Multifunctional and dynamically tunable coherent perfect absorber based on InSb and graphene metasurface

Abstract

We propose a temperature-tunable and dual-broadband switchable coherent perfect absorber (CPA) composed of an annulus-disk-shaped InSb pattern and a complementary graphene layer. By controlling the Fermi level of graphene, the temperature of InSb, or the relative phase of incident beams, the working frequency and absorption of the CPA can be continuously adjusted. For a Fermi energy of 0 eV, the dual-band coherent perfect absorptivities exceed 99%. The designed structure achieves broadband absorptance of over 90% in the frequency range of 0.145 THz to 1.24 THz, with a relative bandwidth of about 158.12% for a Fermi energy of 0.5 eV. Moreover, the temperature-dependent permittivity of InSb enables thermal tuning of the dual-band CPA in the THz region. Furthermore, by altering the relative phase of input beams, the absorptivity can be continuously varied between less than 1.2% and more than 90% in the dual-band and broadband modes. Additionally, the designed CPA exhibits insensitivity to the polarization angle within the range of 0° to 90°. Therefore, this multifunctional CPA holds significant potential for applications in modulation, sensing, all-optical switches, and coherent photodetectors.