Interference between stimulated Raman scattering and self-phase modulationin pressurized methane in highly transient femtosecond pump regime

The mutual interference between the transient stimulated Raman scattering a nd the self-phase modulation was considered a long time ago [Phys, Rev. A 2 (1970) 60]. In this work we have studied experimentally, for the first tim e to our knowledge, the influence of the transient stimulated Raman scatter ing on the self-phase modulation, considering single-shot Raman spectra, Th e stimulated Raman scattering was excited in methane by 140 fs pulses of th e fundamental wave of a Ti:sapphire laser. Narrowing of the Stokes spectrum and suppression of the self-phase modulation structure were observed with increasing Raman gain, in agreement with the theoretical predictions. The e ffect has been observed up to 40 atm of methane pressure, (C) 2000 Elsevier Science B.V. All rights reserved.