Enhanced high-sensitivity mass sensor in a gain-cavity-assisted optomechanical system

In this study, we propose and analyze a highly efficient scheme for realizing sensitive mass sensors in a quadratically coupled optomechanical system, assisted by a gain cavity via a nonlinear second-order sideband process. Moving beyond conventional linearized approximations, we derive analytical expressions for both the second-order sideband efficiency and mass-sensing sensitivity using a perturbation approach. Our scheme enables mass detection by monitoring shifts in the second-order sideband generation efficiency when a target mass is deposited on the dielectric membrane. Using experimentally feasible parameters, we identify the maximum achievable efficiency of the second-order upper sideband and its corresponding optimal sensitivity. Remarkably, with the aid of a gain cavity, both the sideband efficiency and mass sensitivity are significantly enhanced---particularly near the exceptional point, where improvements exceeding three orders of magnitude are demonstrated. This work provides a promising approach to high-precision mass measurement, advancing and complementing existing methodologies.