Theory And Research Of Novel Dual-core Photonic Crystal Fibers

photonic crystal fiber(PCF) has many unique properties that the traditional fiber do not has,with the mature of theory of PCFs, and the development of manufacuring o f PCFS, large numbers of novel kinds of PCFs come out. The traditional dual-core optical fibers have short comings of trivial production process and higher precision requirements for fabrication technology; on the other hand, the dual-core photonic crystal fibers not only have relatively simple production process, but also have good coupling characteristics. So, PCFs has important significance for intergrated optics.In this thesis, two different structures of dual-core photonic crystal fiber have been designed, the characteristics of them are analysised. the full vector finite element method(FEM) is employed to investigate the coupling properties and broadband flat dispersion properties of the designed dual-core PCFs, meanwhile, the relevant application of the novel dual-core PCFs in polarizing splitter have also been researched. The major contents are as follows:(1) The light guiding principle and advantages compared with traditional fiber of dual-core PCF are introduced detailedly. Moreover, the classification, manufacture methods and application of it are briefly introduced. This thesis put forward the research status of the dual-core PCF over abroad to our nation.(2) Several theoretical analysis methods of PCF are described, then focus on introducing the basic principles of the full- vector finite element method(FEM) and the modeling process based on COMSOL software. In addition, the foundamental characteristics of PCF and how to use the FEM to calculate the characteristics in the practical design proc ess are present in detail.(3) A kind of novel elliptical dual-core photonic crystal fiber(PCF) with high birefringence and broadband flat dispersion is proposed, by introducing six elliptical holes in the central region of the fiber to improve its birefringence. The full- vector finite element method and coupled- mode theory are used to investigate the birefringence, coupling length, and dispersion characteristics of the dual-core PCF. The numerical investigations demonstrate that by changing the structural parameters of the fiber, the dual-core PCF exhibits simultaneously a birefringence of up to 10-2, a coupling length of 68.178 mm for the x-polarization and 74.825 mm for the y-polarization, and a broadband flat dispersion ranging from 1.1 mm to 1.6 mm.(4) A new kind of dual-core photonic crystal fiber polarization splitter based on lead silicate glass is put forward, meanwhile, the same structural parameters of quart z glass dual-core photonic crystal fiber polarization splitter is applied to compare. Numerical investigations demonstrate that the polarization splitter we designed has higher extinction ratio and the coupling loss is low, at the wavelength of 1.55 mm, fiber length is 688 mm, the coupling loss is only 0.0019 d B, extinction ratio of core A is-64.1 d B, when the extinction ratio is less than-20 d B, the bandwidth of is 51 nm.