Analytical applications of infrared semiconductor lasers in atmospheric trace gas monitoring

Sensitivity, specifity, high time resolution and cost effective simultaneous measurements of several components using operational systems are the main requirements for atmospheric research and air pollution monitoring. Tunable diode lasers absorption spectroscopy (TDLAS) is increasingly beeing used to measure atmospheric trace gas concentrations down to low ppb-levels (10(exp -9) volume mixing ratio). This optical technique fulfills the requirements for trace gas analysis in the atmosphere for most of the smaller molecules with resolved absorption spectra. Semiconductor lead salt diode lasers give access to the mid infrared spectral region, where the most important atmospheric constituents have strong rotational vibrational absorption bands. The application of high frequency modulation (FM) schemes can further improve sensitivity and detection speed of modem instrumentation.