FDTD Microcavity Simulations: Design and Experimental Realization of Waveguide-Coupled Single-Mode Ring and Whispering-Gallery-Mode Disk Resonators

We investigate the properties of high-Q, wide freespectral-range semiconductor microcavity ring and disk resonators coupled to submicron-width waveguides. Key optical design parameters are characterized using finite-difference timedomain (FDTD) solutions of the full-wave Maxwell’s equations. We report coupling efficiencies and resonant frequencies that include the effects of waveguide dispersion and bending and scattering losses. For diameters of 5 m, the microcavity resonators can have Q’s in the several thousands and a free spectral range of 6 THz (50 nm) in the 1.55 m, wavelength range. Studies of the transmittance characteristics illustrate the transition from singlemode resonances to whispering-gallery-mode resonances as the waveguide width of the microring is increased to form a solid microdisk. We present nanofabrication results and experimentally measured transmission resonances of AlGaAs/GaAs microcavity resonators designed in part with this method.