Nonresonant background suppression in coherent anti-Stokes Raman spectroscopy through cascaded nonlinear optical interactions.

We propose and experimentally validate a technique for four-wave mixing background suppression in coherent anti-Stokes Raman spectroscopy. It is based on the interaction of the signals generated from the Kerr third-order nonlinearity and the cascaded quadratic process in a nonlinear crystal. Theoretical analysis agrees well with the experimental results, which provide a quantitative assessment of different contributions and allow extraction of the nonlinearity parameters.