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Low-power Optical Traps Using Anisotropic Metasurfaces: Asymmetric Potential Barriers and Broadband Response
Physical Review Applied ( IF 4.6 ) Pub Date : 2021-01-11 , DOI: 10.1103/physrevapplied.15.014018
N.K. Paul , J.S. Gomez-Diaz

We propose lateral optical trapping of Rayleigh particles using tailored anisotropic and hyperbolic metasurfaces illuminated with a linearly polarized Gaussian beam. This platform permits optical traps to be engineered at the beam axis with a response governed by nonconservative and giant lateral recoil force coming from the directional excitation of confined surface plasmons during the light-scattering process. Compared to optical traps set over uniform metals, either in bulk or thin-layer configurations, the proposed traps are broadband in the sense that they can be set with beams oscillating at any frequency within a wide range in which the metasurface supports surface plasmons. Over that range, the metasurface dispersion evolves from an anisotropic elliptic to a hyperbolic regime going 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 stable trapping of nanoparticles using low-intensity laser beams. To investigate the performance of this platform, we develop a rigorous formalism based on Lorentz force within the Rayleigh approximation combined with anisotropic Green’s functions and calculate the trapping potential of nonconservative lateral forces using the Helmholtz decomposition method. Tailored anisotropic and hyperbolic metasurfaces, commonly implemented by nanostructuring thin metallic layers, permit to use low-intensity laser sources operating in the visible or infrared frequencies to trap and manipulate particles at the nanoscale, and may enable a wide range of applications in bioengineering, physics, and chemistry.

中文翻译:

使用各向异性超表面的低功率光阱:不对称的势垒和宽带响应

我们建议使用线性偏振高斯光束照射的各向异性和双曲形超表面对瑞利粒子进行横向光学陷波。该平台允许在光束轴上设计光阱,其响应受光散射过程中受限表面等离激元的定向激发产生的非保守和巨大的横向反冲力支配。与在整块金属或薄层结构中设置在均匀金属上的光阱相比,建议的阱是宽带的,从某种意义上说,可以用在超颖表面支撑表面等离激元的宽范围内的任何频率的光束进行设置的形式设置阱。在这个范围内 超表面弥散从各向异性的椭圆形演变为双曲型,并经历了拓扑过渡,并使光阱具有独特的空间不对称电势分布,受激等离子体的动量不平衡引起的局部势垒以及增强的电势深度,从而实现了稳定的阱阱低强度激光束分析纳米粒子。为了研究该平台的性能,我们基于瑞利近似内的洛伦兹力结合各向异性格林函数,开发了一种严格的形式主义,并使用亥姆霍兹分解法计算了非保守侧向力的俘获潜力。量身定制的各向异性和双曲超表面,通常通过纳米结构化薄金属层来实现,
更新日期:2021-01-12
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