Determination of spectral width of laser lines in the IR range using the absorption spectroscopy method

An engineering technique for determining the spectral width of laser lines is proposed, based on the attenuation of the radiation in a cuvette with known gas composition under fixed thermodynamic conditions using absorption spectroscopy. Preliminarily, based on the theoretical analysis and computational procedures, the dependence of the gas transmission function on the laser linewidth is specified for a particular laser transition, and then, using the nomographic chart and the experimental value of the function, the linewidth of the laser line is found. In the remote gas analysis using the differential absorption method the correction of the measured value of the probed gas absorption coefficient is carried out, taking the spectral width of the laser radiation linewidth into account. The technique requires provision with appropriate spectroscopic information. Particular consideration is carried out for the radiation of a carbon monoxide laser, absorbed by water vapour