共查询到20条相似文献，搜索用时 15 毫秒
1.
《等离子体物理论文集》2017,57(6-7):293-310
In this work, using a two‐dimensional particle‐in‐cell Monte Carlo collision computation method, terahertz (THz) radiation generation via the interaction of two‐colour, ultra‐short, high‐power laser pulses with the polyatomic molecular gases sulphur dioxide (SO2) and ammonia (NH3) is examined. The influence of SO2 and NH3 pressures and two‐colour laser pulse parameters, i.e., pulse shape, pulse duration, and beam waist, on the THz radiation generation is studied. It is shown that the THz signal generation from SO2 and NH3 increases with the background gas pressure. It is seen that the THz emission intensity for both gases at higher laser pulse durations is higher. Moreover, for these polyatomic gases, the plasma current density increases with increase in the laser pulse beam waist. A more powerful THz radiation intensity with a larger time to peak of the plasma current density is observed for SO2 compared to NH3. In addition, many THz signals with small intensities are observed for both polyatomic gases. It is seen that for both SO2 and NH3 the generated THz spectral intensity is higher at higher gas pressures. 相似文献
2.
ZnTe晶体中光学整流产生的THz辐射及其电光探测研究 总被引：6，自引：0，他引：6
借助抽运-探测技术研究了ZnTe晶体中光学整流产生的太赫兹(THz)辐射,利用ZnTe晶体的线性电光效应探测THz辐射场分布,观察到了较窄(约为0.2 ps)的THz场分布及相应较宽(响应超过4 THz,半峰宽约为2.4 THz)的THz频谱,并运用琼斯矩阵对实验结果进行了理论拟合. 研究了飞秒激光脉冲波长(750—850 nm)、脉冲宽度(56—225 fs)和晶体旋转与THz辐射产生的关系. 同时改变探测光偏振方向进行偏振调制,并从理论上分析了偏振调制对THz辐射探测的影响. 关键词：THz辐射光学整流电光探测ZnTe 相似文献
3.
The optical guiding of a moderately intense laser pulse in a parabolic preformed plasma channel is analyzed by means of the variational method.Relativistic,ponderomotive and their coupling nonlinearities are included.The conditions for periodic defocusing and focusing,as well as constant spot size propagation are given.It is found that the laser focusing is released by the coupling of relativistic and ponderomotive nonlinearities. 相似文献
4.
The terahertz (THz) frequency radiation production as a result of nonlinear interaction of high intense laser beam with low density ripple in a magnetized plasma has been studied. If the appropriate phase matching conditions are satisfied and the frequency of the ripple is appropriate then this difference frequency can be brought in the THz range. Self focusing (filamentation) of a circularly polarized beam propagating along the direction of static magnetic field in plasma is first investigated within extended‐paraxial ray approximation. The beam gets focused when the initial power of the laser beam is greater than its critical power. Resulting localized beam couples with the pre‐existing density ripple to produce a nonlinear current driving the THz radiation. By changing the strength of the magnetic field, one can enhance or suppress the THz emission. The expressions for the laser beam width parameter, the electric field vector of the THz wave have been obtained. For typical laser beam and plasma parameters with the incident laser intensity ≈ 1014 W/cm2, laser beam radius (r0) = 50 μm, laser frequency (ω0) = 1.8848 × 1014rad/s, electron plasma (low density rippled) wave frequency (ω0) = 1.2848 × 1014 rad/s, plasma density (n0) = 5.025 × 1017cm–3, normalized ripple density amplitude (μ)=0.1, the produced THz emission can be at the level of Giga watt (GW) in power (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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6.
Longhui Zhang Yuanyuan Huang Lipeng Zhu Zehan Yao Qiyi Zhao Wanyi Du Yuhang He Xinlong Xu 《Advanced Optical Materials》2019,7(6)
Recent advances in the development of polarized terahertz (THz) emission from nanomaterials have not only opened up a new “TeraNano” interdiscipline but also provided a new tool for nonlinear optical process research. Herein, THz radiation mechanism of monolayer tungsten disulfide (WS2) is first investigated by both linear and circular polarization laser excitations at room temperature. The results reveal that polarized THz emission is dominated by the optical rectification based on in‐plane nonlinear dipoles, which is totally different from that of bulk WS2. The mechanism is verified by the azimuthal angle and pump polarization angle dependence of THz emission in both experiment and theory. Furthermore, controllably elliptically polarized THz emission is observed with the maximum ellipticity of ≈0.52 based on nonresonant nonlinear process under the circularly polarized excitation. A clear understanding of THz radiation mechanism of 2D materials will facilitate further design, optimization, and polarization control of integrable 2D THz optoelectronics. 相似文献
7.
