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Q: Fachverband Quantenoptik und Photonik
Q 49: Laseranwendungen: Laserspektroskopie
Q 49.1: Talk
Thursday, March 17, 2011, 10:30–10:45, SCH A215
Interferometrically readout micro tuning forks applied in photoacoustic spectroscopy — •Michael Köhring1, Martin Angelmahr1, and Wolfgang Schade1,2 — 1Fraunhofer Heinrich Hertz Institute, Am Stollen 19, 38640 Goslar — 2Clausthal University of Technology, Institut für Energieforschung und Physikalische Technologien, Am Stollen 19, 38640 Goslar
Photoacoustic spectroscopy is an important part of today's optical sensor techniques for insitu trace gas analysis. The usage of a micro tuning fork as detector for the optically induced acoustic waves enables a remarkable miniaturisation of the sensor system. Due to the high resonance frequency of the micro tuning fork and its small bandwidth, the influence of ambient noise can be neglected. Consequently, no reference measurement is required and an open cell design is considerable.
A new technique is presented, in which the tuning fork's deflection is readout interferometrically without the utilization of the piezoelectric effect applied in the so-called QEPAS technology (quartz-enhanced photoacoustic spectroscopy). A comparison between both techniques is drawn resulting in equivalent detection sensitivities limited by the tuning fork's thermal noise.
The interferometric readout leads to another step of miniaturisation and offers complete fiber-coupled photoacoustic trace gas sensors without the need of any energy source or electrical components at the sensor head. First measurements with this new generation of fiber-coupled trace gas sensors are presented.