Sapphire lenses, as excellent optical lenses, have good transmittance in the ultraviolet, infrared, and visible light bands, and can meet the requirements of multi-mode composite guidance. At the same time, sapphire window panels have excellent mechanical properties, chemical stability, and good high-temperature resistance, with high strength and hardness, which can meet the strict requirements of hypersonic missiles for transparent plates.

In terms of preparation, sapphire filters can be produced and then processed into shapes. The finished product has the same performance as the filter, while other components are mainly made by powder hot pressing and sintering, with slightly lower performance than the original. Therefore, sapphire filters have become a good choice for mid wave infrared transparent windows.

Performance requirements for infrared transparent windows:

1. High mechanical strength: Infrared transmission windows need to have 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 should not easily deliquescence;

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

5. Good optical performance, minimal light scattering, and uniform refractive index;

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

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 samples before and after coating was tested. The infrared transmittance performance of coated and uncoated sapphire samples after high temperature and rain 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 samples is significantly higher than that of uncoated sapphire samples; After rain erosion testing, the average transmittance qualification rate loss of the coated sapphire sample is very small, and the infrared transmittance of the coated sapphire is significantly higher than that of the uncoated sapphire.