Theoretical and Experimental Analysis of Mixed Exciton-Polariton Luminescence in CdS Crystals in the Regime of Strong Exciton Damping

This work presents a combined theoretical and experimental study of mixed exciton-polariton luminescence in anisotropic crystals in the regime of strong exciton damping near the A-exciton resonance. A spatially dispersive model of radiative mixed modes is used to analyze the transformation of the spectral contour, peak position, partial modal contributions, and angular dependence of the linewidth. Calculated spectra for emission angles from to are compared with photoluminescence measurements, and good agreement is obtained at K for meV and μm. Unlike conventional approaches that relate the transition to a Lorentzian emission profile only to the condition , we show that this regime additionally requires the transport-related constraint Under these combined conditions, the mixed-mode emission contour approaches a quasiclassical Lorentzian profile with a half-width close to . At the same time, spatial dispersion and intermode interference are not fully suppressed in anisotropic crystals and become more pronounced at larger emission angles or smaller effective diffusion lengths. The results provide a refined criterion for identifying the quasiclassical emission regime and a practical framework for extracting exciton damping and effective diffusion depth from experimental spectra.

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