Berlin 2001 – scientific programme
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Q: Quantenoptik
Q 30: Poster: Laser in Medicine
Q 30.9: Poster
Friday, April 6, 2001, 12:30–15:00, AT2
Infrared evanescent-field fiber sensor — •Ulrike Willer, Torsten Blanke, Dirk Scheel, and Wolfgang Schade — Institut für Physik und Physikalische Technologien, TU Clausthal, Leibnizstrasse 4, 38678 Clausthal-Zellerfeld, www.pe.tu-clausthal.de/AGSchade/index.html
Infrared laser light at 1.57 µm is coupled into an uncoated fused silica fiber. At the end of the fiber an infrared detector is used to record the transmitted laser light. There are two loss mechanisms that will attenuate the laser intensity when passing through the fiber: (a) The frustrated total reflection (FTR) and (b) the attenuated total reflection (ATR). The FTR is related to a change of the index of refraction while the ATR is related to a change of the absorption coefficient. When scanning the laser on an absorption line of a molecule that is outside of the fiber both, FTR and ATR, contribute to the measured spectral line. Similar to the direct laser absorption spectroscopy the recorded line can be used for estimating concentrations of molecules. A practical application of the evanescent-field fiber sensor is shown as H2S is measured online and insitu at the volcano No-dqSolfataraNo-dq in Italy.