Efficient hybrid plasmonic-photonic metasurfaces that simultaneously take advantage of the potential of both pure metallic and all-dielectric nanoantennas are identified as an emerging technology in flat optics. Nevertheless, postfabrication tunable hybrid metasurfaces are still elusive. Here, we present a reconfigurable hybrid metasurface platform by incorporating the phase-change material Ge2Sb2Te5 (GST) into metal-dielectric meta-atoms for active and nonvolatile tuning of properties of light. We systematically design a reduced-dimension meta-atom, which selectively controls the hybrid plasmonic-photonic resonances of the metasurface via the dynamic change of optical constants of GST without compromising the scattering efficiency. As a proof-of-concept, we experimentally demonstrate two tunable metasurfaces that control the amplitude (with relative modulation depth as high as ≈80%) or phase (with tunability >230°) of incident light promising for high-contrast optical switching and efficient anomalous to specular beam deflection, respectively. Our findings further substantiate dynamic hybrid metasurfaces as compelling candidates for next-generation reprogrammable meta-optics.
In contrast to lossy plasmonic metasurfaces (MSs), wideband dielectric MSs comprising subwavelength nanostructures supporting Mie resonances are of great interest in the visible wavelength range. Here, for the first time to our knowledge, we experimentally demonstrate a reflective MS consisting of a square-lattice array of hafnia (HfO2) nanopillars to generate a wide color gamut. To design and optimize these MSs, we use a deep-learning algorithm based on a dimensionality reduction technique. Good agreement is observed between simulation and experimental results in yielding vivid and high-quality colors. We envision that these structures not only empower the high-resolution digital displays and sensitive colorimetric biosensors but also can be applied to on-demand applications of beaming in a wide wavelength range down to deep ultraviolet.
