DE102021108509A1 - Device and method for laser machining a workpiece - Google Patents

Abstract

The present invention relates to a device for laser processing a workpiece (104), which has a material (102) that is transparent for laser processing, comprising a first beam shaping device (106) with a beam splitting element (112) for splitting a beam that is coupled into the first beam shaping device (106). first input beam (108) into a plurality of partial beams (114), and focusing optics (116) assigned to the first beam shaping device (106) for imaging partial beams (114) coupled out of the first beam shaping device (106) into at least one focal zone (122), wherein the splitting of the first input beam (108) by means of the beam splitting element (112) takes place by impressing phases on the first input beam (108), the partial beams (114) for forming the at least one focal zone (122) into different partial regions (120) of the at least one focal zone (122) are focused for laser processing of the workpiece ks (104) the at least one focal zone (122) by means of the focusing optics (116) at at least one angle (a) to an outside (144; 146) of the workpiece (104) is introduced into the material (102), and by impinging on the material (102) by means of the at least one focal zone (122), material modifications (156) are produced in the material (102) which involve a change in one Index of refraction of the material (102) are associated.

Description

The invention relates to a device for laser processing of a workpiece, which has a material that is transparent for laser processing.

The invention further relates to a method for laser processing a workpiece which has a material that is transparent for the laser processing.

From the U.S. 2020/0147729 A1 there is known a method of forming a beveled edge portion on a glass substrate using a laser beam, wherein a shape of the beveled edge portion is adjusted by adjusting an axial energy distribution of the laser beam.

The invention is based on the object of providing a device mentioned at the outset and a method mentioned at the outset which can be used flexibly and in a variety of ways and by means of which, in particular, laser processing of the workpiece along different processing geometries can be carried out in a technically simple manner.

In the device mentioned at the outset, this object is achieved according to the invention in that the device comprises a first beam-shaping device with a beam-splitting element for dividing a first input beam coupled into the first beam-shaping device into a plurality of partial beams, and focusing optics assigned to the first beam-shaping device for imaging from the partial beams decoupled from the first beam-shaping device into at least one focal zone, with the splitting of the first input beam taking place by means of the beam splitting element by impressing phases on the first input beam, the partial beams being focused into different sub-areas of the at least one focal zone to form the at least one focal zone, for laser processing of the workpiece the at least a focus zone is introduced into the material by means of the focusing optics at at least one angle to an outside of the workpiece u nd wherein material modifications which are associated with a change in a refractive index of the material are produced in the material by impinging on the material by means of the at least one focal zone.

The at least one focus zone can be formed with different geometries in a technically simple manner by splitting the first input beam by means of the beam splitting element based on phase imprinting and subsequent focusing of the formed partial beams. As a result, the at least one focal zone can be formed in particular with different sections, each of which has a different geometry and/or a different setting angle. In this way, laser processing of the workpiece with different processing geometries can be achieved in a technically simple manner.

In the solution according to the invention, in particular the at least one focus zone can be introduced into the material at the angle of incidence without it being necessary to position an optical system with respect to the workpiece.

The fact that the material modifications are associated with a change in the refractive index of the material means in particular that the material modifications are accompanied by a change in the refractive index of the material and/or that the refractive index in the material changes when the material modifications are formed.

The beam splitting element is designed in particular as a diffractive beam splitting element and/or as a 3D beam splitting element. The beam splitting element is preferably used to impress a phase on a beam cross section of the first input beam.

In particular, the first input beam is split by means of the beam splitting element by pure phase manipulation of the phase of the first input beam. In particular, the phase imprinting on the first input beam, which is carried out by means of the beam splitting element, can be set and/or defined in a variable manner.

In particular, it can be provided that the at least one focus zone has a plurality of focus distributions and/or is formed from a plurality of focus distributions. For example, the focus distributions are arranged in the different partial areas of the focus zone.

Respective focus distributions of the focus zone are arranged in particular at a distance from one another in the focus zone. However, it is possible for the respective focus distributions to spatially overlap at least in sections.

In particular, the at least one focal zone extends in one plane. The focus distributions from which the at least one focus zone is formed are preferably arranged in one plane. In particular, this plane is perpendicular to a Oriented feed direction, in which the at least one focus zone for laser processing of the workpiece is moved relative to the workpiece.

In particular, each focus distribution of the at least one focus zone is assigned a lens component and/or grating component of the phase distribution imposed by the beam splitting element. In particular, the imposed phase distribution comprises a plurality of superimposed lens components and/or grating components, with each focus distribution of the at least one focus zone being assigned a lens component and/or grating component. As a result, different focus distributions of the focus zone can be arranged with a spatial offset in a plane oriented perpendicularly to a feed direction in which the focus zone for laser processing of the workpiece is moved relative to the workpiece.

For example, the first beam-shaping device is designed as a far-field beam-shaping element or includes one or more far-field beam-shaping elements. The at least one focal zone is formed, for example, by focusing partial beams decoupled from the first beam-shaping device by means of the focusing optics in the respective partial areas of the focal zone.

For example, the focusing optics are designed as a microscope objective or lens element.

In one embodiment, it can be provided that the first beam-shaping device can be rotated or is rotated about an axis parallel to a main propagation direction of the first input beam. As a result, the at least one focus zone can be rotated, for example, about an axis of rotation oriented perpendicularly to a feed direction in which the at least one focus zone is moved relative to the workpiece for laser processing of the workpiece.

Provision can be made for the focusing optics to be integrated into the first beam-shaping device and/or for the focusing optics to be part of the first beam-shaping device and/or for a functionality of the focusing optics to be integrated into the first beam-shaping device.

In particular, the material of the workpiece is made from a material that is transparent to a laser beam from which the at least one focal zone is formed.

A transparent material is to be understood in particular as a material through which at least 70% and in particular at least 80% and in particular at least 90% of a laser energy of a laser beam from which the at least one focal zone is formed is transmitted.

In particular, the first input beam is a first input beam coupled into the first beam shaping device and/or into the beam splitting element.

In particular, it can be provided that the material modifications produced in the material by means of the at least one focal zone are type I and/or type II modifications. As a result, material modifications are produced in the material of the workpiece during laser processing, which are accompanied by a change in the refractive index of the material. In particular, a separation of the material can be carried out on these material modifications.

In one embodiment, the device comprises a second beam-shaping device for beam-shaping the first input beam coupled into the first beam-shaping device, with the second beam-shaping device providing the first input beam with a focus distribution with a defined geometric shape and/or with phase impingement on a second input beam incident on the second beam-shaping device is assigned to a defined intensity profile, so that focus distributions based on this geometric shape and/or based on this intensity profile are formed by focusing the partial beams coupled out of the first beam-shaping device using the focusing optics in different partial areas of the focal zone. As a result, a geometry of focus distributions from which the at least one focus zone is formed can be adapted. This enables a flexible and versatile use of the device.

In particular, the second beam-shaping device is arranged in front of the first beam-shaping device with respect to a main propagation direction of laser beams guided through the device.

The second input beam is in particular an input beam of the second beam-shaping device. For example, the second input beam is a laser beam provided by a laser source of the device and has, in particular, a Gaussian beam profile.

In particular, the first input beam is a beam coupled out of the second beam-shaping device and/or a beam provided by the second beam-shaping device.

In particular, the second beam-shaping device is used to modify and/or adapt a focus distribution associated with the second input beam coupled into the second beam-shaping device. In particular, a focus distribution modified and/or adapted by means of the second beam-shaping device is assigned to the first input beam provided by means of the second beam-shaping device.

In one embodiment, it can be provided that the second beam-shaping device can be rotated or is rotated about an axis parallel to a main propagation direction of the second input beam. As a result, the at least one focus zone can be rotated, for example, about an axis of rotation oriented perpendicularly to a feed direction in which the at least one focus zone is moved relative to the workpiece for laser processing of the workpiece.

In particular, it can be provided that the phase imprint on the second input beam is such that the focus distribution has an elongated shape with respect to an assigned main extension direction, and/or that the phase imprint on the second input beam is such that the focus distribution is a quasi-non-diffractive and/or or Bessel-like intensity profile. As a result, the at least one focus zone can be built up, for example, from a plurality of focus distributions with an elongated shape. In this way, in particular, correspondingly elongated and/or linear material modifications can be formed, as a result of which, for example, an improved introduction of etching liquid for material separation is made possible.

The second beam-shaping device is or includes, in particular, a beam-shaping element for carrying out the phase imprinting, e.g. a diffractive optical element and/or an axicon element.

In particular, the main extension direction of the focus distribution with an elongated shape is oriented transversely and in particular perpendicularly to a feed direction in which the at least one focus zone for laser processing of the workpiece is moved relative to the workpiece.

It can be favorable if the phase imprint on the second input beam is such that the focus distribution has an intensity profile with respect to an associated main extension direction, which, starting from a maximum intensity at an intensity maximum of the intensity profile, is 1/e ² times the maximum intensity by approximately a factor 3 falls faster than is the case with a Gaussian intensity profile, and/or when the phase imprint on the second input beam is such that the focus distribution has an abrupt self-focusing beam shape and/or intensity profile. The rapid drop in intensity of these focus distributions results in more precise material processing with reduced damage to the material to be processed. As a result, the material can be separated in particular with a particularly flat and/or smooth edge.

For example, the intensity drop from the maximum intensity to 1/e ² times the maximum intensity is faster by at least a factor of 2.5 and/or faster by a factor of at most 3.5 than is the case with a Gaussian intensity profile.

