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Bulk samples of holmium and ytterbium rare earth titanates doped with yttrium and bismuth were synthesized. To study the magnetic properties and peculiarities of magnetic interaction in doped and undoped titanates, magnetization curves and temperature dependences of the susceptibility were measured in fields up to 3 T at temperatures from 2 to 300 K. Magnetic properties for doped and undoped titanates with different doping level, as well as doped with different elements, have been compared. Based on study of temperature dependences of the susceptibility, magnetic dipole and exchange interactions have been analyzed. In the case of undoped holmium titanate, the dominant magnetic interaction type has been found to be the dipole one. When doping of holmium titanate with yttrium and bismuth, the magnetic interactions between the rare earth ions are sharply weak. Undoped ytterbium titanates have shown a predominance of the superexchange interaction. Presence of a large number of randomly distributed yttrium or bismuth ions, which occupy positions of ytterbium ions in crystal lattice, leads to the decrease in concentration of R3+-O-R3+ ion pairs in this rare earth titanate, between which there is superexchange. Therefore, in doped compounds, the magnetic dipole interaction capable to act at large distances contrary to the superexchange one begins to predominate. The values of the g-factor have been estimated by the fit of the measured magnetization curves. [ABSTRACT FROM AUTHOR]

A transparent Er3+,Yb3+:GdMgB5O10 single crystal with dimensions up to 24 × 15 × 12 mm was grown successfully by the high-temperature solution growth on dipped seeds technique from K2Mo3O10-based solvent. The grown crystal was characterized using PXRD, DSC and ATR techniques. Differential scanning calorimetry measurements and SEM analysis of the heat-treated solids revealed Er,Yb:GdMgB5O10 to be an incongruent melting compound with an onset point of 1087 °C. The absorption edge of the Er,Yb:GMBO sample is located in the region of 245 nm, which approximates a value of 4.8 eV. Absorption and emission spectra, and luminescence kinetics, were studied. The energy transfer efficiency from ytterbium to erbium ions was determined. The laser operation in continuous-wave mode was realized and output characteristics were measured. The maximal output power of 0.15 W with a slope efficiency of 11% was obtained at 1568 nm. [ABSTRACT FROM AUTHOR]

The Sr3B2O6–YbBO3 diagram was constructed based on samples obtained by the solid-state synthesis. In the system YbBO3, Sr3Yb(BO3)3, Sr3Yb2(BO3)4 and Sr3B2O6 phases were identified by XRD analysis. Diffusion experiments showed formation of solid solutions between all compounds. These solid solutions demonstrate typical near-infrared luminescence in the range of 960-1020 nm, characteristic of Yb3+ and related to 2F5/2 → 2F7/2 transitions in ytterbium ions. [ABSTRACT FROM AUTHOR]

Photodarkening (PD) effect in ytterbium-doped fiber (YDF) has a significant impact on the high-power operational stability of fiber lasers, which seriously hinders the power scaling. In this paper, the relationship between ytterbium ions uniformity and the photodarkening effect in the YDF was investigated, and the fabrication process allowing improving the ytterbium ions uniformity in the core of preforms for suppressing the photodarkening effect was developed. The Modified Chemical Vapor Deposition (MCVD) method combined with Chelate Vapor Deposition (CVD) technology was adopted for multi-layer fiber core deposition, and an all-gas-phase technical process was proposed to improve the ytterbium ions uniformity in the Al/P co-doped glass matrix. The 25/400 μm YDFs obtained by this technology achieved stable 3.5 kW laser output power for 8 h with suppressed PD and nonlinear effects. [ABSTRACT FROM AUTHOR]

The single crystals of CsI-Yb2+ were grown, and their spectroscopic studies were conducted. The observed luminescence in CsI-Yb2+ is due to 5d–4f transitions in Yb2+ ions. Using time-resolved spectroscopy, spin-allowed and spin-forbidden radiative transitions of ytterbium ions at room temperature were found. The excitation spectra of Yb2+ luminescence bands were obtained in the range of 3–45 eV. The mechanism of charge compensation of Yb2+ ions in a CsI crystal was also studied, the spectrum of the thermally stimulated depolarization current was measured, and the activation energies of the two observed peaks were calculated. These peaks belong to impurity–vacancy complexes in two different positions. The charge compensation of Yb2+ occurs via cation vacancies in the nearest-neighbor and next-nearest-neighbor positions.The Yb2+ ions are promising dopants for CsI scintillators and X-ray phosphors in combination with SiPM photodetectors. [ABSTRACT FROM AUTHOR]

The complete computational model of a low-mode ytterbium-erbium doped fiber amplifier, based on the numerical analysis of rate equations, was developed. In contrast to existing models, we considered the effects of the secondary energy transfer and the upconversion as well as the presence of isolated ytterbium ions and clustered erbium ions in the aggregate. In addition, the presence of several transverse modes and the effect of transverse spatial hole burning were took into account, too. Necessary parameters of the active medium were determined experimentally by measuring the luminescence decay of active ions and the output power and optical spectrum of a fiber amplifier. The proposed model allows one to calculate both the power and spectral characteristics of ytterbium-erbium doped fiber amplifiers, and the nonstationary dynamics of the population inversion and the luminescence of active ions. This can help one to select the required concentrations of active ions, the geometry and the length of active fibers for each specific task. [ABSTRACT FROM AUTHOR]

Mass transfer along grain boundaries (GBs) in two kinds of polycrystalline Yb 3 Al 5 O 12 (YbAG) wafers with chemical compositions that deviated slightly in both directions from the stoichiometric composition was investigated at high temperatures by the oxygen permeation technique with 18O 2. Oxygen permeation through both wafers proceeded with mutual diffusion of oxide ions from the higher oxygen partial pressure P O2 (hi) surface side to the lower P O2 (lo) surface side and with the diffusion of ytterbium ions in the opposite direction. The apparent activation energies for oxygen permeation due to GB diffusion of oxide ions and ytterbium ions were 420–440 and 260–300 kJ mol−1, respectively, and almost no difference in the activation energies due to the different chemical compositions was observed. However, the oxygen permeability constants, which were divided by the GB density, for the aluminum-rich YbAG were clearly lower than those for the ytterbium-rich YbAG. [ABSTRACT FROM AUTHOR]

The hot spot extraction agent N,N,N′,N′-tetraoctyl-3-oxoglutaramide (TODGA) has the advantages of novelty, high efficiency and environmental protection in the separation of rare earths by tandem extraction. In this paper, the characteristic parameters for the separation of dysprosium, erbium, thulium and ytterbium ions in the TOGDA–kerosene/hydrochloric acid system for tandem extraction were calculated. Using a 10% TODGA–kerosene/5 mol·L−1 hydrochloric acid extraction system, the mixture containing Dy3+ 0.258 mol·L−1, Er3+ 0.252 mol·L−1, Tm3+ 0.248 mol·L−1 and Yb3+ 0.242 mol·L−1 can be separated by three separation steps, and four products of Dy3+, Er3+, Tm3+ and Yb3+ can be obtained. The purity of the four products was 99.80%, 99.20%, 99.70% and 99.70%, and the yields were 99.03%, 98.97%, 97.88% and 96.98%, in order. In this paper, the reasons were analyzed for the differences in the ability of the TODGA system to extract heavy rare earth ions (REEs) in terms of density functionality, complex structure and bond valence model. These will provide more basic data and guidance for the industrial application of TODGA. [ABSTRACT FROM AUTHOR]

