Mode properties of unstable off-axis resonators with large Fresnel numbers

Off-axis unstable resonators play an important role for high-power diffusion-cooled CO2-laser with slab geometry. Mode properties of these unstable resonators are invesitgated by means of direct iterative diffraction calculations. The method of resonance excitcation that has formerly been applied to stable resonators is used to obtain a set of low order modes. Far-field properties and beam quality of these modes are discussed and compared with experimental results.