work is particularly focused on the power radiated by these lamps, estimated using the net emission coefficient, and depending on several additives (calcium, sodium, tungsten, dysprosium, and thallium or strontium iodides). The results show the strong influence of the additives on the power radiated despite of their small quantity in the mixtures and the increase of visible radiation portion in presence of dysprosium.

  3. RadICalc. A program for estimating radiation intensity of radionuclide mixtures

    SciTech Connect

    Robinson, John W.; Dion, Michael P.; Eiden, Gregory C.; Farmer, Orville T.; Liezers, Martin

    2014-09-24

    RadICalc is a cross-platform program designed to calculate the intensity of radiation released by the decay of arbitrary isotopic mixtures. It was developed to address the need for a program that could calculate the composition, activity, and measurable radiation of a sample over time without significant effort from end-users. RadICalc uses Bateman's solutions for radioactive decay to determine activity over time. Radiation intensities are subsequently calculated using a database containing information about alpha particles, beta electrons, gamma- rays, conversion and Auger electrons, and X-rays. The user interface accepts input for isotopic mixture, initial number of atoms, and time passed since sample composition was known. Results are plotted graphically, and there is a search interface provided to and isotopes of interest. RadICalc can determine activity and radiation expected at specific masses with user-defined molecules in addition to atomic species; the latter is useful in mass based isotope separations for radiometric counting applications, a novel method under development at PNNL.

  4. Radiation dosimetry using decreasing TL intensity in a few variety of silicate crystals.

    PubMed

    Watanabe, Shigueo; Cano, Nilo F; Gundu Rao, T K; Oliveira, Letícia M; Carmo, Lucas S; Chubaci, Jose F D

    2015-11-01

    This study shows that there are some ionic crystals which after irradiation with high gamma dose Dm and subsequent irradiation with low doses ranging up to 500Gy present a decreasing TL intensity as dose increases. This interesting feature can be used as a calibration curve in radiation dosimetry. Such behavior can be found in green quartz, three varieties of beryl and pink tourmaline. In all these silicate crystals it can be shown that irradiation with increasing γ-dose there is a dose Dm for which the TL intensity is maximum. Of course, Dm varies depending on the crystal and irradiated crystal with the dose Dm is stable. If one of these crystals is taken and irradiated with doses from low values up to 400-500Gy, a curve of decreasing TL intensity is obtained; such a curve can be used as a calibration curve. PMID:26277189

  5. Radiation dosimetry using decreasing TL intensity in a few variety of silicate crystals.

    PubMed

    Watanabe, Shigueo; Cano, Nilo F; Gundu Rao, T K; Oliveira, Letícia M; Carmo, Lucas S; Chubaci, Jose F D

    2015-11-01

    This study shows that there are some ionic crystals which after irradiation with high gamma dose Dm and subsequent irradiation with low doses ranging up to 500Gy present a decreasing TL intensity as dose increases. This interesting feature can be used as a calibration curve in radiation dosimetry. Such behavior can be found in green quartz, three varieties of beryl and pink tourmaline. In all these silicate crystals it can be shown that irradiation with increasing γ-dose there is a dose Dm for which the TL intensity is maximum. Of course, Dm varies depending on the crystal and irradiated crystal with the dose Dm is stable. If one of these crystals is taken and irradiated with doses from low values up to 400-500Gy, a curve of decreasing TL intensity is obtained; such a curve can be used as a calibration curve.

  6. A new, low temperature long-pass cell for mid-infrared to terahertz spectroscopy and synchrotron radiation use

    SciTech Connect

    Kwabia Tchana, Fridolin; Willaert, Fabrice; Landsheere, Xavier; Flaud, Jean-Marie; Lago, Leatitia; Chapuis, Mylène; Herbeaux, Christian; Roy, Pascale; Manceron, Laurent

