Abstract: A modified subgridding finite difference time domain method (FDTD) is proposed. For the study of the computational domain filled with different dielectric materials and the reasonable division of coarse and fine grids in different dielectric regions, the second-order accurate FDTD technique at the dielectric interface is employed to analyze the tangential electric field components at the interface. Based on Maxwell’s equations in integral form, the second-order accuracy of the tangential electric fields at the dielectric interface is obtained by the establishment of the nonuniform grids and the introduction of the auxiliary magnetic fields. The overall computational accuracy of the modified subgridding algorithm can be improved effectively, without additional computational capacity, consumed time and complexity in programming. Finally, the numerical simulations for some waveguide structures are carried out to validate the better accuracy of the method proposed in this paper than that of the traditional subgridding method and the standard FDTD method.

Key words: finite difference time domain method (FDTD), dielectric interface, second order accuracy, subgridding method, waveguide