Collecting and concentrating light is an essential process in any system utilizing optics. Conventional lenses collect light and concentrate it to a spot, but the concentration spot moves as light rays strike at different angles or different positions. As a result, sensors and detectors can lose energy as a source moves, and the efficiency of an optical devices is often limited by the angular acceptance of a lens or lens system. In this project, a collaborative team at the University of Central Florida and the University of Texas at El Paso will explore a fundamentally new approach for concentrating light called "photon funnels," which is based on spatially engineered optical lattices. Photon funnels will be designed to leverage an optical phenomenon called "self-collimation" to control how light propagates within an engineered lattice. Using a collaborative approach that combines theory, simulation, fabrication, and optical testing, the team will develop fundamental knowledge that enables scientists and engineers to design photon funnels for a myriad of applications. The benefits to society will include new technologies for imaging, optical detection and sensing, telecommunications and energy harvesting. This interdisciplinary project will give research students cutting-edge training in optical engineering, physics, chemistry, materials science, and design and simulation. Educational outreach activities integrated with the project will bring the excitement of the research to the broader community and will help to improve understanding of science and technology and encourage youth to pursue careers in related fields. The research goals are to: 1) generate fundamental understanding of photon funnels and more generally self-collimating, spatially-variant lattices; 2) establish the fundamental performance-limits of photon funnels; 3) determine to what extent reciprocity limits their light collecting ability; and 4) create design-rules that engineers can use for their own applications. Photon funnels are wavelength-scale aperiodic three-dimensional lattices in which the unit cells are spatially varied in orientation to direct light via self-collimation to a single concentration zone. Because photon funnels work via self-collimation, they are not bound by Snell's law, so in principle they could collect and concentrate light incident at all positions, all angles, and all polarizations. No existing technology offers this extraordinary capability. Photon funnels and spatially-variant lattices are designed by spatially varying the structure of an optical lattices while preserving the self-collimating properties of the unit cells. Spatially-variant lattices are fundamentally different from photonic crystals, metamaterials, and devices based on graded-index and transformation optics. Spatially-variant lattices do not require exotic properties - like refractive index that is high, negative, or less than one - which makes spatially-variant lattices simpler to fabricate and inherently more manufacturable. The project will transform how engineers design optical systems because they could set aside traditional ray optics in certain applications and use photon funnels to concentrate light. Photon funnels and spatially-variant lattices offer tremendous potential because multiple functions can be integrated into a single device, including light collection and concentration, tight beam bending, wavelength separation, and control of polarization, phase, and power.
