Showing papers by "Jong Heo published in 1991"

Remote fiber-optic chemical sensing using evanescent-wave interactions in chalcogenide glass fibers

Abstract: An infrared-transmitting chalcogenide fiber was used as an optical probe to analyze qualitatively and quantitatively various chemical substances in aqueous solutions. An unclad fiber with 380-microm diameter was combined with a Fourier transform infrared spectrometer to monitor the concentration of the analytes in solutions by measuring the changes in the absorbance of their fundamental vibration peaks. A linear relationship was observed between the absorption by the vanescent field and concentrations of various analytes. For this study low concentrations of acetone, ethyl alcohol, and sulfuric acid were detected in aqueous solutions. The minimum detection limit for these three chemical substances was 5, 3, and 2 vol. %, respectively, with a sensor length of 15 cm. It was also demonstrated that the same sensor design is capable of monitoring gaseous species such as dichlorodifluoromethane.

Chalcohalide glasses for infrared fiber optics

Abstract: Chalcohalide glasses are mixtures of chalcogenides and halides. This paper reviews the properties and structure of various glass-forming chalcohalide systems. These materials possess high transmittance in the infrared, which make them candidates for various applications in the area of infrared fiber optics. In general, the packing density, glass transition temperature (Tg), and refractive indices decrease with the addition of a halogen component into binary chalcogenide glasses. It also seems to be theoretically possible that the attenuation loss of the glasses and fibers, especially at 10.6 μm, decreases at the same time. The observed changes in the properties of glasses are in good agreement with the proposed structural model, suggesting degradation of the network connectivity by the addition of network-terminating halogen atoms.