Laser system and method for laser machining a workpiece

Abstract

The present invention relates to a laser system for laser machining a workpiece (104) using an interference pattern (124), comprising: at least one laser beam source (106) for providing a plurality of coherent laser beams (112); an amplification device (118) for forming amplified coherent laser beams (113) by amplifying the coherent laser beams (112); a phase adjustment device (114) for adjusting a respective phase difference between the coherent laser beams (112) and / or the amplified coherent laser beams (113); and a beam convergence region (130) in which output laser beams (102) based on the amplified coherent laser beams (113) or corresponding to the amplified coherent laser beams (113) converge to form the interference pattern (104), wherein at least beam portions from different output laser beams (102) converge in the beam convergence region (130).

Description

[0001] Laser system and method for laser processing a workpiece

[0002] The invention relates to a laser system and a method for laser processing a workpiece using an interference pattern.

[0003] From DE 10 2008 037 042 A1 a device for shaping a laser beam is known, comprising symmetrizing means which can interact with the laser beam to be shaped in such a way that after the interaction at least two sections or partial beams of the laser beam which are different in the transverse direction of the laser beam are spatially coherent with each other at least point-wise or in regions, and superimposing means for superimposing the at least two sections or partial beams with each other, wherein the superimposing means are arranged in the beam path of the laser beam behind the symmetrizing means.

[0004] From DE 10 2018 105 254 B4 a method for processing an object by means of interfering laser beams is known, wherein a collimated laser beam is generated, the intensity distribution and / or the phase curve over the cross section of the laser beam is influenced, the laser beam is split into two partial beams, and the partial beams are deflected and focused so that the partial beams superimpose in a processing zone in the material of the object, wherein the deflection and focusing of the partial beams comprises an aberration correction.

[0005] The invention is based on the object of providing a laser system and method as mentioned above, which are flexible and versatile in use and enable a high degree of control of properties of the interference pattern intended for laser processing of the workpiece.

[0006] This object is achieved according to the invention in the laser system mentioned at the outset in that the laser system comprises at least one laser beam source for providing a plurality of coherent laser beams, an amplification device for forming amplified coherent laser beams by amplifying the coherent laser beams, a phase adjustment device for adjusting a respective phase difference between the coherent laser beams and a beam convergence region in which output laser beams based on the amplified coherent laser beams or corresponding to the amplified coherent laser beams converge to form the interference pattern, wherein at least beam components of different and / or adjacent output laser beams converge in the beam convergence region.

[0007] By means of the laser system and the formed interference pattern, laser processing of the workpiece can be carried out according to the principle of direct laser interference structuring, which is also referred to as "Direct Laser Interference Patterning" (DLIP).

[0008] For example, laser processing of the workpiece is performed using the provided interference pattern on its exterior and / or surface. The exterior or surface is exposed to the interference pattern for laser processing in order to create surface material modifications with specified properties. For example, by applying the interference pattern to the workpiece, material can be removed from the exterior, or depressions or dimple-like structures can be created.

[0009] By means of the laser system according to the invention, for example, workpieces can be processed which are formed from or comprise a glass material and / or plastic material and / or metallic material.

[0010] The laser system according to the invention makes it possible, for example, to split an input laser beam provided by the laser beam source into a plurality of coherent laser beams and then to amplify the respective coherent laser beams, in particular to amplify them spatially separately from one another. The amplification of the coherent laser beams can be achieved, for example, using separate amplification elements. This enables spatially flexible positioning and alignment of the amplified coherent laser beams, on the basis of which the output laser beams are formed. The term "at least beam components of the different and / or adjacent output laser beams converge" means that the different output laser beams or components of the different output laser beams converge and / or converge toward one another to form the interference pattern.More precisely, Poynting vectors associated with the different output laser beams or the components of the different output laser beams converge.

[0011] A coherent laser beam and / or an amplified coherent laser beam and / or an output laser beam is in particular in the form of a bundle of rays and / or a sum of partial beams with a specific spatial extent. In particular, each of these bundles of rays or these partial beams is assigned a Poynting vector with a specific direction or several Poynting vectors with different directions.

[0012] Different output laser beams are understood to mean, in particular, output laser beams which are formed and / or result from different and / or adjacent amplified coherent laser beams.

[0013] In particular, it can be provided that the phase adjustment device and the amplification device and / or a splitting device of the laser system are designed as separate components of the laser system.

[0014] In particular, the coherent laser beams and / or the amplified coherent laser beams are guided within the laser system, at least in sections, in optical waveguides, in particular single-core waveguides. In particular, the coherent laser beams are guided between the splitting device and the phase adjustment device and / or between the phase adjustment device and the amplification elements, each in optical waveguides, in particular single-core waveguides. This enables, in particular, particularly flexible positioning and / or alignment of the amplified coherent laser beams and / or the output laser beams. In particular, it can be provided that the adjacent output laser beams present in the beam convergence region have at least beam components that enclose an angle of at least 0.2° and / or at most 40°, and preferably of at least 1° and / or at most 5°.This allows the interference pattern to be formed in a technically simple way.

[0015] Adjacent output laser beams are understood to mean directly adjacent output laser beams and / or closest output laser beams and / or output beams that are closest to each other. In particular, no further output laser beams are arranged between adjacent output laser beams.

[0016] In particular, it can be provided that adjacent output laser beams in the beam convergence region have beam components that enclose a non-zero first angle associated with a first angular coordinate, wherein the first angle is at least 0.2° and / or at most 40°, and preferably at least 1° and / or at most 5°. This allows, for example, the interference pattern to be formed two-dimensionally.

[0017] It can then be provided that, in the beam convergence region, adjacent output laser beams have beam portions that enclose a non-vanishing second angle associated with a second angular coordinate different from the first angular coordinate, wherein the second angle is at least 0.2° and / or at most 40°, and preferably at least 1° and / or at most 5°. In this case, in particular, both adjacent output laser beams that enclose the non-vanishing first angle with each other and output laser beams that enclose the non-vanishing second angle with each other are present in the beam convergence region.

