We develop the plasmon-pole approximation for an interacting electron gas confined in a semiconductor quantum wire. We argue that the plasmon-pole approximation becomes a more accurate approach in quantum wire systems than in higher dimensional systems because of severe phase-space restrictions on particle-hole excitations in one dimension. As examples, we use the plasmon-pole approximation to ...

We experimentally demonstrate a novel, all-plasmonic nanoscopic cavity exhibiting Q-factors up to 200 at visible frequencies. The Fabry-Pérot type resonator uses tall metallic fins that reflect up to 98% of incident surface plasmon to concentrate light within a subwavelength cavity mode. High aspect ratio metal fins, constructed using lithography and electroplating, reduce surface plasmon scatt...

Hot electrons generated through plasmonic excitations in metal nanostructures show great promise for efficiently driving chemical reactions with light. However, the lifetime, yield, and mechanism of action of plasmon-generated hot electrons involved in a given photocatalytic process are not well understood. Here, we develop ultrafast surface-enhanced Raman scattering (SERS) as a direct probe of...

We examine ultrafast dynamics in a coupled molecule-plasmon system. Using a new ultrafast Raman technique called surface enhanced-femtosecond stimulated Raman spectroscopy (SE-FSRS), we prove that plasmonic nanoparticles and adsorbed molecules are coupled by the appearance of Fano-like lineshapes, which arise from the interaction of narrowband vibrational coherences and the broadband plasmon re...

The optical properties of metallic nanoparticles are highly sensitive to interparticle distance, giving rise to dramatic but frequently irreversible color changes. By electrochemical modification of individual nanoparticles and nanoparticle pairs, we induced equally dramatic, yet reversible, changes in their optical properties. We achieved plasmon tuning by oxidation-reduction chemistry of Ag-A...

Multipolar plasmon oscillation frequencies and corresponding damping rates for nanospheres formed of the simplest free-electron metals are studied. The possibility of controlling plasmon features by choosing the size and dielectric properties of the sphere surroundings is discussed. Optical properties of the studied metals are described within the Drude-Sommerfeld model of the dielectric functi...

The experimentally determined scattering spectra of discrete, crystalline, gold nanorod dimers arranged side-to-side, end-to-end, at right angles in different orientations and also with longitudinal offsets are reported along with the electron micrographs of the individual dimers. The spectra exhibit both red- and blue-shifted surface plasmon resonances, consistent with the plasmon hybridizatio...

We report the coupling of free-space photons (vacuum wavelength of 830 nm) to surface plasmon modes of a silver nanowire. The launch of propagating plasmons, and the subsequent emission of photons, is selective and occurs only at ends and other discontinuities of the nanowire. In addition, we observe that the nanowires redirect the plasmons through turns of radii as small as 4 microm. We exploi...

We present a quantitative analysis of the electron transfer between single gold nanorods and monolayer graphene under no electrical bias. Using single-particle dark-field scattering and photoluminescence spectroscopy to access the homogeneous linewidth, we observe broadening of the surface plasmon resonance for gold nanorods on graphene compared to nanorods on a quartz substrate. Because of the...

In the phenomenon of plasmon-induced transparency, which is a classical analogue of electromagnetically induced transparency (EIT) in atomic gases, the coherent interference between two plasmon modes results in an optical transparency window in a broad absorption spectrum. With the requirement of contrasting lifetimes, typically one of the plasmon modes involved is a dark mode that has limited ...