Lin Linhan, Zheng Yuebing
Department of Mechanical Engineering, Materials Science &Engineering Program, and Texas Materials Institute, The University of Texas at Austin, Austin, TX 78712, USA.
Sci Rep. 2015 Oct 1;5:14788. doi: 10.1038/srep14788.
Plasmonic nanoantennas, which can efficiently convert light from free space into sub-wavelength scale with the local field enhancement, are fundamental building blocks for nanophotonic systems. Predominant design methods, which exploit a single type of near- or far-field coupling in pairs or arrays of plasmonic nanostructures, have limited the tunability of spectral response and the local field enhancement. To overcome this limit, we are developing a general strategy towards exploiting the coordinated effects of multiple coupling. Using Au bowtie nanoantenna arrays with metal-insulator-metal configuration as examples, we numerically demonstrate that coordinated design and implementation of various optical coupling effects leads to both the increased tunability in the spectral response and the significantly enhanced electromagnetic field. Furthermore, we design and analyze a refractive index sensor with an ultra-high figure-of-merit (254), a high signal-to-noise ratio and a wide working range of refractive indices, and a narrow-band near-infrared plasmonic absorber with 100% absorption efficiency, high quality factor of up to 114 and a wide range of tunable wavelength from 800 nm to 1,500 nm. The plasmonic nanoantennas that exploit coordinated multiple coupling will benefit a broad range of applications, including label-free bio-chemical detection, reflective filter, optical trapping, hot-electron generation, and heat-assisted magnetic recording.
表面等离激元纳米天线能够通过局域场增强将自由空间中的光高效转换为亚波长尺度，是纳米光子系统的基本构建单元。主要的设计方法利用等离子体纳米结构对或阵列中的单一类型的近场或远场耦合，限制了光谱响应的可调性和局域场增强。为了克服这一限制，我们正在开发一种利用多重耦合协同效应的通用策略。以具有金属-绝缘体-金属结构的金蝴蝶结纳米天线阵列为例，我们通过数值模拟证明，各种光耦合效应的协同设计和实现既能提高光谱响应的可调性，又能显著增强电磁场。此外，我们设计并分析了一种具有超高品质因数（254）、高信噪比和宽折射率工作范围的折射率传感器，以及一种具有100%吸收效率、高达114的高品质因数和800纳米至1500纳米宽可调波长范围的窄带近红外表面等离激元吸收器。利用多重耦合协同效应的表面等离激元纳米天线将有利于广泛的应用，包括无标记生化检测、反射滤波器、光镊、热电子产生和热辅助磁记录。
