All-fiber side pump combiner for high-power fiber lasers and amplifiers

Abstract

We present an all-fiber side pump combiner for high power fiber lasers and amplifiers. It consists of a capillary with decreasing wall thickness fused around the active fiber in a way that it becomes an additional cladding layer of it. The pump fibers are spliced at the edge of the capillary with the thickest wall. This provides enough room to allocate around 12 pump fibers (100μm diameter) in a standard 400μm double-clad fiber. This side pump combiner offers several advantages such as the fact that it does not interrupt the active fiber core at any point, thus allowing for truly monolithic all fiber lasers and amplifiers. Additionally, the pump light is coupled into the active double-clad fiber all along the combiner's body (~ 1-2 cm long), which avoids the concentration of heat in a very small area, resulting in high pump power handling capabilities. If the taper angle of the capillary wall is low enough a high coupling efficiency (< 95%) is possible. Using this structure we have achieved a maximum combined pump power of 86 Watt from 7 pump diodes. This, we believe, is the highest combined pump power reported so far from a single lumped side pump combiner.