Colloquia & Guest Speakers
Design at the Nanoscale: Reaching the Limits of Light-Matter Interactions
Dr. Owen Miller, MIT
Wednesday, February 24, 2016
Goergen Hall, Room 101
Nanoscience is developing at a rapid pace, with ever more materials, form factors, and structural degrees of freedom now available. To confront these large design spaces, and leverage them for transformative technologies, new theoretical tools are needed. In three areas of optics -- photovoltaics, nanoparticle scattering, and radiative heat transfer -- I will demonstrate that the combination of large-scale computational optimization with new analytical frameworks enables rapid identification of superior designs, and spurs discovery of fundamental limits to wave-matter interactions.
In photovoltaics, the famous ray-optical 4n^2 limit to absorption enhancement has for decades served as a critical design goal, and it motivated the use of quasi-random textures in commercial solar cells. I will show that at subwavelength scales, non-intuitive, computationally designed textures outperform random ones, and can closely approach 4n^2 enhancements. Pivoting to metallic structures, where there has not been an analogous “4n^2” limit, I will show how energy-conservation principles lead to fundamental limits to the optical response of metals, answering a long-standing question about the tradeoff between resonant enhancement and material loss. The limits were stimulated by a computational discovery in nanoparticle optimization, where I will present theoretical designs and experimental measurements (by a collaborator) approaching upper bounds for absorption and scattering. The energy-conservation principles can be extended to the field of thermal radiation, where they generalize the (ray-optical) concept of a "blackbody" to near-field radiative heat transfer.
Dr. Owen Miller is a postdoctoral research associate in MIT Applied Math, working with Steven Johnson. He received his PhD in 2012 from UC Berkeley, where he was advised by Eli Yablonovitch and selected as an NSF Graduate Fellow. He received bachelor's degrees in EE and physics from the University of Virginia in 2007. His research interests center around leveraging large-scale computational optimization and theoretical analysis for nanoscale devices, especially for emerging energy applications.