Phot1x Project Report

Abstract

This report describes the design, fabrication, and data analysis for a Mach-Zehdner Interferometer (MZI) implemented in a silicon on oxide wafer. The device was fabricated using electron beam lithography, and we explored variations in the path length difference of the two arms of the interferometer as well as varying the waveguide geometry. The designs were measured using an swept wavelength source, whereby the transmittance was shown to sinusoidally vary with respect to the input wavelength as expected through theory. We account as well as possible for the losses in coupling light onto and from the chip using grating couplers, and also for propegation losses through the strip waveguides. Finally, the match between the measurements and theory / simulation is evaluated, and we attempt to account for deviations in this match.

Introduction

For this course I designed a collection of Mach Zehnder Interferometers (MZI) to explore the process of designing, fabricating, and testing silicon integrated photonics devices. I was motivated to take this course because I hope to use the knowledge gained here for my work in industry. The MZI device illustrates many important aspects of silicon integrated photonics, making them a good candidate for study.

The devices for this course were fabricated using a 100 keV electron beam lithography process at either of the University of Washington Nanofabrication Facility or Applied Nanotools Inc., Canada. The substrate is a Silicon on insulator (SOI) wafer with 220 nm silicon thickness. The etch parameters are single full etch at an 82º sidewall angle, yielding a minimum feature size of 60 nm. The fabrication area is 605 x 410 μm.

The devices were tested using an automated optical probe station at the University of British Columbia, Canada.

Theory

To analyze our MZI devices we first have to model the individual components of the device. These include the strip waveguide, the bent waveguide, the y-branch splitter/combiner, and the surface grating coupler. Since we are evaluating our components' behaviour