170 research outputs found
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
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
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
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
Metallo-Dielectric Multilayer Structure for Lactose Malabsorption Diagnosis through H2 Breath Test
A metallo-dielectric multilayer structure is proposed as a novel approach to
the analysis of lactose malabsorption. When lactose intolerance occurs, the
bacterial overgrowth in the intestine causes an increased spontaneous emission
of H2 in the human breath. By monitoring the changes in the optical properties
of a multilayer palladium-polymeric structure, one is able to detect the
patient's disease and the level of lactose malabsorption with high sensitivity
and rapid response
Singularity-driven Second and Third Harmonic Generation in a {\epsilon}-near-zero nanolayer
We show a new path to {\epsilon}~0 materials without resorting to metal-based
metamaterial composites. A medium that can be modeled using Lorentz oscillators
usually displays {\epsilon}=0 crossing points, e.g. {\epsilon}=0 at
{\lambda}~7{\mu}m and 20{\mu}m for SiO2 and CaF2, respectively. We show that a
Lorentz medium yields a singularity-driven enhancement of the electric field
followed by dramatic lowering of thresholds for a plethora of nonlinear optical
phenomena. We illustrate the remarkable enhancement of second and third
harmonic generation in a layer of {\epsilon}~0 material 20nm thick, and discuss
the role of nonlinear surface sources
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