APPARATUS AND METHOD FOR LASER MACHINING A WORKPIECE

An apparatus for laser machining a workpiece with a material transparent to the laser machining includes a first beam shaping device with a beam splitting element for splitting a first input beam into a plurality of component beams, and a focusing optical unit configured to image the plurality of component beams into at least one focal zone. The first input beam is split by the beam splitting element by phase imposition on the first input beam. The component beams are focused into different partial regions of the at least one focal zone for forming the at least one focal zone. The at least one focal zone is introduced by the focusing optical unit into the material for laser machining the workpiece. Material modifications associated with a crack formation in the material are produced in the material by exposing the material to the at least one focal zone.

FIELD

Embodiments of the present invention relate to an apparatus for laser machining a workpiece which has a material transparent to the laser machining.

Embodiments of the present invention also relate to a method for laser machining a workpiece which has a material transparent to the laser machining.

BACKGROUND

US 2020/0147729 A1 has disclosed a method for forming an angled edge region on a glass substrate by means of a laser beam, wherein the shape of the angled edge region is adapted by adapting an axial energy distribution of the laser beam.

SUMMARY

Embodiments of the present invention provide an apparatus for laser machining a workpiece with a material transparent to the laser machining. The apparatus includes a first beam shaping device with a beam splitting element for splitting a first input beam input coupled into the first beam shaping device into a plurality of component beams, and a focusing optical unit assigned to the first beam shaping device and configured to image the plurality of component beams output coupled from the first beam shaping device into at least one focal zone. The first input beam is split by the beam splitting element by phase imposition on the first input beam. The component beams are focused into different partial regions of the at least one focal zone for forming the at least one focal zone. The at least one focal zone is introduced by the focusing optical unit into the material at at least one work angle with respect to an outer side of the workpiece for laser machining the workpiece. Material modifications associated with a crack formation in the material are produced in the material by exposing the material to the at least one focal zone.

DETAILED DESCRIPTION

Embodiments of the present invention provide an apparatus and a method, which are flexibly usable in many ways and by means of which, in particular, laser machining of the workpiece along different machining geometries is implementable in technically simple fashion.

According to embodiments of the present invention, the apparatus includes a first beam shaping device with a beam splitting element for splitting a first input beam input coupled into the first beam shaping device into a plurality of component beams, and a focusing optical unit which is assigned to the first beam shaping device and serves to image component beams output coupled from the first beam shaping device into at least one focal zone, wherein the first input beam is split by means of the beam splitting element by phase imposition on the first input beam, wherein the component beams are focused into different partial regions of the at least one focal zone for the purpose of forming the at least one focal zone, wherein the at least one focal zone is introduced by means of the focusing optical unit into the material at at least one work angle with respect to an outer side of the workpiece for laser machining the workpiece, and wherein material modifications which are associated with a crack formation in the material are produced in the material by exposing the material to the at least one focal zone.

By splitting the first input beam by means of the beam splitting element on the basis of phase imposition and by subsequently focusing the formed component beams, it is possible for the at least one focal zone to be formed with different geometries in technically simple fashion. As a result, the at least one focal zone can be formed with different portions in particular, which portions each have a different geometry and/or a different work angle. As a result, laser machining of the workpiece with different machining geometries can be achieved in technically simple fashion.

According to embodiments of the invention, the at least one focal zone, in particular, can be introduced into the material at the work angle without this requiring an angling of an optical unit with respect to the workpiece.

The material modifications being associated with a crack formation in the material should be understood to mean that, in particular, the material modifications are accompanied by a crack formation in the material and/or there is a crack formation in the material when the material modifications are formed.

In particular, the beam splitting element is formed as a diffractive beam splitting element and/or as a 3-D beam splitting element. The beam splitting element preferably brings about a phase imposition 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 way of a pure phase manipulation of the phase of the first input beam. In particular, the phase imposition on the first input beam implemented by means of the beam splitting element is variably adjustable and/or definable.

In particular, provision can be made for the at least one focal zone to have a plurality of focal distributions and/or to be formed from a plurality of focal distributions. By way of example, the focal distributions are arranged in the different partial regions of the focal zone.

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

In particular, the at least one focal zone extends in a plane. The focal distributions from which the at least one focal zone is formed are preferably arranged in a plane. In particular, this plane is oriented perpendicular to an advancement direction in which the at least one focal zone is moved relative to the workpiece for the purpose of laser machining the workpiece.

In particular, a lens component and/or grating component of the phase distribution imposed by means of the beam splitting element is assigned to each focal distribution of the at least one focal zone. In particular, the imposed phase distribution comprises a plurality of superposed lens components and/or grating components, with each focal distribution of the at least one focal zone being assigned a lens component and/or grating component. As a result, it is possible to arrange different focal distributions of the focal zone with a spatial offset in a plane oriented perpendicular to an advancement direction in which the focal zone is moved relative to the workpiece for the purpose of laser machining the workpiece.

By way of example, the first beam shaping device is in the form of a far field beam shaping element or comprises one or more far field beam shaping elements. By way of example, the at least one focal zone is formed by focusing component beams output coupled from the first beam shaping device into the respective partial regions of the focal zone by means of the focusing optical unit.

By way of example, the focusing optical unit is in the form of a microscope objective or lens element.

In an embodiment, provision can be made for the first beam shaping device to be rotatable or rotated about an axis parallel to a main propagation direction of the first input beam. As a result, it is possible to rotate the at least one focal zone, for example about an axis of rotation oriented perpendicular to an advancement direction in which the at least one focal zone is moved relative to the workpiece for the purpose of laser machining the workpiece.

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

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

A transparent material should be understood to mean in particular 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 forming the at least one focal zone is transmitted.

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

In particular, provision can be made for the material modifications produced in the material by means of the at least one focal zone to be Type III modifications. As a result, cracks are produced in the material of the workpiece during the laser machining, by means of which cracks separation of the material is in particular made possible.

In an embodiment, the apparatus comprises a second beam shaping device for beam shaping the first input beam input coupled into the first beam shaping device, wherein a focal distribution with a defined geometric shape and/or with a defined intensity profile is assigned to the first input beam by means of the second beam shaping device by phase imposition on a second input beam incident on the second beam shaping device, with the result that focusing the component beams output coupled from the first beam shaping device into different partial regions of the focal zone by means of the focusing optical unit in each case forms focal distributions which are based on this geometric shape and/or based on this intensity profile. As a result, a geometry of focal distributions from which the at least one focal zone is formed can be adapted. As a result, a flexible and multifaceted use of the apparatus is made possible.

In particular, the second beam shaping device is arranged upstream of the first beam shaping device in relation to a main propagation direction of laser beams guided by the apparatus.

In particular, the second input beam is an input beam of the second beam shaping device. By way of example, the second input beam is a laser beam with in particular a Gaussian beam profile, provided by a laser source of the apparatus.

