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arXiv 2008.00353physics.app-phphysics.optics
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基于各向异性超颖表面的低功率光阱：非对称势垒和宽带响应

Low-Power Optical Traps using Anisotropic Metasurfaces: Asymmetric Potential Barriers and Broadband Response

Nayan K. Paul, J. Sebastian Gomez-Diaz

备注：
39 pages - 8 figures
发表信息：
Phys. Rev. Applied 15, 014018 (2021)
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摘要：

我们提出了使用定制的各向异性和双曲超颖表面与线性偏振高斯光束照明的瑞利粒子的光捕获。该平台允许工程师在光束轴处的光学陷阱，其响应由来自光散射过程中超受限表面等离子体的定向激发的非保守和巨大的反冲力控制。与在大块金属上设置的光学陷阱相比，所提出的陷阱是宽带的，在这个意义上，可以设置在超颖表面支持表面等离子体激元的宽范围内以任何频率振荡的光束。在该范围内，超颖表面通过拓扑过渡从各向异性椭圆形演变为双曲线状态，并使光学陷阱具有独特的空间非对称势分布，由激发的等离子体激元的动量不平衡引起的局部势垒，以及允许使用低强度激光束稳定捕获纳米颗粒的增强的势深度。为了研究该平台的性能，我们开发了一个严格的形式主义的基础上的洛伦兹力结合各向异性格林函数的瑞利近似和计算的捕获潜力的非保守力使用Helmholtz-Hodge分解方法。定制的各向异性和双曲线超颖表面，通常由纳米结构化薄金属层实现，使得能够使用在可见光或IR中操作的低强度激光源来捕获和操纵纳米级的颗粒，并且可以实现生物工程、物理和化学中的广泛应用。

英文摘要：

We propose the optical trapping of Rayleigh particles using tailored anisotropic and hyperbolic metasurfaces illuminated with a linearly polarized Gaussian beam. This platform permits to engineer optical traps at the beam axis with a response governed by nonconservative and giant recoil forces coming from the directional excitation of ultra-confined surface plasmons during the light scattering process. Compared to optical traps set over bulk metals, the proposed traps are broadband in the sense that can be set with beams oscillating at any frequency within the wide range in which the metasurface supports surface plasmons. Over that range, the metasurface evolves from an anisotropic elliptic to a hyperbolic regime through a topological transition and enables optical traps with distinctive spatially asymmetric potential distribution, local potential barriers arising from the momentum imbalance of the excited plasmons, and an enhanced potential depth that permits the stable trapping of nanoparticles using low-intensity laser beams. To investigate the performance of this platform, we develop a rigorous formalism based on the Lorentz force within the Rayleigh approximation combined with anisotropic Green's functions and calculate the trapping potential of nonconservative forces using the Helmholtz-Hodge decomposition method. Tailored anisotropic and hyperbolic metasurfaces, commonly implemented by nanostructuring thin metallic layers, enables using low-intensity laser sources operating in the visible or the IR to trap and manipulate particles at the nanoscale, and may enable a wide range of applications in bioengineering, physics, and chemistry.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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