Femtosecond stimulated Raman spectroscopy (FSRS) is a new technique that produces high-quality vibrational spectra free from background fluorescence. FSRS combines a narrow-bandwidth picosecond Raman pump pulse with an ~80 fs continuum probe pulse to produce stimulated Raman spectra from the pump-induced gain in the probe spectrum. The high intensity of the Raman pump combined with the broad bandwidth of the probe produces high signal-to-noise vibrational spectra with very short data acquisition times. FSRS spectra of standard solutions and solvents such as aqueous Na<sub>2</sub>SO<sub>4</sub>, aqueous KNO<sub>3</sub>, methanol, isopropanol, and cyclohexane are collected in seconds. Furthermore, stimulated Raman spectra can be obtained using just a single pump-probe pulse pair that illuminates the sample for only ~ 1 ps. Fluorescence rejection is demonstrated by collecting FSRS spectra of dyes (rhodamine 6G, chlorophyll a, and DTTCI) with varying degrees of fluorescence background and resonance enhancement. The high signal-to-noise, short data acquisition time, fluorescence rejection, and high spectral and temporal resolution of femtosecond stimulated Raman spectroscopy make it a valuable new vibrational spectroscopic technique.
David W. McCamant, Philipp Kukura, and Richard A. Mathies, "Femtosecond Broadband Stimulated Raman: A New Approach for High-Performance Vibrational Spectroscopy," Appl. Spectrosc. 57, 1317-1323 (2003)