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

In particular, the second beam shaping device modifies and/or adapts a focal distribution assigned to the second input beam input coupled into the second beam shaping device. In particular, a focal 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 an embodiment, provision can be made for the second beam shaping device to be rotatable or rotated about an axis parallel to a main propagation direction of the second input beam. As a result, it is possible to rotate the at least one focal zone, for example about an axis of rotation oriented perpendicular to an advancement direction in which the at least one focal zone is moved relative to the workpiece for the purpose of laser machining the workpiece.

In particular, provision can be made for the phase imposition on the second input beam to be such that the focal distribution has an elongated shape in relation to an assigned main direction of extent and/or for the phase imposition on the second input beam to be such that the focal distribution has a quasi-nondiffractive and/or Bessel-like intensity profile. As a result, the at least one focal zone can be constructed, for example from a plurality of focal distributions with an elongated shape. As a result, it is possible in particular to form the corresponding elongate and/or line-like material modifications, as a result of which an improved introduction of etching liquid for material separation, for example, is enabled.

The second beam shaping device is or comprises a beam shaping element for implementing the phase imposition in particular, for example a diffractive optical element and/or an axicon element.

In particular, the main direction of extent of the focal distribution with the elongated shape is oriented at an angle and in particular perpendicular to an advancement direction in which the at least one focal zone is moved relative to the workpiece for the purpose of laser machining the workpiece.

It may be advantageous if the phase imposition on the second input beam is such that the focal distribution has an intensity profile in relation to an assigned main direction of extent which, proceeding from a maximum intensity at an intensity maximum of the intensity profile, falls to 1/e2-times the maximum intensity faster than in the case of a Gaussian intensity profile by approximately a factor of 3, and/or if the phase imposition on the second input beam is such that the focal distribution has a shape and/or an intensity profile of an abruptly autofocusing beam. As a result of the fast drop in intensity of these focal distributions, there is more precise material machining with reduced damage to the material to be machined. As a result, the material can be separated in particular with a planar and/or smooth edge.

By way of example, the drop in intensity from the maximum intensity to 1/e2-times the maximum intensity is faster than in the case of a Gaussian intensity profile by at least a factor of 2.5 and/or faster by no more than a factor of 3.5.

In particular, proceeding from the intensity maximum in the main direction of extent, the intensity profile has a dropping intensity flank where the intensity drop is formed. In particular, the intensity of the intensity profile in the main direction of extent after the dropping intensity flank is below the value of 1/e2-times the maximum intensity.

Preferably, the dropping intensity flank faces a product piece segment when laser machining the workpiece. As a result, a smooth cutting edge can be realized in particular within the scope of a material separation.

The aforementioned intensity maximum is in particular a principal maximum and/or a 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 principal maximum.

In particular, the secondary maxima are located in a residual workpiece segment and/or scrap segment when laser machining the workpiece. As a result, cracks and/or channels, for example, which promote an etching attack for material separation, can be formed in the residual workpiece segment and/or scrap segment.

In particular, the main direction of extent of these focus distributions is oriented parallel or approximately parallel to a main propagation direction of the second input beam.

Provision can be made for an intermediate image of the focal distribution to be formed by means of the second beam shaping device, wherein in particular the intermediate image of the focal distribution is arranged upstream of the first beam shaping device in relation to a main propagation direction of the second input beam.

The second beam shaping device is in the form of a near field beam shaping device in particular, which is to say imaging of the focal distribution as an intermediate image is implemented by means of the second beam shaping device in particular.

In particular, the intermediate image formed by means of the second beam shaping device is an image representation of the focal distribution assigned to the first input beam input coupled into the first beam shaping device.

In an embodiment, the apparatus comprises a far field optical unit assigned to the second beam shaping device, wherein the far field optical unit is used for far field focusing of an output beam output coupled from the second beam shaping device into a focal plane of the far field optical unit and wherein in particular the first beam shaping device is arranged in a region of this focal plane.

In particular, an output beam output coupled from the far field optical unit then corresponds to the first input beam to be input coupled into the first beam shaping device.

The region of the focal plane should in particular be understood to mean a region extending around the focal plane, which region in particular has a maximum distance of 10% of a focal length of the far field optical unit from the focal plane.

In particular, provision can be made for the far field optical unit to be used for far field focusing of the intermediate image of the focal distribution formed by means of the second beam shaping device into the focal plane.

In particular, the far field optical unit brings about a Fourier transform of the intermediate image produced by means of the second beam shaping device and/or of the focal distribution produced by means of the second beam shaping device.

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

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

Provision can be made for the far field optical unit and the focusing optical unit to form a telescope device, and/or for the far field optical unit and the focusing optical unit to have a common focal plane, wherein in particular the first beam shaping device is arranged in a region of this common focal plane.

In particular, a focal length of the far field optical unit is greater than a focal length of the focusing optical unit.

In particular, provision can be made for the first input beam to be assigned to a focal distribution with a defined geometric shape and/or with a defined intensity profile, wherein the component beams output coupled from the first beam shaping device are likewise assigned this geometric shape and/or this intensity profile, and/or wherein using the focusing optical unit to focus the component beams output coupled from the first beam shaping device into different partial regions of the at least one focal zone leads to the respective formation of focal distributions on the basis of this geometric shape and/or on the basis of this intensity profile. As a result, the at least one focal zone, in particular, can be constructed from mutually spaced apart and/or adjacent focal distributions with a defined geometry. Further, this for example yields a formation of the at least one focal zone by stringing together focal distributions as virtually identical copies on account of beam splitting by means of the beam splitting element.

An assignment of a defined geometric shape and/or defined intensity profile to the first input beam is for example implemented by means of a laser source which provides the first input beam. Alternatively, the assignment is implemented by means of the above-described second beam shaping device.

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

It may be advantageous if the first beam shaping device comprises a beam shaping element for modifying the focal distribution assigned to the first input beam, wherein the beam shaping element is used to bring about a modification and/or alignment of the geometric shape and/or intensity profile of the focal distribution, imaged into the at least one focal zone, in a cross-sectional plane oriented perpendicular to an advancement direction, in which the at least one focal zone is moved relative to the workpiece for laser machining the workpiece, and/or wherein the beam shaping element is used to bring about a modification and/or alignment of the geometric shape and/or intensity profile of the focal distribution, imaged into the at least one focal zone, in a cross-sectional plane oriented parallel to an advancement direction, in which the at least one focal zone is moved relative to the workpiece for laser machining the workpiece.

In particular, the cross-sectional plane oriented parallel to the advancement direction is oriented perpendicular to a main propagation direction of beams from which the focal distribution is formed.

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

In particular, the beam shaping element is or comprises a diffractive or refractive beam shaping element, and/or the beam shaping element is or comprises a diffractive field mapper. In particular, the beam shaping element can be used to impose defined wavefront aberrations onto an input beam input coupled into the beam shaping element.

In particular, the beam shaping element is configured so that the component beams output coupled from the first beam shaping device are assigned the focal distribution modified by means of the beam shaping element, with the result that focusing the component beams, output coupled from the first beam shaping device, by means of the focusing optical unit into different partial regions of the focal zone results in the respective formation of focal distributions with this modified geometric shape and/or with this modified intensity profile.

