The three xylenes, 1,2-, 1,3-, and 1,4-dimethyl benzene, provide a well-characterized family of isomeric molecules within which the melting points vary greatly while fluid-state properties such as boiling points and viscosities remain very similar. Because all pure isomers crystallize rapidly on cooling, their behavior at the low-temperature end of the liquid state, i.e., near the glass transition, has not been studied. We report here differential scanning calorimetry studies of phase relations for the three mixed isomer systems, and identify composition regions in which emulsified and also bulk mixtures can be vitrified at ordinary cooling rates. For one of the latter, 70% m-xylene+ 30% o-xylene by volume, we determine the change in heat capacity through the glass transition. On the assumption that this is the same for pure m-xylene, we assess the Kauzmann limit on liquid behavior, TK, for m-xylene to fall at 104.6 K, Tg/TK to be 1.20, and the excess entropy at Tg to be 15.6 J/mol K or 30.5% of the entropy of fusion. Equivalent data are obtained for the better-known glass former toluene, for which we find Tg/TK=1.16. Comparisons of these results are made with literature data for some saturated analogs. From these comparisons emerges the simple rule that the excess heat capacity of supercooled liquid over crystal can be described as a hyperbolic function of temperature, the one parameter of which varies linearly with the carbon number of the molecule. The plot passes through the origin, and has a greater slope for aromatic than for paraffinic molecules. This is correlated both with the greater ‘‘fragility’’ of the aromatic liquids assessed from viscosity-temperature relations normalized by the calorimetric Tg, and with a simple ‘‘liquid range’’ index Tb/Tg, where Tb is the boiling point.

We demonstrate that the chalcogenide glasses possess large nonlinearities that can enable compact Raman amplifiers as well as fiber lasers and amplifiers in the mid‐IR. These high nonlinearities also allow efficient supercontinuum generation, which is useful for broadband sources in the near and mid‐IR. These materials can also be poled to induce an effective χ(2), opening up the potential of waveguide parametric amplifiers and sources. The Brillouin gain coefficients are relatively large and enable the demonstration of slow light in small core fibers. Results lead to a figure of merit that is about 140 times larger, or a theoretical gain about 45 times larger, than the best silica‐based fiber configurations reported to date.

We demonstrate microstructuring of chalcogenide fiber end faces in order to obtain enhanced transmission due to the antireflective properties of the microstructured surfaces. A variety of molding approaches have been investigated for As(2)S(3) and As(2)Se(3) fibers. Transmission as high as 97% per facet was obtained in the case of As(2)S(3) fiber, compared to the native, Fresnel-loss limited, transmission of 83%. The potential for hydrophobic character was also demonstrated by increasing the contact angle of water droplets to greater than 120°.

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We have detected hazardous and toxic chemicals such as chlorinated hydrocarbons and benzene and its derivatives using evanescent wave spectroscopy with in-house drawn chalcogenide glass fibers. Although, these chemicals have been readily detected down to the volume percent level, we make appropriate recommendations to lower the detection limits to the part per million level. While the current fibers can be used in lengths of up to 30 m for detection and identification of these chemicals, our results indicate that the remote capabilities of these fibers can be significantly improved into the several hundreds of meters range with lower loss fibers, as they become available with improved processing.