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Two neodymium(III) six-coordinate complexes NdCl3(3-Br-4-CH3OC7H7NO)3 (Nd1) and Nd(C7H9NO)5(C4H8O2)(ClO4)3 (Nd2) have been synthesized and characterized. The FT-IR and FT-Raman data were acquired, and a complete vibrational assignment of the fundamental modes of the compounds was carried out. The frequencies calculated for the both ligands and scaled using the B3LYP approach with the 6-311G(2d,2p) basis set correspond very well to the experimental values. The XRD results, IR and Raman spectra were discussed in terms of a possible structure and composition of the studied compounds. The optical absorption and emission spectra were investigated at room temperature. The emission decay is mono exponential indicating that the energy transfer from the ligand occurs straight to the 4F3/2 level. The lifetime of this level is about 2.5 μs? A possibility of the energy transfer between the ligands under study and neodymium ions was considered. The calculations of the spin Hamiltonian parameters and EPR data simulation were performed using the electron paramagnetic resonance and nuclear magnetic resonance (EPR-NMR) program.

Eu3+ complex with 1-(2,6-dihydroxyphenyl)ethanone in the solid state has been synthesized and characterized by elemental analysis, UV-visible, FT-IR and FT-Raman spectroscopies, powder X-ray diffraction, electron emission under femtosecond laser excitation. The stoichiometry and the formula of the studied complex have been proposed. Its physicochemical properties have been analyzed in terms of the structure and DFT calculations performed for the ligand. The luminescence and dynamics of the excited states depopulation have been studied using femtosecond laser excitation. Spectral and energetic transformation of femtosecond light impulses has been studied and possibility of the energy transfer between the ligand and the Eu3+ electron levels has been analyzed.

The electron paramagnetic resonance (EPR), optical absorption, luminescence (emission and excitation) spectra as well as luminescence kinetics of the Nd3+ centres in a series of borate glasses with Li2B4O7:Nd, LiCaBO3:Nd, and CaB4O7:Nd compositions containing 0.5 and 1.0 mol% Nd2O3 have been investigated and analysed. Using EPR and optical spectroscopy data it was shown that the Nd impurity is incorporated into the network of investigated glasses as Nd3+ (4f3, 4I9/2) ions, exclusively. All observed f – f electronic transitions of the Nd3+ centres in optical absorption and luminescence spectra of the investigated glasses were identified. Local structure of the Nd3+ luminescence centres in the borate glasses network is proposed. Theoretical oscillator strengths (ftheor) and phenomenological intensity parameters (Ω2, Ω4, Ω6) for observed Nd3+ absorption transitions containing 1.0 mol% Nd2O3 have been determined using standard Judd–Ofelt theory. The spectroscopic parameters of relevance to laser applications such as the radiative transitions rate (Wr), luminescence branching ratio (β), radiative lifetime (τrad), and emission cross-section (σem) for Nd3+ centres in the Li2B4O7:Nd, LiCaBO3:Nd, and CaB4O7:Nd glasses have been calculated. Luminescence decay curves of the Nd3+ centres from the 4F3/2 emitting level for all investigated glasses were satisfactory described by single exponential decay. The obtained experimental lifetimes were compared with those calculated and quantum efficiency (η) of the 4F3/2 → 4I11/2 transition for Nd3+ centres in the investigated glasses were estimated. Based on the obtained results it can be concluded that the further efforts should be made to improve the Nd-doped borate glasses parameters relevant for neodymium solid state lasers with LED pumping.

A solid state Eu3+ complex with dehydroacetic acid (DHA) has been synthesized and characterized by elemental analysis, UV–visible, FT-IR, FT-Raman, powder and single-crystal X-ray diffraction and optical spectroscopy studies. The complex has formula [Eu(DHA)2(H2O)5]NO3 with DHA = C8H7O4−, where the europium ions is in monocapped distorted square antiprism environment with coordination number nine. Its photophysical properties have been analyzed in terms of its molecular structure and DFT calculations performed for the representative crystal fragment including Eu3+ and two DHA ligands. The luminescence and dynamics of the excited states depopulation have been studied using femtosecond laser excitation. The energy transfer mechanism between the ligand and Eu3+ electronic energy levels has been proposed. The obtained results have been compared to those of Gd3+ dehydroacetic derivative.

Germanotellurite glasses doped with Yb and co-doped with Nd and Yb were produced using the melt-quenching method. Their spectroscopic properties were analyzed at 300 K and at elevated temperatures up to 725 K in terms of their luminescent qualities and application potential in luminescence thermometry. The Nd–Yb transfer dynamics were discussed. Owing to the efficient energy transfer from Nd to Yb ions, a temperature sensing model based on the intensity between emission bands from 4F5/2 (Nd) and 2F5/2 (Yb) levels was established, reaching around 0.7%/K of relative sensitivity. Straight after, the model was successfully tested in practical spectroscopy lab conditions to estimate the temperature increase resulting from high power laser diode excitation. Glass spectroscopic features, in conjunction with an intrinsic method for fast and contactless temperature readout, make GTSN: Nd, Yb a promising material especially for optical temperature sensors.

New europium and terbium [LnCl3L3(H2O)2] polycrystalline complexes were synthesized with the ligand L = 3-bromo-4-methylthio-2,6-lutidine N-oxide. IR, Raman, electron absorption UV-VIS and emission spectra measurements were carried out for these compounds. Re-crystallization of these materials led to formation of single crystals with another composition [LnL(H2O)7]Cl3∙L3, they were characterized by X-ray diffraction technique and spectroscopic measurements. Both types of the materials consist of eight coordinated LnCl3O3O’2 or LnOO’7 polyhedrons containing O - oxygen atoms of the N-oxide group, chlorine atoms or O’ - oxygen atoms of the water units. The crystal structure was solved for two complexes of the formula [Ln(L)(H2O)7]Cl3∙(L)3 where Ln = Eu and Tb. X-ray diffraction analysis reveals that these complexes are isostructural with P21/m space group. The optimization of the molecular system and frequency calculations were carried out using density functional theory (DFT). The DFT quantum chemical calculations of the vibrational wavenumbers were performed for the ligands used for the Eu3+ and Tb3+ ions complexation. The emission measurements were carried out with the femtosecond excitation. The effective ligand-to-metal energy transfer was discovered in the [LnCl3L3(H2O)2] complexes formed in the polycrystalline state.

