Systems and methods for processing transparent materials

Abstract

Disclosed is a system for processing a transparent material, the system comprising: a laser source configured to generate a laser beam including bursts of laser pulses, the pulses defined by a pulse energy and a pulse repetition rate; one or more focusing elements configured to receive the laser beam and direct the laser beam toward the transparent material, the focusing elements comprising a variable focal length configured to be changed from a first focal length to a second focal length along a focusing direction; and a first controller configured to oscillatorily change the variable focal length between the first focal length and the second focal length at a desired control frequency.

Description

[Technical Field]

[0001] The present disclosure relates generally to systems and methods for processing transparent materials. More particularly, the present disclosure relates to processing transparent materials using a laser source. Most particularly, the present disclosure relates to using a laser source to form a filament inside the transparent material such that, for example, the transparent material is split into two separate portions. [Background technology]

[0002] In the field of laser processing, it is known to process transparent materials using lasers. For example, U.S. Patent No. 5,949,623 discloses a method for generating so-called filamentary damage, which creates submicrometer hollow channels in the volume of a glass sheet element. Filamentary damage, or simply filaments, is generated by weakly focusing a laser pulse with high intensity and short duration so that the pulse can self-focus due to the nonlinear Kerr effect resulting in the formation of a plasma. U.S. Patent No. 5,949,623 discloses a method in which a laser is focused to a given focal depth inside a transparent material with a thickness greater than 2 mm while the laser is scanned over the material. The first scan generates damage at a depth smaller than the thickness of the transparent material, so the transparent material is not separated into two parts. For this reason, one or more repeat scans are introduced, each with a different focal depth, thereby finally separating the transparent material into two parts. However, as pointed out in U.S. Patent No. 5,449,623, a problem that can arise when repeatedly scanning a laser beam at different focal depths is that the damage at the depth of the volume of the glass element is not ideally aligned.

[0003] A solution to this problem is given in US Pat. No. 5,629,999, by displacing the point of incidence of the laser pulse on the glass element across its surface along an offset line slightly spaced from the separation line, but this solution is relatively complex.

[0004] The prior art described in US Pat. No. 5,629,999 further describes the processing of transparent thin materials, such as less than 2 mm, by filamentation. Furthermore, the processing of multi-layer or laminated glass by filamentation is further described in US Pat. No. 5,629,499, where the method for separating laminated glass is similar to the method for separating thick glass substrates as described in US Pat. No. 5,629,499, since repeated scans with different focal depths corresponding to the layer positions are used.

[0005] Because multiple scans are problematic, U.S. Patent No. 5,629,999 discloses a solution using a single scan over a glass substrate or laminated glass, particularly by using an extended laser interaction focal volume, i.e., an extended depth of field. The extended depth of field may be provided by generating a Bessel beam, for example, by using an axicon. Alternatively, the extended depth of field may be provided by generating an Airy beam, for example, by using a spatial light modulator (SLM). However, using an extended depth of field by generating a Bessel or Airy beam requires very high laser power, which, as pointed out in U.S. Patent No. 5,629,999, can damage the SLM, for example, and therefore be problematic.

[0006] Furthermore, as pointed out in [1], using an Airy beam also leads to varying side lobes within the focal volume, which causes surface damage and undesirable effects, particularly asymmetric laser modifications of glass sheets that increase with pulse peak intensity. To solve this problem, D. Sohr et al. proposed tilting the Airy beam by using a lateral offset on a phase mask. However, this solution is relatively complicated.

[0007] Therefore, there is a need to provide an uncomplicated solution to a system and method for processing transparent materials. Furthermore, it would be desirable to provide a system and method for processing transparent materials in a single scan without the above-mentioned problems. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] US Patent Application Publication No. 2018 / 0134606 [Patent Document 2] US Patent Application Publication No. 2013 / 0126573 [Patent Document 3] US Patent Application Publication No. 2016 / 0016257 [Non-patent literature]

[0009] [Non-Patent Document 1] Sohr, D. et al., "Using airy beams for combined glass cutting and edge shaping," SPIE LASE, January 2022, San Francisco, USA Summary of the Invention [Problem to be solved by the invention]

[0010] It is an object of the present disclosure to provide an uncomplicated solution to systems and methods for processing transparent materials. It is a further object of the present disclosure to provide a system and method for processing transparent materials in a single scan. [Means for solving the problem]

[0011] These and other objects have been solved by the systems and methods for processing transparent materials as defined in the claims and described below in this disclosure. The present disclosure generally provides a system for processing transparent materials, the system including: a laser source configured to generate a laser beam including bursts of laser pulses, the pulses defined by a pulse energy and a pulse repetition rate; one or more focusing elements configured to receive the laser beam and direct the laser beam toward the transparent material, the focusing elements comprising a variable focal length configured to be changed from a first focal length to a second focal length along a focusing direction; and a first controller configured to oscillatorily change the variable focal length between the first focal length and the second focal length at a desired control frequency.

[0012] The present disclosure further generally provides a method for processing a transparent material, the method comprising: generating a laser beam including bursts of laser pulses using a laser source, the pulses defined by pulse energy and a pulse repetition rate; directing the laser beam toward the transparent material using one or more focusing elements configured to receive the laser beam, the focusing elements comprising a variable focal length configured to be changed from a first focal length to a second focal length along a focusing direction; and varying the variable focal length oscillatorily between the first focal length and the second focal length at a desired control frequency using a first controller.

