超短脉冲高次谐波谱的截止频率分析

Cutoff Frequencies analysis of high-order harmonic generation spectra by ultra-short laser pulses

本文数值计算了超短脉冲(脉冲持续时间为两个光学周期)的高次谐波发射功率谱.研究结果表明,超短脉冲谐波谱的截止频率不再符合IP+3.17UP的截止规则(IP为原子电离势,UP为有质动力能).对此,本文采用"三步"模型给出了合理解释,并用小波变换验证了结果的正确性.

We investigated the high-order harmonic generation （HHG） power spectra from a one dimensional model atom irradiated by ultra-short laser pulses whose duration is two optical cycles. Our numerical results showed that the cutoff frequencies of the HHG spectra don＇t accord with the cutoff formula IP ＋ 3.17Up（ IP is the ionization potential, Up is the ponderomotive energy）. As to this character, a reasonable explanation by ＂three-step＂ model is presented, and the result agreed well with the quantum calculation by the wavelet timefrequency analysis.