Spin splitting of light originates from the interplay between the polarization and spatial degrees of freedom as a fundamental constituent of the emerging spin photonics, providing a prominent pathway for manipulating photon spin and developing exceptional photonic devices. However, previously relevant devices were mainly designed for routing monotonous spin splitting of light. Here, we realize an oscillatory spin splitting of light via metasurface with two channel Pancharatnam–Berry phases. For the incidence of a linearly polarized light, the concomitant phases arising from opposite spin states transition within pathways of the metasurface induce lateral spin splitting of light with alternately changed transport direction during beam guiding. We demonstrate the invariance of this phenomenon with an analogous gauge transformation. This work provides a new insight on steering the photon spin and is expected to explore a novel guiding mechanism of relativistic spinning particles, as well as applications of optical trapping and chirality sorting.

得益于特殊的空间结构，振幅、相位、偏振态面内调控的光场在传输及与物质相互作用过程中展现了诸多引人瞩目的新效应和新现象。随着空间结构光场的深入研究和广泛应用，沿着传输方向的光场调控也逐渐引起注意，由此发展出了一系列具有新颖传播特性，以及空间三维结构的调控光场。本文综述了针对传输方向的光场调控研究进展，包括光场强度沿纵向的调控及由此构建的特殊三维结构光场、沿纵向具有特殊传输轨迹光场的产生原理及方法、绕光轴具有螺旋轨迹传输的光场及其螺旋传输特性、光场偏振态沿纵向调控的基本原理及两类偏振态纵向调控光场。

超表面作为一种人工设计的二维阵列纳米结构，能够在亚波长尺度上实现光场波前振幅、相位和偏振态的灵活调控，为现代光学器件的小型化、集成化提供了全新的实现途径。随着光学成像、显示等应用的发展，在可见光波段具有高工作效率的微型光学器件的需求日益凸显。近年来，由高折射率、低损耗电介质材料制备的光学超表面得到了极大地发展，在消色差光学超透镜、偏振相关全息显示等方面展现出广泛的应用前景。文中围绕电介质超表面的相关研究，首先介绍广义斯涅耳定律及电介质超表面结构调控光场振幅、相位和偏振态的基本原理，在此基础上，重点回顾近年来关于光场波前单一参量调控和多参量联合调控在全息显示、结构光场产生等方面的研究进展，最后讨论电介质超表面发展的可能挑战与前景。

Optical activity (OA) is the rotation of the polarization orientation of the linearly polarized light as it travels through certain materials that are of mirror asymmetry, including gases or solutions of chiral molecules such as sugars and proteins, as well as metamaterials. The necessary condition for achieving OA is the birefringence of two circular polarizations in material. Here, we propose a new kind of self-accelerated OA in free space, based on the intrinsic Gouy phase induced mode birefringence of two kinds of quasi-non-diffracting beams. We provide a detailed insight into this kind of self-accelerated OA by analyzing angular parameters, including angular direction, velocity, acceleration, and even the polarization transformation trajectory. As the Gouy phase exists for any wave, this kind of self-accelerated OA can be implemented in other waves beyond optics, from acoustic and elastic waves to matter waves.