Collaborative Research: Photon Funnels-A Fundamentally New Concept for Concentrating Light

在任何利用光学的系统中，光的收集和聚集都是必不可少的过程。传统的透镜收集光线并将其集中到一个点上，但当光线以不同的角度或不同的位置照射时，聚光点会移动。因此，随着光源的移动，传感器和探测器可能会损失能量，而光学设备的效率往往受到透镜或透镜系统的角度接受的限制。在这个项目中，中佛罗里达大学和德克萨斯大学埃尔帕索分校的一个合作团队将探索一种全新的聚光方法，即基于空间工程光学晶格的光子漏斗。光子漏斗将被设计成利用一种名为“自准直”的光学现象来控制光在工程晶格中的传播方式。使用理论、模拟、制造和光学测试相结合的协作方法，该团队将开发基础知识，使科学家和工程师能够为各种应用设计光子漏斗。给社会带来的好处将包括成像、光学探测和传感、电信和能源收集等新技术。这个跨学科的项目将为研究型学生提供光学工程、物理、化学、材料科学以及设计和模拟方面的尖端培训。与该项目相结合的教育推广活动将为更广泛的社区带来研究的兴奋，并将有助于提高对科学和技术的理解，并鼓励年轻人从事相关领域的职业。研究目标是：1)对光子漏斗和更广泛的自准直、空间变化的晶格有基本的了解；2)建立光子漏斗的基本性能限制；3)确定相互作用在多大程度上限制他们的光收集能力；以及4)创建工程师可以用于他们自己的应用的设计规则。光子漏斗是波长尺度的非周期三维晶格，其中的单胞在空间上取向变化，通过自准直将光引导到单个聚集区。由于光子漏斗通过自准直工作，它们不受斯内尔定律的约束，因此原则上它们可以收集和集中入射到所有位置、所有角度和所有偏振的光。现有的任何技术都没有提供这种非凡的能力。光子漏斗和空间可变晶格是通过在空间上改变光学晶格的结构来设计的，同时保持了单位晶胞的自准直特性。空间变化的晶格与光子晶体、超材料和基于梯度折射率和变换光学的器件有着根本的不同。空间变化的晶格不需要奇异的性质--如高、负或小于1的折射率--这使得空间变化的晶格更容易制造，而且本质上更容易制造。该项目将改变工程师设计光学系统的方式，因为他们可以在某些应用中抛开传统的光线光学，使用光子漏斗来集中光线。光子漏斗和空间可变晶格提供了巨大的潜力，因为可以将多种功能集成到一个设备中，包括光收集和集中、紧密光束弯曲、波长分离以及偏振、相位和功率的控制。

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.