LEAPS-MPS: Controlling polarization of resonant flat optics using symmetries

Nontechnical Optics, the study of light, is centuries old. The control and manipulation of light has played a critical role in civilization from lenses in the ancient world to modern photonics. This project focuses on polarization, a property of light describing how electromagnetic fields oscillate as light travels through space. This project explores interactions between light and matter in pixels with nanoscale features and demonstrate how to control the polarization of light across a nanopatterned piece of glass or semiconductor. New phenomena arise when many nearby pixels act together. Notably, a phenomenon called resonance arises, wherein light is effectively trapped within the layer of pixels. Resonances offer control over the spectrum of light but conventionally comes at the expense of pixel-by-pixel control of polarization. This project overcomes previous limitations to develop resonant devices made with standard manufacturing techniques and offering pixelated control of the polarization of light. Investigators employ design principles based on symmetries, which simplifies the system and allows new avenues of control of light. Devices made from nanostructured materials are compact and lightweight and can be scaled to mass manufacturing. Understanding developed in this project thus has the potential for technological breakthroughs in holography, imaging, and sensing. In parallel, the PI explores the broadening of knowledge and participation of flat polarization optics in an undergraduate setting. While the concepts are accessible to students early on in higher education and are crucial for emerging technologies, they are not often covered. This project helps fill this gap by developing curriculum materials for an experimental lab class and by supporting undergraduate researchers in both theoretical and experimental study of these phenomena. Technical This project advances the design principles, capabilities, and device architectures of an emerging category of flat optical materials called “nonlocal metasurfaces”. In resonant flat optics, nonlocality arises due to the dispersion of waves guided along the structure thin film and resonantly coupled to external light. While these waves can be supported in a pixelated device with subwavelength pixels, the nonlocal resonant coupling to external light is conventionally destroyed when many neighboring pixels are not identical. Yet, pixelated control of polarization requires local control. This project incorporates local, pixel-wise control over the polarization response of nonlocal, guided waves by judicious use of symmetry-based design principles. This project implements two new categories of polarization control that are compatible with a single patterned layer. Chiral responses (in which the handedness of polarization state is differentiated) are particularly challenging to control, yet especially important in applications such as sensing of chiral molecules. This project explores chiral polarization capabilities within nanopatterned thin films of silicon placed upon glass and a metallic mirror layer. Symmetry-based design principles introduced in this project allow the decoupling of several degrees of freedom of the desired response, simplifying the design of pixels and enabling the production of millimeter scale flat optical devices whose geometry is defined by equations. The pixelated control of a resonance manifests in this project in a planarized architectures that achieve handedness-selective beam steering functionalities exclusively within the narrow bandwidth of the resonance. The approaches of this project increase the maximum theoretical efficiency of this functionality to nearly one (previously, one quarter), advancing the state-of-the-art towards high efficiency, multi-functional performance. This project is jointly funded by Office of Strategic Initiatives of the Directorate for Mathematical and Physical sciences and the Electronic and Photonic Materials program in the Division of Materials Research. 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.