Giant enhancement of polariton relaxation in semiconductor microcavities by polariton-free carrier interaction: Experimental evidence and theory

Very large changes in the population distributions of microcavity polaritons are reported under conditions of simultaneous resonant and nonresonant excitation. The strong relaxation bottleneck, which results in weak emission from the lower polariton branch for resonant excitation alone, is fully suppressed if additional nonresonant excitation is employed. By comparison with theory, the massive enhancement of the polariton relaxation is shown to arise from scattering of polaritons by free carriers, present in quantum wells due to residual doping, which are then heated by the nonresonant excitation.