  Electromagnetic fields coupled with mechanical degrees of freedom have
recently shown exceptional and innovative applications, ultimately leading to
mesoscopic optomechanical devices operating in the quantum regime of motion.
Simultaneously, micromechanical elements have provided new ways to enhance and
manipulate the optical properties of passive photonic elements. Following this
concept, in this article we show how combining a chiral metasurface with a GaAs
suspended micromembrane can offer new scenarios for controlling the
polarization state of near-infrared light beams. Starting from the uncommon
properties of chiral metasurface to statically realize target polarization
states and circular and linear dichroism, we report mechanically induced, ~300
kHz polarization modulation, which favorably compares, in terms of speed, with
liquid-crystals commercial devices. Moreover, we demonstrate how the mechanical
resonance can be non-trivially affected by the input light polarization (and
chiral state) via a thermoelastic effect triggered by intracavity photons. This
work inaugurates the field of Polarization Optomechanics, which could pave the
way to fast polarimetric devices, polarization modulators and dynamically
tunable chiral state generators and detectors, as well as giving access to new
form of polarization nonlinearities and control.
