Study On Characteristics Of Multi-core Photonic Crystal Fibers

Photonic crystal fiber (PCF) is one kind of photonic crystal which consists ofarranged air holes with linear defect. Using the ability of its local light to limit thepropagation of light in the core. In recent years, PCFs have been drawn wide attentionsbecause of its particular optical properties and flexible design features. Multi-corephotonic crystal fibers (MC-PCF) with larger area and newer light guiding features havegreat potential in applications on directional couplers, fiber laser, wavelength divisionmultiplexer, etc. In this thesis, five-core photonic crystal fibers with square structure andseven-core photonic crystal fibers with triangle structure are studied, including theinfluences of the structure parameters on the coupling characteristics, the light intensitydistribution in phase mode, intermodal dispersion and confinement loss. The resultsprovide a reference on the study of devices based on multi-core photonic crystal fibers.The primary work could be described as follows:Firstly, the five-core photonic crystal fiber with square structure based on the totalreflection is studied. Using coupled mode theory, the eigenvalues and eigenvectors havebeen obtained. According to the characteristics of its five super-modes, we study therelationship between super-modes and coupling characteristics and give a method tocalculate the coupling length of the PCF. The influences of the wavelength and thestructure parameters on the coupling characteristics of the PCF are numerically studiedin detail by the finite element method (FEM).Secondly, the seven-core photonic crystal fiber with triangle structure isinvestigated. The influence of different wavelengths and structure parameters on lightintensity distribution is observed. By adjusting the structure parameters the modeshaping is achieved. In order to eliminate the intermodal dispersion of seven-core PCF,we dip low refractive index material in the core, and find that zero intermodaldispersion wavelength cover both optical communication windows of1.31μm and1.55μm.The effects of dip index, dip radius on the intermodel dispersion areinvestigated detailly by using full-vector finite element method. We also realize themode shaping in zero intermodal dispersion fibers, which has no interference betweensupermodes and can absorb the pump light more effectively.Additionly, we analyze the effects of cladding layer on the fiberloss. By increasingthe number of layers can limit the magnitude of the loss reaching up to10-7dB/m. Otherstructure factors, such as core index and core radius on the fiber loss are also presented, which can provide a reference to design ultra-low loss MC-PCF.This thesis can provide a theoretical foundation for designing MC-PCFs and theoptoelectronic devices based on MC-PCFs.