The properties of cerium trifluoride scintillating crystals, grown in Russia using the Stockbarger's method, were investigated. The characteristics of CeF3, PbWO4, Bi4Ge3O12, and BaF2 crystals were compared for use in electromagnetic calorimeters to detect electrons and γ-rays of medium and high energies.

A-number of scientific and industrial applications (for instance in the field of telecommunication) require radiation sources with rather wide tunability within the 1.3 μm range. LiF crystals with stable F2- color centers have proved to be efficient source of widely tunable radiation which can be shifted to the desired region by means of Raman converters. In this report the barium nitrate Ba(NO3)2 Raman laser, pumped by tunable LiF:F2- color center (CC) laser was investigated For tuning range broadening the CC laser was pumped by passively Q-switched Nd:YLF laser with shorter oscillation wavelength (1.047 μm).

We have studied transformations of optical spectra of Ce3+ ions with 4f-5d inter-configurational transitions in CaF2 crystal caused by co-doping with optically inactive Sc3+ transition metal ions. The influence of gamma-irradiation of the co-doped crystal on the transformation of Ce3+ optical spectra was also studied. Possible mechanisms for the spectral transformations and the nature of different Ce3+ centers are discussed.

Wideband UV-visible luminescence under laser or CW lamp excitation was observed in y-irradiated Sc and Sc-Ce doped CaF2 crystals: 1) at 380 nm in Sc:CaF2 and Sc:Ce:CaF2 crystals, attributed to Sc2+ ions and 2) at 300 nm in Sc,Ce:CaF2 crystals, due to Sc-Ce aggregate centers.

Stokes and anti-Stokes UV-visible luminescence was investigated in γ-irradiated Sc and Sc-Ce doped CaF2 crystals. Wideband Stokes luminescence under laser or CW lamp excitation was measured: (1) at 380 nm (luminescence decay time τ ~ 17 μs) in Sc: CaF2 and Sc,Ce: CaF2 crystals, attributed to Sc2+ ions and (2) at 300 nm (τ ~ 40 ns) in Sc,Ce: CaF2 crystals, due to Sc-Ce aggregate centers. Anti-Stokes luminescence in the 250–350 nm spectral range with a 1 μs lifetime can be explained by exciton luminescence.

The fluorescence kinetics decay from F-3(3), H-3(5), H-3(4), F-3(4) multiplets of Tm3+ and F-5(5), I-5(5), S-5(2) + I-5(6), I-5(7), multiplets of Ho3+ ions in Y3Al5O12, Lu3Al5O12 and LiYF4 crystals was directly measured. On the basis of these measurements the multiphonon relaxation (MPR) rates of the transitions were determined.The theoretical dependence of multiphonon relaxation rates on the rare-earth ionic radii was derived using the non-linear (NL) theory of multiphonon relaxation. A good qualitative agreement of this dependence with new and earlier measured MPR rates in rare-earth ions in the row from Tm3+ to Pr3+ in YAG, YLF, and LaF3 crystals was obtained. The dependence of multiphonon relaxation rates on the crystal type is also considered.

The nanosecond and microsecond fluorescence kinetics decay from 3F3, 3H4,3H5, 3F4 multiplets of Tm3+ and 5S2,5F5,5I5,5I6,5I7 multiplets of Ho3+ ions in Y3Al5O12, Lu3Al5O12, and LiYF4 crystals with low dopant concentration was directly measured. On the basis of these measurements the multiphonon relaxation (MPR) rates for three, four, and five phonon transitions were determined.The theoretical depedence of multiphonon relaxation rates versus rare-earth ionic radius was derived using the non-linear (NL) theory of multiphonon relaxation. A good qualitative agreement of this dependence with new and earlier measured MPR rates in rare-earth ions in the row from Tm3+ to Pr3+ in YAG, YLF, and LaF3 crystals was obtained. The regularities of multiphonon relaxation rates on the number of phonons n, 4f-4f electronic transitions selection rules, and crystal type are also considered.

