Ultra-low loss hybrid ITO/Si thermo-optic phase shifter with optimized power consumption.

Jorge Parra,Pablo Sanchis,Juan Hurtado,Amadeu Griol

doi:10.1364/oe.386959

Abstract

Typically, materials with large optical losses such as metals are used as microheaters for silicon based thermo-optic phase shifters. Consequently, the heater must be placed far from the waveguide, which could come at the expense of the phase shifter performance. Reducing the gap between the waveguide and the heater allows reducing the power consumption or increasing the switching speed. In this work, we propose an ultra-low loss microheater for thermo-optic tuning by using a CMOS-compatible transparent conducting oxide such as indium tin oxide (ITO) with the aim of drastically reducing the gap. Using finite element method simulations, ITO and Ti based heaters are compared for different cladding configurations and TE and TM polarizations. Furthermore, the proposed ITO based microheaters have also been fabricated using the optimum gap and cladding configuration. Experimental results show power consumption to achieve a π phase shift of 10 mW and switching time of a few microseconds for a 50 µm long ITO heater. The obtained results demonstrate the potential of using ITO as an ultra-low loss microheater for high performance silicon thermo-optic tuning and open an alternative way for enabling the large-scale integration of phase shifters required in emerging integrated photonic applications.

Highlights

The ability to control the phase of the light is one of the most important features in silicon photonic integrated circuits (PICs)
In this work we propose, design and fabricate transparent indium tin oxide (ITO) heaters for high performance TO tuning of silicon photonic structures
Asymmetric Mach-Zehnder interferometers (MZIs) were used to extract the phase shift induced by the hybrid ITO/Si waveguide

Summary

Introduction

The ability to control the phase of the light is one of the most important features in silicon photonic integrated circuits (PICs). The most common way to induce a phase shift is by exploiting the silicon thermo-optic (TO) coefficient (∼ 1.8 × 10−4 K−1) [1]. Thermo-optic tuning can be attained by heating the waveguide with a metallic microheater. This mechanism can be used with negligible optical losses by placing the lossy microheater at a certain distance from the waveguide. The heater is usually located far from the waveguide, which could lead to a low performance in terms of high power consumption or low switching speeds. The influence of the upper-cladding cladding material was investigated by Atabaki et al [14] showing a trade-off between the power consumption and the switching speed. The most straightforward way to improve both parameters is to reduce the gap between the waveguide and the microheater

Methods

Results

Conclusion