Surface-enhanced coherent anti-Stokes Raman scattering at metal-metal and metal-dielectric nanojunctions

Combining coherent anti-Stokes Raman scattering(CARS) with the surface-enhancement effects afforded by plasmonic resonances can probe molecular vibrations down to the single-molecule limit. Recent advances have been encouraging, yet, there are difficulties associated with the reproducibility of these measurements. Here, we present controllable and repeatable wide-field surface-enhanced CARS (SECARS) measurements at metal film-metal particle and metal film-dielectric particle nanojunctions. We demonstrate CARS signal at metal-metal junctions using the lowest average power densities to date. We also show reproducible SECARS measurements at metal-dielectric heterojunctions, opening the possibility of SECARS sensors not constrained by lossy and fragile metallic antenna systems.