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UBC Theses and Dissertations

Spectral tailoring of silicon integrated Bragg gratings Cheng, Rui


Integrated Bragg gratings (IBGs) developed on the silicon-on-insulator (SOI) platform, owning to their high spectral flexibility, have become key components in photonic integrated circuits. Despite the rapid development of silicon IBG devices, there still lacks a comprehensive design methodology to achieve arbitrary, sophisticated, complex (amplitude and phase) spectral responses on IBGs. In addition, various problems also exist in practical designs and implementations of IBGs. The objectives of this thesis are to address these issues and, thus, to facilitate and improve the spectral tailoring of silicon IBG devices. A comprehensive and sophisticated design methodology of IBGs to achieve arbitrary spectral responses has been developed, and each individual step of the design and implementation process has been elaborated in detail. Furthermore, to address the IBG modeling and apodization issues existing in the design process, we have proposed (1) a highly efficient and reliable IBG modeling method by directly synthesizing the physical structure of the gratings; and (2) a high-performance apodization technique for IBGs based on periodic phase modulation. Multichannel photonic Hilbert transformers (MPHTs) based on complex synthesized IBGs have been designed, fabricated, and experimentally characterized. The realizations of these MPHTs are based on using the comprehensive IBG design methodology developed in this thesis. MPHTs with a total wavelength channel number of up to 9 and a single channel bandwidth of up to 625 GHz have been successfully achieved. The impacts of apodization phase errors (APE) on the spectral responses of apodized silicon IBGs have been characterized. The characterization results show that APE can largely distort the spectral responses of apodized IBGs from the designed ones. Then, to address this issue, a methodology to compensate and thus to eliminate APE of an apodized IBG to correct the distorted response has been developed and experimentally validated. A novel apodization profile [k(z)] amplification technique for IBGs has been proposed. Using this k(z) amplification technique for designing IBGs can bring about significant improvements in the apodization performence for the given fabrication constraints. Therefore, this technique can largely overcome the current apodization limitations of silicon IBGs due to fabrication constraints, thus facilitating their spectral tailoring applications.

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