Method and apparatus for processing a workpiece

Abstract

A method for processing a workpiece (1), comprising irradiating the workpiece (1) with laser light (30) from a laser (3). At this time, since the material of the workpiece (1) is at least partially transparent to the laser light (30), the laser light (30) enters the workpiece (1). The laser light (30) is focused by a beam shaping optical system (7) into a focusing zone (35) within the workpiece (1). The focusing zone (35) has a flat shape having a length in the beam direction, a width and a thickness perpendicular thereto, respectively, in a cross section perpendicular to the beam axis. The thickness of the focusing zone (35) is not more than one fifth of the width and the length of the focusing zone at at least one position along the beam axis. Inside the focusing zone (35), a modification zone (10) is introduced based on the intensity of the laser light (30) within the material of the workpiece (1). The modification zone (10) has a flat shape corresponding to the focusing zone (35).

Description

Technical Field

[0001] The present invention relates to material processing in general. In particular, the present invention relates to the processing of materials that are transparent to light in at least one wavelength region by laser radiation.

[0002] From the prior art, non-contact material separation processes are known. In some of these separation processes, laser radiation is used. In particular, laser ablation is mentioned herein. Here, as one of the advantages, it can be mentioned that the process is applicable to almost any material. However, the disadvantage is that ablation is generally very slow, especially when compared to mechanical ablation processes. Another separation process is based on the action of high-intensity laser radiation inside a transparent material. In this process, the material is changed by a non-linear optical process, and in some cases, a plasma is formed, whereby the material is locally damaged. In this way, it is possible to form a channel that is at least partially open along the laser beam within the material. When such local, typically filamentous, damage or channels are repeatedly introduced along the path by the laser, it becomes possible to easily separate the workpiece processed in this way along its path. In particular, from International Publication No. 2017 / 009379 and other prior art cited in this document, a glass separation process by a series of filamentous damages using a laser is known.

[0003] Techniques that introduce filamentous damage along a path and then separate the processed workpiece along that path reach their limits quickly when the separation line is curved or even has corners. In the above-mentioned International Publication No. 2017 / 009379, introducing the filament obliquely to the surface enables separation along a curved separation line. However, this is often not desirable. On the other hand, separation along an arbitrarily extending separation line becomes possible by subsequent etching. The filament expands by etching, and thus the channels formed in this way are connected to cause separation at the separation line. However, etching is time-consuming and slow. Therefore, it is required to further improve the processing of workpieces, such as the separation of transparent materials by laser, by generating modified portions inside the workpiece. This problem is solved by the subject matter of the independent claims. Advantageous configurations of the invention are shown in each dependent claim.

[0004] The method and apparatus according to the present disclosure are particularly based on shaping a laser beam so as to obtain a focus that is two-dimensionally extended within the material of the workpiece to be separated. Thereby, rather than generating at least somewhat linear damage or thin channels within the workpiece when viewed in the propagation direction of the laser beam, a two-dimensionally extended coherent modification zone is generated, particularly in the form of a damage zone, which, in an ideal case, already indicates separation of the material. In particular, there is provided a method of processing a workpiece, in which the workpiece is irradiated with laser light of a pulsed laser, and since the material of the workpiece is at least partially transparent to the laser light, the laser light enters the workpiece. Modification of the material of the workpiece is performed by a non-linear interaction with the laser light based on high light intensity, particularly by non-linear absorption of the laser light. To obtain high light intensity, the laser light is focused by a beam shaping optical system into a focusing zone within the workpiece, where the focusing zone has a flat shape having a length extending in the beam direction of the laser light, and has a width and a thickness in a cross section or a transverse section perpendicular to the beam axis or the beam direction, and at least at one position along the beam axis, the thickness of the focusing zone in the cross section is 1 / 5 or less of the width and the 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, and the extension of the focusing zone is 1 / 5 or less of the extensions along the beam axis and the other direction perpendicular to the beam axis in a direction along one direction perpendicular to the beam axis. Therefore, the shape of the focusing zone can also be expressed as sheet-like or slice-like. The thickness and width in a cross section perpendicular to the beam direction represent the local thickness or width of the focusing zone. Thus, both parameters are variable and usually change along the beam direction. A box can also be arranged around the focusing zone. In that case, the size of this box can be expressed as the overall thickness, width, and length.

[0005] Inside the focusing zone, a modified zone is introduced based on the intensity of the laser beam within the material of the workpiece. This modified zone has a flattened shape corresponding to the focusing zone, and the extent of this shape is particularly larger in the direction of the beam axis and in a direction perpendicular to it, along a second direction perpendicular to the beam axis, compared to the extent along the second direction perpendicular to the beam axis, depending on the shape of the focusing zone. The beam axis and the aforementioned first and second directions particularly form a Cartesian coordinate system. Thus, these three directions form pairs that are perpendicular to each other. According to a preferred embodiment, the workpiece can then be separated into two parts in the modified zone. According to one development, this separation occurs spontaneously if the modified zone has already caused separation of the material. Generally, the modified zone means a region within the material of the workpiece where the material of the workpiece is modified with respect to the surrounding material. In particular, the modified zone can be a damaged zone, i.e., a region where damage has been introduced into the material. Such damage can particularly include separation of the material.

[0006] Optionally, according to another embodiment, the separation can also be performed by additional steps such as applying stress to the material in the region of the modified zone.

[0007] The stress application can be performed mechanically, for example, by compressive stress, tensile stress, or bending stress, thermally, or by heating the surface with a radiation source such as a CO2 laser or cooling with a nozzle. Also, spontaneous self-separation is possible if the glass workpiece is chemically or thermally strengthened.

[0008] A pulsed laser is particularly suitable for providing the radiation intensity necessary to modify the material, particularly to cause damage. For example, in the case of glass and other inorganic materials, so-called ultrashort pulsed lasers have a pulse length in the range of several tens of picoseconds or less and are particularly suitable for causing corresponding damaged zones.

[0009] In addition to the separation of the workpiece, other processing by material modification is also possible. According to another alternative or additional embodiment, the laser light causes a change in the refractive index locally in the material of the workpiece, i.e., within the damage zone. Such a change in material properties can occur at a lower light intensity or power density, especially compared to the separation processing of the workpiece.

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

[0011] Corresponding to the above method, an apparatus for implementing the method is further provided. The processing apparatus for the workpiece particularly includes a laser for emitting laser light, and the laser is adjusted to emit laser light of a certain wavelength. Since the workpiece is at least partially transparent to the laser light of this wavelength, the laser light can enter the workpiece. The apparatus further particularly includes beam shaping optics for focusing the laser light within a focusing zone in the workpiece. Here, the beam shaping optics are designed such that the resulting focusing zone of the laser light has a flat shape with a length, a width, and a thickness extending in the beam direction, where the width and the thickness are perpendicular to the direction of the length. Therefore, the width, the thickness, and the length directions form a pair perpendicular to each other, and the thickness of the focusing zone is less than or equal to one-half, preferably less than or equal to one-fifth, of the width and the length of the focusing zone. The laser and the beam shaping optics are further designed such that laser light with a sufficient intensity to introduce a damage zone within the material of the workpiece is present inside the focusing zone. This damage zone particularly has a flat shape such that the extent of the damage zone in the direction of the beam axis and in a direction perpendicular to it is larger than the extent along a second direction perpendicular to the beam axis, depending on the shape of the focusing zone. The workpiece to be separated may be a component of the apparatus. Further, the apparatus can be provided with equipment for separating the workpiece, particularly in the modification zone, and in particular, equipment for exerting mechanical stress in the modification zone.