Low-dimensional all-inorganic metal halide perovskites (MHPs) have attracted attention due to their promising advantages as semiconductor materials for optoelectronic applications. However, obtaining a low-dimensional MHPs pure phase has been difficult due to its high ionic nature. Here, the one-step in-situ deposition of CsPb 2 Cl 5 films by Aerosol Assisted Chemical Vapor Deposition (AACVD) is reported for the first time. An analysis of the effects of precursor concentrations, using ethanol (EtOH) as antisolvent, and Yb3+ doping on the resulting three-dimensional and/or two-dimensional perovskite phase films is presented. It was found that a lead rich precursor (PbCl 2 :CsCl = 2:1) was necessary to promote the formation of the CsPb 2 Cl 5 phase, in addition, the use of EtOH and doping with hetero-valent Yb3+ ions was required to attain this phase successfully. The excitation and emission photoluminescence spectra analysis for these films is focused on the three principal emissions: i) a narrow emission peak around 418 nm from the CsPbCl 3 phase, ii) a dual broad emission around 550 nm from the CsPb 2 Cl 5 phase, and iii) an emission at 984 nm associated with the Yb3+ ions introduced as dopants in the MHPs lattice. A possible mechanism is proposed for the observed energy transfer from the CsPb 2 Cl 5 matrix to the ytterbium ions and for the interactions between Yb3+ and the excitonic emissions. [ABSTRACT FROM AUTHOR]

The purpose of this study is to evaluate the impact of the location of the Er3+/Yb3+optical amplifier (EYDWA) in passive optical access network downstream (as a post-amplifier or booster, in the middle) and upstream transmission. This can give us an extended connection and a huge distribution ratio for a beneficial implementation of the optical fiber. The transmission quality was compared on the location of the amplifier as well as the length of the link. According to the results obtained by system simulation one noted that there is a clear improvement of the system performance by the effect of the amplifier (EYDWA). One could obtain a distance of more than 200 km for GPON. Moreover by varying the opto-geometric parameters such as concentration of Ytterbium ions and the length of the guide allowed us to improve the quality factor and binary error rate. [ABSTRACT FROM AUTHOR]

Up-conversion luminescence (UCL) spectra of fluorophosphate glasses doped with the rare-earth ions Yb3+ with concentrations of 4–10% and Tm3+ with concentrations of 10–5–3% were investigated using continuous-wave excitation at 975 nm. Each of the observed UCL bands was the result of several processes corresponding to various Tm3+ excited states and characterized by a different degree of nonlinearity regarding the number of absorbed photons required to excite these states. The influence of the pumping power and concentrations of doping ions on the contributions to UCL spectra from excitation processes with various nonlinearities was analyzed. The simultaneous appearance of several lines in each UCL spectral region was shown to be typical of low Tm3+ concentrations (fractions of a percent and less) and rather high Yb3+ concentrations (4–10%). UCL appeared primarily in the 755–840-nm band with a maximum near 793 nm if the Tm3+ concentration was increased up to 3% with an Yb3+ concentration of 5%. [ABSTRACT FROM AUTHOR]

We present a combination of light-sheet excitation and two-dimensional fluorescence intensity ratio (FIR) measurements as a simple and promising technique for three-dimensional temperature mapping. The feasibility of this approach is demonstrated with samples fabricated with sodium yttrium fluoride nanoparticles co-doped with rare-earth ytterbium and erbium ions (NaYF4:Yb3+/Er3+) incorporated into polydimethylsiloxane (PDMS) as a host material. In addition, we also evaluate the technique using lipid-coated NaYF4:Yb3+/Er3+ nanoparticles immersed in agar. The composite materials show upconverted (UC) fluorescence bands when excited by a 980 nm near-infrared laser light-sheet. Using a single CMOS camera and a pair of interferometric optical filters to specifically image the two thermally-coupled bands (at 525 and 550 nm), the two-dimensional FIR and, hence, the temperature map can be readily obtained. The proposed method can take optically sectioned (confocal-like) images with good optical resolution over relatively large samples (up to the millimetric scale) for further 3D temperature reconstruction. [ABSTRACT FROM AUTHOR]

Given the significant impact of microstructure and material composition on material properties, this paper utilizes ytterbium nitrate to enhance the dielectric and magnetic characteristics of NiZnCo ferrite ceramics. In this study, Ni 0.5 Zn 0.4 Co 0.1 Yb 0.075 Fe 1.925 O 4 ferrites with lower magnetic losses and a substantial cutoff frequency were successfully created using the sol-gel self-propagating method. The study reveals that the adding of ytterbium ions rises the lattice constant from 8.3377 to 8.3586 Å, the porosity from 4.77% to 6.92%, theoretical X-ray density from 5.43 to 5.66 g/cm3, and bulk density from 5.18 g/cm3 to 5.27 g/cm3. The incorporation of ytterbium ions in ferrite decreases the dielectric constant as well as dielectric losses, enhances the DC resistance, and lowers the eddy current loss in the frequency range of 100 Hz to 1 MHz. The addition of ytterbium ions decreases the initial permeability and saturation magnetization of the material while increasing its magnetic quality factor. Additionally, the cut-off frequency shifted to a higher frequency range, from 25.7 MHz to 121.61 MHz, while exhibiting lower losses at higher frequencies. The addition of ytterbium ions has expanded the potential applications of NiZnCo ferrite in high-frequency microwave devices and wireless communications. [ABSTRACT FROM AUTHOR]

Yttrium oxide nanostructures doped with erbium and ytterbium ions were incorporated into a titanium dioxide (TiO2) host by a hydrothermal method to modify the bandgap of TiO2. The samples were prepared with different concentrations of nanophosphors (Y2O3: Er3+-Yb3+). Then, the samples were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS), x-ray photoelectron spectroscopy (XPS), and photoluminescence spectroscopy. The XRD analysis revealed the mixture of anatase and rutile crystal structures for all the samples. The TEM measurements showed agglomerated particles with a spherical shape of around 50 nm. TiO2 doped with a high concentration of Y2O3:Er3+-Yb3+ exhibited a strong visible upconversion luminescence under the excitation of 980 nm (infrared laser) as compared to other samples. Photoluminescence studies revealed the green (522 nm), yellow (563 nm), and red emissions (661 nm) corresponding to 2H11/2 → 4I15/2, 4S3/2 → 4I15/2, and 4F9/2 → 4I15/2 transitions of Er3+ in Y2O3:Er3+-Yb3+@TiO2 nanophosphors, respectively. Furthermore, DRS and XPS analyses revealed that Y2O3:Er3+-Yb3+ modified the bandgap of the TiO2 host. [ABSTRACT FROM AUTHOR]

