Enhanced Force Sensitivity Based on Quadratic Optomechanical Coupling and an Optical Parametric Amplifier

Abstract Improving the precision of weak‐force measurements in an optomechanical system by reducing quantum noise has long been a crucial research topic. When nonlinearity is introduced into the system, quantum noise is significantly suppressed. Here, it is studied that how to utilize the joint effect of an optical parametric amplifier (OPA) and quadratic optomechanical coupling (QOC) to achieve force sensitivity that surpasses the standard quantum limit. Our results show that, in the soft‐mode regime (with a negative QOC strength), the sensitivity of force measurement is slightly enhanced compared with the stiff mode (with a positive QOC strength). However, the stiff mode is more effective in maintaining system stability. The introduction of the OPA further enhances the force sensitivity of the system, enabling it to surpass the standard quantum limit even under low‐power conditions. Through a detailed analysis of the noise spectrum, it is demonstrated that both the soft mode and the OPA can reduce shot noise, while the stiff mode can effectively reduce or even eliminate back‐action noise. These findings provide a promising platform for weak‐force sensing research and may also be applied to the development of force sensors based on hybrid optomechanical systems.