Vibrationally enhanced four-wave mixing in 1,8-nonadiyne

The vibrationally enhanced third-order nonlinear optical susceptibility, χ(3), of the acetylenic C–H stretch of 1,8-nonadiyne is measured using infrared four-wave mixing spectroscopy. Two tunable infrared and a visible laser generate four-wave mixing by a nonparametric process that is enhanced by the infrared absorption. The measurement uses the lineshape changes caused by interference between a coherent anti-Stokes Raman process and the nonparametric infrared four-wave mixing. The vibrational enhancement is 7-times larger than the nonresonant electronic χ(3). This enhancement is sufficient for achieving multiresonant infrared four-wave mixing with vibrational resonances.