Four-band highly sensitive tunable absorber based on Al-Cu-Fe quasicrystals

This paper introduces a four-band tunable perfect absorber built on Al-Cu-Fe quasicrystal. The operating frequency range is 4.75 THz to 9.25 THz, which is in the terahertz band. The absorber exhibits multiple narrow bands, polarization incoherence, high sensitivity, and tunability. The structure comprises a gold layer, a silica dielectric layer, and a top layer of Al-Cu-Fe quasicrystal from bottom to top. The Al-Cu-Fe quasicrystal structure at the top consists of a circular ring left after being cut by a 45° rotation of the cruciform and a cruciform design containing a central circular cavity. Simulation results reveal four absorption peaks attributed to cavity resonance and surface plasmon resonance, with absorption efficiencies of 0.998, 0.994, 0.989, and 0.998, respectively. Furthermore, changing the radius of the inner ring in the top layer structure allows for varying the number of absorption peaks. We also propose a new fabrication process for Al-Cu-Fe quasicrystals absorbers. The calculated results demonstrate that the designed absorber, characterized by a simple structure and high sensitivity of 2620 GHz/RIU, holds significant potential for applications in optical switches, optical modulators, biomedicine, and sensing.