H. H. Li. Refractive index of alkali halides and its wavelength and temperature derivatives. J. Phys. Chem. Ref. Data5, 329-528 (1976) and references therein. * Sellmeier formula is derived by critical analysis of experimental data from several sources.
Potassium chloride (KCl) is a salt that finds use in various optical applications due to its wide spectral transmission range. Like its bromide counterpart, potassium chloride is hygroscopic, requiring cautious handling and storage conditions to preserve its optical qualities. It is commonly used as a prismatic or plane-parallel component in infrared spectroscopy, particularly because of its low cost and good transmission in the mid and far-infrared regions. Additionally, it serves as a substrate for specialized optical coatings. Due to its moisture sensitivity, it's less suitable for applications exposed to high humidity or varying environmental conditions. Nonetheless, KCl remains an important material in the toolkit of optical engineers and scientists.