Inverse design of a broadband tunable terahertz metasurface absorber

A tunable terahertz vanadium dioxide (VO2) metasurface absorber based on inverse design is proposed and demonstrated numerically. The inverse design is a novel design method by which the optical structure found is based on the desired functional properties, significantly improving the design efficiency of optical structures. The metasurface absorber accomplishes more than 90% absorption between 2.88 and 7.15 THz. Peak absorption intensity may be dynamically changed between 4% and 96% as VO2 conductivity is changed between 200 S/m and 2 × 105 S/m. The physical mechanism is discussed by interference phase extinction, the theory of impedance matching and field distributions. The suggested absorber can be used for energy harvesting and terahertz filtering.