Abstract

Many important devices use periodic microstructures of alternating layers of dielectric materials to enhance reflection. Usually the refractive index contrast of dielectric layers is low, typically 1% in a distributed Bragg reflector, and a large number of small reflections over a long propagation distance are needed to warrant high reflectivity. Alternatively, periodic microstructures deeply etched into a semiconductor waveguide offer high refractive-index contrasts and much shorter interaction lengths. Examples include air-bridge microcavities [1,2] and very compact Bragg reflectors [3,4,5]. Responding to the quest for miniaturization, these new mirrors implemented in short cavities additionally offer interesting perspectives: large free spectral ranges, small modal volumes as is required for controlling the spontaneous emission of atoms in microcavities, and low threshold lasers. However, for strong corrugations, the Bragg mirror cannot be considered as a perturbation of the uncorrugated waveguide and out-of-plane scattering losses (radiation) in the claddings are inevitable. Apparently strong corrugations required for short interaction lengths and small radiation losses required for high performance seems to be two conflicting objectives.

© 2003 Optical Society of America