Fast axial laser circulating system

This patent describes a fast axial flow folded resonator cavity. It comprises: a resonator mirror mounting member; a high reflector resonator mirror mounted to the resonator mirror mounting member; a resonator output mirror mounted to the resonator mirror mounting member positioned substantially parallel with respect to the high reflector resonator mirror; a retroreflector mounting member positioned opposite to the resonator mirror mounting member. The retroreflector mounting member including first, second and third planar mounting surfaces; at least two substantially parallel discharge-confining bore tubes extending from the resonator mirror mounting member to the retroreflector mounting member. The parallel discharge-confining bore tubes providing parallel beam paths; and first, second and third fold mirrors mounted to the first, second and third planar surfaces of the retroreflector mounting member and adapted to fold the beam paths substantially 180 degrees with respect to each other while providing angular stability for rotations of the retroreflector mounting member in any direction has been changed to a first plane defined by the parallel beam paths, and angular stability in second and third planes which are substantially orthogonal to the first plane.