Experimental determination of nonlinear constants for self-focusing and stimulated Raman emission

Abstract

The nonlinearities characteristic of a liquid medium subjected to a high intensity laser beam were investigated experimentally with the main thrust of the investigation being a study of the self-focusing effect and stimulated Raman scattering in eleven organic liquids. The specific objective was to measure the threshold power density for the onset of self-focusing and stimulated Raman emission for four self-focusing lengths (cell lengths), the Stokes power output for each self-focusing length, and the Stokes lines emitted by each liquid under study. The second order index of refraction was computed from this data for each of the subject liquids which were: benzene, 4.9 x 10^-12 ; acetone, 0.14 x 10^-12 ; carbon disulfide, 45.00 x 10^-12 ; cyclohexane, 0.32 x 10^-12 ; toluene, 3.50 x 10^-12 ; anisole, 3.10 x 10^-12 ; benzaldehyde, 8.00 x 10^-12 ; ethylbenzene, 3.80 x 10^-12 ; iodobenzene, 16.00 x 10^-12 ; isoprene, 4.00 x 10^-12 ; and p-xylene, 3.60 x 10^-12. The critical power for self-focusing was also determined for each of these liquids. The second order index of refraction for benzene is a previously reported figure, and that liquid was used as a basis of comparison for the others. With the exception of toluene and carbon disulfide, the other values have not been previously reported. Threshold data on benzene, toluene, and carbon disulfide for a cell length of 30 centimeters have been previously reported. Data on the other liquids for cell lengths other than 20 centimeters have not been previously reported. The critical power for self-focusing has been previously reported only on benzene, toluene, and nitrobenzene. Stokes lines on anisole, benzaldehyde, and p-xylene have not been previously reported. Threshold data are considered accurate to within ±13%; the second order index of refraction to within ±16%; and the measurement of the spectral lines to within ±0.5 angstrom.