Optical device, optical system, method for machining a sample by means of laser radiation, and sample

Abstract

The invention relates to an optical device for machining a sample by means of laser radiation in at least two machining steps. The device comprises at least one beam splitter, a first optical machining device, and a second optical machining device. The beam splitter is arranged such that a laser beam can be split into at least two partial beams. The partial beams can be oriented towards the sample such that the sample is machined in two machining steps. The optical device comprises a means for changing the power density, so that the power density of the first partial beam is greater than the power density of the second partial beam. The invention also relates to an optical system comprising the optical device, to a method for machining the sample, and to a sample machined by means of the optical device.

Description

[0001] Optical device , optical system and method for processing a sample by means of laser radiation , sample

[0002] The invention relates to an optical device, an optical system and a method for processing a sample by means of laser radiation in at least two processing steps as well as a sample.

[0003] Devices and methods for processing a sample using laser radiation are known from the prior art. The method involves structuring the sample using laser radiation in order to provide it with special surface properties, which is also referred to as surface functionalisation. In this regard, it is known to provide the sample with precise structural geometries using ultrashort laser pulses. However, this gives rise to irregular surface artefacts, for example due to melting effects caused by the thermal interaction of the laser radiation used with the processed sample surface. A further example of such surface artefacts is laser-induced periodic surface structuring (LPS)."Laser-induced periodic surface structures" (LIPSS) in the order of magnitude of the wavelength of the laser radiation used, which form as a result of the polarization of the laser radiation and are dependent on the polarization direction of the ultrashort laser pulses. The surface artifacts are undesirable in many applications because they can impair the desired functionalization of the processed sample. A further disadvantage of the surface artifacts is that they cause tribological effects that impair the friction coefficient of the processed sample.

[0004] Until now, the aforementioned undesirable surface artifacts and their associated disadvantages have been accepted because there was no way to reliably and efficiently remove them. Some known solutions include mechanical post-treatment of the sample, for example by brushing, in order to smooth the sample as much as possible after processing with laser radiation. Post-treatment of the sample using plasma is also known. However, all of the known methods for subsequent processing of the processed sample have low process stability, which prevents their industrial use. Because these methods process the entire sample surface, spatially and / or intensity-selective processing of the sample is not possible. In addition, post-treatment of the sample requires additional equipment to carry out, which means increased costs.In addition, the known methods are associated with a considerable amount of time. Therefore, all of the aforementioned processes are too complex for industrial use.

[0005] It is therefore the object of the invention to eliminate the disadvantages mentioned and in particular to enable efficient post-processing of the sample, wherein in particular the sample should be structured as desired and at the same time the properties of the processed sample should not be impaired by undesired surface artifacts. The object of the invention is achieved by an optical device with the features of claim 1. In this regard, an optical device for processing a sample by means of laser radiation in at least two processing steps is provided with at least one beam splitter, at least one first optical processing device and at least one second optical processing device, wherein the at least one beam splitter is arranged such that a laser beam incident on the optical device can be split into at least two partial beams,wherein the first optical processing device is arranged in such a way that a first partial beam can be aligned onto the sample after the beam splitter and after passing through the first optical processing device in such a way that the sample is processed in the first processing step in a first processing region, wherein the second optical processing device is arranged in such a way that a second partial beam can be aligned onto the sample after the beam splitter and after passing through the second optical processing device in such a way that the sample is processed in a second processing step in a second processing region, wherein the second processing region at least partially overlaps the first processing region, wherein the optical device has at least one power density changing means which is designed in such a way that the power density of the first,partial beam directed at the sample is greater than the power density of the second partial beam directed at the sample.

[0006] Furthermore, the object is achieved by an optical system according to claim 15. The optical system has at least one laser and at least one optical device according to the invention, wherein the laser is designed to emit a laser beam which is aligned with the optical device in such a way that the sample can be processed in the at least two processing steps.

[0007] In terms of the method, the object is achieved by a method according to claim 17, which has the following steps: Providing a laser for emitting a laser beam, wherein the laser beam impinges on a beam splitter in such a way that the laser beam is split into at least two partial beams, wherein a first partial beam is directed onto the sample after passing through a first optical processing device in order to process the sample in a first processing step in a first processing area, wherein a second partial beam is directed onto the sample after passing through a second optical processing device in order to process the sample in a second processing step in a second processing area, wherein the second processing area at least partially overlaps the first processing area, wherein the power density of the first partial beam directed onto the sample is greater than the power density of the second,partial beam directed onto the sample is .,

[0008] The object is also achieved by a sample according to claim 23, which was processed by means of an optical device according to the invention, in particular by means of an optical system according to the invention, and / or by means of a method according to the invention.