    2013-09-15

    A new cell has been designed for accurate spectroscopic measurements in the 80–400 K temperature range with variable path lengths from 3 to more than 141 m. The spectral coverage at these temperatures ranges from the visible to less than 10 cm{sup −1}, thanks to the use of diamond windows. The design of the cryostat and vacuum setups allows vibration-free operation. The equipment provides temperature homogeneity and pressure control to better than 2% over the 100–400 K and the 0.1–1000 mbar ranges. Remote-controlled opto-mechanical systems enable in situ adjustments as well as changes of the optical path length within half an hour, in order to optimize measurement time in an open user facility. It allows then to meet the specific requirements of high resolution measurements on the Far-Infrared AILES beamline at SOLEIL as well at the LISA facility, in Créteil, in the mid-IR. This new instrument opens up the way for many experiments in the field of high-resolution gas-phase IR spectroscopy, in particular, in quantitative spectroscopy for atmospheric applications: measurements of absorption line parameters (absolute intensities, cross sections, and pressure-induced widths) using Fourier transform spectroscopy. The design and performance of the equipment are briefly presented and illustrated on spectroscopic examples.

  7. Low intensity microwave radiation induced oxidative stress, inflammatory response and DNA damage in rat brain.

    PubMed

    Megha, Kanu; Deshmukh, Pravin Suryakantrao; Banerjee, Basu Dev; Tripathi, Ashok Kumar; Ahmed, Rafat; Abegaonkar, Mahesh Pandurang

    2015-12-01

    Over the past decade people have been constantly exposed to microwave radiation mainly from wireless communication devices used in day to day life. Therefore, the concerns over potential adverse effects of microwave radiation on human health are increasing. Until now no study has been proposed to investigate the underlying causes of genotoxic effects induced by low intensity microwave exposure. Thus, the present study was undertaken to determine the influence of low intensity microwave radiation on oxidative stress, inflammatory response and DNA damage in rat brain. The study was carried out on 24 male Fischer 344 rats, randomly divided into four groups (n=6 in each group): group I consisted of sham exposed (control) rats, group II-IV consisted of rats exposed to microwave radiation at frequencies 900, 1800 and 2450 MHz, specific absorption rates (SARs) 0.59, 0.58 and 0.66 mW/kg, respectively in gigahertz transverse electromagnetic (GTEM) cell for 60 days (2h/day, 5 days/week). Rats were sacrificed and decapitated to isolate hippocampus at the end of the exposure duration. Low intensity microwave exposure resulted in a frequency dependent significant increase in oxidative stress markers viz. malondialdehyde (MDA), protein carbonyl (PCO) and catalase (CAT) in microwave exposed groups in comparison to sham exposed group (p<0.05). Whereas, levels of reduced glutathione (GSH) and superoxide dismutase (SOD) were found significantly decreased in microwave exposed groups (p<0.05). A significant increase in levels of pro-inflammatory cytokines (IL-2, IL-6, TNF-α, and IFN-γ) was observed in microwave exposed animal (p<0.05). Furthermore, significant DNA damage was also observed in microwave exposed groups as compared to their corresponding values in sham exposed group (p<0.05). In conclusion, the present study suggests that low intensity microwave radiation induces oxidative stress, inflammatory response and DNA damage in brain by exerting a frequency dependent effect

  8. Predictors of Radiation Pneumonitis in Patients Receiving Intensity Modulated Radiation Therapy for Hodgkin and Non-Hodgkin Lymphoma

    SciTech Connect

    Pinnix, Chelsea C.; Smith, Grace L.; Milgrom, Sarah; Osborne, Eleanor M.; Reddy, Jay P.; Akhtari, Mani; Reed, Valerie; Arzu, Isidora; Allen, Pamela K.; Wogan, Christine F.; Fanale, Michele A.; Oki, Yasuhiro; Turturro, Francesco; Romaguera, Jorge; Fayad, Luis; Fowler, Nathan; Westin, Jason; Nastoupil, Loretta; Hagemeister, Fredrick B.; Rodriguez, M. Alma [Department of Lymphoma and others

