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Evanescent field IR spectroscopy using optical fibres and tunable diode lasers

IR Evaneszentwellen-Spektroskopie mit optischen Fasern und abstimmbaren Diodenlasern


Materials Science and Engineering, B. Solid state materials for advanced technology 5 (1990), S.333-337 : Abb.,Lit.
ISSN: 0921-5107
Fraunhofer IPM ()
ATR; Wasseranalytik; water analysis

A new technique for IR spectroscopic measurements of liquids, pastes and thin films is reported. The technique is based on the evanescent field absorption occurring when the material forming the cladding of a waveguide absorbs light at the wavelength being transmitted. The spectroscopic system, consisting of an IR tunable diode laser source and an unclad multimode IR fibre is described. Design considerations, theretica predictions and experimental verification of the sensor performance are presented. This sensor has a relatively high sensitivity, and it will be very useful for monitoring and controlling concentrations and chemical transformations of liquids and pastes in situ and in real time.