[0013] The variable focal length changing process may be faster than vibratingly changing the transparent material, for example due to the mass of the transparent material. Nevertheless, the present disclosure also generally provides a system for processing transparent materials, the system comprising: a laser source configured to generate a laser beam including bursts of laser pulses, the pulses defined by a pulse energy and a pulse repetition rate; one or more focusing elements configured to receive the laser beam and direct the laser beam towards the transparent material, the transparent material being on a movable stage configured to be varied from a first position to a second position along a stage direction; and a first controller configured to vary the movable stage, wherein the transparent material is also oscillatorily varied between the first and second positions at a desired control frequency.

[0014] The present disclosure further generally provides a method for processing a transparent material, the method comprising: generating a laser beam using a laser source, the laser beam including bursts of laser pulses, the pulses defined by a pulse energy and a pulse repetition rate; directing the laser beam using one or more focusing elements configured to receive the laser beam toward the transparent material, the transparent material being on a movable stage configured to be varied from a first position to a second position along a stage direction; and using a first controller, oscillatory varying the movable stage, and therefore the transparent material, between the first and second positions at a desired control frequency.

[0015] In a first more detailed aspect of the present disclosure, there is provided a system for processing transparent materials, comprising: a laser source configured to generate a laser beam comprising bursts of laser pulses, the pulses defined by a pulse energy and a pulse repetition rate; one or more focusing elements configured to receive the laser beam and direct the laser beam towards the transparent material, the focusing elements comprising a variable focal length configured to be changed from a first focal length to a second focal length along a focusing direction, thereby: i. at the first focal length, when a first beam waist is formed relative to the transparent material, the pulse energy is configured to form a first intensity that causes the first beam waist to form a first Kerr lens effect inside the transparent material, thereby forming a first filament at a first Kerr lens location inside the transparent material; ii. one or more focusing elements, wherein at the second focal length, when a second beam waist is formed relative to the transparent material, the pulse energy is determined to form a second intensity that causes the second beam waist to form a second Kerr lens effect inside the transparent material, thereby forming a second filament at a second Kerr lens position inside the transparent material.

[0016] The system further includes a first controller configured to oscillatorily vary the variable focal length between the first focal length and the second focal length at a desired control frequency, thereby causing the first filament and the second filament to oscillatorily form inside the transparent material.

[0017] In a second more detailed aspect of the present disclosure, there is provided a method for processing a transparent material, the method comprising: generating a laser beam using a laser source comprising a burst of laser pulses, the pulses defined by a pulse energy and a pulse repetition rate; directing the laser beam towards the transparent material using one or more focusing elements configured to receive the laser beam, the focusing elements comprising a variable focal length configured to be changed from a first focal length to a second focal length along a focusing direction, thereby i. at the first focal length, when a first beam waist is formed relative to the transparent material, the pulse energy is configured to form a first intensity that causes the first beam waist to form a first Kerr lens effect inside the transparent material, thereby forming a first filament at a first Kerr lens location inside the transparent material; ii. at the second focal length, when a second beam waist is formed relative to the transparent material, the pulse energy is determined to form a second intensity that causes the second beam waist to form a second Kerr lens effect inside the transparent material, thereby forming a second filament at a second Kerr lens position inside the transparent material.

[0018] The method further includes using a first controller to oscillatorily vary a variable focal length between the first focal length and the second focal length at a desired control frequency, whereby the first filament and the second filament are oscillatorily formed inside the transparent material.

[0019] The oscillatory variable focal length variation for the first and second embodiments of the present disclosure has been found to be a better solution for processing transparent materials compared to using a non-variable focal length, as described in the prior art, e.g., with a small depth of field involving multiple scans with different depths per scan, or an extended depth of field involving a single scan using a Bessel beam or an Airy beam.

[0020] First, the present disclosure provides a system and method that is relatively easy to use, as oscillatory changes in the variable focal length can provide ideal alignment of damage at depth within the volume of the glass element.

[0021] Second, the present invention provides an oscillatory change in the variable focal length, which allows a single scan on the transparent material to be sufficient to process the transparent material. Therefore, the present disclosure provides an efficient solution for processing transparent materials. However, multiple scans may be used.

[0022] Third, the present disclosure allows oscillatory variation of the variable focal length to provide that lower laser powers can be used instead of higher laser powers, thereby not damaging the SLM, for example, if one is used. For this reason, and because lower power lasers are expected to be less expensive than higher power lasers, the present disclosure provides cost-effective systems and methods for processing transparent materials.

[0023] Fourth, the present disclosure has demonstrated that the oscillatory change in variable focal length, when processed, laser cutting or laser cleaving processed the transparent material such that further processing, such as mechanically tapping or breaking the material, was not required.

[0024] Thus, it has been found that the systems and methods of the present disclosure not only overcome the problems of the prior art, but also provide several advantages as discussed above. Further embodiments and advantages of the present disclosure are disclosed below.

