Method for machining workpiece and device for machining workpiece

Abstract

The invention relates to a method for machining a workpiece (1), in which the workpiece (1) is irradiated with laser light (30) of a laser (3), in which-the material of the workpiece (1) is at least partially transparent to the laser light (30) in order to transmit the laser light (30) into the workpiece (1), and in which the laser light (30) is focused in a focal region (35) in the workpiece (1) by means of a beam shaping optical system (7), the focal region (35) has, in a cross-section perpendicular to the beam axis, a flat shape with a length in the direction of the beam and a width and a thickness both perpendicular to the length, the thickness of the focal region (35) being at least five times less than the width and length of the focal region in at least one position along the beam axis, and wherein the focal region (35) has a flat shape in a cross-section perpendicular to the beam axis, and wherein the thickness of the focal region (35) is at least five times less than the width and length of the focal region. -inserting a modification zone (10), which has a flat shape corresponding to the focal zone (35), in the focal zone (35) as a result of the intensity of the laser light (30) in the material of the workpiece (1).

Description

Technical Field

[0001] The present invention relates generally to material processing. In particular, the present invention relates to processing materials that are transparent in at least one wavelength range by laser radiation. Background Art

[0002] Contactless processes for separating materials are known from the prior art. Some of these separation processes make use of laser radiation. Laser ablation is particularly noteworthy here. The advantage is that the process can be used for almost any material. However, the disadvantage is that the ablation rate is usually very slow, especially compared to mechanical abrasion processes. Another separation process is based on the effect of high-intensity laser radiation on the interior of transparent materials. Nonlinear optical processes lead to changes in the material and even to the formation of plasma, which causes local damage to the material. At least partially open channels are formed in the material along the laser beam. If such local, typical filamentary damage or channels are repeatedly inserted along the path by the laser, the workpiece processed in this way can be easily separated along this path. The method for separating glass by arranging filamentary damage with a laser can be found in patent document WO 2017 / 009379 A1 and other prior art mentioned therein.

[0003] This technique of inserting filamentary damage along a path and then separating the processed workpiece along the path will soon reach its limits when the parting line is curved or even angular. In the above-mentioned WO2017 / 009379A1, separation can be achieved along a curved separation line by inserting a filament into the surface at a certain angle. However, this method is not desirable in many cases. On the other hand, separation can be performed along an arbitrarily extended separation line by subsequent etching. Etching extends the filaments until the channels formed in this way are connected to each other and separation is achieved at the parting line. However, etching is time-consuming and slow. In view of this, it is necessary to further improve the processing of the workpiece by modifying the inside of the workpiece, such as using a laser to separate transparent materials. The present invention solves this problem through the subject matter of the independent claim. An advantageous technical solution of the present invention is provided in its corresponding dependent claim. Summary of the invention

[0004] According to the method and the device disclosed in the present invention, a two-dimensionally extending focus is obtained in the material of the workpiece to be separated, in particular based on laser beam shaping. In this way, when observed from the propagation direction of the laser beam, no more or less linear damage or narrow channels are generated in the workpiece, but a two-dimensional, extended coherent modified zone is generated, in particular in the form of a damaged zone, and the material is ideally separated. In particular, a method for machining a workpiece is provided, wherein the workpiece is irradiated with laser light from a pulsed laser, wherein the workpiece material is at least partially transparent to the laser light so that the laser light penetrates into the workpiece. In particular, the workpiece material is modified by nonlinear absorption of the laser light and nonlinear interaction with a high-intensity laser light. In order to achieve high light intensity, the laser light is focused in a focal zone in the workpiece by means of a beam shaping optical device, the focal zone being flat in shape, having a length along the direction of the laser beam, and having a width and a thickness in a cross section or a transverse profile perpendicular to the beam axis or the beam direction, wherein at at least one position along the beam axis, the thickness of the focal zone in the cross section is at least 5 times smaller than the width and length of the focal zone. In other words, the focal region extends along the beam axis of the laser and in two directions perpendicular thereto, wherein the focal region is at least 5 times narrower in the direction perpendicular to the beam axis than in the direction perpendicular to the beam axis and in another direction perpendicular to the beam axis. Therefore, the shape of the focal region may also be referred to as a blade or blade. The thickness and width in a cross section perpendicular to the beam direction represent the local thickness or width of the focal region, respectively. Therefore, both variables may vary along the beam direction and usually do so. A box may also be placed around the focal region. The dimensions of the box may be referred to as overall thickness, width and length.

[0005] Due to the intensity of the laser, within the focal zone, a modified zone is inserted into the workpiece material, the modified zone having a flat shape corresponding to the focal zone, i.e., specifically corresponding to the shape of the focal zone being wider in the direction of the beam axis and in a direction perpendicular to the beam axis than in a second direction perpendicular to the beam axis. In particular, the beam axis forms an orthogonal coordinate system with the above-mentioned first direction and second direction. Therefore, these three directions are mutually perpendicular in pairs. According to a preferred embodiment, the workpiece can be separated into two parts at the modified zone. According to an improved solution, if the modified zone has already led to the separation of the material, then this separation will occur spontaneously. In general, a modified zone is usually understood to be a region of the workpiece material in which the workpiece material is modified compared to the surrounding material. In particular, the modified zone can be a damaged zone, i.e. a region in which the material is damaged. Such damage will in particular also include the separation of the material.

[0006] If desired, according to another embodiment, separation can also be achieved by additional steps, such as by applying stress to the material within the modified zone.

[0007] The stress can be applied mechanically, such as by applying compressive, tensile or bending stress, or thermally, for example by heating the surface with a radiation source (such as a CO2 laser) or cooling the surface with a nozzle. Self-separation can also occur spontaneously if the glass workpiece has been chemically or thermally prestressed.

[0008] Pulsed lasers are particularly suitable for providing the radiation intensity required to produce material modification, especially material damage. For example, so-called ultrashort pulse lasers have pulse lengths in the range of tens of picoseconds or shorter, which are suitable for producing corresponding damaged areas in glass and other inorganic materials.

[0009] In addition to separating the workpieces, other processing operations can also be performed by material modification. According to other alternative or additional embodiments, the refractive index of the workpiece material is locally influenced (i.e., in the damaged area) by the laser. This influence on the material properties can occur at lower intensities or power densities, in particular compared to the processing operation of separating the workpieces.

[0010] This method is particularly suitable for processing inorganic materials that are transparent to the laser light used. This includes especially glass, but also glass ceramics, silicon and other crystalline materials such as aluminum oxide crystals.

[0011] According to the above method, a device for implementing the method is also provided. The device for processing a workpiece particularly comprises a laser for emitting laser light, wherein the laser light is configured to emit laser light whose wavelength is at least partially transparent to the workpiece, so that the laser light can be transmitted into the workpiece. In particular, the device further comprises a beam shaping optical device to focus the laser light into a focal zone of the workpiece, wherein the beam shaping optical device is designed to make the focal zone of the generated laser light have a flat shape, which has a length along the beam direction, a width and a thickness perpendicular to the length direction, so that the width direction, the thickness direction and the length direction are mutually perpendicular in pairs, and the thickness of the focal zone is at least 2 times smaller than the width and length of the focal zone, preferably at least 5 times smaller. The laser and the beam shaping optical device are also designed to make the intensity of the laser light in the focal zone sufficient to insert a flat-shaped damage zone into the workpiece material, in particular, to make the damage zone corresponding to the shape of the focal zone wider along the beam axis direction and the perpendicular direction than along the second direction perpendicular to the beam axis. The workpiece to be separated can also be part of the device. Furthermore, the device can comprise means for separating the workpieces in the modification zone, in particular means for applying a mechanical stress in the modification zone.

