Plasmonics Sheds New Light on Optics Study

HOUSTON, Texas, Nov. 14 -- Scientists studying the way light interacts with metallic nanostructures should throw out their old optics textbooks and bone up on their quantum mechanics instead, according to new research from Rice University.

The new findings offer a new understanding of plasmonics, an emerging field of optics aimed at the study of light at the nanometer scale -- at dimensions far smaller than a wavelength of light, smaller than today’s smallest electronic devices. Rice’s findings, published recently in the journal Science, will make it easier for scientists and engineers to design new optical materials and devices "from the bottom up," using metal particles of specifically tailored shapes.

The field of plasmonics, which has existed for only a few years, has already attracted millions of research dollars from industry and government, the university said. One primary goal of this field is to develop new optical components and systems that are the same size as today’s smallest integrated circuits and that could ultimately be integrated with electronics on the same chip. In the field of chemical sensing, plasmonics offers the possibility of new technologies that will allow doctors, antiterror squads and environmental experts to detect chemicals in quantities as small as a single molecule -- a prospect so intriguing the National Nanotechnology Initiative chose it as one of this past year’s primary funding objectives.

"What this work gives us is a simple, intuitive model that describes how ultrasmall metal structures of various shapes capture and manipulate light," said Naomi Halas, a professor of electrical and computer engineering and of chemistry at Rice. "It provides a practical design tool for nanoscale optical components."

The researchers said the fact that light interacts with nanostructures at all flies in the face of traditional optics, which held for more than a century that light waves couldn’t interact with anything smaller than their own wavelengths. Research over the past five years has turned that assumption on its head, showing that nanoscale objects can amplify and focus light in ways scientists never imagined

"What we’ve found is that plasmons in nanoparticles hybridize with each other in the same way that atomic energy levels hybridize with each other when atoms form molecules," said Peter Nordlander, the theoretical physicist who led the study. "The findings are applicable not only to nanoshells, but to nanoscale wave guides and any other nanophotonic structures."

Nordlander, a professor in both the physics and astronomy and the electrical and computer engineering departments at Rice, said the importance of the research is that it frees researchers from having to describe nanophotonic structures in terms of classical optics, something that plasmonic scientists have struggled with since the field was formed.

For more information, visit: www.rice.edu