Simulations of atomic trajectories near a dielectric surface

We present a semiclassical model of an atom moving in the evanescent field of a microtoroidal resonator. Atoms falling through whispering-gallery modes can achieve strong, coherent coupling with the cavity at distances of approximately 100 nm from the surface; in this regime, surface-induced Casmir–Polder level shifts become significant for atomic motion and detection. Atomic transit events detected in recent experiments are analyzed with our simulation, which is extended to consider atom trapping in the evanescent field of a microtoroid.