超短脉冲高次谐波谱的连续性

Continuum Analysis of High-order Harmonic Generation Spectrum by an Ultra-short Laser Pulse

研究超短脉冲（3个光学周期）高次谐波发射功率谱的性状及其成因。结果表明，短脉冲谐波谱与长脉冲（10个光学周期）相比，其平台区末端的谐波谱变得伪连续。这是由于3个原因导致该现象：（1）在短脉冲情形下，谐波的生成仅经历1-2次辐射，在长脉冲情形下，谐波的生成经历多次辐射的累加；（2）对于相同的谐波级次，短脉冲比长脉冲的谐波线宽宽；（3）短脉冲比长脉冲的激光频谱宽。

We investigated the high-order harmonic generation （HHG） power spectrum by means of an uhra-short laser pulse. Our numerical results show that the harmonics at the end of the plateau of HHG spectrum become successive compared with that of HHG spectrum by a long laser pulse. Three primary reasons cause this character： firstly, in the former, one or two irradiations contribute to the harmonic generation, while in the latter, tile muhi-cyele accumulation of the harmonic generation causes separate sharp peaks; secondly, for the same ttHG, the band width of the power spectrum of the former is wider than that of the latter; finally, the frequency spectrum of the short laser pulse is broader than that of the hmg laser pulse.