[0025] The above and / or additional objects, features, and advantages of the present disclosure will be further described in the following illustrative and non-limiting detailed description of embodiments of the present disclosure, with reference to the accompanying drawings. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a diagram showing an example of a conventional technique. [Figure 2] 1 illustrates an example of a laminated glass substrate processed in accordance with the present disclosure. [Figure 3] FIG. 1 illustrates another example of a laminated glass substrate that can be fabricated in accordance with the present disclosure. [Figure 4] FIG. 1 illustrates an example of how a laminated glass substrate may be processed in accordance with the present disclosure, particularly so that the transparent material is processed along two directions. [Figure 5] FIG. 5 illustrates another example of how the same laminated glass substrate described in connection with FIG. 4 can be processed in accordance with the present disclosure. [Figure 6] 1A and 1B are diagrams illustrating examples of light-collecting elements according to the present disclosure. [Figure 7] FIG. 1 is a diagram showing an example of operation of a system according to the present disclosure. [Figure 8] 1A and 1B show the results of processing a transparent material according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0027] The formation of filaments is described in the background of this disclosure. Prior art may be consulted to learn more about filamentation. However, as described in U.S. Patent No. 5,529,299, the filamentation process is believed to rely primarily on two competing processes. First, the spatial intensity profile of the laser pulse acts like a focusing lens due to the nonlinear optical Kerr effect. This causes the beam to self-focus, resulting in an increase in peak intensity. This effect is limited and balanced by increasing diffraction as the diameter decreases, until a stable beam waist diameter is reached that can propagate many times longer distances than would be expected from a simple calculation of the confocal beam parameters (or depth of focus) from this spot size.

[0028] At high peak intensities, multiphoton ionization, field ionization, and electron impact ionization of the medium begin, creating a low-density plasma in the high-intensity portion of the laser beam. This plasma temporarily reduces the refractive index in the center of the beam path, defocusing the beam and destroying the filament. The dynamic balance between Kerr effect self-focusing and plasma defocusing can result in multiple refocused laser-interacting filaments, but also in the formation of a stable filament, sometimes called a plasma channel.

[0029] The formation of a plasma channel according to the prior art is shown in FIG. 1 of the present disclosure. Here, a laser source is configured to generate a laser beam 1. The laser beam is defined by pulse energy. A focusing element 2 is further configured to receive the laser beam 1 and direct the laser beam 1 toward a transparent material 3. Furthermore, a beam waist 4 is formed relative to the transparent material 3. As shown in FIG. 1, the pulse energy is defined such that the beam waist 4 forms an intensity that causes a first Kerr lens effect 5 to form inside the transparent material 3, thereby forming a first filament 6 at a first Kerr lens location inside the transparent material 3. The formation of the first filament 6 is shown enlarged in an enlarged circle, with the Kerr lens effect 5 circled in the figure, indicating that multiple refocused laser interaction filaments 7 are also formed. These filaments 7 form plasma channels 8 within the transparent material 3, and the filamentation process stops at the bottom of the transparent material 3 because it does not continue in air.

[0030] In accordance with the present disclosure, the inventors of the present disclosure have discovered that by oscillatorily varying the variable focal length, i.e., through a transparent material, a filament can be repeatedly formed at a desired location, for example, which can depend on the first and second focal lengths.

[0031] Thus, in one embodiment of the generally disclosed system and method, the variable focal length is configured to be changed from a first focal length to a second focal length along the focusing direction, and the pulse energy is configured such that at the first focal length, when a first beam waist is formed relative to the transparent material, the pulse energy forms a first intensity that causes the first beam waist to form a first Kerr lens effect inside the transparent material, thereby forming a first filament at a first Kerr lens position inside the transparent material; and at the second focal length, when a second beam waist is formed relative to the transparent material, the pulse energy forms a second intensity that causes a second beam waist to form a second Kerr lens effect inside the transparent material, thereby forming a second filament at a second Kerr lens position inside the transparent material.

[0032] The reasons why it is advantageous to repeatedly or oscillatorily form the first and second filaments may seem counterintuitive when reading the prior art, especially since it describes how the plasma channels are formed and therefore the process does not need to be repeated.

[0033] However, the advantages of doing so will become apparent below. First and second controllers In one embodiment of the present disclosure, the desired control frequency is lower than the pulse repetition rate. This embodiment can ensure that one or more additional filaments are generated between the first and second filaments. This is advantageous when the first and second focal lengths are separated by a relatively long distance, since some filaments can form unseparated or continuous filament channels along the relatively long distance. A relatively long distance is understood here to be a distance longer than the size of the filament. Typically, the size of the filament is on the order of 1 micrometer. This embodiment can be used, for example, to process transparent materials, for example, when the objective is to form a continuous filament channel within the transparent material so that the transparent material separates into two parts. One example of such a process can be glass cutting or glass breaking, where the transparent material is glass or a layer of glass, i.e., a laminated glass substrate.

[0034] With respect to glass cutting or glass breaking of laminated glass, the inventors of the present disclosure have discovered that when one or more additional filaments are generated between the first and second filaments as described above, and the first and second filaments are formed in two or more different layers of the laminated glass substrate, conditions exist for the Kerr lens effect due to vibration along the light focusing direction, thereby initiating a Kerr lens in each layer of the laminate.

[0035] In view of the above, the inventors of the present disclosure have discovered a system and method for processing clear glass, particularly laminated glass substrates, that allows the Kerr lens effect to continue at each layer without the need to pass a beam through a first layer, then focus the beam on the next layer, pass the beam through the next layer, and so on.

[0036] Instead, by oscillating the focal length in accordance with the present disclosure, the beam is simply scanned across the transparent body in a single scan. In one embodiment, the single scan may be performed in stages, with movements or steps along the transparent material occurring after, for example, half or full periods. However, in a preferred embodiment, the single scan is performed continuously, as described in more detail below.

