论文部分内容阅读
为了研究高功率激光系统中的内光路热变形累积效应对光束质量的影响，开展了理论和实验研究。首先，选择三种非稳腔输出的典型高功率激光，激光功率分别为10 kW、50 kW和100 kW，通过热动力学瞬态方法的有限元分析对激光照射的反射镜进行热变形分析。然后，利用光线追迹理论得到激光的波前像差。最终，激光远场光束质量中的Strehl比，因子可以通过Fresnel衍射积分进行计算和对比分析。仿真结果表明，由于内光路反射镜的热变形，远场光束将出现偏心和像散的现象，其中心光强及会聚能力均会下降。随着内光路反射镜的增加，Strehl比减少而因子增加，远场光斑x方向的倾斜、像散及彗差也会逐渐增加，将成为系统的主要像差。为了和上述理论仿真结果进行对比，建立了一个测量反射镜热变形实验平台，实验中采用10 kW的TEA CO2激光器照射99%反射率的铜反射镜，通过等效放大原理，实验结果可以部分代替50 kW和100 kW功率水平。镜面热变形的测量精度小于/15，并和仿真结果吻合得较好。结果表明，反射镜的热变形在激光功率超过10 kW时不能被忽略，且随着激光功率及反射次数的增加，这种热畸变将变得越发严重。所得结果将对高功率激光系统的热畸变分析过程提供指导，并可应用于激光核聚变及激光武器系统等的设计分析中。“,”In order to research the influence on the beam quality due to cumulative effect of the inner channel thermal deformation in the high energy laser system, the theoretical simulation and experimental study were performed. Firstly, three typical laser power 10 kW, 50 kW and 100 kW with the unstable resonator were selected to analyze thermal deformation of mirror through the finite element analyze of thermodynamics instantaneous method. Then the wave front aberration could be calculated by ray-tracing theory. Finally, Strehl ratio, parameter of far-filed beam can be calculated and comparably analyzed by Fresnel diffraction integration. The simulation results show that due to the effect of inner channel thermal deformation, eccentric phenomenon and astigmatism of far-filed beam emerge, and peak power and the focused ability decrease. With the increasing of reflection times, Strehl ratio decreases and parameter increases, and tilt, astigmatism and coma of x direction gradually increase, which become the main aberration. Comparing with above theoretical simulation study, the thermal deformation experimental platform was built to measure the single copper mirror of 99% reflectivity with the 10 kW TEA CO2 laser. Through the equivalent scale rule, the experimental results can also represent the 50 kW and 100kW power level. The measurement precision of thermal deformation of mirror is smaller than /15 and agree well with the simulation results. The results show that the thermal deformation of mirror cannot be neglected when the laser power great than 10 kW and has a great influence on the far-field transmission properties with the power increasing and reflection times. These results can also provide the reference to the thermal aberration analyze for high power laser system and can be applied to the field of laser nuclear fusion and laser weapon etc.