The combined effect of relativistic and ponderomotive nonlinearities on the self‐focusing of an intense cosh‐Gaussian laser beam (CGLB) in magnetized plasma have been investigated. Higher‐order paraxial‐ray approximation has been used to set up the self‐focusing equations, where higher‐order terms in the expansion of the dielectric function and the eikonal are taken into account. The effects of various lasers and plasma parameters viz. laser intensity (a0), decentred parameter (b), and magnetic field (ωc) on the self‐focusing of CGLB have been explored. The results are compared with the Gaussian profile of laser beams and relativistic nonlinearity. Self‐focusing can be enhanced by optimizing and selecting the appropriate laser‐plasma parameters. It is observed that the focusing of CGLB is fast in a nonparaxial region in comparison with that of a Gaussian laser beam and in a paraxial region in magnetized plasma. In addition, strong self‐focusing of CGLB is observed at higher values of a0, b, and ωc. Numerical results show that CGLB can produce ultrahigh laser irradiance over distances much greater than the Rayleigh length, which can be used for various applications. 相似文献
8.
Faure J. Van Tilborg J. Kaindl R. A. Leemans W. P. 《Optical and Quantum Electronics》2004,36(8):681-697
A model describing the generation of THz pulses by optical rectification and the detection of THz pulses by electro-optic sampling is presented. The model is comprehensive and mostly analytical: physical phenomena such as dispersion, group velocity mismatch, multiple reflections and diffraction are represented by one dimensional transfer functions. The model is compared with experimental results and shows good agreement with experiments. It is shown that including diffraction is crucial for retrieving the details of the THz spectrum. 相似文献
9.
太赫兹波发射晶体的亚波长微棱锥增透结构的设计与实验研究 总被引：1，自引：0，他引：1
光学整流方法产生太赫兹(THz)辐射常用的非线性发射晶体在THz波段都具有较高的折射率, 使得很大一部分THz波由于晶体表面的菲涅尔反射而无法有效耦合输出. 本文报道了GaP晶体THz波发射器输出表面上亚波长微棱锥增透结构的设计和实验研究. 利用有效介质模型在理论上验证了亚波长光栅结构的增透效果, 并进一步设计了适用于不同频段的增透结构的参数. 实验中, 通过微机械加工手段在GaP晶体输出端面刻划了多种亚波长微棱锥结构, 验证了其增透效果及参数对增透频带的关系. 理论与实验的符合证明该设计思想也可用于其他THz波发射晶体.关键词：THz波光学整流亚波长微棱锥增透结构微加工 相似文献
10.
Reza Fallah Reza Khooniki Seyed Mohammad Khorashadizadeh Ali Reza Niknam 《等离子体物理论文集》2021,61(2):e202000086
The influence of relativistic-ponderomotive nonlinearities and the plasma inhomogeneity on the nonlinear interaction between a high-power laser beam and a warm underdense plasma are studied. It is clear that the relativistic ponderomotive force and the electron temperature modify the electron density distribution and consequently change the dielectric permittivity of the plasma. Therefore, by presenting the modified electron density and the nonlinear dielectric permittivity of the warm plasma, the electromagnetic wave equation for the propagation of intense laser beam through the plasma is derived. This nonlinear equation is numerically solved and the distributions of electromagnetic fields in the plasma, the variations of electron density, and plasma refractive index are investigated for two different background electron density profiles. The results show that the amplitude of the electric field and electron density oscillations gradually increase and decrease, during propagation in the inhomogeneous warm plasma with linear and exponential density profiles, respectively, and the distribution of electron density becomes extremely sharp in the presence of intense laser beam. It is also indicated that the electron temperature and initial electron density have an impact on the propagation of the laser beam in the plasma and change the plasma refractive index and the oscillations' amplitude and frequency. The obtained results indicate the importance of a proper choice of laser and plasma parameters on the electromagnetic field distributions, density steepening, and plasma refractive index variations in the interaction of an intense laser beam with an inhomogeneous warm plasma. 相似文献
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12.