[0037] Furthermore, in view of the above, the inventors of the present disclosure have also discovered systems and methods for processing transparent glass, particularly laminated glass substrates, that can continue the Kerr lens effect at each layer without the need for an extended depth of focus such as that formed by a Bessel beam or an Airy beam, and therefore without the need for high laser power.

[0038] An example of a laminated glass substrate being processed in accordance with the present disclosure is shown in Figure 2. In view of the present disclosure, Figure 2 illustrates a method of processing a transparent material 3, in this example in the form of a laminated glass substrate 3. The method includes: generating a laser beam 1 comprising bursts of laser pulses using a laser source (not shown), the pulses being defined by a pulse energy and a pulse repetition rate; directing the laser beam 1 towards a transparent material 3 using a focusing element 2 configured to receive the laser beam 1, the focusing element having a variable focal length configured to be changed from a first focal length 9 to a second focal length 10 along a focusing direction 11; i. when a first beam waist 4 is formed relative to the transparent material 3 at a first focal length 9, the pulse energy is set to form a first intensity that causes the first beam waist 4 to form a first Kerr lens effect 5 inside the transparent material 3, thereby forming a first filament 6 at a first Kerr lens position inside the transparent material; ii. At the second focal length 10, when a second beam waist 12 is formed relative to the transparent material, the pulse energy is set so that the second beam waist 12 forms a second intensity that causes a second Kerr lens effect 13 to form inside the transparent material, thereby forming a second filament 14 at a second Kerr lens position inside the transparent material 3.

[0039] The method further comprises using a first controller (not shown) to oscillatorily change the variable focal length between the first focal length 9 and the second focal length 10 at a desired control frequency, whereby the first filament 6 and the second filament 14 are oscillatorily formed inside the transparent material 3.

[0040] Figure 2 shows how the variable focal length changes over time from time t1 to t2. This movement is repeated later (not shown) as the variable focal length changes in an oscillatory manner. In Figure 2, only half a period of oscillation is shown, as the focal length, or more precisely the beam waist (4, 14), changes from the top layer 15 to the bottom layer 16 of the transparent material 3.

[0041] In this example, the desired control frequency is lower than the pulse repetition rate, so in this example an additional filament 17 is created between the first filament 6 and the second filament 14.

[0042] As seen in Figure 2, and as described above, the beam waist (4, 14) varies from the top layer 15 to the bottom layer 16 of the transparent material 3. However, the method does not necessarily have to start from the top layer 15. The starting point may be chosen arbitrarily, and may be, for example, the bottom layer 16.

[0043] FIG. 3 shows another example of a laminated glass substrate being processed according to the present disclosure. Accordingly, FIG. 3 illustrates another example of how the variable focal length varies over time, from time t1 to t2. This movement is repeated later (not shown) as the variable focal length varies in an oscillatory manner. In FIG. 3, only half a period of oscillation is shown, as the focal length, or more precisely, the beam waist (4, 14), varies here from the bottom layer 16 to the top layer 15 of the transparent material 3.

[0044] As seen in Figure 3, and as described above, the beam waist (4, 14) varies from the bottom layer 16 to the top layer 15 of the transparent material 3. However, the method does not necessarily have to start at the bottom layer 16. The starting point may be chosen arbitrarily, for example, at the top layer 15.

[0045] However, the inventors of the present disclosure have discovered that in a preferred embodiment, it is more advantageous to start the method from the bottom layer rather than from the top layer. In other words, the inventors of the present disclosure have discovered that when the focal length is oscillating, i.e., when the filament is formed in a series of alternating upward and downward strokes, it is more advantageous in a preferred embodiment to form the filament only during the upward stroke. Thus, comparing Figures 2 and 3, Figure 3 shows a preferred embodiment in which the method is most efficient.

[0046] The reason for the difference in efficiency may be that the top material layer is unprocessed, so there are no blockages in the intermediate layers, whereby, for example, edges and other defects or material damage can interfere with the focused beam.

[0047] Thus, in a preferred embodiment, the laser source is synchronized with the desired control frequency so that the laser source only generates a beam that includes a burst of laser pulses approximately halfway through the period. For example, a beam shutter may be used to prevent the generation of bursts of laser pulses, and the shutter is synchronized with the desired control frequency. Alternatively, for example, the generation of bursts of laser pulses can be prevented by turning the laser on and off in synchronization with the desired control frequency. When the laser source is synchronized with the desired control frequency so that the laser source only generates a beam that includes a burst of laser pulses approximately halfway through the period, the generation of bursts of laser pulses can be prevented in a preferred embodiment when the focal length is changed to a longer focal length. In other words, the generation of bursts of laser pulses can be prevented in a preferred embodiment when the beam waist is formed on the downstroke.

[0048] In other embodiments, the desired control frequency is set to be near the pulse repetition rate. In a related embodiment, the control frequency may be tuned and / or synchronized to the pulse repetition rate so that a first filament is formed at the top of the transparent material and a second filament is formed at the bottom of the transparent material. This embodiment may be used, for example, to process very thin transparent materials. However, in another related embodiment, the control frequency may also be tuned and / or synchronized to the pulse repetition rate so that the first and second filaments are formed close to each other, for example, between the top and bottom of the transparent material. This embodiment may be used to process specific locations within a transparent material, for example, when the goal is to form a filament within the transparent material so that the transparent material does not separate into two parts. One such example may be ophthalmic surgery, where the transparent material is part of the eye, such as the retina.

