SUPPRESSION OF THE PEDESTAL IN A CHIRPED-PULSE-AMPLIFICATION LASER

The pedestal (prepulse and postpulse) associated with a chirped-pulse-amplification (CPA) laser is studied. Four components have been identified that contribute to the pedestal. Pulses are spectrally shaped by gain narrowing in a frequency-matched, regenerative amplifier, while self-phase modulation is avoided. The intensity contrast is further improved through the use of a saturable absorber, resulting in Gaussian pulses of approximately 0.9-ps duration with an intensity contrast exceeding 10(5):1. Both experimental and numerical descriptions of these processes are presented. This investigation makes possible the study of high-intensity ultrashort laser-plasma interactions with a fiber-grating CPA system.