[0018] The fact that beam components of adjacent output laser beams enclose a non-vanishing angle with respect to one another is to be understood as meaning that at least beam components of the adjacent output laser beams are assigned Poynting vectors which enclose the aforementioned non-vanishing first angle or second angle with respect to one another.

[0019] The first angle extends in a first direction and / or with respect to a first angular coordinate. The second angle extends in particular in a second direction and / or with respect to a second angular coordinate (relative to a specific output laser beam, from which the first angle or the second angle to the adjacent output laser beams is measured). This second direction or second angular coordinate is different from the first direction or first angular coordinate of the first angle α. In particular, the first direction or first angular coordinate is oriented transversely or perpendicularly to the second direction or second angular coordinate.

[0020] When describing an orientation of the output laser beams in spherical coordinates, the first angle corresponds, for example, to the polar angle and the second angle ß to the azimuth angle.

[0021] In particular, it can be provided that adjacent output laser beams present in the beam convergence region, and in particular all adjacent output laser beams present in the beam convergence region, are aligned with one another such that two adjacent output laser beams each have either beam portions that enclose a non-vanishing first angle or beam portions that enclose a non-vanishing second angle. In particular, two adjacent output laser beams each enclosing a non-vanishing first angle then have a vanishing second angle, or vice versa. This can be achieved, for example, by a two-dimensional array of amplified coherent laser beams impinging on a focusing device to form the output laser beams.

[0022] In particular, it can be provided that the output laser beams in the beam convergence region are present as collimated beam bundles and / or plane waves. In particular, the output laser beams in the beam convergence region are present as collimated Gaussian beams or collimated Gaussian-like beams. In particular, the respective output laser beams in the beam convergence region are not present as converging beams. This means that a specific output laser beam does not have any converging beam components and / or partial beams. In particular, a specific output laser beam is not focused into a point.

[0023] In this case, each output laser beam is assigned a single Poynting vector with a unique orientation. The respective Poynting vectors then serve as a reference for specifying the first angle and / or the second angle between two adjacent output laser beams. In particular, in this case, the Poynting vector of a specific output laser beam corresponds to its main propagation direction.

[0024] In particular, in the case of the output laser beams present as collimated beams, the output laser beams converge towards one another in the beam convergence region to form the interference pattern, wherein output laser beams adjacent to one another in the beam convergence region enclose a non-vanishing first angle associated with the first angular coordinate, and / or wherein output laser beams adjacent to one another in the beam convergence region enclose a non-vanishing second angle associated with the second angular coordinate.

[0025] Alternatively, the output laser beams in the beam convergence region may be present as divergent beam bundles and / or spherical waves and / or partial spherical waves. A partial spherical wave is understood to be a geometric subregion and / or a section of a spherical wave.

[0026] Then, in particular, each output laser beam is assigned a plurality of Poynting vectors, wherein the direction of the Poynting vectors can be different for different beam components of a specific output laser beam. The respective Poynting vectors then serve as a reference for specifying the first angle and / or the second angle between respective beam components of two adjacent output laser beams. A main propagation direction of a specific output laser beam then corresponds, in particular, to an averaged direction across all non-vanishing Poynting vectors of the output laser beam.

[0027] In the case of output laser beams present as divergent beam bundles, these in particular only comprise beam components that converge towards one another in the beam convergence region to form the interference pattern, wherein in the beam convergence region only beam components of adjacent output laser beams enclose a non-vanishing first angle associated with the first angular coordinate, and / or wherein in the beam convergence region only beam components of adjacent output laser beams enclose a non-vanishing second angle associated with the second angular coordinate. In particular, in this case, the adjacent output laser beams also comprise other beam components that do not converge towards one another and / or that do not enclose the aforementioned first angle and / or second angle.

[0028] The output laser beams are formed, in particular, by collimating and / or deflecting the amplified coherent laser beams. The deflection is performed, in particular, in such a way that the output laser beams converge to form the interference pattern.

[0029] Amplified coherent laser beams coupled out of the amplification device and / or from amplification elements of the amplification device are present in particular as divergent beam bundles and / or as spherical waves and / or partial spherical waves.

[0030] It may be advantageous for the laser system to have a focusing device for collimating and / or redirecting amplified coherent laser beams incident on the focusing device. This allows, for example, amplified coherent laser beams present as divergent beam bundles to be collimated to provide the output laser beams in a collimated form. The focusing device can generally have one or more focusing elements for collimating and / or redirecting the amplified coherent laser beams. For example, the focusing element is or includes an F-theta lens.

[0031] In one embodiment, the focusing device comprises a focusing element, and in particular a single focusing element, wherein several, and in particular all, of the amplified coherent laser beams are incident on the focusing element, and wherein the amplified coherent laser beams are collimated and deflected by the focusing element to provide the output laser beams. This allows the laser system to be designed compactly and with a reduced number of optical components.

[0032] In particular, the focusing element converts a spatial offset of amplified coherent laser beams incident on it into an angular offset.

[0033] For example, the adjacent amplified coherent laser beams incident on the focusing element are positioned with a spatial offset relative to a first spatial direction and / or relative to a second spatial direction, wherein the second spatial direction is oriented transversely and in particular perpendicular to the first spatial direction. From this spatial offset, an angular offset is then formed between adjacent emerging laser beams by means of the focusing element. These emerging laser beams correspond in particular to the output laser beams. Thus, the angle and / or first angle and / or second angle between the output laser beams can be formed.

[0034] For example, the adjacent amplified coherent laser beams incident on the focusing element are positioned as a one-dimensional or two-dimensional array with respect to the first spatial direction and / or the second spatial direction. In a further embodiment, the focusing device has a plurality of focusing elements, wherein a focusing element is assigned to each amplified coherent laser beam, and wherein the amplified coherent laser beams are each collimated by means of the assigned focusing element.

[0035] In particular, the amplified coherent laser beams incident on and exiting from the respective focusing element then have the same main propagation direction. The adjacent amplified coherent laser beams incident on and / or exiting the focusing element have a spatial offset, for example, with respect to the first spatial direction and / or the second spatial direction and are positioned as an array, in particular with respect to the first spatial direction and / or the second spatial direction.

