Search

The electron absorption-, photoluminescence- and electron paramagnetic-resonance spectra of Mn3+ in red beryl from Wah Wah Mountains (Utah USA) and of pink- and purple vesuvianite from Jeffrey Mine (Asbestos, Canada) were measured at room- and low temperatures. The crystal field stabilization energies are equal to 130.9 kJ/mol for the red beryl, and 151.5-158.0 and 168.0 kJ/mol for for the pink- and the purple vesuvianite, respectively. The red photoluminescence of Mn3+ was not intensive either at room- or at low temperatures. The high Mn content in the crystals caused the emergence of an additional emission band and short photoluminescence-decay lifetimes. The latter are only 183 μs for beryl and 17 μs for vesuvianite. [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]

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]

Abstract: Transparent single crystals of erbium-doped LaVO4 in form of platelets having an average size 0.5×2×2mm3 were obtained by the flux method using Pb2V2O7 as the solvent. Inductively coupled plasma (ICP) measurement revealed that the actual Er/La=0.3% molar ratio in the crystals is lower than Er/La=1% nominal molar ratio due to significant difference of ionic radii of La and Er. Luminescence spectra and luminescence decay curves for Er3+ transitions in the visible and near infrared region were recorded. Unpolarized Raman spectrum of undoped LaVO4 crystal was acquired, too. Up-converted green emission following excitation at 808 and 970nm was observed and dependence of its intensity on incident excitation power was determined. Based on experimental data gathered the relaxation dynamics of excited states of Er3+ was analyzed and mechanisms involved in the up-conversion phenomena were discussed. [Copyright &y& Elsevier]

Abstract: LaPO4 single crystals lightly doped with Er3+, and codoped with Er3+ and Yb3+ have been grown by spontaneous nucleation in a lead phosphate flux. Absorption and luminescence spectra have been measured in the visible and near-IR regions and the excited state dynamics has been studied upon pulsed laser excitation. The obtained results have allowed the evaluation of the effective emission cross-sections around 1.5μm, that have been found to be similar to important oxide laser crystals doped with Er3+. Efficient visible upconversion has been observed upon excitation at 980nm in the codoped crystals. This behaviour is attributed to Yb3+–Er3+ energy transfer processes. [Copyright &y& Elsevier]

Optical absorption spectra and luminescence spectra were recorded as a function of temperature between 295 K and 800 K for single crystal samples of Gd2SiO5:Dy3+, Lu2SiO5:Dy3+, LiNbO3:Dy3+, and Gd3Ga3Al2O12:Dy3+ fabricated by the Czochralski method and of YAl3(BO3)4:Dy3+ fabricated by the top-seeded high temperature solution method. A thermally induced change of fluorescence intensity ratio (FIR) between the 4I15/2→ 6H15/2 and 4F9/2 → 6H15/2 emission bands of Dy3+ was inferred from experimental data. It was found that relative thermal sensitivities SR at 350 K are higher for YAl3(BO3)4:Dy3+ and Lu2SiO5:Dy3+than those for the remaining systems studied. Based on detailed examination of the structural peculiarities of the crystals it was ascertained that the observed difference between thermosensitive features cannot be attributed directly to the dissimilarity of structural factors consisting of the geometry and symmetry of Dy3+ sites, the number of non-equivalent Dy3+ sites, and the host anisotropy. Instead, it was found that a meaningful correlation between relative thermal sensitivity SR and rates of radiative transitions of Dy3+ inferred from the Judd–Ofelt treatment exists. It was concluded that generalization based on the Judd–Ofelt parameters and luminescence branching ratio analysis may be useful during a preliminary assessment of thermosensitive properties of new phosphor materials. [ABSTRACT FROM AUTHOR]

Single crystal of La 3 Ga 5.5 Ta 0.5 O 14 (LGT) doped with Dy3+ was fabricated by the Czochralski technique and investigated employing methods of optical spectroscopy. Polarized optical absorption spectra and luminescence spectra were recorded at room temperature. Unpolarized absorption and luminescence spectra were recorded at 10 K. Spectra of blue luminescence related to transitions 4I 15/2 , 4F 9/2 → 6H 15/2 were recorded at several temperatures in the 300–773 K region. Dy3+ ions have the same symmetry sites in LGT but their spectra show inhomogeneous broadening due to structural disorder of the host and are markedly anisotropic. Results of the Judd-Ofelt treatment made it possible to assess emission cross sections for the 4F 9/2 → 6H 15/2 blue luminescence and for the 4F 9/2 → 6H 13/2 yellow luminescence employing Fuchtbauer-Ladenburg formula and reciprocity method. In particular, a spectral distribution of La 3 Ga 5.5 Ta 0.5 O 14 : Dy3+ σ-polarized luminescence band with an emission cross section σ em = 0.51 × 10−20 cm2 at 573.5 nm is favorable for a laser operation in the visible. Interpretation of the effect of temperature on the blue emission spectra leads to the conclusion that La 3 Ga 5.5 Ta 0.5 O 14 : Dy3+ is promising for application as luminescent thermometer. • Novel single crystal La 3 Ga 5.5 Ta 0.5 O 14 :Dy (LGT:Dy). • Detailed analysis of optical spectra and luminescence decay curves. • Potential visible laser operation at 573.5 nm. • Temperature sensitivity of LGT:Dy luminescence. [ABSTRACT FROM AUTHOR]

