Actively Tunable THz Absorber for Switchable Operations Between Different Absorption Behaviors

Many previous VO
₂
-based perfect metamaterial absorbers can enhance light-matter interaction when VO
₂
is in metal phase but with weak light-matter interaction when VO
₂
is in insulator phase. In this work, an actively tunable terahertz (THz) absorber with the ability to switch between dual-band absorption and single ultra-narrowband absorption is theoretically proposed and numerically demonstrated. The electric dipole resonance, localized surface plasmon resonance, Fabry-Perot resonance and surface lattice resonance are utilized to enhance light-matter interaction. The simulation results show that an absorption peak has an absorptance of 98.6% and the
Q
-factor reaches 351.5 when vanadium dioxide (VO
₂
) is in the insulating phase. Then, two absorption peaks with the absorptance of 96.2% and 99.5% are presented at 2.30 THz and 3.31 THz, respectively, when VO
₂
is in the metallic phase. To better understand the physical mechanisms of this absorber, the influence of parameters is further investigated. The proposed absorber with the dynamically tunable characteristic between such distinct states can pave numerous promising applications in sensing, imaging, active switch and modulator.