Apparatus and method for processing materials with spatially and statistically directed laser pulses around a spatial target value

Abstract

The present invention relates to a method and apparatus for processing a material by laser pulses of a pulsed laser, in which laser pulses are introduced into a material to process the material, the laser pulses (300) are introduced into the material (6) in a manner that is spatially statistically distributed around a spatial target value, and the statistical distribution of the laser pulses can be adjusted and adapted according to a current feed rate.

Description

[Technical Field]

[0001] The present invention relates to an apparatus and method for processing materials with laser pulses of a pulsed laser. [Background technology]

[0002] When processing materials with pulsed lasers, regular structures are often created, for example, due to the beating between the repetition rate and other processing parameters such as the feed rate and the number of material pass repetitions, etc. Such regular structures can, for example, result in interference effects that disrupt the visual impression of the processed material.

[0003] A method and device for laser cutting, in particular for laser cutting stents, is known from EP 3613228 A1.

[0004] A method for structuring a substrate surface is known from DE 10 2017 006 358 A1.

[0005] A machining process with random triggering for ultrashort pulse lasers is known from US Patent Application Publication No. 2018 / 0207748 A1.

[0006] Summary of the Invention Based on the known prior art, it is an object of the present invention to provide an improved method and corresponding device for processing materials.

[0007] This object is achieved by a method for processing materials having the features of claim 1. Advantageous developments result from the dependent claims, the description and the drawings.

[0008] Thereby, a method for processing a material by laser pulses of a pulsed laser is proposed, in which the laser pulses are introduced into the material for processing the material. According to the invention, the laser pulses are introduced into the material in a manner that is spatially and statistically distributed around a spatial target value.

[0009] Here, the material to be processed can be a material such as a metal foil, a polymer, a plastic, etc. The material to be processed can be a semiconductor, for example an elemental semiconductor such as silicon or germanium, or a III-V semiconductor such as gallium arsenide, or an organic semiconductor, or any other type of semiconductor. As an example, the material can be a silicon wafer. In particular, the material can be a layer system, each layer being selected from the group of metal, polymer, plastic, or semiconductor. In particular, the material can be glass, for example sapphire.

[0010] In this case, the laser provides laser pulses of the laser beam, each laser pulse forming the laser beam in the beam propagation direction. In particular, the laser can be an ultrashort pulse laser, with the pulse length of each laser pulse preferably being shorter than 10 ns, preferably shorter than 500 ps.

[0011] Instead of individual laser pulses, the laser can also provide laser bursts, each burst comprising the emission of multiple laser pulses. In this regard, the laser pulses can be emitted immediately after each other, spaced apart by a few picoseconds to nanoseconds for a specific time interval. In particular, the laser bursts can be GHz bursts, in which the sequence of consecutive laser pulses in each burst occurs in the GHz range.

[0012] A laser pulse is introduced into a material, so that the material can be processed. In this case, introduction can mean that the energy of the laser beam is at least partially absorbed in the material. Here, the focal point of the laser beam can be located above or below the surface of the material to be processed in the beam propagation direction within the volume of the material to be processed. The focal point position can also be located exactly on the surface of the material to be processed.

[0013] In particular, the term "focal point" may be generally understood as a targeted increase in intensity, where the laser energy is focused at a "focal region." In particular, the term "focal point" is therefore used hereinafter regardless of the actual beam shape used and the method used to produce the intensity increase. The location of the intensity increase along the beam propagation direction may also be influenced by "focusing." For example, the intensity increase may be substantially point-like, and the focal region may have a Gaussian intensity cross-section, such as provided by a Gaussian laser beam.

[0014] The intensity increase can also be linear, creating a Bessel-type focal region around the focal position, such as can be provided by a non-diffracting beam. Furthermore, other more complex beam shapes are possible, with focal positions extending in three dimensions, such as Gaussian laser beams and / or multi-spot profiles of non-Gaussian intensity distributions.

[0015] As a result of absorbing energy from the laser beam, the material heats up according to the laser's intensity distribution and / or enters a temporary plasma state due to the electromagnetic interaction between the laser and the material. In particular, in addition to linear absorption processes, nonlinear absorption processes can also be used, which are accessible by using high laser energy or laser intensity. This can result in the material being modified, especially at the laser's focus, where the laser beam's intensity is greatest. This can result in, among other things, the separation of a portion of the material from the material compound, for example, by melting or vaporizing. Therefore, known processing processes are possible with regard to the interaction between the laser light and the material being processed; these methods are known, for example, as laser drilling, percussion drilling, or laser ablation.

[0016] Due to the interaction of the laser pulse with the material being processed, material modifications can also be incorporated into or applied to the material.

[0017] The material modification can be, for example, a permanent modification of the network structure of the material or the (local) density of the material, which is caused by local heating induced by direct laser radiation and subsequent cooling and / or electronic relaxation processes.

[0018] A material modification in or on a material can be, for example, a modification of its structure, in particular its crystalline structure and / or amorphous structure and / or chemical structure and / or mechanical structure.

[0019] A material modification is intra-material if it is primarily introduced into the volume of the material. In contrast, a material modification is on-material if it primarily modifies the surface of the material. In particular, however, a material modification can be either introduced into or applied on a material depending on the focal position and beam profile of the laser beam.