We introduce our design, simulation, and fabrication for cm-long waveguides and micro-ring resonators based on fully-etched thin-film lithium niobate on insulator (LNOI) incorporated with rare earth ions. We implant ytterbium ions (Yb 3 + ) into the crystalline host and study their optical properties at 4 K temperature. We measure an intrinsic optical quality factor of higher than 2 × 10 6 after postimplantation annealing. We characterize the photoluminescence spectrum, lifetime, and absorption of Yb 3 + ions. Incorporation of rare earth ions into LNOI as a crystalline and nonlinear photonic element may enable the development of multi-functional quantum photonic devices capable of generating, transducing, manipulating, and storing of quantum optical information. [ABSTRACT FROM AUTHOR]

Fused yttrium-alumoborate glasses doped with ytterbium, silicon, chromium, and sodium were synthesized. The influence of the matrix on the "spectroscopic behavior" of chromium ions and the efficiency of their sensitization of Yb3+ luminescence was established by spectral-luminescence and EPR studies. It was found that (1) chromium in alkali-free glasses is mainly in the oxidation degree Cr(III) with an appreciable admixture of Cr(IV) and Cr(V), (2) the partial replacement of Al2O3 or B2O3 by SiO2 and Y2O3 by Yb2O3 affects to a different extent the relative concentration of optical centers of chromium ions, (3) the addition of alkali results in the formation of Cr(VI) centers as a result of oxidation of less charged chromium ions and predominantly tetracoordinated Cr4+ and Cr5+, (4) Cr3+ ions make the main contribution to the luminescence sensitization of Yb3+ ions, while Cr4+ ions and to a lesser extent Cr5+ play the role of luminescence quencher and internal filter. Sensitization of Yb3+ luminescence through the charge transfer band in Cr(VI) was found. An alkaline glass doped with Cr and Yb upon excitation through the sensitizer produced a luminescence quantum yield of 32% and the conditions for its enhancement were considered. It is shown that the temperature quenching of luminescence of Cr–Yb-containing glasses is significantly lower than that of Cr-containing glasses. [ABSTRACT FROM AUTHOR]

The work is aimed at the investigation of the influence of nonlinear active ions concentration profiles in Yb:YAG laser elements on temperature distribution and wavefront distortions during amplification using sub-kilowatt level diode pumping. A mathematical model is presented for the theoretical study of the amplification process in crystals with cubic crystal system. A detailed comparison of Yb:YAG active elements with the same thickness and absorbed pumping power, but with various concentration profiles of Yb3+, ions is carried out. It is shown that the use of active elements with an increasing dopant concentration in the pump beam direction allows one to optimize the temperature profile inside the active element and, thus, reduce the thermal-induced wavefront distortions of the amplified radiation. Modeling is carried out for the experimentally grown crystal with linear concentration gradient profile. It is shown that the linear doping profile with a gradient of 0.65 at.%/mm allows increasing the small-signal gain up to 10% and decreasing the thermal-induced wavefront distortions by ~15%. [ABSTRACT FROM AUTHOR]

Two series of (Gd, Y, Yb)3Al2Ga3O12 quintuple compounds with a garnet structure and solely doped with Ce and Tb were prepared in the form of ceramics by sintering in oxygen at 1600 °C for two hours and studied for the interaction of activator ions with ytterbium ions entering the matrix. It was shown that the photoluminescence and scintillation of Ce3+ ions are completely suppressed, predominantly by tunneling ionization through the charge transfer state (CTS) of the Ce4+-Yb2+ ions. The photoluminescence of Tb3+ ions is quenched in the presence of ytterbium, but not completely due to the poor resonance conditions of Tb3+ intraconfiguration transitions and the CTS of the single Yb3+ and the CTS of Ce4+-Yb2+ ions. The scintillation in the visible range of both Ce3+- and Tb3+-doped samples is intensely quenched as well, which indicates strong competition from Yb3+ ions to activators in interaction with the Gd substrate. [ABSTRACT FROM AUTHOR]

Perovskite nanocrystals (PeNCs) deliver size‐ and composition‐tunable luminescence of high efficiency and color purity in the visible range. However, attaining efficient electroluminescence (EL) in the near‐infrared (NIR) region from PeNCs is challenging, limiting their potential applications. Here we demonstrate a highly efficient NIR light‐emitting diode (LED) by doping ytterbium ions into a PeNCs host (Yb3+ : PeNCs), extending the EL wavelengths toward 1000 nm, which is achieved through a direct sensitization of Yb3+ ions by the PeNC host. Efficient quantum‐cutting processes enable high photoluminescence quantum yields (PLQYs) of up to 126 % from the Yb3+ : PeNCs. Through halide‐composition engineering and surface passivation to improve both PLQY and charge‐transport balance, we demonstrate an efficient NIR LED with a peak external quantum efficiency of 7.7 % at a central wavelength of 990 nm, representing the most efficient perovskite‐based LEDs with emission wavelengths beyond 850 nm. [ABSTRACT FROM AUTHOR]

This work investigates the optical properties of Yb3+ ions doped GeO2-PbO glasses containing Ag nanoclusters (NCs), produced by the melt-quenching technique. The lack in the literature regarding the energy transfer (ET) between these species in these glasses motivated the present work. Tunable visible emission occurs from blue to orange depending on the Yb3+ concentration which affects the size of the Ag NCs, as observed by transmission electron microscopy. The ET mechanism from Ag NCs to Yb3+ ions (2F7/2 → 2F5/2) was attributed to the S1→T1 decay (spin-forbidden electronic transition between singlet–triplet states) and was corroborated by fast and slow lifetime decrease (at 550 nm) of Ag NCs and photoluminescence (PL) growth at 980 nm, for excitations at 355 and 405 nm. The sample with the highest Yb3+ concentration exhibits the highest PL growth under 355 nm excitation, whereas at 410 nm it is the sample with the lowest concentration. The restriction of Yb3+ ions to the growth of NCs is responsible for these effects. Thus, higher Yb3+ concentration forms smaller Ag NCs, whose excitation at 355 nm leads to more efficient ET to Yb3+ ions compared to 410 nm. These findings have potential applications in the visible to near-infrared regions, such as tunable CW laser sources and photovoltaic devices. [ABSTRACT FROM AUTHOR]

