A.S.S. de Camargo

Spectroscopy thermal and optical properties of Nd3+ -doped chalcogenide glasses

We investigated the spectroscopic, thermo-optical and mechanical properties of 70% Ga2S3:30% La2S3 (mol%) chalcogenide glass and this composition doped with 0.05, and 0.2 mol% Nd2S3, prepared by melt-quenching the sulphides in a vitreous carbon crucible in a silica ampoule. The fluorescence quantum efficiency for the 0.05 mol% Nd3+ doped sample, obtained by thermal lens technique was 1.01±0.07 and the lifetime of the fluorescence of this sample was 78.00±0.05 s. The thermal diffusivity of these samples (2.7±0.1)×10-3 cm2 s-1 was determined by the thermal lens method.

Efficient green and red upconversion emissions in Er3+/Yb3+ co-doped ZnAl2O4 phosphor obtained by combustion reaction

Thin ceramic powders of zinc aluminate ZnAl2O4 co-doped with Er3+ and Yb3+ were prepared by a combustion reaction and characterized from the spectroscopic point of view, with the aim of investigating the effect and mechanisms of upconversion emissions. The characteristic cubic spinel structure was predominantly formed for all doped samples, and intense upconversion emission was observed in the green and red spectral regions, under 980?nm diode laser excitation. The upconversion mechanism of both emissions was confirmed to involve two photon absorptions and it was found that the efficiencies of the emissions are considerably enhanced by increasing the Yb3+ concentration in relation to Er3+. The results indicate the potential of ZnAl2O4:Er3+,Yb3+ phosphor powders for applications in luminescent display panels and other photonic devices.

Spectroscopic properties and energy transfer parameters of Tm3+ ions in gallium lanthanum sulfide glass

This work presents the spectroscopic characterization of Tm3+ doped gallium lanthanum sulfide (GaLaS) chalcogenide glass through absorption, fluorescence and lifetime measurements of excited3H4 and3F4 states, and a study of Tm3+:Tm3+ energy transfer. The cross relaxation 3 H 4,3 H 6 →3 F 4,3 F 4 responsible for the pumping of level3F4 and the laser transition at 1800 nm (3 F 4 →3 H 6), as well as the energy migration 3 H 4,3 H 6 →3 H 4,3 H 6 processes are studied in terms of the microscopic parameters of energy transfer Cda and Cdd obtained by the Kushida model of multipolar interactions and by a rate equation treatment of the dynamics of levels3F4 and3H4. From this treatment it was possible to simulate level3F4 temporal evolution curves for different Tm3+ concentrations, leading to results that are in excellent agreement with experimental ones. All the samples studied in the work present positive optical gain coefficients for excitation densities higher than 12 kW cm−2 indicating the potentiality of GaLaS:Tm3+ glass as a mid-infrared laser active medium.

Luminescent and thermo-optical properties of Nd3+-doped yttrium aluminoborate laser glasses

In this work we performed a thorough spectroscopic and thermo-optical investigation of yttrium aluminoborate glasses doped with neodymium ions. A set of samples, prepared by the conventional melt-quenching technique and with Nd2O3 concentrations varying from 0.1 to 0.75 mol %, were characterized by ground state absorption, photoluminescence, excited state lifetime measurements, and thermal lens technique. For the neodymium emission at 1064 nm (F43/2→I411/2 transition), no significant luminescence concentration quenching was observed and the experimental lifetime values ranged around 70 μs. The obtained values of thermal conductivity and diffusivity of approximately 10.3×10−3 W/cm K and 4.0×10−3 cm2/s, respectively, are comparable to those of commercial laser glasses. Moreover, the fluorescence quantum efficiency of the glasses, calculated using the Judd–Ofelt formalism and luminescence decay, lies in the range from 0.28 to 0.32, larger than the typical values obtained for Nd3+ doped YAl3(BO3)4 crystals.

Effect of Nd3+ concentration quenching in highly doped lead lanthanum zirconate titanate transparent ferroelectric ceramics

The concentration dependence of the fluorescence quantum efficiency in Nd3+ doped lead lanthanum zirconate titanate (PLZT), transparent ceramics, is presented. The total emission decay of the emitting level F3∕24 is close to exponential, even for high Nd3+ concentration Nt, due to the very low probability of the cross relaxation energy transfer processes among ions. Owing to this low probability, it was inferred that Nd:PLZT presents lower concentration quenching than other laser materials as Nd:YAG. The figure of merit ηNt, where η is the fluorescence quantum efficiency, presents a maximum around 6.0wt% Nd2O3, indicating the good prospects of concentrated samples for miniaturization of the laser medium (microchip laser).

