  The work of Braginsky introduced radiation pressure dynamical backaction, in
which a mechanical oscillator that is parametrically coupled to an
electromagnetic mode can experience a change in its rigidity and its damping
rate. The finite cavity electromagnetic decay rate can lead to either
amplification or cooling of the mechanical oscillator, and lead in particular
to a parametric oscillatory instability, associated with regenerative
oscillations of the mechanical oscillator, an effect limiting the circulating
power in laser gravitational wave interferometers. These effects implicitly
rely on an electromagnetic cavity whose dissipation rate vastly exceeds that of
the mechanical oscillator, a condition naturally satisfied in most
optomechanical systems. Here we consider the opposite limit, where the
mechanical dissipation is engineered to dominate over the electromagnetic one,
essentially reversing role of electromagnetic and mechanical degree of freedom.
As a result, the electromagnetic field is now subject to dynamical backaction:
the mechanical oscillator provides a feedback mechanism which modifies the
damping rate of the electromagnetic cavity. We describe this phenomenon in the
spirit of Braginsky's original description, invoking finite cavity delay and
highlighting the role of dissipation. Building on previous experimental work,
we demonstrate this dynamical backaction on light in a superconducting
microwave optomechanical circuit. In particular, we drive the system above the
parametric instability threshold of the microwave mode, leading to maser action
and demonstrate injection locking of the maser, which stabilizes its frequency
and reduces its noise.
