Etude théorique et expérimentale de l'architecture d'un laser à solide monocristallin ou céramique dopé ytterbium pour la génération d'impulsions de grande énergie à haute cadence.

摘要

This work concerns the study of ytterbium doped laser systems for the generation of high energy pulses with high average power, within the pint of a laser for the inertial fusion energy. Ytterbium ion have a lot of advantages for high average power applications - low quatum defect, high fluorescence lifetime, no energy transfert phenomena between electronics levels. Thus, ytterbium doped laser media are able to store highs amount of energy with a low thermal load. About the choice of the laser media, we have proposed a thermomecanical figure of merits which shows that garnets and rare earth sesquioxydes are very well suited ti high average power applications. As far as the laser amplifiers architecture is concerned, we have concluded that longitudinaly diode-pumped thin disk amplifiers cooled by the rear face are an excellent solution to achieve a good management of thermal effects. Thanks to a numeric modeling of ytterbium doped laser amplifiers, we have optimized several parameters of the laser architecture and compared differents ytterbium doped laser media. We have shown that ytterbium doped rare earth sesquioxides appears to be excellent laser media for high average power applications. Moreover, we have shown that low temperatures are a very seducing solution ti improve both thermomecanical properties of amplifiers and spectroscopic properties of ytterbium ion. Thank to a gain switched cryigenic laser cavity, we have experimentaly demonstrated that energetic performances of yttrebium doped rare earth sesquioxides are far better at low temperatures.