EP4327420A2

EP4327420A2 - Combining device and optical system

Info

Publication number: EP4327420A2
Application number: EP22773589.1A
Authority: EP
Inventors: Malte Kumkar; Daniel Grossmann
Original assignee: Trumpf Laser und Systemtechnik GmbH
Current assignee: Trumpf Laser und Systemtechnik GmbH
Priority date: 2021-04-23
Filing date: 2022-04-22
Publication date: 2024-02-28
Also published as: US20240045223A1; US20240045222A1; CN117178442A; WO2022223780A2; EP4327419A1; WO2022223761A1; CN117178443A; WO2022223780A3; DE102021204057A1

Abstract

The invention relates to a combining device (3) comprising: at least two inputs (E₁, E₂, ...) for the input of a respective input beam (1.1, 1.2, …), and one or more outputs (A₁, A₂, ...) for the output of a respective output beam (2.1, 2.2, …), with the combining device (3) being designed to form a respective output beam (2.1, 2.2, …) by coherent combination of two of the input beams (1.1, 1.2, …). The combining device (3) is designed to set a polarization state, more particularly a polarization direction (R), of the respective output beam (2.1, 2.2, …) on the basis of a relative phase angle (Δφ₁₂, …) of the individual phases (φ₁, φ₂, ...) of the two input beams (1.1, 1.2, …) from which the respective output beam (2.1, 2.2, …) is formed by the coherent combination. The invention also relates to an optical system comprising at least one combining device (3) which is designed as described further above.

Description

Combination device and optical system

The present invention relates to a combination device, comprising: at least two inputs for each entry of an input beam, and one or more outputs for each exit of an output beam, wherein the combination device is designed to combine one (or the) output beam by a coherent combination of two of the to form input beams.

The input beams, which are generally mutually coherent, and the output beam(s) formed in the coherent combination are typically laser beams. The combination device described here is preferably designed to superimpose the input beams collinearly, it being possible in particular for a congruent superimposition to the or to a respective output beam to take place.

The interaction of laser radiation with an object to be processed (workpiece, target, substrate, ...) depends on many laser parameters, for example wavelength, intensity or power, pulse duration, repetition rate, pulse shape or else of other parameters such as the beam shape. Depending on the type of object to be processed, the polarization of the laser radiation can also have an impact on the interaction. It can therefore be important for some applications to set the polarization in a targeted manner. In this case, fast polarization switching is usually required to increase productivity. For example, applications such as data storage can be productively implemented in a medium.

Fast polarization modulation can generally be realized by interferometric systems into which a single input beam is coupled and in which the phase is manipulated by phase shifters integrated into the interferometer, see, for example, the article “The rotating linearly polarized light from a polarizing Mach-Zehnder Interferometer: Production and applications”, C. Pawong et al., Opt. Lasers Tee. 43, 461-468 (2011), or the article "Investigation of the use of rotating linearly polarized light for characterizing S1O2 thin-film on Si Substrate", C. Pawong et al., in: Optoelectronic Materials and Devices, G. Duan , ed., Vol. 8308 of Proceedings of SPIE (2011), paper 830811, or DE 102017 104392 A1.

US 2009/0219960 A1 describes a device for superimposing laser beams that has a phase and polarization module that is designed to provide a plurality of laser beams that are phase-locked and orthogonally polarized in pairs. The apparatus includes a controller configured to control the phase and polarization of each laser beam, and a beam combiner for combining a first and a second of the laser beams to produce an output laser beam.

object of the invention

The invention is based on the object of providing a combination device and an optical system with at least one such combination device which enable the polarization state of at least one output beam to be set quickly.

subject of the invention

This object is achieved according to the invention by a combination device of the type mentioned at the outset, which is designed to set a polarization state, in particular a polarization direction, of the respective (or the) output beam as a function of a relative phase position of the individual phases of the two input beams from which the respective Output beam is formed by the coherent combination.

In this case, the coherent combination of (each) two of the input beams makes it possible to quickly modulate or manipulate the properties of the or a respective output beam by quickly manipulating the relative phase position of the input beams. The inventive In the simplest case, the combination device has two inputs and one output and is designed to combine the two input beams entering at the inputs coherently into (exactly) one output beam exiting at the (exactly one) output.

Alternatively, the combination device has more than two inputs and more than one output. In this case, the combination device is designed to form a respective output beam by a coherent combination of two of the input beams entering at the more than two inputs. The polarization state, in particular the polarization direction, of the respective output beam is also in this case (only) determined by the relative phase position of the two input beams from which the output beam is formed in the coherent combination, i.e. the relative phase position of the other input beams has no influence on the Polarization state of this output beam. In this way, the polarization state of a respective output beam emerging from one of the outputs can be adjusted independently of the polarization state of the output beams emerging from the other outputs.

The combination device can be a passive device that does not have any optical elements whose optical properties can be adjusted. If the combination device has optical elements whose optical properties can be adjusted, eg phase shifters, optical rotators, etc., such an adjustment is not usually used to dynamically adjust or adjust the polarization state and, if applicable, the power of the output beam modulate, but typically only to correct undesired, for example, temperature-related changes in the optical properties of the optical components of the combination device, in order to allow in this way, for example, a complete constructive interference of the input beams. The combination device can have conventional optical components for the coherent combination. However, an implementation based on PIC (“Photo Integrated Circuit”) is also possible. The polarization state of the (respective) output laser beam is typically set solely by setting or specifying the relative phase position of the individual phases of the respective two coherently combined input beams with respect to one another. The absolute phase of the input beams is irrelevant for the superposition, so that one phase modulation unit for each pair of superimposed input beams is usually sufficient to set the relative phase position. The setting of the polarization state of the (respective) output beam by specifying or setting the (relative) phase angles of the input beams with the aid of the phase modulation unit can take place highly dynamically with switching durations, for example in the MHz range.

By arranging a phase modulation unit in front of the combination device, it is not necessary for the phase modulation unit to provide the output beam with the required output parameters directly from an input beam. This allows, for example, the use of less powerful components for the modulation of the relative phase angles, in that the power required for the combination device is achieved by amplification downstream of the phase modulation unit. In addition, in the case of input beams generated by an ultrashort pulse laser, the power in the phase modulation unit can be reduced by switching time-extended pulses. Optical components with increased losses can also be used without this having a severely negative effect on the efficiency of the overall system. The modulation of the relative phase angles of the input beams can also take place at a different wavelength than at the wavelength of the output beam.

In one embodiment, the combination device has exactly two inputs and one output and comprises a polarization beam splitter for the coherent combination of the two input beams entering at the inputs to form the output beam, as well as a phase shifting element, in particular a 1/4 delay device, arranged in the beam path after the polarization beam splitter Generation of a linear polarization of the output beam. In this embodiment, the polarization of the two input beams is selected in such a way that the maximum power (ideally the entire power) is transferred to the output beam. For this purpose, the polarization of the first input beam is typically chosen such that its transmission at the PBS is maximum and the polarization of the second input beam is chosen such that its reflection at the PBS is maximum (or vice versa). This can be achieved in that the two input beams are each polarized linearly and perpendicularly to one another and the polarizer axis(s) are aligned parallel to the two mutually perpendicular polarization directions of the input beams. In the loss-free case, the sum of the output powers of the two input beams can be converted into the power of the output beam (see above). The power/energy of the output beam can optionally be adjusted by the additional synchronous adjustment of the power/energy of the two input beams.

