Photonic band gap of superconductor-medium structure: Two-dimensional triangular lattice

• Plane wave expansion is generalized to superconductor-medium periodic structure.
• A wider band gap appears than that in conventional photonic crystals.
• Part of original energy levels are rearranged upon consideration of the superconductivity.
• Band gap width decreases monotonically with penetration length, but not with the filling factor.
• Band gaps can be partially shut down or opened by adjusting filling factor.

Based on London theory a general form of wave equation is formulated for both dielectric medium and superconductor. Using the wave equation and applying plane wave expansion, we have numerically calculated the band structures and density of states of a photonic crystal, whose intersection is constructed by a two-dimensional triangular lattice of superconductor padding in dielectric medium. Results indicate a wider band gap in the superconductor-medium photonic crystal than that in conventional photonic crystals. And part of original energy levels are found to be rearranged upon consideration of the superconductivity. The dependence of band gap on penetration length and filling factor is also discussed. Band gap width decreases monotonically with the penetration length, but not with the filling factor. Band gaps can be partially shut down or opened by adjusting filling factor.