Scientists from the University of Massachusetts (UMass) Lowell, King’s College London, Paris Diderot University, and the University of Hartford have found that several materials with poor nonlinear characteristics can be combined together to form a new metamaterial that exhibits state-of-the-art nonlinear properties. The illustration shows two incoming (red) photons being converted into one reflected (green) photon as result of light interaction with the nanowire structure in the metamaterial. The nanowires are about 100 nanometers apart from center to center, which is about one-fifty-thousandth the diameter of human hair. Courtesy of the University of Massachusetts Lowell. “The enhancement comes from the way the metamaterial reshapes the flow of photons,” said professor Viktor Podolskiy, the project’s principal investigator at UMass Lowell. The new class of metamaterial can be structurally tuned to change the color of the light, resulting in a photon that exhibits a different level of energy. Enabling the interaction of photons is key to faster information processing and optical computing, said Podolskiy. “Unfortunately, this nonlinear process is extremely inefficient, and suitable materials for promoting the photon interaction are very rare,” he said. The team was able to show that reshaping of electromagnetic fields in metamaterials with plasmonic components could be used to transform second-harmonic generation (SHG) from a surface-dominated to volume-dominated regime and to engineer a strong tunable bulk nonlinear response in plasmonic composites. The researchers demonstrated tunable SHG from plasmonic nanorod metamaterials; developed a theoretical description of the observed phenomena; and showed that the nonlinear response could be engineered by changing structural parameters of the composite material. The work demonstrates the emergence of a structurally tunable nonlinear optical response in plasmonic composites and presents a new nonlinear optical platform that could be suitable for integrated nonlinear photonics. This technology could someday enable on-chip optical communication in computer processors, leading to smaller, faster, cheaper, more efficient chips with wider bandwidth and better data storage. The research was published in Optica, a publication of The Optical Society (https://doi.org/10.1364/OPTICA.5.001502).