[0012] The flat, e.g., blade-shaped, shape of the focusing zone can be described as an alternative to or in addition to the ratio of the thickness to the width and / or length of this zone, or by the corresponding ratio of the areas. Thus, alternatively or additionally, in one embodiment, the laser light is focused into the focusing zone such that the projected area of the focusing zone as seen along the direction of the beam axis of the laser light is at most one quarter of the projected area of the focusing zone as seen along the direction of the thickness of the focusing zone.

[0013] The three directions orthogonal to each other, i.e., the extension of the focusing zone along the beam axis and the other two directions, are referred to as the thickness w, width b, and height L as described above. Here, the height L is the extension of the focusing zone in the direction of the beam axis or the beam direction, or the incident direction of the laser light. The thickness w indicates the extension of the cross-section of the focusing zone along a second direction perpendicular to the beam axis, and the extension of the focusing zone along this direction is at most one half, preferably at most one fifth, of the extension along the beam axis and the extension along a first direction perpendicular to the second direction. By means of the beam shaping optical system, it is preferable that a focusing zone having at least one, preferably all, of the following extensions is generated in the workpiece: - The width b, i.e., the extension along a first direction perpendicular to the beam axis, which is in the range of 1 μm to 10 mm, preferably 10 μm to 50 μm. - The thickness w, i.e., the extension along a second direction perpendicular to the beam axis, which is in the range of 0.2 μm to 50 μm, preferably 1 μm ± 0.5 μm. - The height L, i.e., the extension along the beam axis, which is in the range of 2 μm to 20 mm, preferably at least 30 μm, particularly preferably 1 mm to 5 mm.

[0014] The present invention will be described in detail below with reference to the drawings. In the drawings, the same reference numerals indicate the same or corresponding elements, respectively.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Figure 24

Figure 25

Figure 26

[0016] Figure 1 shows an example of a processing apparatus 2, particularly a separation apparatus 2, of a workpiece 1 suitable for carrying out the method described in this specification. The apparatus 2 is not limited to the illustrated example and generally includes a laser 3 and a beam - shaping optical system 7 as central components. The workpiece 1 to be processed is arranged in front of the beam - shaping optical system 7 in the beam direction of the laser 3 such that a focused zone 35 generated from the laser light or laser beam 30 by the beam - shaping optical system 7 is at least partially present inside the workpiece 1.

[0017] Laser 3 has an output intensity sufficient to cause a material change, preferably within a modification zone in the form of a damage zone, based on the intensity of the laser light 30 inside the portion of the focusing zone 35 located within the workpiece 1, and this material change facilitates or already causes the separation of the component 1 in the damage zone.

[0018] Particularly suitable is an ultrashort pulse laser, preferably having a pulse duration in the picosecond range and particularly operable with a pulse duration of 50 ps or less. Different from the conventionally used laser-based separation devices for workpieces by introducing filamentous damage or thin channels, it is provided that the focusing zone 35 and accordingly the damage zone 10 have a flat shape. Depending on the focusing characteristics, the focusing zone can have different structures, for example, it can have the shape of a flat ellipsoid, simply a highly flat cuboid, or a flat plate.

[0019] The flat focusing zone 35 can generally be realized by an anastigmatic or focal line beam shaping optical system 7. In one embodiment, at least one cylindrical lens can be provided as a component of the beam shaping optical system 7.

[0020] Generally, refractive optical elements other than cylindrical lenses can be used as an alternative to or in addition to cylindrical lenses. For example, according to one embodiment, a free-form optical system is provided. Particularly preferred as a component of the beam shaping optical system 7 is a phase mask. The phase mask makes it easily possible to generate a focusing zone 35 with a large length and a small thickness. In contrast, in an optical system such as a cylindrical lens or generally having different refractive powers in directions perpendicular to each other, a reduction in width tends to be accompanied by a shortening of the focusing zone.

[0021] According to one embodiment, the phase mask is designed as a diffractive optical element. Also, a component of the beam shaping optical system as an element for generating the flat focusing zone described in this specification may be another phase mask such as a liquid crystal on silicon (LCOS) spatial light modulator (SLM). The LCOS SLM is a reflective spatial light phase modulator capable of freely modulating the optical phase. Here, the optical phase of the laser is modulated by liquid crystal. Generally, the beam shaping optical system 7 can also include a liquid crystal element for optical phase modulation. Generally, the focusing zone 35 and the modification zone 10 do not have to coincide. In particular, the focusing zone 35 can start outside the workpiece 1 and / or end outside the workpiece 1. In the illustrated example, the length L of the focusing zone 35, that is, the dimension in the direction along the beam axis 31 of the laser beam 30, is larger than the thickness of the workpiece 1. While the focusing zone 35 protrudes from two opposing surface regions 100, 101 of the workpiece 1 which is plate-shaped in this example, the modification zone 10 can of course extend at most between the two surface regions 100, 101. Without being limited to the illustrated example, the method is particularly preferably applied to a plate-shaped workpiece 1. Further, as also shown in the illustrated example, the modification zone is introduced such that the width direction of the damage zone is along the surface regions 100, 101 or perpendicular to the surface normal of the surface regions 100, 101. Thus, the modification zone 10 becomes a narrow cut in the surface regions 100, 101, and this cut facilitates the separation of the workpiece 1 into respective parts in this way.

[0022] To adjust the position of one or more damage zones 10 to be introduced, according to a preferred development of the device 2, a positioning unit 9 is provided. The positioning unit 9, and also the optical system, in particular the laser 3 in this specification, can advantageously be controlled programmatically by the control unit 12. In the illustrated example, the positioning unit 9 comprises an X-Y table on which the plate-shaped workpiece 1 is placed. The orientation of the flat blade-shaped focusing zone generated by the arrangement described in this specification with respect to the beam axis is also important. According to one embodiment, to adjust this orientation, it is provided that the optical system, or the beam shaping optical system 7, is designed to be rotatable about the beam axis. Alternatively or additionally, to achieve the desired orientation of the focusing zone within the workpiece, the workpiece can also be rotated about the beam axis. Thus, according to an alternative or additional embodiment, it is provided that the positioning unit comprises a rotation axis for rotating the workpiece relative to the laser beam in a direction parallel or collinear with the beam direction.

[0023] Particularly if the workpiece is small, a single modification zone 10 may be sufficient for separating the workpiece 1. However, in a preferred configuration, advantageously a plurality of modification zones 10 in the form of damage zones are arranged adjacent to each other along the provided separation line 14, and by separating the workpiece 1 along this separation line 14, two parts 4, 5 are obtained. FIG. 2 shows, for clarity, again by way of example the plate-shaped workpiece 1, and a plurality of modification zones 10 arranged adjacent to each other in this way are provided. The workpiece 1 is illustrated in a top view of the surface area 100. In this figure, the cross-sectional area of the modification zone 10 is perpendicular to the direction of length L. Due to the flat geometry of the damage zone 10, this appears elongated when viewed from the surface area 100, and here it is illustrated in a simplified manner as an elongated rectangle. Here, it is reasonable to arrange the modification zones 10 adjacent to each other such that the longitudinal direction of the elongated cross-section of the modification zone 10 is aligned along the separation line 14. In other words, the modification zones 10 are oriented such that the separation line 14 extends along the width direction of the modification zone 10.

