CW DFB RT diode laser-based sensor for trace-gas detection of ethane using a novel compact multipass gas absorption cell
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The development of a continuous wave, thermoelectrically cooled (TEC), distributed feedback diode laser-based spectroscopic trace-gas sensor for ultra-sensitive and selective ethane (C2H6) concentration measurements is reported. The sensor platform used tunable diode laser absorption spectroscopy (TDLAS) and wavelength modulation spectroscopy as the detection technique. TDLAS was performed using an ultra-compact 57.6 m effective optical path length innovative spherical multipass cell capable of 459 passes between two mirrors separated by 12.5 cm and optimized for the 2.5–4 μm range TEC mercury–cadmium–telluride detector. For an interference-free C2H6 absorption line located at 2,976.8 cm−1, a 1σ minimum detection limit of 740 pptv with a 1 s lock-in amplifier time constant was achieved.
KeywordsC2H6 Concentration Tunable Diode Laser Absorption Spectroscopy Wavelength Modulation Spectroscopy Diode Laser Beam Sensor Architecture
The Rice University group acknowledges the financial support from a National Science Foundation (NSF) Engineering Research Center sub award for “Mid-infrared Technologies for Health and the Environment (MIRTHE)” from Princeton University, a NSF International Collaboration in Chemistry award: NexCILAS CHE-1124577 and grant C-0586 from The Welch Foundation. The development of the laser diode was supported by the European Commission within the project SensHy 223998 of the 7th Framework Program. The laser diode was fabricated by nanoplus GmbH, Germany.
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