Amplified Spontaneous Emission enhanced Forward Stimulated Raman Scattering in dye solutions

We study forward stimulated Raman emission from weakly fluorescent dye 4'-diethylamino-N-methyl-4-stilbazolium tosylate (DEST) in 1,2,dichloroethane solution excited by a 28 ps, 532 nm Nd: YAG laser. Neat 1, 2, dichloroethane emits the first Stokes line at 631 nm with a spectral width of 1.6 nm corresponding to a Raman shift of 2956 per cm. We observe reduction of spectral width with the addition of DEST in 1, 2, dichloroethane solution. The single pass conversion efficiency for forward Raman emission is as high as 20 percent in a 1 cm path length sample. The pulse duration of forward stimulated Raman emission measured by a third order autocorrelation technique is 10 ps in neat 1, 2, dichloroethane, whereas it is nearly 3 ps for 0.04 mM of DEST solution.