The effect of the discharge frequency on the performance of RF excited CO2 waveguide lasers

Abstract

It is well-known that the highest continuous power generation of CO2 lasers, about 20 W per cm3 active medium is obtained with RF discharges in waveguides. For that reason a detailed study of the physics of RF discharges as a function of frequency, gas density and power dissipation in CO2 laser gas mixtures is a challenge. Compared with the longitudinal dc discharges the RF discharges are transversal and mainly characterized by the sheath formation and the oscillating amplitudes of the discharge electrons which causes a part of the electrons to disappear into the electrodes. From a simple theory one finds that the thickness of the sheath decreases with density and frequency. However, the absence of quantitative values of the sheaths and electron behaviour and their relations with other parameters of the discharge and the laser prevented the understanding of experimental results and adequate predictions of the performance.