LAERCIO GOMES
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Resumo IPEN-doc 29660 Study of neodymium laser transition in glasses and influence of up-conversion processes under diode pumping2003 - COURROL, LILIA C.; KASSAB, LUCIANA R.P.; DEL CACHO, VANESSA; WETTER, NIKLAUS U.; GOMES, LAERCIO; VIEIRA JUNIOR, NILSON D.; MESSADDEQ, YOUNES; RIBEIRO, SIDNEY J.L.By solving the rate equations including upconversion for Nd glass hosts under continuous diode pumping, it was possible to calculate the nonlinear behavior of the pumping efficiency and threshold pump intensity as a function of exited-state population.Resumo IPEN-doc 29656 Estudo de processos de conversão ascendente em vidros dopados com Nd3+2003 - LIMA, B.L.S. de; COURROL, L.C.; KASSAB, L.R.P.; DEL CACHO, V.D.; GOMES, L.; WETTER, N.U.Artigo IPEN-doc 29654 Evaluation of the most suitable new glass laser medium to incorporate Ytterbium2002 - COURROL, LILIA C.; KASSAB, LUCIANA R.P.; FUKUMOTO, MARCOS E.; GOMES, LAERCIO; WETTER, NIKLAUS U.; VIEIRA JUNIOR, NILSON D.; CASSANJES, FABIA C.; MESSADDEQ, YOUNES; RIBEIRO, SIDNEY J.L.The most important advantage of Ytterbium compared to others dopants such as Neodymium is its broadband emission nature, which is very suitable for both tunable and ultrafast lasers. In this paper we present the study and characterization of three different glass families: Alkali Niobium Tellurite, Lead Fluoroborate and of Heavy Metal Oxides, all prepared containing Ytterbium. The Ytterbium (Yb) emission spectrum in Tellurite glass samples was obtained by excitation into the absorption peak at 975 nm. The Yb peak emission cross-section was calculated using the fluorescence lineshape, the radiative lifetime (0.59 ms) and the refractive index 2.09. With these values we found the emission cross-section of Yb in Tellurite glass doped. Lead Fluorborate glasses have high refractive index of 2.2, and an absorption band centered at 968nm. The spontaneous emission probability was calculated and we determined that it decreases with the increase of Yb concentration. The same applies for the fluorescence lifetime and to the emission cross-section. We measured the fluorescence lifetime of 0.81ms, and an emission band at 1022nm with an effective emission linewidth of 60nm. Heavy metal oxide glass also has high refractive index (2.5) and transmission cutoff of about 8mm. In this glass the fluorescence effective linewidth was 86nm and radiative lifetime 300 ms. Calculations of the minimum pump intensity are also presented. A comparison of laser properties of these three different glasses and their importance is shown and analyzed.Resumo IPEN-doc 24514 Upconversion luminescence of Yb3+: Tm3+ and Yb3+: Tm3+: Er3+- doped Beta-Tricalcium Phosphate nanoparticles2017 - SILVA, F.R.O.; LIMA, N.B.; BRESSIANI, A.H.A.; GOMES, L.A novel class of fluorescence nanoparticles of 5.5 mol% of Yb3+, 0.5 mol% of Er3+ and 0.5 mol% Tm3+: calcium deficient hydroxyapatite were synthesized by co-precipitation method in aqueous solution (pH adjusted to 6) and specially treated with microwave radiation at 1000°C for 10 minutes to produce nanocrystals of Yb:Tm: and Yb:Tm:Er:-tricalcium phosphate (-TCP). As a result, we report for the first time, a single-phase -TCP:Yb:Tm:Er and -TCP:Yb:Tm exhibiting an efficient visible and near infrared upconversion luminescence from the 1G4 (blue emission), 4S3/2 (green emission), 3F2 (red emission) and 3H4 (near infrared emission) induced by the Yb3+ Tm3+ / Er3+ energy transfer under pulsed laser excitation at 972 nm (Yb3+) with an average energy of 11 mJ. The emission decay curves of the upconversion transients, from 1G4 excited state of Tm3+ and 4S3/2 excited level of Er3+, indicate that ESA process occurs in -TCP:Yb/Tm/Er nanopowder measured for the 550 nm luminescence of Er3+, which has a time constant (t2) of 0.4 s. However, Yb3+ Tm3+ upconversion (Up2) has a time constant (t2) of 14.4 s and does not