  The success of semiconductor electronics is built on the creation of compact,
low-power switching elements that offer routing, logic, and memory functions.
The availability of nanoscale optical switches could have a similarly
transformative impact on the development of dynamic and programmable
metasurfaces, optical neural networks, and quantum information processing.
Phase change materials are uniquely suited to enable their creation as they
offer high-speed electrical switching between amorphous and crystalline states
with notably different optical properties. Their high refractive index has also
been harnessed to fashion them into compact optical antennas. Here, we take the
next important step by realizing electrically-switchable phase change antennas
and metasurfaces that offer strong, reversible, non-volatile, multi-phase
switching and spectral tuning of light scattering in the visible and
near-infrared spectral ranges. Their successful implementation relies on a
careful joint thermal and optical optimization of the antenna elements that
comprise an Ag strip that simultaneously serves as a plasmonic resonator and a
miniature heating stage.