[0009] A basic idea of ​​the invention is that, due to the division of the laser beam by the beam splitter into at least two partial beams and the subsequent feeding of the partial beams to the sample, only a single beam source is required to process the sample in the at least two processing steps. For further processing, in particular in the form of post-processing, of the sample during the second processing step, no further device is therefore required, which means cost savings and accelerates the processing of the sample overall. In addition, the processing of the sample during the second processing step can be carried out in a targeted manner in terms of intensity and spatially in a specific area of ​​the sample. This applies in particular if, within the meaning of the invention, surface topographies which are disruptive to the application of the sample due to thermal interaction of the second partial beam with the sample are eliminated.One application in this regard is the improvement of topographies on which LIPSS structures have formed as a result of interferometric processing of the sample during the first processing step. These structures are then thermally treated and ultimately eliminated during the second processing step, for example, by using longer pulse durations of the second partial beam. In this way, the surface topography of the sample can be significantly improved by the invention.

[0010] According to the invention, undesired surface artifacts, which were formed in particular during the first processing step, can therefore be reliably processed within the second processing step. In particular, the processing of enamel morphological artifacts is possible.

[0011] The invention enables simple, versatile, compact, and efficient processing of the sample, whereby, particularly during the second processing step, undesired surface artifacts that may have formed during the first processing step can be reliably and selectively eliminated. A further advantage of the invention is that only a single laser source is required, which significantly increases the efficiency of the invention. This also results in space savings. The same applies to the system and method according to the invention.

[0012] For the purposes of the invention, the power density of a laser beam corresponds to the spatial distribution of its power, and thus its spatially distributed pulse energy, divided by its pulse duration. In this respect, the power density can also be referred to as energy fluency. In other words, the power density corresponds to the spatial distribution of the pulse energy per temporal pulse duration of the laser beam. Compared to a certain power density of a partial beam, the power density can therefore be reduced, for example, by reducing the pulse energy and / or by increasing the temporal pulse duration.

[0013] In the context of the invention, "sample" refers to the object to be processed in at least two processing steps. This can be, for example, a workpiece or a tool.

[0014] Preferably, the at least one power density changing means is the at least one beam splitter and / or the at least one optical processing device and / or the at least one second optical processing device. For this purpose, the at least one beam splitter can be designed such that the division of the laser beam into the at least two partial beams does not occur uniformly in terms of intensity, so that the intensities of the partial beams are not each the same. For example, the first partial beam after leaving the beam splitter can have approximately 55% to 80% of the intensity of the laser beam impinging on the beam splitter, while the intensity of the second partial beam after leaving the beam splitter has approximately 45% to 20% of the intensity of the laser beam impinging on the beam splitter.The same can apply if the laser beam is split by the beam splitter into at least three partial beams, the intensity of which cannot therefore be evenly distributed. In a further development of the invention, one of the optical processing devices can be designed as a power density changing means in such a way that the beam diameter of the partial beam can be changed by means of a focusing means, for example a lens, in order to change the power density of the partial beam in this way. Alternatively or additionally, one of the optical processing devices can have a pulse duration changing means in order to change the temporal pulse duration of the partial beam, so that in this way the power density of the partial beam can be changed.

[0015] For the purposes of the invention, the parameter of the power density of a laser beam includes, in particular, its peak power density, i.e., the temporal maximum of the spatial distribution of its (pulse) power. In this respect, it can preferably be provided that the power density changing means is designed such that the peak power density of the first partial beam directed at the sample is greater than the peak power density of the second partial beam directed at the sample. The same can apply to all other features relating to the power density, which can thus also include the peak power density.

[0016] Preferably, the power density changing means is designed such that the power density of the first partial beam is at least a factor of 100 greater than the power density of the second partial beam. It can be provided that the pulse energy of the first partial beam is at least a factor of 100 greater than the pulse energy of the second partial beam. It can also be provided that the intensity of the first partial beam is at least a factor of 100 greater than the intensity of the second partial beam. Furthermore, it can be provided that the pulse duration of the first partial beam is at least a factor of 100 greater than the pulse energy of the second partial beam.In particular, it can be provided that the ratio between the power density and / or peak power density and / or pulse energy and / or intensity and / or pulse duration of the first partial beam and the power density and / or peak power density and / or pulse energy and / or intensity and / or pulse duration of the second partial beam is selected such that the first partial beam essentially causes an ablation of the sample and the second partial beam essentially causes a melting of the sample.

