Electromagnetically induced transparency of a plasmonic metamaterial light absorber based on multilayered metallic nanoparticle sheets.

Koichi Okamoto,Ryo Degawa,Daisuke Tanaka,Xinheng Li,Sou Ryuzaki,Kaoru Tamada,Pangpang Wang

doi:10.1038/srep36165

Abstract

In this study, we observed the peak splitting of absorption spectra for two-dimensional sheets of silver nanoparticles due to the electromagnetically induced transparency (EIT) effect. This unique optical phenomenon was observed for the multilayered nanosheets up to 20 layers on a metal substrate, while this phenomenon was not observed on a transparent substrate. The wavelength and intensities of the split peaks depend on the number of layers, and the experimental results were well reproduced by the calculation of the Transfer-Matrix method by employing the effective medium approximation. The Ag nanosheets used in this study can act as a plasmonic metamaterial light absorber, which has a such large oscillator strength. This phenomenon is a fundamental optical property of a thin film on a metal substrate but has never been observed because native materials do not have a large oscillator strength. This new type of EIT effect using a plasmonic metamaterial light absorber presents the potential for the development of future optic and photonic technologies.

Highlights

With reduced-symmetry cavity structures provides an asymmetric dip of the Fano resonance in the absorption spectrum
We found that the resonance band of the multilayered Ag nanoparticle sheet on metal substrates could be tuned by adjusting the number of layers[12]
To evaluate the required optical properties to induce this phenomenon based on the EIT effect, we calculated the absorption spectra of the same Lorentz oscillator model with various extinction coefficients (k)

Summary

Introduction

With reduced-symmetry cavity structures provides an asymmetric dip of the Fano resonance in the absorption spectrum. The Fano dip in the absorption spectrum was observed even for the symmetric heptamer structure of Au nanoshells. To achieve these interference effects in a strong coupling regime, both a narrow bandwidth of the resonance spectrum and a high value of the absorbance are required. We observed unusual absorption spectra that have a narrow bandwidth and high intensity by fabricating multilayered Ag nanoparticle sheet structures[11,12]. We found that the resonance band of the multilayered Ag nanoparticle sheet on metal substrates could be tuned by adjusting the number of layers[12]. We had not noticed the peak splitting due to the EIT effect for multilayered metallic nanoparticle sheets until we have tried the layer deposition more than 5 layers

Methods

Results

Conclusion