System for machining a material by means of ultra-short laser pulses

Abstract

This invention relates to a system (1) for processing materials (2) using an ultrashort laser pulse with the aid of an ultrashort laser (3), the system comprising an ultrashort laser (3), a hollow fiber (4), and a coupling input optics (41), the ultrashort laser being used to generate ultrashort laser pulses and to provide a laser beam (32), the hollow fiber being configured to transmit the laser beam (32) to the output end (42) of the hollow fiber (4), the coupling input optics being configured to couple the laser beam (32) into the input end (40) of the hollow fiber (4), wherein the output end (42) of the hollow fiber (4) is configured to couple the laser beam (32) out from the hollow fiber (4) with a divergence angle (α), and wherein a lens device (8), a beamforming element (6), and a focusing optics (7) are provided. A laser beam (32) coupled out from the hollow fiber (4) is incident on the lens device at the divergence angle (α). A laser beam (32) exiting from the lens device (8) is incident on the beamforming element. The lens device (8) is configured to adjust the divergence angle (α) of the coupled laser beam (32) to adjust the beam diameter (D) of the laser beam (32) on the beamforming element (6). The beamforming element (6) is configured to apply a quasi-non-diffractive beam shape to the laser beam (32) in front of or behind the focusing optics (7). The quasi-non-diffractive beam shape has a focal region (322) elongated in the beam propagation direction. The focusing optics (7) is configured to adjust the focal region (322) to the depth of introduction into or on the material (2).

Description

Technical Field

[0001] The present invention relates to a system for processing materials using ultrashort laser pulses, the system comprising an ultrashort laser, a hollow fiber, and a coupling input optics, wherein the ultrashort laser is used to generate ultrashort laser pulses and to provide a laser beam, the hollow fiber is configured to transmit the laser beam to an output end of the hollow fiber, and the coupling input optics is configured to couple the laser beam into an input end of the hollow fiber. Background Technology

[0002] In the field of laser-assisted micromachining, new applications have emerged in recent years through higher average laser power, shorter laser pulse duration, and optimized laser beam shapes, such as separating transparent materials and welding multiple transparent or transparent and opaque materials. In particular, quasi-non-diffractive laser beams, especially Bessel beams, are advantageous for this type of material processing due to their elongated focal region along the beam propagation direction and the resulting advantages (e.g., large focal position tolerance).

[0003] In EP3169477, a collimated laser beam is proposed for processing materials, wherein the length of the focal region of the Bessel beam is adjusted by adjusting the diameter of the collimated laser beam on the beamforming element.

[0004] To date, connecting typically fixed laser sources to processing optics or beamforming optics has been achieved through free beam guiding using mirrors and lenses. However, this requires expensive optical calibration and stabilizing the positions or angles of the optical elements relative to each other. Furthermore, free beam-guided components are susceptible to contamination, manufacturing inaccuracies, temperature variations, and assembly errors, resulting in deterioration of the laser beam quality and consequently, material processing. Additionally, accurately specifying the position or divergence of the laser beam is either impossible or difficult. This complicates the precise definition of illumination for beamforming elements. Summary of the Invention

[0005] Based on known prior art, the objective of this invention is to provide an improved system for processing materials.

[0006] This task is accomplished by a system for processing materials having the features of claim 1. Advantageous extensions are derived from the dependent claims, the specification, and the drawings.

[0007] Accordingly, a system for processing materials using ultrashort laser pulses from an ultrashort laser is proposed. The system includes an ultrashort laser, a hollow fiber, and coupling input optics. The ultrashort laser generates ultrashort laser pulses and provides a laser beam. The hollow fiber is configured to transmit the laser beam to its output end. The coupling input optics are configured to couple the laser beam into the input end of the hollow fiber. The output end of the hollow fiber is configured to couple the laser beam out from the hollow fiber at a divergence angle. A lens device, a beamforming element, and a focusing optics are provided to focus the laser beam from the hollow fiber. A coupled laser beam is incident on a lens device at a divergence angle, and a laser beam exiting from the lens device is incident on a beamforming element. The lens device is configured to match the divergence angle of the coupled laser beam to match the beam diameter of the laser beam on the beamforming element. The beamforming element is configured to apply a quasi-non-diffractive beam shape to the laser beam in front of or behind a focusing optics device. The quasi-non-diffractive beam shape has a focal region elongated in the beam propagation direction. The focusing optics device is configured to adjust the focal region to an introgression depth in or on the material.

[0008] The material can be a metal, a semiconductor, an insulator, or a combination thereof. In particular, the material can also be glass, glass-ceramic, a polymer, or a semiconductor wafer, such as a silicon wafer.

[0009] Here, an ultrashort pulse laser provides ultrashort laser pulses. "Ultrashort" can refer to pulse lengths, for example, between 500 picoseconds and 1 femtosecond, particularly between 100 picoseconds and 10 femtoseconds. An ultrashort pulse laser can also provide short pulse trains composed of ultrashort laser pulses, where each short pulse train includes the emission of multiple laser pulses. Here, the time interval between laser pulses can be between 10 femtoseconds and 500 nanoseconds, particularly between 10 nanoseconds and 80 nanoseconds. Time-shaped pulses are also considered ultrashort laser pulses, and the notable variation in amplitude of time-shaped pulses is in the range of 50 femtoseconds to 5 picoseconds. The terms pulse or laser pulse are used repeatedly below. In this context, laser pulse trains comprising multiple laser pulses and time-shaped laser pulses are also included, even without a corresponding detailed explanation. The ultrashort laser pulses emitted by the ultrashort pulse laser correspondingly construct a laser beam.

[0010] Hollow-core optical fiber is an optical fiber constructed with a hollow core (Hollow Core Photonic Crystal Fiber – HC-PCF). The basic principles of optical fibers are described, for example, in Benabid, Fetah, “Hollow-core photonic bandgap fibre: new light guidance for new science and technology.” Royal Society Philosophical Papers A: Mathematics, Physics and Engineering Sciences 364.1849 (2006): 3439-3462.

[0011] Optical fibers can be constructed as band gap fibers or, preferably, as antiresonant coupling fibers. In particular, optical fibers can be constructed as tubular fibers. Alternatively, optical fibers can be constructed as inhibited coupling fibers, especially as Kagomé fibers. Hollow-core optical fibers are particularly suitable for guiding ultrashort pulses and are therefore suitable for ultrashort pulse applications.

[0012] The use of hollow-core optical fiber offers several advantages: laser beams can be flexibly guided from a fixed laser to a beamforming element, with a well-defined interface through which the divergence angle and beam position can be determined. In particular, beam quality can be achieved by using hollow-core optical fiber.

[0013] The coupling input optics are components that may include one or more optical elements, particularly lenses and / or mirrors, and that perform the task of imaging a laser beam provided by an ultrashort pulse laser into a hollow fiber. For this purpose, the laser beam of the ultrashort pulse laser can be, for example, focused onto the input end of the hollow fiber. Here, the coupling input optics may have an exit pupil, which may have a diameter on the order of the diameter of the hollow fiber. This allows the laser energy of the laser beam to be coupled into the hollow fiber as completely as possible, and thus transmitted through the hollow fiber to its output end.

[0014] At the output end of the hollow fiber, the laser beam is coupled out from the hollow fiber with a divergence angle. This divergence angle can be determined by the optical properties of the hollow fiber. In particular, for the specific hollow fiber, the divergence angle can be fixedly predetermined.

