Nonlinear couplers with tapered plasmonic waveguides

José R Salgueiro,Yuri S Kivshar

doi:10.1364/oe.20.009403

Abstract

We suggest and demonstrate numerically that, by employing tapered waveguides in the geometry of a directional coupler, we can enhance dramatically the performance for optical switching of nonlinear plasmonic couplers operating at the nanoscale, overcoming the detrimental losses but preserving the subwavelength confinement. We demonstrate that, by an appropriate choice of the taper angle of the coupled metal-dielectric slot waveguides, we can compensate for the amplitude decrease and enhance the sharpness of the response for the switching operation.

Highlights

Recent advances in the study of light propagation in nanophotonic structures suggest many potential applications of subwavelength photonics for light manipulation at the nanoscale, with perspectives for creating functional optical devices [1,2]
We suggest and demonstrate numerically that, by employing tapered waveguides in the geometry of a directional coupler, we can enhance dramatically the performance for optical switching of nonlinear plasmonic couplers operating at the nanoscale, overcoming the detrimental losses but preserving the subwavelength confinement
Nonlinear plasmonic waveguides were studied for a number of years, and it was recently shown that nonlinear slot waveguides created by a nonlinear dielectric slab sandwiched between two metals may support subwavelength nonlinear guided modes of different symmetries [15], including a novel type of asymmetric modes which is important for nonlinear switching, which is the application we are considering for the directional coupler in this paper

Summary

Introduction

Recent advances in the study of light propagation in nanophotonic structures suggest many potential applications of subwavelength photonics for light manipulation at the nanoscale, with perspectives for creating functional optical devices [1,2]. A directional coupler is composed of two coupled waveguides, and for plasmonic waves it was studied theoretically and demonstrated experimentally for different geometries [8,9,10] Such couplers were suggested for converting the modes of a dielectric waveguide into plasmonic modes propagating along a thin metal stripe [11]. [12,13,14]), and it was recently shown that nonlinear slot waveguides created by a nonlinear dielectric slab sandwiched between two metals may support subwavelength nonlinear guided modes of different symmetries [15], including a novel type of asymmetric modes which is important for nonlinear switching, which is the application we are considering for the directional coupler in this paper. One would desire a fast change but it was shown that power losses in the metals completely spoil the sharpness of the change [16]

Model and approach

Results and discussions

Conclusions