[0036] In order to deflect the amplified coherent laser beams emerging from the respective focusing elements, a beam deflection device can then be provided in particular in order to form the output laser beams converging in the beam convergence region.

[0037] In one variant, both the amplified coherent laser beams incident on the focusing elements and the laser beams emerging from them are positioned in a convergent manner. For example, the amplification elements of the amplification device and / or the focusing elements are then positioned in a circular and / or spherical manner. This, in particular, eliminates the need for a separate beam deflection device.

[0038] In particular, it can be provided that the existing focusing elements and / or the amplified coherent laser beams incident on the existing focusing elements are configured and arranged such that laser beams emerging from the focusing elements form the beam convergence region and correspond to the output laser beams. In particular, no further deflection and / or beam shaping of the laser beams emerging from the focusing elements then takes place. In particular, it can be provided that the focusing elements and / or the amplified coherent laser beams incident on the focusing elements are configured and arranged such that laser beams emerging from the focusing elements converge to form the interference pattern. In particular, no separate beam deflection device is then required. The emerging laser beams then form the beam convergence region and correspond to the output laser beams.

[0039] The laser system may include a beam deflection device for deflecting the amplified coherent laser beams to form the output laser beams that converge in the beam convergence region. The beam deflection device comprises, for example, a plurality of mirror elements configured and arranged to deflect the amplified coherent laser beams entering the beam deflection device.

[0040] In one variant, the amplified coherent laser beams coupled out of the amplification device can be provided as divergent beam bundles, with a main propagation direction of adjacent amplified coherent laser beams being oriented parallel or transversely, and with the amplified coherent laser beams corresponding to the output laser beams. By arranging the adjacent coherent laser beams transversely to one another, in this variant, beam components of the output laser beams can be increased, which contribute to the formation of the interference pattern.

[0041] In particular, it can be provided that the interference pattern has at least one interference element for laser processing of the workpiece, which is repeated within the interference pattern and, in particular, at regular intervals, and in particular at equal intervals. This allows, for example, regular and / or periodic structures to be created on the workpiece. The interference pattern can generally be one-dimensional, two-dimensional, or three-dimensional. For example, the interference element is repeated in one, two, or three spatial dimensions.

[0042] For example, the interference element is or comprises at least one focused point and / or at least one focused line, such as a pattern of points and / or lines. The at least one focused point and / or the at least one focused line serve for laser processing of the workpiece and, in particular, have an intensity above a threshold required to perform laser processing of the workpiece.

[0043] It may be advantageous if the interference element is repeated at least 10 times, and especially at least 100 times, and especially at least 1,000 times within the interference pattern. This allows large-area periodic structures to be created on the workpiece in one or a few work steps.

[0044] In particular, it can be provided that the phase adjustment device is configured to adjust a phase difference between all existing coherent laser beams, in particular to adjust them separately. In particular, the phase adjustment device is configured to adjust a phase position of each of the coherent laser beams separately.

[0045] In particular, the phase adjustment device comprises a plurality of phase adjustment elements, with a phase adjustment element preferably being assigned to each coherent laser beam. The phase position of a specific coherent laser beam can then be adjusted, for example, using the phase adjustment element assigned to it.

[0046] It can be advantageous if at least one property of the interference pattern and / or the interference element can be varied by adjusting and / or controlling the phase difference between the coherent laser beams using the phase adjustment device. This allows, for example, dynamic machining of the workpiece. Furthermore, the interference pattern can be adapted to different applications in a technically simple manner.

[0047] The at least one property comprises in particular a spacing of the interference elements and / or a periodicity of the interference elements and / or a peak intensity of the interference elements and / or an intensity profile of the interference elements and / or a geometric shape of the interference elements.

[0048] For example, it can be provided that during operation of the laser system at least a subset of the interference elements of the interference pattern is moved relative to the workpiece and / or scanned over the workpiece by controlling and in particular exclusively by controlling the phase difference between the coherent laser beams.

[0049] In particular, it can be provided that the interference pattern extends with respect to at least one spatial direction over an extension length of at least 0.5 mm, preferably at least 1 mm, and particularly preferably at least 2 mm. For example, the interference pattern extends in at least one spatial direction over an extension length of at most 10 mm.

[0050] In particular, the interference pattern is homogeneous or approximately homogeneous over the extension length with regard to its properties, such as with regard to a peak intensity and / or an intensity profile and / or a geometric shape of interference elements of the interference pattern.

[0051] In particular, the interference pattern is temporally static (with temporally static parameters regarding the respective phase difference between the coherent laser beams). In particular, the interference pattern is completely formed with respect to its extension length at a specific time. In particular, all existing interference elements of the interference pattern are present simultaneously.

[0052] It may be advantageous if the amplification device is arranged downstream of the phase adjustment device with respect to a main propagation direction of the coherent laser beams. This allows, in particular, the respective phase difference between the coherent laser beams to be adjusted using the phase adjustment device at a reduced power (compared to the power of the amplified coherent laser beams). This enables a technically simpler implementation of the phase adjustment device.

[0053] However, it is also possible in principle for the phase adjustment device to be arranged after the amplification device.

[0054] It may be advantageous if the amplification device comprises a plurality of amplification elements for amplifying a respective coherent laser beam, and in particular, the amplification elements are rod-shaped and / or designed as fiber amplifiers. The amplification elements can be arranged in a particularly geometrically flexible manner. For example, they can be arranged as an array. This enables geometrically flexible and simple positioning and alignment of the amplified coherent laser beams coupled out of the amplification elements.

[0055] In particular, each amplification element is assigned to a specific coherent laser beam. In particular, a main propagation direction of the amplified coherent laser beam coupled out of the respective amplification element is oriented parallel to a preferred direction and / or longitudinal center axis of the amplification element.

[0056] In particular, it can be provided that the amplification device is configured to adjust an output power of the respective amplified coherent laser beams, and in particular to adjust the output power separately for each amplified coherent laser beam. For example, the output power of a specific amplified coherent laser beam can be adjusted by means of an amplification element associated with this amplified coherent laser beam.

