Chemical interface damping for propagating surface plasmon polaritons in gold nanostripes

Leakage radiation microscopy has been used to examine chemical interface damping (CID) for the propagating surface plasmon polariton (PSPP) modes of Au nanostripes-nanofabricated structures with heights of 40 or 50 nm, widths between 2 and 4 mu m, and 100 mu mlengths. Real space imaging was used to determine the propagation lengths L-SPP of the leaky PSPP modes, and back focal plane measurements generated omega vs k dispersion curves, which yield the PSPP group velocities v(g). The combination of these two experiments was used to calculate the PSPP lifetime via T-1 = L-SPP/v(g). The difference in T-1 times between bare and thiol coated nanostripes was used to determine the dephasing rate due to CID Gamma(CID) for the adsorbed thiol molecules. A variety of different thiol molecules were examined, as well as nanostripes with different dimensions. The values of Gamma(CID) are similar for the different systems and are an order-of-magnitude smaller than the typical values observed for the localized surface plasmon resonances (LSPRs) of Au nanoparticles. Scaling the measured Gamma(CID) values by the effective path length for electron-surface scattering shows that the CID effect for the PSPP modes of the nanostripes is similar to that for the LSPR modes of nanoparticles. This is somewhat surprising given that PSPPs and LSPRs have different properties: PSPPs have a well-defined momentum, whereas LSPRs do not. The magnitude of Gamma(CID) for the nanostripes could be increased by reducing their dimensions, principally the height of the nanostructures. However, decreasing dimensions for the leaky PSPP mode increases radiation damping, which would make it challenging to accurately measure Gamma(CID). Published under license by AIP Publishing.