Study of visible, NIR, and MIR spectroscopic properties of Er3+-doped tellurite glasses and glass–ceramics

In this paper, the structural, thermal, optical, and spectroscopic properties of Er3+-doped tellurite glasses with the composition 68.25TeO2–19.5ZnO–9.75X–2.5Er2O3 (in mol%) with X = BaO, Na2O, and Bi2O3 are reported. The glasses were prepared using the standard melt quenching method. The investigated glasses exhibit low phonon energy (∼745 cm−1) and low glass transition temperature varying between 300 and 350°C depending on the glass composition. The Raman spectra show a regular tellurite structure with variations in the number of bridging and non-bridging oxygens depending on the glass composition, the Na2O and Bi2O3-containing glasses having the most and the least polymerized network, respectively. A thermal treatment of the glasses leads to the formation of crystals, the composition of which depends on the glass composition, as revealed by X-ray diffraction analysis and confirmed using scanning electron microscope-energy-dispersive spectroscopy. The precipitation of Er-containing crystals in the Na2O and BaO-containing glasses leads to an increase in the intensity of the upconversion emissions. Although the Er3+ ions remain in the amorphous part of the Bi2O3-containing glass after heat treatment, it is the precipitation of Bi3.2Te0.8O6.4 crystals in this glass, which is thought to decrease the distance between the Er3+ ions leading to an increase in the intensity of the upconversion and mid-infrared emissions.publishedVersionPeer reviewe

Spectroscopic properties of Er3+ doped germanate glasses before and after a heat treatment process

In this paper structural, thermal and optical properties of Er3+ doped germanate glasses with the composition of 63.0GeO2-9.8Ga2O3-11.1BaO-4.9X-8.8Na2O-2.5Er2O3 (in mol%), where X = ZnO, TiO2, Al2O3 and Y2O3 are reported. The investigated glasses exhibit low phonon energies (<1000 cm−1) and high glass transition temperature varying between 588 and 642 °C. The Raman spectra evidence about different polymerization degree of the glasses. The thermal treatment leads to the precipitation of various crystals, the composition of which depends on the glass composition. According to the spectroscopic properties Er3+ ions are suspected to have similar local environment in the as-prepared glasses. However, Er-doped crystals are expected to precipitate upon devitrification, which leads to significant change of the spectroscopic properties, in particular increase in the intensity of upconversion and MIR emissions is observed. It is demonstrated that the glasses with Y2O3, ZnO and TiO2 are promising glasses especially for MIR applications.publishedVersionPeer reviewe

Mid-infrared two-octave spanning supercontinuum generation in a Ge-Se-Te glass suspended core fiber

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NuSTAR discovery of a young, energetic pulsar associated with the luminous gamma-ray source Hess J1640-465

We report the discovery of a 206 ms pulsar associated with the TeV gamma-ray source HESS J1640-465 using the Nuclear Spectroscopic Telescope Array (NuSTAR) X-ray observatory. PSR J1640-4631 lies within the shell-type supernova remnant (SNR) G338.3-0.0, and coincides with an X-ray point source and putative pulsar wind nebula (PWN) previously identified in XMM-Newton and Chandra images. It is spinning down rapidly with period derivative Pdot = 9.758(44)E-13, yielding a spin-down luminosity Edot = 4.4E36 erg s-1, characteristic age = P/2Pdot = 3350 yr, and surface dipole magnetic field strength Bs = 1.4E13 G. For the measured distance of 12 kpc to G338.3-0.0, the 0.2 - 10 TeV luminosity of HESS J1640-465 is 6% of the pulsar's present Edot. The Fermi source 1FHL J1640.5-4634 is marginally coincident with PSR J1640-4631, but we find no gamma-ray pulsations in a search using 5 years of Fermi Large Area Telescope (LAT) data. The pulsar energetics support an evolutionary PWN model for the broad-band spectrum of HESS J1640-465, provided that the pulsar's braking index is approximately 2, and that its initial spin period was Po ~ 15 ms.Comment: 9 pages, 5 figures, 5 tables, Latex emulatapj style. Accepted for publication in the Astrophysical Journa

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

Brillouin fiber laser based in step-index tellurite (TeO2) optical fiber

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2-μm Brillouin laser based on infrared nonlinear glass fibers

International audienceInfrared fiber materials such as chalcogenide, tellurite, and heavily germanium-doped silica glasses are attractive materials for many applications based on nonlinear optical effects such as Kerr, Raman, and Brillouin processes. Here, we experimentally demonstrate a close-to-single-frequency Brillouin fiber laser in the 2-μm wavelength region either based on tellurite (TeO2) glass or on heavily germanium-doped silica glass. Our results reveal a strong enhancement of the Brillouin gain efficiency at 2 μm of more than 50 times that of standard silica opticalfibers. A lasing threshold and narrow linewidth of 98 mW and 48 kHz, respectively, have been demonstrated in the tellurite fiber-based laser. This simple Brillouin laser source configuration confirms the potential applications of such fibers for the development of nonlinear photonic devices in the important 2-μm spectral range

Fabrication and characterization of step-index tellurite fibers with varying numerical aperture for near- and mid-infrared nonlinear optics

International audienceWe present an overview of the fabrication process and characterization of tellurite, germanate, and germanate–tellurite step-index fibers with different index contrasts. Several compatible core/cladding glass pairs were first explored for fiber manufacturing under ambient atmosphere. The potential of the resulting waveguides for nonlinear optics is revealed by means of supercontinuum generation experiments using a near-infrared femtosecond fiber laser. Fabrication of the glass preforms was also adapted to dehydration procedures, allowing the drawing of low-OH step-index tellurite fibers. The beneficial impact of glass purification on supercontinuum generation toward the mid-infrared region is confirmed

A Brillouin fiber laser at 2 µm based on a step-index tellurite (TeO2) optical fiber

International audienceWe experimentally demonstrate a single frequency Brillouin fiber laser at 2-µm using a passive fiber ring cavity. A low lasing threshold of 70 mW was achieved with a 2m-length step-index tellurite-glass optical fiber