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

It may be advantageous if an alignment of a main direction of extent of the geometric shape and/or intensity profile of the focal distribution is adjustable or adjusted in a cross-sectional plane oriented perpendicular to the advancement direction by means of the beam shaping element, and in particular if the alignment is adjusted so that the main direction of extent is oriented parallel or approximately parallel to a corresponding local direction of extent of the focal zone. By way of example, a crack formation in the material of the workpiece which are oriented approximately parallel to the local direction of extent of the focal zone can be achieved thereby. In particular, this enables 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 of the intensity profile of the focal distribution to be implemented in such a way that the main direction of extent is oriented at an angle to the corresponding local direction of extent. By way of example, the main direction of extent includes a smallest angle of at least 1° and/or at most 900 with the local direction of extent. As a result, the focal distribution is located for example at least in certain portions in a residual workpiece segment and/or scrap segment that arises during the laser machining of the workpiece. As a result, cracks and/or channels, which promote an etching attack for material separation, are formed, for example, in the residual workpiece segment and/or scrap segment.

As a matter of principle, it is additionally also possible for the focal distribution in the cross-sectional plane oriented perpendicular to the advancement direction to be modified in such a way by means of the beam shaping element that the said focal distribution has a main direction of extent in this cross-sectional plane perpendicular to the advancement direction.

Provision can be made for the focal distribution in the cross-sectional plane oriented perpendicular to the advancement direction to be modified in such a way by means of the beam shaping element that the said focal distribution has a curved longitudinal center axis.

It may be advantageous if the beam shaping element brings about such a modification of the intensity profile of the focal distribution in a cross-sectional plane oriented parallel to the advancement direction that the intensity profile has at least one preferred direction, wherein in particular the at least one preferred direction is oriented parallel or at an angle or perpendicular to the advancement direction. As a result, a crack formation in the material of the workpiece during the laser machining can be controlled and/or optimized in particular. For example, this enables an improved introduction of etching liquid for material separation purposes.

In particular, the at least one preferred direction and the advancement direction are located in a common plane.

By way of example, the intensity profile of the focal distribution is formed for example elliptically or in rectangular or square fashion in the plane parallel to the advancement direction by means of the beam shaping element.

By way of example, a semimajor axis of the ellipse should be understood to mean the preferred direction of a focal distribution in the form of an ellipse.

By way of example, the preferred direction of the focal distribution in the form of an ellipse is oriented parallel or approximately parallel to the advancement direction.

A focal distribution in the form of a square or rectangle has for example two preferred directions, which are each oriented parallel to a connecting direction of two opposing points of the square. By way of example, one of the preferred directions is oriented parallel to the advancement direction and the other is oriented perpendicular thereto.

It may be advantageous if an alignment of the at least one preferred direction of the focal distribution in the cross-sectional plane oriented parallel to the advancement direction is adjustable or adjusted by means of the beam shaping element of the first beam shaping device. As a result, a crack formation in the material of the workpiece during the laser machining can be controlled and/or optimized in particular.

In particular, provision can be made for the at least one work angle of the at least one focal zone to be at least 1° and/or at most 90°. Preferably, the at least one work angle is at least 10°.

The work angle should be understood to mean in particular the smallest angle between a local direction of extent assigned to the at least one focal zone and an outer side of the workpiece. By way of example, the at least one focal zone is input coupled and/or introduced into the material of the workpiece through this outer side.

Provision can be made for the at least one focal zone to have different portions with different local directions of extent and/or work angles.

It may be advantageous if the first beam shaping device comprises a polarization beam splitting element which is configured so that the component beams output coupled from the first beam shaping device each have one of at least two different polarization states, wherein component beams with different polarization states are focused into adjacent partial regions of the at least one focal zone by means of the focusing optical unit. As a result, the at least one focal zone can be formed by stringing together focal points and/or focal distributions with different polarization states.

Focal points and/or focal distributions with different polarization states are formed in particular from mutually incoherent component beams. As a result, the focal points and/or focal distributions can be arranged and/or juxtaposed with a small distance from one another.

The polarization beam splitting element is used, in particular, to split a beam input coupled into the polarization beam splitting element into a plurality of polarized component beams, which each have one of at least two different polarization states.

By way of example, the polarization beam splitting element comprises a birefringent wedge element and/or a birefringent lens element. For example, this allows the generation of a direction offset and/or an angular offset of component beams with different polarization states before the component beams are focused by means of the focusing optical unit. As a result, the component beams with different polarization states can be imaged into spatially different partial regions of the at least one focal zone.

In particular, different polarization states should be understood to mean different linear polarization states.

By way of example, the polarization beam splitter element comprises a quartz crystal for polarization beam splitting purposes.

According to embodiments of the invention, provision is made in the method for a beam splitting element of a first beam shaping device to be used to split a first input beam incident on the beam splitting element into a plurality of component beams and for the component beams output coupled from the first beam shaping device to be focused into at least one focal zone by means of a focusing optical unit assigned to the first beam shaping device, wherein the first input beam is split by means of the beam splitting element by phase imposition on the first input beam, wherein the component beams are focused into different partial regions of the at least one focal zone for the purpose of forming the at least one focal zone, wherein the at least one focal zone is introduced by means of the focusing optical unit into the material at at least one work angle with respect to an outer side of the workpiece for laser machining the workpiece, and wherein material modifications which are associated with a crack formation in the material are produced in the material by exposing the material to the at least one focal zone.

In particular, provision can be made for the at least one focal zone to be moved relative to the material of the workpiece in an advancement direction for the purpose of laser machining the workpiece. In particular, a relative speed, oriented in the advancement direction, between the material and the at least one focal zone is set or is adjustable.

In particular, provision can be made for material modifications to be formed in the material of the workpiece along a machining line and/or machining surface as a result of a relative movement of the at least one focal zone in relation to the workpiece. In particular, the workpiece can be separated along the machining line and/or machining surface as a result.

It may be advantageous if the material of the workpiece is separable or separated along the machining line and/or machining surface by applying thermal loading and/or mechanical stress and/or by etching by means of at least one wet-chemical solution. By way of example, etching is implemented in an ultrasound-assisted etch bath.

In particular, the apparatus according to embodiments of the invention and/or the method according to embodiments of the invention have one or more of the features set forth below:

Provision can be made for the at least one focal zone to extend, and in particular extend continuously, between two different and/or opposing outer sides of the workpiece. By way of example, these outer sides are oriented parallel to one another or at an angle to one another. By way of example, the workpiece can be separated into two different segments as a result, or a segment can be separated from the workpiece for edge machining purposes. As a result, it is possible for example to bevel or chamfer the edge region.

In particular, provision can be made for the at least one focal zone to have focal distributions arranged in such a way that material modifications are formed in a scrap segment and/or residual workpiece segment to be separated from the workpiece. By way of example, the material modifications form channels for improved introduction of etching fluid for material separation purposes.

By way of example, the focal distributions of the at least one focal zone are arranged so that these at least in certain portions are arranged in a residual workpiece segment and/or scrap segment formed during the laser machining of the workpiece, or these at least in certain portions project into a residual workpiece segment formed during the laser machining of the workpiece. By way of example, cracks and/or channels, which promote a supply of etching liquid to material modifications formed during the laser machining, can be formed in the residual workpiece segment and/or scrap segment as a result. This enables an improved material separation along a machining surface at which the material modifications are arranged.

