TE-TM mode coupling in two-dimensional photonic crystals composed of liquid-crystal rods

We theoretically demonstrate the TE-TM mode coupling in two-dimensional photonic crystals composed of liquid-crystal rods due to anisotropies of liquid crystals. In such structures, the classification of the TE and TM modes is generally impossible, that is, the TE-TM mode coupling occurs. Frequencies of the mode coupling are investigated by the plane-wave expansion method, and the mode coupling is discussed by transmittance calculated by the finite-difference time-domain method. Changes of transmittance by rotating directors of liquid crystals are also discussed.