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Abstract: The comprehensive analysis about heat-generating processes is presented in Er:tellutire glass. The heat fraction of each process and total heat fraction during pumping are investigated. The results show that upconversion is an important heat-generation process and heat problem is serious especially at high Er3+ doping level. The influence of pump power on heat fraction is also discussed. Based on the heat analysis, the optimized doping concentration range of Erbium ions is about 0.5mol% to 1.0mol%. [ABSTRACT FROM AUTHOR]

Abstract: Glass with composition of 51SiO2–24.5Al2O3–23MgO–1.5K2O doped with Co2+ ions was prepared by conventional melting method. The glass sample was heated at 900°C for 360min under atmosphere, and the powder XRD measurement showed that crystalline phase successfully precipitated in the sample. As is compared with standard JCPDS card, the crystalline phase identified as a mixture of zirconium titanate (ZrTiO4) and one of the compounds of magnesium aluminum oxide. The crystallite size was confirmed by transmission electron microscope (TEM) observation; it could be estimated as 30nm in diameter from the TEM image. Based on the area ratio of crystalline phase and residual glass phase, the precipitated crystallite phase volume ratio can be estimated to be not higher than 30% in the Co2+ doped glass ceramic sample. The absorption coefficient at 1.54μm for transparent glass ceramic sample is clearly higher than that in base glass, which can be explained by the fact that Co2+ ions entered into the precipitated nano-sized crystal phase and led to higher absorption coefficient at 1.54μm for tetrahedral coordinated Co2+ ion. Consequently, the Co2+ doped transparent glass ceramic sample with thickness of 0.35mm was used as a saturable absorber for 1.54μm Er-glass laser oscillation, and Q switched pulses with pulse energy of 40mJ, pulse width of 42ns, and peak power of 0.95mW were shown in the experiments. [Copyright &y& Elsevier]

Abstract: Two micrometer emission of Ho3+-doped new fluorophosphate glass sensitized by Yb3+ upon excitation of a conventional 980nm laser diode is reported. Based on the measured absorption spectra, the Judd–Ofelt parameters and radiative properties were calculated and discussed. For Yb3+/Ho3+ codoped fluorophosphate glass, the predicted spontaneous transition probability and emission cross-section of Ho3+:5I7→5I8 reaches 73.54s−1 and 4.66×10−21 cm2 , respectively, are much higher than other reported glasses. Larger product of emission cross-section (σem ) and radiative lifetime (τrad ) in the prepared glass shows the prepared glass is expected to be better laser material. In addition, the σem and maximum gain coefficient of Ho3+ in Yb3+/Ho3+ codoped fluorophosphate glass is 12.02% and 12.12% larger than those of Ho3+ singly-doped sample, respectively. The results suggest Yb3+/Ho3+ fluorophosphate glass is a good candidate for efficient 2μm laser. [ABSTRACT FROM AUTHOR]

In this work, the relationship among the thermal history, refractive index (RI), and structures of Yb3+/Al3+/P5+/F−‐co‐doped silica glass is studied. We reveal the structural origin of the thermally induced RI change in the Heraeus F300 and Yb3+/Al3+/P5+/F−‐co‐doped silica glasses with different states of thermal history by advanced solid‐state nuclear magnetic resonance and Raman scattering techniques, and the effect of the thermal history on the beam quality of Yb3+‐doped large‐mode‐area photonic crystal fiber (LMA PCF). The structural analysis demonstrates that the RI change in the glass is inextricably linked to the change in the AlPO4 domains, coordination number of the Al and Si–O–Si rings. An intimate and direct connection of the thermally induced physical behaviors is developed with the structural pictures of glasses, and the beam quality of the LMA PCF is greatly improved by proper thermal annealing. The results provide a significant reference for the precise manipulation of the numerical aperture of Yb3+‐doped active fiber. [ABSTRACT FROM AUTHOR]

