Hollow-glass waveguides may be a viable technology that, in some cases, may supplant heavier multi-pass cells such as White or Herriott cells for performing trace detection using tunable diode laser absorption spectroscopy. We report here a series of experiments for testing the suitability of waveguides for infrared spectroscopy. The loss characteristics of 1 mm bore diameter waveguides have been measured for straight and coiled lengths. Using direct absorption spectroscopy we have found that the absorption pathlength is approximately equal to the physical length of the waveguide. Broadband FM diode laser spectroscopy produces a comparable signal-to-noise ratio with less than a second of signal averaging. Finally, we have also performed near-infrared spectroscopy of nitrous oxide flowing through a waveguide using a telecommunications diode laser.
Revised: January 9, 2009 |
Published: July 10, 2002
Citation
Blake T.A., J.F. Kelly, T.L. Stewart, J.S. Hartman, S.W. Sharpe, and R.L. Sams. 2002.Absorption spectroscopy in hollow-glass waveguides using infrared laser diodes. In Diode Lasers and Applications in Atmospheric Sensing, SPIE Proceedings, edited by A. Fried, 4817, 216-232. Bellingham, Washington:SPIE.PNNL-SA-36856.