Tunable optical properties of a two-dimensional square-lattice superconductor-dielectric Bragg reflector

We numerically analyze the optical properties of a two-dimensional (2D) superconducting Bragg reflector (SBR) using the finite element method in conjunction with a two-fluid model. It is found that the wavelength-dependent reflectance spectra of the proposed 2D SBR are strongly dependent on the polarizations of incident light and can be parametrically tuned by the system temperature and the geometric parameters of embedded dielectric rods. Taking advantage of the dispersive superconductor with its zero-refractive index characteristic and the structural periodicity of the proposed superconducting structure, narrow passband filters can be generated near the threshold wavelength. Furthermore, the narrow passband features of the 2D SBR are found to be sustained up to a very large angle of incidence. The extraordinary optical properties imply that the proposed 2D SBR may be applied to the design of an omnidirectional narrowband transmission filter.