Numerical Study of Light Propagation via Whispering Gallery Modes in Microcylinder Coupled Resonator Optical Waveguides

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By using a discontinuous spectral element method, we analyze evanescent wave coupling of whispering gallery modes (WGMs) in microcylinder coupled resonator optical waveguides (CROWs). We demonstrate successful light propagation by WGMs through a chain of coupled cylinder resonators, and that the speed of such propagation is strongly dependent on the inter-resonator gap sizes. Our simulations also show that light propagates slower by WGMs with bigger azimuthal numbers than by those with smaller azimuthal numbers. On the other hand, the light propagation by WGMs of the same azimuthal number appears to have the same speed in CROWs regardless of the size and the material of the resonators, indicating that the tail (the part of a WGM outside the resonator) determines inter-resonator coupling strength.