The rapid development of optical metasurfaces, 2D ensembles of engineered nanostructures, is presently underpinning a steady drive toward the miniaturization of many optical functionalities and devices. The list of material platforms for optical metasurfaces is rapidly expanding as, over the past few years, we have witnessed a surge in establishing meta-optical elements from high-index, highly transparent materials with strong nonlinear and electro-optic properties. In particular, crystalline lithium niobate (LiNbO₃), already a prime material for integrated photonics, has shown great promise for novel meta-optical components, thanks to its large electro-optical coefficient and second-order nonlinear response and its broad transparency window ranging from the visible to the mid-infrared. Recent advances in nanofabrication technology have indeed marked a new milestone in the miniaturization of LiNbO₃ platforms, hence enabling the first demonstrations of LiNbO₃-based metasurfaces. These seminal works set a steppingstone toward the realization of ultrathin monolithic nonlinear light sources, efficient quantum sources of correlated photon pairs, as well as electro-optical modulators. Here, we review these recent advances by providing a perspective on their potential applications and examining the possible setbacks and limitations of these emerging technologies.

中文翻译：

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铌酸锂超光学

光学超表面（工程纳米结构的二维集合）的快速发展目前正在稳步推动许多光学功能和设备的小型化。光学超表面的材料平台列表正在迅速扩大，因为在过去几年中，我们目睹了使用具有强非线性和电光特性的高折射率、高透明材料建立超光学元件的热潮。特别是结晶铌酸锂 (LiNbO ₃)，已经是集成光子学的主要材料，由于其大的电光系数和二阶非线性响应以及从可见光到中红外的宽透明窗口，在新型超光学元件方面显示出巨大的潜力。纳米制造技术的最新进展确实标志着 LiNbO _{3平台小型化的一个新里程碑，因此实现了 LiNbO 3}的首次演示基于的超表面。这些开创性的工作为实现超薄单片非线性光源、相关光子对的高效量子源以及电光调制器奠定了基础。在这里，我们通过提供有关其潜在应用的观点并检查这些新兴技术可能遇到的挫折和局限性来回顾这些最新进展。