Mode Coupling in a Tapered Slow Light Waveguide

TL;DR

This paper investigates mode coupling phenomena in tapered slow light waveguides, revealing how forward and backward modes interact near critical thicknesses, which impacts the waveguide's slow light properties.

Contribution

It demonstrates the significance of mode coupling in tapered slow light waveguides near critical thicknesses, providing physical insights and implications.

Findings

Mode coupling becomes significant near critical thickness.

Forward and backward modes have well-matched wavevectors.

Coupling affects the slow light behavior.

Abstract

Metamaterials with simultaneous negative permittivity and negative permeability (also called left-handed materials) open new avenues to achieving unprecedented physical properties and functionality unattainable with naturally occurring materials. It has been predicted that a metamaterial slab waveguide can slow down light significantly (even to zero velocity) as the thickness of the core layer approaches a critical thickness. Here we show that coupling between the forward and backward modes becomes significant near the critical thickness due to the good matching of the wavevectors and modal profiles of the two modes. Physical explanation and impact of this coupling are given.