Surface-roughness-induced contradirectional coupling in ring and disk resonators

Abstract

Reflections that are due to random surface roughness in periodic structures such as dielectric rings and disks inherently phase match forward- and backward-propagating modes. Small reflections are thus considerably enhanced and may impair the performance of traveling-wave resonators. In addition, such contradirectional coupling leads to a splitting of the resonant peak. These effects are studied analytically.