[0057] Preferably, the output power can then be controlled from zero to a maximum value. By selecting an output power of zero, the corresponding amplified coherent laser beam, and in particular the output laser beam formed from it, can be deactivated, so that they no longer contribute to the formation of the interference pattern.

[0058] It may be advantageous if the laser system has a splitting device for splitting an input laser beam provided by the laser beam source into several coherent laser beams. This allows, for example, the existing coherent laser beams to be provided by a single laser beam source.

[0059] In principle, it is also possible for the laser system to have several laser beam sources, with one or more coherent laser beams being provided by means of a respective laser beam source.

[0060] In particular, the laser system may include a feed device for adjusting a position and / or orientation of the workpiece relative to the interference pattern. In particular, the feed device is configured to move the workpiece relative to the interference pattern.

[0061] In particular, the workpiece can be arranged and / or fixed to a workpiece holder of the laser system in order to carry out the laser processing.

[0062] The laser beam source provides, in particular, pulsed laser radiation, and in particular, ultrashort pulse laser radiation. In particular, the input laser beam provided by the laser beam source and / or the coherent laser beams and / or the amplified coherent laser beams and / or the output laser beams are pulsed laser beams, and in particular, ultrashort pulse laser beams.

[0063] According to the invention, the method mentioned at the outset provides that a plurality of coherent laser beams are provided by means of at least one laser beam source, amplified coherent laser beams are formed by amplifying the coherent laser beams by means of an amplification device, and a respective phase difference between the coherent laser beams is adjusted by means of a phase adjustment device, wherein output laser beams based on the amplified coherent laser beams or corresponding to the amplified coherent laser beams are formed, which converge in a beam convergence region to form the interference pattern, wherein at least beam components of different output laser beams converge in the beam convergence region.

[0064] The method according to the invention has, in particular, one or more further features and / or advantages of the laser system according to the invention. Advantageous embodiments have already been explained in connection with the laser system.

[0065] The method according to the invention can be carried out in particular by means of the laser system according to the invention. In particular, the method according to the invention is carried out by means of the laser system according to the invention.

[0066] The fact that a first device and / or a first element of the laser system is arranged downstream of a second device and / or a second element of the laser system is to be understood in the present case as meaning that the laser beams guided in the laser system, such as the input laser beam and / or the coherent laser beams and / or the amplified coherent laser beams, first strike the second device and / or the second element and then the first device and / or the first element. The second device and / or the second element is then arranged upstream of the first device and / or the first element. This information always refers to the main propagation direction of the respective laser beams.

[0067] The following description of preferred embodiments, in conjunction with the drawings, serves to explain the invention in more detail. In the drawings: Fig. 1 shows a schematic representation of an embodiment of a laser system, with a beam path indicated in a first cross-sectional plane;

[0068] Fig. 2 is a schematic representation of a section of the laser system according to Fig. 1, wherein a beam path is indicated in a second cross-sectional plane oriented perpendicular to the first cross-sectional plane;

[0069] Fig. 3 is a schematic representation of a portion of an embodiment of the laser system with a focusing element for collimating and redirecting amplified coherent laser beams;

[0070] Fig. 4 is a schematic representation of a portion of an embodiment of the laser system with a plurality of focusing elements for collimating the respective amplified coherent laser beams and a beam deflection device for deflecting them;

[0071] Fig. 5 is a schematic representation of a portion of another embodiment of the laser system with a plurality of focusing elements;

[0072] Fig. 6 is a schematic representation of a portion of an embodiment of the laser system without focusing elements;

[0073] Fig. 7 is a schematic representation of a portion of another embodiment of the laser system without focusing elements;

[0074] Fig. 8a-8c show grayscale representations of an example of an interference pattern intended for laser processing of a workpiece at different scales; Fig. 9a-9c show grayscale representations of another example of an interference pattern intended for laser processing of a workpiece at different scales; and

[0075] Fig. 10 is a grayscale representation of another example of an interference pattern intended for laser processing of a workpiece.

[0076] Identical or functionally equivalent elements are provided with the same reference numerals in all figures.

[0077] An embodiment of a laser system is shown schematically in Figs. 1, 2, and 3 and designated by 100. During operation of the laser system 100, a plurality of output laser beams 102 are provided, which form an interference pattern intended for laser processing of a workpiece 104. The formed interference pattern is based in particular on the principle of direct laser interference patterning (DLIP).

[0078] In the embodiment shown, the laser system 100 comprises a laser beam source 106, by means of which an input laser beam 108 is provided, wherein the input laser beam 108 is split into a plurality of coherent laser beams 112 by means of a splitting device 110.

[0079] The laser beams provided by the laser beam source 106, such as the input laser beam 108 and / or the coherent laser beams 112, are, for example, linearly polarized laser beams. In particular, these laser beams have a high beam quality, wherein a beam quality factor and / or M 2 -value is less than 1.5.

[0080] In particular, each of the coherent laser beams 112 has an average power in the range of 10 W and 500 W.

[0081] In particular, the laser beams provided by the laser beam source 106 are pulsed laser beams, wherein laser pulses of these laser beams preferably have a pulse duration between 10 ps and 1000 ps and / or a repetition rate between 100 kHz and 1 MHz.

[0082] The splitting device 110 can, for example, be implemented using fiber optics and / or comprise at least one fiber optic beam splitter. A fiber optic beam splitter comprises, for example, an input waveguide, to which further waveguides for beam splitting are connected on the output side, in particular by splicing.

[0083] It is also fundamentally possible for multiple laser beam sources 106 to be present to provide the coherent laser beams 112. For example, one or more coherent laser beams 112 are then provided by a respective laser beam source 106.

[0084] The coherent laser beams 112 coupled out of the splitting device 110 are preferably guided in optical waveguides and / or optical fibers, whereby the coherent laser beams 112 can, for example, be guided in single-core waveguides, as indicated in Fig. 1. It is also possible in principle to provide multi-core waveguides for guiding the coherent laser beams 112.