[0012] The flat shape (e.g. blade-shaped) of the focal zone can be alternatively or in addition to the ratio of the thickness to the width and / or the ratio of the thickness to the length of this zone, and can also be described by the ratio of the corresponding surfaces. Therefore, alternatively or additionally, in a certain embodiment, the laser is focused in the focal zone, and when observed along the beam axis direction of the laser, the projected area of ​​the focal zone is at least 4 times smaller than the projected area of ​​the focal zone observed along the thickness direction of the focal zone.

[0013] As mentioned above, the extension of the focal zone along three mutually perpendicular directions, i.e. the beam axis and the other two directions, is referred to as thickness w, width b and height L. In this case, the height L denotes the extension of the focal zone in the direction of the beam axis or beam direction or laser incidence direction. The thickness w denotes the cross-sectional extent of the focal zone along a second direction perpendicular to the beam axis, the extension of the focal zone along this direction being at least 2 times smaller, preferably at least 5 times smaller, than the extension along the beam axis and the first direction (which is perpendicular to the second direction). Preferably, the focal zone is generated in the workpiece by the beam shaping optics, the focal zone having at least one, preferably all, of the following dimensions: - a width b, ie the extension along a first direction perpendicular to the beam axis, ranging from 1 μm to 10 mm, preferably from 10 μm to 50 μm; - a thickness w, ie the extension in a second direction perpendicular to the beam axis, ranging from 0.2 μm to 50 μm, preferably 1 μm ± 0.5 μm; The height L, ie the extension in the direction of the beam axis, ranges from 2 μm to 20 mm, preferably at least 30 μm, particularly preferably from 1 mm to 5 mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will be explained in more detail below in conjunction with the accompanying drawings. In the accompanying drawings, the same reference numerals represent the same or corresponding elements.

[0015] Figure 1 An apparatus for machining a workpiece is shown.

[0016] Figure 2 A workpiece with a damaged area inserted is schematically shown.

[0017] Figure 3 A cross section of the focal region is schematically shown.

[0018] Figure 4 An arrangement is shown where the focal zone is completely within the workpiece.

[0019] Figure 5 Three possible positioning of the focal zone relative to the workpiece are shown.

[0020] Figure 6An apparatus for producing a focal zone using a Bessel beam is shown.

[0021] Figure 7 Shows the intensity curves of the focal area in two perpendicular slices

[0022] Figure 8 An astigmatically focused laser beam is shown.

[0023] Fig. 9 The beam cross sections of the laser beam at four different positions are shown.

[0024] Fig.10 Shows something like Figure 8 Astigmatism-shaped laser beam and ideal 3D beam profile.

[0025] Fig.11 Various possible arrangements of the astigmatic laser beam relative to the workpiece to be machined are shown.

[0026] Fig.12 A beam shaping optic with a diffractive optical element is shown.

[0027] Fig.13 A top view of a diffractive optical element for generating a Gauss-Bessel beam and the phase distribution of the beamlets that can be generated using the mask are shown.

[0028] Fig.14 The phase shift caused by a diffractive optical element in two mutually perpendicular directions is shown as a function of the distance from the center of the element in the radial direction.

[0029] Fig.15 An optical microscopic image of a workpiece surface processed with a laser is shown.

[0030] Fig.16 The position of the focal zone relative to the workpiece surface is schematically shown.

[0031] Fig.17 An optical microscopic image of the surface of the separated workpiece is shown.

[0032] Fig.18 The edge surface of a portion of the workpiece obtained by separation is shown.

[0033] Fig.19 An optical arrangement is shown for producing a focal zone that is curved about an axis perpendicular to the direction of the light beam.

[0034] Fig. 20 An example of such a curved focal zone is shown, wherein partial view (a) shows a workpiece illuminated by the focal zone and partial view (b) shows a perspective view of the focal zone.

[0035] Figure 21 to Figure 26Other embodiments of beam shaping optics for producing a flat focal zone are shown. DETAILED DESCRIPTION

[0036] Figure 1 An embodiment of an apparatus 2 for processing, in particular for separating, a workpiece 1 is shown, which is suitable for carrying out the method described herein. Without being limited to the embodiment shown, the apparatus 2 generally comprises as core components a laser 3 and a beam shaping optical device 7. The workpiece 1 to be processed is arranged in the beam direction of the laser 3 before the beam shaping optical device 7, so that the focal zone 35 generated by the beam shaping optical device 7 from the laser or more specifically the laser beam 30 is at least partially located inside the workpiece 1.

[0037] Due to the intensity of the laser 30 in the partial focus area 35 located in the workpiece 1, the power intensity of the laser 3 is sufficient to cause material changes in the modified area (preferably in the form of a damaged area), which thus easily or already causes the component 1 to separate at the damaged area.

[0038] Ultrashort pulse lasers, preferably those operating with pulse durations in the picosecond range, in particular with pulse durations below 50 ps, ​​are particularly suitable. Unlike previous devices for laser-based separation of workpieces by inserting filamentary damage or narrow channels, the focal zone 35 and the corresponding damage zone 10 are flat in shape. Depending on the focusing characteristics, the focal zone can have different shapes, such as a flat ellipse, a simple highly flat cuboid or a flat disk.

[0039] The flat focal region 35 can usually be achieved by an astigmatic beam shaping optical device or a caustic beam shaping optical device 7. In a certain embodiment, at least one cylindrical lens can be provided as a component of the beam shaping optical device 7.

[0040] In general, other refractive optical elements can also be used as an alternative or in addition to the cylindrical lens. Thus, according to one embodiment, a free-form optical device is provided. Particularly preferably, a phase mask is used as a component of the beam shaping optical device 7. The phase mask can produce a focal zone 35 with a large length and a small thickness in a simple manner. In contrast, in the case of optical systems with cylindrical lenses or with different refractive powers in mutually perpendicular directions, there is a tendency for the width to decrease, which is accompanied by a shortening of the focal zone.

[0041] According to a certain embodiment, the phase mask is designed as a diffractive optical element. Another phase mask, such as an LCOS spatial light modulator (Spatial Light Modulator, SLM), can also be a component of the beam shaping optical device as an element for producing the flat focal zone described in this article. LCOS-SLM is a reflective spatial light phase modulator that can freely modulate the light phase. The light phase of the laser is modulated by liquid crystal. In general, the beam shaping optical device 7 can also include a liquid crystal element for light phase modulation. In general, the focal zone 35 and the modified zone 10 do not have to coincide. Therefore, in particular, the focal zone 35 can start outside the workpiece 1 and / or end outside the workpiece 1. In the embodiment shown, the length L of the focal zone 35, that is, its dimension along the beam axis 31 of the laser 30, is greater than the thickness of the workpiece 1. The focal zone 35 extends beyond the plate-shaped workpiece 1, in the present embodiment, while the modified zone 10 can of course extend at most between the two side surfaces 100, 101. Without being restricted to the illustrated embodiment, the method is particularly preferably applied to a plate-shaped workpiece 1.

[0042] Furthermore, as shown in the present embodiment, the modified region is inserted in such a manner that the width direction of the damaged region is along the side surfaces 100, 101 or perpendicular to the surface normal of the side surfaces 100, 101. The modified region 10 thus appears as a narrow cut in the side surfaces 100, 101, which makes it easier to separate the workpiece 1 into a plurality of components.

[0043] In order to adjust the position of one or more lesion zones 10 to be inserted, a positioning device 9 is provided according to a preferred development of the device 2. The positioning device 9 and the optical system, in particular the laser 3, can be controlled by a controller 12, preferably using programming techniques. In the embodiment shown, the positioning device 9 comprises an xy table, on which the plate-shaped workpiece 1 is placed. With the device described herein, a flat, blade-shaped focal zone is generated, so that the orientation of the focal zone relative to the beam axis is also crucial. In order to adjust this orientation, according to a certain embodiment, the optical system or beam shaping optical device 7 is designed to be rotatable around the beam axis. Alternatively or additionally, the workpiece can also be rotated around the beam axis to obtain the desired orientation of the focal zone in the workpiece. Therefore, according to an alternative or additional embodiment, the positioning device has a rotation axis to rotate the workpiece relative to the laser beam, about a direction parallel to the beam direction or a direction colinear.

