  We study the dynamics of a mechanical resonator parametrically coupled to a
driven dissipative quantum emitter in the ultra-strong coupling regime. We show
that this regime is fully compatible with a semi-classical treatment, and we
derive master equations for the emitter and the resonator. We show that the
fluctuations of the driven emitter's population induce the non-symmetrical
scattering of the mechanical quadratures. At long timescales, such scattering
back-acts on the emitter, which eventually decouples from the driving light.
This optical noise at the quantum limit is observable with state of the art
hybrid devices.
