Thèse de doctorat en Chimie - physique
Soutenue le 08-07-2011
à Dijon en cotutelle avec l'Université de Wuhan (Chine) , dans le cadre de École doctorale Carnot (Dijon ; .....-2012) , en partenariat avec Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB) (Dijon) (laboratoire) .
Le président du jury était Xiujian Zhao.
Les rapporteurs étaient Thierry Cardinal, Jia Cheng Zhong.
Pas de résumé en français
Being compared with oxide glasses, chalcogenide glasses have fine infrared transmissivity and higher optical nonlinearity, and also could be drawn into optical fibers. So chalcogenide glasses and fibers have potential wide applications in the fields of all-optical information processing, infrared lasers, nonlinear optical devices, and so on, the studies of their optical nonlinearity are one of the attractive subjects in the area of optoelectronics at present. The main purpose of this paper is to improve the stability and enhance the intensity of nonlinearity in chalcogenide glasses and fibers by means of exploring new glass compositions, optimizing the external field poling method, designing and fabricating fibers with special structures, all of these will promote their real applications. The main results are concluded as follows . The glass-forming region of GeS2-GA2S3-AgX (X=Cl, Br, I) and GeS2-Ga (In)2S3-CuI systems were determined , the maximal content of the additive halides are 70% and 12% respectively. In both two systems glasses, with the increasing addition of halides, the thermal stability reduce, density and linear refractive index increase, the ultraviolet cut-off edges shift to longer wavelength, while the infrared cut-off edges keep almost the same. 30GeS2 35Ga2S3 35AgCl and 47.5GeS2 17.5Ga2S3 35AgCl surface- and bulk-crystallized glasses that contain AgGaGeS4 nonlinear optical crystallites were prepared. Obvious second harmonic generation (SHG) could be observed in these crystallized glasses, and their intensity relate to the distribution and size of the precipitated AgGaGeS4 crystals, the maximal second-order nonlinearity coefficients is as high as 12.4pm/V. These crystallized glasses have good chemical and SHG stability. For GeS2-Ga (In)2S3-CuI systems glasses, due to their small glass-forming region, they are not suit for the preparation of crystallized glasses that contain CuGaS2 or CuInS2 nonlinear optical crystals. According to the structural studies of two system glasses, the main structural units of theses glasses are [YS4-xXx] (Y=Ge, Ga, In. X=Cl, Br, I) mixed anion tetrahedrons, they form a three-dimensional glassy network through bridging sulphur bonds. When the contents of halides MX(M=Ag, Cu. X=Cl, Br, I) are low, some [XxS3-xGe(Ga)S3-xXx] (X=Cl, Br, I) mixed ethane-like structural units exist in the glass network, and they will gradually transform to [YS4-xXx] (Y=Ge, Ga, In. X=Cl, Br, I) mixed anion tetrahedrons with the increasing content of halides, till totally disappear. Both two system glasses have ultrafast (~150fs) third-order optical nonlinearity and reverse saturation absorption, they belong to self-focusing medium. The third-order optical nonlinearity mainly originate from the distortion of electron cloud of Y-X (Y=Ge, Ga, In, X=Cl, Br, I, S) bonds in the structural units. For GeS2-GA2S3-AgX (X=Cl, Br, I) system glasses, the largest nonlinear susceptibility n2 is 10.50x10-18 m/W, the smallest figure of merit (FOM) is 0.606. In addition, the relation of n2 with n0 do not obey Miller’s rule, but in accordance with the structural variation. Among the glass compositions with different additive halogens, Br-containing glasses have relatively best third-order nonlinearities. For GeS2-Ga (In)2S3-CuI system glasses, the largest nonlinear susceptibility n2 is 9.37x10-18 m/W, the smallest figure of merit (FOM) is 2.237. High purity AS2S3 glass performs and low loss single index fibers with diameter of 100~400µm that drawn form these performs were prepared, the transmission losses between 2~6 µm is only 0.5dB/m. AS2S3 tapered fibers have a uniform diameter of taper wasit, fine surface smoothness, and sharp taper transition part.