Phase-locked phonon laser enhanced ultra-weak force measurement

Optically levitated micro- and nanoparticles are an ideal optomechanical platform for precision measurements, particularly enabling the detection of ultraweak forces. Nevertheless, quantum backaction and inherent instabilities induced by the trapping laser fundamentally restrict further improvements in force sensitivity and resolution. To circumvent these bottlenecks, we actively drive the levitated nanoparticle's mechanical motion in a phase-locked phonon laser mode and integrate a carrier-modulation measurement architecture to enhance force sensing capabilities. The stable and high-amplitude oscillation of the phonon laser allows for the robust trapping under 1 mW-level laser power, which in turn reduces the force noise to 4.0(3)*10^-22 N/Hz^1/2. Furthermore, by using phase-locked phonon laser, the measurement system achieves active stabilization and extended coherence time with the measured signal to 12,500 seconds, realizing a measurement resolution of 8(4)*10^-24 N with a sensitivity of 9.3(7)*10^-22 N/Hz^1/2 under a loaded force. These results establish the phonon laser as a low-noise, long-coherence-time, self-stabilizing platform for precision measurements, as well as in quantum and fundamental physics tests.