Method and device for machining workpieces

Abstract

The invention relates to a method for machining a workpiece (1), in which - the workpiece (1) is irradiated with the laser light (30) of a laser (3), wherein - the material of the workpiece (1) is at least partially transparent to the laser light (30) such that the laser light (30) penetrates into the workpiece (1), and wherein - the laser light (30) is concentrated by means of a beam-shaping optical unit (7) in a focusing zone (35) in the workpiece (1), wherein - the focusing zone (35) has, in cross section perpendicular to the beam axis, a flattened shape with a length situated in the beam direction and a width and thickness which are each perpendicular to the length, wherein the thickness of the focusing zone (35), at least at one position along the beam axis, is smaller by at least a factor of 5 than the width and the length of the focusing zone, and wherein - within the focusing zone (35), on account of the intensity of the laser light (30) in the material of the workpiece (1), there is inserted a modification zone (10) which, corresponding to the focusing zone (35), has a flattened shape.

Description

[0001] Method and device for processing workpieces Description The invention relates generally to material processing. In particular, the invention relates to the processing of materials that are transparent to light in at least one wavelength range, using laser radiation. Non-contact methods for separating materials are known from the prior art. Some of these separation methods make use of laser radiation. Laser ablation is particularly noteworthy here. One advantage is that the method can be applied to almost any material. A disadvantage, however, is that ablation is generally very slow - especially compared to mechanical abrasive methods. Another separation method is based on the action of high-intensity laser radiation inside transparent materials. Non-linear optical processes lead to material changes or even to the formation of plasma, which damages the material locally.In this case, an at least partially open channel can form in the material along the laser beam. If such local, typically filament-shaped damage or channels are repeatedly introduced along a path with the laser, the workpiece thus processed can then be easily separated along the path. A method for separating glasses by a series of damages in the form of filaments using a laser is known, among other things, from WO 2017 / 009379 A1 and the further prior art cited therein. This technique of inserting filament-shaped damage along a path and subsequently separating the processed workpiece along the path quickly reaches its limits if the separation line is curved or even has corners. In the above-mentioned WO 2017 / 009379 A1, separation along a curved separation line is made possible by inserting the filaments at an angle to the surface.However, this is not desired in many cases. Separation along any desired separation line is, on the other hand, possible by subsequent etching. Etching causes the filaments to expand until the channels thus formed connect with one another, resulting in separation along the separation line. However, etching is complex and slow. Therefore, there is a need to further improve the processing of workpieces, such as the separation of transparent materials using a laser, by creating modifications inside the workpiece. This object is achieved by the subject matter of the independent claims. Advantageous embodiments of the invention are specified in the respective dependent claims. The method and device according to this disclosure are based, in particular, on shaping a laser beam such that a two-dimensionally extended focus is obtained in the material of the workpiece to be separated.This does not create more or less linear damage or a thin channel in the workpiece as viewed in the propagation direction of the laser beam, but rather a two-dimensional, extensive and contiguous modification zone, in particular in the form of a damage zone, which ideally already shows a separation of the material. In particular, a method for machining a workpiece is provided, in which the workpiece is irradiated with the laser light of a pulsed laser, wherein the material of the workpiece is at least partially transparent to the laser light, so that the laser light penetrates the workpiece. The modification of the material of the workpiece occurs through nonlinear interaction with the laser light due to the high light intensity, in particular through nonlinear absorption of the laser light.To achieve a high light intensity, the laser light is bundled into a focusing zone in the workpiece by means of beam-shaping optics. The focusing zone has a flattened shape with a length lying in the beam direction of the laser light and a width and a thickness in cross-section perpendicular to the beam axis or beam direction, or in the transverse profile, wherein at least at one position along the beam axis, the thickness of the focusing zone in cross-section is at least a factor of 5 smaller than the width and length of the focusing zone. In other words, the focusing zone extends along the beam axis of the laser light and two directions perpendicular thereto, wherein the focusing zone is at least a factor of 5 narrower in the direction along one of the directions perpendicular to the beam axis than along the beam axis and the other direction perpendicular to the beam axis.The shape of the focusing zone can therefore also be described as sheet-shaped or knife-edge-shaped. The thickness and width in the cross-section perpendicular to the beam direction represent a local thickness and width of the focusing zone, respectively. Both quantities can therefore vary along the beam direction and usually do. A box can also be placed around the focusing zone. The dimensions of this box can then be referred to as the global thickness, width and length. Within the focusing zone, a modification zone is inserted due to the intensity of the laser light in the material of the workpiece. This modification zone has a flattened shape corresponding to the focusing zone. In other words, in particular in accordance with the shape of the focusing zone, it is more extensive in the direction of the beam axis and in a direction perpendicular to it than in a second direction perpendicular to the beam axis.The beam axis and the aforementioned first and second directions form, in particular, an orthogonal coordinate system. Accordingly, these three directions are perpendicular to each other in pairs. The workpiece can then be separated into two parts at the modification zone according to a preferred embodiment. According to a further development, this separation occurs spontaneously if the modification zone already causes a separation of the material. In general, a modification zone is understood to be an area in the material of the workpiece in which the material of the workpiece is modified compared to the surrounding material. In particular, the modification zone can be a damage zone, i.e., an area in which damage has been introduced into the material. Such damage can, in particular, also comprise a separation of the material.Optionally, according to another embodiment, separation can also be achieved by an additional step, for example by applying stress to the material in the region of the modification zone. Stress can be applied mechanically, for example via compressive, tensile, or bending stress, or thermally, or by heating the surface with a radiation source, such as a CO2 laser, or by cooling with a nozzle. Spontaneous self-separation is also possible if the glass workpiece is chemically or thermally tempered. Pulsed lasers are particularly suitable for providing the radiation intensity required to produce the modification, in particular to damage the material.For example, for glasses and other inorganic materials, so-called ultrashort pulse lasers, whose pulses have a length in the range of a few tens of ps or less, are particularly suitable for inducing corresponding damage zones. In addition to separating workpieces, other processing operations involving material modification are also possible. According to another, alternative, or additional embodiment, the laser light induces a change in the refractive index locally in the material of the workpiece, i.e., in the damage zone. Such a change in the material properties can occur, in particular, at lower light intensities or power densities compared to processing for separating the workpiece. The method is particularly suitable for processing inorganic materials that are transparent to the laser light used.This particularly applies to glass, but also to glass ceramics, silicon, and other crystalline materials, such as crystalline aluminum oxide. In accordance with the method described above, a device for carrying out the method is also provided. The device for processing a workpiece comprises, in particular, a laser for emitting laser light, wherein the laser is configured to emit laser light at a wavelength for which the workpiece is at least partially transparent, so that the laser light can penetrate the workpiece.The device further comprises in particular a beam-shaping optics for focusing the laser light in a focusing zone in the workpiece, wherein the beam-shaping optics are designed such that the focusing zone of the laser light generated thereby has a flattened shape with a length lying in the beam direction and a width and a thickness, wherein the