Giant Nonlinear Response of Monolayer MoS2 Induced by Optimal Field-Enhancement Gain Mode on the Surface of Hyperbolic Metamaterials

The electric field (EF) enhancements of resonant modes in metamaterials have been widely utilized to amplify optical response of 2D materials for advanced applications. However, for the vast majority of metamaterials, enhancing optical response of 2D materials by resonant modes seriously suffer from high loss, narrowband, and inside hot-spot (i.e., the region with strong EF enhancements). Here, the periodic hyperbolic metamaterials (PHMM) are proposed, which can provide intensive and broadband EF enhancement on top surface with low absorption, due to theirs specific hyperbolic dispersion and geometry characteristics. Moreover, it is revealed that there exists a broadband range (defined as the high field-enhancement gain (FEG) region), where nonlinear optical responses are stronger than those caused by the resonant mode. By integrating monolayer MoS2 with the PHMM, it is demonstrated that the largest enhancement of second harmonic generation occurs at wavelength of the optimal FEG mode, being as high as 22 145-times with its conversion efficiency up to 1.1 x 10(-6) W-1. The findings demonstrate giant nonlinear response of monolayer 2D materials, and establish an ideal platform for surface enhancement of light-matter interactions, opening a new way for metaoptics applications.