exhibit ESA absorption. This -TCP activated by Yb3+ and Tm3+ ions constitutes a new nanobiomaterial that can be used as diagnostic and therapeutic agents, affording deeper tissue penetration and higher resolution and sensitivity for visible-near infrared bioimaging and treatments.Artigo IPEN-doc 23170 Excited state absorption and energy transfer in Ho3+-doped indium fluoride glass2017 - GOMES, LAERCIO; FORTIN, VINCENT; BERNIER, MARTIN; MAES, FREDERIC; VALLEE, REAL; POULAIN, SAMUEL; POULAIN, MARCEL; JACKSON, STUART D.This investigation examines in detail the rates of energy transfer relevant to the I-5(6) -> I-5(6) transition (at 3930 nm) in Ho3+-doped InF3 glass as a function of the Ho3+ concentration. The decay times, branching ratios and rate parameters for energy transfer were measured in this investigation for Ho3+ (x)-doped InF3 glass with x = 2, 4 and 10 mol.% and they were used as the input parameters for a rate equation analysis. Excited state absorption (ESA) initiating from the lower laser level is included in the study. Numerical simulation of CW laser emission at 3.9 pm was performed using two pump wavelengths, one for upper laser level excitation (i.e., I-5(8) -> (5)1(5) = lambda(P1)) and the other for lower laser level de-excitation (i.e., I-5(6) -> S-5(2) = lambda(P2)). The pump wavelength lambda(P2) = 962 nm was chosen based on the measurements of ESA and the application of the McCumber method. Critically, the estimated ESA cross section at lambda(P2) = 962 nm (sigma(ESA) = 7.1 x 10(-21) cm(2)) is approximately sixteen times larger than ground state (I-5(8)) absorption cross section (sigma(GSA) = 4.3 x 10(-22) cm(2)) and ESA does not overlap with any ground state absorption process. Our calculations suggest that even for high Ho3+ concentration in which cross relaxation has been shown in a previous study to quench the I-5(5) level, ESA is nevertheless strong enough to allow a sufficient population inversion required for practical CW emission.Artigo IPEN-doc 23206 Development of novel upconversion luminescent nanoparticle of Ytterbium/Thulium–doped beta tricalcium phosphate2017 - SILVA, FLAVIA R.O.; LIMA, NELSON B.; YOSHITO, WALTER K.; BRESSIANI, ANA H.A.; GOMES, LAERCIOA novel class of upconversion luminescent nanocrystals of Yb/Tm:calcium deficient hydroxyapatite were synthesized by co-precipitation method in aqueous solution (pH adjusted to 6) and specially heat-treated with microwave radiation at different temperatures (from 900 °C to 1000 °C) and times (2–10 min) to produce small nanocrystals of Yb/Tm:β-tricalcium phosphate (β-TCP). As a result, we report for the first time, a single-phase Yb/Tm-doped β-TCP nanocrystals with a mean crystallite size of 55.3 nm. This material has an efficient visible luminescence from the 1G4 (blue emission) and 3F2 (red emission) and near infrared emission from the 3H4 excited states of Tm3+ induced by the Yb3+→Tm3+ energy transfer under laser excitation (Yb3+) at 972 nm. This β-TCP activated by Yb3+ and Tm3+ ions constitutes a new nano-fluoroprobe that can be used as optical contrast agents, affording high resolution and sensitivity for visible-near infrared applications.Artigo IPEN-doc 23114 Optical properties of europium tetracycline complexes in the presence of High-Density Lipoproteins (HDL) subfractions2017 - SICCHIERI, LETICIA B.; MONTEIRO, ANDREA M.; FIGUEIREDO NETO, ANTONIO M.; GOMES, LAERCIO; COURROL, LILIA C.Standard lipoprotein measurements of triglycerides, total cholesterol, low-density lipoproteins (LDL), and high-density lipoproteins (HDL) fail to identify many lipoprotein abnormalities that contribute to cardiovascular heart diseases (CHD). Studies suggested that the presence of CHD is more strongly associated with the HDL subspecies than with total HDL cholesterol levels. The HDL particles can be collected in at least three subfractions, the HDL2b, HDL2a, and HDL3. More specifically, atherosclerosis is