[0085] To adjust a respective phase difference between the individual coherent laser beams 112, a phase adjustment device 114 is provided, which preferably comprises a plurality of phase adjustment elements 116. By means of a specific phase adjustment element 116, a phase of a coherent laser beam 112 associated with it can be adjusted.

[0086] For example, a phase adjustment element 116 is assigned to each of several or all coherent laser beams 112. In the case of N coherent laser beams 112, the phase adjustment device 114 comprises, for example, N1 or N phase adjustment elements 116. This makes it possible, in particular, to adjust a respective phase difference between all existing coherent laser beams 112. The phase adjustment device 114 and / or the phase adjustment elements 116 can, for example, be integrated into optical fibers in which the coherent laser beams 112 are guided.

[0087] To amplify the respective coherent laser beams 112, the laser system 100 comprises an amplification device 118, which preferably comprises a plurality of amplification elements 120. For example, each amplification element 120 is assigned to a specific coherent laser beam 112. By amplifying the coherent laser beams 112 by means of the amplification device 118, amplified coherent laser beams 113 are formed.

[0088] With respect to a main propagation direction 122, the amplification device 118 or the amplification elements 120 are arranged downstream of the phase adjustment device 114 or the phase adjustment elements 116, ie the respective coherent laser beams 112 pass through the phase adjustment elements 116 first and then the amplification elements 120.

[0089] The main propagation direction 122 is understood to be a respective main direction and / or average direction of the input laser beam 108 or the coherent laser beams 112 or the amplified coherent laser beams 113 or the output laser beams 102, in which they propagate through the laser system 100. In particular, the respective main propagation direction 122 corresponds to a main direction and / or average direction of the Poynting vectors assigned to the corresponding laser beam.

[0090] In particular, coherent laser beams 112 coupled out of the phase adjustment device 114 are coupled into the amplification device 118. In particular, the respective phase differences between the coherent laser beams 112 are adjusted by means of the phase adjustment device 114 before they are coupled into the amplification device 118.

[0091] The amplification elements 118 can, in particular, be arranged and / or aligned separately and / or spatially separated from one another. The amplification elements 120 are, for example, rod-shaped and / or designed as fiber amplifiers. For example, the amplification elements 120 are or comprise "rod-type photonic crystal fiber amplifiers," as known, for example, from J. Limpert et al., "High-power rod-type photonic crystal fiber laser," Opt. Express 13, 1055-1058 (2005).

[0092] It is also possible for the amplification device 118 and / or the amplification elements 120 to be designed as a multi-core waveguide and / or to be integrated into a multi-core waveguide. The individual coherent laser beams 112 and / or amplified coherent laser beams 113 are then separated from one another, particularly in the far field.

[0093] All existing reinforcing elements 120 are advantageously of the same design and / or designed as identical parts.

[0094] The output laser beams 102 of the laser system 100 are those coherent laser beams that are amplified by the amplification device 118 during operation of the laser system 100 and are designed and / or configured to form an interference pattern 124 intended for laser processing of the workpiece 104. The output laser beams 102 are therefore the laser beams that contribute to and / or are configured to form the interference pattern 124.

[0095] The output laser beams 102 converge toward the interference pattern 124 and / or from different directions. The output laser beams 102 extend, in particular, within a beam convergence region 130 of the laser system 100 associated with the interference pattern 124 or form a beam convergence region 130 of the laser system 100 associated with the interference pattern 124.

[0096] The output laser beams 102 are therefore the laser beams contributing to the formation of the interference pattern 124. Depending on the embodiment, the output laser beams 102 are based on or correspond to the coherent laser beams 113 amplified by the amplification device 118. The interference pattern 124 formed by the provided output laser beams 102 extends, for example, in a plane or in a three-dimensional volume.

[0097] It is intended that the workpiece 104 be exposed to the formed interference pattern 124 for laser processing. The laser system 100 can have a workpiece holder 126 on which the workpiece 104 can be arranged and / or fixed in order to apply the interference pattern 124 to it.

[0098] Furthermore, the laser system 100 can have a feed device 128, which is configured to adjust a position and / or orientation of the workpiece 104 relative to the interference pattern 124 and / or which is configured to perform a movement of the workpiece 104 relative to the interference pattern 124. For example, the feed device 128 is configured to move the workpiece holder 126 and the workpiece 104 arranged thereon relative to the interference pattern 124, and in particular to move it along a predetermined trajectory.

[0099] To form the interference pattern 124, it is necessary that the output laser beams 102 contributing to its formation are oriented convergently toward one another and have a non-zero angle to one another. More specifically, the respective main propagation directions 122 and / or Poynting vectors 132 of the adjacent output laser beams 102 have a non-zero angle to one another.

[0100] In a first variant of the laser system 100, all existing output laser beams 102 are arranged in a common plane or surface (see, for example, the three output laser beams 102 shown in Fig. 1), wherein adjacent output laser beams 102 have a non-zero first angle α to one another and each converge at this first angle α, i.e., adjacent output laser beams 102 converge at the first α angle in the direction of the interference pattern 124 to be formed. The first angle α extends in particular in a first direction and / or with respect to a first angular coordinate.

[0101] The interference pattern 124 resulting in this case extends two-dimensionally in the said common plane of the output laser beams 102 and in particular exclusively in this plane (in the example shown in Fig. 1, the zx plane).

[0102] In the example according to Fig. 1, the first variant is realized in that the amplified coherent laser beams 113 emerging from the amplification elements 120 are positioned at a distance from one another in the first spatial direction x and are coupled into a focusing device 134 of the laser system 100. The focusing device 134 has one or more focusing elements 136, each of which comprises or is designed as a focusing optics and / or an F-theta objective. The amplified coherent laser beams 113 incident on the focusing device 134 run, for example, parallel to one another and / or in a plane parallel to the first spatial direction x. For example, the amplification elements 120 and / or the amplified coherent laser beams 113 emerging from them are arranged as an array with respect to the first spatial direction x.

