Nonlinear Response Of Graphene Research Articles

All-optical hybrid plasmonic waveguide modulator based on Kerr nonlinearity of graphene

Compared with previous graphene-based optical modulators that can be tuned electrically with the Fermi level, all-optical modulators have attracted much attention due to their ultrafast and broadband response (bandwidth ≈ 200 GHz). To take advantage of hybrid plasmonic waveguides (HPWs) and the nonlinear response of graphene, we proposed all-optical absorption and phase modulators at the wavelength of 1.55 μm and EF = 0.1 eV. The modulators consist of two different geometries, graphene on an HPW and graphene on a double-slot HPW. Compared with the previous graphene-based all-optical modulators, our design has a short-effective waveguide length and higher modulation depth. This was achieved through the incomparable integration of HPW optics and graphene photonics that can be used to design chip-scale, compact, and high-efficiency all-optical modulators.

Impact of nitrogen doping on the linear and nonlinear terahertz response of graphene

It is well known that impurities play a central role in the linear and nonlinear response of graphene at optical and terahertz frequencies. In this work, we calculate the bands and intraband dipole connection elements for nitrogen-doped monolayer graphene using a density functional tight-binding approach. Employing these results, we calculate the linear and nonlinear response of the doped graphene to terahertz pulses using a density-matrix approach in the length gauge. We present the results for the linear and nonlinear mobility as well as third-harmonic generation in graphene for adsorbed and substitutional nitrogen doping for a variety of doping densities. We show that the conduction bands are more parabolic in graphene structures with substitutional nitrogen doping than for those with adsorbed nitrogen. As a result, substitutional doping has a greater impact on the terahertz mobility and nonlinear response of graphene than adsorbed nitrogen does.

Nonlinear electromagnetic response of graphene: frequency multiplication and theself-consistent-field effects

Graphene is a recently discovered carbon-based material with unique physical properties.This is a monolayer of graphite, and the two-dimensional electrons and holes in it aredescribed by the effective Dirac equation with a vanishing effective mass. As a consequence,the electromagnetic response of graphene is predicted to be strongly nonlinear. Wedevelop a quasi-classical kinetic theory of the nonlinear electromagnetic response ofgraphene, taking into account the self-consistent-field effects. The response ofthe system to both harmonic and pulse excitation is considered. The frequencymultiplication effect, resulting from the nonlinearity of the electromagnetic response,is studied under realistic experimental conditions. The frequency upconversionefficiency is analyzed as a function of the applied electric field and parameters of thesamples. Possible applications of graphene in terahertz electronics are discussed.