Abstract
Using the N-order finite-difference time-domain (FDTD) method, we show that optical resonances of the bowtie nanoaperture (BNA) are due to the combination of a guided mode inside the aperture and Fabry-Perot modes along the metal thickness. The resonance of lower energy, which leads to the well-known light confinement in the gap zone, occurs at the cutoff wavelength of the fundamental guided mode. No plasmon resonance is directly involved in the generation of the light hot spot. We also define a straightforward relationship between the resonance wavelengths of the BNA and its geometrical parameters. This brings a simple tool for the optimization of the BNA design.
Highlights
HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not
bowtie nanoapertures (BNAs) have been successfully used as nanometer-sized light sources for nanolithography [6] and near-field optical imaging [7]
The authors assert that the ability of the BNA to generate a hot spot in the gap region is due to the excitation of a plasmon resonance of the structure
Summary
HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. We demonstrate that a vertical guided mode inside the structure, rather than a localized plasmon resonance, is responsible for the light confinement ability of the BNA. We define an analytical expression between the resonance wavelengths of the BNA and its gap width, lateral size, and metal kind.
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