associated with low levels of HDL2. In this work, the optical spectroscopic properties of europium tetracycline (EuTc) complex in the presence of different HDL subspecies was studied. The results show that the europium spectroscopic properties in the EuTc complex are influenced by sizes and concentrations of subclasses. Eu3þ emission intensity and lifetime can discriminate the subfractions HDL3 and HDL2b.Artigo IPEN-doc 23049 The luminescence parameters of Yb3+:Er3+-doped LiLa(WO4)2 single crystal grown in the form of fiber for up-conversion green emission2017 - GOMES, LAERCIO; DENALDI, RAFAEL L.; MORAES, JAIR R. de; BALDOCHI, SONIA L.This report details the first study of the luminescence properties of a single crystal grown in the form of fiber for prospective application as the gain medium for fiber laser emission at 552 nm. The excited state decay processes related with the 4S3/2→4I15/2 transition in double Yb3+:Er3+-doped LiLa(WO4)2 crystal have been investigated using time-resolved fluorescence spectroscopy with a Er3+ concentration of 0.5 mol% and Yb3+ with 2, 5, 7, 10 and 15 mol%. Selective laser excitation of the 2F5/2 energy level of Yb3+(972 nm) and selective laser excitations of the 4I11/2 and 4I13/2 energy levels of Er3+(972 and 1550 nm), respectively has established that in a similar way to other optical materials, a strong energy-transfer up-conversion by way of a dipole-dipole interactions between an Yb3+ excited and Er3+ ions, the 4F5/2 level (Yb3+) populates the 4S3/2 upper laser level of the 550 nm transition. The 4S3/2 energy level emits luminescence with peaks having the wavelength center at 550 nm with luminescence efficiency increasing from 7% for Er3+ singly doped to 36% for Yb3+(15 mol%) co-doped crystals. The 4S3/2 lifetime of Er3+ is observed to increase due to the saturation of the multiphonon relaxation rate at high excited-state density of Yb3+ ions. At high excited-state density, Yb3+ ions saturates the accepting modes inside of a critical volume of RC=39.4 Å centered at an excited Er3+(4S3/2) ion, by the high-energy phonons generated from emission sideband of Yb3+ ions in Yb(x%):Er(0.5%) crystals. It is established that the green (552 nm) upconversion luminescence of Er3+ is optimized using an Yb3+ concentration of 11.5 mol% for Er(0.5%):LiLa (WO4)2 crystal.Resumo IPEN-doc 23682 Yb:Er-doped LiLa(WO4)2 single crystal fiber growth2016 - DENALDI, R.L.; BALDOCHI, S.L.; GOMES, L.; MAZZOCCHI, V.L.; MORAES, J.R.; PARENTE, C.B.R.Artigo IPEN-doc 22830 The basic spectroscopic parameters of Ho3+-doped fluoroindate glass for emission at 3.9 μm2016 - GOMES, LAERCIO; FORTIN, VINCENT; BERNIER, MARTIN; VALLEE, REAL; POULAIN, SAMUEL; POULAIN, MARCEL; JACKSON, STUART D.This report details the first study of the fundamental spectroscopic properties of a new optical material for prospective application as a gain medium for fiber laser emission at 3.9 mm. We have investigated the decay processes that are relevant to the excited states of the 5I5 / 5I6 transition in singly Ho3þ-doped InF3 (fluoroindate) glass using time-resolved fluorescence spectroscopy. The HoF3 concentration in the glass was 10 mol.%. We excited the 5I7 and 5I6 energy levels using selective excitation at 1982 nm and 1150 nm, respectively.We have established that a strong energy-transfer upconversion process by way of the well-known dipole-dipole interaction between two holmium ions excited to the 5I6 level populate the 5I5 (upper laser) level of the 3.9 mm transition. The 5I6 and 5I5 energy levels emit luminescence with measured peaks located at 2.85 mm and 3.92 mm, respectively and the luminescence efficiencies of these emissions are 78% and 0.2%, respectively. Results from numerical simulations show that for this high Ho3þ concentration, a population inversion for the 3.9 mm transition is reached only for a short time (t < 100 μs) after direct upper laser level pumping at a wavelength of 889 nm.