Assuming the input parameters chosen for the coherent coupling with high interference contrast, in the case of the coherent combination of the input beams entering the polarization beam splitter, an elliptically polarized outgoing beam is formed in the general case, in which the semi-axes (principal axes or directions) of the elliptical polarization under 45° to the two mutually perpendicular polarization directions of the input beams (if these are linearly polarized). By aligning the preferred axis of a 1/4 retardation device with the preferred direction of 45°, the elliptical polarization is converted into a linear polarization whose polarization direction is determined by the main axis ratio and the sense of rotation of the elliptical polarization. Adjusting the relative phase position between the input beams entering the polarization beam splitter changes the aspect ratio between the semi-axes of the elliptical polarization, but not the orientation of the semi-axes at 45° to the two mutually perpendicular polarization directions. Therefore, by adjusting the relative phasing of the input beams, the direction of polarization of the linearly polarized output beam can be adjusted.

In an alternative embodiment, the combination device has two inputs and one output and includes an interferometer, in particular a Mach-Zehnder interferometer, with a first beam channel for propagating a first partial beam and with a second beam channel for the propagation of a second partial beam, wherein the interferometer has a splitting element for splitting the two input beams into the two partial beams and a combination element for the coherent combination of the two partial beams to form the output beam and preferably at least one polarization influencing device for the preferably permanently specified Influencing a polarization state, in particular a polarization direction, having at least one of the partial beams.

With the aid of an interferometer, in particular a Mach-Zehnder interferometer, the state of polarization or the direction of polarization of the output beam can be adjusted by controlled adjustment of the phases of the individual input beams. The interferometer usually has at least one optical component or a combination of optical components for phase and/or polarization adjustment between the two partial beams or between the two beam channels, in order to ensure that with a suitable choice of the relative phase position of the two partial beams to each other maximum constructive interference occurs at the combination element at which the coherent superimposition of the two partial beams takes place. In this embodiment, the path length difference of the two partial beams in the interferometer is adjusted in such a way that maximum constructive interference occurs, i.e. the sum of the powers of the two input beams corresponds to the power of the output beam in the loss-free case. In order to be able to set any desired angle of the polarization direction, the power of the two superimposed partial beams is chosen to be the same, and different losses in the combination device are precompensated, as in other embodiments, by appropriate adjustment of the power of the input partial beams.

In the embodiment described here, the interferometer preferably has at least one polarization influencing device for influencing a polarization state, in particular a polarization direction, of at least one of the partial beams, in particular in a fixed manner. The polarization state of one or both partial beams can be influenced by a suitable polarization influencing device in such a way that at least one phase angle of the two partial beams relative to one another at the combination element is maximum constructive interference occurs. A permanently predetermined influencing of the state of polarization is understood to mean that the state of polarization is not dynamically influenced, since the dynamic setting of the state of polarization of the output beam takes place solely by setting the relative phase angles of the input beams. However, the polarization influencing device can in principle be designed to be controllable in order to compensate for different parasitic losses in the two beam channels, thermal effects, etc.

The polarization influencing device(s) are preferably in the form of polarization-rotating optical devices or elements (polarization rotators), in particular in the form of optical rotators, for example in the form of optical crystals which, given their crystalline structure and with a suitable orientation, have an intrinsic polarization rotation. e.g. crystalline quartz, which has a high transparency and performance capability in a broad wavelength range from UV to NIR. In principle, Faraday rotators can also be used as a polarization influencing device. However, Faraday rotators require an external magnetic field for polarization rotation and are therefore more complex to manufacture and operate than optical crystals. For the present application, it is favorable or necessary for the polarization rotation of the partial beam(s) to take place independently of the polarization direction of the respective partial beam. Such a polarization rotation is typically not possible with birefringent retardation devices, e.g. with 1/2 retardation elements, since these allow a rotation of the polarization direction only with a predetermined polarization direction of the respective partial beam.

The splitting element and the combination element can be embodied as intensity beam splitters, for example, and the interferometer can have at least one polarization-rotating optical device, in particular an optical rotator, as a polarization influencing device for perpendicular alignment of the polarization directions of the two partial beams relative to one another. Under an intensity beam splitter is understood in the context of this application, a beam splitter that is a split or combination of two or more partial beams in Essentially allows regardless of their polarization state. The intensity beam splitters described here are generally designed as 50% beam splitters, ie they combine two beams entering the intensity beam splitter with the same weighting to form one exiting beam. The intensity beam splitter can be implemented, for example, in the form of a dielectric layer system on the surface of a transparent substrate. With a suitable alignment of the surface to the beam incidence direction, the desired polarization-independent reflectivity and transmission of essentially 50% each can be achieved.

In the simplest case, to align the polarization directions of the two partial beams, an optical rotator can be arranged in one of the two beam channels of the interferometer, which rotates the polarization direction of the partial beam propagating in this beam channel by 90°. However, it goes without saying that two or possibly more than two polarization-rotating optical devices or elements can be arranged in the beam channels of the interferometer in order to align the polarization directions of the two partial beams at an angle of 90° relative to one another.

For the formation of a linearly polarized output beam in the interferometer, it is typically necessary for the two input beams with circular polarization and opposite directions of rotation to be fed to the splitting element of the interferometer. In this case, the two partial beams in the beam channels each have a linear polarization with two polarization directions aligned perpendicular to one another. By rotating the polarization direction of one of the two partial beams by 90° in the optical rotator, the polarization directions of the two partial beams, which are coherently combined by the combination element, are aligned in parallel. In this case, the relative phase position of the two input beams can be used to set the polarization direction of this linearly polarized output beam.

In a further embodiment, the combination device has more than two inputs and more than one output and is designed to combine a respective output beam exiting at an output with a coherent combination to form two of the input beams entering at the more than two inputs. The basic types of combination device described above with two inputs and one output, in which the coherent combination of the two input beams to form the output beam takes place by means of a polarization beam splitter or by means of an interferometer, can - suitably modified - also be used in a combination device that has more than has two inputs and more than one output (“multi-channel coupling device”), as described in more detail below.

In a development of this embodiment, the combination device has a number of inputs that is twice as large as the number of outputs. In this development, the combination device is, in the simplest case, a parallel arrangement of coupling devices that correspond to one of the two basic forms described above with the two inputs and one output. However, it is also possible for the coupling device to retain the basic structure of the respective basic form, i.e. its optical components (possibly apart from their dimensions) and only the number of inputs or input beams and the number of outputs or output beams is scaled by a factor N. In the simplest case, the first input of the combiner described above is replaced by a set of N first inputs through which N collimated input beams enter the combiner. Correspondingly, the second input is replaced by a group of N second inputs through which N further collimated input beams enter the combiner. In this case, the respective pairs of input beams, which are combined to form one of the output beams, pass through the optical components of the combining device with a lateral offset and emerge from the coupling device at one of N outputs.

