Abstract
A deep but finite minimum in the dispersion of the Brillouin scattering cross section has been found in the wavelength region of the resonant cancellation at 562.4 nm (T=300 K) in CdS. This minimum is interpreted as arising from the contribution of the imaginary part of photoelastic constant P66, whose existence has been overlooked so far. The lifetime broadening is introduced to obtain the imaginary part by replacing the photon energy hω with hω+iΓ (Γ: damping energy) in the piezobirefringence theory. The damping energy is found to be Γ=0.5 meV at 300 K from the best fitting of the theoretical curve to the experimental results.
