Technical: This project, supported by the Electronic and Photonic Materials Program and the Condensed Matter Physics Program, is on experimental and theoretical investigation of quasi-crystalline and multiscale plasmonic crystals. Built on the previous research by the PIs on plasmonic materials, especially on nanoparticles as well as nanostructured metal films and surfaces created using soft nanolithography techniques, the current project moves in new directions and emphasizes broadband, aperiodic, and low-symmetry metal lattices, whose properties are mostly unknown in the plasmonics field because the structures cannot easily be fabricated, and especially not over large areas (> 1 cm2). Such structures and their measured and calculated dispersion properties are important because they can provide new insight into enhanced optical transmission and other light-surface plasmon coupling mechanisms. Scientific issues such as enhanced transmission, coupled long/short range plasmon interactions, s-polarized optical responses, and coupled Rayleigh anomaly/surface plasmon polariton modes will be studied.
The project addresses basic research issues in a topical area of science with high technological relevance. Nanophotonics is an emerging research area that will have impacts on optical communication, information storage, and chemical sensors. The project will train a high tech work force in experimental and theoretical nanophotonics research. One example is a course on Nanopatterning: Top-down Meets Bottom-up. Some aspects of the optical property modeling are being adapted to General Chemistry courses that the PIs also teach. Moreover, the simple nanopatterning techniques developed by the PIs are disseminated worldwide through the web and are being tested with international partners, including professors and students in several Africa counties.
Plasmonics is a rapidly growing field focused on how light interacts with metal nanostructures. In particular, nanostructured materials have high potential in photovoltaics and optoelectronics. This project focused on designing and modeling new types of artificially structured materials with symmetries not found in nature. The new geometries discovered in this project were able to trap light over a broad visible spectrum and over a range of incident angles, which is critical for broadband photovoltaics. Because these materials were constructed out of noble metals such as gold and silver and other so-called "plasmonic" materials, their optical properties also contained rich and complex spectral features not possible in periodic nanostructures. Our high rotational symmetry and multi-scale structured materials provided new insight into unusual phenomena such as enhanced optical transmission and other light-matter interactions at the nanoscale. The major intellectual merit outcomes include: (1) the realization of plasmonic substrates with rotational symmetries up to three times higher than that found in natural materials (36 fold) and the development of a new analytical model to index their optical properties; and (2) the invention of "liquid" plasmonics and the ability to tune the plasmonic properties by controlling the phase (liquid or solid) of the material (gallium and liquid metal alloys). The primary broader impact outcomes include: (1) the generation of large-area nanopatterns that can exhibit structural color; and (2) the development of hands-on nanophotonics labs using our macroscale nanofabrication and assembly methods. The tools enable a critical step for integrating nanoscale systems into practical photonic and optoelectronic devices.
