Photonic band structures of a two-dimensional ionic dielectric medium

The photonic band structures of the two-dimensional square lattice of air cylinders embedded in an ionic crystal are calculated using the plane-wave method, The dielectric function of the ionic crystal is taken as epsilon(omega)=epsilon(infinity)-(omega(LO)(2)-omega(2))/(omega(TO)(2)-omega(2)), with epsilon(infinity), omega(TO), and omega(LO) denoting the high-frequency dielectric constant and transverse- and longitudinal-optical-phonon frequencies, respectively. The frequencies of the electromagnetic modes are determined from the zeros of the determinants of the matrix equation. Both E and H polarizations are considered. Our calculation shows that the low-frequency photonic bands resemble the bands of a frequency-independent dielectric medium, while the bands near the transverse-optical-phonon frequency omega(TO) are strongly Battened. Our study also suggests that while the plane-wave method gives reliable photonic bands for the frequency below omega(TO), a better method has to be used for the photonic bands very near or above omega(TO).