光路交叠对强光传输的影响

Thermal Effects on Laser Beam Due to Superposition of Beam Path

实验中观察到高能激光束通过光程总长、气体环境等条件相同,但局部布置不同的光路后,其接收光斑峰值功率密度、波前离焦和高阶像差等光束参量有差异.对此问题,选择Z型和X型两种总长度相等的光路在相同气体环境下进行了数值研究.结果表明,产生上述差异的主要原因是由于两种光路中光束交叠区域大小和形状不同引起的气体热效应产生的附加相位有所不同.而且对不同特性的光束,该差异也不同.对高斯光束,两种光路中气体热效应对光束影响的差异较小;对平顶高斯空心光束,两种光路中气体热效应对光束影响的差异较明显.因此,为抑制气体热效应对光束的影响,在考虑其它因素的同时,应尽可能减小光路中的光束交叠区域.

It was seen in experiment that when high power density laser propagating through different path with same total length and gas environment but different position of reflecting mirror, some parameters such as the peak energy density,wave front defocus and high-order aberration were different. To research this phenomenon,a numerical study of laser beam propagating through a X-shape and a Z-shape path in air with same total length was carried out. Results show that the difference referred above caused by the different summations and shapes of superposed areas on beam path. The difference mainly behave as the decreasing of the peak energy density and the increasing of the wave front defocus and high-order aberration in the X-like beam path in which the superposed areas is bigger. It was greater to super-Gaussian beam than to Gaussian beam. In order to depress the gas thermal effects on laser propagation,it should be considered to minimize the superposed areas in belm path