[0103] The amplified coherent laser beams 113 emerge from the respective amplification elements 120 in particular as a divergent beam bundle 138 and / or as spherical waves or at least as partial regions of spherical waves (e.g., indicated in Fig. 6) and, in this form, are incident on the focusing device 134. The focusing device 134 is designed to collimate the respective amplified coherent laser beams 113 incident thereon. The output laser beams 102, each formed from an amplified coherent laser beam 113 incident on the focusing device 134, each emerge from the focusing device 134 as a collimated beam bundle 140 and / or as plane waves (e.g., indicated in Fig. 3).

[0104] In the example shown in Figs. 1, 2, and 3, a single focusing element 136 is assigned to all existing amplified coherent laser beams 113. Adjacent amplified coherent laser beams 113 impinge on the focusing element 136 with a spatial offset relative to the first spatial direction x, wherein the spatial offset after the focusing element 136 results in an angular offset between the output laser beams 102 formed from the amplified coherent laser beams 113 in the form of the aforementioned first angle α between adjacent output laser beams 102.

[0105] The spatial offset of the amplified coherent laser beams 113 or the resulting first angle α can be the same for all or for a subset of the amplified coherent laser beams 113 or output laser beams 102. However, it is also possible for the spatial offset or first angle α to be selected differently between different neighboring amplified coherent laser beams 113 or output laser beams 102.

[0106] In a second variant, several planes or surfaces are present in which the existing output laser beams 102 extend, wherein, in particular, different subsets of output laser beams 102 are assigned to different planes. The output laser beams 102 assigned to a specific subset then extend in the same plane or surface.

[0107] In the example according to Figs. 1, 2, and 3, the second variant can be realized by providing both amplified coherent laser beams 113 spaced apart from one another in the first spatial direction x and amplified coherent laser beams 113 spaced apart from one another in a second spatial direction y oriented transversely and, in particular, perpendicularly to the first spatial direction x. For example, the amplification elements 120 and / or the amplified coherent laser beams 113 emerging from them are arranged as a two-dimensional array with respect to the first spatial direction x and the second spatial direction y.

[0108] There are then both adjacent output laser beams 102 which have a non-vanishing first angle α to each other and each converge at this first angle α (Fig. 1), and adjacent output laser beams 102 which have a non-vanishing second angle β to each other and each converge at this second angle β (Fig. 2).

[0109] The second angle β extends in particular in a second direction and / or with respect to a second angular coordinate (relative to a specific output laser beam 102, from which the first angle α or second angle β is measured relative to the adjacent output laser beams 102). This second direction or second angular coordinate is different from the first direction or first angular coordinate of the first angle α. In particular, the first direction is oriented transversely or perpendicularly to the second direction.

[0110] When describing the orientation of the output laser beams 102 in spherical coordinates, the first angle α corresponds, for example, to the polar angle and the second angle β to the azimuth angle.

[0111] The interference pattern 124 formed in the case of the second variant extends three-dimensionally in space (in the example shown in Fig. 1 in all three spatial directions x, y and z).

[0112] The output laser beams 102 converging in the beam convergence region 130 are thus realized in the variants described above by means of the spatial offset of the amplified coherent laser beams 113 incident on the focusing element 136 and the resulting angular offset in the form of the first angle α and / or the second angle β.

[0113] To form the interference pattern 124, the angular offset between adjacent output laser beams must be within a specific range. The theoretically possible range in which the formation of the interference pattern 124 can occur is between 2° and 180°. Preferably, the first angle α and / or the second angle β have values ​​between 15° and 25°. The example shown in Fig. 4 differs from the examples described above in that the focusing device 134 comprises a plurality of focusing elements 136 and that the laser system 100 has a beam deflection device 142 to form the angular offset between the output laser beams 102. Otherwise, this example has the same structure and / or the same mode of operation as the examples described above.

[0114] In the example shown, each of the amplification elements 120 and / or each of the amplified coherent laser beams 113 emerging from the amplification elements 120 is assigned a focusing element 136 and in particular a single focusing element 136.

[0115] The amplified coherent laser beams 113 emerge from the respective associated amplification elements 120 as divergent beam bundles 138 and are converted into collimated beam bundles 140 by the focusing elements 136. The amplified coherent laser beams 113 emerging from the respective focusing elements 136 are oriented parallel to each other, for example.

[0116] Thus, in this example, the focusing device 134 and / or the focusing elements 136 cause a collimation of the respective amplified coherent laser beams 113 and in particular no focusing thereof.

[0117] To form the output laser beams 102 that converge in the beam convergence region 130 and form the interference pattern 124, the amplified coherent laser beams 113 emerging from the focusing elements 136 are coupled into the beam deflection device 142. This device is configured to form the output laser beams 102 from the coupled-in amplified coherent laser beams 113 with the angular offset described above. The adjacent output laser beams 102 are then convergently aligned with one another and each have the non-zero first angle α and / or second angle β with one another. The beam deflection device 142 can, for example, have a plurality of mirror elements 144 that are configured and arranged such that the converging output laser beams 102 are formed from the coupled-in amplified coherent laser beams 113, which are oriented parallel to one another, for example.

[0118] In the example shown in Fig. 5, the focusing device 134, analogous to the embodiment according to Fig. 4, has a plurality of focusing elements 136, wherein a specific focusing element 136 effects collimation of the amplified coherent laser beam 113 associated with it. For example, each amplification element 120 is assigned a focusing element 136.

[0119] The focusing elements 136 and / or the amplified coherent laser beams 113 impinging on the focusing elements 136 are configured and arranged such that the laser beams emerging from the focusing elements 136 are already convergent to one another and have the described angular offset from one another in order to form the interference pattern 124. These emerging laser beams thus correspond to the output laser beams 102 or have the described properties of the output laser beams 102.

[0120] For example, the amplification elements 120 are arranged and / or configured such that the coherent laser beams 120 coupled out of them and impinging on the focusing elements 136 already exhibit the aforementioned angular offset in the form of the first angle α and / or the second angle β. Accordingly, in this example, the output laser beams 102 coupled out of the focusing elements 136 exhibit the angular offset from one another in order to form the interference pattern 124.

