Resonance shifts of counterpropagating whispering-gallery modes: Degenerate perturbation theory and application to resonator sensors with axial symmetry

Research output: Contribution to journalArticle

Abstract

A theory is presented that considers the resonance shift of degenerate whispering-gallery modes (WGMs) in sensor applications. The theory is then applied to a pair of counterpropagating waves in a spheroidal resonator. Adsorption of a particle lifts the twofold degeneracy, resulting in a pair of standing waves with a symmetric field around the particle, a standing symmetric wave (SSW) and an antisymmetric wave (ASW). The shift for a SSW is twice as large as the one for a nondegenerate WGM when the particle radius is sufficiently smaller than the wavelength, whereas the shift for an ASW is nearly zero. The ratio of the split to the mean shift gives an estimate of the particle size, whereas the mean shift is sensitive to its polarizability. With an increasing particle radius, the ratio of the split to the mean shift decreases. There is a particle radius that maximizes the split.

Original languageEnglish (US)
Pages (from-to)1321-1329
Number of pages9
JournalJournal of the Optical Society of America B: Optical Physics
Volume26
Issue number7
DOIs
StatePublished - Jul 1 2009

ASJC Scopus subject areas

  • Statistical and Nonlinear Physics
  • Atomic and Molecular Physics, and Optics

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