[0044] Where appropriate, especially in the case of small workpieces, a single modified zone 10 is sufficient to separate the workpiece 1. However, in a preferred embodiment, a plurality of modified zones 10 (preferably in the form of damaged zones) are arranged together so that they follow the desired separation line 14, wherein the workpiece 1 is separated at the separation line 14, thereby obtaining two parts 4, 5. For the sake of clarity, as an example, Figure 2 A plate-shaped workpiece 1 having a plurality of such modified regions 10 arranged in a row is shown. A top view of a side surface 100 of the workpiece 1 is shown in the figure. From this figure it can be seen that the cross section of the modified region 10 is perpendicular to the direction of the length L. Due to the flat geometry of the damaged region 10, it can be seen from the side surface 100 that the damaged region 10 has an elongated shape, which is simplified to an elongated rectangle in this figure. In this context, it is reasonable that the modified regions 10 are arranged with respect to each other in such a way that the longitudinal direction of the elongated cross section of the modified region 10 is aligned along the separation line 14. In other words, the modified region 10 is oriented so that the separation line 14 extends along the width direction of the modified region 10.

[0045] According to the invention, the insertion of a flat, cut-shaped or slit-shaped modified zone 10 can also make it easier to separate the workpiece 1 along a curved separation line or at least a section of a curved separation line 14, without the need for an additional etching step to support or initiate the final separation. Therefore, according to an alternative or additional improvement, it is provided that the damage zone 10 is inserted along a separation line 14 that is at least partially curved. If (in the embodiment shown) the separation line 14 is closed, the separation process will be more difficult. Compared with pre-separation by inserting filamentary damage, it is much easier to use the method described herein. According to another alternative or additional embodiment of the method, the modified zone 10 is inserted along a closed separation line 14, and then the internal component defined by the separation line is preferably separated from the workpiece 1. In the embodiment shown, the component 4 is an internal component 6. In this article, the separation line 14 is circular, and the internal component 6 is correspondingly also plate-shaped.

[0046] In the embodiment shown, these modified regions 10 are still spatially separated. However, it is generally also possible to allow the modified regions 10 to overlap in order to further facilitate the separation of the components 4,5.

[0047] In addition to the cuts arranged in the length direction, modified zones 10 can also be inserted so that their widths point to each other. In this way, a correspondingly wider material modified zone is obtained. This also facilitates the cutting out of internal components. Another method is not to cut through the workpiece, but to form a groove with a single-side opening by repeatedly inserting adjacent modified zones in the workpiece. For example, this can also make hinges in brittle materials by locally reducing the thickness of the workpiece. In addition, the stress in the material can also be changed. For example, in the case of prestressed glass, if the local compressive stress on at least one side is reduced by material modification, a kink or bend can be generated in the workpiece 1. In addition, other material modification methods that do not require the removal of material can also be implemented. The change of the refractive index is only one embodiment. For example, material modification is used to produce a surface refractive index change, thereby generating a dielectric reflector, such as a volume Bragg grating (Volumen-Bragg-Gittern, VBG).

[0048] Figure 3 The cross section A of the focal zone 35 observed in the direction of the beam axis 31 is schematically shown. In this direction, the dimensions of the width b and the thickness w in the cross section can be seen at the position of the maximum extension of the focal zone 35. In the present embodiment, the focal zone 35 has an elliptical cross section, but it is clear to a person skilled in the art that other cross-sectional shapes are also possible depending on the characteristics of the beam shaping optical device 7. In this case, the beam shaping optical device 7 is designed so that it has a sufficiently small cross section in the focal zone. According to a preferred embodiment, a pulsed laser 3 is used, whose laser light 30 is focused in the focal zone 35 so that the light intensity is sufficient to change the material of the workpiece 1. In a preferred embodiment, its laser light 30 is focused into the focal zone 35 so that the cross section A of the focal zone 35 is small enough so that the light intensity in the focal zone 35 exceeds 10 13 W / cm 2 , the formula is E pulse / (A·t pulse ). In the above terms, E pulse represents the energy of the laser pulse, t pulse represents the pulse duration. In order to achieve high light intensity, in addition to reducing the cross-sectional area, shortening the pulse duration also has advantages. Therefore, according to another embodiment, the pulse duration is less than 100ps. Particularly preferably, the pulse duration ranges from 50fs to 50ps.

[0049] There are many options for the size and positioning of the focal zone 35 relative to the substrate. The length L of the focal zone 35 can be greater or less than the thickness of the workpiece 1. If the focal zone 35 length is greater than the workpiece thickness, the focal zone 35 can penetrate two opposing surfaces of the workpiece 1. Alternatively, the focal zone 35 can also be positioned to penetrate only one surface, i.e., the focal zone 35 ends in the workpiece 1. If the focal zone 35 length is less than the workpiece thickness, it is possible that the focal zone 35 is completely located in the workpiece 1. The latter case is Figure 4 As shown in FIG. 1 , partial views (a) and (b) show cross sections of a workpiece 1 observed from different directions. In partial view (a), the focal zone 35 is shown in a direction perpendicular to the beam axis and perpendicular to the width b. In partial view (b), the narrow side direction of the focal zone 35, i.e., the thickness w, is shown. It is also desirable to separate the workpiece 1 along this direction. It can be seen from these two partial views that the length L of the focal zone 35 is less than the extension of the workpiece 1 in this direction, and the focal zone 35 is completely located between the side surfaces 100, 101 in the workpiece 1.

[0050] exist Figure 5 In the example of the embodiment of the invention, the length L of the focal zone is greater than the thickness of the workpiece 1. Therefore, as shown in the partial view (a), the focal zone 35 is positioned so that it penetrates two opposite side surfaces. Similarly, the focal zone 35 can be positioned so that it starts at the workpiece (partial view (b)) or ends at the workpiece (partial view (c)) with respect to the beam direction, wherein in each case one of the side surfaces 100, 101 is penetrated. In summary, generally without being limited to the specific examples shown, in a refinement of the method, the focal zone can be positioned so that one of the following features is met: - the focal zone 35 is completely located inside the workpiece 1; The focal zone starts or ends inside the workpiece 1 and extends beyond the tool surface or one of the side surfaces 100 , 101 of the workpiece 1 ; The focal zone 35 has a length greater than the thickness of the workpiece 1 and penetrates two opposite surfaces of the workpiece 1 , in particular two opposite side surfaces 100 , 101 .

[0051] In particular, a flat blade-shaped focal zone 35 can be produced by astigmatic beam shaping or by caustic beam shaping. In particular, one-dimensional caustic beam shaping can also be used to produce a corresponding Airy beam, whose focal zone is no longer flat, but is bent around an axis transverse to the beam direction, preferably perpendicular to the axis. The generation of such a beam is also described in Froehly, L., Courvoisier, F., Mathis, A., Jacquot, M., Furaro, L., Giust, R. et al. (2011): Arbitrary Accelerating Micron-Scale Caustic Beams in Two and Three Dimensions, Optics Express 19 (17), p. 16455–16465, DOI: 10.1364 / OE.19.016455. The beam profile and the optical device for generating the beam profile also all fall within the scope of the present disclosure. Reference will be made to Fig.19 and Fig. 20 Detailed Description of One-Dimensional Caustic Beam Shaping In this context, the term "one-dimensional" means that the caustics are formed substantially along a single spatial direction, or in that the focal region is substantially curved in only one spatial direction.

