Experimental Study Of Injection Locking TEA CO₂ Laser

A frequency stabilized single longitudinal mode (SLM) TEA CO₂ laser is the most important part of coherent detection CO₂ laser radar. TEA CO₂ laser frequency locking technique is mainly studied in this paper. Injection locking technique is used to choose SLM, and it is designed that by monitoring the changes of the beat signal to feedback control TEA CO₂ laser. The research on the injection system of TEA CO₂ laser has been done theoretically and experimentally. Finally, experiment on heterodyne beat between the TEA CO₂ laser and the local oscillator has been done, and the result has been analyzed.A set of Electromagnetic field equations which fits to the injected TEA CO₂ laser has been developed. And a mathematical model has been built by coupling the field equations and the rate equations. The influence of different detuned angles and injected power on the shape of output pulsed laser and the inversed population in the TEA section gain medium was simulated, analyzed and explained using this model. Using the results of the simulations, one can easily explain the phenomena in TEA CO₂ laser, such as the early start of laser pulse, lower pulse power, and broadening of the pulse duration, all of which were verified in later experiment.Two mainly parts of experiments were carried on, the injection experiment and the heterodyne beat experiment. At the beginning of the injection experiment, we mainly resolved the problem of the influence of the pulsed laser reflected by the zeroth order of the grating on the beating signal: inject with a deflection angle. The theoretical analysis on the condition of deflection angle and mismatching was done. We got the output pulse at 10.59μm on injection successfully, with the phenomena of early start of laser pulse, lowered pulsed power, and broadening of the pulse duration, corresponded well with the theoretical simulations and analysis. In the heterodyne beat section, continuous light beating and pulse light beating were done, the frequency of the beat signals were agreed with the frequency set, which means the success of the heterodyne beat experiment. Further more, the beat signal could be offered to the feedback system as the error signal, and finally achieves the injection locking.