Differential absorption lidar system sensitivity with heterodyne reception

It is noted that wavelengths other than in the UV or visible regions have the potential to substantially increase the number of chemical species that can be detected by incoherent backscatter differential absorption lidar systems. For instance, in the IR heterodyne reception has shown the further advantage of immunity against background, yielding a decreased minimum detectable signal as compared to direct detection and a better range capability than usually expected for a given laser energy. A calculation procedure is presented for determining the signal-to-noise ratio in systems employing heterodyne reception. It is assumed that the systems operate under ideal conditions, i.e., atmospheric scintillation and excess detector noise are neglected