Unidirectional and diffractionless surface plasmon polaritons on three-dimensional nonreciprocal plasmonic platforms
Unidirectional and diffractionless surface plasmon polaritons on three-dimensional nonreciprocal plasmonic platforms
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DOI：
10.1103/physrevb.99.245414
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发表时间：
2019-06-18
影响因子：
3.7
通讯作者：
Monticone, Francesco
中科院分区：
文献类型：
--
作者：
Gangaraj, S. Ali Hassani;Hanson, George W.;Monticone, Francesco
传统纳米光子结构中的光-物质相互作用通常缺乏方向性。例如，与微波天线系统不同，大多数光发射器（例如，激发的原子/分子和简单的纳米天线）表现出具有低方向性的准各向同性偶极辐射图案。此外，由常规材料衬底支持的表面波通常不具有优先传播方向，并且它们的波前在其沿着表面传播时倾向于扩散，除非表面或激发被适当地设计和结构化。在这篇文章中，我们从理论上证明了在一个非互易平台上，即在一个旋向性磁化等离子体中实现单向无衍射表面等离子体激元模式的可能性。基于严格的绿色函数的方法，我们提供了一个全面和系统的分析所有可用的物理机制，可能赋予系统的方向性，无论是在单向激发表面波的意义上，并在定向无衍射传播沿着表面。所考虑的机制包括（i）强和弱形式的非互易性的效果，（ii）椭圆形或双曲线状拓扑的模式色散表面，和（iii）源偏振态，与相关的可能性的手性表面波激发由角动量匹配。我们发现，三维回旋等离子体平台支持以前未被注意的波传播制度，同时表现出这些物理机制中的几个，使我们能够从理论上证明单向表面等离子体极化激元模式，作为一个单一的ultransarrow无衍射光束传播。我们还评估了耗散和非局部效应的影响。我们的理论研究结果可能使新一代的等离子体结构和设备具有高度的方向性响应。
Light-matter interactions in conventional nanophotonic structures typically lack directionality. For example, differently from microwave antenna systems, most optical emitters (e.g., excited atoms/molecules and simple nanoantennas) exhibit quasi-isotropic dipolar radiation patterns with low directivity. Furthermore, surface waves supported by conventional material substrates do not usually have a preferential direction of propagation, and their wavefront tends to spread as it propagates along the surface, unless the surface or the excitation is properly engineered and structured. In this article, we theoretically demonstrate the possibility of realizing unidirectional and diffractionless surface plasmon polariton modes on a nonreciprocal platform, namely, a gyrotropic magnetized plasma. Based on a rigorous Green's function approach, we provide a comprehensive and systematic analysis of all the available physical mechanisms that may bestow the system with directionality, both in the sense of one-way excitation of surface waves and in the sense of directive diffractionless propagation along the surface. The considered mechanisms include (i) the effect of strong and weak forms of nonreciprocity, (ii) the elliptic-like or hyperbolic-like topology of the modal dispersion surfaces, and (iii) the source polarization state, with the associated possibility of chiral surface-wave excitation governed by angular-momentum matching. We find that three-dimensional gyrotropic plasmonic platforms support a previously unnoticed wave-propagation regime that exhibit several of these physical mechanisms simultaneously, allowing us to theoretically demonstrate unidirectional surface plasmon polariton modes that propagate as a single ultranarrow diffractionless beam. We also assess the impact of dissipation and nonlocal effects. Our theoretical findings may enable a new generation of plasmonic structures and devices with highly directional response.