In particular, starting from the intensity maximum in the main direction of extent, the intensity profile has an intensity drop edge, on which the intensity drop is formed. In particular, the intensity of the intensity profile in the main extension direction following the intensity drop edge is below the value of 1/e ² times the maximum intensity.

Preferably, the intensity drop edge faces a workpiece segment during laser processing of the workpiece. As a result, a particularly smooth cutting edge can be achieved when cutting the material.

The intensity maximum mentioned is in particular a main maximum and/or global maximum of the intensity profile. In particular, the intensity profile has one or more secondary maxima, which adjoin the intensity maximum counter to the main direction of extent. In particular, a respective maximum intensity of the secondary maxima decreases with increasing distance from the main maximum.

In particular, the secondary maxima lie in a residual workpiece segment and/or waste segment during laser processing of the workpiece. As a result, cracks and/or channels, for example, can be formed in the remaining workpiece segment and/or waste segment, which favor an etching attack for material separation.

The main extension direction of these focus distributions is in particular oriented parallel or approximately parallel to a main propagation direction of the second input beam.

It can be provided that an intermediate image of the focus distribution is formed by means of the second beam shaping device, in particular special the intermediate image of the focus distribution is arranged in front of the first beam-shaping device with respect to a main propagation direction of the second input beam.

The second beam-shaping device is designed in particular as a near-field beam-shaping device, i.e. the focus distribution is imaged as an intermediate image in particular by means of the second beam-shaping device.

The intermediate image formed by means of the second beam-shaping device is in particular an image of the focus distribution which is associated with the first input beam coupled into the first beam-shaping device.

In one embodiment, the device comprises far-field optics assigned to the second beam-shaping device, with the far-field optics being used to far-field focus an output beam coupled out of the second beam-shaping device into a focal plane of the far-field optics, and with the first beam-shaping device in particular being arranged in a region of this focal plane.

In particular, an output beam coupled out of the far-field optics then corresponds to the first input beam to be coupled into the first beam-shaping device.

The area of the focal plane is to be understood in particular as an area extending around the focal plane, which in particular has a maximum distance of 10% of a focal length of the far-field optics from the focal plane.

In particular, it can be provided that far-field focusing of the intermediate image of the focus distribution formed by the second beam-shaping device takes place in the focal plane by means of the far-field optics.

In particular, the far-field optics perform a Fourier transformation of the intermediate image generated by the second beam-shaping device and/or of the focus distribution generated by the second beam-shaping device.

Provision can be made for the far-field optics to be integrated into the second beam-shaping device and/or for the far-field optics to be part of the second beam-shaping device and/or for a functionality of the far-field optics to be integrated into the second beam-shaping device.

In particular, a transverse intensity distribution of the first input beam in the focal plane has a ring structure and/or a ring segment structure.

It can be provided that the far-field optics and the focusing optics form a telescope device and/or that the far-field optics and the focusing optics have a common focal plane, with the first beam-shaping device in particular being arranged in a region of this common focal plane.

In particular, a focal length of the far-field optics is greater than a focal length of the focusing optics.

In particular, it can be provided that the first input beam is assigned a focus distribution with a defined geometric shape and/or with a defined intensity profile, with the partial beams coupled out of the first beam-shaping device also being assigned this geometric shape and/or this intensity profile and/or focus distributions based on this geometric shape and/or based on this intensity profile being formed in different partial areas of the at least one focus zone by focusing the partial beams coupled out of the first beam shaping device by means of the focusing optics. In this way, the at least one focus zone can be constructed from focus distributions that are spaced apart from and/or adjacent to one another and have a defined geometry. This also results, for example, in a formation of the at least one focus zone by arranging focus distributions in a row as approximately identical copies due to beam splitting by means of the beam splitting element.

A defined geometric shape and/or a defined intensity profile is assigned to the first input beam, for example, by means of a laser source that provides the first input beam. As an alternative to this, the assignment takes place by means of the second beam-shaping device described above.

In one embodiment, the first input beam incident on the beam splitting element and/or on the first beam shaping device has a Gaussian intensity profile, e.g., when it originates directly from a laser source. As a result, for example, the at least one focus zone is then built up and/or formed from a plurality of adjacent “focus points” with a Gaussian shape and/or Gaussian intensity profile.

It can be favorable if the first beam-shaping device is a beam-shaping element modification of the focus distribution assigned to the first input beam, wherein the beam-shaping element is used to modify and/or align the geometric shape and/or the intensity profile of the focus distribution imaged in the at least one focus zone in a direction relative to a feed direction, in which the at least one focus zone is used for laser processing of the workpiece is moved relative to the workpiece, in a vertically oriented cross-sectional plane, and/or wherein the beam-shaping element is used to modify and/or align the geometric shape and/or the intensity profile of the focus distribution imaged in the at least one focus zone in a direction relative to a feed direction in which the at least one focus zone for laser processing of the workpiece is moved relative to the workpiece, takes place in a cross-sectional plane oriented parallel.

In particular, the cross-sectional plane oriented parallel to the feed direction is oriented perpendicular to a main propagation direction of rays from which the focus distribution is formed.

The beam-shaping element of the first beam-shaping device is used in particular to modify the input beam coupled into the first beam-shaping device within and/or by means of the first beam-shaping device.

In particular, the beam-shaping element is or includes a diffractive or refractive beam-shaping element, and/or the beam-shaping element is or includes a diffractive field mapper. In particular, wavefront aberrations defined by the beam-shaping element can be impressed on an input beam coupled into the beam-shaping element.

The beam-shaping element is set up in particular in such a way that the partial beams coupled out of the first beam-shaping device are assigned the focus distribution modified by means of the beam-shaping element, so that focus distributions with this modified geometric shape and /or be formed with this modified intensity profile.

In particular, this modified shape and/or this modified intensity distribution is based on an original shape and/or on an original intensity profile which is assigned to the first input beam. A modified shape and/or modified intensity distribution is to be understood in particular as a modification based on the original shape and/or on the original intensity profile.

It can be favorable if an alignment of a main extension direction of the geometric shape and/or the intensity profile of the focus distribution can be set or is adjusted by means of the beam-shaping element in a cross-sectional plane oriented perpendicularly to the feed direction, and in particular if the alignment is adjusted in such a way that the main extension direction is parallel or is oriented approximately parallel to a corresponding local extension direction of the focal zone. This makes it possible, for example, to achieve a formation of material modifications in the material of the workpiece that is oriented approximately parallel to the local extension direction of the focal zone. This enables in particular an optimized separation of the material.

Provision can also be made for the alignment of the main direction of extent of the geometric shape and/or the intensity profile of the focus distribution to take place in such a way that the main direction of extent is oriented transversely to the corresponding local direction of extent. For example, the main extension direction encloses a smallest angle of at least 1° and/or at most 90° with the local extension direction. As a result, the focus distribution lies, for example, at least in sections in a residual workpiece segment and/or waste segment that occurs during the laser processing of the workpiece. As a result, material modifications and/or channels are formed, for example in the remaining workpiece segment and/or waste segment, which promote an etching attack for material separation.

In principle, it is also possible for the beam-shaping element to modify the focus distribution in the cross-sectional plane perpendicular to the feed direction in such a way that it has a main extension direction in this cross-sectional plane perpendicular to the feed direction.

It can be provided that the focus distribution in the cross-sectional plane oriented perpendicularly to the feed direction is modified by means of the beam-shaping element in such a way that it has a curved longitudinal central axis.

It can be favorable if the intensity profile of the focus distribution is modified by means of the beam-shaping element in a cross-sectional plane oriented parallel to the feed direction in such a way that the intensity profile has at least one preferred direction, wherein in particular the at least one preferred direction is oriented parallel or transverse or perpendicular to the feed direction. In this way, it is possible in particular to control and/or optimize the formation of material modifications in the material of the workpiece during laser processing. This enables, for example, an improved introduction of etching liquid for material separation.

In particular, the at least one preferred direction and the feed direction lie in a common plane.

For example, the intensity profile of the focus distribution in the plane parallel to the feed direction is formed, for example, elliptically or rectangularly or squarely by means of the beam-shaping element.

The preferred direction of a focus distribution designed as an ellipse is to be understood as meaning, for example, a major semi-axis of the ellipse.

For example, the preferred direction of the focus distribution designed as an ellipse is oriented parallel or approximately parallel to the feed direction.

A focus distribution designed as a square or rectangle has, for example, two preferred directions which are each oriented parallel to a direction connecting two opposite points of the square. For example, one of the preferred directions is then oriented parallel to the feed direction and the other perpendicular to it.

It can be advantageous if an alignment of the at least one preferred direction of the focus distribution in the cross-sectional plane oriented parallel to the feed direction can be set or is set by means of the beam-shaping element of the first beam-shaping device. In this way, it is possible in particular to control and/or optimize the formation of material modifications in the material of the workpiece during laser processing.

In particular, it can be provided that the at least one angle of incidence of the at least one focus zone is at least 1° and/or at most 90°. The at least one angle of attack is preferably at least 10°.

The setting angle is to be understood in particular as a smallest angle between one of the local extension directions associated with the at least one focus zone and an outside of the workpiece. For example, the at least one focus zone is coupled and/or introduced through this outside into the material of the workpiece.

Provision can be made for the at least one focal zone to have different sections with different local directions of extension and/or angles of incidence.

