Momentum-space spectroscopy for advanced analysis of dielectric-loaded surface plasmon polariton coupled and bent waveguides

TL;DR

This paper introduces momentum-space spectroscopy combined with leakage microscopy to analyze dielectric-loaded plasmonic waveguides, revealing energy transfer dynamics, mode degeneracy lifting, and curvature effects with experimental and theoretical validation.

Contribution

It presents a novel application of momentum-space spectroscopy for detailed analysis of coupled and curved plasmonic waveguides, including experimental, numerical, and analytical insights.

Findings

Degeneracy lifting of effective indices in strongly coupled waveguides

Momentum-space imaging reveals curvature effects on waveguides

Experimental results align with theoretical models

Abstract

We perform advanced radiation leakage microscopy of routing dielectric-loaded plasmonic waveguiding structures. By direct plane imaging and momentum-space spectroscopy, we analyze the energy transfer between coupled waveguides as a function of gap distance and reveal the momentum distribution of curved geometries. Specifically, we observed a clear degeneracy lift of the effective indices for strongly interacting waveguides in agreement with coupled-mode theory. We use momentum-space representations to discuss the effect of curvature on dielectric-loaded waveguides. The experimental images are successfully reproduced by a numerical and an analytical model of the mode propagating in a curved plasmonic waveguide.