Silent-enhancement of multiple Raman modes via tuning optical properties of graphene nanostructures

Abstract: Raman scattering signal can be enhanced through localization of incident field into sub-wavelength hot-spots through plasmonic nano-structures (Surface-enhanced Raman scattering-SERS). Recently, further enhancement of SERS signal via quantum objects are proposed by [1] without increasing the hot-spot intensity (\textit{silent-enhancement}) where this suggestion prevents the modification of vibrational modes or the breakdown of molecules. The method utilizes path interference in the non-linear response of Stokes-shifted Raman modes. In this work, we extend this phenomenon to tune the spectral position of \textit{silent-enhancement} factor where the multiple vibrational modes can be detected with a better signal-to-noise ratio, simultaneously. This can be achieved in two different schemes by employing either (i) graphene structures with quantum emitters or (ii) replacing quantum emitters with graphene spherical nano-shell in \cite{Postaci2018}. In addition, the latter system is exactly solvable in the steady-state. These suggestions not only preserve conventional non-linear Raman processes but also provide flexibility to enhance (silently) multiple vibrational Raman modes due to the tunable optical properties of graphene.