[0049] In other embodiments, for example, when the goal is to form a single filament within the transparent material, the desired control frequency is set higher than the pulse repetition rate. In another related embodiment, the control frequency is tuned and / or synchronized to the pulse repetition rate so that the first and second filaments are formed at the same location or at least close to each other, for example, between the top and bottom of the transparent material. This embodiment may be used to process specific locations within a transparent material, for example, when the goal is to form a filament within the transparent material so that the transparent material does not separate into two parts. One such example may be ophthalmic surgery, where the transparent material is a part of the eye, such as the retina.

[0050] In one embodiment of the present disclosure, the desired control frequency is 1 Hz to 1000 Hz. The desired control frequency may depend on the purpose and / or the transparent material. In some embodiments, the desired control frequency is preferably 20 Hz to 800 Hz. In other embodiments, the desired control frequency is more preferably 30 to 700 Hz, such as around 50 to 150 Hz, or around 130 Hz.

[0051] In most embodiments, the system further comprises a second controller configured to move the focusing element along a separation direction different from the focusing direction such that the transparent material is processed along two directions, and / or to move the transparent material along a separation direction different from the focusing direction such that the transparent material is processed along two directions.

[0052] FIG. 4 illustrates an example of how a laminated glass substrate can be processed according to the present disclosure, specifically, as described above, processing a transparent material along two directions. FIG. 4 shows the results of a computer simulation, with several input parameters used in the simulation. First, the transparent material 3 is selected to be in the form of a laminated glass substrate having 10 layers of glass, each separated by a layer of air. The total thickness of the laminated glass substrate is approximately 2.5 mm. According to the present disclosure, the pulses generated by the laser source are defined by pulse energy and pulse repetition rate, which in this example is 10,000 Hz. Furthermore, according to the present disclosure, the variable focal length is configured to be changed from a first focal length to a second focal length along the focusing direction 11, which in this example is along the Z axis. According to the present disclosure, the variable focal length is oscillatory changed between the first focal length and the second focal length at a desired control frequency, which in this example is set to 125 Hz. Therefore, in this example, the desired control frequency is lower than the pulse repetition rate.

[0053] Furthermore, according to the presently described embodiment, the focusing element moves along a separation direction different from the focusing direction, with the separation direction 18 in this example being along the X-axis, so that the transparent material 3 is processed along two directions. Thus, cutting or breaking, as provided by filamentation formation, occurs along two directions, namely along the X-axis and the Z-axis, and thus in the XZ plane. Furthermore, in this example, the focusing element moves along the separation direction 18 at a desired speed, which in this example is set to 0.01 m / s.

[0054] Using these input parameters, it can be seen from FIG. 4 that the vibration pattern 19 is aligned with the X axis due to movement along the X direction, and in this example the period of the vibration pattern 19 is such that it machines, or cuts, approximately 0.5 micrometers of the laminated glass substrate along the X axis.

[0055] The vibration pattern 19 includes several dots, each representing a laser pulse and thus a location where a filament (6, 14, 17) will be formed. As shown in FIG. 4, each dot has a certain diameter. However, this diameter does not represent the actual (real-world) dimensions of the filament. As previously mentioned, each filament has a diameter of approximately 1 micrometer. Therefore, since the period of the vibration pattern cuts 0.5 micrometers of the laminated glass substrate along the X-axis, the filaments will overlap in an actual (real-world) laminated glass substrate. For this reason, vibrational filament formation, according to the present disclosure, cuts through the laminated glass substrate 3 in a single scan, particularly along the X-axis.

[0056] Thus, by having a second controller configured to move the focusing element along a separation direction different from the focusing direction so that the transparent material is processed along two directions, and / or to move the transparent material along a separation direction different from the focusing direction so that the transparent material is processed along two directions, an efficient system and / or method for processing transparent material is provided.

[0057] As shown in the above example, there is significant overlap of filaments along both the X and Z axes in the laminated glass substrate. It is clear from FIG. 4 that there are multiple filaments per layer, which may not be required. Therefore, the process may be further optimized to reduce filament overlap and / or for specific transparent materials. In particular, the pulse repetition rate, control frequency, and desired speed of moving the focusing element and / or speed of moving the transparent material may be adjusted to optimize the methods and / or systems according to the present disclosure.

[0058] To process laminated glass substrates having multiple glass layers, the inventors of the present disclosure have discovered that the laser beam can be configured to form two or more pulses per layer in preferred embodiments.

[0059] Under such circumstances, the first pulse can set up a waveguide channel in the glass layer, which then spatially compresses the laser pulse to create a plasma, thereby initiating cracking of the glass layer.

[0060] In a preferred embodiment, the pulse repetition rate and desired control frequency are selected to form two or more pulses per layer. In another preferred embodiment, the desired speed at which the focusing element is moved and / or the speed at which the transparent material is moved is selected to be dependent on the control frequency, and / or the beam waist, and / or the filament size.

[0061] In yet another preferred embodiment, the desired speed at which the focusing element is moved and / or the speed at which the transparent material is moved is selected to be 0.01 m / s or greater, preferably 0.1 m / s or greater, most preferably 1 m / s or greater.

