Active optical switch and polarization-selective absorption in a VO2 based metasurface in THz region

Active metasurfaces with the capability of dynamic control enable versatile functions by applying external stimuli. In this paper, the two functions of switch and polarizer is realized by integrating vanadium dioxide (VO2) into a double-aperture array. With the VO2 phase transition from insulator to metallic phase, the absorption of VO2 based metasurface is switched from -0 to -1 at 2.68 THz, which behaves as a high-efficiency switch. Simultaneously, the same array at metallic VO2 state shows dual-band polarization selectivity. The giant linear dichroism (0.86) could be weakened to -0 by switching the phase of VO2 to insulator. In addition, the mechanism of the two-function switchable metasurface is discussed. The proposed VO2 based active metasurface possesses the merit of flexible dynamic control for both absorption strength and polarization selectivity in a fixed nanostructure, which will promote the development of THz system integration.