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1.
The electric field profiles of broad-bandwidth coherent terahertz (THz) pulses, emitted by laser-wakefield-accelerated electron bunches, are studied. The near-single-cycle THz pulses are measured with two single-shot techniques in the temporal and spatial domains. Spectra of 0-6 THz and peak fields up to approximately or = 0.4 MV cm(-1) are observed. The measured field substructure demonstrates the manifestation of spatiotemporal coupling at focus, which affects the interpretation of THz radiation as a bunch diagnostic and in high-field pump-probe experiments. 相似文献
2.
Shen Y Watanabe T Arena DA Kao CC Murphy JB Tsang TY Wang XJ Carr GL 《Physical review letters》2007,99(4):043901
We have demonstrated nonlinear cross-phase modulation in electro-optic crystals using intense, single-cycle terahertz (THz) radiation. Individual THz pulses, generated by coherent transition radiation emitted by subpicosecond electron bunches, have peak energies of up to 100 microJ per pulse. The time-dependent electric field of the intense THz pulses induces cross-phase modulation in electro-optic crystals through the Pockels effect, leading to spectral shifting, broadening, and modulation of copropagating laser pulses. The observed THz-induced cross-phase modulation agrees well with a time-dependent phase-shift model. 相似文献
4.
Characteristics of terahertz coherent transition radiation generated from picosecond ultrashort electron bunches
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This paper presents a method of generating terahertz (THz)
coherent transition radiation (CTR) from picosecond ultrashort
electron bunches including single and train bunches, which are
produced by a photocathode radio frequency gun. The radiation
characteristics of THz CTR including formation factor and energy
spectrum are analysed in detail. With the help of a 2-dimensional
particle-in-cell simulation, the radiation characteristics including
power, energy and magnetic field are analysed. The results show that
the radiation frequency can be adjusted by tuning the repetition
frequency of the train bunch and the energy can be enhanced with the
train bunches. 相似文献
5.
We report the observation of enhanced coherent Smith-Purcell radiation (SPR) at terahertz (THz) frequencies from a train of picosecond bunches of 15 MeV electrons passing above a grating. SPR is more intense than other sources, such as transition radiation, by a factor of Ng, the number of grating periods. For electron bunches that are short compared with the radiation wavelength, coherent emission occurs, enhanced by a factor of Ne, the number of electrons in the bunch. The electron beam consists of a train of Nb bunches, giving an energy density spectrum restricted to harmonics of the 17 GHz bunch train frequency, with an increased energy density at these frequencies by a factor of Nb. We report the first observation of SPR displaying all three of these enhancements, NgNeNb. This powerful SPR THz radiation can be detected with a high signal to noise ratio by a heterodyne receiver. 相似文献
6.
Leemans WP Geddes CG Faure J Tóth C van Tilborg J Schroeder CB Esarey E Fubiani G Auerbach D Marcelis B Carnahan MA Kaindl RA Byrd J Martin MC 《Physical review letters》2003,91(7):074802
Coherent radiation in the 0.3-3 THz range has been generated from femtosecond electron bunches at a plasma-vacuum boundary via transition radiation. The bunches produced by a laser-plasma accelerator contained 1.5 nC of charge. The THz energy per pulse within a limited 30 mrad collection angle was 3-5 nJ and scaled quadratically with bunch charge, consistent with coherent emission. Modeling indicates that this broadband source produces about 0.3 microJ per pulse within a 100 mrad angle, and that increasing the transverse plasma size and electron beam energy could provide more than 100 microJ/pulse. 相似文献
7.
Terahertz (THz) science and technology have already become the research highlight at present. In this paper, we put forward a proposal to generate THz radiation at tens of MW peak power. As a result of the ultrafast laser and the high accelerating field of photocathode RF gun, we can generate and accelerate an electron beam to several MeV, of which the bunch length is less than sub-ps. When the short electron bunches are injected into the wiggler, THz radiation based on Coherent Synchrotron Radiation could be achieved with tens of MW peak power. The whole THz FEL facility can be scaled to the size of a tabletop. 相似文献
8.
Terahertz (THz) science and technology have already become the research highlight at present. In this paper, we put forward a proposal to generate THz radiation at tens of MW peak power. As a result of the ultrafast laser and the high accelerating field of photocathode RF gun, we can generate and accelerate an electron beam to several MeV, of which the bunch length is less than sub-ps. When the short electron bunches are injected into the wiggler, THz radiation based on Coherent Synchrotron Radiation could be achieved with tens of MW peak power. The whole THz FEL facility can be scaled to the size of a tabletop.
相似文献9.
Yong Yin Yang Yan Yaxin Zhang Min Hu Renbin Zhong Shenggang Liu 《International Journal of Infrared and Millimeter Waves》2007,28(10):797-809
In the modern science and technology a compact and having enough output power terahertz radiation source working in room temperature
have earned great attention. This paper is devoted to utilize electron bunches stimulate Vavilov-Cherenkov Radiation (VCR)
in a special three-mirror quasi-optical cavity to generate coherent THz waves. This novel three-mirror quasi-optical resonant
cavity has the coaxial field pattern which enables field establish in this cavity effectively. The analytical theory of the
radiation exited by a train of electron bunches in the special kind of three-mirror cavity has been carried out and the coherent
VCR has been achieved by the computer simulation. All those shows that this method can be used to establish useful THz radiation
source by the normal electron gun and the commonly used microwave devices. 相似文献
10.
