基于不同非共线结构的光参量放大器的带宽特性研究

Bandwidth Investigation of Optical Parametric Amplifier in Different Noncollinear Geometries

研究了多种非共线结构下基于周期极化铌酸锂晶体的皮秒脉冲光参量放大器的调谐带宽和参量带宽特性,确定了当能够获得大且稳定的调谐带宽时应使用的最佳非共线结构、抽运光波矢和晶体光栅矢量间的最佳非共线角θ以及最佳极化周期,同时给出了用于计算不同温度下周期极化铌酸锂晶体的最佳极化周期的数学公式。此外,通过对相位失配进行泰勒级数展开,分别得到了保留一阶、二阶和三阶导数项时的参量带宽计算公式,随后将利用这些公式和相位失配表达式计算得到的参量带宽进行了对比,进而分析了高阶导数项对参量带宽的影响。在此基础上提出了一个用于最大化光参量放大过程的调谐带宽和参量带宽、确定非共线角α和工作温度等最佳工作参数的可行方案。

The tunable bandwidth and the parametric bandwidth of periodically poled LiNbO3 （PPLN） based on picosecond optical parametric amplifier with different noncollinear geometries are investigated theoretically and numerically. By utilizing an noncollinear geometry recommended by ourself and setting both the noncollinear angle between the wave vectors of the pump and the quasi-phase-matching grating and the grating period of PPLN at optimal values, broad and stable tunable bandwidth can be obtained. An expression is proposed to calculate the optimal grating period for PPLN. By expanding the wave-vector mismatch in a Taylor series and retaining terms through first order, second order and third order, respectively, three equations are presented to determine the parametric bandwidth. The results calculated from these equations are analyzed and compared with that calculation by employing the wave-vector mismatch directly, and then the effect of high order series on the parametric bandwidth is studied. At the end, a feasible scheme is presented to determine the working temperature and noncollinear angle a, maximize the tunable bandwidth and parametric bandwidth, and simplify the experimental operation.