In this development, an output beam can also be generated from two superimposed input beams which—apart from parasitic losses when passing through the optical components of the combination device—corresponds to the sum of the powers of the two input beams. The combination device thus makes it possible at the respective output to create a complete constructive interference of the input beams, so that the output beam has the maximum possible power (100% of the sum of the powers of the input beams).

The power of the input beams that enter the combination device at the respective inputs is typically essentially the same for all input beams, i.e. the power of a respective input beam is not used to dynamically adjust the polarization state or, if necessary, the power of the output beam. In principle, however, it is possible to deviate (usually slightly) from an identical intensity of the input beams in order to ensure the above-described complete constructive interference of the input beams when they are superimposed on the output beam. This can be necessary, for example, if the losses of the input beams are of different magnitudes as they pass through the combination device.

In a further development, the combination device for the coherent combination of in each case two of the input beams entering at the inputs to form a respective output beam has a polarization beam splitter which is preferably common to all input beams and, for generating a linear polarization of the respective output beam, has a phase shifting element which is arranged in the beam path after the polarization beam splitter and is preferably common to all output beams , In particular a 1/4 delay device. As described above, when there is a common polarization beam splitter for all input beams, the input beams of a respective group pass through the polarization beam splitter laterally offset and the output beams pass through the common phase shifting element laterally offset. It goes without saying that alternatively several polarization beam splitters and several phase shifting elements can be used in the combining device in order to coherently combine the respective pairs of input beams into a respective output beam or to generate a linear polarization for a respective output beam.

In a further development, the combination device is designed to feed two input beams to be combined to the polarization beam splitter, which have two polarization directions perpendicular to one another, the combination device preferably having a polarization-rotating device for rotating a polarization direction in the beam path upstream of the polarization beam splitter, in each case one of the two input beams which are combined at the polarization beam splitter to form the respective output beam. The polarization-rotating device can be used when the combination device is supplied with the input beams each having the same linear polarization direction, in order to rotate the polarization direction of one of the input beams and to supply the two input beams with mutually perpendicular polarization directions to the polarization beam splitter. Since the direction of polarization of the input beams is predetermined, in this case polarization can be rotated by means of a polarization-rotating device in the form of a birefringent retardation device, for example in the form of a 1/2 retardation element. The direction of polarization of one of the two groups of N input beams can be rotated with the aid of a common polarization-rotating device.

Correspondingly, an alternative embodiment of the combination device with groups of N first input beams and N second input beams for generating a group of N output beams with one interferometer or up to N interferometers can also be provided.

In an alternative development of the embodiment described above, the combination device has at least one splitting element for splitting a respective input beam into two partial beams and preferably at least one combination element for coherently combining two of the partial beams to form a respective output beam. In this embodiment, the power of a respective input beam is divided into two sub-beams (usually preferably equally divided, ie 50:50) prior to coherent combination, one of which is combined with a respective sub-beam of another input beam to form one of the output beams. In the case described here, it is therefore typically required that all input beams, or at least each input beam and two to be superimposed on it, be coherent with one another, while in the alternative embodiment described above this is only for each requires two of the input beams to be coherently combined into a respective output beam. In this case, the relative phase position of the two input beams, whose partial beams are combined coherently to form an output beam, can be used to set the polarization state of the respective output beam, ie the polarization state of a respective output beam can be set individually. Typically, in this case, all input beams have the same amplitude and polarization state.

In a development of this embodiment, the combination device has a number of inputs that is greater by one than a number of outputs. Since a number of 2 N + 2 partial beams are generated at the splitting element when the N + 1 input beams are divided, but only N outputs are available, the power of an input beam (more precisely the sum of the powers of two partial beams) is lost in this development. In the case described here, the entire power of the input beams is not converted into the power of the (two or more) output beams, i.e. the power of the output beams does not correspond to 100% of the sum of the powers of the input beams. This power of the two partial beams that are not used for the coherent combination can be used as diagnostic beams. As described above, the input beams typically enter the combiner at the inputs laterally offset from one another, and the inputs are typically also laterally offset from one another. The two sub-beams that are not combined coherently and that are used as diagnostic beams are typically sub-beams of two input beams entering the combiner at the first input and the last input (N+1). The diagnostic beams can be evaluated directly or superimposed for diagnostic purposes. The development described here is advantageous if a large number of output beams is desired, since these can be generated with a small number of input beams.

Polarization beam splitters, for example, can be used as the splitting element(s) and as the combining element(s). In this case, polarization can be a respective input beam entering the combination device, be elliptical, with a preferred direction of the elliptical polarization being aligned at 45° to the s-component or to the p-component of the polarization beam splitter. However, the polarization of a respective input beam is preferably chosen to be either linearly or circularly polarized. If the linear polarization is aligned at 45° to the s or p component of the polarization beam splitter, the power of a respective input beam is divided equally between the partial beams. As in the above-described embodiments, a phase shifting element, in particular a 1/4 delay device, can be arranged in the beam path downstream of the polarization beam splitter serving as a combination element, possibly common to all output beams, in order to generate linear polarization of the respective output beam.

In a further development, the combination device has a number N+1 of polarization beam splitters, which corresponds to the number N+1 of input beams and each serve as a splitting element, and a number N of polarization beam splitters reduced by one serves as a combination element. In this embodiment, exactly one polarization beam splitter is assigned to each input, which splits the respective input beam into two partial beams. The polarization beam splitters are arranged in such a way that in all but one of the polarization beam splitters, one of the partial beams propagates in the direction of the respective output, while the other partial beam in each case is deflected to an adjacent polarization beam splitter and is coherently superimposed with the partial beam that is passing through it is transmitted and propagated to the respective output. In this embodiment, the polarization beam splitters are usually arranged next to one another in a row. The two PBS that do not serve as a combiner are typically the first and last of the PBS in this row. The path length differences occurring when the partial beams are combined at the polarization beam splitters arranged in the row can be pre-compensated for a good coherent combination. For the suppression of undesired interference effects between the individual output beams, it can be advantageous if a time offset is generated between the output beams in pulsed operation, which is achieved by compensating for the path length difference is favored. The embodiment described here manages without deflection elements and is easily scalable.

In an alternative development, the combination device has a common polarization beam splitter as a splitting element common to all input beams and/or the combination device has a common polarization beam splitter as a combination element common to all output beams. In particular, one and the same polarization beam splitter can serve as a common splitting element and as a common combining element. The partial beams that are generated at the common splitting element in the form of the polarization beam splitter can be deflected back to the polarization beam splitter at a respective deflection device, for example in the form of a deflection mirror, in order to carry out the coherent combination of the partial beams. This development can also be implemented in a compact design.

It goes without saying that a group of input beams that does not include all of the input beams can also be divided at a common splitting element and/or combined at a common combining element. In principle, the input beams can be variably combined into groups which are each divided at a common splitting element and/or combined at a common combination element or which are split at a respective individual splitting element and/or combined at a respective individual combination element.