[0020] Material modification can also be a direct change in physical properties, such as the strength and / or flexural strength and / or resistance of a material to bending and shear forces, as well as shear and tensile stresses. In particular, material modification can be a local change in density, which can depend on the material selected. For example, density variations in a material can cause stress and compression zones with higher material hardness than the untreated material. Material modification can also determine the visual properties of a material, for example, by scattering light transmitted through a transparent material, making the material appear diffuse.

[0021] According to the method proposed here, laser pulses are introduced into the material in a spatially statistically distributed manner around a spatial target value.

[0022] The spatial target values ​​can be given, for example, by points or coordinates on the material, but can also be given by trajectories or point clouds on the material.

[0023] The spatial target values ​​may correspond to the actual intended processing trajectory, for example, the weld seam to be created, the separation contour to be introduced, and / or the surface treatment to be introduced. In other words, the spatial target values ​​are the spatial positions where the material processing is conventionally performed and the laser pulses for processing are introduced accordingly.

[0024] Laser pulses that are spatially statistically distributed around a spatial target value therefore have a statistical distribution of spatial distances from the spatial target value such that the laser pulses are introduced into the material at irregular distances from the spatial target value due to the spatial distribution.

[0025] However, the laser pulses also have different distances from each other. The spatial distribution of the distances results in the spatial frequency distribution of the laser pulses being introduced into the spatial frequency space, for example, via a Fourier transform. The greater the difference in distances, the greater the bandwidth of the spatial frequency distribution. In particular, both the distance to the spatial target value and the spatial frequency distribution can correspond to statistical distributions.

[0026] This has the advantage that the laser pulses are introduced into the material at irregular distances from each other so that destructive optical effects such as interference are reduced or avoided.

[0027] The laser pulses can also be introduced into the material in an energetically statistically distributed manner around an energetic target value.

[0028] The energetic target value can be, for example, a correspondingly selected energy. Due to the different energies applied, the material modifications can, for example, vary in size, which can further disrupt regularly occurring patterns on or in the processed material surface.

[0029] The laser pulses may be statistically dispersed in at least one spatial dimension.

[0030] This may mean that the laser pulses may have a statistical distribution, for example along the x-axis or the y-axis or the z-axis.

[0031] However, this may also mean that the laser pulses may have such a statistical distribution in two or three dimensions.

[0032] For example, the laser pulses may have a Gaussian distribution along the x-axis. The distance between the laser pulses along the x-axis is then, for example, Gaussian-distributed. This is due to the fact that the Fourier transform of a Gaussian function is also a Gaussian function.

[0033] For example, the laser pulse may also have a Gaussian distribution along the x- and z-axes, where the laser pulse is statistically distributed along the surface and depth of the material.

[0034] The laser beam and the material may be displaced relative to each other by feeding.

[0035] By "displaceable relative to each other" it is meant that the laser beam can be translationally displaced relative to the stationary material and the material can be displaced relative to the laser beam, or both the material and the laser beam can move.

[0036] In particular, this allows the focal point of the laser beam to be positioned at different locations on the material to introduce laser pulses. In this case, the laser pulses are positioned, in particular, on a so-called feed path. The feed path can be, for example, linear or curved. In particular, the local feed direction is always the y-direction, while the z-axis is parallel to the surface normal and the x-axis is aligned perpendicular to the y-axis, which is parallel to the material surface.

[0037] This allows, for example, the laser beam to be sent and moved along while the laser pulses are emitted into or onto the material.

[0038] In particular, the laser pulses can be emitted in a temporal statistical distribution around a temporal target value during feeding.

[0039] As a result, the temporal statistical emission of the laser pulses can in particular result in a spatial statistical distribution of the laser pulses in the material, the feed then being preferably uniform.

[0040] For example, when a sequence of laser pulses is emitted by a laser, the pulses are spaced apart in time. Specifically, this results in the frequency of the laser pulse output in frequency space over time via a Fourier transform. If the time intervals between the laser pulses are also different, the laser pulses will be distributed around the frequency of the laser pulse output in frequency space.

[0041] Thus, the laser pulses statistically distributed over time around a target value exhibit a distribution of time intervals relative to each other, such that the temporal distribution results in the laser pulses being introduced into the material irregularly over time. The target value determines the temporal magnitude order in which the laser pulse output occurs, and the statistical distribution, so to speak, determines the microstructure of the laser pulse output. When the laser beam and the material are moved by feeding during exposure to the laser pulses, the temporal statistical distribution around the target value results in a spatial statistical distribution around the target value.

[0042] The time target value can be, for example, the base frequency of the laser or a system clock, but the target value can also be any kind of trigger signal.

[0043] The statistical distribution of the laser pulses may correspond to a Gaussian distribution or a uniform distribution or a triangular distribution or a sawtooth distribution.

[0044] For example, the spatial target value may correspond to the expectation value of a Gaussian distribution, where the statistical distribution may be characterized by a half-width. The expectation value may be, for example, a straight line trajectory on the material, with a standard deviation of 10 μm, where more than 68% of the laser pulses around the trajectory are emitted within ±10 μm.

