Power scaling of laser systems can be achieved by coupling individual laser sources. The total power at the target is then the sum of the individual contributions. But the intensity distribution depends on the type of coupling. Due to the wave nature of the laser radiation, a significant increase in the peak intensity can be achieved by the principle of interference effects through the superposition of multiple sources. For this purpose, the individual waves must have a constant phase relative to each other. In the simple superposition of individual sources, this is usually not the case; the peak intensity obtained is at most the sum of the individual intensities. For coherent coupling, the beams of the individual emitters must have a constant phase relative to each other. The individual lasers can thus be regarded as sub-apertures of a single laser source, similar to the diffraction of a two-dimensional grid. In the coherent coupling of N sources, this results in an interference pattern with up to N times the peak intensity with respect to simple superposition. The active phase manipulation and control necessary for this is being studied in oscillator-amplifier systems at the Institute of Technical Physics, and has already been successfully demonstrated.