As an intrinsic property of light, angular momentum has always been an important research object of light field. In the past few years, the interactions between spin angular momentum and orbital angular momentum in tightly focused structured light have attracted much attention. Different from the independent conservation in the paraxial condition, the polarization-dependent spin angular momentum and the phase-dependent orbital angular momentum are coupled under tight focusing condition based on different physical mechanisms. The research on spin-orbit interaction will be helpful to deeply understand the nature of photon as well as extend the applications of light. Here, different forms of spin-orbit interaction during the tight focusing of structured light have been briefly introduced and classified. Besides, the existing problems and development prospects in the research about spin-orbit interaction of light are discussed, including the quantitative detection of the local distribution of optical spin and orbital angular momentum in experiments and the further applications of spin-orbit interaction.

Digital light processing has significant advantages, such as high repeatability, low failure rate, and no extrusion shear force. To make it possible to print complex structures with high resolution, the consecutive development of photocurable ink materials is indispensable. In this work, photo-functionalized pullulan (Pul-NB) was prepared by introducing norbornene groups into pullulan chains, and an ink material suitable for photocurable printing was prepared by thiol-ene click reaction. The rheology, water absorption, and mechanical properties of the Pul-NB precursor solution and photocurable hydrogel were investigated. The optimal composition of Pul-NB ink for three-dimensional (3D) printing was obtained by adjusting the degree of substitution, Pul-NB concentration, and thiol crosslinking agent. This novel bioink for digital light processing 3D printing showed good printability and high shape fidelity. This ink material provides an excellent alternative for printing biomimetic soft tissue organs, high-throughput tissue models, soft robots, etc.

High-order vortex beams carrying orbital angular momentum in the visible wavelength range are of tremendous interest for a diversity of applications, including super-resolution imaging, microfabrication, and underwater communications. Such beams can be generated directly from compact solid-state lasers; however, they generally have low topological charge number. In this work, we demonstrate the generation of high-order Laguerre–Gaussian (LG) modes from a simple Pr:YLF laser cavity and demonstrate its application in the measurement of angular velocity. We utilize enhanced intracavity spherical aberration to generate LG0,±m modes with m selectable up to 34, directly from a Pr:YLF laser operating at 640 nm. We utilize this laser beam in an off-axis illumination geometry in conjunction with the rotational Doppler effect, to measure the angular velocity of a spinning object. The demonstration highlights a potential application for these types of vortex laser.

Colorectal cancer (CRC) is one of the most common cancers worldwide. Early detection and removal of colorectal polyps during colonoscopy are crucial for preventing such cancers. With the development of artificial intelligence (AI) technology, it has become possible to detect and localize colorectal polyps in real time during colonoscopy using computer-aided diagnosis (CAD). This provides a reliable endoscopist reference and leads to more accurate diagnosis and treatment. This paper reviews AI-based algorithms for real-time detection of colorectal polyps, with a particular focus on the development of deep learning algorithms aimed at optimizing both efficiency and correctness. Furthermore, the challenges and prospects of AI-based colorectal polyp detection are discussed.

The spatial structure of polarization in the vector optical beam provides an additional degree of freedom to manipulate light and control the light–matter interaction. The manipulation of polarization in the propagation (longitudinal) direction opens new ways to enrich the vector optical beam, which also faces the problems of monotony at present. Here, we demonstrate an amplitude-phase-polarization joint modulation method to accurately control the variation of localized polarization during propagation, mapping arbitrary circular trajectory on the Poincaré sphere. In addition, a dual-mode vector optical beam has been generated, which realizes the cascading of independent variations of polarization in different longitudinal ranges.

The discovery of the rotational Doppler effect (RDE) provides opportunities to achieve fast, accurate, and contactless measurement of angular velocity. As the RDE signal is sensitive to the illumination light and its scattering characteristic, how to effectively extract the angular velocity of a detected target becomes one of the key difficulties in this measurement technique. Here, we put forward a scattering modified RDE model to fully understand the frequency-domain behavior of an RDE signal in misaligned illumination. A robust strategy based on the peak-to-peak intervals in a wideband spectrum of the RDE signal is demonstrated to acquire accurate angular velocity, without strict requirement to the alignment of illumination and roughness of the detected surface. Furthermore, the feasibility to extract the spin angular velocity from a composite motion of spin and translation is discussed.