  Cavity optomechanics implements a unique platform where moving objects can be
probed by quantum fields, either laser light or microwave signals. With a pump
tone driving at a frequency above the cavity resonance, self-sustained
oscillations can be triggered at large injected powers. These limit cycle
dynamics are particularly rich, presenting hysteretic behaviours, broad comb
signals and especially large motion amplitudes. All of these features can be
exploited for both fundamental quantum research and engineering. Here we
present low temperature microwave experiments performed on a high-Q cavity
resonance capacitively coupled to the flexure of a beam resonator. We study the
limit cycle dynamics phase space as a function of pump parameters (detuning,
power). Unexpectedly, we find that in a region of this phase space the
microwave resonance is irremediably destroyed: only a dramatic power-reset can
restore the dynamics to its original state. The phenomenon can be understood as
an optical instability linked to the Kerr nonlinearity of the cavity. A theory
supporting this claim is presented, reproducing almost quantitatively the
measurement. This remarkable feature might be further optimized and represents
a new resource for quantum microwave circuits.
