EXCITONIC EFFECTS, LUMINESCENCE, AND LASING IN SEMICONDUCTOR MICROCAVITIES

Semiconductor microcavities containing one or more narrow-linewidth qu antum wells exhibit two transmission peaks when the exciton and cavity are in resonance. It will be shown that the transmission and photolum inescence proper ties of this system are very sensitive to excitonic o ptical nonlinearities such as exciton broadening; bandgap renormalizat ion, and state filling. When the cavity mode is detuned to energies ab ove the exciton, at low densities the emission from the lower branch i s much larger than that from the upper branch. But as the density is i ncreased tile lower emission saturates and the upper emission grows ra pidly. lasing at a density less than a factor of two above crossover. It will be shown that this striking crossover is not ''boser action'' due to a condensation into tile upper branch as suggested by [1,2]. Ra ther it results from the density dependence of the transmission and ca rrier distribution functions as shown by the good agreement with a ful ly quantum mechanical microscopic theory for tile luminescence from a microcavity.