Coupled whispering gallery modes in a multilayer-coated microsphere
I. Teraoka, and S. Arnold
Opt. Lett. 32, No. 9, 1147 (2007)

Whispering gallery modes in a microsphere coated with three layers of high, low, and high refractive indices
(RIs) are considered. Coastal modes and inland modes, centered on the outer and inner high-RI layers, exist
as different radial modes. At right values of RI and thickness of the three layers, an inland mode and a
coastal mode couple to produce a radial distribution of the photonic field that resembles bonding and antibonding
orbitals. The coupling occurs across a layer of the middle low-RI layer, much thicker than the wavelength
of light. The coupling is analyzed in a quantum-mechanical analog of a one-dimensional particle in a
double-well potential.