  The resonant buildup of light within optical microcavities elevates the
radiation pressure which mediates coupling of optical modes to the mechanical
modes of a microcavity. Above a certain threshold pump power, regenerative
mechanical oscillation occurs causing oscillation of certain mechanical
eigenmodes. Here, we present a methodology to spatially image the
micro-mechanical resonances of a toroid microcavity using a scanning probe
technique. The method relies on recording the induced frequency shift of the
mechanical eigenmode when in contact with a scanning probe tip. The method is
passive in nature and achieves a sensitivity sufficient to spatially resolve
the vibrational mode pattern associated with the thermally agitated
displacement at room temperature. The recorded mechanical mode patterns are in
good qualitative agreement with the theoretical strain fields as obtained by
finite element simulations.
