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Hammood, Mustafa

University of British Columbia

This dissertation investigates the theory, design, and implementation of Bragg and sub-wavelength-based devices in silicon photonics, focusing on their applicability to current and emerging data communication (datacom) applications. These technologies form the backbone of data center communication infrastructure, enabling advancements such as the internet and artificial intelligence. Such devices leverage periodic refractive index perturbations in waveguiding structures to control the propagating modes. Despite their potential, challenges such manufacturing non-idealities, limited performance for wideband filtering, and low channel crosstalk in wavelength-division multiplexing (WDM) applications have restricted their use. In this work, I model, design, and experimentally demonstrate various contra-directional coupler (contra-DC)-based devices and adiabatic wavelength filters, emphasizing process-aware design methodologies and predictive computational lithography models to achieve high performance. Contra-DCs are Bragg grating-based waveguide couplers in which two, asymmetric, periodically perturbed waveguides are coupled. These structures can be designed to couple energy between the possible modes in a device, creating wavelength-selective filters. I present a study of contra-DCs, discussing the background theory, and presenting a design process that makes use of an analytical model enabled by numerical simulation tools to accurately model the device. I discuss practical challenges of using such devices in high-volume deep-ultraviolet (DUV) lithography processes. I present and experimentally demonstrate methods to emulate the performance of silicon photonic devices fabricated using DUV lithography processes on a rapid-prototyping electron-beam (EBeam) lithography. Using such design models and process understanding, applications of contra-DCs and sub-wavelength devices are presented such as series-cascaded contra-DC configurations with an adjacent isolation of 53 dB and a low insertion loss of 0.83 dB. Ultra-broadband wavelength-selective filters using chirped contra-DCs are experimentally demonstrated, achieving 3 dB bandwidths of up to 88.1 nm. Spiral contra-DCs as well as sub-wavelength-assisted contra-DCs are additionally demonstrated, both devices can be used to further improve the performance of wideband filters. The design and experimental measurements of a low-pass/high-pass sub-wavelength adiabatic filters is presented. Such devices make use of sub-wavelength waveguide to reduce the device's footprint and excess losses. The experimental results show devices with excess losses of 0.9 dB and 0.4 dB at the short-wavelength pass port and long-wavelength pass port, respectively.

Text

2024-12-05

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/89785

Electrical and Computer Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/