Can past gamma-ray bursts explain both INTEGRAL and ATIC/PAMELA/Fermi anomalies simultaneously?

Gamma-ray bursts (GRBs) have been invoked to explain both the 511 keV emission from the galactic bulge and the high-energy positron excess inferred from the ATIC, PAMELA, and Fermi data. While independent explanations can be responsible for these phenomena, we explore the possibility of their common GRB-related origin by modeling the GRB distribution and estimating the rates. For an expected Milky Way long GRB rate, neither of the two signals is generic; the local excess requires a 2% coincidence, while the signal from the galactic center requires a 20% coincidence with respect to the timing of the latest GRB. The simultaneous explanation requires a 0.4% coincidence. Considering the large number of statistical "trials" created by multiple searches for new physics, the coincidences of a few per cent cannot be dismissed as unlikely. Alternatively, both phenomena can be explained by GRBs if the galactic rate is higher than expected. We also show that a similar result is difficult to obtain assuming a simplified short GRB distribution.Comment: 4 pages; version accepted for publicatio

Influence of NaX (X=I or Cl) additions on GeS2-​Ga2S3 based glasses

International audienceChalcogenide glasses in the pseudo-​ternary system NaX-​GeS2-​Ga2S3 (X=Cl or I) were synthesized. Different series were investigated in order to highlight the influence of the sodium halide addn. on two different host glasses (GeS2)​80(Ga2S3)​20 and (GeS2)​72(Ga2S3)​28. Macroscopic properties including d. and characteristic temps., such as glass transition temps. Tg and crystn. temp. Tx, were detd. for a max. molar content of NaX equal to 15​%. The evolution of the optical band-​gap and the chem. stability following the compn. were also studied. Cond. measurements were also performed and compared to other Li-​based GeS2-​Ga2S3 glasses. The results were discussed taking into account the cation and anion nature and also the glass packing d

Moldable multispectral glasses in GeS2–Ga2S3–CsCl system transparent from the visible up to the thermal infrared regions

International audienceThis work is based on the development of glasses with extremely wide optical transmission range for multispectral imaging (visible + thermal imaging for example) with the same optical system. Glass compns. based on the GeS2-​Ga2S3-​CsCl system have been selected in order to obtain glasses transparent from the visible up to the 8-​12 μm region. An increase of CsCl content can greatly improve the visible transmission of the glasses which however will be more sensitive to ambient moisture. Two glasses with different chromatic dispersion, necessary for the design of an optical system, are developed and characterized. Molding tests on aspheric surfaces demonstrate clearly the ability of these two glasses to be molded into complex optics without crystn. and with excellent roughness. In order to test the ability of an anti-​reflective coating to protect these glasses against the atm. aggression, a ZnS coating has been applied to these glasses. An effective protection can be achieved with a ZnS coating of less than 1 μm of thickness. These results allow considering the use of compns. with higher CsCl content if still more transparency in the visible region is desired

Adressage de modes d’ordre élevé dans une cavité photonique à l’aide d’une masque de phase programmable

National audienc

Multispectral glass transparent from visible to thermal infrared

International audienceThe thermal imaging market has experienced a strong growth during the recent years due to continued cost redn. of night vision devices. The development of uncooled focal plane detector arrays is the major reason for the cost redn. Another reason is the continuous improvement of the optical soln. In this paper, we present a new multispectral material which responds to the increasing demand for optics operating simultaneously in the visible​/SWIR (Short Wave IR) and the thermal IR region. The most important properties of some glasses from the GeS2-​Ga2S3-​CsCl system are highlighted in this study. A stable compn. 15Ga2S3-​75GeS2-​10CsCl allowed the synthesis of a large glass without crystn. The refractive index of this glass was precisely measured from 0.6 to 10.4μm by using the Littrow method. The chromatic dispersion was then calcd. and compared with other multispectral materials

Selective excitation of high-order modes in 2D cavityresonator integrated grating filters (CRIGFs)

International audienceThe selective spatial mode excitation of a bi-dimensional grating-coupled micro-cavity called a cavity resonator integrated grating filter (CRIGF) is reported using an incident beam shaped to reproduce the theoretical emission profiles of the device in one and subsequently two dimensions. In both cases, the selective excitation of modes up to order 10 (per direction) is confirmed by responses exhibiting one (respectively two) spectrally narrowband resonance(s) with a good extinction of the other modes, the latter being shown to depend on the parity and order(s) of the involved modes. These results pave the way toward the demonstration of multi-wavelength spatially selective reflectors or fiber-to-waveguide couplers. Also, subject to an appropriate choice of the materials constituting the CRIGF, this work can be extended to obtain mode-selectable laser emission or nonlinear frequency conversion

Guided-mode resonance optical filters and components for embedded photonics

International audienceGuided-mode resonance filters are a new class of optical filters relying on subwavelength structuring ontop of an optical waveguide.From this simple coupling of waveguide and subwavelength structures, a whole taxonomy of optical filters can be derived: ultranarrow tunable filters, polarizing or polarisation-independent filters, transmission filters, small-size, angularly-tolerant filters at fixed wavelength.These filters rely on generic design rules and have been demonstrated in the visible, near-infrared, telecom infrared and mid-infrared.Compared to thin-film multistack technologies used for traditional optical filters, the fabrication of guided-mode resonance filters has a number of specific advantages and challenges that will be presented

Lithium-niobate-based Cavity Resonator-Integrated Guided-mode Resonance Filters

International audienc