Small scale self-focusing effect of stacked chirped pulse propagation

Fine structure of the temporal distribution of stacked chirped pulse is discussed with different spectral width, phase and chirp. The peak power of stacked pulse is 1.5 to 3.0 times of narrow band pulse with small variation of spectral width and it is always 3.0 times of narrowband pulse with random phase fluctuation. Theoretical nonlinear propagation model of stack pulse is established. Numerical simulation shows that stacked chirped pulse has larger small scale modulation gain than narrow band pulse with the same energy. It is indicated that nonlinear optical damage may occur when we use stacked chirped pulse in high power laser systems.