[0024] By introducing the notch-shaped or slit-shaped flat modification zone 10 provided by the present invention, it is further possible to more easily separate the workpiece 1 along the curved separation line 14 or at least along a part of the curved separation line 14 without the final separation being assisted or caused by an additional etching step. Thus, according to an alternative or additional further development, it is provided that the damage zone 10 is introduced at least partially along the curved separation line 14. Furthermore, when the separation line 14 is closed as also shown in the illustrated example, further difficulties occur during separation. This is also much more easily possible when using the method described herein than when introducing filamentous damage for pre-separation. According to another alternative or additional embodiment of the method, the modification zone 10 is introduced along the closed separation line 14, and then preferably the inner part defined by this separation line is separated from the workpiece 1. In the illustrated example, the part 4 is the inner part 6. The separation line 14 is circular here, and thus the inner part 6 has the shape of a disc.

[0025] In the illustrated example, each modification zone 10 is still spatially separated. However, in general, it is also possible to overlap each modification zone 10 in order to make the separation into parts 4, 5 even easier.

[0026] In addition to arranging the cuts adjacent to each other in the longitudinal direction, it is also possible to introduce the modification zones 10 with their widths facing each other. In this way, corresponding wider regions are generated where the material is modified. Thereby, the cutting of the inner part can also be easily performed. As another possibility, without penetrating the workpiece, a plurality of adjacent modification zones are introduced into the workpiece a plurality of times to form a recess with one side open. Thereby, for example, in a brittle material, it is also possible to generate a hinge by locally reducing the thickness of the workpiece, for example. Furthermore, it is also possible to change the stress within the material. For example, in the case of tempered glass, if the compressive stress is locally reduced by material modification at least on one side, folds or bends can be generated in the workpiece 1. Furthermore, it is also possible to perform other material modifications that do not require material removal. Here, in particular, a change in the refractive index is applicable. In this way, by material modification, a change in the refractive index can be caused within a certain region, whereby, for example, a dielectric mirror is manufactured in the form of a volume-type holographic diffraction grating, for example.

[0027] FIG. 3 schematically shows a cross-section A of the focusing zone 35 as viewed in the direction along the beam axis 31. In this direction, at the position of the maximum extent of the focusing zone 35, the dimensions of the width b and the thickness w of the cross-section can be read. In this example, the focusing zone 35 has an elliptical cross-section, but it is obvious to those skilled in the art that other cross-sectional shapes are also possible depending on the characteristics of the beam shaping optical system 7. The beam shaping optical system 7 is designed such that the beam shaping optical system 7 has a sufficiently small cross-section in the focusing zone. According to a preferred embodiment, a pulsed laser 3 is used, and it is provided that the laser light 30 is focused into the focusing zone 35 with a light intensity high enough to change the material of the workpiece 1. In that case, in a preferred embodiment, the laser light 30 is focused into the focusing zone 35, and the cross-section A of this focusing zone 35 is small, and E pulse / (A·t pulse ) of the light intensity in the focusing zone 35 is provided to exceed a value of 10 13 W / cm 2 . In the above formula, E pulserepresents the energy of the laser pulse, and t pulse represents the pulse duration. To obtain a high light intensity, it is not only advantageous for the cross-sectional area to be small, but particularly for the pulse duration to be short. Therefore, according to a further embodiment, it is provided that the pulse duration is less than 100 ps. Particularly preferably, the pulse duration ranges from 50 fs to 50 ps.

[0028] There are various possibilities for sizing the focusing zone 35 and positioning it with respect to the substrate. The length L of the focusing zone 35 may be greater than or less than the thickness of the workpiece 1. When the focusing zone 35 is longer than the thickness of the workpiece, the focusing zone 35 can penetrate two opposing surfaces of the workpiece 1. Alternatively, only one surface can be penetrated and the focusing zone 35 can be positioned so that the focusing zone 35 ends within the workpiece 1. When the focusing zone 35 is shorter than the thickness of the workpiece, there is a further possibility that the focusing zone 35 is completely present inside the workpiece 1. The latter case is shown in FIG. 4. Sub-figures (a) and (b) show cross-sections of the workpiece 1 when viewed from different directions. In sub-figure (a), the focusing zone 35 is illustrated in a direction perpendicular to the beam axis and perpendicular to the width b. In sub-figure (b), the focusing zone 35 is shown as viewed in the narrow side, i.e., in the direction of the thickness w. The separation of the workpiece 1 is also planned to be carried out along this direction. As is apparent from these sub-figures, the length L of the focusing zone 35 is smaller than the extent of the workpiece 1 in this direction, and the focusing zone 35 is completely located between its surface regions 100, 101 within the workpiece 1.

[0029] In the example of 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, as shown in sub - figure (a), such that the focusing zone 35 penetrates two opposing surface regions. Similarly, the focusing zone 35 can be positioned such that the focusing zone 35 starts (sub - figure (b)) or ends (sub - figure (c)) within the workpiece with respect to the beam direction, in which case one of the surface regions 100, 101 is penetrated. Generally speaking, without being limited to the specific examples shown, in a development form of the method, the focusing zone can be positioned such that one of the following characteristics is satisfied.

[0030] - The focusing zone 35 is completely inside the workpiece 1. - The focusing zone starts or ends inside the workpiece 1 and protrudes from one of the tool surface or the surface regions 100, 101 of the workpiece 1. - The focusing zone 35 is longer than the thickness of the workpiece 1 and penetrates two opposing surfaces of the workpiece 1, in particular two opposing surface regions 100, 101.

[0031] In particular, a flat slice-shaped focusing zone 35 can be generated by means of astigmatic beam shaping or focal line beam shaping. One-dimensional focal line beam shaping can also be used, in particular, for the generation of the corresponding airy beam, the focusing zone of which is no longer planar, but transverse to the beam direction and advantageously curved around an axis perpendicular thereto. 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), S. 16455-16465, DOI: 10.1364 / OE.19.016455. The beam profile and the optical arrangement for its generation are also fully the subject of the present disclosure. One-dimensional focal line beam shaping will be explained in more detail below with reference to FIGS. 19 and 20. In this context, the term "one-dimensional" means that the focal line is formed substantially along a single spatial direction or that the focusing zone is bent substantially only in one spatial direction.

[0032] For further consideration, the z-coordinate is set as the coordinate in the beam direction. Thus, this direction is the direction of the height L of the focusing zone 35. The coordinates x, y perpendicular thereto correspond to the first and second directions already described above and define a plane transverse to the beam direction. Without loss of generality, in this case, the y-direction is referred to as the strong convergence or strong focusing direction, and the x-direction is referred to as the weak convergence or weak focusing direction. The naming of the directions can, of course, be chosen arbitrarily. Thus, the beam can also be strongly convergent in the x-direction.

[0033] Convergent beam shaping can be achieved by focusing on a refractive surface, in particular a cylindrical lens as in the example of FIG. 1. In this case, the focal lengths f x and f y for, fy <<f x is satisfied. Advantageously here, the focal length in the y direction is 1 / 5 or less of the focal length in the x direction. Regarding the height L of the focusing zone 35, in Gaussian optics

Equation

[0034] Other interference patterns, that is, interference patterns that produce a linear focus in the plane defined by the strong focusing direction and the beam direction, that is, the yz plane, are also possible. Examples include, in particular, accelerating beams such as Airy beams.

[0035] In one development of the method and apparatus 2, without being limited to a specific example, a beam shaping optical system 7 is provided that generates a focusing zone 35 having the intensity profile of a Gaussian beam, a Bessel beam, or an Airy beam on a certain plane, or at least approximating any of these beams.

