Refractive index and absorption of lead bromide crystals

Lead bromide (PbBr2) crystals in [001] orientation were obtained by the Bridgman growth method. The orientation of the principal refractive axes of the crystals was determined, and their principal refractive indices were measured by the least deviation angle at eight selected wavelengths. The optical axial angle and the dispersion of refractive index in the visible spectral range were calculated by Sellmeier’s formula. Optical transmission and reflection spectra were measured and the absorption coefficient α was determined. Using the calculated α(hν) dependence, the bandgap width corresponding to indirect transition was determined.