Fast identification of trace substance by single-photon detection of characteristic Raman scatterings with gated coincidence technique and multipixel photon counters

We report a method for fast identification of trace substances. It is based on the single-photon detection of characteristic Raman scatterings by using a gated dual-wavelength coincidence technique and multipixel photon counters. The objective of this study is to overcome the drawback of the low-speed detection of trace substances by Raman spectroscopy and other ultraweak spectra. Analysis indicates that a trace substance in the single-molecule level can be identified within 1 ms. As an example, a fast measurement of a CCl4 concentration with a high intrinsic peak-to-background ratio was demonstrated using this method.