Calculation of coupling between tapered fiber modes and whispering-gallery modes of a spherical microlaser

Abstract

Scope and Method of Study: Coupled-mode theory is used to numerically calculate the coupling coefficients between modes of a tapered fiber and those of a fused-silica microsphere. The coupling coefficients are used to determine the optimal fiber taper radius. They are also used to calculate whispering-gallery mode spectra that take into account the eccentricity of the microsphere and the fact that in an experiment the tapered fiber is not necessarily perfectly aligned with the equatorial plane of the microsphere. The spectra are used to model multimode lasing in a microsphere.