Nonlinear Optical Effects And Applications In Silicon Waveguides With Micro-or Nano-scale Structures

In recent years, silicon photonics has become a rapidly growing area. Thenonlinear effects in silicon waveguides are attracting attention because of the largevalues of the Kerr parameter, Raman gain coefficient and the tight confinement ofthe optical mode. In this dissertation, we have investigated the four-wave mixing(FWM), cross-phase modulation (XPM), Raman scattering and their applications insilicon waveguide. The main contents and innovations of this dissertation aresummarized as follows:1. After considering the linear loss, dispersion, Raman scattering effect, Kerreffect, two photon absorption and free carrier effects, the nonlinear propagationequation for ultrafast pulse evolving in silicon waveguide is derived from Maxwell’sequations.2. Femtosecond wavelength conversion in the telecommunication bands viafour-wave mixing in SOI waveguide is theoretically investigated. It is difficult toachieve a efficient wavelength conversion when the pulse widths are close to or lessthan100fs because of the spectral overlap between pump, signal and idler. Theinfluence of repetition rate on conversion efficiency is also investigated, and theconversion efficiency decreases for a high repetition rate due to the larger free carrierabsorption.3. The impact of dispersion profiles of SOI waveguides on femtosecond opticalparametric amplification based on FWM is theoretically investigated. It is found thatflat quasi-phase-matching, smooth temporal profiles and separable spectra can beobtained by tailoring the cross-section of SOI waveguide.4. A width-modulated SOI waveguide is proposed to realize non-degeneratephase sensitive optical parametric amplification based on FWM. It is found that therelative phase at the input of the phase sensitive amplifier can be tuned by tailoringthe width and length of the second segment of the width-modulated silicon waveguide, which will influence the gain in the parametric amplification process.5. Terahertz (THz) wave generation via four-wave mixing (FWM) in siliconmembrane waveguides is theoretically proposed. It is found that the pumpwavelength located in the normal GVD regime is required to realize collinear phasematching for the THz-wave generation via FWM. Moreover, THz-wave can beobtained via FWM with high efficiency exceeding1%.6. The influence of three-photon absorption (3PA) on XPM effect in themid-infrared (IR) region is theoretically investigated in SOS waveguides. It is foundthat the3PA-induced nonlinear losses will be considerable when the pump intensityis high enough. For the XPM process, the3PA and3PA-induced free-carrier effectscan affect the spectrum and temporal profiles of the pump and signal pulses, and theXPM-induced blue and red shifts are reduced due to3PA.7. Raman amplification and anti-Stokes Raman scattering wavelengthconversion are theoretically investigated in silicon-on-sapphire (SOS) waveguides inthe Mid-infrared (IR) region. When the linear phase mismatch is close to zero, theStokes gain and conversion efficiency drop down quickly due to the effect ofparametric gain suppression when the Stokes-pump input ratio is sufficiently large.The conversion efficiency at exact linear phase matching is smaller than the peakconversion efficiency by a factor of about28dB because of the influence ofparametric gain suppression.8. The phase matching for wavelength conversion based on CARS withorthogonal polarized Pump and Stokes waves is investigated in SOS waveguides.It is found that phase mismatch induced by birefringence together with materialdispersion-induced phase mismatch can counteract the large phase mismatch inducedby waveguide dispersion. Moreover, compared with phase matching for identicallypolarized pump and Stokes waves, the phase matching for orthogonal polarizedPump and Stokes waves can be realized in a SOS waveguide with much smallercross section.9. Wavelength conversion based on SOI waveguide is experimentallyinvestigated. The influence of pump power on the conversion efficiency is analyzed, and the influence of SOI waveguides with different width and length on theconversion efficiency is discussed.