D. F. de Sousa

Spectroscopy of Nd3+ and Yb3+ codoped fluoroindogallate glasses

The Nd–Nd and Nd–Yb energy transfer processes are studied in lead fluoroindogallate glasses with the following molar composition: 30PbF2–20GaF3–15InF3–15ZnF2–(20–X)CaF2–XNdF3 (with X=0.1, 0.5, 1, 2, 4, and 5), 30PbF2–20GaF3–15InF3–15ZnF2–(20–X)CaF2–XYbF3 (with X=0.1, 0.5, 1, 2, 3, and 5), and 30PbF2–20GaF3–15InF3–15ZnF2–(19–X)CaF2–XYbF3–1NdF3 (with X=0.1, 0.5, 1, 2, 3, and 5.5). The Dexter, Yokota–Tanimoto, and Holstein formalisms were used to treat the experimental data. The following microparameters of energy transfer were obtained: CDD(Nd–Nd)≈7×10−40, CDA(Nd–Nd)=2.5×10−40, and CDA(Nd–Yb)≈3×10−40 cm6/s. It was also shown that the energy migration between Nd ions depends on the third power of temperature (T3) up to a saturation value of about 80 K. This behavior was attributed to the site to site energy migration. The Yb doped samples presented no nonradiative losses for the Yb3+ emission at 969 nm.

On the observation of 2.8 μm emission from diode-pumped Er3+- and Yb3+-doped low silica calcium aluminate glasses

In this letter, we investigate the midinfrared photoluminescence of a series of diode-pumped Er3+-doped and Er3+, Yb3+-codoped low-silica content aluminosilicate glasses. Emission at 2.8 μm was observed in both single doped and codoped samples. The effect of Yb3+ codoping of the Er3+-doped samples was such that, for example, for a 2 wt % Er3+-doped, the photoluminescence yield at 2.8 μm was found to be roughly three times larger than that of the single 2 wt % Er3+-doped sample. This behavior was attributed to the efficient sensitization of Er3+ by Yb3+ in our oxide based host glasses. The results reported in this letter, together with the outstanding mechanical, chemical, and thermal properties of these glasses, suggest that rare-earth doped calcium aluminate glasses may become an attractive host for the development of solid state lasers operating in the midinfrared.

Er3+:Yb3+ codoped lead fluoroindogallate glasses for mid infrared and upconversion applications

In this work, two sets of lead fluoroindogallate glasses were studied with the aim of using them as active media for laser devices at the mid infrared (∼2.8 μm) and visible (∼0.54 μm) regions. The infrared and upconverted emissions of Er3+ in single and Er3+:Yb3+ codoped samples were analyzed, and it was observed that the best set of samples for 2.8 μm emission was the single doped one, and that as the upconversion (anti-Stokes luminescence) increased as a function of Yb3+ concentration, the infrared emission decreased in the same manner. The results suggest that the codoping with Yb3+ favors only the upconversion processes which depopulate the 4I11/2 level, reducing the 2.8 μm emission intensity. On the other hand, the Yb3+ codoping will certainly increase the efficiency of an upconversion based device. Quantum efficiencies of infrared emissions and radiative lifetimes were calculated by using the Judd–Ofelt approximation. Er3+–Er3+ and Er3+–Yb3+ energy transfer efficiencies were calculated using the mea...

Cooperative luminescence in Yb3+-doped phosphate glasses

In this paper we present results on cooperative luminescence performed on Yb3+-doped metaphosphate glasses under 980 nm excitation. We have measured emission spectra and decay lifetimes in the visible and infrared regions as a function of Yb concentration. It was observed that, up to 10% of Yb concentration, cooperative emission increases while lifetime is observed to decrease. Such behaviour is attributed to the Yb interaction with OH− radicals and energy migration among Yb ions.

Evaluation of the energy transfer rate for the Yb3+:Pr3+ system in lead fluoroindogallate glasses

In this article, we report on spectroscopic studies of Pr 3+ :Yb 3+ codoped lead fluoroindogallate glasses. By pumping with a diode laser in 0.98 μm, it was verified that the intensity of infrared luminescence at 1.3 μm of Pr 3+ ( 1 G 4 → 3 H 5 ) is highly increased (approximately 40 times) by the presence of Yb 3+ . Anti-Stokes luminescence (upconversion), which represents a loss mechanism for the infrared emission, was also observed. These features were attributed to an efficient energy transfer process from Yb 3+ to Pr 3+ . Calculation of the energy transfer constant (C s−a ) and energy transfer rate (P s−a ) showed that the process from Yb 3+ to Pr 3+ is nearly one order of magnitude greater than in the opposite direction. The energy transfer efficiency obtained was about 92%. The best molar ratio Pr 3+ :Yb 3+ is 1:4 for both infrared and upconverted luminescence signals.

A demonstration of dry and viscous damping of an oscillating pendulum

Damped oscillatory motion is one of the most widely studied movements in physics courses. Despite this fact, dry damped oscillatory motion is not commonly discussed in physics textbooks. In this work, we discuss the dry and viscous damped pendulum, in a teaching experiment that can easily be performed by physics or engineering students.

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.

Optical measurements of Nd3+/Yb3+ codoped fluoroindogallate glasses

We report on the optical properties of Nd 3+ -Yb 3 codoped lead fluoroindogallate melted glasses, with the following molar composition: 30PbF 2 -20GaF 3 -15InF 3 -15ZnF 2 -(20-x)CaF 2 -xNdF 3 and 30PbF 2 -20GaF 3 -15InF 3 -15ZnF 2 -(19-x)CaF 2 -xYbF 3 -1NdF 3 (with x = 0.1, 0.5, 1, 2, 4, 5). Photoluminescence and time resolved photoluminescence measurements were performed to investigate energy transfer processes among Nd 3+ and Yb 3+ ions. The time decay of the 4 F 3/2 Nd 3+ level was monitored as a function of Yb concentration. As a result, it was concluded that the C DA parameter characterizing the cross-relaxation among Nd 3+ ions is C DA(Nd Nd) = 1.3 × 10 -40 cm 6 /s and the energy transfer efficiency from Nd 3+ to Yb 3+ ions is about 85% for the 1 mol% Nd 3+ :5 mol% Yb 3+ sample.

Upconversion in Nd3+-doped glasses: Microscopic theory and spectroscopic measurements

In this work, we report a systematic investigation of upconversion losses and their effects on fluorescence quantum efficiency and fractional thermal loading in Nd3+-doped fluoride glasses. The energy transfer upconversion (γup) parameter, which describes upconversion losses, was experimentally determined using different methods: thermal lens (TL) technique and steady state luminescence (SSL) measurements. Additionally, the upconversion parameter was also obtained from energy transfer models and excited state absorption measurements. The results reveal that the microscopic treatment provided by the energy transfer models is similar to the macroscopic ones achieved from the TL and SSL measurements because similar γup parameters were obtained. Besides, the achieved results also point out the migration-assisted energy transfer according to diffusion-limited regime rather than hopping regime as responsible for the upconversion losses in Nd-doped glasses.

Looping mechanism in Er-doped fluoroindogallate glasses

In this work we report a room temperature green upconversion in Er-doped fluoroindogallate glasses, pumped at 833 nm. The rise time and stationary intensity of the 4S3/2+2H11/2→4I15/2 Er3+ transition as a function of laser intensity were monitored. Some possible pumping mechanisms are discussed in detail, and it is concluded that the main pumping route may be described in terms of the looping mechanism. It is also shown that cross relaxation among neighboring pairs of Er3+ ions is near the threshold value to achieve the photon avalanche region.