Structured optical fields embedded with polarization singularities (PSs) have attracted extensive attention due to their capability to retain topological invariance during propagation. Many advances in PS research have been made over the past 20 years in the areas of mathematical description, generation and detection technologies, propagation dynamics, and applications. However, one of the most crucial and difficult tasks continues to be manipulating PSs with multiple degrees of freedom, especially in three-dimensional (3D) tailored optical fields. We propose and demonstrate the longitudinal PS lines obtained by superimposing Bessel-like modes with orthogonal polarization states on composite vector optical fields (VOFs). The embedded PSs in the fields can be manipulated to propagate robustly along arbitrary trajectories, or to annihilate, revive, and transform each other at on-demand positions in 3D space, allowing complex PS’ topological morphology and intensity patterns to be flexibly customized. Our findings could spur further research into singular optics and help with applications such as micromanipulation, microstructure fabrication, and optical encryption.

作为表征光具有振动偏向性的本征参量，一直以来偏振都是光场空域调控中重要的研究对象。相较于传统标量光场，具有偏振非均匀分布的矢量光场强调了这种振动偏向性会存在空间差异。早期研究者对矢量光场的调控研究仅限于单个二维平面，主要实现单一偏振参量的模式控制；在此基础上研究人员又对其振幅与相位进行控制，实现了涵盖三个基本调控自由度的多模态矢量光场生成。近年来随着多模态矢量光场在光信息传输、焦场设计、光学微操纵等领域的深度应用，其调控效率的提高与调控维度的纵向延伸两方面研究内容备受关注。研究人员一方面减少调控过程中不必要的能量损耗，另一方面对多模态矢量光场在三维空间中的的空间构型与传播演化过程进行了研究，总结了纵向变化规律，阐明了纵向调控机制，论证了纵向调控可行性。本文回顾了近年来多模态矢量光场的三维空域调控研究进展，首先介绍了数个近年来提出的具有高效化、紧凑化特点的新型矢量场生成装置；之后概述了三种目前相对有效的可实现三维空域多模态控制的矢量场调控方法及其相关调控案例，第一种方案考虑衍射过程，后两种方案则适用于聚焦过程；最后进行了简要总结与展望。

Photonic nanojets (PNJs) are subwavelength jet-like propagating waves generated by illuminating a dielectric microstructure with an electromagnetic wave, conventionally a linearly polarized plane wave. Here, we study the donut-like PNJ produced when a circularly polarized vortex beam is used instead. This novel PNJ also has a reverse energy flow at the donut-like focal plane depending on both the optical vortex topological charge and microsphere size. Our tunable PNJ, which we investigate numerically and analytically, can find applications in optical micromanipulation and trapping.

We develop a method for completely shaping optical vector beams with controllable amplitude, phase, and polarization gradients along three-dimensional freestyle trajectories. We design theoretically and demonstrate experimentally curvilinear Poincaré vector beams that exhibit high intensity gradients and accurate state of polarization prescribed along the beam trajectory.

We present a highly efficient method of generating and shaping ellipse perfect vector beams (EPVBs) with a prescribed ellipse intensity profile and continuously variant linear polarization state. The scheme is based on the coaxial superposition of two orthogonally polarized ellipse laser beams of controllable phase vortex serving as the base vector components. The phase-only computer-generated hologram is specifically designed by means of a modified iteration algorithm involving a complex amplitude constraint, which is able to generate an EPVB with high diffraction efficiency in the vector optical field generator. We experimentally demonstrate that the efficiency of generating the EPVB has a notable improvement from 1.83% in the conventional complex amplitude modulation based technique to 11.1% in our method. We also discuss and demonstrate the simultaneous shaping of multiple EPVBs with independent tunable ellipticity and polarization vortex in both transversal (2D) and axial (3D) focusing structures, proving potentials in a variety of polarization-mediated applications such as trapping and transportation of particles in more complex geometric circumstances.

We propose and simulate a method for generating a three-dimensional (3D) optical cage in the vicinity of focus by focusing a double-ring shaped radially and azimuthally polarized beam. Our study shows that the combination of an inner ring with an azimuthally polarized field and an outer ring with a radially polarized field and a phase factor can produce an optical cage with a dark region enclosed by higher intensity. The shape of the cage can be tailored by appropriately adjusting the parameters of double-mode beams. Furthermore, multiple 3D optical cages can be realized by applying the shift theorem of the Fourier transform and macro-pixel sampling algorithm to a double-ring shaped radially and azimuthally polarized beam.

No instrument is able to measure directly the quantum entanglement of a system. However, both theory and experiment, following the well-known Bell inequality, reveal the existence of the entanglement phenomenon in quantum mechanics. To examine the characterization of quantum entanglement, here we present a two-site cavity system, in which each cavity contains a Λ-type three-level atom and the two sites are identical and coupled with each other. We investigate and calculate the bipartite entanglement entropy of the system for the ground states. For photons of different types, corresponding to the two ground states of the atom, we investigate the correlations and violation of the Bell inequality.