Abstract

Lasers with cavities with dimensions on the order of a wavelength will have such a large free spectral range that they can only emit radiation into a single longitudinal mode. By careful design one can direct most of the emitted radiation into the same transverse mode. This is in sharp contrast to conventional lasers, which emit only one out of 104-105 spontaneous photons into the lasing mode. The high spontaneous-emission efficiency of microcavity lasers, together with the fact that they intrinsically have small active volumes, may pave the way for lasers with threshold currents in the microampere range. Such lasers will have smooth output-powerversus-pump current curves, in contrast to the sharp transition a conventional laser exhibits when going from below to above threshold. The fact that they can have a high quantum efficiency also makes it possible for them to emit light with sub-shot-noise intensity below, at, and above threshold pumping if the pump noise is suppressed. Finally, the large free spectral range of the cavity allows a wide bandwidth and a short photon decay time, even for a high-finesse cavity. The amplitude modulation bandwidth for such lasers may go from a few gigahertz to as high as 1 THz for lasers driven far above threshold.

© 1990 Optical Society of America