Dynamically controlled terahertz coherent absorber engineered with VO2-integrated Dirac semimetal metamaterials

Abstract The authors theoretically demonstrated a tunable- and switchable-metamaterial absorber at the terahertz (THz) frequency. The proposed absorber comprising Bulk Dirac semimetal (BDS) metamaterials and vanadium dioxide (VO2) continuous film, which can be switched between a traditional and coherent absorber by tailoring the conductivity of VO2 film. When VO2 is in its metallic state, the proposed absorber behaves as a traditional absorber, and it achieves an absorptivity of 92% for y-polarised incidence at 3 THz with a single illumination at normal incidence. Decreasing the conductivity of VO2 leads to a metallic-to-insulating phase transition for the continuous VO2 film that is accompanied by a significantly reduced absorptivity for this traditional absorber. At this time, coherent perfect absorption concept is introduced to realise a coherent absorber. The coherent absorptivity of y-polarised incidence can be dynamically modified from 0.21% to 98.5% by manipulating the mutual phase between two coherent counter-propagating incidences at the position of absorber. Furthermore, the absorption performance of traditional and coherent absorbers can be tuned individually by modifying the geometric parameters of the metamaterial structure and the Fermi energy of the BDS from 85 to 125 meV. These simulation results provide an alternative approach for the design of multi-controlled tunable absorbers in the terahertz band, exhibiting promising applications in the fields of light modulation, cloaking, and signal processing.