周期性极化晶体的群速匹配飞秒脉冲光学参量放大

Femtosecond Optical Parametric Amplification with Group Velocity Matching for Periodically Poled KTP

研究了周期性极化晶体非共线参量放大的群速匹配和群速色散.提出了估算光学参量放大(OPA)光谱带宽的一般性方法.光谱带宽由波矢失配中泰勒级数展开式的第一、第二项决定,当展开式中一级项为零时,三个非共线相互作用波是群速是匹配的,这时参量带宽由群速色散决定.选择合适的光栅周期,能获得调谐范围较宽的群速匹配脉冲参量放大,参量带宽与晶体长度、非共线角及群速色散有关.研究了增益带宽与晶体长度及抽运光强度的关系,也研究了离散角和有效非线性系数等.由于群速匹配,参量带宽很大,大大增加了最大有效长度和能量转换效率.

The group velocity matching and group velocity dispersion have been investigated for noncollinear optical parametric amplification with periodically poled KTiOPO4 （KTP）. A general mathematic model for evaluating the spectral bandwidth of optical parametric amplification （OPA） is developed. The spectral bandwidth is determined by expanding the wave vector mismatch in a Taylor series and retaining terms through second order. If the first-order term vanishes, noncollinear interaction tree waves are group matching. And the spectral bandwidth is determined by group velocity dispersion. The dependences of gain bandwidth on crystal length and pump intensity are also studied. Selecting appropriate grating period, wider tunable range can be obtained with group velocity matching. The parametric bandwidth is relating to crystal length, noncolinear angle, group velocity and group velocity dispersion. Because group velocity is matched, the parametric bandwidth is very large. The effective nonlinear coefficient is nearly equal to d33. And maximum effective length and conversion efficiency are enhanced largely.