Nonlinear optical compression of Er/sup 3+/-fiber amplified 1.5-/spl mu/m laser diode pulses

Femtosecond optical pulses of 110-200-fs width have been produced using a gain-switched distributed-feedback semiconductor laser followed successively by a linear compression stage and a nonlinear compression stage. Analysis is focused on this last stage where pulses with peak powers corresponding to 10and 12-order solitons are fed at the fiber input end. Experimental results are well described using both the modified nonlinear Schrodinger equation and an accurate intensity and phase model of the gain-switched laser diode. Experiments are shown to be correctly described only if both intrapulse stimulated Raman scattering and third-order dispersion are taken into account. Guidelines are then given to optimize the nonlinear fiber compression using laser diodes and fiber amplifiers. The influence of the third-order dispersion in the fiber compressor is first evaluated. Second, the nonlinear self-phase modulation induced in the fiber amplifier is studied. It is shown to be the main factor limiting any further pulse shortening with this technique.