Growth of yttrium orthovanadate by LHPG in isostatic oxygen atmosphere

Abstract The growth of undoped and Nd 3+ -doped YVO 4 crystals in isostatic oxygen atmosphere by the laser-heated pedestal growth technique was investigated. Absorption, photoluminescence, X-ray powder diffraction and Raman shift spectra were used to characterize the grown crystals. Differences in Y–V and oxygen stoichiometries were identified and discussed in terms of the starting materials processing, crystal growth dynamics and post-growth thermal treatment. The experimental results indicate that single crystal fibers with general optical and spectroscopic properties close to those of the best respective available bulk single crystals were grown.

Fluorescence quantum efficiency measurements of excitation and nonradiative deexcitation processes of rare earth 4f-states in chalcogenide glasses

Thermal lens spectroscopic measurements were performed to quantitatively determine the fluorescence quantum efficiency (eta) of different luminescence mechanisms in Nd3+ chalcogenide glasses. Low energy (<1.7 eV) direct resonant pumping at Nd3+ infrared lines resulted in eta ~1. High energy (~2.4 eV) indirect excitation via energy transfer (ET) from glass conduction band to Nd3+ 4f states, resulted in eta = ~0.4 (ET probability ~40%). A minimum eta ~0.2 was obtained for intermediate excitation energies (~2.2 eV) and attributed to back ET from the Nd3+ 4f state to the glass host.

Thermo-optical characteristics and concentration quenching effects in Nd3+ doped yttrium calcium borate glasses.

In this work we present a comprehensive study of the spectroscopic and thermo-optical properties of a set of samples with composition xNd(2)O(3)-(5-x)Y(2)O(3-)40CaO-55B(2)O(3) (0 ≤ x ≤ 1.0 mol%). Their fluorescence quantum efficiency (η) values were determined using the thermal lens technique and the dependence on the ionic concentration was analyzed in terms of energy transfer processes, based on the Förster-Dexter model of multipolar ion-ion interactions. A maximum η = 0.54 was found to be substantially higher than for yttrium aluminoborate crystals and glasses with comparable Nd(3+) content. As for the thermo-optical properties of yttrium calcium borate, they are comparable to other well-known laser glasses. The obtained energy transfer microparameters and the weak dependence of η on the Nd(3+) concentration with a high optimum Nd(3+) concentration put this system as a strong candidate for photonics applications.

Luminescent polymer electrolytes based on chitosan and containing europium triflate

Abstract Solid polymer electrolytes based on chitosan and europium triflate were prepared by solvent casting and characterized by X-ray diffraction, scanning electron microscopy (SEM), atomic force microscopy (AFM), and photoluminescence spectroscopy. The X-ray diffraction exhibited that the samples were essentially amorphous with organized regions over the whole range of the salt content studied. The AFM analysis demonstrated that the smoother sample had roughness of 4.39 nm. Surface visualization through SEM revealed good homogeneity without any phase separation for more conductive samples and the less conductive showed some imperfections on the surface. The emission and excitation spectra displayed the characteristic bands of Eu(CF 3 SO 3 ) 3 in addition to broad bands corresponding to the polymer host. The excited state 5 D 0 lifetime values ranged from 0.29–0.37 ms for the studied samples.

Oxyfluoride glass and glass ceramics doped with Er 3+ , Yb 3+ and Nd 3+ for near-infrared applications

Oxyfluoride glasses, and more recently, glass ceramics, doped with trivalent rare earth ions (RE) have attracted much attention for near-infrared laser applications with the promise to combine the merits of fluorides (low phonon energy, moderate refractive indexes, extensive IR window) and oxides (high chemical and mechanical stability, higher RE solubility. In the past few years we have studied compositions doped with Er3+, Yb3+ and/or Nd3+ with excellent optical quality, long excited state lifetimes and high quantum efficiency values. This presentation will give an overview of this class of optical materials and discuss the most recent results which characterize them as potential candidates for infrared laser applications.