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Influence of temperature on spectroscopic and thermal properties of Tm 3+ and Er 3+ -doped GdVO 4 and LuVO 4 crystals was examined. Polarized absorption and emission spectra as well as excited state luminescence lifetimes have been measured and analyzed especially at cryogenic temperatures in the 1.5–1.6 μm and 1.8–1.9 μm spectral ranges to assess laser qualities of these materials. The emission cross sections for 4 I 132 → 4 I 15/2 (Er) and 3 F 4 → 3 H 6 (Tm) transitions at T = 77 K were determined and confronted to the results obtained at room temperature. Effective emission cross sections estimated for aforementioned erbium and thulium transitions indicate that effective laser operation at cryogenic temperatures can be achieved in the gadolinium and lutetium vanadate crystals. Efficiency of laser material depends on its ability to heat distribution upon high-power energy pumping process. Accordingly, it has been found that the anisotropy of thermal conductivity for the undoped crystals is weakly influenced by the temperature albeit conductivity values for the GdVO 4 are higher than those for LuVO 4 at all temperatures. Incorporation of erbium or thulium ions results in a decrease of thermal conductivity in the two vanadate crystals and an anomalous temperature dependence of thermal conductivity in the LuVO 4 was observed. Anisotropy of temperature dependence of thermal conductivity was found for the LuVO 4 :3.2 at%Tm 3+ crystal. In this case the thermal conductivity along c-axis is inferior to that along a-axis of the crystal. [ABSTRACT FROM AUTHOR]

Highlights: [•] LGT:Er single crystals obtained by Czochralski method. [•] Analysis of absorption and emission spectra as well as decay curves of luminescence. [•] Influence of the temperature on the LGT:Er spectroscopic properties. [•] Spectroscopic evaluation of the LGT:Er potential laser qualities. [ABSTRACT FROM AUTHOR]

Highlights: [•] Influence of temperature on optical properties of the Gd3Ga5O12:Sm single crystals. [•] Analysis of absorption and emission spectra as well as luminescence lifetimes. [•] Estimation of energies of crystal field components of Sm3+ in the Gd3Ga5O12 crystal. [•] Study on energy transfer phenomena using the classical Inokuti–Hirayama model. [ABSTRACT FROM AUTHOR]

Abstract: Spectroscopic properties of lutetium aluminum garnet Lu3Al5O12 (LuAG) single crystal doped with 1at.% of Pr3+ were investigated. The crystal was grown by the Czochralski method. Optical absorption, emission, excitation spectra and luminescence decay curves were recorded for this system in 5–500K temperature range. Excitation spectra in VUV–UV range (150–330nm) were also measured exploiting synchrotron radiation. It has been found that among bands of luminescence related to the 3PJ, 1D2 → 3HJ, 3FJ transition of Pr3+ in the visible region the 3P0 → 3H4 one, occurring ca. 488nm, is the most prominent. Luminescence lifetimes for the 3P0,1 and 1D2 levels were estimated to be 13 and 200μs respectively (at room temperature). VUV-excited emission spectrum stretches over the whole visible region. It has been concluded that the material under study is a promising phosphor that can be efficiently pumped by broad absorption bands centered at 240 and 280nm. [Copyright &y& Elsevier]

Optical, structural and morphological properties of Tm3+/Yb3+ co-doped NaYF 4 -based nano-glass-ceramic and a precursor glass have been investigated. The controlled heat-treatment of multicomponent oxyfluoride glass at 640 °C for 2 h was used to obtain crystalline precipitations. The differences in optical characteristics have been discussed analysing spectra recorded within wide VUV–VIS–NIR spectral range and considering relaxation dynamic of involved excited states. Optical spectra and luminescence decay curves were measured as a function of temperature in the range of 295–725 K. Based on up-converted emission spectra excited at 975 nm, temperature sensing properties of glass-ceramic were verified. The fluorescence intensity ratio between the up-converted emission bands located at around 795 nm (Tm3+:3H 4 –3H 6) and 695 nm (Tm3+:3F 3,2 –3H 6) was studied. The maximum relative temperature sensitivity was determined to be 0.35% K−1 at 445 K. • Tm3+,Yb3+ co-doped NaYF 4 -based oxufluoride nano-glass-ceramic. • Conversion of VUV excitation into thulium visible emission. • Impact of 295–725 K temperature on emission efficiency of Tm3+ and Yb3+. • Verification of Tm,Yb –co-doped glass-ceramic temperature sensor quality. [ABSTRACT FROM AUTHOR]

