High-resolution mass sensing in a hybrid spinning optomechanical system enhanced by phonon pump

In order to achieve high-precision mass detection of biomolecules, a high-resolution mass sensing scheme based on a hybrid spinning optomechanical system is proposed, in which a spinning whispering-gallery-mode optomechanical cavity driven by a phonon pump is coupled to another optical gain whispering-gallery-mode cavity. First, the Sagnac effect is generated by rotating the optomechanical cavity clockwise or counterclockwise, enabling nonreciprocal control of the cavity field frequency. Second, an optical gain cavity is introduced to construct a parity-time symmetric or broken system, enhancing the amplitude intensity of the transmission spectrum. Meanwhile, a phonon pump is employed to coherently drive the mechanical breathing mode, further strengthening the optical response of the system. By solving the quantum Langevin equations and applying the input-output formalism, the transmission spectrum of the probe field is obtained. When biomolecules (such as baculoviruses or coronaviruses) are deposited on the surface of the optomechanical cavity, the mass of the target molecules can be retrieved by monitoring the resonance frequency shift of the mechanical sideband peak in the transmission spectrum. Numerical results show that the Sagnac effect, optical gain cavity, and phonon pump collectively enhance the amplitude intensity of the transmission spectrum, thereby improving the sensitivity of mass sensing. Compared with conventional optical mass sensing schemes based on single-cavity optomechanical systems, the sensitivity of the proposed scheme is improved by approximately one order of magnitude, and the minimum detectable mass reaches the picogram level (~1 pg). This scheme achieves ultrasensitive, high-resolution biomolecule mass detection and provides a new physical platform for chip-scale ultrahigh-resolution sensing devices.