The growing maturity of nanofabrication has ushered massive sophisticated optical structures available on a photonic chip. The integration of subwavelength-structured metasurfaces and metamaterials on the canonical building block of optical waveguides is gradually reshaping the landscape of photonic integrated circuits, giving rise to numerous meta-waveguides with unprecedented strength in controlling guided electromagnetic waves. Here, we review recent advances in meta-structured waveguides that synergize various functional subwavelength photonic architectures with diverse waveguide platforms, such as dielectric or plasmonic waveguides and optical fibers. Foundational results and representative applications are comprehensively summarized. Brief physical models with explicit design tutorials, either physical intuition-based design methods or computer algorithms-based inverse designs, are cataloged as well. We highlight how meta-optics can infuse new degrees of freedom to waveguide-based devices and systems, by enhancing light-matter interaction strength to drastically boost device performance, or offering a versatile designer media for manipulating light in nanoscale to enable novel functionalities. We further discuss current challenges and outline emerging opportunities of this vibrant field for various applications in photonic integrated circuits, biomedical sensing, artificial intelligence and beyond.

纳米加工的日益成熟催生了光子芯片上大量复杂的光学结构。亚波长结构的超表面和超材料在光波导的标准构建块上的集成正在逐渐重塑光子集成电路的格局，产生了众多在控制引导电磁波方面具有前所未有的强度的超波导。在这里，我们回顾了元结构波导的最新进展，这些波导将各种功能亚波长光子架构与不同的波导平台（例如介电或等离子体波导和光纤）协同作用。全面总结了基础成果和代表性应用。还对带有明确设计教程的简短物理模型（基于物理直觉的设计方法或基于计算机算法的逆设计）进行了编目。我们重点介绍元光学如何为基于波导的设备和系统注入新的自由度，通过增强光与物质的相互作用强度来大幅提高设备性能，或者提供一种多功能的设计介质来操纵纳米级的光以实现新颖的功能。我们进一步讨论当前的挑战，并概述这个充满活力的领域在光子集成电路、生物医学传感、人工智能等领域的各种应用的新兴机遇。