Switchable Tri-Functional Terahertz Metamaterial Integrated with Vanadium Dioxide and Photosensitive Silicon

This work presents a theoretical and numerical investigation of a switchable tri-functional terahertz metamaterial incorporating vanadium dioxide (VO₂) and photosensitive silicon. The selective absorption, broadband linear-to-linear polarization conversion, and dual-band asymmetric transmission (AT) can be realized by utilizing the phase transition characteristic of VO₂. When VO₂ behaves as a metal, the proposed metamaterial functions as a selective perfect absorber for <i>x</i>-polarized waves at 2.84 THz, while exhibiting near-zero absorption for <i>y</i>-polarized waves. When VO₂ is in its insulating state, the proposed metamaterial acts as a linear polarization converter, achieving a polarization conversion ratio exceeding 99% within the frequency range of 1.07 to 4.29 THz. Meanwhile, a dual-band AT effect can be simultaneously realized associated with the broadband near-perfect polarization conversion. Furthermore, the polarization conversion efficiency and AT can be actively modulated by adjusting the conductivity of the photosensitive silicon, offering a novel approach for realizing multifunctional terahertz devices.