Third-order nonlinear optical properties of fullerene molecules

The third- order nonlinear optical properties of two kinds of fullerenes (molecules of C60 and C70), which are solved in toluene, were studied through a degenerate four wave mixing process respectively. The third-order hyperpolarizabilities γ1111 of C70 molecule and C60 molecule are measured to be 1. 2 × 10-30esu and 4. 0 × 10-31esu, corresponding to an estimated third-order optical susceptibility x1111(3) of 2. 5 × 10-8esu and 8. 5× 10-9esu for solid-state materials, respectively. The origin of the large nonlinear optical response of fullerene family is explained successfully with the free electron model.