Reconfigurable VO2 metasurfaces with hybrid electro-optical control: manipulating THz radiation with 0.3 W/cm2 light

Abstract

Dynamicallyprogrammable metasurfaces capable of manipulating terahertz (THz) wavefronts in various manners depending on external controls are highly desired for next-generation wireless communication systems and new tools for THz diagnostics. Such metasurfaces may utilize the insulator-to-metal transition in VO2, which can be induced both electrically and optically. Optical control is especially convenient for individual addressing to each meta-atom, but it is hampered by the high optical switching threshold of VO2. We experimentally realize VO2-based THz metasurfaces with hybrid electro-optical control when the metasurface is brought close to the transition point by an almost-threshold current, and then is easily switched by unfocused continuous-wave light. We were able to control the metasurface THz transmission by 0.4W/cm2 near-IR light, while purely optical switching required tightly focused light with an intensity of >3×105W/cm2. After correcting for the fact that a tightly focused spot dissipates heat easier, we estimate that the optical switching threshold reduction due to the electric current alone is ∼2 orders of magnitude. Finally, coating the metasurface with Au nanoparticles further reduced the threshold by 30% due to plasmonic effects.