[0062] FIG. 5 shows another example of how the same laminated glass substrate described in connection with FIG. 4 can be processed according to the present disclosure, particularly where the transparent material is processed along two directions, but with several different input parameters. According to the present disclosure, pulses generated by the laser source are defined by pulse energy and pulse repetition rate. In this example, the pulse repetition rate is 500,000 Hz, i.e., 50 times the pulse repetition rate of the previous example. As in the previous example, according to the present disclosure, the variable focal length is configured to be changed from a first focal length to a second focal length along the focusing direction 11, which in this example is along the Z axis. According to the present disclosure, the variable focal length is changed to oscillate between the first focal length and the second focal length at a desired control frequency, which in this example is set to 1000 Hz, i.e., 8 times the control frequency of the previous example. Also in this example, the desired control frequency is lower than the pulse repetition rate.

[0063] Furthermore, according to the embodiment just described, the focusing element moves along a separation direction different from the focusing direction, as in the previous example, such that the transparent material 3 is processed along two directions, with the separation direction 18 in this example being along the X-axis. Thus, cutting or breaking, as provided by filamentation formation, occurs along two directions, namely along the X-axis and the Z-axis, and thus in the XZ plane. Furthermore, in this example, the focusing element moves along the separation direction 18 at a desired speed, which in this example is set to 1 m / s, i.e., 100 times faster than the speed in the previous example.

[0064] With these input parameters, it can be seen from FIG. 5 that the vibration pattern 19 is along the X axis due to the movement along the X direction, and in this example the period of the vibration pattern 19 is such that it machines or cuts about 6 micrometers of the laminated glass substrate along the X axis, i.e. 12 times more than in the previous example.

[0065] As the desired control frequency and pulse repetition rate increase, there are dozens of laser pulse impingements per glass layer, i.e., along the Z axis. For this reason, there can be a high amount of filament overlap along the Z axis. Therefore, the example shows that the pulse repetition rate and desired control frequency are selected to create two or more pulses per layer. However, because the period of vibration pattern 19 processes approximately 6 micrometers of the laminated glass substrate along the X axis, there may be no filament overlap along the X axis, for example, in the top and bottom layers, and therefore a desired speed of 1 m / s may not provide cutting or cleaving of all glass layers. This is because the filaments may be on the order of approximately 1 micrometer. However, in some embodiments, the size of the filaments may be greater than 1 micrometer, such as 1 micrometer to 5 micrometers. In such cases, the filaments along the X axis may overlap, and therefore a desired speed of 1 m / s may provide cutting or cleaving of all glass layers.

[0066] In one embodiment, the first controller is further configured to change the variable focal length simultaneously with the second controller moving the focusing element and / or the transparent material along the separation direction, which is more efficient than, for example, changing the variable focal length before and after moving the focusing element and / or the transparent material.

[0067] In another embodiment, the first controller and the second controller operate independently. This embodiment may allow for greater flexibility and ease of programming the controllers. For example, this embodiment may allow a digital motion controller to control the movement of the focusing element and / or the transparent material along the separation direction, and an analog motion controller to control the change in the variable focal length along the focusing direction.

[0068] In some embodiments, the first controller and the second controller are calibrated to each other, for example, such that the starting point (in the real world) is set to be the same for both controllers.

[0069] Light-collecting element In one embodiment, the focusing element comprises one or more optical lenses configured to move along the focusing direction. Such a focusing element 2 is shown, for example, in Figure 6A, where the focusing further comprises a fixed objective lens 20 for focusing the beam 1. In this example, the focusing element 2 is configured to move up and down in an oscillatory manner, as indicated by double arrow 21, thereby forming an oscillating filament (6, 14, 17), also indicated by double arrow 21.

[0070] In another embodiment, the focusing element comprises a deformable lens configured to change its curvature. Such a focusing element 2 is shown, for example, in Figure 6B, where the focusing further comprises a fixed objective lens 20 for focusing the beam 1. In this example, the focusing element 2 is configured to change its curvature in an oscillatory manner, thereby forming an oscillating filament (6, 14, 17) indicated by double arrow 21.

[0071] In yet another embodiment, the focusing element comprises an adaptive beam-shaping element, such as a spatial light modulator (SLM) or an optical microelectromechanical system (MEMS), also known as a MOEMS. An SLM 22 is shown, for example, in FIG. 6C, where the focusing element further comprises a fixed objective lens 20 for focusing beam 1. In this example, the focusing element comprises both focusing lens 2 and SLM 22. In this example, SLM 22 is configured to oscillatorily vary its phase, thereby forming an oscillating filament (6, 14, 17), indicated by double arrow 21. The SLM may be in a variety of configurations, some or many of which may be used for the present system and / or method. These configurations may be phase-only, transmission-only, reflection-only, and / or a mixture thereof. In transmission-only or reflection-only configurations, the beam may be shaped, for example, using micromirrors. In phase-only configurations, the beam may be shaped, for example, using liquid crystals. As can be seen in FIG. 6C, the SLM is set up to modulate the phase of the beam, and is a reflection setup. An advantage of using an adaptive beam shaping element such as an SLM is that it is adaptive. Therefore, an adaptive optics element such as an SLM may be used to modify a beam to a desired beam profile. For example, an SLM may be used to generate an Airy beam or a Bessel beam. In one embodiment, the SLM or any other type of adaptive optics is configured to both shape the desired beam profile and oscillatorily change the focal length.

