Stimulated emission of exciton polaritons in a semiconductor microcavity

Summary form only given.We carried out experiments to prove the existence of large occupation numbers for microcavity polaritons. Two pump beams (from a coherent Ti:sapphire ring laser) at opposite and large angles (51) inject exciton populations at opposite in-plane momenta. Exciton-exciton collisions result in the creation of lower (LP) and upper (UP) cavity polaritons. Final state stimulation is induced by injecting LP by a probe beam (an external cavity semiconductor laser) at normal incidence. The emission from the sample is measured in the normal direction and is separated from the incident probe beam via a nonpolarizing beam splitter (55% transmission).