Sol-gel derived water proof coating for laser glass

A two layer coating was deposited by sol-gel dip-coating method on phosphate laser glass. First silica film was coated from Sie, colloidal suspension derived from ammonia catalyzed hydrolysis of tetraethoxysilane in ethanol. Then a methyl containing silicate film was covered. It was fabricated from a solution prepared by the hydrolysis of methyltriethoxysilane(MTES) in the presence of hydrogen chloride catalyst. A 130 degrees C, 16h heat-treatment was done after coating process. It is confirmed by optical microscope that the two layer coating improves obviously the chemical durability of phosphate laser glass. The laser damage threshold of this coating is measured to be 31 J/cm(2) at 1060nm wavelength of 10 ns pulse duration. It is found that silica film contributes to the improvement on both film adhension to phosphate glass substrate and laser damage threshold of film. The methyl containing silicate single film has only 18 J/cm(2) laser damage threshold and can be easily dissolved in ethanol solution when it was coated on the phosphate laser glass substrate.