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Y 3+ /Er 3+ ions co-doped oxyfluoride glass-ceramics were investigated to realize efficient 2.7 μm emission. Incorporation of Er 3+ ions into the fluoride nanocrystals was confirmed by the X-ray diffraction patterns, absorption spectra, emission spectra and Judd-Ofelt analysis. With an increase in the Y 3+ /Er 3+ ratio, radiative lifetime, quantum efficiency and emission cross section of the 2.7 μm emission from Er 3+ ions were greatly improved, due to the reduced effective concentration of Er 3+ ions and suppressed cross relaxation processes among Er 3+ ions in the fluoride nanocrystals. Compared to other Er 3+ -doped glasses, Y 3+ /Er 3+ co-doped oxyfluoride glass-ceramics showed a promising potential for gain medium. [ABSTRACT FROM AUTHOR]

Spectroscopic property and energy transfer processes of singly doped and codoped Er 3+ and Nd 3+ fluoroaluminate glasses with low phosphate content are systematically analyzed. The absorption spectra of these glasses are tested, and the Judd–Ofelt (J–O) and radiative parameters are discussed based on J–O theory and the parameters changes substantially because of the other codoping ions. As for Nd 3+ : the main emission bands at 0.9 and 1.05 μm decrease in the codoped sample under the excitation of an 800 nm laser diode from the emission spectra because the Er 3+ : 4 I 11/2 level reduces the Nd 3+ : 4 F 3/2 level effectively through the energy transfer process Nd 3+ : 4 F 3/2 → Er 3+ : 4 I 11/2 . For Er 3+ , the emission at 1.5 μm is restrained by codoping with Nd 3+ ions from the energy transfer process Er 3+ : 4 I 13/2 → Nd 3+ : 4 I 15/2 . The emission at 2.7 μm is enhanced because the Nd 3+ ions deplete the lower level and exert a positive effect on the upper laser level. The microparameters of the energy transfer between the Er 3+ and Nd 3+ ions are calculated and discussed using Forster–Dexter theory. The energy transfer efficiencies of the Nd 3+ : 4 F 3/2 to the Er 3+ : 4 I 11/2 and the Er 3+ : 4 I 13/2 to the Nd 3+ : 4 I 15/2 are 28.8% and 74.5%, respectively. These results indicate that Nd 3+ can be an efficient sensitizer for Er 3+ to obtain Mid-infrared (Mid-IR) emission and the codoped Er 3+ /Nd 3+ fluoroaluminate glass with low phosphate content is suitable to be used as the fiber optical gain media for 2.7 μm laser generation. [ABSTRACT FROM AUTHOR]

Highlights: [•] We presented the growth process of high quality Pr3+/Er3+:CaYAlO4 single crystal. [•] Pr3+ ions were co-doped in the crystal to suppress the self-termination bottleneck. [•] The up-conversion and NIR emission are almost quenched by co-doping Pr3+ ion. [•] 4I13/2 level depopulated much faster than 4I11/2 by co-doping Pr3+ ion. [•] The energy transfer mechanisms and energy transfer coefficients are studied. [ABSTRACT FROM AUTHOR]

Abstract: We present spectroscopic studies on the ∼5μm mid-infrared emission and energy transfer properties of Tb3+ doped KPb2Br5 and Nd3+ doped KPb2Br5 sensitized by Tm3+ ions. A series of co-doped Tm, Tb: KPb2Br5 and Tm, Nd: KPb2Br5 samples were prepared from purified starting materials of PbBr2, KBr, and rare-earth bromides. Resonant excitation into the 3H6 → 3F4 absorption transition of Tm3+ at ∼1.76μm resulted in an enhanced 5μm emission from Tb3+ and Nd3+ ions in Tm, Tb: KPb2Br5 and Tm, Nd: KPb2Br5, respectively. The existence of energy transfer between Tm→Tb and Tm→Nd in KPB was further evidenced by the quenching of the emission decay times of the 3F4 → 3H6 transition of Tm3+ in doubly doped Tm, Tb: KPb2Br5 and Tm, Nd: KPb2Br5 compared to singly doped Tm: KPb2Br5. [Copyright &y& Elsevier]