Using a Fabry–Perot Cavity to Augment the Enhancement Factor for Surface-Enhanced Raman Spectroscopy and Tip-Enhanced Raman Spectroscopy

We propose the use of Fabry–Perot cavities as a means to augment the enhancement factor in surface-enhanced Raman spectroscopy (SERS) and tip-enhanced Raman spectroscopy (TERS) experiments by optical interference. Using both clean-room and bench-top fabrication approaches, we demonstrate that such a design can be readily realized and provides an additional 12× SERS enhancement and 5× TERS enhancement, in good agreement with expectations from electromagnetic modeling. The mechanism of optical interference enhancement is of far-field nature and is independent of the enhancement mechanisms relying on plasmonic and molecular resonances. Therefore, the Fabry–Perot cavity substrate can be applied generally without material and molecular limitations. The Fabry–Perot cavity structure provides enhancement at large incidence angles away from the surface normal, particularly suitable for low-light Raman measurements with side illumination.