Growth And The Spectra Properties Of Er:Yb:Y_0.5Gd_0.5VO₄ Laser Crystal

Yttrium Gadolinium vanadate crystal (Y_xGd_1-xVO₄) is a new laser host material. It has good laser properties such as large wide absorption band, high thermal conductivity and low threshold, which is same as GdVO₄ crystal. Y_xGd_1-xVO₄ crystal is a promising laser material for application of higher power LD pumping laser. In this thesis, polycrystalline raw materials were synthesized by liquid-phase reaction method. And the synthesized raw materials were detected by infrared spectrophotometer, differential thermal gravimetric analysis, X-ray powder diffraction method, respectively. Several Er,Yb:Y_0.5Gd_0.5VO₄ crystals with different concentration of Er, Yb have been grown by Czochralski method, The growth condition, atmosphere and annealing technology were investigated. The concentration and the effective segregation coefficients of the doped ions in Y_0.5Gd_0.5VO₄ crystals were detected and analyzed by ICP method. The lattice constants were measured by X-ray powder diffraction method. The laser damage threshold, the thermal expansion coefficient, specific heat and the thermal diffusivity of the crystals were also determined. The thermal conductivity of the crystals was calculated. After being oriented, cut and polished, the grown crystals were processed into a series of wafers. The polarization and non-polarization absorption spectra and fluorescence spectra of these wafers were measured at room temperature. The fluorescence decay curves were also measured in order to fit the fluorescence lifetime of the corresponding levels. The effect of ion concentration on luminescence and lifetime of Er³⁺ ions in Y_0.5Gd_0.5VO₄ host were studied in detail. According to the absorption spectra, the phenomenological intensity parameters Ω_λof Er³⁺ ions have been fitted based on the Judd—Ofelt theory. Moreover, the spectral parameters of Er³⁺ ions including radiative transition probabilities AJJ', oscillator strengths P_JJ', radiative lifetime Ï„and integrated emission cross-section Σhave been calculated. From the parameters mentioned above, the laser emission probability of Er,Yb:Y0.5Gd0.5VO4 crystal was discussed. The up-conversion mechanism of Er3+ ions and Er3+ sensitized by Yb3+ ions were also discussed. And the efficiencies of energy transfer from Yb3+ to Er3+ ions were calculated. The defects of crystals were observed by the polarismicroscope and the defects'concentration of crystals were calculated.