It can be favorable if the first beam-shaping device has a polarization beam-splitting element, which is set up in such a way that the partial beams coupled out of the first beam-shaping device each have one of at least two different polarization states, with the focusing optics being used to direct partial beams with different polarization states into adjacent partial regions of the at least be focused on a focal zone. As a result, the at least one focal zone can be formed by lining up focal points and/or focal distributions with different states of polarization.

Focus points and/or focus distributions with different states of polarization are formed in particular from mutually incoherent partial beams. As a result, the focus points and/or focus distributions can be arranged and/or lined up with a particularly small distance from one another.

In particular, the polarization beam splitting element is used to split a beam coupled into the polarization beam splitting element into a plurality of polarized partial beams, each of which has one of at least two different polarization states.

For example, the polarization beam splitting element comprises a birefringent wedge element and/or a birefringent lens element. A directional offset and/or an angular offset of partial beams with different states of polarization can thus be generated, for example, before the focusing of the partial beams by means of the focusing optics. As a result, the partial beams with different states of polarization can be imaged in spatially different sub-areas of the at least one focal zone.

In particular, different states of polarization are to be understood as meaning different states of linear polarization.

For example, the polarization beam splitting element includes a quartz crystal for polarization beam splitting.

According to the invention, in the method mentioned at the outset it is provided that a first input beam incident on the beam splitting element is divided into a plurality of partial beams by means of a beam splitting element of a first beam shaping device, and the partial beams coupled out of the first beam shaping device are divided into at least one focal zone by means of focusing optics assigned to the first beam shaping device be focused, whereby the splitting of the first input beam takes place by means of the beam splitting element by phase impingement on the first input beam, the partial beams are focused into different partial areas of the at least one focus zone to form the at least one focus zone, for laser processing of the workpiece the at least one focus zone using the focusing optics at least one angle of attack to an outside of the workpiece is introduced into the material and by acting on the M aterials are generated in the material by means of the at least one focal zone material modifications, which are associated with a change in a refractive index of the material.

The method according to the invention has in particular one or more features and/or advantages of the device according to the invention.

In particular, the method according to the invention can be carried out using the device according to the invention. In particular, the device according to the invention carries out the method according to the invention.

In particular, it can be provided that for the laser processing of the workpiece, the at least one focus zone is moved in a feed direction relative to the material of the workpiece. In particular, a relative speed between the material and the at least one focus zone, which is oriented in the feed direction, is set or can be set.

In particular, it can be provided that material modifications are formed in the material of the workpiece along a machining line and/or machining surface by moving the at least one focal zone relative to the workpiece. In particular, this allows the workpiece to be separated along the machining line and/or machining surface.

It can be advantageous if the material of the workpiece can be separated or is separated along the processing line and/or processing surface by applying thermal stress and/or mechanical stress and/or by etching using at least one wet-chemical solution. For example, the etching takes place in an ultrasonically assisted etching bath.

• Es kann vorgesehen sein, dass sich die mindestens eine Fokuszone zwischen zwei unterschiedlichen und/oder gegenüberliegenden Außenseiten des Werkstücks erstreckt und insbesondere durchgängig erstreckt. Beispielsweise sind diese Außenseiten parallel zueinander orientiert oder quer zueinander orientiert. Es lässt sich dadurch das Werkstück beispielsweise in zwei voneinander verschiedene Segmente trennen oder es lässt sich zur Kantenbearbeitung ein Segment vom Werkstück abtrennen. Dadurch lässt sich der Kantenbereich beispielsweise abschrägen oder anfasen.

In particular, the device according to the invention and/or the method according to the invention have one or more of the following features:

• It can be provided that the at least one focal zone extends between two different and/or opposite outer sides of the workpiece and in particular extends continuously. For example, these outer sides are oriented parallel to one another or oriented transversely to one another. In this way, the workpiece can be separated into two different segments, for example, or a segment can be separated from the workpiece for edge processing. This allows the edge area to be beveled or chamfered, for example.

In particular, it can be provided that the at least one focus zone has focus distributions which are arranged in such a way that material modifications are formed in a residual workpiece segment and/or waste segment to be separated from the workpiece. These material modifications form, for example, channels for improved introduction of etching liquid for material separation.

For example, the focus distributions of the at least one focus zone are arranged in such a way that they are arranged at least in sections in a residual workpiece segment and/or waste segment formed during the laser processing of the workpiece or at least partially protrude into a residual workpiece segment formed in the laser processing of the workpiece. In this way, for example, material modifications and/or channels can be formed in the remaining workpiece segment and/or offcut segment, which promote a supply of etching liquid to material modifications formed during laser processing. This enables improved material separation along a machining surface on which the material modifications are arranged.

For the same reason, it can be favorable if the focus distributions of the at least one focus zone are arranged in such a way that a main maximum and/or a global maximum of the respective focus distribution faces a workpiece segment created during the laser processing of the workpiece and/or faces away from a residual workpiece segment.

A good piece segment is, for example, one that is formed when the workpiece is separated To understand end useful segment (in contrast to a remaining workpiece segment and / or waste segment).

In particular, focus distributions of the focus zone from which the focus zone is formed have intensity fluctuations of at most 20%.

In particular, the device includes a workpiece holder for the workpiece, which preferably has a non-reflective and/or highly scattering surface.

In particular, it can be provided that the device has a laser source for providing a laser beam, from which the at least one focus zone can be formed or is formed. In particular, a pulsed laser beam and/or an ultra-short pulsed laser beam is provided by the laser source.

In particular, the at least one focal zone is formed from an ultracourse pulsed laser beam or is provided by means of an ultracourse pulsed laser beam. This ultra-short-pulse laser beam includes, in particular, ultra-short laser pulses.

For example, a wavelength of the laser beam from which the at least one focus zone can be formed or is formed is at least 300 nm and/or at most 1500 nm. For example, the wavelength is 515 nm or 1030 nm.

In particular, the laser beam from which the at least one focal zone can be formed or is formed has an average power of at least 1 W to 1 kW. For example, the laser beam includes pulses with a pulse energy of at least 10 μJ and/or at most 50 mJ. It can be provided that the laser beam comprises individual pulses or bursts, the bursts having 2 to 20 sub-pulses and in particular a time interval of approximately 20 ns.

Provision can be made for the at least one focal zone to be rotatable about an axis of rotation oriented perpendicularly to a feed direction in which the at least one focal zone is moved relative to the workpiece for laser processing of the workpiece. As a result, the workpiece can be machined, for example, along a curved machining line and/or machining surface.

In particular, the at least one focal zone forms a spatially coherent interaction area for laser processing of the workpiece, in which case localized material modifications can be formed in the interaction area, in particular by subjecting the material of the workpiece to this interaction area, by means of which a separation of the material is made possible in particular. In particular, cracking and/or a change in a refractive index of the material occurs between adjacent material modifications.

The material modifications introduced into transparent materials by ultrashort laser pulses are divided into three different classes, see K. Itoh et al. "Ultrafast Processes for Bulk Modification of Transparent Materials" MRS Bulletin, vol. 31 p.620 (2006): Type I is an isotropic refractive index change; Type II is a birefringent refractive index change; and Type III is a so-called void. The material modification produced depends on the laser parameters of the laser beam from which the focal zone is formed, such as the pulse duration, the wavelength, the pulse energy and the repetition frequency of the laser beam, and on the material properties, such as the electronic structure and the thermal expansion coefficient, as well as on the numerical aperture (NA) of focusing.

The type I isotropic refractive index changes are attributed to localized melting caused by the laser pulses and rapid resolidification of the transparent material. For example, with fused silica, the density and refractive index of the material is higher when the fused silica is rapidly cooled from a higher temperature. So if the material in the focus volume melts and then cools down quickly, the quartz glass has a higher refractive index in the areas of material modification than in the unmodified areas.

The type II birefringent refractive index changes can arise, for example, as a result of interference between the ultrashort laser pulse and the electric field of the plasma generated by the laser pulses. This interference leads to periodic modulations in the electron plasma density, which leads to a birefringent property, i.e. direction-dependent refractive indices, of the transparent material when it solidifies. A type II modification is also accompanied, for example, by the formation of so-called nanogratings.

The voids (cavities) of the type III modifications can be generated with a high laser pulse energy, for example. The formation of the voids is attributed to an explosive expansion of highly excited, vaporized material from the focus volume into the surrounding material. This process is also called microexplode designated. Because this expansion occurs within the bulk of the material, the microblast leaves behind a less dense or hollow core (the void), or submicron or atomic-scale microscopic defect, surrounded by a densified shell of material. Due to the compression at the impact front of the microexplosion, stresses arise in the transparent material, which can lead to spontaneous cracking or can promote cracking.

In particular, the formation of voids can also be associated with type I and type II modifications. For example, Type I and Type II modifications can arise in the less stressed areas around the introduced laser pulses. Therefore, if a type III modification is introduced, then in any case a less dense or hollow core or a defect is present. For example, in a type III modification of sapphire, the microexplosion does not create a cavity, but rather an area of lower density. Due to the material stresses that occur in a type III modification, such a modification is often accompanied by cracking or at least promotes it. The formation of type I and type II modifications cannot be completely prevented or avoided when introducing type III modifications. Finding "pure" Type III modifications is therefore not likely.

