• Allan variance is introduced to evaluate the stability of the optically optomechanical system for actual force detection performance. • The system obtains a force detection sensitivity of 4.34 zN/Hz^1/2 at 7.9 × 10⁻⁹ mbar under parametric feedback cooling, which is the best force sensitivity in a levitated optomechanical system so far. • The optimal measurement time is 2751 s, and the force detection resolution corresponding to this time scale is approximately 166.40 ± 55.48 yN, which is also the best force resolution in a levitated optomechanical system so far.

The nanomechanical resonator based on a levitated particle exhibits unique advantages in the development of ultrasensitive electric field detectors. We demonstrate a three-dimensional, high-sensitivity electric field measurement technology using the optically levitated nanoparticle with known net charge. By scanning the relative position between nanoparticle and parallel electrodes, the three-dimensional electric field distribution with microscale resolution is obtained. The measured noise equivalent electric intensity with charges of 100 e reaches the order of 1 μV ⋅ cm − 1 ⋅ Hz − 1 / 2 at 1.4 × 10 − 7 mbar . Linearity analysis near resonance frequency shows a measured linear range over 91 dB limited only by the maximum output voltage of the driving equipment. This work may provide an avenue for developing a high-sensitivity electric field sensor based on an optically levitated nano-resonator.

A dual-fiber optical trap system to trap and rotate a borosilicate microsphere has been proposed and experimentally demonstrated. The trapping system can be used as a probe to measure environmental parameters, such as torque, force, and viscosity of the surrounding medium. Under various conditions with different fiber misalignments, optical power, and fiber separation, the trapped sphere will exhibit three motion profiles including random oscillation, round rotation, and abnormal rotation. The power spectrum analysis method is used to measure rotation rates up to 385 Hz, which can be further increased by increasing laser power. In addition, simulation and experiment show consistent results in rotation rates and motion trajectory, which verifies the validity and accuracy of dynamic analysis.

As a versatile tool for trapping and manipulating neutral particles, optical tweezers have been studied in a broad range of fields such as molecular biology, nanotechnology, and experimentally...

We presented faster and more accurate simulations and experiments describing the revolution of a suspended particle in optical tweezers under a low pressure. Instead of the state-of-the-art offline method of pinhole alignment, we proposed an in situ method of revolution suppression by adjusting the laser beam while observing the power spectral density and time-domain plot of the particle centroid displacement. The experimental results under different air pressures show that our method is more effective at low pressures. We observed that “revolution occurs when radial alignment error is below the threshold” and uncovered the mechanism behind this phenomenon. The rapidly growing Q value of the revolution indicates a high-precision resonance measurement method under lower air pressure compared with random translation measurements.

Optical trapping of single nanoparticles in vacuum has various applications in both precise measurements and fundamental physics. However, to date, the number and size of randomly loaded nanoparticles in an optical trap is difficult to determine unless in vacuum. In this Letter, an efficient method for nanoparticle size estimation in an optical tweezer system before the evacuation of air was proposed and demonstrated experimentally, using scattering light from levitated particles. The particle radii deduced from the scattering light power in our proposal and from the kinetic theory of particles in gas match well (with the differences of less than 10 % ). For sample particles with radii ranging within 50–100 nm, we also provide a preselection rule based on this method, where over half of the trapped particles are verified as single particles. Such a particle analysis method is applicable also for the size estimation of levitated diamond particles, gold particles, and other plasmonic particles and can be applied to discovering novel scattering effects.