Search

Abstract: The spectroscopic investigation of Tm3+ or (Nd, Yb, Tm)-doped Sc2O3 transparent ceramics, as laser-active media for visible and IR emission, was performed. The spectra are dominated by Tm3+ ions in sites of C2 symmetry and an energy level scheme and other spectral parameters were determined. The strong concentration quenching of 3H4 level emission in Tm:Sc2O3 at 300K is discussed by considering the resonant cross-relaxation (3H4→3F4)−(3H6→3F4) process and multipolar interactions of various orders. The main energy-transfer processes leading to the blue upconversion emission from the 1G4 Tm3+ level in (Tm, Nd, Yb):Sc2O3 ceramic, under pulsed pumping at 808.3nm were evidenced. [Copyright &y& Elsevier]

Abstract: An analysis of the high resolution spectra of the Pr3+ in strontium lanthanum aluminates, charge compensated with magnesium Sr1−x Pr y La x−y Mg x Al12−x O19, (on a large composition range) is presented. The spectra are mainly dependent on the composition parameter x, and show more Pr3+ centers, two of them stable. Based on composition dependence and polarization data, structural models for the main two centers are proposed. [Copyright &y& Elsevier]

Abstract: A comparative discussion of the spectroscopic and energy transfer properties of the Yb3+ ion in single crystals and transparent ceramics of cubic sesquioxide materials is presented. The spectroscopic studies of Yb3+ and of other rare earth ions co-doped with Yb3+ in transparent ceramic sesquioxides with ceramic grains of tens of microns show that the variety of structural centres of the doping ions and the distribution of the doping ions in these centres as well as the crystal field interaction, the electron–phonon interaction and the energy transfer processes in these materials are similar to those from single crystals. The cooperative absorption and emission of Yb3+ in transparent Sc2O3 ceramics, facilitated by the very suitable packing of the cationic sites, corresponds to the trends observed in the crystalline materials, showing that no obvious agglomeration of Yb3+ in these ceramics takes place. [Copyright &y& Elsevier]

Several aspects of the RE3+ pairs effects in garnets and sesquioxides, such as static and dynamic spectral features and their nature are analyzed. The data on Nd3+, Eu3+, Er3+ or Yb3+ pairs in YAG or Y2O3 are especially discussed. Data showing that the ionic radii misfit between RE3+ and replaced host ion leads to the spectral shifts of pair satellites from the isolated ion lines and even to anisotropic effects are presented. Although the direct ion–ion short-range magnetic (superexchange) interactions have a strong effect on the emission decay of the pairs, their static effects are relatively small in these lattices. The data on energy transfer in RE3+ pairs of similar or different centers (in the case of sesquioxides) or cooperative processes and the characteristics of ion–ion interactions function on ion, transitions and matrix are discussed. [Copyright &y& Elsevier]

The paper presents the results on the energy transfer processes of Nd3+ doped Y2O3 transparent polycrystalline ceramics. The 4F3/2 decays are highly non-exponential at concentrations larger than 0.1 at%. For concentrations up to 3 at% the emission kinetics can be described in terms of a static cross-relaxation (calculated by using the discrete structure and two types of interactions—short range and dipole–dipole) plus a migration term. Only C2 sites are considered in the quenching. The transfer parameters that describe coherently the decays up to 3 at% are determined. The high concentration effects and the concentration dependence of the quantum efficiency are discussed. [Copyright &y& Elsevier]

Reduction of the quantum defect in four-level lasers by pumping directly into the emitting level can improve laser emission parameters and diminish heat generation. Using concentrated components can compensate reduced absorption in the emitting level of Nd laser materials. These benefits are demonstrated by stable and highly efficient 1064 nm continuous-wave laser emission of Nd:YVO4 components of 1, 2 and 3 at.% Nd under end-pumping into 4F3/2 at 878.6 nm with a Ti:sapphire laser. [Copyright &y& Elsevier]

Abstract: The paper reports the first observation of cooperative optical absorption and emission processes in Yb3+:Sc2O3 transparent laser ceramics. The intensity of cooperative processes in highly transparent ceramics Yb3+:Sc2O3 with up to 30at.% Yb scales well with the data existing on single crystals and indicates that the distribution of the Yb3+ ions is random, without regions of agglomeration. [Copyright &y& Elsevier]

