Glass Microspheres as Optical Resonators

We present and discuss an analytical model for the propagation of light in a glass microsphere resonator based on wave optics and Maxwell's equations in the formulation of vector and scalar Debye's potential. References and connections with geometrical optics and quantum mechanics theory are given in order to better understand the electromagnetic phenomenon of whispering-gallery modes (WGMs). The problem of light coupling into a glass microsphere and the various strategies usually adopted for this purpose are also detailed.