Temporal fluorescence rejection in Raman spectroscopy using femtosecond up-conversion with single- and multi-channel detection

The up-conversion method was utilized for temporal fluorescence rejection in Raman spectroscopy. The up-converted Raman spectra were measured by both single-channel and multi-channel detection methods, and it was demonstrated that the up-conversion can provide sensitivity high enough to measure Raman spectra. An unprecedented short gate time as high as 160 fs and a rejection efficiency higher than 104 were achieved in temporal fluorescence rejection. It was also shown that the femtosecond excitation with a temporal gated detection shorter than the Raman vibrational coherent time caused a significant band broadening in the observed spontaneous Raman spectra.