Abstract

We present an alternative approach to force sensing with optomechanical systems. The operation is based on a nonlinear dynamical mechanism, which locks the mechanical oscillation and the associated cavity field pattern of a system when two external drive tones satisfy a frequency match condition. Under a weak force that adds a slight detuning to the external driving fields, the cavity field will undergo a transition between two locked patterns while the locked mechanical oscillation is well preserved, thus having the small modifications to its sidebands. The force sensing is realized by detecting the intensity changes of the cavity field sidebands in such process. With the currently available optomechanical systems, the sensitivity of force detection can reach the level of attonewton and can be further improved with improved system parameters and longer detection time. One important feature of the applied dynamical scenario is that thermal noise insignificantly affects the cavity field sidebands of the locked states, so that the scheme can work well even at room temperature. This method is hopeful to reduce the difficulty in the practical applications of force sensing.