Abstract
We report numerically electromagnetic-induced transparency (EIT) and Fano resonances in simple plasmonic metasurfaces consisting of gold nanobars arranged in pi, H, and four-shaped fashion. The bright and dark elements in the metasurfaces are responsible for the emergence of EIT and Fano effects in the transmission spectrum. The concept of symmetry breaking is also introduced by incorporating multiple cavities in the metasurface, which relaxes the dipole coupling selection rules resulting in a mixture of dipole and higher order modes that interact and engenders EIT and Fano modes simultaneously in a nanostructure. Furthermore, the EIT and Fano resonances experience a significant red shift by increasing the refractive index of the background medium due to which high sensitivity of around 574 nmRIU−1, figure of merit of 32, and contrast ratio of 41% are realized. Moreover, the effective group index of the proposed metasurface is retrieved and is observed to be very high around the steep asymmetric Fano line shape and within the EIT window, signifying its potential use in slow light applications.
Highlights
Plasmonic nanoparticles exhibiting electromagnetic-induced transparency (EIT) and Fano resonances have received more consideration over the past few years due to their potential applications in high performance sensors [1], switching [2], and slow light devices [3]
We report numerically electromagnetic-induced transparency (EIT) and Fano resonances in simple plasmonic metasurfaces consist of gold nanobars arranged in Pi, H and four shaped fashion
The phenomena of EIT and Fano resonance are similar to one another, which emerges due to the interference of the wide continuum mode and narrow discrete mode that modifies the properties of the medium by creating a narrow transparency window, where a very strong dispersion exist, which gives rise to slow light [4, 5]
Summary
Plasmonic nanoparticles exhibiting electromagnetic-induced transparency (EIT) and Fano resonances have received more consideration over the past few years due to their potential applications in high performance sensors [1], switching [2], and slow light devices [3]. Zhang et al, was the first who realized the EIT effect theoretically in the metamaterials which consists of plasmonic resonators coupled in the nanoscale where maximum value of group index of 41 is achieved [7]. Due to the lateral displacement of the structure the coupling of bright and dark modes takes place which results in the achievement of EIT effect. Sarkar et al, have proposed an asymmetric double C resonators (DCRs) structure and obtained a multiband EIT effect due to the strong field coupling between the bright and dark modes of the cut-wires of the structure. Li et al, have proposed a new type U-shaped coupled resonant structure, which provides strong EIT resonances that finds applications in tunable slow light devices [13]. The COMSOL Multiphysics software which is based on three-dimensional finite element technique is used to carry out the entire simulations
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