[0045] For example, the spatial statistical distribution can be a uniform distribution, where each distance of the interval around the target value occurs with equal probability. The target value can be, for example, given by the center of the material. The interval can be less than ±100 μm around the center of the material surface. In that case, the laser pulse is equally likely to have distances of 7 μm, −8.5 μm, 9 μm, 9.3 μm, −12 μm, 56.2 μm, −99 μm, and 100 μm relative to the center point.

[0046] The spatial statistical distribution may be, for example, a triangular distribution. In this case, the spatial target value may be the most probable value, and the variation range is determined by the length of the legs of the probability distribution. For example, the variation range may be -5 μm to +10 μm, while the target value may be 20 μm relative to the currently approached point on the feed trajectory. This may result in an inherent asymmetry in the triangular distribution.

[0047] The spatial statistical distribution can be, for example, a sawtooth distribution. The most probable value can then be a spatial target value, and the variation range is determined by the length of the falling edge of the probability distribution. The target value can be, for example, 30 μm, while the variation range is +11 μm. The laser pulses then have a spatial distance of 30 μm to 41 μm accordingly.

[0048] The temporal target value may correspond, for example, to the expectation of a Gaussian distribution. The expectation may, for example, be given by a specific time point, with a standard deviation of 20 μs, in which case more than 68% of the laser pulses around the trajectory are emitted within ±20 μs. For example, in time-frequency space, the target value may be given by a frequency such as the base frequency of the laser or a common system clock. The laser pulses may then be distributed in time-frequency space around the base frequency according to the expectation.

[0049] The energy statistical distribution can be, for example, a sawtooth distribution. The target value can be, for example, 0.1 mJ, while the variation range is +0.4 mJ. The laser pulses then have corresponding energies in the range of 0.1 mJ to 5 mJ.

[0050] In particular, the laser pulses may have a spatial statistical distribution and an energy statistical distribution and / or a temporal statistical distribution.

[0051] In general, the statistical distribution can consist of different statistical distributions. For example, it is possible to superimpose a normal distribution and a uniform distribution. However, it is also possible for the statistical distribution to be asymmetric. For example, a Gaussian distribution can also have a skew.

[0052] The statistical distribution of the laser pulses makes it particularly easy to disrupt and randomize regular structures.

[0053] In particular, the statistical distribution may be adjustable.

[0054] For example, the half-width of the Gaussian distribution may be adjustable, or the expectation of the distribution may be adjustable.

[0055] For example, the temporal distribution can be set to better than 1 μs, which can mean that the temporal power of the laser pulses is set to an accuracy of exactly 1 μs so that the temporal laser pulse power follows the desired temporal distribution.

[0056] In particular, the feed rate may be selected such that laser pulses emitted in immediate succession do not overlap.

[0057] This is especially the case when the feed rate is greater than the ratio of the diameter of the laser focus to the time interval between laser pulses.

[0058] Above this minimum feed rate, the introduced material modifications do not overlap, in particular this achieves a single pulse modification that is not based on the heat accumulation of successively introduced pulses.

[0059] For example, the diameter of the laser focus is 5 μm and the repetition rate of the laser pulses is 10 kHz, which results in a minimum delivery rate of 0.5 m / s.

[0060] In particular, variations in spatial and / or temporal distribution can be fitted, for example, in curves that are typically scanned at a slower speed, which prevents successive laser pulses from overlapping in the workpiece.

[0061] For example, successive laser pulses at regular time intervals will slowly overlap in a material, whereas such overlap can be avoided if the temporal statistical distribution is broadened, for example, by increasing the standard deviation and / or expectation value.

[0062] The statistical distribution of the laser pulses can be adjusted according to the current feed rate.

[0063] This may mean that a first statistical distribution is used for a first low feed rate and a second statistical distribution is used for a second higher feed rate.

[0064] For example, a uniform distribution of laser pulses can be used at low feed rates, where the spatial distance between the laser pulses must be kept as large as possible to avoid pulse overlap, while at higher feed rates it can be useful to distribute the laser pulses in a Gaussian manner so that they are more concentrated on the feed trajectory.

[0065] However, it is also possible that the variation range (e.g., expected value) is adjusted to be smaller at higher feed rates, i.e., at higher feed rates so that the actual spatial variation range of the laser pulse on the material is always similar or the same.

[0066] In particular, the temporal statistical distribution may be adjusted relative to the feed rate, for example, so that the spatial statistical distribution produced on the material by the laser pulses remains the same or changes as the feed rate changes.

[0067] The statistical distribution can be adjusted according to the process phase.

[0068] For example, a first statistical distribution may be useful for a first fabrication process, and a second statistical distribution may be useful for a second statistical process.

[0069] For example, when machining a surface, it may be useful to use a serpentine feed trajectory, with the laser pulses spatially distributed in a Gaussian manner around the serpentine. By having adjacent lines of the serpentine approach each other anti-parallel and overlapping Gaussian distributions on the edges, homogeneous machining of material can be achieved on the surface.

