Study on mode degeneracy in photonic crystal fibers
光子晶体光纤模式的简并特性研究

A novel full vector model is applied to analyze the photonic crystal fibers (PCF). From symmetry analysis of modes of a waveguide, we classify the modes of PCF into nondegenerate or degenerate pairs according to the minimum waveguide sectors and its appropriate boundary conditions. We present the modes of PCF that can be labeled by its step index fiber analogs. It is shown that these modes either exhibit the full waveguide symmetry and nondegenerate or occur in degenerate pairs that support this symmetry only in combination. The doublet of the degenerate pairs in which both have the same symmetry as PCF will be split into two nondegenerate modes.