Dual-wavelength-pumped Raman-resonant four-wave mixing

A new method of anti-Stokes Raman conversion is proposed, termed dual-wavelength-pumped Raman-resonant four-wave mixing, in which a relatively intense secondary pump is applied in the phase-matched direction to enhance anti-Stokes conversion of the primary pump. Conditions for optimizing the conversion efficiency and the effect of phase mismatch are investigated theoretically. A remarkable feature of this method is that the optimum coversion efficiency relative to the primary pump intensity is independent of the initial intensity of the primary pump. It has been shown that nearly 60% of anti-Stokes conversion efficiency is theoretically possible in the vacuum-UV region. The new method of Raman conversion is shown to have advantages in avoiding the effects of beam walk-off and finite coherence lengths because the interaction length required for optimum conversion with this method can be made much shorter than that required in the ordinary single-pump Raman method for a reasonable conversion efficiency.