Numerical Simulation Of New Configurations In Photonic Crystal Fibers

This paper present several new configurations of photonic crystal fibers, the properties and characteristics of which are analyzed by various numerical methods. Upon the emergence of problems with the scientific and technological development and increased communication demands, the development of conventional silica optical fibers becomes more and more difficult. At this very time, the appearance of a new kind of optical fibers───photonic crystal fibers, famous for their intrinsic configurations and properties, set forth a new vital force and energy in the optical fiber field. Photonic crystal fibers are very possible to replace conventional optical fiber as a candidate of the next generation of optical fibers. Based on the study and analysis of photonic crystsal fibers, this paper present the design and analysis of several new configurations of photonic crystal fibers. Firstly, Numerical methods suitable for the simulation of photonic crystal fibers are discussed. Upon the consideration of large refractive index difference and complexity of photonic crystal fibers, the applicability of different methods (especially the finite-difference time-domain method and the beam propagation method) to photonic crystal fibers is discussed. A kind of rectangular lattice photonic crystal fibers is proposed. The anisotropic properties of the cladding are analyzed by the the plane-wave expansion method together with the effective index method. The relationship between the anisotropic properties of the claddings and birefringence of the fibers is presented. The birefringence of the fibers is analyzed by the compact two-dimensional finite-difference time-domain method. We also proposed increasing birefringence by adding a small air hole at the center of the defect solid core. After the normalized propagation constants of the fibers are analyzed, the polarization dependent confinement losses in the fibers are confirmed by the multipole method. A new kind of single-mode single-polarization photonic crystal fiber is possible by appropriate selecting of the fiber's parameters. As for the situation where dual-polarizations are needed, a sandwich structure with the rectangular lattice in the center and triangular lattice in the outer space is brought forward to reducing the confinement loss and also the differential loss. Fabricating techniques are discussed finally, and a stacking-drawing technique for rectangular lattice photonic crystal fibers is proposed. Increased birefringence in rectangular lattice photonic crystal fibers with elliptical hole is analyzed; the influence of rectangular lattice and elliptical hole on the birefringence is presented and interpreted. Finally, results of introducing circular and elliptical hole to the center of the defect core are discussed. Coupling characteristics of dual-core rectangular lattice photonic crystal fibers are analyzed by the plane-wave expansion method. Coupling lengths in the fibers are found to be polarization dependent, and the difference of which can be tuned by the proper selection of structure parameters. Polarization splitters based on the properties are designed and analyzed by the beam propagation method. Another phenomenon is that for some structures, there is a frequency point at which the coupling lengths of the two polarization states are equal. Tuning the interact point by the insertion of an air-hole in the center of the defect core is also proposed. We present two new kinds of photonic bandgap structures: square structure and modified honeycomb structure. The bandgaps of which are calculated by plane-wave expansion method. Wide bandgap and very small air-guiding bandgap are found in the square structure. Photonic bandgap fibers based on the structure are presented and analyzed. Based on the analysis of honeycomb and triangular structures, we present a modified honeycomb structure, which has larger bandgaps than those of honeycomb and triangular structures.