Optical phonon scattering of cavity polaritons in an electroluminescent device

A signature of the scattering between microcavity polaritons and longitudinal optical phonons has been observed in the electroluminescence spectrum of an intersubband device operating in the light-matter strong-coupling regime. By electrical pumping we resonantly populate the upper polariton branch at different energies as a function of the applied bias. The electroluminescent signal arising from these states is seconded by a phonon replica from the lower branch.