In an alternative development, the combination device has an interferometer, in particular a Mach-Zehnder interferometer, which includes a first beam channel for propagating a first sub-beam and a second beam channel for propagating a second sub-beam, with the interferometer having a further splitting element for dividing the partial beams from two different input beams into the two beam channels and preferably at least one polarization influencing device for influencing a polarization state, in particular a polarization direction, in particular in a fixed manner, at least one of the partial beams. This embodiment basically corresponds to the basic form of the combination device described above, which has two inputs and one output as well as an interferometer for the coherent combination. The embodiment described here differs from the embodiment described above in that the interferometer, more precisely the further splitting element, is fed not two input beams, but two groups of partial beams, each group belonging to one of the two partial beams of a respective input beam, which at which (at least one) splitting element was created. One partial beam from each of the two groups is fed to the further splitting element of the interferometer, where the splitting into the two beam arms takes place. Since a coherent combination of the two partial beams takes place at the further splitting element of the interferometer, the partial beams propagating in the two beam arms are referred to as sub-partial beams. The sub-beams can be combined to form a respective output beam, as in the embodiment described above, at a combination element that is part of the interferometer.

In this case, too, the state of polarization of a respective output beam can be adjusted as a function of the relative phase position of the respective input beams, as described above. The path length of the sub-beams in the two beam arms of the interferometer is set in such a way that there is maximum constructive interference at the respective output. In this way, half the sum of the powers of the respective superimposed partial beams of the input beams can be converted into the power of the corresponding output beam.

In a further development, the combination device is designed to supply the further splitting element with two partial beams of different input beams that are circularly polarized in opposite directions, with the combination device preferably having at least one phase-influencing element for influencing the phase of one of the two partial beams. The phase-influencing element can be, for example, a Act half-wave delay element through which the sense of rotation of the circular polarization is reversed.

The partial beams, which are split between the two beam arms at the further splitting element of the interferometer, are typically circular and polarized in opposite directions to one another. In this case, with the aid of the polarization-rotating device in the interferometer, the perpendicular alignment of the polarization direction of the partial sub-beams in the two beam arms can be converted into a parallel alignment, as was described further above. In order to generate the partial beams which are circularly polarized in opposite directions, for example input beams with circular polarization of the same direction of rotation can be provided at the inputs of the combination device. The (at least one) phase-influencing element can be used to influence the phase of one of the two partial beams that are generated at the splitting element in such a way that the direction of rotation of the circular polarization of this partial beam is reversed, so that the two partial beams at the further splitting element of the interferometer have opposite circular polarization.

The invention also relates to an optical system, comprising: a beam source for generating a laser beam, a splitting device for splitting the laser beam into at least two coherent input beams, a phase modulation device for modulating the relative phase angles of the input beams, and a combination device configured as above is, to form at least one output beam by coherently combining the at least two input beams. The optical system and also the combination device can be realized with discrete optical components, fiber optic, integrated optical or as a hybrid system.

The beam source is preferably a seed laser of a MOPA (Master Oscillator Power Amplifier) system. In this case, the input beams are generated by amplifying the seed laser beam. In principle it is possible to arrange the phase modulation device in the beam path directly in front of the inputs of the combination device. However, in the event that it is a MOPA system, it is beneficial if the setting of the relative Phase positions of the input beams are carried out with the aid of a phase modulation device, which is arranged in front of the power amplifier of the MOPA system. In this way, optical elements can be used in the phase modulation device that do not have to have high performance or high efficiency. The average power and/or the peak power of the at least one output beam can be high in such a MOPA system and, for example, more than 1 W, 10 W, 1 kW, 10 kW or even 1 MW. lie.

The at least one output beam is typically fed to an application device of the optical system, which is usually a processing device for processing, e.g. a processing head, for processing a workpiece with the aid of the output beam. Translation units for moving the processing head and/or the workpiece can also be provided for the positioning of the output beam(s) relative to the workpiece. Dynamic beam positioning (2D, 2.5D), spatial-temporal beam shaping, position detection (before the process) and process control (in-situ, ex-situ) can also be carried out.

Polarization can also be influenced in the application device when the at least one output beam is fed to the workpiece. For example, the application device for supplying the output beam to the workpiece can have a birefringent component, for example an optical fiber, in particular a fiber-based amplifier. In this case, the combination device can carry out a pre-compensation of the birefringence generated when the output beam is fed to the workpiece. Typically, the pre-compensation is carried out by suitably adapting the relative phase angles, which are set by the phase modulation device, so that the combination of polarization state and power of the output beam that is to be achieved is set on the workpiece. In this way, non-polarization-maintaining transport fibers can also be used, or the MOPA concept can be modified by superimposing before the (typically fiber-based) final amplifier, which in this case is integrated into the application device. In addition to the application of the optical system for writing voxels for data storage in transparent materials, the optical system can also be used for the production of optical components based on a spatially dependent polarization manipulation. The rapid change in polarization that is generated with the optical system can also be used advantageously for other applications, for example for analysis methods.

The optical system can also have a conversion device which is arranged between the phase modulation device and the combination device. The conversion device can be an optical amplifier device, for example the output amplifier or amplifiers of the MOPA system described above. The conversion device can also fulfill another function.

The conversion device can be designed, for example, for frequency conversion of the input beams. This is favorable because for the (respective) output beam or for the application for which the (respective) output beam is used, wavelengths are often of interest for which no high-performance amplifier system, no high-performance phase modulation device or other optical components are available. In this case, the coherent coupling in the combination device can be combined with a frequency conversion that generally takes place in the beam path before the combination device. The optical system described here, in particular in the form of a MOPA system, is compatible with a frequency conversion device arranged between the beam source and the combination arrangement.

The beam source for generating the laser beam can be designed to generate a cw laser beam and/or a pulsed laser beam. In particular, the beam source can be designed to generate an ultra-short-pulse laser beam with laser pulses whose pulse durations are on the order of ps or fs. In the case of ultra-short pulse lasers, what is known as chirped pulse amplification (CPA) is often used, in which time-stretched pulses are amplified and subsequently compressed. The CPA technology can be combined with the coherent coupling of the four input beams to the output beam described here, and in particular with the independent adjustment of the polarization state and the power of the output beam. In this case, the conversion device can contain, for example, a pulse compressor of the CPA system. However, the conversion device can also generally be designed for pulse shaping of the input beams, which are pulsed in this case.

It goes without saying that the conversion device can also be designed to fulfill a number of the functions described above or that the optical system can have a number of conversion devices in order to set beam parameters adapted to the respective application.

In the beam path between the beam source and the combination device, in particular in the beam path between the conversion device and the combination device, and in the beam path of the output beam(s) behind the combination device, a suitable beam guide can be provided, which can include scanner optics, for example.

In one embodiment, the optical system is designed to feed the input beams to the inputs of the combiner with essentially the same power. As described above, it is favorable for the coherent combination if the mutually coherent input beams have essentially the same power or intensity. This can be achieved, for example, if the power of a laser beam, which is generated by the beam source, is split in equal parts in the splitting device between the mutually coherent input beams. As described above, the input beams may deviate from identical power if they experience different losses as they pass through the combiner. The power of the individual input beams can be adjusted to compensate for the different losses as they pass through the combiner, so that an optimal interference contrast is produced in the coherent combination. In a further embodiment, the optical system is designed to feed input beams to the inputs of the combination device with linear polarization with a predetermined direction of polarization or with circular polarization. As described above, it is advantageous if the input beams are fed to the combination device with a defined polarization state that depends on the respective configuration of the combination device.

