SOLITON FREQUENCY-SHIFT AND DELOCALIZATION IN MEDIA WITH 2 TIME-SCALENONLINEAR RESPONSE

The soliton frequency self-shift and the associated soliton delocaliza tion is investigated for a medium with a multiple nonlinear response. It is shown that when there are two nonlinearities, a fast one which i s responsible for the soliton formation and a slow one which is essent ially nonlocal in time, an ultrashort soliton experiences a significan t acceleration, radiative damping and delocalization. The relations de rived for the frequency shift rate are significantly different from th e well-known Gordon formula for broad solitons suffering Raman losses.