6 May 2011 Photoacoustic detection of volatile organic compounds
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We present first results of a research project that has the goal to develop an analyzer for volatile organic compounds (VOCs) with extraordinarily high detection sensitivity and detection selectivity. Due to its high potential concerning these two key parameters, optical spectroscopy is employed. The new detection scheme is based on photoacoustic spectroscopy (PAS). PA detection utilizes the fact, that the excitation energy of light absorbing molecules is essentially transferred into kinetic energy of the surrounding molecules via inelastic collisions. This causes a local pressure increase in the absorbing gas. If the excitation source is modulated, a sound wave is generated that can be detected by a microphone and phase-sensitively measured using a lock-in amplifier. A considerable challenge of this project is represented by the broad and strongly overlapping absorption bands of the hydrocarbons. Discrimination of the VOCs is possible only by using a spectrally tunable monochromatic radiation source in combination with a sophisticated data analysis algorithm. Therefore, we apply an optical parametric oscillator (OPO) with spectral emission between 3 and 4 μm.
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Marcus Wolff, Marcus Wolff, Henry Bruhns, Henry Bruhns, Wenyi Zhang, Wenyi Zhang, } "Photoacoustic detection of volatile organic compounds", Proc. SPIE 8073, Optical Sensors 2011; and Photonic Crystal Fibers V, 80730Z (6 May 2011); doi: 10.1117/12.888966; https://doi.org/10.1117/12.888966

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