Ultrahigh-resolution stimulated Raman phase shift spectroscopy

We present a Raman spectroscopic technique, termed stimulated Raman phase shift (SRPS) spectroscopy. SRPS spectroscopy depends on the ultrahigh-resolution detection of the Stokes laser phase shift (Δ φ ) induced by stimulated Raman scattering. To evaluate the performance of SRPS spectroscopy, SRPS spectra of neat dimethyl sulfoxide were measured. The apparent full width at half maximum (FWHM) of the processed SRPS spectral feature was less than 0.00002 cm -1 , corresponding to a Raman peak position determination precision at the 10 −5  cm -1 level. The detection limit for pump power was lower than 0.85 mW, and the standard deviations of the measured Raman shift and intensity were less than ±0.078 cm -1 and ±0.23 rad/cm -1 , respectively. The developed SRPS spectroscopy can resolve individual Raman modes, which cannot be directly distinguished in stimulated Raman gain spectra or their derivative.