Search Results (235)

Optimized designs of the ytterbium-doped fiber (YDF) have been effective at mitigating transverse mode instability (TMI) and enabling high-power scaling. In this study, the use of low-NA confined-doped YDFs is explored to achieve high-power nearly-single-mode continuous-wave lasers. Three types of 25/500 µm YDFs are manufactured with ~80% doping ratio and respective NAs of 0.058, 0.053, and 0.048. Experimental results indicate that the corresponding TMI thresholds increase with the descending NA in the YDFs. Based on the YDF with a NA of 0.048, the master oscillation power amplification (MOPA) fiber laser is scaled to 6.79 kW with nearly-single-mode beam quality. Full article

In this study, we present the development of a high-average-power, exceptionally stable extreme-ultraviolet (EUV) laser source based on a high-order harmonic generation (HHG) technique. The spectrum of an ytterbium-doped laser is broadened through self-phase modulation (SPM) in a gas-filled hollow fiber and compressed down to 25.3 fs for efficient harmonic generation. The high harmonics are generated in a krypton (Kr) gas cell, delivering a total power of 241 μW within the 30–60 nm spectral range, corresponding to a single harmonic output of 166 μW at a central wavelength of 46.8 nm. Notably, the system demonstrates good power stability with a root-mean-square (RMS) deviation of only 1.95% over 12 h of continuous operation. This advanced light source holds great potential for applications in nano- and quantum-material development and in semiconductor wafer defect detection. Future work aims to further enhance the output power in the 30–60 nm band to the milliwatt level, which would significantly bolster scientific research and technological development in related fields. Full article

The paper reports on obtaining visually appealing images from opal matrices to artificial samples comprising regular packing of monodisperse silica globules. We show the images of iridescence, photoluminescence, and both of them simultaneously, exciting upconversion luminescence of Er³⁺ ions from BaTiO₃ xerogel/opal matrix. Opal matrix with BaTiO₃ xerogel doped with Er³⁺ and Yb³⁺ ions demonstrates upconversion luminescence under excitation with the wavelength 980 nm of the laser with the main bands ranging from 500 to 570 nm and 640–700 nm, corresponding to the transitions from the excited states ²H_11/2, ⁴S_3/2, ⁴F_9/2, ⁴I_9/2 to the ground state ⁴I_15/2 of trivalent Er ions. In our view, the synthesis of opal matrices along with the generation of luminescent xerogels doped, for example, with trivalent lanthanides, is a promising approach for obtaining colorful images, always very individual and often very attractive, bringing joy and pleasure at concerts and other show business events. Full article

The ion doping of hydroxyapatite (HA) has gained appeal as a chemical method of improving and adding new characteristics to materials used in biomedical engineering. Dimension, morphology, porosity, surface charge, topology, composition, and other material characteristics make doped HA more suitable for specific biomedical applications. The main aim of this review study was to highlight the role of iHA (iHA) in developing drug delivery systems, tissue engineering, implant coating, wound healing, and multimodal imaging. To the best of our knowledge, depending on the dopant, iHA can have inherent distinct mechanical, physicochemical, and biological properties that make it eligible for biomedical application. More importantly, some ions make iHA a potent antibacterial agent and drug carrier for wound healing (e.g., silver, copper, zinc), have tissue engineering capabilities, improved proangiogenic and osteoconductive properties (e.g., strontium, cobalt, nickel), drug loading capacity (e.g., magnesium, ferric, strontium), metallic implant coating properties (e.g., manganese, silver, copper), and multimodal imaging potential (e.g., terbium, ytterbium, cerium). The concentration of ions and the number of dopants played a vital role in developing new approaches based on iHA. In conclusion, iHA, compared to HA, could show better improvements in biomedical applications. Full article

