Broadband and tunable enhanced chiral light-matter interactions at the visible with new ultrathin helical metamaterials

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Nontechnical description: This project advances understanding about how light passes around edges and corners which are created by configurations of very small three-dimensional objects. The light path can be manipulated and controlled by the size and geometry of spring-like nanoobjects, leading to artificially engineered materials with unique properties and functionalities. The research team utilizes experimental and computational approaches to predict, manufacture and test new ultrathin optical nanostructures which will be arranged in configurations that are expected to support next generation optical communications and sensing technologies. Thereby the study closes a gap in the manipulation of light by using specific geometrical arrangements of nanostructures. By that, the research benefits the economy and society of the United States. The project supports undergraduate and graduate student involvement in research as a means of encouraging pursuit of advanced study and research careers in new optical materials. The research team extends the impact of this research to introduce advanced optical concepts relevant to the current project to underrepresented demographic groups in the STEM pipeline, including presentations to the Conference for Undergraduate Women in Physical Sciences (WoPhys) events at the University of Nebraska-Lincoln and the annual outreach and Research Experiences for Undergraduates programs of the Nebraska Center for Materials and Nanoscience. Further, the investigators leverage their research findings to create one video to teach the broader public about the properties of light, current research activities for advancing optical materials, and future device technologies towards high-performance quantum optical and photonic applications.Technical description: Recent advances in nanofabrication techniques have enabled the development of optical nanoscale metamaterials to enhance electromagnetic chirality. However, current nanophotonic metamaterial designs that exhibit chiral light-matter interactions have an extremely weak and narrowband nature, are difficult to control and enhance, usually operate at infrared frequencies, and cannot be made tunable. In this project, the research team tackles these problems by designing new dielectric compact subwavelength helical metamaterials to strongly enhance and tune their chiroptical response at record-breaking levels and at the entire visible spectrum. The proposed new artificially engineered dielectric nanomaterials are expected to unlock novel ways for the efficient and coherent manipulation of the broadband chirality, spin angular momentum of photons, and transverse photon spin of incident electromagnetic waves. The new approach is anticipated to lead to directional spin-polarized radiation and unperturbed chiral edge modes along interfaces with different handedness. Low-loss all-dielectric helical metamaterials are investigated both theoretically and experimentally and applied to different exciting new applications, such as in the design of new chiral nanowaveguides and nanocavities. The structurally induced strong chiroptical response of the dielectric nanohelices is tuned to different frequencies at the visible by varying their geometry. The fundamental understanding and experimental realization of the proposed new nanomaterials is expected to be transformative to the emerging field of chiral quantum optics.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.