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

TL;DR

This paper demonstrates that transition-metal-dichalcogenide nanotriangles exhibit large, tunable second-order nonlinear optical responses due to plasmon and two-photon resonances, making them promising for nonlinear nanophotonics applications.

Contribution

It introduces the calculation of large, tunable second-order susceptibility in TMD nanotriangles, highlighting their potential for enhanced nonlinear optical processes.

Findings

$ ext{Re}[ ext{Im}] \, ext{part of } \\chi^{(2)}$ peaks near resonances

$ ext{Maximum } \\chi^{(2)}$ reaches $10^{-6}$ m/V

Resonance alignment enhances nonlinear response

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.