Abstract
The Nike laser is a 3-5-kJ KrF facility under construction at the Naval Research Laboratory to address technological and physics issues of direct-drive laser fusion. One of the key issues is the ability to produce a focal spot whose time-averaged intensity is smooth and controllable to within a few percent. To accomplish this, Nike will implement the echelon-free ISI technique,1 in which the desired focal profile F(r) formed at the output of a spatially and temporally incoherent oscillator2 is imaged onto the target through the laser system. Because the amplifier stages are located in the quasifar-field of F (r), the large scale gain and phase non uniformities that they inevitably produce will have little effect on the image. However, small-scale phase nonuniformities can perturb the image, and must be minimized to maintain good control over it. The compensation of systematic phase aberrations in the Nike optical design has been discussed earlier.3 Here, we report on numerical simulations of profile distortion due to random phase nonuniformities, self-phase modulation, and self-seeded stimulated rotational Raman scattering (SRRS), and describe the steps being taken to minimize these effects.
© 1992 Optical Society of America
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