Abstract: A method of operating a laser and a gas analyzer to reduce low frequency and high frequency power non-linearity errors passes a laser beam through a sample gas to a detector. Intensity measurements are taken and compared to a reference set of measurements. The reference set of measurements can be calculated by measuring pressure and temperature of the sample gas. The laser wave number tuning width is locked to tune a high frequency of an absorption path fringe to a predetermined reference value. The analyzer can be operated without taking a reference set of measurements and the analyzer is much smaller than previous analyzers.

Abstract: A tunable laser trace gas analyzer determines the concentration of a target gas in a sample by comparison to a reference gas having a known concentration of the target gas. The trace gas analyzer includes a wavenumber-tunable laser and a gas receiving assembly through which the laser beam is transmitted. The gas receiving assembly comprises a sample gas chamber and a reference gas chamber. Radiation intensity sensors are positioned at remote ends of the sample gas chamber and the reference gas chamber to detect the intensity of the laser transmissions through the sample and reference gases. A beam splitter is positioned within the gas receiving assembly to direct one laser beam portion to one of the radiation intensity sensors and another laser beam portion to the other radiation intensity sensor. The concentration of the target gas in the sample is determined by repetitively modulating the laser drive current to cyclicly vary the laser emission wavenumber about an absorption line of the target gas.