A comprehensive experimental and theoretical study of the optimization of a continuous-wave radiofrequency (rf) excited CO2 waveguide laser is presented. The numerical simulation includes the modelling of the gas-discharge plasma parameters like the plasma impedance and energy deposition, the laser kinetics and finally the influence of the resonator feedback on the lasing process. Along with this theoretical study, an extensive experimental research program enabled us to optimize the laser performance of the CO2 waveguide laser. As a result, a total output power of 42 W and a specific output power of 1.1 W/cm were obtained.

The results of an optimization procedure performed for a continuous wave rf excited sealed CO2 waveguide laser are presented. Parameters that affect laser performance, such as the excitation frequency, the gas pressure, and composition, as well as the electrode temperature and different kinds of circuit losses have been analyzed. An output power of 41 W (17.7 kW/ℓ) with an efficiency of 12% has been obtained from an optimized laser with an active length 37 cm.

An atomic Xe laser with a transverse rf excitation has been operated in a cw mode in the intermediate pressure regime. The laser output spectrum consisted of 5 Xe lines with wavelengths of 2.03, 2.63, 2.65, 3.37, and 3.51 μm. The unoptimized total output power of 330 mW was obtained for a gas mixture Ar:He:Xe=59:40:1 at a pressure of 85 Torr and a rf input power of 150 W and excitation frequency of 121 MHz.

The small-signal gain and the laser output power have been measured in a cw sealed-off rf-excited CO2 waveguide laser for two different electrode materials, gold-plated copper and aluminum, at several excitation frequencies, gas pressures and mixture compositions. In the case of the goldplated electrodes an enhancement of the gain up to a factor of 2 and the output power up to a factor of 1.4 with time at a frequency of 190 MHz and 60 Torr of 1:1:5+5% (C0,:N2:He+Xe) mixture is observed. This is believed to be the result of the gold catalytic activities which are favored by increased electrode temperatures and helium rich gas compositions.During the last two decades rf-excited COz waveguide lasers have received considerable attention1 because of their compactness, discharge stability, and high output power density of more than 1 W/cm.2 They are suitable for many applications where long sealed lifetime from a compact device is required. However, the high-power density in a rf discharge causes severe decomposition reactions of the initial COz:N2:He+Xe gas mixture. The main detrimental reactions to the laser performance that produce both the loss of COz and the buildup of O2 are COz+e--+CO+O+e and/or CO,+e-+CO+O-.

An investigation and optimisation of a single channel transverse RF excited CW sealed CO2 waveguide laser is presented. The laser performance has been studied as a function of various parameters like the excitation frequency, gas pressure, gas mixture composition, and cooling temperature for two pairs of metal electrodes with equivalent sizes, but made of different material -gold plated copper and aluminium. The waveguide structure used was metal-ceramic with an active discharge volume of 2.5x2.5x370 mm3. Single-pass small-signal gain measurements for the two sets of electrodes have been performed, as well.The experiments show that the influence of the electrode material on the laser behaviour is significant, while it was generally accepted as a factor of no importance. The best result we obtained with the Al electrodes was a specific output power of 0.78 W/cm with an efficiency of 1 1% at 125 MHz excitation frequency and 140 Ton of 1:1:5+5% (C02:N2:He+Xe) gas mixture, which is very close to the highest specific power of 0.85 W/cm, previously reported. With the gold plated electrodes a specffic output power of 1. 1 W/cm with an efficiency of about 13 % was achieved at 190 MHz and 100 Ton 1 : 1 :5+5% gas mixture. This improvement is most likely related to the catalytic properties of the gold layers. This favourable process is accelerated at elevated temperatures, so that an intensive cooling is not necessary for good laser performance. The gain measurements confirmed this behaviour. With gold plated electrodes at certain experimental conditions an increase ofthe gain ofa factor 2 was observed.