Differential absorption measurements of carbon dioxide using a temperature tunable distributed feedback diode laser

The design and performance of an absorption measurement instrument for monitoring carbon dioxide are presented. The instrument is based on a temperature tunable distributed feedback diode laser capable of tuning between 2.001 and 2.005 mu m. Within this wavelength range are 12 absorption lines for carbon dioxide and 9 absorption lines for water vapor. Initial measurements of laser transmission as a function of carbon dioxide concentration are made using a 2 m long absorption cell. The measured values compare well with the expected values using the known line strength of the carbon dioxide absorption feature. Carbon dioxide measurements over a 77.5 m path length made outside the laboratory show the potential for carbon dioxide concentration monitoring.