[0052] For further observation, the coordinate in the direction of the light beam is set as the z coordinate. Accordingly, this direction is the direction of the height L of the focusing area 35. The coordinates x, y perpendicular to this direction correspond to the first direction and the second direction mentioned above, and are developed into a plane transverse to the direction of the light beam. Without being limited to the general premise, the y direction is called the strong convergence or strong focusing direction, and the x direction is called the weak convergence or weak focusing direction. Of course, the names of these directions are optional. Therefore, the light beam can also be strongly converged in the x direction.

[0053] like Figure 1 As shown in the example of , converging beam shaping can be achieved by focusing with a refractive surface (especially a cylindrical lens). In this case, the focal length f in the x-direction and y-direction is x and f y Satisfy: f y < <f x Preferably, the focal length in the y direction is at least 5 times smaller than the focal length in the x direction. Under Gaussian optical conditions, the height L of the focal region 35 satisfies: L≈2 ZR ,in ZR is the Rayleigh length on the xz plane. By means of this device, a focus area 35 with a Gaussian profile can be generated in the plane extending in the strong focusing direction and the light beam direction (ie, the yz plane).

[0054] Other interference modes can also be used to produce linear focusing in the plane between the strong focusing direction and the beam direction (i.e., the yz plane), such as accelerated beams, especially Airy beams.

[0055] In an improved embodiment of the method and device 2, but not limited to the specific embodiment, a beam shaping optical device 7 is provided, which produces a focal zone 35 having an intensity curve of a Gaussian beam, a Bessel beam or an Airy beam or at least approximates one of the beams in one plane.

[0056] Figure 6 The apparatus for generating the focal zone 35 with a Bessel beam is schematically shown. In this embodiment, the beam shaping optical device 7 comprises an axicon 73, onto the bottom surface 730 of which the laser beam is directed. A roof prism is not suitable to replace the axicon 73, because the roof prism forks the laser light 30, refracting through two mutually inclined refractive surfaces 731, 732, and separating the laser light 30, which initially has an intensity profile, preferably an intensity profile with a Gaussian profile 36, into two partial beams, which converge and intersect after being emitted from the roof prism 73. However, this results in a lack of positioning. A Bessel profile 37 is shown in the region of the intersecting beams. As shown in the figure, the light intensity in such a profile increases significantly in a narrow central region. This results in the formation of a flat focal zone of length L, which substantially corresponds to the length of the region where the partial beams overlap.

[0057] Figure 7 Shown using Fig.13 The phase mask shown produces a beam profile 37. This non-broadened intensity profile along the y direction Almost corresponds to Figure 6 The ideal, rotationally symmetric Bessel beam is shown. The partial image (b) shows the broadened intensity profile in the perpendicular x-direction. Due to the non-diffraction characteristics of the Bessel beam, the intensity profile in the region along the propagation direction z is approximately constant. Therefore, it is equivalent to the intensity profile in the xz plane or yz plane described below. In the xz plane, the laser 30 is partially weakly focused, and the high-intensity region defining the focal zone 35 is relatively wide compared to the high-intensity region in the yz plane. The width b of the focal zone 35 can be defined as the half-width of the beam profile in this plane, but is not limited to the embodiment shown in the partial figure (b). The width of the Bessel profile 37 formed in the yz plane is defined by its first zero point: w=a0λ / (πsin(α)), where λ is the wavelength of the laser 30 and α is the beam aperture half angle, that is, the effective Bessel cone angle. This value can be defined as the thickness w of the focal zone 35. The a0 value is 2.4044, and the value of the first zero point of the Bessel function measured is J0. Similar values ​​can also be obtained using prisms or lenses of other shapes. Therefore, without being limited to the exemplary embodiment or the generation of the focal zone by a roof prism, in the improved scheme of the method and the apparatus, the value of the thickness w of the focal zone 35 is generally in the range of 1.39 times to 10 times the wavelength of the laser 30. Generally, a non-diffracting beam (such as the aforementioned Bessel beam) is preferably used to generate the focal zone 35. An Airy beam also represents a non-diffracting beam. Such a non-diffracting beam is defined as a beam having a constant intensity profile in the lateral direction along its propagation direction. This is very different from the conventional behavior of light, which is generally focused to a small point and then dispersed.

[0058] In practice, due to the limited lateral aperture size of the optical device and the limited energy of the laser beam, the area with non-diffraction characteristics during the beam propagation is also limited.

[0059] Therefore, without being limited to a specific embodiment, it is conceivable that the beam shaping optical device 7 is designed to generate a non-diffracted light beam that shapes the focal area 35.

[0060] Typically, the optical strength of the focusing element is too weak, and the volume occupied by the flat or cut-out focusing area 35 is too large to achieve sufficient strength to achieve material changes in the workpiece 1. Therefore, in an improved solution of the method and the device 2, it is configured to reduce the focal length of the original defocus. In other words, a magnification factor M<1 is adopted. According to a certain embodiment, this focus reduction can be achieved by a telescope device, preferably a 4F structure or a 6F structure. Therefore, without being limited to a specific embodiment, according to a certain embodiment, the beam shaping optical device 7 is configured to include a 4F device or a 6F device with a magnification factor of M<1. Generally, another focus reduction optical device can also be used, that is, a focus reduction telescope that does not rely on a 4F structure or a 6F structure, that is, a telescope with a magnification factor of M<1. The magnification factor generally depends on the focal length of the optical elements (especially lenses) included in the beam shaping optical device. According to a certain embodiment, the beam shaping optical device includes a 4F telescope having a lens with a long focal length f1=500mm and an effective short focal length f MO = 10mm microscope objective. This results in a magnification factor of M = f MO / f1 = 1 / 50. Without being limited to this specific embodiment, for this purpose, a modification of the device 2 is provided, in which the beam shaping optical device 7 is provided as a telescope with a magnification factor of M < 1 / 10, preferably M < 1 / 25. This reduction in focus reduces the focal area laterally by M 2 times, the longitudinal direction (i.e. the beam direction) is reduced by M 3 This effect is also very beneficial for achieving high beam intensity in the focal region. This effect is also shown in the following table, which compares the functional relationship between the reduction of the focal region size and the magnification factor M:

[0061] Original size Reduce size thickness w’ w=Mw' width b’ b=Mb' high L’ <![CDATA[L=M 2 L’]]> volume V'=w'b'L' <![CDATA[V=M 4 In]]>

[0062] For the purposes of the present disclosure, in a further developed embodiment, astigmatic beam shaping means, inter alia, creating two or more mutually perpendicularly oriented flat focal zones instead of a single focal zone with a substantially circular cross-section. Figure 8 and Fig. 9 There is more detailed explanation on this. Figure 8 shows an astigmatic focused laser beam, Fig. 9 The beam cross sections of the laser beam at four different positions are shown. Fig. 9 The positions A, B, C, and D of the beam cross sections are shown in Figure 8 All are marked. Figure 8 The beam direction of the laser 30 is directed from position A to positions B, C, and D. Figure 8Optical elements for astigmatic beam shaping are not shown. Position A is the focus of the last lens or lens system (such as a microscope objective). At this first transverse conjugate point, the lateral dimensions of the beam profile are essentially the same. Position B is the focus of the strongly focused beam axis in the y direction. At this position, a meridian focal line 35 parallel to the x direction is formed. Position C is the second transverse conjugate point. Similar to position A, the beam profile is essentially circularly symmetrical. If the optical system is weakly focused in the x direction, the beam diameter at the second conjugate point is smaller than the beam diameter at the first conjugate point or position A. Finally, position D is the focus of the weakly focused beam axis x, that is, the so-called sagittal focal line parallel to the y direction. If the laser 30 is shaped by a 4F device, the corresponding focal length is proportional to the coefficient M. 2 to zoom in or out.

[0063] The distance d between the focus in the strong focusing direction at position B and the second conjugate point at position C cp Satisfy the following formula:

[0064] Among them, f y represents the focal length of strong focus in the y direction, f x Indicates the focal length of weak focus in the x direction. If the two focal lengths f x 、f y There is a big difference between x Significantly longer than f y (f x →∞), then we can infer that d cp ≈f y .

