Spontaneous emission from excitons in cylindrical dielectric waveguides and the spontaneous-emission factor of microcavity ring lasers

Abstract

The modification of the spontaneous emission from various dipoles in a cylindrical dielectric waveguide is studied as a function of the refractive index and the radius of the waveguide. It is found that the emission rates of the axial dipoles and the radial dipoles can be modified to enhance greatly the fraction of radial dipole emission that goes into the guided lasing modes. The total emission from the axial dipoles can be suppressed. This combination gives a high spontaneous-emission factor β for a microcavity ring laser. Other microlaser structures that have high β values are also discussed. We conclude that microlasers based on strongly guided single-mode dielectric waveguides are promising devices for achieving high β values and low lasing thresholds.