Tunable plasmon-enhanced second-order optical nonlinearity in transition metal dichalcogenide nanotriangles

Abstract

The development of nanomaterials with a large nonlinear susceptibility is essential for nonlinear nanophotonics. We show that transition-metal-dichalcogenide (TMD) nanotriangles have a large effective second-order susceptibility [${\chi }^{(2)}$] at mid-infrared to near-infrared frequencies owing to their broken centrosymmetry. ${\chi }^{(2)}$ is calculated within the density-matrix formalism that accounts for dissipation and screening. ${\chi }^{(2)}$ peaks in the vicinity of both two-photon resonances (specified by the geometry) and plasmon resonances (tunable via the carrier density). Aligning the resonances yields the values of ${\chi }^{(2)}$ as high as $10^{-6}$ m/V. These findings underscore the potential of TMD nanotriangles for nonlinear nanophotonics, particularly second-harmonic generation.

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