Resonant Transmission Through a Single Subwavelength Slit for Varied Metallic Permittivities and Its Modal Orthogonality

Jong-Eon Park,Young-Ki Cho,Hosung Choo

doi:10.3390/app10020660

Jong-Eon Park, Young-Ki Cho + Show 1 more

Open Access

https://doi.org/10.3390/app10020660

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Abstract

This article investigates resonant transmission phenomena through a single metallic subwavelength slit when the permittivity of a real metal varies. The single metallic slit is utilized as a metal–insulator–metal waveguide, and a mode-matching technique is employed to obtain the transmitted power. The periodic resonant transmission phenomena (in terms of the metallic plate thickness) are solved, and the resonances can be understood by their guide wavelengths. Even when the permittivity of the real metal includes imaginary parts (i.e., metal with loss), the resonant transmittances are obtained. However, the peaks of the transmittances decrease, as the plate thickness increases. The orthogonal relationship of an incomplete orthogonal set is maintained despite metallic loss (given a relatively small amount of loss), due to the complex permittivity of the real metal.

Highlights

Electromagnetic resonant transmission through one- or two-dimensional slits has been discussed for several decades, and research on extraordinary optical transmission [1,2,3,4] has led to significant physical and practical achievements
The mode-matching technique (MMT) provides physical meanings by obtaining the guide wavelengths of an MIM waveguide, making it easy to understand the resonant transmittance as a function of the metallic plate thickness
When the metal of an MIM waveguide is a perfect electric conductors (PECs), field profiles of entire modes can be expressed and the sinusoidal modal variations are found in the slit of the waveguide, while field profiles cannot be expressed in the PEC region

Summary

Introduction

Electromagnetic resonant transmission through one- or two-dimensional slits has been discussed for several decades, and research on extraordinary optical transmission [1,2,3,4] has led to significant physical and practical achievements. It remains important to investigate resonant transmission phenomena through real metallic slits by considering actual permittivities of metals, when the frequency goes beyond the microwave range. Thanks to this fundamental research, resonant transmission phenomena have been investigated at wide THz frequencies by taking into account actual permittivities for various real metals [10,11] and discussing transmittances through periodic metallic slits [12] These studies found that transmittance phenomena through metallic slits. The MMT provides physical meanings by obtaining the guide wavelengths of an MIM waveguide, making it easy to understand the resonant transmittance as a function of the metallic plate thickness. We observe changes in guide wavelengths and resonant transmittances, as the imaginary part of the permittivity of the metal decreases, which cannot be obtained by other numerical techniques, such as the FDTD method or finite element method. Transmission weregsystematically solved as a function of resonantand transmission phenomena systematically metallic permittivity, their periodicity can bewere understood. solved as a function of metallic permittivity, and their periodicity can be understood

Transmittance

Orthogonality and Discussions

Orthogonal relationships among the first gap width

Conclusions