Large difference of ultrafast third-order optical response between two C60 derivatives

The ultrafast third-order optical nonlinearity of two C60 derivatives was measured by using the optical Kerr effect (OKE) at 830 nm wavelength, with laser pulse duration of 115 fs. Tremendous difference in OKE responses was observed due to the different attached bond site. For the [5,6]azafulleriod, a supposition was suggested and the large OKE response of solution subtracting from the contribution of solvent was obtained and its second-order hyperpolarizability γ was deduced as large as 2.9 × 10−31 esu, which is three orders of magnitude larger than the value of C60. While, for the [6,6]azafullerene, no any enhancement is observed in comparing with that of C60.