Preparation of MgF2-SiO2 thin films with a low refractive index by a solgel process

Porous MgF2-SiO2 thin films consisting of MgF2 particles connected by an amorphous SiO2 binder are prepared by a solgel process. The films have a low refractive index of 1.26, sufficient strength to withstand wiping by a cloth, and a high environmental resistance. The refractive index of the film can be controlled by changing the processing conditions. Films can be uniformly formed on curved substrates and at relatively low temperatures, such as 100 degrees C. The low refractive index of the film, which cannot be achieved by conventional dry processes, is effective in improving the performance of antireflective coatings.(c) 2008 Optical Society of America.