Femtosecond Optical Pulses In Photonic Crystal Fiber Nonlinear Transmission Characteristics

Since the photonic crystal fiber was firstly demonstrated by J. C. Knight in 1996s, its great flexibility in design and unique optical properties have attracted considerable attention. Compared to conventional fiber, PCFs have many unusual characteristics, such as endless single mode propagation, controllable dispersion properties, strong nonlinear effects and high birefringence, which make PCFs have wide application in the field of nonlinearity optics, optical communication, fiber sense and many other fields. Therefore, PCFs have become one of research interests in the past years.This thesis is mainly focused on research of nonlinear propagation of ultra-short femtosecond pulses in PCFs; the main contents are listed below:First, contents of the concept, optical properties and preparation of PCFs are introduced detaily. Applications of nonlinear effects of PCFs, as well as theories of fine feather of PCFs, are analyzed.Second, generalized nonlinear Schrodinger equation(GNLSE) as model of nonlinear propagation of ultra-short laser pulses in PCFs is found from Maxwell's equation. The predictor-corrector symmetrized split-step Fourier method is proposed for solving the GNLSE, and based on the arithmetic, Matlab is aided for design of computer program, which is used to investigate nonlinear propagation of ultra-short laser pulses in PCFs numerically.Third, based on GNLSE, the numerical investigation of nonlinear propagation of chirp-free femtosecond pulses in PCFs with anomalous dispersion is presented. It is found that the compressed spectral width is strongly dependent on the initial peak power, central wavelength and propagation length of the incident pulse. The mechanisms responsible for the spectral compression are discussed.Fourth, femtosecond laser pulse propagation and supercontinuum (SC) generation in PCFs are investigated numerically based on GNLSE. The effects of the parameters of the initial laser pulse, peak power, initial chirp and fiber length on spectral properties of SC are analyzed systematically for optimizing SC. Fifth, the coupled nonlinear Schrodinger equations (CNLSE) are adopted to describe the evolution of ultra-short laser pulse propagation in bierfringent photonic crystal fibers, and solved with the symmetrized split-step Fourier method. It has been investigated of generation and polarization properties of the supercontinuum by ultra-short pulse in bierfringent photonic crystal fibers with different dispersion profiles in the 1550-nm window by numerical stimulation. The impact of high-order dispersion and nonlinear effects is analyzed with different dispersion profiles.