Optical sensor instrumentation using absorption- and fluorescence-based capillary waveguide optrodes

Bernhard H. Weigl; Sonja Draxler; Dietmar Kieslinger; H. Lehmann; Wolfgang Trettnak; Otto S. Wolfbeis; Max E. Lippitsch

doi:10.1117/12.221733

29 September 1995 Optical sensor instrumentation using absorption- and fluorescence-based capillary waveguide optrodes

Bernhard H. Weigl, Sonja Draxler, Dietmar Kieslinger, H. Lehmann, Wolfgang Trettnak, Otto S. Wolfbeis, Max E. Lippitsch

Proceedings Volume 2508, Chemical, Biochemical, and Environmental Fiber Sensors VII; (1995) https://doi.org/10.1117/12.221733
Event: European Symposium on Optics for Environmental and Public Safety, 1995, Munich, Germany

Abstract

An analytical instrument comprising absorption- and fluorescence-based capillary waveguide optrodes (CWOs) is described. Glass capillaries with a chemically sensitive coating on the inner surface are used for optical chemical sensing in gaseous and liquid samples. In case of absorption-based CWOs, light from a LED is coupled into and out of the capillary under a defined angle via a rigid waveguide and an immersion coupler. The coated glass capillary forms an inhomogeneous waveguide, in which the light is guided in both the glass and the coating. The portion of the light which is absorbed in the chemically sensitive coating is proportional to a chemcial concentration or activity. This principle is demonstrated with a pCO₂-sensitive inner coating. Typical relative light intensity signal changes with this type of optical interrogation are 98%, with an active capillary length of 10 mm. For fluorescence- based CWOs, the excitation light from an LED is coupled diffusely into the glass capillary and the optical sensor layer. A major portion of the excited fluorescence light is then collected within the coated capillary, and guided to the photodiode, which is located on the distal end of the capillary waveguide. Hereby, the excitation light is separated very efficiently from the fluorescent light. As an example, a CWO for pO2 is described. By applying this optical geometry, it was possible to utilize fluorescence decay time of the sensor layer as the transducer signal even when using solid state components (LEDs and photodiodes).

Citation Download Citation

Bernhard H. Weigl, Sonja Draxler, Dietmar Kieslinger, H. Lehmann, Wolfgang Trettnak, Otto S. Wolfbeis, and Max E. Lippitsch "Optical sensor instrumentation using absorption- and fluorescence-based capillary waveguide optrodes", Proc. SPIE 2508, Chemical, Biochemical, and Environmental Fiber Sensors VII, (29 September 1995); https://doi.org/10.1117/12.221733

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