Eu 3+ complex with 2-hydroxy-4-metoxy-benzophenone (HMBP) in solid state has been synthesized and characterized by elemental analysis, UV–visible, FT-IR, FT-Raman spectroscopies, powder X-ray diffraction, electron emission excited by femtosecond pulses. The stoichiometry and formula of the studied complex have been proposed. Its physicochemical properties have been analyzed in terms of structure and DFT calculations performed for the ligand. The luminescence and dynamics of the excited states depopulation were studied using femtosecond laser excitation. The spectral and energetic transformation of femtosecond light pulses have been discussed and a possibility of an energy transfer between the singlet state of the ligand and the Eu 3+ electron levels has been considered.

Erbium-doped lead silicate glass has been investigated for near-infrared emission and up-conversion applications. Near-infrared emission due to 4 I 13/2 → 4 I 15/2 transition of Er 3+ is relatively broad (70.5 nm) and long-lived (3.7 ms). Also, up-conversion luminescence spectra of Er 3+ ions in lead silicate glass have been examined as a function of temperature. The relative intensities of luminescence 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. The fluorescence intensity ratio and temperature sensitivity were calculated. The maximum sensitivity for Er 3+ doped lead silicate glass is close to 26.4 × 10 −4 K −1 at T = 590 K.

GTSN: Nd (GeO2-TeO2-SrF2-Nb2O5–Nd2O3) glasses of varying (0.2–3%) Nd concentration were obtained using the melt-quenching method. Their thermal properties were evaluated using differential scanning calorimetry, showing highly favorable glass thermal stability. Glass structure was analyzed using XRD, IR and Raman spectroscopy. Combining the advantages of germanate, tellurite and fluoride optical systems, a promising glass laser material was achieved, as proven with optical spectroscopy methods, such as absorption, emission and fluorescence lifetime spectroscopies. Utilizing the fluorescence intensity ratios between emission bands from Nd excited levels, several models for luminescent thermometry were established for GTSN: Nd. One of the models was tested in a laser power-dependence experiment, allowing to estimate temperature increase during high power optical excitation. Great thermal stability and spectroscopic performance of the material, along with a built-in method for contactless temperature measurement, make GTSN: Nd a promising material for glass-based optically active elements.

Nanocrystalline MIY(WO4)2 double tungstates (MI = Li, Na, K and Rb) co-doped with Er3+ and Tm3+ ions were synthesized by hydrothermal and Pechini techniques and characterised by means of X-ray diffraction, infrared absorption and electron absorption spectra. Their emission spectra and luminescence decay kinetics were recorded at ambient temperature. These investigations were focused on impact of structural changes and morphology inducing by the alkaline ion on the Er ↔ Tm energy transfer efficiency in the studied nanocrystalline oxide systems. The effect of the thermal treatment on morphology and spectroscopic properties of the synthesized nano-materials was studied. Furthermore, emission spectra attained under different excitation as well as study on luminescence decay curves made it possible to determine the differences and dynamics of feeding and relaxation of excited states involved in luminescence phenomena. The energy transfer mechanism between Er3+ and Tm3+ ions was proposed and analysed in terms its usefulness in the phosphors and optical amplifiers operating at 1.8 μm.

[Ln2(2-hydroxy-5-methyl-nicotinic acid)6(H2O)4] and Ln2(5-methyl-nicotinic acid)6(H2O)4] complexes (Ln = Gd, Tb) have been synthesized and characterized by means of powder X-ray diffraction, IR, Raman, electron UV–Vis and emission measurements. The luminescence and dynamics of the excited states depopulation have been studied using femtosecond laser excitation. The singlet and triplet states of nicotinic acid were localized using DFT quantum chemical calculations. The energy transfer mechanism between the electron levels of the ligands and Tb3+ ion have been proposed.

The electron paramagnetic resonance (EPR), optical absorption, and luminescence (emission and excitation) spectra as well as luminescence kinetics of the Er-doped glasses with Li 2 B 4 O 7 composition were investigated and analysed. The high optical quality glasses with Li 2 B 4 O 7 :Er composition containing 0.5 and 1.0 mol.% Er 2 O 3 were obtained from corresponding polycrystalline compound by standard glass synthesis. The EPR spectroscopy in the 4.2–300 K temperature range and optical spectroscopy at 300 K show that the Er impurity is incorporated into the network of Li 2 B 4 O 7 glass as Er 3+ (4 f 11 , 4 I 15/2 ) ions, exclusively. The local structure of the Er 3+ luminescence centres in Li sites of the glass network is proposed. Based on the standard Judd–Ofelt theory the oscillator strength ( P cal ) and experimental oscillator strength ( P exp ) for observed absorption transitions as well as phenomenological intensity parameters (Ω 2 , Ω 4 , Ω 6 ) for Er 3+ centres in the Li 2 B 4 O 7 :Er glass containing 1.0 mol.% Er 2 O 3 were calculated. Spectroscopic parameters of relevance for laser applications, including emission probabilities of transitions ( W r ), branching ratios ( β ), and radiative lifetime ( τ rad ) have been calculated for main observed emission transitions of the Er 3+ centres in Li 2 B 4 O 7 :Er glasses. Experimental and calculated lifetimes were compared and quantum efficiency ( η ) for green ( 4 S 3/2 → 4 I 15/2 transition) and infrared ( 4 I 13/2 → 4 I 15/2 transition) emission bands has been estimated.

The SrB 2 O 4 single crystal doped with 0.5 at% of europium has been grown by the Czochralski method. The Eu 2+ broad emission in bulk crystal has been observed, upon excitation by a femtosecond laser. However, the efficiency of this emission does not exceed a value of 23% at 5 K, assessed in the frame of the Inokuti–Hirayama model. The critical distance R 0 was calculated to be 20.6 A, C da 5.40×10 −45 m 6 /s for S =6. The calculated radiative lifetime based on the Inokuti–Hirayama equation is 14.28 ns.

