Laboratory of Nanotechnology, Instrumentation and Optics, ICD CNRS UMR 6281, University of Technology of Troyes, 10000, Troyes, France.
Nanotechnology. 2017 May 5;28(18):185201. doi: 10.1088/1361-6528/aa6826. Epub 2017 Mar 21.
Overcoming the diffraction limit to achieve high optical resolution is one of the main challenges in the fields of plasmonics, nanooptics and nanophotonics. In this work, we introduce novel plasmonic structures consisting of nanoantennas (nanoprisms, single bowtie nanoantennas and double bowtie nanoantennas) integrated in the center of ring diffraction gratings. Propagating surface plasmon polaritons (SPPs) are generated by the ring grating and coupled with localized surface plasmons (LSPs) at the nanoantennas exciting emitters placed in their gap. SPPs are widely used for optical waveguiding but provide low resolution due to their weak spatial confinement. In contrast, LSPs provide excellent sub-wavelength confinement but induce large losses. The phenomenon of SPP-LSP coupling witnessed in our structures allows for achieving more precise focusing at the nanoscale, causing an increase in the fluorescence emission of the emitters. Finite-difference time-domain simulations as well as experimental fabrication and optical characterization results are presented to study plasmon-emitter coupling between an ensemble of dye molecules and our integrated plasmonic structures. A comparison is given to highlight the importance of each structure on the photoluminescence and radiative decay enhancement of the molecules.
克服衍射极限以实现高光学分辨率是等离子体学、纳米光学和纳米光子学领域的主要挑战之一。在这项工作中，我们引入了由纳米天线（纳米棱镜、单蝴蝶结纳米天线和双蝴蝶结纳米天线）集成在环形衍射光栅中心的新型等离子体结构。环形光栅产生传播表面等离激元（SPP），并与纳米天线中的局域表面等离激元（LSP）耦合，激发置于其间隙中的发射器。SPP 广泛用于光学波导，但由于其空间限制较弱，因此分辨率较低。相比之下，LSP 提供了出色的亚波长限制，但会引起较大的损耗。我们的结构中观察到的 SPP-LSP 耦合现象可实现更精确的纳米级聚焦，从而增加发射器的荧光发射。提出了有限差分时域模拟以及实验制造和光学特性研究结果，以研究染料分子与我们集成的等离子体结构之间的等离子体-发射器耦合。给出了比较，以突出每个结构对分子的光致发光和辐射衰减增强的重要性。
