Sapphire window plate is an ideal multispectral broadband window material. Compared with ordinary broadband window materials, it has many excellent mechanical and optical properties and is suitable for laser instruments, optoelectronic devices, window materials, etc. SiO2 thin films were prepared on sapphire substrates using sputtering method, and the infrared transmittance of sapphire products before and after coating was tested. The infrared transmittance performance of coated and uncoated sapphire products after high temperature and rainwater erosion was tested and analyzed. The results showed that after coating SiO2 film on sapphire substrate, the infrared transmittance was significantly improved.

At high temperatures, SiO2 thin films still have good anti reflection effects, and the average transmittance of coated sapphire window plates is significantly higher than that of uncoated sapphire; After rainwater erosion testing, the average transmittance qualification rate of coated sapphire products has little loss, and the infrared transmittance of coated sapphire is significantly higher than that of uncoated sapphire.

Performance requirements for infrared transparent windows:

1. High mechanical strength: Infrared transmission windows require high strength to withstand decompression loads during high-speed motion.

2. Good thermal stability: The infrared window on the head should be able to withstand the temperature effects caused by aerodynamic heating and height changes, and the transmittance and refractive index should not change significantly with temperature changes.

3. Good chemical stability: When exposed to air, the infrared transparent window should be able to prevent corrosion from salt solutions or corrosive gases in the atmosphere, and not easily deliquescent.

4. High optical transmittance: capable of effectively transmitting radiation in the ultraviolet to mid infrared wavelength range.

5. Good optical performance: small optical scattering and good uniformity of refractive index.

6. Can meet the requirements of large-sized windows.

Sapphire window plates have good transmittance in the ultraviolet, infrared, and visible light bands, which can meet the requirements of multi-mode composite guidance. Meanwhile, sapphire filters have excellent mechanical properties, chemical stability, and high temperature resistance. It has good performance, high strength and hardness, and can meet the requirements of the transparent plate at the same time.