Switchable VO <sub>2</sub> -metasurface for terahertz polarization converter and absorber
Jian-Di Li, Yinghua Wang, Xiaoman Li, Xu-Zhen Gao, Yue Pan, Hong-Zhong Cao, Ren-De Ma, Zhong‐Xiao Man, Shi‐Tong Xu
Abstract
The integration of metasurfaces with functional materials has attracted significant attention for the development of active terahertz (THz) devices. In this study, we demonstrate a switchable THz metasurface incorporating vanadium dioxide (VO 2 ) phase-change material, capable of dynamically switching between three distinct operational modes: half-wave plate (HWP), quarter-wave plate (QWP), and broadband absorber. Specifically, when both VO 2 layers are in the insulating phase (IP) state, the proposed structure functions as an efficient HWP, achieving a polarization conversion ratio (PCR) exceeding 72% across a broad frequency range of 1.39-2.52 THz. When the middle VO 2 layer transitions from IP to the metallic phase (MP) state, the device switches to a QWP mode, achieving an exceptional polarization elliptical ratio (PER) of 0.98 within the frequency range of 1.20-2.20 THz. Furthermore, when both VO 2 layers are in the MP state, the metasurface functions as a broadband absorber, maintaining absorption efficiency above 68% over an ultra-wide bandwidth spanning 0.60-2.46 THz. Notably, the designed metasurface exhibits significant overlapping bandwidth characteristics within its operational frequency range. This work presents a highly effective strategy for developing reconfigurable THz devices, highlighting their significant potential for practical applications.