[0070] In the separation process, it may be advantageous to process the material ahead in the direction of the feed trajectory, i.e., to position the laser pulse partially before the target position of the laser beam. For example, a spatial sawtooth distribution may be used accordingly to achieve particularly clean separation of the material. In this case, the laser pulse is directed sporadically in the feed direction before the current position of the laser beam so that the material is already weakened there in a targeted manner. This may result in targeted crack propagation, for example, from the current position of the laser beam corresponding to the target value to the isolated position of the laser pulse.

[0071] The method according to the invention can be advantageously used in a number of processing processes.

[0072] For example, the material processing process can be a separation process, i.e., a deep engraving process, in which material is removed in multiple passes with spatial overlap of successive laser pulses. By randomizing the laser pulse power in the feed direction, a uniform distribution of the laser pulses can be achieved, resulting in a high-quality edge cut or engraving. In particular, the engraving does not have a periodic structure, so that there are no destructive diffraction phenomena that can spoil the visual impression.

[0073] The machining process can also be used for metal structuring or surface removal. In this case, the visual impression depends heavily on the surface quality. In particular, the randomization of the laser pulses ensures that no undesired patterns are imposed on the material's surface.

[0074] Another important processing process is the so-called dimple structuring of surfaces for anti-glare functionalization. In other words, dimples or craters can be imposed on the surface of a material by laser pulses that scatter the incident light. This allows a matte surface finish to be achieved on the material.

[0075] In particular, the method according to the present invention can be used to achieve particularly advantageous visual and tactile target properties of the material after dimple structuring. For example, such dimple structuring can be used when processing display glass, especially cover glass. For example, sparkle, which is a measure of irregular intensity and color variation, can be set. In this regard, sparkle is related to the size of the dimples. In particular, sparkle can be set to less than 4%. When the glass is placed on a display with very high resolution, it is advantageous to reduce the size of the dimples to ensure a low sparkle value.

[0076] Another important parameter is called image clarity. This parameter is a measure of the clarity of the user information being read. In this context, image clarity is inversely proportional to the scattering, or diffusion, of light through the display cover glass. Image clarity can be set to greater than 70% using the method according to the present invention. In particular, image clarity can be set by area filling of the display glass with dimples, the area filling preferably comprising 40% to 95% of the display area.

[0077] Another important parameter is the diffusion, which is a measure of the scattering strength of the display glass. In particular, the diffusion also depends on the shape and composition of the individual dimples. For example, the diffusion of the display glass can be set to more than 22%.

[0078] Additionally, methods in accordance with the present invention can avoid Moiré effects that typically occur when the pixel period of a display panel is on the same order of magnitude as the period of the dimple array. By randomly introducing dimples into the display glass through statistical distribution, Moiré effects can be avoided.

[0079] In particular, the material modification can take the form of protrusions, i.e., bumps in the material, created by brief melting and thermal expansion of the material.

[0080] In particular, material modifications, especially bumps and depressions, also achieve tactile changes in the material surface.

[0081] Roughness can, for example, serve as a tactile target. In particular, the tactile impression can be adjusted by the density of the modification. A higher density typically creates a stronger or rougher tactile impression.

[0082] By successive interactions of at least two laser pulses with the same material region, so-called laser-induced surface periodic structures (LIPSS) can be generated.

[0083] In this regard, dimples and LIPSS are suitable for functionalizing the surface of a component, which can affect, among other things, the visual, wetting and tribological properties.

[0084] In a particularly preferred embodiment, the method produces dimples with diameters between 13 μm and 20 μm, and the laser-induced surface periodic structures have a periodicity between 650 nm and 1000 nm.

[0085] The above object is further achieved by an apparatus for processing materials having the features of claim 10. Advantageous further developments of the method may be found in the dependent claims, the description and the drawings.

[0086] Thereby, an apparatus for processing a material is proposed, comprising: a system clock generator designed to provide a system clock signal; a statistical generator designed to receive the system clock signal, impose a temporal statistical distribution on the system clock signal and provide a statistical clock signal; a laser designed to receive the statistical clock signal or the system clock signal and to emit a laser pulse when the clock signal is received; a feeder designed to move the laser beam and the material relative to each other; and a processing optical unit configured to transmit the laser beam to a focal zone and introduce the laser beam into the material, thereby processing the material.

[0087] The system clock generator may provide a clock to the entire device so that all devices used can synchronize to a common clock. In this regard, the system clock generator may, for example, output a pulsed base signal having a base frequency.

[0088] It is also possible that the base signal of the system clock generator corresponds directly to, for example, a time target value of the statistical distribution of the time pulse output. However, it is also possible that the base signal needs to be passed through an appropriate multiplier to provide the time target value of the time pulse output. In the following, the former is always assumed. However, it is also possible that the system clock generator outputs only isolated signal pulses as the system clock signal, i.e., the system clock signal does not have a fixed base frequency.

[0089] The system clock generator may be, for example, built into the pulsed laser itself and correspond, for example, to the repetition rate, or may be an external pulse generator. However, it is also possible that the system clock appears irregularly and simply represents a general trigger signal, output by the feed device or the position offset device.

[0090] The statistical generator may receive the system clock signal and impose a statistical distribution on the signal pulses of the system clock signal, for example, the signal pulses may have a Gaussian distribution around the original signal pulse.