Further advantages of the invention result from the description and the undersigned statement. Likewise, the features mentioned above and those listed below can each be used individually or together in any combination. The embodiments shown and described are not to be understood as an exhaustive enumeration, but rather have an exemplary character for the description of the invention.

Show it:

1a shows a schematic representation of a combination device which has a polarization beam splitter and a 1/4 delay device for the coherent combination of two mutually coherent input beams to form an output beam,

Fig. 1 b is a schematic representation analogous to Fig. 1a, the coherent

combination of two of a number of 2N input beams to form one of N output beams,

2a, b schematic representations of two combination devices, which are designed to split N+1 input beams into two partial beams and to coherently combine two partial beams of different input beams into one of N output beams,

3a shows a schematic representation of a combination device, which is used for the coherent combination of two mutually coherent input beams to an output beam has a Mach-Zehnder interferometer,

3b shows a schematic representation of a combining device analogous to FIG

FIG. 4 shows a schematic representation of an optical system which has a combination device according to FIG. 1a.

In the following description of the drawings, identical reference symbols are used for identical or functionally identical components.

1a shows a combination device 3 for the coherent combination of two mutually coherent input beams 1.1, 1.2 to form a combined output beam 2.1. The combination device 3 has two inputs Ei, E2, each of which is used for entry of one of the input beams 1.1, 1.2. The combination device 3 also has an output Ai, which serves to exit the output beam 2.1 formed during the coherent superimposition. The combination device 3 is designed to superimpose the two input beams 1.1, 1.2 collinearly, with the example shown being superimposed congruently with the output beam 2.1.

The combination device 3 shown in FIG. 1a makes it possible to set the state of polarization of the output beam 2.1. In the examples shown, the polarization state that is set with the aid of the combination device 3 is the direction of polarization R of a linearly polarized output beam 2.1.

While the beam paths in FIG. 1a and in the following figures are shown in the plane of the drawing, the states of polarization are shown in a propagation direction perpendicular to the plane of the drawing. The Y direction of the in 1a corresponds to the s-component, the X-direction to the p-component of the polarization.

The combination device 3 shown in FIG. 1a makes it possible to set a power PA of the output beam 2.1 which—apart from parasitic losses when passing through the optical elements of the combination device 3—corresponds to the sum of the powers Pi, P2 of the input beams 1.1, 1.2 be combined coherently to the output beam 2.1.

The setting of the direction of polarization R of the output beam 2.1 is made possible by setting a relative phase position Df- ₁₂ of the phases fi, y2 of the two input beams 1.1, 1.2 shown in FIG. 1a. The polarization direction R of the output beam 2.1 is typically set exclusively by setting the relative phase position Df- ₁₂ of the two input beams 1.1, 1.2, ie without changing other parameters of the two input beams 1.1, 1.2 or parameters of optical components of the combination device 3 for this purpose will. The powers Pi, P2 of the input beams 1.1, 1.2 are usually the same or they are selected differently in order to carry out a pre-compensation for parasitic losses. The power Pi, P2 of the two input beams 1.1, 1.2 are also not changed for the adjustment. Since the relative phase angle Df- ₁₂ of the two input beams 1.1, 1.2 can be adjusted in a highly dynamic manner, the direction of polarization R of the output beam 2.1 can also be adjusted in a highly dynamic manner using the combination device 3.

The combination device 3 shown in FIG. 1a has a polarization beam splitter 4 for the coherent superimposition of the first and second input beams 1.1, 1.2. The polarization beam splitter 4 is identified in FIG. 1a and in the following figures with a dot and a double arrow in order to distinguish it from other non-polarization-sensitive components, for example intensity beam splitters. As can also be seen in FIG. 1a, the directions of polarization R1, R2 of the two input beams 1.1, 1.2 are aligned perpendicular to one another. The polarizer axes of the polarization beam splitter 4 are parallel to the polarization directions R1, R2 of respective input beams 1.1, 1.2 aligned in order to produce a maximum transmission of the first input beam 1.1 and a maximum reflection of the second input beam 1.2 at the polarization beam splitter 4.

With the coherent combination of the input beams 1.1, 1.2 entering the polarization beam splitter 4, an elliptically polarized exiting beam is formed in which the semi-axes (principal axes or directions) of the elliptical polarization are at 45° to the two mutually perpendicular polarization directions R1, R2 of the input beams 1.1, 1.2 are aligned. By aligning the preferred axis of a phase shifting element in the form of a 1/4 delay device 5 with the 45° preferred direction, the elliptical polarization is converted into a linear polarization of the output beam 2.1, whose polarization direction R is determined by the main axis ratio and the sense of rotation of the elliptical polarization . The setting of the relative phase position Df _ΐ 2 between the input beams 1.1, 1.2 entering the polarization beam splitter 4 changes the aspect ratio between the semi-axes of the elliptical polarization, but not the orientation of the semi-axes at 45° to the two mutually perpendicular polarization directions R1, R2. The direction of polarization R of the linearly polarized output beam 2.1 can therefore be set by setting the relative phase position Dfΐ2 of the two input beams 1.1, 1.2. In the combination device 3 shown in FIG. 1a, the two input beams 1.1, 1.2 are aligned in parallel and the second input beam 1.2 is deflected by 90° on a deflection mirror 6 in the beam path in front of the polarization beam splitter 4, but this is not absolutely necessary.

The combination device 3 shown in FIG. _1b differs from the combination device 3 shown in FIG. 4, 5, ...) which is twice as large as the number N of outputs Ai, ..., AN. The combination device 3 is used for the coherent combination of two 1.1, 1.N+1; 1.2, 1.N+2; ... of the input rays 1.1, ..., 1.N entering at the inputs Ei, ..., E2N+1 to a respective output beam Ai, ..., AN. As can be seen in FIG. 1b, a first group of N input beams 1.1, 1.N is radiated directly onto a polarization beam splitter 4 common to all input beams 1.1, . . . , 1.2N and a second group of N input beams 1.N+ 1 , . . . , 1 2N is deflected to the polarization beam splitter 4 via a deflection mirror 6 . The coherent combination of one of the input beams 1.1, ..., 1.N of the first group with one of the input beams 1.N+1, ..., 1.2N of the second group at the polarization beam splitter 4 takes place as in connection with Fig. 1a, forming N output beams 2.1, ..., 2.N. The input beams 1.1, ..., 1.2N, which are combined to form different output beams 2.1, ..., 2.N, impinge on the common polarization beam splitter 4 at positions that are laterally offset from one another. All output beams 2.1, ..., 2 .N common phase shifting element in the form of a 1/4 delay device 5 serves to generate a linear polarization of the respective output beam 2.1, ..., 2.N. The polarization direction of a linearly polarized output beam 2.1, ..., 2.N can use the relative phase between the respective entrance rays 1.1, 1.n+1, 1.2, ..., 1.n+2, ... be set, as shown in Fig. 1b by differently oriented arrows.

