飞秒脉冲测量过程的光路精确调节理论分析研究

Theoretical analysis of optical path accurate adjustment in femtosecond pulse measurement process

针对单发次飞秒激光脉冲波形的测量,入射光夹角和晶体的偏转姿态是光路精确调节中的关键影响因素,为了精确描述入射光夹角和晶体的偏转与输出自相关信号的关系,我们对和频过程进行理论分析和推导。文中对入射光夹角的取值范围进行数学推导和计算,并定量分析了输出的自相关信号与晶体的姿态的关系。结果表明,要满足位相匹配条件,入射夹角存在一个最小值为30.114°;产生的自相关信号输出方向对晶体的转动姿态不敏感,输出强度对参与耦合的两入射光束的夹角敏感;对晶体的转动姿态容量较大,且晶体越薄越不敏感;自相关信号的时间分辨力由晶体内参与耦合的两入射光束的夹角决定,改变晶体外的夹角不会改变时间分辨力。

For the measurement of single shot femtosecond laser pulse,to describe the influence of incident angle and crystal rotation on the output signal accurately,the third harmonic process is analyzed and deduced.In this article,the range of the angle of incident light is derived and calculated mathematically.At the same time,the relationship between the output autocorrelation signal and the crystal’s attitude is analyzed quantitatively.The results show that,to satisfy the phase matching condition,the minimum value of the incident angle is 30.114°.The output direction of the autocorrelation signal is insensitive to the rotation of the crystal.However,the output intensity is sensitive to the intersection angle of two incident beams.The capacity of the crystal rotation is large,and the thinner the crystal is,the less sensitive it is.Moreover,the time resolution of the correlation signal is determined by the angle between the two incident beams in the crystal,the change of the angle outside the crystal does not change the time resolution.The study has reference value for the precise adjustment of femtosecond laser pulse measurements.