Continuous-wave coherent Raman spectroscopy via plasmonic enhancement for picomolar detection (Conference Presentation)

We report a successful combination of stimulated Raman spectroscopy (SRS) and surface-enhanced Raman scattering (SERS) using cw laser sources and gold/silica nanoparticles with embedded reporter molecules. We describe the preparation method for our gold/silica nanoparticles as well as the effect of probe wavelength, pump and probe power, polarization and sample concentration on the cwSESRS signal. Altogether, a stable 10-12 orders of magnitude enhancement in the stimulated Raman signal is achieved because of the amplification of both pump and probe beams, leading us to detect pico-molar nanoparticle concentrations. The coherent Raman spectra matches the incoherent conventional Raman spectra of the reporter molecules. Unlike conventional incoherent SERS, this approach offers several advantages including improved trace analyte detection, the low cost accessibility of cw sources, and a coherent stimulated signal of microwatt intensities for applications such as Molecular Holography.