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Q: Quantenoptik
Q 38: Laser in Medicine
Q 38.6: Talk
Friday, April 6, 2001, 18:45–19:00, H 2013
A PPLN-based difference-frequency laser system for cavity leak-out spectroscopy in the 3 µm region — •S. Stry, D. Kleine, H. Dahnke, P. Hering, and M. Mürtz — Institut für Lasermedizin, Universität Düsseldorf
Cavity Leak-Out Spectroscopy (CALOS) is a fast and sensitive method for real-time trace gas detection. The sample gas is filled into a high-finesse optical cavity. The cw excitation of the resonator leads to an effective absorption length of several kilometers, leading to detection limits on the ppb level. Many medical and environmental relevant molecules show strong absorption bands in the mid-infrared region and can be spectroscopically distinguished by means of a narrow-linewidth cw laser. Up to now the construction of a portable CALO-Spectrometer in the mid-infrared has been prevented by the lack of an appropriate small-sized laser device with a sufficiently narrow linewidth and wide tunability. We developed a difference-frequency laser system as a light source for a CALO-Spectrometer, which is tunable from 2797 cm−1 to 3196 cm−1 with a fast, mode-hop free tuning range of 1.8 cm−1 (54 GHz) and a conversion efficiency of 0.2 %/W . We demonstrate the detection of hydrocarbons, like methane and ethane in natural air on the ppb level, with our portable CALO-Spectrometer. The noise-equivalent absorption coefficients are in the order of 1 × 10−8/cm. This work is supported by the German Federal Foundation for Environmental Research (Deutsche Bundesstiftung Umwelt).