Infrared absorption in low-loss KCl single crystals near 10.6 μm

Abstract
The infrared absorption in KCl single crystals near 10.6 μm has been studied using calorimetric techniques with fixed-frequency and tunable CO2 laser sources. By use of crystals grown in a reactive CCl4 atmosphere, with surfaces carefully prepared by chemical polishing, it is possible to obtain absorption coefficients of 0.0002 cm−1 or less in samples several centimeters thick. This residual absorption is composed of a surface and a bulk part. It is possible to show that the bulk absorption approaches the estimated intrinsic limit of 0.00008 cm−1. An absorption band near 9.8 μm is present in all samples examined and appears to be largely associated with the surface.