1,720,999 research outputs found
Nd3+ --> Yb3+ energy transfer in a codoped metaphosphate glass as a model for Yb3+ laser operation around 980 nm
No full textA complete spectroscopic investigation of a metaphosphate glass with composition Pb(PO3)(2) doped with various amounts of Nd3+ and Yb3+ ( 1 up to 10 at.%) is reported. Efficient Nd3+ --> Yb3+ energy transfers occur both radiatively and non-radiatively, the latter being dominant and partly resonant and partly phonon-assisted by phonons of the order of 950 cm(-1), which fits well with the reported Raman spectrum of the material. These transfers mainly concern the F-4(3/2) --> I-4(9/2) emission and the F-2(7) --> F-2(5/2) absorption transitions of the Nd3+ and Yb3+ ions around 900 nm, respectively. They are analysed both via spectral and temporal data. The results show that about 5% Nd3+ and 5% Yb3+ ions have to be incorporated to reach energy transfers exceeding about 65%, which is in agreement with data recently reported in the case of a YAl3(BO3)(4) crystal. Simulations based on the obtained data show that laser thresholds of a few tens of mW should be easily attainable by operating the materials in a channel waveguide configuratio
Fluorescence dynamics of YVO4:Tm3+, YVO4:Tm3+, Tb3+ and YVO4:Tm3+, Ho3+ crystals
No full textThe fluorescence dynamics of the 3H4 and 3F4 energy levels of Tm3+ in YVO4 single crystals codoped or not codoped with Tb3+ and Ho3+ ions was experimentally investigated and compared with classical energy-transfer models. In the YVO4:1% Tm3+ and YVO4:1% Tm3+, 1% Ho3+ crystals, the 3H4 state relaxes predominantly by internal cross-relaxation-type energy transfers, whereas in the YVO4:0.5% Tm3+, 1% Tb3+ and YVO4:1% Tm3+, 1% Tb3+ crystals the relaxation is dominated by direct energy transfers to the 7F1 state of the Tb3+ ions. In all of the codoped systems, strong energy transfers from the 3F4 state of the Tm3+ ions to the 7F1 and 5I7 states of the Tb3+ and Ho3+ codopants were evident. The electric dipole-electric dipole coupling parameter was evaluated for several cross-relaxation and direct-energy-transfer processes
Crystal growth, spectroscopic properties and laser performance of Nd:LuVO4, a new infrared laser material
No full textCompact diode-pumped passively Q-switched tunable Er-Yb double-clad fiber laser
Full text linkHighly-efficient repetitive passive Q-switching of a cladding-pumped Er-Yb fiber laser has been demonstrated by employing an external cavity configuration containing a Co2+:ZnS crystal as saturable absorber. Energies up to 60µJ in pulses of duration as short as 3.5ns (FWHM), corresponding to a peak power >10kW, have been generated, and the maximum slope efficiency with respect to absorbed pump power was 13%. Using a bulk diffraction grating in Littrow configuration to provide wavelength selective feedback, the passively Q-switched fiber laser was tuned over 31nm from 1532nm to 1563nm. The prospects for further improvement in performance will be discussed
Beneficial effect of Lu3+ and Yb3+ ions in UV laser materials
No full textSeveral Lu3+- and Y3+-based oxide and fluoride single crystals with isomorphic structures and doped with Ce3+ (or Pr3+) or codoped with Yb3+ ions have been grown and studied to show the beneficial effects of the Lu3+ and Yb3+ ions on their broad-band UV luminescence properties. Time-resolved color center absorption measurements clearly show the reduction of the usually observed UV laser pump-induced optical losses and thus confirm the previous gain and laser results obtained in these materials. Some preliminary interpretations of the involved mechanisms are advanced
LHPG and FLUX growth of various Nd:YVO4 single crystals: A comparative characterization
No full textThe growth of YVO4 single crystals was investigated by the Laser-Heated Pedestal Growth method (LHPG) and flux technique. Several crystal growth experiments using LHPG were performed to optimize growth conditions by varying the Y2O3 and V2O5 proportions of the starting powders, the growth atmosphere, the laser power, and the pulling rate. The crystals were characterized by X-ray diffraction (XRD), optical microscopy, energy dispersive X-ray (EDX) microprobe, chemical analysis, and Raman spectroscopy. © 1993 Elsevier Science Ltd
Growth, spectroscopic characterization, and laser performance of Nd:LuVO4, a new infrared laser material that is suitable for diode pumping
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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