For the same reason, it may be advantageous if the focal distributions of the at least one focal zone are arranged so that a principal maximum and/or a global maximum of the respective focal distribution faces a product piece segment that arises during the laser machining of the workpiece and/or faces away from a residual workpiece segment.

By way of example, a product piece segment should be understood to mean a useful segment (in contrast to a residual workpiece segment and/or scrap segment) that arises during the separation of the workpiece.

In particular, focal distributions of the focal zone, from which the focal zone is formed, have intensity fluctuations of no more than 20%.

In particular, the apparatus comprises a workpiece mount for the workpiece, which preferably has a nonreflective and/or strongly scattering surface.

In particular, provision can be made for the apparatus to have a laser source for providing a laser beam, from which the at least one focal zone is formable or formed. In particular, a pulsed laser beam and/or an ultrashort pulse laser beam is provided by means of the laser source.

In particular, the at least one focal zone is formed from an ultrashort pulse laser beam or provided by means of an ultrashort pulse laser beam. This ultrashort pulse laser beam comprises ultrashort laser pulses in particular.

By way of example, a wavelength of the laser beam from which the at least one focal zone is formable or formed is at least 300 nm and/or no more than 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 is formable or formed has a mean power of at least 1 W to 1 kW. For example, the laser beam comprises pulses with a pulse energy of at least 10 μJ and/or at most 50 mJ. Provision can be made for the laser beam to comprise individual pulses or bursts, with the bursts having 2 to 20 subpulses 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 perpendicular to an advancement direction in which the at least one focal zone is moved relative to the workpiece for the purpose of laser machining the workpiece. As a result, the workpiece can be machined along a curved machining line and/or machining surface, for example.

In particular, the at least one focal zone forms a spatially contiguous interaction region for laser machining the workpiece, with localized material modifications which enable a separation of the material in particular being able to be formed in the interaction region in particular by exposing the material of the workpiece to this interaction region. In particular, there is a crack formation and/or a change in a refractive index of the material between mutually adjacent material modifications.

The material modifications introduced into transparent materials by ultrashort laser pulses are subdivided 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 what is known as a void or cavity. In this respect, the material modification created depends on laser parameters of the laser beam, from which the focal zone is formed, such as for example the pulse duration, the wavelength, the pulse energy, and the repetition frequency of the laser beam, and on the material properties such as, among other things, the electronic structure and the coefficient of thermal expansion, and also on the numerical aperture (NA) of the focusing.

The Type I type isotropic refractive index changes are traced back to locally restricted fusing by way of the laser pulses and fast resolidification of the transparent material. For example, quartz glass has a higher density and refractive index of the material if the quartz glass is cooled more quickly from a higher temperature. Thus, if the material in the focal volume melts and subsequently cools down quickly, then the quartz glass has a higher refractive index in the regions of the material modification than in the non-modified regions.

The Type II type birefringent refractive index changes may arise for example due to 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, which is to say directionally dependent refractive indices, of the transparent material upon solidification. A Type II modification is for example also accompanied by the formation of what are known as nanogratings.

By way of example, the voids (cavities) of the Type III modifications can be produced with a high laser pulse energy. In this context, the formation of the voids is ascribed to an explosion-like expansion of highly excited, vaporized material from the focal volume into the surrounding material. This process is also referred to as a micro-explosion. Since this expansion occurs within the mass of the material, the micro-explosion results in a less dense or hollow core (the void), or a microscopic defect in the sub-micrometer range or in the atomic range, which void or defect is surrounded by a densified material envelope. Stresses which may lead to a spontaneous formation of cracks or which may promote a formation of cracks arise in the transparent material on account of the compaction at the shock front of the micro-explosion.

In particular, the formation of voids may also be accompanied by Type I and Type II modifications. By way of example, Type I and Type II modifications may arise in the less stressed areas around the introduced laser pulses. Accordingly, if reference is made to the introduction of a Type III modification, then a less dense or hollow core or a defect is present in any case. By way of example, it is not a cavity but a region of lower density that is produced in sapphire by the micro-explosion of the Type III modification. On account of the material stresses that arise in the case of a Type III modification, such a modification moreover often is accompanied by, or at least promotes, a formation of cracks. The formation of Type I and Type II modifications cannot be completely suppressed or avoided when Type III modifications are introduced. Finding “pure” Type III modifications is therefore unlikely.

In the case of high laser beam repetition rates, the material is unable to cool down completely between the pulses, with the result that cumulative effects of the heat introduced from pulse to pulse may influence the material modification. By way of example, the laser beam repetition frequency may be higher than the reciprocal of the thermal diffusion time of the material, with the result that heat accumulation as a result of successive absorptions of laser energy may occur in the focal zone until the melting temperature of the material has been reached. Moreover, a region larger than the focal zone can be fused as a result of heat transport of the thermal energy into the areas surrounding the focal zone. The heated material cools quickly following the introduction of ultrashort laser pulses, and so the density and other structural properties of the high-temperature state are, as it were, frozen in the material.

The at least one focal zone comprises in particular a plurality of spaced apart and/or adjacent focal distributions, wherein the focal zone may have interruptions and/or zeros, where there is in particular no interaction or negligible interaction with the material, between adjacent focal distributions. In particular, these interruptions of the focal zone have a spatial extent of no more than 10% of a maximum extent and/or maximum length of the focal zone. In particular, these interruptions have a spatial extent of no more than 100 μm and in particular of no more than 50 μm. If there are relatively large interruptions of intensity distributions present, then this should be understood to mean different focal zones.

By way of 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, for example a respective length and/or a respective diameter, the focal zone is considered in a modified intensity distribution which only contains intensity values located above a specific intensity threshold. In this respect, the intensity threshold is selected, for example, such that values below this intensity threshold have such a low intensity that they are no longer relevant for interaction with the material for the purpose of forming material modifications. For example, the intensity threshold is 50% of a global intensity maximum of the actual intensity distribution. A length of the respective focal zone, or a diameter of the respective focal zone, should then be understood to mean a maximum length of extent and/or a length of maximum extent of the respective focal zone along a longitudinal center axis of the focal zone, or in a plane oriented perpendicular to the longitudinal center axis, taken on the basis of the modified intensity distribution.

In particular, the indications “at least approximately” or “approximately” are to be understood in general to mean a deviation of no more than 10%. Unless stated otherwise, the indications “at least approximately” or “approximately” are to be understood to 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 by no more than 10% from an ideal geometric shape.

Elements that are the same or have equivalent functions are denoted by the same reference signs in all the exemplary embodiments.

An exemplary embodiment of an apparatus for the laser machining of a workpiece is shown inFIG.1and is denoted by100in that figure. The apparatus100can be used to create localized material modifications in a material102of the workpiece104, such as for example defects on the submicron scale or on the atomic scale which weaken the material. At these material modifications, the workpiece can for example be separated into different segments or a segment can for example be separated from the workpiece104in a subsequent step. In particular, the apparatus100can be used to introduce material modifications into the material102at a work angle so that an edge region of the workpiece104can be beveled or chamfered as a result of the separation of a corresponding segment from the workpiece104.

