Validation of FDTD-2D for high-Q resonances description

The objective of the study is to assess the accuracy of a standard FDTD code in description of high-Q resonances such as whispering-gallery-mode (WGM) ones excited in circular dielectric resonators. To achieve the goal, we consider circular resonators excited by line currents and extract the data on FDTD accuracy from comparisons between the FDTD-solution and the exact one obtained by the Mie-series solutions. The near-field and far-field characteristics are studied for resonators of various sizes, made of quartz and silicon. Both E - and H - polarizations are considered. The computational error, i.e. a resonance frequency shift observed for the FDTD solution, is analyzed and compared for several WGMs having different Q-factors.