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

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.