The luminescence of Er3+ and Ho3+ ions was sensitised by Cr4+ ions in an yttrium orthosilicate Y2SiO5 (YSO) crystal. The luminescence spectra of YSO : Cr : Er and YSO : Cr : Ho crystals and the kinetics of the luminescence of the Cr donor ions were investigated at 77 K and 300 K and analysed. Radiative energy transfer from Cr4+ to Ho3+ was observed in a Y2SiO5: 0.2% Cr : 0.5% Ho crystal. The Cr4+—Er3+ energy transfer in a Y2SiO5 : 0.1% Cr : 1.3% Er crystal at 77 K involved a nonradiative dipole—dipole static mechanism in the interval 2.7–24 μs. The efficiency of nonradiative energy transfer from Cr4+ to Er3+ was estimated to be 14%—19% at 77 K.

The 2μm Ho:Tm lasers are primary candidates for several remote sensing missions on NASA Mission to Planet Earth. Such lasers should find other remote sensing missions in terrestrial applications. Furthermore, these lasers have many other potential uses in the field of medicine, communications, and so forth. They can be efficient, even operating at room temperature, by utilizing laser diode pumping. However, the physics associated with their operation is very complicated due to the many manifolds involved and due to the many processes associated with each manifold. To understand the physics of these devices, and thence to optimize their performance, requires parameters describing the properties of these manifolds. One of the important parameters is the nonradiative transition rate. It was the intention of this work to experimentally measure these parameters. Subsequently, these new data were used to verify existing scaling laws which describe the nonradiative transition rate in terms of the properties of the laser material and the specific manifolds of rare- earth ions.

Passive Q-switching of 1.3 micrometers neodymium lasers with Nd2+:SrF2 and V3+:YAG crystalline saturable absorbers are studied. Giant pulses up to 5 mJ energy and 40 ns duration were obtained. Efficient Raman shifting of the 1.3 micrometers pulses of passively Q-switched lasers to 1.55 micrometers wavelength are realized in Ba(NO3)2 crystal.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Passive Q-switching of 1.3μm Nd:YAG, Nd:YAP and Cr, Nd:GGG lasers with Nd2+:SrF2 and V3+:YAG crystalline saturable absorbers is studied. Single transverse mode output laser pulses up to 5 mJ energy and 40 ns duration were obtained. Efficient stimulated Raman shifting of the 1.338 μm pulses of passively Q-switched Nd:YAG laser to 1.556 μm wavelength is realized in Ba(NO3)2 crystal for intracavity and out of cavity pumping schemes.

A gain medium for 1.3 μm amplifiers of fiber communication networks has to have (a) high and isotropic gain in (1.28-1.32) μm range, and (b) high pumping efficiency at wavelengths of most suitable pump sources (for instance, diode lasers). The utilization of 4F3/2-4I13/2 transition of Nd3+ ions in crystals and glasses is one of the ways to solve this problem. But two main difficulties have to be overcome for Nd doped media. First of all, it is necessary to shift Nd3+ emission to the desired spectral position, since the fluorescence of Nd3+ ions is usually observed at wavelengths around 1.34 μm. The second obstacle is excited state absorption (ESA) at 4F3/2-4G7/2 transition, that can reduce or suppress totally gain at 4F3/2-4Il3/2 transition.

For a number of neodymium doped fluoride crystals both with regular and disordered structure the Judd-Ofelt analysis of absorption spectra have been performed, and fluorescence and lasing spectra were studied in order to reveal the most promising materials for optical amplification in a 1.3 micrometers telecommunication window. The most suitable crystalline media investigated was found to be cubic disordered fluorides based on (50 - 70%) SrF2 - (50 - 30%) CaF2 solid solutions with Nd3+ optical centers having tetragonal local symmetry. These crystals have (1) low value of excited state absorption line strength, (2) high metastable level lifetime (1.2 - 1.3 ms), (3) high enough emission cross section for fluorescence (approximately 4 X 10-21 cm2), and (4) proper fluorescence peak at about 1310 nm wavelength and comparatively wide fluorescence band with about 20 nm FWHM.

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not.The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.Cr, Ce, Nd : GGG crystal as active medium for efficient flashlamp pumped solid-state lasers