Beating the standard quantum limit for force sensing with a coupled two-mode optomechanical system

Understand

Optomechanics allows the transduction of weak forces to optical fields, with many efforts approaching the standard quantum limit.

• We consider force-sensing using a mirror-in-the-middle setup and use two coupled cavity modes originated from normal mode splitting for separating pump and probe fields.
• We find that this two-mode model can be reduced to an effective single-mode model, if we drive the pump mode strongly and detect the signal from the weak probe mode.
• The optimal force detection sensitivity at zero frequency (DC) is calculated and we show that one can beat the standard quantum limit by driving the cavity close to instability.