    2015-05-01

    Purpose: Few studies to date have evaluated factors associated with the development of radiation pneumonitis (RP) in patients with Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL), especially in patients treated with contemporary radiation techniques. These patients represent a unique group owing to the often large radiation target volumes within the mediastinum and to the potential to receive several lines of chemotherapy that add to pulmonary toxicity for relapsed or refractory disease. Our objective was to determine the incidence and clinical and dosimetric risk factors associated with RP in lymphoma patients treated with intensity modulated radiation therapy (IMRT) at a single institution. Methods and Materials: We retrospectively reviewed clinical charts and radiation records of 150 consecutive patients who received mediastinal IMRT for HL and NHL from 2009 through 2013. Clinical and dosimetric predictors associated with RP according to Radiation Therapy Oncology Group (RTOG) acute toxicity criteria were identified in univariate analysis using the Pearson χ{sup 2} test and logistic multivariate regression. Results: Mediastinal radiation was administered as consolidation therapy in 110 patients with newly diagnosed HL or NHL and in 40 patients with relapsed or refractory disease. The overall incidence of RP (RTOG grades 1-3) was 14% in the entire cohort. Risk of RP was increased for patients who received radiation for relapsed or refractory disease (25%) versus those who received consolidation therapy (10%, P=.019). Several dosimetric parameters predicted RP, including mean lung dose of >13.5 Gy, V{sub 20} of >30%, V{sub 15} of >35%, V{sub 10} of >40%, and V{sub 5} of >55%. The likelihood ratio χ{sup 2} value was highest for V{sub 5} >55% (χ{sup 2} = 19.37). Conclusions: In using IMRT to treat mediastinal lymphoma, all dosimetric parameters predicted RP, although small doses to large volumes of lung had the greatest influence. Patients with relapsed

  9. Imaging Changes in Pediatric Intracranial Ependymoma Patients Treated With Proton Beam Radiation Therapy Compared to Intensity Modulated Radiation Therapy

    SciTech Connect

    Gunther, Jillian R.; Sato, Mariko; Chintagumpala, Murali; Ketonen, Leena; Jones, Jeremy Y.; Allen, Pamela K.; Paulino, Arnold C.; Okcu, M. Fatih; Su, Jack M.; Weinberg, Jeffrey; Boehling, Nicholas S.; Khatua, Soumen; Adesina, Adekunle; Dauser, Robert; Whitehead, William E.; Mahajan, Anita

    2015-09-01

    Purpose: The clinical significance of magnetic resonance imaging (MRI) changes after radiation therapy (RT) in children with ependymoma is not well defined. We compared imaging changes following proton beam radiation therapy (PBRT) to those after photon-based intensity modulated RT (IMRT). Methods and Materials: Seventy-two patients with nonmetastatic intracranial ependymoma who received postoperative RT (37 PBRT, 35 IMRT) were analyzed retrospectively. MRI images were reviewed by 2 neuroradiologists. Results: Sixteen PBRT patients (43%) developed postradiation MRI changes at 3.8 months (median) with resolution by 6.1 months. Six IMRT patients (17%) developed changes at 5.3 months (median) with 8.3 months to resolution. Mean age at radiation was 4.4 and 6.9 years for PBRT and IMRT, respectively (P=.06). Age at diagnosis (>3 years) and time of radiation (≥3 years) was associated with fewer imaging changes on univariate analysis (odds ratio [OR]: 0.35, P=.048; OR: 0.36, P=.05). PBRT (compared to IMRT) was associated with more frequent imaging changes, both on univariate (OR: 3.68, P=.019) and multivariate (OR: 3.89, P=.024) analyses. Seven (3 IMRT, 4 PBRT) of 22 patients with changes had symptoms requiring intervention. Most patients were treated with steroids; some PBRT patients also received bevacizumab and hyperbaric oxygen therapy. None of the IMRT patients had lasting deficits, but 2 patients died from recurrent disease. Three PBRT patients had persistent neurological deficits, and 1 child died secondarily to complications from radiation necrosis. Conclusions: Postradiation MRI changes are more common with PBRT and in patients less than 3 years of age at diagnosis and treatment. It is difficult to predict causes for development of imaging changes that progress to clinical significance. These changes are usually self-limiting, but some require medical intervention, especially those involving the brainstem.