In this paper, we developed a promising technique for luminescent infrared (IR) diagnostics of neoplasms of visually and endoscopically accessible localization (dermatology, gynecology, dentistry) using ytterbium complexes of porphyrins. Possible mechanisms of accumulation of a pharmaceutical composition based on the ytterbium complex of 2,4-di(α-methoxyethyl)deuteroporphyrin IX (Yb-DMDP) in tumor tissues were studied. Studies on the pharmacokinetics and biodistribution of this substance in various organs and neoplasms of laboratory animals showed a significant selectivity of the accumulation of nanoparticles with ytterbium ions in tumors as early as 24 h after intravenous administration. For the purposes of luminescent IR diagnostics, a highly sensitive laser-fiber fluorimeter operating in the spectral range of 900–1100 nm was developed. Preclinical tests of the developed method of fluorescent IR cancer diagnostics were carried out and its prospects were shown. [ABSTRACT FROM AUTHOR]

In this paper, the features of catalytic cracking of propane with a step-wise change in the composition of the catalyst from Pr2Zr2O7 to Yb2Zr2O7 were considered. For the research, samples of catalysts Pr2Zr2O7, (Pr0.75Yb0.25)2Zr2O7, (Pr0.5Yb0.5)2Zr2O7, (Pr0.25Yb0.75)2Zr2O7 and Yb2Zr2O7 were synthesized and analyzed. Analysis of the results from catalytic experiments showed that for the catalyst (Pr0.25Yb0.75)2Zr2O7, at a temperature of 700 °C, the conversion of propane reaches values of 100%, but for Yb2Zr2O7, this indicator decreases to 84%. The selectivity for ethylene is consistently reduced from 85% to 28% in several catalysts (Pr0.75Yb0.25)2Zr2O7 > Pr2Zr2O7 > (Pr0.5Yb0.5)2Zr2O7 >(Pr0.25Yb0.75)2Zr2O7 > Yb2Zr2O7. An increase in the number of surface adsorption centers leads to a predominant rupture of the C–C bond in the propane molecule with the formation of ethylene. When ytterbium ions are introduced into the catalyst, the amount of ethylene in the reaction products decreases, but the selectivity for propylene increases in the series Pr2Zr2O7 < (Pr0.75Yb0.25)2Zr2O7 < (Pr0.5Yb0.5)2Zr2O7 < Yb2Zr2O7 < (Pr0.25Yb0.75)2Zr2O7, which is associated with a decrease in the binding energy of carbon atoms in propane with the catalytic center during adsorption. [ABSTRACT FROM AUTHOR]

Here, we report on the opportunity to suppress Yb3+ to Yb2+ dopant-ion reduction in LiYbxY1−xF4 mixed crystals during growth processes, using the Bridgmen–Stocbarger technique in graphite crucibles in vacuum. This was carried out by the additional doping of the LiF-YF3-YbF3 powder mixture with 1% of BiF3 additive. The crystals of LiY0.8Yb0.2F4 and LiY0.8Yb0.2F4 with BiF3 doping in the charge, were grown. The spatial distribution of the spectral-kinetic properties of Yb3+ and Yb2+ ions along the grown crystalline-boules were studied. It was established that the Yb2+ concentration rises during the LiY0.8Yb0.2F4 crystal-growth processes without the BiF3 additive: the absorption coefficient of Yb2+ (π-polarization) at 340 nm rises from 0 (at the beginning of the boule) to 2.5 cm−1 (at the end of the boule). In contrast, the undetectable absorption of Yb2+ along the crystals grown from the BiF3 doped melt was displayed. The luminescence-decay time of Yb3+ decreases from 3.7 to 1.8 ms from the beginning to the end of the LiY0.8Yb0.2F4 boule grown from the BiF3 undoped melt, and stays constant (~3.7 ms) along the samples grown with BiF3. Here we demonstrate a positive effect of BiF3 doping on the optical homogeneity of LiYF4:Yb3+ crystals. [ABSTRACT FROM AUTHOR]

In this paper, CaGa 2 S 4 :3%Nd,5%Yb; CaGa 2 S 4 :5%Yb; CaGa 2 S 4 :3%Nd compounds were synthesized, and their photoluminescence (PL) spectra, PL excitation (PLE) spectra and PL decay properties were studied at room temperature under one-photon and multi-photon excitation in a wide range of excitation intensities. The synthesis of the CaGa 2 S 4 compound was carried out by a solid-phase reaction of a stoichiometric mixture of CaS and Ga 2 S 3 powders in a quartz ampoule. Yb and Nd doping was carried out during the synthesis process using YbF 3 and NdF 3. PLE spectra were studied in the wavelength range from 250 to 850 nm, and PL spectra in the range of 400–1500 nm. It has been shown that after introducing Yb3+ ions into thiogallate crystals with Nd3+ ions, a new band near 488 nm is formed and the PL intensity increases by 1–2 orders of magnitude. The anti-Stokes PL spectra of CaGa 2 S 4 : Nd, Yb crystals in the visible region of the spectrum (400–700 nm) were studied when excited by continuous wave laser radiation with a wavelength of 975 nm. The kinetics of PL decay of all types of compounds at different wavelengths of single- and multi-photon excitation were determined. Depending on the PLE conditions, wavelength and intensity of the exciting radiation, monoexponential and non-monoexponential decay kinetics were observed with decay times in the range of 20–90 μs. Possible mechanisms of PLE and PL of CaGa 2 S 4 crystals doped with neodymium and ytterbium ions are discussed. • The photoluminescence (PL) efficiency of CaGa 2 S 4 :3%Nd doped with Yb3+ upon Stokes excitation increases by 1–2 orders of magnitude. • The increase in PL efficiency is explained by the formation of charge transfer states of the Yb3+ ion with the matrix. • The charge transfer of the Yb3+ ion to the matrix is manifested in the PL excitation spectrum and its decay kinetics. • During anti-Stokes excitation, the population of the upper excited state occurs with the participation of two-photon absorption of Yb3+ ions, and emission is with the predominant participation of Yb2+ ions. [ABSTRACT FROM AUTHOR]

Replacing conventional powder polycrystalline materials with crystalline materials is an effective strategy to improve the sensing sensitivity, responsiveness, and anti-interference capabilities of the fluorescence intensity ratio (FIR) based optical temperature sensing techniques. In this work, Yb3+/Er3+ codoped bimolybdate single crystals, NaBi(MoO 4) 2 (NBM) with different Er3+ ion doping concentrations, were grown by the Czochralski method, in which is expected to be used for optical temperature sensing applications. The structure of the crystals was fully characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and transmission electron microscopy (TEM). Under 980 nm laser excitation, the crystals demonstrated notable green and slight red upconversion (UC) emissions, and the mechanism of UC luminescence was thoroughly investigated. The luminescence intensity was found to be contingent upon the doping concentration, which gradually decayed with increase of Er3+ ions. The optical temperature sensing performance of Yb3+/Er3+ codoped NBM single crystals was evaluated by the FIR technique based on the thermally coupled level of Er3+ ions (2H 11/2 /4S 3/2). The experimental findings revealed that the 10 at% Yb3+, 10 at% Er3+: NBM crystal exhibited highest sensor sensitivity among the synthesized crystals, with a maximum absolute sensitivity of approximately 1.22 % K−1 at 510 K. Furthermore, the temperature sensing characteristics of the crystals appeared to be dependent on the doping concentration of Er3+ ions. In summary, the Yb3+/Er3+ codoped NBM single crystal showcased excellent sensor sensitivity and held considerable promise as materials for optical temperature sensing applications. • Bulk Yb3+/Er3+ codoped bimolybdate single crystals were grown for utilization in optical temperature sensing applications. • The optical temperature sensing properties of Yb3+/Er3+ codoped NBM single crystals were assessed utilizing the FIR technique. • The temperature sensing characteristics of the crystals were contingent upon the doping concentration of Er3+ ions. • A maximum absolute sensitivity of approximately 1.22 % K−1 at 510 K was achieved among the synthesized crystals. [ABSTRACT FROM AUTHOR]

