表面层对1064nm高反射镜损伤阈值影响

Influence of outmost layer on laser induced damage threshold of 1064nm high-reflection mirrors

采用电子束蒸发的方法制备了3种具有不同表面层材料及结构的中心波长为1 064 nm的零度高反镜,3种膜系表面层分别为1/4波长光学厚度的HfO2,1/2波长光学厚度的SiO2,以及1/4波长光学厚度的SiO2。光谱测试表明:三者在1 064 nm处均有较高的反射率(高于99.8%),利用热透镜的方法测量得到3个膜系辐照激光正入射情况下,薄膜对光的吸收比例分别为3.0×10-6,5.0×10-6和6.5×10-6,其损伤阈值分别为32.5,45.2和28.4 J/cm2。并在膜层内部电场分布和膜层材料物理特性的基础上分析了3种不同表面层膜系吸收和损伤阈值差别的原因。

Electron beam evaporation method was applied to deposit three sets of 1 064 nm laser mirrors with different outmost layers： quarter-wavelength HfO2,half-wavelength SiO2 and quarter-wavelength SiO2 layers,respectively.High reflectivity（more than 99.8%） has been achieved for all the stacks,and irradiated at normal incidence photothermal measurements of absorption are 3.0×10-6,5.0×10-6 and 6.5×10-6,respectively.Corresponding laser induced damage thresholds（LIDTs） are 32.5 J/cm2,45.2 J/cm2 and 28.4 J/cm2.The relations of electric field distribution,absorption,layer material characters and LIDT are also discussed.