[0015] Next, the laser beam illuminates a lens assembly: a laser beam coupled from a hollow optical fiber is incident on the lens assembly at a divergence angle. Here, the lens device is configured to adjust the divergence angle of the coupled laser beam to match the beam diameter of the laser beam on the beamforming element.

[0016] Therefore, the lens assembly may include one or more lenses. The lens assembly may also include a corresponding shaped surface of the beamforming element, or diffraction microstructures on the surface of the beamforming element and / or in the volume of the beamforming element. Here, the lens assembly is ultimately configured to influence the diameter of the laser beam incident on the beamforming element. Finally, by changing the beam diameter of the laser beam incident on the beamforming element, the focal length of the focal region can be affected.

[0017] Then, the laser beam, adjusted by means of a lens assembly, is incident on a beamforming element with the diameter of that beam as described above. This beamforming element is arranged with a total spacing from the output end of the hollow fiber, and applies an intensity distribution to the laser beam in the beam propagation direction and perpendicular to it. The overall intensity characteristics are described by the beam profile. In particular, the shape of the applied beam profile depends on the mode of illumination, especially the illumination intensity, or also on the diameter of the laser beam on the beamforming element, such that the shape of the applied beam profile can be adjusted by adjusting the total spacing.

[0018] In particular, so-called non-diffractive beams can be generated using beamforming elements. Non-diffractive beams satisfy the Helmholtz equation:

[0019]

[0020] Furthermore, it possesses clear separability, separating into horizontal and vertical correlations, in the form of:

[0021] U(x,y,z)=U t (x,y)exp(ik z z).

[0022] Here, k = ω / c is the wave vector, which has a transverse component and a longitudinal component k. 2 =k z 2 +k t 2 U t(x,y) is an arbitrary complex-valued function that depends only on the transverse coordinates x,y. In U(x,y,z), the z-correlation in the beam propagation direction results in pure phase modulation, such that the intensity I of the solution is propagation invariant or non-diffractive.

[0023] I(x,y,z)=|U(x,y,z)| 2 =I(x,y)

[0024] The scheme provides different solution categories in different coordinate systems, such as the Mathieu beam in elliptical-cylindrical coordinates or the Bessel beam in circular-cylindrical coordinates.

[0025] Experiments have shown that several well-approximated non-diffractive beams, or quasi-non-diffractive beams, can be realized. Unlike the theoretical structure, these quasi-non-diffractive beams carry only a finite amount of power. The propagation invariance length L of these quasi-non-diffractive beams is also finite.

[0026] Based on the standard ISO 11146 1-3 regarding laser beam characteristics, the beam diameter is determined by the so-called second moment. Here, the power or zeroth moment of the laser beam is defined as:

[0027] P = ∫dx dyI(x,y).

[0028] The first-order spatial moment indicates the centroid of the intensity distribution and is defined as:

[0029]

[0030]

[0031] Based on the above equations, the second-order spatial moment of the transverse intensity distribution can be calculated:

[0032]

[0033]

[0034]

[0035] By utilizing the fully defined second-order spatial moments of the laser beam, the beam diameter or focal region size can be determined along the principal axis. Here, the principal axis is the direction of the minimum and maximum extension scales (Ausdehnung) of the transverse beam profile, i.e., the intensity distribution perpendicular to the beam propagation direction, the directions of which always extend orthogonally to each other. The focal region d of the laser beam is then derived as follows:

[0036]

[0037]

[0038] in,

[0039]

[0040] In particular, through the value d x and d y The long and short principal axes of the lateral focal zone are determined.

[0041] Therefore, the focal region of the Gaussian beam is determined by the second moment of the beam. In particular, the size d of the transverse focal region is derived from this. GF x,y And the longitudinal extension scale of the focal region, i.e., the Rayleigh length z R Rayleigh length z R via z R =π(d GF x,y ) 2 / 4λ is given. This Rayleigh length describes the distance along the beam propagation direction from the location of maximum intensity, at which the area of ​​the focal region increases by a factor of 2.

[0042] The focal region of the quasi-non-diffractive beam is also determined by the second moment of the beam. In particular, the focal region is determined by the size d of the transverse focal region. ND x,y The characteristic length L is derived from the longitudinal extension scale of the focal region. The characteristic length L of a quasi-non-diffractive beam is defined by an intensity decrease of up to 50% along the beam propagation direction from the local intensity maximum.

[0043] Just when for d ND x,y ≈d GF x,y That is, for similar horizontal dimensions, when the feature length L is significantly greater than the Rayleigh length of the associated Gaussian focus, for example when L > 10z R At that time, there exists a quasi-non-diffractive beam.

[0044] As a subset of quasi-non-diffractive beams, quasi-Bessel beams or quasi-Bessel beams (also referred to herein as Bessel beams) are known. Here, the transverse field distribution near the optical axis readily and approximately obeys an nth-order Bessel function of the first kind. Another subset of this type of beam is the Bessel-Gaussian beam, which is widely used due to its ease of generation. Therefore, in refractive, diffractive, or reflective embodiments using collimated Gaussian beams, illumination by an axial conic section allows for the shaping of Bessel-Gaussian beams. Here, the associated transverse field distribution near the optical axis readily and approximately obeys a 0th-order Bessel function of the first kind, which is enveloped by a Gaussian distribution.

[0045] Accordingly, it is advantageous to use quasi-non-diffractive beams, especially Bessel beams, to process materials, as this allows for large focal position tolerances.

[0046] For example, a typical Bessel-Gauss beam used for processing materials has a size of d. ND x,y The lateral focal region is 2.5 μm, while the feature length can be 50 μm. However, for a feature with a size of d... GF x,y A Gaussian beam with a transverse focal region of 2.5 μm has a Rayleigh length in air of only z when λ = 1 μm. R ≈5μm. Therefore, in these cases relevant to material processing, L>>10z R It is applicable.

[0047] In particular, the lateral focal region of a quasi-non-diffractive beam can be non-radially symmetrical.

[0048] Here, non-radial symmetry means, for example, that the lateral focal region is stretched in one direction. However, a non-radial symmetric focal region can also mean that the focal region is, for example, cross-shaped, triangular, or N-shaped, such as pentagonal. Furthermore, a non-radial symmetric focal region can include additional rotationally symmetric and mirror-symmetric beam cross-sections.

[0049] For example, there can be an elliptical focal region perpendicular to the direction of propagation, wherein the ellipse has a major axis d. x and minor axis d y Therefore, when the ratio d x / d y When it is greater than 1, especially when d x / d y When = 1.5, an elliptical focal region exists. The elliptical focal region of a specific beam can correspond to an ideal mathematical ellipse. However, the current specific focal region of a quasi-non-diffracting beam can also only have the proportions of the long principal axis and the short principal axis b mentioned above, but can have different contours—for example, an approximate mathematical ellipse, a dumbbell shape, or other symmetrical or asymmetrical contours that are enveloped by a mathematically ideal ellipse.

[0050] In particular, elliptical quasi-non-diffractive beams can be generated using quasi-non-diffractive beams. These elliptical quasi-non-diffractive beams possess specific characteristics derived from analysis of beam intensity. For example, an elliptical quasi-non-diffractive beam has a principal maximum value that coincides with the center of the beam. The center of the beam is given by the location where the principal axes intersect. In particular, an elliptical quasi-non-diffractive beam can be obtained by superimposing multiple intensity maximum values, where, in this case, only the envelope of the participating intensity maximum values ​​is elliptical. Furthermore, each intensity maximum value need not have an elliptical intensity profile.