[0121] The reinforcement elements 120 are, for example, rod-shaped and / or designed as "rod-type photonic crystal fiber amplifiers," wherein the respective main propagation direction 122 of the amplified coherent laser beam 113 emerging from a specific reinforcement element 120 is parallel or at least approximately parallel to a longitudinal center axis 146 of the reinforcement element 120. For example, the longitudinal center axes 146 of adjacent reinforcement elements 120 are then aligned with each other with the angular offset in the form of the first angle α and / or the second angle β. Respective centers of the reinforcement elements 120 are positioned, for example, in a circular and / or spherical manner.

[0122] In the above-described embodiments according to Figures 1 to 5, the output laser beams 102 are each present as collimated beam bundles 140 and / or in the form of plane waves. In this case, the output laser beams 102 are each assigned exactly one Poynting vector 132, which corresponds to the main propagation direction 122. In this case, the Poynting vector 132 is a globally uniform property of the respective collimated output laser beam 102.

[0123] In the embodiments of the laser system 100 shown in Figs. 6 and 7, the output laser beams 102 provided for forming the interference pattern 124 are provided in the form of divergent beam bundles 138 and / or spherical waves. In this case, the Poynting vector 132 is always oriented perpendicular to the orientation of the wavefront of the spherical waves of a specific output laser beam 102 and thus has a different orientation locally (indicated in Fig. 6). The non-vanishing Poynting vectors 132 assigned to a specific output laser beam 102 thus cover a specific angular range. The main propagation direction 122 of the output laser beam 102 is then understood to be an averaged direction across all non-vanishing Poynting vectors 132.

[0124] The amplification elements 120 are arranged and / or configured such that at least beam components of adjacent laser beams coupled out from them have Poynting vectors 132 with an angular offset in the form of the first angle α and / or the second angle β.

[0125] For example, the amplification elements 120 are arranged and / or configured such that the output laser beams 102 coupled out from them and impinging on the focusing elements 136 already exhibit the aforementioned angular offset in the form of the first angle α and / or the second angle β. Accordingly, in this example, the beam portions of the output laser beams 102 coupled out from the focusing elements 136 exhibit the appropriate angular offset from one another to form the interference pattern 124. These laser beams emerging from the amplification elements 120 thus correspond in this case to the output laser beams 102 or at least partially exhibit the properties necessary to form the interference pattern 124.

[0126] In particular, in the embodiments according to Figures 6 and 7, no focusing device 134 and / or no focusing elements 136 are provided for collimating the laser beams emerging from the amplification elements 120.

[0127] In the example shown in Fig. 6, the longitudinal center axes 146 of the gain elements 120 and / or the main propagation directions 122 of adjacent output laser beams 102 are oriented parallel or at least approximately parallel. To enlarge the respective beam components of adjacent output laser beams 102, which have a suitable angular offset in the form of the first angle α and / or the second angle β, in order to form the interference pattern 124, it can be provided that the respective main propagation directions 122 of the adjacent output laser beams 102 are angled to one another in a converging manner (Fig. 7). The main propagation directions 122 of the adjacent output laser beams 102 then have a non-zero first angle α and / or second angle β to one another, which can be, for example, between 1° and 180°.

[0128] A first example of an interference pattern 124 formed by the laser system 100 is shown in Figs. 8a, 8b, and 8c as a grayscale representation at different scales, with lighter gray values ​​representing higher intensities. The interference pattern 124 has an interference element 150 that repeats several times in at least one spatial direction x, y, z, wherein the repeating interference elements 150 are spaced apart from one another in this at least one spatial direction and, in particular, are arranged adjacent to one another at the same distance from one another. In the example shown in Figs. 8a to 8c, the interference element 150 is formed as a single point and / or focal point.

[0129] For example, the interference element 150 repeats itself flatly in the first spatial direction x and in the second spatial direction y, or as a three-dimensional volume in all three spatial directions. The interference element 150, in particular, forms the interference pattern 124.

[0130] In the example shown in Figs. 9a to 9c, the interference element 150 is designed as a stripe-shaped and / or as a single focused stripe.

[0131] In the example shown in Fig. 10, the interference element 150 consists of a dot pattern and / or a plurality of focused dots.

[0132] The Laser System 100 works as follows:

[0133] During operation of the laser system 100, the interference pattern 124 is formed by means of the output laser beams 102 and the workpiece 124 arranged on the workpiece holder 126 is exposed to the interference pattern 124 in order to carry out the laser processing.

[0134] A typical application may, for example, involve performing large-area machining of the workpiece 104 on an outer side 152 of the workpiece 104 and / or in the region of an outer side 152 of the workpiece 104. For example, periodic structures with predetermined properties can be generated on the outer side 152 using the interference pattern 124.

[0135] It can be provided that the workpiece 124 is positioned and / or aligned relative to the interference pattern 124 by means of the feed device 128 in order to carry out the laser processing, and / or is moved relative to the interference pattern 124.

[0136] By changing the current between the coherent laser beams 112

[0137] By adjusting phase differences using the phase adjustment elements 116, the phase differences between the amplified coherent laser beams 113 and / or between the output laser beams 102 can be changed accordingly. This allows the properties of the interference pattern 124 and / or the interference elements 150 of the interference pattern 124 to be adjusted.

[0138] During operation of the laser system 100, a distance 154 between adjacent interference elements 150 can be adjusted, for example, by varying the phase differences using the phase adjustment elements 116. Furthermore, a periodicity of the interference elements 150 can be adjusted, such as a regularity of the positioning of the interference elements 150. In addition, an intensity profile and / or a geometric shape of the interference elements 150 can be adjusted, for example. For example, the interference elements 150 and / or selected interference elements 150 can be scanned across the workpiece 104 by controlling the phase differences, and in particular exclusively by controlling the phase differences, using the phase adjustment elements 116.

