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 20 nm 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.

单粒子跟踪 (SPT) 是一种非常有价值的技术，用于研究生命科学和物理学中的各种过程。它可以帮助研究人员更好地了解高度动态或需要长时间成像的系统中单个对象的位置、路径和交互。在这里，我们提出了一种全电介质一维光子晶体（1D PC），它增强了三维（3D）SPT的自旋到轨道角动量转换。这种精心设计的一维 PC 可以作为光学显微镜的基底。我们将这种效应引入干涉散射 (iSCAT) 技术，从而产生双螺旋点扩散函数 (DH-PSF)。与传统显微镜的 PSF 相比，DH-PSF 为 3D 位置估计提供了更统一的 Fisher 信息，例如在 DH-PSF 波瓣的角方向上编码单个粒子的轴向位置，从而为 3D SPT 提供了一种手段。这种方法可以解决 3D SPT 中 iSCAT 的挑战，因为当单个粒子沿轴向行进时，DH-PSF iSCAT 不会经历多次对比度反转。 DH-PSF iSCAT 显微镜用于记录附着在鞭毛上的单个微珠的 3D 轨迹，有助于精确分析运动动力学的波动。还证明了其跟踪单个纳米颗粒的能力，例如甘油溶液中 20 nm 金纳米颗粒的 3D 扩散轨迹。由 1D PC 支持的 DH-PSF iSCAT 技术为物理、生物和化学科学的未来应用带来了潜在的前景。