A Hybrid 2D/3D cylindrical FDTD method based on azimuthal mode decomposition

A method to overcome unfavorably small time steps in FDTD simulations on cylindrical meshes is proposed in this paper. A three dimensional cylindrical grid for azimuthally inhomogeneous regions apart from the z-axis is coupled to a multi modal two dimensional grid in the vicinity of the origin. This leads to a diminished ammount of mesh cells and, furthermore, permits the employment of a larger time step. The method is demonstrated by means of a time domain simulation of a microgear resonator to determine its resonant frequencies.