Anping Yang

High-resolution chalcogenide fiber bundles for infrared imaging

An ordered chalcogenide fiber bundle with a high resolution for infrared imaging was fabricated using a stack-and-draw approach. The fiber bundle consisted of about 810,000 single fibers with an As2S3 glass core of 9 μm in diameter and a polyetherimide (PEI) polymer cladding of 10 μm in diameter. The As2S3/PEI fibers showed good transparency in the 1.5-6.5 μm spectral region. It presented a resolution of ∼45  lp/mm and a crosstalk of ∼2.5%. Fine thermal images of a hot soldering iron tip were delivered through the fiber bundle.

Chemical environment of rare earth ions in Ge28.125Ga6.25S65.625 glass-ceramics doped with Dy3+

We have annealed Ge28.125Ga6.25S65.625 glasses doped with 0.5% Dy to create glass-ceramics in order to examine the local chemical environment of the rare earth ions (REI). More than 12 times enhancement of the emission at 2.9 and 3.5 μm was achieved in glass-ceramics produced using prolonged annealing time. Elemental mapping showed clear evidence that Ga2S3 crystalline grains with a size of 50 nm were dispersed in a Ge-S glass matrix in the glass-ceramics, and the REI could only be found near the Ga2S3 crystalline grains. From the unchanged lineshape of the emissions at 2.9 and 3.5 μm and lack of splitting of the absorption peaks, we concluded that the REI were bonded to Ga on the surface of the Ga2S3 crystals.

Structural origin of fragility in Ge-As-S glasses investigated by calorimetry and Raman spectroscopy.

The fragility index (m) of a series of Ge-As-S glasses covering a wide range of mean coordination (⟨r⟩) and stoichiometry is measured by differential scanning calorimetry. The evolution of the fragility index appears to be better predicted by the stoichiometry than the mean coordination, and m shows a well-defined dependence on the departure from stoichiometry quantified as the at. % excess or deficiency in sulfur. The effect of stoichiometry on the fragility of Ge-As-S glasses is very similar to that observed in the Ge-As-Se system. A systematic Raman spectroscopy investigation also indicates the presence of large fractions of molecular species such as S8, As4S4, and As4S3 in the structure of some glasses. The presence of molecular species is shown to increase the fragility and decrease the glass transition temperature (Tg). These results emphasize that short-range order rather than long-range characteristics such as structural rigidity appears to control the fragility of chalcogenide glasses.

High-resolution chalcogenide fiber bundles for longwave infrared imaging

A flexible chalcogenide fiber bundle (FB) with a resolution as high as ~31 lp/mm has been fabricated for delivering thermal images of objects at room temperature. The FB is composed of ~200,000 single fibers with a Ge-As-Te-Se glass core 15 μm in diameter and a polyetherimide (PEI) cladding 16.8 μm in diameter. These Ge-As-Te-Se/PEI fibers show good transparency in the 3-12 μm spectral region. The fabricated FB presents a filling factor of ~72% and a crosstalk of ~1%. High-quality thermal images of a human hand were obtained through the FB, demonstrating good potential of the FB for longwave infrared imaging in the areas such as medicine, industry and defense.