[0091] The statistical generator can be, for example, an FPGA or a computer or a microchip or an application specific integrated circuit (ASIC) or a microcontroller, which makes it particularly easy to set up, for example, different statistical distributions.

[0092] The statistical clock signal can be received by a laser that is preferably equipped with a pulse-on-demand function, whereby the laser emits a laser pulse each time it receives a pulse from the system clock signal. The emitted laser pulse therefore has the same time course as the pulse of the statistical clock signal. In other words, the pulse-on-demand signal from the system clock generator for the pulsed laser is manipulated by the statistical generator.

[0093] In this regard, the statistical variation of the received pulses of the base signal can be introduced by a statistical generator with a clock rate of more than 1 MHz, which has the advantage that even at very high clock rates the statistical generator can still reliably impose the same statistical distribution on the pulses of the base signal.

[0094] The apparatus further comprises a processing optical unit capable of focusing the laser beam into the material, in particular the processing optical unit capable of converting an angular offset into a spatial offset, such that in the case of a statistical angular deviation as described below, a statistical spatial deviation is particularly easily generated.

[0095] The laser beam can be focused into / on the workpiece by a processing optical unit or a scanner unit, where the processing optical unit has a numerical aperture of NA>0.01 and the scanner unit has a numerical aperture of NA<0.1.

[0096] For example, the processing optical unit has a numerical aperture of 0.01 to 0.2, particularly 0.04.

[0097] The numerical aperture NA essentially indicates the angular aperture of the laser beam at the focal point, and a large numerical aperture means a large angular aperture, which allows adjusting the expansion of the focal zone in the beam propagation direction, and thus the size of the material modification in the beam propagation direction.

[0098] The apparatus may also include a feeder for moving the laser beam and the material relative to one another.

[0099] The feed device may preferably comprise a shaft device and / or a scanner device.

[0100] For example, an axis device can be used to mechanically move the material, while a scanner device is used to move the laser beam across the material. In particular, the axis device can be an XYZ table with stepper motor control. However, the axis device can also be designed with piezoelectric adjustment to achieve the fastest possible adjustment. In particular, the scanner device can be a galvo scanner. However, it is also possible for the feed device to be a roll-to-roll device.

[0101] The sending device may receive a system clock.

[0102] For example, the system clock can be used to clock a stepper motor so that a certain number of steps are made per second. The feed rate can therefore be set particularly easily by adjusting a multiplier on the motor. For example, the system clock can be the normal clock by which a scanner periodically deflects a laser beam over a material.

[0103] The sending device may receive a statistical clock signal.

[0104] For example, the feed device may then form a non-uniform feed trajectory, which also generates a statistical distribution around the feed trajectory, and in particular also in the direction of the feed trajectory.

[0105] However, it is also possible for the sending device to provide the system clock.

[0106] This allows the feeder to output the system clock itself, which is sent to the statistics generator. This eliminates the need for an external component to generate the system clock, and the laser pulse output is adapted to the feeder, and thereby automatically adapted to the current position and velocity.

[0107] In the simplest case, the feeder may output a system clock signal each time it moves a certain distance. Laser pulses may then be emitted automatically depending on the distance moved and independent of the feed rate. In this case, this is referred to as a position synchronization signal output by the feeder. In particular, the current speed may be estimated from the position synchronization signal in order to adjust the statistical distribution if necessary.

[0108] The apparatus may include a position offset device designed to receive a statistical clock signal and to impose a spatial statistical distribution on the laser pulses about a spatial target value.

[0109] In particular, the position offset device may be an electro-optical deflector and / or an acousto-optical deflector and / or may be based on coherent beam combining. The position offset device may receive a statistical clock signal and deflect the laser pulses accordingly.

[0110] In an acousto-optic deflector, an AC voltage is applied to a piezoelectric crystal in an optically adjacent material to generate acoustic waves that periodically modulate the refractive index of the material. Here, the waves can propagate through the optical material, for example, as propagating waves, as wave packets, or in the form of standing waves. The periodic modulation of the refractive index creates a diffraction grating for the incident laser beam. The incident laser beam is diffracted by the diffraction grating, thereby at least partially deflecting it at an angle relative to its original beam propagation direction. The grating constant of the diffraction grating, and therefore the deflection angle, depend, inter alia, on the wavelength of the acoustic waves and, therefore, the frequency of the applied AC voltage.

[0111] Electro-optic deflectors are based on prisms made of electro-optic crystals. By applying a voltage, the refractive index of the electro-optic crystal changes so that the path of the laser beam through the prism changes.

[0112] Spatial statistical distribution using electro-optical and / or acousto-optical deflectors can be implemented at clock rates exceeding 1 MHz, allowing laser pulses to be repositioned millions of times per second. In particular, electro-optical and / or acousto-optical deflectors can be used to reposition laser pulses with single-pulse precision, so that individual laser pulses are introduced to different locations on the material.

[0113] However, the position offset device can be a wobble prism, which in this case includes a prism that deflects the laser beam at an angle, where mechanical deflection of the prism achieves spatial deflection of the laser beam.

[0114] The wavelength of the laser pulses can be between 200 nm and 3000 nm, which makes the method adaptable to many different materials and processing processes.

