lntraband and interband relaxation of excitonic polaritons

Abstract

A well-defined doublet structure due to polariton emission has been found in the spectra of resonance exciton luminescence emitted by the black modification of ZnP, crystals at T = 2 K. The shape of the spectra is analyzed on the basis of the theory of spectral and spatial diffusion of polaritons under boundary conditions consistent with experimental reflection data. The relative contributions of polaritons belonging to the upper (UBP) and lower (LBP) dispersion branches are determined for the first time. It is shown that the UBP contribution to the emitted radiation depends significantly on the rate of interband UBP-+LBP relaxation and the LBP spatial and energy distribution. The LBP distribution function is largely established as a result of intraband relaxation between LBP states. The ratio of LBP to UBP emission intensities is used to determine the effective depth of the LBP spatial distribution.