Abstract The thermal and optical properties of oxyfluorotellurite (65-x)TeO 2 -20ZnF 2 -12PbO-3Nb 2 O 5 -xSm 2 O 3 (x = 0.5, 2 and 5) glass systems were investigated. Glass thermal stability were monitored by differential thermal analysis (DTA) and adequate thermal stability criteria ΔT, H' and S were determined. It was shown that the thermal stability of the investigated materials increases with the increasing of samarium ions content. The absorption and emission spectra of Sm3+ ions in oxyfluorotellurite glass were recorded in the wide spectral range from UV to NIR. Based on the Judd-Ofelt (J–O) procedure oscillator strengths, phenomenological Judd-Ofelt intensity parameters Ω 2,4,6, radiative transition probabilities, branching ratios and radiative lifetimes of luminescent levels were determined. The luminescence decay curves of the 4G 5/2 (Sm3+) excited state were recorded for three different concentrations of Sm3+ and corresponding experimental lifetimes were determined. Photoluminescence emission spectra were measured in the temperature range from 300 K up to 725 K to evaluate the materials under study as luminescent temperature sensor. Highlights • (65-x)TeO2-20ZnF2-12PbO-3Nb2O5-xSm2O3 (x = 0.5, 2, 5 mol%) glasses were prepared. • Thermal properties of glasses were analyzed as a function the Sm3+ concentrations. • The optical properties of Sm3+ ions in oxyfluorotellurite glass were assessed. • The materials under study were evaluated as luminescent temperature sensors. [ABSTRACT FROM AUTHOR]

The paper shows some results related to thermal and optical properties of Eu 3+ -doped (65-x)TeO 2 -20ZnF 2 -12PbO-3Nb 2 O 5 -xEu 2 O 3 glass systems. Concentration of the Eu 2 O 3 was different (x = 0.5, 2 and 5 mol%) so it could determine the influence of active admixture on relevant properties of oxyfluorotellurite glass. Thermal stability and crystalline phases formed by the glass matrix were examined by differential thermal analysis (DTA). The characteristic temperatures (glass transition temperature and oxide glass crystallization temperature) have been determined. Optical absorption and emission spectra of Eu 3+ ions in oxyfluorotellurite glasses have been investigated at room temperature in the ultraviolet (UV), visible (VIS) and near-infrared (NIR) region. Oscillator strengths, phenomenological Judd-Ofelt intensity parameters Ω 2,4,6 , radiative transition probabilities, branching ratios and radiative lifetimes of luminescent levels have been also estimated. Lifetimes and the luminescence dynamics were studied as a function of the Eu 2 O 3 concentration. [ABSTRACT FROM AUTHOR]

Highlights: [•] Samarium doped langatate crystal was grown by Czochralski method. [•] Thermal dependences of Sm3+ emission and absorption have been measured. [•] Judd–Ofelt analysis was carried out and radiative transition rates were calculated. [•] Inhomogeneous broadening of spectral lines has been observed. [ABSTRACT FROM AUTHOR]

