Detection of high-temperature water vapor at 940 nm with vertical-cavity surface-emitting lasers

A vertical-cavity surface-emitting laser was used to study the absorption of water vapor in the 940 nm region. Measurements for several absorption lines within the 2 v1 + V3 vibrational band were performed. Line strengths at room temperature and in a heated absorption cell over the temperature range of 420-970 K were obtained. The line strength values were in good agreement with simulations based on the values of the HITRAN 2004 database. The measurements also showed that water vapor transitions near 940 nm are suitable for sensitive temperature determination.