Splicing and end facet optimization of large-mode-area photonic crystal fiber for high power application

In recent years, there is a very fast development in high power fiber laser technology. However, problems like strong nonlinear effect, thermal injury at the fiber end facet and so on arise with increase of the laser power. One of the promising methods is to use rare earth-doped photonic crystal fiber (PCF) with a large mode area as gain medium, but the commonly used free-space coupling method limits efficiency, flexibility and stability of fiber lasers. Here we use a kind of double-clad large-mode-area PCF of 500 μm outer diameter to splice with the traditional solid fiber and achieved a high power coupling ratio up to 72%. We also optimize the end facet quality of the PCF at the output port to obtain a good output.