The spectroscopic and luminescence properties of a series Sm-doped Li2B4O7, CaB4O7, and LiCaBO3 borate glasses are investigated using optical absorption, photoluminescence, and decay kinetics techniques as well as Judd–Ofelt (J–O) analysis. Borate glasses of high chemical purity and optical quality, doped with Sm2O3 in amounts of 0.5 and 1.0 mol.% were obtained from the corresponding polycrystalline compounds in the air atmosphere using standard glass synthesis technology. The J–O intensity parameters have been calculated using the spectral intensities of the Sm3+ absorption bands. Radiative properties such as transition probabilities, branching ratios, stimulated emission cross-sections, and radiative lifetimes are estimated for 4G5/2 → 6HJ (J = 5/2, 7/2, 9/2, and 11/2) emission transitions of the Sm3+ ions. The luminescence kinetics of the Sm3+ centres are characterised by slightly non exponential decay with lifetime values, which depend on the basic glass composition and Sm impurity concentration. The measured lifetimes were compared with those calculated and quantum efficiencies have been estimated. The obtained high quantum efficiencies of emission transitions (∼70%) and high quantum yields of luminescence (∼14%) of the Sm3+ centres show that the investigated borate glasses belong to perspective luminescent and laser materials.

Solid-solution crystals Lu2SiO5 - Gd2SiO5 (LGSO) single doped with Tb3+ with concentrations 0.8, 1.5 and 4.0 at% and co-doped with 4.0 at% Tb3+ + 0.6 at% Ce3+ were fabricated by the Czochralski technique. Optical absorption spectra were recorded with polarized light. Luminescence and excitation spectra for Tb3+ and Ce3+ were recorded upon CW excitation. Time resolved spectra of Tb3+ and Ce3+luminescence excited by femtosecond light pulses were recorded with a streak camera. It was observed that in Tb3+-doped samples the 5D4 luminescence excited into f-d bands in UV shows an initial rising stage whose dynamics is governed by the decay time of the higher energy 5D3 level. In the LGSO:Tb, Ce phosphor the highest luminescence intensity occurs for excitation wavelengths between 320 nm and 370 nm providing a broad –band emission consisting of vibronic transitions of Ce3+ ions and of 5D4 emission of Tb3+ that is fed from excited Ce3+ ions. It was concluded that LGSO:Tb, Ce is a promising visible phosphor for application purposes.

International audience; Lanthanide complexes with phthalocyanines (Pc) and porphyrins are of great interest because of unique luminescence behavior and many applications, mainly in medicine, optoelectronics, lasers and solar energy conversion. This paper is focused on photophysical studies of axially chloro substituted ytterbium mono-phthalocyanine chelate in the solid state, solutions, lattice of PMMA polymer. These latter systems are fundamental for applications. The structures, IR, and Raman spectra were calculated basing on Hartree-Fock (HF) and Density Functional Theory (DFT) methods. The theory reproduces correctly experimental results of spectroscopic frequencies of PcYbCl2 CH3OH chelate. Recently we published the absorption spectra of metalophthalocyanine compound in PMMA polymer, however neither its structure nor emission properties were studied. Now we have made the effort to study the emission behavior of PcYbCl 2 CH3OH chelate in different media. Immobilization of molecule in polymer and inorganic matrices on lanthanide ions and the phthalocyanine emission spectra were analysed. The radiative and non-radiative processes, energy transfer and multi-phonon relaxation were investigated. The non-linear processes and dynamics in excited states were discussed.

The electron absorption and emission spectra were measured for the pyramidal LnPc(OAc) complexes in the solid state and co-doped in silica glass, where Ln=Er, Eu and Ho. The theoretical electron spectra were determined from the quantum chemical DFT calculation using four approximations CAM-B3LYP/LANL2DZ, CAM-B3LYP/CC-PVDZ, B3LYP/LANL2DZ and B3LYP/CC-PVDZ. It was shown that the best agreement between the calculated and experimental structural parameters and spectroscopic data was reached for the CAM-B3LYP/LANL2DZ model. The emission spectra were measured using the excitations both in the ligand and lanthanide absorption ranges. The possibility of energy transfer between the phthalocyanine ligand and excited states of lanthanide ions was discussed. It was shown that the back energy transfer from metal states to phthalocyanine state is responsible for the observed emission of the studied complexes both in the polycrystalline state and silica glass.

Micro-crystalline powders of Na 3 Ce(PO 4 ) 2 orthophosphate doped with Cr 3+ ions were synthesized and characterised by means of X-ray diffraction, IR and Raman, electron absorption, magnetic and EPR studies. The emission and excitation spectra and fluorescence decay time were recorded in the temperature range 70–293 K. The spectroscopic properties of Ce 3+ and Cr 3+ ions in the studied materials were discussed in terms of the structure and local symmetry of the optical ions. These data were compared to those obtained for NaCe(PO 3 ) 4 metaphosphate.

The undoped and Cr3+-doped NaCe(PO3)4 metaphosphates were synthesized by the modified Pechini method and obtained as the crystalline powders. They were characterized by means of X-ray diffraction, vibrational and optical spectroscopy to clarify the structure and mechanism of Cr3+ emission in NaCe(PO3)4. This phosphor crystallizes in the monoclinic P121/n1 structure with an infinite (PO3)n chain. The Cr3+ ions can substitute the C1 symmetry site occupied by cerium ions. They can also occupy the tunnels formed in the anionic layer. Spectroscopic properties of the Cr3+ and Ce3+ ions were discussed in terms of structure of the studied crystalline powders. IR and Raman data confirm the predicted structure and indicate C1 site symmetry of the Cr3+ active ions. The Cr3+ ions appear in the distorted octahedral environment of the weak crystal field. Optical studies were confirmed by EPR results carried out in the temperature range of 4–293 K. In addition, the magnetic measurements were performed up to 305 K. The Cr3+ ions reveal negligible ferromagnetic interactions while the Ce3+ ions change their magnetic interactions from slightly antiferromagnetic to significantly ferromagnetic above 20 K.

