Analytical study of the microdisk's resonant modes coupling with a waveguide based on the perturbation theory

An analytical method for the calculation of the coupling between a microdisk and a waveguide is presented. The theoretical analysis is based on the perturbation theory well known in integrated optics. Only whispering-gallery modes with high quality factor are considered to be propagating in this study when the microresonator is used as a laser structure. The influence of the distance disk/waveguide is investigated. These results are compared with calculations obtained with a two-dimensional finite-difference time domain needing more computational requirements. A good agreement between both methods is shown.