With rapid development towards shrinking the size of traditional photonic systems such as cameras, spectrometers, displays and illumination systems, there is an urgent need for high performance and ultra-compact functional optical elements. The large footprint of traditional bulky optical elements, their monofunctional response and the inability for direct integration into nanophotonic devices have severely limited progress in this area. Metasurfaces, consisting of an array of subwavelength nanoscatterers with spatially varying geometries, have shown remarkable performance as ultrathin multifunctional optical elements. Here, based on an all-dielectric metasurface, we propose and experimentally demonstrate a spatial domain optical depolarizer capable of efficiently depolarizing linearly polarized light in the visible spectral band from 450 nm to 670 nm, with a degree of polarization of less than 10 %. Remarkably, it is capable of depolarizing light beam with a diameter down to several micrometers, about two orders of magnitude smaller than commercial liquid crystal depolarizers. Furthermore, the long response time, bulky footprint, tight optical alignment tolerance and large pixel size severely limit the performance and system integration of commercial depolarizers. We envision the metasurface depolarizer to find applications in next generation ultra-compact grating spectrometers and illumination systems.

中文翻译：

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基于介电超表面的超紧凑型可见光消偏器

随着相机、光谱仪、显示器和照明系统等传统光子系统尺寸的快速缩小，迫切需要高性能和超紧凑的功能光学元件。传统笨重的光学元件占用空间大，它们的单功能响应以及无法直接集成到纳米光子器件中，严重限制了该领域的进展。超表面由一系列具有空间变化几何形状的亚波长纳米散射体组成，作为超薄多功能光学元件已显示出卓越的性能。在这里，基于全介电超表面，我们提出并通过实验证明了一种空间域光学消偏器，能够有效地消偏振可见光谱带中从 450 nm 到 670 nm 的线性偏振光，偏振度小于 10%。值得注意的是，它能够对直径低至几微米的光束进行消偏，比商用液晶消偏器小两个数量级。此外，响应时间长、占用空间大、光学对准公差严格和像素尺寸大，严重限制了商用消偏器的性能和系统集成。我们设想超表面消偏器在下一代超紧凑型光栅光谱仪和照明系统中找到应用。它能够对直径低至几微米的光束进行消偏，比商用液晶消偏器小两个数量级。此外，响应时间长、占用空间大、光学对准公差严格和像素尺寸大，严重限制了商用消偏器的性能和系统集成。我们设想超表面消偏器在下一代超紧凑型光栅光谱仪和照明系统中找到应用。它能够对直径低至几微米的光束进行消偏，比商用液晶消偏器小两个数量级。此外，响应时间长、占用空间大、光学对准公差严格和像素尺寸大，严重限制了商用消偏器的性能和系统集成。我们设想超表面消偏器在下一代超紧凑型光栅光谱仪和照明系统中找到应用。