[0017] Preferably, the first optical processing device is designed for structuring the sample, in particular for periodic structuring of the sample, for example by means of interference of laser beams, and / or preferably the second optical processing device is designed for post-processing of the sample, in particular for topographical smoothing of the sample. In the sense of the invention, the structuring of the sample in the first processing step comprises in particular the formation of at least one depression on the surface of the sample facing the first partial beam. Structuring the sample by means of the partial beam ensures that the at least one depression, in particular all of the formed depressions, are formed with an identical dimension within the manufacturing tolerance.The formation of at least one depression of the sample is therefore reproducible, in particular with regard to several depressions of the first processing step and / or with regard to several samples structured one after the other in the first processing step.

[0018] For example, the structuring of the sample can take place within the scope of the first processing step using a single partial beam, which is also referred to in particular as “direct laser writing”. The use of at least two first partial beams can also be possible. To structure the sample, the first partial beam can be focussed by the first optical processing device onto the position where the sample is to be processed in order to increase the energy and power density. The first optical processing device can be designed such that the first partial beam is movable relative to the sample, which is also referred to as scanning. This can be done for example using a laser scanner as a component of the first optical processing device, in particular using a mirror scanner, which can be designed as a galvo scanner and / or as a polygon scanner.The laser scanner is preferably designed for one- or two-dimensional deflection of the first partial beam. In a further embodiment of the invention, the sample can be movable translationally—relative to the first partial beam, which is particularly fixed in space—for example, by means of at least one servo motor and / or a conveyor belt. In a particularly advantageous development of the invention, the first partial beam and the sample are movable one- and / or two-dimensionally in order to enable particularly rapid structuring of the sample.

[0019] To increase the process efficiency, the first processing step can also provide for the use of at least two first partial beams in the sense of the "Direct Laser Writing" described above during the first processing step in order to structure the sample. In a further development of the invention, the first partial beam assigned to the first optical processing device, which is also referred to as the "seed beam", can be split into at least two first partial beams by means of the first optical processing device, for example by means of a further beam splitter or a diffractive optical element.The at least two first partial beams obtained on the basis of the original first partial beam can be aligned onto the sample by the first optical processing device for structuring the sample, wherein it can be provided that at least one of the first partial beams, in particular several, preferably all of the first partial beams can be or will be focused onto the sample independently of one another by the first optical processing device after passing through it. The at least two first partial beams can be aligned to one another in a specific spatial relationship after passing through the first optical processing device, in particular with the use of at least one diffractive optical element as a component of the first optical processing device as already described.

[0020] Furthermore, it can be provided that the first optical processing device is designed such that the first partial beam can be split into at least two partial beams, which, after passing through the first optical processing device, can be aligned such that the at least two partial beams interfere with one another in the first processing region of the sample and process the sample. Preferably, the first optical processing device is designed such that the first partial beam can be split into exactly two partial beams.

[0021] A further development of the invention provides that the optical processing device is designed such that the first partial beam can be split into three partial beams which, after passing through the first optical processing device, can be aligned such that the three partial beams interfere with one another in the first processing region of the sample and process the sample. This makes it possible, for example, to structure the sample with depressions in a hexagonal pattern. In this case, the structure has three axes along the surface of the sample, along which a depression is each arranged in a lateral period, wherein, within the meaning of the invention, in the hexagonal pattern the lateral periods for the three axes are each identical.

[0022] In addition, the first partial beam can be split into four partial beams which, after passing through the first optical processing device, can be aligned such that the four partial beams interfere with one another in the first processing area of ​​the sample and process the sample, for example to create a square pattern of depressions when structuring the sample. It can be provided that the first partial beam can be split into a maximum of nine partial beams which, after passing through the first optical processing device, can be aligned such that the maximum of nine partial beams interfere with one another in the first processing area of ​​the sample and process the sample.

