A theoretical electrostatic approach for determination of plasmon eigenresonances and absorption cross section
spectra of arbitrarily shaped metal nanoparticles with cylindrical symmetry in stratified geometries is presented.
The method is based on a surface integral equation for the surface polarization charge density. From symmetry
considerations and by incorporating all effects of the stratified surrounding into the Green's function we show
how the three dimensional analysis can be reduced to a single integral over the polar angle along the surface of the
metal nanoparticle. The theoretical scheme is exemplified by analyzing silver nanoparticles shaped as spheres,
oblate spheroids, and nanodisks in different surroundings involving silicon. The effect of varying the distance
between a silver sphere and a silicon surface on plasmonic eigenvalues and absorption cross section spectra is
presented. By flattening silver oblate spheroids and nanodisks embedded in a homogenous silicon surrounding
it is shown how the fundamental horizontally polarized plasmon resonance can be shifted into the near infrared
wavelength range. Also the effect of varying the thickness of thin silicon films with silver nanoparticles embedded
is presented. The results indicate that silver nanoparticles embedded in silicon could be interesting for plasmon
assisted solar cells.
Scattering resonances of metal nano-strip resonators are described as a consequence of formation of standing waves due
to counter-propagating short-range (and slow) surface plasmon polaritons and gap plasmon polaritons, which are
electromagnetic waves bound to and propagating along a nanometer-thin metal film, and a nanometer-sized gap between
metal surfaces, respectively. Scattering spectra and resonant fields are presented for single-metal-nano-strip resonators
and gap plasmon resonators with two closely spaced metal nano-strips. It is shown how strip resonators can be designed
for any resonance wavelength in the range from 600nm to 1600nm.
Surface-plasmon-polariton (SPP) resonators consisting of metal strips in free space, and gap plasmon polariton
resonators consisting of a metal strip close to either a block of metal or a metal surface, are studied as optical
resonators. The analysis is performed using the Green's function surface integral equation method. For strips
in free space, we show how the scattering resonances can be understood, by thinking of the strips as optical
resonators for short-range SPPs. The two gap resonator configurations, strip-block and strip-surface, have
different structure terminations as the width of the strip and the block are identical whereas the surface is
infinite. In the strip-surface configuration, the scattering resonances are broader and red-shifted, compared to
the strip-block configuration. This is explained as a consequence of the effective length of the resonator being
larger in the strip-surface configuration. By varying the gap size, we study the transition from a SPP resonator
to a gap plasmon polariton resonator. In the strip-surface configuration, light can be scattered into both out-of-plane propagating waves and into SPPs that propagate along the surface. For small gaps of a few tens of
nanometers, a large enhancement in the scattering cross section is seen due to strong scattering into SPPs.
We report on experimental realization of different metal-insulator geometries that are used as plasmonic waveguides
guiding electromagnetic radiation along metal-dielectric interfaces via excitation of surface plasmon polaritons (SPPs).
Three configurations are considered: metal strips, symmetric nanowires and nanowire pairs embedded in a dielectric, and
metal V-shaped grooves. Planar plasmonic waveguides based on nm-thin and μm-wide gold strips embedded in a
polymer that support propagation of long-range SPPs are shown to constitute an alternative for integrated optical
circuits. Using uniform and thickness-modulated gold strips different waveguide components including reflecting
gratings can be realized. For applications where polarization is random or changing, metal nanowire waveguides are
shown to be suitable candidates for efficient guiding of arbitrary polarized light. Plasmonic waveguides based on metal
V-grooves that offer subwavelength confinement are also considered. We focus on recent advances in manufacturing of
nanostructured metal strips and metal V-grooves using combined UV, electron-beam and nanoimprint lithography.
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