MEASUREMENT METHOD OF NONRESONANT 3RD-ORDER SUSCEPTIBILITY BY USING OFF-RESONANT COHERENT ANTI-STOKES-RAMAN SPECTROSCOPY

Nonresonant third-order susceptibilities (chi nr) of N-2 and Ar gases by using an off-resonant coherent anti-Stokes Raman spectroscopy of th e N-2 and branch, whose spectral profile is highly sensitive to the va lue of (chi nr), have been measured to demonstrate the possibility of the present method. The (chi nr) of N-2 and Ar using the off-resonant coherent anti-Stokes Raman spectroscopy were 8.4 +/- 0.2 and 9.7 +/- 0 .8 (x(10-18) cm(3)/erg/amagat), respectively. These values are in good agreement with those of previous studies. The off-resonant spectra we re theoretically calculated by using the Raman linewidth given by a mo dified exponential gap model, and they were compared with the experime ntal ones to determine (chi nr). The effects of uncertainties of the R aman linewidth of the N-2 and branch on the determination of (chi nr) were investigated by changing the parameters in the modified exponenti al gap model. The determined (chi nr) value changed by only 0.05% with 50% change of the Raman linewidth. The potential advantages of this m ethod are no requirements of high spectral resolution measurements, no accurate Raman linewidth data for each experimental condition, and no optical delay between pump beams.