An on-axis solution to the nonlinear instability treatment is presented where a single "sinusoidal" spike is superimposed on a constant plane laser background. Introduction of the phenomenological depletion of the background leads to the stabilization of intensity in the spike and an accurate prediction of its diameter.

• Received 23 August 1982

DOI:https://doi.org/10.1103/PhysRevLett.50.160