热处理对低损耗高反膜特性的影响分析

Analysis of effects of thermal treatment on optical properties of low loss high reflective coatings

低损耗激光薄膜反射镜是环形激光器谐振腔的关键元件之一,首先设计和制备了工作角度为45°的低损耗高反膜。为了提高低损耗高反膜的光学性能,采用高温热处理的方式,研究了热处理对低损耗高反膜的透射率、散射系数、表面粗糙度、相移等特性的影响。高温热处理对高反膜的散射系数、表面粗糙度影响较小,随着热处理温度的增加,高反膜相移逐渐降低。当退火温度为550℃时,环形激光器输出性能稳定性最好,当工作230 h后,输出能量仅下降到初始值的90.5%。实验结果表明,采用合适的热处理方式,可以有效改善低损耗高反膜特性以及环形激光器的输出性能。

Low loss optical coatings mirror is the most critical elements for resonant cavity of ring laser. In this paper, low loss high reflective coatings working at the angle of 45° were designed and prepared. In order to improve optical properties of low loss high reflective coatings, high temperature thermal treatment was chosen and the impact of thermal treatment on transmittance, scattering, surface roughness and phase shift of low loss high reflective coatings was researched. The impact of thermal treatment on scattering and surface roughness was very low. With the increase of annealing temperature, the phase shift of low loss high reflective coatings reduced gradually. When the annealing temperature was 550, the optical stability of ring laser output energy was the best. After working for 230 hours, laser output energy dropped to 90.5% of its initial value. The results have shown that optical properties of low loss high reflective coatings and output energy properties of ring laser can be improved by the proper thermal treatment.