Continuous-wave stimulated Raman scattering was observed in 11–13-µm-diameter benzene and toluene microdroplets at pump intensities as low as 8 and 24 kW/cm2, respectively. Low thresholds were achieved by exploiting simultaneous pump and Stokes wave resonance in the droplets and Raman gains that were cavity QED enhanced ~50 times with respect to bulk liquid values. Based on a photon-state conservation argument, the cavity gain enhancement factor may be approximated by the ratio of the spectral spacing between resonant modes of the same order to that of the homogeneous Raman linewidth. This relation appears to be consistent with the relative experimental behavior of benzene, ethanol, and toluene.
H.-B. Lin, J. D. Eversole, and A. J. Campillo, "Continuous-wave stimulated Raman scattering in microdroplets," Opt. Lett. 17, 828-830 (1992)