Interaction of aerosol particle with a standing wave optical field
John J. Curry
Trajectories of spherical dielectric particles carried across an optical standing wave by a flowing medium areinvestigated. Trajectories are determined by a three-dimensional Monte Carlo calculation that includes drag forces, Brownian motion, and optical gradient forces. We analyze the case of polystyrene particles with radii of order 100 nm carried across a Gaussian-mode standing wave by slowly owing air. Particles are injected into the flowing air from a small source area such as the end of a capillary tube. Different sizes are dispersed continuously in space on the opposite side of the standing wave, demonstrating a practical way to sort particles. The positions of the particles on the output side enable us to calculate the dispersion and resolution of the system. Certain discrete values of particle size show no interaction with the optical eld, independent of intensity. These particles can be sorted with exceptionally high resolution. For example, we showing sorting of particles with radii of 275 nm being sorted with 1 nm resolution. The system has the advantages of accommodating a high throughput, producing a continuous stream of continuously dispersed particles, and exhibiting excellent size resolution. The Monte Carlo results are in agreement with those obtained by a much simpler, and faster, fluid calculation based on effective velocities and effective diffusion coefficients, both obtained by averaging trajectories over multiple fringes of the optical field.
Interaction of aerosol particle with a standing wave optical field, Optical Trapping and Optical Micromanipulation, San Diego, , [online], https://doi.org/10.1117/12.2237845
(Accessed June 8, 2023)