The Transmission Characteristics Of The Light Pulse In Photonic Crystal Fibers

Photonic crystal fibers (PCF) have become a focus of attention in the field of optoelectronics worldwide. They will be widely used in the fields of optical communication, nonlinear optics, ultrashort laser pulses and harmonics, atomic spectroscopy, photonic crystal physics, high-precision spectroscopy, photonic biology and optical data transfer. With the nonlinear properties of PCF's, pulse compression and supercontinuum generation in photonic crystal fibers have elementarily applied in femtosecond pulse compression and phase stabilization, multiwavelength optical sources and laser color display, et al. Hence there is a great scientific value in the theoretical investigation on the propagation of the laser pulses in photonic crystal fibers.The theoretical investigation with the method of split-step Fourier is presented on the propagation of the input pulse in photonic crystal fibers. The summary of the dissertation paper is as follows:1. The history and development of the studies of photonic crystal fibers and their applications are introduced, especially on the optical properties and applied studies of PCF.2. The physical processes of laser pulse propagation in fused-silica fibers are discussed, focuses on the linear and nonlinear properties of optical fiber that alter the intensity of laser pulses. The nonlinear Schro|¨dinger equation (NLSE) is introduced which can explicitly the physical processes of pulse propagation in fibers. A very powerful method in numerically solving the NLSE is provided, known as the split-step Fourier method.3. The theoretical investigation on the propagation of the picosecond pulse and the femtosecond pulse in photonic crystal fiber is presented. The effects of initial chirp and input pulse power on pulse compression factor, quality factor , optimum fiber length, peak power are simulated and analyzed. The comparisons between the compression factor , quality factor , optimum fiber length, peak power of the picosecond pulse and those of the femtosecond pulse are given.4. Laser pulses with different wavelength, peak power and initial chirp transmitting in PCFs' different dispersion regions are simulated and analyzed. The explanation to the supercontinuum generation in PCF is given.5. Optimum supercontinuum generation is a complicated matter of mutilple parameters optimum combination of pulse and PCF. It is founded that supercontinuum bandwidth increases with fiber length and initial chirp. There exist an optimum fiber length and an optimum initial chirp which increases with linear pulse power. Supercontinuum bandwidth with optimum chirp increases along with pluse peak power increases. These conclusions provide significant reference for supercontinuum generation in photonic crystal fibers.