Narrow plasmonic resonances in an asymmetric refractive index (RI) environment under normal incidence are desired for miniaturized sensors in clinical evaluation and lab-on-a-chip devices. We demonstrate that a thin alumina layer between Au nanoparticle (NP) lattices and a quartz substrate can induce total internal reflections and nonvanishing out-of-plane electric fields, resulting in ultranarrow quadrupole surface lattice resonances (SLRs). The SLRs show a line width below 1 nm with high-quality factors up to 1865 in simulations and up to 640 in experiments under normal incidence in the visible range. High-performance RI sensing based on SLRs is demonstrated for glucose in aqueous solutions and DMSO/water mixtures, which show a one magnitude improvement in the figure of merit compared with the Au NP lattices on the bare quartz substrate. This substrate modification opens a new avenue to design and generate high-quality plasmonic resonances for light-matter interactions and sensing applications.

中文翻译：

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正常入射下等离激元纳米颗粒晶格的高质量共振


临床评估和芯片实验室设备中的小型传感器需要在法向入射的不对称折射率 (RI) 环境中实现窄等离子体共振。我们证明，金纳米颗粒（NP）晶格和石英基板之间的薄氧化铝层可以引起全内反射和不消失的面外电场，从而产生超窄四极表面晶格共振（SLR）。 SLR 显示出低于 1 nm 的线宽，在可见光范围内法向入射下，模拟中的高质量因子高达 1865，实验中的高质量因子高达 640。基于 SLR 的高性能 RI 传感针对水溶液和 DMSO/水混合物中的葡萄糖进行了演示，与裸石英基板上的 Au NP 晶格相比，其品质因数提高了一个数量级。这种基底修饰为设计和产生用于光-物质相互作用和传感应用的高质量等离子体共振开辟了一条新途径。