in Various Tellurite Glasses B. Burtan, J. Cisowski, J. Wasylak, R. Lisiecki, W. Ryba-Rymanowski, J. Jarzibek and M. Reben Institute of Physics, Cracow University of Technology, Podchori»ych 1, 30-084 Cracow, Poland Faculty of Materials Sciences and Ceramics, AGH University of Science and Technology, al. A. Mickiewicza 30, 30-059 Cracow, Poland Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Okolna 2, 50-950 Wrocaaw, Poland d Centre of Polymer and Carbon Materials, Polish Academy of Sciences, M. Curie-Skaodowskiej 34, 41-819 Zabrze, Poland

Neodymium phosphate materials were considered as possible laser media. NaNdP2O7, NaNd(PO3)4, Na3Nd(PO4)2 and Nd3(PO4)O3 phosphates have been synthesized in the solid state reaction protecting the proper conditions characteristic for the each synthesis. Structure, optical properties and vibrational characteristics for the obtained samples have been analyzed taking into account the relations between them. Considering the structure influence of the studied phosphates on their optical properties it was found that the emission efficiency, in that the lifetime in investigated phosphates was not clearly dependent on the type of structure of these materials. Significant improvement of the emission properties is observed only for the NaNd(PO3)4 metaphosphate where the longest Nd–Nd distance appears and the luminescence lifetime of the 4F3/2 level in this material was measured to be 112 μs. It means that among investigated compounds solely NaNd(PO3)4 metaphosphate can be considered as promising stoichiometric laser active material.

Glass-ceramics containing NaYF4 nanocrystals were prepared by heat-treatment from oxyfluoride silicate-based glass doped with Ho3+ and Yb3+ ions. The formation of crystalline fluoride phase was confirmed by X-ray diffraction and transmission electron microscopy. Absorption and emission spectra revealed that a fraction of Ho3+ and Yb3+ ions is incorporated into the NaYF4 ordered lattice influencing spectroscopic features of glass-ceramics in comparison with those of precursor glass. Green up-conversion emission (545 nm) originating in the 5S2 level in glass-ceramics and up-converted red emission (650 nm) originating in the 5F5 level in as-melted glass were observed under optical pumping into Yb3+ absorption band and analyzed. Although both emissions in both materials are achieved by two-photon excitations, the relation between green and red emission intensity in glass-ceramics and glass implies that processes relevant to up-conversion phenomena are different. Based on a careful analysis of relaxation dynamics of Ho3+ and Yb3+ excited states, the mechanisms involved in conversion of the infrared radiation into the visible emission in these materials are proposed and discussed.

Single crystals of gadolinium orthosilicate Gd2SiO5 containing 0.5 at% and 5 at% of Sm3+ were grown by the Czochralski method. Optical absorption spectra, luminescence spectra and luminescence decay curves were recorded for these systems at 10 K and at room temperature. Comparison of optical spectra recorded in polarized light revealed that the anisotropy of this optically biaxial host affects the intensity distribution within absorption and emission bands related to transitions between multiplets rather than the overall band intensity. It has been found that among four bands of luminescence related to the 4G5/2→6HJ (J=5/2–11/2) transitions of Sm3+ in the visible and near infrared region the 4G5/2 →6H7/2 one has the highest intensity with a peak emission cross section of 3.54×10−21 cm2 at 601 nm for light polarized parallel to the crystallographic axis c of the crystal. The luminescence decay curve recorded for Gd2SiO5:0.5 at% Sm3+ follows a single exponential time dependence with a lifetime 1.74 ms, in good agreement with the 4G5/2 radiative lifetime τrad=1.78 ms calculated in the framework of Judd-Ofelt theory. Considerably faster and non-exponential luminescence decay recorded for Gd2SiO5:5 at% Sm3+ sample was fitted to that predicted by the Inokuti-Hirayama theory yielding the microparameter of Sm3+–Sm3+ energy transfer Cda=1.264×10−52 cm6×s−1.

This work is concentrated on growth, spectroscopy and laser performance of thulium-doped vanadate crystals. At the beginning the growth techniques are analyzed and then the matrix of vanadates crystal, its structure and physicochemical properties are explained together with the rare earth activators influence. Detailed spectroscopy of the thulium-doped vanadate crystals then follows. On the background of this theoretical analysis and state of the art of the subject the description of thulium vanadate lasers (especially Tm:YVO4, Tm:GdVO4, and Tm:LuVO4) together with their generated output radiation characteristics are presented.

Correlation between structure and optical properties of rare earth ions in lead borate glasses and glass-ceramics was evidenced by X-ray-diffraction, Raman, FT-IR and luminescence spectroscopy. The rare earths were limited to Eu(3+) and Er(3+) ions. The observed BO(3)↔BO(4) conversion strongly depends on the relative PbO/B(2)O(3) ratios in glass composition, giving important contribution to the luminescence intensities associated to (5)D(0)-(7)F(2) and (5)D(0)-(7)F(1) transitions of Eu(3+). The near-infrared luminescence and up-conversion spectra for Er(3+) ions in lead borate glasses before and after heat treatment were measured. The more intense and narrowing luminescence lines suggest partial incorporation of Er(3+) ions into the orthorhombic PbF(2) crystalline phase, which was identified using X-ray diffraction analysis.

Ln-doped oxychloride lead borate glasses were studied using luminescence spectroscopy. Rare earth ions were limited to trivalent Pr 3+ , Tm 3+ , Eu 3+ and Er 3+ . Luminescence spectra were registered, which correspond to 3 P 0 – 3 H 4 and 1 D 2 – 3 H 4 transitions of Pr 3+ , 1 G 4 – 3 H 5 and 1 G 4 – 3 F 4 transitions of Tm 3+ , 5 D 0 – 7 F J ( J =0, 1, 2, 3, 4) transitions of Eu 3+ and 4 S 3/2 , 2 H 11/2 – 4 I 15/2 and 4 I 13/2 – 4 I 15/2 transitions of Er 3+ . Luminescence decays from the excited states of Ln 3+ 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.

