Switchable Multi-Functional VO2-Integrated Metamaterial Devices in the Terahertz Region

In this paper, we present a multi-functional terahertz metamaterial device based on the gold and vanadium dioxide (VO2). Availing of the phase transition characteristic of VO2, the switchable performance between perfect absorption and broadband asymmetric transmission (AT) can be realized. When VO2 acts like a metal, the proposed metamaterial device behaves as a selectively perfect absorber for linearly polarized lights. By transforming the phase of VO2 into isolating state, broadband AT with high efficiencies over 90% can be achieved in the region from 1.5 THz to 2.5 THz. Moreover, perfect polarization conversion can be simultaneously realized associated with the AT effect. The Fabry-Perot-like cavity model and the electric field distributions are employed to explain the physical mechanism of the above phenomena. Besides, the proposed metamaterial shows a high tolerance to the incident angle for achieving perfect absorption and broadband AT effect. Our designed device may provide a new avenue for developing multi-functional metamaterial devices in the THz region.