基于准相位匹配晶体的宽带可调谐光参量放大过程研究

系统分析了基于准相位匹配晶体的光参量放大过程中极化周期和非共线结构对信号光调谐带宽的影响.提出了最大极化周期的概念，用于描述非共线相位匹配和群速度匹配同时满足时晶体的极化周期所能达到的最大值,给出了用于计算不同温度下周期极化铌酸锂晶体的最大极化周期的数学公式，并确定了宽带可调谐光参量放大过程应使用的最佳非共线结构.当采用此非共线结构时,通过将晶体的极化周期设定为最大极化周期可以在相对最大的波长范围内实现信号光的调谐放大输出.在此基础上提出了一个用于最大化光参量放大过程的信号光调谐带宽、确定工作温度等最佳工作参数以及简化实验操作方法的可行性方案.最后对最大极化周期和非共线结构对光参量放大的参量带宽的影响进行了研究. 关键词： 光参量放大 极化周期 非共线结构 带宽

Broadband tunable pulses in quasi-phase-matched crystal based optical parametric amplification

The influence of grating period and noncollinear geometry on the broadly tunable bandwidth of optical parametric amplification are investigated theoretically and numerically for quasi phase matched crystal. The concept of maximum grating period is proposed to achieve the phase matching and group velocity matching simultaneously in a wide range. By employing the maximum grating period, geometry Ⅰ is recommended due to the much wider signal tunable range compared with geometry Ⅱ. An expression is proposed to calculate the maximum grating period for congruent periodically poled LiNbO₃ with 800 nm pump wave. A feasible scheme is presented to determine the working temperature and noncollinear angle α, maximize the tunable range and simplify the tuning by rotating angle θ only. Finally, the parametric bandwidth is studied with consideration of the influences of the maximum grating period and noncollinear geometry.