PARAMETRIC SUPPRESSION OF RAMAN GAIN IN COHERENT RAMAN PROBE SCATTERING

We report on the observation of Raman gain suppression by parametric f our-wave mixing in coherent Raman probe scattering with a noncollinear pump and probe arrangement. The effect has been observed in coherent Stokes scattering of picosecond pulses from polaritons in a LiIO3 crys tal. The angular intensity pattern of Stokes probe scattering shows a distinct dip in phase-matching directions of a noncollinear parametric four-photon interaction K-L + K'(L) = K-S + K-A, where two photons at the laser frequency, one from the pump beam and another one from the probe beam scatter into Stokes and anti-Stokes photons. The interferen ce between this process and Raman scattering results in an additional dark ring in the angular intensity pattern of Stokes scattering of the pump pulse. (C) 1998 Elsevier Science B.V. All rights reserved.