Method and device for laser processing of transparent materials
Invention relates to the field of lasers, particularly to laser processing of transparent materials and can be used for cutting, breaking and other kind of processing of transparent materials, such as glass, chemically strengthened glass, sapphire and other crystalline materials, employing ultrashort pulse asymmetric Gauss-Bessel intensity profile laser beam. Gaussian intensity profile ultrashort pulse laser beam is transformed to asymmetric Gauss-Bessel intensity profile laser beam by inserting an optical element in Gaussian or Gauss-Bessel intensity profile laser beam path. Asymmetry of Gauss-Bessel intensity profile laser beam is set by selecting appropriate material of the optical element and/or parameters of the optical element and/or position of the optical element in the optical beam path in such a manner, that Gauss-Bessel intensity profile laser beam, localized in the workpiece, has an elongated shape in the propagation direction of the laser beam and in the plane, perpendicular to the direction of propagation of said laser beam and induces correspondingly elongated shape damage region in the workpiece. Controlled displacement of the workpiece and the laser beam in respect to each other is performed to create a required number of additional elongated shape damage regions and to arrange them in the workpiece longitudinally one after other along the predefined trajectory forming the cutting and/or breaking plane of the workpiece.
1 . A device for processing a workpiece, comprising:
a laser source for generating a laser beam,
an optical system, for forming a Gauss-Bessel laser beam having a Gauss-Bessel intensity profile from the laser beam and localizing the Gauss-Bessel laser beam in the workpiece to form a damage region in the workpiece along a beam propagation direction, wherein the workpiece is transparent to the Gauss-Bessel laser beam,
a positioning mechanism comprising a first movable stage and a second movable stage controlled by a controller, wherein the first movable stage is coupled to the optical system and the second movable stage is coupled to the workpiece to displace the workpiece and the Gauss-Bessel laser beam with respect to each other, so that a plurality of damage regions are created in a predefined trajectory in order to form a cutting or breaking plane of the workpiece,
wherein an optical element is placed in the optical path of the laser beam or the optical path of the Gauss-Bessel laser beam, wherein the optical element comprises a transparent plate covering the Gauss-Bessel laser beam, the covered portion of the Gauss-Bessel laser beam passing through the transparent plate such that a symmetry of the Gauss-Bessel laser beam is disrupted to form an asymmetric Gauss-Bessel laser beam localized in the workpiece, the asymmetric Gauss-Bessel laser beam having an elongated shape in a plane perpendicular to a laser beam propagation direction and inducing the damage region having an elongated shape in the plane perpendicular to the laser beam propagation direction, and
wherein the positioning mechanism is configured to perform a controlled displacement of the workpiece and the Gauss-Bessel laser beam relative to each other such that the damaged regions having the elongated shape from among the plurality of damage regions are induced longitudinally one after another along the predefined trajectory of the cutting or breaking plane in the workpiece.
2 . The device of claim 1 , wherein the laser source generates an ultrashort pulse Gaussian laser beam and directs it to the optical system, wherein a laser pulse duration and a laser pulse energy of the ultrashort pulse Gaussian laser beam is selected to exceed a material damage threshold of the workpiece.
3 . The device of claim 1 , wherein the transparent plate is arranged to create the asymmetric Gauss-Bessel laser beam by introducing an additional optical path for part of the Gauss-Bessel laser beam with respect to the other part of the Gauss-Bessel laser beam.
4 . The device of claim 1 , wherein the transparent plate is placed in the optical path of the Gauss-Bessel laser beam for partial coverage of the Gauss-Bessel laser beam for splitting the Gauss-Bessel laser beam into asymmetric parts, the asymmetric parts forming the asymmetric Gauss-Bessel laser beam.
5 . The device of claim 1 , wherein the transparent plate is positioned in the optical path of the laser beam or the optical path of the Gauss-Bessel laser beam covering part of the laser beam or the Gauss-Bessel laser beam, where the covered and uncovered parts of the laser beam or the Gauss-Bessel laser beam are symmetrical.
6 . The device of claim 1 , wherein the transparent plate comprises a first zone and a second zone of different thickness, which is placed in the optical path of the laser beam or the optical path of the Gauss-Bessel laser beam such that the laser beam or the Gauss-Bessel laser beam is split into a first part and a second part, where the first part passes through the first zone of the transparent plate and the second part passes through the second zone of the transparent plate.
7 . The device of claim 1 , wherein the transparent plate comprises a first zone and a second zone of different refractive index placed in the optical path of the laser beam or the optical path of the Gauss-Bessel laser beam such that the laser beam or the Gauss-Bessel laser beam is split into a first part and a second part, where the first part passes through the first zone of the plate and the second part passes through the second zone of the plate.
8 . The device of claim 1 , wherein the first movable stage is a rotary stage, to which the optical element is attached, and the second movable stage is a linear motion stage, to which the workpiece is attached, and
wherein the rotary stage and the linear motion stage are controlled by the controller, the controller receiving commands from a computer according to the predefined trajectory of the cutting or breaking plane such that the direction of trajectory of the cutting or breaking plane is controlled by the rotary stage rotating the optical element, and the positioning of the plurality of damage regions in the workpiece at a certain displacement distance is controlled by the linear motion stage moving the workpiece.
