5 February 2010 VCSEL based Faraday rotation spectroscopy at 762nm for battery powered trace molecular oxygen detection
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Abstract
Faraday Rotation Spectroscopy (FRS) is a polarization based spectroscopic technique which can provide higher sensitivity concentration measurements of paramagnetic gases and free radicals than direct absorption spectroscopic techniques. We have developed sensor systems which require only 0.2W to perform TDLAS (tunable diode laser absorption spectroscopy), and can additionally be quickly duty cycled, enabling operation in wireless sensor networks of laser-based trace gas sensors We adapted our integrated TDLAS electronics to perform FRS in a compact and more sensitive system for quantification of molecular oxygen (O2) using a 762.3nm VCSEL in the A band. Using an AC magnetic field, we demonstrate detector noise dominated performance, achieving 2.1×10-6/Hz1/2 equivalent detectable fractional absorption and a minimum detection limit of 462 ppmv O2 in 1 second in a 15cm path. At longer paths and integration times, such a sensor will enable oxygen measurements at biotic respiration levels (<1ppmv) to measure CO2 - O2 exchange for mapping natural exchange of greenhouse gases. Potential improvement of detection limits by increasing various system performance parameters is described.
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Stephen So, Stephen So, Gerard Wysocki, Gerard Wysocki, "VCSEL based Faraday rotation spectroscopy at 762nm for battery powered trace molecular oxygen detection", Proc. SPIE 7615, Vertical-Cavity Surface-Emitting Lasers XIV, 761509 (5 February 2010); doi: 10.1117/12.840990; https://doi.org/10.1117/12.840990
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