Coherent Beam Combination of Ultrafast Fiber Lasers

Abstract

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.

Ultrafast Fiber Lasers: An Expanding Versatile Toolbox

“…To further scaling pulse energy and average power, divided pulse amplification (DPA) (Zhou et al, 2007) and coherent beam combining (CBC) are introduced into fiber CPA systems. A thorough review of this technique can be found in Hanna et al, 2016;Klenke et al, 2018. The red circles in Figure 4 present recent Yb-fiber CPA systems incorporating DPA and CBC (Kienel et al, 2016;Klenke et al, 2013Klenke et al, , 2014Mueller et al, 2020;Muller et al, 2016Muller et al, , 2018Stark et al, 2019); femtosecond pulses with >100 mJ energy and >10 kW average power are expected in the near future.…”

Coherent combining of high brightness tapered amplifiers for efficient non-linear conversion

“…Different approaches have been demonstrated: active phase locking of amplifiers seeded by a single frequency laser split into several beams or passive phase locking of emitters in an extended cavity [14]. Impressive results for CBC using a limited number of high power fiber amplifiers (P > 100W per channel) show the potential of power scaling by CBC reaching kW level powers [15,16]. CBC with diode lasers and amplifiers is still limited to lower power levels but has been demonstrated in various configurations.…”

Adaptive Nonlinear Phase Compensation in a Femtosecond Hybrid Laser with Varying Pulse Repetition Rate

“…This is especially true in fiber lasers, where the high-energy pulses are confined to a small fiber core. To overcome this problem, many advanced techniques have been demonstrated, among which is coherent beam combining [14,15], pulse stacking [16], the use of tapered fiber amplifiers [17,18] and the use of optical fibers with large core diameters [19,20]. Although these systems offer some outstanding results in terms of power scaling, their relative complexity hinders their applicability in industrial laser applications.…”