吸收杂质热辐射诱导光学薄膜破坏的热力机制

光学元件的破坏是限制高功率激光系统发展的主要问题,理解光学元件的破坏机制对于高功率激光系统的设计、运行参量选择以及器件技术发展有重要影响。以热辐射模型为基础研究了杂质吸收诱导光学薄膜破坏的热力过程。研究发现薄膜发生初始破坏所需时间很短,脉冲的大部分时间是引起薄膜发生更大的破坏。在考虑吸收杂质发生相变的情况下,计算了吸收杂质汽化对薄膜产生的蒸汽压力,论证了薄膜发生宏观破坏的可能性。此模型能很好地解释光学薄膜的平底坑破坏形貌。

The damage of optical elements is a main limiting factor for a large laser system. The understanding of damage mechanisms can promote system design, choice of operational parameters and technology development. Thermodynamics damage of optical coatings induced by absorbing inclusions was studied based on thermal irradiation model. It is shown that the initial damage time of optical coatings during a laser pulse is very short and the most part of the laser pulse generates larger damage. Considering the phase change of absorbing inclusion, we calculated the gas pressure exerting on coatings due to the gas phase change of absorbing inclusion and discussed the possibility of the macro damage of optical coatings. This model can well interpret the flat bottom pit damage morphology of optical coatings.