The Guiding Light: Probing and Controlling the Microscopic World with Computational Holography

Abstract:

Holographic trapping organizes micrometer-scale colloidal particles into any desired three-dimensional configuration by imposing specified patterns of force and torque.  This level of control is achieved by imprinting computer-designed patterns of amplitude, phase and polarization onto the wave fronts of a laser beam that is projected into the colloidal dispersion.  Holographic video microscopy offers a complementary view into how the particles respond to these forces, and why.  Each holographic snapshot yields the three-dimensional position of each particle in the field of view, typically with nanometer resolution over a range extending to hundreds of micrometers.  The same analysis also yields each particle's size to within a nanometer and its refractive index to within a part per thousand.  No other technique yields such a wealth of particle-resolved characterization data.  Techniques developed for holographic characterization, in turn, provide insights into light scattering that can be used to design novel approaches to optical micromanipulation, including the first experimental demonstration of a practical tractor beam.

Host: Professor Eric Dufresne

Wednesday, January 21, 2015

Mason Lab 107

Refreshments 2:15pm