No abstract

A mid-infrared (MIR) supercontinuum (SC) has been demonstrated in a low-loss telluride glass fiber. The doublecladding fiber, fabricated using a novel extrusion method, exhibits excellent transmission at 8-14 μm: < 10 dB/m in the range of 8-13.5 μm and 6 dB/m at 11 μm. Launched intense ultrashort pulsed with a central wavelength of 7 μm, the step-index fiber generates a MIR SC spanning from ß2.0 μm to 16 μm, for a 40-dB spectral flatness. This is a fresh experimental demonstration to reveal that telluride glass fiber can emit across the all MIR molecular fingerprint region, which is of key importance for applications such as diagnostics, gas sensing, and greenhouse CO 2 detection.

Three groups of Ge–Sb–Se glasses with compositions Ge x Sb10Se90–x , Ge x Sb15Se85–x , and Ge x Sb20Se80–x have been systematically studied with the aim of understanding the role of chemical composition and mean coordination number (MCN) in determining their structural and physical properties. For each group of glasses, it was found that the optical bandgap increases and the refractive index decreases with increasing Ge concentration up to a transition point which corresponds to glasses that have chemically stoichiometric compositions. Raman spectra were measured and decomposed into different structural units. While the relative number of the heteropolar bonds changes in a reasonable manner with chemical composition, the evolution of the optical bandgap and refractive index correlated closely with the number of the homopolar bonds, suggesting that the band-tails formed by homopolar bonds could reduce the optical bandgap. On the other hand, the transitions at the chemically stoichiometric compositions could be attributed to “demixing” of networks above the chemical thresholds. These transition thresholds in the three groups of glasses demonstrated that the chemical composition has significant effects on the physical properties in the Ge–Sb–Se system.

No abstract

Crystallization kinetics of phase change materials (PCMs) at high temperatures is of key importance for the extreme speed of data writing and erasing. In this work, the crystallization behavior of one of the typical PCMs, GeTe, has been studied using ultrafast differential scanning calorimetry (DSC) at high heating rates up to 4 × 104 K s–1. A strong non-Arrhenius temperature-dependent viscosity has been observed. We considered two viscosity models for estimating the crystal growth kinetics coefficient (U kin). The results showed that the MYEGA model was more suitable to describe the temperature-dependent viscosity and the crystal growth kinetics for supercooled liquid GeTe. The glass transition temperature (T g) and fragility m were estimated to be 432.1 K and 130.7, respectively. The temperature-dependent crystal growth rates, which were extrapolated by the MYEGA model, were in line with the experimental results that were measured by in situ transmission electron microscopy at a given temperature. The crystal growth rate reached a maximum of 3.5 m s–1 at 790 K. These results based on ultrafast DSC with the MYEGA model offer a revelation for crystallization kinetics of supercooled liquid GeTe.

No abstract

A miniature polarimetric interferometer with the twist of a highly-birefringent microfiber is demonstrated. Good transmission spectral characteristics, which are co-governed by the birefringence and the twist degree of the microfiber, are investigated. The structure exhibits extremely-high sensitivity of around 24,373 nm per refractive-index unit and excellent temperature stability of better than 0.005 nm/°C. Featured with compactness, reconfigurability, stability, robustness, and compatibility with other fiberized components, our device has potential in tunable filtering, sensing, multi-wavelength lasing, and etc.

Surface plasmon resonance (SPR) of noble metal nanoparticles (NPs) fostered a new area of nanophotonics, especially in the selective photon absorption and scattering. The precipitation of Ag NPs in glass would enhance the emission efficiency. Here, we studied the effects of annealing temperature (resulted in the increased Ag NPs’ concentration) or AgCl concentration on the luminescence properties of Er3+/Yb3+ codoped bismuth-germanate glasses which were synthesized by a single-step melting–quenching technique. The SPR peak of Ag NPs appears around 600 nm, and the size of precipitated Ag NPs (spherical, hexagonal) ranges from 5 to 15 nm. With the precipitation of the Ag NPs, more intense green (527 nm, 548 nm) and red (661 nm) upconversion (UC) emission bands are observed up to 7.7, 10.1, and 6.5 folds in the glass containing 1 wt % AgCl annealed at 480 °C for 24 h, respectively. The Ag NPs embedded glasses showed significantly local field change that allowed for more bright UC emission by SPR.