Design And Study Of The Characteristics Of Several Photonic Crystal Fibers

Due to the unique structure of photonic crystal fibers, they process many excellent optical properties that traditional fibers don’t have, such as strong nonlinearity, dispersion, unusual high birefringence and transmission characteristics of single mode cutoff frequency etc. These special properties also make their applications in communication fields, especially in long-distance communication system, very promising and far exceed the traditional fibers. Therefore, photonic crystal fibers have been attracting the attention of researchers, no matter they are a single material or filled or coated. In our paper, three single and dual core photonic crystal fibers with polarization characteristics are designed and the functions of polarization splitting, polarization filtering and single mode single polarization are achieved by using these special characteristics. The main contents are described as follows:Firstly, we introduce the research backgrounds and their basic characteristics of photonic crystal fibers and summarize the main theoretical research methods. Then we describe the theoretical basis of photonic crystal fiber based on surface plasmon, In addition, we expound the drawing and application of photonic crystal fiber.Secondly, based on the mode coupling theory, a kind of polarization splitter based on dual-core photonic crystal fiber with unsymmetry core is designed by using finite element method. The transmission and coupling characteristics are analyzed.Thirdly,a novel design of unsymmetry Au-filled photonic crystal fiber has been proposed. By adjusting the parameters, we study the filtering effects of polarization filter at the wavelength of 1.55μm and 1.31μm, which is simulated by finite element method. In addition, the effects of the two polarization direction are also studied by altering the symmetry around the Au-filled holes, which is a novel idea relative to blindly improve birefringence.Finally, an optimum structure is found for single-polarization single-mode photonic crystal fiber.The single-polarization single-mode operation is realized with three different background materials at different wavelengths. By finite element method, the variation of effective refractive index and loss with wavelength are analyzed, and the single-mode single-polarization regions of three different substrate materials are obtained. Moreover, we analysis the influence of the elliptical hole and the whole compression at the Y direction on the single mode single polarization regions. It is useful for mid-infrared optical fiber communication in the near future. All these properties contribute to the design of high bandwidth and multiwave band single-polarization single-mode photonic crystal fiber.