• A novel fiber amplifier leveraging ytterbium-erbium co-doping achieves simultaneous amplification of 1 μm and 1.5 μm laser signals by exploiting the bottleneck effect of energy transfer from ytterbium to erbium ions. • Under 976 nm pumping, the amplifier realizes balanced output powers of 17.5 W at 1550 nm and 18.1 W at 1064 nm, with an optical-to-optical efficiency of 50.9 %, representing the highest reported output power and efficiency for a dual-band fiber amplifier operating at 1 and 1.5 µm. • By adjusting the signal power ratio and selecting different pump sources, an increase in the output power of 1064 nm laser is achieved while maintaining effective amplification at 1550 nm, offering novel avenues for enhancing pump power utilization efficiency. We report a fiber amplifier crafted with commercially available Erbium/Ytterbium codoped fiber, concurrently amplifying 1 μm and 1.5 μm laser signals by utilizing the bottleneck effect of energy transfer from Yb to Er irons. The amplifier achieved a single-frequency balanced laser output of 17.5 W at 1550 nm and 18.1 W at 1064 nm after the optimization of pump wavelength and signal power ratio, and showcasing an overall optical-to-optical efficiency of 50.9 %. The technology holds promise for compact mid-infrared laser devices based on difference frequency generation and may find applications in space laser communication and related fields. [ABSTRACT FROM AUTHOR]

Yb3+ ions hold promises for high power emission in the near infrared (NIR). Yet, relevant matrices, comprising mediators to excite Yb3+, have to be found and the optical mechanisms have to be studied in detail. The purpose of this study is to report on the optical excitation and emission mechanisms of NIR photoluminescence (PL) of Yb-doped crystalline aluminum oxynitride thin films prepared at room temperature using reactive magnetron sputtering. Crystal structure and chemical composition are analyzed by transmission electron microscope and Rutherford backscattering spectrometry, respectively. Photoluminescence spectroscopies are used to investigate the excitation and emission mechanisms. NIR emission at 985 nm is obtained under indirect optical excitation using the 325 nm line of a He-Cd laser, the excitation mechanism is explored by photoluminescence excitation measurement (PLE), and the fine structure of the emitted energy levels is investigated by performing PL measurements at low temperature (LTPL). PLE shows that the host defects play the role of mediators to transfer the excitation energy to Yb ions. This offers different possibilities for the development of multiple excitation channels for Yb3+. Stark splitting of the energy levels of the 2F5/2 and 2F7/2 transitions is evidenced using LTPL in the 78 to 295 K range. Electronic transitions are ascribed to experimental emission lines based on good agreement with theoretical values. Moreover, the activation energies for PL thermal quenching are determined and correspond to the energy difference between highest energy quenched lines and thermally activated “hotlines.” [ABSTRACT FROM AUTHOR]

Quantum repeaters based on heralded entanglement require quantum nodes that are able to generate multimode quantum correlations between memories and telecommunication photons. The communication rate scales linearly with the number of modes, yet highly multimode quantum storage remains challenging. In this work, we demonstrate an atomic frequency comb quantum memory with a time-domain mode capacity of 1250 modes and a bandwidth of 100 MHz. The memory is based on a Y2SiO5 crystal doped with 171Yb3+ ions, with a memory wavelength of 979 nm. The memory is interfaced with a source of non-degenerate photon pairs at 979 and 1550 nm, bandwidth-matched to the quantum memory. We obtain strong non-classical second-order cross correlations over all modes, for storage times of up to 25 μs. The telecommunication photons propagated through 5 km of fiber before the release of the memory photons, a key capability for quantum repeaters based on heralded entanglement and feed-forward operations. Building on this experiment should allow distribution of entanglement between remote quantum nodes, with enhanced rates owing to the high multimode capacity. Multimode operation would greatly improve the performances of quantum repeaters. Here, the authors demonstrate a fixed-delay atomic frequency comb quantum memory, based on a Y2SiO5 crystal doped with Ytterbium ions, with a time-domain mode capacity of 1250 modes and a bandwidth of 100 MHz. [ABSTRACT FROM AUTHOR]

The trivalent lanthanoid formamidinates, [Yb2(DFForm)4F2(py)2] ⋅ CH3CN (1) (DFForm=N,N′‐bis(2,6‐difluorophenyl)formamidinate), and [La6(DFForm)8F8O(CH3CN)2] ⋅ 6CH3CN (2) have been prepared from redox transmetallation (RT) reactions employing lanthanoid metals and silver formamidinate (AgDFForm) in CH3CN. C−F activation was observed in both reactions. The structure of 1 is a fluorine bridged dimer with two seven‐coordinate ytterbium metal ions. Surprisingly the lanthanum complex is a trivalent cage with an unexpected central oxygen atom. [La6(DFForm)8F8O(CH3CN)2] ⋅ 6CH3CN (2) formed a 15 membered ring cage of six La atoms, eight F and one O at the centre. There are three different La3+ ions in 2 with two different coordination numbers. All the La atoms are coordinated by four bridging fluorides and the central oxygen. [ABSTRACT FROM AUTHOR]

Optical atomic clocks are currently one of the most sensitive tools making it possible to precisely test the fundamental symmetry properties of spacetime and Einstein's theory of relativity. At the same time, the extremely high stability and accuracy of compact transportable optical clocks open new perspectives in important fields, such as satellite navigation, relativistic geodesy, and the global time and frequency network. Our project aimed to develop a compact transportable optical clock based on a single ytterbium ion. We present the first prototype of the Yb + clock (298 kg in 1 m 3 ) and present several solutions aimed to improve the clock's robustness to approach the demands of a space-qualified system. We present spectroscopic studies of a 435.5 nm quadrupole clock transition with Fourier-limited spectra of 25 Hz. The estimated instability of the output frequency at 1 GHz, which was down-converted with an optical frequency comb (OFC), is at the level of 9 × 10 − 15 / τ , and the long-term instability and inaccuracy are at the level of 5 × 10 − 16 . As the next steps, we present a new design for the clock laser and the OFC. [ABSTRACT FROM AUTHOR]