[0065] For other distances, it is also applicable: AB = f y , f y ≤d cp , and AD=f x .

[0066] Similar to Figure 8 , Fig.10 It is also shown that for the limiting case f x →∞ astigmatic shaping laser, the idealized three-dimensional beam profile is schematically shown next to the beam. In the case of astigmatic beam shaping, in addition to the flat focal area 35, secondary focal areas 38 and 39 can also be formed. Fig.10In the figure, the focal region 35 and the secondary focal regions 38 and 39 are idealized as rectangular parallelepipeds. As shown in the figure, the secondary focal regions 38 and 39 can also have a flat shape. These secondary focal regions 38 and 39 are usually located in the region of conjugate points A and C. In the embodiment shown, in the case of a flat shape, the directions of these secondary focal regions 38 and 39 are also perpendicular to the width b and thickness w of the focal region 35. Therefore, without being limited to the embodiment shown, in a certain embodiment, the laser 30 is shaped by the beam shaping optical device 7, thereby generating two flat secondary focal regions 38 and 39 in addition to the focal region 35, wherein the focal region 35 is arranged between the secondary focal regions 38 and 39 in the beam direction. In a further improvement, the width and thickness directions of the secondary focal regions 38 and 39 are perpendicular to the width and thickness directions of the focal region 35, as seen from the beam direction. Depending on the beam shaping method, the light intensity of these secondary focal regions 38 and 39 is usually lower than the light intensity of the focal region 35 in the middle, but can still reach the same order of magnitude as the focal region 35. These secondary focusing regions 38, 39 may also be referred to as parasitic focuses, since they are conjugated in their transverse direction with respect to the focusing zone, so that the respective damage zone is perpendicular to the desired direction of material modification. Therefore, according to a preferred embodiment, material processing or separation of the workpiece 1 is performed exclusively via the focusing zone 35. The focusing zone 35 typically extends around a position B, i.e. around the focal position in the direction of strong focus. Therefore, in a preferred embodiment, the beam shaping optical device 7 and the workpiece 1 are positioned relative to each other such that the focal point in the direction of strong focus of the astigmatic beam shaping optical device 7 is located on the material of the workpiece 1 or particularly preferably in its material. However, in embodiments in which the focusing zone 35 ends or starts in the workpiece 1, this point may also be located outside the workpiece 1. For example, Figure 5 This configuration can be seen in examples (b) and (c).

[0067] For the processing of transparent workpieces 1, for example made of glass, glass ceramic or crystalline material, the adverse effects of parasitic focal spots or secondary focus areas 38, 39 can be surprisingly easily minimized. To this end, according to a first embodiment, the beam shaping optics 7 and the workpiece 1 are arranged and / or adjusted relative to one another so that, in addition to the focal area, there is at least one secondary focus area 38, 39 at least partially located inside the workpiece 1. In this case, the intensity of the laser light 30 can be adjusted such that the light intensity in the secondary focus areas 38, 39 is below a threshold value for permanent changes in the material of the workpiece 1. However, the intensity is preferably adjusted such that the light intensity in the focal area 35 is above this threshold value.

[0068] According to another embodiment, the focal zone 35 is arranged relative to the workpiece 1 in such a way that the focal zone 35 is at least partially located inside the workpiece 1 and the secondary focal regions 38, 39 are located outside the workpiece 1. In particular, this can be achieved if the height L of the focal zone 35 is greater than or equal to the thickness of the workpiece 1 and / or the distance between the focal zone 35 and the secondary focal regions 38, 39 is sufficiently large.

[0069] Fig.11 Various possible arrangements (I), (II), (III), (IV) and (V) are shown when machining a workpiece 1 with an astigmatic laser beam. In case (I), both the focal zone 35 and the two secondary focal zones 38, 39 are located inside the workpiece 1. In this case, it is advantageous, as described above, that the power of the laser is adapted so that the light intensity of the secondary focal zones 38, 39 is below the threshold for permanent changes in the material of the workpiece 1 and the light intensity of the focal zone 35 is above this threshold. In cases (IV) and (V), the two secondary focal zones 38, 39 are far apart from each other so that the laser beam position can be positioned so that the secondary focal zones 38, 39 are located outside the workpiece 1.

[0070] In the cases (II) and (III), at least one side surface 100, 101 or at least one surface of the workpiece 1 is located in each case within one of the secondary focus regions 38, 39, respectively. These cases are rather unfavorable and not preferred. The reason for this is that the damage threshold of a surface exposed to ultrashort pulse laser radiation is usually an order of magnitude lower than that of the bulk. The processes that cause material changes in the workpiece 1 are usually based on multiphoton absorption or avalanche ionization.

[0071] Generally, the length of the focusing region 35 inside the workpiece 1 is greater than its length outside the workpiece 1. Specifically, the portion of the focusing region 35 located inside the workpiece is elongated by a factor equal to the refractive index of the material of the workpiece 1.

[0072] As mentioned above, the beam shaping optical device 7 can include a roof prism 73 and / or a cylindrical lens 71 for generating an astigmatic laser beam. Another possible solution is to use a diffractive optical element. Such an element can be designed in particular as a phase mask. With such a mask, for example, the laser can form a Bessel-Gaussian beam. The phase mask also has the advantage that the focal zone of the Bessel-Gaussian beam can be formed at a certain distance from the beam shaping optical device 7. This can simplify the handling and positioning of the workpiece in the device 2. Fig.12An embodiment of such a beam shaping optical device 7 is shown. In general, without being limited to the embodiment shown, in a refinement of the apparatus and method, an astigmatic laser beam formed by a laser is provided, wherein a phase mask 70 provided, in particular forming a diffractive optical element 74, is arranged before an optical telescope or alternatively before a focus reduction device or a combination of optical elements. In the embodiment shown, the diffractive optical element is arranged in the beam direction before a combination of a lens 72 and an objective lens 75 located downstream in the beam path. The focal length of the objective lens 75 is smaller than the focal length of the lens 72, so that the resulting focus reduction ratio corresponds to the focal length ratio of the objective lens 75 and the lens 72. In the embodiment shown, the focal length of the lens 72 is 500 mm and the focal length of the objective lens is 10 mm, resulting in a magnification factor of the focus reduction of M=0.02. The lens 72 can in particular be spherical or non-spherical. In the exemplary embodiment, a laser beam with a diameter of 6.6 mm is also used to irradiate the phase mask 70.

[0073] Fig.13 , shows an embodiment of a phase mask 70 in the form of a diffractive optical element 74, with the partial view (a) being a top view. The lines represent the position of the phase every 2π radial movement from the center (marked with a cross). For example, the phase shift of the second innermost concentric line from the center is 4π. Generally speaking, the phase mask 70 is formed according to a certain improvement scheme (which can also be implemented in the embodiment shown), which causes the laser phase to shift radially from the center of the phase mask by an increasing factor in the embodiment shown, wherein the phase shift period differs by a factor of 2nπ in two directions perpendicular to each other, or as a function of the distance from the center, the phase shift in the first radial direction is greater than the phase shift in the second radial direction (perpendicular to the first radial direction). In the embodiment shown, according to this definition, the first direction starting from the center is the vertical direction and the second direction is the horizontal direction. Fig.14 The x-direction ( Fig.13 ) and y directions ( Fig.13 The phase shift in the vertical direction (in the vertical direction) is measured in radians (rad). According to an exemplary embodiment, the diffractive optical element 74 can generate a phase distribution of a Bessel beamlet at an angle of 7.5° or a total angle of 14.8° with the beam axis. The focal length can be allocated in these two directions, and the focal length can be obtained by the square of the phase distribution or Fig.14 This corresponds to the quadratic phase term k0·ρ of the thin lens. 2 / (2f).