[0023] Preferably, the first optical processing device is designed to structure the sample by means of interference of at least two first partial beams during the first processing step. By using at least two interfering first partial beams, a comparatively large first processing area of ​​the sample can be processed in a comparatively short time, so that the process efficiency of the processing of the sample is also improved. In particular, the sample can be provided with a full-area surface structuring in the micrometer and / or nanometer scale range in a comparatively short processing time during the first processing step, which leads to significantly higher process efficiency and thus lower manufacturing costs compared to other known processing options.

[0024] The first processing step can provide that the at least one depression in the sample is produced with a dimension, in particular with a depth compared to an unstructured region of the active surface, of between 10 nm and 50 pm, in particular between 100 nm and 15 pm or between 1 pm and 25 pm. In further embodiments of the invention, the first processing step can provide that the dimension of the depression corresponds to its length in the x and / or y direction, wherein, in the sense of the invention, in the case of several depressions, the y direction corresponds to the offset direction of the depressions, while the x direction is arranged perpendicular to this. The x and y directions are each perpendicular to the normal of the active surface and thus each extend along the active surface. In the sense of the invention, a dimension can also be a combination of the x and y directions, which in this respect corresponds to a generally lateral direction.

[0025] In a further embodiment of the invention, it can be provided that in the first processing step at least two depressions with essentially identical dimensions, in particular with essentially identical depths, are produced. For the purposes of the invention, two dimensions have essentially identical dimensions if their deviations do not exceed the processing tolerance customary in comparable processes. At least two adjacent depressions can be arranged at a distance of 10 nm to 50 pm, in particular between 100 nm and 15 pm or between 1 pm and 25 pm. By means of the sample structured in this way, structural geometries in the order of magnitude between 10 nm and 50 pm, in particular between 100 nm and 15 pm or between 1 pm and 25 pm, can be realized on the same sample at an industrially relevant process speed while at the same time ensuring reproducibility.The first processing step preferably provides for at least one group of depressions to be produced on the sample in a periodic pattern, since this structure can be produced particularly easily by means of interfering first partial beams. In the context of the present invention, the period refers to the distance between two identical structural features of different depressions of the periodic pattern, for example the distance between the start of a first depression of the periodic pattern and the start of the depression of the same periodic pattern adjacent to this depression. Alternatively or additionally, the period within the meaning of the invention can refer to the distance between a center point of the first depression of the periodic pattern and the center point of the depression of the same periodic pattern adjacent to this depression.Since the depressions of the periodic pattern are laterally offset, in the sense of the invention, reference is also made to the lateral period, which, as already mentioned, refers to the distance between recurring structural features of adjacent depressions of the periodic pattern.

[0026] The first processing step preferably provides that the group of depressions in the periodic pattern is produced on the sample with a lateral period of between 10 nm and 50 pm, in particular between 100 nm and 15 pm or between 1 pm and 25 pm, in at least one direction along the active surface. Periodic structuring of the sample as part of the first processing step with a lateral period of this magnitude enables the formation of advantageous surface functionalities with which the sample is to be provided. The group of depressions in the periodic pattern can also have different periods in different directions, for example when three, four or more interfering first partial beams are used to structure the sample.In an advantageous development, the group of depressions in the periodic pattern has identical periods in two different directions. Furthermore, it can be provided that the group of depressions in the periodic pattern has identical periods in three different directions, which corresponds, for example, to a hexagonal arrangement of the depressions. The group of depressions is designed, for example, as a sinusoidal line structure, in which depressions and elevations are each arranged one behind the other in the same lateral period.

[0027] In a further embodiment of the invention, the first processing step can provide for at least one group of depressions to be produced on the sample with a linear profile and / or with a rectangular, preferably square, basic shape and / or with a circular basic shape. The basic shape of the depressions can be polygonal, in particular hexagonal. As a special case, the depressions can be designed as lines, which can be offset, in particular, perpendicular to their direction of extension and / or arranged in a defined lateral period.

[0028] Preferably, the depressions, in particular the group of depressions, have a lateral extent, in particular in a direction parallel to the direction of the lateral period, of between 10 nm and 49 pm, in particular between 10 nm and 10 pm or between 1 pm and 25 pm, in order to obtain particularly advantageous non-stick properties of the sample. Particularly preferably, all of the depressions each have a lateral extent of substantially 10 nm to 49 μm, in particular between 10 nm and 10 μm or between 1 μm and 25 μm.

[0029] Preferably, the depressions, in particular the group of depressions, have an aspect ratio between 0.01 and 5, in particular between 0.01 and 1, wherein the aspect ratio in the sense of the invention corresponds to the ratio of the depth of the depression to a lateral extent of the depression.

