Sapphire windows serve as an ideal multispectral window material due to their superior mechanical and optical properties compared to conventional materials. These properties make sapphire suitable for applications in laser instruments, optoelectronic devices, and window materials. In this study, SiO2 films were deposited on sapphire substrates using a sputtering method. The infrared transmittance of the sapphire products was measured both before and after coating. Additionally, the infrared transmittance of coated and uncoated sapphire samples was evaluated following exposure to high temperatures and rain erosion. The results indicate that the infrared transmittance of the sapphire substrate is significantly enhanced after the application of the SiO2 film.

At high temperatures, the SiO2 film exhibits a significant anti-reflection effect, and the average transmittance of the coated sapphire window is notably higher than that of the uncoated sapphire. Following the rain erosion test, the average transmittance of the coated sapphire products exhibited minimal loss, and the infrared transmittance of the coated sapphire was found to be significantly higher than that of the uncoated sapphire.

Performance requirements of infrared transmission window

1. High mechanical strength 

Infrared transmission windows should exhibit high strength in order to resist decompression loads during periods of high-speed motion.

2.Excellent thermal stability

Infrared windows of adequate quality should be able to withstand the temperature effects caused by aerodynamic heating and changes in height, and their transmittance and refractive index should not change significantly with temperature change.

3.Excellent chemical stability

In the event of exposure to air, the infrared transparent window is capable of preventing the corrosion of salt solutions or corrosive gases in the atmosphere. Furthermore, it is not susceptible to air slaking.

 4.High light transmission

Infrared transmission windows demonstrate effective transmission of radiation within the ultraviolet to mid-infrared wavelength. 

5.Exceptional optical properties

The optical scattering of infrared windows is minimal, and the refractive index is consistent and uniform. 

6. Infrared transmission windows are capable of meeting the requirements of large-size windows.

Sapphire windows demonstrate high transmittance in ultraviolet, infrared and visible wavelengths, thus meeting the requirements of multi-mode composite guidance. Additionally, the sapphire light filter exhibits exceptional mechanical properties, chemical stability, and high temperature resistance. It displays excellent performance, including high strength and hardness, which also renders it well-suited for utilization as a wave-transmitting plate.