中红外高功率激光系统强光元件热损伤特性

Thermal damage mechanism of the optical element used in mid-infrared high power laser system

依托闭腔式氟化氘中红外高能激光器,测量了元件表面污染物在连续波高能激光(3.16 k W/cm2)辐照下的温度,测量发现污染物在1s内达到了热平衡,温度维持在1 720 K;建立了描述强光辐照下污染物热平衡过程的物理模型,分析了污染物导致强光元件热损伤的物理机制;研究发现污染物的尺度对强光元件的热损伤具有重要影响.对于中红外高反射强光光学元件,若污染物的尺度小于20μm一般不会造成强光元件的损伤,若污染物的尺度大于200μm一般会导致强光元件的损伤.研究结果对于提高强光元件的抗损伤性能,保障中红外高能激光系统稳定运行具有重要意义.

Based on the closed-cavity mid-infrared laser, the temperature of the contaminant was meas- ured when it was irradiated by a cw high energy laser with power intensity 3.16 kW/cm^2. It was found that the contaminant achieves thermal equilibrium in a second and then the temperature stays at 1720 K. A physical model was established to describe the process of the thermal equilibrium. The mechanism of the mirror＇ s thermal damage was analyzed. It shows that the contaminant size plays an important role in the thermal damage of the optical mirror. Only when the contaminant size is smaller than a critical size （ -20μm）, the contaminant may reach thermal equilibrium and the optical mirror work well in the high energy laser system. If the contaminant size is quite large （ 〉 200μm）, the optical mirror will be damaged under the irradiation of high energy laser. The results are of great help for improving the anti-damage capability of the mirror and maintaining the security of the high energy laser system.