Optimal Design Of Silicon Waveguides For High-Efficiency Broadband And Polarization-Independent Wavelength Conversion

With the development of fabrication technology of silicon waveguide based on the SOI (silicon-on-insulator) structure, it becomes possible to integrate the electrical and optical devices on a single silicon chip. Besides devices based on its linear optical properties, sili-con can also be used to realize all-optical signal processing required in the next-generation optical communication system by using its nonlinear optical effects. This thesis is devoted to investigate four-wave mixing (FWM)-based all-optical wavelength conversion in SOI waveguides. By optimizing the waveguide structures and dimensions, high-efficiency or polarization-independent broadband wavelength conversion is achieved.High-efficiency broadband wavelength conversion is achieved by optimizing the waveg-uide dimension in a slot waveguide filled with silicon nanocrystal. The dependence of dispersion on the waveguide dimensions of the TE and TM modes is studied and a low-dispersion-discrepancy waveguide configuration is obtained for polarization-independent wavelength conversion.In this thesis, we first introduce the research background of nonlinear silicon photonics and silicon-based signal processing. And then, the principle of FWM-based wavelength conversion in a silicon waveguide is presented. The third order nonlinearities in silicon and the theoretical model of FWM process in silicon waveguides are summarized.A slot waveguide structure provides high field confinement in the low-index area. By filling high nonlinear silicon nanocrystal in the slot area and using its high optical intensity property, high efficiency broadband wavelength conversion is achieved. With the dispersion optimized, a 3-dB bandwidth of over 400 nm can be achieved in a 4 mm long waveguide with an efficiency of-2.38 dB.The dependence of dispersion on the waveguide dimensions of the TE and TM modes is also studied and a low-dispersion-discrepancy waveguide configuration is achieved for polarization-independent wavelength conversion. Based on an angled-pumped wavelength conversion scheme, al-dB polarization-independent bandwidth of 400 nm is achieved in a 0.8 cm long waveguide. It is also shown that an optimized waveguide can operate with low polarization sensitivity as the pump wavelength, pump angle and signal wavelength changes.