Tailoring cavity coupled plasmonic substrates for SERS applications.

Surface-enhanced Raman spectroscopy (SERS) has been effectively used in biosensing applications due to its high sensitivity and specificity. Enhancing the coupling of light into plasmonic nanostructures can lead to engineered SERS substrates with improved sensitivity and performance. In the current study, we demonstrate a cavity-coupled structure that assists in enhancing the light-matter interaction leading to an improved SERS performance. Using numerical simulations, we demonstrate that the cavity-coupled structures can either enhance or suppress the SERS signal depending on the cavity length and the wavelength of interest. Furthermore, the proposed substrates are fabricated using low-cost large-area techniques. The cavity-coupled plasmonic substrate consists of a layer of gold nanospheres on an Indium Tin oxide (ITO)-Au-glass substrate. The fabricated substrates exhibit nearly a 9 times improvement in SERS enhancement as compared to the uncoupled substrate. The demonstrated cavity-coupling approach can also be used for enhancing other plasmonic phenomena like plasmonic trapping, plasmon-enhanced catalysis, and non-linear signal generation.