Broadband Plasmon-Enhanced Four-Wave Mixing In Monolayer Mos2

Two-dimensional transition-metal dichalcogenide monolayers have remarkably large optical nonlinearity. However, the nonlinear optical conversion efficiency in monolayer transitionmetal dichalcogenides is typically low due to small light-matter interaction length at the atomic thickness, which significantly obstructs their applications. Here, for the first time, we report broadband (up to similar to 150 nm) enhancement of optical nonlinearity in monolayer MoS2 with plasmonic structures. Substantial enhancement of four-wave mixing is demonstrated with the enhancement factor up to three orders of magnitude for broadband frequency conversion, covering the major visible spectral region. The equivalent third-order nonlinearity of the hybrid MoS2-plasmonic structure is in the order of 10(-17) m(2)/V-2, far superior (similar to 10-100-times larger) to the widely used conventional bulk materials (e.g., LiNbO3, BBO) and nanomaterials (e.g., gold nanofilms). Such a considerable and broadband enhancement arises from the strongly confined electric field in the plasmonic structure, promising for numerous nonlinear photonic applications of two-dimensional materials.