Coherent beam superposition of ten diode lasers with a Dammann grating

We demonstrate the use of a binary diffractive optical element in a very simple setup to convert the multilobed beam from a low fill factor array of coherent laser diodes into a quasi-Gaussian beam. The phase profile of the grating is determined with a phase retrieval algorithm. Experimentally, the conversion efficiency reaches more than 44%. We also establish that this setup can be used to make an effective measurement of the coherency of the laser array

DNA-Destabilizing Agents as an Alternative Approach for Targeting DNA: Mechanisms of Action and Cellular Consequences

DNA targeting drugs represent a large proportion of the actual anticancer drug pharmacopeia, both in terms of drug brands and prescription volumes. Small DNA-interacting molecules share the ability of certain proteins to change the DNA helix's overall organization and geometrical orientation via tilt, roll, twist, slip, and flip effects. In this ocean of DNA-interacting compounds, most stabilize both DNA strands and very few display helix-destabilizing properties. These types of DNA-destabilizing effect are observed with certain mono- or bis-intercalators and DNA alkylating agents (some of which have been or are being developed as cancer drugs). The formation of locally destabilized DNA portions could interfere with protein/DNA recognition and potentially affect several crucial cellular processes, such as DNA repair, replication, and transcription. The present paper describes the molecular basis of DNA destabilization, the cellular impact on protein recognition, and DNA repair processes and the latter's relationships with antitumour efficacy

Narrow-line coherently combined tapered laser diodes in a Talbot external cavity with a volume Bragg grating

We present the phase locking of an array of index-guided tapered laser diodes. An external cavity based on the self-imaging Talbot effect has been built. A volume Bragg grating is used as the output coupler to stabilize and narrow the spectrum at 976 nm. A power of 1.7 W is achieved in the in-phase single main lobe mode with a high visibility. We have checked that each emitter is locked to the Bragg wavelength with a 100 pm spectrum linewidth. The experimental results compare well with numerical simulations performed with two-dimensional wide-angle finite difference beam propagation method

Narrow line width operation of a 980 nm gain guided tapered diode laser bar

We demonstrate two different schemes for the spectral narrowing of a 12 emitter 980 nm gain guided tapered diode laser bar. In the first scheme, a reflective grating has been used in a Littman Metcalf configuration and the wavelength of the laser emission could be narrowed down from more than 5.5 nm in the free running mode to 0.04 nm (FWHM) at an operating current of 30 A with an output power of 8 W. The spectrum was found to be tunable within a range of 16 nm. In the second scheme, a volume Bragg grating has been used to narrow the wavelength of the laser bar from over 5 nm to less than 0.2 nm with an output of 5 W at 20 A. To our knowledge, this is the first time spectral narrowing has been performed on a gain guided tapered diode laser bar. In the Littman Metcalf configuration, the spectral brightness has been increased by 86 times and in the volume Bragg grating cavity the spectral brightness has been improved over 18 times when compared to the free running operation. These schemes could be also extended for other wavelengths of interest in the future

GeoQAIR : Quantification de l'apport d'une plateforme d'observations Géostationnaires pour la surveillance de la Qualité de l'AIR en Europe

Monitoring of air quality (AQ) and its transport at the continental scale, as well as the development of efficient forecast systems for air quality is one of the issues included in the GMES (Global Monitoring for Environment and Security) European Programme for the establishment of a European capacity for Earth Observation. The availability of satellite instruments which have the ability to monitor tropospheric ozone in the lowermost troposphere would be a step forward for this system. To monitor small scale and short term processes as involved in pollution event development, a geostationary Earth orbit (GEO) observing system is particularly well adapted. Future GEO missions dedicated to air quality monitoring using thermal infrared (TIR) instruments are planned to be operating over the USA, Japan and Korea, while existing and planned missions over Europe are not well adapted for this task. One of the objectives of the GeoQAIR project is to evaluate different satellite instrument concepts for their ability to monitor AQ and in particular quantify the possible impact for AQ forecasting. Four instruments have been considered for this study: the existing instrument IASI on MetOp-A (Low Earth Orbit - LEO - mission), the planned IASI-NG on the EPS-SG platform (LEO mission) and IRS on Sentinel4/MTG platform (GEO mission mainly dedicated to meteorology) and a new GEO mission concept, MAGEAQ, dedicated to AQ monitoring and proposed at the last Earth Explorer 8 call of ESA. Pseudo-observations for the four instruments have been generated to simulate one month of ozone observations over Europe. About 45 millions of individual measurements have been simulated using the EGI facilities. A first analysis of the performances of the different instruments to measure ozone in the lowermost troposphere demonstrates that the short time and space scale processes implied in air pollution development will not be correctly apprehended with the current existing and planned missions. Dedicated instrument with sufficient spectral resolution and signal to noise ratio, as proposed within the MAGEAQ mission concept, are necessary to correctly represent these processes

