Magnetically-tunable cutoff in asymmetric thin metal film plasmonic waveguide

TL;DR

This paper presents a theoretical study of how magnetic fields can control the cutoff states of surface plasmon polaritons in asymmetric thin metal films, enabling switchable radiation direction.

Contribution

It introduces an analytical model predicting magnetic-field-induced degeneracy in cutoff states of plasmonic waveguides, a novel mechanism for tunable plasmonic devices.

Findings

Magnetic bias can switch radiation direction in plasmonic waveguides.

Degenerate cutoff states are achievable with specific magnetic field biases.

The required magnetization bias scales with film thickness and wavelength.

Abstract

We theoretically investigated the magnetically-tunable cutoff of long-range surface plasmon polariton along thin metal film surrounded by a magneto-optic material on one side and by a nonmagnetic dielectric on the other side. The analytically derived cutoff condition predicts that a magnetic field bias can induce a novel degenerate cutoff-state near which the beyond-cutoff radiation in one side can be switched to that in the other side by a minor variation of the magnetic field from the bias. The magnetization bias needed for the degeneracy is in proportion to the metal film thickness and in inverse proportion to the wavelength.