  We study an optomechanical cavity, in which a buckled suspended beam serves
as a mirror. The mechanical resonance frequency of the beam obtains a minimum
value near the buckling temperature. Contrary to the common case, in which
self-excited oscillations of the suspended mirror are optically induced by
injecting blue detuned laser light, in our case self-excited oscillations are
observed with red detuned light. These observations are attributed to a
retarded thermal (i.e. bolometric) force acting on the buckled mirror in the
inwards direction (i.e. towards to other mirror). With relatively high laser
power other interesting effects are observed including period doubling of
self-excited oscillations and intermode coupling.