[0074] The following describes the process of forming a light surface using Bessel beamlets. Here, Bessel beamlets refer to individual cone-shaped phases that contribute to the beam shape. Fig.13The partial diagram (b) schematically shows the Fig.13 The phase mask 74 shown in the partial figure (a) generates the phase distribution of the Bessel beamlet 32 ​​in the x direction. The total phase of the phase mask 74 Given by:

[0075]

[0076] This is obtained by adding n cone components (Bessel beamlets 32), each at position ρ i =(x i ,y i ). For example, the linear lateral shape satisfies the following equation:

[0077]

[0078] Other transverse profiles can also be chosen to create a light surface that is flat along the beam direction, but also locally curved around an axis parallel to the beam direction. Alternatively, this beam shaping can be applied to any transverse profile along the beam propagation direction, thereby forming a surface with the same profile in cross section at different locations along the beam propagation direction.

[0079] Weighting factors can be used to achieve a favorable light intensity distribution along the line or, in this embodiment, along the flat focal area 35. Preferably, these weighting factors a i Can include position function ρ i =(x i ,y i ). For example, the following equation can be satisfied:

[0080] α i (ρ i )=c|ρ i |

[0081] where c is a constant.

[0082] The total scaling factor s is used to normalize the sum of the Bessel beamlets 32. For example, the effective opening angle α of the Bessel Gaussian beam satisfies the following equation:

[0083]

[0084] The thickness w' of the focal region 35 is given by the first zero of the Bessel function at 2.405:

[0085]

[0086] An alternative method for generating a light profile based on Bessel beams is described in Alessandro Zannotti; Cornelia Denz; Miguel A. Alonso; Mark R. Dennis: Shaping Caustics into Propagation-Invariant Light, Nat Commun 11(1) pp. 1-7. DOI: 10.1038 / s41467-020-17439-3. Beam profiles and optical devices for generating beam profiles also fall within the scope of the present disclosure.

[0087] When a Gaussian beam with half-width w0 is used as the input beam on the phase mask, the length of the focal zone can be estimated as: l = w0 / cos(α). Other intensity distributions of the input beam are also possible, such as a TopHat distribution with uniform intensity over the entire width. In particular, the amplitude distribution and the phase distribution can be adjusted to achieve as uniform an intensity distribution as possible along the length of the focal zone.

[0088] Test results for glass workpiece material processing are shown below. Fig.15 An optical microscopic image of a side surface 100 of a workpiece 1 processed with a laser is shown. As can be seen from the figure, three rows of material modified or damaged areas 10 marked with (a), (b), (c) are inserted into the workpiece 1 made of borosilicate glass. The focal areas of these three rows are located at different positions relative to the surface. Fig.16 The position of the focal region 35 is shown. Fig.16 It can be seen that the focal zone 35 is closest to the photographed surface in the (a) row of damage zones and is deepest in the (c) row. However, in each case, the focal zone 35 is completely positioned inside the workpiece 1. Specifically, the (a) row shows an elongated damage zone 10 in the form of a blade-shaped slit 16. The other damage zones 10 also show surface damage caused by a secondary focusing area 38, which is also blade-shaped and perpendicular to the main damage zone, resulting in the overall flat cross shape of the damage zone 10 with two short arms and two long arms. For processing, the laser is operated in pulse group mode, each pulse group having two pulses. In this mode, the laser emits laser light in the form of a pulse group or a rapid burst of pulse sequences. The pulse length of a single pulse is 1.5ps, and the total energy of the pulse group is 36μJ. According to Fig.12 In the arrangement shown, the focal length is 10 mm. To penetrate the damaged region 10 at different depths, the distance between the workpiece 1 and the objective lens 75 is reduced row by row by dz=20 μm. The distance within the workpiece is n·dz, where n is the refractive index of the glass.

[0089] The method and apparatus described herein are particularly suitable for separating a workpiece 1 into two or more parts, for example in order to cut parts of a specific contour from a workpiece in the form of a glass sheet. Fig.17 and Fig.18 Give an example. Fig.17 An optical microscopic image of the surface of the separated workpiece 1 is shown. Fig.18 FIG. 1 shows a portion of the edge surface of a workpiece 1 obtained by separation. Fig.15 The workpiece in the embodiment is ground to a thickness of 40 μm to remove each portion of the damaged area 10 caused by the secondary focusing areas 38, 39. Then, the workpiece 1 is separated at the damaged area 10 in one of the rows (a), (b), and (c). Fig.17 The two components 4, 5 thus obtained are shown side by side. The characteristic edge surfaces of the components 4, 5 are obtained by the special shape and arrangement of the damaged areas 10, which are as follows Fig.18 As shown. It can be seen that the edge surface 18 of the components 4 and 5 has damage zones 10 separated from each other along the edge surface, and the fracture surface 18 is located between the damage zones 10. Unlike the separation at rows of filamentary damage described in patent document WO 2017 / 009379A1, the damage zone 10 here is flatter relative to the range along the edge surface 18 or along the circumference. This is because the focusing area 35 is in the shape of a flat blade or knife, so the range of the damage zone 10 is also correspondingly flat. The difference between the damage zone 10 and the fracture surface 19 is that the damage zone 10 has material modification, such as plasma generated in the damage zone by a strong laser. Therefore, the components 4 and 5 made by this method are a plate-shaped element made of an inorganic material (preferably glass) that is at least partially transparent to the laser. 8, having two opposite side surfaces 100, 101 and a peripheral edge surface 18, the edge surface 18 having alternating fracture surfaces 19 and damaged areas 10, the damaged areas 10 exhibiting material modification, in particular by the formation of plasma in the component material, and the extension of the damaged areas 10 from the edge surface 18 into the component 8 is at least 5 times smaller than the extension from the edge surface 18 in the peripheral direction. Fig.18 In the picture, the circumferential direction is from left to right, that is, the direction parallel to the side surfaces 100 and 101.

[0090] Generally, this has the advantage that only a relatively small number of damaged areas 10 are required to separate the workpiece into multiple components. In extreme cases, separation can be achieved using a single shot or by inserting a single damaged area 10.

[0091] In the above-described embodiment, the flat focal region 35 has a flat shape. According to another embodiment, the focal region 35 may also have a curved shape. In this embodiment, the focal region 35 forms a curved caustic surface. The flat shape, in particular the blade shape, of the focal region 35 is curved around an axis (preferably an axis perpendicular to the beam direction). Fig. 20 Such an embodiment is shown in FIG. 1 , where partial view (a) shows a side view of a caustic focused laser beam 30 penetrating a workpiece 1. In general, a caustic focused beam can be understood as a beam in which a portion of the beam forms a tangent line with a surface or a flat focal zone 35. The curved focal zone 35 generated by the caustic is marked by a dashed boundary line. Another feature of caustic focusing is that, ideally, the phase of the laser beam changes in an idealized manner in only one direction. For further explanation, partial view (b) shows a perspective view of such a curved focal zone 35. For clarity, the width b, height L and thickness w are shown in the figure as well as the beam axis 31. As shown in the figure, the focal zone 35 is curved but has a flat shape, and the width b and thickness w can be specified for a cross section perpendicular to the beam axis 31 or the beam direction. Unlike the idealized representation, these dimensions can vary along the focal zone 35. Therefore, the focal zone 35 can have a minimum thickness w, especially at at least one position along the beam axis 31. When separating the workpiece 1, the curved focal zone 35 is generally particularly advantageous for producing a concave or convex edge surface.

