▎ 摘　　要

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 chi((3)) of 2.2 x 10(-9) esu ( i.e., 3.1 x 10(-17) m(2)/V-2 in SI units) at 532nm excitation. Comparison with other carbon allotropes shows that this value is 5 x 10(7) times higher than that of C-60 but similar to 50 times lower than that of graphene, fully exhibiting the electronic origin of SSPM. Published by AIP Publishing.