  10. Terahertz Schottky Multiplier Sources

    NASA Technical Reports Server (NTRS)

    Schlecht, Erich T.

    2007-01-01

    This viewgraph presentation reviews the multiplier source technologies and the status/Performance of THz multiplier sources. An example of a THz application is imaging radar. The presentation reviews areas of requirements for THz sources: (1) Figures of merit, (i.e., Frequency Terahertz for high resolution Bandwidth of at least 15 GHz for high range resolution Efficiency (i.e., minimize power supply requirements) (2) Output power: (i.e., Milliwatts below 800 GHz, 10s of microwatts above 1 THz, 1-2 microwatts near 2 THz (3) Mechanical--stability, compact, low mass (4) Environmental -- radiation, vibration, thermal. Several sources for 0.3 - 2 THz are reviewed: FIR lasers, quantum cascade lasers (QCL), backward-wave oscillator (BWO), and Multiplier sources. The current state of the art (SoA) is shown as Substrateless Technology. It also shows where the SoA is for devices beyond 1 THz. The presentation concludes by reviewing the options for future development, and 2 technology roadmaps

  11. Terahertz plasmonic Bessel beamformer

    SciTech Connect

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

    2015-01-12

    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.

  12. Metamaterials for terahertz polarimetric devices

    SciTech Connect

    O'hara, John F; Taylor, Antoinette J; Smirnova, Evgenya; Azad, Abul

    2008-01-01

    We present experimental and numerical investigations of planar terahertz metamaterial structures designed to interact with the state of polarization. The dependence of metamaterial resonances on polarization results in unique amplitude and phase characteristics of the terahertz transmission, providing the basis for polarimetric terahertz devices. We highlight some potential applications for polarimetric devices and present simulations of a terahertz quarter-wave plate and a polarizing terahertz beam splitter. Although this work was performed at terahertz frequencies, it may find applications in other frequency ranges as well.

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

    NASA Astrophysics Data System (ADS)

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

    2002-11-01

    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.

  14. Terahertz quantum transport in semiconductor nanostructures with the UCSB free electron lasers

    SciTech Connect

    Allen, S.J.

    1995-12-31

    Quantum transport in semiconductor nanostructures takes on new dimensions in the presence of intense terahertz electric fields. Terahertz frequencies lift us into the regime where the scattering and relaxation is not so important and strong terahertz electric fields provided by the UCSB FEL`s explore non-linear dynamics far from the perturbative limit. New quantum transport channels that are assisted by the absorption or emission of a photon appear in current voltage characteristics. We will describe some of these experiments, the new phenomena they expose and the potential impact on future terahertz semiconductor electronics.

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

    PubMed

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

    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.

  16. Terahertz Light Source and User Area at FACET

    SciTech Connect

    Wu, Z.; Li, S.Z.; Litos, M.; Fisher, A.D.; Hogan, M.J.; /SLAC

    2011-11-08

    FACET at SLAC provides high charge, high peak current, low emittance electron beam that is bunched at THz wavelength scale during its normal operation. A THz light source based coherent transition radiation (CTR) from this beam would potentially be the brightest short-pulse THz source ever constructed. Efforts have been put into building this photon source together with a user area, to provide a platform to utilize this unique THz radiation for novel nonlinear and ultrafast phenomena researches and experiments. Being a long-time underutilized portion of the electromagnetic spectrum, terahertz (100 GHz {approx} 10 THz) spectral range is experiencing a renaissance in recent years, with broad interests from chemical and biological imaging, material science, telecommunication, semiconductor and superconductor research, etc. Nevertheless, the paucity of THz sources especially strong THz radiation hinders both its commercial applications and nonlinear processes research. FACET - Facilities for Accelerator science and Experimental Test beams at SLAC - provides 23 GeV electron beam with peak currents of {approx} 20 kA that can be focused down to 100 {mu}m{sup 2} transversely. Such an intense electron beam, when compressed to sub-picosecond longitudinal bunch length, coherently radiates high intensity EM fields well within THz frequency range that are orders of magnitude stronger than those available from laboratory tabletop THz sources, which will enable a wide variety of THz related research opportunities. Together with a description of the FACET beamline and electron beam parameters, this paper will report FACET THz radiation generation via coherent transition radiation and calculated photon yield and power spectrum. A user table is being set up along the THz radiation extraction sites, and equipped with various signal diagnostics including THz power detector, Michelson interferometer, sample stages, and sets of motorized optical components. This setup will also be

