This phenomenon can be explained by the diffraction effect of the Gaussian beam from the laser induced phase hole in the nonlinear medium caused by Kerr effect and thermo optic effect.

Based on the diffraction integral theory, the quasi-focused characteristics of a laser beam with waviness modulation have been studied theoretically and numerically in the paper.

Several mainstream laser beam combination methods, including stimulated Brillouin scattering, diffraction optics units and all fiber beam combination, are introduced.