LAERCIO GOMES
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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 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.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.Artigo IPEN-doc 13165 Determination of a dose-like curve for active colour centres produced in LiF single crystals by ultrashort high intensity laser pulses and a preliminary investigation of their spectral and spatial properties by confocal and atomic microscopies2008 - COURROL, L.C.; SAMAD, R.E.; MARTINEZ, O.E.; GOMES, L.; RANIERI, I.M.; BALDOCHI, S.L.; FREITAS, A.Z. de; VIEIRA JUNIOR, NILSON D.Artigo IPEN-doc 14273 Energy transfer rates and population inversion of sup(4)Isub(11/2) excited state of Ersup(3+) investigated by means of numerical solutions of the rate equations system in Er:LiYFsub(4) crystal2009 - GOMES, LAERCIO; LIBRANTZ, ANDRE F.H.; JAGOSICH, FABIO H.; ALVES, WONDER A.L.; RANIERI, IZILDA M.; BALDOCHI, SONIA L.In this work, we present the spectroscopic properties of LIYF4 (YLF) single crystals activated by high doping of erbium ions. The most important processes that lead to the up-conversion erbium emissions in the infrared region were identified. A time-resolved luminescence spectroscopy technique was employed to measure the luminescence decays and to determine the most important mechanisms involved in the up-conversion processes that populate the 4S3/2 excited state. A study of the energy transfer up-conversion (ETU) processes in Er:YLF showed that an ETU rate can be obtained from the 4I11/2 (ETU1) and 4S3/2 (ETU2) up-conversion luminescence transient analysis, i.e., from best fittings of the acceptor state luminescence. An analysis of the ETU rate dependence on the wavelength and intensity of pulsed laser excitations allowed us to obtain the ETU rate constants from the lower 4I13/2 and upper 4I11/2 laser levels to use them in the numerical solutions of the rate equation system for the Er-doped YLF crystal (15 mol %) pumped [continuous wave (cw)] at 972 nm. As a result, we found that the 4I11/2 ➝ 4I13/2 laser emission (or small signal gain) shows a temporal profile intensity, which passes through a maximum at around 820 μs before getting the steady state regime. It was demonstrated that the ETU2 process (from the 4I11/2 level) is the mechanism responsible for the laser gain profile observed. The results of the numerical simulation of the rate equation system showed that the highest population inversion density of 8.5 x 1019 cm-3 for Er3+ (or a small signal gain of 2.54 cm-1) is obtained for 15 mol % of erbium in the YLF crystal when it is pumped by a cw laser at 972 nm using a pump intensity of 5.4 kW cm-2 (or a pumping rate of 300 s-1) for the laser transition near 2.75 μm. It was seen also that a pumping rate of 300 s-1 maximizes the population inversion in the cw pump regime. A simulation using a square wave pump with a pumping time of 1 ms showed a population inversion increasing by a factor of 1.31 with respect to the population inversion obtained in the continuous pump simulation.Artigo IPEN-doc 14873 Population inversion of sup(1)Gsub(4) excited state of Tmsup(3+) investigated by means of numerical solutions of the equations system in Yb:Tm:Nd:LiYFsub(4) crystal2009 - LIBRANTZ, ANDRE F.H.; GOMES, LAERCIO; COURROL, LILIA C.; RANIERI, IZILDA M.; BALDOCHI, SONIA L.Artigo IPEN-doc 15933 Energy level decay and excited state absorption processes in dysprosium-doped fluoride glass2010 - GOMES, LAERCIO; LIBRANTZ, ANDRE F.H.; JACKSON, STUART D.The primary excited state decay processes relating to the 6H13/2→6H15/2 3 m laser transition in singly Dy3+-doped fluoride ZBLAN glass have been investigated in detail using time-resolved f luorescence spectroscopy. Selective laser excitation of the 6F9/2, 6H7/2 energy levels at 1125 nm and 6F11/2, 6H9/2 energy levels at 1358 nm established that the energy levels above the 6H11/2 level, excluding the 4F9/2 level, are entirely quenched by multiphonon emission in ZBLAN glass. The 6H11/2 and 6H13/2 energy levels emit luminescence with peaks at 1700 and 2880 nm, respectively, but at low quantum luminescence efficiencies. The quantum efficiency of the 6H11/2 level and 6H13/2 level is 9 10−5 and 1.3 10−2, respectively, for Dy3+=0.5 mol % based on calculations of the radiative lifetimes using the Judd–Ofelt theory. Excited state absorption ESA was detected by monitoring the rise time of the 1700 nm luminescence after tuning the probe wavelength across the spectral range from 1100 to 1400 nm. As a result of nonradiative decay of the higher excited states, ESA contributes to the heating of 3 m fiber lasers based on Dy3+-doped f luoride glass. For Dy3+ up to 4 mol %, we found no evidence of energy transfer processes between Dy3+ ions that influence the decay characteristics of the 6H11/2 and 6H13/2 energy levels.Artigo IPEN-doc 17226 Energy transfer rates and population inversion investigation of sup(1)Gsub(4) and sup(1)Dsub(2) excited states of Tmsup(3+) in Yb:Tm:Nd:KYsub(3)Fsub(10) crystals2011 - LINHARES, HORACIO M. da S.M.D.; LIBRANTZ, ANDRE F.H.; GOMES, LAERCIO; COURROL, LILIA C.; BALDOCHI, S.L.; RANIERI, IZILDA M.