研究目的
Investigating the effect of surface roughness in coaxial nanoapertures resonating at mid-infrared frequencies.
研究成果
The study demonstrates that nanoscale surface roughness significantly affects the resonance shift of individual samples in coaxial nanoapertures. However, the impact of nonlocal effects can still be clearly observed. The roughness-induced perturbation on the peak resonance strongly correlates with the effective gap size for each individual sample. Averaging over a large number of samples can suppress fluctuations due to fabrication imperfections, providing a precise measure of the ideal system’s optical properties.
研究不足
The study is limited to roughness on the cross-sectional plane of the systems, neglecting line-edge roughness and assuming the apertures to be perfectly circular. The approach does not account for full three-dimensional surface roughness, which might lead to different conclusions.
1：Experimental Design and Method Selection:
The study employs numerical calculations to analyze the impact of nanoscale surface roughness on coaxial nanoapertures. The methodology includes solving Maxwell’s equations using the 2.5D technique, which exploits the axis symmetry of the geometry to simplify the problem.
2：5D technique, which exploits the axis symmetry of the geometry to simplify the problem.
Sample Selection and Data Sources:
2. Sample Selection and Data Sources: The study considers coaxial nanoapertures with gaps varying from 2 to 10 nm, characterized by internal diameter D = 250 nm and gold film thickness H = 150 nm. The structures are excited by a plane wave impinging at normal incidence through an infinite sapphire substrate.
3：List of Experimental Equipment and Materials:
The study uses a commercially available finite-element method software, Comsol Multiphysics, for numerical calculations. The geometry is created using a Matlab script.
4：Experimental Procedures and Operational Workflow:
The study generates 20 different numerical samples for each nominal gap size, considering both conformal and fully random gap roughness. The absorption efficiency is computed to characterize the optical response of the systems.
5：Data Analysis Methods:
The study analyzes the resonance shift and the impact of roughness on the peak resonance, correlating it with the effective gap size for each individual sample.
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