Comparative analyses of three olive mill solid residues from different countries and processes for energy recovery by gasification

International audienceBiomass is a renewable energy source which may provide a significant contribution to the reduction of fossil fuels consumption and the associated environmental impacts. The use of agricultural or agro-industrial waste such as solid residues from olive oil production is particularly relevant since it may combine several benefits. Gasification is a promising waste-to-energy technique for this type of lignocellulosic residues. The technology however is adapted to a relatively limited panel of solid waste fuels of defined specifications, which must therefore be characterized properly to assess their adaptation. The purpose of this research was to analyze and compare three different olive mill solid residues by complementary techniques such as Fourier transform infrared spectroscopy (FTIR) and thermochemical methods, in order to characterize these residues as potential fuels for gasification. The results obtained underlined the complex nature of the residues and indicated that they were mainly organic, with very little mineral matter. In addition to the major organic components (cellulose, hemicelluloses and lignin), the presence of several minor organic constituents was shown by thermogravimetry coupled to differential scanning calorimetry and FTIR. The gas produced from pyrolysis was analyzed by gas chromatography and mass spectrometry. It was found to contain several degradation products from lignocellulosic material and olive oil, such as hydroxyacetone, furfural and methoxyphenols. The influence of the olive oil extraction process (two-phase or three-phase) was also demonstrated. It was shown that the thermochemical degradation of olive mill residues followed a complex pathway but the composition of the residues met the requirements for gasification for most parameters

Tunable Single-frequency operation of a diode-pumped Vertical-External Cavity Laser at the Caesium D2 line

International audienceWe report on a diode-pumped vertical external-cavity surface-emitting laser emitting around 852 nm for Cesium atomic clocks experiments. We have designed a 7-quantum-well semiconductor structure optimized for low laser threshold. An output power of 330 mW was achieved for 1.1 W of incident pump power. Furthermore a compact setup was built for low-power single-requency emission. We obtained an output power of 17 mW in a single longitudinal mode, exhibiting both broad (9 nm) and continuous (14 GHz) tunability around the Cesium D2 line. The laser frequency has been stabilized on an atomic transition with residual frequency fluctuations ~ 300 kHz. Through a beatnote experiment the -3 dB laser linewidth has been measured to < 500 kHz over 10 ms

Galactic Cosmic Rays from PBHs and Primordial Spectra with a Scale

We consider the observational constraints from the detection of antiprotons in the Galaxy on the amount of Primordial Black Holes (PBH) produced from primordial power spectra with a bumpy mass variance. Though essentially equivalent at the present time to the constraints from the diffuse $\gamma$-ray background, they allow a widely independent approach and they should improve sensibly in the nearby future. We discuss the resulting constraints on inflationary parameters using a Broken Scale Invariance (BSI) model as a concrete example.Comment: 10 pages, 3 figures Version accepted in Phys. Lett. B, conclusions unchange

COMPACT AND ROBUST SINGLE-FREQUENCY DIODE-PUMPED VECSEL AT THE CESIUM D2 LINE FOR ATOMIC CLOCKS

This work reports on an optically-pumped vertical external-cavity surface­emitting laser emitting around 852 nm dedicated to atomic physics experiments with cold Cs atoms. The design of the semiconductor active structure has been optimized to provide a low threshold. A low-power diode-pumped compact prototype has been developed with improved stability. With this setup, we obtained a 17-mW single frequency emission exhibiting large tunability around the Cesium D2 line. The laser linewidth has been measured to less than 500 kHz on a 10 ms time

900 nm Emission of a Nd:ASL Laser Pumped by an Extended-Cavity Tapered Laser Diode

PosterWe describe here the use of a 798-nm-stabilized high-brightness tapered laser diode to pump a Nd:ASL crystal for 900 nm laser operation. An output power of 150 mW is obtained