Multicomponent lead borate glasses modified by PbX 2 (X = F, Cl or Br) were examined. For the first time, lead tungstate PbWO 4 crystallites dispersed into glass matrices were successfully obtained from controlled crystallization. Excitation by 310 nm line leads to broad blue luminescence related to the radiative transition which occurred in the PbWO 4 crystallites. It was found that halogen X ions (X = F, Cl or Br) were also incorporated in the distorted crystal system of PbWO 4 . It was proved by results obtained from X-ray diffraction as well as luminescence measurements.

A P 2 O 5 -CaO-SrO-BaO phosphate glass doped with Tm 3+ and glasses doped with (Tm 3+ , Pr 3+ ) were used for this study. The photo-luminescence behaviors of Tm 3+ and Pr 3+ in phosphate glass were investigated by absorption, excitation and emission spectroscopy. The energy transfer between Tm 3+ and Pr 3+ in phosphate glasses (which exhibit a variety of transfer efficiencies) was studied. The experimental quantum efficiencies of the luminescence of Tm 3 + η 0 and (Tm 3+ , Pr 3+ ) doped phosphate glasses were measured to give η/η 0 = 0.447, 0.305, and 0.179 for (0.4 mol% Pr 3+ , 1.0 mol% Tm 3+ ), (0.8%Pr 3+ , 1.0%Tm 3+ ) and (1.6 mol% Pr 3+ , 1.0 mol% Tm 3+ ), respectively. In order to verify the nature of the ion coupling in our phosphate glass system, we applied the Inokuti–Hirayama model. The non-radiative energy transfer rate from Tm 3+ to Pr 3+ , transfer efficiencies, and the donor–acceptor distance have been calculated and compared with obtained experimental data. As usual, the efficiency and the probability of energy transfer increase with the concentration of the acceptor.

Single crystal of YAl 3 (BO 3 ) 4 (YAB) containing 1 at.% of Sm 3+ was grown by the top seeded high temperature solution method. Optical absorption, excitation and luminescence spectra as well as luminescence decay curves were recorded for this system at 10 K and at room temperature. Crystal field splitting of Sm 3+ multiplets involved in absorption and emission transitions was derived from low temperature optical spectra and used to interpret peculiarities of emission bands. Careful analysis of low temperature optical spectra points to the presence of one type of Sm 3+ site in contrast to two non-equivalent sites reported for Yb 3+ :YAB system. It was found that among numerous radiative transitions originating in the single metastable 4 G 5/2 level of Sm 3+ the 4 G 5/2 – 6 H 7/2 transition around 598 nm is particularly intense in YAB. The transition terminates on the excited multiplet well above the ground state and thereby is consistent with the four level laser operation scheme. The 4 G 5/2 luminescence was found to be long-lived with the lifetime value of 2 ms at room temperature indicating small contribution of non-radiative transitions to the 4 G 5/2 relaxation.

Lithium and potassium–lithium tetraborate glasses doped with Cu (Li2B4O7:Cu and KLiB4O7:Cu) of high optical quality were obtained from polycrystalline compounds by fast cooling of the corresponding melt. Cu impurity was added to the Li2B4O7 and KLiB4O7 compounds in the form of a CuO oxide in the amounts of 0.4 and 1.6 mol.%. On the basis of EPR and optical spectroscopy (absorption, emission and luminescence excitation and kinetics) data analysis it was shown that the Cu impurity was incorporated into the tetraborate glass network as Cu2+ (3d9) and Cu+ (3d10) ions. The EPR spectra of Cu2+ centers were almost identical in glasses with the Li2B4O7:Cu and KLiB4O7:Cu compositions and were characteristic for glassy compounds. The Cu2+ EPR spectra parameters (g-values, hyperfine constants and peak-to-peak linewidths) in the Li2B4O7:Cu and KLiB4O7:Cu glasses were obtained at T = 300 K. The characteristic broad absorption band peaked near 750 nm was assigned to the 2B1g → 2B2g transition of the Cu2+ centers. An intense absorption in the UV region (λ

Dysprosium-doped lead borate glasses before and after heat treatment have been studied. Lead tungstate PbWO 4 crystallites were identified in lead borate glasses after heat treatment. Luminescence was examined under different excitation wavelengths. Blue luminescence of PbWO 4 crystallites embedded in lead borate glass is observed upon 310 nm excitation. Luminescence spectra measured under excitation at 390 nm consists of two characteristic blue and yellow bands, which correspond to 4 F 9/2 – 6 H 15/2 and 4 F 9/2 – 6 H 13/2 transitions of Dy 3+ . Blue band is enhanced and broadened in comparison to yellow 4 F 9/2 – 6 H 13/2 transition, when Dy 3+ and PbWO 4 crystallites in lead borate glass after heat treatment are simultaneously excited by 360 nm line.

Er3+-doped KCaY(VO4)2 microcrystalline samples were synthesized using a high temperature solid-state reaction technique. Spectroscopic properties of Er3+: KCaY(VO4)2 are studied and the nature of emissions is discussed. A strong green and infrared luminescence were observed under excitation at 314 nm in the O2−→V5+ charge-transfer transitions and direct excitation of Er3+ ions at 435 nm. A strong emission lines in the blue region are due to the transitions of VO43− ions have been observed at 77 K. The Judd–Ofelt parametrization scheme has been applied to the analysis of the room temperature absorption spectra in order to evaluate the intensity parameters, the branching ratios and the radiative lifetimes of the 4I13/2, 4I11/2, 4F9/2 and 4S3/2 emitting levels. The effective cross-section has been calculated for the 4I13/2→4I15/2 transition, indicating that the title compounds is a promising active medium for application in the three-level laser system. The up-conversion emission in Er3+: KCaY(VO4)2 was investigated at 300 K. The decay profiles of the Stokes and anti-Stokes emissions were measured and the mechanism of up-conversion luminescence is discussed.