[0051] Here, the submaximum, derived from the solution of the Helmholtz equations, which is closest to the principal maximum, has a relative intensity greater than 17%. Therefore, depending on the laser energy transmitted in the principal maximum, so much laser energy is also directed in the submaximum, enabling material processing. Furthermore, the closest submaximum always lies on a straight line perpendicular to the long principal axis or parallel to the short principal axis and extends through the principal maximum.

[0052] Here, the elliptical quasi-non-diffractive beam can have non-zero intensity along the long principal axis, especially exhibiting interference contrast I. max -I min / (I max +I min The value of ) < 0.9 allows the laser energy to be transmitted throughout the long main axis of the beam.

[0053] I max Here is the maximum beam intensity along the long principal axis, while I min It is the minimum beam intensity. When I min When I = 0, complete interference occurs along the long principal axis, resulting in an interference contrast of 1. When I min When the value is greater than 0, interference occurs only partially or not at all along the long principal axis, resulting in an interference contrast of less than 1.

[0054] For example, if the interference contrast along the long principal axis is less than 0.9, then complete interference will not occur along the long principal axis, but only partial interference will occur. This partial interference will not cause the laser intensity to reach the minimum value I. min The beam is completely erased at the location. This is the case, for example, when a quasi-non-diffractive beam is generated by means of a birefringent element, such as a Quartz Angle Displacer or a Quartz Beam Displacer, or a combination thereof.

[0055] However, an elliptical quasi-diffractive beam can also have a non-zero intensity and an interference contrast of 1 along its long principal axis, preventing the beam from propagating laser energy everywhere along the long principal axis. This is, for example, when a quasi-diffractive beam is generated using a modified axial cone.

[0056] A focusing optics device can be a lens or a combination of lenses and / or mirrors, wherein the focusing optics device focuses a quasi-non-diffractive beam onto or into a material, i.e., images it onto a focal point or a focal plane. This can mean that the focal point of the laser beam is located above, precisely on, or within the volume of the material, via the focusing optics device.

[0057] In particular, the term "focus" can generally be understood as a targeted intensity enhancement, in which laser energy is concentrated into a "focal region." Therefore, in particular, the term "focus" will be used below regardless of the actual beam shape used or the method used to induce the intensity enhancement. "Focusing" can also influence the location of the intensity enhancement along the beam propagation direction. For example, the intensity enhancement can be constructed linearly, in which a Bezier-shaped focal region is formed around the focal location, as can be provided by a non-diffractive beam.

[0058] Correspondingly, a laser beam can be focused along the propagation direction using focusing optics. During focusing, the intensity of the laser beam is maximized towards the laser focal point. Consequently, the intensity of the laser beam is less in front of or behind the laser focal point along the beam propagation direction than at the laser focal point.

[0059] In a mathematically ideal scenario, the focal plane of a focusing optics is a plane perpendicular to the beam propagation direction. This plane preferably extends parallel to the surface of the material to be processed, and the processing of the material should take place within this plane. However, in practical implementations, optical elements in the beam path cause slight bending and distortion of this focal plane, resulting in a focal plane that is typically at least locally bent. Furthermore, the focal point of a laser beam has a finite volume within which the material can be processed. Therefore, what is derived from a focusing optics is not a focal plane, but rather a usable focal volume within which material processing can be performed. This is always considered in the case of either a focal point or a focal plane.

[0060] Therefore, the penetration depth of the laser beam can be determined relative to the surface of the material to be processed by shifting the position of the laser focus along the beam propagation direction or by shifting the focus. This penetration depth is given by the distance between the focus position and the surface of the material.

[0061] A beamforming element can apply a quasi-non-diffractive beam shape to a laser beam in front of and / or behind the focusing optics. When the beamforming element applies a quasi-non-diffractive beam shape to the laser beam in front of the focusing optics, the penetration depth into the material from the focal region can be determined by focusing. However, the beamforming element can also be configured such that a non-diffractive beam shape is not produced, but rather the quasi-non-diffractive beam shape is obtained through imaging using the focusing optics.

[0062] The laser beam is at least partially absorbed by the material, causing the material to be heated, for example, thermally heated, or transitioned to a temporary plasma state and evaporated, thereby being processed. In particular, it is also possible to utilize nonlinear absorption processes in addition to linear absorption processes, which become available through the use of high laser energy.

[0063] For example, materials processing can involve the microstructuring of materials. Microstructuring can mean introducing one-dimensional, two-dimensional, or three-dimensional structures, patterns, or material modifications into the material, where the size of the structure is typically in the micrometer range, or the resolution of the structure is on the order of the wavelength of the laser used. In particular, such materials processing also includes processes known as laser drilling, laser cutting, or laser polishing.

[0064] However, processing materials can also mean separating them along a defined separation line.

[0065] However, the processing of materials can also include the introduction of material modifications. Material modification is a permanent stofflich change in the material at thermal equilibrium, caused by direct laser radiation.

[0066] Here, material modification can be a modification of the material's structure, particularly a crystalline structure and / or an amorphous structure and / or a mechanical structure. For example, a material modification introduced into an amorphous glass material can involve obtaining a modified network structure only in that region of the glass material through localized heating. Material modification can be, in particular, a localized density change, which can also depend on the material chosen.

[0067] Material processing can also involve welding. Here, mating components are arranged overlapping each other, and a laser beam is focused onto the resulting interface. By melting one or both mating components in the focal region, the resulting molten metal can bridge the interface between the mating components and establish a permanent connection between them after cooling.

[0068] The intensity of material processing depends primarily on the location of the focal zone achieved through focusing optics. For example, the focal zone can be located within the total volume of the material to be processed, or it can be positioned on a surface. In the first case, processing can occur within the volume, while in the second case, surface processing can be performed.

[0069] The total distance between the output end of the hollow fiber and the beamforming element can be adjusted to adjust the illumination at the input end of the beamforming element and thus adjust the length of the elongated focal region.

[0070] In particular, the shape of the applied beam profile depends on the illumination method, for example, on the diameter of the laser beam on the beamforming element. Therefore, the diameter of the laser beam on the beamforming element and thus the shape of the applied beam profile can be adjusted by adjusting the total spacing.

[0071] The beamforming element can be an axial cone or a diffractive optical element, wherein the length of the elongated laser focal region in the beam propagation direction is determined by the diameter of the laser beam at the input end of the beamforming element.

[0072] An axial cone is an optical element ground into a cone shape that can impart a quasi-diffractive beam profile to a Gaussian laser beam as it passes through. Specifically, the axial cone has a cone angle α, which is the distance from the beam incident surface to the side surface of the cone. It is used for calculation.

[0073] Diffraction elements also allow the laser beam to be fanned out in space onto a pre-defined geometry.

[0074] As described above, the laser beam exits from the output end of the hollow fiber at a divergence angle, causing the diameter of the laser beam to increase or decrease in the beam propagation direction according to this divergence angle. In particular, the laser beam thus has a defined beam diameter after the corresponding total spacing.

[0075] Since the laser beam passes through the beam incident surface of the beamforming element and penetrates into the beamforming element, a quasi-non-diffractive beam with an elongated focal region can be formed from the laser beam by refraction and / or diffraction and / or reflection.

