Plasmon-enhanced Raman spectroscopy to estimate near-electric-field enhancement

Near-electric-field enhancement induced by the nanoscale light-matter interactions has been advancing plasmonics such as plasmon-enhanced spectroscopy, leading to a linear scaling of the observed far-field spectral signals in theory. However, the contributions of an additionally existed chemical effect to the propagated optical signals from near- to far-field are commonly irregular. Here, inspired by the physical origin of surface-enhanced Raman spectroscopy (SERS), we experimentally map the far-field signals on the near-field properties through utilizing the purely electromagnetic coupled plasmon-molecule interactions of particular Raman probe molecules, thereby enabling the precise estimation for the enhanced local electric field in the subwavelength dimension only with the SERS intensity. This work can truly accelerate the translation of SERS into a quantitative analysis tool, but also lays the foundation of an intuitive probing into the plasmonic excited field employing plasmon-enhanced spectroscopic techniques.