Theory of non-linear optical response in C60, C70, and higher fullerenes

Non-linear optical properties in the fullerene C60 and the extracted higher fullerenes, C70, C76, C78 and C84, are theoretically investigated. Magnitudes of off-resonant third-order susceptibility are calculated by the exciton formalism and the sum-over-states method. We find that optical non-linearities of higher fullerenes are a few times larger than those of C60. The magnitudes of the non-linearity tend to increase as the optical gap decreases in higher fullerenes. Relations with experiments are discussed.