Using steady-state luminescence measurements, the luminescence spectra of Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Dy3+, Er3+ and Yb3+ for the agrellite sample from the Kipawa River region have been measured. The emission spectra of Eu3+ and Dy3+ next to those of Sm3+ and Pr3+ have been measured for characteristic excitation conditions. The most efficient luminescence activator in the studied sample was Ce3+. This ion was also a sensitizer of Pr3+, Sm3+, Eu3+, and Dy3+ luminescence. [ABSTRACT FROM AUTHOR]

Samarium(2+) doped single crystals of SrCl 2 , SrBr 2 and SrI 2 with a nominal samarium concentration of 0.12, 0.16 and 0.13 at%, respectively, were grown by the Bridgman method. XRD examination revealed that obtained samples are single phase and their structures are consistent with those intentional. Based on preliminary spectroscopic measurement it was ascertained that Sm 2+ ions are incorporated without traces of Sm 3+ contamination. High resolution absorption, luminescence and excitation spectra as well as luminescence decay curves were measured as a function of temperature in the 4.2–300 K region. It was found that structural peculiarities of the host crystals affect strongly spectroscopic features of incorporated Sm 2+ ions. At room temperature all systems under study show a broad-band luminescence related to the parity allowed inter-configurational 4f 5 5d 1 – 4f 6 transitions of Sm 2+ . At 5 K a broad band luminescence vanishes in SrCl 2 :Sm 2+ and a resulting luminescence spectrum shows a rich fine structure consisting of narrow lines that we attribute to magnetic dipole transitions within the 4f 6 configuration of Sm 2+ ions located in centro-symmetric sites and/or their vibrational side bands. Based on an analysis of luminescence decay curves we attribute numerous narrow lines that appear in luminescence spectra of SrBr 2 :Sm 2+ recorded below 25 K to the 5 D 0 – 7 F J ( J = 0–4) intra-configurational transitions of Sm 2+ ions located in sites with C 4 and C 1 symmetry. A long-lived luminescence related to intra-configurational transitions was not observed in SrI 2 :Sm 2+ even at 4.2 K. [ABSTRACT FROM AUTHOR]

Up-conversion luminescence spectra of Er 3+ ions in PbO–Ga 2 O 3 –GeO 2 and PbO–Ga 2 O 3 –SiO 2 glasses have been examined as a function of temperature in the 298–650 K range. The relative emission intensities of green bands corresponding to 2 H 11/2 → 4 I 15/2 and 4 S 3/2 → 4 I 15/2 transitions of Er 3+ were determined with temperature. Based on up-conversion luminescence spectra of Er 3+ , the fluorescence intensity ratio and temperature sensitivity for glasses based on PbO–Ga 2 O 3 –XO 2 (X = Ge, Si) were calculated. The maximum sensitivity is equal to 20.4 × 10 − 4 K − 1 at T = 620 K (X = Ge) and 26.4 × 10 − 4 K − 1 at T = 590 K (X = Si) suggesting potential application in optical sensor thermometry. [ABSTRACT FROM AUTHOR]

Abstract: Luminescence of lead bismuthate glasses PbO-Bi2O3-Ga2O3 containing Dy3+ ions has been studied. Two overlapping luminescence bands corresponding to 3P1–1S0 transition of Bi3+ and 4F9/2 –6H13/2 transition of Dy3+ were detected under 480nm excitation. Comparison of luminescence features for the system under study to those reported for dysprosium-doped lead borate glass PbO-B2O3-Ga2O3 indicates that the luminescence of Dy3+ is efficiently quenched by Bi3+ ions. Analysis of luminescence dynamics implies that the excitation energy transfer from Dy3+ to Bi3+ is nonradiative. The theoretical calculations using Inokuti–Hirayama model confirm strong luminescence of Dy3+ ions in lead bismuthate glasses. [Copyright &y& Elsevier]

Abstract: Ln-doped oxychloride lead borate glasses were studied using luminescence spectroscopy. Rare earth ions were limited to trivalent Pr3+, Tm3+, Eu3+ and Er3+. Luminescence spectra were registered, which correspond to 3P0–3H4 and 1D2–3H4 transitions of Pr3+, 1G4–3H5 and 1G4–3F4 transitions of Tm3+, 5D0–7F J (J=0, 1, 2, 3, 4) transitions of Eu3+ and 4S3/2,2H11/2–4I15/2 and 4I13/2–4I15/2 transitions of Er3+. Luminescence decays from the excited states of Ln3+ ions were analyzed in detail. The experimental results indicate that relatively high phonon energy of the host gives important contribution to the excited state relaxation of rare earth ions. [Copyright &y& Elsevier]

Temperature-dependent up-conversion luminescence spectra of Er 3+ in lead-free germanate glass have been examined under 800 nm and 980 nm diode laser excitation. Green up-conversion luminescence spectra measured in the 500–580 nm ranges correspond to transitions originating from thermally coupled 2 H 11/2 and 4 S 3/2 levels to 4 I 15/2 ground level of Er 3+ . The relative emission band intensities of 2 H 11/2 → 4 I 15/2 and 4 S 3/2 → 4 I 15/2 transitions of Er 3+ are changed with temperature. The rate of fluorescence intensity ratio varying with temperature was calculated for glass sample excited at 800 nm and 980 nm, respectively. The maximum temperature sensitivity is nearly 20% higher for glass sample pumped at 980 nm than 800 nm. [ABSTRACT FROM AUTHOR]

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]