Croissance par la méthode Czochralski de cristaux non linéaires de borate : premières caractérisations

Abstract : The low temperature phase of baryum metaborate possesses non linear optical properties (NLO) that offer advantages regarding the generation of U.V. by frequency doubling.Lithium tetraborate is currently being studied for application to linear systems.The work presented concerns the growth of these materials and a first evaluation of their potential. The Czochralski method was used et lab to obtain crystals directly from a pure melt. The production of good quality crystals resulted from some key points. The initial choice of starting materials and the synthesis of powders from BBO in particular. The setup of thermal parameters such as temperature gradients and the temperature at the surface of the melt, as well as the adaptation of our equipement to the Czochralski growth technique for each material. The preparation of samples using polishing techniques respecting the hygroscopy of borate crystals and using original orientation techniques of BBO samples by micro-Raman spectroscopy and conoscopy. Original characterizations were made from the obtained samples. From absorption measures and effective ONL coefficients from Second Harmonic Generation, (SHG) we were able to not only validate the choice of -BBO crystal growth technique, but also perform a comparison with crystals from the liquid crystal growth technique, the most widely used method in industry. The obtained results are very encouraging regarding the generation of U.V. d by SHG. LTB crystals were available to the laboratory for characterization by Raman spectroscopy or by electro-optical measures
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Hermance Moussambi Membetsi. Croissance par la méthode Czochralski de cristaux non linéaires de borate : premières caractérisations. Autre [cond-mat.other]. Université Paul Verlaine - Metz, 2004. Français. ⟨NNT : 2004METZ007S⟩. ⟨tel-01750240⟩

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