Optimal Design And Simulation Of Silicon-on-Insulator Nanowire Waveguides For Four-Wave Mixing-Based Broadband Wavelength Conversion

With the development of optical communication technology, silicon nanowire waveguides base on the SOI (silicon-on-insulator) structure have been widely used in the fields of nonlinear optics due to their relative low-cost fabrication process, large third-order nonlinearity and tight confinement of optical waves. The theory of four-wave mixing-based wavelength conversion in a SOI waveguide is investigated and the waveguides used to realize the wavelength conversion are optimized.Firstly, the development of silicon photonics for optical communication is introduced, and the research progress of four-wave mixing-based wavelength conversion in the silicon nanowire waveguides is summarized.The basic theory of optical waveguides is then introduced. The analytical and approximate methods to analyze the modal field of optical waveguides are briefly described, and the numerical methods such as the finite difference method and the beam propagation method are discussed.The theory of four-wave mixing-based broadband wavelength conversion in a SOI nanowire waveguide is investigated, and the influence of loss and absorption in the waveguide on the phase-matching condition is analyzed. The dispersion tailoring by the adjustment of the cross-section size of the waveguide core is numerically simulated. The conversion band is enhanced and the maximum conversion efficiency is achieved at the end of the waveguide by optimizing the cross-section size, the waveguide length and the input power of the pump light.A new structure of multi-layered silicon nanowire waveguide is presented, where two overlayers with lower and higher refractive indices are sequentially added underneath and on top of the silicon core. The impact of the core width and the thicknesses of core and two overlayers on the zero-dispersion wavelength and the dispersion slope are analyzed, respectively. The optimal design of the multi-layered nanowire waveguides for the broadband conversion is proposed based on the numerical simulation.The conversion efficiency is tightly determined by the state of polarization (SOP) of the input signal with respect to the pump. Since the SOP of the signal in a real transmission system may fluctuate with time and distance, it is necessary to realize polarization insensitive wavelength conversion schemes. A proposal for polarization-independent wavelength conversion is presented based on the four-wave mixing in a SOI nanowire waveguide by using an angled-polarization pump. The basic theory of the polarization-independent wavelength conversion is analyzed and the polarization angle of pump is optimized. The influence of the dispersion change of TE and TM modes induced by the adjustment of the core cross-section size on the wavelength conversion band is investigated.