Rare earth doped lead borate glasses and transparent glass-ceramics have been studied using optical spectroscopy. Based on the absorption, emission and its decay and the Judd-Ofelt calculations, several radiative and laser parameters for Ln 3+ (Ln = Pr, Nd, Eu, Dy, Er, Tm) were evaluated. The large values of luminescence lifetime, quantum efficiency of excited state and room temperature peak stimulated emission cross-section suggest efficient laser transitions of Ln 3+ ions in lead borate glasses. The obtained results indicate that lead borate glasses and glass-ceramics containing Ln 3+ ions are promising host matrices for solid-state laser applications.

In this paper, we present the photoluminescence properties of Pr3+, Sm3+ and Er3+ doped phosphate glasses. Optical absorption and emission spectra of lanthanide active ions in P2O5–CaO–SrO–BaO glass have been investigated at room temperature. These glasses have shown strong absorption bands in the near-infrared (NIR) and visible (VIS) region. For Pr3+ doped glass, emission bands centered at 608 nm (3P0 → 3H6 + 1D2 − 3H4), 640 nm (3P0 → 3F2), 686 nm (3P0–3F3) and 723 nm (3P0 → 3F4) have been observed with 480 nm (3H4 → 3P0) excitation wavelength. Of them, 686 nm has shown bright red emission. Emission bands of (4G5/2 → 6H5/2) 560 nm, (4G5/2 → 6H7/2) 600 nm and (4G5/2 → 6H9/2) 645 nm for the Sm3+ phosphate glass, with excitation at (6H5/2 → 4F7/2) 400 nm have been recorded. With regard to the Er3+ phosphate glass, a bright fluorescent green–yellow emission at 546 nm (4S3/2 → 4I15/2) have been observed. Analysis of decay curves of luminescence revealed occurrence of the strong luminescence quenching originating from the 3P0 metastable level of Pr3+ and 4S3/2 state of Er3+ mainly by a multiphonon relaxation processes to 1D2, 4F9/2 levels respectively. Moreover these results are compared with those obtained by using the Judd–Ofelt theory. According to the Judd–Ofelt theory, the Judd–Ofelt intensity parameters Ω2,4,6 were calculated, by which the radiative transition probabilities and radiative lifetimes of luminescent levels were obtained.

Spectroscopic and kinetics properties of Lu2SiO5:Dy3+ (LSO:Dy) single crystal with 1 and 5 at.% of activator were investigated. The polarised absorption and unpolarised emission spectra were measured at 10–300 K. Parameters characterising radiative relaxations of LSO:Dy were estimated by the Judd–Ofelt model. The crystal-field energy structure was derived from low-temperature optical spectra exhibiting the presence of two non-equivalent Dy3+ sites. It was found that dysprosium ions in site 1 and in site 2 do not form isolated subsystems; these subsystems are coupled by an effective spectral energy migration process. The LSO:Dy crystal exhibits a strong luminescence in the visible. Strong ion–ion interactions were observed for LSO:Dy (5 at.%); luminescence decays are non-exponential and the macro-parameter of donor–acceptor interaction C da amounts to 5.3 (10−52 m6 s−1) and 7.8 (10−52 m6 s−1) at 10 and 300 K, respectively. Laser potential related to the 4F9/2→6H13/2 yellow luminescence in Dy:LSO was assessed based on evaluation of the emission cross section values. It was concluded that the crystal is a promising material for visible laser operation.

The luminescence spectra of Pr3+ and Sm3+ ions in apatite Ca5[F∣(PO4)3] crystals from Spain and Russia have been compared with those for phosphate glasses doped with Pr3+, Sm3+ and Pr3+, Sm3+ ions. Time-resolved spectra measurements confirm that, in apatites, samarium ions occupy two non-equivalent crystal sites; the same is assumed for praseodymium ions. For the first time in minerals, the Stark splitting energy levels ΔE for 3H6 and 1D2 of Pr3+ ion and 6H7/2 of Sm3+ ion were determined. Some small differences in ΔE values for the Spanish and Russian apatite are discussed. The decay times of the excited levels of Pr3+, Sm3+ and Pr3+, Sm3+ doped in phosphate glass were measured at room temperature and at 77 K. The energy transfer process between samarium and praseodymium ions was observed and the energy transfer rate was calculated.

Spectroscopic properties of the Dy3+:Gd2SiO5 (GSO) single crystal were investigated. The polarized absorption and unpolarized emission spectra were measured at temperature ranging from 10 K to 300 K. Experimental oscillator strengths were determined from room temperature polarized absorption spectra and phenomenological intensity parameters Ω t were calculated by using the standard Judd–Ofelt theory. Low-temperature measurements were used to determine the energy level structure of two nonequivalent Dy3+ sites in the GSO crystalline host. Analysis of spectra and decay curves of the 4F9/2 emission revealed that Dy3+ ions entering nine-coordinated sites with C 3v symmetry and Dy3+ ions entering the seven-coordinated sites with C s symmetry form two distinct, well-isolated subsystems weakly coupled by the spectral energy migration process. In addition to dissimilar crystal field splitting of multiplets, the two subsystems differ significantly in the efficiency of excitation energy transfer between dysprosium ions, thereby showing dissimilar self-quenching of the 4F9/2 emission. Besides, only one of the two Dy3+ subsystems is coupled to Gd3+ ions by nonradiative Gd3+–Dy3+ energy transfer process. Laser potential related to the 4F9/2→6H13/2 yellow luminescence of dysprosium ions was assessed based on evaluation of the emission cross-section values. It was concluded that the Dy:Gd2SiO5 (Dy:GSO) is a promising material for the visible laser operation.

