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Generalized local analogue model for nonlocal plasmonic nanostructures based on multiple-fluid hydrodynamic framework
摘要： The control and manipulation of light waves is a long-standing ambition with profound implications for the development of science and technology. Recent advances in nanofabrication allow for a rapid progress in engineering plasmonic nano-devices which collect and concentrate light or electromagnetic waves into a subwavelength region, enabling various applications in nanophotonics, such as bio-sensor with enhanced sensitivity, plasmonic laser, plasmonic colors and quantum plasmonics, to name a few. Spatial dispersion plays a critical role in nanophotonics when small plasmonic structures with feature sizes of few nanometers are handled. Such nonlocality is typically considered in a hydrodynamic framework and generally requires solving coupled partial differential equations, and therefore is involved. We develop a generalized local analogue model to reflect the nonlocal effects of plasmonic structures and avoid the complicated analysis within the multiple-fluid hydrodynamic framework, where more than one kind of charge carriers is considered. We show that spatial nonlocality can be represented by simply replacing the nonlocal surface region with an in-situ artificial local dispersive film. With such an elegant and simple-to-use alternative, the conventional analysis and simulations in the local regime acquire nonlocal capability, sufficient for a quantitative description of various plasmonic structures in nanoscale, rendering a much simpler process and great practical advantages in the numerical treatment.
关键词： multiple fluid,in-situ local model,nonlocal response,hydrodynamic Drude model
更新于2025-09-23 15:21:01
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Impact of Surface Roughness in Nanogap Plasmonic Systems
摘要： Recent results have shown unprecedented control over separation distances between two metallic elements hundreds of nanometers in size, underlying the effects of free-electron nonlocal response also at mid-infrared wavelengths. Most of metallic systems however, still suffer from some degree of inhomogeneity due to fabrication-induced surface roughness. Nanoscale roughness in such systems might hinder the understanding of the role of microscopic interactions. Here we investigate the effect of surface roughness in coaxial nanoapertures resonating at mid-infrared frequencies. We show that although random roughness shifts the resonances in an unpredictable way, the impact of nonlocal effects can still be clearly observed. Roughness-induced perturbation on the peak resonance of the system shows a strong correlation with the effective gap size of the individual samples. Fluctuations due to fabrication imperfections then can be suppressed by performing measurements on structure ensembles in which averaging over a large number of samples provides a precise measure of the ideal system’s optical properties.
关键词： hydrodynamic model,nonlocal response,coaxial aperture,plasmonics,epsilon-near-zero mode,surface roughness
更新于2025-09-19 17:13:59