近日，中国科学技术大学的张斗国&袁军华及其研究团队取得一项新进展。经过不懈努力，他们提出用于增强单粒子跟踪自旋轨道角动量转换的一维光子晶体。相关研究成果已于2024年9月26日在国际知名学术期刊《光：科学与应用》上发表。

该研究团队提出一种全介质一维光子晶体（1D PC），它能增强三维（3D）单粒子追踪（SPT）中的自旋到轨道角动量转换。这一精心设计的1D PC可作为光学显微镜的基底。研究人员将此效应引入干涉散射（iSCAT）技术中，从而产生了双螺旋点扩散函数（DH-PSF）。与传统显微镜的点扩散函数相比，DH-PSF为3D位置估计提供了更为均匀的费雪信息，例如，通过将单粒子的轴向位置编码在DH-PSF波瓣的角向中，为3D SPT提供了一种手段。

此方法能够解决iSCAT在3D SPT中面临的挑战，因为当单粒子沿轴向移动时，DH-PSF iSCAT不会经历多次对比度反转。研究人员利用DH-PSF iSCAT显微镜记录了附着在鞭毛上的单个微珠的3D轨迹，从而便于对马达动力学的波动进行精确分析。此外，该技术还展示了追踪单个纳米粒子（如甘油溶液中20nm金纳米粒子的3D扩散轨迹）的能力。由1D PC实现的DH-PSF iSCAT技术，在未来物理、生物和化学科学领域的应用中展现出巨大的潜力。

据悉，单粒子追踪（SPT）技术是生命科学和物理学领域中研究多种过程的一种极具价值的技术。它能够帮助研究人员更好地理解高度动态系统或需要长时间成像的系统中单个物体的位置、轨迹及相互作用。

附：英文原文

Title: One-dimensional photonic crystal enhancing spin-to-orbital angular momentum conversion for single-particle tracking

Author: Huang, Mingchuan, Chen, Qiankun, Liu, Yang, Zhang, Chi, Zhang, Rongjin, Yuan, Junhua, Zhang, Douguo

Issue&Volume: 2024-09-26

Abstract: Single-particle tracking (SPT) is an immensely valuable technique for studying a variety of processes in the life sciences and physics. It can help researchers better understand the positions, paths, and interactions of single objects in systems that are highly dynamic or require imaging over an extended time. Here, we propose an all-dielectric one-dimensional photonic crystal (1D PC) that enhances spin-to-orbital angular momentum conversion for three-dimensional (3D) SPTs. This well-designed 1D PC can work as a substrate for optical microscopy. We introduce this effect into the interferometric scattering (iSCAT) technique, resulting in a double-helix point spread function (DH-PSF). DH-PSF provides more uniform Fisher information for 3D position estimation than the PSFs of conventional microscopy, such as encoding the axial position of a single particle in the angular orientation of DH-PSF lobes, thus providing a means for 3D SPT. This approach can address the challenge of iSCAT in 3D SPT because DH-PSF iSCAT will not experience multiple contrast inversions when a single particle travels along the axial direction. DH-PSF iSCAT microscopy was used to record the 3D trajectory of a single microbead attached to the flagellum, facilitating precise analysis of fluctuations in motor dynamics. Its ability to track single nanoparticles, such as 3D diffusion trajectories of 20nm gold nanoparticles in glycerol solution, was also demonstrated. The DH-PSF iSCAT technique enabled by a 1D PC holds potential promise for future applications in physical, biological, and chemical science.

DOI: 10.1038/s41377-024-01623-x

Source: https://www.nature.com/articles/s41377-024-01623-x