  Linear mechanical oscillators have been applied to measure very small forces,
mostly with the help of noise suppression. In contrast, adding noise to
non-linear oscillators can improve the measurement conditions. Here, this
effect of stochastic resonance is demonstrated in a macroscopic torsion
oscillator, for an optomechanical non-linear potential. The signal output is
enhanced for a sub-threshold electronic signal. This non-linear oscillator
serves as a model system for the enhancement of signal-to-noise ratio in high
precision optomechanical experiments.
