Temperature-switchable mode selector in superconducting photonic crystals based on the Thue–Morse sequence

Abstract

In this paper, a novel one-dimensional superconducting photonic crystal based on the quasi-periodic Thue–Morse (ThM) arrangement is theoretically investigated by the transfer matrix method, which can switch two transmission properties by controlling ambient temperature. Its transmission spectrum realizes omnidirectional photonic band gap (OBG) characteristics in low-temperature zones (about 10 K) and wide-angle broadband absorption characteristics in high-temperature zones (about 90 K) as the whole structure remains the same in the terahertz regime. The intrinsic reason for switchable functions can be ascribed to the superconducting negative permittivity that is dependent on both temperature and frequency under the superconducting state, which causes an OBG corresponding to the zero-averaged (volume) refractive index (zero- n ¯ ) and broadband absorption induced by high permittivity dissipation. From the numerical results, the OBG from the Bragg gap or absorption bandwidth can be notably tuned by manipulating the periodicity of the ThM sequence and dielectric or superconducting thicknesses. The effects of incident angle and polarization modes on the proposed structure are also considered. We report that the proposed structure has a preeminent zero- n ¯ OBG ranging from 0.1 to 1.7 THz at 10 K and stable broadband absorption for a wide angle (at most 70 deg) in TM mode at 90 K, which provides theoretical guidance for the design and application of the temperature-switchable mode selector.