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UBC Theses and Dissertations

Reconfigurable silicon photonic integrated circuits Shoman, Hossam


Integrating photonics with state-of-the-art nanoelectronics in Silicon (Si) is key to enabling new computing paradigms and sensing applications, as it leverages the well-established complementary metal-oxide-semiconductor (CMOS) foundries used to manufacture the electronics chips at a large-scale with low-cost. Towards this goal, great efforts have been made to integrate all the fundamental photonic building blocks on Si. However, due to a number of challenges, there has been no demonstration of a complete fully-integrated silicon photonic (SiP) chip. This dissertation addresses some of the challenges that hold back the deployment of complete fully-integrated Si chips. Due to Si’s temperature dependency, the performance of ring-based filters, switches, and modulators degrade when the surrounding temperature fluctuates. Second, fabrication imperfections lead to a discrepancy between the designed and measured ring-based filters’, switches’, and modulators’ spectral responses. Third, because of Si’s reciprocal lattice, Si cannot be used to realize optical isolators, which are required to integrate lasers on Si as they block back-reflections from flowing back to the laser and destabilizing its operation. This dissertation addresses the aforementioned challenges as follows. By slightly doping the Si waveguides, defect states are introduced which enable sensing and manipulating light in Si waveguides while absorbing minimal optical power. These doped waveguides are introduced into ring-based filters and switches to correct for fabrication errors and demonstrate the tuning of the largest yet most compact ring-based 16×16 optical switch matrix and 14-ring coupled-resonator optical waveguide (CROW) filter. Second, a new design of a microring modulator (MRM) is demonstrated that allows correcting the spectral features (wavelength, bandwidth (BW) and/or extinction ratio (ER)) of fabricated MRMs and maintain the MRM’s free-spectral range (FSR). Third, a new method for measuring propagation losses in optical waveguides is demonstrated. Finally, a stable quantum well (QW) distributed feedback (DFB) laser without an isolator is demonstrated for the first time. Instead of depositing Si-incompatible magneto-optic (MO) materials, a reflection-cancellation circuit (RCC) is proposed and used to demonstrate laser stability against varying levels of back-reflections in real-time. The same circuit was used to further reduce the linewidth of the DFB laser down to 3 kHz.

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