Effect of gain dispersion on ultrashort pulse amplification in semiconductor laser amplifiers

The effect of gain dispersion in semiconductor laser amplifiers is discussed by considering an amplifier model that includes both gain saturation and gain dispersion. The saturated and unsaturated amplification regimes corresponding to whether the pulse energy is comparable to or much smaller than the saturation energy, are discussed separately. In the unsaturated regime, gain-induced group-velocity dispersion is found to play an important role. The amplified pulse can be compressed or broadened depending on whether the input pulse is chirped or unchirped. The pulse spectrum remains largely unaffected in the linear regime. In the saturation regime, self-phase modulation leads to considerable changes in the pulse spectrum