Coupling of the TE and TM modes of electromagnetic waves in two-dimensional photonic crystals with surface defects of liquid crystals.

We theoretically demonstrate the coupling of the TE and TM modes of electromagnetic waves in two-dimensional photonic crystals with surface defects of liquid crystals. Due to anisotropies of liquid crystals, the TE and TM modes cannot be classified generally in the surface defects, which causes the coupling of the TE and TM modes. The coupling of the TE and TM modes occurs strongly at frequencies at which group velocities of electromagnetic waves become zero, especially at surface defect modes. Possibility of the sharp tunability and the switching of the transmittance in this system has been demonstrated theoretically by the control of directors of liquid crystals by applied electric field due to their anisotropy.