Large Absolute Band Gap in 2D Anisotropic Photonic Crystals

Absolute photonic band gaps can be substantially improved in two-dimensional square and triangular lattices of cylinders by introducing anisotropy in material dielectricity. Owing to different refractive indices for electromagnetic waves with $E$ and $H$ polarization, the band gaps for the two polarization modes can be freely adjusted and matched to overlap optimally. Large absolute band gaps can be created for uniaxial cylinders in air with a positive anisotropy. In the case of air holes in background uniaxial dielectric with even a weak negative anisotropy, the absolute band gap can be increased 2–3 times.