At high repetition rates of the laser beam, the material cannot cool down completely between the pulses, so that cumulative effects of the introduced heat from pulse to pulse can influence the material modification. For example, the repetition frequency of the laser beam can be higher than the reciprocal of the thermal diffusion time of the material, so that heat accumulation can take place in the focal zone by successive absorption of laser energy until the melting temperature of the material is reached. In addition, a larger area than the focus zone can be melted due to the thermal transport of the thermal energy into the areas surrounding the focus zone. After the introduction of ultrashort laser pulses, the heated material cools rapidly, so that the density and other structural properties of the high-temperature state in the material are effectively frozen.

The at least one focal zone comprises in particular a plurality of mutually spaced and/or adjacent focal distributions, wherein the focal zone can have interruptions and/or zero points between mutually adjacent focal distributions, at which in particular there is no or negligible interaction with the material. In particular, these interruptions in the focal zone have a spatial extent of at most 10% of a maximum extent and/or a maximum length of the focal zone. In particular, these interruptions have a spatial extension of at most 100 μm and in particular at most 50 μm. If there are larger interruptions in intensity distributions, this means different focal zones.

For example, the at least one focal zone has an overall length of between 50 μm and 5000 μm.

To determine spatial dimensions of the at least one focal zone, such as a respective length and/or a respective diameter, the focal zone is viewed in a modified intensity distribution that only has intensity values that are above a specific intensity threshold. The intensity threshold is selected here, for example, in such a way that values lying below this intensity threshold have such a low intensity that they are no longer relevant for an interaction with the material for the formation of material modifications. For example, the intensity threshold is 50% of a global intensity maximum of the actual intensity distribution. Under a length of the respective focus zone or under a diameter of the respective focus zone, a maximum extension length and/or a length of maximum extent of the respective focus zone along a longitudinal center axis of the focus zone or in a plane oriented perpendicularly to the longitudinal center axis, based on the modified intensity distribution to understand.

In particular, the statements “at least approximately” or “approximately” generally mean a deviation of no more than 10%. Unless otherwise stated, the statements “at least approximately” or “approximately” mean in particular that an actual value and/or distance and/or angle deviates by no more than 10% from an ideal value and/or distance and/or angle , and/or that an actual geometric shape deviates from an ideal geometric shape by no more than 10%.

• 1 eine schematische Darstellung eines Ausführungsbeispiels einer Vorrichtung zur Laserbearbeitung eines Werkstücks;
• 2 eine schematische Darstellung eines weiteren Ausführungsbeispiels einer Vorrichtung zur Laserbearbeitung eines Werkstücks;
• 3a schematische Querschnittsdarstellungen eines Ausführungsbeispiels einer Fokusverteilung einer Fokuszone zur Laserbearbeitung des Werkstücks;
• 3b schematische Querschnittsdarstellungen eines weiteren Ausführungsbeispiels einer Fokusverteilung einer Fokuszone zur Laserbearbeitung des Werkstücks;
• 3c schematische Querschnittsdarstellungen eines weiteren Ausführungsbeispiels einer Fokusverteilung einer Fokuszone zur Laserbearbeitung des Werkstücks;
• 4a eine schematische Querschnittsdarstellung eines Abschnitts eines Beispiels einer Fokuszone, welche in ein Material des Werkstücks eingebracht ist;
• 4b eine schematische Querschnittsdarstellung eines Abschnitts eines weiteren Beispiels einer Fokuszone, welche in ein Material des Werkstücks eingebracht ist;
• 5 eine schematische Querschnittsdarstellung einer Fokuszone, welche das Werkstück von einer ersten Außenseite zu einer zweiten Außenseite vollständig durchdringt;
• 6 eine schematische Querschnittsdarstellung von mittels einer Fokuszone erzeugten Materialmodifikationen im Material des Werkstücks, wobei diese Materialmodifikationen mit einer Rissbildung des Materials einhergehen;
• 7 eine schematische Querschnittsdarstellung von mittels einer Fokuszone erzeugten Materialmodifikationen im Material des Werkstücks, wobei diese Materialmodifikationen mittels Wärmeakkumulation erzeugt sind und/oder mit einer Brechungsindexänderung des Materials einhergehen;
• 8 eine Querschnittsdarstellung einer simulierten Intensitätsverteilung eines Beispiels einer Fokuszone, welche eine Mehrzahl zueinander beabstandeter langgezogener Fokusverteilungen aufweist;
• 9a eine Querschnittsdarstellung einer simulierten Intensitätsverteilung eines Beispiels eines abrupt-selbstfokussierenden Laserstrahls;
• 9b eine Intensitätsverteilung des abrupt-selbstfokussierenden Laserstrahls gemäß 9a entlang einer Haupterstreckungsrichtung dieses Laserstrahls;
• 10 eine Querschnittsdarstellung einer simulierten Intensitätsverteilung einer Fokuszone, welche eine Mehrzahl zueinander beabstandeter Fokusverteilungen aufweist, die als abrupt-selbstfokussierende Strahlen ausgebildet sind;
• 11 eine schematische Darstellung einer den abrupt-selbstfokussierenden Strahlen zugeordneten Phasenverteilung;
• 12a,c,e Querschnittsdarstellungen von simulierten Intensitätsverteilungen von drei unterschiedlichen Ausführungsbeispielen der Fokuszone,
• 12b,d,f schematische Darstellungen von Phasenverteilungen, welchen den Querschnittsdarstellungen gemäß 12a bzw. 12c bzw. 12e zugeordnet sind;
• 13a eine schematische perspektivische Darstellung von Materialmodifikationen, welche in dem Material des Werkstücks entlang einer Bearbeitungslinie und/oder Bearbeitungsfläche erzeugt werden; und
• 13b eine schematische Darstellung von zwei Segmenten des Werkstücks, welche durch Trennung des Werkstücks an der Bearbeitungslinie und/oder Bearbeitungsfläche gebildet werden.

The following description of preferred embodiments serves to explain the invention in more detail in conjunction with the drawings. Show it:

• 1 a schematic representation of an embodiment of a device for laser processing of a workpiece;
• 2 a schematic representation of a further exemplary embodiment of a device for laser machining a workpiece;
• 3a schematic cross-sectional representations of an exemplary embodiment of a focus distribution of a focus zone for laser processing of the workpiece;
• 3b schematic cross-sectional representations of a further exemplary embodiment of a focus distribution of a focus zone for laser processing of the workpiece;
• 3c schematic cross-sectional representations of a further exemplary embodiment of a focus distribution of a focus zone for laser processing of the workpiece;
• 4a a schematic cross-sectional representation of a portion of an example of a focal zone, which is introduced into a material of the workpiece;
• 4b a schematic cross-sectional representation of a section of a further example of a focal zone, which is introduced into a material of the workpiece;
• 5 a schematic cross-sectional representation of a focal zone, which completely penetrates the workpiece from a first outer side to a second outer side;
• 6 a schematic cross-sectional representation of material modifications produced by means of a focus zone in the material of the workpiece, these material modifications being associated with cracking of the material;
• 7 a schematic cross-sectional representation of material modifications in the material of the workpiece produced by means of a focal zone, these material modifications being produced by means of heat accumulation and/or being accompanied by a change in the refractive index of the material;
• 8th a cross-sectional representation of a simulated intensity distribution of an example of a focal zone, which has a plurality of mutually spaced elongated focal distributions;
• 9a Fig. 12 is a cross-sectional representation of a simulated intensity distribution of an example of an abrupt self-focusing laser beam;
• 9b an intensity distribution of the abrupt self-focusing laser beam according to FIG 9a along a main extension direction of this laser beam;
• 10 a cross-sectional representation of a simulated intensity distribution of a focus zone, which has a plurality of mutually spaced focus distributions, which are formed as abrupt self-focusing beams;
• 11 a schematic representation of a phase distribution associated with the abrupt self-focusing beams;
• 12a,c ,e Cross-sectional representations of simulated intensity distributions of three different embodiments of the focal zone,
• 12b,d ,f schematic representations of phase distributions, which correspond to the cross-sectional representations 12a or. 12c or. 12e assigned;
• 13a a schematic perspective representation of material modifications which are produced in the material of the workpiece along a processing line and/or processing surface; and
• 13b a schematic representation of two segments of the workpiece, which are formed by separating the workpiece at the processing line and/or processing surface.

Identical or functionally equivalent elements are denoted by the same reference symbols in all exemplary embodiments.

An embodiment of a device for laser machining a workpiece is in 1 shown and labeled 100 there. The device 100 can be used to produce localized material modifications in a material 102 of the workpiece 104, such as defects in the submicrometer range or at the atomic level, which result in a material weakening. At these material modifications, the workpiece can be separated into different segments, for example, in a subsequent step, or a segment can be separated from the workpiece 104, for example. In particular, the device 100 can be used to introduce material modifications into the material 102 at an angle of attack, so that an edge region of the workpiece 104 can be chamfered or beveled by separating a corresponding segment from the workpiece 104 .

The device 100 comprises a first beam shaping device 106 into which a first input beam 108 is coupled. This first input beam 108 is a laser beam, for example, which is provided, for example, by means of a laser source 110 and/or is coupled out of a laser source 110 . Below the first input beam 108 is in particular a bundle of rays understand, which includes a plurality of particular parallel beams.

The laser beam provided by the laser source 110 is in particular a pulsed laser beam and/or an ultra-short pulse laser beam.

The first beam shaping device 106 comprises a beam splitting element 112, by means of which the first input beam 108 is divided into a plurality of partial beams 114 and/or partial beam bundles. At the in 1 In the example shown, two different partial beams 114a and 114b are indicated.

The first beam-shaping device 106 and/or the beam-splitting element 112 are each embodied as a far-field beam-shaping element, for example.

