Switchable dual-band and ultra-wideband terahertz wave absorber

In this paper, we introduced a switchable dual-band and ultra-wideband terahertz wave absorber based on photoconductive silicon combining with vanadium dioxide (VO2). In the terahertz absorber, photoconductive silicon cross array, silicon dioxide layer, vanadium dioxide windmill type array, silicon dioxide dielectric layer, and gold ground plane are placed from the top layer to bottom layer in sequence. When VO2 is in a metallic state and the conductivity of photoconductive silicon is 2.5x10(-4) S/m, the designed structure represents an ultra-wideband absorber with an absorption larger than 90% in the range of 3.14 similar to 7.80 THz. As VO2 is in an insulation state and the conductivity of photoconductive silicon becomes 8.0x10(4) S/m, the designed device acts as two absorption bands, with a terahertz wave absorber with absorption more than 98% at 1.78 similar to 2.90 THz and 7.35 similar to 8.45 THz. The results show that the absorption band (dual-band or ultra-wideband) and absorption intensity (from 2% to 99%) can be switched by changing the phase transition of the VO2 and the conductivity of photoconductive silicon. Furthermore, the proposed device exhibits polarization insensitive and wide incident angles (lager than 70 degrees) for TE- and TM- polarizations incidence. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement