Two-frequency lidar based on an ammonium laser

A two-frequency differential absorption lidar is proposed in which the reference beam is formed from CO₂ laser radiation and the radiation frequency of the working beam is tuned consequently to the lines of the NH₃ laser spectrum. It is shown that this lidar can be used to measure the concentration of freons and some other atmospheric pollutants as low as ~1 ppm with an error of about 20%.