  17. Propagation and absorption of high-intensity femtosecond laser radiation in diamond

    SciTech Connect

    Kononenko, V V; Konov, V I; Gololobov, V M; Zavedeev, E V

    2014-12-31

    Femtosecond interferometry has been used to experimentally study the photoexcitation of the electron subsystem of diamond exposed to femtosecond laser pulses of intensity 10{sup 11} to 10{sup 14} W cm{sup -2}. The carrier concentration has been determined as a function of incident intensity for three harmonics of a Ti : sapphire laser (800, 400 and 266 nm). The results demonstrate that, in a wide range of laser fluences (up to those resulting in surface and bulk graphitisation), a well-defined multiphoton absorption prevails. We have estimated nonlinear absorption coefficients for pulsed radiation at λ = 800 nm (four-photon transition) and at 400 and 266 nm (indirect and direct two-photon transitions, respectively). It has also been shown that, at any considerable path length of a femtosecond pulse in diamond (tens of microns or longer), the laser beam experiences a severe nonlinear transformation, determining the amount of energy absorbed by the lattice, which is important for the development of technology for diamond photostructuring by ultrashort pulses. The competition between wave packet self-focusing and the plasma defocusing effect is examined as a major mechanism governing the propagation of intense laser pulses in diamond. (interaction of laser radiation with matter. laser plasma)

  18. Active terahertz metamaterials

    SciTech Connect

    Chen, Hou-tong

    2009-01-01

    We demonstrate planar terahertz metamaterial devices enabling actively controllable transmission amplitude, phase, or frequency at room temperature via carrier depletion or photoexcitation in the semiconductor substrate or in semiconductor materials incorporated into the metamaterial structure.

  19. It's time for terahertz

    NASA Astrophysics Data System (ADS)

    Cooper, Keith

    2016-06-01

    The quest is on to make terahertz sources that are small, portable and capable of operating at room temperature. Such a breakthrough could lead to advances in everything from cancer screening to astronomy, reports Keith Cooper.

  20. Whole-brain hippocampal sparing radiation therapy: Volume-modulated arc therapy vs intensity-modulated radiation therapy case study.

    PubMed

    Lee, Katrina; Lenards, Nishele; Holson, Janice

    2016-01-01

    The hippocampus is responsible for memory and cognitive function. An ongoing phase II clinical trial suggests that sparing dose to the hippocampus during whole-brain radiation therapy can help preserve a patient׳s neurocognitive function. Progressive research and advancements in treatment techniques have made treatment planning more sophisticated but beneficial for patients undergoing treatment. The aim of this study is to evaluate and compare hippocampal sparing whole-brain (HS-WB) radiation therapy treatment planning techniques using volume-modulated arc therapy (VMAT) and intensity-modulated radiation therapy (IMRT). We randomly selected 3 patients to compare different treatment techniques that could be used for reducing dose to the hippocampal region. We created 2 treatment plans, a VMAT and an IMRT, from each patient׳s data set and planned on the Eclipse 11.0 treatment planning system (TPS). A total of 6 plans (3 IMRT and 3 VMAT) were created and evaluated for this case study. The physician contoured the hippocampus as per the Radiation Therapy Oncology Group (RTOG) 0933 protocol atlas. The organs at risk (OR) were contoured and evaluated for the plan comparison, which included the spinal cord, optic chiasm, the right and left eyes, lenses, and optic nerves. Both treatment plans produced adequate coverage on the planning target volume (PTV) while significantly reducing dose to the hippocampal region. The VMAT treatment plans produced a more homogenous dose distribution throughout the PTV while decreasing the maximum point dose to the target. However, both treatment techniques demonstrated hippocampal sparing when irradiating the whole brain. PMID:26235550