Analysis of illumination uniformity affected by small-scale self-focusing of a pump beam in the radial smoothing scheme.

In the radial smoothing (RS) scheme, small-scale self-focusing (SSSF) can degrade beam quality of a pump beam with a Gaussian pulse train, resulting in the degradation of the smoothing performance of the RS scheme. Considering SSSF of the pump beam in an optical Kerr medium (OKM), the propagation model of the laser beam in the RS scheme has been developed, and the effects of the characteristics of the pump beam and the thickness of the optical Kerr medium on the RS performance have further been numerically simulated and analyzed. The results show that SSSF decreases the illumination uniformity in the RS scheme by inducing distorted wavefront modulation of the pump beam. Consequently, the beam quality of the pump beam should be controlled to avoid the degradation of the RS performance affected by SSSF. In addition, the peak intensity of the pump beam and the thickness of the OKM should be reasonable to ensure RS performance while mitigating the impact of SSSF.