Plugs of lignite coal from multiple formations were subjected to a series of tests to determine the amount of rare-earth elements (REEs) to be extracted from coal in an in situ mining operation. These tests were used to determine if extraction of REEs and other critical minerals in an in situ environment would be possible for future attempts as an alternative to extraction mining. The tests involved subjecting whole lignite coal plugs from the Twin Butte coal seams in North Dakota to flow-through tests of water, and concentrations of 1.0 M ammonium nitrate, 1.0 M and 1.5 M sulfuric acid, and 1.0 M and 1.5 M hydrochloric acid (HCl) solvents at different concentrations and combinations. The flow-through testing was conducted by alternating the solvent and water flow-through to simulate an in situ mining scenario. The samples were analyzed for their concentrations of REEs (lanthanum [La], cerium [Ce], praseodymium [Pr], neodymium [Nd], samarium [Sm], europium [Eu], gadolinium [Gd], terbium [Tb], dysprosium [Dy], holmium [Ho], erbium [Er], thulium [Tm], ytterbium [Yb], lutetium [Lu], yttrium [Y], and scandium [Sc], as well as germanium [Ge] and cobalt [Co], manganese [Mn], nickel [Ni], and barium [Ba]). Results from the testing showed that REEs were extracted in concentrations that were on average higher using sulfuric acid (8.9%) than with HCl (5.8%), which had a higher recovery than ammonium nitrate. Tests were performed over a standard time interval for comparison between solvents, while a second set of testing was done to determine recovery rates of REEs and critical minerals under certain static and constant flow-through times to determine extraction in relation to time. Critical minerals had a higher recovery rate than the REEs across all tests, with a slightly higher recovery of light REEs over heavy REEs. Full article

The spectral characteristics of pump laser diodes (LDs) introduce significant ambiguity into the performance evaluation of high-power ytterbium-doped fiber lasers (YDFLs), obscuring their intrinsic efficiency and hindering reliable system design. Here, we introduce a rigorous quantitative framework that decouples these pump-induced effects by referencing laser performance to the absorbed, rather than the launched, pump power. Our analysis demonstrates that the widely reported discrepancies in conventional optical-to-optical (OO) and slope efficiencies are governed almost entirely by variations in pump absorption, while the influence of the quantum defect is negligible. This approach provides a robust metric for intrinsic laser performance that is independent of the LD’s spectral properties, proving particularly valuable for systems pumped by non-wavelength-stabilized LDs (nWS-LDs). We uncover a non-monotonic evolution of the unabsorbed residual pump power, revealing that the peak thermal load on system components occurs at an intermediate operational state, not at maximum pump power. This finding challenges conventional thermal management strategies and is critical for ensuring the long-term operational reliability of high-power YDFLs. Full article

A one-pot synthetic methodology that combines an Ugi-Zhu three-component reaction (UZ-3CR) with a cascade sequence (intermolecular aza Diels–Alder cycloaddition/intramolecular N-acylation/decarboxylation/dehydration) using microwave-heating conditions, ytterbium (III) triflate (Yb(OTf)₃) as the catalyst, and chlorobenzene (for the first time in a multi-component reaction (MCR)) as the solvent, was developed to synthesize twelve new fluorinated-pyrrolo[3,4-b]pyridin-5-ones containing a 4-amino-7-chloroquinoline moiety, yielding 50–77% in 95 min per product, with associated atom economies around 88%, also per product. Additionally, by in vitro tests, compounds 19d and 19i were found to effectively stop early SARS-CoV-2 replication, IC₅₀ = 6.74 µM and 5.29 µM, at 0 h and 1 h respectively, while cell viability remained above 90% relative to the control vehicle at 10 µM. Additional computer-based studies revealed that the most active compounds formed strong favorable interactions with important viral proteins (M_pro, NTDα and NTDo) of coronavirus, supporting a two-pronged approach that affects both how the virus infects the cells and how it replicates its genetic material. Finally, quantum chemistry analyses of non-covalent interactions were performed from Density-Functional Theory (DFT) to better understand how the active compounds hit the virus. Full article

We describe the output characteristics of a compact, passively Q-switched, diode-end-pumped (Er/Yb):Glass laser operating in a multi-pulse burst mode. Such operation enables much higher optical efficiency and larger output of total energy than possible with conventional solitary pulse emissions. The laser generated a 15-pulse burst of pulses at 1.5 μm with a combined energy of 5.8 mJ. Measurements of pulse energies, spatial mode characteristics, output beam divergence, and impact of thermal effects in the (Er/Yb):Glass are described. These results are compared to predictions of a numerical simulation using a finite-difference beam propagation method (FD-BPM) that incorporates thermal effects caused by distributed local heating in the glass. We show good agreement between the measured and simulated laser output characteristics. Full article

