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High resolution spectra of optical absorption and luminescence were recorded at temperatures below 6 K for Pr3+, Sm3+, Er3+, and Yb3+ ions embedded in Gd3Ga5O12–Gd3Al5O12 and Lu2SiO5–Gd2SiO5 solid solution crystals fabricated by the Czochralski method. Detailed analysis of acquired spectral bands related to transitions between the lowest energy components (0–0) lines of initial and terminal multiplets provided quantitative information regarding bandwidths, peak transition energies and number of band components. Combination of these data with structural peculiarities of the hosts made it possible to propose the interpretation of optical interaction in systems under study.

Up-conversion nanoparticles have garnered lots of attention due to their ability to transform low energy light (near-infrared) into high-energy (visible) light, enabling their potential use as remote visible light nano-transducers. However, their low efficiency restricts their full potential. To overcome this disadvantage, fluoroindate glasses (InF3) doped at different molar concentrations of Yb3+ and Er3+ were obtained using the melting–quenching technique, reaching the highest green emission at 1.4Yb and 1.75Er (mol%), which corresponds to the 4S3/2 / 4I15/2 (540–552 nm) transition. The particles possess the amorphous nature of the glass and have a high thermostability, as corroborated by thermogravimetric assay. Furthermore, the spectral decay curve analysis showed efficient energy transfer as the rare-earth ions varied. This was corroborated with the absolute quantum yield (QY) obtained (85%) upon excitation at 385 nm with QYEr ¼ 17% and QYYb ¼ 68%. Additionally, InF3–1.4Yb–1.75Er was milled and functionalized using poly(ethylene glycol) to impart biocompatibility, which is essential for biomedical applications. Such functionalization was verified using FTIR, TG/DSC, and XRD.

© 2021 Elsevier B.V.Tm3+:KY(WO4)2 (KYW) single crystals were grown by the modified Czochralski method. The factors affecting the crystallization processes are studied focusing on optimization of crystallization mode and improving of crystals qualitative parameters. Laser-related spectroscopic properties of Tm3+:KYW crystal, absorption and luminescence spectra as well as kinetics of luminescence decay are studied.

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.

Luminescence properties of the Er-doped and Er–Ag co-doped glasses with Li2B4O7 (Li2O–2B2O3) basic composition are investigated and analysed. The Li2B4O7 glasses of high chemical purity and optical quality, doped with Er and co-doped with Er and Ag were obtained in the air using standard glass technology. Spectroscopic properties of the Li2B4O7:Er and Li2B4O7:Er,Ag glasses were studied using optical absorption and photoluminescence (excitation, emission, decay kinetics) experimental techniques as well as Judd–Ofelt analysis. The theoretical and experimental oscillator strengths for observed absorption transitions as well as Judd–Ofelt intensity parameters (Ω2, Ω4, Ω6) have been calculated. Photoluminescence spectra of the Li2B4O7:Er and Li2B4O7:Er,Ag glasses reveal intense infrared (4I13/2 → 4I15/2 transition, λmax = 1530 nm) and green (4S3/2 → 4I15/2 transition, λmax = 546 nm) emission bands. Radiative properties such as transition probabilities (Arad), luminescence branching ratios (β), stimulated emission cross-sections (σem), and radiative lifetimes (τrad) are estimated. Experimental and radiative lifetimes were compared and quantum efficiency (η) has been evaluated. Considerable enhancement of the Er3+ green luminescence in the Li2B4O7:Er,Ag glasses has been observed. The observed enhancement is attributed to energy transfer from Ag+ to Er3+ ions as well as local field effects induced by surface plasmon resonance of the silver metallic nanoparticles.

Correction for ‘Highly efficient green up-conversion emission from fluoroindate glass nanoparticles functionalized with a biocompatible polymer’ by G. Lesly Jimenez et al., RSC Adv., 2022, 12, 20074–20079, https://doi.org/10.1039/D2RA03171J.

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.

Single crystals of Gd3Al2.5Ga2.5O12, single-doped with Pr3+ ions and double-doped with Pr3+ and Yb3+ ions, were fabricated by the Czochralski technique. Transition intensities and relaxation dynamics of Pr3+ ions were determined employing the Judd–Ofelt treatment. Crystal field splitting of excited multiplets of incorporated luminescent ions were determined on the basis of optical spectra recorded at liquid helium temperature. The Pr3+ → Yb3+ energy-transfer phenomena were determined analyzing the effect of Yb3+ concentration on luminescence spectra and decay curves of Pr3+ ions. It was concluded that the observed downconversion phenomenon involves a quantum-cutting mechanism consisting of a two-step energy transfer from Pr3+ to Yb3+. We observed a phenomenon of nonresonant conversion of femtosecond pulses of infrared light into visible Pr3+ emission that was weakly affected by the wavelength of incident light at least in the 1100–1600 nm region. It was concluded that excitation mechanisms consist of mult...

