Based on the transverse-longitudinal mapping of Bessel beams, we propose a simple method to construct a self-similar Bessel-like beam whose transverse profile maintains a stretched form during propagation. Specifically, the propagating-variant width of this beam can be flexibly predesigned. We experimentally demonstrate three types of self-similar Bessel-like beams whose width variations are linear, piecewise, and period functions of propagation distance, respectively. The experimental results match well with the theoretical predictions. We also demonstrate that our approach enables the generation of self-similar higher-order vortex Bessel-like beams.

The spin Hall effect of a light beam is essentially a product of circular birefringence but is rarely demonstrated. Here, we provide a scheme for initiating off-axis circular birefringence based on the spin-dependent wave vector bifurcation of Bessel beams via a single liquid crystal Pancharatnam–Berry phase element. The tilted Bessel beam shows a detectable photonic spin Hall effect. By introducing the nonlinear propagation trajectories, the spin Hall effect is greatly enhanced. More surprisingly, the two spin states exactly propagate along the scaled trajectories, enabling flexible control of the spin separation. This phenomenon is also applicable to other Bessel-like beams with nonlinear trajectories, which have been already reported.

We numerically demonstrate that the tight focusing of Bessel beams can generate focal fields with an ultra-long depth of focus (DOF). The ultra-long focal field can be controlled by appropriately regulating the order of the Bessel function and the polarization. An optical needle and an optical dark channel with nearly 100λ DOF are generated. The optical needle has a DOF of ∼104.9λ and a super-diffraction-limited focal spot with the size of 0.19λ2. The dark channel has a full-width at half-maximum of ∼0.346λ and a DOF of ∼103.8λ. Furthermore, the oscillating focal field with an ultra-long DOF can be also generated by merely changing the order of the input Bessel beam. Our results are expected to contribute to potential applications in optical tweezers, atom guidance and capture, and laser processing.

偏振是光的固有属性之一，用于描述电矢量的振动方向，也是光场的一个重要信息参量。光场的偏振测量，尤其是具有复杂空间结构光场的偏振分布测量，是研究光场偏振特性及其应用的重要课题。本文从偏振测量的相关原理出发，总结评述近年来有关光场偏振分布测量和材料光学各向异性测量方法的发展动态，以及不同条件下光场的斯托克斯参量、光学各向异性材料的琼斯矩阵和双折射参数的测量方法及其应用。

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。

The generation of an autofocusing circular Airy beam (CAB) is realized via a liquid crystal (LC) geometric phase plate with a simple configuration. The fabrication of the LC plate is based on the photoalignment technology and dynamic exposure skill. A focal length of 74 cm is obtained, and the propagation dynamics are consistent with the simulations. Besides, a defocusing CAB is also generated, and the switch between the autofocusing and defocusing CABs can be achieved by controlling the input polarization state. This work provides a convenient and flexible approach to acquire CABs, which will promote the CAB-related applications and researches.