Spectral compression in supercontinuum generation through the higher-order nonlinear Schr?dinger equation with non-Kerr terms using subnanojoule femtosecond pulses

摘要

We investigate numerically the supercontinuum generation (SCG) phenomenon, using femtosecond pulses in the subnanoscale of energies through the generalized nonlinear Schr?dinger equation that includes non-Kerr terms. Our results with 50 fs pulses in the anomalous dispersion regime show that, in comparison to the single cubic Kerr nonlinearity (CKN) case, the cooperative nonlinearities improve the spectral broadening, while the competing ones compress the spectral SCG bandwidth. Surprisingly, with the reduction of the pulse width, the cooperative nonlinearities induce a spectral compression while the competing ones keep the SCG bandwidth nearly constant from the input to the output of the considered waveguide. The increase of both the energy and the nonlinearity confirms this feature, showing that spectral compression is also obtained in the single CKN case, but less than in the case of cooperative nonlinearities.