width and thickness are perpendicular to the direction of the length, thus the directions of the width, thickness and length are perpendicular to one another in pairs, and wherein the thickness of the focusing zone is at least a factor of two, preferably at least a factor of 5, smaller than the width and length of the focusing zone.The laser and the beam-shaping optics are further configured such that sufficient laser light intensity is present within the focusing zone to introduce a damage zone into the material of the workpiece. This damage zone has a flattened shape, in particular such that the damage zone, corresponding to the shape of the focusing zone, is more extensive in the direction of the beam axis and a direction perpendicular thereto than along a second direction perpendicular to the beam axis. The workpiece to be separated can also be part of the device. Furthermore, the device can comprise a device for separating the workpiece at the modification zone, in particular a device for exerting mechanical stress on the modification zone.The flattened, for example blade-like shape of the focusing zone can, alternatively or in addition to the ratios of thickness to width and / or length of this zone, also be described by the ratios of the corresponding areas. Thus, alternatively or additionally, one embodiment provides for the laser light to be bundled in a focusing zone such that the projection area of ​​the focusing zone, viewed along the direction of the beam axis of the laser light, is at least a factor of four smaller than the projection area of ​​the focusing zone, viewed along the direction of the thickness of the focusing zone. The dimensions of the focusing zone along the three mutually perpendicular directions, i.e., the beam axis and the other two directions, are referred to as thickness w, width b, and height L, as already described above.The height L is the extension of the focusing zone in the direction of the beam axis or beam direction, or the direction of incidence of the laser light. The thickness w denotes the extension of the cross-section of the focusing zone along a second direction perpendicular to the beam axis, along which the focusing zone is narrower by at least a factor of 2, preferably at least a factor of 5, than along the beam axis and a first direction perpendicular to the second direction.It is preferred that the beam-shaping optics are used to create a focusing zone in the workpiece which has at least one, preferably all of the following dimensions: - a width b, i.e. an extent along a first direction perpendicular to the beam axis in the range from 1 µm to 10 mm, preferably 10 µm to 50 µm, - a thickness w, i.e. an extent along a second direction perpendicular to the beam axis in the range from 0.2 µm to 50 µm, preferably 1 µm ± 0.5 µm, - a height L, i.e. an extent along the beam axis in the range from 2 µm to 20 mm, preferably at least 30 µm, particularly preferably 1 mm to 5 mm. The invention is explained in more detail below with reference to the figures. In the figures, the same reference numerals refer to the same or corresponding elements. Brief description of the figures: Fig. 1 shows a device for machining workpieces. Fig.2 shows a schematic representation of a workpiece with damage zones inserted into it. Fig.3 shows a schematic cross-section of a focusing zone. Fig. 4 shows an arrangement with a focusing zone positioned completely in the workpiece. Fig. 5 shows three possible positionings of a focusing zone relative to a workpiece. Fig. 6 shows an arrangement for generating a focusing zone with a Bessel beam. Fig. 7 shows the intensity curve in a focusing zone in two mutually perpendicular sectional planes. Fig. 8 shows an astigmatically focused laser beam and Fig. 9 the beam cross-section of the laser beam at four different positions. Fig. 10 shows, similar to Fig. 8, an astigmatically shaped laser beam together with idealized three-dimensional beam profiles. Fig. 11 shows various possible arrangements of an astigmatic laser beam relative to a workpiece to be processed. Fig. 12 shows beam shaping optics with a diffractive optical element. Fig.Figure 13 shows a plan view of a diffractive optical element for generating a Gauss-Bessel beam and the phase curve of beamlets that can be generated with this mask. Figure 14 shows the phase shift caused by a diffractive optical element for two mutually perpendicular directions as a function of the distance in the radial direction to the center of the element. Figure 15 shows an optical micrograph of the surfaces of a workpiece processed with laser light. Figure 16 schematically shows the position of the focusing areas relative to the surface of the workpiece. Figure 17 shows an optical micrograph of the surface of a separated workpiece, and Figure 18 shows the edge surface of a part of the workpiece obtained by the separation. Figure 19 shows an optical arrangement for generating a focusing zone curved around an axis perpendicular to the beam direction.20 shows examples with a curved focusing zone, with partial image (a) showing a workpiece through which the focusing zone shines and partial image (b) showing a focusing zone in perspective. FIGS. 21 to 26 show further embodiments of beam-shaping optics for generating flattened focusing zones. FIG. 1 shows an embodiment of a device 2 for processing, in particular for separating, a workpiece 1, as is suitable for carrying out the method described herein. The device 2 generally comprises, without limitation to the example shown, as central components a laser 3 and beam-shaping optics 7. A workpiece 1 to be processed is arranged in front of the beam-shaping optics 7 in the beam direction of the laser 3 such that the focusing zone 35 generated by the beam-shaping optics 7 from the laser light, or rather the laser beam 30, lies at least partially within the workpiece 1.The laser 3 is sufficiently powerful to induce a material change in a modification zone, preferably in the form of a damage zone, due to the intensity of the laser light 30 within the part of the focusing zone 35 located in the workpiece 1, which either facilitates or already causes the separation of the element 1 at the damage zone. An ultrashort pulse laser is particularly suitable, preferably with pulse durations in the picosecond range, in particular operable with pulse durations below 50 ps. Unlike previously used devices for laser-based separation of workpieces by introducing filament-shaped damage or thin channels, the focusing zone 35 and, accordingly, the damage zone 10 are provided with a flattened shape.Depending on the focusing properties, the focusing zone can have different shapes, for example the shape of a flattened ellipsoid or simply a highly flattened cuboid or a flat disk. A flattened focusing zone 35 can generally be achieved by an astigmatic or caustic beam-shaping optic 7. In one embodiment, at least one cylindrical lens can be provided as a component of the beam-shaping optic 7. In general, another refractive optical element can also be used alternatively or in addition to a cylindrical lens. Thus, according to one embodiment, a freeform optic is provided. A phase mask is particularly preferred as a component of the beam-shaping optic 7. A phase mask makes it easy to create a focusing zone 35 that is both long and thin.In contrast, with a cylindrical lens or, in general, an optic with different refractive powers in mutually perpendicular directions, there is a tendency for a reduction in width to also be accompanied by a shortening of the focusing zone. According to one embodiment, the phase mask is designed as a diffractive optical element. Another phase mask, such as an LCOS spatial light modulator (SLM), can also be part of the beam-shaping optics as an element for generating the flattened focusing zone described here. An LCOS SLM is a reflective spatial light phase modulator that can freely modulate the optical phase. The optical phase of the laser is modulated by a liquid crystal. In general, the beam-shaping optics 7 can therefore also comprise a liquid crystal element for phase modulation of the light. In general, the focusing zone 35 and the modification zone 10 do not have to coincide.In particular, the focusing zone 35 can begin outside the workpiece 1 and / or end outside the workpiece 1. In the example shown, the length L of the focusing zone 35, i.e. its dimension in the direction along the beam axis 31 of the laser light 30, is greater than the thickness of the workpiece 1. The focusing zone 35 protrudes beyond both opposite side surfaces 100, 101 of the disk-shaped workpiece 1 in this example, while the modification zone 10 can of course extend at most between the two side surfaces 100, 101. Without being limited to the example shown, the method is particularly preferably applied to disk-shaped workpieces 1. Furthermore, as in the example shown, the modification zone is inserted such that the direction of the width of the damage zone lies along the side surfaces 100, 101, or perpendicular to the surface normal of a side surface 100, 101.The modification zone 10 thus represents a narrow cut in a side surface 100, 101, which thus facilitates the separation of the workpiece 1 into parts. In order to adjust the position of the one or more damage zones 10 to be introduced, a positioning device 9 is provided according to a preferred development of the device 2. The positioning device 9 and also the optical system, here in particular the laser 3, can be controlled, preferably