Quasi-optical launcher converter designs for high power gyrotrons use perturbations of the waveguide surface to convert the high order cavity mode to a Gaussian like beam. These designs of these converters is based on an analytic theory that specifies the mode amplitudes to obtain a Gaussian like distribution of the field in the azimuthal and axial directions. This approach can generate a beam with high Gaussian content and low diffraction losses. However, by optimizing the mode amplitudes to obtain a Gaussian like distribution of the field in the radial (instead of the azimuthal) direction, designs with significantly less diffraction loss, reduced beam divergence angles and higher Gaussian beam content can be achieved.