Numerical study on pulse trapping in birefringent photonic crystal fibers

Using an adaptive split-step Fourier method, the coupled nonlinear Schrödinger equations have been numerically solved in this paper. The nonlinear propagation of an ultrashort optical pulse in the birefringent photonic crystal fibers is investigated numerically. It is found that the phenomenon of pulse trapping occurs when the incident pulse is deviating from the principal axis of the fiber with some angle. Owing to the birefringence effect, the incident pulse can be regarded as two orthogonal polarized pulses. The phenomenon of pulse trapping occurs because of the cross phase modulation (XPM) between the two components. As a result, the bandwidth of the supercontinuum (SC) decreases compared with the case that the incident pulse is input along the principal axis. When the polarization direction of the incident pulse is parallel to the fast axis, the bandwidth of the supercontinuum is maximal.