Highly transparent Sc2O3 ceramics with uniform doping up to 0.5 at. % Nd and with (Nd, Yb) codoping are reported. The spectroscopic and emission decay properties of Nd:Sc2O3 ceramics are similar to those of single crystals. Highly efficient Nd-to-Yb energy transfer is observed in the codoped ceramics. It is inferred that these materials have potential for construction of Nd or Nd-sensitised-Yb lasers. [ABSTRACT FROM AUTHOR]

Neodymium-doped strontium lanthanum aluminate crystals Sr1-xLax-yNdyMgxAl12-xO19 contain two structural Nd centers with slightly different spectroscopic properties, whose proportion is determined by the composition parameter x. By choosing a composition with x=0.4, which grants the dominance of one of these centers (the center C1), whose properties are suitable for quasi-three-level Nd laser scheme, efficient 901 nm continuous-wave laser emission (slope efficiency ∼0.74) was obtained under 792 nm Ti:sapphire laser pumping. Preliminary experiments evidence the possibility of obtaining 450.5 nm radiation by frequency doubling. Owing to the large absorption linewidth (∼4 nm) this crystal shows good prospect for diode laser pumping. [ABSTRACT FROM AUTHOR]

The possibility of basic enhancement of the overall optical-to-optical efficiency of intracavity frequency-doubling devices for the 1 μm continuous-wave (cw) Nd lasers by direct pumping into the emitting level and by using concentrated laser materials is discussed. This possibility is demonstrated for 1.0 and 2.4 at. % Nd:Y[sub 3]Al[sub 5]O[sub 12] (Nd:YAG) crystals pumped by a Ti:sapphire laser at 885 nm. A slope efficiency of 0.79 in absorbed pump power was obtained for the 1064 nm emission of a 1.0 at. % Nd:YAG crystal. The effect of enhancement of intracavity emission on the second-harmonic emission is manifested in a drastic reduction of emission threshold and in an increased dependence on the absorbed power. The use of concentrated Nd:YAG crystal enables a better use of the pump power and improves the overall optical efficiency of the intracavity frequency-doubling devices. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

One-micron continuous-wave (cw) laser emission with 0.80 slope efficiency (0.79 optical-to-optical efficiency) under Ti: sapphire and 0.75 slope efficiency relative to absorbed power under diode-laser pumping at 880 nm into the emitting level is demonstrated in a 1-mm-thick, 1.0-at. % Nd:YVO[sub 4] crystal. These values are superior to those obtained with 809-nm pumping into the level [sup 4]F[sub 5/2], and can be explained consistently by the effect of the quantum defect between the pump and laser radiation, the superposition of pump and laser mode volumes, the pump-level efficiency and the residual optical losses. In the analysis of the 809-nm pumping data a pump-level efficiency equal to the unity was employed, as determined with a method based on the pump-saturation effects on absorption. [ABSTRACT FROM AUTHOR]

The possibilities of improvement of laser emission characteristics and reduction of heat generation by direct pumping at 887 nm into the emitting level [sup 4]F[sub 3/2] of Nd[sup 3+] in the self-frequency-doubling crystal Nd-GdCOB [GdCa[sub 4]O(BO[sub 3])[sub 3]] are discussed. Enhanced laser emission performances at fundamental 1060 nm, and especially at the self-frequency-doubled 530 nm wavelengths as compared to the traditional 811 nm pumping into the [sup 4]F[sub 5/2] level, are demonstrated. [ABSTRACT FROM AUTHOR]

Highly efficient 1064 nm continuous-wave laser emission under 885 nm diode pumping in concentrated Nd: Yttrium aluminum garnet (YAG) crystals (up to 3.5 at. % Nd) and ceramics (up to 3.8 at. % Nd) is reported. A highly doped (2.4 at. %) Nd:YAG laser, passively Q switched by a Cr[sup 4+]:YAG saturable absorber, is demonstrated. [ABSTRACT FROM AUTHOR]