[0115] The repetition rate of the laser may be between 10 kHz and 100 MHz, in particular between 10 kHz and 2 MHz. In this regard, the repetition rate determines the time interval between two or more successive laser pulses.

[0116] The laser pulse may consist of multiple laser burst pulses, particularly 2 to 100 laser burst pulses. In this regard, the laser burst pulses may be emitted at particularly high frequencies above 1 GHz instead of a single laser pulse. In this case, a single laser burst pulse deflection is used instead of a single pulse deflection.

[0117] The fluence can be greater than 0.05 J / cm², especially between 0.1 J / cm² and 50 J / cm², which makes the method adaptable to many different materials and processing processes.

[0118] The laser pulse duration may be between 10 fs and 100 ns, in particular between 100 fs and 100 ps.

[0119] For example, the length of the laser pulses may be 100 ps to 100 ns, particularly 1 ns to 20 ns, the wavelength may be 300 nm to 550 nm, particularly 355 nm, the repetition rate of the laser pulses may be 10 kHz to 100 kHz, particularly 10 kHz to 50 kHz, the laser pulses may have an energy of 60 μJ to 300 μJ, and 1 to 4 pulses may be emitted per spot.

[0120] For example, the length of the laser pulse may be 200 fs to 1000 fs, particularly 300 fs to 450 fs, the wavelength may be 900 nm to 2300 nm, particularly 1030 nm, the repetition rate of the laser pulse may be 10 kHz to 400 kHz, the laser pulses may be emitted in laser bursts, each laser burst may include 2 to 4 laser pulses, the laser burst may have an energy of 100 μJ to 400 μJ, and the numerical aperture may be 0.01 to 0.2, particularly 0.08.

[0121] In particular, the laser may also comprise an unstable seed laser and an amplifier, the unstable seed laser including a statistical generator and emitting laser pulses having a temporal statistical distribution, and the amplifier amplifying the laser pulses of the seed laser.

[0122] The laser beam may also have a Gaussian beam shape or a non-diffracting beam shape.

[0123] A Gaussian beam is to be understood in particular as a beam whose intensity cross section corresponds to a Gaussian bell curve.

[0124] A non-diffracting beam and / or a Bessel-type beam is to be understood in particular as a beam whose transverse intensity distribution is propagation-invariant. In particular, for a non-diffracting beam and / or a Bessel-type beam, the transverse intensity distribution along the longitudinal direction and / or propagation direction of the beam is essentially constant.

[0125] For the definition and properties of non-diffracting beams, please refer to the following book: "Structured Light Fields: Applications in Optical Trapping, Manipulation and Organisation", M Wordemann, Springer Science & Business Media (2012), ISBN 978-3-642-29322-1, to which full explicit reference is made.

[0126] A non-diffracting laser beam is thereby advantageous in that it may have an intensity distribution that is elongated in the direction of beam propagation to a greater extent than the transverse dimension of the intensity distribution, in particular this allows for the creation of material modifications that are elongated in the direction of beam propagation, so that they can penetrate two sides of a workpiece particularly easily.

[0127] Furthermore, the laser beam may have a flat-top beam shape and / or a super-Gaussian beam shape and / or a top-hat beam shape. [Brief explanation of the drawings]

[0128] Further preferred embodiments of the invention are explained in more detail by the following description of the drawings. [Figure 1] 1 shows a schematic structure of a device according to the prior art. [Figure 2A] 2 shows a further schematic structure of the device according to the invention; [Figure 2B] 2 shows a further schematic structure of the device according to the invention; [Figure 2C] 2 shows a further schematic structure of the device according to the invention; [Figure 2D] 2 shows a further schematic structure of the device according to the invention; [Figure 3] 2 shows a further schematic structure of the device according to the invention; [Figure 4] 1 shows a method according to the prior art. [Figure 5A] 1 illustrates a method according to the invention using a spatial statistical distribution of laser pulses. [Figure 5B] 1 illustrates a method according to the invention using a spatial statistical distribution of laser pulses. [Figure 6A] 1 illustrates a method according to the invention that uses the spatial and temporal statistical distribution of laser pulses. [Figure 6B] 1 illustrates a method according to the invention that uses the spatial and temporal statistical distribution of laser pulses. [Figure 7] 1 shows a further method according to the invention using the spatial and temporal statistical distribution of laser pulses. [Figure 8] 1 shows a further method according to the invention using a spatial and temporal distribution of laser pulses. DETAILED DESCRIPTION OF THE INVENTION

[0129] Preferred exemplary embodiments are described below with reference to the drawings, in which elements that are the same, similar, or have the same effect are given the same reference numerals in different drawings, and repeated descriptions of these elements have been omitted in some cases to avoid redundancy.

[0130] 1 shows a schematic diagram of an apparatus according to the invention for processing a material 6. The apparatus comprises a system clock generator 1. The system clock generator 1 preferably outputs a signal pulse of a fixed frequency, which is the system clock signal. In particular, the system clock generator 1 can be a pulse generator. However, the system clock generator 1 can also be formed inherently in one of the other installed apparatus elements, as will be explained below.

