Near-field gap effects on small microcavity whispering-gallery mode resonators

Zhixiong Guo, Haiyong Quan, Stanley Pau

Research output: Contribution to journalArticlepeer-review

49 Scopus citations


The near-field gap effects are investigated in planar dielectric microdisc and waveguide coupling structures, emphasizing miniaturization of integrated sensor systems. The simulation results show that the resonance frequency is not obviously affected by the gap dimension when the gap between a microcavity and its coupler is larger than 300 nm. However, the resonance frequency shifts observably with a further decreasing gap to the nanometre level. This shift is generally larger than the cavity resonance linewidth in the 10 νm diameter microdisc system, but is comparable to the cavity resonance linewidth in the 2 νm diameter microdisc system. With increasing gap, the cavity Q increases exponentially until it is saturated at a limit Q factor. An optimal gap dimension exists for maximum light energy transfer and storage. The concept of optimum gap is introduced and defined at the gap dimension where half-maximum energy storage capability is achieved; meanwhile, the cavity Q is high and the resonance frequency remains stable.

Original languageEnglish (US)
Article number006
Pages (from-to)5133-5136
Number of pages4
JournalJournal of Physics D: Applied Physics
Issue number24
StatePublished - Dec 21 2006

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Acoustics and Ultrasonics
  • Surfaces, Coatings and Films


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