Growth And Spectroscopic Study Of BaGd₂?MoO₄?₄ Crystals

Diode pumped all-solid-state lasers have the advantages of high efficiency,compact structure.To develop the efficient new crystals suitable for LD pumping laser is still a hot research focus in the field of laser materials.Due to the special structure and the random distribution of cation ions,BaGd₂?MoO₄?₄ has good physical and chemical stability,can high concentration doped with rare earth ions,broaden the absorption and emission bandwidth.The main research of the article includes the following sections:1.We systematically analyzed the research status and development prospect of the molybdate crystals,and point out the research necessity and purposes on BaGd₂?MoO₄?₄ crystals.2.We studied on the growth technology of Nd/Yb and Yb/Tm co-doped BaGd₂?MoO₄?₄,crystals.First polycrystalline raw material were prepared by solid-state reaction method,then the single crystal was grown by Czochraski method.3.The physical and chemical properties of two kinds of crystals have been characterized.We identified the crystal structure and calculated the crystal lattice parameters by using X-ray diffraction analysis technology?XRD?.The XRD pattern indicated the crystal belongs to monoclinic crystal system,C2/c group.The concentration of the doping rare earth ions were analyzed using ICP-AES method and the segregation coefficient is calculated out.Thermal properties of the crystals were analyzed by the differential calorimeter scanning analysis technology.The melting point is 1070? and has relative stable chemical and physical property in high temperature condition according to the TG-DSC curve.4.The spectra property of two kinds of crystals was systematic studied.The absorption and emission spectrum of the Nd/Yb:BaGd₂?MoO₄?₄ and Yb/Tm:BaGd₂?MoO₄?₄ were recorded.The absorption cross section were calculated.Judd-Ofelt parameters,spontaneous transition rate,fluorescent branching ratio and radiative lifetime were calculated based on Judd-Ofelt theory.The energy transfer mechanism was investigated also.Based on the fluorescence spectrum of the two kinds of rare earth co-doped crystal,The intensity of the fluorescence peak doped with 10at%Nd³⁺/10at%Yb³⁺ BaGd₂?MoO₄?₄ crystals significantly weaker than doping with 5at%Nd³⁺/10at%Yb³⁺BaGd₂?MoO₄?₄ crystal,and the fluorescence lifetime decreases as the concentration of Nd³⁺ ion increases.For Yb/Tm: BaGd₂?MoO₄?₄ crystal,it has a strong emission peak at 1809 nm,with the increase of Yb ion concentration,the full width at half maximum of the luminous intensity gradually increases and its luminous bandwidth is 176 nm,this indicates the crystal well matches LD pumping source,and can be a promising candidate in laser operating.