324 research outputs found
Fano collective resonance as complex mode in a two-dimensional planar metasurface of plasmonic nanoparticles
Fano collective resonance as complex mode in a two dimensional planar metasurface of plasmonic nanoparticles
Fano resonances are features in transmissivity/reflectivity/absorption that
owe their origin to the interaction between a bright resonance and a dark
(i.e., sub-radiant) narrower resonance, and may emerge in the optical
properties of planar two-dimensional (2D) periodic arrays (metasurfaces) of
plasmonic nanoparticles. In this Letter, we provide a thorough assessment of
their nature for the general case of normal and oblique plane wave incidence,
highlighting when a Fano resonance is affected by the mutual coupling in an
array and its capability to support free modal solutions. We analyze the
representative case of a metasurface of plasmonic nanoshells at ultraviolet
frequencies and compute its absorption under TE- and TM-polarized, oblique
plane-wave incidence. In particular, we find that plasmonic metasurfaces
display two distinct types of resonances observable as absorption peaks: one is
related to the Mie, dipolar resonance of each nanoparticle; the other is due to
the forced excitation of free modes with small attenuation constant, usually
found at oblique incidence. The latter is thus an array-induced collective Fano
resonance. This realization opens up to manifold flexible designs at optical
frequencies mixing individual and collective resonances. We explain the
physical origin of such Fano resonances using the modal analysis, which allows
to calculate the free modes with complex wavenumber supported by the
metasurface. We define equivalent array dipolar polarizabilities that are
directly related to the absorption physics at oblique incidence and show a
direct dependence between array modal phase and attenuation constant and Fano
resonances. We thus provide a more complete picture of Fano resonances that may
lead to the design of filters, energy-harvesting devices, photodetectors, and
sensors at ultraviolet frequencies.Comment: 6 pages, 5 figure
Second harmonic double resonance cones in dispersive hyperbolic metamaterials
We study the formation of second harmonic double-resonance cones in
hyperbolic metamaterials. An electric dipole on the surface of the structure
induces second harmonic light to propagate into two distinct volume
plasmon-polariton channels: A signal that propagates within its own peculiar
resonance cone; and a phase-locked signal that is trapped under the pump's
resonance cone. Metamaterial dispersion and birefringence induce a large
angular divergence between the two volume plasmon-polaritons, making these
structures ideal for subwavelength second and higher harmonic imaging
microscopy
Enhanced third harmonic generation from the epsilon-near-zero modes of ultrathin films
We experimentally demonstrate efficient third harmonic generation from an
indium tin oxide (ITO) nanofilm (lambda/42 thick) on a glass substrate for a
pump wavelength of 1.4 um. A conversion efficiency of 3.3x10^-6 is achieved by
exploiting the field enhancement properties of the epsilon-near-zero (ENZ) mode
with an enhancement factor of 200. This nanoscale frequency conversion method
is applicable to other plasmonic materials and reststrahlen materials in
proximity of the longitudinal optical phonon frequencies.Comment: 13 pages, 5 figure
Gain assisted harmonic generation in near-zero permittivity metamaterials made of plasmonic nanoshells
Viscoelastic optical nonlocality of low-loss epsilon-near-zero nanofilms
Optical nonlocalities are elusive and hardly observable in traditional
plasmonic materials like noble and alkali metals. Here we report experimental
observation of viscoelastic nonlocalities in the infrared optical response of
doped cadmium-oxide, epsilon-near-zero nanofilms. The nonlocality is detectable
thanks to the low damping rate of conduction electrons and the virtual absence
of interband transitions at infrared wavelengths. We describe the motion of
conduction electrons using a hydrodynamic model for a viscoelastic fluid, and
find excellent agreement with experimental results. The electrons elasticity
blue-shifts the infrared plasmonic resonance associated with the main
epsilon-near-zero mode, and triggers the onset of higher-order resonances due
to the excitation of electron-pressure modes above the bulk plasma frequency.
We also provide evidence of the existence of nonlocal damping, i.e., viscosity,
in the motion of optically-excited conduction electrons using a combination of
spectroscopic ellipsometry data and predictions based on the viscoelastic
hydrodynamic model.Comment: 19 pages, 5 figure
Recommended from our members
Volatile Extraction and Detection from Frozen Lunar Regolith Simulants in Preparation for the LUVMI Rover
Recommended from our members
LUVMI: an innovative payload for the sampling of volatiles at the Lunar poles
The ISECG identifies one of the first exploration steps as in situ investigations of the moon or asteroids. Europe is developing payload concepts for drilling and sample analysis, a contribution to a 250kg rover as well as for sample return. To achieve these missions, ESA depends on international partnerships.
Such missions will be seldom, expensive and the drill/sample site selected will be based on observations from orbit not calibrated with ground truth data. Many of the international science community’s objectives can be met at lower cost, or the chances of mission success improved and the quality of the science increased by making use of an innovative, low mass, mobile robotic payload following the LEAG
recommendations.
LUVMI provides a smart, low mass, innovative, modular mobile payload comprising surface and subsurface sensing with an in-situ sampling technology capable of depth-resolved extraction of volatiles, combined with a volatile analyser (mass spectrometer) capable of identifying the chemical composition of the most important volatiles. This will allow LUVMI to: traverse the lunar surface prospecting for volatiles; sample subsurface up to a depth of 10 cm (with a goal of 20 cm); extract water and other loosely bound volatiles; identify the chemical species extracted; access and sample permanently shadowed regions (PSR).
The main innovation of LUVMI is to develop an in situ sampling technology capable of depth-resolved extraction of volatiles, and then to package within this tool, the analyser itself, so as to maximise transfer
efficiency and minimise sample handling and its attendant mass requirements and risk of sample alteration. By building on national, EC and ESA funded research and developments, this project will develop to TRL6 instruments that together form a smart modular mobile payload that could be flight ready in 2020.
The LUVMI sampling instrument will be tested in a highly representative environment including thermal, vacuum and regolith simulant and the integrated payload demonstrated in a representative environment
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