A novel side coupling technique for rugged all-fiber lasers and amplifiers

A novel side coupling technique between two multimode high NA fibers is described. The technique is used to efficiently pump fiber lasers and amplifiers by low brightness fiber coupled pump diodes. With the presented technique, identical multimode fibers with 0.46NA and core diameters extending from 125mm to 400mm, can be coupled together, and provide pump coupling efficiency of >90%. Direct coupling to a rare-earth doped fiber is possible. In this configuration one fiber is used as the pump guiding fiber and the second fiber is the rare-earth doped double clad fiber. By utilizing the presented pump coupling technique, highly efficient, rugged and low cost short pulse and CW all-fiber lasers were implemented, with average output power extending to 300W and peak power of 600kW.