基于复杂光散射动力学的自由变形聚合，实现极高效率的光束控制
Freeform metagratings based on complex light scattering dynamics for extreme, high efficiency beam steering
摘要：
传统的相控阵超颖表面利用共振纳米粒子或共振波导来指定对光的空间依赖的振幅和相位响应。在几乎所有这些实现中，亚波长尺度元件被缝合在一起，同时最小化相邻元件之间的耦合。在这份报告中，我们从理论上分析了元表面设计的替代方法，利用自由形式的逆向设计方法，支持显着提高效率相比，传统的设计。我们的设计过程优化了波长级元件，从而大大增加了光学工程的设计空间。超广角光束偏转器和波长分离器的深入耦合模式分析表明，我们的设计的非凡性能源于大量的传播模式支持的metagrating，结合复杂的多重散射动力学表现出这些模式。我们还将耦合模式分析应用于传统的基于超颖表面的超颖表面，以了解和量化限制这些器件效率的因素。我们设想，自由形式的超颖表面设计方法将开辟新的途径，真正的高性能，多功能的光学利用强耦合纳米光子模式和元素。
英文摘要：
Conventional phased-array metasurfaces utilize resonant nanoparticles or nanowaveguides to specify spatially-dependent amplitude and phase responses to light. In nearly all these implementations, subwavelength-scale elements are stitched together while minimizing coupling between adjacent elements. In this report, we theoretically analyze an alternate method of metasurface design, utilizing freeform inverse design methods, which support significantly enhanced efficiencies compared to conventional designs. Our design process optimizes wavelength-scale elements, which dramatically increases the design space for optical engineering. An in-depth coupled mode analysis of ultra-wide-angle beam deflectors and wavelength splitters shows that the extraordinary performance of our designs originates from the large number of propagating modes supported by the metagrating, in combination with complex multiple scattering dynamics exhibited by these modes. We also apply our coupled mode analysis to conventional nanowaveguide-based metasurfaces to understand and quantify the factors limiting the efficiencies of these devices. We envision that freeform metasurface design methods will open new avenues towards truly high-performance, multi-functional optics by utilizing strongly coupled nanophotonic modes and elements.
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