A comparative spectroscopic investigation of dysprosium-doped YAl3(BO3)4, LiNbO3 single crystals, fluorosilicate glass and fluorogermanate glass was performed with special attention directed to laser potential associated with the 4F9/2 → 6H13/2 transition of Dy3+ near 570 nm in the visible. Optical absorption spectra were acquired and analysed in the framework of the Judd–Ofelt theory. Values of radiative transition rates and luminescence branching ratios calculated using phenomenological intensity parameters Ωt were compared to corresponding experimental values derived from measurement of luminescence decay curves and luminescence spectra. Importance of the self-quenching of the 4F9/2 emission was assessed for the systems under study based on results of lifetime measurement with samples containing different Dy3+ concentrations. Feasibility of the visible laser operation was considered taking into account availability of bands accessible for optical pumping, the 4F9/2 quantum efficiency and emission cross-section for the potential 4F9/2 → 6H13/2 transition. It was concluded that among considered systems the Dy:YAl3(BO3)4 is the most promising material for the visible laser operation. It shows advantageously low matrix absorption in the optical pump region between 400 and 340 nm. The 4F9/2 quantum efficiency is close to unity for a low Dy3+ concentration and it is weakly affected by the self-quenching effect at increased concentration. The 4F9/2 → 6H13/2 emission consists of narrow lines with high peak emission cross-section with maximum value of 1.9 × 10−20 cm2 at 575.5 nm for π-polarisation.

Nanocrystals of tripotassium neodymium bis-phosphate(V) doped with ytterbium ions, K3Nd(PO4)2: Yb3+, were synthesized by Pechini method. The obtained grains, having an average size of about 40 nm, were characterised by X-ray, electron microscopic, electron absorption, luminescence and IR studies. Moreover, fluorescence decay studies were carried out at room temperature. The energy transfer from the Nd3+ to Yb3+ was described and discussed. The results were compared to those of the K3Nd(PO4)2 bulk crystal.

Er3+ and Yb3+ doped K3La(PO4)2 ortho- and KLa(PO3)4 metaphosphates were synthesised by the solid state reaction method. The obtained powders were characterised by XRD method, IR and Raman spectroscopy as well as optical absorption spectroscopy. The emission spectra were measured and fluorescence decay studies were carried out at room temperature. The energy transfer from Yb3+ to Er3+ and two-photon up-conversion processes were observed and discussed. The influence of the ortho- and metaphosphate host on efficiency of the luminescence was discussed.

The structural and optical features of gallium gadolinium garnet (GGG) nanopowders doped with neodymium were investigated. Nanopowders of GGG:Nd were prepared by modified sol-gel method using acetic acid as complexing agent. This way permitted to incorporate large amounts of dopant (up to 10 %) without destroying garnet structure. Small single crystals of Nd:GGG were grown by a μ-pulling down method and spectroscopic features of nanopowders and their single crystal counterparts were compared. It has concluded that the Nd3+ ions are located preferentially in the same type of sites in crystal lattices of GGG:Nd nanopowders and their single crystal counterparts. In addition, it follows from the perfect agreement of emission wavelengths and line width recorded for nanopowders and single crystal samples that the crystal lattice of GGG in nanopowders is not distorted. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Excitation and relaxation phenomena within the Yb 3+ –Tm 3+ system in the YAl 3 (BO 3 ) 4 (YAB) crystal were investigated upon continuous wave and short pulse excitation at 975 and 660 nm. With the 975 nm excitation, an unusually intense luminescence from 3 H 4 , and a considerably weaker one from 1 G 4 of Tm 3+ have been observed at 800 (IR) and 480 nm (VIS), respectively. The intensity ratio of the IR to VIS up-converted emissions is strongly affected by dopant concentrations. The dependence of the anti-Stokes emission intensities on the excitation power implies a two-step excitation mechanism of the 3 H 4 luminescence and a three-step excitation of the 1 G 4 one. Down-converted emission from the 2 F 5/2 ytterbium level has been observed following the 660 nm excitation of the 3 F 2 thulium state. The optical and kinetics results provided that energy transfer processes are responsibly for the up- and down-conversion phenomena. Even though the Yb 3+ –Tm 3+ energetic system is far from resonance, the energy transfer processes are surprisingly efficient in the YAB host. A high intensity of the up-converted emission at 800 nm may offer a laser potential.

Optical absorption, luminescence excitation and emission spectra of Er 3+ centres in Ca 3 Ga 2 Ge 3 O 12 :Er glass with Er content of 1.46wt% are presented and analysed. Luminescence kinetics for the main Er 3+ transitions was satisfactorily described by single exponential decays with characteristic lifetimes. Oscillator strengths, phenomenological Judd-Ofelt intensity parameters, radiative decay rates (emission probabilities of transitions), branching ratios and radiative lifetimes for Er 3+ centres in Ca 3 Ga 2 -Ge 3 O 12 :Er glass are calculated and compared with the corresponding parameters of the Ca 3 Sc 2 Ge 3 O 12 :Er 3+ garnet and other crystals and glasses. Quantum efficiency, n, of the 4 I 13/2 → 4 I 15/2 Er 3* transition is determined. Incorporation peculiarities and local structure of Er 3+ luminescence centres in Ca 3 Ga 2 Ge 3 O 12 :Er + glass are discussed in comparison with garnet crystals and oxide glasses. On the basis of the presented results and referenced EXAFS data for Er, Eu and Ho impurities (L 3 -edge) it has been shown that Er 3* centres in Ca 3 Ga 2 Ge 3 O 12 glass occupy network sites with the coordination number to oxygen of N=6.

Yb + Tm co-doped Bi 2 TeO 5 single crystals were grown by the Czochralski method. Optical absorption and luminescence spectra of the crystals were determined and interpreted. The dynamics of the Tm and Yb excited states were followed by luminescence decay curves. Up-conversion processes were detected after 980 nm diode laser excitation, that resulted in an 800 nm and a weaker 475 nm emission corresponding to the 3 H 4 → 3 H 6 and 1 G 4 → 3 H 6 transitions of Tm 3+ . The excitation power dependence of the integrated intensity of the up-converted emission implied two-step excitation process including Yb–Tm energy transfer for the 800 nm emission, and three-photon excitation process for the 475 nm up-converted emission. Examination of absorption and emission spectra of Yb and Tm ions revealed that the consecutive energy transfer steps did not fulfill the resonance conditions, and they have to be assisted by phonon emission.

