72 research outputs found
Loss mechanisms of surface plasmon polaritons on gold probed by cathodoluminescence imaging spectroscopy
We use cathodoluminescence imaging spectroscopy to excite surface plasmon polaritons and measure their decay length on single crystal and polycrystalline gold surfaces. The surface plasmon polaritons are excited on the gold surface by a nanoscale focused electron beam and are coupled into free space radiation by gratings fabricated into the surface. By scanning the electron beam on a line perpendicular to the gratings, the propagation length is determined. Data for single-crystal gold are in agreement with calculations based on dielectric constants. For polycrystalline films, grain boundary scattering is identified as additional loss mechanism, with a scattering coefficient SG=0.2%
Local density of states, spectrum, and far-field interference of surface plasmon polaritons probed by cathodoluminescence
The surface plasmon polariton (SPP) field intensity in the vicinity of gratings patterned in an otherwise planar gold surface is spatially resolved using cathodoluminescence (CL). A detailed theoretical analysis is presented that successfully explains the measured CL signal based upon interference of transition radiation directly generated by electron impact and SPPs launched by the electron and outcoupled by the grating. The measured spectral dependence of the SPP yield per incoming electron is in excellent agreement with rigorous electromagnetic calculations. The CL emission is shown to be similar to that of a dipole oriented perpendicular to the surface and situated at the point of electron impact, which allows us to establish a solid connection between the CL signal and the photonic local density of states associated to the SPPs
Surface plasmon polariton modes in a single-crystal Au nanoresonator fabricated using focused-ion-beam milling
We use focused-ion-beam milling of a single-crystal Au surface to fabricate a
590-nm-long linear ridge that acts as a surface plasmon nanoresonator.
Cathodoluminescence imaging spectroscopy is then used to excite and image
surface plasmons on the ridge. Principal component analysis reveals distinct
plasmonic modes, which proves confinement of surface-plasmon oscillations to
the ridge. Boundary-element-method calculations confirm that a linear ridge is
able to support highly-localized surface-plasmon modes (mode diameter < 100
nm). The results demonstrate that focused-ion-beam milling can be used in rapid
prototyping of nanoscale single-crystal plasmonic components.Comment: 4 pages, 4 figure
Mapping localized surface plasmons within silver nanocubes using cathodoluminescence hyperspectral imaging
Localized surface plasmons within silver nanocubes less than 50 nm in size are investigated using high resolution cathodoluminescence hyperspectral imaging. Multivariate statistical analysis of the multidimensional luminescence dataset allows both the identification of distinct spectral features in the emission and the mapping of their spatial distribution. These results show a 490 nm peak emitted from the cube faces, with shorter wavelength luminescence coming from the vertices and edges; this provides direct experimental confirmation of theoretical predictions
Atomic-scale confinement of optical fields
In the presence of matter there is no fundamental limit preventing
confinement of visible light even down to atomic scales. Achieving such
confinement and the corresponding intensity enhancement inevitably requires
simultaneous control over atomic-scale details of material structures and over
the optical modes that such structures support. By means of self-assembly we
have obtained side-by-side aligned gold nanorod dimers with robust
atomically-defined gaps reaching below 0.5 nm. The existence of
atomically-confined light fields in these gaps is demonstrated by observing
extreme Coulomb splitting of corresponding symmetric and anti-symmetric dimer
eigenmodes of more than 800 meV in white-light scattering experiments. Our
results open new perspectives for atomically-resolved spectroscopic imaging,
deeply nonlinear optics, ultra-sensing, cavity optomechanics as well as for the
realization of novel quantum-optical devices
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