Oxyfluorotellurite (65- x)TeO 2 –20ZnF 2 –12PbO–3Nb 2 O 5 – x Tm 2 O 3 (x = 0.5, 2 and 5) and (65- x - y)TeO 2 –20ZnF 2 –12PbO–3Nb 2 O 5 – x Tm 2 O 3 – y Yb 2 O 3 (x = 0.5, y = 2 and x = 0.5, y = 5) glass systems were manufactured. Glass thermal stability was examined by means of differential thermal analysis (DTA) and some thermal stability criteria ΔT , H ' and S were determined. Absorption spectrum was utilized to prepare Judd-Ofelt (J-O) calculations and consequently oscillator strengths, intensity parameters Ω 2,4,6 , radiative transition probabilities, branching ratios and radiative lifetimes of luminescent levels were estimated. Emission spectra and luminescence decay curves were measured as a function of temperature in the 300–625 K range. Based on the upconversion luminescence of Tm3+ the optical temperature sensor qualities have been evaluated for Tm3+/Yb3+ co-doped sample. The fluorescence intensity ratio (FIR) between transitions 700 nm (Tm3+:3F 2,3 → 3H 6)/800 nm (Tm3+:3H 4 → 3H 6) for 975 nm excitation and 700 nm (Tm3+:3F 2,3 → 3H 6)/470 nm (Tm3+:1G 4 → 3H 6) for 803 nm excitation were determined and an adequate relative thermal sensitivity S was estimated. The significant value of relative thermal sensitivity 1.12 %K−1 was determined when NIR Yb3+ and Tm3+ emission bands were analyzed, however. Effective emission cross section was calculated for 3F 4 → 3H 6 potential laser transition of thulium around 1.9 μm in single-doped Tm3+ glass. Furthermore, effect of temperature on down-converted and up-converted thulium and ytterbium emission and on relaxation dynamic of involved excited states was studied in details. • Oyfluorotellurite glasses singly-doped and co-doped Tm3+ and Yb3+ were prepared. • Thermal and optical properties of tested materials were determined. • Thermal properties of glasses depend on the Tm3+/Yb3+ ions concentrations. • Investigated materials have advantageous properties for NIR optical gain. • TZPN glasses activated with RE3+ ions can be used in luminescence thermometry. [ABSTRACT FROM AUTHOR]

Terbium ions in Gd 3 Ga 3 Al 2 O 12 (GGAG) single crystal exhibit strong luminescence originated in the 5D 3 and 5D 4 multiplets. The decay time of the 5D 3 state is 1072 μs and 724 μs at 5 K and 300 K, respectively. The time dependence of luminescence originated from the 5D 4 multiplet is consistent with single exponential decay, with lifetime values 3579 μs at low temperature and 2902 μs at 300 K. The non-exponential decay curves have been fitted in the frame of Inokuti-Hirayama model, indicating that the dipole-dipole interaction plays an important role in the fluorescence quenching of the 5D 3 level. The calculated R 0 parameter values are equal to 11.56 Å and 12.86 Å for 5 and K 300 K, respectively. The positions of multiplets up to 40000 cm−1 are determined employing the f-shell empirical programs. CIE 1931 coordinates are x = 0.298 , y = 0.664 (green) at 5 K and x = 0.360, y = 0.538 (yellowish green) at 300 K. • A new material has been obtained in the form of single crystal. • A starting stoichiometry is given to minimize segregation process. • Low temperature positions of 4f and 5d states have been determined. • Energy transfer processes have been examined. • Influence of temperature on the Tb transition ratio has been investigated. [ABSTRACT FROM AUTHOR]

The CsCaI 3 single crystals doped with Tm 2+ were grown by Bridgman technique. Divalent thulium luminescence related to the 4f 13 -4f 13 intra-configurational and 4f 12 5d 1 -4f 13 inter-configurational transitions were analyzed as a function of temperature. Excited state excitation spectroscopy has been applied within a wide spectral range to examine peculiarities of transitions between different 4f 12 5d 1 excited states of Tm 2+ . This two-color excitation experiment was useful to assess d-d photon-absorption processes that are relevant to observed up-conversion phenomena attributed to effective anti-Stokes green luminescence around 550 nm. Furthermore, activation energy of 4f 12 5d 1 → 4f 13 luminescence quenching was estimated and high value of 2 F 5/2 → 2 F 7/2 emission cross-section was determined in CsCaI 3 :Tm 2+ . Our spectroscopic study was performed to complement and verify the previous investigation in this field. [ABSTRACT FROM AUTHOR]