[0131] The system clock generator 1 is designed to transmit a system clock signal to the statistics generator 2. The statistics generator 2 receives a pulsed base signal from the system clock generator 1 and may impose a statistical distribution on the pulses of the base signal. In particular, the statistics generator 2 may vary the interval between pulses of the system clock signal so that the signal pulses of the system clock signal exhibit a statistical distribution. For example, the interval between pulses of the base signal may be adjusted for this purpose. For example, the statistical distribution may result from the time interval between adjusted and unaltered signal pulses of the system clock signal.

[0132] These statistical clock signals may be received by the laser 3. For each signal pulse received by the laser 3, the laser 3 may emit a laser pulse 300 that propagates along the laser beam 30 of the laser 3. This functionality is also referred to as pulse-on-demand. The laser pulse 30 may then be focused by the processing optical unit 5 into or onto the surface of the material 6. Thereby, the laser pulse 300 is introduced with the statistical distribution of the statistical generator 2.

[0133] The laser pulse 300 may cause material processing of the material 6 such that processing of the material 6 occurs.

[0134] The feeding device 4 can move the material 6 and the laser beam 30 relative to each other so that the laser beam 30 moves along a feeding trajectory by feeding. For example, the feeding device here is designed as a scanner device, in which the laser beam 30 moves periodically over the material 6. When laser pulses 300 with a statistical distribution are triggered and introduced into the material 6 during feeding, material modifications also exist in the material 6 with a certain statistical distribution. In particular, it should be emphasized here that the statistical distribution of the laser pulses 300 is a temporal distribution, while the statistical distribution of the material modifications in the material 6 shows a local statistical distribution due to simultaneous feeding.

[0135] The device according to the invention is shown in FIG. 2A. Here, pulse generation of the laser 3 is performed in the same way as in FIG. 1. However, a position offset device 7 is arranged behind the laser 3 in the beam propagation direction. The position offset device 7 can be, for example, an acousto-optic deflector. The acousto-optic deflector 7 can also receive a signal from the statistical generator 2 and spatially deflect the laser pulse 300 triggered by the laser 3 accordingly. In this case, the temporal deviation of the signal pulse from the base frequency can be converted, for example, into a spatial deflection. At the same time, the laser 3 can receive a statistical clock signal from the statistical generator 2 and impose a temporal variation on the laser pulse 300.

[0136] 2B, it is also possible that only the position offset device 7 provides the spatial statistical distribution of the laser pulses 300 and that the laser 3 is operated via the system clock generator 1. The laser 3 then emits the laser pulses 300 at regular intervals according to the base frequency, and only the position offset device generates the spatial statistical distribution of the laser pulses 300.

[0137] 2C, it is also possible for the feed device 4 to output a system clock signal, which, for example, triggers the laser pulse 300 after traveling a certain distance. In addition, the system clock signal can be influenced by the statistics generator 2, such that the position offset device 7 provides an additional spatial statistical distribution of the laser pulse 300.

[0138] 2D, it is also possible for the feed device 4 to output a system clock signal, which is influenced by the statistical generator 2. In particular, the laser 3 can thereby receive a statistical clock signal, which can be used, for example, to implement pulse triggering according to a statistical distribution. In addition, the position offset device 7 can effect a spatial statistical distribution of the laser pulses 300 by means of the received statistical signal.

[0139] It is also possible for the laser 3 to receive a statistical clock signal, thereby imposing an additional temporal statistical distribution.

[0140] A further possible embodiment of the device is shown in Figure 3. Here, the laser 3 comprises an unstable seed laser 34 and an amplifier 36. When the seed laser 34 receives pulses of a base signal from a system clock generator, the seed laser emits laser pulses that are amplified by the amplifier. The temporal emission of laser pulses by the seed laser 34 is thereby essentially statistically distributed due to the instability.

[0141] Figure 4 shows a prior art method, in which laser pulses are emitted at regular intervals and introduced into the material, which therefore have only one temporal frequency, the repetition rate.

[0142] While the laser 3 emits the laser pulses 300, the material 6 can be moved uniformly relative to the laser beam 30 using a feeder. As a result, the laser pulses 300 on the material 6 are also uniformly spaced such that the laser pulses in spatial frequency space have only one spatial frequency.

[0143] 5A shows a method according to the present invention for processing a material 6 with laser pulses 300 of a pulsed laser 3, which are introduced into the material 6 for processing the material 6. In this case, the laser 3 emits the laser pulses 300 at a certain frequency, which corresponds, for example, to the system clock of the system clock generator 1. Here, the triggered laser pulses fall on a position offset device 7 and are deflected from there. The position offset device 7 can be controlled, for example, via the statistical generator 2. Thereby, the laser pulses 300 are deflected with a statistical distribution, for example, perpendicular to the feed direction. By deflecting the laser pulses 300, the laser pulses are therefore spatially and statistically distributed around the feed trajectory.

[0144] Figure 5B illustrates such a method: a laser beam 30 moves periodically in a serpentine manner over a material 6, while the laser pulses are deflected perpendicular to the trajectory by a position offset device 7. Due to the non-uniform pulse output, the laser pulses are present in a regular pattern in the y-direction, but have a spatial statistical distribution perpendicular to the serpentine structure.