In order to focus the partial beams 114 coupled out of the first beam-shaping device 106, the device 100 comprises focusing optics 116, into which the partial beams 114 are coupled. For example, different partial beams 114 impinge on the focusing optics 116 with a spatial offset and/or angular offset.

For example, the focusing optics 116 are designed as a microscope objective or lens element.

The partial beams 114 are focused by means of the focusing optics 116 in different partial areas 120 of a focus zone 122, which is introduced into the material 102 of the workpiece 104 for laser processing.

In 1 For example, two different partial areas 120a and 120b are indicated, into which the partial beams 114 are focused to form the focal zone 122. The partial area 120a is assigned to the partial beam 114a, for example, and the partial area 120b is assigned to the partial beam 114b.

A specific focus distribution is assigned to the first input beam 108 coupled into the first beam-shaping device 106 . This focus distribution is to be understood as meaning a geometric shape and/or an intensity profile which would be formed by focusing the first input beam 108 before it is coupled into the first beam-shaping device 106 .

For example, the first input beam 108, which is provided, for example, by means of the laser source 108, has a Gaussian beam profile. In this case, a focus distribution with a Gaussian shape and/or a Gaussian intensity profile would be formed by focusing the first input beam 108 before it is coupled into the first beam-shaping device 106 .

In particular, the form of the focus distribution means a characteristic spatial form and/or spatial extent of the focus distribution.

The first input beam 108 coupled into the first beam shaping device 106 is split by means of the beam splitting element 112 in such a way that the partial beams 114 are also assigned this focus distribution. By focusing these partial beams 114 using the focusing optics 116, focus distributions 124 are formed in the different partial areas 120 of the focus zone 122, with these focus distributions 124 being based on the focus distribution assigned to the first input beam 108.

The focus zone 122 is thereby built up and/or formed by arranging different focus distributions 124 in a row. In the present case, different focus distributions 124 are to be understood as meaning focus distributions 124 at different spatial positions of the focus zone 122, these different focus distributions 124 having at least approximately the same geometric shape and/or the same geometric intensity profile.

Different focus distributions 124 are arranged at a distance from one another in the focus zone 122 . In principle, it is possible for different focus distributions 124 that are adjacent to one another to spatially overlap.

In particular, focus distributions are formed as identical copies by beam splitting by means of the beam splitting element 112 , which are imaged in different partial regions 120 of the focus zone 122 .

For example, the beam splitting element 112 is designed as a 3D beam splitting element. With regard to the technical realization and properties of the beam splitting element 112, reference is made to the scientific publication "Structured light for ultrafast laser micro- and nanoprocessing" by D. Flamm et al., arXiv:2012.10119v1 [physics.optics], December 18, 2020. Reference is made expressly and in full to this.

In particular, a distance d1 and/or a spatial offset between adjacent focus distributions 124 can be set by means of the beam splitting element 112 .

For example, a distance dx and/or a spatial offset in an x-direction and a distance dz and/or a spatial offset in a z-direction oriented perpendicularly to the x-direction can be set between mutually adjacent focus distributions 124 .

For this purpose, partial beams 114 that differ from one another are formed, for example by means of the beam splitting element 112, in such a way that they impinge on the focusing optics 116 with a specific spatial offset and/or with a specific convergence and/or divergence. The mutually different partial beams 114 are then imaged by means of the focusing optics 116 with a resulting spatial offset in the x-direction and/or z-direction.

A defined transverse phase distribution is impressed on a transverse beam cross section of the first input beam 108 in order to carry out the beam splitting by means of the beam splitting element 112 . Examples of transverse phase distributions of beams coupled out of the beam splitting element 112 and associated focal zones 112 are shown, for example, in FIGS 12a, b or. 12c, i.e or. 12e, f shown.

To generate the spatial offset in the x-direction and/or in the z-direction, the phase is impressed by means of the beam splitting element 112, for example in such a way that the assigned phase distribution for each focus distribution 124 has a specific optical grating component and/or optical lens component. Due to the optical grating portion, there is an angular deflection of partial beams 114 in front of the focusing optics 116, which results in a spatial offset in the x-direction after focusing has taken place. Due to the optical lens component, partial beams 116 with different convergence and/or divergence impinge on the focusing optics 116, which results in a spatial offset in the z-direction after focusing has taken place.

Provision can be made for the first beam-shaping device 106 to have a polarization beam-splitting element 126 . The polarization beam splitting element 126 is used to carry out a polarization beam splitting of the first input beam 108 and/or a beam coupled out of the beam splitting element 112 into beams which each have one of at least two different polarization states.

As a result of polarization beam splitting by means of the polarization beam splitting element 126, the partial beams 114 coupled out of the first beam shaping device 106 each have one of at least two different polarization states. These partial beams 114 with different states of polarization are focused into the different partial regions 120 of the focal zone 122 by means of the focusing optics 116 .

For example, the polarization beam splitting element 126 is arranged in front of or behind the beam splitting element 116 with respect to a main propagation direction 128 of the first input beam 108 coupled into the first beam shaping device 106 .

In the example shown, the main propagation direction 128 is oriented parallel or approximately parallel to the z-direction. In particular, the x-direction and the z-direction are each oriented perpendicular to a y-direction. In the example shown, this y-direction is oriented parallel or approximately parallel to a feed direction 129 in which the focus distributions 124 for laser processing of the workpiece 104 are moved relative to the workpiece 104 .

With regard to the functioning and design of the polarization beam splitting element 126, reference is made to the unpublished German patent applications with file numbers 10 2020 207 715.0 (Filing date: June 22, 2020) and with file number 10 2019 217 577.5 (Filing date: November 14, 2019) from the same applicant. Reference is made expressly and in full to this.

In particular, the polarization states of the partial beams 114 are linear polarization states, with two different polarization states being provided, for example, and/or with the respective polarization directions of partial beams that are different from one another being aligned at an angle of 90° to one another.

In particular, the partial beams 114 are polarized in such a way that an electric field is oriented in a plane perpendicular to their direction of propagation (transversally electric).

For polarization beam splitting, the polarization beam splitting element 126 has, for example, a birefringent lens element and/or a birefringent wedge element. The birefringent lens element and/or the birefringent wedge element are made of, for example, a quartz crystal or comprise a quartz crystal.

The birefringent lens element is used, for example, to form partial beams 114 with different polarization states in such a way that, by focusing using the focusing optics 116, they can be offset with a spatial offset in the z-Rich tion and/or x-direction are mapped. As a result, for example, focus distributions 124 formed from partial beams 114 with different polarization states can be arranged in the focus zone 122 with a spatial offset in the z-direction and/or x-direction.

By means of the polarization beam splitting element 126, for example, a series of focus distributions 124 can be implemented in the focus zone 122, wherein mutually adjacent focus distributions 124 are each formed from partial beams 114 with different polarization states.

Furthermore, it can be provided that the first beam-shaping device 106 has a beam-shaping element 130, by means of which the focus distribution assigned to the first input beam 108 can be modified after it has been coupled into the first beam-shaping device 106.

With regard to the technical realization and properties of the beam shaping element 130, reference is made to the scientific publication "Structured light for ultrafast laser micro- and nanoprocessing" by D. Flamm et al., arXiv:2012.10119v1 [physics.optics], December 18, 2020, and on the book Laser Beam Shaping: Theory and Techniques, Fred M. Dickey, ed., CRC press, 2014. This is expressly and fully referred to.

The beam-shaping element 130 is designed, for example, as a diffractive or refractive phase element for impressing defined wavefront aberrations on a beam coupled into the beam-shaping element 130 . For example, the beam-shaping element 130 is designed as a diffractive field mapper.

For example, the beam-shaping element 130 is arranged in front of or behind the beam-splitting element 112 with respect to the main propagation direction 128 of the first input beam 108 .

At the in 1 In the example shown, the beam-shaping element 130 is arranged between the beam-splitting element 112 and the polarization beam-splitting element 126 . For example, the input beam 108 is first processed with the beam splitting element 112 and then with the beam shaping element 130 and/or with the polarization beam splitting element 126.

A geometric shape and/or an intensity profile of the focus distributions 124 imaged in the focus zone 122 can be modified by means of the beam-shaping element 130 .

A modification of the focus distributions 124 of the focus zone 122 by means of the beam-shaping element 130 can take place in a cross-sectional plane parallel to the feed direction 129, with this cross-sectional plane being oriented in particular perpendicular to the main propagation direction 128 and/or perpendicular to the z-direction ( 3a , 3b and 3c ).

Furthermore, the focus distributions 124 of the focus zone 122 can be modified by means of the beam-shaping element 130 in a cross-sectional plane perpendicular to the feed direction 129 ( 4a and 4b) . In the example shown, this cross-sectional plane is oriented parallel to the x-direction and parallel to the main propagation direction 128 and/or z-direction.

With regard to the cross-sectional plane oriented parallel to the feed direction 129, the focus distribution 124 is modified, for example, in such a way that the shape and/or the intensity profile of the focus distribution 124 has a preferred direction 132 in this cross-sectional plane. This preferred direction 132 is to be understood in particular as a direction in which an extension length of the focus distribution 124 is maximized locally or globally. For example, the preferred direction 132 is to be understood as meaning a main extension direction of the focus distribution 124 .

At the in 3b In the example shown, the focus distribution 124 in the plane parallel to the feed direction 129 is elliptical and/or embodied as an ellipse. In this case, the preferred direction 132 is oriented parallel to a major semi-axis of this ellipse.

