Effect of initial frequency chirp on the supercontinuum generation in all-normal dispersion photonic crystal fibers

Abstract

The effect of initial frequency chirp of input pulses on pulse dynamics and spectral broadening in all-normal dispersion photonic crystal fibers are investigated numerically. When the input peak power is low, for small initial frequency chirp the positive chirps can enhance the bandwidth of supercontinuum while the negative chirps can compress the spectrum. When the initial frequency chirp increases the bandwidth of supercontinuum can be further increased and the spectral broadening is similar for both signs of the initial frequency chirp. Especially, the simulations show that there exists an optimal chirp value that makes the supercontinuum flattest almost without the fine spectral structures. For high input peak power the initial frequency chirps have a little effect on the supercontinuum generation and the significant fine spectral structures appear which makes the coherence of supercontinuum become worse. In addition, the effects of input pulse parameters such as peak power, pulse duration and central wavelength on the supercontinuum generation have also been investigated. It is found that the broadest spectra can be obtained when central wavelength of pump pulse located near the maximum of the fiber dispersion curve.