Spontaneous emission from excitons in thin dielectric layers.

Spontaneous emission from quantum-well excitons in a thin, high-refractive-index dielectric layer embedded in a low-refractive-index bulk dielectric is studied as a function of the layer thickness and refractive-index ratio. Total spontaneous emission rates for a thin layer decrease linearly with the index ratio for dipoles in the plane of the layer and as the fifth power of the index ratio for dipoles with orientations perpendicular to the layer. These results are of interest in the design of optical microstructures that control the exciton emission dynamics of semiconductor quantum wells.