[0030] In a further development of the invention, the first processing step can provide that at least two first depressions, in particular a first group of depressions, with a first lateral period between 10 nm and 50 gm, in particular between 100 nm and 15 gm or between 1 gm and 25 gm, are produced and at least two second depressions, in particular a second group of depressions, with a second lateral period are produced, wherein in particular the second lateral period is smaller than the first lateral period. The first lateral period can be between 100 nm and 999 gm. The second lateral period can also be larger than or identical to the first lateral period.The second group of depressions can be configured mathematically similarly to the first group of depressions, so that the second group of depressions results from the first group of depressions by means of at least one mathematical similarity transformation, for example, translation, rotation, stretching, and / or scaling. Preferably, the second group of depressions corresponds to a 90° rotation of the first group of depressions around an axis perpendicular to the tool surface.

[0031] Alternatively or additionally, the first processing step can provide for at least two first depressions, in particular a first group of depressions, to be produced with a first dimension between 10 nm and 50 pm, in particular between 100 nm and 15 pm or between 1 pm and 25 pm, and for at least two second depressions, in particular a second group of depressions, to be produced with a second dimension, wherein the second dimension is in particular smaller than the first dimension. As already stated, the dimension of the depression within the meaning of the invention can correspond to its depth.

[0032] In addition, the first processing step can provide that, in addition to the second depressions, at least two third depressions, in particular a third group of depressions, with a third lateral period and / or a third dimension are produced, wherein the third lateral period and / or the third dimension are in particular smaller than the second lateral period and / or the second dimension. In further developments, the first processing step can provide that up to ten groups of depressions, each with one lateral period and / or one dimension, are produced, wherein in particular the lateral period and / or the dimension of a group are always smaller than the lateral period and / or the dimensions of the previous groups.

[0033] The first processing step preferably provides that the area of ​​the second depressions, in particular of the second group of depressions, at least partially overlaps the area of ​​the first depressions, in particular of the first group of depressions. The same applies to any third depressions that may be produced, in particular the third group of depressions. Such an overlap makes it possible, within the scope of the first processing step, to combine structures with different lateral periods and / or dimensions with one another, in particular to modulate them in a mathematical sense, and to provide the sample with complex surface structures that are not possible with simple structuring. The sample can therefore be provided with improved non-stick properties.In the sense of the invention, the first processing area corresponds to the union of all depressions produced in the first processing step.

[0034] The first processing step preferably provides that the first depressions, in particular the first group of depressions, and the second depressions, in particular the second group of depressions, are produced in a single work step or in separate work steps. The production of the first depressions and the second depressions in a single work step increases the process speed. In contrast, the design of the production of the first depressions and the second depressions in separate work steps particularly includes structuring the sample with different interference patterns. For example, it can be provided that the sample is movable or is moved between two successive work steps within the scope of the first processing step. It can preferably be provided that the sample is rotatable or is rotatable between two work steps of the first processing step.is rotated, in particular by an angle of 90°, so that depressions can be formed particularly easily, for example as a cross structure pattern and / or so-called Penrose structure pattern. The depressions of the second group can be arranged perpendicular to the depressions of the first group, so that the lateral period of the second group of depressions is arranged perpendicular to the lateral period of the first group of depressions. In addition, the lateral period of the second group of depressions can be aligned parallel to the lateral period of the first group of depressions or can enclose an angle between 0° and 180°.

[0035] Preferably, the first processing step involves generating the second group of depressions by means of a polarization of the at least one first partial beam, in particular of the at least two first partial beams, selected as a function of the sample material to be structured, whereby, in particular, laser-induced periodic surface structuring can be formed, in particular in a joint processing step with the formation of the first group of depressions. The lateral period of the second group of depressions corresponds, for example, at most to the wavelength used for the at least one first partial beam.The polarization of the at least one first partial beam can be aligned linearly, wherein the polarization vector is arranged substantially perpendicular to the direction of extension of the laser-induced periodic structuring and / or parallel to the lateral period associated with the laser-induced periodic structuring. In addition, the direction of the polarization vector of the at least one first partial beam can be aligned at an angle between 0° and 180° relative to the lateral period of the first group of depressions, so that the arrangement of the second group of depressions can be adjusted, in particular relative to the first group of depressions, by aligning the polarization vector of the laser beams.

