大口径光学红外望远镜是我国天文学领域的国之重器。钠导星激光技术是提高大口径望远镜的灵敏度和空间分辨率的关键，LBO晶体薄膜技术是钠导星激光器的核心技术。随着准连续长脉冲钠导星激光发展，晶体薄膜的各向异性裂纹、熔融状损伤和光学性能退化是瓶颈问题。本项目提出薄膜-晶体-薄膜系统研究理念，开展多层膜设计方法与损伤机理、多层膜光学性能的退化规律、薄膜各向异性裂纹产生的机理和控制、以及多层膜吸收和应力调控制备技术等研究。创新性提出晶相转化与应力耦合诱导裂纹损伤机理、离子束溅射(HfO2)x(Al2O3)1-x新型薄膜材料、亚微米量级节瘤缺陷的控制等，解决限制钠导星激光器技术发展的瓶颈问题，研制出高损伤阈值晶体薄膜（λ=1064nm,重频500Hz,单脉冲~1J,脉宽~150μs,损伤阈值>20MW/cm2,工作时间>20min）。本项目对我国钠信标激光技术和大口径光学望远镜的发展具有重要科学意义。

Large aperture optical infrared telescope is one of the most important instruments in our country to occupy the commanding height in astronomy field. Sodium-guided star laser technology is the key to improve the sensitivity and spatial resolution of large aperture telescope. The technology of LBO crystal thin film is the core technology of sodium-guided star laser. With the development of quasi-continuous long pulse sodium-guided star laser, anisotropic cracks, melting damage and optical degradation of thin film on the crystal surface are bottleneck problems. In this project, the concept of systematic research on the integrated structure of thin film-crystal-thin film is put forward, the design method and damage mechanism of multilayer film, the degradation rule of optical properties of multilayer film, the generation mechanism and control of anisotropic crack in thin film, and the preparation technology of multilayer film absorption and stress control are carried out. The mechanism of crack damage induced by crystal phase transformation and stress coupling, the new (HfO2)x(Al2O3)1-x thin film materials prepared by ion beam sputtering technology, the control of sub-micron nodular defects are proposed to solve the bottleneck problem of limiting the development of sodium-guided star laser technology, and the crystal thin films with high damage threshold (λ=1064 nm, the repetition frequency of 500 Hz, the single pulse energy ~ 1J, the pulse width ~150μs, the laser damage threshold > 20MW/cm2, the working time > 20min) would be manufactured. This project has important scientific significance and application value for the construction of sodium beacon laser technology and large aperture infrared optical telescope in our country.