High power PCF-based pump combiners

We present record-breaking experimental data on high power transmission through novel 7X1 and 19X1 multimode combiners based on Photonic Crystal Fiber technology. Both combiners are monolithic, have losses of similar to 0.2 dB, show very high thermal robustness and can handle record high optical powers. We have transmitted 100 W through the 7X1 and 310 W through the 19X1 combiner without evidence of any degradation or critical heating. The powers were limited only by available pump power. The combiners are based on Air-clad technology, where a ring of air-holes running along the length of the device provide guiding for the light. This Air-clad offers three major advantages for the device: 1: It is well suited for high optical powers as no polymer coating gets into contact with the light; 2: it is much easier to package as mechanical contact can be made anywhere on the device without risk of optical performance penalty; 3: the Numerical Aperture of the light can be increased beyond the limits imposed by polymer coatings. The presented pump combiners are especially well suited for high power fiber lasers, since such combiners can be spliced directly onto the active fiber, thereby enabling a robust, stabile laser solution with excellent efficiency and beam quality.