Optical Transmittance of Fused Silica at Elevated Temperatures

The absorption spectra of fused-silica samples, selected for their “typical” optical properties, are presented. The ultraviolet absorption edge shifts some 30 mμ toward the ir, between 22° and 982°C sample temperatures. In the same range, the 1.4-μ absorption peak passes through a maximum in absorption and the 2.23-μ peak passes through an absorption minimum; both move toward the ir. The water band at 2.75 μ shifts first toward the uv, then toward the ir, with increasing temperature, while monotonically decreasing in absorption.