Caractérisation spectroscopique du niobate de lithium sous forme de cristaux massifs et de guides d'onde

Abstract : Due to is large transparency and its important elctro-optic and non linaire optic constants lithium niobate (LN) is one of the most interesting materials for applications in integrated optics. This work deals with the characterisation of LN single crystals as well as LN wave guides by means of Raman spectroscopy (RS) and polaron luminescence (PL). In its congruent composition LN exhibits different types of point defects. Their concentration depends on the composition of the crystal. Our special interest was aimed at bulk crystals of under congruent composition. We managed to extend the linear law which connects the width of certain Raman lines with the composition of the crystal. This law now enables us to measure the out-diffusion of lithium into the titanium guides on a microscopic scale. PL can be observed within a wide range at ~800nm. Its intensity is directly correlated to the degree of the material's chemical reduction. We also demonstrated the relation between the luminescence and the incident intensity and the existence of a value of saturation. The PL was studied in pure, oxidized, reduced and in doped massif crystals as well as in wave guides. We defined a charactérisation method for those crystals. Thus we were able to deduce the spatial mapping of the chemical reduction of LN:Ti wave guide from the mapping of luminescence. This method was also applied to periodically polarised structures PPLN. We have shown that the Raman spectroscopy and the polaron luminescence are non-destructive, efficient and reliable methods for the characterisation of wave guides and PPLN on a microscopic scale
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Yun Zhang. Caractérisation spectroscopique du niobate de lithium sous forme de cristaux massifs et de guides d'onde. Autre [cond-mat.other]. Université Paul Verlaine - Metz, 2004. Français. ⟨NNT : 2004METZ002S⟩. ⟨tel-01750257⟩

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