[0076] For example, a laser beam with a beam diameter defined by the total spacing can be incident perpendicularly onto the beam incident surface of an axial cone mirror, wherein the axial cone mirror has a first refractive index n1. Since the laser beam is incident perpendicularly onto the beam incident surface, almost all the energy is transferred into the axial cone mirror. However, in particular, the laser beam is not refracted due to its perpendicular incidence.

[0077] Next, the laser beam passes through the conical surface of the axial cone and transitions from the medium of the axial cone into the surrounding medium, which has a second refractive index n2, which is n2 = 1 for air. Due to the cone angle, the laser beam is incident at an angle on the (inner) interface of the axial cone, causing it to refract towards the optical axis. Here, compared to a beam further from the edge, the beam from the edge requires an additional propagation path to intersect the optical axis. This deformation of the laser beam results in an elongated focal region behind the axial cone. The length of this elongated focal region depends on the diameter of the incident laser beam and on the refractive index and cone angle of the axial cone. This is approximately derived from Snell's law of refraction.

[0078] The beamforming element can additionally form at least a portion of the lens device and can have additional optical imaging characteristics, such as having at least a segmentally, spherically shaped side oriented against the beam propagation direction to affect the divergence angle of the coupled output laser beam as it passes through the beamforming element.

[0079] Because the beamforming element has segmented, spherically shaped sides, it can have a lens-like effect. This lens-like effect can be influenced by the radius of curvature of the segmented, spherically shaped sides. This lens-like effect means that the laser beam can be focused or scattered. Therefore, it is possible to avoid additional optical elements in the beam path between the output end of the hollow fiber and the beam path.

[0080] Because the beamforming element is oriented in a segmented, spherical manner against the direction of beam propagation, the beamforming element that primarily performs beamforming is also oriented in a direction against the direction of beam propagation. Therefore, before laser beamforming, the laser beam first undergoes focusing, diffusion, or collimation. Correspondingly, the laser beam diameter affected by this certainly influences the length of the elongated focal region.

[0081] To construct optical imaging characteristics, alternatively or additionally, the beamforming element may have diffraction microstructures on a surface and / or in the volume of the beamforming element, the surface being, for example, a side of the beamforming element oriented against the direction of beam propagation. With the aid of diffraction microstructures, the effects mentioned above regarding the spherically shaped side of the beamforming element can be achieved, for example.

[0082] However, optical imaging characteristics can also include the function of beamforming elements as phase masks. For example, diffractive optical elements can simultaneously and in combination perform both beamforming and collimation of a laser beam. Alternatively, the back side of an axicon may be combined with a Fresnel lens, such as a lens written into or etched into the axicon.

[0083] However, it is also possible that aspherical surfaces or free-form surfaces with unilateral structure can be used as beamforming elements with optical imaging characteristics, or that aspherical surfaces or free-form surfaces can be combined with beamforming elements to form beamforming elements with optical imaging characteristics.

[0084] The lens device can be configured to adjust the divergence angle of the coupled output laser beam, wherein the lens device is arranged between the output end of the hollow fiber and the input end of the beamforming element at a first distance, and wherein the lens device includes a first lens having a first focal length and being positioned at a first distance from the output end of the hollow fiber, wherein the first distance is fixed or adjustable.

[0085] Here, the focal length of the lens is the length along the optical axis, after which a parallel laser beam is focused.

[0086] The distance between the first lens of the lens device and the beamforming element is the difference between the total distance and the first distance. Here, the first lens is positioned in the beam propagation direction with a first distance from the output end of the hollow fiber, such that the first lens focuses, scatters, or collimates the laser beam from the hollow fiber. Specifically, it is possible to adjust, through the first distance, whether the divergence angle of the laser beam from the hollow fiber should be increased or decreased. However, it is also possible that the first distance is set to a fixed value, so that its size cannot be adjusted.

[0087] This has the following advantages: the divergence angle of the laser beam behind the lens device can be adjusted by the lens device, and therefore the diameter of the laser beam on the beamforming element can be adjusted by the distance between the first lens and the input end of the beamforming element and the divergence angle.

[0088] The first lens can be a scattering lens.

[0089] This allows for an increase in the divergence angle of the laser beam originating from the input end of the hollow fiber.

[0090] This allows the laser beam to achieve the desired beam diameter after a relatively short propagation period. Consequently, the structural size of the optical system can be significantly reduced.

[0091] This allows the characteristics of the laser beam to be optimally adapted to the optical characteristics of the subsequent lens device.

[0092] A beam splitter optics device can be arranged behind the first lens in the beam direction. This beam splitter optics device is configured to deflect a portion of the laser beam from the beam direction.

[0093] For example, the beam splitter optics can be a beam splitter cube or a beam splitter plate, wherein, as the laser beam passes through the beam splitter optics, the laser beam splits into at least two sub-beams. The two sub-beams can have the same intensity or different intensities, depending on the resolution of the beam splitter optics. And so on. In particular, the beam splitter optics can be arranged such that only a portion of the laser beam is deflected from the beam direction, while the other portion continues to propagate along the original beam direction.

[0094] The deflected portion of the laser beam can be provided to at least one additional beamforming element and at least one additional processing optics.

[0095] This makes it possible to split the laser beam provided by an ultrashort pulse laser, and thus process the material at different locations using sub-laser beams. Alternatively, other materials or other workpieces can be processed simultaneously.

[0096] The lens device may additionally have a second lens and the second lens may be positioned behind the first lens in the beam direction with a second distance from the first lens, wherein the second distance is fixed or adjustable.

[0097] The second spacing is measured, in particular, relative to the position of the first lens, such that the spacing between the second lens and the beamforming element is given by the total spacing and the difference between the sum of the first and second spacings.

[0098] By using a lens device that includes a first lens and a second lens, it is particularly possible to manufacture optical components that function like a telescope. In particular, this enables both magnified and reduced optical imaging. It also allows for precise adjustment of the diameter of the laser beam on the beamforming element. Furthermore, the divergence angle of the laser beam can be adjusted more accurately using the two lenses of the lens device.

[0099] In a preferred embodiment, the first spacing may be fixed, wherein the first spacing is equal to the first focal length and thereby collimates the laser beam by the first lens, wherein, in order to adjust the diameter of the laser beam on the beamforming element, the first lens is replaced with another first lens having another first focal length, which is arranged in front of the output end of the hollow fiber with another first spacing, the other first spacing being equal to another first focal length, and thereby collimates the laser beam by the other first lens.

[0100] This has the following advantages: the first lens and another first lens collimate the laser beam at a first spacing or another first spacing, respectively, so that a defined beam diameter is achieved on the beamforming element after the total spacing. Since the first spacings are fixed and therefore cannot be adjusted, there is no need to calibrate critical components, such as telescopes with lenses or calibrable lenses whose position changes are possible.

[0101] Since the first lenses are arranged at different intervals behind the output end of the hollow fiber and the divergence angle of the hollow fiber is constant, the beam diameter changes as follows: the laser beam is incident on the first lens with this beam diameter. However, since the distance between the first lens and the hollow fiber is equal to the first focal length, the laser beam is collimated in both cases, wherein the diameter of the collimated laser beam on the beamforming element corresponds to the diameter of the laser beam on the first lens.

