Conventional thermal emitters, such as a blackbody or the incandescent filament of a light bulb, lack the directionality or narrow linewidth required in many applications such as thermophotovoltaics and infrared sensing. Although thermal emission from bulk materials is well understood based on phenomenological heat transfer concepts like emissivity and the framework of classical electrodynamics, there still remains a significant gap in our understanding of thermal emission at the nanoscale. In this work, by leveraging the quasi-normal mode theory, we derive a general and self-consistent formalism to describe the thermal radiation from nanoscale resonant thermal emitters with high-order symmetric geometries, which are the basic building blocks of metasurfaces and metamaterials. The complex symmetrical geometries of the emitters yield degeneracy of quasi-normal modes. The introduction of the degeneracy can strongly mediate far-field thermal emission from nanoscale resonators, which is closely correlated to the number of degenerate modes and the coupling among the degenerate modes. Our formalism from the quasi-normal mode theory serves as a general guideline to design the complex metastructures with high-ordered degeneracy to achieve optimized absorption or emission capabilities.

中文翻译：

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简并介导的高阶对称性纳米级光学谐振器的热发射


传统的热发射器，如黑体或灯泡的白炽灯丝，缺乏热光伏和红外传感等许多应用所需的方向性或窄线宽。尽管根据发射率等现象学传热概念和经典电动力学框架，对块状材料的热发射进行了很好的理解，但我们对纳米尺度热发射的理解仍然存在很大差距。在这项工作中，通过利用准正态理论，我们推导出了一个通用的、自洽的形式来描述具有高阶对称几何形状的纳米级谐振热发射器的热辐射，这些热辐射是超表面和超材料的基本组成部分。发射器的复杂对称几何结构产生了准法则模式的简并性。简并性的引入可以强烈介导纳米级谐振器的远场热发射，这与简并模式的数量和简并模式之间的耦合密切相关。我们来自准正态理论的形式主义作为设计具有高阶简并性的复杂超结构以实现优化的吸收或发射能力的一般指南。