T. Iqbal

Synthesis, characterization, and potential application of highly chemically durable glasses based on AlF3

Fluorozirconate glasses are stable with respect to devitrification but have poor chemical durability and only fair mechanical strength. AlF 3 -based glasses with improved chemical durability and enhanced mechanical strength are reported here. The optical, mechanical, and thermal properties of these glasses are contrasted to the more familiar ZBLAN composition. The infrared edge of these glasses lies at shorter wavelengths than ZrF 4 -based glasses, but aluminum fluoride glasses offer some interesting opportunities for short-range IR fiber applications such as sensing, remote spectroscopy, and laser power propagation.

Optical properties of AIF 3 -based glasses doped with Pr 3+ , Yb 3+ and Lu 3+

Rare-earth ions can easily be incorporated into fluoride glasses in moderate to large concentrations. Because these glasses possess low fundamental frequencies, they appear to have many advantages over oxide glasses as hosts for rare-earth ions used in optical amplifiers and lasers. We have investigated the optical properties (fluorescence, absorption, and excited-state lifetimes) of AlF(3)-based glass doped with Pr(3+), Yb(3+) and Lu(3+). The effects of different dopant levels on the optical properties of this glass system have also been investigated. These results are compared to those obtained for the same ions in other glass hosts.

Remote infrared chemical sensing using highly durable AlF 3 -based glass fibers

Unclad, low-loss AlF(3)-based glass fibers with enhanced chemical durability have been successfully used for the first time to our knowledge as intrinsic evanescent infrared sensors for monitoring liquid chemicals. Different liquids with absorption bands between 1 and 4.5 microm, such as alcohol, acetonitrile, and mixtures of alcohol/acetonitrile and water/acetonitrile, have been tested. These fibers have also been used successfully as distributed sensors for simultaneous monitoring of different chemical species.

Preliminary study of fiber drawing of AlF3-based glasses

Abstract Although AlF 3 -based glasses have shown superior chemical durability and mechanical strength relative to ZrF 4 -based glasses, devitrification problems near the drawing temperature have limited their fiber applications. We have investigated the effect of atmosphere, particularly moisture, on the surface crystallization during the fiber drawing of these glasses. The crystallization behavior has been monitored by optical microscopy, scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) techniques. Preforms of AlF 3 -based glasses have also been drawn into long fibers in a tower enclosed by a unique three-stage vertical glove box in which the moisture levels are maintained below 1 ppm.

Mechanical properties of aluminum fluoride glass fibers

The effect of high temperature aqueous solutions of various pH values on the mechanical properties of polymer coated optical fibers of an aluminum fluoride-based composition are examined. It was found that such fibers retain much more strength when aged in these aqueous environments than fibers of the more common zirconium fluoride-based composition. The aging is not affected by pH unless the fiber is under stress, in which case a low pH solution decreases the time to failure of the fiber. In static fatigue, the time to failure of the aluminum fluoride-based fibers is 20 times greater than that of the zirconium fluoride-based fibers.

The effect of rare earth ions on the thermal stability of AlF3-based glasses

Abstract The effect of rare earth ions on the thermal stability of AlF 3 -based glasses has been investigated. Different concentrations of NdF 3 , ErF 3 and PrF 3 ranging from 0.25 to 2.0 wt% have been added to a well characterized base glass. Differential scanning calorimetry (DSC) measurements were carried out to determine the time-temperature-transformation (TTT) curves, critical cooling rates and Hruby parameters for both the base glass as well as for the selectively doped glasses. It was found that the thermal stability of AlF 3 -based glasses actually increased following the addition of the above rare earth ions up to certain concentrations and then started to gradually decrease but still remained higher than the original base glass. This behavior of AlF 3 -based glasses is in contrast to those based on ZrF 4 and may offer certain advantages in the fabrication of active fiber devices.

Effect of processing on the optical scattering of AlF3-based glasses

The effect of starting materials purity, crucible material, and melting conditions on the optical scattering of AlF 3 -based glasses has been investigated. Platinum and vitreous carbon crucibles have been used to melt the glasses under nitrogen and reactive atmosphere (RAP) conditions. The optical quality of the bulk glass was evaluated by molecular light scattering in the Mie and Rayleigh regimes as a function of scattering angle and polarization at 0.647 μ m. From an analysis of the angular scattering of both vertically and horizontally polarized beams, the sizes of the scattering sites have been estimated to be in the range of 0.02 to 2.0 μ m. Glasses made with EM (BDH Limited) materials and melted in platinum crucibles without any reactive atmosphere exhibit lower values of scattering losses than those melted in the vitreous carbon crucibles under RAP.

Spectroscopy of some infrared-transmitting waveguides for sensor and laser applications

Spectral attenuation measurements were obtained on some JR transmitting waveguides to evaluate their applicability for remote sensing and laser power delivery. Since there is such a wide variety of applications for fiber optics in these areas, it is important to evaluate materials with various physical and optical properties. Three categories of waveguides where analyzed: glass, crystalline, and hollow tubes. A fluoroaluminate glass optical fiber was fabricated and the attenuation was considerably higher (102103 times higher) than the more common ZBLAN fluoride optical fibers. A Te-Se-Br glass optical fiber was evaluated and it exhibited an extended JR edge to approximately 14 rim. Attenuation measurements were conducted on single crystal sapphire, silicon, KRS-13, and KBr core/KC1 clad optical fibers. The spectral characteristics of alumina, silica glass, and mullite hollow waveguides were also determined, and all measurements were obtained using a Fourier Transform Infrared Spectrometer.

Optical properties of aluminum fluoride based glasses

Transparent and colorless glass rods have been obtained from the A1F3-ZrF4-YF3-CaF2-SrF2-BaF2-NaF (AZYCSBN) and A1F3-BaF2- CaF2-YF3-SrF2 (ABCYS) systems. Chemical durability and certain optical properties of these glasses have been investigated and compared with ZBLAN. The infrared transparency of AZYCSBN is slightly less than ZBLAN but higher than the ABCYS glass system. A1F3 based glasses appear to offer some interesting opportunities for short range IR fiber applications such as sensing, remote spectroscopy and laser power propagation.