光子学报, 2016, 45 (10): 1030002, 网络出版: 2016-11-14
双色激光偏振夹角对产生太赫兹辐射的影响
Terahertz Emission Dependence on the Polarization Angle between Two-color Lasers
摘要
基于改进的二维光电流模型,研究了双色激光偏振夹角对太赫兹辐射产生的影响.通过改变基频光以及其对应的倍频光的偏振夹角发现,在激光等离子体中辐射的太赫兹波的强度与双色激光的偏振夹角呈周期性变化,并且最佳偏振夹角和不同激光强度也有关系.在相对较低的激光强度下(≤2×1014W/cm2),当两束激光具备相同的偏振方向,即偏振夹角为0°时,太赫兹幅值达到最大;然而,当激光强度足够高(>2×1014W/cm2)时,最佳的偏振夹角会随着激光强度的增加而变大.从电子密度的角度来分析产生这种现象的原因,并用剩余漂移电流来揭示其潜在的物理机制.研究表明,剩余漂移电流是激光诱导等离子体产生太赫兹波的本质根源,对太赫兹波的产量起着决定性作用.
Abstract
The influence of the polarization angle between two-color lasers on the Terahertz (THz) emission was investigated based on a modified two-dimensional transient current model. By changing the polarization angle between the fundamental frequency laser and its second harmonic laser beam, it is found that, the emitted THz amplitude varys periodically with the chaning of the polarization angle in laser plasma, and the optimal angle is also changed with the different laser intensity. Under the comparatively low laser intensity (≤2×1014W/cm2), the THz amplitude can reach the maximum when the two-color lasers have the same polarization. However, the optimal angle will increase with the increasing of the total laser intensity when the laser intensity is high enough(>2×1014W/cm2). The electron density was firstly used to analyze this phenomenon under comparatively low laser intensity and then the residual drift current was utilized to reveal the underlying physical mechanism. It was found that, the residual current density is the essential source of the THz waves and which can determine the intensity of THz emission
谢军, 范文慧, 汤洁. 双色激光偏振夹角对产生太赫兹辐射的影响[J]. 光子学报, 2016, 45(10): 1030002. XIE Jun, FAN Wen-hui, TANG Jie. Terahertz Emission Dependence on the Polarization Angle between Two-color Lasers[J]. ACTA PHOTONICA SINICA, 2016, 45(10): 1030002.