Rapid mass determination of airborne microparticles based on release and recapture from a free-space optical dipole force trap

We describe a method for the rapid determination of the mass of particles confined in an optical dipole force trap.* The technique relies on direct imaging of drop-and-restore experiments in a free-space environment. In these experiments, the trapping light is rapidly shuttered with an acousto-optic modulator, releasing and subsequently recapturing the particle using the trapping force. Both the fall and restoration trajectories, imaged using a high-speed CMOS sensor, are combined to determine the particle mass. We corroborate these measurements using an analysis of position autocorrelation functions and the mean-square displacement of the trapped particles. We report a statistical uncertainty of less than 2% for masses on the order of 5×10^-14 kg in approximately 90 s of data acquisition.

*Carlse et al. Phys. Rev Appl. 14, 024017 (2020)