Study On The Nonlinear Parametric Process In Photonic Crystal Fiber

It has been twelve years since photonic crystal fiber (PCF) was produced. Comparing with conventional fibers, PCF has many novel properties. Its zero dispersion wavelength can be designed towards shorter wavelength such as the operation wavelength of Ti:sapphire laser. However, conventional dispersion-shifted fiber can only be adjusted to longer wavelength. Besides, PCF can be designed to deliver the endless single-mode transmission, which is impossible for the conventional fibers. PCF can be engineered to have small fiber core area, so that its nonlinear coefficient can be one order larger than that of the conventional fibers.In quantum communication domain, the properties of entangled photon pairs have been studied intensively. In initial stage, crystals were utilized to provide gain. Subsequently, the presence of the fibers attracted more attention for its lower loss and longer distance as a gain medium. In recent years, new scientific investigations based on PCFs to produce entangled photon pairs have been developed, and remarkable achievements have been obtained. The entangled photon pairs are created by theχ(3)-nonlinear parametric process in the fiber, therefore, it is very important to investigate the specialities of the process in a PCF, and the relations between the control parameters.The main works in the thesis are as follows:1,We have derived non-monochromatic light Four-wave mixing gain expression, and analyzed the properties of the gain curves with pump wavelength at abnormal dispersion region and at the neighborhood of zero dispersion wavelength, respectively. It can be found that gain curve, generated by a narrow bandwidth pump pulse, keeps good symmetry. Thus, we should choice an appropriate narrowband pulse in the experiments. Comparing the gain curves, obtained in the experiment, with that of theoretics, it is clear that there is a good agreement.2,We have discussed how the Raman scattering affects the Four-wave mixing process. The relations on the Signal-to-Noise Ratio, which is defined the radio between the FWM and the RS, with the dispersion, effective fiber core area, and zero dispersion wavelength of the PCF, as well as the central wavelength of pump pulse, have been studied. The parameters in favor of generation of entangled photon pairs are presented.3,Spectral function and phase-matching fuction of the PCF of the FWM in a PCF are derived. Impacts of the slope at zero-dispersion wavelength and the nonlinear coefficient of the PCF on spectral function are studied, and the optimum filtering position is presented. The results can provide a theoretical reference for the experiment of entangled photon pairs'generation.4,Impact of the structure parameters on high order dispersion coefficients is analyzed by multipolar software based on Multipolarization Method. How high order dispersion coefficients affect gain curves is discussed. A novel PCF has been designed to escape from Raman scattering region and to dominate a broadly tunable bandwidth.