This study looks at the effect of surface conditioners hydrofluoric acid (HFA), Ytterbium fibre laser (YFL), and Hydroxyapatite nanoparticles (HANPs) on the surface roughness (Ra) and shear bond strength (SBS) of different viscosity resin cements to lithium disilicate glass ceramic (LDC). A total of 78 IPS Emax discs were prepared and categorized into groups based on conditioning methods. Group 1 HFA–Silane (S), Group 2: YFL-S, and Group 3: HANPs-S. A scanning electron microscope (n = 1) and profilometer (n = 5) were used on each conditioned group for the assessment of surface topography and Ra. A total of 20 LDC discs for each conditioned group were subsequently categorized into two subgroups based on the application of high- and low-viscosity dual-cured resin cement. SBS and failure mode were assessed. ANOVA and post hoc Tukey tests were employed to identify significant differences in Ra and SBS among different groups. LDC conditioned with HFA-S, HANPs-S, and YFL-S demonstrated comparable Ra scores (p > 0.05). Also, irrespective of the type of conditioning regime, the use of low-viscosity cement improves bond values when bonded to the LDC. LDC treated with YFL-S and HANPs-S can serve as an effective substitute for HFA-S in enhancing the Ra and surface characteristics of LDC. The low-viscosity resin cement demonstrated superior performance by achieving greater bond strength. Full article

Achieving high quantum yields for Yb³⁺ ion emission in complexes with organic ligands is a challenging task, as most Yb³⁺ complexes with such ligands typically exhibit efficiencies below 3.5%. Our research demonstrates that the introduction of heavy atom-containing ancillary ligands, such as TPPO or TPAO, along with the careful engineering of the main β-diketone ligand, can increase the luminescence efficiency up to 20-fold by the alteration of the energy migration pathway. It is demonstrated that the combination of two distinct organic ligands leads to the blockage of singlet–triplet intersystem crossing (ISC), alongside electronic energy transfer from β-diketone to Yb³⁺ ions through charge transfer states. The synthesized complexes exhibit quantum yields of 6.5% and 7.0% in the solid state, which places them at the top globally among this class of materials with simple non-deuterated and non-fluorinated ligands. Full article

Integrated optical waveguide amplifiers, with their compact footprint, low power consumption, and scalability, are the basis for optical communications. The realization of high gain in such integrated devices is made more challenging by the tight optical constraints. In this work, we present efficient amplification in an erbium–ytterbium-based hybrid slot waveguide consisting of a silicon nitride waveguide and a thin-film active layer/electron-beam resist. The electron-beam resist as the upper cladding layer not only possesses the role of protecting the waveguide but also has tighter optical confinement in the vertical cross-section direction. On this basis, an accurate and comprehensive dynamic model of an erbium–ytterbium co-doped amplifier is realized by introducing quenched ions. A modal gain of above 20 dB is achieved at the signal wavelength of 1530 nm in a 1.4 cm long hybrid slot waveguide, with fractions of quenched ions f_q = 30%. In addition, the proposed hybrid waveguide amplifiers exhibit higher modal gain than conventional air-clad amplifiers under the same conditions. Endowing silicon nitride photonic integrated circuits with efficient amplification enriches the integration of various active functionalities on silicon. Full article

In this work, we report the formation of multiple mode-locking states in an Erbium/Ytterbium co-doped fiber laser, such as domain-wall (DW) dark pulses, high-order dark harmonic pulses, dissipative soliton resonance (DSR) pulses, and dual-wavelength h-shaped pulses. By increasing the pump power and adjusting the quarter-wave retarder (QWR) plates, we experimentally achieve 310th-order harmonic dark pulses. DSR pulses emerge at a pump power of 1.01 W and remain stable up to 9.07 W, reaching a maximum pulse width of 676 ns and a pulse energy of 1.608 µJ, while Dual-wavelength h-shaped pulses have a threshold of 1.42 W and maintain stability up to 9.07 W. Using a monochromator, we confirm that these h-shaped pulses result from the superposition of a soliton-like pulse and a DSR-like pulse, emitting at different wavelengths but locked in time. The fundamental repetition rate for dark pulsing, DSR, and h-shaped pulses is 321.34 kHz. This study provides new insights into complex pulse dynamics in fiber lasers and demonstrates the versatile emission regimes achievable through precise pump and polarization control. Full article

