A bandgap phenomenon in non-periodic plasmonic waveguides

TL;DR

This paper introduces a dispersion bandgap in layered plasmonic waveguides, explaining its origin, broad spectral properties, and potential for controlling surface plasmon coupling with free-space waves.

Contribution

It reveals a novel plasmonic bandgap phenomenon in non-periodic waveguides, with detailed analysis and methods for tuning its spectral properties.

Findings

Confirmed the existence of a broad-spectrum plasmonic bandgap.

Linked the bandgap to near-zero effective permittivity.

Demonstrated control of surface plasmon coupling using waveguide modifications.

Abstract

The phenomenon of a dispersion bandgap opening between low-loss spectral windows of odd and even plasmonic modes in a layered insulator-metal-insulator plasmonic waveguide is introduced. Beginning with a three layer plasmonic dispersion relation, we explain and numerically confirm the existence of the plasmonic bandgap, and investigate its properties at a very broad spectrum range from ultraviolet to far infrared. The nature of the observed bandgap opening is explained in terms of the near-zero value of an effective permittivity for plasmonic modes in the waveguide. The adjustment of the plasmonic bandgap spectrum is demonstrated with the structural modification of the plasmonic waveguide. As an application example, we illustrate a new concept of coupling control between surface plasmons and free-space excitation waves, by employing a tapered non-adiabatic insulator-metal-insulator waveguide.