BBOⅡ类共线相位匹配结构中群速失配的补偿

Compensating Group Velocity Mismatch in BBO Type-Ⅱ Collinear Phase-Matched Configuration

为了消除群速失配对飞秒光参量放大(OPA)的不利影响,描述了在Ⅱ类共线相位匹配的飞秒BBO光参量放大中,同时倾斜抽运光和信号光的脉冲波面完全补偿三波群速失配的方法。理论计算了三波群速匹配时,相位匹配角、抽运光和信号光的脉冲波面倾斜角随信号光波长的变化。并分析了三波群速匹配对抽运光光斑尺寸的要求和对参量带宽的影响。结果表明,利用该方法不仅能够完全补偿飞秒BBO光参量放大在连续调谐时三波的群速失配,而且能够实现最大的参量带宽。此外,选取合适的抽运光光斑尺寸对提高参量增益至关重要。

In order to avoid adverse effect arisen from group velocity mismatch in femtosecond optical parametric amplification (OPA), a method that compensates completely the group velocity mismatch among three waves is presented, by tilting simultaneously wave fronts of pump and signal pulses, for femtosecond OPA in β-BaB_2O_4 (BBO) type-Ⅱ collinear phase-matched configuration. When the group velocities of three waves are matched, the variations of the phase-matched angle and the wave front tilting angles of pump and signal pulses with the signal wavelength are calculated theoretically, and the effects on the pump beam size and the parametric bandwidth are analyzed. The results indicate that this method not only can match completely group velocities among three waves, but also can achieve maximal parametric bandwidth for continuous tunable femtosecond BBO OPA. In addition, for increasing parametric gain, it is very importance to appropriately choose the pump beam size.