Nonlinear anti-directional couplers with gain and loss

TL;DR

This paper introduces a nonlinear coupled waveguide system with gain and loss, demonstrating novel multistability states and efficient light control mechanisms with low threshold intensities and high amplification ratios.

Contribution

It proposes a new nonlinear anti-directional coupler system based on $\

Findings

Multiple bi- and multi-stability states identified.

Low-threshold intensity transitions between states.

High amplification ratios enabling efficient light control.

Abstract

Following the concept of $\mathcal{PT}$-symmetric couplers, we propose a linearly coupled system of nonlinear waveguides, made of positive- and negative-index materials, which carry, respectively, gain and loss. We report novel bi- and multi-stability states pertaining to transmitted and reflective intensities, which are controlled by the ratio of the gain and loss coefficients, and phase mismatch between the waveguides. These states offer transmission regimes with extremely low threshold intensities for transitions between coexisting states, and very large amplification ratio between the input and output intensities leading to an efficient way of controlling light with light.