光谱相位相干技术测量飞秒脉冲的倍频误差

从理论上推导了第Ⅱ类相位匹配下宽带飞秒脉冲的二次谐波光场,分析输入飞秒脉冲的非共线相位匹配方式、脉冲带宽引起相位失配与群速失配对测量的影响。结果表明,为了消除飞秒脉冲的带宽影响,需要对测量记录的光强乘以一个调制因子;测量相位误差与非共线相位匹配的夹角和晶体长度成正比;相位失配与群速失配产生相位测量误差,且第Ⅱ类相位匹配方式下脉冲附加相位值较大;强度和相位误差需要在脉冲重建结果中补偿。

With type II phase matching, a detailed description of second-harmonic generation (SHG) for ultrabroad-band pulse was presented. The phase errors induced by noncollinear phase matching, phase mismatch and group-velocity mismatch for ultrabroad-band pulse were analyzed. The results show that it is necessary to multiply a modulation function for the recorded interferometric intensity to avoid the effect of pulses bandwidth. The phase error generated by bandwidth is proportional to the nonlinear crystal length and the beams intersect angle. The phase error generated by phase mismatch and group-velocity mismatch is relatively large with type II phase matching. The intensity and phase errors in the reconstructed pulses should be compensated.