封闭管道中热耦合效应对激光传输的影响

Thermal coupling effects on laser propagaton in closed tube

建立了封闭竖直管道热耦合效应物理模型,采用流固耦合方法,数值模拟了封闭管道中介质气体、光学玻璃之间的热相互作用造成流场分布的变化,研究了热耦合作用对近场波前相差和远场光束质量的影响。数值模拟结果表明,光束质量可以由封闭管道内介质气体温度分布来决定,气体在管道内流动改变温度分布,使得相差分布不断变化,造成远场光束质量的振荡起伏;光学镜与介质气体热相互作用对流场分布有较大影响,尤其是竖直管道底部的光学镜对激光束远场光束质量影响明显。热耦合效应放大了光束质量的变化:当介质模型中光束质量变差,热耦合模型中热耦合效应使光束质量变得更差;当介质模型中光束质量变好,耦合模型中的热耦合作用使光束质量变得更好,即光束质量随着流场分布的变化而振荡。

A thermal coupling model between a medium gas and glasses in a vertical closed tube is established to study ther real effects on laser propagation. Using the thermal coupling method of gas and solid, the gas temperature distributions are simu- lated, which decide laser wavefront phase distributions in near field and laser beam quality in far field. It is shown that under gravity, gas temperature increase results in its flow in the tube, and the thermal coupling effects between gas and two glasses, one in the top and the other in the bottom, are important for gas temperature distribution, especially the bottom glass. Thus, laser wavefront phase distributions and beam quality change all along during laser propagation. Compared with not considering thermal coupling effects, the gas temperature distribution and beam quality in far field change much.