by program technology, by means of a controller 12. In the example shown, the positioning device 9 comprises an xy table on which the disk-shaped workpiece 1 is placed. Due to the flattened, blade-shaped focusing zone created with the arrangement described here, its orientation relative to the beam axis is also relevant.To adjust this orientation, one embodiment provides for the optical system, or rather the beam-shaping optics 7, to be rotatable about the beam axis. Alternatively or additionally, the workpiece can also be rotated about the beam axis to achieve a desired orientation of the focusing zone in the workpiece. Therefore, an alternative or additional embodiment provides for the positioning device to have an axis of rotation in order to rotate the workpiece relative to the laser beam in a direction parallel or collinear to the beam direction. If necessary, a single modification zone 10 may already be sufficient for separating the workpiece 1, particularly in the case of small workpieces.In a preferred embodiment, however, a plurality of modification zones 10, preferably in the form of damage zones, are arranged in a row such that they follow a provided parting line 14, the workpiece 1 being separated along the parting line 14 so that two parts 4, 5 are obtained. For clarification, Fig. 2 shows a disk-shaped workpiece 1, here again as an example, with a plurality of such modification zones 10 arranged in a row. The workpiece 1 is shown in a plan view of a side surface 100. In this illustration, the cross-sectional area of ​​the modification zones 10 can be seen perpendicular to the direction of the length L. Due to the flattened geometry of the damage zone 10, it can be recognized as an elongated shape from the side surface 100, shown here in a simplified manner as an elongated rectangle.It is expedient to arrange the modification zones 10 in such a way that the longitudinal directions of the elongated cross sections of the modification zones 10 are aligned along the separating line 14. In other words, the modification zones 10 are oriented such that the separating line 14 runs along the width direction of the modification zones 10. The insertion of flattened, cut-like, or gap-like modification zones 10, as provided for by the invention, also enables easier separation of the workpiece 1 along a curved separating line 14, or at least along a section of it, without a final separation being assisted or caused by an additional etching step. According to an alternative or additional development, it is therefore provided that the damage zones 10 are inserted along a separating line 14 that is at least partially curved.A further difficulty during separation arises when the separation line 14 is closed, as in the example shown. This is also much easier with the method described here compared to pre-separation by introducing filament-shaped damage. According to another alternative or additional embodiment of the method, modification zones 10 are inserted along a closed separation line 14 and then, preferably, an inner part delimited by this separation line is separated from the workpiece 1. In the example shown, part 4 is an inner part 6. The separation line 14 is circular here and the inner part 6 accordingly has the shape of a circular disk. In the example shown, the modification zones 10 are still spatially separated. However, it is generally also possible to allow the modification zones 10 to overlap in order to further facilitate separation into parts 4, 5.In addition to arranging the cuts in a longitudinal direction, it is also possible to insert the modification zones 10 with their widths facing each other. In this way, a correspondingly wider area with material modifications is created. This can also make it easier to cut out internal parts. Another possibility is not to cut through the workpieces, but to create a recess that is open on one side by inserting multiple modification zones next to each other in a workpiece. This also enables, for example, the production of hinges in brittle materials by locally reducing the thickness of the workpiece. Furthermore, the stress in the material can also be changed. For example, in tempered glass, a kink or bend can be created in the workpiece 1 if the compressive stress is locally reduced on at least one side by means of a material modification.Furthermore, other material modifications can also be carried out that do not require the removal of material. This includes, among other things, changes in the refractive index. For example, surface changes in the refractive index can be induced by means of the material modification in order to produce dielectric reflectors, for example in the form of volume Bragg gratings. Fig. 3 shows a schematic cross-section A of a focusing zone 35, viewed in the direction along the beam axis 31. In this direction, the dimensions of the width b and thickness w can be read off the cross-section at the location of the maximum extent of the focusing zone 35. In the example, the focusing zone 35 has an elliptical cross-section, but it will be apparent to a person skilled in the art that, depending on the properties of the beam-shaping optics 7, other cross-sectional shapes are also possible. The beam-shaping optics 7 is now designed such that it has a sufficiently small cross-section in the focusing zone.According to a preferred embodiment, a pulsed laser 3 is used, the laser light 30 of which is focused in the focusing zone 35 such that the light intensity is sufficiently high for a material change of the workpiece 1. In a preferred embodiment, the laser light 30 is focused into a focusing zone 35 whose cross-section A is so small that the light intensity in the focusing zone 35, given by E, pulse / (A∙t pulse ) a value of 10 13 W / cm 2 In the above term, E pulsethe energy of a laser pulse and tpulse the pulse duration. In order to achieve high light intensities, in addition to a small cross-sectional area, short pulse durations are particularly advantageous. According to a further embodiment, the pulse duration is therefore shorter than 100 ps. The pulse duration is particularly preferably in a range from 50 fs to 50 ps. There are various options for dimensioning and positioning the focusing zone 35 relative to the substrate. The length L of the focusing zone 35 can be either greater or smaller than the thickness of the workpiece 1. If the focusing zone 35 is longer than the thickness of the workpiece, the focusing zone 35 can pierce through both opposite surfaces of the workpiece 1. Alternatively, the focusing zone 35 can also be positioned so that only one surface is pierced and the focusing zone 35 ends in the workpiece 1.If the focusing zone 35 is shorter than the thickness of the workpiece, there is the further possibility that the focusing zone 35 lies completely within the workpiece 1. The latter case is illustrated in Fig. 4. The partial images (a) and (b) show the workpiece 1 in cross-section, viewed from different directions. In partial image (a), the focusing zone 35 is shown in the direction perpendicular to the beam axis and perpendicular to the width b. In partial image (b), the focusing zone 35 is shown looking towards the narrow side, i.e., the thickness w. The separation of the workpiece 1 is also intended along this direction. As can be seen from the partial images, the length L of the focusing zone 35 is smaller than the extension of the workpiece 1 in this direction, and the focusing zone 35 lies completely within the workpiece 1 between its side surfaces 100, 101. In the examples in Fig. 5, the length L of the focusing zone is greater than the thickness of the workpiece 1.This makes it possible to position the focusing zone 35 so that it penetrates both opposite side surfaces, as shown in partial image (a). Likewise, the focusing zone 35 can be positioned so that, with respect to the beam direction, it begins in the workpiece (partial image (b)) or ends in the workpiece (partial image (c)), with one of the side surfaces 100, 101 being penetrated in each case.In summary, in general, without limitation to the specific examples shown, in a further development of the method the focusing zone can be positioned such that one of the following features is met: - the focusing zone 35 lies completely within the workpiece 1, - the focusing zone begins or ends within the workpiece 1 and projects beyond a tool surface or one of the side surfaces 100, 101 of the workpiece 1, - the focusing zone 35 is longer than the thickness of the workpiece 1 and breaks through two opposite surfaces, in particular the two opposite side surfaces 100, 101 of a workpiece 1. A flattened, cutting-edge focusing zone 35 can be produced in particular by astigmatic beam shaping or by caustic beam shaping.One-dimensional caustic beam shaping can also be used, in particular, to generate a corresponding Airy beam whose focusing zone is no longer flat, but curved around an axis transverse to, preferably perpendicular to, the beam direction. The generation of such beams is also described in Froehly, L.; Courvoisier, F.; Mathis, A.; Jacquot, M.; Furfaro, L.; Giust, R. et al. (2011): “Arbitrary accelerating micron-scale caustic beams in two and three dimensions”, Optics express 19 (17), pp. 16455–16465, DOI: 10.1364 / OE.19.016455. The beam profiles and the optical arrangements for their generation are also fully incorporated into the present disclosure. One-dimensional caustic beam shaping is described in more detail below with reference to