  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, post-fabrication tunable hybrid metasurfaces are still elusive.
Here, we present a reconfigurable hybrid metasurface platform by incorporating
the phase-change material Ge$_{2}$Sb$_{2}$Te$_{5}$ (GST) into metal-dielectric
meta-atoms for active and non-volatile tuning of properties of light. We
systematically design a reduced-dimension meta-atom, which selectively controls
the fundamental 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 miniaturized
tunable metasurfaces that control the amplitude and phase of incident light
necessary for high-contrast optical switching and anomalous to specular beam
deflection, respectively. Finally, we leverage a deep learning-based approach
to present an intuitive low-dimensional visualization of the enhanced range of
response reconfiguration enabled by the addition of GST. Our findings further
substantiate dynamically tunable hybrid metasurfaces as promising candidates
for the development of small-footprint energy harvesting, imaging, and optical
signal processing devices.
