Effect of phase perturbation on high power ultraviolet laser beams in long air path

Using the model of transient stimulated rotational Raman scattering (SRRS) and considering many factors such as phase change of laser beams, the pulsedshape, the depletion of pump laser, the nonlinear amplification of the Stokes field, and the initial random Stokes scattered field, etc, the effect of the spatial phase perturbation on the SRRS of highpower ultraviolet laser beams in long air path has been studied. It is shown that the effects on the threshold of SRRS and the temporal pulse profile are weak. However, the effect on the beam quality is very evident. It is also shown that the energy distribution of the beam becomes more nonuniform and the beam intensity contrast increases sharply as the phase perturbation grows, reducing the beam quality. When the propagation distance is