The optical resonator is formed by the front and rear mirrors and two parallel RF-electrodes. Excitation of the laser gas takes place in the RF field between the water-cooled electrodes. The heat generated in the gas is dissipated by the water-cooled electrodes (diffusion-cooled). Thus, the conventional gas circulation systems involving roots blowers or turbines are not required. A beam shaping module is integrated into the laser head and produces a high quality round symmetrical beam. The resonator design produces a 45° linearly polarized beam.