发表机构
Tata Institute of Fundamental Research; Indian Institute of Science Education and Research Kolkata（塔塔基础研究所; 印度科学教育研究学院加尔各答分校）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文提出利用分层介质折射率梯度工程，以单高斯光束实现扩展三维光捕获，通过球差形成多稳定捕获区，为全息光镊提供简化替代方案。
AI 中文摘要
我们展示了一种简单有效的方法，通过利用具有工程化折射率梯度的分层介质中传播的单一线偏振高斯光束，实现扩展体积光捕获。通过修改梯度，焦场发生轴向伸长并产生多个局部强度极大值，从而能够在不同轴向平面同时捕获粒子。实验上观察到了轴上和离轴两种捕获配置，形成了体积粒子分布，无需复杂全息光束整形。采用基于Debye-Wolf衍射理论与广义Lorenz-Mie理论相结合的严格理论框架，对聚焦场及由此产生的光力进行建模。该分析通过数值模拟验证，表明由折射率不连续性引起的球差在重新分配光能中起关键作用，导致多个稳定捕获区域的形成。轴向捕获势随失配度增加而单调减小，表明多位点捕获能力与捕获势之间存在权衡，这与实验观测定量一致。这项工作确立了折射率工程作为利用最小光学复杂度定制三维光力景观的强大工具，从而为传统全息光镊提供了一种可扩展的替代方案，适用于胶体组装、微操控和生物光子学等应用。
英文摘要
We demonstrate a simple and effective approach for realizing extended volumetric optical trapping using a single linearly polarized Gaussian beam propagating through a stratified medium with engineered refractive index gradients. On modifying the gradients, the focal field undergoes axial elongation and develops multiple localized intensity maxima, enabling simultaneous trapping of particles at distinct axial planes. Both on-axis and off-axis trapping configurations are experimentally observed, forming a volumetric particle distribution without the need for complex holographic beam shaping. A rigorous theoretical framework based on the Debye Wolf diffraction formalism combined with Generalized Lorenz-Mie Theory is employed to model the focused field and the resulting optical forces. The analysis, substantiated with numerical simulations, shows that spherical aberration arising from refractive-index discontinuities plays a crucial role in redistributing optical energy, leading to the formation of multiple stable trapping regions. The axial trapping potential decreases monotonically with increasing mismatch, indicating a trade-off between multi-site trapping capability and trapping potential, which is in quantitative agreement with experimental observations. This work establishes refractive index engineering as a powerful tool for tailoring three-dimensional optical force landscapes using minimal optical complexity, thus offering a scalable alternative to conventional holographic optical tweezers towards applications in colloidal assembly, micromanipulation, and biophotonics.
Comments12 pages, 7 figures
