Slanted annular aperture arrays as enhanced-transmission metamaterials: Excitation of the plasmonic transverse electromagnetic guided mode

International audienceWe present here the fabrication and the optical characterization of slanted annular aperture arrays engraved into silver film. An experimental enhanced transmission based on the excitation of the cutoff-less plasmonic guided mode of the nano-waveguides (the transmission electron microscopy mode) is demonstrated and agrees well with the theoretical predicted results. By the way, even if it is less efficient (70% → 20%), an enhanced transmission can occur at larger wavelength value (720 nm-930 nm) compared to conventional annular aperture arrays structure by correctly setting the metal thickness

Gratings: Theory and Numeric Applications

International audienceThe book containes 11 chapters written by an international team of specialist in electromagnetic theory, numerical methods for modelling of light diffraction by periodic structures having one-, two-, or three-dimensional periodicity, and aiming numerous applications in many classical domains like optical engineering, spectroscopy, and optical telecommunications, together with newly born fields such as photonics, plasmonics, photovoltaics, metamaterials studies, cloaking, negative refraction, and super-lensing. Each chapter presents in detail a specific theoretical method aiming to a direct numerical application by university and industrial researchers and engineers

Gratings: Theory and Numeric Applications, Second Revisited Edition

International audienceThe second Edition of the Book contains 13 chapters, written by an international team of specialist in electromagnetic theory, numerical methods for modelling of light diffraction by periodic structures having one-, two-, or three-dimensional periodicity, and aiming numerous applications in many classical domains like optical engineering, spectroscopy, and optical telecommunications, together with newly born fields such as photonics, plasmonics, photovoltaics, metamaterials studies, cloaking, negative refraction, and super-lensing. Each chapter presents in detail a specific theoretical method aiming to a direct numerical application by university and industrial researchers and engineers.In comparison with the First Edition, we have added two more chapters (ch.12 and ch.13), and revised four other chapters (ch.6, ch.7, ch.10, and ch.11

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Finite difference time domain method for grating structures

International audienceIn this chapter, we present a brief review on the fundamentals of the FDTD method. We show how to adapt it to the calculation of the photonic band gap structures in the case of 2D periodic (invariant in the third direction) structures. The both in-plane, for the TE and TM polarizations, and off-plane propagations are considered. The last part of this chapter is devoted to FDTD general formulation, based on the Split Field Method technique, for the modeling of bi-periodic gratings that are finished according to the third direction

Conception de lames demi-onde ultra-minces pour les gammes micro-onde et optique

National audience&nbsp

Exalted transmission through a periodic structure of metallic C-shaped apertures sub-wavelength

