Investigation of improving strength and transmission for sapphire

Infrared antireflective double layer films of SiO2/Si3N4 were prepared on sapphire(α-Al2O3) by radio frequency magnetron reactive sputtering.The high temperature strength and transmission of sapphire are measured.The results show that the high temperature strength of sapphire coated with the double layer films of SiO2/Si3N4 on both sides and transmission of sapphire have been improved greatly.The high strength of sapphire coated with SiO2/Si3N4 films is 41.0% higher than uncoated sapphire sample at 800 ℃;the transmission of sapphire coated with SiO2/Si3N4 films on both sides is 8.0% higher than uncoated sapphire sample at wavelengths from 3 to 5 μm at room temperature.Double layer films of SiO2/Si3N4 have high heat-stability and high adhesion with sapphire.