ELECTRODYNAMICS OF A HIGH-POWER ULTRASHORT-PULSE IN RAMAN-ACTIVE MEDIA

The self-consistent nonlinear problem of propagation of an intense fem tosecond pulse in a Raman-active medium is analyzed. An analytic solut ion that describes in explicit form the evolution of the light pulse i s derived. The field structure changes over a time scale comparable to the period of optical oscillations. As a result, the pulse of suffici ently high energy is divided into stretched and compressed domains whe re the field decreases and increases, respectively. A novel mechanism for high-harmonic generation is proposed and the ''plateau'' effect an d sharp cutoff of the spectrum are predicted. The results of analytica l and numerical investigation of the propagation of a space-limited ul trashort light pulse are presented. It is found that self-induced focu sing and defocusing arise, depending on the pulse energy.