This study provides an investigation into the influence of surface roughness, porosity, and chemistry on the wettability and infiltration behavior of calcia-magnesia-alumino-silicates (CMASs) in thermal and environmental barrier coatings (T/EBCs) used in high-temperature gas turbine engines. High-temperature contact angle measurements were performed at 1260 °C on 7 wt.% yttria-stabilized zirconia (7YSZ) and yttrium ytterbium disilicate (YYbDS, (Y_1/2Yb_1/2)₂Si₂O₇) to evaluate the interaction of CMASs with different surface finishes and coating microstructures. The findings demonstrate that porosity plays a dominant role in determining CMAS infiltration dynamics. In YYbDS, increasing porosity from 6.3% to 22.7% facilitated the formation of an apatite layer that limited CMAS penetration to approximately 2 µm. Surface roughness exhibited a subtler influence in that reducing Sa from 0.61 µm to 0.05 µm increased the change in the contact angle by ~2°, although its impact was found to be less significant compared to porosity and reactive chemistry. These results indicate that an integrated approach that optimizes porosity, chemistry, and surface morphology can significantly enhance CMAS resistance. The study emphasizes that leveraging both microstructural and chemical properties is critical to developing coatings capable of withstanding the harsh conditions encountered in aerospace environments. Full article

The development of efficient scintillators emitting in the red and/or infrared spectral range represents an important scientific challenge, as such materials could find numerous practical applications. This work studies newly grown CsI:Yb,Sm and CsI:Eu,Sm single crystals demonstrating red and infrared luminescence. We measured luminescence spectra in the visible and near-IR range, excitation spectra across visible, UV, VUV, and X-ray ranges, Raman spectra, and thermoluminescence spectra. The results show that divalent europium and ytterbium ions can efficiently transfer excitation to samarium ions. The light output of the obtained crystals under X-ray excitation was roughly estimated from the X-ray luminescence spectra, with expected values of 37,000 photons/MeV for CsI:Yb,Sm and 40,000 photons/MeV for CsI:Eu,Sm. Full article

In this paper, we report on the growth and characterization of high doping concentration (2.1 at%) ytterbium (Yb) doped lithium niobate (Yb:LiNbO₃) crystal. By using a slightly modified Czochralski method, we have successfully grown a usable size (2 mm × 2 mm × 30 mm) Yb:LiNbO₃ single crystal. We also conducted the energy-dispersive X-ray spectroscopy (EDS) and the X-ray diffraction (XRD) analyses, which experimentally confirm that the grown crystal is a Yb:LiNbO₃ single crystal. We also measured the absorption and emission spectra of the grown crystal. It was found out that there is a near-flat broad emission within a spectral range of 1004–1030 nm when excited at 980 nm for this high doping concentration Yb:LiNbO₃ crystal. Such a near-flat broad emission can be very useful for realizing high slope efficiency ultrafast (femtosecond) lasing in the Yb:LiNbO₃ crystal due to the low quantum defect of the Yb:LiNbO₃ crystal. We also investigated the electro-optic effect of the Yb:LiNbO₃. The experimental result confirms that the electro-optic (EO) effect of a highly doped (2.1 at%) lithium niobate crystal is close to the EO value of the pure lithium niobate. Thus, the highly doped Yb:LiNbO₃ crystal can still be an effective electrically tunable lasing medium. It can enable electrically tunable, high slope efficiency femtosecond lasing due to the combined features, including (1) a near flat broad emission spectrum at the spectral range of 1004–1030 nm, (2) a non-compromised electro-optic effect at high doping concentration Yb:LiNbO₃ crystal, and (3) a low quantum defect. Full article