Manipulating the Meta-Atom

Reposted from Swanson School of Engineering - https://www.engineering.pitt.edu/News/2019/Ravi-Shankar-NSF-Metamaterials/

Metamaterials are a unique class of intricate composites engineered to interact with electromagnetic radiation – such as light – in ways that go beyond conventional materials. By designing their structure at the nanometer scale, such materials can steer, scatter and rotate the polarization of the light in unusual ways. Realizing their full potential in sectors like consumer electronics, bioimaging or defense, requires the ability to manipulate their intricate structure. This presents a daunting challenge – how to manipulate the nanoscale meta-atoms making up metamaterials to then manipulate light?

Thanks to a combined $1.7 million from the National Science Foundation, a research group led by faculty at the University of Pittsburgh’s Swanson School of Engineering hope to utilize “meta-atoms” to fine-tune metamaterials with light and in turn, control how they interact with the light itself. The projects are funded through the NSF’s Designing Materials to Revolutionize and Engineer our Future (DMREF) program.

“Consider something like photochromatic lenses, which have a simple reaction of darkening when exposed to ultraviolet light, and then lighten when you return indoors,” explained M. Ravi Shankar, principal investigator and professor of industrial engineering at the Swanson School. “Instead, if we harness the light to physically manipulate arrays of nano-scale structures we call meta-atoms, we can program much more complex responses.”

Because of the complexity of the problem, Dr. Shankar assembled a multi-disciplinary team from three other universities: Mark Brongersma, professor of materials science and engineering at Stanford University;  Robert P. Lipton, the Nicholson Professor of Mathematics at Louisiana State University; Hae Young Noh, assistant professor and Kaushik Dayal, professor of civil and environmental engineering at Carnegie Mellon University. The team hopes to discover new classes of dynamically programmable metamaterials using theories of plasmonic structures, which are aided by machine-learning algorithms. These will feed into experimental efforts to fabricate these structures.

Ultimately, the team envisions demonstrating a range of optical components, including beam steering devices, wave-front shaping systems and polarization converters, which are organized and controlled at the nanometer-scale. This would make them orders-of-magnitude more compact than conventional optical systems. Furthermore, these devices will be powered directly using light itself, without relying on electronics or on-board power sources. This opens a pathway for integrating these compact optical elements in applications ranging from autonomous vehicles, biomedicine and communication devices.