Metasurfaces have been enabling the miniaturization and integration of complex optical functionalities within an ultrathin platform by engineering the scattering features of localized modes. However, these efforts have mostly been limited to the manipulation of externally produced coherent light, e.g., from a laser. In parallel, the past two decades have seen the development of structured surfaces that emit partially coherent radiation via thermally populated, spatially extended (nonlocal) modes. However, the control over thermally emitted light is severely limited compared to optical metasurfaces, and even basic functionalities such as unidirectional emission to an arbitrary angle and polarization remain elusive. Here, we derive the necessary conditions to achieve full control over thermally emitted light, pointing to the need for simultaneously tailoring local and nonlocal scattering features across the structure. Based on these findings, we introduce a platform for thermal metasurfaces based on quasibound states in the continuum that satisfies these requirements and completes the program of compactification of optical systems by enabling a full degree of control of partially coherent light emission from structured thin films, including unidirectional emission of circularly polarized light, focusing, and control of spatial and temporal coherence, as well as wave-front control with designer spin and angular orbital momenta.

中文翻译：

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热超表面：通过结合局部和非局部光-物质相互作用来完全控制发射

通过设计局部模式的散射特征，超表面一直在实现超薄平台内复杂光学功能的小型化和集成。然而，这些努力主要限于操纵外部产生的相干光，例如来自激光器。与此同时，在过去的二十年里，结构化表面的发展通过热填充、空间扩展（非局部）模式发射部分相干辐射。然而，与光学超表面相比，对热发射光的控制受到严重限制，甚至诸如单向发射到任意角度和偏振等基本功能仍然难以实现。在这里，我们推导出实现对热发射光的完全控制的必要条件，指出需要同时定制整个结构的局部和非局部散射特征。基于这些发现，我们引入了一个基于连续体中准束缚态的热超表面平台，该平台满足这些要求，并通过完全控制结构化薄膜的部分相干光发射来完成光学系统的紧凑化程序，包括圆偏振光的单向发射、聚焦和空间和时间相干的控制，以及设计者自旋和角轨道动量的波前控制。