[0102] In another preferred embodiment, the first spacing may be adjustable, wherein the divergence angle of the laser beam from the hollow fiber is adjusted by adjusting the first spacing, wherein the second spacing may be adjustable and adjusted such that the focal point of the second lens coincides with the point from which the laser beam with the adjusted divergence angle is apparently scheinbared, and the second lens is configured to collimate the diverging laser beam, wherein the diameter of the laser beam on the beamforming element can be adjusted by adjusting the first spacing and the second spacing.

[0103] Specifically, the diverging laser beam from the output end of the hollow fiber is incident on the first lens after the first spacing, thereby correspondingly changing the divergence of the laser beam. The second lens is mounted at the aforementioned spacing such that the focal point of the second lens is located at a point from which the laser beam used for the second lens apparently originates. Correspondingly, the spacing of the second lens is adjusted via the first lens according to the divergence angle of the laser beam. If the length of the focal region needs to be changed, then not only the first spacing of the first lens is changed, but also the second spacing of the second lens is changed.

[0104] This allows for simple adjustment of the beam diameter on the beamforming element.

[0105] For example, the divergence or numerical aperture NA from the hollow fiber can be 0.02. The first lens can have a focal length f1 of -200 mm and can be positioned with a distance of 33.7 mm from the output end of the hollow fiber. The second lens can have a focal length F2 equal to 150 mm and can be positioned with a distance of -121.2 mm from the first lens. Therefore, an approximate collimated beam diameter of 7.5 mm is obtained behind the second lens. If the first distance is changed to 118.3 mm and the second distance is changed to 75.5 mm, a collimated sub-beam is also generated, but this collimated sub-beam has a beam diameter of 10.2 mm.

[0106] If only one of the two lenses moves, this results in a diverging or converging laser beam. Correspondingly, as the initial distance increases, the beam diameter becomes larger.

[0107] Here, an additional, more compact construction can be achieved by positioning the divergence of the hollow fiber using an additional lens positioned in front of the first lens, thereby improving the divergence.

[0108] In another preferred embodiment, the total pitch can be adjustable, wherein the diameter of the laser beam on the beamforming element can be adjusted by adjusting the total pitch.

[0109] For example, the beamforming element can thus possess optical imaging characteristics. For instance, the beamforming element can be an axonocone and can have at least a segmentally, spherically shaped side oriented against the beam propagation direction to influence the divergence angle of the coupled output laser beam as it passes through the axonocone. However, it is also possible that the beamforming element is a diffractive optical element, wherein a lensing effect is simultaneously incorporated into the diffractive optical element, such that the beamforming element possesses both a lensing effect and a beamforming effect.

[0110] For example, the radius of the back side of the spherical surface of the axial cone can be 75 mm. This results in a collimated laser beam with a beam diameter of approximately 6.5 mm, where the distance between the output end of the hollow fiber and the beamforming element corresponds to twice the radius and is therefore 150 mm. When the axial cone is displaced, the laser beam is no longer collimated but diverges, causing a change in the length of the focal region through the beamforming element. For example, when the distance between the hollow fiber and the axial cone becomes shorter, the focal region becomes shorter. Conversely, when the distance between the hollow fiber and the axial cone becomes longer, the focal region becomes longer.

[0111] In another preferred embodiment, the first spacing may be fixed, while the total spacing may be adjustable, and the diameter of the laser beam on the beamforming element may be adjusted by adjusting the total spacing.

[0112] For example, a divergent beam from the output end of a hollow fiber, having a NA of, for example, 0.02, can be incident on a first lens. This first lens has a fixed distance from the output end of the hollow fiber. To adjust the length of the focal region, the total distance between the beamforming element and the output end of the hollow fiber is changed.

[0113] For example, the first spacing can be 41 mm, where the first focal length can be 56 mm. The total spacing can be 241 mm, such that the spacing between the first lens and the beamforming element is 200 mm. In this case, the beam diameter on the beamforming element is approximately 4 mm. If the total spacing is increased to 441 mm, such that the spacing between the beamforming element and the first lens is 400 mm, the beam diameter increases to approximately 6.3 mm.

[0114] The effects on the focal region caused by an uncollimated beam can be compensated for by shifting the focusing optics along or against the direction of beam propagation.

[0115] In another preferred embodiment, the first spacing may be adjustable and the total spacing may be fixed, wherein the diameter of the laser beam on the beamforming element is adjusted by adjusting the first spacing.

[0116] This allows for the generation of highly targeted, divergent sub-beams.

[0117] For example, starting from the possible numerical aperture of a fiber with NA = 0.02, the first lens can be shifted. The first spacing of the first lens can be, for example, 56 mm, where the first focal length is also 56 mm. The distance between the output end of the hollow fiber and the beamforming element, i.e., the total spacing, can be 256 mm, resulting in a beam diameter of 2.38 mm on the beamforming element. If the first spacing is changed to 46 mm, the beam diameter on the beamforming element increases to 3.54 mm. It becomes particularly clear that when the first spacing between the first lens and the output end of the hollow fiber becomes smaller, the beam diameter on the beamforming element becomes larger, and therefore the length of the focal region also becomes larger.

[0118] The effects on the focal region caused by an uncollimated beam can be compensated for by shifting the focusing optics along or against the direction of beam propagation.

[0119] Of all the lens assemblies described above, a particularly preferred configuration is a lens assembly having up to two lenses, wherein one of these lenses may have been integrated into a beamforming element, for example, in the form of a spherically shaped side oriented against the beam propagation direction, or in the form of a diffraction microstructure on the surface of the beamforming element and / or in the form of a diffraction microstructure in the volume of the beamforming element, the surface being, for example, oriented against the beam propagation direction. Constructing the lens assembly in this manner, as indicated, provides a system for processing materials that can be easily calibrated, wherein the length of the focal region can be adjusted. Attached Figure Description

[0120] Further preferred embodiments of the invention will be described in more detail below with reference to the accompanying drawings. As shown herein:

[0121] Figure 1 A schematic configuration of the first embodiment is shown;

[0122] Figure 2 A schematic diagram of an axial cone mirror and the generation of an elongated focal region in the beam propagation direction are shown.

[0123] Figure 3 A and B show schematic diagrams illustrating the generation of different beam diameters according to the first embodiment;

[0124] Figure 4 A schematic construction of the second embodiment is shown;

[0125] Figure 5 A, B, and C show schematic diagrams illustrating the generation of different beam diameters according to the second embodiment;

[0126] Figure 6 A schematic structure of the third embodiment is shown;

[0127] Figure 7 A schematic diagram of a segmented, spherical back-side axial cone is shown;

[0128] Figure 8 A schematic configuration of the fourth embodiment is shown;

[0129] Figure 9 A schematic configuration of the fifth embodiment is shown;

[0130] Figure 10A Figures B, C, and D show schematic diagrams of quasi-non-diffractive beams. Detailed Implementation

[0131] Preferred embodiments will now be described with reference to the accompanying drawings. Here, in different drawings, elements with the same, similar, or identical functions are given the same reference numerals, and to avoid redundancy, some repeated descriptions of these elements are omitted.

[0132] In the following figures, only the axial conical mirrors are shown as beamforming elements 6; however, these axial conical mirrors should be understood to represent other beamforming elements, in particular axial conical mirrors, diffractive optical elements, general-purpose axial conical mirrors, or reflecting axial conical mirrors.

