Filtering properties of photonic crystal dual-channel tunable filter containing superconducting defects

In this work, we analyze filtering properties in a photonic crystal (PC) dual-channel tunable filter. The filter structure containing twin superconducting thin films is denoted as (1/2) ^M S₁(2/1) ^N S₂(1/2) ^M . Here, 1 and 2 are dielectrics of SrTiO₃ and Al₂O₃, respectively. S₁ and S₂ are two high-temperature superconducting thin films taken to be the typical system, YBa₂Cu₃O_7-x . The two channel frequencies can be designed to locate within the photonic band gap (PBG) of the original PC (1/2) ^M . Channel frequencies can be significantly changed by changing N, the stack number of the center PC. With the use of superconducting defects, channel frequencies are temperature-dependent, that is, the filter is thermally tunable. The proposed filter structure is of technical use in superconducting photonic applications at terahertz frequency.