The apparatus100comprises a first beam shaping device106, into which a first input beam108is input coupled. By way of example, this first input beam108is a laser beam which for example is provided by means of a laser source110and/or output coupled from a laser source110. In particular, the first input beam108should be understood to mean a ray bundle comprising a plurality of rays running in parallel in particular.

The laser beam provided by means of the laser source110is in particular a pulsed laser beam and/or an ultrashort pulse laser beam.

The first beam shaping device106comprises a beam splitting element112, by means of which the first input beam108is split into a plurality of component beams114and/or component ray bundles. In the example shown inFIG.1, two mutually different component beams114aand114bare indicated.

The first beam shaping device106and/or the beam splitting element112are each formed as a far field beam shaping element, for example.

For the purpose of focusing the component beams114output coupled from the first beam shaping device106, the apparatus100comprises a focusing optical unit116, into which the component beams114are input coupled. By way of example, mutually different component beams114are incident on the focusing optical unit116with a spatial offset and/or angular offset.

By way of example, the focusing optical unit116is in the form of a microscope objective or lens element.

The component beams114are focused by means of the focusing optical unit116into different partial regions120of a focal zone122, which are introduced into the material102of the workpiece104for the laser machining thereof.

By way of example,FIG.1indicates two different partial regions120aand120b, into which the component beams114are focused for the purpose of forming the focal zone122. Here, for example, the partial region120ais assigned to the component beam114aand the partial region120bis assigned to the component beam114b.

A specific focal distribution is assigned to the first input beam108which is input coupled into the first beam shaping device106. This focal distribution should be understood to mean a geometric shape and/or an intensity profile which would be formed by focusing the first input beam108prior to the input coupling into the first beam shaping device106.

By way of example, the first input beam108, for example provided by means of the laser source108, has a Gaussian beam profile. Focusing the first input beam108prior to the input coupling into the first beam shaping device106would lead to a focal distribution with a Gaussian shape and/or Gaussian intensity profile being formed in this case.

In particular, the shape of the focal distribution should be understood to mean a characteristic spatial shape and/or a spatial extent of the focal distribution.

The first input beam108input coupled into the first beam shaping device106is split in such a way by means of the beam splitting element112that this focal distribution is likewise assigned to the component beams114. Respective focal distributions124are formed by focusing these component beams114into the different partial regions120of the focal zone122by means of the focusing optical unit116, with these focal distributions124being based on the focal distribution assigned to the first input beam108.

As a result, the focal zone122is constructed and/or formed by stringing together different focal distributions124. Presently, different focal distributions124should be understood to mean focal distributions124at different spatial positions of the focal zone122, with these different focal distributions124having at least approximately the same geometric shape and/or the same geometric intensity profile.

Different focal distributions124are arranged in the focal zone122at a distance from one another. In principle, it is possible for mutually adjacent different focal distributions124to overlap in space.

Beam splitting by means of the beam splitting element112in particular causes focal distributions to be formed as identical copies, which are imaged in different partial regions120of the focal zone122.

By way of example, the beam splitting element112is in the form of a 3-D beam splitting element. In respect of the technical realization and properties of the beam splitting element112, 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], Dec. 18, 2020. Express reference is made to the entire content thereof.

In particular, a distance dl and/or a spatial offset between mutually adjacent focal distributions124can be set by means of the beam splitting element112.

By way of example, a distance dx and/or spatial offset in an x-direction and a distance dz and/or spatial offset in a z-direction oriented perpendicular to the x-direction can be set between mutually adjacent focal distributions124.

To this end, mutually different component beams114are for example formed in such a way by means of the beam splitting element112that the said different component beams are incident on the focusing optical unit116with a specific spatial offset and/or with a specific convergence and/or divergence. The mutually different component beams114are then imaged with a spatial offset in the x-direction and/or z-direction arising therefrom by means of the focusing optical unit116.

To carry out the beam splitting by means of the beam splitting element112, a defined transverse phase distribution is imposed on a transverse beam cross section of the first input beam108. By way of example, examples of transverse phase distributions of beams output coupled from the beam splitting element112and associated focal zones112are respectively shown inFIGS.12a,band12c,dand12e,f.

To generate the spatial offset in the x-direction and/or in the z-direction, the phase imposition by means of the beam splitting element112is for example implemented in such a way that the assigned phase distribution for each focal distribution124has a specific optical grating component and/or optical lens component. On account of the optical grating component, there is an angular deflection of component beams114upstream of the focusing optical unit116, which post-focusing results in a spatial offset in the x-direction. On account of the optical lens component, component beams116are incident on the focusing optical unit116with different convergence and/or divergence, which post-focusing results in a spatial offset in the z-direction.

Provision can be made for the first beam shaping device106to have a polarization beam splitting element126. The polarization beam splitting element126is used to carry out polarization beam splitting of the first input beam108and/or a beam output coupled from the beam splitting element112into 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 element126, the component beams114output coupled from the first beam shaping device106each have one of at least two different polarization states. These component beams114with different polarization states are focused by means of the focusing optical unit116into the different partial regions120of the focal zone122.

By way of example, the polarization beam splitting element126is arranged upstream or downstream of the beam splitting element116in relation to a main propagation direction128of the first input beam108input coupled into the first beam shaping device106.

In the example shown, the main propagation direction128is 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 an advancement direction129, in which the focal distributions127are moved relative to the workpiece104for laser machining the workpiece104.

In terms of the functionality and design of the polarization beam splitting element126, reference is made to the German patent applications with the reference number DE 102020207715.0 (filing date: Jun. 22, 2020) and with the reference number DE 102019217577.5 (filing date: Nov. 14, 2019), neither of which is a prior publication, by the same applicant. Express reference is made to the entire content thereof.

In particular, the polarization states of the component beams114should be understood to be linear polarization states, wherein for example two different polarization states are provided and/or wherein for example respective polarization directions of mutually different component beams are aligned at an angle of 90° with respect to one another.

In particular, the component beams114are polarized in such a way that an electric field is oriented in a plane perpendicular to the propagation direction of the said component beams (transverse electric).

For the polarization beam splitting, the polarization beam splitting element126for example has a birefringent lens element and/or a birefringent wedge element. By way of example, the birefringent lens element and/or the birefringent wedge element are produced from a quartz crystal or comprise a quartz crystal.

By way of example, component beams114with different polarization states are formed in such a way by means of the birefringent lens element that the said component beams are imaged with a spatial offset in the z-direction and/or x-direction as a result of focusing by means of the focusing optical unit116. As a result, focal distributions124formed from component beams114with different polarization states can be arranged with a spatial offset in the z-direction and/or x-direction, for example in the focal zone122.

By way of example, a juxtaposition of focal distributions124can be realized in the focal zone122by means of the polarization beam splitting element126, wherein mutually adjacent focal distributions124are each formed from component beams114with different polarization states.

