Meta-Surfaces for Far-Field Radiation Control and Near-Field Radiation Enhancement

辐射是一种重要的能量传递过程，在能量收集、生产和利用中有着广泛的应用。辐射能量传递可以通过远场辐射完成，在远场辐射中，辐射表面之间的距离比辐射波长长（通常为几到几十微米），在近场辐射中，表面之间的距离比辐射波长短。在这个项目中，研究了具有特别设计的非常小（微尺度）图案的工程表面，称为元表面，以实现特定的远场辐射特性，并增强近场辐射，用于太阳能收集中的热光伏等应用。该项目旨在产生丰富的科学和工程知识，以推进辐射能量转移的基础和工程。它还可以应用于其他科学和工程领域，包括高分辨率成像、传感和红外辐射源。此外，该项目向下一代科学家和工程师提供教育和培训，扩大代表性不足群体的参与，并提高公众对辐射科学和技术的认识。本项目设计新颖的元表面，对期望的辐射特性和传递过程具有优势。具体地说，除了电辐射场外，还研究了能够增强磁辐射场的元表面。这种方法提供了设计空间来操纵电和磁性能，以实现所需的远场和近场性能，同时使用相对简单的二维元表面结构。本项目采用了先进的实验技术，包括表面分离距离为几十纳米的近场辐射测量、傅立叶变换红外光谱（FTIR）结合近场扫描光学显微镜、FTIR近场发射显微镜和远场FTIR光谱。这些研究为设计的元表面提供了一个完整的微观到宏观的光谱图，从而验证了设计理论，从而推进了远场和近场辐射的研究并促进了它们的应用。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Radiation is an important energy transfer process that has wide applications in energy harvesting, production, and utilization. Radiation energy transfer can be accomplished by far-field radiation, where radiative surfaces are separated by a distance longer than the radiation wavelength (typically several to tens of micrometers) and near-field radiation, in which the surfaces are separated by a distance shorter than the radiation wavelength. In this project, engineered surfaces with specifically designed very small (microscale) patterns, called meta-surfaces, are studied to achieve specific far-field radiation properties and to enhance near-field radiation for applications such as thermal-photovoltaics in solar energy harvesting. The project aims to generate a wealth of scientific and engineering knowledge to advance the fundamentals and engineering of radiation energy transfer. It can also be applied to other fields of science and engineering, including high resolution imaging, sensing, and infrared radiation sources. In addition, the project provides education and training to the next generation scientists and engineers, broadens participation of underrepresented groups, and increases public awareness of radiation science and technology.This project designs novel meta-surfaces that are advantages for the desired radiation properties and transfer processes. Specifically, meta-surfaces capable of enhancing the magnetic radiation field in addition to the electrical radiation field are studied. This approach provides the design space for manipulating both electric and magnetic properties to achieve desired far- and near-field performances, while using relatively simple two-dimensional meta-surface structures. Advanced experimental techniques are used in this project, including near-field radiation measurements with surface separation distances of tens of nanometers, FTIR (Fourier Transform Infrared spectroscopy) coupled with near-field scanning optical microscopy, FTIR near-field emission microscopy, and far-field FTIR spectroscopy. These studies provide a complete micro-to-macro spectroscopic picture of the designed meta-surfaces to validate the design theories, therefore, to advance far- and near-field radiation research and facilitate their applications.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.