[0036] FIG. 6 schematically shows an arrangement for generating a focusing zone 35 by a Bessel beam. In the present embodiment, the beam shaping optical system 7 includes an axicon 73, and a laser beam is directed onto the base surface 730 of the axicon 73. A roof prism is not easily suitable in place of the axicon 73. This is because the roof prism divides the laser light 30, which originally has an intensity profile in the form of a Gaussian profile 36, into two partial beams by refraction at two inclined refractive surfaces 731, 732, and these partial beams merge and cross after exiting the roof prism 73. However, this does not lead to localization. A Bessel profile 37 is inscribed in the region of the intersecting beams. As shown, the light intensity in this profile increases significantly in a narrow central region. Thereby, a flat focusing zone of length L is formed. This length L substantially corresponds to the length of the region where the partial beams overlap.

[0037] FIG. 7 shows the beam profile 37 that can be generated by the phase mask shown in FIG. 13. Along the y direction, this non-broadened intensity profile substantially coincides with the intensity profile of an ideal rotationally symmetric Bessel beam, as shown in FIG. 6. Subfigure (b) shows the broadened intensity profile in the x direction perpendicular thereto. Since the Bessel beam has no diffractivity, the intensity profile is substantially constant within the range along the propagation direction z. Therefore, it is equivalent to describe below the intensity profile in the xz plane or the yz plane. In the xz plane, since the laser light 30 is partially weakly focused, 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 full-width at half-maximum of the beam profile in this plane, without being limited to the illustrated example, according to subfigure (b). The Bessel profile 37 formed in the yz plane has a width w = a0λ / (πsin(α)) defined by its first zero point, where λ represents the wavelength of the laser light 30, and α represents the half-value angle of the beam aperture, i.e., 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, which is the first zero point of the numerically determined Bessel function J0. Similar values can be obtained with other prism and lens shapes. Therefore, without being limited to the generation of the focusing zone by the embodiments and the roof prism, it is provided that in general in the developed forms of the method and apparatus, 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. Generally, to generate the focusing zone 35, a non-diffracting beam such as the above-described example of the Bessel beam is preferred. The Airy beam is also a non-diffracting beam. A non-diffracting beam is an optical beam having a constant intensity profile in the lateral direction along propagation. This is in contrast to the normal behavior of light that propagates after being focused into a small spot.

[0038] In practice, due to the finite lateral aperture size of the optical system and the finite energy of the laser beam, the propagation range in which the beam has non-diffracting characteristics is limited.

[0039] Thus, without being limited to a specific embodiment, it is provided that the beam shaping optical system 7 is designed to generate a non-diffracting beam that forms the focusing zone 35.

[0040] Normally, the optical power of the focusing element is too weak, and the volume occupied by the flat or blade-shaped focusing zone 35 is too large, so sufficient strength cannot be obtained for material changes within the workpiece 1. Thus, in one development of the method and apparatus 2, it is provided to reduce the original aberration-free focus. In other words, a magnification M < 1 is used. This reduction can be achieved, according to one embodiment, in a telescopic arrangement, preferably a 4F configuration or a 6F configuration. Thus, without being limited to a specific example, according to one embodiment, it is provided that the beam shaping optical system 7 includes a 4F arrangement or a 6F arrangement with a magnification M < 1. Generally, other reduction optical systems can also be used, that is, independently of the 4F configuration or the 6F configuration, a reduction telescope, i.e., a telescope with a magnification M < 1, can also be used. The magnification is generally determined by the focal lengths of the optical elements included in the beam shaping optical system, especially the lenses. According to one example, the beam shaping optical system comprises a 4F telescope with a lens having a long focal length f1 = 500 mm and a microscope objective lens with a short effective focal length f MO = 10 mm. Thereby, a magnification M = f MO / f1 = 1 / 50 is obtained. Without being limited to this specific example, in a further development of the apparatus 2, it is provided that the apparatus 2 comprises a beam shaping optical system 7 with a telescope having a magnification M < 1 / 10, preferably M < 1 / 25. In this case, due to the reduction, the area of the focusing zone becomes 1 / M in the transverse direction and 1 / M in the longitudinal direction, i.e., the beam direction, which is also very advantageous for achieving a high beam intensity in the focusing zone. This effect is also evident in the following table, in which the reduction in the dimensions of the focusing zone is compared according to the magnification M: 2 -th, and in the longitudinal direction, i.e., the beam direction, it becomes 1 / M 3 -th, which is also very convenient for achieving a high beam intensity in the focusing zone. This effect is also clear in the following table, in which the reduction in the dimensions of the focusing zone is compared according to the magnification M:

Table 1

[0041] In the context of the present disclosure, in a development form, anastigmatic beam shaping in particular means that instead of a single focal region having a substantially round cross-section, two or more flat focusing zones are formed that are oriented perpendicular to each other. This is explained in more detail in FIGS. 8 and 9. Here, FIG. 8 shows an anastigmatic focused laser beam, and FIG. 9 shows the beam cross-sections of the laser beam at four different positions. The positions A, B, C, and D of the beam cross-sections shown in FIG. 9 are marked in FIG. 8. The beam direction of the laser light 30 in FIG. 8 indicates the direction from position A to positions B, C, and D. The optical element for anastigmatic beam shaping is not shown in FIG. 8. At position A, there is a focus of the last lens or lens system, such as a microscope objective lens for example. The transverse dimension of the beam profile at this conjugate point in the first transverse direction is substantially the same. At position B, the focus of the strongly focused beam axis exists in the y direction. At this position, a meridional focal line 35 extending parallel to the x direction is formed. The second transverse conjugate point exists at position C. Similar to the case of position A, the beam profile is substantially rotationally symmetric. If the optical system is weakly focused in the x direction, the beam diameter at this second conjugate point is smaller than that at the first conjugate point, or position A. Finally, at position D, there is a focus of the weakly focused beam axis x, a so-called sagittal focal line, which extends parallel to the y direction. When the laser light 30 is further shaped by a 4F configuration, each focal length is scaled by a factor of M 2 and the coefficient of.

[0042] The distance d between the focus in the strongly focused direction at position B and the second conjugate point at position C cp has the following relationship:

Equation

Number

[0043] For other intervals, even more so AB = f y , f y ≤ d cp and AD = fx also holds.

[0044] Figure 10 is also a boundary example f similar to Figure 8 x→∞ shows an anastigmatic shaped laser beam, where, in addition to the beam, an ideal three-dimensional beam profile is schematically illustrated. In anastigmatic beam shaping, in addition to the flattened focusing zone 35, secondary focal regions 38, 39 may be formed. The focusing zone 35 and the secondary focal regions 38, 39 are illustrated as rectangular parallelepipeds in an idealized state in FIG. 10. As shown, the secondary focal regions 38, 39 may also have a flattened shape. These secondary focal regions 38, 39 typically exist in the regions of the conjugate points A and C. In the case of a flattened shape, as in the example shown, these secondary focal regions 38, 39 are further oriented with respect to the width b and the thickness w perpendicular to the focusing zone 35. Without being limited to the example shown, in one embodiment, it is provided that the laser beam 30 is shaped by the beam shaping optical system 7 such that, in addition to the focusing zone 35, two secondary focal regions 38, 39 of flattened shape are generated and the focusing zone 35 is arranged between the secondary focal regions 38, 39 in the beam direction. In a developed form, in this case, the secondary focal regions 38, 39 are oriented perpendicular to the width and thickness directions of the focusing zone 35 when viewed in the beam direction with respect to their width and thickness directions. These secondary focal regions 38, 39 typically have a lower light intensity than the intermediate focusing zone 35 depending on the beam shaping method, but still this light intensity can reach an order of magnitude comparable to that of the focusing zone 35. These secondary focal regions 38, 39 can also be called parasitic foci because of the prominent transverse alignment conjugate to the focusing zone, and thus their respective damage zones are perpendicular to the desired alignment 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 the focusing zone 35. This focusing zone 35 typically extends around the position B, i.e., around the position of the focus in the strong focusing direction. Therefore, in a preferred embodiment, it is provided that the beam shaping optical system 7 and the workpiece 1 are positioned relative to each other such that the focus in the strong focusing direction of the anastigmatic beam shaping optical system 7 is located on the material of the workpiece 1, or particularly preferably within the material of the workpiece 1.However, in embodiments where the focusing zone 35 ends or begins within the workpiece 1, this point can be located outside the workpiece 1. Such a configuration can exist, for example, in the cases of examples (b) and (c) of FIG. 5.

