Ge 基底LaF₃-ZnS-Ge 高耐用中波红外增透膜

Evaporation characteristics and optical constants of LaF₃ materials in 2.5-12 μm infrared band were investigated. With low refractive index LaF₃ materials, high-durability antireflection (AR) coatings in 3.7-4.8 μm medium-wavelength infrared bands were designed and fabricated on Ge substrate. SEM image of the AR coatings with the LaF₃ shows that the surface nanocrystals is uniform and densified. The measured optical properties by Fourier tranform infrared spectrometer indicate that the peak transmittance is as high as 99.4%, and the average transmittance increases to 98.8% from 47.7% in 3.7-4.8 μm after double-sided coating. The firmness and durability environmental tests signify that this AR coating can work in harsh environment while maintaining good optical properties.