[0133] exist Figure 1 The diagram schematically illustrates a first embodiment of a system 1 for processing material 2 using an ultrashort laser pulse via an ultrashort laser 3.

[0134] Accordingly, system 1 includes an ultrashort pulse laser 3 that provides a laser beam 32 composed of ultrashort laser pulses 30. The laser beam 32 is coupled into the input end 40 of a hollow fiber 4 via a coupling input optics 41. Here, the hollow fiber 4 can transmit the coupled laser beam to the output end 42 of the hollow fiber 4 with almost no loss. Thus, it is particularly possible that the generation of the laser beam 32 in the fixed ultrashort pulse laser 3 is spatially separate from the actual optical elements 6, 7, 8, and 9 of system 1, which will be described later.

[0135] At the output end 42 of the hollow fiber 4, a laser beam 32 is coupled out from the hollow fiber 4 with a divergence angle α. The first lens 81 of the lens device 8 detects the laser beam 32 and deforms the laser beam according to the optical characteristics of the lens 81. This means that the divergence angle α of the laser beam 32 can be adjusted, for example, reduced, by the first lens 81.

[0136] Next, the laser beam 32 is incident on the beam splitter optics 9, wherein the laser beam 32 is split into a first sub-laser beam 32 and a second sub-laser beam 32'. The first sub-laser beam 32 is conveyed to the beamforming element 6, which is configured to apply a quasi-non-diffractive beam shape to the laser beam 32, the quasi-non-diffractive beam shape having a focal region 320 elongated in the beam propagation direction. The quasi-non-diffractive laser beam 320 is then conveyed through a focusing optics 7, which can be composed of a lens assembly, and in particular, the length of the laser focal spot is adjusted in this manner. This allows for the determination of the penetration depth of the focal region 322 of the laser beam 32.

[0137] The focusing optics 7 can be, in particular, a telescope that images the non-diffractive beam, thereby allowing adjustment of the lateral diameter and the length in the beam propagation direction of the elongated focal region 322. The position of the non-diffractive beam in or on the workpiece in the beam propagation direction is typically adjusted by movement of the focusing optics 7 and the beam-forming element 6, wherein the laser beam 32 is preferably collimated.

[0138] Material 2 absorbs at least partially the energy provided by the laser beam 32. Through linear or nonlinear absorption mechanisms, material 2 can be heated or optically and mechanically ablated, resulting in material processing. Here, the shape of the processed region corresponds to the shape of the focal region 322 of the quasi-non-diffractive laser beam 320.

[0139] exist Figure 1 In the current embodiment, the lens device 8 includes only a first lens 81, which is arranged in the beam direction at a variable spacing x1 behind the output end of the hollow fiber 42. Here, the first lens 81 has a first focal length f1. Depending on the size of the first spacing x1 between the first lens 81 and the output end 42 of the hollow fiber 42, the divergence angle α of the laser beam 32 can be adjusted. In particular, the first lens 81 can be arranged at a spacing of the first focal length f1 behind the output end 42 of the hollow fiber 4, such that the first lens 81 collimates the laser beam 32. If the laser beam 32 is collimated, it means that the edge beams of the laser beam 32 extend parallel to each other, such that the laser beam 32 has a constant diameter D as it propagates further from the first lens 81 to the beamforming element 6.

[0140] The diameter D on the beamforming element 6 determines the size of the focal region 322 of the laser beam 320 elongated in the beam propagation direction behind the beamforming element 6. Therefore, in particular, by changing the diameter D of the laser beam 32 on the beamforming element 6, the size of the focal region 322 of the laser beam 320 elongated in the beam propagation direction behind the beamforming element 6 can be affected.

[0141] In particular, in this first embodiment, the laser beam 32 can be divided into a first sub-laser beam 32 and a second sub-laser beam 32' at the beam splitter 9. The first sub-laser beam is transmitted to the beamforming element 6 already described, and the second sub-laser beam is transmitted to another beamforming element 6' and another focusing optics 7'.

[0142] exist Figure 2The diagram schematically illustrates how the beam diameter D on the beamforming element 6 determines the length L of the elongated focal region 322 in the beam propagation direction. Axicone 62 is shown very schematically as beamforming element 6. Axicone 62 is a tapered optical element that, in this case, has a flat back side 622 oriented against the beam propagation direction or facing the laser beam 32. Additionally, axicone 62 has a tapered side surface 620, wherein the tapered side forms an angle β with the flat back side of axicone 62. When incident perpendicularly on the flat back side of axicone 62, the parallel laser beam 32 continues to propagate through the material of the axicone in an unrefractive manner. However, the laser beam 32 eventually incident on the tapered side of axicone 62, such that the laser beam 32 forms an angle β with the surface normal of axicone 62. Accordingly, according to Snell's law of refraction, the laser beam 32 is refracted as it transitions from the axial conical mirror 62 into the surrounding medium. Because the laser beam 32 transitions from a medium of higher optical density, i.e., within the axial conical mirror 62, to air, it is refracted towards the optical axis. Since the axial conical mirror 62 is constructed in a rotationally symmetric manner, this results in refraction of the laser beam towards the optical axis 624 occurring over the entire diameter of the axial conical mirror 62. For basic trigonometry, it is ultimately concluded that the angle of refraction γ and diameter D of the incident laser beam 320 give the length L of a region in which an artificial intensity increase is produced by the axial conical mirror 62.

[0143] exist Figure 3 Examples are shown in A and 3B, illustrating how it is possible to use Figure 1 The implementation method is used to adjust the diameter of the laser beam on the beamforming element 6.

[0144] exist Figure 3 In A, the first lens 81 is arranged with a distance x1 from the output end 42 of the hollow fiber 4. Here, the first distance x1 corresponds to the first focal length f1 of the first lens 81. As a result, the diverging laser beam 32 originating from the hollow fiber 4 is transformed into a parallel laser beam 32. Here, the diameter D of the laser beam 32 on the beamforming element 6 is obtained from the divergence angle α of the laser beam from the hollow fiber 4 and the focal length f1 of the first lens 81.

[0145] exist Figure 3In B, the first lens 81 is replaced by another first lens 81'. This other first lens 81' has a different first focal length f1'. To shape a parallel laser beam 32 from the diverging laser beam 32 of the hollow fiber 4, the other first lens must be arranged behind the output end 42 of the hollow fiber 4 with a different first spacing x1'. Since the divergence of the laser beam behind the output end 42 of the hollow fiber 4 is independent of the lens focal length, different spacings x1 and x1' result in different diameters D' of the laser beam 32 on the first lens 81'. Because the laser beam 32 extends parallel after passing through the first lens 81', the diameter D' of the laser beam 32 on the beamforming element 6 corresponds to the diameter D' of the laser beam 32 on the first lens 81'.

[0146] The length L of the elongated focal region 322 is changed by altering the diameters D and D' of the laser beam 32 on the beamforming element 6.

[0147] exist Figure 4 The second embodiment of system 1 is shown. Here, a lens device 8 is arranged behind the output end 42 of the hollow fiber 4 in the beam propagation direction. The lens device includes two lenses 81 and 82. The spacing of the first lens 81, which is arranged with a first spacing x1 to the output end 42 of the hollow fiber 4, and the spacing of the second lens 82, which is arranged with a second spacing x2 to the first lens 81, can be changed.

