Modeling the Temporal-Pulse-Shape Dynamics of an Actively Stabilized Regenerative Amplifier for OMEGA Pulse-Shaping Applications

18 LLE Review, Volume 69 Advances in laser-fusion technology indicate that the temporal profile of the laser pulse applied to laser-fusion targets is important for improving the performance of these targets.1 The OMEGA laser is a 60-beam laser-fusion system capable of producing a total of 30 kJ of ultraviolet (351-nm) energy on target, where the temporal profile of the optical pulse applied to a laser-fusion target can be specified in advance. This is accomplished by a pulse-shaping system that produces an optical pulse with a specific temporal pulse shape at the nanojoule energy level.2 This pulse seeds an actively stabilized Nd:YLF regenerative amplifier3 (regen) followed by and wavelength matched (1053 nm) to a series of Nd:glass amplifiers. The beams are then frequency tripled to the third harmonic using KDP nonlinear crystals. To achieve the desired on-target optical pulse shape, the temporal dynamics of the entire OMEGA laser system must be accurately modeled to determine the specific temporal profile of the seed pulse required from the pulse-shaping system at the beginning of the laser. The temporal profile of this low-energy seed pulse, when amplified and frequency tripled by the laser system, will then compensate for the temporal distortions caused by gain saturation in the regen and amplifiers and by the tripling process, and will produce the desired pulse shape on target.