[0036] For example, the first processing step can provide that the first depressions, in particular the first group of depressions, are produced by means of interference of the at least two first partial beams, wherein the second depressions, in particular the second group of depressions, are produced by means of interference of at least two further first partial beams and / or by means of a single further first partial beam. This means that the first depressions are always produced with the first partial beams interfering with one another, whereas this does not necessarily have to be the case for the production of the second depressions. The production of the second depressions by means of a single further first partial beam can be expedient if the number of second depressions is small compared to the number of first depressions and / or if the area of ​​the second depressions is small compared to the area of ​​the first depressions.If the second depressions are also produced by means of further partial beams interfering with one another, it can be provided that the number of further partial beams interfering with one another differs from or is identical to the number of the first depressions.

[0037] Preferably, the first processing step provides for the production of at least two groups of depressions, each in a periodic pattern, wherein the lateral period of the first group of depressions is arranged at an angle other than 0° to the lateral period of the second group of depressions, in particular at an angle of 90°.

[0038] For the purposes of the invention, processes in which the already existing topography of the sample, in particular that created during the first processing step, is not significantly changed are referred to as post-processing of the sample. For example, there is no significant extension, in particular no enlargement of an already existing deep structure of the sample. In this respect, the post-processing does not correspond to a new structuring of the sample, but rather to processing of the already existing structure of the sample. The second processing step comprises, for example, the removal of melt morphological artifacts or smoothing of the already existing topography. During the post-processing of the sample in the second processing step, a significantly greater thermal interaction of the second partial beam with the sample can occur compared to the structuring of the sample in the first processing step.

[0039] Preferably, the at least one beam splitter comprises at least one of the following components: mirror, semi-transparent mirror, prism, biprism, wave plate, polarizer, power measuring device, beam profile measuring device. As already mentioned, the beam splitter can be designed to split the laser beam into at least two partial beams with unevenly distributed intensities. Furthermore, within the meaning of the invention, a beam splitter is not necessarily limited to the optical component for splitting the laser beam per se, but can also comprise further components, in particular a combination of the aforementioned components.

[0040] The beam splitter can have a lambda / 4 plate as a wave plate in order to change the polarization of the laser beam incident on it, in particular before it is split into the at least two partial beams. By means of a lambda / 4 plate, for example, circularly or elliptically polarized radiation can be linearly polarized and vice versa. Alternatively or additionally, the beam splitter can have a lambda / 2 plate with which the orientation of the polarization vector can be rotated, in particular by a user-defined angle, in the case of linearly polarized radiation or the helicity can be inverted, so that in this case a left-hand circular polarization becomes a right-hand circular polarization and vice versa.The polarization of the laser beam, which can be user-defined and adjusted by means of a polarizer, in particular by means of the wave plates, can be used to split the laser beam into the at least two partial beams, for example in conjunction with a birefringent optical component. To split the laser beam into the at least two partial beams, the beam splitter can have a mirror, in particular a partially transparent mirror, which is designed, for example, such that the first partial beam is reflected by the mirror and the second partial beam penetrates the mirror. In a similar way, a prism, in particular a biprism, can be designed as a component of the beam splitter.

[0041] To analyze the laser beam and / or at least one of the partial beams, the beam splitter may have a power measuring device, which is designed in particular to determine the intensity of the laser beam and / or at least one of the partial beams. To characterize the beam profile of the laser beam and / or at least one of the partial beams, the beam splitter may have a beam profile measuring device, which is designed to determine a parameter of the beam profile. For example, this is the parameter M 2 , which corresponds to the quality index, beam quality, or diffraction index of a laser beam and indicates how close the geometry of the specifically measured laser beam comes to the model of the optimal Gaussian laser beam. In further developments of the invention, it can be provided that the optical device, in particular one of the optical processing devices, has a power measuring device and / or a beam profile measuring device.

[0042] The optical device can provide that the at least one beam splitter is designed such that the first partial beam after the beam splitter has a greater power density than the second partial beam.

