Enhancement of Raman scattering by parametric mixing of the pump with its harmonic

Abstract A strong focusing of the pump laser is generally used to reduce the Stimulated Raman Scattering (SRS) threshold, but it also produces a phase matching condition in the region of strong gain. This causes a large threshold for SRS in the near infrared due both to the increased diffraction limit and to the destructive interaction of antiStokes–Stokes processes. However the phase matching condition can be used to reduce the threshold by Raman parametric mixing (RPM) of the pump with the second harmonic generated by a fraction of pump. It this way we have observed a lowering of the threshold of about a factor 2.3 and an increase of the SRS of the pump.