Model of smallscale selffocusing and noise in high power laser driver

The nonlinear laser beam propagation in high power laser driver and the influence of the smallscale selffocusing and phase noise on beam quality in disk amplifier have been analyzed by a linear model. The quantitative relations between intensities of phase noise, Bintegral, and the beam intensity contrast in near field are given explicitly. A spectrum specification of phase noise can be given when modulation contrast of output beam is very small.