  Optical metasurfaces (OMSs) have shown unprecedented capabilities for
versatile wavefront manipulations at the subwavelength scale, thus opening
fascinating perspectives for next generation ultracompact optical devices and
systems. However, to date, most well-established OMSs are static, featuring
well-defined optical responses determined by OMS configurations set during
their fabrication. Dynamic OMS configurations investigated so far by using
controlled constituent materials or geometrical parameters often exhibit
specific limitations and reduced reconfigurability. Here, by combining a
thin-film piezoelectric micro-electro-mechanical system (MEMS) with a
gap-surface plasmon based OMS, we develop an electrically driven dynamic
MEMS-OMS platform that offers controllable phase and amplitude modulation of
the reflected light by finely actuating the MEMS mirror. Using this platform,
we demonstrate MEMS-OMS components for polarization-independent beam steering
and two-dimensional focusing with high modulation efficiencies (~ 50%),
broadband operation (~ 20% near the operating wavelength of 800 nm) and fast
responses (< 0.4 ms). The developed MEMS-OMS platform offers flexible solutions
for realizing complex dynamic 2D wavefront manipulations that could be used in
reconfigurable and adaptive optical networks and systems.
