Nano Lett. 2018 Aug 8;18(8):5024-5029. doi: 10.1021/acs.nanolett.8b01844. Epub 2018 Jul 2.
The ability to manipulate small objects with focused laser beams opens a broad spectrum of opportunities in fundamental and applied studies, for which precise control over mechanical path and stability is required. Although conventional optical tweezers are based on refractive optics, the development of compact trapping devices that could be integrated within fluid cells is in high demand. Here, a plasmonic polarization-sensitive metasurface-based lens, embedded within a fluid, is demonstrated to provide several stable trapping centers along the optical axis. The position of a particle is controlled with the polarization of the incident light, interacting with plasmonic nanoscale patch antennas, organized within overlapping Fresnel zones of the lens. While standard diffractive optical elements face challenges in trapping objects in the axial direction outside the depth of focus, bifocal Fresnel meta-lens demonstrates the capability to manipulate a bead along a 4 μm line. An additional fluorescent module, incorporated within the optical trapping setup, was implemented and enabled the accurate mapping of optical potentials via a particle-tracking algorithm. Auxiliary micro- and nanostructures, integrated within fluidic devices, provide numerous opportunities to achieve flexible optomechanical manipulation, including transport, trapping, and sorting, which are in high demand for lab-on-a-chip applications and many others.
利用聚焦激光束操纵微小物体为基础研究和应用研究开辟了广阔的机会，这需要对机械路径和稳定性进行精确控制。尽管传统的光学镊子基于折射光学，但需要开发可集成在流体单元内的紧凑型捕获装置。在这里，演示了一种基于等离子体极化敏感超表面的透镜，嵌入在流体中，可以沿着光轴提供多个稳定的捕获中心。通过与透镜的菲涅耳区重叠的等离子体纳米级补丁天线相互作用，利用入射光的偏振来控制粒子的位置。虽然标准的衍射光学元件在捕获焦深外轴向物体方面面临挑战，但双焦菲涅耳元透镜展示了沿 4μm 线操纵珠子的能力。通过在光学捕获设置中加入一个附加的荧光模块，实现了通过粒子跟踪算法准确绘制光学势的能力。集成在流体装置内的辅助微纳结构为实现灵活的光机械操纵提供了众多机会，包括运输、捕获和分类，这在芯片实验室应用和许多其他领域都有很高的需求。
