Park Sang-Min, Lee Kang Sup, Kim Jin-Ho, Yeon Gyu Jin, Shin Hyun-Hang, Park Sangwon, Kim Zee Hwan
Department of Chemistry, Seoul National University, Seoul 08826, Korea.
Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea.
J Phys Chem Lett. 2020 Nov 5;11(21):9313-9320. doi: 10.1021/acs.jpclett.0c02494. Epub 2020 Oct 22.
Dimers of metallic nanowires (NWs) with nanometric gaps could be an alternative to overcome the limitations of existing plasmonic waveguides. The gap-surface plasmon polaritons (gap-SPPs) of the dimers may propagate along the NW without crosstalk and greatly enhance the coupling efficiency with an emitter, enabling ultracompact optical circuits. Such a possibility has not been realized, and we experimentally show its possibility. The gap-SPPs of the AgNW-molecule-AgNW structure, with a gap of 3-5 nm defined by the molecules, are visualized using the surface-enhanced Raman scattering (SERS) of the molecules. The SERS images, representing the gap-field intensity distribution, reveal the decay and beating of the monopole-monopole and dipole-dipole gap modes. The propagation lengths of the two ( = 0.5-2 μm and = 5-8 μm) closely follow the model prediction with a uniform gap, confirming that the scattering loss induced by the gap irregularities is surprisingly low.
具有纳米级间隙的金属纳米线（NWs）二聚体可能是克服现有等离子体波导局限性的一种替代方案。二聚体的间隙表面等离子体激元（间隙 - SPPs）可以沿着纳米线传播而无串扰，并极大地提高与发射器的耦合效率，从而实现超紧凑光学电路。这种可能性尚未实现，而我们通过实验证明了其可能性。由分子定义间隙为3 - 5 nm的AgNW - 分子 - AgNW结构的间隙 - SPPs，利用分子的表面增强拉曼散射（SERS）进行可视化。代表间隙场强度分布的SERS图像揭示了单极 - 单极和偶极 - 偶极间隙模式的衰减和拍频。两者的传播长度（分别为0.5 - 2μm和5 - 8μm）与均匀间隙的模型预测紧密相符，证实由间隙不规则性引起的散射损耗出奇地低。
