Brillouin Scattering of Thermal Phonons in CdS

Thermal Brillouin scattering spectra in CdS have been obtained at room temperature by using a sensitive photoelectric detection, a gas-scanning Fabry-Perot interferometer and a He-Ne laser with wave-length 632.8 nm. The elastic and the photoelastic anisotropy in CdS have been explored from a combination of measurements of frequency shifts and intensities of the components in polarized spectra at scattering angle 90°. From them, the absolute values of elastic constants and relative magnitudes of photoelastic constants are determined. The scattering intensities of CdS are compared with those of materials whose photoelastic constants are known, e.g. quartz, and the absolute value of unknown photoelastic constant P 44 of CdS is determined to be 0.049.