Opportunisme ou équité ? Le cas des contrats d'approvisionnement de défense

How are extra costs resulting from the occurrence of unanticipated risks allocated in a procurement setting? This paper develops a theoretical framework combining transaction cost economics with equity theory in order to explain why parties endorse cooperative strategies, basically a 50-50 sharing rule, that prevail over their propensity to behave opportunistically. We derive two propositions that we test on a dataset of 48 contracts in the French defence procurement. We find that perception of equity turns out to be a key factor in the contractual relationship. This interpretation challenges the prevailing interpretation of a key assumption in transaction cost economics.Comment sont répartis les surcoûts qui résultent de la matérialisation de risques dans le cadre de relations contractuelles ? Nous proposons une réponse qui combine théorie des coûts de transaction et approche en termes d'équité, de manière à expliquer pourquoi des stratégies coopératives de répartition du type 50-50 prévalent sur la propension des partenaires à se comporter de façon opportuniste. Nous en dérivons deux propositions que nous confrontons à une base de données inédite composée de 48 contrats concernant l'approvisionnement de défense en France. Nous montrons que, sous certaines conditions, la perception d'une allocation équitable se révèle un facteur clé de la relation contractuelle, ce qui constitue un défi pour l'interprétation habituelle de la théorie des coûts de transaction

Opportunisme ou équité ? Le cas des contrats d'approvisionnement de défense

Comment sont répartis les surcoûts qui résultent de la matérialisation de risques dans le cadre de relations contractuelles ? Nous proposons une réponse qui combine théorie des coûts de transaction et approche en termes d'équité, de manière à expliquer pourquoi des stratégies coopératives de répartition du type 50-50 prévalent sur la propension des partenaires à se comporter de façon opportuniste. Nous en dérivons deux propositions que nous confrontons à une base de données inédite composée de 48 contrats concernant l'approvisionnement de défense en France. Nous montrons que, sous certaines conditions, la perception d'une allocation équitable se révèle un facteur clé de la relation contractuelle, ce qui constitue un défi pour l'interprétation habituelle de la théorie des coûts de transaction.Contrats; équité; coûts de transaction; défense

High-field THz source centered at 2.7 THz

We demonstrate a table-top high-field terahertz (THz) source based on optical rectification of a collimated near-infrared pulse in gallium phosphide (GaP) to produce peak fields exceeding 130 kV/cm with a spectrum centered at 2.7 THz. The experimental configuration, based on tilted-pulse-front phase matching, is implemented with a phase grating etched directly onto the front surface of the GaP crystal. Although the THz generation efficiency starts showing a saturation onset as the near-infrared pulse energy reaches 0.57 mJ, we can expect our configuration to yield THz peak fields up to 400 kV/cm when a 5 mJ generation NIR pulse is used. This work paves the way towards broadband, high-field THz sources able to access a new class of THz coherent control and nonlinear phenomena driven at frequencies above 2 THz.Comment: 8 pages, 3 figure

Hybrid THz architectures for molecular polaritonics

Physical and chemical properties of materials can be modified by a resonant optical mode. Such recent demonstrations have mostly relied on a planar cavity geometry, others have relied on a plasmonic resonator. However, the combination of these two device architectures have remained largely unexplored, especially in the context of maximizing light-matter interactions. Here, we investigate several schemes of electromagnetic field confinement aimed at facilitating the collective coupling of a localized photonic mode to molecular vibrations in the terahertz region. The key aspects are the use of metasurface plasmonic structures combined with standard Fabry-Perot configurations and the deposition of a thin layer of glucose, via a spray coating technique, within a tightly focused electromagnetic mode volume. More importantly, we demonstrate enhanced vacuum Rabi splittings reaching up to 200 GHz when combining plasmonic resonances, photonic cavity modes and low-energy molecular resonances. Furthermore, we demonstrate how a cavity mode can be utilized to enhance the zero-point electric field amplitude of a plasmonic resonator. Our study provides key insight into the design of polaritonic platforms with organic molecules to harvest the unique properties of hybrid light-matter states.Comment: 7 pages (5 Figures) + 7 pages Appendix (5 Figures), updated versio

