激光陶瓷基底上薄膜的激光损伤特性及机理研究

Laser coatings with high laser resistance are necessary for the applications of laser ceramics in the high-energy and high-repetition laser systems. However, studies on the laser induced damage about the laser ceramics are mainly focused on their bulk intrinsic damage thresholds and little has been reported about the coatings deposited on the laser ceramic substrates.This project will study on the laser damage characteristics and mechanisms of the coatings deposited on the laser ceramic substrates irradiated by the fundamental frequency laser in the nanosecond regime. The microstructures of the coatings will be analyzed from experimental and theoretical aspects, and the physical model about the influences of the microstructures on the laser damage resistance of the coatings will be put forward. Based on the investigations of the defect features and their damage behaviors of the coatings deposited on the laser ceramics, the laser damage characteristics determined by grain boundaries and pores of the laser ceramics will be shown and their damage mechanisms will be modeled. The above works will provide the theoretical basis and engineering instructions for the depositions of high-quality laser coatings on the laser ceramics as well as the preparations of the laser ceramics.

高抗激光损伤能力的薄膜是激光陶瓷作为增益介质应用于高能重频激光系统的必要前提之一。然而，目前激光陶瓷材料的损伤研究还主要集中在其体材料的本征损伤方面，对沉积于其上的激光薄膜的损伤研究还鲜有报道。本项目拟针对纳秒基频激光作用下激光陶瓷基底上薄膜的损伤特性进行基础理论和实验研究。通过对激光陶瓷基底上薄膜的微观结构的实验和理论分析，建模分析微观结构对其抗激光损伤能力的影响；基于对陶瓷基底上薄膜的缺陷特征和损伤特性分析，明确激光陶瓷基底上的晶界及气孔对薄膜损伤特性的影响，并对晶界及气孔诱导膜层损伤的机制建模分析。上述研究内容及研究结果将为激光陶瓷基底上高损伤阈值激光薄膜的制备和激光陶瓷基底的制备及加工提供理论依据和工程指导。

高损伤阈值的薄膜是激光陶瓷作为增益介质应用于高能激光系统的必要前提之一，然而目前激光陶瓷的损伤研究还主要集中在其体材料的本征损伤方面。本项目主要针对纳秒基频激光作用下激光陶瓷以及激光陶瓷基底上薄膜的损伤特性和力学特性进行了基础理论和实验研究（主要涉及YAG及LuAG激光陶瓷）。通过对目前国产激光陶瓷的损伤特性分析发现激光陶瓷的体损伤阈值低于表面损伤阈值，透过率越高，其体损伤阈值越高；通过对比激光陶瓷及其上薄膜的损伤特性，发现陶瓷基底镀制薄膜后，其表面损伤阈值高于陶瓷的体损伤阈值，并高于未镀制前的表面损伤阈值，这可能与薄膜与基底间的附着力有关；通过对熔石英、K9、晶体和陶瓷基底上HfO2薄膜的微观结构和力学特性进行对比研究，发现基底的晶态结构影响着其上薄膜的微观结构和力学特性，HfO2薄膜呈多晶态结构，单晶晶体与薄膜晶态差异较大，结合力较差，为3.99mN，而多晶陶瓷与薄膜晶态差异较小，结合力较好，为7.74mN。上述研究为陶瓷制备及陶瓷基底上激光薄膜的制备提供理论依据和工程指导。