[0045] For example, in the case of machining a transparent workpiece 1 composed of glass, glass ceramic or crystalline material, the adverse effects of the parasitic focus or the secondary focus regions 38, 39 can be surprisingly well and easily minimized. For this purpose, according to a first embodiment, the beam shaping optical system 7 and the workpiece 1 are arranged and / or adjusted relative to each other such that at least one of the secondary focus regions 38, 39 is at least partially present inside the workpiece 1 in addition to the focusing zone. In this case, the intensity of the laser beam 30 can be adjusted such that the light intensity in the secondary focus regions 38, 39 is below the threshold of the permanent material change of the workpiece 1. However, in this case, advantageously, the intensity is adjusted such that the light intensity in the focusing zone 35 is above this threshold.

[0046] According to a further embodiment, the focusing zone 35 is arranged relative to the workpiece 1 such that the focusing zone 35 is at least partially present inside the workpiece 1 and the secondary focus regions 38, 39 are present outside the workpiece 1. This is particularly feasible 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.

[0047] Figure 11 shows various possible arrangements (I), (II), (III), (IV) and (V) when machining the workpiece 1 with an astigmatic laser beam. In the case of (I), both the focusing zone 35 and the two secondary focal regions 38, 39 are inside the workpiece 1. In this case, as described above, it is advantageous if the laser output is adapted such that the light intensity in the secondary focal regions 38, 39 is below the threshold for permanent material change of the workpiece 1 and the light intensity in the focusing zone 35 is above this threshold. In the cases of (IV) and (V), since the two secondary focal regions 38, 39 are separated from each other, the position of the laser beam can be positioned such that the secondary focal regions 38, 39 are outside the workpiece 1.

[0048] In the cases of (II) and (III) respectively, at least one of the surface regions 100, 101, or at least one surface of the workpiece 1 is inside one of the secondary focal regions 38, 39. These cases are not very advantageous and are not preferred. This is because the damage threshold of the surface to the action of ultrashort pulse laser radiation is typically one order lower than in the case of the volume. Here, the process leading to material change in the workpiece 1 is typically based on multiphoton absorption or avalanche ionization.

[0049] Generally, the length of the focusing zone 35 inside the workpiece 1 is longer than that outside. In particular, the portion of the focusing zone 35 present inside the workpiece is extended by a factor corresponding to the refractive index of the material of the workpiece 1.

[0050] As described above, the beam shaping optical system 7 for generating an astigmatic laser beam can include a roof prism 73 and / or a cylindrical lens 71. Another possibility is to use a diffractive optical element. Such an element can be designed in particular as a phase mask. Using such a mask, for example, a Bessel Gaussian beam can be shaped from the laser light. Using a phase mask also has the advantage that the focusing zone of the Bessel Gaussian beam can be formed at a certain distance from the beam shaping optical system 7. This facilitates the handling and positioning of the workpiece in the apparatus 2. An embodiment of such a beam shaping optical system 7 is shown in FIG. 12. Here, generally, without being limited to the illustrated example, in developed forms of the apparatus and method, an astigmatic laser beam from the laser light is shaped by a beam shaping optical system 7 that forms a phase mask 70, in particular a diffractive optical element 74, and this diffractive optical element 74 is provided to be arranged in front of a telescopic optical system, or alternatively in front of a reduced arrangement form of the optical element, or in front of a combination thereof. In the illustrated example, the diffractive optical element is arranged in front of a combination of a lens 72 and an objective lens 75 positioned in the beam path behind it in the beam direction. In this case, the focal length of the objective lens 75 is shorter than that of the lens 72, and a reduction corresponding to the ratio of the focal length of the objective lens 75 to the focal length of the lens 72 is generated. In the illustrated example, the focal length of the lens 72 is 500 mm and the focal length of the objective lens is 10 mm, and as a result, the reduction is a magnification M = 0.02. The lens 72 can in particular have a spherical or aspherical shape. In the embodiment, furthermore, a laser beam with a diameter of 6.6 mm was used and incident on the phase mask 70.

[0051] Sub - figure (a) of FIG. 13 shows an embodiment of the phase mask 70 in the form of a diffractive optical element 74 in a top view. The lines respectively indicate positions where the radial phase shifts by 2π starting from the center indicated by the cross. Thus, the phase shift is 4π at the line on the second - concentric circle from the inside with respect to the center, for example. Generally, the phase mask 70 according to one development form, which is also realized in the illustrated example, is formed such that the phase of the laser light shifts by an increasing factor in the radial direction from the center of the phase mask, where the period of the phase shift differs by multiples of 2nπ in two directions perpendicular to each other, or the phase shift with respect to the distance to the center along the first radial direction is larger than that in the case of the second radial direction perpendicular thereto. In the illustrated example, according to this definition, the first direction is perpendicular starting from the center, and the second direction is horizontal. FIG. 14 further shows, in addition to this, the phase shifts in the direction x (horizontal direction in FIG. 13) and direction y (vertical direction in FIG. 13) in radians. According to one embodiment, using the diffractive optical element 74, it is possible to generate the phase distribution of a Bessel beamlet with an angle of 7.5° with respect to the beam axis or a total angle of 14.8°. The focal lengths can be assigned in two directions, and these can be calculated from the quadratic fit of the phase distribution or the curve shown in FIG. 14. These correspond to the quadratic phase term k 0· ρ 2 / (2f).

[0052] Hereinafter, a method for shaping a light surface using a Bessel beamlet will be described. A Bessel beamlet, as used herein, represents a single conical phase contribution to the beam shape. Sub - figure (b) of FIG. 13 schematically shows the phase profile of the Bessel beamlet 32 in the x - direction that can be generated by the phase mask 74 according to sub - figure (a) of FIG. 13. The total phase φ total of the phase mask 74 is

Equation

[0053] This is composed of n conical parts, that is, at respective positions ρ i =(xi , y i is obtained by adding a Bessel beamlet 32 localized at (). For a linear cross-sectional profile, for example, the following:

Number

[0054] Although it extends linearly along the beam direction, other cross-sectional profiles can also be selected in the same way, for example, to generate a smooth surface that shows local curvature around an axis parallel to the beam direction. In other words, this beam shaping helps to expand any lateral profile along the beam propagation and generate regions with the same profile at cross-sections at different points along the beam propagation.

[0055] Using weighting coefficients, a favorable intensity distribution can be realized along a line or here along a flat focusing zone 35. These weighting coefficients a i advantageously can include a function of the position ρ i =(x i , y i ). For example, the following:

Number

[0056] The overall scaling coefficient s is used to normalize the sum of the Bessel beamlets 32. The effective opening angle α of the Bessel Gaussian beam is, for example, the following:

Number

[0057] The thickness w’ of the focusing zone 35 is obtained from the first zero point of the Bessel function at 2.405:

Number

[0058] An alternative Bessel beam-based smooth light generation method is described in Alessandro Zannotti; Cornelia Denz; Miguel A. Alonso; Mark R. Dennis: Shaping caustics into propagation-invariant light. In: Nat Commun 11 (1), S. 1-7. DOI: 10.1038 / s41467-020-17439-3. The beam profile and the optical arrangement for its generation are also fully the subject of the present disclosure.