Enrique Casado Maria C. Garcia Dorota A. Krawczyk Francisco‐Jos Romero‐Salguero Antonio Rodero 《Plasma Processes and Polymers》2020,17(9)
The interaction of an argon microwave plasma jet with a benzene layer on water has been analyzed under different conditions (power, gas flow, plasma‐sample distance, and treatment time) in this study. Main products formed upon treatment are phenol, catechol, and nitrobenzene, which shows that this jet is a source of radicals •OH and •NO2, inducing benzene oxidation and nitration. Excited argon species in the plasma have been proven to play an outstanding role in degradation processes, which mostly occur at the gas phase. Results are compared with those from the direct interaction of the plasma jet with water. For this purpose, aqueous solutions of 3‐coumarin carboxylic acid are treated and the hydroxylation of this compound is studied. The effect of the benzene layer preventing water evaporation is demonstrated. 相似文献
13.
经典物理学指出,在电磁场中作加速运动的带电粒子将不断向外辐射能量.在晶体沟道中运动的带电粒子也不例外,晶格场可以使带电粒子的辐射能量达到很高.对于10MeV的正电子,辐射能量可达keV量级.粒子在沟道中的运动行为决定于粒子晶体的相互作用势,常用的相互作用势有Lindhard势、Moliere势和正弦平方势.由于粒子在沟道中的运动行为十分类似于震荡器中运动的自由电子,可望把沟道辐射改造为Χ射线激光或γ射线激光.从Lindhard势出发,将其展开到四次项,在经典力学框架内,粒子的运动方程可以化为含立方项的二阶非线性微分方程,并利用Jacobian椭圆函数和第一类全椭圆积分解析地表示了系统的解和粒子运动周期,导出了正电子面沟道辐射的瞬时辐射强度、平均辐射强度和最大辐射频率,指出了利用沟道辐射作为γ激光的可能性. 相似文献
14.
M. Hashemzadeh 《等离子体物理论文集》2019,59(7)
Modification of electron density of an inhomogeneous, unmagnetized plasma by the relativistic ponderomotive force of intense microwave beams near the critical density is studied. Using the Maxwell and fluid equations and taking into account the relativistic mass, relativistic ponderomotive force, linear inhomogeneity for electron temperature, and tangential inhomogeneity for electron density, the non‐linear electron density, non‐linear dielectric permittivity, and non‐linear wave equations are derived. Results show that positive and negative values of σ1 and σ2 (degree of inhomogeneity of the background electron density and electron temperature, respectively) parameters can affect the electric and magnetic field profiles. In addition, profiles of the non‐linear electron density indicate that by decreasing the σ1 parameter, the amplitude of the peaks increases near the critical density. For positive values of the σ2 parameter, by increasing this parameter the amplitude of the peaks increases, while for negative values of the σ2 parameter, by decreasing this parameter the amplitude of the peaks increases. 相似文献
15.
A theoretical model was proposed to describe the effects of external bias electric field on terahertz(THz)generated in air plasma.The model predicted that for a plasma in a bias electric field,the amplification effect of the THz wave intensity increases with the increase of the excitation laser wavelength.We experimentally observed the relationship between the THz enhancement effect and the electric field strength at different wavelengths.Experimental results showed a good agreement with the model predictions.These results enhance our understanding of the physical mechanism by which femtosecond lasers excite air to generate THz and extend the practical applications of THz generation and modulation. 相似文献
16.
A review on the recent development of intense laser‐driven terahertz (THz) sources is provided here. The technologies discussed include various types of sources based on optical rectification (OR), spintronic emitters, and laser‐filament‐induced plasma. The emphasis is on OR using pump pulses with tilted intensity front. Illustrative examples of newly emerging applications are briefly discussed, in particular strong‐field THz control of materials and acceleration and manipulation of charged particles. 相似文献
17.
