Spectroscopic detection of ethane in the 3-μm wavelength region was performed by means of a cw optical parametric oscillator and cavity leak-out. We achieved a minimum detectable absorption coefficient of 1.6×10<sup>-10</sup> cm<sup>-1</sup>/√Hz, corresponding to an ethane detection limit of 6 parts per trillion /√Hz. For 3-min integration time the detection limit was 0.5 parts per trillion. The levels are to our knowledge the best demonstrated so far. These frequency-tuning capabilities facilitated multigas analysis with simultaneous monitoring of ethane, methane, and water vapor in human breath.
© 2004 Optical Society of America
Golo von Basum, Daniel Halmer, Peter Hering, Manfred Mürtz, Stephan Schiller, Frank Müller, Alexander Popp, and Frank Kühnemann, "Parts per trillion sensitivity for ethane in air with an optical parametric oscillator cavity leak-out spectrometer," Opt. Lett. 29, 797-799 (2004)