Characteristics of amplification of ultrashort laser pulses in excimer media

Energy extraction in XeCl amplifier is theoretically studied for 0.16- and 3-ps initial laser pulse durations. Since an amplification gain is defined by the degree of matching between a gain spectrum and a propagating laser pulse spectrum, when a laser pulse is amplified by a gain medium with a multilined and inhomogeneously broadened spectrum, the saturation behavior of the amplified energy depends on characteristics of change in the laser spectrum during the amplification. Therefore, a saturation energy cannot be simply defined as a unique value for certain initial laser pulsewidth, and depends on amplification history of the pulse, amplified laser energy level, and initial carrier frequency. When a laser pulse is amplified to extremely high energy level (> 5 mJ/cm²), the laser pulse spectrum, which is filtered by the gain spectrum in small-signal amplification regime, is nonlinearly distorted and tends to shift its peak to the red spectrum side.