ULTRAHIGH SENSITIVITY STIMULATED RAMAN GAIN SPECTROSCOPY

Using a synchronously pumped mode-locked dye laser system, the authors have obtained a factor of 300 improvement in signal to noise ratio (S/N) over previous CW experiments using stimulated Raman gain spectroscopy, and achieved an S/N equals 200,000 for a 1 s integration time in bulk benzene. This result confirms the sensitivity of the picosecond Raman gain approach and would allow the detection of a monolayer using a pump intensity of 100 MW/cm**2.