Confocal unstable optical resonator with asymmetrical magnification

The appropriate combination of spherical and cylindrical mirrors allows one to arrange an unstable laser cavity with asymmetrical magnification and to generate collimated output as well. By introducing two additional cylindrical mirrors into the cavity the aberration problems of tilted mirror systems are avoided. On the other hand, this modification is a low-cost alternative to cavities with diamond-turned mirrors with ellipsoidal surface curvature. In the geometrical-optics limit there exists a unique combination of mirror radii of curvature for a given ratio of magnification at fixed distances between the mirrors.