A perturbation theory for the calculation of optical modes in circular microdisks with a small local boundary deformation of arbitrary shape is introduced. Two examples are studied in detail: a small notch and a localized corrugation at the boundary. In the generic situation where the first moment of the deformation function does not vanish, very good agreement to the full numerical simulations of Maxwell's equations is found in terms of frequencies, decay rates, and light-emission directionality.

• Received 23 April 2012

DOI:https://doi.org/10.1103/PhysRevA.85.063838