Ion beam milling of silica for IR transmission

Ion beam etching is applied to produce specimens less than 1 μm thick with a free aperture of 4 mm in diameter. Plane specimens which have the same chemical composition and structure as the bulk material can be obtained. Infrared transmission spectra were obtained from fused silica samples Herasil and Suprasil W. The shapes of these transmission spectra are discussed. The absorption bands in the region 5 to 7 μm have the same intensity for both glasses independent of the OH content of the silica. They are supposed to be overtones of the basic Si-O vibrations at 9.4 μm and 12.4 μm. (author)