[0072] In most embodiments, the first focal length and the second focal length differ by more than 20 mm, such as more than 2 mm, preferably more than 10 mm, and more preferably more than 50 mm. For example, as seen in both Figures 4 and 5, the focal length difference was 4 mm. In some embodiments, as also shown in Figures 4 and 5, the focal length difference exceeds the thickness of the transparent material. In this manner, for example, the separation of the filaments along the separation direction can be increased to efficiently process the transparent material.

[0073] In some embodiments, the change in focus and its control are managed by an optical encoder in contact with one or more focusing elements, particularly when the focusing elements comprise one or more optical lenses configured to move along the focusing direction.

[0074] In other embodiments, the change in focus and its control are managed by a back focus sensor or triangulation sensor in contact with one or more focusing elements. These embodiments may be advantageous in handling high desired control frequencies.

[0075] In a preferred embodiment, the change and control of the focus is managed in combination with a modulation of the laser beam, which may be such that the irradiance remains constant as the beam moves from a first focus position to a second focus position along the focusing direction. The irradiance of a laser beam, or rather of a laser pulse, is the optical power delivered per unit area.

[0076] The laser beam may be modulated in a particular way, for example, so that the power is low when the focal length is short and the power is high when the focal length is long, in other words, the laser beam may be modulated out of phase with changes in focus in the time domain.

[0077] The change in focus, along with the modulation of the laser beam, may be controlled by the first controller in one embodiment, in this way optimizing the synchronization between focus and laser power.

[0078] As mentioned above, the system for processing transparent materials may be used to process transparent materials, for example, when the goal is to form a filament-continuous channel in the transparent material so that the transparent material separates into two parts. One such example may be glass cutting or glass breaking, where the transparent material is glass or a layer of glass, i.e., a laminated glass substrate.

[0079] When cleaving a laminated glass substrate, there may be N layers of glass. As the focal point moves through the laminated glass substrate, optical losses may occur in each of the N layers. These optical losses may be caused by Fresnel reflections.

[0080] The inventors of the present disclosure have determined that the power setting P N+1 We have found a simplified model for estimating the . The model is as follows:

[0081] P N+1 =α 2N β(N,Z) where α is the Fresnel loss and β(N,Z) is the shading function. In most embodiments, α is between 0.9 and 1, such as about α=0.96.

[0082] In most embodiments, β(N,Z) can be derived experimentally. However, to a first approximation, in one embodiment, β(N,Z)=0.8N. Generally, the inventors of the present disclosure have discovered that in some embodiments, the power of the laser beam is adjusted while the focus is changed from one focus to another, and by doing so, the inventors have discovered that cleaving can be optimized, for example, to provide a stable process that is repeatable.

[0083] laser light source In one embodiment of the present disclosure, the pulse repetition rate is less than 200 MHz, preferably less than 1000 kHz. For example, a pulse repetition rate of about 500 kHz has been found to be a preferred pulse repetition rate for processing, i.e., cutting or breaking, solid glass.

[0084] In another embodiment, the pulse energy is less than 1000 μJ, more preferably less than 200 μJ, even more preferably less than 100 μJ, and most preferably less than 80 μJ. The inventors of the present disclosure have discovered that filamentation using oscillatory motion and the aforementioned low pulse energies achieves good filamentary damage. The aforementioned low pulse energies are much lower than those used in conventional setups where focal length oscillation is not used. Thus, the inventors of the present disclosure have discovered that cutting or cleaving of transparent materials can be performed using lasers with pulse peak powers much lower than those required for Bessel beam or Airy beam approaches. Thus, the present disclosure provides a low-cost solution to processing transparent materials.

[0085] In most embodiments, the beam is Gaussian. Gaussian beams are known to have rapid divergence. For example, in some embodiments, the numerical aperture is less than 0.5, more preferably less than 0.2. With such small numerical apertures, cutting or cleaving occurs only in a localized area. Therefore, by using a Gaussian beam, the focal length oscillation is comparable to using a Bessel beam or an Airy beam, but provides an extended area with more pulse energy. In these embodiments, the beam can be described as a different Bessel beam or different Airy beam. However, in other embodiments, the laser beam is an Airy beam or a Bessel beam. The advantage of using an Airy beam or a Bessel beam is that it provides an extended depth of field, as known from the prior art and described above. However, the use of an Airy beam or a Bessel beam in combination with an oscillating focal length according to the present disclosure can provide an even greater depth of field, allowing for processing of very thick transparent materials.

[0086] transparent material In most embodiments, the transparent material is a material that is transparent to the laser beam. In one embodiment, the transparent material is glass, e.g., solid glass or a laminated glass substrate. Figure 7 shows an example of the operation of a system according to the present disclosure, in which a solid glass having a thickness of 1 mm is processed according to the present disclosure. Beam 1 is translated across the glass surface by moving a focusing lens between optical lenses that oscillate up and down on the solid glass in this example.

[0087] In another embodiment, the transparent material is a polymer, for example, a solid polymer or a laminated polymer substrate. In other embodiments, the transparent material may be an organic material, such as, for example, retina.

[0088] method In one embodiment, the method comprises: using a second controller configured to move the focusing element, moving the focusing element along a separation direction different from the focusing direction such that the transparent material is processed along two directions; and / or The method further includes using a second controller configured to move the transparent material along a separation direction different from the collection direction such that the transparent material is processed along two directions.

