Research On Ultrafast Nonlinear Optical Effects And Applications Based On Silicon-on-insulator Waveguides

With the rapid developments of large-scale-integration, the degree of electroniccircuits almost approach the integration limits at present. Therefore, people hope toreplace electronic circuits by photonic circuits to obtain higher speed informationdelivering and processing. Silicon-on-insulator (SOI) waveguides have been regardedas an effective opt-electric integrated platform due to the large refractive indexdifference between the core and cladding of the waveguide and received much intenseattention. Both theoretical and experimental investigations are becoming boomingnowdays. Compared with conventional optical waveguides used, SOI waveguideshave many outstanding and special structure and material features. For example, thereexists large refractive index difference between the silicon core and silica cladding,which gives rise to the strong light confined in the SOI waveguides. Additionally, thenonlinear coefficient of the silicon waveguides is three orders of magnitude than thatof optical fibers. Thus the nonlinear optical effects in the SOI waveguides is intensethan other waveguides, including the Kerr effect and stimulated Raman scattering(SRS) effect. However, due to the features of the material, SOI waveguide has someadditional nonlinear effects that are weak or not existed in fibers, such as two-photonabsorption (TPA), free-carrier absorption (FCA), and free-carrier dispersion (FCD).We have summarized the recent progress of the silicon photonics both in theoryand experiments firstly. The different nonlinear optical effects in SOI waveguideshave been investigated with an emphasis on third-order nonlinearities of SOIwaveguides. The objective is to understand the nonlinear optical effects inside SOIwaveguides profound, the potential applications of SOI waveguides, and the intrinsicdifficulties this structure faces for broad and real applications process. Further, weexplore and design all kinds of applications models based on the nonlinear opticaleffects functions.The main contents of this research works and innovations of this dissertation aresummarized as follows:1. We first research the mode and dispersion properties of the SOI waveguides.In order to obtain the accurate and effective results, three main mathematicalmethods including FDFD, FEM and BPM for calculating the modes anddispersion of the SOI waveguides are adopted. Compare the computed results from the standpoint of accuracy and efficiency. Based on the modes anddispersions computing, the dispersion properties of the SOI waveguides andthe zero-dispersion wavelength (ZDWL) can be tailored easily throughadjusting the geometry parameters of the waveguide practically.2. The full theoretical model of ultra-fast pulse propagation in SOI waveguide isconstructed, which described the origination and process of the nonlinearoptics effects detailly. The theoretical model includes the effects of self-phasemodulation (SPM), cross-phase modulation (XPM), stimulated Ramanscattering (SRS), and four-wave mixing (FWM), two-photon absorption(TPA), the free-carrier absorption (FCA) and free-carrier dispersion (FCD)and so on.3. The femtosecond pulse propagation and the supercontinuum generation inSOI waveguide are investigated numerically. The numerical results show thatthe soliton fission and dispersive wave emission are important for thesupercontinuum generation. The initial chirp parameters of the input pulsesare significant for the bandwidth and flatness of the supercontinuumgeneration in SOI waveguide, and we can optimize the initial chirp parameterto controlling the supercontinuum generation process.4. The theoretical model of multi-pulse propagation in SOI waveguide underthe dependence condition is provided as the multi-wave nonlinear coupledequations, which describes the evolutions of pump, signal and idler waveswhen three waves satisfies the phase matching condition. We make use of theSOI waveguide to realize the high conversion efficiency optical parametricamplifier in mid-infrared range. The nonlinear loss of two-photon absorptionand free-carrier absorption are reduced to increase the conversion efficiencyof the OPA clearly. Moreover, we research the widely tunable femtosecondoptical parametric oscillator based on SOI waveguide. Due to the cooperationof the high-order dispersions and high nonlinearity, broadband phasematching can be achieved and wavelength can be tuned over266nm.5. Cascaded four-wave mixing in SOI waveguide has been researchednumerically. We consider the impacts of the pump power, waveguide lengthand dispersion slope on the generation of cascaded four-wave mixingproducts. The numerical results show that the cascaded four-wave mixingproducts can generate in short SOI waveguide over1000nm, which form the frequency-comb like feature in spectral domain.6. We research the Er-doped mode-locked fiber lasers and femtosecond opticalparametric oscillator based on photonic crystal fibers theoretically andexperimentally. The mode-locked fiber laser is based on the SESAMtechnique with the output power to1W and the repeat frequency25MHz.The operation zone of the fiber laser is anomalous dispersion regime and thestate of pulse is soliton mode-locked. We use the fiber laser and amplifier asthe pump wave and couple it to the high nonlinear PCF to generateparametric process. The femtosecond optical parametric oscillator isconstructed, and we focus on the tunablity of the optical parametric oscillator.We also analysis the influence of the couple efficiency, polarized state andpump-signal synchronization on the oscillation. The initial experimentalresults have been obtained and the research is further on.