[0059] When using a Gaussian beam with a half-width w0 as the input beam to the phase mask, the length of the focusing zone can be estimated as l = w0 / cos(α). Other intensity profiles of the input beam are possible, for example, a top-hat distribution with uniform intensity across the full width is also possible. In particular, the amplitude distribution and the phase distribution can be adapted so that a uniform intensity distribution as uniform as possible is obtained along the length of the focusing zone.

[0060] The test results of material processing related to the glass workpiece are shown below. FIG. 15 is a diagram showing an optical micrograph on the surface area 100 of the workpiece 1 processed with a laser beam. As can be seen from the photograph, three rows of material modification or damage zones 10 marked with the signs (a), (b), and (c) were introduced into the workpiece 1 made of borosilicate glass. These rows have different positions of the focusing region with respect to the surface. The position of the focusing zone 35 is shown in FIG. 16. As can be seen from FIG. 16, the focusing region 35 is closest to the imaging surface in the case of the damage zone in row (a), and the deepest in row (c). However, in any case, the focusing zone 35 is positioned entirely inside the workpiece 1. In particular, in row (a), an elongated damage zone 10 can be seen in the form of a sheet-like slit 16. In the other damage zones 10, surface damage due to the secondary focal region 38 can also be seen. This surface damage is also sheet-like and perpendicular to the main damage. Therefore, overall, a damage zone 10 having a flat cross shape with two short arms and two long arms is formed. For the processing, the laser was operated in burst mode with two pulses per burst. In this mode, the laser emits the laser beam in the form of a pulse packet, that is, a sequence of pulses continuously emitted at high speed. The pulse width of a single pulse is 1.5 ps, and the total energy of the burst was 36 μJ. The focal length was 10 mm according to the arrangement in FIG. 12. In order to introduce the damage zones 10 at various depths, the interval between the workpiece 1 and the objective lens 75 was decreased by dz = 20 μm for each row. In that case, this interval is n·dz inside the workpiece, where n is the refractive index of the glass.

[0061] By the method and apparatus described herein, in particular preferably, the separation of the workpiece 1 into two or more parts is carried out, for example, to cut off a part with a specific contour from a workpiece in the form of sheet glass. An example related thereto will be described below with reference to FIGS. 17 and 18. FIG. 17 shows an optical micrograph of the surface of the separated workpiece 1, and FIG. 18 shows an edge surface of a part of the workpiece 1 obtained by separation. For this purpose, the workpiece in the example of FIG. 15 was polished to a thickness of 40 μm to eliminate the part of the damage zone 10 caused by the secondary focal regions 38, 39. Thereafter, the workpiece 1 was separated along one of the rows (a), (b), (c) of the damage zone 10. The two parts 4, 5 thus obtained are shown side by side in FIG. 17. Due to the specific shape and arrangement of the damage zone 10, characteristic edge surfaces of the parts 4, 5 are formed, which are shown in FIG. 18. As can be seen, the edge surfaces 18 of the parts 4, 5 have damage zones 10 spaced apart from each other along the edge surfaces, and a fracture surface 18 exists between these damage zones 10. Different from the case of separation by adjacent filamentous damage as known, for example, from WO 2017 / 009379, the damage zone 10 in this specification is much flatter compared to the extension in the direction along the edge surface 18 or in the circumferential direction. This can be attributed to the fact that the focusing zone 35 and thus the corresponding extension of the damage zone 10 are also in a flat sheet-like or slice-like shape. The damage zone 10 is different from the fracture surface 19 in that the damage zone 10 exhibits material modification, for example, material modification by plasma generated by intense laser light within the damage zone. Therefore, the parts 4, 5 manufactured in this way represent a plate-like element 8 having two opposing surface regions 100, 101 and a peripheral surface 18, which is at least partially transparent to laser light, preferably made of glass. The edge surface 18 has the fracture surface 19 and the damage zone 10 alternately, and the damage zone 10 has material modification, in particular, by the formation of plasma in the material of the element. The extension of the damage zone 10 in the direction of the edge surface 18 extending within the element 8 is less than one fifth of the circumferential direction of the edge surface 18. The circumferential direction extends from left to right in the photograph of FIG. 18 and is thus also parallel to the direction extending in the surface regions 100, 101.

[0062] Generally, the advantage here is that the workpiece can be separated into each part of a relatively small number of damaged zones 10. In an extreme case, in this case, the separation can be carried out in one shot, or by introducing a single damaged zone 10.

[0063] In the conventional embodiment, the flat 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 focal plane. The flat, particularly sheet-like shape of the focusing zone 35 is, in this case, advantageously bent about an axis perpendicular to the beam direction. FIG. 20 shows such an example. In subfigure (a), a focal line focused laser beam 30 passing through the workpiece 1 is shown in a side view. Generally, a focal line focused beam is understood to be a beam in which the participating partial beams form a tangent in a plane, or in a flat focusing zone 35. The curved focusing zone 35 produced by the focal line is indicated by a dashed boundary line. Focal line focusing is further characterized in that the phase of the laser beam changes ideally in only one direction. For greater clarity, subfigure (b) shows such a curved focusing zone 35 in a perspective view. For clarity, the width b, height L and thickness w, as well as the beam axis 31 are indicated. The focusing zone 35 has a flat shape despite its curved shape, and it is clear that it is possible to assign a width b and a thickness w to a cross-section perpendicular to the beam axis 31 or the beam direction. Different from the idealized illustration, these parameters can vary along the focusing zone 35. For example, the focusing zone 35 can have a minimum thickness w at at least one position along the beam axis 31. The curved focusing zone 35 is generally particularly advantageous for generating a concave or convex edge surface when separating the workpiece 1.

[0064] FIG. 19 shows a possible beam shaping optical system 7 with a bent focusing zone 35 for generating such a beam. The beam shaping optical system 7 comprises, for example, a one-dimensional phase mask 70 in the shape of a diffractive optical element 74. The one-dimensional phase mask 70 is invariant in the x direction. A cylindrical lens 71 that focuses in the y direction is disposed behind the phase mask 70. A one-dimensional phase mask is understood in particular as a phase mask having a phase distribution that is constant in one spatial direction, for example the x direction, and not constant in the direction perpendicular thereto (y direction), for example having a cubic distribution. Instead of a diffractive optical element, another component such as an LCOS-SLM can also be used as the phase mask. The boundary of the focusing zone 35 is shown as a dashed line. As can be seen, the focusing zone 35 is bent. Without being limited to a specific example, such a shaped focusing zone 35 can be achieved with a beam shaped by an appropriate phase mask 74 with an airy beam that is substantially one-dimensional or compressed in one spatial direction. In this case, the complex amplitude of the airy beam is

Equation

Equation

[0065] Regarding the length L' of the focusing zone obtained therefrom, the following holds:

Equation

[0066] This length is defined as the length within which the intensity exceeds 1 / e of the maximum intensity 2 . Regarding the full width at half maximum w' of the focusing zone, the following holds:

Equation

[0067] Here, regarding the parameters in the above formula, the following: [Number] (Equation) holds, where w0 represents the full-width at half-maximum of the Gaussian input beam on which the three-dimensional phase is imprinted.

