Optical heterodyning in differential tunable CO2 laser systems

Long-wave infrared (LWIR) differential laser systems based on single-frequency pulsed CO2 lasers are used in heterodyne lidars for detection of atmospheric pollutions at extremely far distances. Issues related to control of the two-channel tunable single-frequency CO2 laser system, which includes two pulsed TEA laser and four CW wave-guide CO2 lasers (two injectors and two local oscillators) are discussed. The special hardware and software - Automatic Frequency Control system (AFC) - have been developed for the effective operation in wide spectral range (> 60 lines Of CO2 laser). The main task of this system is to keep optimal ratio between a frequency of the injection laser generation and modes of the TEA laser's resonator. The optimal ratio provides maximal probability of the single-frequency pulse generation taking the TEA chirp into account. Experimental data presented on the temporal and spectral structure of the TEA laser pulse generated with injection of the single-frequency CW radiation.