Up-conversion luminescence spectra of Er3+ ions in multicomponent oxyfluoride glasses GeO2 – BaO – BaF2 – Ga2O3 – Er2O3 were examined. It was found that the up-conversion luminescence spectra of Er3+ are dependent on pumping wavelengths. The spectra recorded upon the excitation at 800 nm contained an intense green up-conversion luminescence corresponding to the 2H11/2, 4S3/2 → 4I15/2 transitions and a very weak red luminescence related to the 4F9/2 - 4I15/2 transition. In spectra recorded upon 980 nm excitation the contribution of the red luminescence was markedly higher. The interaction mechanisms involved in up-conversion processes are proposed and observed dependence of intensity of up-converted luminescence on excitation power is discussed. The experimental results suggest that Er3+ singly doped lead-free oxyfluoride germanate glass is useful for up-conversion luminescence applications.

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.

Spectroscopic properties of the Tm3+ (4f12, 3H6) ions in Tm-doped and Tm–Ag co-doped glasses with Li2B4O7 (or Li2O–2B2O3) basic composition are studied. All investigated glasses show intense blue, red, and infrared emission bands of the Tm3+ ions. Experimental and theoretical oscillator strengths (fexp and fcal), Judd–Ofelt intensity parameters (Ω2, Ω4, Ω6) and radiative properties such as probabilities of radiative transition (Arad), branching ratios (β), radiative lifetimes (τrad), and quantum efficiencies (η) of the Tm3+ luminescence in the Li2B4O7:Tm and Li2B4O7:Tm,Ag were calculated. Presence of the Ag0 (4d105s1, 2S1/2) and Ag2+ (4d9, 2D5/2) paramagnetic centres and their aggregates in the Li2B4O7:Tm,Ag glass was confirmed by electron paramagnetic resonance. Luminescence spectra and decay kinetics of the Ag+ (4d10, 1S0) ions and small non-plasmonic Ag aggregates were registered and discussed. Increasing of quantum efficiency and yield of the Tm3+ luminescence in the Li2B4O7:Tm,Ag glass is explained by energy transfer from Ag species to the Tm3+ ions.

The most commonly applied luminescent thermometry (LTs) approach, which are based on the luminescence intensity ratio (LIR), requires integration of the analyzed emission bands. This analysis is often cumbersome and technically challenging due to spectral overlap and vicinity of the two emission bands. These limitations can be overcome by a new, single emission band ratiometric (SBR) approach which involves excitation through thermally induced excited state absorption (ESA) and ground state absorption (GSA). What is more, the frequent problem of low intensity of one of the radiative transitions, which are analyzed in conventional luminescent thermometry, is overcome owing to the involving of the SBR approach. Due to the opposable behavior of the emission intensity with temperature changes upon these two excitation schemes, improved thermal sensitivity can be achieved. In this work, the suitability of Nd3+-doped oxyfluorotellurite (65-x)TeO2–20ZnF2–12PbO–3Nb2O5–xNd2O3 (x = 0.1, 1, 2, 5 and 10) glasses (TZPN) was analyzed for SBR-based luminescent thermometry. To excite Nd3+ ions, the 808 nm and 1060 nm wavelengths, which are related to GSA and ESA, respectively, were involved. In the biological temperature range the relative sensitivity reached SR = 2.95%/°C. The highest value of SR = 6.15%/°C was obtained at low temperature range for the 10%Nd3+:TZPN glass LT and decreased below 1%/°C only at temperatures above 200 °C.

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.

Eu

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.

Results of detailed spectroscopic investigation of Sm3+ and Dy3+ ions incorporated in crystal structures of Yal YAl3(BO3)4, LiNbO3, Gd3Ga5O12, Gd2SiO5, Lu2SiO5 and (Gd, Lu)2SiO5 are reported and discussed. The impact of the hosts on transition intensities and excited state relaxation dynamics of incorporated luminescent ions was examined. Distribution of luminescence intensity among spectral bands in terms of luminescence branching ratios was evaluated based on numerical integration of luminescence bands. Intensities of UV and blue absorption bands potentially useful for optical pumping were determined quantitatively in units of absorption cross section. The most intense luminescence bands related to potential laser transitions 4 G 5/2 → 6 H 7/2 of Sm3+ around 600 nm and 4 F 9/2 → 6 H 13/2 of Dy3+ around 580 nm were calibrated in units of emission cross section. Evaluated peak values of emission cross section range from 0.43 × 10−20 cm2 for Sm3+ in (Gd, Lu)2SiO5 to 1.17 × 10−20 cm2 for Sm3+ in LiNbO3. Those for dysprosium-doped crystals range from 0.63 × 10−20 cm2 for LiNbO3:Dy3+ to 2.0 × 10−20 cm2 for Yal YAl3(BO3)4:Dy3+. It follows from these considerations that samarium-doped crystals show promise for laser application owing to the combination of a strong absorption that matches radiation of commercial laser diodes emitting near 405 nm and long luminescence lifetime. Major shortcoming of dysprosium-doped crystals results from a weak intensity of absorption bands available for optical pumping near 450 nm and 385 nm combined with relatively strong self-quenching of luminescence.

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.

