Research On Growth And Characterization Of Re-doped And Undoped NaGd（MoO₄）₂Crystals

Diode laser pumped solid-state lasers have the advantages of high efficiency andcompact structure. Up to now, developing novel laser crystals with wide absorptionband which can match LD radiation band still attracts much attention. Owing tospecial structure, double molybdate crystals present many good properties, such ashigh concentration doped with rare earth ions, broadened lines of spectrum of rareearth ions, high integral absorption and fluorescence cross-sections and largethird-order nonlinear optical susceptibility. In addition, double molybdate crystalshave good features of stable physical and chemical property, melting congruently andno polymorph transitions existing. These properties make double molybdate crystalscan match LD pump well and can be grown conveniently. Thus, double molybdatecrystals are promising commercial laser host. NaGd(MoO4)2is a kind of doublemolybdate crystal, but no report is found in the field of Raman property and2μmemission. In this paper the physical and chemical property, Raman property and2μmemission in rare earth doped NaGd(MoO4)2crystal are investigated.Polycrystalline NaGd(MoO4)2was prepared by solid state reaction, single crystalwas grown by CZ method and was annealed at930℃. XRD pattern indicated thecrystal belongs to tetragonal system, I41/a group. Thermal properties of crystal wereanalyzed by using TG-DSC curve. The melting point is1182℃, the specific heat is0.5J/g K at300K, which indicated the crystal has relative stable chemical property.Raman spectrum was measured, all Raman bands were assigned, and the maximumRaman shift of crystal is886cm-1. The crystal has potential to be used as Ramancrystal.Yb3+/Ho3+、Tm3+/Ho3+co-doped system were introduced in to crystal toinvestigate2μm emission. Yb3+/Ho3+: NaGd(MoO4)2and Tm3+/Ho3+: NaGd(MoO4)2single crystal were grown by CZ method. Crystal structure was identified and latticeconstant was calculated by using of the XRD pattern. The absorption and fluorescencespectrum were measured. J-O parameters, spontaneous transition rate, fluorescent branching ratio and radiative lifetime were calculated based on J-O theory. The energytransfer mechanism was investigated also. Fluorescent band during1.9μm-2.1μm(with bandwidth of110nm) and1.75μm-2.1μm (with bandwidth of350nm) weremeasured for Yb3+/Ho3+: NaGd(MoO4)2and Tm3+/Ho3+: NaGd(MoO4)2respectively.Thus the grown crystals have potential in realizing2μm turnable lasing.