90 research outputs found
Absorption control in pseudodisordered photonic-crystal thin film
The positive effects of various perturbations introduced in a bidimensional
photonic-crystal patterned membrane on its integrated absorption are
investigated numerically and theoretically. Two phenomena responsible for the
enhanced absorption observed are identified: an increase of the spectral
density of modes, obtained thanks to folding mechanisms in the reciprocal
lattice, and a better coupling of the modes with the incident light. By
introducing a proper pseudodisordered pattern, we show that those two effects
can be exploited so as to overcome the integrated absorption obtained for an
optimized and single pattern unit cell photonic crystal
Photonic crystals and optical mode engineering for thin film photovoltaics
International audienceIn this paper, we present the design, analysis, and experimental results on the integration of 2D photonic crystals in thin film photovoltaic solar cells based on hydrogenated amorphous silicon. We introduce an analytical approach based on time domain coupled mode theory to investigate the impact of the photon lifetime and anisotropy of the optical resonances on the absorption efficiency. Specific design rules are derived from this analysis. We also show that, due to the specific properties of the photonic crystal resonances, the angular acceptance of such solar cells is particularly high. Rigorous Coupled Wave Analysis simulations show that the absorption in the a-Si:H active layers, integrated from 300 to 750nm, is only decreased from 65.7% to 60% while the incidence angle is increased from 0 to 55°. Experimental results confirm the stability of the incident light absorption in the patterned stack, for angles of incidence up to 50°
La dénutrition du sujet âgé (conseils apportés par le pharmacien d officine lors de la délivrance des aliments destinés à des fins médicales spécialisées)
Dans une première partie, les causes de la dénutrition et la notion de fragilité du sujet âgé sont abordées ainsi que les prévalences de la dénutrition à l hôpital, à domicile et dans les EHPAD. Puis, après avoir décrit les critères (anamnestiques, cliniques et biologiques) d évaluation de l état nutritionnel, les différentes stratégies thérapeutiques seront proposées et le rôle du pharmacien d officine et du prestataire de service sera étudié.In the first part, the causes of malnutrition and the ederly s concept of fragility are talked about, in addition to the prevalence data in hospital, at home and in long-term nursing care. Then, after describing the characteristics (anamnectics, clinics and biologics) of nutrition assessment, the different therapeutics strategies are being proposed and pharmacist s and service provider s role are being studied.ANGERS-BU Médecine-Pharmacie (490072105) / SudocSudocFranceF
Magic configurations in Moir\'e Superlattice of Bilayer Photonic crystal: Almost-Perfect Flatbands and Unconventional Localization
We investigate the physics of photonic band structures of the moir\'e
patterns that emerged when overlapping two uni-dimensional (1D) photonic
crystal slabs with mismatched periods. The band structure of our system is a
result of the interplay between intra-layer and inter-layer coupling
mechanisms, which can be fine-tuned via the distance separating the two layers.
We derive an effective Hamiltonian that captures the essential physics of the
system and reproduces all numerical simulations of electromagnetic solutions
with high accuracy. Most interestingly, \textit{magic distances} corresponding
to the emergence of photonic flatbands within the whole Brillouin zone of the
moir\'e superlattice are observed. We demonstrate that these flatband modes are
tightly localized within a moir\'e period. Moreover, we suggest a single-band
tight-binding model that describes the moir\'e minibands, of which the
tunnelling rate can be continuously tuned via the inter-layer strength. Our
results show that the band structure of bilayer photonic moir\'e can be
engineered in the same fashion as the electronic/excitonic counterparts. It
would pave the way to study many-body physics at photonic moir\'e flatbands and
novel optoelectronic devices.Comment: 6 pages + Supplement. Comments are welcome
Blue light absorption enhancement based on vertically channelling modes in nano-holes arrays
We investigate the specific optical regime occurring at short wavelengths, in
the high absorption regime, in silicon thin-films patterned by periodically
arranged nano-holes. Near-field scanning optical microscopy indicates that the
incoming light is coupled to vertically channelling modes. Optical modelling
and simulations show that the light, travelling inside the low-index regions,
is absorbed at the direct vicinity of the nano-holes sidewalls. This
channelling regime should be taken into account for light management in
optoelectronic devices
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