[0139] List of reference symbols a first angle ß second angle x first spatial direction y second spatial direction

[0140] 100 laser system

[0141] 102 Output laser beam

[0142] 104 Workpiece

[0143] 106 Laser beam source

[0144] 108 input laser beam

[0145] 110 Distribution device

[0146] 112 coherent laser beam

[0147] 113 amplified coherent laser beam

[0148] 114 Phase adjustment device

[0149] 116 Phase adjustment element

[0150] 118 amplification device

[0151] 120 reinforcement element

[0152] 122 Main propagation direction

[0153] 124 interference patterns

[0154] 126 Workpiece holder

[0155] 128 Feed device

[0156] 130 beam convergence area

[0157] 132 Poynting vector

[0158] 134 Focusing device

[0159] 136 Focusing element

[0160] 138 divergent beam

[0161] 140 collimated beam

[0162] 142 beam deflection device

[0163] 144 mirror element

[0164] 146 Longitudinal center axis

[0165] 148 Center

[0166] 150 interference elements

[0167] 152 Outside

[0168] 154 distance

Claims

Patent claims Laser system for laser processing of a workpiece (104) by means of an interference pattern (124), comprising at least one laser beam source (106) for providing a plurality of coherent laser beams (112), an amplification device (118) for forming amplified coherent laser beams (113) by amplifying the coherent laser beams (112), a phase adjustment device (114) for adjusting a respective phase difference between the coherent laser beams (112) and / or the amplified coherent laser beams (113), and a beam convergence region (130) in which output laser beams (102) based on the amplified coherent laser beams (113) or corresponding to the amplified coherent laser beams (113) converge to form the interference pattern (104), wherein in the beam convergence region (130) at least beam components of different output laser beams (102) converge.Laser system according to claim 1, characterized in that the mutually adjacent output laser beams (102) present in the beam convergence region (130) have at least beam components that enclose an angle (α, β) of at least 0.2° and / or at most 40°, and preferably of at least 1° and / or at most 5°. Laser system according to claim 1 or 2, characterized in that in the beam convergence region (130) mutually adjacent output laser beams (102) have beam components that enclose a non-vanishing first angle (α) assigned to a first angular coordinate, wherein the first angle (α) is at least 0.2° and / or at most 40°, and preferably at least 1° and / or at most 5°.Laser system according to claim 3, characterized in that in the beam convergence region (130) adjacent output laser beams (102) have beam components which have a second angular coordinate different from the first angular coordinate. associated non-vanishing second angle (ß), wherein the second angle (ß) is at least 0.2° and / or at most 40° and preferably at least 1° and / or at most 5°. Laser system according to claim 4, characterized in that adjacent output laser beams (102) present in the beam convergence region (130) are aligned with one another in such a way that in each case two adjacent output laser beams (102) either have beam components which enclose a non-vanishing first angle (α) or have beam components which enclose a non-vanishing second angle (β). Laser system according to one of the preceding claims, characterized in that the output laser beams (102) in the beam convergence region (130) are present as collimated beam bundles (140), or that the output laser beams (102) in the beam convergence region (130) are present as divergent beam bundles (138).Laser system according to one of the preceding claims, characterized by a focusing device (134) for collimating and / or deflecting amplified coherent laser beams (113) incident on the focusing device (134). Laser system according to claim 7, characterized in that the focusing device (134) has a focusing element (136), and in particular a single focusing element (136), wherein several, and in particular all, existing amplified coherent laser beams (113) are incident on the focusing element (136), and wherein the amplified coherent laser beams (113) are collimated and deflected by means of the focusing element (136) in order to provide the output laser beams (102).Laser system according to claim 7, characterized in that the focusing device (134) has a plurality of focusing elements (136), wherein a respective focusing element (136) is assigned to an amplified coherent laser beam (113), and wherein the amplified coherent laser beams. (113) are each collimated by means of the associated focusing element (136). Laser system according to one of claims 7 to 9, characterized in that the existing focusing elements (136) and / or the amplified coherent laser beams (113) incident on the existing focusing elements (136) are configured and arranged such that laser beams emerging from the focusing elements (136) form the beam convergence region (130) and correspond to the output laser beams (102). Laser system according to one of the preceding claims, characterized by a beam deflection device (142) for deflecting the amplified coherent laser beams (113) in order to form the output laser beams (102) converging in the beam convergence region (130).Laser system according to one of the preceding claims, characterized in that the amplified coherent laser beams (113) coupled out of the amplification device (118) are present as divergent beam bundles (138), wherein a main propagation direction (122) of adjacent amplified coherent laser beams (113) is oriented parallel or transversely, and wherein the amplified coherent laser beams (113) correspond to the output laser beams (102). Laser system according to one of the preceding claims, characterized in that the interference pattern (124) has at least one interference element (150) for laser processing the workpiece (104), which interference element is repeated within the interference pattern (124) and in particular is repeated at regular intervals (154).Laser system according to claim 13, characterized in that the interference element (150) is repeated within the interference pattern (124) at least 10 times and in particular at least 100 times and in particular at least 1000 times. Laser system according to claim 13 or 14, characterized in that by adjusting the phase difference between the coherent laser beams (112) or amplified coherent laser beams (113) by means of the phase adjustment device (114), at least one property of the interference pattern (124) and / or of the interference element (150) is variable or is varied, wherein the at least one property comprises in particular a spacing (154) of the interference elements (150) and / or a periodicity of the interference elements (150) and / or a peak intensity of the interference elements (150) and / or an intensity profile of the interference elements (150) and / or a geometric shape of the interference elements (150).Laser system according to one of the preceding claims, characterized in that the amplification device (118) has a plurality of amplification elements (120) for amplifying a respective coherent laser beam (112), and in particular characterized in that the amplification elements (120) are rod-shaped and / or designed as fiber amplifiers.Method for laser machining a workpiece by means of an interference pattern (124), in which a plurality of coherent laser beams (112) are provided by means of at least one laser beam source (106), amplified coherent laser beams (113) are formed by amplifying the coherent laser beams (112) by means of an amplification device (118), and a respective phase difference between the coherent laser beams (112) and / or the amplified coherent laser beams (113) is set by means of a phase adjustment device (114), wherein output laser beams (102) based on the amplified coherent laser beams (113) or corresponding to the amplified coherent laser beams (113) are formed, which output laser beams converge in a beam convergence region (130) to form the interference pattern (124), wherein in the beam convergence region (130) at least beam components of different Output laser beams (102) converge.

Images