Guided Optical Modes in Metal-Cladded Tunable Hyperbolic Metamaterial Slab Waveguides

Marcin Kieliszczyk,Anna Tyszka-Zawadzka,Paweł Szczepański,Bartosz Janaszek

doi:10.3390/cryst10030176

Abstract

We have theoretically investigated metal-cladded waveguides of tunable hyperbolic metamaterial (THMM) cores, employing graphene sheets as a tunable layer, in terms of guided waves propagation over near- to mid-infrared range, following the effective medium approximation. We have proven that these subwavelength guiding structures offer a number of effects usually not found in other types of waveguides, including controllable propagation gap and number of modes, inversion of power flow direction with respect to phase velocity, TM mode propagation, and absence of the fundamental mode, which occur as a result of controlled change of the guiding layer dispersion regime. This is the first time that the above-mentioned effects are obtained with a single, voltage-controlled waveguiding structure comprising graphene sheets and a dielectric, although the presented methodology allows us to incorporate other tunable materials beyond graphene equally well. We believe that such or similar structures, feasible by means of current planar deposition techniques, will ultimately find their practical applications in optical signal processing, controlled phase matching, controlled coupling, signal modulation, or the enhancement of nonlinear effects.

Highlights

Metamaterials are artificially composed media designed to produce an electromagnetic response that is not possible with constituent materials alone
When no biasing voltage is applied, again, the guiding layer medium exhibits positive elliptic dispersion. This time, transverse magnetic (TM) and transverse electric (TE) modes of a certain order reveal different cut-off widths, the behavior inherited after the effective anisotropy, see Figure 6a, which is evident from Equations (6)
We present a comprehensive analytical analysis of guiding conditions in Within this paper, we present a comprehensive analytical analysis of guiding conditions in metal-cladded tunable hyperbolic metamaterial (THMM) slab waveguides by example of a graphene-based multilayer nanostructure metal-cladded THMM slab waveguides by example of a graphene-based multilayer nanostructure employed as a guiding layer

Summary

Introduction

Metamaterials are artificially composed media designed to produce an electromagnetic response that is not possible with constituent materials alone. Novel media of this type exhibit negative refractive index, which results in a number of remarkable properties, including antiparallel group and phase velocities, or the occurrence of an inverse Doppler effect [1]. Most of the reported work concerned symmetrical slab waveguides with a DNG-metamaterial core layer cladded with a dielectric [6,7]. Studies devoted to such waveguiding structures have proven the existence of guided optical modes, which possess a number of unusual properties, such as the absence of the fundamental mode or sign-varying energy flux [6].

Results

Discussion

Conclusion