Dynamics of self-focused femtosecond laser pulses in the near and far fields

We investigate the propagation of femtosecond pulses in a nonlinear, disper sive medium at powers several times greater than the critical power for sel f focusing. The combined effects of diffraction, normal dispersion and cubi c nonlinearity lead to pulse splitting. We show that detailed theoretical d escription of the linear propagation of the pulse from the exit face of the nonlinear medium (near field) to the measuring device (far field) is cruci al for quantitative interpretation of experimental data. (C) 1998 Optical S ociety of America.