Propagating and Localized Surface Plasmon Co-Enhanced Raman Scattering Based on a Waveguide Coupling Surface Plasmon Resonance Structure

Abstract

We propose a waveguide-coupled surface plasmon resonance (WCSPR) structure with MgF2 as the waveguide layer to enhance Raman scattering. The WCSPR was a five-layer resonance structure composed of prism/Ag film/MgF2 film/outer Ag film layers. The electromagnetic field was stronger with the WCSPR structure than with a traditional SPR structure. Furthermore, localized and propagating surface plasmon co-enhanced Raman scattering of 4-mercaptopyridine was observed on the WCSPR/4-Mpy/silver-nanoparticle sandwich structure. The most effective coupling of the localized and propagating surface plasmons resulted in a 60-fold enhancement in the signal intensity relative to that obtained with a conventional SPR structure. The enhancement factor of the WCSPR/4-Mpy/silver-nanoparticle configuration was 3.6 × 107.