[0089] In another embodiment, the step of changing the variable focal length is simultaneous with moving the focusing element along the separation direction. The advantages of the two above mentioned embodiments have already been described in relation to the controller.

[0090] In a preferred embodiment, the separation direction specifies a path on the transparent material such that processing the transparent material along two directions splits the transparent material into two separate portions. An example of such a result is shown in FIG. 8, where a first portion of the transparent material 3 is on the left and a second portion of the transparent material 3 is on the right. In this example, the transparent material is a laminated glass substrate. The laminated glass substrate was processed according to the method of the present disclosure. In this example, the control frequency was set to approximately 1 Hz. Thus, the cut along path 23 is fairly rough, as indicated by the damage along the path. As previously mentioned, the control frequency can be varied and therefore optimized for a particular material. In this case, the control frequency was not optimally set. However, as previously mentioned, simulations can be used to find optimal conditions.

Claims

1. 1. A system for processing a transparent material, comprising: a laser source configured to generate a laser beam comprising bursts of laser pulses, the pulses defined by a pulse energy and a pulse repetition rate; one or more focusing elements configured to receive the laser beam and direct the laser beam towards the transparent material, the focusing elements comprising a variable focal length configured to be changed from a first focal length to a second focal length along a focusing direction, whereby: i. at the first focal length, when a first beam waist is formed relative to the transparent material, the pulse energy is configured to form a first intensity that causes the first beam waist to form a first Kerr lens effect inside the transparent material, thereby forming a first filament at a first Kerr lens location inside the transparent material; ii. one or more focusing elements, wherein at the second focal length, when a second beam waist is formed relative to the transparent material, the pulse energy forms a second intensity that causes the second beam waist to form a second Kerr lens effect inside the transparent material, thereby forming a second filament at a second Kerr lens position inside the transparent material; a first controller configured to oscillatorily vary a variable focal length between the first focal length and the second focal length at a desired control frequency, whereby the first filament and the second filament are oscillatorily formed inside the transparent material, wherein the desired control frequency is lower than the pulse repetition rate.

2. The system of claim 1 , wherein the desired control frequency is between 1 and 1000 Hz, preferably between 20 Hz and 800 Hz, more preferably between 30 Hz and 700 Hz, such as about 130 Hz, such as about 50-150 Hz.

3. 3. The system of claim 1 or 2, wherein the focusing element comprises one or more of the following: one or more optical lenses configured to move along the focusing direction; a deformable lens configured to change its curvature; an adaptive beam shaping element such as a spatial light modulator (SLM).

4. The system of any one of claims 1 to 3, wherein the first focal length and the second focal length differ by more than 20 mm, such as more than 2 mm, preferably more than 10 mm, more preferably more than 50 mm.

5. The system of any one of claims 1 to 4, wherein the pulse repetition rate is less than 200 MHz.

6. The system of any one of claims 1 to 5, wherein the pulse energy is less than 1000 μJ, more preferably less than 200 μJ, even more preferably less than 100 μJ, and most preferably less than 80 μJ.

7. The system of any one of claims 1 to 6, wherein the transparent material is glass or a polymer.

8. 8. The system of claim 7, wherein the glass is a laminated glass substrate, the polymer is a laminated polymer substrate, or both.

9. The system includes a second controller, the second controller comprising: moving the focusing element along a separation direction different from the focusing direction so that the transparent material is processed along two directions; 9. The system of claim 1, configured to move the transparent material along a separation direction different from the collection direction, or both, so that the transparent material is processed along two directions.

10. 10. The system of claim 9, wherein the first controller is further configured to vary the variable focal length simultaneously with the second controller moving the focusing element, the transparent material, or both along the separation direction.

11. 11. The system of claim 9 or 10, wherein the first controller and the second controller operate independently.

12. 1. A method for processing a transparent material, comprising: generating a laser beam using a laser source comprising a burst of laser pulses, the pulses defined by a pulse energy and a pulse repetition rate; directing the laser beam towards the transparent material using one or more focusing elements configured to receive the laser beam, the focusing elements comprising a variable focal length configured to be changed from a first focal length to a second focal length along a focusing direction, thereby i. at the first focal length, when a first beam waist is formed relative to the transparent material, the pulse energy is configured to form a first intensity that causes the first beam waist to form a first Kerr lens effect inside the transparent material, thereby forming a first filament at a first Kerr lens location inside the transparent material; ii. at the second focal length, when a second beam waist is formed relative to the transparent material, the pulse energy is configured to form a second intensity that causes the second beam waist to form a second Kerr lens effect inside the transparent material, thereby forming a second filament at a second Kerr lens position inside the transparent material; and using a first controller to oscillatorily vary a variable focal length between the first focal length and the second focal length at a desired control frequency, whereby the first filament and the second filament are oscillatorily formed inside the transparent material, and the desired control frequency is lower than the pulse repetition rate.

13. using a second controller configured to move the focusing element, moving the focusing element along a separation direction different from the focusing direction such that the transparent material is processed along two directions; and using a second controller configured to move the transparent material along a separation direction different from the collection direction such that the transparent material is processed along two directions.

14. The method of claim 13 , wherein the variable focal length changing step is performed simultaneously with moving the focusing element along the separation direction.

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