[0043] The optical device preferably has at least one pulse duration modulation means which is designed to change the pulse duration of the partial beam assigned to the pulse duration modulation means. The pulse duration modulation means is preferably designed as a pulse expander which extends the temporal pulse duration of the partial beam assigned to it and passing through it. The pulse expander can be designed as a component of the second optical processing device and / or assigned to the second partial beam. The pulse duration modulation means can be designed as a pulse compressor which shortens the temporal pulse duration of the partial beam assigned to it and passing through it. In this way, finer structures can be produced during the first processing step. The pulse compressor can be designed as a component of the first optical processing device and / or assigned to the first partial beam.Using a pulse expander as a component of the second optical processing device and / or a pulse compressor as a component of the first optical processing device, it is possible to ensure that the power density of the first partial beam directed at the sample is greater than the power density of the second partial beam directed at the sample. In particular, if the sample has been interferometrically processed as a result of processing by the first partial beam after passing through the first optical processing device, and in particular if the sample thereby has laser-induced periodic surface structures (LIPSS), the sample can be processed with a comparatively greater thermal interaction by the second partial beam after passing through the second optical processing device, the power density of which, according to the invention, is lower than that of the first partial beam, in order to improve the surface topography of the sample.This can be achieved approximately through melting effects, which compensate for small surface irregularities relative to the dimensions of the surface topography. The same applies to droplets that have formed as a result of thermal interaction between the first partial beam and the sample during the first processing step, which can then be removed by the second partial beam during the second processing step.

[0044] Preferably, at least one of the optical processing devices has at least one optical deflection means for directing the partial beam assigned to the optical processing device in the direction of the sample to be processed, wherein the at least one optical deflection means is arranged in particular downstream of the pulse duration modulation means. In this respect, the optical deflection means can be assigned to the first partial beam as a component of the first optical processing device and / or to the second partial beam as a component of the second optical processing device.

[0045] The at least one optical deflection means preferably has at least one of the following components: laser scanner, galvanometer scanner, polygon scanner, optical focusing means. The optical deflection means has, for example, at least one mirror and / or at least one lens, in particular at least one lens system, and can be aligned such that the partial beam assigned to the deflection means is directed onto the sample to be processed. The at least one mirror and / or the at least one lens can be adjustable such that the partial beam assigned to the deflection means is moved relative to the sample. In this way, the sample can be easily processed in the first processing area as part of the first processing step. The optical deflection means can be designed to deflect the partial beam assigned to the deflection means in at least one, in particular in two dimensions.The optical deflection means can be designed such that the partial beam assigned to the deflection means can be focused in one plane, wherein the focal plane can coincide with the sample surface to be processed. In a particular further development, the optical deflection means has two mirrors, each tiltable in two axes, and a converging lens, wherein the design can also be referred to as F-theta optics or F-theta objective. In a further embodiment, the optical deflection means can be designed as a galvanometer scanner. The optical deflection means can have a mirror which is rotatable about an axis and at which the partial beam assigned to the optical deflection means can be reflected. In a further development of the invention, the mirror can have a polygonal basic shape which is provided with a mirrored surface.In this respect, the optical deflection means can be designed as a polygon scanner, wherein the polygon scanner can have a galvanometer for moving at least one mirror. With the aid of the optical deflection means, the sample can be processed, in particular structured, within the scope of the first processing step using a single partial beam. This is also referred to as "single-beam processing" or "single-beam direct laser writing". The beam focusing means of the optical deflection means can have at least one lens, in particular a lens system, preferably a telescope.

[0046] The optical deflection means preferably has a beam splitter and a focusing means arranged downstream of the beam splitter. The beam splitter is designed in particular to split the partial beam assigned to the deflection means into at least two partial beams, wherein these partial beams can be aligned, for example by means of further deflection means and / or focusing means, in particular independently of one another, onto the sample to be processed. In this respect, the optical deflection means can be designed as a multi-beam scanner, with which the sample can be processed, in particular structured, with several partial beams during the first processing step, which is also referred to as "multi-beam processing" or "multi-beam direct laser writing".

[0047] Preferably, the first optical processing device, in particular the optical deflection means, is designed for interferometric structuring of the sample. For this purpose, the optical deflection means can have a beam splitter for splitting the partial beam assigned to the deflection means and at least one lens for focusing these partial beams in the direction of the sample, wherein the beam splitter and the lens are aligned such that the partial beams interfere at least in the first processing region of the sample and, in particular, structure the sample flatly. This is also referred to as direct laser interference patterning (DLIP).

[0048] The second optical processing device can be configured to process the sample in the second processing step using a single partial beam in order to process the sample in a spatially targeted manner, so that, in particular, only spatially undesirable surface artifacts can be eliminated by the second optical processing device without the sample having to be processed over its entire surface during the second processing step. In this respect, the second optical processing device can be configured to process the sample using "direct laser writing."

