基于少周期激光脉冲与气体等离子体作用的太赫兹到中红外超宽带辐射产生

From terahertz to mid-infrared ultra-broadband radiation generated from few-cycle laser pulse interaction with gas plasma filament

超强少周期激光脉冲与气体等离子体作用可以产生强的宽带太赫兹脉冲辐射。本文以数值计算为主要工具研究了少周期激光脉冲与气体等离子体成丝作用产生的等离子体电流及对应的太赫兹辐射特性。该过程中的等离子体电离处于多光子电离和隧道电离的过渡阶段。结果显示,该机制能够产生从太赫兹到中红外的超宽带辐射,且辐射的电场振幅是少周期激光脉冲载波相位的周期函数。太赫兹脉冲由激光脉冲脉宽和等离子体电离的时间演化确定,而不是由等离子体密度决定。本文为基于少周期激光脉冲与气体等离子体作用产生超宽带太赫兹辐射的实验提供了一定的理论参考。

The strong few-cycle laser pulse interaction with the gas plasma filament can generate strong and broad⁃band terahertz radiation.Here,we investigate the detail of plasma current and its terahertz radiation produced by the few-cycle laser pulse interaction with the gas plasma based on the calculations.The ionization during the plas⁃ma filamentation is in the transition between the tunnel ionization and the multiphoton ionization.The results show that this scheme can generate ultra-broadband radiation from the range of terahertz to mid-infrared,and its amplitude is a periodic function of the carrier-envelope phase of the few-cycle laser pulse.The frequency of the terahertz pulse is determined by the duration of the laser pulse,the time evolution of ionization and the plasma cur⁃rent,rather than by the density of the plasma.This work might give a useful clue to carry out the experiment of ul⁃tra-broadband terahertz generation by the few-cycle laser pulse interaction with the gas plasma filament.