Vanadium dioxide-based broadband spin-decoupled metasurface for wavefront control and modulation

Effective independent control of the phase and polarization of orthogonal circularly polarized (CP) light on a single metasurface is desirable in the terahertz band. However, most of the spin-decoupled metasurfaces reported so far suffer from the problem of non-adjustable and limited bandwidth. In this work, we proposed a vanadium dioxide assisted metasurface to independently control the wavefront of the left-hand circular polarized (LCP) and right-hand circular polarized (RCP) waves. By changing the phase state of Vanadium dioxide (VO2) to turn on or off circular dichroism (CD), the wavefront of the RCP can be dynamically manipulated without affecting the LCP. As a proof of concept, we designed five metasurfaces that can produce focused beams at arbitrary positions, vortex beams carrying orbital angular momentum (OAM) with incident spin-dependent topological charges, and switchable focusing beams, vortex beams, etc. These devices have a fractional bandwidth of 66% (1-2 THz). Such tunable and diversified functional devices have promising applications in terahertz super-resolution imaging and terahertz communication, chiral spectroscopy.