Superposition device and optical system

A superposition device for the coherent superposition of four mutually coherent input beams to form an output beam, the superposition device comprising:

• four inputs, each respective input for entry of a respective one of the four input beams,
• an output for exit of the output beam,
• a first combination device for coherent combination of a first input beam and a second input beam of the four input beams to form a first superposition beam,
• a second combination device for coherent combination of a third input beam and a fourth input beam of the four input beams to form a second superposition beam, and
• a third combination device for forming the output beam by coherent combination of the first superposition beam and the second superposition beam,
• wherein the superposition device is configured to set both a polarization direction and a power of the output beam independently of one another based on relative phase positions of individual phases of the four input beams fed to the four inputs in relation to one another;
• wherein each of the first combination device, the second combination device, and/or the third combination device comprises or forms an interferometer, with a first beam channel for propagation of a first partial beam and a second beam channel for propagation of a second partial beam.