Fig. 19 and Fig. 20.The term "one-dimensional" in this context means that the caustic is essentially formed along a single spatial direction, or that the focusing zone is curved in essentially only one spatial direction. For further discussion, the coordinate in the beam direction is set as the z-coordinate. This direction is therefore the direction of the height L of the focusing zone 35. The perpendicular coordinates x, y correspond to the first and second directions mentioned above and span a plane transverse to the beam direction. Without loss of generality, the y-direction is referred to as the strongly converging or strongly focused direction and the x-direction as the weakly converging or weakly focused direction. The designations of the directions are of course selectable. Accordingly, the beam can also strongly converge in the x-direction.Converging beam shaping can be achieved by focusing with a refracting surface, in particular a cylindrical lens, as in the example in Fig. 1. In this case, the focal lengths fx and fy in the x- and y-directions are fy< <fx. Vorzugsweise ist dabei die Brennweite in y-Richtung um mindestens einen Faktor 5 kleiner als in x-Richtung. Für die Höhe L der Fokussierungszone 35 gilt mit Gaußscher Optik L≈2zR, wobei zR die Rayleigh-Länge in der xz-Ebene ist. Mit einer solchen Anordnung kann also eine Fokussierungszone 35 mit einem Gauß-Profil in der durch die Richtung der starken Fokussierung und der Strahlrichtung aufgespannten Ebene, also der yz-Ebene, erzeugt werden. Es sind auch andere Interferenzmuster möglich, die einen in einer mit der Richtung der starken Fokussierung und der Strahlrichtung aufgespannten Ebene, also in der yz-Ebene, linienartigen Fokus hervorrufen. Beispiele sind beschleunigte Strahlen, wie insbesondere ein Airy-Strahl.In a further development of the method and device 2, without limitation to specific examples, beam-shaping optics 7 are provided, which generate a focusing zone 35 that has the intensity profile of a Gaussian beam, a Bessel beam, or an Airy beam in one plane, or at least approximates one of these beams. Fig. 6 schematically shows an arrangement for generating a focusing zone 35 with a Bessel beam. In this embodiment, the beam-shaping optics 7 comprises an axicon 73, onto whose base surface 730 the laser beam is directed. A roof prism instead of an axicon 73 is not necessarily suitable, since a roof prism splits the laser light 30, which originally has an intensity profile preferably in the form of a Gaussian profile 36, into two partial beams by refraction at the two mutually inclined refractive surfaces 731, 732, which converge and intersect after exiting the roof prism 73.However, this does not lead to localization. The Bessel profile 37 is shown in the region of the intersecting beams. As shown, the light intensity in this profile is greatly increased in a narrow central region. This leads to the formation of a flat focusing zone of length L, whereby this length L essentially corresponds to the length of the region in which the partial beams overlap. Fig. 7 shows the beam profile 37 as it can be generated with a phase mask as shown in Fig. 13. Along the y-direction, this non-broadened intensity profile corresponds almost to that of the ideal, rotationally symmetric Bessel beam, as shown in Fig. 6. Part (b) shows the broadened intensity profile in the x-direction perpendicular to it. Due to the non-diffractive nature of the Bessel beam, the intensity profile is almost constant in a region along the propagation direction z.Therefore, it is equivalent to refer to the intensity profiles in the xz-plane and the yz-plane, respectively. In the xz-plane, the laser light 30 is partially weakly focused, so that the high-intensity region defining the focusing zone 35 is relatively wide compared to the high-intensity region in the yz-plane. The width b of the focusing zone 35 can be defined as the half-width of the beam profile in this plane, without limitation to the examples shown in sub-image (b). The Bessel profile 37, which forms in the yz-plane, has a width defined by its first zeros of w = a0^ ^ ^ ^ ^ sin( ^ ^ ^ ^, where λ is the wavelength of the laser light 30 and ^ is the half-angle of the beam aperture or, in other words, the effective Bessel cone angle. This value can be defined as the thickness w of the focusing zone 35. The value of a0 is 2.4044, and the numerically determined first zero of the Bessel function is J0.Similar values ​​can also be achieved with other prism or lens shapes. Without being limited to the exemplary embodiments or to the generation of the focusing zone using a roof prism, it is therefore generally provided in a further development of the method and the device that the thickness w of the focusing zone 35 has a value in the range of 1.39 times to 10 times the wavelength of the laser light 30. In general, non-diffractive beams, such as the aforementioned example of the Bessel beam, are preferred for generating the focusing zone 35. An Airy beam also represents a non-diffractive beam. Light beams that have a constant intensity profile along their propagation in the lateral direction are referred to as non-diffractive rays. This is in contrast to the usual behavior of light that spreads out after being focused to a small point.In practice, the region along the propagation path in which the beam has a non-diffractive character is limited due to the finite lateral aperture size of the optics and the finite energy of the laser beam. Without limitation to specific embodiments, it is therefore provided that the beam-shaping optics 7 is designed to generate a non-diffractive beam that forms the focusing zone 35. Normally, the optical strength of a focusing element is too weak, and the flattened or edge-like focusing zone 35 would occupy too large a volume to achieve sufficient intensity for a material change in the workpiece 1. Therefore, in a further development of the method and the device 2, it is provided to reduce the original astigmatic focus. In other words, a magnification factor M<1 is used.According to one embodiment, this reduction in size can be achieved by means of a telescope arrangement, preferably in a 4F configuration or a 6F configuration. Without being limited to specific examples, one embodiment therefore provides that the beam-shaping optics 7 comprise a 4F or 6F arrangement with a magnification M<1. In general, another reducing optics can also be used, i.e., a reducing telescope, i.e., a telescope with a magnification factor M<1, regardless of a 4F or 6F configuration. The magnification factor is generally determined by the focal lengths of the optical elements contained in the beam-shaping optics, in particular lenses. According to one embodiment, the beam-shaping optics comprise a 4F telescope with a lens with a long focal length f1=500 mm and a microscope objective with a short effective focal length fMO=10 mm. This results in a magnification factor M=f. MO / f1= 1 / 50. Without being limited to this specific example, a further development of the device 2 provides for the device to comprise a beam-shaping optics 7 with a telescope with a magnification factor M < 1 / 10, preferably M < 1 / 25. Also very advantageous for achieving high beam intensities in the focusing zone is the effect that the reduction reduces the area of ​​the focusing zone transversely by a factor M 2 and longitudinally, i.e. in the beam direction by a factor M 3 This effect is also illustrated in the following table, which compares the reduction in the dimensions of the focusing zone depending on the magnification factor M: In the sense of this disclosure, astigmatic beam shaping means, in particular, that instead of a single focus area with a substantially round cross-section, two or more flattened focusing zones oriented perpendicular to one another are created. This is explained in more detail with reference to Fig. 8 and Fig. 9. Fig. 8 shows an astigmatically focused laser beam and Fig. 9 shows beam cross-sections of the laser beam at four different positions. Positions A, B, C, D of the beam cross-sections shown in Fig. 9 are shown in Fig. 8. The beam direction of the laser light 30 in Fig. 8 points from position A towards positions B, C, D. The optical elements for astigmatic beam shaping are not shown in Fig. 8. The focus of the last lens or the last lens system, such as a microscope objective, is at position A.The transverse dimensions of the beam profile at this first transverse conjugate point are essentially the same. At position B, the focus of the strongly focusing beam axis is located in the y-direction. At this position, a meridional focus line 35 is formed, which runs parallel to the x-direction. The second transverse conjugate point is located at position C. Similar to position A, the beam profile is essentially circularly symmetric. If the optical system is weakly focusing in the x-direction, then the beam diameter at this second conjugate point is smaller than at the first conjugate point, or at position A. Finally, at position D lies the focus of the weakly focusing beam axis x, the so-called sagittal focus line, which is parallel to the y-direction. If the laser light 30 is additionally shaped by a 4F arrangement, the respective focal lengths scale by a factor of M. 2. The distance dcp between the focus in the strong focusing direction at position B and the second conjugate point at position C is given by the following relationship: Here, fy denotes the focal length in the strongly focusing