RESONANT BRILLOUIN-SCATTERING AS A FORM OF MODULATION SPECTROSCOPY

A discussion is given on resonant Brillouin scattering in connection with first-derivative modulation spectroscopy such as thermoreflectance, piezoreflectance, and wave-length-modulation spectroscopy. It is shown that the Brillouin scattering efficiency is expressed by the first derivative of the dielectric constant with respect to the incident light wavelength (or equivalently to the band gap energy), which is the same as the expression for the first-derivative modulation spectroscopy. A comparison of the Brillouin scattering efficiencies derived experimentally with the first-derivative modulation spectra shows that they agree quite well with each other and also with the theoretical curves of the Brillouin scattering efficiency when the lifetime broadening is taken into account in the Brillouin scattering analyses.