In principle, it is also possible for the focus distribution 124 to have a plurality of preferred directions 132 . At the in 3c In the example shown, the focus distribution 124 in the plane parallel to the feed direction 129 is rectangular and/or rectangular and in particular square. In this case, the focus distribution 124 has a first preferred direction 132'a, which is oriented, for example, parallel to the x-direction, and a second preferred direction 132'b, which is oriented, for example, transverse and in particular perpendicular to the x-direction, ie in the one shown Example parallel to the y-direction.

For example, the first preferred direction 132'a and the second preferred direction 132'b are each parallel to connecting lines between opposite corners of the rectangle.

It can be provided that the focus distribution assigned to the first input beam 108 124 has an elongate and/or elongated shape in the cross-sectional plane oriented perpendicularly to the feed direction 129 ( 4a and 4b) . This is realized, for example, in that the first input beam 108, which is coupled into the first beam-shaping device 106, is assigned a quasi-non-diffracting and/or Bessel-like beam profile.

Focus distribution 124 has, for example, a main direction of extent 134, along which focus distribution 124 has, in particular, a greatest length and/or in particular a greatest extent in the cross-sectional plane oriented perpendicularly to feed direction 129 (see also 3c ).

For example, the direction of main extent 134 is oriented parallel to a connecting line between a starting point and an end point of the focus distribution 124 with respect to a direction of greatest extent of the focus distribution 124 .

In particular, it can be provided that an alignment 136 and/or orientation of the focus distribution 124 in the cross-sectional plane oriented perpendicularly to the feed direction 129 can be adjusted by means of the beam-shaping element 130, with the alignment 136 of the respective main extension direction 134 of the focus distribution 124 being adjustable, for example.

At the in the 4a and 4b In the examples shown, the orientation 136 of the respective focus distribution 124 in the xz plane can be adjusted.

The respective alignment 136 of the focus distributions 124 is adjusted by means of the beam-shaping element 130, for example, in such a way that the alignment 136 is oriented parallel or approximately parallel to a local direction of extension 138 of the focus zone 122 associated with the respective focus distribution 124 .

The local extension direction 138 of the focus zone 122 is to be understood, for example, as a local distance direction from adjacent focus distributions 124, for example from two or three adjacent focus distributions 124. The focus distributions 124 of the focus zone 122 can be arranged, for example, in different sections of the focus zone 122 with different local directions of extension 138 .

In the cross-sectional plane oriented perpendicularly to the feed direction 129, the focus distribution 124 can be provided with a curved shape, for example, by adaptation using the beam-shaping element 130 ( 4b) . For example, the focus distribution 124 can thereby be generated as a curved Bessel-like beam and/or as an accelerated Bessel-like beam.

With regard to the formation and properties of quasi-non-diffractive and/or Bessel-like beams with curved shapes, reference is made to the scientific publication "Bessel-like optical beams with arbitrary trajectories" by I. Chremmos et al., Optics Letters, Vol. 37, No . 23, December 1, 2012.

For example, the focus distribution 124 has a longitudinal central axis 140 along which it extends. This longitudinal center axis 140 is, for example, formed in a straight line ( 4a) . In the case of a focus distribution with a curved shape, the longitudinal central axis 140 has a curved shape or a shape that is curved in sections ( 4b) .

The focus distributions 124 assigned to the focus zone 122 are arranged by means of the first beam-shaping device 106 along a longitudinal axis 142 of the focus zone 122, which is formed, for example, in a straight line ( 4a and 4b) .

The longitudinal axis 142 is not necessarily formed in a straight line and/or continuously. For example, the longitudinal axis 142 can be curved at least in sections. It is also possible for the longitudinal axis 142 to have changes of direction and, in particular, discontinuous changes of direction.

At the in 5 In the example shown, the focal zone 122 in the material 102 of the workpiece 104 extends from a first outer side 144 of the workpiece 104 to a second outer side 146 of the workpiece 104, the second outer side 146 being spaced apart from the first outer side 144 with respect to a depth direction 148 of the workpiece 104 . In particular, the focus zone 122 runs through the workpiece 104 completely and/or without interruption in the depth direction 144 .

The first outer side 144 and the second outer side 146 of the workpiece 104 are oriented parallel or approximately parallel to one another, for example.

For the laser processing of the workpiece 104, the focal zone 122 is introduced and/or coupled into the material 102 of the workpiece 104, for example through the first outer side 144 or through the second outer side 146.

The focus zone 122 has a first section 150 emanating from the first outer side 144 , which is adjoined by a second section 152 of the focus zone 122 in the depth direction 148 . Furthermore, the focal zone 122 has a third section 154 following this second section 152 in the depth direction 148 .

In the example shown, the longitudinal axis 142 of the focal zone 122 is rectilinear in each of the sections 150, 152 and 154, with the longitudinal axis 142 being at the transitions from the first section 150 to the second section 152 and from the second section 152 to the third section 154 in particular has a change of direction in each case.

Each of these sections 150, 152 and 154 is assigned a different local extension direction 138 with which the focus distributions 122 are arranged.

Furthermore, each of the sections 150, 152 and 154 is assigned a specific angle of attack α. This angle of incidence α is to be understood as a smallest angle between the local extension direction 138 of the corresponding section 150, 152, 154 and the first outer side 144 and/or second outer side 146.

For example, the first section 150 and the third section 154 have an angle of attack α of 45° and the second section 152 has an angle of attack α of 90°.

The material 102 of the workpiece 104 is made of transparent material for a wavelength of laser beams from which the focus zone 122 and/or the focus distributions 124 are formed.

The focal zone 122 is introduced into the material 102 for the laser processing of the material 102 . As a result of this exposure of the material 102 to the focal zone 122, localized material modifications 156 are formed on the focal distributions 124 ( 6 ), which are arranged at a distance from one another, for example, along the longitudinal axis 142 of the focal zone 122 .

By suitably selecting processing parameters, such as laser parameters and/or feed rate, the material modifications 156 can be produced as type III modifications, which lead to the spontaneous formation of cracks 157 in the material 102 ( 6 ). The cracks 157 formed during the laser processing of the material 102 extend in particular between adjacent material modifications 156.

The feed rate is a speed of a relative movement between the focus zone 122 and the material 102 in the feed direction 129 .

As an alternative to this, it is possible, by suitably selecting the processing parameters, to produce the material modifications 156 as type I and/or type II modifications, which are associated with heat accumulation in the material 102 and/or with a change in a refractive index of the material 102 .

The formation of the material modifications 156 as Type I and/or Type II modifications is associated with heat accumulation in the material 102 of the workpiece 104 . In particular, the material modifications 156 produced are so close to one another in this case that this accumulation of heat occurs when the material 102 is exposed to the focal zone 122 (indicated in 7 ).

In one embodiment, the device 100 comprises a second beam-shaping device 158 which is arranged in front of this first beam-shaping device 106 with respect to the main propagation direction 128 of the first input beam 108 coupled into the first beam-shaping device 106 . The focus distribution assigned to the first input beam 108 can be adapted by means of the second beam-shaping device 158 before it is coupled into the first beam-shaping device 106 .

In this embodiment, a second input beam 160 is coupled into the second beam-shaping device 158, which is provided in particular by means of the laser source 110 and/or is a laser beam coupled out of the laser source 100.

Analogously to the first input beam 108, the second input beam 160 is therefore to be understood in particular as a bundle of rays which comprises a plurality of rays, in particular running parallel.

In the example shown, the first input beam 128 coupled into the first beam-shaping device 106 is a beam coupled out of the second beam-shaping device 158 and/or a beam bundle coupled out of the second beam-shaping device 158 .

The second beam-shaping device 158 applies a phase to the second input beam 160, as a result of which the focus distribution associated with the first input beam 108 coupled into the first beam-shaping device 106 is defined. As a result, the geometric shape and/or the intensity profile of the focus distribution assigned to the first input beam 108 can be defined by means of the second beam shaping device 158 .

The second input beam 160 coupled into the second beam-shaping device 158 has, for example, a Gaussian beam profile, ie the second input beam 160 has a Gaussian shape and/or a Gaussian intensity profile.

In one embodiment, the second beam-shaping device 158 is set up and configured such that the second beam-shaping device 158 is used to assign a quasi-non-diffracting and/or Bessel-like beam profile to the first input beam 108 coupled into the first beam-shaping device 106 .

As a result, the first input beam 108 can be imaged in particular in a focus distribution with a quasi-non-diffracting and/or Bessel-like beam profile. In this embodiment, the focus distribution 124 imaged into the focal zone 122 has an elongated shape and/or an elongated intensity profile ( 2 and 8th ). In particular, the focus distribution 124 in this embodiment has a main extension direction 162 along which it extends.

For example, the second beam shaping device 158 is or includes a diffractive optical element and/or an axicon element for impressing the phase distribution on the second input beam 160 to form the focus distribution 124 with an elongated shape and/or elongated intensity profile.

The first input beam 108 provided by the second beam-shaping device 158 in this specific embodiment is coupled into the first beam-shaping device 106 . As described above, this first input beam 108 is divided into mutually different partial beams 114 by means of the beam splitting element 112 of the first beam shaping device 106 , which are imaged in the different partial regions 120 of the focal zone 122 by means of the focusing optics 116 . Focus distributions 124 imaged in focus zone 122 by means of focusing optics 116 represent, in terms of their shape and/or their intensity profile, copies of the focus distribution assigned to first input beam 108, with focusing by means of focusing optics 116 in particular resulting in reduced imaging of focus distributions 124.

