Single-atom detection using whispering-gallery modes of microdisk resonators

We investigate the possibility of using dielectric microdisk resonators for the optical detection of single atoms trapped and cooled in magnetic microtraps near the surface of a substrate. The bound and evanescent fields of optical whispering-gallery modes are calculated and the coupling to straight waveguides is investigated using finite-difference time domain solutions of Maxwell's equations. Results are compared with semianalytical solutions based on coupled mode theory. We discuss atom detection efficiencies and the feasibility of nondestructive measurements in such a system depending on key parameters such as disk size, disk-waveguide coupling, and scattering losses.