Optical Nanostructures for Enhanced Light-Matter Interactions and Energy Harvesting

The talk will focus on the design and development of high throughput, large scale and low cost fabrication of optical nanostructures for enhanced light-matter interactions in artificially structured metal/dielectric structures (metamaterials, plasmonic nanostructures), transformation optics for display/camouflage, strong coupling between photonic and plasmonic resonances and trapping light in thin film solar cells. We are currently pursuing approaches based on proximity field nanopatterning, soft nanoimprint lithography and nanotransfer printing patterning techniques. In their current forms, these methods can produce diverse classes of 3D and quasi-3D nanostructures with excellent structural uniformity and small features sizes. Their operational characteristics avoid practical challenges in patterning speed and area coverage associated with established techniques such as electron and focused ion beam lithography. In one example, we developed a nanotransfer printing based fabrication approach to large-area, high-quality negative index metamaterials (NIMs) with three-dimensional layouts with throughputs and areal coverage that are approximately one hundred million times higher than those possible with conventional techniques. Measurements and simulations show expected negative index behaviors, with figures of merit that exceed those of small samples fabricated in the usual way. In other work, we used soft nanoimprint lithography to create structures with plasmonic responses that couple strongly to modes of integrated, asymmetric Fabry-Perot cavities. We demonstrated that this arrangement can exhibit highly enhanced or diminished reflection properties, effectively like a narrow band absorber, but in a way that can be tuned reversibly using the techniques of opto-fluidics. We also developed wave optics light trapping schemes to enhance light absorption in thin-film silicon solar cells and demonstrated cell efficiency of >10% in just 2.8µm thick c-Si cells.