UBC Theses and Dissertations
Silicon-on-insulator microring resonator based filters with bent couplers Eid, Nourhan
In this thesis, we present and study the use of bent couplers in silicon-on-insulator (SOI) microring resonator (MRR) based filters. MRR based filters are attractive candidates in wavelength division-multiplexing (WDM) transceivers because of their compactness and low power consumptions. However, they suffer from drawbacks that include a limited free spectral range (FSR) which limit the number of channels that can be simultaneously multiplexed and/or demultiplexed. Our work investigates SOI single-ring MRR filters with bent couplers that have extended FSRs, enhanced filter performance (such as bandwidth, out-of-band rejection ratio, side-mode suppression, extinction ratio, and insertion loss) while maintaining compact footprints. Our aim is to make these filters attractive candidates to the current state-of-the-art WDM transceivers. We first demonstrated a 2.75 μm radius MRR filter that employs bent directional couplers in its coupling regions. This MRR filter was fabricated using a 248 nm photolithography process. Our filter has a 33.4 nm FSR and a 3-dB bandwidth of 25 GHz. Also, our MRR achieved an out-of-band-rejection ratio of 42 dB, an extinction ratio of 19 dB, and a drop-port insertion loss that is less than 1 dB. Lastly, our MRR filter has a tuning efficiency of 12 mW/FSR. Then, we theoretically and experimentally demonstrated an MRR filter with bent contra-directional couplers that exhibits an FSR-free response, at both the drop and through ports, while achieving a compact footprint. Also, using bent contra-directional couplers in the coupling regions of MRRs allows us to achieve larger side-mode suppressions than MRRs with straight CDCs. The fabricated MRR filter has a minimum suppression ratio of more than 15 dB, a 3dB-bandwidth of ~23 GHz, a through-port extinction ratio of ~18 dB, and a drop-port insertion loss of ~1 dB. High-speed data transmission through the MRR filter is demonstrated at data rates of 12.5 Gbps, 20 Gbps, and 28 Gbps.
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