International audience<span style="left: 122.6px; top: 411.588px; font-size: 20px; font-family: serif; transform: scaleX(1.05058);"&gtThe objective of this work is to study the properties of the t</span&gt<span style="left: 620.8px; top: 411.588px; font-size: 20px; font-family: serif; transform: scaleX(1.02406);"&gtransmission through a periodic </span&gt<span style="left: 118px; top: 434.588px; font-size: 20px; font-family: serif; transform: scaleX(1.00073);"&gtarray</span&gt<span style="left: 164.2px; top: 434.588px; font-size: 20px; font-family: serif; transform: scaleX(1.00926);"&gtof the sub</span&gt<span style="left: 243.8px; top: 434.588px; font-size: 20px; font-family: serif;"&gt-</span&gt<span style="left: 250.6px; top: 434.588px; font-size: 20px; font-family: serif; transform: scaleX(1.00027);"&gtwavelength</span&gt<span style="left: 348.2px; top: 434.588px; font-size: 20px; font-family: serif;"&gtC</span&gt<span style="left: 361.6px; top: 434.588px; font-size: 20px; font-family: serif;"&gt-</span&gt<span style="left: 368.2px; top: 434.588px; font-size: 20px; font-family: serif; transform: scaleX(1.00027);"&gtshaped</span&gt<span style="left: 429px; top: 434.588px; font-size: 20px; font-family: serif; transform: scaleX(1.00379);"&gtapertures engraved</span&gt<span style="left: 586.4px; top: 434.588px; font-size: 20px; font-family: serif; transform: scaleX(1.01037);"&gtin a metal film</span&gt<span style="left: 710.2px; top: 434.588px; font-size: 20px; font-family: serif; transform: scaleX(1.00306);"&gt(see figure</span&gt<span style="left: 800.6px; top: 434.588px; font-size: 20px; font-family: serif;"&gt1</span&gt<span style="left: 810.6px; top: 434.588px; font-size: 20px; font-family: serif;"&gt-</span&gt<span style="left: 817.4px; top: 434.588px; font-size: 20px; font-family: serif; transform: scaleX(1.00097);"&gta)</span&gt<span style="left: 832.8px; top: 434.588px; font-size: 20px; font-family: serif; transform: scaleX(1);"&gt. </span&gt<span style="left: 842.8px; top: 434.588px; font-size: 20px; font-family: serif; transform: scaleX(1);"&gtThe </span&gt<span style="left: 118px; top: 457.588px; font-size: 20px; font-family: serif; transform: scaleX(1.05196);"&gtnumerical study of this type of structure is realized by the Finite Difference Time Domain </span&gt<span style="left: 118px; top: 480.588px; font-size: 20px; font-family: serif; transform: scaleX(1.00816);"&gt(FDTD), which is a house code developed </span&gt<span style="left: 464.4px; top: 480.588px; font-size: 20px; font-family: serif; transform: scaleX(1.00853);"&gtwithin our team. The annular C</span&gt<span style="left: 717.6px; top: 480.588px; font-size: 20px; font-family: serif;"&gt-</span&gt<span style="left: 724.4px; top: 480.588px; font-size: 20px; font-family: serif; transform: scaleX(1.00497);"&gtshaped structure is </span&gt<span style="left: 118px; top: 503.588px; font-size: 20px; font-family: serif; transform: scaleX(0.978441);"&gtcompact and has the advantage of having the fundamental mode TE</span&gt<span style="left: 698.194px; top: 512.062px; font-size: 13.4px; font-family: serif; transform: scaleX(1);"&gt10</span&gt<span style="left: 720.4px; top: 503.588px; font-size: 20px; font-family: serif; transform: scaleX(0.975432);"&gt(see figure 1</span&gt<span style="left: 827.6px; top: 503.588px; font-size: 20px; font-family: serif;"&gt-</span&gt<span style="left: 834.2px; top: 503.588px; font-size: 20px; font-family: serif; transform: scaleX(1.00046);"&gtb) </span&gt<span style="left: 859.8px; top: 503.588px; font-size: 20px; font-family: serif; transform: scaleX(0.988417);"&gtat </span&gt<span style="left: 118px; top: 526.588px; font-size: 20px; font-family: serif; transform: scaleX(1.00049);"&gtwavelengths much greater than those of the fundamental modes of the other guiding structures </span&gt<span style="left: 118px; top: 549.588px; font-size: 20px; font-family: serif; transform: scaleX(1.00773);"&gtsuch as the coaxial cavity</span&gt<span style="left: 328.8px; top: 549.588px; font-size: 20px; font-family: serif; transform: scaleX(1.00901);"&gt[1], </span&gt<span style="left: 362.8px; top: 549.588px; font-size: 20px; font-family: serif;"&gtr</span&gt<span style="left: 369.4px; top: 549.588px; font-size: 20px; font-family: serif; transform: scaleX(1.0006);"&gtectangular</span&gt<span style="left: 458px; top: 549.588px; font-size: 20px; font-family: serif; transform: scaleX(1.00086);"&gt[2]</span&gt<span style="left: 481.6px; top: 549.588px; font-size: 20px; font-family: serif; transform: scaleX(1.00231);"&gt, etc. </span&gt<span style="left: 525.4px; top: 549.588px; font-size: 20px; font-family: serif; transform: scaleX(1.00556);"&gtand while moving away from Rayleigh and </span&gt<span style="left: 118px; top: 572.588px; font-size: 20px; font-family: serif; transform: scaleX(1.00368);"&gtplasmonic anomalies. </span&gt<span style="left: 307.6px; top: 572.588px; font-size: 20px; font-family: serif; transform: scaleX(1.01057);"&gtIn addition to its compactness, this structure provides a breaking </span&gt<span style="left: 118px; top: 595.588px; font-size: 20px; font-family: serif; transform: scaleX(1.00698);"&gtsymmetry and therefore it is promising for the realization of metamaterials exhibiting original </span&gt<span style="left: 118px; top: 618.588px; font-size: 20px; font-family: serif; transform: scaleX(1.00027);"&gtprop</span&gt<span style="left: 154.6px; top: 618.588px; font-size: 20px; font-family: serif; transform: scaleX(0.982947);"&gterties such as negative refractive index or artificial anisotropy [</span&gt<span style="left: 696px; top: 618.588px; font-size: 20px; font-family: serif; transform: scaleX(1.0006);"&gt2]</span&gt<span style="left: 721.8px; top: 618.588px; font-size: 20px; font-family: serif; transform: scaleX(1.00039);"&gtwit</span&gt<span style="left: 747.4px; top: 618.588px; font-size: 20px; font-family: serif; transform: scaleX(0.992953);"&gth extraordinary </span&gt<span style="left: 118px; top: 642.588px; font-size: 20px; font-family: serif; transform: scaleX(0.998477);"&gtbirefringence (</span&gt<span style="left: 236.2px; top: 645.41px; font-size: 20px; font-family: sans-serif;"&gt∆</span&gt<span style="left: 247.4px; top: 642.588px; font-size: 20px; font-family: serif; transform: scaleX(1.00008);"&gtn= 0.75 </span&gt<span style="left: 313.6px; top: 642.588px; font-size: 20px; font-family: serif;"&gt[</span&gt<span style="left: 320.6px; top: 642.588px; font-size: 20px; font-family: serif;"&gt3</span&gt<span style="left: 330.6px; top: 642.588px; font-size: 20px; font-family: serif; transform: scaleX(1.00109);"&gt])</span&g

