A new fluorescence-rejected Raman spectroscopy using frequency-domain four-wave-mixing is demonstrated. This method utilizes a broadband light pulse created by continuum generation as one of two pump pulses and a quasi-CW pulse with narrow bandwidth as a probe pulse. The resulting signal is spectrally analyzed by a monochromator-CCD detector combination. Owing to nonlinear character of this method with spatial discrimination of Raman signal from fluorescence, it is possible to measure Raman signal under fluorescent contamination, the limiting concentration of which is about 1, 000 times higher than that obtained by ordinary Raman spectroscopy.
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