Remote plasmon-mediated SERS of single-walled carbon nanotubes via silver nanowire plasmonic waveguides

The remote plasmon-mediated surface enhanced Raman scattering (SERS) of single-walled carbon nanotube (SWNT) quantum emitters was realized through propagating surface plasmon polaritons (SPPs) in silver nanowire (Ag-NW) plasmonic waveguides of varying lengths (8-12 µm) and geometries (straight and bent). Although the propagation length of SPPs is ∼4.0 µm, the surface-enhanced Raman scattering (SERS) of SWNT is remotely excited at distal (∼12 µm) locations on the nanowire. This observation demonstrates efficient, low-loss energy transfer mediated by plasmonic coupling to the electronic transitions of the SWNTs. The efficient remote SPP coupling is evidenced by a two-order-of-magnitude increase in the enhancement factor compared with local excitations. Finite difference time-domain (FDTD) simulations show the development of a helical SPP propagation profile in Ag-NW, which results from the coherent superposition of three low-order SPP fundamental modes that emerge at incident polarization angles (0° < θ < 90°) of the electromagnetic field with respect to the long axis of the nanowire. These findings establish Ag-NWs as highly efficient nanoscale optical antennas, facilitating the distal optical imaging and spectroscopic characterization of quantum emitters. This architecture provides a robust platform for the integration of individual quantum emitters within on-chip plasmonic circuitry.