Effect of refractive-index nonlinearity on the optical quality of high-power laser beams

Both small-scale and large-scale partial self-focusing produce phase distortions which result in loss of optical quality of the beam. Both effects are herein studied and both can result in significant power loss. Incipient fine-scale self-focusing losses can be mitigated by spatial filtering. Nonlinear lensing, i.e., partial large-scale self-focusing, is more or less serious depending on the size of the target onto which the beam is to be focused.