Investigation of thermal radiation effect on optical dome of sapphire coated yttrium oxide

Compared to traditional optical domes, domes of sapphire coated with films can effectively reduce emissivity and increase transmittance. The purpose of this work is to investigate the thermal radiation effect on sapphire optical dome coated with yttrium oxide by a radio frequency magnetron sputtering method. The emissivity of sapphire coated with Y2O3 films is studied by both numerical and experimental methods. The results indicate that the emissivity of sapphire substrate is reduced effectively with increasing the thickness of the Y2O3 film. In addition, a finite element model is developed to simulate the radiation intensity of the optical dome. The thermal responses indicate that the maximum temperature is reduced apparently compared with the uncoated sapphire as Y2O3 film thicknesses increase. The average irradiance distribution at different film thicknesses with time shows that the self-thermal radiation disturbance of sapphire optical dome delays 0.93 s when the thickness of Y2O3 film is 200 mu m, which can guarantee the dome works properly and effectively even in a harsh environment.