Online monitoring of ethane traces in exhaled breath with a difference frequency generation spectrometer
We report a transportable mid-infrared laser cavity leak-out spectrometer for online detection of trace gases. The laser spectrometer is based on continuous-wave difference-frequency generation in the wavelength region around 3 μm. Sensitive spectroscopic trace gas monitoring was achieved using a high-finesse ring-down cavity. For difference-frequency generation, we use a periodically poled lithium niobate (PPLN) crystal, pumped by a Nd:YAG laser (signal wave) and a diode laser (pump wave) with a tapered amplifier. A maximum power of 280 μW near λ=3.3 μm is achieved using a pump power of 180 mW at 807 nm, a signal power of 890 mW at 1064.46 nm, and a 50-mm-long PPLN crystal. The resulting system proved to be a unique tool with high sensitivity and specificity for rapid and precise breath testing. We demonstrate spectroscopic online monitoring of ethane traces in exhaled human breath with a precision of 270 parts per trillion (1σ) and a time resolution of 1 s.
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- 12.T.H. Risby, in Breath Analysis for Clinical Diagnosis and Therapeutic Monitoring, ed. by A. Amann, D. Smith (World Scientific, Singapore, 2005), pp. 251–265Google Scholar
- 13.G. von Basum, H. Dahnke, D. Halmer, P. Hering, M. Mürtz, J. Appl. Physiol. 95, 2583 (2003)Google Scholar
- 22.HITRAN2000 database, www.hitran.comGoogle Scholar