Multi-resonant high-Q plasmonic metasurfaces

Resonant metasurfaces are devices composed of nanostructured sub-wavelength scatterers that generate narrow optical resonances, enabling applications in filtering, nonlinear optics, and molecular fingerprinting. It is highly desirable for these applications to incorporate such devices with multiple, high-quality-factor resonances; however, it can be challenging to obtain more than a pair of narrow resonances in a single plasmonic surface. Here, we demonstrate a multi-resonant metasurface that operates by extending the functionality of surface lattice resonances, which are the collective responses of arrays of metallic nanoparticles. This device features a series of resonances with high quality factors (Q ~ 40), an order of magnitude larger than what is typically achievable with plasmonic nanoparticles, as well as a narrow free spectral range. This design methodology can be used to better tailor the transmission spectrum of resonant metasurfaces and represents an important step towards the miniaturization of optical devices.Comment: 8 pages, 4 figures, includes MATLAB code in Supplementary Material

Ultra-high-Q resonances in plasmonic metasurfaces

Plasmonic nanostructures hold promise for the realization of ultra-thin sub-wavelength devices, reducing power operating thresholds and enabling nonlinear optical functionality in metasurfaces. However, this promise is substantially undercut by absorption introduced by resistive losses, causing the metasurface community to turn away from plasmonics in favour of alternative material platforms (e.g., dielectrics) that provide weaker field enhancement, but more tolerable losses. Here, we report a plasmonic metasurface with a quality-factor (Q-factor) of 2340 in the telecommunication C band by exploiting surface lattice resonances (SLRs), exceeding the record by an order of magnitude. Additionally, we show that SLRs retain many of the same benefits as localized plasmonic resonances, such as field enhancement and strong confinement of light along the metal surface. Our results demonstrate that SLRs provide an exciting and unexplored method to tailor incident light fields, and could pave the way to flexible wavelength-scale devices for any optical resonating application.Comment: 15 pages, includes supporting informatio

From In Situ to satellite observations of pelagic Sargassum distribution and aggregation in the Tropical North Atlantic Ocean

International audienceThe present study reports on observations carried out in the Tropical North Atlantic in summer and autumn 2017, documenting Sargassum aggregations using both ship-deck observations and satellite sensor observations at three resolutions (MSI-10 m, OLCI-300 m, VIIRS-750 m and MODIS-1 km). Both datasets reported that in summer, Sargassum aggre-gations were mainly observed off Brazil and near the Caribbean Islands, while they accumulated near the African coast in autumn. Based on in situ observations, we propose a five-class typology allowing standardisation of the description of in situ Sargassum raft shapes and sizes. The most commonly observed Sargassum raft type was windrows, but large rafts composed of a quasi-circular patch hundreds of meters wide were also observed. Satellite imagery showed that these rafts formed larger Sargassum aggregations over a wide range of scales, with smaller aggregations (of tens of m 2 area) nested within larger ones (of hundreds of km 2). Match-ups between different satellite sensors and in situ observations were limited for this dataset, mainly because of high cloud cover during the periods of observation. Nevertheless, comparisons between the two datasets showed that satellite sensors successfully detected Sargassum abundance and aggregation patterns consistent with in situ observations. MODIS and VIIRS sensors were better suited to describing the Sargas-sum aggregation distribution and dynamics at Atlantic scale, while the new sensors, OLCI and MSI, proved their ability to detect Sargassum aggregations and to describe their (sub-) mesoscale nested structure. The high variability in raft shape, size, thickness, depth and biomass density observed in situ means that caution is called for when using satellite maps of Sargassum distribution and biomass estimation. Improvements would require additional in situ and airborne observations or very high-resolution satellite imagery