Abstract.
We report a portable mid-infrared spectrometer for trace-gas analysis which is based on an all-solid-state difference-frequency-generation laser. The spectrometer provides in situ absorption path lengths of more than 3 km by means of the cavity leak-out method, a cw variant of the cavity ring-down technique. The design, performance, and application of this spectrometer are presented. The light source utilizes difference-frequency generation in a periodically poled lithium niobate (PPLN) crystal pumped by two single-frequency solid-state lasers. A maximum power of 27 μW in the wavelength region near 3.3 μm is achieved using a pump power of 20 mW at 808 nm, a signal power of 660 mW at 1064 nm, and a 50-mm-long PPLN crystal. This corresponds to a conversion efficiency of 0.42 mW/(W2 cm). We demonstrate that this portable laser system is suitable as a light source in a cavity leak-out spectrometer. We achieved a minimum detectable absorption coefficient of 1×10-8/cm (integration time: 2 s), corresponding, for example, to a detection limit of 1 part per billion ethane. This compact trace-gas analyzer with high sensitivity and specificity is promising for various environmental and medical applications.
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Received: 8 April 2002 / Revised version: 28 May 2002 / Published online: 21 August 2002
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Stry, S., Hering, P. & Mürtz, M. Portable difference-frequency laser-based cavity leak-out spectrometer for trace-gas analysis. Appl Phys B 75, 297–303 (2002). https://doi.org/10.1007/s00340-002-0966-9
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DOI: https://doi.org/10.1007/s00340-002-0966-9