  Vibrational resonance amplifies a weak low-frequency signal by use of an
additional non-resonant high-frequency modulation. The realization of weak
signal enhancement in integrated nonlinear optical nanocavities is of great
interest for nanophotonic applications where optical signals may be of low
power. Here, we report experimental observation of vibrational resonance in a
thermo-optically bistable photonic crystal optomechanical resonator with an
amplification up to +16 dB. The characterization of the bistability can
interestingly be done using a mechanical resonance of the membrane, which is
submitted to a strong thermo-elastic coupling with the cavity.
