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 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.