Physics Colloquium: Simulating Colloidal Particle Dynamics in Optical Vortex Beams: Down to a T

Physics Colloquium
Simulating Colloidal Particle Dynamics in Optical Vortex Beams: Down to a T

Dr. Jerome Fung
Associate Professor, Department of Physics and Astronomy
Ithaca College

Abstract:
A tightly-focused Gaussian beam (an idealized laser beam) can form optical tweezers that trap nanometer-to-micrometer-scale particles stably. Laguerre-Gaussian beams generalize Gaussian beams: they are optical vortices in which the light forms rings around a dark axis and carries orbital angular momentum that can drive particle motion around that axis. I will discuss simulations of the dynamics of colloidal sphere clusters (small particles suspended in a liquid) trapped in Laguerre-Gaussian beams. The clusters orbit the beam axis while also spinning about their own center, revealing surprising interplay between the orbital and spin angular momenta of the beam. Our Brownian dynamics simulations rely on a mathematical description of how particles scatter light called the T matrix. I will also discuss using the discrete dipole approximation to calculate T matrices for arbitrarily-shaped particles, which will broaden the particle shapes we can simulate.

Speaker Bio:
Jerome Fung is Associate Professor of Physics at Ithaca College, where he teaches courses across the curriculum and mentors undergraduates in computational and experimental research in optics and soft condensed matter physics. Before coming to Ithaca College, Jerome was Lecturer in Physics at Wellesley College. Prior to that, he performed postdoctoral research on colloidal membranes formed from filamentous bacteriophages at Brandeis University. Jerome earned his PhD in Physics at Harvard University, studying holographic microscopy and colloidal suspensions. Jerome completed his undergraduate studies at Swarthmore College, where his first exposure to research was in experimental plasma physics.

Intended Audience:
Beginners, undergraduates, graduates. Those with interest in the topic.

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