Hoffmann MC Schulz S Wesch S Wunderlich S Cavalleri A Schmidt B 《Optics letters》2011,36(23):4473-4475
Terahertz (THz) pulses with energies up to 100 μJ and corresponding electric fields up to 1 MV/cm were generated by coherent transition radiation from 500 MeV electron bunches at the free-electron laser Freie-Elektronen-Laser in Hamburg (FLASH). The pulses were characterized in the time domain by electro-optical sampling by a synchronized femtosecond laser with jitter of less than 100 fs. High THz field strengths and quality of synchronization with an optical laser will enable observation of nonlinear THz phenomena. 相似文献
11.
We report the evolution of the high power THz source program at Jefferson Lab. The source is based on coherent synchrotron radiation in which short bunches of relativistic electrons radiate when traversing a dipolar magnetic field. In our first accelerator we produced 20 W of broadband THz light. Our upgraded accelerator with higher current and improved THz extraction optics will considerably enhance the output power to >100 W. In this paper we describe the source in some detail and present theoretical calculations for the upgrade. 相似文献
12.
The properties of terahertz (THz) radiation pulses emitted by a metallic, large aspect ratio carbon nanotube antenna have been studied both in the THz waveforms and field distribution. The peak THz field up to 2.66 and 1.26 kV/cm are observed at the probe points. The proposed antenna is designed to operate for dual frequency applications from 2.36 to 2.58 THz and from 7.27 to 7.5 THz for less than -10 dB return loss. 相似文献
13.
JETP Letters - In the theory of radiation emitted by bunches of charged particles, the effects of coherence are commonly taken into account by multiplying the intensity of radiation generated by a... 相似文献
14.
15.
A new facility is under construction at the Shanghai Institute of Applied Physics,to generate femto-second electron bunches and intense coherent THz radiation pulses.A thermionic RF-gun is used to be the electron source of the linac,which is 1.6 cell,π/2,side coupled in design.In the following of this paper,the design,manufacture and beam operation of this gun are presented. 相似文献
16.
Emission of terahertz (THz) radiation as a result of optical rectification of intense femtosecond laser pulses on thin gold films has been studied by time-domain THz spectroscopy. The THz amplitude was measured as a function of film thickness and incidence angle. The experiments reveal that the emitted THz field is suppressed for a thickness below 100 nm, which gives evidence of the nonlocal character of the response. The variation of incidence angle allows us to estimate the components of susceptibility tensor chi2ijk. For thicker films and near grazing incidence, the emitted THz field attains a peak value of 4 kV/cm. 相似文献
17.
A. Schmidt F. Garwe U. Hübner T. May W. Paa M. Zeisberger G. Zieger H. Stafast 《Applied physics. B, Lasers and optics》2012,109(4):631-642
The THz radiation emission of Au-coated nanogratings (fused silica substrate, 30?nm Au layer thickness, 500?nm grating constant) upon fs laser irradiation (785?nm, 150?fs, 1?kHz,???1?mJ/pulse) is observed in both directions along the laser beam axis (forward and backward) and for both, illumination of the Au/air or the Au/silica interface. THz radiation along the laser beam propagation is emitted in a narrow solid angle of about 15°?fwhm independent on the laser pulse fluence, the angle of incidence and the nanograting profile. The bar width and groove depth of the nanograting as well as the angle of laser beam incidence strongly affect the THz radiation yield. The energy of single THz light pulses is measured absolutely (2?fJ in the 0.3?C0.38?THz range) using a highly sensitive and fast superconducting transition edge sensor. The bi-directional emission of THz radiation is in agreement with the model assumption of surface plasmon polaritons propagating simultaneously on both Au layer interfaces (Au/air and Au/silica). 相似文献
18.
Intense Cherenkov-type terahertz electromagnetic radiation from ultrafast laser-plasma interaction
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A Cherenkov-type terahertz electromagnetic radiation is revealed,
which results efficiently from the collective effects in the
time-domain of ultrafast pulsed electron current produced by
ultrafast intense laser--plasma interaction. The emitted pulse
waveform and spectrum, and the dependence of laser pulse parameters
on the structure of the radiation field are investigated numerically.
The condition of THz radiation generation in this regime and
Cherenkov geometry of the radiation field are studied analytically. 相似文献
19.
20.
We have investigated the ultrafast optical and optoelectronic characteristics of multi-energy proton-bombarded GaAs (GaAs:H+) material and devices in some detail. Photo-excited carrier lifetimes of GaAs:H+ were observed to be as low as 350 ± 50 fs. Photoconductive switches (PCS) fabricated on GaAs:H+ were found to exhibit lower dark currents (15 nA at a bias of 10 V) and higher breakdown voltage (> 100 kV/cm) than PCS's fabricated on semi-insulating (S.I.) GaAs. The temporal response of the GaAs:H+ PCS was about 2 ps at full-wave half minimum. Optically excited terahertz (THz) radiation from GaAs:H+ was reported for the first time to our knowledge. The temporal response and spectral bandwidth of the emitted THz radiation were 0.7 ps and 1.25 THz, respectively. The field strength of the THz signal was about 20 mV/cm. From the THz data, we are able to deduce that the effective carrier mobility of GaAs:H+ was less than 1 cm2/V-sec. 相似文献