基于光学薄膜与环境因素的耦合过程及激光与光学薄膜相互作用的热力损伤过程，分析了真空环境下光学薄膜激光损伤的本征机制。研究显示，真空环境下水的解析引起了电子束沉积的多孔薄膜孔隙率的释放，使得电子束沉积的多孔薄膜折射率及热导率降低，最终导致了薄膜热力损伤过程的加剧，导致了电子束沉积的多孔薄膜在真空环境下损伤阈值极大地降低。

The intrinsic damage mechanisms for optical thin film in vacuum environments is investigated through the inter- coupling process between optical film and environment and the thermal- mechanical damage process between laser and optical film. It is found that water vapor desorption of the film layers exposed to vacuum environment results in the decrease of the refractive index and the thermal conductivity of the film layer and hence leads to the serious decrease of laser- induced damage threshold for e- beam evaporated porous coatings in vacuum.