All input beams 1.1, . . . , 1 2N are fed to the combination device 3 shown in FIG. In order to achieve a vertical alignment of the polarization directions R1, R2 of the respective input beams 1.1, 1.N+1; 1.2, 1.N+2, ..., the second group of input beams 1.N+1, ..., 1.2N passes through a polarization-rotating device 7, which is designed as a 1/2 delay element in the example shown, to rotate the direction of polarization of the second group of input beams 1.N+1 , ..., 1.2N by 90° before they hit the polarization beam splitter 4 .

Fig. 2a,b show two examples of combination devices 3, which differ from the combination devices 3 shown in Fig. 1a.b in that they have a number N+1 of inputs Ei,...,EN+I, which are um One is greater than the number N of outputs Ai,...,AN. The combination devices 3 are formed, the N+1 input beams 1.1, . . . , 1.N+1 each have two partial beams 8.1a, 8.1b; _8.2a , 8.2b, - be coherently combined into one of the N output beams 2.1, ..., 2.N. A number of polarization beam splitters _4.1 , 2b a common polarization beam splitter 4 is used for this purpose.

In the combination device 3 shown in FIG. 2a, the first N polarization beam splitters 4.1, ..., 4.N serve as a combination element for the coherent combination of a first partial beam 8.1a, ..., 8.Na of a respective input beam 1.1, ..., 1.N, which is radiated from an associated input Ei, ..., E _N onto the respective polarization beam splitter 4.1, ..., 4.N and transmitted by it, with a second partial beam 8.2b, ..., 8. N+1b of a respective adjacent input beam 1.2, ..., 1st N+1, which is reflected by the adjacent polarization beam splitter 4.2, ..., 4th N+1 associated with this input beam 1.2, ..., 1st N+1 becomes. The output beams 2.1,..., 2.N are linearly polarized with the aid of a respective phase shifting device 5.1,..., 5.N. The direction of polarization of a linearly polarized output beam 2.1, .

In the example shown in FIG. 2b, a common polarization beam splitter 4 serves both as a common splitting element for splitting all input beams 1.1, . . . , 1.N+1 into two partial beams 8.1a, 8.1b; 8.2a, 8.2b, ... . The polarization beam splitter 4 also serves as a common combination element for combining two of the partial beams 8.1a, 8.2b; 8.2a, 8.3b, ... of adjacent input beams 1.1, ..., IN to a respective output beam 2.1, ..., 2.N. In order to be able to use the polarization beam splitter 4 both as a splitting element and as a combination element, a group of first partial beams 8.1a, ..., 8.1Na, which are transmitted by the polarization beam splitter 4, is directed 90° back to the polarization beam splitter at a first deflection mirror 6a 4 deflected and a group of second partial beams 8.1b, ... 8.N + 1b is one second deflection mirror 6b deflected back to the polarization beam splitter 4. The first partial beam 8.1a of the first input beam 1.1 and the second partial beam 8.N+1b of the N+1th input beam 1.N+1 serve as diagnostic beams Di, DN+I and are not used for the coherent combination. In the combination device 3 shown in FIG. 2b, a common phase shifting device in the form of a 1/4 delay device 5 is used to generate a linear polarization of the respective output beam 2.1, . . . , 2.N with an adjustable polarization direction.

FIG. 3a shows a combination device 3 which, like the combination device 3 shown in FIG. 1a, has two inputs Ei, E2 for the entry of a respective input beam 1.1, 1.2 and an output Ai for the exit of an output beam 2.1. The combination device 3 includes a Mach-Zehnder interferometer 9, which has a first beam channel 12a for propagating a first partial beam Ta and a second beam channel 12b for propagating a second partial beam Tb. The Mach-Zehnder interferometer 9 also includes a splitting element 10 in the form of an intensity beam splitter for splitting the two input beams 1.1, 1.2 into the two partial beams Ta, Tb and a combination element 11 in the form of an intensity beam splitter for the coherent combination of the two partial beams Ta, Tb to form the Output beam 2.1. A first reflector in the form of a deflection mirror 6a is arranged in the first beam channel 12a and deflects the first partial beam Ta by 90° to the combination element 11 . Correspondingly, a second reflector 6b in the form of a deflection mirror is arranged in the second beam channel 12b, which deflects the second partial beam Tb by 90° to the combination element 11 .

For the coherent combination, the combination device 3 is supplied with the first input beam 1.1 and the second input beam 1.2 with circular polarization, ie with a circular polarization state, with a direction of rotation D1 of the circular polarization state of the first input beam 1.1 being opposite to a direction of rotation D2 of the circular polarization state of the second input beam 1.2 runs. As can also be seen in FIG. 3a, the second input beam 1.2 is deflected by a further reflector in the form of a further deflection mirror 6c by 90° to the splitting element 10 of the Mach-Zehnder Interferometer 9 deflected.

In the coherent combination at the splitting element 10 of the Mach-Zehnder interferometer 9, the two partial beams Ta, Tb described above are formed from the two oppositely circularly polarized input beams 1.1, 1.2, which are linearly polarized and whose polarization directions R1, R2 are initially rotated by 90 ° are rotated to one another, but with the aid of a polarization influencing device arranged in the Mach-Zehnder interferometer 9 in the form of an optical rotator 13, more precisely a suitably aligned quartz crystal, the polarization direction R1 of the first partial beam Ta is rotated by 90°, so that the direction of polarization R1 of the first partial beam Ta is aligned parallel to the direction of polarization R2 of the second partial beam Tb after passing through the optical rotator 13 .

It goes without saying that such a parallel alignment of the polarization directions R1, R2 of the two partial beams Ta, Ta can also be achieved if, instead of a single optical rotator 13, two or more optical rotators are arranged in the respective beam channels 12a, 12b, the one cause suitable rotation of the respective polarization directions R1, R2 of the two partial beams Ta, Tb. By setting the relative phase position Df _ΐ 2 between the first input beam 1.1 and the second input beam 1.2, the polarization direction R1, R2 of the two partial beams Ta, Tb and thus the polarization direction R of the linearly polarized output beam 2.1 of the combination device 3 can be set in the coherent combination . Instead of the intensity beam splitter, polarization beam splitters can also be used in the Mach-Zehnder interferometer 9 as a splitting element 10 and as a combining element 11 .

FIG. 3b shows a combination device 3, which differs from the combination device 3 shown in FIG. 3a in that it has four inputs Ei to E4 and three outputs Ai to A3. The combination device 3 of FIG. 3b thus represents a special case (N=3) of a combination device 3 with a number of N+1 inputs and N outputs. As described above in connection with FIGS. 2a, b, the combination device 3 on a splitting element 10, which in Fig. 3b as Intensity beam splitter is formed and the four input beams 1.1 to 1.4, which enter the combination device 3 at the respective inputs Ei to E ₄ , each have a first partial beam 8.1a to 8.3a, D ₄ and a second partial beam Di, 8.2b to 8.4 b splits. As described above in connection with FIGS. 2a, b, the second partial beam of the first input beam 1.1 serves as diagnostic beam Di. Correspondingly, the first partial beam of fourth input beam 1.4 also serves as diagnostic beam D _4. The remaining first partial beams 8.1a to 8.3a are combined in pairs with the second partial beams 8.2b to 8.4b to form the three output beams 2.1 to 2.3, which emerge at the three outputs Ai, A ₂ , A ₃ .

