COHERENT-LIGHT EMISSION FROM EXCITON CONDENSATES IN SEMICONDUCTOR QUANTUM-WELLS

We show that a quasi-two dimensional condensate of optically active ex citons emits coherent light even in the absence of population inversio n. This allows an unambiguous and clear experimental detection of the condensed phase. We prove that, due to the exciton-photon coupling, qu antum and thermal fluctuations do not destroy condensation at finite t emperature. Suitable conditions to achieve condensation are temperatur es of a few K for typical exciton densities and the use of a pulsed an d preferably circularly polarized, laser. (C) 1998 Elsevier Science Lt d. All rights reserved.