Spectroscopic properties of the Tm-doped borate glass with LiKB 4 O 7 (0.5Li 2 O–0.5K 2 O–2B 2 O 3 ) basic composition are investigated and analysed using optical absorption and photoluminescence (excitation, emission, decay kinetics) experimental techniques as well as Judd–Ofelt analysis. Optical absorption spectra exhibit absorption bands related with transitions of Tm 3+ ions. The theoretical and experimental oscillator strengths for observed absorption transitions as well as Judd–Ofelt intensity parameters (Ω 2 , Ω 4 , Ω 6 ) have been calculated. Photoluminescence spectra reveal a lot of emission bands in the visible and infrared spectral ranges related with 4 f – 4 f transitions of Tm 3+ ions. Luminescence decay kinetics of several excited states was detailed investigated and analysed. Radiative properties such as radiative transition probabilities ( A rad ), luminescence branching ratios ( β ), radiative lifetimes ( τ rad ), quantum efficiency ( η ), and stimulated emission cross-section ( σ em ) have been estimated. The obtained results show that the investigated LiKB 4 O 7 :Tm glass belongs to perspective luminescent and laser materials in the visible and infrared spectral ranges.

The goal of this study was to investigate influence of the synthesis parameters on the luminescence properties of Ca- α -Sialon doped with Eu2+. The compound of Eu0:07Ca0:73Si9:6Al2:4O0:8N15:2 was prepared by the solid state reaction method from the mixture of the relevant oxides, Si3N4 and CaCO3. Synthesis was carried out in the temperature range of 1600-1700°C for 2-8 h in a reduction atmosphere (N2+CO). The structure and morphology of obtained powders were analyzed by XRD and SEM/EDS methods, respectively. Content of nitrogen/oxygen was also measured. Optical properties were investigated by excitation, emission and reflection spectra. Obtained results show strong influence of synthesis temperature on the phase composition and intensity of emission of Ca- -Sialon:Eu2+ powder compound.

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

Solid solution crystals (LuxGd1−x)2SiO5 single doped with Sm 3+ and Dy were grown by the Czochralski method. Segregation coe cients Lu/Gd, melting temperatures and structures of solid solution crystals were determined for 0.15 ≤ x ≤ 0.8. It was found that for x ≥ 0.17 the crystals belong to the monoclinic system within a space group C2/c and their melting temperature diminishes monotonously from 1990 ◦C to 1780 ◦C when x decreases from 0.8 to 0.15. Disparity of ionic radii of Lu and Gd induces structural disorder that brings about an inhomogeneous broadening of spectral lines in absorption and emission spectra of incorporated luminescent Sm and Dy ions. Optical properties of obtained crystals were determined based on results of measurement of absorption and emission spectra and luminescence decay curves. Spectroscopic investigation revealed that Sm doped crystals show intense emission distributed in the visible-near infrared region with the most intense band centred at 605 nm and characterized by a branching ratio of 0.43. Emission spectrum of Dy doped crystals is dominated by a band centred at 575 nm and characterized by a branching ratio of 0.58. It has been concluded that the systems under study are potential laser materials able to generate visible emission upon GaN/InGaN laser diode pumping.

Electron paramagnetic resonance (EPR), optical absorption and photoluminescence spectra as well as luminescence kinetics of the Li 2 B 4 O 7 :Cr and KLiB 4 O 7 :Cr tetraborate glasses were investigated at T = 300 K. The Li 2 B 4 O 7 :Cr and KLiB 4 O 7 :Cr glasses containing 0.4 and 1.6 mol.% Cr 2 O 3 of high optical quality were obtained from polycrystalline compounds by fast cooling of the melts. The X-band EPR spectroscopy shows that the Cr impurity is incorporated in the tetraborate glass network as isolated Cr 3+ centers and Cr 3+ –Cr 3+ pairs coupled by magnetic dipolar and exchange interactions. The EPR spectral parameters ( g eff and Δ B pp ) of both Cr 3+ and Cr 3+ –Cr 3+ centers in the Li 2 B 4 O 7 :Cr and KLiB 4 O 7 :Cr glasses were measured and analyzed. All transitions in optical absorption, luminescence excitation and emission spectra of these glasses are identified. Broad complex bands that peak near 615, 405, and 350 nm in optical absorption and luminescence excitation spectra correspond to the 4 A 2g (F) → 4 T 2g (F), 4 A 2g (F) → 4 T 1g (F), and 4 A 2g (F) → 4 T 1g (P) spin-allowed transitions of the Cr 3+ centers in distorted octahedral sites of the tetraborate glass network. The octahedral (cubic) crystal field strength (10 Dq ) and Racach parameters ( B and C ) for Cr 3+ centers in Li 2 B 4 O 7 :Cr and KLiB 4 O 7 :Cr glasses are estimated. Narrow and broad emission bands in red – NIR regions are assigned to the 2 E g (F) → 4 A 2g (F) (R 1 line) and 4 T 2g (F) → 4 A 2g (F) (electron-vibration) transitions, which correspond to the Cr 3+ centers in high-field and low-field sites, respectively. All observed emission bands are characterized by non-exponential decay. Measured average lifetimes and local structure of the Cr 3+ centers in high-field and low-field sites of the Li 2 B 4 O 7 :Cr and KLiB 4 O 7 :Cr glass network have been discussed.

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.