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 2.5×10⁻⁴ S/m, the designed structure represents an ultra-wideband absorber with an absorption larger than 90% in the range of 3.14∼7.80 THz. As VO₂ is in an insulation state and the conductivity of photoconductive silicon becomes 8.0×10⁴ S/m, the designed device acts as two absorption bands, with a terahertz wave absorber with absorption more than 98% at 1.78∼2.90 THz and 7.35∼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°) for TE- and TM- polarizations incidence.

中文翻译：

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可切换的双频和超宽带太赫兹波吸收器

在本文中，我们介绍了一种基于光电导硅结合二氧化钒 (VO ₂ )的可切换双频和超宽带太赫兹波吸收器。在太赫兹吸收体中，从顶层到底层依次放置了光电导硅十字阵列、二氧化硅层、二氧化钒风车型阵列、二氧化硅介质层、金地平面。当VO ₂处于金属态且光电导硅的电导率为2.5×10 ^-4 S/m 时，设计的结构代表了在3.14∼7.80 THz 范围内吸收大于90% 的超宽带吸收体。由于VO ₂处于绝缘状态，光电导硅的电导率变为8.0×10 ⁴S/m，设计的器件作为两个吸收带，在 1.78∼2.90 THz 和 7.35∼8.45 THz 处有一个太赫兹波吸收体，吸收率超过 98%。结果表明，通过改变VO ₂的相变和光电导硅的电导率，可以切换吸收带（双带或超宽带）和吸收强度（从2%到99%）。此外，所提出的器件对于 TE 和 TM 偏振入射表现出偏振不敏感和宽入射角（大于 70°）。