LiB3O5晶体上四倍频增透膜设计

采用矢量法设计了三硼酸锂（LiB3O5，LBO）晶体上1064nm、532nm、355nm和266nm四倍频增透膜．结果表明，在1064nm、532nm、355nm和266nm波长的剩余反射率分别为0．0019％、0．0031％、0．0061％和0．0047％．根据容差分析，薄膜制备时沉积速率准确度控制在＋6．5％时，基频、二倍频、三倍频和四倍频波长的剩余反射率分别增加至0．24％、0．92％、2．38％和4．37％．当薄膜材料折射率的变化控制在＋3％时，1064nm波长的剩余反射率增大为0．18％，532nm、355nm和266nm波长分别达0．61％，0．59％，0．20％．与薄膜物理厚度相比，膜层折射率对剩余反射率的影响大．对膜系敏感层的分析表明，在1064nm和266nm波长，从入射介质向基底过渡的第二层膜厚度变化对剩余反射率的影响最大，其次是第一膜层．在532nm和355nm波长，从入射介质向基底过渡的第一和第四膜层是该膜系的敏感层．误差分析也表明，薄膜材料的色散对特定波长的剩余反射率具有明显影响，即1064nm、532nm、355nm和266nm波长的剩余反射率分别增加至0．30％、0．23％、0．58％和3．13％．

1064 nm, 532 nm, 355 nm, 266 nm frequency-quadrupled antireflection (AR) coating is designed on LiB<inf>3</inf>O<inf>5</inf> (LBO) substrate using vector method. The design result shows that the reflectance at wavelength of 1064 nm, 532 nm, 355 nm and 266 nm can be 0.0019%, 0.0031%, 0.0061% and 0.0047%, respectively. According to tolerance analysis, the reflectance increases to 0.24% at 1064 nm, 0.92% at 532 nm, 2.38% at 355 nm and 4.37% at 266 nm when the precision of deposition rate is controlled to be +6.5%. If the refractive index accuracy is +3%, the reflectance reaches 0.18% at 1064 nm, 0.61% at 532 nm, 0.59% at 355 nm and 0.20% at 266 nm, respectively. The refractive index has more effect on the reflectance of the AR coating than the thickness. From the incident medium to the substrate, the variation of the second layer's thickness has the most obvious effect on the reflectance of the AR coating at 1064 nm and 266 nm, secondly is the first layer. At 532 nm and 355 nm, the first and forth layers are the sensitive layers of the AR coating design. The reflectance of the AR coating at 1064 nm, 532 nm, 355 nm and 266 nm increases to 0.30%, 0.23%, 0.58% and 3.13%, respectively due to the dispersions of the coating materials.