Phase matching and optical geometry considerations in ultrafast non-degenerate six-wave-mixing experiments

The generation in solution of optically induced second harmonics, through six-wave mixing, has been observed using three distinct optical geometries. The established phase-conjugate geometry is not useful for ultrafast time-resolved experiments. A grating scattering geometry, with the pump and probe pulses entering from the same side of the sample, provides the highest time resolution and signal strength although there is a strong interfering signal at time zero. A collinear geometry, which introduces a means for the coherent control of molecular orientation, is also discussed.