Spectroscopy and CW first laser operation of Yb-doped Gd_3(Al_05Ga_05)_5O_12 crystal

We present the spectroscopic characterization and laser operation of a 2%at. Yb doped Gd3(Al0.5Ga0.5)5O12 (Yb:GAGG) crystal, grown with the Czochralski method. We determined the absorption and the emission spectrum, the upper level lifetime, and the thermal conductivity. The internal disordered structure determines a significant broadening of the emission band (12.1 nm FWHM) with respect to the parent composition Yb:GGG (8 nm FWHM). The laser performances were evaluated on an end pumped cavity, using a CW semiconductor laser as the pump source. We obtained a maximum slope efficiency of 60.8% and an optical to optical efficiency of 46.0%, with a maximum output power of 4 W, limited only by the available pump power. The tuning range extends from 995 nm to 1050 nm. To our knowledge this is the first spectroscopic investigation and the first assessment of the laser performance of an Yb:GAGG crystal with this composition (i.e. Al/Ga balance = 0.5/0.5)

Near-infrared luminescence of rare earth ions in oxyfluoride lead borate glasses and transparent glass-ceramic materials

Oxyfluoride lead borate glasses singly doped with Nd3+ and Er3+ ions have been studied before and after thermal treatment. The orthorhombic PbF2 crystallites are formed during thermal treatment, which was evidenced by X-ray diffraction analysis. Near-infrared luminescence spectra at 1.06 μm and 1.53 μm have been registered for samples before and after annealing, which correspond to the main 4F3/2–4I11/2 and 4I13/2–4I15/2 laser transitions of Nd3+ and Er3+ ions, respectively. Luminescence decays from 4F3/2 state of Nd3+ and 4I13/2 state of Er3+ have been analyzed in detail. Contrary to Nd-doped samples, the luminescence lines obtained for Er-doped transparent oxyfluoride glass-ceramics are more intense and narrowed, whereas the luminescence decays from 4I13/2 state of Er3+ are slightly longer in comparison to precursor glasses

Physical properties of InF3-based glasses

Results of X-ray diffraction (XRD), differential scanning calorymetry (DSC), electron probe microanalysis (EPMA) and optical absorption of InF3-based glasses are reported. Different concentrations of rare earth ions have been added to a base glass. XRD results show that no crystalline phases are formed. Characteristic temperatures were determined by DSC and values of glass stability parameters were calculated. Also, the effect of rare earth ions on the thermal stability of InF3-based glasses has been investigated. From the optical absorption measurements and Judd- Ofelt method the intensity parameters have been calculated. In consequence the trends of the intensity parameters are discussed as a function of the number of 4/electrons

Broadband near-infrared luminescence in lead germanate glass triply doped with Yb3+/Er3+/Tm3+

This paper deals with broadband near-infrared luminescence properties of lead germanate glass triply doped with Yb3+/Er3+/Tm3+. Samples were excited at 800 nm and 975 nm. Their emission intensities and lifetimes depend significantly on Er3+ and Tm3+ concentrations. For samples excited at 800 nm, broadband emissions corresponding to the overlapped 3H4 ! 3F4 (Tm3+) and 4I13/2 ! 4I15/2 (Er3+) transitions centered at 1.45 m and 1.5 m was identified. Measurements of decay curves confirm reduction of 3H4 (Tm3+), 2F5/2 (Yb3+) and 4I13/2 (Er3+) luminescence lifetimes and the presence of energy-transfer processes. The maximal spectral bandwidth equal to 269 nm for the 3F4 ! 3H6 transition of Tm3+ suggests that our glass co-doped with Yb3+/Er3+/Tm3+ is a good candidate for broadband near-infrared emission. The energy transfer from 4I13/2 (Er3+) to 3F4 (Tm3+) and cross-relaxation processes are responsible for the enhancement of broadband luminescence near 1.8 m attributed to the 3F4 !3H6 transition of thulium ions in lead germanate glass under excitation of Yb3+ ions at 975 nm

Influence of PbX2 (X = F, Cl, Br) content and thermal treatment on structure and optical properties of lead borate glasses doped with rare earth ions

