We demonstrate tunable diode laser absorption spectroscopy of CO<sub>2</sub> and NH<sub>3</sub> near 1.5 μm using a distributed feedback diode laser in conjunction with hollow optical waveguides as long-path sample cells. The waveguides are coiled to reduce the physical extent of the system. The small volume of the waveguide provides rapid instrument response to changes in gas concentration. To reduce the pressure drop associated with long lengths and high flow rates, we perforate the waveguides in a novel geometry providing parallel pneumatic paths while maintaining optical path length. A minimum detectable absorbance of 3.5 × 10<sup>−5</sup> in a 3-m section of waveguide is demonstrated.
© 2002 Optical Society of America
Gregory J. Fetzer, Anthony S. Pittner, William L. Ryder, and Dorothy A. Brown, "Tunable Diode Laser Absorption Spectroscopy in Coiled Hollow Optical Waveguides," Appl. Opt. 41, 3613-3621 (2002)