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光学薄膜的激光损伤阈值是评价其激光耐受性能好坏的一个重要指标。对薄膜激光损伤阈值的准确评价和测定,是判断其激光耐受性能和进行相互比对的基础。通过对激光损伤阈值测试系统误差的溯源分析和计算机模拟,给出了优化测试系统的方向。研究结果表明:在激光光斑确定的情况下,激光能量越高,能量密度的误差越大。因此在满足需要的情况下,应该尽可能选取较低的激光能量。在激光能量确定的情况下,存在一个临界光斑,当小于临界光斑时,能量密度误差变化非常剧烈,光斑越小,能量密度误差越大。测试系统的激光光斑大于临界光斑时系统的误差较小,小于临界光斑时系统的误差急剧变大。因此,在激光损伤阈值测试系统中,应该优选临界光斑或者大于临界光斑。激光损伤阈值拟合产生的最大误差为最大能级的激光能量误差,因此要尽可能降低激光器的脉冲能量。由此可见,设计合理的系统参数,可以最大程度降低测量结果的不确定度。
Laser damage threshold of optical thin film is an important index to evaluate its laser resistance. Accurate evaluation and determination of the laser damage threshold of the thin film is the basis for judging the laser resistance and mutual comparison. Through the traceability analysis and computer simulation of the laser damage threshold test system error, the direction of optimizing the test system is given. The results show that the higher the laser energy, the larger the error of energy density in the case of laser spot. Therefore, to meet the needs of the circumstances, it should be possible to choose a lower laser energy. In the case of laser energy, there is a critical spot, when less than the critical spot, the energy density error changes very intense, the smaller the spot, the greater the energy density error. When the laser spot of the test system is larger than the critical spot, the error of the system will be small. When the critical spot is smaller than the critical spot, the error of the system will increase drastically. Therefore, in the laser damage threshold test system, the critical flare should be preferred or larger than the critical flare. The maximum error of the laser damage threshold fitting is the laser energy error of the maximum energy level, so the pulse energy of the laser should be reduced as much as possible. Thus, the design of reasonable system parameters, can minimize the uncertainty of the measurement results.