Polarization-dependent thermal emission from plasmonic metasurfaces

在过去的二十年中，热辐射的控制由于其在先进能源系统、制造、遥感、热管理和高分辨率热成像中的重要性而引起了极大的关注。来自块状材料的热发射通常是宽带的并且在很大程度上是漫射的。然而，最近已经取得了显着的发展，构建方向选择性和波长依赖性的发射器和吸收器使用微/纳米结构材料。电磁波的极化状态是根据其电场在波传播时如何变化来确定的。众所周知，偏振光探测在空间和大气遥感、目标探测、表面表征和生物医学诊断中具有重要的应用。然而，热辐射中的偏振效应尚未得到广泛的研究。这个理论和实验相结合的项目旨在建模，设计，制造和表征具有独特的偏振相关热辐射的微/纳米结构材料表面。这项研究将使一个基本的理解的性质的热发射的状态和程度的偏振。所获得的知识将潜在地有益于从能量收集和表面成像到物体识别和生物医学传感的应用。此外，还将致力于推进以学生为中心的教学方法，扩大国际合作。由薄纳米结构层或超材料表面制成的超材料有望控制热辐射的偏振态。本计画将采用时域有限差分法及矩阵公式来模拟超颖表面的反射与吸收，同时考虑线极化与圆极化入射。重点将给予圆偏振发射器使用等离子体超材料与不对称的金属微/纳米结构。本地化的领域将分析线性和圆偏振入射波，探索在微/纳米尺度的共振机制和等离子体激元局部加热。此外，波动耗散定理将被用来直接模拟场分量和它们的相关性，使用各向异性并矢绿色函数。直接和间接的方法将被用来预测发射度组件定义的斯托克斯参数的基础上。将测量的红外反射率和发射率的制造等离子体超颖表面的结果进行比较。在发射度测量中，组合的延迟器和偏振器布置将使得能够表征所有斯托克斯参数。热辐射的性质将通过研究相干程度、偏振程度、方向和偏振依赖性、局部状态密度等来探索。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

In the past two decades, the control of thermal radiation has attracted immense attention due to its importance in advanced energy systems, manufacturing, remote sensing, thermal management, and high-resolution thermal imaging. Thermal emission from bulk materials is typically broadband and largely diffuse. However, significant development has been made lately to construct directional-selective and wavelength-dependent emitters and absorbers using micro/nanostructured materials. The polarization state of an electromagnetic wave is determined based on how its electric field varies as the wave propagates. It is well known that polarized light detection has important applications in space and atmospheric remote sensing, target detection, surface characterization, and biomedical diagnostics. However, the polarization effect in thermal radiation has not been extensively examined. This combined theoretical and experimental project aims to model, design, fabricate, and characterize micro/nanostructured material surfaces with unique polarization-dependent thermal radiation. The study will enable a fundamental understanding of the nature of thermal emission in terms of the state and degree of polarization. The knowledge obtained will potentially benefit applications ranging from energy harvesting and surface imaging, to object recognition and biomedical sensing. Significant efforts will also be devoted to advancing student-centered pedagogy and expanding international collaboration.Metamaterials made of thin nanostructured layers, or metasurfaces, hold promise for controlling the polarization state of thermal emission. This project will employ the finite-difference time-domain method and the matrix formulation to model the reflection and absorption of metasurfaces, considering both linearly and circularly polarized incidence. Emphasis will be given to circularly polarized emitters using plasmonic metamaterials with asymmetric metallic micro/nanostructures. The localized fields will be analyzed for both linearly and circularly polarized incident waves to explore the resonance mechanisms and plasmonic local heating at the micro/nanoscales. Furthermore, the fluctuation-dissipation theorem will be employed to directly model the field components and their correlations using anisotropic dyadic Green’s functions. Both the direct and indirect methods will be used to predict the emittance components defined based on Stokes’ parameters. The results will be compared with the measured infrared reflectance and emittance of fabricated plasmonic metasurfaces. In the emittance measurements, combined retarder and polarizer arrangements will enable a characterization of all of Stokes’ parameters. The nature of thermal radiation will be explored by studying the degree of coherence, degree of polarization, directional and polarization dependence, local density of states, etc.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.