飞秒光参量放大中三波群速失配的补偿

为了消除群速失配对参量放大的不利影响，描述了利用脉冲波面倾斜与非共线相位匹配相结 合，完全补偿飞秒光参量放大（OPA）中三波群速失配的新方法.计算了在BBOⅠ类、Ⅱ类相 位匹配条件下， 三波实现群速匹配时，相位匹配角、脉冲波面倾斜角以及非共线角随信号 光波长的变化.并分析了三波群速匹配对空间走离长度、参量增益和参量带宽的影响.结果表 明，在BBOⅠ类、Ⅱ类相位匹配条件下，利用该方法均能实现飞秒OPA连续调谐时三波的群速 匹配，从而大大增加了三波的有效互作用长度，为能够获得高增益，窄脉宽的参量光脉冲提 供了理论依据和指导. 关键词： 群速匹配 脉冲波面倾斜 非共线相位匹配 飞秒光参量放大

Compensation of group velocity mismatching of three pulses in femtosecond optical parametric amplification

For avoiding adverse effect arising from group velocity mismatching in parametri c amplification, a new method is presented, in which we combine pulse front slan t and noncollinear phase matching to completely compensate group velocity mismat ching of three pulses, in femtosecond optical parametric amplification (OPA). Th e change of the phase matching angle, the pulse front slant angle and the noncol linear angle with the signal wavelength are calculated, when group velocity matc hing of three pulses is achieved in BBO crystal type_Ⅰ and type Ⅱ phase matching configurations. The effect of group velocity matching of three pulses on the spatial walk_off length, the parametric gain and the parametric bandwidth is analyzed. The results indicate that, using this method can make matching of gro up velocities of three pulses, when tuned continuously in both BBO type_I and Ⅱ phase matching femtosecond OPA, and thus the effective interaction length of th ree pulses is increased considerably. This calculation method and the analysis r esults provided a theoretical guidance for obtaining parametric pulses with high er gain and shorter duration.