Study On The Birefringence Of Photonic Crystal Fiber And Its Application

The appearance, development, light-guiding mechanism, classification, wide range of unique optical properties and their application, numerical and analytical method of photonic crystal fibers (PCFs) are introduced in this dissertation. Then we investigate the birefringent properties of PCFs and propose some new highly birefringent PCF designs. Finally, based on single-polarization single-mode (SPSM) PCF, we propose a novel design of SPSM PCF coupler. The details are described as follows:1. We propose a high-phase-low-group modal birefringence PCF with helical air hole cladding for the first time. Using a full-vector finite-element method, we theoretically study its phase and group modal birefringence. Numerical result shows that its phase modal birefringence is as large as 10-4 magnitude; however, the group modal birefringence of this PCF is at 10-7-10-6. This birefringent characteristic is of great importance to minimize the impact of polarization mode dispersion (PMD) in telecommunication systems. We further investigate the dispersion, confinement loss, impact of lateral stress, fabrication tolerance of this PCF.2. We propose a novel design, highly birefringent elliptical-hole PCF with two big circular air holes adjacent to the core, for the first time. It is based on two factors that bring birefringence into PCFs: elliptical air hole cladding and adding two big air holes near the fiber core. Using a full-vector finite-element method, we theoretically analyze its birefringent property. The analysis illustrates that the PCF with such a structure has higher phase and group modal birefringence and its modal birefringence is induced by these two factors together.3. Theoretically design an extraordinarily high birefringent PCF. We numerically analyze the modal birefringent and chromatic dispersion properties of elliptical-hole PCF with squeezed hexagonal lattice. Such a PCF exhibits an extraordinarily high modal birefringence and its modal birefringence can be of magnitude of 10-2 for a quite broad wavelength span. At 1550nm, the phase modal birefringence can even achieve 3.78×10-2, which is the highest in index-guiding PCFs to date. Moreover, a broadband large negative dispersion that can be used for broadband dispersion compensation is also obtained.4. We propose a novel design of single-polarization single-mode (SPSM) PCF coupler for the first time. Using a vector plane-wave expansion method and a vector finite-element method, we investigate the guiding modes, coupling properties, and the characteristic changes with respect to different structural parameters of such a PCF coupler. Numerical result indicates that the SPSM coupling range can be of several hundred nanometers. Through choosing appropriate structural parameters, we can tailor the position and width of the SPSM coupling region.