Bifunctional terahertz meta-device with switchable properties between dual-narrowband absorption and broadband absorption

Metamaterial-based optical devices have attracted considerable attention due to their significant potential for applications, but they encounter numerous challenges with regard to multifunctional integration and dynamic tunability. In this paper, we propose a tunable terahertz meta-device that exhibits multifunctionality, utilizing gold and vanadium dioxide (VO₂) surface patterned structures. The electromagnetic field polarization switching enables two types of operating modes of dual-narrowband absorption and broadband absorption, achieving a dual-function absorption meta-device. Maintaining the polarization angle constant, the phase transition of VO₂ provides the ability to independently modulate the absorbance of these two types of operating modes. The physical mechanism of the bifunctional terahertz absorption meta-device is elucidated through impedance matching theory and surface electric field distributions in different operating modes. Both of these operating modes have the characteristic of large-angle tolerance, and further research has been conducted on the use of dual-narrowband absorption mode for sensing applications. The merits of the aforementioned meta-device, encompassing structural simplicity, integration of multiple functions and dynamic tunability, are noteworthy and may stimulate interest in the development of powerful, compact and practical integrated terahertz components.