Design considerations of microcavity ring resonators

This study presents an accurate numerical analysis of a microcavity ring resonator based on high-index-contrast waveguide. The analysis is carried out using a multiresolution time domain (MRTD) scheme that provides high numerical precision without the strict limitation on the space discretisation as compared to the commonly used finite-difference time domain (FDTD). By relying on higher-order approximation of discretisation in space, the proposed MRTD approach outperforms the FDTD method and is thus a more suitable candidate for large-scale simulations. The uniaxial perfectly matched layer is carefully applied to truncate the computational domain. The analysed parameters are the coupling coefficients between the input/output waveguides and the ring, the resonance frequencies and the free spectral range. The effect of the structure geometry parameters such as the gap between the ring and input/output waveguides, the ring radius and the width of the input/output waveguide and the ring resonator is thoroughly investigated. The numerical results reveal that the suggested MRTD allows using about twice the spatial step size required by FDTD yet providing same level of accuracy.