Suppression of higher-order radial whispering gallery modes in waveguide-coupled microcavity disk resonators

In comparison to single-mode microring resonators, microcavity disk resonators supporting whispering gallery modes (WGMs) have the advantage of less side-wall scattering loss and higher Q. However, the microdisk resonator has multiple sets of resonances corresponding to fundamental and higher-order radial WGMs of the disk. Suppression of the higher-order modes is necessary in order to use microdisks as single-mode laser sources or as WDM devices with low crosstalk across a wide spectrum. We have investigated methods for suppressing the higher-order modes using FDTD simulations. As the radial order of the WGM increases, the mode width increases and the peak of the mode shifts toward the center of disk. Therefore, we can manipulate the resonances by taking advantage of the spatial characteristics of the WGMs