Figure 1:

Enhancement of SERS signal with the help of an auxiliary QE.

(A) The setup we consider for a double resonance scheme. A gold MNP dimer manifests two plasmon modes, depicted in (B). A Raman-active molecule (blue), placed close to the dimer gap, produces the Stokes signal. A QE (purple) is positioned in the vicinity of the gap and interacts with the $a^R$ plasmon mode, into which the Stokes signal emerges. (Details can be found in the text.) The presence of the QE does not change the intensity on the Raman-active molecule but enhances the Stokes signal.