External seeding of stimulated Raman scattering in microdroplets

External seeding of stimulated Raman scattering (SRS) in microdroplets is achieved by light injection into the droplet at the Raman-shifted frequency. Two implementations permit observation of the seeding effect. First, a broadband seed laser (~2 nm FWHM) is used to spectrally discriminate the elastically scattered seed light from the narrow-linewidth SRS. Second, a crossed analyzer is used to reduce by several orders of magnitude the intensity of the detected elastically scattered seed laser, preventing saturation of the detector. Seeding of SRS in microdroplets is effective in enhancing the signal from weak-gain Raman modes but does not significantly increase the SRS intensity from strong-gain Raman modes.