Coherent Beam Combination of Ultrafast Fiber Lasers

The performance of fiber laser systems has drastically increased over recent decades, which has opened up new industrial and scientific applications for this technology. However, currently a number of physical effects prevents further power scaling. Coherent combination of beams from multiple emitters has been established as a power scaling technique beyond these limitations. It is possible to increase the average power, and for pulsed laser systems, also parameters such as the pulse energy and the peak power. To realize such laser systems, various aspects have to be taken into account that include beam combination elements, stabilization systems, and the output parameters of the individual amplifiers. After an introduction to the topic, various ways of implementing coherent beam combination for ultrashort pulses are explored. Besides the spatial combination of beams, the combination of pulses in time will also be discussed. Recent experimental results will be presented, including multidimensional (i.e., spatial and temporal) combination. Finally, an outlook on possible further developments is given, focused on scaling the number of combinable beams and pulses.