Ultrashort pulse propagation in krf laser amplifiers

We consider the propagation of picosecond and subpicosecond pulses in KrF amplifiers. For pulses of -1-psec duration, the Frantz-Nodvik model provides an excellent fit to the experimentally measured gains as well as to the predictions of a more general coherent-propagation model. For 0.1-psec pulses, however, the Frantz-Nodvik and coherent-propagation theories predict different pulse shapes, although the predicted output fluences are in excellent agreement. We discuss the question of how short an input pulse can be without incurring substantial temporal broadening as well as the effective lower-level decay rate and line shape, the saturation fluence, and the effect of nonsaturable absorbers in the amplifying medium.