Spectroscopic features and laser performance of a novel thulium-doped scandium yttrium silicate crystal Tm 3+ :ScYSiO 5 (Tm:SYSO) are presented. The experimental lifetime of luminescence related to the 3 F 4 – 3 H 6 laser transition of Tm 3+ amounts to 1.1 ms, which is smaller by a factor of three than the calculated radiative lifetime value due to the contribution of nonradiative relaxation. As a consequence of the internal disordered structure of the SYSO host crystal, the luminescence bands of 3 F 4 – 3 H 6 and 3 H 4 - 3 H 6 show significant inhomogeneous spectral broadening as compared with that of SSO. The laser performances were evaluated in an end-pumped cavity using a CW semiconductor laser as a pump source. In a free run regime, the Tm:SYSO laser delivered a maximum output power of 580 mW at 2022 nm, corresponding to a slope efficiency of 17.4%. With a birefringent quartz plate inserted into laser cavity, the laser output wavelength was continuously tuned from 1950 nm to 2057 nm and dual wavelength operations at 2011 nm and 2020 nm, 1987 nm and 2045 nm, 2022 nm and 2044 nm were observed. [ABSTRACT FROM AUTHOR]

Single crystal of Gd 3 Ga 3 Al 2 O 12 (GGAG) doped with 1 at.% Sm 3+ was fabricated by the Czochralski method. Optical absorption and emission spectra as well as luminescence decay curves for this crystal was recorded at different temperatures ranging from 5 K to 300 K. The energies of the crystal field sublevels of selected multiplets were determined based on optical spectra recorded at T = 5 K. It has been found that widths of emission spectral lines related to transitions between individual crystal field levels of multiplets are stable up to 100 K, then new Stark component of higher the 4 G 5/2 multiplets starts to appear in the spectrum. The spectral widths (FWHM) are in the range 7–30 cm −1 what is caused with solid solution composition of the crystal. Five local positions of the Sm 3+ have been found in this material. Judd-Ofelt calculation of branching ratios has been done. The color of luminescence is orange-red with CIE coordinates as x = 0.606 and y = 0.393 and the total efficiency 45%. [ABSTRACT FROM AUTHOR]

Optical absorption and emission spectra of Dy 3+ ions in Gd 3 Ga 3 Al 2 O 12 single crystal were investigated at room temperature and T = 5 K in the visible (VIS) and near-infrared (NIR) region. Low-temperature spectra were utilized to determine the energy level structure of Dy 3+ in the GGAG host. The detailed analysis implied that optically active ions reside mainly into well-defined sites in the crystal studied. Judd–Ofelt (JO) theory was used to calculate oscillator strengths, transitions intensity parameters Ω 2,4,6 , radiative transition probabilities, luminescence branching ratios and radiative lifetime of dysprosium luminescent level. Relaxation dynamic of 4 F 9/2 excited state was examined as a function of temperature. High quantum efficiency of dysprosium luminescence level, value of the 4 F 9/2 → 6 H 13/2 yellow emission cross-section and the quality of remaining spectroscopic parameters indicate that the Gd 3 Ga 3 Al 2 O 12 :Dy 3+ optical system can be considered as promising phosphor and visible laser material. [ABSTRACT FROM AUTHOR]