[0068] Based on FIGS. 21 to 27, further embodiments of the processing apparatus 2 for the transparent workpiece 1, particularly further embodiments of the beam shaping optical system 7 of such an apparatus 2, are illustrated. Also in the embodiment according to FIG. 21, a diffractive optical element 74 acting as a phase mask and arranged in front of the reduced arrangement form of the optical element in the beam path of the laser beam 30 is provided. This arrangement form is formed by two lenses 72, 76 and further a cylindrical lens 71 in the xz plane. In this case, the workpiece-side lenses L2, 76 have a shorter focal length than the lenses L1, 72 located behind the diffractive optical element 74. In this example, the lenses L1, 72 have a focal length of 500 mm, the lenses L1, 76 have a focal length of 100 mm, and the cylindrical lens 71 has a focal length of 5 mm in the y direction. In order to increase the beam focusing degree in the x direction, as in the example, the original beam width of the laser beam in front of the beam shaping optical system 7 can also be reduced. In this example, the beam width is reduced from 6 mm to 3.3 mm.

[0069] The embodiment according to FIG. 22 is generally based on two cylindrical lenses 71, 77 arranged side by side with different focal lengths and intersecting focusing directions, and the strong focusing cylindrical lens 77 is arranged on the workpiece side. Advantageously, the focal lengths of the cylindrical lenses 71, 77 differ by at least a factor of 10. In the illustrated example, the magnification is further 1000 mm / 5 mm = 200. Sub - figure (a) shows the beam - shaping optical system 7 and the workpiece 1 to be processed arranged in front of it. Sub - figure (b) shows a cross - section in the xy - plane perpendicular to the beam direction of the focal region 35 achievable by this arrangement. In the simplest case, the focal region 35 has a flattened elliptical cross - section as shown when the output beam has a circular beam profile. The foci of the lenses can be located at the same point, as in FIG. 22. Thereby, a pure elliptical beam without spherical aberration is generated. However, this is generally not the case.

[0070] In the embodiment according to FIG. 23, it is possible to adjust the width of the focusing zone 35. Further, the optical system can generate an airy beam by means of an appropriate phase mask. The beam - shaping optical system 7, according to a first aspect, is characterized in that two nested telescopic optical systems are provided regardless of whether an airy beam or another beam profile such as a Gaussian - Bessel beam is generated. Here, the first telescopic optical system comprises two cylindrical lenses 71, 77, and the second telescopic optical system comprises two lenses 72, 76. In particular, the focusing directions of the cylindrical lenses 71, 77 intersect as in the embodiment of FIG. 22.

[0071] According to one development form that is also realized in the illustrated example, a telescopic optical system having two lenses 72, 76 is disposed between the cylindrical lenses 71, 77. In order to achieve reduction, advantageously f2 < f1 holds. According to another development form, a phase mask 74 is provided, particularly for generating an airy beam in the plane within the workpiece 1, thereby obtaining a flat focusing zone. The distance between the conjugate points of the inner telescope composed of the lenses 72, 76 functions as a delay section 79 for generating the airy beam.

[0072] FIG. 24 shows an even simpler configuration. This embodiment is a combination of, for example, a phase mask 70 forming a diffractive optical element 74 and a 2F arrangement form. In the simplest case, the 2F arrangement form can be formed by a single lens, advantageously a lens of a microscope objective lens 75, as shown.

[0073] FIG. 25 shows a modification of the arrangement form of FIG. 24. In the modification according to FIG. 25, a larger interval is selected between the diffractive optical element 74 and the lens or microscope objective lens 75. This arrangement form can be referred to as a quasi-4F configuration. Regarding this, in both arrangement forms, the beam shaping optical system on the light output side is characterized by including, as the last element, a microscope objective lens 75 and a phase mask in the form of a diffractive optical element 74 located in front of this microscope objective lens 75. According to one development form, no further beam shaping element is provided in the beam shaping optical system 7.

[0074] Under certain circumstances, the output of the laser may be insufficient to achieve material modification in the focusing zone 35 or, in particular, sufficient light intensity for damage. One possibility for achieving a higher intensity is described below. The beam shaping optical system including the beam shaping optical system 7 can be designed such that a greater reduction is achieved, i.e., the focusing zone 35 is further reduced. This can be achieved by generating a beam having an extended beam profile from the laser beam 30 before focusing. Thereby, upon focusing, the extent of the focusing zone is such that the beam profile further decreases in the extending direction before focusing by the beam shaping optical system 7. This effect will be described in more detail using the schematic example of FIG. 26. Here, according to one embodiment, the beam shaping optical system 7 comprises a beam shaping optical system, by which, when the laser beam 30 is incident on the focusing optical system as part of the beam shaping optical system 7, it has an extended beam profile, where the extending direction is transverse, preferably perpendicular, to the width direction of the focusing zone 35 and accordingly in the thickness direction of the focusing zone 35, it is provided that the laser beam 30 is deformed. In this way, the thickness of the focusing zone 35 is further compressed and the intensity within the focusing zone 35 increases. In the illustrated example, an anamorphic optical system 80 is provided as the beam shaping element, which generates an output beam having a beam profile extended in the y direction when incident on the focusing optical system 81. The beam profile can be elliptical as shown, so that the major semi-axis line of the profile in the example is located in the y direction. Here, the focusing optical system 81 is generally oriented such that the width direction of the focusing zone 35 is perpendicular thereto, i.e., in the x direction in the example. In particular, by using an elliptical input beam having a sufficiently short minor semi-axis line, it is possible to achieve an expansion of the width of the focusing zone even when focusing with a rotationally symmetric focusing lens such as a microscope objective.

[0075] Generally, for material modification, material separation, or slit generation in the focusing zone, it is convenient to use a high-power laser with an output of at least 100 W, preferably at least 150 W. Examples of appropriate parameters for the laser and beam shaping optics are shown in the following table. In the first table, laser parameters suitable for the arrangement according to FIG. 22 are listed.

[0076] [Table 2]

[0077] The parameters in the following table are suitable for the embodiment according to FIG. 12.

[0078] [Table 3]

[0079] The following table shows the laser parameters for Bessel-Gaussian beam shaping for three examples: [Table 4]

[0080] In the following table, the laser parameters suitable for the shaping of an airy beam using the bent focusing zone 35 are described. The arrangement according to FIG. 12 is also suitable for these parameters: [Table 5] [Explanation of Signs]

[0081] 1 Workpiece 2 Processing device for workpiece 1 3 Laser 4, 5 Part of 1 6 Inner part 7 Beam shaping optics 8 Plate-like element 9 Positioning unit 10 Damage zone 12 Control unit 14 Separation line 16 Slit 18 Edge surface 19 Fracture surface 30 Laser light, laser beam 31 Beam axis 32 Beamlet 35 Focusing zone 36 Gaussian profile 37 Bessel profile 38,39 Secondary focal region 70 Phase mask 71,77 Cylindrical lens 72,76 Lens 73 Elliptical axicon 74 Diffractive optical element 75 Microscope objective lens 79 Delay interval 80 Anamorphic optical system 81 Focusing optical system 83 Output beam of 80 84 Extended beam profile 100,101 Surface area of 1 730 Base surface of 73 731 Cone vertex of 73 732 Strong focusing direction 733 Weak focusing direction

Claims

1. A method for processing a workpiece (1), comprising: irradiating the workpiece (1) with laser light (30) from a laser (3), wherein since the material of the workpiece (1) is at least partially transparent to the laser light (30), the laser light (30) enters the workpiece (1); focusing the laser light (30) into a focusing zone (35) within the workpiece (1) by a beam shaping optical system (7); the focusing zone (35) has a flat shape having a length in the beam direction, and a width and a thickness perpendicular thereto, respectively, in a cross section perpendicular to the beam axis, and the thickness of the focusing zone (35) is at most one fifth of the width and the length of the focusing zone at at least one position along the beam axis; introducing a modification zone (10) within the focusing zone (35) based on the intensity of the laser light (30) within the material of the workpiece (1), the modification zone (10) having a flat shape corresponding to the focusing zone (35).

