Multifunctional Terahertz Transparency of a Thermally Oxidized Vanadium Metasurface over Insulator Metal Transition

Abstract Vanadium dioxide (VO 2 ) is one of the most promising materials for active metasurfaces due to the insulator‐metal transition, urging the development of an etching‐free patterning method and realization of multifunctionality in various spectral bands. Here, without etching, photolithography of vanadium metal followed by thermal oxidation achieve all‐VO 2 slit array metasurfaces that can be exploited as a multifunctional terahertz (THz) transparent electrode. The metasurfaces retain approximately constant THz transparency over the phase transition while the electrical conductivity of the VO 2 lines changes about a thousand times, and near‐infrared (NIR) diffraction is switched selectively. Numerical simulation shows that, during the phase transition, a decrease in THz transmission through the VO 2 lines is compensated for by funneling through the slits, which is especially efficient with a deep subwavelength period. On the contrary, at the NIR range, the optical path difference between the slits and the VO 2 lines is controlled according to the VO 2 phase, enabling switching between constructive and destructive interferences for a specific diffraction order. It is expected that the demonstrated patterning method and multifunctional THz transparency will promote VO 2 ‐based metasurfaces, finding multispectral applications such as THz/NIR hybrid communication.