Mixed garnet crystals with nominal stoichiometry Gd 3 Al 2.5 Ga 2.5 O 12 undoped, single doped with Sm 3+ , Ho 3+ , Er 3+ and Yb 3+ and co-doped with Ho 3+ + Yb 3+ and Er 3+ + Yb 3+ were grown by the Czochralski method. Optical spectra and thermal conductivity of obtained single crystal samples were measured and analyzed. Recorded optical absorption spectra revealed that the intensity and spectral characteristics of color centre absorption in the UV region, close to the UV absorption edge of the host, are affected by the type of incorporated rare earth ions. On the other hand, spectral characteristics of stable color centers induced by an intense UV irradiation of crystals depend weakly on the rare earth admixture. Low temperature optical spectra provided the evidence that Sm 3+ ions and Er 3+ ions occupy at least two different types of sites in this host but Yb 3+ ions seem to be located preferentially in identical sites. Thermal conductivity of the crystals at 300 K, weakly affected by incorporated rare earth ions, is comparable to that reported for ordered gallium gadolinium garnet crystals. At cryogenic temperatures, i.e. below ca 80 K, thermal conductivities of the crystals containing rare earth ions are markedly smaller than that of undoped one, however. [ABSTRACT FROM AUTHOR]

Undoped and samarium-doped SrB 4 O 7 polycrystalline samples were prepared by a solid state reaction method in air. XRD examination revealed that the undoped sample is consistent with the pure SrB 4 O 7 phase but in samarium-doped sample in addition to the main tetraborate SrB 4 O 7 phase there is a little amount of metaborate. Based on preliminary spectroscopic examination it was ascertained that Sm 2+ ions are incorporated without measurable traces of Sm 3+ admixture. High resolution luminescence spectra and decay curves of Sm 2+ luminescence were measured as a function of temperature in the 5–550 K temperature region. Energies of crystal field components of the 7 F J (J = 1–5) multiplets at 5 K and those of the 5 D 1 multiplet at 300 K were determined from luminescence spectra and used subsequently as input data for the crystal field calculation. Performed crystal field calculation predicts the energy level scheme for the 4f 6 configuration of Sm 2+ in SrB 4 O 7 up to 29000 cm −1 and makes it possible to assess the contribution of transitions from the excited states above the 5 D 1 to luminescence phenomena. Evaluated activation energy E a ∼4600 cm −1 characterizing a steep decrease of the 5 D 0 lifetime of Sm 2+ between 320 K and 550 K indicates strongly that electronic origin of the lowest energy 7 F 0 – 4f 5 d 1 vibronic transitions is located around 19200 cm −1 , slightly below the 7 F 0 – 5 D 3 transition energy. [ABSTRACT FROM AUTHOR]

Abstract: Nd-doped CaF2 crystal with high optical quality was obtained by a temperature gradient technique (TGT). Energies of the crystal field levels of Nd3+ multiplets relevant to laser operation were determined based on optical spectra recorded at T =10K. Room temperature absorption spectra were analyzed in the framework of the Judd–Ofelt theory to calculate radiative transition rates and luminescence branching ratios for the 4F3/2 level. The 4F3/2 radiative lifetime was calculated to be 1295μs whereas a monotonous decrease of the 4F3/2 luminescence lifetime value from 1.45ms to 0.9ms was observed when the temperature increased from 10K to 300K. The stimulated emission cross-section of 1.48×10−20 cm2 at 1061nm was determined using the Fuchtbauer–Ladenburg relation. All the results showed that Nd:CaF2 would be a promising gain media in solid-state lasers. [Copyright &y& Elsevier]

Abstract: Selected heavy metal glasses containing Yb3+ and Er3+ ions have been studied. Near-infrared luminescence spectra at 1.53μm and up-conversion spectra of Er3+ ions were registered under excitation of Yb3+ ions by 975nm diode laser line. The luminescence bands correspond to 4I13/2–4I15/2 (NIR), 4S3/2–4I15/2 (green) and 4F9/2–4I15/2 (red) transitions of Er3+, respectively. The optical transitions of rare earth ions have been examined as a function of glass host. The unusual large spectral linewidth nearly close to 110nm for 4I13/2–4I15/2 transition of Er3+ ions in Yb–Er co-doped lead borate glass was obtained, whereas long-lived NIR luminescence at 1.53μm was detected in lead germanate glass. The NIR luminescence and up-conversion phenomena strongly depend on stretching vibrations of glass host, which was confirmed by FT-IR spectroscopy. [Copyright &y& Elsevier]