Second Harmonic Generation in Gapped Graphene

The second-order nonlinear optical susceptibility $\Pi^{(2)}$ for second harmonic generation is calculated for gapped graphene. The linear and second-order nonlinear plasmon excitations are investigated in context of second harmonic generation (SHG). We report a red shift and an order of magnitude enhancement of the SHG resonance with growing gap, or alternatively, reduced electro-chemical potential.Comment: 10 pages,10 figure

Theory of enhanced dynamical photo-thermal bi-stability effects in cuprous oxide/organic hybrid heterostructure

We theoretically demonstrate the formation of multiple bi-stability regions in the temperature pattern on the interface between a cuprous oxide quantum well and DCM2:CA:PS organic compound. The Frenkel molecular exciton of the DCM2 is brought into resonance with the $1S$ quadrupole Wannier-Mott exciton in the cuprous oxide by "solvatochromism" with CA. The resulting hybrid is thermalized with surrounding helium bath. This leads to strongly non-linear temperature dependence of the laser field detuning from the quadrupole exciton energy band which is associated with the temperature induced red shift of the Wannier exciton energy. Numerical up and down-scan for the detuning reveals hysteresis-like temperature distribution. The obtained \emph{multiple} bi-stability regions are at least three orders of magnitude bigger ($meV$) than the experimentally observed bi-stability in bulk cuprous oxide ($\mu eV$). The effective absorption curve exhibits highly asymmetrical behavior for the Frenkel-like (above the $1S$ energy) and Wannier-like (below the $1S$ energy) branches of the hybrid.Comment: 6 pages, 7 Figure