The Characteristic Analysis And Structure Design Of Photonic Crystal Fibers

The photonic crystal fiber (PCF) is a new kind of optical fibers that employ the structured arrangement of the photonic crystal. It has many unique optical characteristics and has been the direction of the development of the optical fiber technology.Based on the study of a great number of references, we introduce achievements and developments of PCFs, respectively. After we discussed finite difference method (FDM) and finite difference time difference method (FDTD), in detail, a FDTD algorithm with heterogeneous gridding in the cylindrical coordinate system is proposed for the analyses of complex optical waveguides, in which short-time steps with fine domains are used for fine structures and long-time steps with coarse domains for the others. By applying the Linear Interpolation method, the jumping errors between the junction parts with heterogeneous gridding have been overcome. And then we educe the modified algorithm with detailed program, by which the propagation characters of optical fiber are simulated and analyzed.Comparing with conventional fibers, photonic crystal fibers present many unique dispersion properties because of their unusual geometry structures. These dispersion properties:dispersion tailoring, anomalous dispersion at short wavelength, nearly zero ultraflattened dispersion and so on. With the APSS software ,we simulate the unique characterizes of PCF and propose a kind of six-ring photonic crystal fiber with two different air-hole sizes and triangle equilateral polygon distribution in center. Optimizing three geometrical parameters for zero dispersion and ultra-flatten, the dispersion of PCF in wide band range can be efficiently designed.Photonic crystal fibers also present unique polarization characteristics. Because of the design flexibility and the large index contrast between material and air hole, high birefringence can be easily realized in PCFs. Based on the high birefringence, ultra-wideband quarter-wave plate can be designed. With the APSS software, we propose a new design method for quarter-wave plate (QWP) with photonic crystal fiber based on the characteristic of its unique polarization properties. The influence of the construction and size of PCF on the wavelength versus effective index has been analyzed. In order to obtain ultra-wideband device, the increasing rate of effective index difference should correspond with the rate of wavelength.