System for asymmetric optical beam shaping

An optical system for beam shaping of a laser beam for processing a material, which is transparent for the laser beam, by modifying the material in a focus zone that is elongated in a propagation direction of the laser beam and in a further direction transverse to the propagation direction, the optical system comprising;

• an optical element configured to shape the focus zone in the propagation direction and to shape the focus zone in a further direction transverse to the propagation direction, wherein the optical element comprises a diffractive optical beam shaping element configured to impose one or more phase distributions on the laser beam;
• a further optical element positioned downstream of the optical element and configured to shape the focus zone in the further direction transverse to the propagation direction, wherein the further optical element is configured as a beam aperture, such that the focus zone comprises a plurality of intensity maxima, which are transverse flattened in a flattening direction and form a transverse sequence of asymmetric intensity maxima in a sequence direction;
• a near field optics arranged downstream of the optical element at a beam shaping distance and configured to focus the laser beam into the focus zone,
• wherein at least one phase distribution of the one or more phase distributions causes a virtual optical image of an elongated focus zone to be located upstream of the diffractive optical beam shaping element, or causes a real optical image of the elongated focus zone to be located after the diffractive optical beam shaping element,
• the beam shaping distance corresponds to a propagation length of the laser beam, within which the one or more phase distributions transforms the transverse input intensity profile into a transverse output intensity profile in a region of the near field optics, and the transverse output intensity profile has, in comparison with the input intensity profile, at least one local maximum lying outside of a beam axis, and
• the beam aperture delimits the laser beam such that imaging of the attributed optical images results in an asymmetric transverse intensity distribution in the elongated focus zone that comprises the plurality of intensity maxima.

An optical system for beam shaping of a laser beam for processing a material, which is transparent for the laser beam, by modifying the material in a focus zone of the laser beam that is elongated in a propagation direction of the laser beam and in a further direction transverse to the propagation direction, the optical system comprising;

• an optical element comprising a diffractive optical beam shaping element configured to impose a plurality of phase distributions on the laser beam,
• wherein the optical element is configured to shape the focus zone in the propagation direction and to shape the focus zone of the laser beam in the further direction transverse to the propagation direction;
• and
• a further optical element positioned downstream of the optical element and configured to shape the focus zone in the further direction transverse to the propagation direction, wherein the further optical element is configured as a beam aperture, such that the focus zone comprises a plurality of intensity maxima, which are transverse flattened in a flattening direction and form a transverse sequence of asymmetric intensity maxima in a sequence direction
• a near field optics arranged downstream of the optical element at a beam shaping distance and configured to focus the laser beam into the focus zone, wherein
• at least one phase distribution of the plurality of phase distributions causes a virtual optical image of an elongated focus zone to be located upstream of the diffractive optical beam shaping element, or causes a real optical image of an elongated focus zone to be located after the diffractive optical beam shaping element,
• the beam shaping distance corresponds to a propagation length of the laser beam, within which the plurality of phase distributions transforms the transverse input intensity profile into a transverse output intensity profile in a region of the near field optics, and the transverse output intensity profile has, in comparison with the input intensity profile, at least one local maximum lying outside of a beam axis.

A laser processing machine for processing a material with a laser beam by modifying the material in a common focus zone, which is elongated in a propagation direction of the laser beam, and the material is transparent for the laser beam, comprising:

• a laser beam source;
• an optical system comprising
• an optical element configured to shape a focus zone of a laser beam from the laser beam source in a propagation direction of the laser beam, wherein the optical element comprises a diffractive optical beam shaping element configured to impose one or more phase distributions on the laser beam and to shape the focus zone in a direction transverse to the propagation direction and configured as a beam shaping element, and
• a near field optics arranged downstream of the optical element at a beam shaping distance and configured to focus the laser beam into the focus zone,
• wherein at least one phase distribution of the one or more phase distributions causes a virtual optical image of an elongated focus zone to be located upstream of the diffractive optical beam shaping element, or causes a real optical image of an elongated focus zone to be located after the diffractive optical beam shaping element,
• the beam shaping distance corresponds to a propagation length of the laser beam, within which the one or more phase distributions transforms the transverse input intensity profile into a transverse output intensity profile in a region of the near field optics, and the transverse output intensity profile has, in comparison with the input intensity profile, at least one local maximum lying outside of a beam axis, and
• the beam aperture delimits the laser beam such that imaging of the attributed optical images results in an asymmetric transverse intensity distribution in the elongated focus zone that comprises the plurality of intensity maxima;
• and
• a control unit for orienting a transverse asymmetric intensity distribution with respect to a preferred direction, wherein the control unit is configured to set a rotation angle of the beam aperture with respect to the beam axis of the incident laser beam;
• or
• wherein the control unit is configured for the alignment of the optical system and the work-piece such that a preferred direction of the workpiece processing, which is given by the asymmetric beam profile, can be adapted to the feed direction.

A method for material processing of a material, which is transparent to a laser beam, by generating pulsed laser beam modifications that are formed in an asymmetric manner transverse to a propagation direction of the laser beam, the method comprising:

• generating the pulsed laser beam modifications by beam shaping each laser beam pulse, of a plurality of laser beam pulses, to form, for each laser beam pulse of the plurality of laser beam pulses, an elongated asymmetric focus zone in the material, wherein the elongated asymmetric focus zone is configured such that it comprises a plurality of intensity maxima, which are transverse flattened in a flattening direction and form a transverse sequence of asymmetric intensity maxima in a sequence direction, wherein the flattening direction and the sequence direction each are transverse to the propagation direction;
• positioning the elongated asymmetric focus zone in the material;
• moving the material and the elongated asymmetric focus zone relative to each other in or across to the flattening direction or in or across to the sequence direction;
• guiding a crack for separating or preparing the separation of the material, wherein successive pulsed laser beam modifications are displaced with respect to each other along a relative movement direction between the laser beam propagation direction and the material, and each of the pulsed laser beam modifications has a preferred direction in a crack formation, wherein the preferred direction depends on the material or laser beam parameters, either across to or longitudinal with respect to a length axis relating to the largest transverse extent of the pulsed laser beam modification, and the relative movement direction and the preferred direction are adapted to each other;
• generating the transverse sequence of asymmetric intensity maxima in a feed direction, an intensity of the transverse sequence of asymmetric intensity maxima is lower on a feed side of the transverse sequence than on a backside of the transverse sequence;
• and
• performing the relative movement in the feed direction, so that, at the backside, a stronger development of a preferred direction in the crack formation is present than at the feed side, so that a crack formation towards the previously created modification is initiated, but an advancing crack formation is suppressed, such that a crack formation to a previously created modification is initiated already by the creation of the modification.