Relaxed alignment tolerance of monolithic ring lasers

An investigation of relaxed alignment tolerance in monolithic ring lasers is presented. It was found that the relaxed alignment tolerance is strongly dependent on the out-of-plane angle. A preferred region for the out-of-plane angle is proposed. In this region the resonator has greatly relaxed alignment tolerances, and the unidirectional operation can be obtained under a much-lower magnetic field. Two lasers have been constructed in the region, and satisfactory performance was found, in good agreement with the theoretical analysis.