This BeamLab demo shows a high-power Gaussian beam incident on a block of fused silica where it then converges to a small spot due to the self-focusing effect by taking into account the nonlinear change of the intensity-dependent refractive index.
BeamLab demo script: selffocusing.m
This video shows how the intensity distribution changes along the propagation distance z. The left figure shows the two-dimensional intensity distribution I(x,y) normalized to the input intensity and displayed on linear scale. The right figure shows a three-dimensional view of the intensity dependent nonlinear refractive index.
After the calculation has finished, the intensity distribution as a function of propagation distance z is plotted. The figure above depicts the intensity distribution I(x,z) at y = 0 µm. The white line indicates the start of the block of fused silica.
This figure shows a compact three-dimensional view of stacked plots, each portraying the intensity distribution I(x,y) at different distances z.