Enhanced Optical Second-Harmonic Generation from the Current-Biased Graphene/SiO₂/Si(001) Structure

Abstract

We find that optical second-harmonic generation (SHG) in reflection from a chemical-vapor-deposition graphene monolayer transferred onto a SiO2/Si(001) substrate is enhanced about 3 times by the flow of direct current electric current in graphene. Measurements of rotational-anisotropy SHG revealed that the current-induced SHG from the current-biased graphene/SiO2/Si(001) structure undergoes a phase inversion as the measurement location on graphene is shifted laterally along the current flow direction. The enhancement is due to current-associated charge trapping at the graphene/SiO2 interface, which introduces a vertical electric field across the SiO2/Si interface that produces electric field-induced SHG. The phase inversion is due to the positive-to-negative polarity switch in the current direction of the trapped charges at the current-biased graphene/SiO2 interface.

Third-order nonlinearity of graphene: Effects of phenomenological relaxation and finite temperature

“…Yet, they show a strong and complicated photon-energy dependence in pristine graphene because resonant transitions always exist for any photon energy, due to the vanishing gap and the presence of free carriers, leading to some similarities with a metal film [33]. These complexities have been observed in experimental studies of parametric frequency conversion [31], THG [32,33,35], Kerr effects, and two photon absorption [3,[36][37][38], two-color coherent control [39][40][41], and SHG [17][18][19][20][21]27] in graphene.…”

Numerical study of the optical nonlinearity of doped and gapped graphene: From weak to strong field excitation

“…(19) and (20) work for a field dependent conductivity σ nl (ω c ); further, since we extract σ nl (ω c ) from a numerical calculation with the incident field in Eq. (11) we can identify…”

“…At present, both experiments and theories are still at an early stage. Experiments have investigated parametric frequency conversion [4], third harmonic generation (THG) [10][11][12], Kerr effects and twophoton absorption [6,[13][14][15], second harmonic generation (SHG) [16][17][18][19][20][21], and two-color coherent control [22][23][24], and extracted some third order susceptibilities of graphene which are orders of magnitude higher than that of normal metal and semiconductor materials. However, the dependence of the nonlinearity on chemical potential, temperature, and the excitation frequency have not been systematically measured.…”

Observation of optical second harmonic generation from suspended single-layer and bi-layer graphene

“…[5][6][7][8][9][10][11] Nonlinear response of graphene family has also been experimentally investigated recently. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] The intensity of optical third harmonic generation was found to be notable. 25,27 Remarkable efficiency of four wave mixing 19,26 and two photon absorption 13,15,18,20 were also observed in graphene, revealing that graphene has good applications such as optical limiting and saturable absorber in laser cavity.…”