Full-space metasurface in mid-infrared based on phase change material of VO2.

Most of the traditional metasurfaces are passive and work with a single function, which limits their application in integrated devices. Phase change materials based metasurfaces offer flexible functions. In this work, we proposed a full-space tunable metasurface working at wavelength of 8.5 μm based on vanadium dioxide (VO₂). When the VO₂ is metallic, the metasurface works as a half-wave plate in reflective mode and the polarization conversion efficiency through the metasurface could be greater than 90% over a broadband range of 1.32 μm. When the VO₂ is insulated, the metasurface works as a focusing lens in transmission mode with focusing efficiency up to 65% and full-width half-maximum (FWHM) of 0.67 λ. This result may provide a new route for the development of multifunctional devices. [ABSTRACT FROM AUTHOR]