Excited state absorption (ESA) of Tm3+ ions in YVO4 crystal was measured using a pump and probe technique. The measurements have been performed in the wide spectral range in both the near infrared and visible region between 6000 cm-1 (NIR) and 24000 cm-1 (VIS). ESA absorption cross section spectra have been calculated for transitions from the 3 F 4 and 3 H 4 states of Tm3+ and compared to those evaluated experimentally. The excited state absorption in YVO4:Tm3+ should not influence the laser operation related to the 3F4→3H6 transition around 1900 nm, but it will be a significant loss factor for a potential laser action associated with the 3H4→3F4 transition around 1.48 μm.

Influence of impurities and thermal treatment on spectroscopic properties and laser performance of thulium-doped yttrium vanadate crystals was examined. YVO4 crystals nominally pure, single doped with Tm3+ and co-doped with Tm3+ and Ca2+ were grown by the Czochralski method and then thermally treated at 1150 °C for several hours in a reducing atmosphere (vacuum) or oxidizing atmosphere (air). Samples of crystals were investigated by nuclear magnetic resonance spectroscopy (NMR) and by optical spectroscopy methods. Laser performance of samples was examined upon laser diode pumping. For pure YVO4 and for YVO4 containing 0.5 at. % of Tm a single-site NMR spectrum of 51V nuclei was observed with central line widths of 2.5 and 3.2 kHz (FWHM), respectively. For samples containing 5 at. % of Tm the NMR spectrum was a superposition of multi-site spectra indicating at least three kinds of vanadium sites with axial symmetry. Optical absorption spectra did not contain bands that could be ascribed to V4+ ions in tetragonal sites. Level of matrix absorption in the visible region and its increase with decreasing wavelength from about 600 to 370 nm was found to be substantially dependent on conditions of thermal treatment. Thermal treatment of crystals and additional doping with Ca did not influence the 3 F 4 lifetime of thulium and laser performance of crystals, however. Infrared absorption spectra revealed OH- contamination in all samples. It has been concluded that the quenching of the 3 F 4 emission in samples containing 5 at. % of thulium is related to migration-accelerated energy transfer to hydroxyl ions acting as energy sinks.

Glasses with composition 50GeO 2 -(50-x)PbO-5PbF2-xLnF3 (Ln = Pr 3+ -Yb 3+ ) were prepared from commercial raw materials. The content of PbF 2 was constant and amounted to 5 mol% whereas the concentration of luminescent ions was diverse (0.2 and 2 mol%). Thermal stability of the glasses were monitored by differential thermal analysis (DTA). It has been found that increase of rare-earth fluoride content from 0.2 mol% to 2 mol% brings about a shift of the glass crystallization onset from 450 °C to 487 °C for Nd-doped samples and from 466 °C to 482 °C for Tm-doped samples. Optical absorption and emission spectra of Ln active ions in oxyfluoride glass 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 estimated. Analysis of decay curves of luminescence revealed that the increase of rare-earth fluoride content from 0.2 mol% to 2 mol% shortens the lifetime of the 4 F 3/2 level of Nd 3+ from 224 μs to 90 μs.

Single crystal of bismuth tellurite Bi2TeO5 (BTO) doped with trivalent thulium (Tm3+) was grown by the Czochralski method and investigated by spectroscopic techniques (absorption, emission). Absorption and emission of the Tm:BTO crystal collected in the VIS-IR spectral range are presented. Spectroscopic features were investigated as a function of the excitation light polarisation (E//X, Y, and Z axis of optical indicatrix) and sample temperature. The oscillator strength of the 3H6 → 3F4 transition at 1.7 μm was determined by numerical integration of the X, Y and Z polarised absorption spectra. The obtained values are: PX = 4.7 × 10−6, PY = 6.8 × 10−6 and PZ = 5.9 × 10−6 that gives a mean value Pmean = 5.8 × 10−6. Emission was observed from the 1G4 and 3H4 levels. The 3H4 and 1G4 excited state dynamics was studied. Decay curves and time constants of luminescence were collected at 5 and 300 K and analysed. The 3F4 → 3H6 luminescence at around 1.8 μm was too weak to be acquired from the low concentrated sample. However, based on optical data it was possible to estimate the radiative probability Arad of this transition and the 3F4 radiative lifetime. The resultant values are: Arad = 668 ± 0.4 s−1 and τrad = 1.5 ms. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The up-conversion of infrared radiation at 808 nm, emitted by a diode laser, into blue emission centered at 480 nm in 1 at.% Tm, 5 at.% Yb: YVO4; 1 at.% Tm, 8 at.% Yb: YVO4 and 2 at.% Tm, 5 at.% Yb: YVO4 has been studied. The highest intensity of blue emission is found for the 1 at.% Tm, 8 at.%Yb: YVO4 system. The power dependence of up-converted emission upon continuous-wave excitation as well as the time evolution of its intensity upon short-pulse excitation were found to be consistent with a two-step excitation mechanism in which the forward Tm3+–Yb3+ energy transfer is followed by the back Yb3+–Tm3+ energy transfer. The effect of dopant concentrations on the up-conversion process is interpreted taking into account dynamics of the excited states involved.

Up-conversion processes in Yb 3+ and Tm 3+ doped YVO 4 crystals have been investigated upon continuous wave and short pulse excitation around 975 nm. The energy transfer efficiency from Yb 3+ to Tm 3+ has been experimentally assessed, using results of pulsed laser excitation. Infrared emission originating in the 3 H 4 level and a considerably weaker blue emission originating in the 1 G 4 level of Tm 3+ has been observed. The ratio of the IR to blue up-converted emission intensities is about 25:1 at room temperature. The dependence of the intensity of both emissions on the excitation power implies a two-step excitation mechanism of the 3 H 4 emission and a three-step excitation one of the 1 G 4 emission. Temperature dependencies of IR and blue up-converted emission have been discussed based on optical absorption and emission spectra and lifetimes recorded at several temperatures between 4.2 and 300 K. Up-converted blue emission in YVO 4 :Yb+Tm is qualitatively similar to that observed in other matrices containing ytterbium and thulium but high intensity of up-converted IR emission associated with the 3 H 4 – 3 H 6 transition of Tm 3+ may offer a laser potential.