y-direction and fx the focal length in the weakly focusing x-direction. If there is a large difference between the two focal lengths f x , f y , so if f x much longer than f y is (f x →∞), it follows that cp ≈ f y . For the other distances, AB=fy, fy≤dcp and AD=fx also apply. Similar to Fig.8, Fig.10 shows the astigmatically shaped laser light for the limiting case f x→∞, now with idealized three-dimensional beam profiles schematically shown next to the beam. With astigmatic beam shaping, in addition to the flattened focusing zone 35, secondary focus regions 38, 39 can also form. The focusing zone 35 and the secondary focus regions 38, 39 are shown ideally as cuboids in Fig. 10. As shown, the secondary focus regions 38, 39 can also have a flattened shape. These secondary focus regions 38, 39 are typically located in the area of ​​the conjugate points A and C. With a flattened shape, as in the example shown, these secondary focus regions 38, 39 are also oriented perpendicular to the focusing region 35 with respect to the directions of the width b and thickness w.Without being limited to the example shown, one embodiment provides for the laser light 30 to be shaped by the beam-shaping optics 7 in such a way that, in addition to the focusing zone 35, two secondary focus regions 38, 39 with a flattened shape are generated, wherein the focusing zone 35 is arranged between the secondary focus regions 38, 39 in the beam direction. In a further development, the secondary focus regions 38, 39 are oriented perpendicular to the directions of the width and thickness of the focusing zone 35 with respect to the directions of their width and thickness, viewed in the beam direction. These secondary focus regions 38, 39 typically have, depending on the type and manner of beam shaping, a lower light intensity than the intermediate focusing zone 35, which can nevertheless reach the same order of magnitude as in the focusing zone 35.These secondary focus regions 38, 39 can also be referred to as parasitic foci, since their transverse alignment is conjugated to the focusing zone and therefore their respective damage zones are perpendicular to the desired orientation of the material modification. Therefore, according to a preferred embodiment, the material processing, or the separation of the workpiece 1, is carried out only by means of the focusing zone 35. This focusing zone 35 typically extends around position B, i.e., around the position of the focus of the strong focusing direction. Accordingly, in a preferred embodiment, it is provided that the beam-shaping optics 7 and the workpiece 1 are positioned relative to one another such that the focus of the strong focusing direction of the astigmatic beam-shaping optics 7 lies on, or particularly preferably in, the material of the workpiece 1.In embodiments in which the focusing zone 35 ends or begins in the workpiece 1, this point can also lie outside the workpiece 1. Such a configuration can be present, for example, in examples (b) and (c) in Fig. 5. For the processing of transparent workpieces 1, for example made of glass, glass ceramic or crystalline materials, a disadvantageous effect of parasitic foci, or the secondary focus regions 38, 39, can be minimized surprisingly well and easily. For this purpose, according to a first embodiment, the beam-shaping optics 7 and the workpiece 1 are arranged and / or adjusted relative to one another such that, in addition to the focusing zone, at least one of the secondary focus regions 38, 39 lies at least partially within the workpiece 1.In this case, the intensity of the laser light 30 can be adjusted so that the light intensity of the secondary focus region 38, 39 is below the threshold for a permanent material change in the workpiece 1. However, the intensity is preferably adjusted so that the light intensity in the focusing zone 35 is above this threshold. According to a further embodiment, the focusing zone 35 is arranged relative to the workpiece 1 such that the focusing zone 35 lies at least partially within the workpiece 1 and the secondary focus regions 38, 39 lie outside the workpiece 1. This can be done in particular when the height L of the focusing zone 35 is greater than or equal to the thickness of the workpiece 1, and / or when the distance between the focusing zone 35 and the secondary focus regions 38, 39 is sufficiently large. Fig.11 shows various possible arrangements (I), (II), (III), (IV), and (V) for processing a workpiece 1 with an astigmatic laser beam. In case (I), both the focusing zone 35 and the two secondary focus regions 38, 39 are located within the workpiece 1. In this case, it is advantageous if, as described above, the laser power is adjusted so that the light intensity of the secondary focus regions 38, 39 is below the threshold for a permanent material change in the workpiece 1 and the light intensity in the focusing zone 35 is above this threshold. In cases (IV) and (V), the two secondary focus regions 38, 39 are so far apart that the position of the laser beam can be positioned so that the secondary focus regions 38, 39 are outside the workpiece 1.In cases (II) and (III), at least one of the side surfaces 100, 101, or at least one surface of the workpiece 1, lies within one of the secondary focus areas 38, 39. These cases are rather unfavorable and not preferred. This is because the damage threshold at the surface for the action of ultrashort pulse laser radiation is typically an order of magnitude lower than in the volume. The processes that lead to material changes in the workpiece 1 are typically based on multiphoton absorption or avalanche ionization. In general, the length of the focusing zone 35 is longer inside the workpiece 1 than outside. In particular, parts of the focusing zone 35 located inside the workpiece are lengthened by a factor corresponding to the refractive index of the material of the workpiece 1. As described above, the beam-shaping optics 7 can comprise a roof prism 73 and / or a cylindrical lens 71 for generating an astigmatic laser beam.Another possibility is the use of a diffractive optical element. Such an element can be designed, in particular, as a phase mask. With such a mask, a Bessel-Gaussian beam can be formed from the laser light. A phase mask also offers the advantage that the focusing zone of the Bessel-Gaussian beam can be formed at a certain distance from the beam-shaping optics 7. This simplifies the handling and positioning of the workpiece in the device 2. An exemplary embodiment of such a beam-shaping optics 7 is shown in Fig. 12.In general, without being limited to the example shown, a further development of the device and method provides for an astigmatic laser beam to be formed from the laser light using beam-shaping optics 7, in which a phase mask 70, which in particular forms a diffractive optical element 74, is provided, which is arranged in front of a telescope optics, or alternatively in front of a reducing arrangement of optical elements or a combination thereof. In the example shown, the diffractive optical element is arranged in the beam direction in front of a combination of a lens 72 and an objective 75 positioned subsequently in the beam path. The objective 75 has a shorter focal length than the lens 72, so that a reduction is produced corresponding to the ratio of the focal lengths of the objective 75 to the lens 72.In the example shown, the lens 72 has a focal length of 500 mm and the objective a focal length of 10 mm, resulting in a reduction with a magnification factor M=0.02. The lens 72 can, in particular, be spherically or aspherically shaped. In the exemplary embodiment, a laser beam with a diameter of 6.6 mm was also used, which was irradiated onto the phase mask 70. An embodiment of a phase mask 70 in the form of a diffractive optical element 74 is shown in Fig. 13, partial image (a) in plan view. The lines each indicate positions at which the phase has shifted further in the radial direction - starting from the center marked by a cross - by 2π. The phase shift is therefore, for example, 4π at the second innermost concentric line relative to the center.In general, according to a further development, which is also implemented in the example shown, the phase mask 70 is shaped such that it causes the phase of the laser light to be shifted in the radial direction starting from the center of the phase mask by an increasing factor, wherein the period of the phase shifts differs by a factor of 2nπ in two mutually perpendicular directions, or wherein the phase shift as a function of the distance from the center along a first radial direction is greater than in a second radial direction perpendicular thereto. In the example shown, according to this definition, the first direction starting from the center is vertical, the second direction is horizontal. Fig. 14 also shows the phase shift for the directions x (horizontal direction in Fig. 13) and y (vertical direction in Fig. 13) given in radians.According to one embodiment, the diffractive optical element 74 can be used to generate a phase distribution of Bessel beamlets with an angle to the beam axis of 7.5°, or a total angle of 14.8°. Focal lengths can be assigned to the two directions, which can be calculated from quadratic fits to the phase distributions, or to the curves shown in Fig. 14. These then correspond to the quadratic phase terms k0 ^ ^. 