Laboratory of Bio-optical Imaging, Singapore Bioimaging Consortium, Agency for Science Technology and Research (A*STAR), Singapore, Singapore.
Sci Rep. 2017 Nov 14;7(1):15587. doi: 10.1038/s41598-017-15675-0.
A theoretical design and analysis of a tapered-coupler structure on a silicon nitride integrated-photonic platform for coupling optical energy from a dielectric waveguide to a plasmonic tip is presented. The proposed design can be considered as a hybrid photonic-plasmonic structure that generally supports hybrid symmetric and asymmetric modes. Along the taper, one of the hybrid modes approaches the cut-off, while the other approaches the short-range surface plasmon mode that generates localized fields. Potential use of the proposed novel tapered-coupler plasmonic structure for highly sensitive biosensing applications using surface enhanced Raman scattering (SERS) and metal enhanced fluorescence (MEF) techniques is discussed. For SERS, a theoretical electromagnetic enhancement factor as high as 1.23 × 10 is deduced for taper tip widths as small as 20 nm. The proposed tapered-coupler sets up interesting possibilities towards moving to an all-integrated on-chip SERS and MEF based bio-sensor platform - away from traditional free-space based illumination strategies.
提出了一种在氮化硅集成光子平台上的锥形耦合器结构的理论设计和分析，用于将光能量从介质波导耦合到等离子体尖端。所提出的设计可以被认为是一种混合光子-等离子体结构，通常支持混合对称和非对称模式。在锥形部分，其中一个混合模式接近截止，而另一个模式接近产生局域场的短程表面等离激元模式。讨论了所提出的新型锥形耦合等离子体结构在基于表面增强拉曼散射（SERS）和金属增强荧光（MEF）技术的高灵敏度生物传感应用中的潜在用途。对于 SERS，对于宽度小至 20nm 的锥形尖端，理论上得出的电磁增强因子高达 1.23×10。所提出的锥形耦合器为向全集成片上 SERS 和 MEF 生物传感器平台的发展提供了有趣的可能性 - 远离传统的基于自由空间的照明策略。
