| The PCF is a new kind of optical fiber with photonic crystal (PC) structure. There are many unique optical characteristics in the PCF, such as endless single mode, low loss, flexible dispersions, adjustable non-linear and high birefringence. The PCF has attracted a lot of interests during past years. In this thesis, the propagation characteristics of PCF are investigated with two simulation methods. The main contents include:(1) Based upon the Block theory in the periodic dielectric, the reciprocal lattice and the first Brillouin zone, the plane-wave method (PWM) is implemented with MATLAB, which is used to analyze the band gap map and mode field distribution of the two dimensional square lattice and triangular lattice.(2) Basing on the program of the finite difference frequency domain(FDFD), two kinds of typical commercial PCFs: type-LMA-20 large mode area and the photonic band gap are analyzed. The characteristics of PCF, such as cut-off property, mode field, mode field radius, effective area, are discussed. The results of simulation are agreed with that of testing well.(3) A new highly birefringent PCF structure was proposed. The PCF are constructed with regular circular air holes and the core formed by enlarging two air holes in the center, the space distance is different along two perpendicular directions, which includes either global effect or local effect. The new PCF was analyzed by full-vector FDFD methods. The numerical results showed that birefringence in the PCF can approach the order of 10-3 with broad single-mode region (800nm--1800nm) by choosing suitable relative structure parameters. A set of optimal structure parameter was found out by numerical simulation. It is also shown that a low confinement loss can be obtained in a properly designed geometrical structure of PCF.(4) Based on former analysis, we elementarily design a Graphical User Interfaces in MATLAB to realize PCF propagation characteristics. |
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