We demonstrate what we believe is the first application of the recently developed electrically pumped GaAs/AlGaAs quantum-cascade lasers in a spectroscopic gas-sensing system by use of hollow waveguides. Laser light with an emission maximum at 10.009 μm is used to investigate the mid-infrared absorption of ethene at atmospheric pressure. We used a 434-mm-long silver-coated silica hollow waveguide as a sensing element, which served as a gas absorption cell. Different mixtures of helium and ethene with known concentrations are flushed through the waveguide while the laser radiation that passes through the waveguide is analyzed with a Fourier-transform infrared spectrometer. The experimentally obtained discrete ethene spectrum agrees well with the calculated spectrum. A detection threshold of 250 parts per million is achieved with the current setup.
© 2000 Optical Society of America
(060.2370) Fiber optics and optical communications : Fiber optics sensors
(140.3600) Lasers and laser optics : Lasers, tunable
(300.1030) Spectroscopy : Absorption
(300.6260) Spectroscopy : Spectroscopy, diode lasers
(300.6390) Spectroscopy : Spectroscopy, molecular
Lubos Hvozdara, Stefan Gianordoli, Gottfried Strasser, Werner Schrenk, Karl Unterrainer, Erich Gornik, Chavali S. S. S. Murthy, Martin Kraft, Viktor Pustogow, Boris Mizaikoff, Alexandra Inberg, and Nathan Croitoru, "Spectroscopy in the Gas Phase with GaAs/AlGaAs Quantum-Cascade Lasers," Appl. Opt. 39, 6926-6930 (2000)