Measurement of pulse amplitude and phase distortion in a semiconductor optical amplifier: from pulse compression to breakup

We have performed extensive measurements of the propagation of ultrashort pulses in a semiconductor bulk amplifier using an ultrasensitive cross frequency-resolved optical gating technique. Pulses of 175-fs duration with energies from below 1 fJ to above 100 pJ are measured both in amplitude and phase after propagation through the device. While only moderate reshaping effects occur at pulse energies of below 1 pJ, strong amplitude distortion together with nonlinear chirp is found for input energies of 5-100 pJ. This leads to a pulse narrowing by more than a factor of two when the amplifier is biased for material transparency or absorption and to a pronounced pulse breakup in the gain regime.