Defect mode computation in two-dimensional photonic crystals consisting ofnearly-free-electron metals

Defect modes in two-dimensional photonic crystals consisting of nearly-free -electron metals are considered. To avoid any time-consuming time convoluti on, modified time stepping formulae are used in a finite-difference time-do main (FDTD) method. Compared to the FDTD transmission spectra method, the p resent method significantly reduces the computation domain. With the presen t method one can also End defect modes that are not excited by the incident plane wave in the FDTD transmission spectra method.