2 / (2f) of a thin lens. The following describes the process of forming a light surface with Bessel beamlets. A Bessel beamlet here refers to a single conical phase contribution to the beam shape. Part (b) of Fig. 13 schematically shows the phase curve of Bessel beamlets 32 for the x-direction, as they can be generated with a phase mask 74 according to Fig. 13, part (a). The total phase ^total of the phase mask 74 is given by This is obtained by adding n conical components, the Bessel beamlets 32, each located at the position ^i=(xi, yi). For a linear transverse contour, for example, Other transverse contours can also be selected to create a light surface that is straight along the beam direction, but may, for example, exhibit local curvatures around axes parallel to the beam direction. Alternatively, this beam shaping serves to extend any lateral contour along the beam propagation, resulting in a surface that has the same contour in transverse sections at different points along the beam propagation. Weighting factors can be used to achieve a favorable intensity distribution along the line, or here along the flattened focusing zone 35. These weighting factors ai can preferably be a function of the position ^ i =(xi , y i ). For example, , where c is a constant. The overall scaling factor s serves to normalize the sum of the Bessel beamlets 32. For example, an effective aperture angle α of the Bessel-Gaussian beam is obtained with: The thickness w´ of the focusing zone 35 results from the first zero of the Bessel function at 2.405: ^ ^′ ^ 2.405 ^^ ^ ^ sin ^^An alternative Bessel beam-based method for generating a light surface is described in Alessandro Zannotti; Cornelia Denz; Miguel A. Alonso; Mark R. Dennis: Shaping caustics into propagation-invariant light. In: Nat Commun 11 (1), pp. 1–7. DOI: 10.1038 / s41467-020-17439-3. The beam profiles and the optical arrangements for generating them are also fully incorporated into the present disclosure. The length of the focusing zone can be estimated as l = w0 / cos(α) if a Gaussian beam with half-width w0 is used as the input beam on the phase mask. Other intensity profiles for the input beam are possible, e.g., a top-hat distribution that has a uniform intensity across the entire width. In particular, the amplitude and phase distribution can be adjusted to achieve the most homogeneous intensity distribution possible along the length of the focusing zone.The following shows the results of material processing experiments on glass workpieces. Fig. 15 shows a light microscope image of the side surface 100 of a workpiece 1 processed with laser light. As can be seen from the image, material modifications, or damage zones 10, were inserted into the borosilicate glass workpiece 1 in three rows labeled (a), (b), and (c). The rows differ in terms of the position of the focusing area relative to the surface. The positions of the focusing zones 35 are illustrated in Fig. 16. As can be seen from Fig. 16, the focusing area 35 is closest to the photographed surface for the damage zones in row (a) and deepest in row (c). In all cases, however, the focusing zone 35 is positioned completely within the workpiece 1.Particularly in row (a), an elongated damage zone 10 in the form of a leaf-shaped gap 16 is visible. The other damage zones 10 also show superficial damage through a secondary focus area 38, which is also leaf-shaped and perpendicular to the main damage, resulting in a total damage zone 10 in the shape of a flattened cross with two short and two long arms. For processing, the laser was operated in burst mode with two pulses per burst. In this mode, the laser emits the laser light in the form of pulse packets, or sequences of pulses emitted in quick succession. The pulse length of the individual pulses was 1.5 ps and the total energy of the burst was 36 µJ. The focal length was 1210 mm, corresponding to the arrangement in Fig. In order to insert the damage zones 10 at the different depths, the distance of the workpiece 1 to the lens 75 was reduced from row to row by dz=20 µm.The distance in the workpiece is then n∙dz, where n is the refractive index of the glass. The method and device described herein are particularly preferably used to separate workpieces 1 into two or more parts, for example to cut parts with a specific outline from a workpiece in the form of a glass pane. An example of this is explained below with reference to Figs. 17 and 18. Fig. 17 shows an optical micrograph of the surface of a separated workpiece 1, and Fig. 18 shows the edge surface of a part of the workpiece 1 obtained by the separation. For this purpose, the workpiece of the example from Fig. 15 was ground down to a thickness of 40 µm in order to remove the sections of the damage zones 10 caused by the secondary focus areas 38, 39. The workpiece 1 was then separated at one of the rows (a), (b), (c) of damage zones 10. The two parts 4, 5 thus obtained are shown side by side in Fig.17.The special shape and arrangement of the damage zones 10 results in a characteristic edge surface of the parts 4, 5, which is shown in Fig. 18. As can be seen, the edge surface 18 of the parts 4, 5 has damage zones 10 spaced apart from one another along the edge surface, with fracture surfaces 18 located between the damage zones 10. Unlike when separating along filament-shaped damages arranged in a row, as is known, for example, from WO 2017 / 009379 A1, the damage zones 10 here are significantly flatter compared to their extent along the edge surface 18, or in the circumferential direction. This is due to the flattened, leaf- or blade-shaped shape of the focusing zone 35 and thus also to the corresponding extent of the damage zones 10.The damage zones 10 differ from the fracture surfaces 19 in that the damage zones 10 have a material modification, for example, due to a plasma generated in the damage zone by the intense laser light. Accordingly, a part 4, 5 produced in this way represents a disk-shaped element 8 made of an inorganic material, preferably glass, that is at least partially transparent to laser light, with two opposite side surfaces 100, 101, and a circumferential edge surface 18, wherein the edge surface 18 has alternating fracture surfaces 19 and damage zones 10, wherein the damage zones 10 have a material modification, in particular due to the formation of a plasma in the material of the element, and wherein the extent of the damage zones 10 in the direction from the edge surface 18 into the element 8 is at least a factor of 5 smaller than in the circumferential direction of the edge surface 18. The circumferential direction runs in the recording of Fig.18 from left to right, i.e. also parallel to a direction lying in a side surface 100, 101. In general, one advantage here is that a separation of a workpiece into parts with a comparatively small number of damage zones 10 can take place. In extreme cases, a separation can take place with a single shot or by inserting a single damage zone 10. In the previous embodiments, the flattened focusing zone 35 has a planar shape. According to another embodiment, the focusing zone 35 can also have a curved shape. In this embodiment, the focusing zone 35 forms a curved caustic surface. The flattened, in particular leaf-shaped shape of the focusing zone 35 is bent around an axis preferably lying perpendicular to the beam direction. One such example is shown in Fig. 20.Partial image (a) shows a side view of a caustically focused laser beam 30 penetrating a workpiece 1. Generally, a caustically focused beam can be understood as a beam in which the constituent partial beams form tangents to a surface, or rather, the flattened focusing zone 35. The curved focusing zone 35 resulting from the caustics is marked with dashed boundary lines. Caustic focusing is further characterized by the fact that the phase of the laser beam ideally varies only in one direction. For further clarity, part of image (b) shows such a curved focusing zone 35 in a perspective view. The width b, height L, and thickness w, as well as the beam axis 31, are shown for clarity.It can be seen that the focusing zone 35, despite its curved shape, has a flattened configuration and, for cross-sections perpendicular to the beam axis 31 or beam direction, a width b and thickness w can be assigned. Unlike in the idealized representation, these variables can change along the focusing zone 35. For example, the focusing zone 35 can have a minimum thickness w, in particular at least one position along the beam axis 31. Curved focusing zones 35 are generally particularly advantageous for producing concave or convex edge surfaces when separating the workpiece 1. Fig. 19 shows a possible beam-shaping optics 7 for generating such a beam with a curved focusing zone 35. The beam-shaping optics 7 comprise a one-dimensional phase mask 70, for example in the form of a diffractive optical element 74. The one-dimensional phase mask 70 is invariant in the x-direction.The phase mask 70 is followed by a cylindrical lens 71 focusing in the y-direction. A one-dimensional phase mask is understood specifically to be a phase mask having a phase distribution that is constant in one spatial direction, e.g. the x-direction, and has a non-constant, e.g. cubic, distribution in a direction perpendicular thereto (y-direction). Instead of the diffractive optical element, another component such as an LCOS-SLM can also serve as the phase mask. The boundaries of the focusing zone 35 are shown as dashed lines. As can be seen, the focusing zone 35 is curved. Without being limited to specific examples, a focusing zone 35 shaped in this way can be achieved with an