Investigation And Calculation On Properties In Photonic Crystal Fibers

Photonic crystal fibers (PCFs) are a new generation of optical fibers based on photonic crystal techniques. Compared with traditional optical fibers, many superior characteristics such as endless single mode operation,low loss, high birefringence, high nonlinearity etc can be achieved in PCFs by reasonable design of fiber structure. Thus the investigation of PCFs and PCF-based devices has become a hot research topic worldwide, and has attracted a great deal of attention from both academic circle and industrial community. In order to improve one or some of optical properties significantly, starting from PCFs with simple structures, this dissertation adopts numerical methods to further design and optimize the models of PCFs. The main contents of this dissertation are listed as follows:(1) PCFs with simple structures are analyzed using effective index method. According to certain selection rules of fiber parameters, the structures of PCFs can be changed. Furthermore, optical properties and design rules of PCFs are obtained. It is proved that effective index method is an effective and convenient numerical method to analyze PCFs when the structures of PCFs are not very complex.(2) Various models of PCFs can be achieved by adjusting the physical parameters (e.g. the size and shape of air holes, the hole pitch) of PCFs. By means of finite element method, the effects of the structural parameters of PCFs on optical properties are investigated, which will be a theoretical reference for design and application of PCFs.(3) The effects of the structural parameters of PCFs on propagation characteristics and nonlinearity properties are discussed emphatically. A few models of PCFs with superior propagation characteristics are designed in optical fiber communication domain.(4) We design a dual-core PCF, which have an inner low-index core and an outer high-index core. The inner core of dual-core PCF is an air hole, and the structure looks like photonic band gap PCF. The outer core is pure silica,and the structure looks like total internal reflection PCF. We used the finite element and plane-wave expansion methods to calculate the characteristic of the PCF. At last, we changed the structural parameters of the fibers and obtained the curves of relations about the propagation and nonlinear.