Measurement method of nonresonant third-order susceptibility by using off-resonant coherent anti-Stokes Raman spectroscopy.
Nonresonant third-order susceptibilities (χ(nr)) of N(2) and Ar gases by using an off-resonant coherent anti-Stokes Raman spectroscopy of the N(2) Q branch, whose spectral profile is highly sensitive to the value of χ(nr), have been measured to demonstrate the possibility of the present method. The χ(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 (× 10(-18)cm(3) /erg/amagat), respectively. These values are in good agreement with those of previous studies. The off-resonant spectra were theoretically calculated by using the Raman linewidth given by a modified exponential gap model, and they were compared with the experimental ones to determine χ(nr). The effects of uncertainties of the Raman linewidth of the N(2) Q branch on the determination of χ(nr) were investigated by changing the parameters in the modified exponential gap model. The determined χ(nr) value changed by only 0.05% with 50% change of the Raman linewidth. The potential advantages of this method are no requirements of high spectral resolution measurements, no accurate Raman linewidth data for each experimental condition, and no optical delay between pump beams.
Akihama
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K
Asai
T
T
Yamazaki
S
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