Forward stimulated Rayleigh-wing scattering in CS2 by pumping with a Bessel beam

We have studied forward stimulated Rayleigh-wing scattering (SRWS) of picosecond pulses in bulk CS2 via Bessel beam pump geometry, which provides angular separation of pump and Stokes and strong suppression of self-phase modulation of the pump. Near the threshold of SRWS a sharp Stokes Line with frequency shift Ohm = 2.5 cm(-1) has been observed. We found out also a double structure in the spectral distribution of the SRWS consisting of two sharp Stokes lines, with frequency shifts fluctuating in the range Ohm(1) approximate to 2.5-3.5 cm(-1) and Ohm(2) approximate to 5.5-8 cm(-1). The observed spectral behavior is interpreted as being due to four-photon parametric coupling process driven by the SRWS beam, which strongly influences the frequency dependence of the gain factor in the forward direction. (C) 1998 Elsevier Science B.V. All rights reserved.