Numerical method for computing defect modes in two-dimensional photonic crystals with dielectric or metallic inclusions

A numerical method based on the finite-difference time-domain (FDTD) scheme for computing defect modes in two-dimensional photonic crystals (with diel ectric or metallic inclusions) is presented. Compared to the FDTD transmiss ion spectra method, the present method reduces the computation domain signi ficantly. By means of it one can find as many defect modes as possible, inc luding those that are inactive to the incident plane wave in the FDTD trans mission spectra method. The calculated eigenfrequencies and field patterns for a defect in a square array of dielectric rods are consistent with those obtained by the plane wave expansion method. Modes for a defect in a squar e array of copper rods are also studied, and the calculated eigenfrequencie s are in a very good agreement with experimental results.