Athermal Laser Designs on Si and Heterogeneous III-V/Si3N4 Integration

This dissertation presents each component of and a path towards heterogeneously integrated GaAs type III-V lasers bonded to Si3N4 passive waveguides on silicon, targeting visible integrated photonics on silicon. A continuous-wave Fabry-P\'erot laser, tapered mode converters from III-V to Si3N4, and Si3N4 sidewall distributed Bragg reflector elements, all made with an integrable process flow, are demonstrated to prove this principle. The goal of this integration is to combine electrically pumped InGaAs multiple quantum well (MQW) active material with low-loss, spectrally wide-bandwidth waveguides to enable compact, novel photonic integrated circuits. An additional benefit with Si3N4 is its lower thermal drift relative to silicon. Additionally, demonstrations of TiO2 based guides with ~pm/K thermal drift are presented to explore the possibilities of athermalized waveguides on silicon. Both TiO2 core and clad waveguides are studied, and new materials information on amorphous sputtered TiO2 are reported. As integration with such waveguides could open opportunities for novel athermal lasers, some passively athermal designs and designs with integrated athermal wavelength references are presented which show the merit of an integrated approach.As much process development was required to bring all of the device demonstrations presented in this dissertation to fruition, key process developments are highlighted and explained in detail to assist in any similar future developments.Finally, the vision of heterogeneous integration as an enabler for ultra-broadband photonic integrated circuits beyond existing InP/Si photonic integrated circuits is presented as future work

Dynamics of free carrier absorption and refractive index dispersion in Si and Si/polySi microrings

We report pump-probe measurements of time resolved optical transmission spectra of Si and Si/poly-Si microrings after high free carrier densities have been generated by two-photon absorption of the pump pulse. From measurements, we can extract the recovery dynamics of free carrier absorption, refractive index dispersion, generated free carriers and finally the effective initial free carrier lifetimes. The method is validated by comparing modelling and simulations with measurements; the obtained results are in very good agreement with what predicted by the Shockley-Read-Hall recombination model for trap assisted recombination. We also propose a method for determining the empirical relations for free carrier absorption and refractive index dispersion in poly-Si waveguides

Static and Dynamic Nonlinear Effects in Silicon Micro-Rings: Impact of Trap Assisted Shockley Read Hall Carrier Recombination

We present a new model for the analysis of non-linear effects in silicon micro-ring resonators based on the Shockley Read Hall model for carrier recombination in the silicon core. We can reproduce both measured ring transmission spectra varying input power and measured ring oscillating regimes. We report also pump-probe experiments for extracting the recovery dynamics of the effective loss and refractive index change

CW Emission and Self-Pulsing in a III-V/SiN Hybrid Laser With Narrow Band Mirror

We report on how external cavity III-V/SiN hybrid lasers operate in regimes of ultra-damped relaxation oscillations or in CW unstable dynamical regimes (self-pulsing or approaching turbulence) as a consequence of mirror dispersion, non-zero linewidth enhancement factor, and four-wave mixing in the gain medium. The impact of the dispersive mirror bandwidth and different mirror effective lengths on the laser tolerance to external optical feedback is also discussed

Damping of relaxation oscillations,photon-photon resonance, and tolerance to external optical feedback of III-V/SiN hybrid lasers with dispersive narrow band mirror

We address the stability of a tunable hybrid laser based on a III-V Reflective Semiconductor Optical Amplifier (RSOA) edge-coupled with a Silicon Photonic (SiPh) dispersive mirror through a model of time-delayed algebraic differential equations that accounts for the narrow band mirror. Our results allow to (i) analyze the stability of single mode lasing, (ii) quantify the impact of the mirror bandwidth on the damping of the laser relaxation oscillations and the emergence of photon-photon resonance, and (iii) study the tolerance of the laser to the external optical feedback. Thanks to this analysis, we find a mirror design that gives ultra-high stability up to an external feedback level of −10 dB. The aim of the work is providing a tool for understanding and interpreting the dynamics of these lasers and design configurations for isolator-free operation

Design of hybrid lasers for silicon photonics: efficiency, optical feedback tolerance and laser dynamics

We present the design and the simulation of the dynamics of hybrid lasers based on a reflective SOA edgecoupled to a silicon photonics integrated reflector realized with waveguide rings. We design the laser for high efficiency and tolerance to spurious optical feedback and we compare the best designs in SiN and SOI platforms. By simulating the laser dynamics with a Time Domain Travelling Wave approach we show that the hybrid solitary laser (ie: without feedback) can operate in various regimes from CW to self-pulsing. These regimes are triggered by the linewidth enhancement factor of the SOA and can be controlled by a phase control section. The tolerance to the optical feedback is also further enhanced by the damping of the relaxation oscillations filtered by the narrowband reflector

Wavelength Conversion in Low Loss Si3N4 Waveguides

We show wavelength conversion in a compact Si3N4 waveguide. Combining low loss, long length, relatively large nonlinear coefficient, high-power handling and absence of two-photon absorption, this platform is promising for integrated nonlinear optics applications

Efficient and Optical Feedback Tolerant Hybrid Laser Design for Silicon Photonics Applications

We present a design of a tunable hybrid laser based on III-V Reflective Semiconductor Optical Amplifier (RSOA) and Silicon Photonics (SiPh) external mirror that represents a good trade off between high Wall-Plug Efficiency (WPE) and high tolerance to optical feedback caused by unwanted back reflections from the rest of the SiPh chip. The sensitivity to optical feedback of different configurations, an important issue in many SiPh applications, is evaluated through the calculation of the critical feedback level based on an effective Lang-Kobayashi model and the main results are validated through numerical simulations of laser dynamics. We conclude that hybrid lasers with long effective external cavities typically designed to reduce the laser linewidth can be also exploited to improve the tolerance to spurious optical feedback

Athermal Laser Designs on Si and Heterogeneous III-V/Si3N4 Integration

This dissertation presents each component of and a path towards heterogeneously integrated GaAs type III-V lasers bonded to Si3N4 passive waveguides on silicon, targeting visible integrated photonics on silicon. A continuous-wave Fabry-P\'erot laser, tapered mode converters from III-V to Si3N4, and Si3N4 sidewall distributed Bragg reflector elements, all made with an integrable process flow, are demonstrated to prove this principle. The goal of this integration is to combine electrically pumped InGaAs multiple quantum well (MQW) active material with low-loss, spectrally wide-bandwidth waveguides to enable compact, novel photonic integrated circuits. An additional benefit with Si3N4 is its lower thermal drift relative to silicon. Additionally, demonstrations of TiO2 based guides with ~pm/K thermal drift are presented to explore the possibilities of athermalized waveguides on silicon. Both TiO2 core and clad waveguides are studied, and new materials information on amorphous sputtered TiO2 are reported. As integration with such waveguides could open opportunities for novel athermal lasers, some passively athermal designs and designs with integrated athermal wavelength references are presented which show the merit of an integrated approach.As much process development was required to bring all of the device demonstrations presented in this dissertation to fruition, key process developments are highlighted and explained in detail to assist in any similar future developments.Finally, the vision of heterogeneous integration as an enabler for ultra-broadband photonic integrated circuits beyond existing InP/Si photonic integrated circuits is presented as future work

Measurements and modelling of free carrier lifetimes in Si and Si/poly-Si microrings

We report pump-probe experiments for measuring free carrier lifetime in Si and Si/poly-Si microrings and compare results with trap-assisted Shockley-Read-Hall recombination model