Measurement of the resonant third-order nonlinear susceptibility of C60 by nondegenerate four-wave mixing

Ten orders of magnitude discrepancy exists in the literature for the third-order nonlinear susceptibilities of C60. To elucidate the problem, we used four-wave mixing to measure the resonant nonlinear optical response to C60 by fitting the line-shapes resulting from interference between a standard and sample. High accuracy is achieved because absolute intensity measurements are not necessary. The measurements show the nonlinearity is much lower and can only constrain the C60 second-order molecular hyperpolarizability to 3.7 × 10−35 esu. This limit is only 57× as high as that of benzene and is lower than any value reported in the literature.