[0092] Fig.19 A beam shaping optical device 7 for a light beam is shown, which is used to generate such a light beam with a curved focal zone 35. The beam shaping optical device 7 includes a one-dimensional phase mask 70, for example in the form of a diffractive optical element 74. The one-dimensional phase mask 70 is constant in the x-direction. Downstream of the phase mask 70 is a cylindrical lens 71 focusing in the y-direction. A one-dimensional phase mask body refers to a phase mask having a constant phase distribution in one spatial direction (for example, the x-direction) and a non-constant phase distribution (for example, a cubic distribution (kubische Verteilung)) in its perpendicular direction (y-direction). Other components such as LCOS-SLM can also be used instead of diffractive optical elements as a phase mask. The boundary of the focal zone 35 is marked with a dotted line. As shown in the figure, the focal zone 35 is curved. Without being limited to a specific embodiment, the focal zone 35 formed in this way can be beam shaped by a suitable phase mask 74 to obtain a substantially one-dimensional or compressed Airy beam in one spatial direction. The complex amplitude of the Airy beam satisfies the following formula:

[0093]

[0094] is described by a cubic scaling factor β. This produces an intensity profile according to:

[0095]

[0096] The length L' of the focal region obtained satisfies the following formula:

[0097]

[0098] This length is defined as the length where the intensity is greater than 1 / e of the maximum intensity. 2 The half width w′ of the focal area satisfies the following formula:

[0099] w′≈1.6·x0

[0100] The parameters in the above formula satisfy the following conditions:

[0101]

[0102] and

[0103]

[0104] w0 represents the half-width of the Gaussian input beam on which the cubic phase is imposed.

[0105] Figure 21 to Figure 2 7 shows a further embodiment of a device 2 for processing a transparent workpiece 1, in particular a beam shaping optical device 7 of such a device 2. Fig.21 In the embodiment shown, a diffractive optical element 74 is also provided as a phase mask, which is arranged in the beam path of the laser 30 and before the focusing device of the optical element. This device is formed by two lenses 72, 76 and an additional cylindrical lens 71 in the xz plane. The focal length of the lens L2, 76 on the workpiece side is smaller than the focal length of the lens L1, 72 downstream of the diffractive optical element 74. In the present embodiment, the focal length of the lens L1, 72 is 500 mm, the focal length of the lens L2, 76 is 100 mm, and the focal length of the cylindrical lens 71 in the y direction is 5 mm. In order to achieve a higher beam focus in the x direction, it is also possible to reduce the original beam width of the laser in front of the beam shaping optical device 7, as in the present embodiment. In the present embodiment, the beam width is reduced from 6 mm to 3.3 mm.

[0106] Fig. 22The illustrated embodiments are generally based on two cylindrically shaped lenses 71, 77 arranged one behind the other, which have different focal lengths and intersecting focusing directions, with the 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 illustrated embodiment, this factor is even 1000 mm / 5 mm = 200. Detail (a) shows the beam shaping optics 7 and the workpiece 1 to be processed in front of it. Detail (b) shows the focal region 35 that can be achieved in a cross-section in the xy plane perpendicular to the beam direction. In the simplest case, as shown, for an output beam with a circular beam profile, the cross-section of its focal region 35 is a flattened ellipse. The lens foci can be located at Fig. 22 the same point. This results in an astigmatism-free, purely elliptical beam. However, this is generally not the case.

[0107] According to Fig.23 the illustrated embodiments, the width of the focal region 35 can be adjusted. Additionally, the optics can generate an Airy beam through a suitable phase mask. According to a first aspect, the beam shaping optics 7 is characterized in that, whether generating an Airy beam or another beam path such as a Bessel-Gauss beam, two optical telescopes nested one inside the other are provided. The first optical telescope includes two cylindrical lenses 71, 77, and the second optical telescope includes two lenses 72, 76. In particular, the focusing directions of the cylindrical lenses 71, 77 intersect, just as in Fig. 22 the embodiments.

[0108] According to another refinement, in the illustrated embodiment, it is also possible to arrange the optical telescope with the two lenses 72, 76 between the cylindrical lenses 71, 77. To generate defocusing, preferably f2 < f1 is satisfied. According to another refinement, a phase mask 74 is provided in order to generate an Airy beam, in particular in a plane in the workpiece 1, thereby obtaining a flattened focal region. The distance between the conjugate points of the internal telescope constructed with the lenses 72, 76 is used as the delay distance 79 for generating the Airy beam.

[0109] Fig.24 shows a simpler structure. This embodiment represents, for example, a combination of the phase mask 70 forming the diffractive optical element 74 and the 2F arrangement. In the simplest case as shown, the 2F arrangement can be formed by a single lens, preferably by the lens of the microscope objective 75.

[0110] Fig.25 shows Fig.24 a variant of the illustrated device. According to Fig.25In the variant of , the distance between the diffractive optical element 74 and the lens or microscope objective 75 is greater. This arrangement can be referred to as a 4F-like structure. Both arrangements are characterized in that the beam shaping optical device comprises a microscope objective 75 as the last element on the light output side and a phase mask upstream of the microscope objective 75, in particular in the form of a diffractive optical element 74. According to a development, no further beam shaping elements are arranged in the beam shaping optical device 7.

[0111] In some cases, the power of the laser may not be sufficient to achieve a sufficient intensity in the focal zone 35 to modify or in particular damage the material. A way of achieving a higher intensity will be described below. The beam shaping optics, including the beam shaping optics 7, can be designed in such a way that a stronger reduction in focus is achieved, i.e. a further reduction in the focal zone 35. This can be achieved by the laser beam 30 generating a beam with an elongated beam profile before focusing. During the focusing process, this leads to a further reduction in the size of the focal zone in the direction in which the beam profile is elongated in the beam shaping optics 7 before focusing. Fig.26 This effect is explained in detail by the schematic example in FIG. According to one embodiment, the beam shaping optics 7 comprises a beam shaping optics which shapes the laser beam 30 in such a way that when the laser beam strikes the focusing optics as part of the beam shaping optics 7, it has an elongated beam profile, which is elongated in a direction transverse to the width direction of the focal zone 35, preferably perpendicular to the width direction of the focal zone 35, and accordingly in a thickness direction of the focal zone 35. In this way, the thickness of the focal zone 35 is further compressed and the intensity within the focal zone 35 is increased. In the illustrated embodiment, an anamorphic optic 80 is provided as a beam shaping element, which produces an output beam having a beam profile that is elongated in the y direction when it strikes the focusing optics 81. As shown in the figure, the beam profile can be elliptical, so that in the present embodiment the major semi-axis of the profile is in the y direction. The focusing optics 81 is generally oriented so that the width direction of the focal zone 35 is perpendicular to it, i.e. in the present embodiment the x direction. In particular, by using an elliptical input beam with a sufficiently small minor semi-axis, the width of the focal zone can be increased even when focusing with a rotationally symmetric focusing lens (eg with a microscope objective).

[0112] Generally, a high power laser with a power of at least 100 W, preferably at least 150 W, is used to modify the material in the focal zone, which is useful for separating the material or creating the slit. The following table lists examples of parameters suitable for the laser and beam shaping optics. The first table lists parameters suitable for Fig. 22 Laser parameters of the shown setup.

[0113] Laser parameters Pulse group [μJ] 300 Number of pulses per pulse group1 Pulse duration [ps] 3

[0114] Gaussian beam shaping

[0115] The parameters in the following table apply to Fig.12 An embodiment shown.