The division of each pair of partial beams 8.1a, 8.2.b; 8.2a, 8.3b; 8.3a, 8.4b of adjacent input beams 1.1 to 1.4 on one of three first sub-beams T1a, T2a, T3a, which pass through the first beam arm 12a, and on one of three second sub-beams T1b, T2b, T3b, the second beam arm 12b, takes place at a further splitting element 14 of the interferometer 9, which is designed in the form of an intensity beam splitter, which also serves as a splitting element 10 and as a combination element 11 in the example shown in FIG. 3b.

The input beams 1.1 to 1.4 enter the combination device 3 at the inputs Ei to E ₄ in a circularly polarized manner and have a first direction of rotation D1. The second partial beams Di, 8.2b to 8.4b of the four input beams 1.1 to 1.4 pass through a phase-influencing element 15 in the beam path before the further splitting element 14, which is used to reverse the direction of rotation D1 of the circular polarization of the second partial beams Di, 8.2b to 8.4b. The first partial beams 8.1a to _8.3a , D4 and the second partial beams Di, 8.2b to 8.4b therefore impinge on the further splitting device 14 in a circularly polarized manner and with opposite directions of rotation D1, D2. The coherent combining in the interferometer 9 takes place using an optical rotator 13, as described above in connection with Figure 3a. The combination device 3 also has three reflectors in the form of deflection mirrors 6a, c, 6a, 6d.

Fig. 4 shows an optical system 30, a beam source 31 for generating a laser beam E and a splitting device 32 for splitting the laser beam E (more precisely, the power of the laser beam E) in equal parts to the two mutually coherent input beams 1.1, 1.2, so that the two input beams 1.1, 1.2 have identical powers after the division. The optical system 30 further includes a phase modulation device 33, which is designed for rapid modulation of the relative phase position Df _ΐ 2 (see FIG. 1a) of the two laser beams 1, 2, which, after an (optional) conversion (see below), the two Form input beams 1.1, 1.2 of the combination device 3, which is arranged in the beam path after the phase modulation device 33. In the optical system 30 shown in FIG. 4, the splitting device 32 is arranged in the beam source 31 and the beam source 31 couples the two input beams 1.1, 1.2 into the phase modulation device 33.

In the example shown, the combination device 3 is designed as shown in FIG. 1a and superimposes the two input beams 1.1, 1.2 coherently to form the output beam 2.1. The combination device 3 can also be used as shown in Fig. 1b, Fig.

2a, b or as shown in Fig. 3a, b and in this case has a correspondingly adapted number of inputs and outputs.

The optical system 30 has an application device 34, which in the example shown is a processing device in the form of a processing head, which is used to process a workpiece with the aid of the output beam 2.1. For the positioning of the output beam 2.1 or several output beams 2.1, 2.2, . . . relative to the workpiece, the application device 34 can have translation units for moving the processing head and/or the workpiece. The application device can also have a scanner device for dynamic beam positioning (2 D, 2.5 D) and/or spatio-temporal beam shaping, position detection (before the process) and/or process control (in-situ, ex-situ ) to perform.

A conversion device 35 is arranged in the optical system 30 between the phase modulation device 33 and the combination device 3 . The conversion device 35 can fulfill one or more functions and can be designed in different ways, as will be described in more detail below. In the example shown in FIG. 4, the beam source 31 is a seed laser of a MOPA (Master Oscillator Power Amplifier) system. In this case, the conversion device 35 contains at least one output amplifier of the MOPA system, in which the two input beams 1.1, 1.2 are amplified before they are fed to the combination device 3. In this case, the phase modulation device 33 is arranged in the beam path in front of the final amplifier or the conversion device 35 . This is favorable since in this case optical components can be used in the phase modulation device 33 which do not have to have a high level of performance capability or high efficiency. In terms of a suitable overall system design, the seed laser typically has a low but appropriate power, in that pre-amplification is already carried out in the seed laser if required. In contrast, the average power and/or the peak power of the output beam 2.1 is high in an optical system 30 in the form of a MOPA system due to the use of the final amplifier. However, the conversion device 35 of the optical system 30 can also be a different type of optical amplifier.

The beam source 31 can be designed to generate a c/w laser beam and/or a pulsed laser beam E. The beam source 31 can, for example, generate an ultra-short-pulse laser beam with laser pulses whose pulse durations are on the order of ps or fs. So-called chirped pulse amplification (CPA) is often used in ultra-short pulse lasers, in which time-stretched pulses are amplified and then compressed. In this case, the beam source typically provides time-stretched pulses, with the stretching taking place before the splitting device 32 . The CPA technology can be combined with the coherent coupling of the two input beams 1.1, 1.2 to form the output beam 2.1 in the combination device 3, as described here. In this case, the conversion device 35 can form or contain a pulse compressor of the CPA system, for example. However, the conversion device 35 can also generally be designed for pulse shaping of the input beams 1.1, 1.2, which are pulsed in this case. The conversion device 35 can also be used for frequency conversion of the input beams 1.1, 1.2. In this case, the coherent superimposition in the combination device 3 is combined with a frequency conversion taking place in the conversion device 35 in the beam path before the combination device 3 . The optical system 30, also in the form of a MOPA system, is compatible with a frequency conversion device arranged between the beam source 31 and the combining device 3.

It goes without saying that the conversion device 35 can also be designed to fulfill several of the functions described above or other functions. For example, the conversion device 35 can be used to set or adapt the beam or pulse parameters such as pulse energy, pulse duration, etc. required for the respective application. The conversion device 35 can also be used for beam transport or for flexible beam guidance. The optical system 30 can also have a number of conversion devices 35 .

For example, a conversion device 35 can be integrated into the application device 34 and can be used to influence the polarization of the output beam 2.1. For example, the application device 34 or the conversion device 35 for supplying the output beam 2.1 to the workpiece can have a birefringent component, for example an optical fiber, in particular a fiber-based amplifier. In this case, the combination device 3 can carry out a pre-compensation of the birefringence generated when the output beam 6 is fed to the workpiece. Typically, the pre-compensation is carried out by suitably adapting the relative phase position Df _ΐ 2 , which is set by the phase modulation device 33, so that the polarization state to be achieved or the polarization direction R of the output beam 2.1 is set on the workpiece. In this way, non-polarization-maintaining transport fibers can also be used in the optical system 30 or the MOPA concept can be modified by superimposing before the (typically fiber-based) final amplifier, which in this case is integrated into the application device 34 . The optical system 30 described above can be used, for example, for writing voxels into transparent materials for data storage. The optical system 30 can also be used for the manufacture of optical components based on spatially dependent polarization manipulation. The rapid change in polarization that is generated with the optical system 30 can also be used advantageously for other applications, for example for analysis methods. It goes without saying that the functionalities that are implemented with the aid of the optical components or components of the optical system 30 described further above can also be implemented with the aid of optical components that are designed in a different way and fulfill the same functionality.

