High Altitude Water Vapor Concentration Measurement Using Diode Laser Interferometry

40467 OPTRA, Inc. More detailed atmospheric data and a better understanding of atmospheric chemistry are important to gauge what effects energy sources contribute to pollution problems, such as the ¿greenhouse effect.¿ This project will demonstrate the feasibility of sensing water vapor concentrations by measuring the change in the index of refraction of a gas sample as a diode laser is tuned through a water vapor absorption line. The behavior of the index of refraction in the vicinity of an absorption line is known as the anomalous dispersion. This technique will be demonstrated by measuring a water vapor concentration of 2 x 10l3 molecules/cm3. Anticipated Results/Potential Commercial Applications as described by the awardee: This project should result in a more stable and reliable water vapor sensor for use on unmanned aircraft in the upper atmosphere. The laser-based sensor should also have applications in the natural gas industry, semiconductor manufacturing, and for process control and environmental monitoring.