Further, provision can be made for the first beam shaping device106to have a beam shaping element130, by means of which the focal distribution assigned to the first input beam108is modifiable following the input coupling thereof into the first beam shaping device106.

In respect of the technical realization and properties of the beam shaping element130, 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], Dec. 18, 2020, and to the book “Laser Beam Shaping: Theory and Techniques”, Fred M. Dickey, ed., CRC press, 2014. Express reference is made to the entire content thereof.

By way of example, the beam shaping element130is formed as a diffractive or refractive phase element for imposing defined wavefront aberrations on a beam input coupled into the beam shaping element130. By way of example, the beam shaping element130is in the form of a diffractive field mapper.

By way of example, the beam shaping element130is arranged upstream or downstream of the beam splitting element112in relation to the main propagation direction128of the first input beam108.

In the example shown inFIG.1, the beam shaping element130is arranged between the beam splitting element112and the polarization beam splitting element126. By way of example, the input beam108is processed first with the beam splitting element112and subsequently with the beam shaping element130and/or with the polarization beam splitting element126.

The beam shaping element130renders modifiable a geometric shape and/or an intensity profile of the focal distributions124imaged into the focal zone122.

A modification of the focal distributions124of the focal zone122by means of the beam shaping element130can be implemented in a cross-sectional plane parallel to the advancement direction129, wherein this cross-sectional plane is oriented perpendicular to the main propagation direction128and/or perpendicular to the z-direction in particular (FIGS.3a,3b, and3c).

Further, the focal distributions124of the focal zone122can be modified in a cross-sectional plane perpendicular to the advancement direction129by means of the beam shaping element130(FIGS.4aand4b). In the example shown, this cross-sectional plane is oriented parallel to the x-direction and parallel to the main propagation direction128and/or z-direction.

In relation to the cross-sectional plane oriented parallel to the advancement direction129, the focal distribution124is for example modified in such a way that the shape and/or the intensity profile of the focal distribution124has a preferred direction132in this cross-sectional plane. In particular, this preferred direction132should be understood to mean a direction in which a length of extent of the focal distribution124is maximized either locally or globally. By way of example, the preferred direction132should be understood to be a main direction of extent of the focal distribution124.

In the example shown inFIG.3b, the focal distribution124is formed elliptically and/or as an ellipse in the plane parallel to the advancement direction129. In this case, the preferred direction132is oriented parallel to a semimajor axis of this ellipse.

In principle, it is also possible for the focal distribution124to have a plurality of preferred directions132. In the example shown inFIG.3c, the focal distribution124is formed to be rectangular and/or as a rectangle and in particular as a square in the plane parallel to the advancement direction129. In this case, the focal distribution124has a first preferred direction132′a, which for example is oriented parallel to the x-direction, and a second preferred direction132′b, which for example is oriented at an angle and in particular perpendicular to the x-direction, which is to say parallel to the y-direction in the example shown.

By way of example, the first preferred direction132′aand the second preferred direction132′bare each parallel to connecting lines between mutually opposite corners of the rectangle.

Provision can be made for the focal distribution124assigned to the first input beam108to have an elongate and/or elongated shape in the cross-sectional plane oriented perpendicular to the advancement direction129(FIGS.4aand4b). By way of example, this is realized by virtue of a quasi-nondiffractive and/or Bessel-like beam profile being assigned to the first input beam108which is input coupled into the first beam shaping device106.

By way of example, the focal distribution124has a main direction of extent134, along which the focal distribution124has in particular a greater length and/or in particular a greatest extent in the cross-sectional plane oriented perpendicular to the advancement direction129(see alsoFIG.3c). By way of example, the main direction of extent134is oriented parallel to a connecting line between a start point and an end point of the focal distribution124in relation to a direction of the greatest extent of the focal distribution124.

In particular, provision can be made for an alignment136and/or orientation of the focal distribution124in the cross-sectional plane oriented perpendicular to the advancement direction129to be adaptable by means of the beam shaping element130, wherein for example the alignment136of the respective main direction of extent134of the focal distribution124is adaptable.

In the examples shown inFIGS.4aand4b, the alignment136of the respective focal distribution124is adaptable in the x-z-plane.

By way of example, the respective alignment136of the focal distributions124is adapted by means of the beam shaping element130in such a way that the alignment136is oriented parallel or approximately parallel to a local direction of extent138of the focal zone122assigned to the respective focal distribution124.

By way of example, the local direction of extent138of the focal zone122should understood to be a local spacing direction of adjacent focal distributions124, for example of two or three adjacent focal distributions124. By way of example, the focal distributions124of the focal zone122can be arranged in different portions of the focal zone122with different local directions of extent138.

In the cross-sectional plane oriented perpendicular to the advancement direction129, the focal distribution124can for example be provided with a curved shape by way of an adaptation by means of the beam shaping element130(FIG.4b). By way of example, this makes it possible to generate the focal distribution124in the form of a curved Bessel-like beam and/or accelerated Bessel-like beam.

In terms of the formation and properties of quasi-nondiffractive 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, Dec. 1, 2012.

By way of example, the focal distribution124has a longitudinal center axis140along which it extends. By way of example, this longitudinal center axis140has a rectilinear form (FIG.4a). In the case of a focal distribution with a curved shape, the longitudinal center axis140has a curved shape or a shape curved in certain portions (FIG.4b).

The focal distributions124assigned to the focal zone122are arranged along a longitudinal axis142, which for example has a rectilinear form, of the focal zone122by means of the first beam shaping device106(FIGS.4aand4b).

The longitudinal axis142need not necessarily have a rectilinear and/or continuous form. By way of example, the longitudinal axis142can be curved at least in certain portions. It is also possible for the longitudinal axis142to have directional changes and, in particular, non-continuous directional changes.

In the example shown inFIG.5, the focal zone122extends within the material102of the workpiece104from a first outer side144of the workpiece104to a second outer side146of the workpiece104, wherein the second outer side146is spaced apart from the first outer side144in relation to a depth direction148of the workpiece104. In particular, the focal zone122passes through the workpiece104throughout and/or without interruptions in the depth direction144.

The first outer side144and the second outer side146of the workpiece104are oriented parallel or approximately parallel to one another, for example.

By way of example, for laser machining the workpiece104, the focal zone122is introduced and/or input coupled into the material102of the workpiece104through the first outer side144or through the second outer side146.

The focal zone122has a first portion150starting from the first outer side144, a second portion152of the focal zone122adjoining the said first portion in the depth direction148. Further, the focal zone122has a third portion154following this second portion152in the depth direction148.

In the example shown, the longitudinal axis142of the focal zone122has a rectilinear form in each of the portions150,152, and154, wherein the longitudinal axis142has a directional change, in particular in each case, at the transitions from the first portion150to the second portion152and from the second portion152to the third portion154.

Each of these portions150,152, and154is assigned a different local direction of extent138, in terms of which the focal distributions122are arranged.

Further, a specific work angle α is assigned to each of the portions150,152, and154. This work angle α should be understood to mean a smallest angle between the local direction of extent138of the corresponding portion150,152,154and the first outer side144and/or second outer side146.

