Abstract

Recent theoretical and experimental studies of the self-focusing of femtosecond pulses^1,2 have shown that the inclusion of a small amount of positive group-velocity dispersion (GVD) substantially alters the nonlinear dynamics of the self-focusing process. The theoretical analysis is based on the (3D + 1) nonlinear Schrödinger equation (NLSE), and the most significant prediction is that the pulse undergoes temporal splitting as it self-focuses in the nonlinear medium. This pulse-splitting behavior was confirmed by experiments performed in glass.² More recently, the NLSE was extended for pulse envelopes down to the single-cycle regime.³ This nonlinear envelope equation (NEE) includes in a self-consistent fashion the effects of space-time focusing⁴ and self-steepening.⁵

© 1998 Optical Society of America