essentially one-dimensional Airy beam, or one that is compressed in one spatial direction, by beam shaping using a suitable phase mask 74. The complex amplitude of the Airy beam is determined by with a cubic scaling factor ^. This results in an intensity profile according to the following equation: The length L' of the resulting focusing zone is: This length is defined as the length within which the intensity is more than 1 / e 2 of the maximum intensity. The half-width w´ of the focusing zone is: ^^ ᇱ ^ 1.6 ∙ ^^ ^ The following applies to the parameters in the above equations: and . w0 denotes the half-width of the Gaussian input beam onto which the cubic phase is impressed. Further embodiments of a device 2 for processing transparent workpieces 1, specifically the beam-shaping optics 7 of such a device 2, are illustrated in Figs. 21 to 27. The embodiment according to Fig. 21 also includes a diffractive optical element 74, which acts as a phase mask and is arranged in the beam path of the laser light 30 in front of a reducing arrangement of optical elements. This arrangement is formed by two lenses 72, 76 and, in the xz plane, additionally by a cylindrical lens 71. The workpiece-side lens L2, 76 has a shorter focal length than the lens L1, 72 downstream of the diffractive optical element 74. In the example, the lens L1, 72 has a focal length of 500 mm, the lens L1, 76 has a focal length of 100 mm, and the cylindrical lens 71 has a focal length in the y-direction of 5 mm.In order to achieve greater beam concentration in the x-direction, the original beam width of the laser light can be reduced in front of the beam-shaping optics 7, as in the example. In the example, the beam width is reduced from 6 mm to 3.3 mm. The embodiment according to Fig. 22 is generally based on two cylindrical lenses 71, 77 arranged one behind the other with different focal lengths and crossed focusing directions, with the more strongly focusing cylindrical lens 77 being arranged on the workpiece side. Preferably, the focal lengths of the cylindrical lenses 71, 77 differ by at least a factor of 10. In the example shown, the factor is even 1000 mm / 5 mm = 200. Partial image (a) shows the beam-shaping optics 7 with the workpiece 1 to be machined arranged in front of it. Partial image (b) shows the focus area 35 achievable with this arrangement in cross-section in the xy plane perpendicular to the beam direction.In the simplest case, as shown, the focus area 35 has a flat elliptical cross-section for an output beam with a round beam profile. The foci of the lenses can be located at the same point, as in Fig. 22. This would produce a purely elliptical beam without astigmatism. However, this is generally not the case. The embodiment according to Fig. 23 allows the width of the focusing zone 35 to be adjusted. Furthermore, the optics can generate an Airy beam using a suitable phase mask. According to a first aspect, the beam-shaping optics 7, regardless of whether an Airy beam or another beam path, such as a Gauss-Bessel beam, is generated, is characterized in that two nested telescope optics are provided. A first telescope optics comprises two cylindrical lenses 71, 77, and a second telescope optics comprises two lenses 72, 76.In particular, the focusing directions of the cylindrical lenses 71, 77 are crossed, as in the embodiment of Fig. 22. According to a further development also realized in the example shown, the telescope optics with the two lenses 72, 76 is arranged between the cylindrical lenses 71, 77. To create a reduction, preferably f2 <f1. Gemäß noch einer Weiterbildung ist eine Phasenmaske 74 vorgesehen, insbesondere, um im Werkstück 1 in einer Ebene einen Airy-Strahl zu erzeugen, so dass eine abgeflachte Fokussierungszone erhalten wird. Die Strecke zwischen den konjugierten Punkten des inneren, mit den Linsen 72, 76 aufgebauten Teleskops dient als Verzögerungsstrecke 79 für die Erzeugung des Airy-Strahls. Eine noch einfachere Konfiguration zeigt Fig.24. Diese Ausführungsform stellt eine Kombination einer Phasenmaske 70, die beispielsweise ein diffraktives optisches Element 74 bildet und einer 2F-Anordnung dar.In the simplest case, as shown, the 2F arrangement can be formed by a single lens, preferably a lens of a microscope objective 75. Fig. 25 shows a variant of the arrangement from Fig. 24. In the variant according to Fig. 25, a greater distance is selected between the diffractive optical element 74 and the lens or a microscope objective 75. This arrangement can be referred to as a quasi-4F configuration. Both arrangements can be characterized in that the beam-shaping optics comprise, on the light output side, as the last elements, a microscope objective 75 and a phase mask, in particular in the form of a diffractive optical element 74, arranged upstream of this microscope objective 75. According to a further development, no further beam-shaping elements are provided in the beam-shaping optics 7.Under certain circumstances, the laser power may not be sufficient to achieve a light intensity in the focusing zone 35 that is sufficient for material modification or, in particular, damage. One possibility for achieving higher intensities is described below. The beam-shaping optics, including the beam-shaping optics 7, can be designed to achieve greater reduction in size, i.e., to further reduce the size of the focusing zone 35. This can be achieved by generating a beam with an elongated beam profile from the laser beam 30 before focusing. During focusing, this leads to the extent of the focusing zone further decreasing in the direction in which the beam profile is elongated before focusing in the beam-shaping optics 7. This effect is explained in more detail using the schematic example in Fig. 26.According to one embodiment, the beam-shaping optics 7 comprise beam-shaping optics which reshapes the laser beam 30 such that, upon impinging on a focusing optics as part of the beam-shaping optics 7, the beam has an elongated beam profile, wherein the direction of the elongation lies transversely to the direction of the width of the focusing zone 35, preferably perpendicular thereto and accordingly in the direction of the thickness of the focusing zone 35. In this way, the thickness of the focusing zone 35 is further compressed and the intensity in the focusing zone 35 is increased. In the example shown, an anamorphic optic 80 is provided as the beam-shaping element, which generates an output beam which, upon impinging on a focusing optic 81, has a beam profile elongated in the y-direction. The beam profile can be elliptical, as shown, so that the long semi-axis of the profile lies in the y-direction in the example.The focusing optics 81 are generally oriented such that the direction of the width of the focusing zone 35 is perpendicular to it, in the example in the x-direction. In particular, by using an elliptical input beam with a sufficiently small short semi-axis, even when focusing with a rotationally symmetrical focusing lens, e.g., with a microscope objective, an increase in the width of the focusing zone can be achieved. In general, for material modifications in the focusing zone, which may include splitting the material or creating a gap, it is advantageous to use high-power lasers with a power of at least 100 W, preferably at least 150 W. The following tables list exemplary embodiments of suitable parameters of the laser and the beam-shaping optics. The first table lists suitable laser parameters for an arrangement according to Fig. 22. L. aserparameterBurst [µJ] 300 pulses per burst 1 pulse duration [ps] 3 G auss-Strahlformung Beam diameter D [mm] 6.6 Wavelength ^ ^ ^[µm] 1.064 31 21.03.2023 P05897 WO The parameters in the following table are suitable for an embodiment according to Fig. 12. L aserparameter Burst [µJ] 250 pulses per burst 1 pulse duration [ps] 3 T eleskop-Setup Beam diameter D [mm] 6.6 f1 [mm] 1000 f2 [mm] fMO [mm] 10 M 0.01 G auss-StrahlformungWavelength ^ ^ ^[µm] 1.064 Beam diameter after MO lens [mm] 0.066 Effective focal length x of PM [mm] 5,000 Effective focal length y of PM [mm] 1,200 fx after MO lens [µm] 500 fy after MO lens [µm] 120 NAy after MO lens 0.28 dcp [µm] 74 Thickness v.35: w=2 w0 [µm] 2.5 Width of 35 [µm] 66 Height: L= 2 x Rayleigh length [µm] 36 Intensity in center plane [W / cm²] 5.1E+13 The following table shows laser parameters for Bessel-Gauss beam shaping for three examples: 32 21.03.2023 P05897 WO BG-Beamlet 1a BG beamlet 1b BG beamlet 1cTelescope setupBeam diameter D [mm] 6.6 6.6 6.6 f 1[mm] 500 500 500 f2 [mm] f MO[mm] 10 20 20M 0.02 0.04 0.04Refractive index glass 1.47 1.47 1.47Wavelength ^ ^ ^[µm] 1.064 1.064 1.064Beam diameter after MO lens [mm] 0.132 0.264 0.264Width [µm] 132 264 264Bessel-Gauss beam shapingBessel angle in air[°] 0.38 0.38 0.15Bessel angle after telescope [°] 18.4 9.4 3.8Bessel angle in glass[°] 12.4 6.4 2.6Thickness w BG [µm] 2.6 5.0 12.3 Width b [µm] 132 264 264 Ideal Bessel height: L=D / 2tan ^ [µm] 198 794 1985Measured length of the usable focusing zone [µm] (determined from ablation patterns) 20 100 250 The following table describes suitable laser parameters for forming an Airy beam with a curved focusing zone 35. An arrangement according to Fig.12 is also suitable for these parameters: Telescope setup Beam diameter D [mm] 6.6 f1 [mm] 200 f2 [mm] 300 fMO [mm] 10 M 1.50 Refractive index of glass 1.47 33 21.03.2023 P05897 WO Wavelength ^ ^ ^[µm] 1.064 Beam diameter after MO lens[mm] 0.0135 Width [µm] 14 Airy beam shaping: Beta cubic phase [ / m] 1082.

