Study On Ultrashort Laser Pulses Propagating In Birefringent Photonic Crystal Fiber

Photonic Crystal Fiber (PCF) is a special fiber which has a two-dimensional and periodic structure. Owing to the adjustable structure parameters, PCF has so much strange characteristics such as dispersion, birefringence and nonlinear effect that the traditional optical fibers do not have, so PCF has become an important medium to investigate the propagation of ultrashort laser pulse and nonlinear effect. This paper numerically studies the nonlinear propagation of ultrashort laser pulse in the birefringent photonic crystal fiber. The influences of PCF and the laser pulse's parameters on supercontinuum and pulse trapping have been mainly researched. The major work we have done is as follows:Firstly, research status and development trends of photonic crystal fiber are clarified. The application prospects and fundamental characteristics of optical fiber are introduced.Secondly, utilizing the multipole method, we propose a novel birefringent PCF, whose air holes form isosceles triangle other than equilateral triangle. Then the influences of proportion factorηand the radius of the air holes in cladding on the birefringence, dispersion and nonlinear coefficient are investigated and analyzed.Thirdly, using an adaptive split-step Fourier method, the coupled nonlinear Schr?dinger equations between the two polarized components in birefringent PCF have been numerically solved. The nonlinear propagation of a laser pulse in the anomalous dispersion region of the birefringent photonic crystal fiber is simulated. The influences of the propagation length, the average power of pulse and polarization on the performance of supercontinuum are analyzed.Finally, the phenomenon of pulse trapping in birefringent PCF can be obtained. By adjusting the parameters of incident pulse to change the characteristics of spectra and capture rate, a method to improve the capture rate in birefringent PCF has been found.The results in this paper have great significance on the controlling and optimizing of supercontinuum and improving the performance of optical switching in birefringent PCF.