The paper presents the results of a study into the physicochemical and spectral-luminescent properties of fluorophosphate glasses doped with thulium ions and a thulium/ytterbium pair. The DSC analysis performed showed that an increase in the concentration of rare earth ions leads to an increase in the crystallization stability of glasses. The measurement and analysis of luminescence spectra in the infrared region of the spectrum, as well as the study of energy transfer from ytterbium ions to thulium ions, showed that an increase in the concentration of thulium ions leads to efficient population of the upper laser level due to the cross-relaxation process. When glass is activated with a thulium/ytterbium pair, efficient energy transfer from ytterbium ions to thulium ions is observed at thulium fluoride concentrations above 0.5 mol %, which also leads to population of the upper laser level and an increase in the luminescence intensity in the wavelength range of 1700–1800 nm. [ABSTRACT FROM AUTHOR]

Fiber single-frequency lasers are currently being actively developed, primarily due to the growing number of applications that require compact and reliable narrow-band sources. However, the most developed single-frequency fiber lasers based on phosphate fibers have the disadvantages of low mechanical strength of both the phosphate fibers themselves and their splices. In this paper we demonstrate a single-frequency laser based on a new composite Yb3+-doped active fiber. The core of this fiber is made of phosphate glass with a high concentration of ytterbium ions and its cladding is made of standard silica glass. This structure ensures a higher splicing strength of the fiber compared to the phosphate fibers and provides high resistance to atmospheric moisture. Despite the multimode structure of this fiber, we achieved stable single-frequency lasing with an average power of 10 mW and a spectral contrast of more than 60 dB in the scheme with a short (1.1 cm) cavity formed by two fiber Bragg gratings. We believe that further optimization of this fiber will make it possible to create powerful and reliable single-frequency lasers in the one-micron wavelength range. [ABSTRACT FROM AUTHOR]

The work is aimed at the investigation of the influence of nonlinear active ions concentration profiles in Yb:YAG laser elements on temperature distribution and wavefront distortions during amplification using sub-kilowatt level diode pumping. A mathematical model is presented for the theoretical study of the amplification process in crystals with cubic crystal system. A detailed comparison of Yb:YAG active elements with the same thickness and absorbed pumping power, but with various concentration profiles of Yb3+, ions is carried out. It is shown that the use of active elements with an increasing dopant concentration in the pump beam direction allows one to optimize the temperature profile inside the active element and, thus, reduce the thermal-induced wavefront distortions of the amplified radiation. Modeling is carried out for the experimentally grown crystal with linear concentration gradient profile. It is shown that the linear doping profile with a gradient of 0.65 at.%/mm allows increasing the small-signal gain up to 10% and decreasing the thermal-induced wavefront distortions by ~15%.

Barium titanium borate glasses doped with ytterbium ions were fabricated via standard melt quenching technique. The building structure of the glass matrices doped with ascendant ratios of ytterbium ions were studied using Raman and FTIR spectroscopies. The UV–Vis–NIR optical absorption spectra were investigated and used to calculate optical bandgaps, Urbach energies, refractive indices, metallization criterion, optical basicity, and dispersion parameters. The absorption and emission cross-sections and gain spectra for 2F5/2 → 2F7/2 transition of ytterbium ions were investigated. The high values of the emission cross-sections of the studied glasses make them strong candidates for laser and amplifier applications. [ABSTRACT FROM AUTHOR]

The spectral-kinetic properties of Yb3+ optical centers in YScO 3 crystal fiber were studied using selective laser spectroscopy. Three distinct types of Yb3+ optical centers were identified. Various spectral characteristics of the Yb3+ optical centers were determined, including homogeneous and inhomogeneous broadening values, Stark level splitting, and the Yb3+ ions lifetime. The first optical center, with a lifetime of τ I 77K = 4.05 ms, was formed due to the substitution of Y3+ for Yb3+ ions in the local site of С 3 i. The other two Yb3+ optical centers, with lifetimes of τ I 77K = 1.0 ms (С II 2 (Y3+) center) and τ II 77K = 0.620 ms (С II 2 (Sc3+)), respectively, were formed as a result of the substitution of Y3+ and Sc3+ for Yb3+ in the local site of C 2. • For the first time three distinct types of Yb3+ optical centers were identified and analyzed in detail in YScO 3 crystal. • The first, long-lived, optical center was formed due to the substitution of Y3+ for Yb3+ ions in the local site of С 3 i. • The other two Yb3+ centers were formed as a result of the substitution of Y3+ and Sc3+ for Yb3+ in the local site of C 2. [ABSTRACT FROM AUTHOR]

The manifestation of ytterbium ions in the microcrystals of the Sr 2 Y 6.8 YbSi 6 O 26 :Er 0.2 solid solution with apatite structure was studied on the basis of low-temperature photoluminescence (PL) spectroscopy and spectral-kinetic measurement data. Intracenter down-conversion luminescence of Er3+ ions in the visible and IR ranges was detected. Up-conversion luminescence of Er3+ ions is observed upon IR excitation due to excitation of Yb3+ ions and subsequent energy transfer Yb3+ → Er3+. Overlapping bands at 412 and 430 nm with a Stokes shift of less than 0.3 eV are observed in the PL spectra at room temperature. These emission bands are assigned to the spin-allowed and spin-forbidden 4 f 1 35 d → 4 f 14 transitions from the low-spin and high-spin exciting states of Yb2+ ion, respectively. The PL decay kinetics for transitions from the low-spin states is characterized by a dominant component τ = 0.39 ns. An alternative model of Yb3+ luminescence center associated with a charge transfer band does not explain the data of low-temperature (5K) PL spectroscopy. At T = 5 K, a new wide emission band with a maximum at 696 nm and a Stokes shift of 1.1 eV appears in the PL spectrum. Two options of this PL band nature are considered. The first is the luminescence of defects having a vacancy nature. The second possible option is the manifestation of anomalous luminescence of Yb2+ ions, which occupy a different crystallographic position in the apatite crystal structure. [Display omitted] • Microcrystalline powder with apatite structure was synthesized via solid state reaction. • Down- and up-conversion luminescence in Er3+ ions is observed upon both UV and IR photoexcitation due to Yb3+ → Er3+ energy transfer. • Spin-allowed and spin-forbidden 4 f 135 d →4 f 14 radiation transitions in Yb2+ ions are observed. [ABSTRACT FROM AUTHOR]

This work investigates the optical properties of Yb3+ ions doped GeO2-PbO glasses containing Ag nanoclusters (NCs), produced by the melt-quenching technique. The lack in the literature regarding the energy transfer (ET) between these species in these glasses motivated the present work. Tunable visible emission occurs from blue to orange depending on the Yb3+ concentration which affects the size of the Ag NCs, as observed by transmission electron microscopy. The ET mechanism from Ag NCs to Yb3+ ions (2F7/2 → 2F5/2) was attributed to the S1→T1 decay (spin-forbidden electronic transition between singlet–triplet states) and was corroborated by fast and slow lifetime decrease (at 550 nm) of Ag NCs and photoluminescence (PL) growth at 980 nm, for excitations at 355 and 405 nm. The sample with the highest Yb3+ concentration exhibits the highest PL growth under 355 nm excitation, whereas at 410 nm it is the sample with the lowest concentration. The restriction of Yb3+ ions to the growth of NCs is responsible for these effects. Thus, higher Yb3+ concentration forms smaller Ag NCs, whose excitation at 355 nm leads to more efficient ET to Yb3+ ions compared to 410 nm. These findings have potential applications in the visible to near-infrared regions, such as tunable CW laser sources and photovoltaic devices.

