TRANSITION FROM A MICROCAVITY EXCITON-POLARITON TO A PHOTON LASER

In a previous paper [Phys. Rev. A 54, R1789 (1996)], we reported the o bservation of a laserlike transition in a single GaAs quantum well mic rocavity and gave the interpretation as spontaneous buildup of coheren t exciton-polariton population via stimulated polariton-phonon emissio n. In this Brief Report, we present new experimental data and correct our previous interpretation for the microcavity polariton system at hi gh density. We observe a continuous transition from a microcavity pola riton emission to a bare photon laser. This conclusion is based on the measurements of the angular resolved photoluminescence, linewidth, an d intensity of the lasing line as well as the reflection spectrum unde r cw pumping.