Oxyhalide lead borate glasses doped with rare earth ions have been studied before and after thermal treatment. The rare earths as optically active ions were limited to the Er3+ ions. Near-infrared luminescence due to the main 4I13/2–4I15/2 laser transition of Er3+ was registered. The introduction of PbX2 to the borate glass results in a reduction of spectral linewidth and an increase of luminescence lifetime of 4I13/2 state of Er3+ ions. The unusual large spectral linewidth for 4I13/2–4I15/2 transition of Er3+ in the oxide glass host was obtained, whereas the luminescence decay from 4I13/2 state is longer for a sample with PbF2 than PbCl2 and PbBr2. Heat treatment introduces transformation from a glass to transparent glass-ceramic (TGC). The coordination sphere around Er3+ ions is changed, giving important contribution to the luminescence characteristics. The spectroscopic consequence of this transformation is the increase of luminescence lifetime and the narrowing of spectral lines of Er3+

Optical and EPR spectroscopy of Er3+ in lithium yttrium borate, Li6Y(BO3)3:Er single crystals

The energy levels of Er3+ ions have been determined in lithium yttrium borate (Li6Y(BO3)3) single crystals in a wide spectral range between 6000 and 40000 cm-1 together with an analysis of the ground state, using optical and EPR spectroscopy. The crystal field splittings of the 4I15/2 ground state and those of nearly all excited states up to the 4D7/2 manifold have been obtained at low temperature from luminescence (T = 5 K) and absorption (T = 9 K) measurements, respectively. The numbers of experimentally observed Stark sublevels agree well with those expected theoretically for Er3+ ions occupying a single low symmetry (C1) site. A full set of g- and 167Er hyperfine tensor parameters are presented for the ground state characterized by EPR; the measured Orbach-type spin-relaxation rates viz. the involved activation energies correspond to the optically derived lowest excited sublevels

First-principles study on the energetics and vibrational properties of the S2 - impurity in alkali-halide crystals

金沢大学大学院自然科学研究科計算科学金沢大学理学部We have performed first-principles electronic structure calculations for the S2 and S2- molecules in the vacuum and found that the calculated equilibrium bond lengths and vibrational spectroscopic constants are in good agreement with the experiments as well as the previous calculations. Based on this conformation we extended these calculations to the substitutional S2- molecule in the alkali halides, such as NaCl, NaBr, NaI, KCI, KBr, KI, RbCl, RbBr, and RbI. It is found from these calculations that the S2- center aligned to [110] direction is generally favorable over those with the [100] and [111] orientations, in agreement with the experiments. We also found that the vibrational frequencies of the S2- anion in the alkali halides shift to higher energies with decreasing lattice parameters. These results suggest that the change in the bond length of the S2- anion in the matrices depends on the species of halogen atom, while the frequencies are influenced by the species of alkali atom

Effect of symmetry reduction on the electronic transitions in polytypic GdAl3(BO3)4:Eu:Tb crystals

The existence of a recently described monoclinic phase (C2/c, Z=8) in addition to the well-known Huntite type rhombohedral (R32) polytypic modification of the GdAl3(BO3)4 (GAB) crystal at room temperature provides a unique possibility to investigate the incorporation of rare earth dopants into slightly modified crystal lattice by spectroscopic methods. In these characteristic GAB structures the dopant ions, e.g Tb3+ or Eu3+ , possess slightly different neighbor geometries and local symmetries. The Tb3+:7F6 → 5D4 and Eu3+:7F0,1,2 → 5D0,1,2 electronic transitions were successfully identified in the absorption spectra using polarization, concentration and temperature dependent measurements in both polytypic modifications. The positions of the investigated Tb lines are shifted by up to 10 cm−1 due to symmetry changes. In addition, some of the Eu lines show splittings of about 4–30 cm−1 as a consequence of the change of the local environment. From the room temperature absorption measurements some of the low energy crystal field levels of 7F and 5D states of the Eu3+ ions were successfully determined for both modifications

The investigation of YAlO3-NdAlO3 system, synthesis and characterization

The binary phase diagram of the YAlO3 (YAP) - NdAlO3 (NAP) system was determined by differential thermal analysis (DTA) and X-ray powder diffraction (XRD) measurements. High purity nanocrystalline powders and small single crystals of Y_{1-x}Nd_{x}AlO_3 (0 \leq x \leq 1) have been produced successfully by modified sol-gel (Pechini) and micro-pulling-down methods, respectively. Both end members show high mutual solubility >25% in the solid phase, with a miscibility gap for intermediate compositions. A solid solution with x \approx 0.2 melts azeotropic ca. 20 degrees below pure YAP. Such crystals can be grown from the melt without segregation. The narrow solid/liquid region near the azeotrope point could be measured with a "cycling" DTA measurement technique.Comment: 12 pages, 8 figures, submitted to J. Alloys. Comp