Hybrid metasurface for broadband enhancing optical absorption and Raman spectroscopy of graphene

A wafer-scale, hybrid metasurface consisting of randomly-distributed silver nanoparticles and silver substrate separated by a dielectric spacer is reported to realize the enhancement of optical absorption and Raman spectroscopy of graphene. Induced by the surface plasmon resonance, strong localized optical field and broadband absorption from the designed hybrid metasurface are achieved at visible frequencies. As a result, with graphene sheet transferred on the top of the metasurface, the absorption of graphene is remarkably improved across the entire visible region and its signal of surface enhanced Raman scattering is boosted more than 50-fold than that of single layer silver nanoparticles without silver substrate. We envision this lithography-free, hybrid metasurface would be a promising candidate as a platform for the optoelectronic applications of ultrathin two-dimensional materials. (C) 2017 Optical Society of America