Reconfigurable photonic crystal waveguides created by selective liquid infiltration

A Casas Bedoya,B J Eggleton,E Li,E.C Mägi,C Monat,C Grillet,P Domachuk

doi:10.1364/oe.20.011046

Abstract

We experimentally demonstrate reconfigurable photonic crystal waveguides created directly by infiltrating high refractive index (n≈2.01) liquids into selected air holes of a two-dimensional hexagonal periodic lattice in silicon. The resulting effective index contrast is large enough that a single row of infiltrated holes enables light propagation at near-infrared wavelengths. We include a detailed comparison between modeling and experimental results of single line defect waveguides and show how our infiltration procedure is reversible and repeatable. We achieve infiltration accuracy down to the single air hole level and demonstrate control on the volume of liquid infused into the holes by simply changing the infiltration velocity. This method is promising for achieving a wide range of targeted optical functionalities on a "blank" photonic crystal membrane that can be reconfigured on demand.

Highlights

Photonic crystals (PhC) are an attractive platform for the development of compact optical devices
Reconfigurable photonic crystal waveguides created by selectrive liquid infiltration
We experimentally demonstrate reconfigurable photonic crystal waveguides created directly by infiltrating high refractive index (n≈2.01) liquids into selected air holes of a two-dimensional hexagonal periodic lattice in silicon

Summary

Introduction

Photonic crystals (PhC) are an attractive platform for the development of compact optical devices. Local liquid infiltration has been experimentally applied to the creation of photonic crystal cavities [20,21,28,29] Both the large effective index contrast and high level of accuracy required to create a PhC waveguide through infiltrating a single row of holes has far prevented such a demonstration. Apart from a fine control on the infiltration process, one of the main factors influencing the selective PhC infiltration, as expressed by Eli Yablonovitch [30] a decade ago, is the angle formed between the liquid and the material surface, i.e. the contact angle This physical condition imposes a restriction on the amount of liquid to be infiltrated, affecting directly the effective refractive index changes afforded by the infiltration and adding an extra challenge [26] to the creation of PhC waveguides based on single row infiltration. We explain the selective infiltration process, how the liquid behaves inside the PhC sub-micrometric holes and its consequences, and in sections four and five, we explain and discuss the experimental results and different possibilities that can be explored using the selective infiltration technique

Fabrication of the silicon photonic crystal membranes

Selective infiltration of photonic crystals

Selective infiltration technique for creating more complex optical functions

Findings

Conclusion