Band Structure of a Two-Dimensional Photonic Crystal with aTriangular Lattice of Anisotropic Elliptic Cylinders

The plane-wave expansion method is used to calculate the band structure of a two-dimensional photonic crystal formed by a triangular lattice of anisotropic elliptic cylinders. After optimizing the parameters of the elliptic cylinders, we find a large bandgap (about 0.0449 ω_e, ω_e = 2πc/a) at high frequencies beside a coexisting large absolute gap (about 0.035 ω_e) at low frequencies. Numerical results show that the optimal design is very stable under any parameter pertubation.