Order-selective Raman conversion by dual-wavelength-pumped four-wave mixing

By choice of a suitable angular configuration of the incident beams in dual-wavelength-pumped Raman-resonant four-wave mixing, it is theoretically shown that the primary pump laser energy can be converted into collimated beams of either its first anti-Stokes, second anti-Stokes, or first Stokes wave. A typical theoretical conversion efficiency of 80–90% is obtained. For this energy conversion to occur it is required that the initial secondary pump intensity be much greater than the initial primary pump intensity. Temporal and spatial intensity evolutions of the converted and depleted waves and spatial evolutions of the pulse energy are numerically calculated. The calculations are performed under both phase-matched and phase-mismatched conditions.