Abstract
Abstract Monolayer transition metal dichalcogenides (TMDs) possess large second-order nonlinear responses due to the broken inversion symmetry, which can extend their intriguing applications in nonlinear nanophotonics and optoelectronics. However, the atomic thickness of monolayer TMDs severely decreases the interaction length with free light with respect to bulk materials, leading to rather low second-harmonic generation (SHG) conversion efficiency. Here, we demonstrate a hybrid structure consisting of a monolayer MoS2 on a suspended perforated silver film, on which the SHG signal emitted from the monolayer MoS2 is enhanced by more than three orders of magnitude at room temperature. The pronounced SHG enhancement is attributed to the distinct electric field amplification nearby the nanoholes, which is induced by the symmetric surface plasmon polaritons (SPPs) existing in the ultrathin suspended silver grating. Our results reported here may establish the substrate-free engineering of nonlinear optical effects via plasmonic nanostructures on demand.
Highlights
Two-dimensional (2D) atomic crystals have attracted a tremendous amount of interest in science due to their unique physical properties and potential applications when the thickness is down to an atomic layer [1,2,3]
The pronounced second-harmonic generation (SHG) enhancement is attributed to the distinct electric field amplification nearby the nanoholes, which is induced by the symmetric surface plasmon polaritons (SPPs) existing in the ultrathin suspended silver grating
We demonstrate the symmetric SPP enhanced SHG of monolayer MoS2 on a suspended transition metal dichalcogenides (TMDs)/ultrathinAg-film hybrid structure with a rational designed periodic hole array
Summary
Two-dimensional (2D) atomic crystals have attracted a tremendous amount of interest in science due to their unique physical properties and potential applications when the thickness is down to an atomic layer [1,2,3]. The hybrid plasmonic structure consisting of nonlinear nanomaterial and metal film can achieve the highly efficient SHG emission due to plasmon-assisted enhanced light–matter interaction [28,29,30] Localized surface plasmon, such as gap plasmons excited in the nanoparticle/dielectric film/metallic film [31] or metal/ dielectric/metal nanostructures [32, 33], possesses the extremely strong electromagnetic field, which can enhances the interaction between the TMDs and free light. Random dispersion of metallic nanoparticle leads to the blocking and nonuniformity of light emission from TMDs. Surface plasmon polaritons (SPPs) can produces the homogeneous strong electromagnetic field in the surface of periodic structures, which can efficiently enhance the SHG emission of monolayer TMDs in the vicinity [34, 35]. Our results provide a way to tailor the nonlinear optical properties of monolayer TMDs, with potential applications for on-chip programmable nonlinear photonic devices
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