(Color online) Beam width parameter f₊ plotted against the dimensionless distance of propagation ζ by solving self-focusing equation with and without coupling with self-compression equation. The other parameters are the same as that of Fig. 2. (a) At a = 0.06; (b) At a = 0.07; (c) At a = 0.08; (d) At a = 0.09.