Nonlinear optical properties of fullerenes

Nonlinear optical properties of fullerenes, studied by transverse second-harmonic and wave-dispersed third-harmonic generation, are reviewed and discussed. The origin of second-harmonic generation in C60, as well as its absence, at the limit of dielectric breakdown in C70 thin films is also discussed. The observed third-harmonic generation χ(3) susceptibility dispersion in both lower fullerenes C60 and C70 is described in terms of the three-level model. In both molecules the two-photon level is found to lie below the one-photon transition level, in good agreement with theoretical calculations and other experimental determinations.