连续面形分立驱动变形镜(CFDA-DM)是自适应光学系统中最重要的器件。在高能激光系统中, 此种变形镜(DM)很容易产生热变形,这对DM的补偿能力和输出光束质量有较大影响。通过构建实验平台对DM热变形进行研究, 利用功率为2.5 kW的激光对DM镜面连续辐照130 s, 镜面波前峰谷值(dPV)由辐照前的0.0806λ增长到0.5423λ, 面形像差中高阶成分有0.1220λ, 低阶成分主要是离焦和像散。利用DM将波前dPV为0.4853λ的0°像散补偿到dPV为0.0707λ后再用功率为2.5 kW的激光对DM镜面连续辐照180 s, 此时波前dPV由0.0707λ增加到0.7548λ, 其中高阶成分有0.2487λ。可见热变形不但产生低阶像差, 还产生较大成分的高阶像差。此高阶像差不能用DM自身进行校正, 是影响高能激光系统输出光束质量的重要因素。

Continuous faceplate discrete actuator deformable mirror (CFDA-DM) is the most important device in adaptive optics. In high power laser systems, this kind of deformable mirror (DM) is apt to produce thermal deformation, which can seriously affect the compensation ability of DM and the output beam quality. Experimental platform is set up to study DM thermal deformation. In the experiment, when DM is continuously irradiated by 2.5 kW laser for 130 s, the peak-to-valley value (dPV) of wavefront increases from 0.0806λ (before irradiation) to 0.5423λ, the higher order aberration of faceplate is 0.1220λ, and the low order aberration is mainly defocus and astigmatism. After dPV of a zero degree astigmatism is compensated from 0.4853λ to 0.0707λ, DM is irradiated by 2.5 kW laser for 180 s again. In consequence, the dPV of wavefront increases from 0.0707λ to 0.7548λ, and the higher order aberration of wavefront is 0.2487λ. The above results show that the thermal deformation does not only lead to lower order aberration, but also produce higher order aberration, which cannot be compensated by DM itself. The higher order aberration is the key factor that influences the output beam quality of high power laser systems.