Surface Plasmon Polaritons (SPPs) are coherent electron motions that propagate at metal-dielectric interfaces. The timescales for energy relaxation of these motions are extremely fast and are hard to measure by conventional techniques. In this talk, it will be shown that the dephasing times for the leaky SPP modes of noble metal nanostripes can be measured by combining real-space scattered light microscopy images with Fourier-space (or back focal plane) images. These measurements have been performed for bare nanostripes, and nanostripes coated with semiconductors such as TiO2 or Al2O3, or self-assembled monolayers. Subtracting the results for the bare and coated nanostripes provides information about the SPP dephasing induced by the coating, and generates unique information about the timescales for electron transfer from SPPs to semiconductor or molecule species via the hot-electron generation mechanism. Experiments have also be performed on nanostripes coated with thin films of excitonic species (dye molecules or quantum dots), where hybrid plasmon-exciton states can be created. These measurements show that the coupled states have very different lifetimes compared to the uncoupled states.

Surface chemistry effects on the ultrafast dynamics of propagating surface plasmon polaritons in metal nanostructures

2019 Spring National Meeting

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