By way of example, the first portion150and the third portion154have a work angle α of 45° and the second portion152has a work angle α of 90°.

The material102of the workpiece104is produced from a material transparent to a wavelength of laser beams from which the focal zone122and/or the focal distributions124are formed.

The focal zone122is introduced into the material102for the purpose of laser machining the material102. Respective localized material modifications156are formed at the focal distributions124by way of this exposure of the material102to the focal zone122(FIG.6), which material modifications are for example arranged at a distance from one another along the longitudinal axis142of the focal zone122.

A suitable choice of machining parameters, such as laser parameters and/or advancement speed for example, makes it possible to produce the material modifications156as Type III modifications, which lead to a spontaneous formation of cracks157in the material102(FIG.6). The cracks157formed during the laser machining of the material102extend between mutually adjacent material modifications156in particular.

The advancement speed should be understood to mean a speed of a relative motion between the focal zone122and the material102in the advancement direction129.

As an alternative, a suitable choice of the machining parameters makes it possible to produce the material modifications156as Type I and/or Type II modifications, which are accompanied by a heat accumulation in the material102and/or a change in a refractive index of the material102.

The formation of the material modifications156as Type I and/or Type II modifications is associated with a heat accumulation in the material102of the workpiece104. In particular, the produced material modifications156are so close together in this case that, during the formation thereof by exposing the material102to the focal zone122, this heat accumulation arises (indicated inFIG.7).

In an embodiment, the apparatus100comprises a second beam shaping device158which, in relation to the main propagation direction128of the first input beam108input coupled into the first beam shaping device106, is arranged upstream of this first beam shaping device106. By means of the second beam shaping device158, it is possible to adapt the focal distribution assigned to the first input beam108before the latter is input coupled into the first beam shaping device106.

In this embodiment, a second input beam160which, in particular, is provided by means of the laser source110and/or is a laser beam output coupled from the laser source100is input coupled into the second beam shaping device158.

In a manner analogous to the first input beam108, the second input beam160should accordingly be understood to mean, in particular, a ray bundle comprising a plurality of rays running in parallel in particular.

In the example shown, the first input beam128input coupled into the first beam shaping device106is a beam output coupled from the second beam shaping device158and/or a ray bundle output coupled from the second beam shaping device158.

By means of the second beam shaping device158there is a phase imposition on the second input beam160, as a result of which the focal distribution assigned to the first input beam108input coupled into the first beam shaping device106is defined. As a result, the geometric shape and/or the intensity profile of the focal distribution assigned to the first input beam108can be defined by means of the second beam shaping device158.

By way of example, the second input beam160input coupled into the second beam shaping device158has a Gaussian beam profile, which is to say the second input beam160has a Gaussian shape and/or a Gaussian intensity profile.

In an embodiment, the second beam shaping device158is configured and designed in such a way that, by means of the second beam shaping device158, a quasi-nondiffractive and/or Bessel-like beam profile is assigned to the first input beam108input coupled into the first beam shaping device106.

As a result, the first input beam108can be imaged in particular into a focal distribution with a quasi-nondiffractive and/or Bessel-like beam profile. In this embodiment, the focal distribution124imaged into the focal zone122has an elongated shape and/or an elongated intensity profile (FIG.2andFIG.8). In particular, the focal distribution124of this embodiment has a main direction of extent162, along which it extends.

By way of example, the second beam shaping device158is or comprises a diffractive optical element and/or axicon element for imposing the phase distribution onto the second input beam160for the purpose of forming the focal distribution124with the elongated shape and/or elongated intensity profile.

The first input beam108provided by means of the second beam shaping device158in this embodiment is input coupled into the first beam shaping device106. As described above, this first input beam108is split into mutually different component beams114by means of the beam splitting element112of the first beam shaping device106, the different component beams being imaged into the different partial regions120of the focal zone122by means of the focusing optical unit116. In respect of their shape and/or intensity profile, the focal distributions124imaged into the focal zone122by means of the focusing optical unit116represent copies of the focal distribution assigned to the first input beam108, wherein focusing by means of the focusing optical unit116brings about size-reducing imaging of the focal distributions124in particular.

An example of focal distributions124with elongated shape and/or elongated intensity profile, imaged into the focal zone122by means of the focusing optical unit116, is depicted inFIG.8as a grayscale value distribution, with brighter grayscale values representing greater intensities.

In the example shown inFIG.8, the focal distributions124are oriented at an angle to the longitudinal axis142and/or to the local direction of extent138.

Provision may be made for beam shaping by means of the beam shaping element130and/or beam splitting by means of the polarization beam splitting element126to be carried out in the first beam shaping device106, as described above. In this case, the focal distributions124imaged by means of the focusing optical unit116are based in respect of their shape and/or their intensity profile on the focal distribution assigned to the first input beam108but have a modified shape and/or modified polarization properties vis-à-vis the focal distribution assigned to the first input beam108on account of the processing by means of the beam shaping element130and/or the polarization beam splitting element126.

In a further embodiment, the second beam shaping device158is configured and designed so that, by means of the second beam shaping device158, the first input beam108input coupled into the first beam shaping device106is assigned a beam profile, the intensity profile of which, proceeding from an intensity maximum164, has an abrupt drop in intensity in relation to a main direction of extent166and/or main axis of extent (FIGS.9aand9b). Such beams are referred to as abruptly autofocusing beams, for example.

As a result, the focal zone122can be formed from a plurality of focal distributions124with such an intensity profile by way of imaging the component beams114output coupled from the first beam shaping device106(FIG.10). In particular, the intensity profile of each of the focal distributions124of the focal zone122then has the abrupt drop in intensity.

A grayscale value representation of an associated two-dimensional phase distribution of beams output coupled from the second beam shaping device158is depicted inFIG.11, with the assigned grayscale value scale ranging from white (a phase of +pi) to black (a phase of −pi).

In particular, the phase distribution has a radially symmetric and/or rotationally symmetrically form vis-à-vis an assigned center axis167and/or beam center axis. By way of example, this center axis167is oriented parallel or approximately parallel to a main propagation direction267of the second input beam160incident on the second beam shaping device158.

In particular, proceeding from the center axis167, a phase frequency assigned to the phase distribution increases in the radial direction367with increasing radial distance from the center axis167.

In this embodiment, a shape and/or an intensity profile of an abruptly autofocusing beam is assigned to the first input beam108input coupled into the first beam shaping device106. In respect of the formation and properties of such beams, 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. Express reference is made to the entire content thereof.

In the embodiment shown inFIGS.9aand9b, the focal distribution124has a dropping intensity flank165in the main direction of extent166when proceeding from the intensity maximum164.

It is a characteristic of the abruptly autofocusing beam that, at the dropping intensity flank165, the intensity proceeding from the intensity maximum164drops to a value of 1/e2approximately 3 times faster than would be the case for a Gaussian intensity profile.

The intensity maximum164is in particular a principal maximum and/or a global maximum of the intensity profile of the abruptly autofocusing beam. In particular, the intensity profile has one or more secondary maxima164awhich, proceeding from the intensity maximum164, follow the intensity maximum164counter to the main direction of extent166. In particular, with increasing distance from the intensity maximum164in relation to the main direction of extent166, the secondary maxima164each have a lower maximum intensity value.

