相位—啁啾调控对高次谐波光谱的影响

Effect of phase-chirp modulation on high order harmonic spectrum

理论研究了在激光相位和啁啾调控共同影响下高次谐波光谱的变化.结果表明:当激光相位为0时,一阶啁啾调控使谐波能量延伸.二阶啁啾调控会呈现高强度谐波平台区.当激光相位为0.5π时,一阶啁啾调控可以获得连续平台区,但是强度较弱.在二阶啁啾调控下,谐波能量得到明显增大.通过谐波时频分析给出了不同激光波形下产生高次谐波光谱的原因.

The change of high order harmonic spectrum under the influence of laser phase and chirp modulation is theoretically studied. The results show that when the laser phase is 0,the first order chirp modulation makes the harmonic cutoff energy extend. Second order chirp modulation presents high-intensity harmonic plateau.When the laser phase is 0. 5π,although the harmonic plateau can be obtained by first order chirp modulation,the intensity is weak. Under the control of second order chirp modulation,the harmonic cutoff energy remarkably increases. Through using the time-frequency analyses of harmonics,the reason for producing high order harmonic spectrum under different laser waveforms is given.