Compact laser beam combiner

Solid-state laser resonators’ operational repetition rate and average output power are often limited by thermal effects including thermally induced lensing in the gain media. Changes in the average pumping power cause changes in the resonator’s stability, which results in changes to the output power, divergence and beam quality. To produce higher repetition rates and/or higher average power systems, laser engineers often combine the outputs of multiple resonators. We report on the development of a compact method of beam combination using a rotating rhomboid prism. The prism is mounted on a motorized rotational stage and sequentially directs the output from multiple parallel resonators into a single beam. Rhomboid prisms are inherently insensitive to misalignment, so the entire system is very compact, stable, and simple to align. The first several iterations were used for combining four Ho:YAG resonators resulting in a system with a 2.13μm output of over 200 watts at 40Hz. Although the methodology was initially demonstrated with Ho:YAG resonators, it is flexible and may be used for combining different types of lasers including multiple wavelengths.