Fabrication and optical properties of sol-gel-derived interference coating for high power laser applications

A single layer sol-gel derived TiO2 thin films and 6 periods SiO2/TiO2 multilayer coating were designed and prepared on GaAs substrates as anti-reflection coating or near-IR-reflective coating for high power semiconductor laser applications. Crack free TiO2 thin films having thickness of 80-150 nm, and refractive indices of 1.8-2.1 have been obtained by simply sol-gel method upon heating at different temperatures. The obtained TiO2 thin films on GaAs substrates have shown reflectance of <EQ 1 percent in the wavelength of about 808 nm. Thin films of TiO2 and SiO2 were also used to fabricate near IR reflector ion GaAs substrates. The reflector consisted of 6 SiO2/TiO2 bi-layers, designed with a high-reflective band in the wavelength of 1064 nm. A minimum transmittance of <EQ 2 percent in the wavelength range between 950 and 1100 nm has been obtained in the present multilayer SiO2/TiO2 coating.