使用箔上纳米粒子构建的等离子体热点
Accessing Plasmonic Hotspots using Nanoparticle-on-Foil Constructs
摘要：
典型的镜面上纳米粒子几何形状（NPoM）中的金属-绝缘体-金属（MIM）纳米间隙提供具有小于$V/V_0$ $<$ $10^{-6}$的模体积的光的深亚波长限制。然而，对这些热点的访问受限于捕获光的高平面内$k_{//}$与自由空间平面波之间的阻抗失配，使得光的输入耦合和输出耦合困难。在这里，通过构建具有薄金属膜的箔上纳米颗粒（NPoF）系统，我们展示了绝缘体-金属-绝缘体（IMI）模式和MIM间隙模式的混合，从而产生MIMI模式。这种混合通过从金属膜的两侧入射的光提供了对等离子体纳米腔的多通道访问。通过白光散射和表面增强拉曼散射实验测量了薄箔MIMI模的红调谐和近场强度。我们进一步讨论了NPoF系统的实用性，因为几何形状允许严格限制的光通过不同的端口简单地访问。
英文摘要：
Metal-insulator-metal (MIM) nanogaps in canonical nanoparticle-on-mirror geometry (NPoM) provide deep-subwavelength confinement of light with mode volumes smaller than $V/V_0$ $<$ $10^{-6}$. However, access to these hotspots is limited by the impendence mismatch between the high in-plane $k_{//}$ of trapped light and free-space plane-waves, making the in- and out-coupling of light difficult. Here, by constructing a nanoparticle-on-foil (NPoF) system with thin metal films, we show the mixing of insulator-metal-insulator (IMI) modes and MIM gap modes resulting in MIMI modes. This mixing provides multi-channel access to the plasmonic nanocavity through light incident from both sides of the metal film. The red-tuning and near-field strength of MIMI modes for thinner foils is measured experimentally with white-light scattering and surface-enhanced Raman scattering from individual NPoFs. We discuss further the utility of NPoF systems since the geometry allows tightly confined light to be accessed simply and through different ports.
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