54 research outputs found
Heat flux splitter for near-field thermal radiation
We demonstrate the possibility to efficiently split the near-field heat flux
exchanged between graphene nano-disks by tuning their doping. This result paves
the way for the developement of an active control of propagation directions for
heat fluxes exchanged in near-field throughout integrated nanostructures
networks
Plasmonic-photonic crystal coupled nanolaser
We propose and demonstrate a hybrid photonic-plasmonic nanolaser that
combines the light harvesting features of a dielectric photonic crystal cavity
with the extraordinary confining properties of an optical nano-antenna. In that
purpose, we developed a novel fabrication method based on multi-step
electron-beam lithography. We show that it enables the robust and reproducible
production of hybrid structures, using fully top down approach to accurately
position the antenna. Coherent coupling of the photonic and plasmonic modes is
highlighted and opens up a broad range of new hybrid nanophotonic devices
Interfacial thermal resistance between porous layers: impact on thermal conductivity of a multilayered porous structure
Features of thermal transport in multilayered porous silicon nanostructures
are considered. Such nanostructures were fabricated by electrochemical etching
of monocrystalline Si substrates by applying periodically changed current
density. Hereby, the multilayered structures with specific phononic properties
were formed. Photoacoustic (PA) technique in gas-microphone configuration was
applied for thermal conductivity evaluation. Experimental amplitude-frequency
dependencies were adjusted by temperature distribution simulation with thermal
conductivity of the multilayered porous structure as a fitting parameter. The
experimentally determined values of thermal conductivity were found to be
significantly lower than theoretically calculated ones. Such difference was
associated with the presence of thermal resistance at the interfaces between
porous layers with different porosities arising because of elastic parameters
mismatch (acoustical mismatch). Accordingly, the magnitude of this interfacial
thermal resistance was experimentally evaluated for the first time.
Furthermore, crucial impact of the resistance on thermal transport perturbation
in a multilayered porous silicon structure was revealed
Optimal overlayer inspired by Photuris firefly improves light-extraction efficiency of existing light-emitting diodes
In this paper the design, fabrication and characterization of a bioinspired
overlayer deposited on a GaN LED is described. The purpose of this overlayer is
to improve light extraction into air from the diode's high refractive-index
active material. The layer design is inspired by the microstructure found in
the firefly Photuris sp. The actual dimensions and material composition have
been optimized to take into account the high refractive index of the GaN diode
stack. This two-dimensional pattern contrasts other designs by its unusual
profile, its larger dimensions and the fact that it can be tailored to an
existing diode design rather than requiring a complete redesign of the diode
geometry. The gain of light extraction reaches values up to 55% with respect to
the reference unprocessed LED.Comment: 9 pages, 9 Figures, published in Optics Expres
Engineering high aspect-ratio silicon nanostructures
Large-area high density vertical silicon nanowire arrays are fabricated by metal-assisted chemical etching. Two-dimensional silica colloidal crystal template or laser interference lithography are used to create gold metal nanohole arrays on a silicon substrate, which enables to precisely control the final diameter of the nanowires. The formation of ordered silicon nanowire arrays is due to selective and highly anisotropic etching of silicon induced by the gold patterned mask
Tuning the electromagnetic local density of states in graphene-covered systems via strong coupling with graphene plasmons
It is known that the near-field spectrum of the local density of states of
the electromagnetic field above a SiC/air interface displays an intense narrow
peak due to the presence of a surface polariton. It has been recently shown
that this surface wave can be strongly coupled with the sheet plasmon of
graphene in graphene-SiC heterosystems. Here, we explore the interplay between
these two phenomena and demonstrate that the spectrum of the electromagnetic
local density of states in these systems presents two peaks whose position
depends dramatically both on the distance to the interface and on the chemical
potential of graphene. This paves the way towards the active control of the
local density of states.Comment: 6 pages, 4 figure
New concepts of integrated photonic biosensors based on porous silicon
International audienceno abstrac
Chemical composition of nanoporous layer formed by electrochemical etching of p-type GaAs
Abstract : We have performed a detailed characterization study of electrochemically etched p-type GaAs in a hydrofluoric acid-based electrolyte. The samples were investigated and characterized through cathodoluminescence (CL), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). It was found that after electrochemical etching, the porous layer showed a major decrease in the CL intensity and a change in chemical composition and in the crystalline phase. Contrary to previous reports on p-GaAs porosification, which stated that the formed layer is composed of porous GaAs, we report evidence that the porous layer is in fact mainly constituted of porous As2O3. Finally, a qualitative model is proposed to explain the porous As2O3 layer formation on p-GaAs substrate
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