[0148] In this configuration, the first lens 81 has the task of matching the divergence angle α of the laser beam 32 emitted from the output end 42 of the hollow fiber 4. Specifically, the divergence angle α of the laser beam 32 can be changed after the first lens 81 by adjusting the first distance x1 from the output end 42 of the hollow fiber 4. In this case, the second lens 82 is arranged with a distance x2 from the first lens 81 such that the focal point of the second lens 82 coincides with a point from which the laser beam 32 appears to originate. Thus, collimation of the laser beam 32 is achieved, particularly relative to the position of the first lens 81, after the second lens 82.

[0149] exist Figure 5 Different scenarios of the second embodiment are shown in A, 5B, and 5C.

[0150] exist Figure 5In A, the laser beam 32 from the output end 42 of the hollow fiber 4 is incident on the first lens 81 of the lens device 8 after a distance x1, wherein the first lens 81 is a scattering lens. With the scattering lens, the divergence angle α of the laser beam 32 increases. Thus, a larger diameter D of the laser beam is achieved on the second lens 82 of the lens device 8 after a shorter distance x2. This makes it particularly possible that the laser beam 32 is already collimated after a shorter total distance xG, thereby reducing the overall optical structure length of the system (not shown). Here, the second lens 82 is arranged with a distance x2 from the first lens 81, wherein the distance x2 is not equal to the focal length F2. In particular, the distance x2 is chosen such that the focal point of the lens 82 coincides with the point at which the laser beam 32 appears to originate from the second lens 82. This point can be located, in particular, between the scattering lens 81 and the output end 42 of the hollow fiber 4.

[0151] exist Figure 5 The second embodiment is illustrated in example B, where the two lenses 81 and 82 of the lens device 8 are converging lenses, which typically reduce the divergence angle α of the laser beam. Specifically, the first lens 81 is arranged with a distance x1 from the output end 42 of the hollow fiber 4, while the second lens 82 is arranged with a distance x2 from the first lens 81. The first lens 81 does not collimate the laser beam 32. Collimation of the laser beam 32 is performed by the second lens 82. This makes it particularly possible to accurately adjust the diameter D of the laser beam 32 on the beamforming element 6.

[0152] exist Figure 5 C illustrates the following situation: In this situation, the first lens 81 of the lens device 8 is compared to... Figure 5 In component B, a small spacing x1' is arranged behind the output end 42 of the hollow fiber 4. Because the spacings x1 and x1' are different, the resulting beam diameters D and D' produced by the first lenses 81 and 81' are different. The second lenses 82 and 82' correspondingly collimate the laser beam 32. Therefore, in Figure 5 In B and 5C, different beam diameters D and D' are generated on the beamforming element 6 by different illumination from the first and second lenses 81 and 82.

[0153] exist Figure 6 The third embodiment is shown, in which the beamforming element 6 has additional optical imaging characteristics. In particular, this embodiment shows an axial cone 62 having at least a segmented, spherical back side 622. In other words, the beamforming element 6 also has a lens device 8 in the form of a spherical back side 622.

[0154] In this embodiment, the total spacing xG between the output end 42 of the hollow fiber 4 and the beamforming element 6 can be changed to adjust the beam diameter D of the laser beam 32 set on the beamforming element 6. Here, the beam diameter D is given directly by the divergence angle α of the hollow fiber 4 and the total spacing xG. The segmentally, spherically constructed back side 622 of this axial cone has, for example, the function of at least partially collimating the laser beam 32, or deflecting the laser beam 32 into a suitable trajectory so that the subsequent focusing optics 7 can accordingly introduce the laser beam 320 into the material 2.

[0155] exist Figure 7 For example, from Figure 6 A schematic detailed drawing of an embodiment of an axial cone mirror 62 having a segmented, spherical back side 622. A laser beam 32 is incident on the spherical back side 622 of the axial cone mirror 62 with a divergence angle α. The spherical back side 622 enables collimation of the laser beam 32 in the medium of the axial cone mirror at a suitable spacing xG, resulting in an elongated focal region 322 on the optical axis 624 of the axial cone mirror 62.

[0156] If the axial cone mirror 62 should not be arranged at a spacing of x1 such that the beam extends non-parallel within the axial cone mirror 62, the divergence of the laser beam 320 can be compensated by means of a corresponding focusing optics 7.

[0157] To construct optical imaging characteristics, alternatively or additionally, the axial cone 62 may have diffraction microstructures (not shown) on its surface and / or in the volume of the axial cone 62, the surface being, for example, the back side 622 of the axial cone 62 oriented against the direction of beam propagation. With the aid of these diffraction microstructures, the effects mentioned above regarding the spherically shaped back side 622 of the axial cone 62 can be achieved, for example, and instead of a spherical back side, for example, in… Figure 2 The diffraction microstructure is disposed on the flat back side 622 shown.

[0158] exist Figure 8 The fourth embodiment is shown in the figure. In this fourth embodiment, the first spacing x1 of the first lens 62 is fixed, and the total spacing xG between the beamforming element 6 and the output end 42 of the hollow fiber 4 can be adjusted.

[0159] The laser beam 32 is incident on the first lens 81 at a divergence angle α. Here, the first lens 81 can be, for example, a converging lens that at least partially collimates the laser beam 32. In other words, if, for example, the divergence angle α is too large for the corresponding configuration, "pre-collimation" of the diverging laser beam 32 can be almost performed. Therefore, by varying the distance between the first lens 81 and the beamforming element 6, the diameter D of the laser beam 32 on the beamforming element 6 can be changed, and thus the length L of the focal region can be changed.

[0160] exist Figure 9 The fifth embodiment is shown, in which the lens device 8 includes only a first lens 81, which is arranged with an adjustable distance x1 between itself and the output end 42 of the hollow fiber 4. The total distance xG between the beamforming element 6 and the output end 42 of the hollow fiber 4 is fixed in this embodiment. Correspondingly, the diameter D of the laser beam 32 on the beamforming element 6 can be adjusted by moving the first lens 81 between the beamforming element and the output end 42 of the hollow fiber 4. This allows for adjustment of the diameter D of the laser beam 32 on the beamforming element 6. The residual divergence of the beam 32 remaining after the beamforming element 6 can be compensated for by a suitable arrangement of the focusing optics 7.

[0161] In all the embodiments shown, additional optical elements, such as filters, light shields, beam splitters, wedges, and birefringent lenses, can be arranged in the beam path after the axicon. Additionally, the first lens of the subsequent telescope, shown in the figures, can also be integrated into the axicon.

[0162] exist Figure 10A The intensity curve of the quasi-non-diffractive laser beam 320 is shown. In particular, the quasi-non-diffractive beam 320 is a Bessel-Gaussian beam. In the transverse focal region in the xy plane, the Bessel-Gaussian beam has radial symmetry, such that the intensity of the laser beam depends only on the distance from the optical axis.

[0163] exist Figure 10B The image shows the longitudinal focal region along the beam propagation direction. The focal region 322 is elongated in the beam propagation direction and is approximately 3 mm long. Therefore, the focal region 322 is significantly larger in the propagation direction than the transverse focal region in the xy plane.

[0164] exist Figure 10C In, with Figure 10A Similarly, a quasi-non-diffractive beam is shown, whose transverse focal region is non-radially symmetric. In particular, the transverse focal region appears to be stretched in the y-direction, almost elliptical, resulting in a long principal axis and a short principal axis, with the long principal axis having an extension scale of approximately 3 μm in the example shown.

