Superposition device and optical system
A superposition device includes four inputs, each respective input for entry of a respective one of four input beams, an output for exit of an output beam, a first combination device for coherent combination of a first input beam and a second input beam to form a first superposition beam, a second combination device for coherent combination of a third input beam and a fourth input beam 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. 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.
1 . 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.
2 . The superposition device as claimed in claim 1 ,
wherein the interferometer of the first combination device comprises:
a first splitting element for splitting the coherently superposed first input beam and second input beam into the first partial beam and the second partial beam, and
a first combination element for coherent superposition of the first partial beam and the second partial beam to form the first superposition beam,
and/or
wherein the interferometer of the second combination device comprises:
a second splitting element for splitting the coherently superposed third input beam and fourth input beam into the first partial beam and the second partial beam, and
a second combination element for the coherent superposition of the first partial beam and the second partial beam to form the second superposition beam.
3 . The superposition device as claimed in claim 1 , wherein the interferometer of the third combination device comprises a splitting element for splitting the first superposition beam and the second superposition beam into the first partial beam and the second partial beam, and a combination element for coherent superposition of the first partial beam and the second partial beam to form the output beam.
4 . The superposition device as claimed in claim 1 , wherein the interferometer comprises at least one polarization-influencing device for influencing a polarization direction of at least one of the first partial beam and the second partial beam in fixedly predefined fashion.
5 . The superposition device as claimed in claim 4 , wherein the interferometer comprises a splitting element and a combination element in a form of intensity beam splitters, and the interferometer comprises, as the polarization-influencing device, an optical rotator for aligning the polarization directions of the first partial beam and the second partial beam perpendicularly relative to one another.
6 . The superposition device as claimed in claim 5 , being configured to feed the first input beam and the second input beam, the third input beam and the fourth input beam, or the first superposition beam and the second superposition beam, with circular polarization and respective opposite directions of rotation, to the splitting element of the interferometer.
7 . The superposition device as claimed in claim 4 , wherein the interferometer comprises a splitting element and a combination element in a form of polarization beam splitters, and the interferometer comprises, as the polarization-influencing devices, two optical rotators for rotating a polarization direction of a respective one of the first partial beam and the second partial beam by 45°.
8 . The superposition device as claimed in claim 7 , further comprising: at least two polarization-rotating optical elements, arranged upstream of the splitting element of the interferometer in a beam path and configured to rotate a polarization direction of the first input beam and the second input beam, of the third input beam and the fourth input beam, or of the first superposition beam and the second superposition beam by 45°.
9 . The superposition device as claimed in claim 1 , wherein the first combination device for the coherent combination of the first input beam and the second input beam, the second combination device for the coherent combination of the third input beam and the fourth input beam, and/or the third combination device for the coherent combination of the first superposition beam and the second superposition beam have/has an intensity beam splitter or a polarization beam splitter.
10 . The superposition device as claimed in claim 9 , being configured to feed the first input beam and the second input beam, the third input beam and the fourth input beam, or the first superposition beam and the second superposition beam with a respective identical polarization direction, to the intensity beam splitter.
11 . The superposition device as claimed in claim 9 , being configured to feed the first input beam and the second input beam, the third input beam and the fourth input beam, or the first superposition beam and the second superposition beam, having two mutually perpendicular polarization directions, to the polarization beam splitter.
12 . The superposition device as claimed in claim 9 , wherein the first combination device is configured to rotate a polarization direction of the first superposition beam based on a relative phase position between the first linearly polarized input beam and the second linearly polarized input beam,
and/or
wherein the second combination device is configured to rotate a polarization direction of the second superposition beam based on a relative phase position between the third linearly polarized input beam and the fourth linearly polarized input beam,
and/or
wherein the third combination device is configured to rotate a polarization direction of the output laser beam, based on a relative phase position between the first superposition beam and the second superposition beam.
13 . The superposition device as claimed in claim 9 , wherein the first combination device, the second combination device, and/or the third combination device, in order to generate a linear polarization of the first superposition beam, of the second superposition beam, and/or of the output beam, comprises a phase shifting element, arranged downstream of the intensity beam splitter or the polarization beam splitter in a beam path.
14 . The superposition device as claimed in claim 9 , wherein the four inputs are configured for entry of at least four further input beams, and the output is configured for exit of at least one further output beam that is a coherent combination of the at least four further input beams.
15 . An optical system comprising:
a beam source for generating a laser beam,
a splitting device for splitting the laser beam into four mutually coherent input beams,
a phase modulation device for modulating relative phase positions of the four input beams, and
a superposition device as claimed in claim 1 for the coherent superposition of the four input beams to form the output beam.
16 . The optical system as claimed in claim 15 , wherein the splitting device is configured to split the laser beam or a further laser beam generated by the beam source into at least four further mutually coherent input beams, wherein the phase modulation device is configured to modulate relative phase positions of the at least four further input beams, and wherein the superposition device is configured for coherent superposition of the at least four further input beams to form at least one further output beam.
17 . The optical system as claimed in claim 15 , being configured to feed the four input beams to the four inputs of the superposition device with substantially a same power.
18 . The optical system as claimed in claim 15 , being configured to feed the four input beams to the four inputs of the superposition device with linear polarization having a predefined polarization direction or with circular polarization.