SERS Detection via Individual Bowtie Nanoantennas Integrated in Si3N4 Waveguides

Plasmonic resonances in metallic nanostructures provide a way for broadband enhanced light–matter interaction in subwavelength regions, which can be used to boost a variety of physical phenomena, notably including Raman scattering. Such nanostructures can be integrated on silicon chips and driven via dielectric waveguides, which may improve the performance of photonic integrated circuits in terms of foot-print, efficiency, sensitivity or power consumption, amongst other figures of merit. Here, we show that an isolated plasmonic nanoantenna can be efficiently integrated into a silicon nitride waveguide to detect surface-enhanced Raman scattering (SERS) spectra from molecular monolayers. We study numerically and experimentally two different configurations, both enabling the recording of Raman spectra at the output: nanoantenna on top of the waveguide and nanoantenna inserted in a subwavelength gap built in the waveguide. We also compare both configurations, which may pave the way toward massive integration of SERS devices for lab-on-a-chip applications.