Habich, U.U.HabichDu, K.K.DuBauer, A.A.BauerPlum, Heinz-DieterHeinz-DieterPlumLoosen, PeterPeterLoosen2022-03-082022-03-081997https://publica.fraunhofer.de/handle/publica/303657The description refers to a laser resonator for the utilization of media having an annular-shaped cross-section and two end mirrors. The invention is characterized by the end mirrors having a torus-shaped surface and an end mirror having at least opening through which the laser beam can be coupled out.de608621patent1990-4028170