Comprehensive Analysis of Thermal Lensing Effects on the Coaxial Resonator of a High Power RF-Excited CO2 Laser

The influence of a variety of parameters, such as the gas composition, pressure and lateral variation of Joule heat release of the discharge at employed frequency, are taken into account to derive a distributed thermal lensing expression and to numerically calculate the focal length as a function of position within the inter-electrode gap. The process of widening of the beam inside the resonator is investigated by means of complex ray methodology. The findings are incorporated into the optimization process of the optical resonator in the stable direction and the impact on the beam quality and power stability is verified by experimental results.