[论文解读] Extraordinary optical transmission through metal films with sub wavelength holes and slits

A. S. Vengurlekar|arXiv (Cornell University)|Apr 5, 2010

Plasmonic and Surface Plasmon Research参考文献 67被引用 34

一句话总结

本文综述了金属薄膜中亚波长孔洞与狭缝的异常光学透射（EOT）现象，其中光透过率远超经典理论预测，这是由于表面等离激元极化激元被激发所致。主要贡献在于对理论与实验洞察的全面整合，阐明了增强透射的机制，特别是耦合表面等离激元在介导光通过纳米孔洞高效耦合中的作用。

ABSTRACT

Continuous films of metals like gold and silver with a thickness of a few tens of nm have poor optical transmission in the visible and infrared. However, the same films become largely transparent when the transmission is mediated by coupled surface plasmon polaritons on the two surfaces of the film. Likewise, it is expected that optical transmission through a hole in an opaque metal film would be negligible if the size of the hole is much smaller than the wavelength of the incident radiation. Contrary to this, it was found a few years ago that opaque metal films perforated with a periodic array of sub wavelength holes exhibit large transmission at certain wavelengths. Such extraordinary optical properties of the metal films have attracted much attention in recent years. They have led to several proposals and demonstrations of nanophotonic applications in a wide range of areas, such as microscopy, spectroscopy, optoelectronics, optical data storage, bio-chemical sensing and so on. In parallel, extensive effort has been made to elucidate the mechanisms of efficient light energy transfer across metal films with arrays of sub wavelength apertures like holes and slits. Despite this effort, not all aspects of the underlying physics of the phenomena are fully understood yet. Here, we provide a short review of the various concepts put forth to explicate the large transmission of light across continuous metal films and films with sub wavelength apertures.

研究动机与目标

• 分析并综合现有理论，以解释金属薄膜中亚波长孔洞的异常光学透射现象。
• 阐明表面等离激元极化激元在实现超越经典衍射极限的增强透射中的作用。
• 对连续金属薄膜中纳米尺度孔洞的光耦合机制提出机制进行批判性综述。
• 尽管研究广泛，仍强调基础物理中未解决的问题。
• 通过整合当前对EOT的理解，为未来纳米光子器件的发展提供支持。

提出的方法

• 系统性回顾与异常光学透射（EOT）相关的理论模型与实验观测。
• 分析穿孔薄膜金属-介质界面处表面等离激元极化激元（SPP）的激发。
• 研究周期性孔洞阵列对耦合效率与共振透射峰的影响。
• 比较具有孔洞与狭缝的薄膜的透射行为，强调几何依赖的SPP模式。
• 评估近场耦合与干涉效应在增强透射中的作用。
• 综合多项研究的发现，以识别支配EOT的稳定物理原理。

实验结果

研究问题

• RQ1 何种物理机制使得光能通过原本不透明金属薄膜中的亚波长孔洞透射？
• RQ2 表面等离激元极化激元如何促进周期性孔洞阵列中的透射增强？
• RQ3 为何单个亚波长孔洞的透射仍可忽略不计，而周期性阵列却表现出强烈的共振透射？
• RQ4 几何参数（孔径尺寸、周期性、薄膜厚度）在多大程度上影响EOT效率？
• RQ5 尽管已有大量实验与理论工作，其基础物理中仍存在哪些未解决的问题？

主要发现

• 在金和银薄膜的周期性亚波长孔洞阵列中，特定共振波长下的透射率可超过入射光功率的100%，远超经典预期。
• 增强透射主要归因于金属薄膜输入与输出界面处表面等离激元极化激元的激发与耦合。
• 透射效率强烈依赖于孔洞阵列的周期性与几何形状，当光栅动量匹配SPP波矢时出现共振峰。
• 该现象不仅限于孔洞；在亚波长狭缝中也观察到类似效应，表明其涉及表面等离激元耦合的普遍机制。
• 尽管研究广泛，局部与传播等离激元模式在EOT中精确相互作用机制仍不完全清楚。
• 本综述指出，近场耦合与远场衍射效应均对整体透射增强有贡献，但其相对作用仍存在争议。