高功率激光放大器反激光能流分布的模拟

Simulation analysis for backward-reflected laser in high power laser amplifier

从Frantz-Nodvik模型出发,采用包含弛豫作用的速率方程组,将放大器对反激光的放大当作多程放大处理,模拟计算了光路中反激光的能流分布。光路为钕玻璃放大系统,激光脉宽1.0 ns,输出能量2.5kJ。放大器剩余增益的较大差异导致光路中各个元件反激光能流密度分布显著不同。与使用1级φ70 mm棒状放大器相比,采用2级φ70 mm棒状放大器时反激光能流相对集中,具有潜在的破坏危险。

Based on the Frantz-Nodvik physical model, the energy fluence of backward-reflected laser in a high power laser amplifier has been investigated by solving the rate equations in consideration of relaxation between lower and upper laser states. The laser chain is composed of Nd-doped phosphate glass amplifiers that can provide 2.50 kJ with the pulse duration of 1.0 ns. Due to the considerable difference of remaining gain in laser amplifiers, the energy fluence is significantly different. Compared with that utilizing one amplifier with the diameter of 70 mm, the laser chain including two may take a bigger risk of being destroyed.