BBO晶体Ⅱ类相位匹配光参量放大理论分析

理论研究了BBO晶体在Ⅱ类相位匹配下非共线情况时的参量放大特性。计算了在不同非共线夹角下的相位匹配角度。在增益谱分布的模拟计算中发现Ⅱ类匹配具有非常窄的增益带宽，并在其参量带宽的模拟计算中得到了证实。数值模拟了转换效率随晶体长度的变化曲线。分析了抽运光脉冲和信号光脉冲的时间不同步以及初始输入的信号光脉冲形状对转换效率的影响。选择最佳晶体长度和同步时间，最大转换效率可达到25％。研究结果表明BBO的Ⅱ类相位匹配具有非常窄的参量带宽和增益带宽，这对于窄带的激光参量放大的研究有重要意义，并拓宽了BBO晶体在光参量放大技术中的用途。

Theoretical Analysis of Type-Ⅱ Phase Matching Optical Parametric Amplification in BBO Crystal

The noncollinear optical parametric amplification of BBO (β-BaB2O4) type-Ⅱ phase matching is theoretically investigated. The phase matching angle is calculated under different noncollinear angles. It shows that BBO type-Ⅱ phase matching has very narrow bandwidth in the simulation of the gain spectrum, which is confirmed in the numerical calculation of the parametric bandwidth. The dependence of the parametric conversion efficiency on the crystal length is simulated. The effects of the non-synchronization of the pump-pulse and signal-pulse and the shape of the incident signal-pulse on the parametric conversion effciency are also discussed. The parametric conversion efficiency has a maximum of 25% corresponding to the optimized crystal length and synchronization. The results indicate that BBO type-Ⅱ phase matching has very narrow parametric bandwidth and gain bandwidth. The approach is useful to the study of the narrow band optical parametric amplification. It also makes BBO crystal more useful in the optical parametric amplification.