Enabling practical deployment of silicon ring resonator-based systems

Microring resonators (MRRs) on silicon photonic platforms allow for low-power, dense, and large-scale manipulation of optical signals on-chip. MRR-based modulators, switches, and filters have become key building blocks in integrated optical circuits for applications in future data communications, high-performance computing, and sensing. This thesis presents solutions for overcoming several challenges towards practical deployment of MRR systems. The performance of MRR is highly susceptible to temperature and fabrication variations, which cause significant shifts in the MRR's spectral responses. In-resonator photoconductive heaters (IRPHs), formed by doping MRRs’ waveguides show high responsivities. As IRPHs do not require additional material depositions, photodetectors, or power taps and use the same contact pads for both sense and tune operations, they can be used to automatically tune and temperature stabilize MRRs without compromising the cost or area of the devices. Automatic tuning and stabilization of one- and two-ring filters are demonstrated. Multi-ring filters offer attractive spectral features such as wide pass-bands, steep roll-offs, and large extinction ratios. Using IRPHS, automatic tuning of a four-ring Vernier ring filter across a record 37.6 nm wavelength and wavelength locking to account for a record 65 degrees temperature variation is demonstrated. A tuning algorithm in which the number of iterations scales linearly with the number of coupled rings in the system is presented. As this method typically does not rely on the output spectral shape of the filter, it is applicable to a wider range of coupled resonator systems. Application of this tuning method is then demonstrated for various multi-ring filters by both simulation and experiment. Crosstalk can be a major source of signal degradation in large-scale MRR systems. Interchannel and intrachannel crosstalk of one- and two-ring MRR filters are experimentally investigated. The power penalties due to interchannel crosstalk are presented as functions of channel spacing and adjacent channel isolation. Intrachannel crosstalk of one-ring, cascaded, and series-coupled add-drop filters are compared and spectral conditions that will ensure low intrachannel crosstalk is presented. MRR filters with extremely small radii of 2.75 um, large free spectral ranges of 34.3 nm, and high thermal tuning efficiencies of 2.78 nm/mW are presented.Applied Science, Faculty ofElectrical and Computer Engineering, Department ofGraduat

Analytical Modelling of Carrier Depletion Silicon-on-insulator Optical Modulation Diodes

We derive an analytical model for the depletion capacitance of silicon-on-insulator (SOI) optical modulation diodes. This model accurately describes the parasitic fringe capacitances due to a lateral pn junction and can be extended to other geometries, such as vertical and interleaved junctions. Analytical results show excellent agreement with numerical simulations. The model is used to identify the waveguide slab to rib height ratio as a key geometric scaling parameter for the modulation e ciency and bandwidth for lateral diodes. We characterise the fringe capacitance as a parasitic e ffect that leads to a decrease of about 20% in modulation bandwidth of typical SOI diodes without a corresponding increase in modulation effi ciency. From the scaling relations, the most e ffective way to increase the modulation bandwidth is to reduce the series resistance of the diode. In the light of our analysis, we propose high-speed and low power microdisk structures for future SOI modulators.MAS