Computing Electromagnetic Bandgap for Parallel Nanorod Structure with Double Negative Refractive Index inside Triangular Lattice

Complete electromagnetic bandgap is analytically computed for parallel nanorod structure when placed inside a triangular lattice in symmetric fashion. Being a metamaterial or double negative refractive index material, this structure exhibits tunable bandgap when dimension of the cylinder, i.e., fill factor of the structure is changed within feasible mechanical limit. Formation of bandgap becomes only possible for magnetic polarization, whereas even quasi bandgap is not observed for electric polarization. Maximum bandgap width is obtained for 0.45 value of normalized radius of the nanorod, and corresponding midband frequency is computed. Field patterns are also obtained for the desired frequency values. Maximum and minimum bandgap inside first Brillouin zone is calculated which plays critical role for photonic filter design.