In FIG 8th represented as a grayscale distribution, with lighter grayscale values representing greater intensities.

At the in 8th In the example shown, the focus distributions 124 are oriented transversely to the longitudinal axis 142 and/or to the local direction of extent 138.

It can be provided that in the first beam shaping device 106, as described above, beam shaping is carried out by means of the beam shaping element 130 and/or beam splitting by means of the polarization beam splitting element 126. In this case, the shape and/or intensity profile of the focus distributions 124 imaged by the focusing optics 116 are based on the focus distribution assigned to the first input beam 108, but due to the processing by the beam-shaping element 130 and/or the polarization beam-splitting element 126 they point in comparison to that of the first Input beam 108 associated focus distribution has a modified shape and / or modified polarization properties.

In a further embodiment, the second beam-shaping device 158 is set up and configured such that the second beam-shaping device 158 is used to assign a beam profile to the first input beam 108 coupled into the first beam-shaping device 106, the intensity profile of which is based on an intensity maximum 164 with respect to a main extension direction 166 and/or main extension axis has an abrupt drop in intensity ( 9a and 9b) . Such beams are referred to, for example, as abrupt self-focusing beams.

As a result, the focus zone 122 can be formed from a plurality of focus distributions 124 with such an intensity profile by imaging the partial beams 114 coupled out of the first beam-shaping device 106 ( 10 ). In particular, the intensity profile of each of the focus distributions 124 of the focus zone 122 then has the abrupt drop in intensity.

A grayscale representation of an associated two-dimensional phase distribution of beams coupled out of the second beam-shaping device 158 is shown in FIG 11 with the associated gray scale ranging from white (phase +Pi) to black (phase -Pi).

In particular, the phase distribution is radially symmetrical and/or rotationally symmetrical with respect to an associated center axis 167 and/or beam center axis. This central axis 167 is, for example, parallel or approximately parallel to a main direction of propagation 267 of the beam shaping onto the second means 158 incident second input beam 160 oriented.

In particular, a phase frequency associated with the phase distribution increases in the radial direction 367 starting from the central axis 167 with an increasing radial distance from the central axis 167 .

In this specific embodiment, the first input beam 108 coupled into the first beam-shaping device 106 is assigned a shape and/or an intensity profile of an abruptly self-focusing beam. With regard to the formation and properties of such rays, reference is made to the scientific publications "Abruptly autofocusing waves" by Efremidis, Nikolaos K., and Demetrios N. Christodoulides, Optics letters 35.23 (2010): 4045-4047 and "Observation of abruptly autofocusing waves" by Papazoglou et al., Optics letters 36.10 (2011): 1842-1844. Reference is made expressly and in full to this.

At the in the 9a and 9b In the embodiment shown, the focus distribution 124 has an intensity drop edge 165 starting from the intensity maximum 164 in the main extension direction 166 .

It is characteristic of the abrupt self-focusing beam that at the intensity drop edge 165 the intensity, starting from the intensity maximum 164, drops to a value of 1/e ² approximately 3 times faster than would be the case with a Gaussian intensity profile.

In particular, the intensity maximum 164 is a main maximum and/or global maximum of the intensity profile of the abrupt self-focusing beam. In particular, the intensity profile has one or more secondary maxima 164a, which, starting from the intensity maximum 164, follow the intensity maximum 164 counter to the main extension direction 166. In particular, the secondary maxima 164 each have lower maximum intensity values as the distance from the intensity maximum 164 with respect to the main extension direction 166 increases.

In particular, provision can be made for the second beam-shaping device 158 to be in the form of a near-field beam-shaping device.

For example, an intermediate image 168 (indicated in 2 ) of the focus distribution associated with the first input beam 108 is formed. This intermediate image 168 is arranged between the second beam-shaping device 158 and the first beam-shaping device 106 with respect to the main propagation direction 128 of the first input beam 108 .

In particular, the second beam-shaping device 158 is assigned far-field optics 170, by means of which far-field focusing of an output beam 172 and/or output beam bundle coupled out of the second beam-shaping device 158 into a focal plane 174 of the far-field optics 170 takes place.

In particular, the far-field optics 170 are used to focus the intermediate image 168 far-field into the focal plane 174.

An intensity distribution in the form of a ring structure and/or ring segment structure is formed in this focal plane 174 by the far field focusing of the output beam 172 and/or output beam bundle, which is arranged in particular around an optical axis 176 of the far field optics 170 .

At the in 2 In the example shown, a telescope device 178 of the device 100 is formed by means of the far-field optics 170 and the focusing optics 116 . For this purpose, the far-field optics 170 have, in particular, a greater focal length than the focusing optics 116.

The focal plane 174 is in particular a common focal plane of the far-field optics 170 and the focusing optics 116. In particular, the focal plane 174 is a focal plane of the telescope device 178.

The first beam-shaping device 106 is arranged in particular in the focal plane 174 and/or in a region of the focal plane 174. This area is to be understood as an area extending around the focal plane 174, which has a maximum distance of 10% of the focal length of the far-field optics 170 from the focal plane 174, for example. A distance direction of this maximum distance is in particular oriented parallel to the optical axis 176 and/or to the main propagation direction 128 of the first input beam 108 .

The region of focal plane 174 mentioned is to be understood in particular as a far-field region of telescope device 178 in which, in particular, there is a far-field focusing of output beam 172 coupled out of second beam-shaping device 158 and/or of first input beam 108 to be coupled into first beam-shaping device 106.

Using the beam splitting element 112 of the device 100, it is basically possible to arrange the focus distributions 124 along different paths and thereby form focus zones with different geometries.

At the in the 12a and 12b In the example shown, the focus distributions 124 are arranged along the longitudinal axis 142 of the focus zone 122, with the longitudinal axis 142 being formed in a straight line. In this case, for example, the focal zone 122 is assigned a single angle of incidence α, with which the focal zone 122 is angled with respect to the first outer side 144 and/or the second outer side 146 . In particular, the focal zone 122 in this exemplary embodiment has the same local direction of extent 138 throughout, ie the local direction of extent 138 is constant in particular over the entire extent of the focal zone 122 .

In the embodiment according to the 12c and 12d the focus zone 122 has a first section 180 and a second section 182, wherein the focus distributions 124 of the focus zone 122 in the first section 180 and in the second section 182 are each arranged with a different local direction of extent 138. For example, in this exemplary embodiment, the focal zone 122 has the same local direction of extent 138 throughout in the first section 180 and in the second section 182 .

In particular, the focal zone 122 has the same angle of incidence α in the first section 180 and in the second section 182, at which the focal zone 122 is angled with respect to the first outer side 144 and/or the second outer side 146. In particular, a smallest angle between the respective local extension direction 138 of the first section 180 and the second section 182 is then twice as large as the angle of attack α.

The longitudinal axis 142 of the focal zone 122, along which the focal distributions 124 are arranged, is not necessarily formed in a straight line. For example, it can be provided that the longitudinal axis 142 has a curved shape at least in sections. For example, the focus zone 122 in the in the 12e and 12f examples shown on a continuously curved shape.

For example, the focus zone 122 then has a varying local direction of extent 138, i.e. the local direction of extent 138 of the focus zone 122 is different at different positions of the focus zone 122 and/or at different focus distributions 124 of the focus zone 122.

In the , and is one den , or. associated phase distribution of beams coupled out of the beam splitting element 112, with the associated gray scale ranging from white (phase +Pi) to black (phase -Pi).

The device 100 according to the invention works as follows:

To carry out the laser processing, the material 102 of the workpiece 104 is acted upon by the focal zone 122 and the focal zone 122 is moved in the feed direction 129 relative to the workpiece 104 through its material 102 .

In this case, the material 102 is in particular a material that is transparent or partially transparent for a wavelength of rays from which the focal zone 122 is formed. For example, the material 102 is a glass material.

The focal zone 122 is moved through the material 102 of the workpiece 104 along a predefined processing line 184 and/or processing surface, for example. The processing line 184 can have straight and/or curved sections, for example.

By subjecting the material 102 to the focal zone 122, material modifications 156 are formed in the material 102, which are arranged along the longitudinal axis 142 of the focal zone 122 ( 5 and 13a) . As a result, modification lines 186 are formed in the material, on which the material modifications 156 are arranged, these modification lines 186 in particular having a shape corresponding to the longitudinal axis 142 of the focal zone 122 . At the in 13a shown example, the modification lines 186 extend from the first outer side 144 to the second outer side 146.

Due to the relative movement of the focal zone 122 with respect to the material 102, a plurality of modification lines 186 are formed, which are positioned parallel to the feed direction 129 at a distance. This results in particular in a planar formation of material modifications 156 in the material 102 ( 13a) .

A distance between modification lines 186 that are adjacent in feed direction 129 can be defined, for example, by suitably selecting a pulse duration of a laser beam from which focus zone 122 is formed and/or a feed rate oriented in feed direction 129 .

The material modifications 156 formed along the processing line 184 and/or processing surface result in particular in a reduction in the strength of the material 102 . As a result, the material 102 can be separated into two different segments 188a and 188b after the material modifications 156 have been formed on the processing line 184 and/or processing surface, for example by exerting a mechanical force ( 13b) .

In the example shown, the segment 188b is a good item segment with a desired edge shape. In this case, segment 188a is a remaining workpiece segment and/or waste segment.

