ENHANCED SELECTIVITY FOR SPECTROCHEMICAL MEASUREMENT BY MODE SELECTION IN FULLY RESONANT NONLINEAR MIXING

In this paper, we demonstrate the feasibility of a new family of mode-selective spectroscopies based on multiresonant nonlinear mixing. Three tunable lasers are used for fully resonant four-wave mixing so the output signal depends on the simultaneous contribution from three resonances. Mode selection is accomplished by tuning the lasers to a particular vibrational resonance. Vibrational spectra are obtained by scanning the second resonance. The resulting spectrum shows selective enhancements of all the modes that are related to the mode selected by the first resonance. In this paper, we demonstrate the capabilities of this approach for enhancing features that are very weak in conventional spectroscopies and for separating features that are spectrally overlapped.