Third-Order Nonlinear Optical Properties of C60 CT Complexes with Aromatic Amines

We have investigated third-order nonlinear optical properties of charge-transfer (CT) complexes of C60 with various aromatic amines with different ionization potentials. The third-order nonlinear optical susceptibility |χ(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 second hyperpolarizability γ of CT complexes increases with an increase of the oscillator strength, which depends on the ionization potential. The highest hyperpolarizability among CT complexes studied here is 5.2 × 10-28 esu for C60/aniline CT complex.