Experimental studies of optical trapping

A focused laser beam can grab hold of and exert forces and torques on microscopic particles about 100 times smaller than the diameter of a human hair. This is known as optical tweezers. We have built an optical tweezers microscope at Ithaca College and plan to use it to study how particles with complex shapes can be trapped and manipulated. We are also about to begin a new project where we will use the optical tweezers to measure the interactions between squishy, temperature-sensitive polymer spheres.

A 1.0-micrometer-diameter silica sphere trapped in our optical tweezers! The trapping laser beam is alternately blocked and unblocked.

Computational studies of optical trapping

Predicting how non-spherical particles behave in optical tweezers is not possible analytically. Instead, computer simulations are required. We are performing physically realistic simulations of the behavior of non-spherical particles in optical tweezers and other complex optical fields. We run the simulations both locally and on the Comet cluster at the San Diego Supercomputer Center. Our simulations help guide our experiments and help us gain insight into nanoscale interactions between light and matter more broadly.

Simulation of a cluster of two 1.6-micrometer-diameter silica spheres trapped in a circularly-polarized beam (slowed 5x). The cluster rotates because spin angular momentum in the beam gets transferred to the cluster.

Members of the Team