LAUSR

A breakthrough result of a kW-level Nd: YAG slab laser with a unidirectional unstable ring resonator is presented. The reverse wave is efficiently suppressed by a diaphragm placed at the focal point of the negative-branch unstable ring resonator. With specifically developed multi-function sensor and precision placement of the diaphragm, we have achieved the maximum output power of 1350 W with reverse suppression ratio of 54:1 corresponding to an optical–optical efficiency of 21.6% and a slope efficiency of 33.7%. The output power is currently limited by the available pump power. To the best of our knowledge, this is the highest power demonstrated from an Nd: YAG slab laser based on an unstable ring resonator with efficient reverse wave suppression, which is a paramount step to the further development of high power solid-state unidirectional ring lasers.