Multiresonant nanostructures for surface-enhanced coherent anti-Stokes Raman spectroscopy

Coherent anti-Stokes Raman scattering (CARS) is a well-known tool in molecular spectroscopy. In this work we combine CARS with surface plasmon enhancement on a periodic metasurface. The proposed metal-insulator-grating nanostructured geometry supports three resonances, as required by the CARS scenario. We briefly discuss the knobs to tune these resonances, so that the spectral distance between them could eventually match the Raman shift of selected molecules. In this report, we focus on one particular tuning possibility that is available after the metasurface fabrication. With each of the resonances providing field enhancement by more than 2 orders of magnitude, we achieve CARS signal enhancement factors of the order of 1018.