2. With respect to the workpiece (1), performing at least one of: separating the workpiece (1) into two parts (4, 5) in the modification zone (10); causing a change in refractive index within a damage zone in the material of the workpiece (1) by the laser light. The method according to claim 1, characterized in that.

3. By the beam shaping optical system, in the workpiece (1), the width b is in the range of 1 μm to 10 mm, preferably 10 μm to 50 μm; the thickness w is in the range of 0.2 μm to 50 μm, preferably 1 μm ± 0.5 μm; the thickness w is in the range of 1.39 times to 10 times the wavelength of the laser light 30; the height L is in the range of 2 μm to 20 mm, preferably 1 mm to 5 mm; the projected area when viewed along the direction of the beam axis (31) of the laser light (3) is at most one quarter of the projected area of the focusing zone (35) when viewed along the thickness direction of the focusing zone (35). The method according to claim 2, characterized in that a focusing zone (35) having at least one of the dimensions, preferably all of the dimensions, is generated.

4. The method according to any one of claims 1 to 3, characterized in that a workpiece (1) made of an inorganic material, preferably glass, glass ceramic or crystalline material, is processed.

5. The method according to any one of claims 1 to 4, characterized in that the focusing zone (35) is generated by astigmatic beam shaping or focal line beam shaping.

6. The method according to any one of claims 1 to 5, characterized in that a focusing zone (35) having a bent shape is generated, and the focusing zone (35) is bent about an axis perpendicular to the beam direction.

7. The method according to claim 6, characterized in that the laser beam (30) is shaped by the beam shaping optical system (7) such that, in addition to the focusing zone (35), two flattened secondary focal regions (38, 39) are generated, and the focusing zone (35) is arranged between the secondary focal regions (38, 39) in the beam direction.

8. The beam shaping optical system (7) and the workpiece (1) are arranged and adjusted such that at least one of the secondary focal regions (38, 39) is at least partially present inside the workpiece (1), in addition to the focusing zone (35). At this time, the intensity of the laser beam (30) is adjusted such that the light intensity of the secondary focal regions (38, 39) is below the threshold for permanent material change of the workpiece (1), and the light intensity of the focusing zone (35) is above the threshold. The focusing zone (35) is arranged with respect to the workpiece (1) such that the focusing zone (35) is at least partially present inside the workpiece (1), and the secondary focal regions (38, 39) are present outside the workpiece (1). The method according to claim 7, characterized by at least one of the above features.

9. The method according to any one of claims 1 to 8, characterized in that a plurality of modification zones (10) in the form of damage zones in particular are arranged adjacent to each other along a separation line (14) provided with the modification zones (10), and the workpiece (1) is separated at the separation line (14) to obtain two parts (4, 5).

10. The modification zone (10) is oriented such that the separation line (14) extends along the width direction of the modification zone (10). The modification zone (10) is introduced along a separation line (14) that is at least partially curved. The modification zone (10) is introduced along a closed separation line (14), and the inner part defined by the separation line is separated from the workpiece (1). The method according to claim 9, characterized by at least one of the features thereof.

11. Focus the laser beam (30) on the focusing zone (35), the cross-section A of the focusing zone (35) is small, and E ｐｕｌｓｅ / (A · t ｐｕｌｓｅ ) the light intensity in the focusing zone (35) given by is 10 １３ W / cm ２ exceeds the value of, where E ｐｕｌｓｅ represents the energy of the laser pulse, and t represents the pulse duration, and the method according to any one of claims 1 to 10, characterized in that.

12. Positioning the focusing zone (35) such that the focusing zone (35) is completely inside the workpiece (1); the focusing zone (35) starts or ends inside the workpiece (1) and protrudes from one of the surface regions (100, 101) of the workpiece (1); the focusing zone (35) is longer than the thickness of the workpiece (1) and penetrates two opposing surface regions (100, 101) of the workpiece (1). The method according to any one of claims 1 to 11, characterized in that it is positioned such that one of the features is satisfied.

13. A processing apparatus for a workpiece (1), the processing apparatus comprising: a laser (3) for emitting a laser beam (30), the laser (3) being adjusted to emit a laser beam (30) of a certain wavelength, the workpiece (1) being at least partially transparent to the laser beam of said wavelength so that the laser beam (30) can enter the workpiece (1), and the processing apparatus further comprising: a beam shaping optical system (7) for focusing the laser beam (30) into a focusing zone (35) inside the workpiece (1), where the beam shaping optical system (7) is such that the focusing zone (35) generated by the beam shaping optical system (7) has a flat shape having a length, a width, and a thickness in the beam direction, where the thickness of the focusing zone (35) is designed to be 1 / 5 or less of the width and the length of the focusing zone, and the laser (3) and the beam shaping optical system (7) are designed such that the laser beam (30) having a strength sufficient to introduce a modification zone (10) into the material of the workpiece (1) is present inside the focusing zone (35), the modification zone (10) having a flat shape corresponding to the shape of the focusing zone (35), and in particular thereby, the modification zone (10) is larger in the direction of the beam axis (31) and in one direction perpendicular thereto than when along a second direction perpendicular to the beam axis (31).

14. The beam shaping optical system (7) is of the anastigmatic type or the focal line type. The beam shaping optical system (7) comprises a phase mask (70). The beam shaping optical system (7) comprises at least one cylindrical lens (71). The beam shaping optical system (7) has at least one of the features of comprising a 4F arrangement or a 6F arrangement with a magnification M < 1. The apparatus according to claim 13, characterized in that the beam shaping optical system (7) has at least one of the above features.

15. The apparatus according to claim 13 or 14, characterized in that the beam shaping optical system (7) generates a focusing zone (35) having an intensity profile of a Gaussian beam, a Bessel beam or an Airy beam on a certain plane.

16. The beam shaping optical system (7) is an optical element for generating an astigmatic laser beam. A refractive optical element, particularly a free-form optical system A cylindrical lens (71) A diffractive optical element (74) A phase mask (70), particularly an LCOS spatial light modulator (SLM) The apparatus according to any one of claims 13 to 15, characterized in that it comprises at least one of the above.

17. The beam shaping optical system (7) preferably comprises a phase mask (70) in the form of a diffractive optical element (74), and the phase shift of the laser light with respect to the distance to the center of the diffractive optical element (74) along a first radial direction is larger than that in the case of a second radial direction perpendicular thereto. The beam shaping optical system (7) preferably comprises a phase mask (70) in the form of a diffractive optical element (74), and the phase mask (70) is arranged in front of the reduced arrangement of the optical element. The beam shaping optical system (7) comprises a beam shaping optical system, and when the laser light (30) is incident on a focusing optical system (81) as part of the beam shaping optical system (7) by the beam shaping optical system, the laser beam (30) is deformed so as to have an elongated beam profile, where the elongation direction is transverse, preferably perpendicular, to the width direction of the focusing zone 35. The apparatus according to claim 16, characterized in that it has at least one of the above features.

18. A plate-like element (8) composed of an inorganic material that is at least partially transparent to laser light, having two opposing surface regions (100, 101) and a peripheral surface (18), wherein the peripheral surface (18) alternately has a fracture surface (19) and a damage zone (10), the damage zone (10) has a material modification, particularly by the formation of a plasma in the material of the element, and the extent of the damage zone (10) in the direction of the peripheral surface extending within the element 8 is not more than one fifth (1 / 5) of the circumferential direction (5) of the peripheral surface (18).

Images