Modal properties of a strip-loaded horizontal slot waveguide

Ségolène Pélisset,Seppo Honkanen,Janne Laukkanen,Matthieu Roussey,Markku Kuittinen

doi:10.1186/s41476-017-0065-5

Ségolène Pélisset, Seppo Honkanen + Show 3 more

Open Access

https://doi.org/10.1186/s41476-017-0065-5

Copy DOI

Abstract

BackgroundChannel waveguides have been developed for years to comply with the need for smaller footprint and better integration in photonics circuits. However, they are still suffering from fabrication complexity and optical losses. These two limitations can be addressed by combining two types of channel waveguides, namely strip-loaded and slot waveguide.MethodsWe present a systematic study of the geometrical parameters of a strip-loaded horizontal slot waveguide and their influence on the characteristics of the device. Simulations and experiments are carried out to understand the behavior of the electromagnetic field inside such a waveguide. In particular, the influence of the high and low refractive index layers and the loading-strip on the key characteristics of the structure, i.e., the confinement factor and the effective index, are investigated theoretically and compared with experimental values.ResultsThe main properties of this waveguide platform are a low lateral index contrast, a high vertical field confinement, and low-propagation losses (1.4 dB/cm).ConclusionsOur results show that this platform is highly versatile, easy to fabricate and low-losses. We also show that the geometry of the mode can be tuned to suit the application.

Highlights

Channel waveguides have been developed for years to comply with the need for smaller footprint and better integration in photonics circuits
One of the main drawbacks of this structure is that the field is confined at the boundaries between high and low index materials, which implies a high sensitivity to the surface quality, especially the sidewall roughness of the rails [7]
The field enhancement in this region is maximized in the case of transverse magnetic (TM) modes, for which the major field component is Ey, perpendicular to the interfaces. For this purpose we focus on three specific aspects of this platform: 1) The confinement factor should be maximized in the region with a minimum effective mode area; 2) The effective index difference between the slab mode of the horizontal slot waveguide without and with a loading material on top has to be maximized to allow small features; 3) The structure should be single-mode which is achieved by tuning the loading-strip width and thickness

Summary

Introduction

Channel waveguides have been developed for years to comply with the need for smaller footprint and better integration in photonics circuits. These two limitations can be addressed by combining two types of channel waveguides, namely strip-loaded and slot waveguide Since it was introduced in 2004 by Almeida et al [1], the slot waveguide has arisen a huge interest for photonic integrated circuits from telecommunication applications, to highly non-linear devices, and to sensing [2,3,4,5,6]. The potential of this structure lays in the high light confinement achievable in a tiny gap of low refractive index.

Objectives

Methods

Results