[0116] Laser parameters Pulse group [μJ] 250 Number of pulses per pulse group1 Pulse duration [ps] 3

[0117] Telescope settings

[0118] Gaussian beam shaping

[0119] The following table illustrates Bessel-Gaussian (BG) beam shaping laser parameters for three examples: Bessel-Gaussian beam shaping

[0120] The following table describes suitable laser parameters for shaping the Airy beam using a curved focal region 35. Fig.12 These parameters also apply to the device shown:

[0121] Telescope settings

[0122] Airy beam shaping: Reference numerals list

Claims

1. A method for machining a workpiece (1), wherein: - irradiating the workpiece (1) with laser light (30) from a laser (3), in, - the material of the workpiece (1) is at least partially transparent to the laser light (30), so that the laser light (30) is transmitted into the workpiece (1); and wherein, - focusing the laser light (30) into a focal zone (35) of the workpiece (1) by means of a beam shaping optical device (7), wherein: - the focal zone (35) has a flat shape in a cross section perpendicular to the beam axis, having a width and a thickness along a length lying in the direction of the beam and in any case perpendicular to said length, wherein, at at least one position along the beam axis, said thickness of the focal zone (35) is at least 5 times smaller than said width and said length of the focal zone; and wherein, Due to the intensity of the laser (30) in the material of the workpiece (1), a modified zone (10) is inserted within the focal zone (35), the modified zone (10) having a flat shape corresponding to the focal zone (35).

2. The method according to the preceding claim, characterized in that At least one of the following machining operations is performed on the workpiece (1): - separating the workpiece (1) into two parts (4, 5) at the modification zone (10); The refractive index of the material of the workpiece (1) in the damaged area is influenced by the laser.

3. The method according to the preceding claim, characterized in that Using the beam shaping optics, a focal zone (35) is generated in the workpiece (1), the focal zone (35) having at least one, preferably all, of the following dimensions: - a width b in the range of 1 μm to 10 mm, preferably 10 μm to 50 μm; - a thickness w ranging from 0.2 μm to 50 μm, preferably 1 μm ± 0.5 μm; - a thickness w ranging from 1.39 to 10 times the wavelength of the laser (30); - a height L ranging from 2 μm to 20 mm, preferably from 1 mm to 5 mm, The projected area observed along the direction of the beam axis (31) of the laser (3) is at least 4 times smaller than the projected area of ​​the focal zone (35) observed along the thickness direction of the focal zone (35).

4. The method according to any one of the preceding claims, characterized in that A workpiece (1) made of an inorganic material, preferably glass, glass ceramic or a crystalline material, is machined.

5. The method according to any one of the preceding claims, characterized in that The focal region (35) is produced by astigmatic beam shaping or caustic beam shaping.

6. The method according to any one of the preceding claims, characterized in that A focusing region (35) having a curved shape is produced, wherein the focusing region (35) is curved about an axis perpendicular to the beam direction.

7. The method according to the preceding claim, characterized in that The laser light (30) is shaped by the beam shaping optical element (7) in such a way that, in addition to the focal zone (35), two secondary focal zones (38, 39) with a flat shape are generated, wherein the focal zone (35) is arranged between the secondary focal zones (38, 39) in the beam direction.

8. The method according to the preceding claim, characterized in that Include at least one of the following features: - the beam shaping optical device (7) and the workpiece (1) are arranged and adjusted so that, in addition to the focal zone (35), at least one of the secondary focal zones (38, 39) is at least partially located inside the workpiece (1), wherein the intensity of the laser light (30) is adjusted so that the light intensity in the secondary focal zones (38, 39) is below a threshold value for permanent changes in the material of the workpiece (1) and the light intensity in the focal zone (35) is above the threshold value; The focal zone (35) is arranged relative to the workpiece (1) in such a way that the focal zone (35) is at least partially located inside the workpiece (1) and the secondary focal regions (38, 39) are located outside the workpiece (1).

9. The method according to any one of the preceding claims, characterized in that A plurality of modified regions (10), in particular modified regions (10) in the form of damaged regions, are arranged in such a way that they follow a desired separation line (14), wherein the workpiece (1) is separated at the separation line (14), thereby obtaining two components (4, 5).

10. The method according to the preceding claim, characterized in that The method comprises at least one of the following features: - the modified zone (10) is oriented so that the separation line (14) extends along the width direction of the modified zone (10); - the modified zone (10) is inserted along a separation line (14) which is at least partially curved; The modified zone (10) is inserted along a closed separation line (14) and separates the inner part delimited by the separation line from the workpiece (1).

11. The method according to any one of the preceding claims, characterized in that The laser (30) is focused into a focal region (35) whose cross section A is small enough to make the light intensity in the focal region (35) exceed 10 13 W / cm 2 , the formula is E pulse / (A·t pulse ), where E pulse represents the laser pulse energy, and t represents the pulse duration.

12. The method according to any one of the preceding claims, characterized in that The focusing area (35) is positioned to meet one of the following characteristics: - the focal zone (35) is completely located inside the workpiece (1); - the focal zone (35) starts or ends inside the workpiece (1) and beyond one of the side surfaces (100, 101) of the workpiece (1); The focal zone (35) has a length greater than the thickness of the workpiece (1) and penetrates two opposite side surfaces (100, 101) of the workpiece (1).

13. An apparatus 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), the wavelength of which the workpiece (1) is at least partially transparent, so that the laser light (30) can be transmitted into the workpiece (1); and wherein, - the device comprises a beam shaping optical device (7) for focusing the laser light (30) to a focal zone (35) in the workpiece (1); wherein - the beam shaping optical device (7) is designed so that the resulting focal zone (35) has a flat shape with a length in the beam direction and a width and a thickness, wherein the thickness of the focal zone (35) is at least 5 times smaller than the width and length of the focal zone; and wherein, The laser (3) and the beam shaping optics (7) are designed so that the intensity of the laser light (30) in the focal zone (35) is sufficient to insert a modified zone (10) in the material of the workpiece (1), the modified zone (10) having a flat shape corresponding to the shape of the focal zone (35), in particular so that the extension of the modified zone (10) in a direction along the beam axis (35) and in a direction perpendicular to the beam axis is greater than its extension in a second direction perpendicular to the beam axis (35).

14. Device according to the preceding claim, characterized in that The beam shaping optical device (7) has at least one of the following features: - the beam shaping optical device (7) is of astigmatic or caustic type; - the beam shaping optics (7) comprises a phase mask (70); - the beam shaping optics (7) comprises at least one cylindrical lens (71); - The beam shaping optics (7) comprises a 4F or 6F device with a magnification factor M<1.

15. Device according to any of the two preceding claims, characterised in that The beam shaping optics (7) produce a focal zone (35) having an intensity profile of a Gaussian beam, a Bessel beam or an Airy beam in a plane.

16. Device according to any of the three preceding claims, characterised in that The beam shaping optical device (7) comprises at least one of the following optical elements to generate an astigmatic laser beam: - refractive optical elements, in particular free-form optical elements; - a cylindrical lens (71); - a diffractive optical element (74); - A phase mask (70), in particular a LCOS spatial light modulator SLM.

17. Device according to the preceding claim, characterised in that At least one of the following characteristics: the beam shaping optics (7) comprising a phase mask (70), preferably in the form of a diffractive optical element (74), which causes the laser light to have a greater phase shift in a first radial direction than in a second radial direction as a function of the distance from the center of the diffractive optical element (74), wherein the second radial direction is perpendicular to the first radial direction; - the beam shaping optics (7) comprises a phase mask (70), preferably in the form of a diffractive optical element (74), arranged before the focusing device of the optical element; - the beam shaping optics (7) comprises a beam shaping optics for shaping the laser beam (30) in such a way that when the laser beam hits a focusing optics (81) as part of the beam shaping optics (7), it has an elongated beam profile, wherein the elongation direction is transverse to the width direction of the focal zone (35), preferably perpendicular to the width direction of the focal zone (35).

18. A plate-shaped element (8) made of an inorganic material at least partially transparent to laser light, having two opposite side surfaces (100, 101) and a peripheral edge surface (18), wherein: The edge surface (18) has alternating fracture surfaces (19) and damaged areas (10), wherein the damaged areas (10) have a material modification, in particular by forming a plasma in the material of the element, and wherein the extension of the damaged areas (10) in a direction from the edge surface (18) into the element (8) is at least 5 times smaller than the extension of the edge surface (18) in a circumferential direction.

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