Ultra-High Resolution Temperature Sensing Based on Microcavity Optomechanical Self-Oscillation

High-resolution sensing methods hold significant importance in the advancement of sensor technology. Whispering gallery mode (WGM) microcavities have been extensively investigated due to their superior sensitivity and precision, yet their resolution is often constrained by the modal linewidth, posing challenges for further enhancement. In this paper, we propose a resolution-enhanced sensing approach based on ultra-narrow linewidth optomechanical self-oscillation and experimentally demonstrate its application in high-resolution temperature sensing. By harnessing the optomechanical dynamical backaction within the system, the microcavity is driven into a self-oscillation state at room temperature, leading to a substantial narrowing of the mechanical linewidth down to 0.345 mHz. When temperature variations alter the refractive index of the microcavity, causing spectral shifts, the subsequent mechanical frequency shift enables high-resolution readout. Leveraging the low phase noise and high oscillation frequency of the optomechanical self-oscillation, we employ a phase-locked loop technique to directly convert the sensing signal into a direct current (DC) feedback voltage, ultimately achieving an ultra-high temperature resolution of 4.19 micro-Kelvin (μK). This represents a significant improvement of approximately 37 times compared to sensing solely based on whispering gallery modes. This approach presents a novel pathway for high-resolution sensing and can be extended to other sensing applications, offering a promising avenue for advancing sensing capabilities.