  Surface plasmon polaritons (SPPs) are locally excited at silver surfaces
using (~100) nm-sized nanodiamonds (NDs) with multiple nitrogen-vacancy (NV)
centers (~400). The fluorescence from an externally illuminated (at 532 nm) ND
and from nearby NDs, which are not illuminated but produce out-of-plane
scattering of SPPs excited by the illuminated ND, exhibit distinctly different
wavelength spectra, showing short-wavelength filtering due to the SPP
propagation loss. The results indicate that NDs with multiple NV centers can be
used as efficient sub-wavelength SPP sources in planar integrated plasmonics
for various applications.
