Optical processes in microcavities

Optical microresonators can now be fabricated with dimensions of the order of half a wavelength on a side. For semiconductor microresonators this results in only a few optical modes interacting with the emitting material in the cavity. In this limit the threshold lasing characteristics are dramatically modified. Semiconductor microdisc experiments will be described where as much as 20% of the spontaneous emission is captured into the single lasing mode. This strong coupling of the radiation field with the resonant mode can cause anomalous laser linewidths and fluctuation phenomena. These experiments provide a good test of detailed models of dense, non-equilibrium electron-hole gases. Extensions of optical microcavities to a broad range of material systems will also be discussed.