TRANSMISSION AND DAMPING OF EXCITONIC POLARITONS IN CDS

The optical spectra of direct band semiconductors like CdS in the spectral region of the ground states of free excitons can be calculated from the dispersion curves of excitonic polaritons and the distribution of the incoming field strength of the different propagation modes of the polaritons due to the effect of spatial dispersion. While the real part of the dielectric function has been determined most directly with resonant Brillouin scattering and thin prism refraction, the imaginary part, being governed by the interaction of the polaritons with other elementary excitation of the crystal, has been introduced into the calculation up to now only by a phenomenological mostly wavelength independent damping factor GAMMA . In order to determine the damping function GAMMA ( omega ) experiments were performed in which the transmission and the reflectivity of thin CdS platelets have been analyzed simultaneously. 10 refs.