Rayleigh Scattering of Whispering Gallery Modes of Microspheres due to a Single Scatterer: Myths and Reality

TL;DR

This paper challenges the conventional understanding of how a single scatterer affects whispering gallery modes in microspheres, offering a new exact theory that explains experimental observations and predicts novel effects.

Contribution

It develops an exact theoretical framework for WGM interaction with a single defect, correcting misconceptions and unifying the explanation of spectral doublets and Q-factor degradation.

Findings

Existing models are conceptually incorrect.

The new theory explains experimental data accurately.

Predictions of new phenomena due to single scatterers.

Abstract

The interaction of whispering gallery modes (WGM) of optical microresonators with subwavelength imperfections has been studied both experimentally and theoretically. This interaction is responsible for the formation of spectral doublets in place of single resonance peaks, and for degrading of Q-factors of the resonances. Within the currently accepted framework the spectral doublets are explained as a result of degeneracy removal of clockwise and counterclockwise WGMs due to their coupling caused by defect-induced backscattering, while the degrading of the Q-factor is described phenomenologically as an additional contribution to the overall decay rate of WGM due to coupling between WGM and radiative modes. Here we show that the existing understanding of this phenomenon is conceptually wrong and develop an exact theory of WGM interaction with a single defect, which provides a unified treatment for both aspects of this interaction explaining existing experiments and predicting new phenomena.