Silver metaphosphate glass wires inside silica fibers--a new approach for hybrid optical fibers.

Phosphate glasses represent promising candidates for next-generation photonic devices due to their unique characteristics, such as vastly tunable optical properties, and high rare earth solubility. Here we show that silver metaphosphate wires with bulk optical properties and diameters as small as 2 µm can be integrated into silica fibers using pressure-assisted melt filling. By analyzing two types of hybrid metaphosphate-silica fibers, we show that the filled metaphosphate glass has only negligible higher attenuation and a refractive index that is identical to the bulk material. The presented results pave the way towards new fiber-type optical devices relying on metaphosphate glasses, which are promising materials for applications in nonlinear optics, sensing and spectral filtering.

Octave-spanning supercontinuum generation in hybrid silver metaphosphate/silica step-index fibers.

We reveal the potential of step-index fibers consisting of a metaphosphate glass core and a silica cladding as an ultrafast octave-spanning supercontinuum source. The hybrid waveguide was fabricated by pressure-assisted melt filling and possesses a sophisticated dispersion behavior with two zero-dispersion points in the proximity of the Erbium laser bands. The fiber generates an octave-spanning supercontinuum from 0.7 to 2.4 µm if pumped at 1.56 µm with 30 fs pulses and energies as low as 300 pJ. Numerical simulations reveal soliton fission and double dispersive wave generation as the dominant broadening effect. This study highlights phosphate glasses as a promising new candidate for the next generation of broadband photonic devices, as they allow for high rare earth-doping levels and dispersion posttuning via plasmonic nanoparticle growth.

Cationic constraint effects in metaphosphate glasses.

Temperature-dependent bond constraint theory (BCT) relies on counting the number of atomic degrees of freedom for a given topology of a glass network. It has been proven useful as a simplistic approach towards the prediction of glass properties. However, it breaks down at the inclusion of ionic bonds and is therefore presently unable to distinguish the effects of varying cationic species with predominantly ionic bonding. Here, we consider the treatment of modifier ions in the scope of BCT. Using the example of metaphosphate glasses with a broad range of modifier cation species, we find that the theory fails to predict the glass properties because of the specific contribution of each modifier species to the rigidity of the glass network. We therefore introduce the concept of constraint strength, which is a simplistic measure of how strongly the modifiers are bound to the surrounding oxygens through columbic forces.

An extended topological model for binary phosphate glasses.

We present a topological model for binary phosphate glasses that builds on the previously introduced concepts of the modifying ion sub-network and the strength of modifier constraints. The validity of the model is confirmed by the correct prediction of Tg(x) for covalent polyphosphoric acids where the model reduces to classical constraint counting. The constraints on the modifying cations are linear constraints to first neighbor non-bridging oxygens, and all angular constraints are broken as expected for ionic bonding. For small modifying cations, such as Li(+), the linear constraints are almost fully intact, but for larger ions, a significant fraction is broken. By accounting for the fraction of intact modifying ion related constraints, qγ, the Tg(x) of alkali phosphate glasses is predicted. By examining alkali, alkaline earth, and rare earth metaphosphate glasses, we find that the effective number of intact constraints per modifying cation is linearly related to the charge-to-distance ratio of the modifying cation to oxygen.

Loading and thermal behaviour of ZIF-8 metal-organic framework-inorganic glass composites.

Here we describe the synthesis of a compositional series of metal-organic framework crystalline-inorganic glass composites (MOF-CIGCs) containing ZIF-8 and an inorganic phosphate glass, 20Na2O-10NaCl-70P2O5, to expand the library of host matrices for metal-organic frameworks. By careful selection of the inorganic glass component, a relatively high loading of ZIF-8 (70 wt%) was achieved, which is the active component of the composite. A Zn⋯O-P interfacial bond, previously identified in similar composites/hybrid blends, was suggested by analysis of the total scattering pair distribution function data. Additionally, CO2 and N2 sorption and variable-temperature PXRD experiments were performed to assess the composites' properties.

Structural insights into hybrid immiscible blends of metal-organic framework and sodium ultraphosphate glasses.

Recently, increased attention has been focused on amorphous metal-organic frameworks (MOFs) and, more specifically, MOF glasses, the first new glass category discovered since the 1970s. In this work, we explore the fabrication of a compositional series of hybrid blends, the first example of blending a MOF and inorganic glass. We combine ZIF-62(Zn) glass and an inorganic glass, 30Na2O-70P2O5, to combine the chemical versatility of the MOF glass with the mechanical properties of the inorganic glass. We investigate the interfacial interactions between the two components using pair distribution function analysis and solid state NMR spectroscopy, and suggest potential interactions between the two phases. Thermal analysis of the blend samples indicated that they were less thermally stable than the starting materials and had a Tg shifted relative to the pristine materials. Annular dark field scanning transmission electron microscopy tomography, X-ray energy dispersive spectroscopy (EDS), nanoindentation and 31P NMR all indicated close mixing of the two phases, suggesting the formation of immiscible blends.