Investigation of modes and dispersion relation for photonic crystal fiber

The symmetry of PCF's mode is determined by PCF's structure. Calculation can be simplified by selecting the appropriate expanding functions according to the symmetry of the modes. In view of this idea, we calculated the dispersion of the PCF with triangular structure and obtained the structure parameters with which the dispersion of fundamental mode at 1.55 μm could be zero. We also calculated the magnetic field distribution of the third order guiding mode of honeycomb-based PCF and proved that the interstitial holes in the PCF had no effect on the mode distribution. To the hollow core PCF, our calculation result showed that the effective propagation index was smaller than 1.