9 . The device of claim 1 , wherein the first movable stage is a rotary stage, to which the optical element is attached, and the second movable stage is a linear motion stage, to which the workpiece is attached, the positioning mechanism comprising:
a Dove prism attached to the rotary stage and placed behind the optical element along the direction of propagation of the laser beam or the Gauss-Bessel laser beam, and
wherein the rotary stage and linear motion stage are controlled by the controller, the controller receiving commands from a computer according to the predefined trajectory of the cutting or breaking plane such that the direction of trajectory of the cutting or breaking plane is controlled by the rotary stage rotating the Dove prism and the positioning of the plurality of damage regions in the workpiece at a certain displacement distance is controlled by the linear motion stage moving the workpiece.
10 . The device of claim 9 , further comprising a quarter wave phase plate placed between the optical element and the Dove prism along the direction of propagation of the laser beam or the Gauss-Bessel laser beam, the quarter wave phase plate changing the polarization state of the laser beam to circular.
11 . The device of claim 9 , further comprising a half wave phase plate placed between the optical element and the Dove prism along the direction of propagation of the laser beam or the Gauss-Bessel laser beam.
12 . The device of claim 1 , wherein the transparent plate comprises a planar input surface opposite a planar output surface.
13 . The device of claim 1 , wherein
the optical element is a first optical element placed in the optical path of the laser beam or the optical path of the Gauss-Bessel laser beam;
a second optical element is placed in the optical path of the laser beam or the optical path of the Gauss-Bessel laser beam; and
the first optical element is disposed between the laser source and the second optical element.
14 . The device of claim 13 , wherein the first optical element is configured to convert a symmetric Gaussian laser beam having a symmetric Gaussian intensity profile to an asymmetric Gaussian laser beam having an asymmetric Gaussian intensity profile and the second optical element is configured to convert the asymmetric Gaussian laser beam to the asymmetric Gauss-Bessel laser beam having the asymmetric Gauss-Bessel intensity profile.
15 . The device of claim 13 , wherein the first optical element is configured to convert a symmetric Gaussian laser beam having a symmetric Gaussian intensity profile to a symmetric Gauss-Bessel laser beam having a symmetric Gauss-Bessel intensity profile and the second optical element is configured to convert the symmetric Gauss-Bessel laser beam to the asymmetric Gauss-Bessel laser beam having the asymmetric Gauss-Bessel intensity profile.
16 . The device of claim 1 , wherein the transparent plate partially covers less than the entire Gauss-Bessel laser beam.
17 . The device of claim 16 , wherein the transparent plate covers half of the Gauss-Bessel laser beam such that covered and uncovered parts of the Gauss-Bessel laser beam are symmetrical.
18 . The device of claim 1 , wherein the intensity profile of the Gauss-Bessel laser beam has a half of a cone angle in the range from 4 to 45 degrees.
19 . A method for processing transparent materials comprising the steps of:
generalizing a Gauss-Bessel intensity profile laser beam,
localizing the Gauss-Bessel intensity profile laser beam in a workplace, wherein the material of the workplace is transparent to the Gauss-Bessel intensity profile laser beam, to form a damage region in the workpiece, the damage region extending a distance in the direction of propagation of the laser beam,
performing controlled displacement of the workpiece and the laser beam with respect to each other to create additional adjacent damage regions in a predefined trajectory in order to form a cutting and/or breaking plane of the workpiece,
wherein the generating a Gauss-Bessel intensity profile laser beam comprises generating an asymmetric Gauss-Bessel intensity profile laser beam by placing an optical element in an optical path of the beam, and
wherein the asymmetry of the asymmetric Gauss-Bessel intensity profile laser beam is set by selecting a material of the optical element and/or parameters of the optical element and/or position of the optical element in the optical laser beam path in order to form an elongated shape of the Gauss-Bessel intensity profile laser beam in the plane perpendicular to the direction of propagation of the laser beam, the elongated shape having a longer axis and a shorter axis, the Gauss-Bessel intensity profile laser beam inducing a correspondingly elongated damage region in the workpiece, and
wherein the controlled displacement of the workpiece and the asymmetric Gauss-Bessel intensity profile laser beam relative to each other is performed in such a manner that a plurality of the induced elongated shape damage regions are arranged in the workpiece longitudinally one after other along the predefined trajectory of the cutting and/or breaking plane.
20 . The method of claim 19 , wherein the Gauss-Bessel intensity profile laser beam is generated from a Gaussian intensity profile laser beam.
21 . The method of claim 19 , wherein the elongated damage region has an elliptical shape.
22 . The method of claim 19 , wherein the elongated shape damage regions in the plurality are positioned at a distance dx from another along the trajectory of the cutting and/or breaking plane, and
wherein the distance dx between the centers of adjacent elongated shape damage regions is in the range from 0.5 to 15 times a length of the elongated shape damage region along the longer axis, and
wherein the length of the elongated shape damage region along the longer axis from 1 μm to 20 μm, and the length of the elongated shape damage region along the axis is from 1.3 to 5 times larger than a length of the elongated shape damage region along the shorted axis.
23 . The method of claim 19 , wherein the workpiece is selected from the group consisting of glass, chemically strengthened glass, sapphire or other crystalline material.
24 . The method of claim 19 , wherein the distance of the damage region included in the workplace along the laser beam propagation direction is shorter than the thickness of the workpiece and is not adjoined to any of the surfaces of the workpiece, or the distance of the damage region coincides with the thickness of the workpiece and is adjoined to both of the surfaces of the workpiece, or the distance pf the damage region is shorter than the thickness of the workpiece and is adjoined to only one of the surfaces.