Enrico Cavalli

Growth, spectroscopic characterization, and laser performance of Nd:LuVO_4, a new infrared laser material that is suitable for diode pumping

The spectroscopic properties and laser operation of a new neodymium-doped vanadate crystal, Nd:LuVO4, grown by the flux technique are reported. Polarized absorption and emission spectra were recorded at low and room temperatures, excited-state absorption was measured near 1060 and 1340 nm, and laser emission at 1066 nm was obtained after pumping near 809 and 880 nm.

Luminescence Dynamics in Tb3+-Doped CaWO4 and CaMoO4 Crystals

Single crystals of CaWO(4) and CaMoO(4) doped with Tb(3+) have been grown by the flux growth method. Their luminescence properties have been investigated in the 10-600 K temperature range under different experimental conditions. In spite of very similar spectra at low temperature upon excitation at 365 nm, the crystals show a very different behavior as the temperature is raised or the excitation wavelength is changed. These differences have been accounted for on the basis of models that take into consideration the position of the energy levels of the rare earth relative to the bandgap of the host material.

Optical spectra of yttrium phosphate and yttrium vanadate single crystals activated with Dy3

Abstract The optical spectra of YPO 4 :Dy 3+ and YVO 4 :Dy 3+ single crystals have been measured at 10 and 298 K. The luminescence spectra are dominated by a strong emission in the 575 nm region. Other bands have been observed in the 480, 665, 750 and 840 nm regions. They have been assigned to transitions from 4 F 9/2 to lower lying states on the basis of the energy level scheme deduced from the 10 K absorption spectra. The Stark structure of the manifolds observed in the low temperature spectra has been reliably reproduced by a standard crystal field (CF) calculation. The room temperature absorption spectra of YVO 4 :Dy 3+ have been analyzed using the Judd–Ofelt parameterization scheme, and the intensity parameters have been determined. Using these data the radiative lifetime for the 4 F 9/2 level has been calculated. The comparison with the effective decay times deduced from time-resolved measurements allows evaluation of the efficiency of the non-radiative processes.

Optical spectroscopy, fluorescence dynamics and crystal-field analysis of Er3+ in YVO4

Abstract The polarized absorption spectra, emission spectra and fluorescence dynamics of Er 3+ doped in YVO 4 are presented and analyzed in detail. Judd-Ofelt theory is applied to the measured absorption data to calculate the radiative decay rates for the various transitions of Er 3+ in YVO 4 . A comparison of the experimental fluorescence lifetimes and the calculated radiative transition rates is made. Thermalization of the 2 H 11/2 level from the lower-lying 4 S 3/2 is studied. Crystal-field analysis is performed that is based on a Hamiltonian of D 2d point-group symmetry. A best-fit analysis is performed resulting in an rms deviation of 6.7 cm −1 .

Emission quenching induced by intervalence charge transfer in Pr3+- or Tb3+-doped YNbO4 and CaNb2O6

The excitation and emission properties of Pr3+ and Tb3+ ions doped into YNbO4 (hereafter YNB) and CaNb2O6 (hereafter CNB) have been studied as a function of the temperature in the 10–600 K range. The observed quenching of the luminescence from the 3P0 (Pr3+) and 5D3 (Tb3+) states has been related to an electron transfer process from the trivalent rare earth to the Nb5+ ion inducing the formation of an intervalence charge transfer (IVCT) state. On this basis a detailed picture of the excited-state dynamics of the investigated compounds is presented, taking into account the characteristics of the host lattices and of the involved optically active ions.

About red afterglow in Pr3+ doped titanate perovskites

The red phosphor CaTiO3 : Pr3+ is known to show a persistent luminescence in the red spectral region upon irradiation in the UV. Although a number of studies have been dedicated to the enhancement of the afterglow efficiency in this perovskite by varying the preparation method, the chemical composition or the particle size, no clear explanation of the mechanisms involved in the afterglow process has been given yet. The purpose of this paper is to start investigating this aspect on the basis of a recently developed model and by using the luminescence and afterglow properties of the solid solution (Ca, Sr)TiO3 : Pr3+ as experimental support.

Growth and fluorescence properties of Tm3+ doped YVO4 and Y2O3 single crystals

Abstract This work is focused on the growth and the analysis of the potentials of Tm 3+ doped YVO 4 and Y 2 O 3 single crystals for diode-pumped laser emission around the 1.5 μm eye safe laser wavelenght. Both systems show broad-band absorptions around 800 nm and large stimulated emission cross sections around 1.5 μm.

Optical spectroscopy of Ca3Sc2Ge3O12 : Ni2+

Abstract The optical spectra of Ca3Sc2Ge3O12 (CaSGG) single crystals doped with Ni2+ are presented. Analysis of the absorption spectrum shows that the dopant substitutes mainly for Sc3+ in octahedral sites and, to a lesser extent, Ge4+ in tetrahedral sites. The optical transitions were assigned in the framework of the Ligand Field theory and the Dq, B and C parameters were obtained for both coordination geometries. Three emission transitions were observed in the green, red and infrared regions and were assigned to the 1T2(1D) → 3A2(3F), 1T2(1D) → 3T2(3F) and 3T2(3F) → 3A2(3F) transitions of Ni2+ in octahedral sites, respectively. No luminescence from Ni2+ in tetrahedral sites was observed.

Excited state dynamics of Pr3+ in YVO4 crystals

The quenching mechanism of the emission from the P03 level of Pr3+ doped into YVO4 has been investigated by means of optical spectroscopy techniques. Continuous wave and time-resolved emission and excitation measurements have been carried out as a function of the temperature and of the dopant concentration in order to obtain information on the energy-transfer processes involved in the host sensitization of the red luminescence and in the depopulation of the emitting states. The experiments have also been extended to LaVO4:Pr3+ and YPO4:Pr3+, i.e., two crystals for which the P03 emission is stronger than for YVO4:Pr3+, with the aim of studying the relationship between of the host properties and the optical behavior of the Pr3+ ion.

Lanthanide 4f-level location in AVO4:Ln3+ (A = La, Gd, Lu) crystals

The spectral properties of LaVO(4), GdVO(4) and LuVO(4) crystals doped with Ce(3+), Pr(3+), Eu(3+) or Tb(3+) have been investigated in order to determine the position of the energy levels relative to the valence and conduction bands of the hosts along the trivalent and divalent lanthanide series. Pr(3+) and Tb(3+) ground state levels are positioned based on the electron transfer energy from those states to the conduction band, the so-called intervalence charge transfer (IVCT). This approach is compared with an alternative model that is based on electron transfer from the valence band to a lanthanide.