ABSTRACT
A novel cavity design based on a stable resonator configuration is presented. The output coupler of the new stable resonator has a circular partial-reflection region in the center that is surrounded by an antireflection region. This resonator operates in a large-volume TEM(00) mode that is mainly determined by the partial-reflection region of the output coupler and is characterized by the use of an additional laser beam that is spread from the optical path in the cavity because of diffraction and is amplified by a laser medium. By combining part of a beam transmitted from the partial-reflection region with the amplified diffraction beam, a laser beam having a large diameter is obtained. A diffraction-limited output beam with the M(2) factor of 1.3 is obtained, as predicted theoretically when the new stable resonator is applied to a high-power cw CO(2) laser.