The effects of the structural parameters of the planer photonic crystal on the characteristics of its forbidden band and defect mode have been studied by using the Finite-Difference Time-Domain(FDTD) method.After defects are introduced in the air hole structure
the dielectric band frequency will move upwaaard with the increase of the radius of the acceptor defect air hole
while the air band frequency will move downward with the decrease of the radius of the donor defect air hole.