[0002] List of reference symbols:

Claims

Claim 1. A method for processing a workpiece (1) in which: - the workpiece (1) is irradiated with the laser light (30) of a laser (3), wherein: - the material of the workpiece (1) is at least partially transparent to the laser light (30) so that the laser light (30) penetrates the workpiece (1), and wherein: - the laser light (30) is focused in a focusing zone (35) in the workpiece (1) by means of a beam shaping optic (7), wherein: - the focusing zone (35) has a flattened shape in cross-section perpendicular to the beam axis with a length in the beam direction and width and thickness perpendicular thereto, wherein the thickness of the focusing zone (35) is at least at one position along the beam axis less than the width and length of the focusing zone.and wherein, within the focusing zone (35), a modification zone (10) is introduced into the material of the workpiece (1) due to the intensity of the laser light (30), which has a flattened shape corresponding to the focusing zone (35).

2. Method according to the preceding claim, characterized in that at least one of the following operations is performed on the workpiece (1): - the workpiece (1) is separated into two parts (4, 5) at the modification zone (10) - a change in the refractive index is caused in the material of the workpiece (1) in the damage zone by the laser light.

3. Method according to the preceding claim, characterized in that a focusing zone (35) is created in the workpiece (1) with the beam shaping optics, which has at least one, preferably all of the following, The dimensions are: - a width b in the range of 1 µm to 10 mm, preferably 10 µm to 50 µm, - a thickness w in the range of 0.2 µm to 50 µm, preferably 1 µm ± 0.5 µm, - a thickness w in the range of 1.39 times to 10 times the wavelength of the laser light 30, - a height L in the range of 2 µm to 20 mm, preferably 1 mm to 5 mm, - a projection area viewed along the direction of the beam axis (31) of the laser light (3), which is at least four times smaller than the projection area of ​​the focusing zone (35) viewed along the direction of the thickness of the focusing zone (35).

4. A method according to one of the preceding claims, characterized in that a workpiece (1) made of inorganic material, preferably glass, glass-ceramic or a crystalline material, is processed. 5.A method according to any one of the preceding claims, characterized in that the focusing zone (35) is generated by astigmatic beam shaping or caustic beam shaping.

6. A method according to any one of the preceding claims, characterized in that a focusing zone (35) is generated which has a curved shape, wherein the focusing zone (35) is curved about an axis perpendicular to the beam direction.

7. A method according to the preceding claim, characterized in that the laser light (30) is shaped by means of the beam shaping optics (7) such that, in addition to the focusing zone (35), two secondary focus areas (38, 39) with a flattened shape are generated, wherein the focusing zone (35) is arranged between the secondary focus areas (38, 39) in the beam direction.

8. Method according to the preceding claim, characterized by at least one of the following features: - the beam shaping optics (7) and the workpiece (1) are arranged and adjusted such that, in addition to the focusing zone (35), at least one of the secondary focus areas (38, 39) lies at least partially within the workpiece (1), wherein the intensity of the laser light (30) is adjusted such that the light intensity of the secondary focus area (38, 39) is below the threshold for a permanent material change of the workpiece (1) and the light intensity in the focusing zone (35) is above this threshold, - the focusing zone (35) is arranged relative to the workpiece (1) such that the focusing zone (35) lies at least partially within the workpiece (1) and the secondary focus areas (38, 39) lie outside the workpiece (1). 9.A method according to one of the preceding claims, characterized in that several modification zones (10), in particular in the form of damage zones, are arranged in succession such that they follow a provided parting line (14), and wherein the workpiece (1) is separated at the parting line (14) so ​​that two parts (4, 5) are obtained.

10. A method according to the preceding claim, characterized by at least one of the following features: - the modification zones (10) are oriented such that the parting line (14) runs along the direction of the width of the modification zone (10), - the modification zones (10) are inserted along a parting line (14) that is curved at least in sections, - the modification zones (10) are inserted along a closed parting line (14) and an inner part bounded by this parting line is separated from the workpiece (1). 11.Method according to one of the preceding claims, characterized in that the laser light (30) is focused into a focusing zone (35) whose. Cross-section A is so small that the light intensity in the focusing zone (35), given by E pulse / (A∙t pulse ) a value of 10 13 W / cm 2exceeds, where Epulse denotes the energy of a laser pulse and t the pulse duration.

12. Method according to one of the preceding claims, characterized in that the focusing zone (35) is positioned such that one of the following features is fulfilled: - the focusing zone (35) lies completely within the workpiece (1), - the focusing zone (35) begins or ends within the workpiece (1) and projects beyond one of the side faces (100, 101) of the workpiece (1), - the focusing zone (35) is longer than the thickness of the workpiece (1) and penetrates two opposite side faces (100, 101) of the workpiece (1).

13. Device for processing a workpiece (1), comprising - a laser (3) for emitting laser light (30), wherein the laser (3) is configured to emit laser light (30) of a wavelength for which the workpiece (1) is at least partially transparent, so that the laser light (30) can penetrate the workpiece (1),and wherein the device comprises a beam shaping optic (7) for focusing the laser light (30) in a focusing zone (35) in the workpiece (1), wherein the beam shaping optic (7) is configured such that the focusing zone (35) thereby produced has a flattened shape with a length and width and thickness in the beam direction, wherein the thickness of the focusing zone (35) is at least a factor of 5 less than the width and length of the focusing zone, and wherein the laser (3) and the beam shaping optic (7) are configured such that a sufficient intensity of the laser light (30) is present within the focusing zone (35) to introduce a modification zone (10) into the material of the workpiece (1), which has a flattened shape corresponding to the shape of the focusing zone (35), in particular such that the modification zone (10) extends in the direction of the beam axis, (35) and is more extended along a direction perpendicular to it than along a second direction perpendicular to the beam axis (35).

14. Device according to the preceding claim, characterized by a beam shaping optic (7) with at least one of the following features: - the beam shaping optic (7) is astigmatic or caustic, - the beam shaping optic (7) comprises a phase mask (70), - the beam shaping optic (7) comprises at least one cylindrical lens (71), - the beam shaping optic (7) comprises a 4F or 6F arrangement with a magnification M<1.

15. Device according to one of the two preceding claims, characterized by a beam shaping optic (7) which generates a focusing zone (35) which has the intensity profile of a Gaussian beam, a Bessel beam, or an Airy beam in one plane. 16.Device according to one of the three preceding claims, characterized in that the beam shaping optics (7) comprises at least one of the following optical elements for generating an astigmatic laser beam: - a refractive optical element, in particular a freeform optic - a cylindrical lens (71), - a diffractive optical element (74) - a phase mask (70), in particular an LCOS Spatial Light Modulator (SLM) 17. Device according to the preceding claim, characterized by at least one of the following features: - the beam shaping optics (7) comprises a phase mask (70), preferably in the form of a diffractive optical element (74), which causes the phase shift of the laser light to be a function of the distance to the center of the diffractive optical element (74) along a first radial direction. larger than in a second radial direction perpendicular to it, - the beam shaping optics (7) comprises a phase mask (70), preferably in the form of a diffractive optical element (74), which is arranged in front of a reduction arrangement of optical elements, - the beam shaping optics (7) comprises a beam shaping optic which shapes the laser beam (30) such that, upon striking a focusing optic (81) as part of the beam shaping optics (7), it has an elongated beam profile, wherein the direction of the elongation is transverse to the direction of the width of the focusing zone 35, preferably perpendicular to it. 18.A disk-shaped element (8) made of an inorganic material that is at least partially transparent to laser light, with two opposing side surfaces (100, 101), and a circumferential edge surface (18), wherein the edge surface (18) has alternating fracture surfaces (19) and damage zones (10), wherein the damage zones (10) have a material modification, in particular by the formation of a plasma in the material of the element, and wherein the extent of the damage zones (10) in the direction from the edge surface (18) into the element 8 is less by at least a factor (5) than in the circumferential direction of the edge surface (18).

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