Métamatériaux à biréfringence extraordinaire pour le THz, le micro-onde et le visible

National audience&nbsp

Modélisation des résonances Fano dans les structures périodiques métallo-diélectriques pour exciter les résonances de Fano

International audience<span style="left: 165.4px; top: 342.038px; font-size: 15px; font-family: serif; transform: scaleX(0.956111);"&gtNotre travail a porté sur l'étude et la modélisation des structures périodiques métallo</span&gt<span style="left: 691.405px; top: 342.038px; font-size: 15px; font-family: serif; transform: scaleX(0.972646);"&gt-diélectriques pouvant </span&gt<span style="left: 165.4px; top: 359.243px; font-size: 15px; font-family: serif; transform: scaleX(0.955462);"&gtsupporter des résonances Fano correspondant au couplage d'un mode de Bloch non radiatif avec une onde </span&gt<span style="left: 165.4px; top: 376.448px; font-size: 15px; font-family: serif; transform: scaleX(1.02312);"&gtplane incidente. Après avoir effectué un test de validation des codes de calcul utilisés, nous avons mené une </span&gt<span style="left: 165.4px; top: 393.653px; font-size: 15px; font-family: serif; transform: scaleX(0.947641);"&gtétude FDTD (calcul de bande et de diffraction</span&gt<span style="left: 452.605px; top: 393.653px; font-size: 15px; font-family: serif; transform: scaleX(0.967289);"&gt) montrant</span&gt<span style="left: 517px; top: 393.653px; font-size: 15px; font-family: serif; transform: scaleX(0.94997);"&gt l 'excitation des résonances Fano dans les cristaux </span&gt<span style="left: 165.4px; top: 411.053px; font-size: 15px; font-family: serif; transform: scaleX(1.00262);"&gtphotoniques.</span&g

Geographic information-driven two-stage optimization model for location decision of solar power plant: A case study of an Algerian municipality

This paper presents an interdisciplinary framework for optimal mapping and integration of solar photovoltaic based DG systems. In a two-stage process, the proposed framework combines both spatial and technical-economic analysis, and uses efficient optimization techniques to make decisions. First, a GIS and a MCDM are used to identify the sites with the highest potential for hosting PV power plants. Second, the Backward-Forward Sweep (BFS) load flow algorithm is used to investigate nominated sites, taking into account three indices, namely, active power losses, VSI, and voltage profile improvement. In addition, a techno-economic feasibility assessment is performed based on the characteristics of a real distribution grid in N'goussa region, Algeria. The results show that 78% of the studied area is suitable for installing PV farms. The optimal zone represents only 1.52% of the obtained suitable area. In addition, two zones are eliminated from 7 suitable zones, as they are too far from the existing grid busbars. Based on the BFS method, and considering VSI and voltage profile, the busbar 104 is the optimal point for the connected PV-farm. Furthermore, the techno-economic assessment for the investigated system indicates that the LCOE is decreased by 0.4 $/kWh for each penetration-rate