Optical metasurfaces—planar nanostructured devices that can arbitrarily tailor the wavefront of light—may be reconfigured by changing their dielectric environment. The application of external stimuli to liquid crystals is a particularly promising means of tuning the optical properties of embedded metasurfaces because of liquid crystals’ large and broadband optical anisotropy. However, the detailed behavior of liquid crystals immediately adjacent to the nanostructured meta-atoms elements is often overlooked, despite the optics of the device depending sensitively on this behavior (e.g., the spectral position of the meta-atom resonances). This is of increasing concern as the wavelength of operation further approaches the short-wavelength end of the visible spectrum and, therefore, the length scale of the inhomogeneities in the liquid crystal director field. In this manuscript, we undertake a fully comprehensive study, across the metasurface geometrical parameter space, of broadband (450–700 nm) all-dielectric liquid crystal tunable metasurfaces operating in the visible. Through combined experimental characterization, liquid crystal modeling, and optical simulations, we reveal and quantify the improved accuracy with which the optical properties of the liquid crystal tunable metasurfaces may be described, and identify the underlying physical mechanism: the three-dimensional spatial overlap of the liquid crystal director field and metasurface optical near fields in the vicinity of the meta-atoms.

中文翻译：

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可见光中的宽带液晶可调超颖表面：跨超颖表面参数空间的液晶不均匀性

光学超表面（可以任意调整光波前的平面纳米结构器件）可以通过更改其介电环境进行重新配置。由于液晶的大且宽带的光学各向异性，将外部刺激应用于液晶是一种特别有希望的方法，可以调节嵌入的超表面的光学特性。然而，尽管装置的光学系统敏感地取决于这种行为（例如，亚原子共振的光谱位置），但是常常忽略了紧邻纳米结构的亚原子元素的液晶的详细行为。随着操作波长进一步接近可见光谱的短波长端，因此，这一点越来越引起人们的关注，因此，液晶指向矢场中不均匀性的长度尺度。在本手稿中，我们在超表面几何参数空间内对在可见光范围内工作的宽带（450-700 nm）全介电液晶可调超表面进行了全面的研究。通过组合的实验表征，液晶建模和光学模拟，我们揭示并量化了可用来描述液晶可调超表面的光学特性的提高的精度，并确定了潜在的物理机制：三维空间重叠液晶指向矢场和超原子附近的超表面光学近场。可见光中工作的宽带（450-700 nm）全介电液晶可调超颖表面的数量。通过组合的实验表征，液晶建模和光学模拟，我们揭示并量化了可用来描述液晶可调超表面的光学特性的提高的精度，并确定了潜在的物理机制：三维空间重叠液晶指向矢场和超原子附近的超表面光学近场。可见光中工作的宽带（450-700 nm）全介电液晶可调超颖表面的数量。通过组合的实验表征，液晶建模和光学模拟，我们揭示并量化了可用来描述液晶可调超表面的光学特性的提高的精度，并确定了潜在的物理机制：三维空间重叠液晶指向矢场和超原子附近的超表面光学近场。