大口径高能量激光测量中后向散射能量研究

Research of backscattered laser energy within the energy measurement for large caliber high energy lasers

锥形吸收腔高能量激光能量计测量过程中的后向散射能量分布是影响测量准确度的一个关键参量。依据锥形腔能量计内表面与入射激光相互作用的光学定律,推导了能量计内入射激光光束能量的分布函数;并结合复化辛普森数值计算方法,计算分析了当能量计反射系数一定,而入射激光光束直径与吸收腔直径之比不同时,锥形吸收腔开口处光功率密度分布和后向散射总功率。计算结果表明,对于大口径高能量激光,后向散射能量损失将达到0.5%至2.5%左右。根据后向散射光功率密度分布计算得到后向散射总能量,对测量结果进行修正,将有效改善高能量激光能量测量准确度。

Backscattered laser energy profile is very important parameter in a cone-shaped laser energy meter because it affects the measurement precision of the instrument. From the reflection rule of laser in the surface of energy meter obeyed, the distribution function of power of laser beam in energy meter surface is deduced. Using the Simpson numerical calculation method, the distribution of laser power density in the opening of absorption body and the total backscattered laser power are obtained when the reflective index is fixed but the ratio of laser diameter and absorption cavity diameter is changed. The calculation results show that the backscattered energy loss is up to 0.5% - 2.5% for a large caliber high energy laser. According to the backscattered laser power density profile,total backscattered laser energy can be gotten to compensate the measurement result, which will greatly improve the accuracy of high energy laser energy measurement.