Claims

patent claims

1. Combination device (3), comprising: at least two inputs (Ei, E2, ...) for the entry of an input beam (1.1, 1.2, ...), and one or more outputs (Ai, A2, ...) for exiting one output beam (2.1, 2.2, ...), the combination device (3) being designed to combine one output beam (2.1, 2.2, ...) by a coherent combination of two of the input beams (1.1, 1.2, . ..), characterized in that the combination device (3) is designed to determine a polarization state, in particular a polarization direction (R), of the respective output beam (2.1, 2.2, ...) as a function of a relative phase position (Df- ₁₂ , ...) of the individual phases (fi, y ₂ , ...) of the two input beams (1.1, 1.2, ...) from which the respective output beam (2.1, 2.2, ...) through the coherent combination is formed.

2. Combination device according to Claim 1, which has exactly two inputs (Ei, E2) and one output (Ai), the combination device having a polarization beam splitter (4) for the coherent combination of the two input beams (1.1, 1.2) to the output beam (2.1) and a phase shifting element arranged in the beam path after the polarization beam splitter (4), in particular a 1/4 delay device (5), for generating a linear polarization of the output beam (2.1).

3. Combination device according to Claim 1, which has exactly two inputs (Ei, E2) and one output (Ai), the combination device being an interferometer, in particular a Mach-Zehnder interferometer (9), with a first beam channel (12a) for propagation a first partial beam (Ta) and with a second beam channel (12b) for propagating a second partial beam (Tb), the interferometer (9) comprising a splitting element (10) for splitting the two input beams (1.1, 1.2) into the two partial beams (Ta, Tb), a combination element ( 11) for the coherent combination of the two partial beams (Ta, Tb) to form the output beam (2.1) and preferably at least one polarization influencing device (13) for influencing a polarization state, in particular a polarization direction (R1, R2), of at least one of the partial beams, in particular in a fixed manner (Ta, Tb).

4. Combination device according to claim 1, which has more than two inputs (Ei, ..., E2N; EI, ..., EN) and more than one output (Ai, ... AN) and which is designed, a respective an output beam (2.1, ..., 2.N) exiting at an output (Ai, ..., AN) by a coherent combination of two of the two inputs (Ei , ... , E2N ; Ei , ... , EN) entering input beams (1.1 , ..., 1.N) to form.

5. Combination device according to claim 4, which has a number of inputs (Ei,

... , E2N) which is twice as large as a number of outputs (Ai ,

AN) and which is designed to combine two of the input beams (Ei, ..., E2N) entering at the inputs (Ei, ..., E2N) coherently into a respective output beam (Ai, ..., AN).

6. Combining device according to claim 5, which is used for the coherent combination of two of the input beams (1.1, ..., 1.N) entering at the inputs (Ei, ... E2N) to form a respective output beam (2.1, ..., 2.N) a preferably all input beams (1.1, ..., 1.N) common polarization beam splitter (4), and to generate a linear polarization of the respective output beam (2.1, ..., 2.N) in the beam path after the Polarization beam splitter (4) arranged, preferably common to all output beams (2.1, ..., 2.N) phase shifting element, in particular a 1/4 delay device (5).

7. Combination device according to claim 6, which is designed, the polarization beam splitter (4) to supply two input beams (1.1, 1.N+1; 1.2, 1.N+2; ...) to be combined, which have two polarization directions (R1, R2) perpendicular to one another, the combining device (3) preferably in the beam path before the polarization beam splitter (4) has a polarization-rotating device (7) for rotating a polarization direction (R2) of one of the two input beams (1.1, 1.N+1; 1.2, 1.N+2; ...), which are combined at the polarization beam splitter (4) to form the respective output beam (2.1, ..., 2.N).

8. Combination device according to Claim 4, which has at least one splitting element (4.1, ..., 4.N+1; 4) for splitting a respective input beam (1.1, ..., 1.N+1) into two partial beams (8.1a , 8.1b; ..., 8.N+1a, 8.N+1b) and preferably at least one combination element (4.1, ..., 4.N, 4) for the coherent combination of two partial beams (8.1a, 8.2b ; 8.2a, 8.3b, ...) to a respective output beam (2.1, ..., 2.N).

9. Combination device according to claim 8, which has a number of inputs (Ei, E2, ..., EN + I) which is greater by one than a number of outputs (Ai, A2, ..., AN) and the is formed, a number of pairs of partial beams (8.1a, 8.2b; 8.2a, 8.3b, ...) corresponding to the number of outputs (Ai, A2, ..., AN) coherently with one of the output beams (2.1 , ..., 2.N) to combine.

10. Combination device according to Claim 9, which has a number of polarization beam splitters (4.1, ..., 4.N+1) corresponding to the number of input beams (1.1, ..., 1.N+1), each serving as a splitting element , wherein a number of polarization beam splitters (4.1, ..., 4.N) reduced by one each serve as a combination element.

11. Combining device according to Claim 8 or 9, which has a common polarization beam splitter (4) as a splitting element common to all input beams (1.1, ..., 1.N+1) and/or which has a common polarization beam splitter (4) as a splitting element to all output beams (2.1, ..., 2.N) common combination element has a common polarization beam splitter (4).

12. Combination device according to claim 8, which has an interferometer, in particular a Mach-Zehnder interferometer (9), which has a first beam channel (12a) for propagating a respective first sub-beam (T1a, T2a, T3a) and a second beam channel (12b) for the propagation of a respective second sub-beam (T1b, T2b, T3b), wherein the interferometer (9) comprises a further splitting element (14) for splitting the sub-beams (8.1a, 8.2.b; 8.2a, 8.3b; 8.3a, 8.4b) from two different input beams (1.1 to 1.4) to the two beam channels (12a, 12b) and preferably at least one polarization influencing device (13) for influencing a polarization state, in particular a polarization direction, of at least one of the sub - Partial beams (T1a, T2a, T3a;

T1b, T2b, T3b).

13. Combining device according to claim 12, which is designed to feed two partial beams (8.1a, 8.2b; 8.2a, 8.3b; 8.3a, 8.4b) from different input beams (1.1 to 1.4) to the further splitting element (14), which are circularly polarized in opposite directions, the combination device (3) preferably having at least one phase-influencing element (15) for influencing the phase of one of the two partial beams (8.1a, 8.2.b; 8.2a,

8.3b; 8.3a, 8.4b).

14. Optical system (30) comprising: a beam source (31) for generating a laser beam (E), a splitting device (32) for splitting the laser beam (E) into at least two coherent input beams (1.1, 1.2), a phase modulation device ( 33) to modulate the relative

Phase position (Df-12) of the input beams (1.1, 1.2), and a combination device (3) according to any one of the preceding claims for

Formation of at least one output beam (2.1) by a coherent combination of the at least two input beams (1.1, 1.2).

15. Optical system according to claim 14, which is designed to feed the input beams (1.1, 1.2) to the inputs (Ei, E2) of the combination device (3) with essentially the same power (Pi, P2).

16. Optical system according to one of claims 14 or 15, which is designed to direct the input beams (1.1, 1.2) to the inputs (Ei, E2) of the combination device (3) with linear polarization with a predetermined polarization direction (R1, R2) or with circular supply polarization.