[0165] exist Figure 10D The image shows a cross-section of the longitudinal focal region of the quasi-non-diffractive beam in the xy plane. The focal region extends approximately 3 mm along the z-axis. Correspondingly, the quasi-non-diffractive beam also has a focal region 322 that is elongated in the beam propagation direction.

[0166] Wherever available, all individual features shown in the embodiments may be combined and / or interchanged with each other without departing from the scope of the invention.

[0167] List of reference numerals

[0168] 1 System

[0169] 2. Materials

[0170] 3. Laser

[0171] 30 laser pulses

[0172] 32 laser beams

[0173] 320 non-diffraction beam

[0174] 322 Elongated focal area

[0175] 4. Hollow-core optical fiber

[0176] 40. Input end of hollow fiber

[0177] 41 Coupled Input Optics

[0178] 42 Output end of hollow fiber

[0179] 6. Beamforming element

[0180] 62-axis conical mirror

[0181] 620 side surface

[0182] 622 Dorsal side

[0183] 624 Optical Axis

[0184] 7. Focusing Optical Devices

[0185] 8. Lens Equipment

[0186] 81 First Lens

[0187] 82 Second Lens

[0188] 83 Other lenses

[0189] 9. Beam splitter optics

[0190] α divergence angle

[0191] x1 First spacing

[0192] x2 Second spacing

[0193] xG Total Spacing

[0194] L is the length of the focal region.

[0195] D is the diameter of the laser beam.

[0196] d. Diameter of the focal region

[0197] f1 First focal length

[0198] f2 Second focal length

Claims

1. A system (1) for processing materials (2) using an ultrashort laser pulse (3), the system comprising: An ultrashort pulse laser (3) is used to generate ultrashort laser pulses and to provide a laser beam (32). Hollow-core optical fiber (4), wherein the hollow-core optical fiber is provided for transmitting the laser beam (32) to the output end (42) of the hollow-core optical fiber (4). A coupling input optics (41) is provided for coupling the laser beam (32) into the input end (40) of the hollow fiber (4). The output end (42) of the hollow fiber (4) is configured to couple and output the laser beam (32) from the hollow fiber (4) at a divergence angle (α). The device includes a lens assembly (8), a beamforming element (6), and a focusing optics device (7). A laser beam (32) coupled out from the hollow fiber (4) irradiates the lens assembly at the divergence angle (α), and a laser beam (32) emitted from the lens assembly (8) irradiates the beamforming element. The lens device (8) is configured to match the divergence angle (α) of the coupled output laser beam (32) to match the beam diameter (D) of the laser beam (32) on the beamforming element (6), and to adjust the divergence angle (α) of the coupled output laser beam (32). The lens device (8) is arranged between the output end (42) of the hollow fiber (4) and the input end of the beamforming element (6) with a first spacing (x1). The lens device (8) includes a first lens (81) having a first focal length (f1) and positioned with respect to the output end (42) of the hollow fiber (4) at the first spacing (x1). The first spacing (x1) is fixed or adjustable. The beamforming element (6) is configured to apply a quasi-non-diffractive beam shape to the laser beam (32) in front of or behind the focusing optics (7), the quasi-non-diffractive beam shape having a focal region (322) elongated in the beam propagation direction. The focusing optics (7) is configured to adjust the focal area (322) to the material (2) or to the material at a depth of introduction.

2. The system (1) according to claim 1, characterized in that, The total distance (xG) from the output end (42) of the hollow fiber (4) to the beamforming element (6) can be adjusted in order to adjust the illumination at the input end of the beamforming element (6) and thus adjust the length (L) of the focal region (322) that is elongated in the beam propagation direction.

3. The system (1) according to any one of claims 1 or 2, characterized in that, The duration of the laser pulse is between 0.01 ps and 100 ps.

4. The system (1) according to claim 1 or 2, characterized in that, The beamforming element (6) is an axonocone (62) or a diffractive optical element, wherein the length (L) of the laser focal region (322) elongated in the beam propagation direction is determined by the diameter (D) of the laser beam (32) at the input end of the beamforming element (6).

5. The system (1) according to claim 1 or 2, characterized in that, The beamforming element (6) additionally constitutes at least a portion of the lens device (8).

6. The system (1) according to claim 5, characterized in that, The beamforming element (6) has at least a segmentally and spherically shaped side (622) oriented against the direction of beam propagation and / or a diffraction microstructure on the side (622) oriented against the direction of beam propagation and / or a diffraction microstructure in the volume of the beamforming element (6) to influence the divergence angle (α) of the laser beam (32) as it passes through the beamforming element (6).

7. The system (1) according to claim 1 or 2, characterized in that, The first lens (81) is a scattering lens.

8. The system (1) according to claim 1 or 2, characterized in that, A beam splitter optics (9) is arranged behind the first lens (81) in the beam direction. The beam splitter optics are configured to deflect a portion of the laser beam (32) from the beam direction.

9. The system (1) according to claim 8, characterized in that, The deflected portion (32') of the laser beam (32) is provided to an additional beamforming element (6') and an additional focusing optics (7').

10. The system (1) according to claim 1 or 2, characterized in that, The lens device (8) additionally has a second lens (82) positioned behind the first lens (81) in the beam direction with a second distance (x2) from the first lens (81), wherein the second distance is fixed or adjustable.

11. The system (1) according to claim 1 or 2, characterized in that, The first spacing (x1) is fixed and equal to the first focal length (f1), and thus the laser beam (32) is collimated by the first lens (81). In order to adjust the diameter (D) of the laser beam (32) on the beamforming element (6), the first lens (81) is replaced with another first lens (81') having another first focal length (f1'), wherein the other first lens (81') is arranged in front of the output end (42) of the hollow fiber (4) with another first spacing (x1') and the other first spacing (x1') is equal to the other first focal length (f1'), and thus the laser beam (32) is collimated by the other first lens (81').

12. The system (1) according to claim 10, characterized in that, The first spacing (x1) can be adjusted and the divergence angle (α) of the laser beam (32) from the hollow fiber (4) can be adjusted by adjusting the first spacing (x1), wherein the second spacing (x2) can be adjusted and is adjusted such that the focal point of the second lens (82) coincides with the point from which the laser beam (32) having the adjusted divergence angle appears to originate, wherein the second lens (82) is configured to collimate the diverging laser beam (32), wherein the diameter (D) of the laser beam (32) on the beamforming element (6) is adjusted by adjusting the first spacing (x1) and the second spacing (x2).

13. The system (1) according to claim 5, characterized in that, The total distance (xG) from the output end (42) of the hollow fiber (4) to the beamforming element (6) can be adjusted, and the diameter (D) of the laser beam (32) on the beamforming element (6) can be adjusted by adjusting the total distance (xG).

14. The system (1) according to claim 1 or 2, characterized in that, The first spacing (x1) is fixed, and the total spacing (xG) from the output end (42) of the hollow fiber (4) to the beamforming element (6) can be adjusted, wherein the diameter (D) of the laser beam (32) on the beamforming element (6) is adjusted by adjusting the total spacing (xG).

15. The system (1) according to claim 1 or 2, characterized in that, The first spacing (x1) can be adjusted, and the total spacing (xG) from the output end (42) of the hollow fiber (4) to the beamforming element (6) is fixed, wherein the diameter (D) of the laser beam (32) on the beamforming element (6) is adjusted by adjusting the first spacing (x1).

Images