Based on the material properties of 47 Yb3+‐doped phosphate fibers with different sizes and lengths, a laser performance estimation model was established to estimate the laser wavelength just above the threshold (λth), the laser threshold (Pth), and the laser slope efficiency (η). This model was solved via a numerical computing method with an accuracy of 0.01. Under the material constraints of this model, λth, Pth, and η were investigated by sensitivity analysis and Monte Carlo numerical simulation. The results show that short fibers with a small core diameter may more easily produce a shorter λth. Additionally, for constant material properties, fibers with a longer λth may have a lower Pth and higher η than other fibers. Verifying the above conjecture, an output power of 8.7 W with 35% enhancement in slope efficiency was obtained from an optimized phosphate fiber for an optical path in which the output of the short‐wave laser was inhibited. This model can be extended to simulate the lasing wavelength of multi‐composition fibers, providing a theoretical basis for special laser bands, laser material preparation, and fiber structure design. [ABSTRACT FROM AUTHOR]

Single-mode ytterbium-doped phosphate all-solid photonic crystal fiber (AS-PCF) with 13.8 W output power and 32% slope efficiency was reported. By altering the diameter of the rods around the doped core and thus breaking the symmetry of the fiber, a polarization-maintaining AS-PCF with degree of polarization of >85% was also achieved, for the first time to knowledge, in a phosphate PCF. [ABSTRACT FROM AUTHOR]

Yb 3+ /Al 3+ -co-doped silica glasses with different F − content were prepared in this work by sol–gel method combined with high temperature sintering. XRF, FTIR and XPS methods were used to confirm the presence of F − . The effects of F − on the optical and spectroscopic properties of these glasses have been investigated. It is worth to notice that the F − /Si 4+ mass ratio equal to 9% is a significant value showing a real change in the variation trends of numerous following parameters: refractive index, UV absorption edge, absorption and emission cross sections, scalar crystal-field N J and fluorescent lifetimes. Furthermore, introduction of F − can adjust the refractive index of Yb 3+ /Al 3+ -co-doped silica glass and it is useful for large mode area (LMA) fibers. [ABSTRACT FROM AUTHOR]

Highlights: [•] LMA PCF was prepared by sol–gel method and stack-capillary-draw technique. [•] The spectra properties of Yb3+, Al3+ co-doped silica glass were discussed. [•] The laser experiment and laser behaviors were illustrated. [ABSTRACT FROM AUTHOR]

Abstract: Tm3+ and Ho3+ co-doped TeO2–ZnO–Bi2O3 (TZB) glasses were prepared by the conventional melt-quenching method. Two micrometre emission properties of the TZB glasses exited by 808nm Laser Diode (LD) were analyzed and discussed. The Judd–Ofelt parameters, spontaneous radiative transition probabilities and radiative lifetime of Ho3+ were calculated based on the absorption spectra by using Judd–Ofelt theory. The absorption spectra and fluorescence spectra were measured. The predicted spontaneous radiative transition rate of 5I7 → 5I8 of Ho3+ is as high as 466.8 s−1. The result of fluorescence spectra indicates that the maximum emission intensity of Ho3+ 2.0μm and of Tm3+ 1.47μm emission can be achieved at the concentration of 1mol% Tm2O3 and 1mol% Ho2O3 in TZB glasses. The maximum absorption and emission cross-section of Ho3+ near 2.0μm are 0.87×10−20 cm2 at 1951nm and 1.07×10−20 cm2 at 2047nm, respectively. [Copyright &y& Elsevier]

Abstract: The lead-free boron silicon bismuthate glasses were investigated in terms of their physical, optical and structural properties. The physical properties of these glasses have been explored by compositional variation of X-ray diffraction (XRD), differential thermal analysis (DTA) and density. The optical properties of theses glasses have been investigated by UV–Vis and mid-infrared transmittance spectra, and refractive index. The structure of these glasses has been characterized by infrared (IR) absorption and Raman spectra. [Copyright &y& Elsevier]

Abstract: In this paper, 2μm emission spectra of Yb–Ho doped fluorophosphate glass are investigated and compared with Yb–Tm–Ho doped fluorophosphate glass. The 2μm emission intensity of Yb–Ho doped fluorophosphate glass is much stronger than that of Yb–Tm–Ho doped fluorophosphate glass, exhibiting that Yb–Ho doping is an appropriate doping system to 2μm application. As the doping concentration of Yb3+ ions in Yb–Ho doped fluorophosphate glass increases, the 2μm emission intensity increases monotonously and possesses a maximum for 10% Yb ions concentration. Therefore, 10% is the optimization of Yb ions doping concentration for 2μm emission. Otherwise, the up-conversion emission of Ho3+ ions is also studied. Combining with the energy transfer processes, the mechanism is discussed. [Copyright &y& Elsevier]