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Investigation par spectroscopie Raman des propriétés photoréfractives et microstructurales de LiNbO3 dopé

Abstract : Lithium niobate LiNbO3 (LN) is an excellent material for various applications in particular thanks to its photorefractive (PR) properties. One of the research goals for this material consists in performing efficient PR optical waveguides for integrated optics.The objective of the thesis is to determine the optimum performing conditions for the iron (Fe) diffusion in LN, by controling its microstructure and estimating its PR properties with only one technique, Raman spectroscopy.Several LN:Fe samples have been studied within this work. The aim is, among others, to control the iron diffusion profile, and to estimate the influence of the oxidizing or reducing treatment on the different crystals.Indeed I was able to show that the microstructure has been affected not only by the introduction of a dopant as Fe, but also by the various treatments. I showed for the first time the mecanism of Fe ions incorporation in LN structures obtained by diffusion.Otherwise, I proposed a new approach of the Raman activity rules, in the way they can take into account optical nonlinearities of the second order, which is generally neglected in litterature. Thus I have established the Raman configurations where, or the intensities of the lines are enhanced, or new lines are activated by a nonlinear process. These predictions have been confirmed by experimental results obtained on many samples. At last, I was able to propose a new method for the estimation of the PR efficiency, allowing to compare usefully several samples according to their doping or treatments.
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Submitted on : Thursday, March 29, 2018 - 1:58:15 PM
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Sabrina Mignoni. Investigation par spectroscopie Raman des propriétés photoréfractives et microstructurales de LiNbO3 dopé. Autre [cond-mat.other]. Université Paul Verlaine - Metz, 2010. Français. ⟨NNT : 2010METZ017S⟩. ⟨tel-01752795⟩



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