Unified approach to mode splitting and scattering loss in high-Q whispering-gallery-mode microresonators

Current theoretical treatments of mode splitting and scattering loss resulting from subwavelength scatterers attached to the surface of high-quality-factor whispering-gallery-mode microresonators are not satisfactory. Different models proposed for distinct scatterer regimes cannot be reconciled. In addition, many experimental results are difficult to understand within the existing theoretical framework. Here, we develop a unified approach that applies to an arbitrary number of scatterers. Comparison with the existing theoretical models reveals their applicable conditions and limits. Moreover, many new understandings on the mode splitting and scattering loss are achieved, which are supported by numerical and experimental evidence.