Optical thin films grown by surface chemical reaction for high-power lasers

Abstract

We prepared optical thin films grown with surface chemical reactions using TiCl4 and H2O for TiO2. The nonuniformity of thickness distribution was under 1% over 240 mm in diameter. The structure of TiO2 film grown at 25 degrees Celsius was amorphous. The structure changed into polycrystalline with an increase of growth temperature up to 400 degrees Celsius. Secondary ion mass spectrometry showed that chloride residents presented in the films at every growth temperature. However, these chloride residents could be removed by thermal annealing at 400 degrees Celsius. The TiO2 film at the growth temperature of 25 degrees Celsius had a laser-induced damage threshold of 5 J/cm2 for 1-ns, 1064 nm laser pulse. The damage threshold of TiO2 films decreased at higher growth temperature. Chloride in the films had no influence on the laser-induced damage threshold.