Design of 1064 nm, 532 nm, 355 nm frequency-tripled antireflection coating for LBO

1064 nm, 532 nm, 355 nm frequency-tripled antireflection (AR) coating was designed on LiB3O5 (LBO) substrate with vector method. The design result showed that the residual reflectivity at wavelength of 1064 nm, 532 nm and 355 nm could be 0.0017%, 0.0002% and 0.0013%, respectively. According to error analysis, the reflectivity increased to 0.20% at 1064 nm, 0.84% at 532 nm and 1.89% at 355 nm when the precision of deposition rate was controlled at + 5.5%. If the refractive index accuracy was + 3%, the reflectivity reached 0.20% at 1064 nm, 0.88% at 532 nm and 0.24% at 355 nm, respectively. The refractive index had more effect on the residual reflectivity of the antireflection coating than the physical thickness. From the incident medium to the substrate, the thickness variation of the second layer had the most effect on the reflectivity of the antireflection coating at 1064 nm and 355 nm, followed by the first layer, and the layer next to the substrate was most insensitive. At 532 nm, the first and third layers were the sensitive layers of the antireflection coating design. The reflectance of the antireflection coating at 1064 nm, 532 nm and 355 nm increased to 0.15%, 0.31% and 1.52%, respectively due to the dispersion of the coating materials.