ED Sciences Chimiques
Total Synthesis of the Vescalagin - Natural Bioactive Product of the C-Glucosidic Ellagitannins Family
by Romain LARRIEU (Institut des Sciences Moléculaires)
The defense will take place at 10h00 - Salle de conférence Institut des Sciences Moléculaires, Bâtiment A12 3ème étage Est, 351 Cours de la Libération, 33405 TALENCE
in front of the jury composed of
- Stéphane QUIDEAU - Professeur des universités - Université de Bordeaux - CoDirecteur de these
- Nicolas BLANCHARD - Directeur de recherche - Université de Strasbourg - Rapporteur
- Erwan POUPON - Professeur des universités - Université Paris-Saclay - Rapporteur
- Shinnosuke WAKAMORI - Assistant professor - Tokyo University of Agriculture - Examinateur
- Yannick LANDAIS - Professeur des universités - Université de Bordeaux - Examinateur
- Denis DEFFIEUX - Professeur des universités - Université de Bordeaux - CoDirecteur de these
(–)-Vescalagin, an emblematic member of the C-glucosidic ellagitannin family, is a water-soluble compound that can notably be extracted from oak (Quercus) or chestnut (Castanea) heartwood. Vescalagin is known to express various biological activities. For example, it acts as a preferential catalytic inhibitor of the α-isoform of the human DNA topoisomerase II, an enzyme targeted by anti-cancer drugs. Vescalagin also acts as an anti-actin agent capable of disrupting filamentous actin in cells and expresses an actin-dependent inhibition of bone resorption by osteoclastic cells. From a structural point of view, vescalagin features two atropoisomerically-defined bi- and teraryl units made up of galloyl units: a 4,6-hexahydroxydiphenoyl unit (HHDP) and a 2,3,5-nonahydroxyterphenoyl unit (NHTP), which are esterified onto an open-chain D-glucose core. Its other characteristic structural element is the presence of a C-arylglucosidic bond linking the NHTP unit to the carbon-1 center of the glucose core. This bioinspired synthesis exploits copper(II)•(di)amine oxidizing complexes for the coupling of galloyl units. Throughout this synthesis leading to vescalagin, other natural substances were produced such as tellimagrandin I, pedunculagin and castalagin.
ED Sciences Physiques et de l'Ingénieur
Experimental and numerical study of a high-power 2 µm monolithic fiber laser source in continuous-wave
by Félix SANSON (Centre Lasers Intenses et Applications)
The defense will take place at 9h30 - Amphi F Université de Bordeaux, campus de Peixotto Bâtiment A29 351 cours de la Libération 33405 Talence
in front of the jury composed of
- Inka MANEK-HÖNNINGER - Professeure des universités - Université de Bordeaux - Directeur de these
- Sébastien FEVRIER - Professeur des universités - Institut de Recherche XLIM-UMR7252 - Rapporteur
- Marwan ABDOU AHMED - Directeur de recherche - Institut für Strahlwerkzeuge (IFSW) - Rapporteur
- Sylvie PAOLACCI-RIERA - Docteure - Agence de l'innovation de défense (AID) - Examinateur
- Philippe BALCOU - Directeur de recherche - Université de Bordeaux - Examinateur
Many applications require lasers with beam propagation over long distances, for example telecommunications, LIDARs, laser weapon systems, or directed infrared countermeasures. Therefore, there is a need of high-power laser sources delivering several hundreds of watts with a good beam quality and at a wavelength adapted to propagation over long distances in the atmosphere. The transmission window around 2 µm is particularly interesting and can be achieved with lasers based on active media doped with rare-earth ions such as thulium or holmium. Fiber lasers are often privileged thanks to their ability to produce high output power and their potential of an alignment-free architecture. For a long time, the Master-Oscillator Power Amplifier (MOPA) architecture was seen as the solution for scaling up 2 µm fiber laser sources to several kilowatts, as for 1 µm sources. However, for the past fifteen years, this architecture has shown technological limitations, and no source has exceeded 1.2 kW. The high heating of both fibers and components is largely responsible for this limitation. A new strategy has been studied in recent years, involving the combination of several sources with moderate power levels. This combination can be spectral for example and requires the use of several primary sources delivering a few hundred watts at 2 µm. For reasons of compactness, robustness and compatibility with a combined source onboarding, the single-oscillator architecture is a perfect approach. To date, all-fiber thulium-doped fiber lasers demonstrated in the literature achieved up to 570 W of power. However, they exhibited very large spectra, broadened by nonlinear effects and high heating of the fiber Bragg gratings that composed the laser cavity, and a beam quality not totally suitable for long-distance propagation. This work is devoted to the study of the behavior of 2 µm all-fiber single-oscillator thulium-doped fiber laser sources. An in-house algorithm developed in this manuscript and used to perform simulations and an active splicing method for fiber splice optimization lead to the achievement of 680 W at 2036 nm (44 % optical-optical efficiency), which is the highest 2 µm output power achieved by an all-fiber single oscillator. Beyond the power record, its 1.6 nm spectrum width and its beam quality factor M² lower than 2 make it a primary source perfectly suited to beam-combining methods.