Shen Shaoxin, Zeng Yue, Zheng Zehuan, Gao Renxian, Sun Guoya, Yang Zhilin
Opt Express. 2022 Jan 17;30(2):2610-2625. doi: 10.1364/OE.449337.
Plasmonic nanocavities offer prospects for the amplification of inherently weak nonlinear responses at subwavelength scales. However, constructing these nanocavities with tunable modal volumes and reduced optical losses remains an open challenge in the development of nonlinear nanophotonics. Herein, we design and fabricate three-dimensional (3D) metal-dielectric-metal (MDM) plasmonic nanocavities that are capable of amplifying second-harmonic lights by up to three orders of magnitude with respect to dielectric-metal counterparts. In combination with experimental estimations of quantitative contributions of constituent parts in proposed 3D MDM designs, we further theoretically disclose the mechanism governing this signal amplification. We discover that this phenomenon can be attributed to the plasmon hybridization of both dipolar plasmon resonances and gap cavity resonances, such that an energy exchange channel can be attained and helps expand modal volumes while maintaining strong field localizations. Our results may advance the understanding of efficient nonlinear harmonic generations in 3D plasmonic nanostructures.
等离子体纳米腔为在亚波长尺度上放大固有的微弱非线性响应提供了前景。然而，构建具有可调谐模态体积并降低光学损耗的这些纳米腔，仍然是非线性纳米光子学发展中的一个开放性挑战。在此，我们设计并制造了三维（3D）金属 - 电介质 - 金属（MDM）等离子体纳米腔，相对于电介质 - 金属对应物，其能够将二次谐波光放大多达三个数量级。结合对所提出的3D MDM设计中组成部分定量贡献的实验估计，我们进一步从理论上揭示了控制这种信号放大的机制。我们发现这种现象可归因于偶极等离子体共振和间隙腔共振的等离子体杂交，从而可以获得一个能量交换通道，有助于在保持强场局域化的同时扩大模态体积。我们的结果可能会推进对3D等离子体纳米结构中高效非线性谐波产生的理解。
