Fluorescence-encoded time-domain coherent Raman spectroscopy through single-photon counting

Fluorescence-encoded Raman spectroscopy has become increasingly more popular by virtue of its high chemical specificity and sensitivity. However, current fluorescence-encoding methods are narrowband and lack sensitivity in the low wavenumber region which if addressed could further enhance these methods. To overcome these limitations, we propose and experimentally demonstrate a novel broadband method for fluorescence-encoded Raman spectroscopy, termed fluorescence-encoded time-domain coherent Raman spectroscopy (FLETCHERS), which is capable of probing molecular vibrations in the lower fingerprint region (200 – 750 cm-1 ) with sample concentrations as dilute as 100 nM and laser powers as low as 20 mW.