Evanescent-wave excitation of surface-enhanced Raman scattering substrates by an optical-fiber taper

We present a way of guiding light to planar surface-enhanced Raman scattering (SERS) substrates by using evanescent-wave coupling. Using nanostructured chalcogenide glass-based SERS substrates, we experimentally show the incident-angle dependence of plasmon resonances of the SERS substrates, demonstrating strong resonances at large incident angles. This allows the evanescent-wave excitation of SERS substrates through tapered optical fibers. Experiments show that fiber-taper-excited SERS substrates exhibit a significant enhancement of the Raman spectra of Rhodamine-6G analyte molecules. This configuration forms the basis of fiber-optic-based, reproducible, highly compact, and sensitive SERS systems.