▎ 摘　　要

We observe optical third harmonic generation from graphene and few-layer graphite flakes produced by exfoliation. The emission scales with the cube of the intensity of the incident near-infrared femtosecond pulses and has a wavelength that is one-third of the incident wavelength, both consistent with third harmonic generation. We extract an effective third-order susceptibility for graphene that is on the order of 10(-16) m(2)/V-2, which is comparable to that for materials that are resonantly excited, but larger than for materials that are transparent at the fundamental and third harmonic wavelengths. DOI: 10.1103/PhysRevB.87.121406