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<p>Ytterbium-doped optical fibers have extensive applications in high-power fiber lasers, optical amplifiers, and amplified spontaneous emission light sources. In this thesis two sub-projects associated with ytterbium doped fibers are discussed.</p> <p>Numerical simulations have been used to model high-repetition rate ultrafast ytterbium-doped fiber amplifier systems assuming continuous-wave input signals under variable situations, such as one-sided and two-sided pumping. Different system configurations are also developed, such as a single-stage amplification system, a two-stage amplification system and a separated amplification system, providing alternative choices for experiments and applications. The simulation results are compared with experimental data and the simulation results from some other software. The influence of nonlinear effects in the fiber is also very briefly discussed in this thesis.</p> <p>In a second research activity, the distribution of ytterbium atoms is being investigated in a range of double-clad ytterbium-doped fibers. Using aberration-corrected electron microscopy, ytterbium atoms are directly observed from the wedge-shaped specimen, which was prepared from ytterbium-doped optical fibers by tripod polishing combined with ion milling. Challenges related to sample preparation and the interpretations of images are discussed, but the approach shows great potential to investigate the doping behaviors down to atomic scale in the fibers. The work is expected to help reveal mechanisms affecting the performance for the doped fibers, such as photodarkening which is potentially associated with clustering effects.</p> / Master of Applied Science (MASc)

The ever-increasing bandwidth requirements to support telecommunications infrastructure necessitates large-scale fabrication of low-cost and scalable silicon photonic integrated circuits. Wavelength-division multiplexing (WDM) schemes are fundamentally limited in the number of channels supported in long-haul transmission by the erbium doped fiber amplifier (EDFA). To address this, researchers have turned focus toward the thulium doped fiber amplifier (TDFA), which provides 3× more bandwidth. This thesis describes the development of high-speed silicon-on-insulator (SOI) micro-ring resonator (MRR) modulators optimized for wavelengths in the TDFA band. Chapter 2 presents a theoretical performance comparison between MRR modulators designed for optimized use at EDFA and TDFA wavelengths. Chapter 3 presents an experimental study of optical loss mechanisms at extended wavelengths which suggests reduced waveguide scattering and enhanced divacancy defect absorption as well as larger bending and substrate leakage losses when compared with shorter wavelengths. An electronic variable optical attenuator is characterized in Chapter 4 to experimentally verify the predicted 1.7× TDFA-band free-carrier effect enhancement over EDFA-band wavelengths. The first steady-state operation of an MMR modulator near a central wavelength of 1.97 µm is also demonstrated under the enhanced free-carrier effect. Chapter 5 demonstrates the first high-speed reverse bias operation of an MRR modulator with a measured bandwidth of 12.5 GHz, and an on-chip optical link consisting of a modulator followed by a defectmediated detector with open eye-diagrams up to data rates of 12.5 Gbps. Chapter 6 introduces an electrically-driven post-fabrication defect-assisted resonance trimming technique via local annealing for use in MRR devices. Chapter 7 presents a Monte Carlo simulation of resonance alignment in multi-MRR systems subjected to spatially-correlated wafer variation created through the Virtual Wafer Model process to predict thermal power consumption and power reduction through resonance trimming. / Thesis / Doctor of Philosophy (PhD)

This research introduces tellurium oxide (TeO2) glass doped with optically active erbium ions (Er3+) as an active oxide cladding material for silicon-on-insulator (SOI) waveguides for realization of a silicon-based erbium-doped waveguide amplifier (EDWA) for integrated optics. Optical amplification of this nature is enabled by energy transitions, such as stimulated absorption and emission, within the shielded 4f shell of the rare-earth atomic structure caused by excitation from photons incident on the system. Er3+ ions are doped into the TeO2 film during deposition onto the SOI waveguides using a reactive magnetron co-sputtering system operated by McMaster’s Centre for Emerging Device Technologies (CEDT). Prior to fabrication, the waveguides are designed using photonic CAD software packages, for optimization of the modal behaviour in the device, and Matlab, for characterization of the optical gain performance through numerical analysis of the rate and propagation equations of the Er3+-based energy system. Post fabrication, the waveguide loss and gain of the coated devices are experimentally measured. The fabricated waveguide amplifier produces a peak signal enhancement of 3.84 dB at 1533 nm wavelength for a 1.7 cm-long waveguide device. High measured waveguide losses (> 10 dB/cm) produce a negative internal net gain per unit length. However, the demonstration and implementation of an active rare-earth doped cladding material on a silicon waveguide is successful, which is a major step in developing integrated optical amplifiers for conventional silicon photonics platforms. / Thesis / Master of Applied Science (MASc)