Multisites Cr3+ in GGG and GSGG garnets

The emission and excitation spectra of Cr³⁺ -doped Gd₃Ga₅O₁₂ (GGG) and Gd₃Sc₂Ga₃O₁₂ (GSGG) are explained in the light of multisite effects. The situation is particularly complicated in the case of GSGG, where the different sites have²E energy levels near each other which overlap with the⁴A₂ ⁴T₂ absorption bands. The spectra obtained under selective excitations are interpreted on the multisite assumption.     

Raman and optical absorption spectroscopic investigation of Yb-Er codoped phosphate glasses containing SiO_2

Yb-Er codoped Na2O-Al2O3-P2O5-xSiO2 glasses containing 0 - 20 mol% SiO2 were prepared successfully. The addition of SiO2 to the phosphate glass not only lengthens the bond between pS＋ and non-bridging oxygen but also reduces the number of P=O bond. In contrast with silicate glass in which there is only four-fold coordinated Si4＋, most probably there coexist [SiO4] tetrahedron and [SiO6] oetahedron in our glasses. Within the range of 0 - 20 mol% SiO2 addition, the stimulated emission cross-section of Era＋ ion only decreases no more than 10%. The Judd-Ofelt intensity parameters of Er3＋, Ω2 does not change greatly, but Ω4 and Ω6 decrease obviously with increasing SiO2 addition, because the bond between Er3＋ and O2- is more strongly eovalently bonded.     

Luminescent properties of cobalt-doped α-ZnAl2S4 spinel type single crystals

The absorption and luminescent properties of α-ZnAl₂S₄:Co spinel type crystals grown by chemical transport reactions method are investigated. The spectra are assigned to the electronic transitions of Co²⁺ ions located in tetrahedral sites. It is shown, that the revealed four radiative spectral components are caused by the ²A(²G)→⁴T₁(⁴F), ⁴T₁(⁴P)→⁴T₂(⁴F), ²E(²G)→ ⁴T₂(⁴F) and ²E(²G)→⁴T₁(⁴F) transitions.     

From optical spectroscopy to a concentration quenching model and a theoretical approach to laser optimization for Yb3+-doped YLiF4 crystals

A spectroscopic characterization was carried out to identify crystal-field levels for magnetic-dipole transitions of Yb³⁺ ions located in the Y³⁺ dodecahedral S₄ crystallographic site in YLiF₄ (YLF) crystals which were grown either by the Czochralski technique or by the laser heated pedestal growth (LHPG) technique. The concentration dependence of the measured decay time of the ²F_5/2 excited level of Yb³⁺ was analysed in order to understand relevant concentration quenching mechanisms. Under Yb³⁺ ion infrared pumping, self-trapping and up-conversion non-radiative energy transfer to trace rare-earth impurities (Er³⁺, Tm³⁺) has been observed over the visible region and interpreted by a limited-diffusion process within the Yb³⁺ doping ion subsystem to the impurities. The principal parameters useful for a theoretical approach for potential laser applications of Yb³⁺-doped YLiF₄ crystals have also been given.     

Laser spectroscopy of spinel microcrystallites in a Cr3+ doped silicate glass

Laser spectroscopy of Cr³⁺ ions makes it possible to follow the crystallization process in a cordiente glass (52 SiO₂, 347 Al₂O₃, 12.5 MgO and 08 Cr₂O₃) Absorption and fluorescence are interpreted by structural considerations showing the variation of Cr³⁺ environment during heat treatment Fluorescence line narrowing is performed at 4 2 K giving information on the detailed crystal structure in MgAl₂O₄ spinel microcrystallites formed during heat treatment The splitting of the ²E level is close to 70 cm^?1 and the ¦2D¦ parameter ranges between 0 95 and 1 35 cm^?1 This wide distribution is associated with the well known disordered distribution of Mg²⁺ and Al³⁺ cations in MgAl₂O₄ spinels.     

Spectroscopic properties of Yb3+-doped Y3Al5O12 nano-ceramics obtained under different sintering pressures

Yb³⁺:YAG nano-ceramics have been obtained by a low temperature/high pressure sintering process. Structural properties have been studied by X-ray diffraction (XRD). Grain sizes and R.M.S micro-strains have been calculated based on the XRD patterns by Rietveld analysis method. Emission spectra and decay curves have been recorded and analyzed. It has been observed that the decay time decreases with the increase of sintering pressure. Presence of Yb³⁺–Yb³⁺ pairs have been detected by cooperative emission spectroscopy.     

Comparative first-principle analysis of un-doped and V3+-doped α-ZnAl2S4 spinel

The experimental and theoretical studies of the optical properties of pure α-ZnAl₂S₄ and α-ZnAl₂S₄:V³⁺ crystals were carried out. The ab initio and crystal field calculations of the structural and optical properties of α-ZnAl₂S₄:V³⁺ were compared with the corresponding experimental data. It was shown that the lowest vanadium 3d states are located at about 1.36 eV above the valence band's top. The complete energy level scheme of the α-ZnAl₂S₄:V³⁺ system, which includes the host's electronic band structure and impurity ion's energy levels, was suggested on the basis of the performed calculations.