Etude et développement de sources laser à fibre dopées Ytterbium émettant à des longueurs d'ondes exotiques pour des applications industrielles et médicales

Abstract : Gas laser technology (Ar ion and HeCd lasers) is now largely obsolete, with new production rapidly disappearing. Given the vast application domain based around these wavelengths (488nm, 325 nm…), it seems extremely important to develop alternative solutions. The work presented in this thesis covers the study of relevant solutions via frequency conversion of Yb fiber lasers emitting on the three level transition at 976 nm. The necessary conditions for laser operation in this zone where absorption and emission peaks are superimposed are presented. Next, we present the development of a single mode, single frequency source at 976 nm giving a record 35W output power with diffraction limited performance (M2<1.1). Frequency doubling of the fundamental radiation in a PPSLT crystal allowed the generation of more than 4W of output at 488 nm in a single pass configuration with extremely low noise (0.05%RMS from 100Hz to 10MHz).Subsequently, 760 mW of output power was generated at 325 nm via frequency tripling of a multi-watt nanosecond source at 976 nm (5ns, 100 kHz). Type I and type II interactions in LBO were used in this case allowing us to demonstrate an overall conversion efficiency of 10% from IR to UV.Finally, we report on the generation of 2W of output power at 325 nm by frequency tripling of a 15 ps laser generating 16W at 976 nm, representing a pulse energy of 0.8μJ and a peak power of 52 kW (conversion efficiency of 12%).
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Romain Dubrasquet. Etude et développement de sources laser à fibre dopées Ytterbium émettant à des longueurs d'ondes exotiques pour des applications industrielles et médicales. Micro et nanotechnologies/Microélectronique. Université de Bordeaux, 2014. Français. ⟨NNT : 2014BORD0415⟩. ⟨tel-02164591⟩

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