The material 102 is preferably acted upon by the focal zone 122 in such a way that the focal zone 122 penetrates the material 102 . For example, the focal zone 122 extends continuously and/or without interruption over an entire thickness D of the material 102 through the material 102. As a result, for example, as in FIGS 13a and 13b shown to achieve complete separation of the material across its thickness D.

It is also possible to process an edge area 190 of the material 102 using the focal zone 122 (indicated in 13a) . For example, the focus zone 122 then extends continuously and/or without interruption between outer sides of the workpiece 104 oriented transversely to one another. An edge segment can thereby be separated from the workpiece 104 in the edge region 190, for example. As a result, the workpiece 104 can be beveled and/or chamfered in the edge region 190, for example.

The material 102 of the workpiece 104 is quartz glass, for example. For example, to form the material modifications 156 as type I and/or type II modifications, a laser beam from which the focus distributions 124 of the focus zone 122 are formed has a wavelength of 1030 nm and a pulse duration of 1 ps. Furthermore, a numerical aperture assigned to the focusing optics 116 is 0.4 and a pulse energy assigned to a single focus distribution 124 is 100 nJ.

For forming the material modifications 156 as type III modifications, with otherwise the same parameters, the pulse energy assigned to a single focus distribution 124 is 1000 nJ.

Reference List

a

angle of attack

D

thickness

d1

Distance

dx

distance in x-direction

double

distance in z-direction

100

contraption

102

material

104

workpiece

106

first beam shaping device

108

first input beam

110

laser source

112

beam splitting element

114

partial beam

114a

partial beam

114b

partial beam

116

focusing optics

120

subarea

120a

subarea

120b

subarea

122

focus zone

124

focus distribution

126

polarization beam splitting element

128

main propagation direction

129

feed direction

130

beam shaping element

132

preferred direction

132'a

first preferred direction

132'b

second preferred direction

134

main extension direction

136

alignment

138

local extension direction

140

longitudinal central axis

142

longitudinal axis

144

first outside

146

second outside

148

depth direction

150

first section

152

second part

154

third section

156

material modification

157

Crack

158

second beam shaping device

160

second input beam

162

main extension direction

164

maximum intensity

164a

secondary maximum

165

intensity falling edge

166

main extension direction

167

central axis

267

main propagation direction

367

radial direction

168

intermediate image

170

far field optics

172

output beam

174

focal plane

176

optical axis

178

telescopic device

180

first section

182

second part

184

editing line

186

modification line

188a

segment

188b

segment

190

edge area

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• US 2020/0147729 A1 [0003]
• DE 102020207715 [0137]
• DE 102019217577 [0137]

Claims (15)

Device for laser processing a workpiece (104), which has a material (102) that is transparent for the laser processing, comprising a first beam shaping device (106) with a beam splitting element (112) for splitting a first input beam (108) coupled into the first beam shaping device (106) into a plurality of partial beams (114), and focusing optics (116) assigned to the first beam-shaping device (106) for imaging partial beams (114) coupled out of the first beam-shaping device (106) into at least one focal zone (122), with the division of the first input beam (108) by means of the beam splitting element (112) by phase impingement on the first input beam (108), the partial beams (114) are focused in different partial areas (120) of the at least one focus zone (122) to form the at least one focus zone (122). , for laser processing of the workpiece (104) the at least one focus zone ( 122) by means of the focusing optics (116) at at least one angle (a) to an outside (144; 146) of the workpiece (104) is introduced into the material (102), and by impinging on the material (102) by means of the at least one focal zone (122), material modifications (156) are produced in the material (102) which involve a change in one Index of refraction of the material (102) are associated. device after claim 1 , characterized in that the material modifications (156) produced in the material (102) by means of the at least one focal zone (122) are type I and/or type II modifications. device after claim 1 or 2 , characterized by a second beam-shaping device (158) for beam-shaping the first input beam (108) coupled into the first beam-shaping device (106), with the second beam-shaping device (158) being used to impress a phase on a second input beam (160 ) a focus distribution with a defined geometric shape and/or with a defined intensity profile is assigned to the first input beam (108), so that by focusing the partial beams (114) coupled out of the first beam shaping device (106) by means of the focusing optics (116) in different partial areas ( 120) of the focus zone (122) in each case focus distributions (124) are formed based on this geometric shape and/or based on this intensity profile. device after claim 3 , characterized in that the phase imprint on the second input beam (160) is such that the focus distribution (124) has an elongated shape with respect to an associated main extension direction (162), and/or that the phase imprint on the second input beam (160) is such that the focus distribution (124) has a quasi-non-diffracting and/or Bessel-like intensity profile. device after claim 3 or 4 , characterized in that the phase imprinting on the second input beam (160) is such that the focus distribution (124) has an intensity profile with respect to an associated main extension direction (166) which, starting from a maximum intensity at an intensity maximum (164) of the intensity profile, extends to the 1st /e ² -times the maximum intensity decreases by approximately a factor of 3 faster than is the case with a Gaussian intensity profile, and/or that the phase imprint on the second input beam (160) is such that the focus distribution (124) has a shape and/or or has an intensity profile of an abrupt self-focusing beam. Device according to one of claims 3 until 5 , characterized in that an intermediate image (168) of the focus distribution (124) is formed by means of the second beam shaping device (158), and in particular characterized in that the intermediate image (168) of the focus distribution (124) with respect to a main propagation direction (267) of the second input beam (160) is arranged in front of the first beam shaping device (106). Device according to one of claims 3 until 6 , characterized by far-field optics (170) assigned to the second beam-shaping device (158), with the far-field optics (170) being used to focus an output beam (172) coupled out of the second beam-shaping device (158) into a focal plane (174) of the far-field optics (170). , and in particular characterized in that the first beam shaping device (106) is arranged in a region of this focal plane (174). device after claim 6 and 7 , characterized in that the intermediate image (168) of the focus distribution (124) formed by the second beam-shaping device (158) is far-field focused into the focal plane (174) by means of the far-field optics (170). device after claim 7 or 8th , characterized in that the far-field optics (170) and the focusing optics (116) form a telescope device (178), and/or that the far-field optics (170) and the focusing optics (116) have a common focal plane (174), in particular special the first beam shaping device (106) is arranged in a region of this common focal plane (174). Device according to one of the preceding claims, characterized in that the first input beam (108) is assigned a focus distribution with a defined geometric shape and/or with a defined intensity profile, the partial beams (114) coupled out of the first beam-shaping device (106) also having this geometric shape and/or this intensity profile is assigned, and/or wherein focus distributions (124 ) based on this geometric shape and/or based on this intensity profile. Device according to one of the preceding claims, characterized in that the first beam-shaping device (106) has a beam-shaping element (130) for modifying a focus distribution assigned to the first input beam (108), the beam-shaping element (130) being used to modify and/or align the geometric Shape and/or the intensity profile of the focus distribution (124) imaged in the at least one focus zone (122) in a feed direction (129) in which the at least one focus zone (122) for laser processing the workpiece (104) relative to the workpiece ( 104) is moved, in a vertically oriented cross-sectional plane, and/or wherein the beam-shaping element (130) is used to modify and/or align the geometric shape and/or the intensity profile of the focus distribution (124) imaged in the at least one focus zone (122) in a to a feed direction (129) in which the at least one focal zone (122) for the laser processing of the workpiece (104) is moved relative to the workpiece (104), takes place in a parallel-oriented cross-sectional plane. device after claim 11 , characterized in that by means of the beam-shaping element (130) an alignment (136) of a main extension direction (134) of the geometric shape and/or of the intensity profile of the focus distribution (124) can be set or is set in a cross-sectional plane oriented perpendicularly to the feed direction (129), and in particular characterized in that the alignment (136) is adjusted in such a way that the main extension direction (134) is oriented parallel or approximately parallel to a corresponding local extension direction (138) of the focal zone (122). device after claim 11 or 12 , characterized in that the beam-shaping element (130) is used to modify the intensity profile of the focus distribution (124) in a cross-sectional plane oriented parallel to the feed direction (129) in such a way that the intensity profile has at least one preferred direction (132), the at least one preferred direction in particular (132) is oriented parallel or transverse or perpendicular to the feed direction (129). Device according to one of the preceding claims, characterized in that the first beam shaping device (106) has a polarization beam splitting element (126), which is set up in such a way that the partial beams (114) coupled out of the first beam shaping device (106) each have one of at least two have different states of polarization, with the focusing optics (116) being used to focus partial beams (114) with different states of polarization in adjacent partial regions (120) of the at least one focal zone (122). Method for laser processing a workpiece (104), which has a material (102) that is transparent for the laser processing, in which, by means of a beam splitting element (112) of a first beam shaping device (106), a first input beam (108) coupled into the first beam shaping device (106) is a plurality of partial beams (114) is divided and the partial beams (114) coupled out of the first beam-shaping device (106) are focused into at least one focal zone (122) by means of focusing optics (116) assigned to the first beam-shaping device (106), the splitting of the first input beam (108) by means of the beam splitting element (112) by phase imprinting on the first input beam (108), the partial beams (114) for forming the at least one focal zone (122) are focused into different partial regions (120) of the at least one focal zone (122). are, for laser processing of the workpiece (104) at least ei ne focal zone (122) by means of the focusing optics (116) at at least one angle (a) to an outside (144; 146) of the workpiece (104) is introduced into the material (102), and by impinging on the material (102) by means of the at least one focal zone (122), material modifications (156) are produced in the material (102) which involve a change in one Index of refraction of the material (102) are associated.

Images