首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到10条相似文献,搜索用时 15 毫秒
1.
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   

2.
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   

3.
A survey on the mechanisms of powerful terahertz (THz) radiation from laser plasmas is presented.Firstly,an analytical model is described,showing that a transverse net current formed in a plasma can be converted into THz radiations at the plasma oscillation frequency.This theory is applied to explain THz generation in a gas driven by two-color laser pulses.It is also applied to THz generation in a tenuous plasma driven by a chirped laser pulse,a few-cycle laser pulse,a DC/AC bias electric field.These are well verified by particle-in-cell simulations,demonstrating that THz radiations produced in these approaches are nearly single-cycles and linear polarized.In the chirped laser scheme and the few-cycle laser scheme,THz radiations with the peak field strength of tens of MV/cm and the peak power of gigawatt can be achieved with the incident laser intensity less than 10 17 W/cm 2.  相似文献   

4.
Mechanism of terahertz (THz) pulse generation in gases irradiated by ultrashort laser pulses is investigated theoretically. Quasi-static transverse currents produced by laser field ionization of gases and the longitudinal modulation in formed plasmas are responsible for the THz emission at the electron plasma frequency, as demonstrated by particle-in-cell simulations including field ionization. The THz field amplitude scaling with the laser amplitude within a large range is also discussed.  相似文献   

5.
Mechanism of terahertz (THz) pulse generation in gases irradiated by ultrashort laser pulses is investigated theoretically. Quasi-static transverse currents produced by laser field ionization of gases and the longitudinal modulation in formed plasmas are responsible for the THz emission at the electron plasma frequency, as demonstrated by particle-in-cell simulations including field ionization. The THz field amplitude scaling with the laser amplitude within a large range is also discussed.  相似文献   

6.
Previous research shows that few-cycle laser(FCL) pulses with low energy and without a bias field can be used to coherently detect terahertz(THz) pulses. As we know, it is very difficult to stabilize the carrier envelope phase(CEP) of FCL pulses, i.e., there are some random fluctuations for the CEP. Here we theoretically investigate the influence of such instability on the accuracy of THz detection. Our results show that although there is an optimum CEP for THz detection, the fluctuations of the CEP will lead to terrible thorns on the detected THz waveform. In order to solve this problem, we propose an approach using two few-cycle laser pulses with opposite CEPs, i.e., their CEPs are differed by π.  相似文献   

7.
The evolution of terahertz (THz) waveform in air plasma driven by low-energy few-cycle laser pulses is investigated to improve the accuracy of the carrier envelope phase (CEP) determination. Based on the transient photocurrent model, a balanced spatial distribution of the Kerr and free-electron effects in the plasma is found at 109 μJ input energy. THz inversion occurs only once at the initial CEP of 0.5π, in which high-precision measurement of the CEP of few-cycle laser pulses is achieved.  相似文献   

8.
施宇蕾  周庆莉  张存林 《中国物理 B》2009,18(12):5511-5517
The spatiotemporal and spectral characteristics of ultrawide-band terahertz pulses after passing through a Fresnel lens are studied by using the scalar diffraction theory.The simulation shows that the transmitted terahertz waveforms compress with increasing propagation distance,and the multi-frequency focusing phenomenon at different focal points is observed.Additionally,the distribution of terahertz fields in a plane perpendicular to the axis is also discussed,and it is found that the diffraction not only induces focusing on-axis but also inhibits focusing at off-axis positions.Therefore,the Fresnel lens may be a useful alternative approach to being a terahertz filter.Moreover,the terahertz pulses travelling as a basic mode of a Gaussian beam are discussed in detail.  相似文献   

9.
We present a review of the development of a compact and high-power broadband terahertz (THz) source optically excited by a femtosecond photonic crystal fiber (PCF) amplifier.The large mode area of the PCF and the stretcher-free configuration make the pump source compact and very efficient.Broadband THz pulses of 150 μW extending from 0.1 to 3.5 THz are generated from a 3-mm-thick GaP crystal through optical rectification of 12-W pump pulses with duration of 66 fs and a repetition rate of 52 MHz.A strong saturation effect is observed,which is attributed to pump pulse absorption;a Z-scan measurement shows that three-photon absorption dominates the nonlinear absorption when the crystal is pumped by femtosecond pulses at 1 040 nm.A further scale-up of the THz source power is expected to find important applications in THz nonlinear optics and nonlinear THz spectroscopy.  相似文献   

10.
The optical absorption of GaAs nanorings (NRs) under adc electric field and a terahertz (THz) ac electric field applied in the plane containing the NRs is investigated theoretically. The NRs may enclose some magnetic flux in the presence of a magnetic field perpendicular to the NRs plane. Numerical calculation shows that the excitonic effects are essential to correctly describe the optical absorption in NRs. The applied lateral THz electric field, as well as the dc field leads to reduction, broadening and splitting of the exciton peak. In contrast to the presence of a dc field, significant optical absorption peak arises below the zero-field bandgap in the presence ofa THz electric field at a certain frequency. The optical absorption spectrum depends evidently on the frequency and amplitude of the applied THz field and on the magnetic flux threading the NRs. This promises potential applications of NRs for magneto-optical and THz electro-optical sensing.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号