Silicon photonic subwavelength gratings for dense photonic integration and polarization control



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Silicon photonics is a promising optical chip platform, providing a low-cost solution with large-scale photonic integrated circuits. Advances in silicon photonics demand a high-density chip integration, but it is challenged by the optical crosstalk. In recent years, subwavelength gratings (SWGs) forming anisotropic metamaterials have been proposed to manipulate wave behaviors, shrinking the chip footprint and enhancing the device performance. In this thesis, I explore the fundamentals of SWG metamaterials and utilize those properties to enhance photonic device performance. First, exceptional coupling that completely suppresses the crosstalk between closely spaced waveguides is achieved. Anisotropic dielectric perturbation, introduced by SWG metamaterials, is the key to achieving such phenomena, drastically increasing the chip integration density. Second, SWGs are used for designing mode-evolution-based polarization beam splitter (PBS). Due to the reduced skin-depth via SWGs and adiabatic transition, ultra-broadband PBS is achieved with a high fabrication tolerance. Third, by engineering the coupling behaviors with SWGs, a broadband polarization splitter-rotator (PSR) via mode evolution is designed. The SWGs induce a large coupling strength that reduces the modal conversion length, while adiabatic transition allows a broad bandwidth and a large fabrication tolerance. Additionally, a heterogeneous photonic structure is designed to achieve extremely high group velocity dispersion (GVD). The analytical representation of the induced GVDs is presented, with their engineering capability in coupling wavelengths and dispersion peaks. To conclude, I discuss the potential research directions utilizing the SWG metamaterials and summarize my outlook for future silicon photonics.

Embargo status: Restricted until 09/2023. To request the author grant access, click on the PDF link to the left.



Silicon Photonics, Photonics Integrated Circuits, Polarization Control, Subwavelength Gratings