被动调Q固体激光器上转换效应的数值模拟

Numerical Simulations of Upconversion Effects in Passively Q-Switched Solid-State Lasers

在主动调Q固体激光器上转换效应(ETU)理论的基础上,给出了包含上转换效应项的被动调Q固体激光系统的耦合速率方程组。采用变步长龙格-库塔数值方法,针对Nd∶YAG激光晶体和Cr4+∶YAG可饱和吸收体,对上转换效应对输出脉冲参数的影响进行了数值分析。在低抽运功率条件下,上转换效应对输出脉冲的能量和峰值功率影响较大;在高抽运功率条件下,上转换效应对平均输出功率影响较大。在抽运功率逐渐增加的过程中,上转换效应对输出脉冲能量和峰值功率的影响逐渐减弱,对输出激光的脉冲宽度(FWHM)和重复频率的影响则可以被忽略。数值计算结果与实验所得结果基本一致。

Based on the theories of the energy-transfer upconversion （ETU） effects in actively Q-switched solid-state lasers, coupling passively Q-switched rate equations including ETU parameters are established. The ETU effects in the Nd： YAG laser crystals and the Cr^4＋ ： YAG saturable absorbers are numerically simulated by a variation stepping Runge-Kuttaa method. The pulse energy and peak power are affected obviously at low pump power, and average power is affected obviously at high pump power. The effects of ETU on the pulse energy and peak power are decreased with the pump power increasing. And the effect to the pulse duration （full width at half maximum） and the repetition rate can be neglected with the pump power increasing. The numerical calculation results are coincident with the experiments .