Lasers transverse modes are often selected by the Fresnel number of the resonators. However, the Fresnel number of the thickness direction and width direction is very different in slab lasers, so lasers transverse modes of the thickness direction and width direction can not be selected only by the length of the resonators at the same time. The output coupling mirror with one-dimensional variable reflectivity is used in the stable/unstable resonators. The structure can select the low transverse modes of the thickness direction and width direction at the same time. In this paper, the losses of different resonators have been calculated. The theoretical analysis has been verified by the results of the preliminary experiments.