The Research Of Improving Media Excited In TEA CO₂ Laser Resonator--Pre-ionization And Clean Gas Mixture

The normal glow discharge between the main electrodes and the rapid flow of the unpolluted gas mixtures are necessary conditions for the output of high average power for TEA CO2 laser. Under high air pressure, a critical problem for the normal discharge is whether enough pre-ionization can be achieved in the laser media or not. However, the cycling pumping oil steam emerging during the flow of the gas mixture and the vapor infiltrating from outside have a strong absorption of the infrared light or a role of counteracting the excitation. Therefore, either reinforcing the pre-ionization or eliminating the harmful impurity is propitious to increasing the effective excitation of the laser media in the resonator so as to increase the output power.The present thesis is devoted to improving the excitation of the laser media (gas mixture) in the resonator of the high-average-power TEA CO2 Laser by means of reinforcing the pre-ionization and eliminating the harmful impurity. It is show that, for the ultraviolet pre-ionization TEA CO2 Laser, the absorption of two photos in the process of the photo-ionization plays an important role. Starting from the theory of two photoionization, we simplified the model of the ultraviolet light source, derived the equation for the spatial distributions of the initial electron density between the main electrodes, and then gave a simple method to homegenize the spatial distribution of the initial electron density between the main electrodes. The output spot-size of our non-flowing TEA CO2 Laser is quite large, only slightly smaller than the section of the excited media, this agrees with the calculated spatial distributions of the initial electron density for pre-ionization well. In order to improve the output quality of the laser, we brought forward the concept of double pre-ionization, which is beneficial for the effective excitation of the laser media in the resonator. Thetheoretical calculations and the experiments suggest that, double pre-ionization has an obvious advantage for increasing the initial electron density between the main electrodes. In addition, from the angle of removing the negative gain media in the cycling gas and the excitation-counteracting media, we put forward the eliminating the impurity by using of the non-uniform stationary electrical field and the swirling electrical field so as to improve the effective excitation of the laser media.