Orbital dynamics at atmospheric pressure in a lensed dual-beam optical trap

Orbital dynamics of a dielectric microparticle in air using a lensed counter-propagating dual-beam trap was studied experimentally and by numerical simulations. Relationships between the dynamic parameters, trap geometry, and optical power were examined both experimentally and computationally. We found that this scheme can provide narrow bandwidth (δν/ν≈10^-3) detection that is at least two orders of magnitude below typical values attainable with previously studied geometries. We predict that this characteristic makes the approach suitable for ultrasensitive in-situ detection of particle mass changes. In our experimental conditions, silica microspheres orbited on trajectories spanning tens of µm, at frequencies of up to ∼2kHz, at atmospheric pressure. With the help of simulations, we briefly discuss how the dual-beam lensed orbital trap approach can be further enhanced to gain unmatched capabilities to measure changes in the physical parameters associated with a particle interacting with its surrounding medium.