Sequential splicing of high power suitable fiber arrays

Delivering high power via fibers, and scaling the power level via arrays of such fibers is a crucial topic in many field of high power applications, in particular for materials processing, but also for long range energy delivery and others. Monolithic fiber connections to end caps, already known from freespace to fiber coupling of kW of optical power, can be expanded to 1D or even 2D fiber arrays, using a CO2-laser to splice each fiber sequential to an end cap substrate. As the CO2 laser radiation melts the glass at its surface, it realizes a monolithic glass-to-glass bond, enabling kW levels of power transmission through this interface without catastrophic damage. We report about an axicon setup for a ring-shaped CO2 laser focus illumination of local areas on an end cap substrate, to bond single or multimode fibers with a pitch of down to 250 micron in 1D or even 2D arrays to the substrate, at a lateral positioning tolerance <10 micron. A structured illumination of the ring allows for not damaging the previously assembled fibers, and the quality of bond enables high power transmission at lowest wavefront deformations.