No abstract

We report unambiguous observation of spatial self-phase modulation (SSPM) in a dispersive suspension of graphite flakes. This coherent nonlinear optical effect in bulk graphite is found to be broadband and large, with a third-order nonlinear susceptibility χ(3) of 2.2 × 10−9 esu (i.e., 3.1 × 10−17 m2/V2 in SI units) at 532 nm excitation. Comparison with other carbon allotropes shows that this value is 5 × 107 times higher than that of C60 but ∼50 times lower than that of graphene, fully exhibiting the electronic origin of SSPM.