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UBC Theses and Dissertations

Silicon-on-insulator, free-spectral-range-free devices for wavelength-division multiplexing applications Mistry, Ajay


Silicon-on-insulator (SOI) microring resonator (MRR)-based modulators and filters have been researched extensively for use in wavelength-division multiplexing (WDM) systems due to their attractive spectral characteristics and small device footprints. However, an inherent drawback of using MRRs in WDM systems is their free-spectral-ranges (FSR). The FSR limits the aggregate data rate of the system, as it limits the number of channels that can be selectively modulated in a WDM transmitter, or simultaneously de-multiplexed in a WDM receiver. The goal of this thesis is to present and demonstrate SOI, MRR-based modulators and filters with FSR-free responses. We first experimentally demonstrate an SOI, FSR-free, MRR-based filter with a reconfigurable bandwidth. The device uses a grating-assisted coupler integrated into the MRR cavity to achieve an FSR-free response. Here, we demonstrate a nonadjacent channel isolation, for 400-GHz WDM, greater than 26.7 dB. A thermally tunable coupling scheme is utilized to compensate for fabrication variations and to demonstrate the reconfigurable filter bandwidth. We then demonstrate how lithography effects affect the performance of SOI devices, which include grating-based components. Using lithography models developed for deep ultraviolet lithography processes, we analyze the effects of lithography on the performance of an MRR with an integrated, grating-assisted coupler. We show that, if the effects of lithography are not taken in account during device design flow, large discrepancies result between the predicted “as fabricated” and “as-designed” device performance. We also demonstrate how to use the lithography models to compensate for lithographic-effects in future device designs. Lastly, we experimentally demonstrate an FSR-free, MRR-based, coupling modulator. We demonstrate open eye diagrams at 2.5 Gbps and discuss how the effects of DUV lithography limited the electro-optic bandwidth of the fabricated modulator to 2.6 GHz. We also discuss the effects of lithography on the modulation crosstalk of the device and how to significantly improve the electro-optic bandwidth and how to minimize crosstalk in future implementations of the device.

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