S. G. Moiseev 《Journal of Applied Spectroscopy》2004,71(2):257-262
The problem on the interaction of optical radiation with a nanostructure representing a one-dimensional (linear) chain of electrodynamically interacting dipole centers — atoms — has been considered. It has been shown that the number of optical resonances of the nanostructure and the detuning of the resonance frequencies from the eigenfrequency of the atom are only determined by the internal parameters of the nanostructure. The dependence of the number of resonances on the number of atoms in the nanostructure has been established. For nanostructures having a symmetry center, the number of resonances in atoms depends also on the orientation of the nanostructure axis with respect to the direction of external-wave propagation. 相似文献
18.
Generation of the terahertz (THz) radiation based on the beating of two cross‐focused high intensity Gaussian laser beams in a warm rippled density plasma is numerically investigated, taking into account the ponderomotive force, Ohmic heating, and collisional nonlinearities. The beat ponderomotive force as a result of cross‐focusing of beams induces a vertical velocity component that by coupling with the rippled density gives rise to a nonlinear current deriving THz radiation. The effect of laser beams spot size evolution and plasma parameters on the THz generation is studied. It was found that there exist special electron temperature and laser intensity ranges with “turning points” where the generation of THz radiation reaches its maximum value and outside of these ranges, it disappears. The results also indicated that increasing the background electron density as well as taking into account the collision frequency help THz generation. Moreover, the maximum yield of THz radiation occurs when the beat wave frequency approaches the plasma frequency. 相似文献
19.
R. Fallah;R. Khooniki;S. M. Khorashadizadeh;A. R. Niknam; 《等离子体物理论文集》2024,64(1):e202300077
The nonlinear absorption in the interaction of an intense laser pulse with a collisional magnetized plasma is studied by considering the effects of plasma inhomogeneity, ohmic heating, and ponderomotive force. For this purpose, we obtain the plasma electron density, the effective dielectric permittivity, and the wave equation using the Maxwell and hydrodynamic equations and solve this equation by the Runge–Kutta numerical method. The results are shown that by increasing the plasma inhomogeneity, the inverse bremsstrahlung absorption coefficient is increased, and also the density ramp parameter σ1$$ left({sigma}_1right) $$ and its sign can affect more the absorption coefficient than the temperature ramp parameter σ2$$ left({sigma}_2right) $$. However, when the initial electron density and temperature increase, the laser field amplitude and the absorption coefficient are increased and the spatial damping rate of the laser pulse becomes highly peaked inside the plasma. It is shown by increasing laser pulse energy, the nonlinear bremsstrahlung absorption coefficient is decreased significantly. The results also indicate that by increasing the external magnetic field, the dielectric permittivity is decreased while the laser energy spatial damping, and the absorption coefficient are increased. Moreover, it is found that by considering the ohmic heating effect, the electrons absorb further energy from the fields and consequently the nonlinear absorption is increased. 相似文献
20.
J. Badziak 《辐射效应与固体损伤》2015,170(4):256-270
This paper summarizes briefly the main experimental and numerical results of the IPPLM team studies on the generation of ultra-intense ion beams by a short (≤1?ps) laser pulse. Basic laser-driven ion acceleration schemes capable of generating such ion beams are described including the target normal sheath acceleration (TNSA) scheme, the skin-layer ponderomotive acceleration (SLPA) scheme and the laser-induced cavity pressure acceleration (LICPA) scheme. It is shown that an efficient way for achieving high ion beam intensities and fluencies lies in using a short-wavelength laser driver of circular light polarization. In such a case, SLPA clearly dominates over TNSA, and dense and compact ion bunch is generated with high energetic efficiency. The LICPA scheme operating in the photon (radiation) pressure regime can be even more efficient than SLPA. As it is demonstrated by particle-in-cell simulations, the LICPA accelerator with a picosecond, circularly polarized laser driver of intensity ～ 1021?W/cm2 can produce sub-picosecond light ion beams of intensity ～ 1022?W/cm2 and fluence?>?1?GJ/cm2 with the energetic efficiency of tens of percent. Laser-driven ion beams of such extreme parameters could open up new research areas in high-energy-density science, inertial fusion or nuclear physics. 相似文献