In particular, provision can be made for the second beam shaping device158to be formed as a near field beam shaping device.

By way of example, an intermediate image168(indicated inFIG.2) of the focal distribution assigned to the first input beam108is formed by means of the second beam shaping device158. In relation to the main propagation direction128of the first input beam108, this intermediate image168is arranged between the second beam shaping device158and the first beam shaping device106.

In particular, the second beam shaping device158is assigned a far field optical unit170, by means of which far field focusing into a focal plane174of the far field optical unit170of an output beam172and/or output ray bundle output coupled from the second beam shaping device158is implemented.

In particular, far field focusing of the intermediate image168into the focal plane174is implemented by means of the far field optical unit170.

In this focal plane174, the far field focusing of the output beam172and/or output ray bundle causes the formation of an intensity distribution in the shape of a ring structure and/or ring segment structure, arranged in particular about an optical axis176of the far field optical unit170.

In the example shown inFIG.2, a telescope device178of the apparatus100is formed by means of the far field optical unit170and the focusing optical unit116. To this end, the far field optical unit170has in particular a greater focal length than the focusing optical unit116.

In particular, the focal plane174is a common focal plane of the far field optical unit170and the focusing optical unit116. In particular, the focal plane174is a focal plane of the telescope device178.

The first beam shaping device106is in particular arranged in the focal plane174and/or in a region of the focal plane174. This region should be understood to mean a region extending around the focal plane174, which region for example has a maximum distance of 10% of the focal length of the far field optical unit170from the focal plane174. A spacing direction of this maximum distance is oriented parallel to the optical axis176and/or main propagation direction128of the first input beam108in particular.

The aforementioned region of the focal plane174should in particular be understood to be a far field region of the telescope device178, in which far field region there is in particular far field focusing of the output beam172output coupled from the second beam shaping device158and/or of the first input beam108to be input coupled into the first beam shaping device106.

By means of the beam splitting element112of the apparatus100it is possible, in principle, to arrange the focal distributions124along different paths and thus form focal zones with different geometries.

In the example shown inFIGS.12aand12b, the focal distributions124are arranged along the longitudinal axis142of the focal zone122, with the longitudinal axis142having a rectilinear form. In this case, the focal zone122is assigned a single work angle α, for example, by means of which the focal zone122is angled vis-à-vis the first outer side144and/or the second outer side146. In particular, the focal zone122in this exemplary embodiment has the same local direction of extent138throughout, which is to say the local direction of extent138is constant over the entire extent of the focal zone122in particular.

In the exemplary embodiment according toFIGS.12cand12d, the focal zone122has a first portion180and a second portion182, wherein the focal distributions124of the focal zone122are arranged in the first portion180and in the second portion182with a different local direction of extent138in each case. By way of example, the focal zone122in this exemplary embodiment has the same local direction of extent138, respectively throughout, in the first portion180and in the second portion182.

In particular, the focal zone122has the same work angle α in the first portion180and in the second portion182, the focal zone122being angled at said work angle in relation to the first outer side144and/or the second outer side146. In particular, the smallest angle between the respective local direction of extent138of the first portion180and of the second portion182is twice as large in that case as the work angle α.

The longitudinal axis142of the focal zone122, along which the focal distributions124are arranged, need not necessarily have a rectilinear form. By way of example, provision can be made for the longitudinal axis142to have a curved form at least in certain portions. By way of example, in the examples shown inFIGS.12eand12f, the focal zone122has a curved form throughout.

By way of example, the focal zone122then has a varying local direction of extent138, which is to say the local direction of extent138of the focal zone122is respectively different at different positions of the focal zone122and/or at different focal distributions124of the focal zone122.

FIGS.12b,12d, and12feach show a phase distribution assigned toFIGS.12a,12c, and12e, respectively, of beams output coupled from the beam splitting element112, wherein the assigned grayscale value scale ranges from white (a phase of +pi) to black (a phase of −pi).

The apparatus100according to embodiments of the invention operates as follows:

To carry out the laser machining, the material102of the workpiece104is exposed to the focal zone122and the focal zone122is moved relative to the workpiece104and through the material102thereof in the advancement direction129.

In this case, the material102is in particular a material transparent or partly transparent to a wavelength of beams from which the focal zone122is formed. For example, the material102is a glass material.

By way of example, the focal zone122is moved through the material102of the workpiece104along a predefined machining line184and/or machining surface. The machining line184may for example have straight and/or curved portions.

By exposing the material102to the focal zone122, material modifications156which are arranged along the longitudinal axis142of the focal zone122are formed in the material102(FIG.5andFIG.13a). As a result, modification lines186at which the material modifications156are arranged are formed in the material, with these modification lines186in particular having a form corresponding to the longitudinal axis142of the focal zone122. In the example shown inFIG.13a, the modification lines186extend from the first outer side144to the second outer side146.

A plurality of modification lines186which are positioned spaced apart from one another parallel to the advancement direction129are formed on account of the relative motion of the focal zone122vis-à-vis the material102. In particular, this yields an extensive formation of material modifications156in the material102(FIG.13a).

By way of example, spacing of modification lines186adjacent in the advancement direction129can be defined by a suitable choice of a pulse duration of a laser beam, from which the focal zone122is formed, and/or of an advancement speed oriented in the advancement direction129.

In particular, the material modifications156formed along the machining line184and/or machining surface have a reduction in a strength of the material102as a consequence. This makes it possible to separate the material102into two different segments188aand188bafter the material modifications156have been formed on the machining line184and/or machining surface (FIG.13b), for example by applying a mechanical force.

In the example shown, the segment188bis a product piece segment with a desired edge shape. In this case, the segment188ais a residual workpiece segment and/or scrap segment.

Preferably, the material102is exposed to the focal zone122in such a way that the focal zone122penetrates through the material102. By way of example, the focal zone122extends through the material102continuously and/or without interruptions over the entire thickness D of the material102. By way of example, as shown inFIGS.13aand13b, a complete separation of the material over its thickness D can be obtained as a result.

It is also possible to machine an edge region190of the material102by means of the focal zone122(indicated inFIG.13a). By way of example, the focal zone122then extends continuously and/or without interruptions between outer sides of the workpiece104that are oriented at an angle to one another. By way of example, an edge segment can be separated from the workpiece104in the edge region190as a result. As a result, the workpiece104can be beveled and/or chamfered, for example, in the edge region190.

By way of example, the material102of the workpiece104is quartz glass. By way of example, for the purpose of forming the material modifications156as Type I and/or Type II modifications, a laser beam from which the focal distributions124of the focal zone122are formed then has a wavelength of 1030 nm and a pulse duration of 1 ps. Further, a numerical aperture assigned to the focusing optical unit116then is 0.4 and a pulse energy assigned to a single focal distribution124then is 100 nJ.

To form the material modifications156as Type III modifications with otherwise unchanged parameters, the pulse energy assigned to a single focal distribution124is 1000 nJ.