Birefringence And Polarization Dependent Coupling In Photonic Crystal Fibers

Photonic crystal fiber is a kind of novel optical fiber structure, which hasrevolutionized fiber optics and attracted extensive attentions. Also, thephotonic crystal fiber has a high potential to realize optical processingcomponents of high performance on basis of its many unique properties oflightwave guiding. In this thesis, birefringence in the photonic crystal fibers is discussed byemploying beam propagation method. One can obtain high birefringence due toa sharp index contrast between air and silica in photonic crystal fibers. Weproposed two kinds of polarization maintaining fibers based on the photoniccrystal fibers, in which the birefringence can be much higher than theconventional ones. Influences of structure parameters and incident wavelengthon the birefringence are also analyzed. It is achieved in optical waveguides forthe first time that the polarity of the polarization maintaining fibers can becontrolled by changing the incident wavelength. Another topic of this thesis is on polarization coupling in the photoniccrystal fibers. Novel polarization splitters of high performance can be obtainedby introducing strong birefringence into the dual-core photonic crystal fibers.Capitalizing on polarization dependent coupling and polarization selectivecoupling principles, we have designed the polarization splitters with highextinction ratios and short lengths for the first time. The role of silica bridgesconnecting the two cores in polarization splitting is discussed, and some ideasabout designing such polarization splitters are given. At the end, we brieflyanalyzed the nonreciprocal coupling in the photonic crystal fibers.