Graphene and few-layer graphite probed by second-harmonic generation: Theory and experiment

Abstract

We have measured second-harmonic generation ͑SHG͒ from graphene and other graphitic films, from two layers to bulk graphite, at room temperature; all samples are mounted on a 300 nm oxide layer of a Si͑001͒ substrate. With 800 nm, 150 fs fundamental pulses, the anisotropic response was recorded for combinations of p-, sand nd diagonally polarized fundamental and second-harmonic beams as the samples were rotated about their normal. Graphene samples display SHG signatures only slightly different from that of the bare substrate which shows SHG with fourfold rotational symmetry. All other layered systems show threefold symmetry, although the ratio of isotropic to anisotropic response varies with the number of layers. A model based on linear light propagation in layered media with interface dipole and bulk quadrupole SHG sources is presented for the analysis. We show that data from all layered samples can be understood in terms of well-known linear optical properties, the SHG response of the bare substrate and four independent, complex nonlinear dipole susceptibility tensor elements of the graphene/air interface.

Third harmonic generation in graphene and few-layer graphite films

“…Graphene flakes mounted on oxidized Si substrates have produced second harmonic signals, but the signal from the graphene is weaker than that from the substrate [37,41]. For bilayers and fewlayer graphite samples similarly mounted, the second harmonic signal is dominated by the graphite films, but it is weak [37,41].…”

“…Graphene flakes mounted on oxidized Si substrates have produced second harmonic signals, but the signal from the graphene is weaker than that from the substrate [37,41]. For bilayers and fewlayer graphite samples similarly mounted, the second harmonic signal is dominated by the graphite films, but it is weak [37,41].In addition, the third order nonlinear optical responses associated with saturable absorption of graphene [42][43][44], few-layer graphite films [10,[43][44][45][46][47][48][49][50][51][52][53][54][55][56], and suspensions of graphene flakes [57] have been measured and timeresolved using a variety of pump-probe configurations. Typically, in these experiments, the interband absorption of the pump pulse produces nonequilibrium electron and hole populations, which subsequently relax by carrier-carrier scattering, phonon emission, diffusion and recombination.…”

“…By comparison, for multilayer graphite, the bulk can contribute, depending upon the stacking arrangement [37]. Indeed, second harmonic generation has been investigated both theoretically [38][39][40] and experimentally [37,41] in graphene and few-layer graphite films. Graphene flakes mounted on oxidized Si substrates have produced second harmonic signals, but the signal from the graphene is weaker than that from the substrate [37,41].…”

“…Indeed, second harmonic generation has been investigated both theoretically [38][39][40] and experimentally [37,41] in graphene and few-layer graphite films. Graphene flakes mounted on oxidized Si substrates have produced second harmonic signals, but the signal from the graphene is weaker than that from the substrate [37,41]. For bilayers and fewlayer graphite samples similarly mounted, the second harmonic signal is dominated by the graphite films, but it is weak [37,41].…”

Optical Third-Harmonic Generation in Graphene

“…The potential of graphene as a functional nonlinear optical material has engendered many nonlinear optical studies. Second-order-nonlinear optical effects, particularly second-harmonic generation (SHG), have been investigated theoretically [22][23][24][25] and experimentally [22,26]. Because ideal freestanding monolayer graphene is centrosymmetric, its second-order nonlinear response vanishes within the dipole approximation [24].…”