Radiation Transfer in Whispering-Gallery Mode Microcavities

Micro/nanoscale radiation transfer in whispering-gallery mode (WGM) microcavities is investigated. Each cavity consists of a waveguide and a microdisk coupled in a planar chip. In order to characterize the WGM resonance phenomena, studies of configuration parameters, specifically the microdisk size, the gap distance separating the microdisk and waveguide, and the waveguide width are numerically conducted. The finite element method is used for solving Maxwell’s equations which govern the propagation of electromagnetic (EM) field and the radiation energy transport in the micro/nanoscale WGM structures. The EM fields and the radiation energy distributions in the microcavities are then obtained. The scattering spectra for three different microdisk sizes are also obtained; and through which the WGM resonant properties such as the quality factor, the full-width at half maximum (FWHM), the free spectral range, and the finesse of the resonant modes are analyzed. It is found that the resonant frequencies and their free spectral ranges are predominantly determined by the size of the microcavity; while the FWHM, finesse, and quality factor are strong functions of the gap.