A new finite-difference time-domain method for photonic crystals consisting of nearly-free-electron metals

A finite-difference time-domain method is developed to treat a nearly-free-electron metal by rewriting the time-domain Maxwell's equations into three coupled partial differential equations for three vector functions. The method is used to calculate the band structures of two-dimensional metallic photonic crystals, and the numerical results are compared with those obtained by other methods. The new time-stepping formulae are also used to investigate the defect modes by calculating the transmission spectrum.