Energy transfer by the normal modes in the exciton resonance region

Abstract For a dielectric medium with isolated exciton resonance, expressions for the energy density and energy flux density of a radiation field, given in a general form, are derived, taking into account energy absorption and spatial dispersion. The energy fluxes associated with individual normal modes are considered. It is shown that in the case of nonzero damping the interference between different normal modes gives rise to interference energy fluxes. The behaviour of the energy flux on the crystal surface is analysed. It is found that the energy flux across the medium boundary is continuous, if the coefficients in the relation between exciton polarization at the surface and its derivative along the normal are real. The numerical calculations of energy distribution between the modes, including the interference fluxes, are carried out for the case of light transmission through the CdS crystal boundary in the energy region of A n =1 exciton resonance.

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