Multi-controlled broadband terahertz absorber engineered with VO 2 -integrated borophene metamaterials

We demonstrated a dynamically controlled broadband terahertz (THz) metamaterials absorber, which composed of continuous vanadium dioxide (VO2) film, a silicon dioxide (SiO2) layer, and a structured borophene layer. When VO2 is in its metallic state and the armchair direction of borophene along x axis, the proposed absorber realizes an absorptivity peak value of 100% at 7.2 THz for y polarized normal incidence, and an absorptivity peak value of 79% at 8.9 THz for x polarized normal incidence. It is the anisotropic property of borophene that results in the absorptivity difference for x and y polarization in the whole frequency range. Simulated electric field distribution and surface current oscillation has been extracted to explain the physical mechanism of THz wave absorption. Through modifying the geometric parameters of metamaterials microstructure, the broadband absorption performance can be tailored passively. Additionally, the proposed metamaterials absorber has been actively controlled by manipulating the carrier density of borophene and the conductivity of VO2, respectively. The absorptivity can be switched from 45% to 100% at 7.2 THz by changing the carrier density of borophene, and from 22% to 100% at 7.2 THz by changing the conductivity of VO2. Moreover, the proposed absorber exhibits an excellent operation tolerance for oblique TE and TE polarized incidence from 0° to 60°. This work provides a novel approach to design dynamically controlled broadband THz absorbers, which reveals promising applications in the devices of optoelectronic switches, cloakings, filters, and sensors, etc.