Inorganic glasses co-doped with rare-earth ions have a key potential application value in the field of optical communications. In this paper, we have fabricated and then characterized multicomponent TiO2-modified germanate glasses co-doped with Yb3+/Ln3+ (Ln = Pr, Er, Tm, Ho) with excellent spectroscopic properties. Glass systems were directly excited at 980 nm (the 2F7/2 → 2F5/2 transition of Yb3+). We demonstrated that the introduction of TiO2 is a promising option to significantly enhance the main near-infrared luminescence bands located at the optical telecommunication window at 1.3 μm (Pr3+: 1G4 → 3H5), 1.5 μm (Er3+: 4I13/2 → 4I15/2), 1.8 μm (Tm3+: 3F4 → 3H6) and 2.0 μm (Ho3+: 5I7 → 7I8). Based on the lifetime values, the energy transfer efficiencies (ηET) were estimated. The values of ηET are changed from 31% for Yb3+/Ho3+ glass to nearly 53% for Yb3+/Pr3+ glass. The investigations show that obtained titanate–germanate glass is an interesting type of special glasses integrating luminescence properties and spectroscopic parameters, which may be a promising candidate for application in laser sources emitting radiation and broadband tunable amplifiers operating in the near-infrared range. [ABSTRACT FROM AUTHOR]

The development of high-power diode lasers enabled new solid-state laser concepts such as thin-disk, fiber, and Innoslab lasers based on trivalent ytterbium as the laser-active ion, which resulted in a tremendous increase in the efficiency and beam quality of cw lasers compared to previously used lamp-pumped rod or slab lasers and the realization of ultrafast lasers with several 100 W or even kilowatts of average power. In addition to their beneficial thermo-optical properties, these architectures offer characteristic benefits making them especially suitable to obtain dedicated laser properties. This review article comprises milestone developments, characteristic challenges, and benefits, and summarizes the state of the art of high-power solid-state lasers with the focus on ultrafast lasers. [ABSTRACT FROM AUTHOR]

• ZnO optical ceramics containing 0–2 wt% Yb are prepared by uniaxial hot pressing. • Yb ions form a cubic Yb2O3 phase located at the ZnO grain boundaries. • The ceramics exhibit a total transmittance up to 60 % in the visible. • Absorption and photoluminescence of Yb3+ ions correspond to those in Yb 2 O 3 crystals. • Addition of Yb affects the spectra and fastens the decay of X-ray induced luminescence. Zinc oxide optical ceramics containing 0–2 wt% ytterbium are prepared by uniaxial hot pressing of commercial oxides at 1150 and 1180 °C. The ceramics have the main crystalline phase of hexagonal wurtzite-type ZnO. Ytterbium ions do not enter the ZnO crystals but form a cubic sesquioxide phase of Yb 2 O 3 located at the ZnO grain boundaries. Yb acts as an inhibitor for the ZnO grain growth. The ceramics exhibit transmittance up to 60 % in the visible. Their transmission in the infrared is determined by the free charge carrier absorption. The Yb3+ ions are found in C 2 and C 3i sites in Yb 2 O 3 crystals. Under X-ray excitation, the ceramics exhibit intense luminescence bands in the blue (near-band-edge emission) and green (defect emission) whose positions, intensities and decay times depend on the Yb content. Yb 2 O 3 causes a redistribution of luminescence intensity in favor of the near-band-edge emission and fastens the emission decay. [ABSTRACT FROM AUTHOR]

Lanthanide ions doped glasses are studied by researchers for upconversion luminescence. Rare earth doped bismuth tellurite glasses codoped with and without silver nanoparticle were synthesized by melt and quench procedure for the study of enhanced upconversion luminescence. Physical parameters as molar mass, molar volume, and density were evaluated. Amorphous nature of samples was verified by x-ray diffraction. DSC is carried for information of thermal properties. UV-Visible absorption and fluorescence spectra is obtained to get detail information of upconversion luminescence. Upconversion mechanism of rare earth erbium and ytterbium ions discussed. Three prominent upconversion luminescence is observed two in green region and one is in red. [ABSTRACT FROM AUTHOR]

The oxygen permeability of ytterbium disilicate (YbDS) topcoat (TC) and silicon dioxide (SiO2) thermally grown oxide (TGO) is evaluated. The primary goal is to elucidate the oxidation mechanisms in environmental barrier coatings (EBCs). For this purpose, oxidant diffusion is investigated using physics‐based and numerical modeling. The oxygen permeability constants are systematically evaluated and quantified in terms of thermodynamics using defect reactions and the parabolic rate constant (kp), respectively. Dry oxygen and wet oxygen conditions as well as different temperatures, partial pressures, and topcoat modifiers are investigated. The results offer evidence that the oxygen permeability constant for the YbDS topcoat is an order of magnitude higher than for the TGO. As such, the TGO hinders the oxidant diffusion stronger, proving to be the diffusion rate‐controlling layer. Moreover, water vapor strongly increases the oxidant permeation with defect reactions playing a key role. It is suggested that the mass transfer through the topcoat is primarily by outward ytterbium ion diffusion and inward oxygen ion movement, with the latter being dominant, particularly in wet environments. The effect of topcoat modifiers on oxidant permeation is composition sensitive and seems to be related to their interaction with oxygen ions and their mobility. [ABSTRACT FROM AUTHOR]

We present an overview of contemporary quantum computing with ytterbium ion traps, placing the emphasis on industry implementations. We provide brief, concrete descriptions of various key features, such as trap loading, electronic structure, qubit function, gates, error analysis, and benchmarking. We focus on the underlying science and current technologies to provide readers with a holistic picture of available techniques for using ytterbium in contemporary ion trap designs. [ABSTRACT FROM AUTHOR]

Yttrium aluminium perovskite YAlO3 (YAP) crystal, doped with rare-earth ions, has been extensively studied as a diode-pumped laser host material. The wide interest to rare-earth ions doped YAP crystals is explained by its good thermal and mechanical properties, high natural birefringence, widely used Czochralski growth method. The aim of this work was to study the Yb3+:YAlO3 crystal as an active medium for high power mode-locked laser.Yb3+-doped perovskite-like aluminate crystals have unique spectroscopic and thermooptical properties that allowed using these crystals as an active medium of high power continuous wave (CW) and modelocked (ML) bulk lasers with diode pumping.growth method. The aim of this work was to study the Yb3+:YAlO3 crystal as an active medium for high power mode-locked laser.In our work spectroscopic properties of Yb:YAP crystal and laser characteristics in CW and ML regimes are investigated. Maximum output power of 4 W with optical-to-optical efficiency of 16.3 % and 140 fs pulse duration have been obtained for Yb:YAP E //c-polarization with 10 % output coupler transmittance. Tunability range as wide as 67 nm confirms high promise of using Yb:YAP crystal for lasers working in wide spectral range.

