Spatial nonlinearity in anisotropic metamaterial plasmonic slot waveguides

TL;DR

This paper investigates nonlinear solutions in anisotropic metamaterial plasmonic slot waveguides, revealing enhanced nonlinear effects in elliptical cores and the absence of asymmetric modes in hyperbolic cases, with implications for stable waveguide design.

Contribution

It demonstrates how anisotropic metamaterials influence nonlinear mode bifurcation thresholds and stability, providing new insights into waveguide behavior with elliptical and hyperbolic cores.

Findings

Bifurcation threshold reduced to 50 MW/m in elliptical cores.

Asymmetric modes are absent in hyperbolic cases.

Effective nonlinearity can become negative in hyperbolic metamaterials.

Abstract

We study the main nonlinear solutions of plasmonic slot waveguides made from an anisotropic metamaterial core with a positive Kerr-type nonlinearity surrounded by two semi-infinite metal regions. First, we demonstrate that for a highly anisotropic diagonal elliptical core, the bifurcation threshold of the asymmetric mode is reduced from GW/m threshold for the isotropic case to 50 MW/m one indicating a strong enhancement of the spatial nonlinear effects, and that the slope of the dispersion curve of the asymmetric mode stays positive, at least near the bifurcation, suggesting a stable mode. Second, we show that for the hyperbolic case there is no physically meaningful asymmetric mode, and that the sign of the effective nonlinearity can become negative.