[0145] In addition to the spatial statistical distribution provided by the position offset device 7, the laser 3 may also emit laser pulses 300 with a temporal statistical distribution, for example, by triggering the pulse-on-demand function of the laser 3 with a signal from the statistical generator 2. This is shown in FIG. 6A. The temporal statistical fluctuations of the laser pulse power are evident at the provided feed in that the laser pulses 300 are also distributed along the feed direction, as shown in FIG. 6B. The laser pulses have a Gaussian distribution in both the x and y directions. Notably, the laser pulses 300 are also offset from one another in the feed direction (at a constant feed rate).

[0146] As shown in FIG. 7, the temporal statistical distribution and the spatial statistical distribution can be different distributions, for example, a triangular distribution and a uniform distribution.

[0147] 8 also shows that the pulses (dashed lines) of the system clock signal may be triggered at irregular intervals, for example because the feeder 4 outputs such a system clock signal only after moving a certain distance. In particular, such irregular pulse outputs may occur during periods of non-uniform speed. By receiving a signal from the feeder 4, the statistical generator 2 may impose an additional temporal statistical distribution so that the laser pulses are introduced into the material 6 at irregular intervals.

[0148] Where applicable, all individual features presented in the exemplary embodiments may be combined with one another and / or interchanged without departing from the scope of the present invention. [Explanation of symbols]

[0149] 1 System Clock Generator 2 Statistics Generator 3 Laser 30 Laser Beam 32 focal zones 300 laser pulses 34 Seed Laser 36 Amplifier 4 Feeder 40 axis device 42 Scanner device 400 feed orbit 5 Processing optical unit 6 Materials 7 Position offset device

Claims

1. 1. A method for processing a material (6) by laser pulses (300) of a pulsed laser (3), wherein the laser pulses (300) are introduced into the material (6) to process the material (6), comprising:

10. The method of claim 1, wherein the laser pulses (300) are introduced into the material (6) in a spatially statistically distributed manner around a spatial target value, and the statistical distribution of the laser pulses can be adjusted and adapted according to a current feed rate.

2. The method of claim 1, wherein the laser pulses (300) are statistically distributed in at least one spatial dimension.

3. 3. A method according to claim 1 or 2, characterized in that the laser beam (30) and the material (6) are displaced relative to each other by feeding, the feeding rate being in particular greater than 50 mm / s.

4. 4. The method according to claim 1, wherein the laser pulses are emitted with a temporal statistical distribution around a temporal target value during the feeding.

5. Method according to any one of claims 1 to 4, characterized in that the statistical distribution of the laser pulses (300) corresponds to a Gaussian distribution or a uniform distribution or a triangular distribution or a sawtooth distribution.

6. The method according to any one of claims 1 to 5, characterized in that the statistical distribution has upper and / or lower cut-off values.

7. 7. The method according to claim 1, wherein the laser pulses emitted in immediate succession do not overlap.

8. Method according to any one of claims 1 to 7, characterized in that the temporal statistical distribution of the laser pulses is adapted according to the current feed rate.

9. An apparatus for processing a material (6), comprising: a system clock generator (1) designed to provide a system clock signal; a statistical generator (2) designed to receive a system clock, impose a temporal statistical distribution on said system clock, and provide a statistical clock signal; a laser (3) designed to receive the statistical clock signal or the system clock signal and to emit a laser pulse (300) when the system clock signal is received; a feeder (4) designed to move the laser beam (30) and said material (6) relative to each other; a processing optical unit (5) designed to transmit the laser beam (30) to a focal zone (32) and to introduce the laser beam (30) into the material (6), thereby processing the material (6).

10. 10. The apparatus according to claim 9, further comprising a position offset device (7) designed to receive the statistical clock signal and to impose a spatial statistical distribution on the laser pulses (300) around a spatial target value.

11. 11. Apparatus according to claim 9 or 10, characterized in that the sending device (4) receives the system clock signal, or receives the statistics clock signal, or provides the system clock signal.

12. 12. Apparatus according to any one of claims 9 to 11, characterized in that the position offset device (7) is an electro-optical and / or acousto-optical deflector and / or is based on coherent beam combining, receives the statistical clock signal and deflects the laser pulses (300) accordingly, preferably the spatial statistical distribution is performed at a clock rate of more than 100 kHz, preferably 1 MHz.

13. the wavelength of said laser pulses (300) is between 200 nm and 3000 nm, and / or the repetition rate of said laser is between 10 kHz and 100 MHz, in particular between 10 kHz and 100 MHz, and / or the laser pulse (300) consists of a plurality of burst pulses, in particular 2 to 100 burst pulses, and / or the fluence is greater than 0.05 J / cm2, in particular between 0.1 J / cm2 and 50 J / cm2, and / or - Device according to any one of claims 9 to 12, characterized in that the laser pulse duration is between 10 fs and 100 ns, in particular between 100 fs and 100 ps.

14. 14. Apparatus according to any one of claims 9 to 13, characterized in that the laser beam (30) has a Gaussian beam shape or a non-diffracting beam shape, in particular a flat-top beam shape and / or a super-Gaussian beam shape and / or a top-hat beam shape.

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