Compact diode-pumped chirped pulse regenerative amplifier systems with pulse repetition rate of hundreds kilohertz based on Yb3+-doped crystals are of practical importance for wide range of applications such as materials processing, medicine, scientific research, etc. The aim of this work was to study the Yb3+:LuAlO crystal based dual wavelength chirped pulse regenerative amplifier.Perovskite-like aluminate crystals have unique spectroscopic properties that allowed to use amplifier active element gain spectrum as an amplitude filter for amplified pulse spectrum and even obtained dual wavelength amplification without any additional components.In our work a simple way to obtain dual-wavelength operation of chirped pulse regenerative amplifier by using the active medium gain spectrum as an amplitude filter for the formation of the amplified pulses spectrum demonstrated for the first time to our knowledge. Maximum output power of 5.4 W of chirped pulses (3.8 W after compression) and optical-to-optical efficiency of 22.5 % have been obtained for Yb:LuAP E//b-polarization at 200 kHz repetition rate. Compressed amplified pulse duration was about 708 fs while separate spectral components durations were 643 fs and 536 fs at 1018.3 nm and 1041.1 nm central wavelengths, respectively. Performed investigations show high potential of Yb3+:LuAP crystals as active elements of compact diode pumped chirped pulse regenerative amplifiers

Experimental realizations of two qubit entangling gates with trapped ions typically rely on addressing spectroscopically resolved motional sidebands, limiting gate speed to the secular frequency. Fast entangling gates using ultrafast pulsed lasers overcome this speed limit. This approach is based on state-dependent photon recoil kicks from a sequence of counter-propagating, resonant, ultrafast pulse pairs, which can allow sub-microsecond gate speeds. Here, we demonstrate a key component of the ultrafast gate protocol, the coherent excitation of a 171Yb+ ion across the 2S1∕2-2P1∕2 transition with a single near-resonant short optical pulse at 369.53 nm. We achieve a maximum population transfer of 94(1)% using a picosecond pulsed laser that can be tuned across the 2S1∕2-2P1∕2 transition and 42.5(9)% with 190(7) GHz detuning. [ABSTRACT FROM AUTHOR]

In order to prevent counterfeiting of down fiber from consumers, rare earth fluorescent materials are developed in the field of material identification and anticounterfeiting. Herein, the development of verifiable down fiber based on infrared excitation-infrared emission was described. A novel method was approached to prepare security down fiber, which involved modification of down-conversion nanoparticles (DCNPs) by sulfonic groups and self-assembly onto down fiber through electrostatic force. DCNPs were successfully prepared from ytterbium-deposited NaYF4 nanoparticles using a complexation precipitation approach, in which the trivalent ytterbium ions served as the luminescent center. Sulfonic down-conversion nanoparticles (SO3-SiO2@DCNPs) were fabricated by the hydrolysis of 3-mercaptopropyl triethoxysilane (MPTES) and next oxidation to enhance the combination of the DCNPs with down fiber. The synthesis of DCNPs and SO3-SiO2@DCNPs and its pendant to down were confirmed by XRD, SEM, XPS, FT-IR, Zeta potential meter, and PL, which revealed the presence of DCNPs in the size average 86 nm. The obtained DCNPs and security down fiber were launching an invisible red-shifted emission of 930∼1080 nm (corresponding to the 2F5/2 ⟶ 2F7/2 transitions in Yb3+). After washing, the infrared emission of security down fiber was evaluated and proved to be effective with fine results, which showed its potential application in the field of security. [ABSTRACT FROM AUTHOR]

The comparison of optical oscillators is used both to determine their spectral characteristics and to perform fundamental research. To describe each individual laser system, it is necessary to compare at least three independent laser oscillators. Three ultrastable lasers with wavelengths of 1140, 1550, and 871 nm located in different laboratories at the Lebedev Physical Institute have been compared. A femtosecond frequency comb has been used to transfer stability between different spectral ranges. A fractional frequency instability has been obtained with the three-cornered hat method and phase noise of each laser has been analyzed. Using this method, it has been shown that the characteristics of the laser system at a wavelength of 871 nm are appropriate to control the quantum state of an optical qubit on a quadrupole transition in an ytterbium ion with a n-atural width of 3.1 Hz. [ABSTRACT FROM AUTHOR]

Yb3+ and Er3+-doped Bi 3 TeBO 9 ceramics exhibit efficient upconversion luminescence in the visible spectral range upon laser diode excitation at 975 nm. Bi 3 TeBO 9 :Yb3+/Er3+ powder was prepared by means of the modified Pechini method. A series of Bi 3 TeBO 9 :Yb3+/Er3+ ceramic samples was fabricated using the high-pressure low-temperature technique, by sintering Bi 3 TeBO 9 :Yb3+/Er3+ powder under different pressures (2, 4, 6 or 8 GPa). The structure and morphology of the above-mentioned samples were analyzed using XRD, SEM and EDX measurements. The phonon energy of Bi 3 TeBO 9 matrix associated with the vibrations of TeO 6 and BO 3 molecular groups was revealed using μ-Raman spectroscopy. The low phonon energy of Bi 3 TeBO 9 matrix allows the effective energy transfer between Yb3+ and Er3+ ions as well as the 2H 11/2 → 4I 15/2 , 4S 3/2 → 4I 15/2 and 4F 9/2 → 4I 15/2 transitions from the excited to ground states of Er3+ ions, resulting in efficient upconversion emission at 523, 540 and 653 nm, respectively. The decay times determined for all analyzed emissions were longer for Bi 3 TeBO 9 :Yb3+/Er3+ ceramics than for the powder sample. The highest values of decay times were detected for the ceramics obtained under a pressure of 8 GPa and were equal to 174, 172 and 175 μs for the emissions at 523, 540 and 653 nm, respectively. The obtained results suggest that Bi 3 TeBO 9 :Yb3+/Er3+ ceramics can be proposed as efficient spectral converters in the new type solar cells enhancing the efficiency of the photovoltaic effect. • Bi 3 TeBO 9 :Yb3+/Er3+ ceramics were fabricated using the HPLT technique. • Bi 3 TeBO 9 :Yb3+/Er3+ ceramics have hexagonal structure of P 6 3 space group. • Phonon energy of Bi 3 TeBO 9 matrix was investigated using μ-Raman spectroscopy. • Bi 3 TeBO 9 :Yb3+/Er3+ ceramics show emission in VIS upon excitation in NIR. • Bi 3 TeBO 9 :Yb3+/Er3+ ceramics can be used as spectral converters in the solar cells. [ABSTRACT FROM AUTHOR]