The dispersion relation, the field distribution. and the lifetime of the ra
diational eigenmodes in two-dimensional photonic crystals composed of metal
lic cylinders were calculated for the E polarization by means of the numeri
cal simulation of the dipole radiation based on the finite-difference time-
domain (FDTD) method. The convergence and the central processing unit time
were compared with the plane-wave expansion method. The opaque frequency ra
nges in the transmission spectra calculated by the method of Pendry and Mac
Kinnon corresponded quite well to the band gaps and the antisymmetric modes
found in the photonic band diagram. The dispersion relation and the symmet
ry of the eigenmodes obtained by the numerical calculation were consistent
with the prediction of the group theory and the analytical expression by th
e long-wavelength approximation.