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Etude des distributions angulaires d'absorption et d'autodoublage de fréquence du cristal biaxe monoclinique YCa4O(BO3)3 dopé avec des ions Nd 3+

Abstract : The work reported in this thesis is about new fundamental developments of linear and non linear crystal optics in biaxial media. First, it is about the study of the angular distribution of the absorption coefficient in polarized light, secondly the study of self-frequency doubling is concerned, this last property combining simultaneously laser effect and second harmonic generation in the same crystal. These two studies have been performed in the monoclinic biaxial crystal Ca4YO(BO3)3 doped with Nd3+ ions (Nd:YCOB) and cut as a sphere. Our study of the angular distribution of the absorption in the mirror plane of Nd :YCOB showed, for the first time to our knowledge, that in a monoclinic crystal the angle between the absorption frame and the dielectric frame strongly depends on the involved electronic transition. This fundamental result occurring in monoclinic and triclinic crystals has important consequences for devices since it is necessary to know the orientation of the absorption frame and of the fluorescence frame for their corresponding wavelength in order to implement a laser using a monoclinic or a triclinic crystal. The measurement of the angular distribution of the absorption in all directions of Nd:YCOB showed that it is based on two layers propagating the two polarization modes of the medium. They cross along continuous lines defining continuous directions of propagation for which the absorption is polarization independent. These particular directions could be very interesting when dealing with thermal effects. These results are completely original and all biaxial crystals are concerned i.e. from the orthorhombic, monoclinic or triclinic crystallographic systems. Having in mind how difficult it is to optimize simultaneously absorption properties, fluorescence properties and phase-matching conditions, we implemented a method of direct characterization of self-doubling frequency, the studied crystal being cut as a sphere and inserted between two mirrors. In these conditions, we showed that it is possible to directly measure all self-doubling frequency phase-matching directions in only one sample of the studied crystal. It is also the first time, to our knowledge, that a laser which gain medium is cut as a sphere is reported.
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Submitted on : Wednesday, May 26, 2010 - 12:07:25 PM
Last modification on : Thursday, November 19, 2020 - 1:01:01 PM
Long-term archiving on: : Thursday, September 16, 2010 - 3:08:10 PM

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  • HAL Id : tel-00486685, version 1

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Simon Joly. Etude des distributions angulaires d'absorption et d'autodoublage de fréquence du cristal biaxe monoclinique YCa4O(BO3)3 dopé avec des ions Nd 3+. Physique Atomique [physics.atom-ph]. Institut National Polytechnique de Grenoble - INPG, 2009. Français. ⟨tel-00486685⟩

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