Directional emission of surface-enhanced Raman scattering based on a planar-film plasmonic antenna

A planar-film plasmonic antenna for surface-enhanced Raman scattering (SERS) with good emission directivity (divergence angle < 3°) was realized on a Kretschmann prism configuration with Raman-active analytes as emitters. The simulated results of finite-difference time-domain method show the emission efficiency, the directivity and the gain of the planar-film antenna were expected to be 50%, 300 and 22 dB, respectively. Angle-resolved spectroscopy was used to characterize its properties in SERS. The experimental results show that the SERS signal of analytes was remarkably enhanced when a laser excited this planar-film plasmonic antenna at the resonance angle. Meanwhile, the radiation of SERS was concentrated in a small region in space. The planar-film antenna with high gain coefficient can be a promising light harvesting and emitting device. The good emission directivity allows high collection efficiency. This advantage opens up interesting prospects in the applications for plasmon-enhanced spectroscopy and single-phonon detections.