Third-order nonlinear optical properties of C-60 CT complexes with aromatic amines

We have investigated third-order nonlinear optical properties of charge-tra nsfer (CT) complexes of C-60 with various aromatic amines with different io nization potentials. The third-order nonlinear optical susceptibility \chi( (3))\ measured by degenerate four-wave mixing shows a resonant enhancement at the absorption band due to the CT transition. We have found that the sec ond hyperpolarizability gamma of CT complexes increases with an increase of the oscillator strength, which depends on the ionization potential. The hi ghest hyperpolarizability among CT complexes studied here is 5.2 x 10(-28) esu for C-60/aniline CT complex.