[0049] Preferably, at least one optical processing device has a beam shaping means which is designed to change the beam profile of the partial beam assigned to the optical processing device. The beam shaping means is designed, for example, to change a beam parameter of the partial beam representing the beam profile, for example by widening the beam diameter or reducing it. The beam shaping means can be designed to change the beam quality parameter of the partial beam, which is also referred to as M 2and indicates how close the partial beam comes to the theoretical model of a Gaussian laser beam. The beam shaping means can be designed to convert an elliptical beam profile into a polygonal, in particular rectangular profile, which is also referred to as a "top hat" profile. In addition, the beam shaping means can be designed for the reverse conversion, in which a rectangular beam profile is converted into an elliptical beam profile. In particular, the second optical processing device has the beam shaping means.

[0050] Further embodiments of the invention can provide that the first optical processing device is designed to process the sample in the first processing step by means of a partial beam, by means of at least two partial beams and / or by means of interference of at least two partial beams. The optical device can have a power determination means for determining the power of a partial beam, in particular of the second partial beam. The optical device can have at least one partially transparent mirror for splitting the second partial beam, wherein it is provided in particular that a power determination means is assigned to the partially transparent mirror in such a way that the power determination means is designed to determine the power of one of the partial beams. In particular, the power of the second partial beam can be determined therefrom.The optical device can have at least one beam blocking means which is designed to block at least one partial beam, in particular in a user-defined manner, such that the partial beam assigned to the beam blocking means does not impinge on the sample.

[0051] The optical device preferably comprises a lubricating device for applying a lubricant, in particular a grease-containing lubricant, to the sample, particularly after the first processing step of the sample. This allows the friction coefficient associated with the sample to be reduced, particularly after the second processing step, during which heat can be applied to the lubricant.

[0052] Due to the structuring of the sample during the first processing step, its surface is enlarged, particularly due to the at least one depression, and allows for better wetting of the sample by the lubricant. To the applicant's knowledge, after application to the sample, the lubricant is drawn into the depressions of the sample by capillary forces occurring in the microstructure area and remains stored there, at least temporarily. This improves the non-stick properties of the processed sample, which can therefore be used for tribological applications.

[0053] The lubricant, in particular one containing fat, preferably comprises at least one component from the following group: oil-based lubricant, oil, food-grade oil, vegetable oil, sunflower oil, rapeseed oil, food-grade chain oil, grease, food-grade fat, vegetable fat, animal fat, synthetic fat, polyalkylene glycol, dry lubricant, food-grade dry lubricant, solid lubricant, carbon-based lubricant, graphite. For the purposes of the invention, lubricants that can be considered food-grade are those that correspond to classification H1 and / or satisfy the requirements of EC Directive 93 / 43 / EEC. For the purposes of the invention, lubricants are considered food-grade in particular if unintentional contact with food is possible and tolerable by humans.Food-grade lubricants may contain additives that are safe for human consumption and may only be transferred to food in limited quantities. The lubricant can be liquid or solid.

[0054] In particular, it can be provided that the preferably fat-containing lubricant can be applied to the sample in such a way that the lubricant forms a flat surface, which improves the non-stick properties of the sample.

[0055] Preferably, the optical device comprises a heating device for applying heat to the sample, in particular after the application of the lubricant, in particular containing fat, to the sample by the lubricating device.

[0056] By applying heat to the sample, and thus by thermally treating the sample and the lubricant applied to it, polymerization, oxidation and hydrolysis of the lubricant can occur in the second processing step, in particular at least partial decomposition or splitting of the carbon groups due to the prevailing high energies. As a result, reaction products are incorporated into at least one depression in the sample and, due to the aforementioned surface enlargement, adhere particularly well to the surface of the sample, so that the applied lubricant forms a lubricating film, which is also referred to as a tribofilm. By structuring the sample in the first processing step, these properties are particularly long-lasting and protect the sample from mechanical wear for as long as possible.The sample is processed in an environmentally friendly manner and results in a durable sample with stable non-stick properties even after extended use. Furthermore, no additional cleaning steps are required after the second processing step, so the sample is immediately ready for use after the second processing step. The heating device is preferably designed to apply heat for a duration of at least 1 minute.

[0057] Processing the sample in the second processing step also ensures that the resulting processed lubricant can be introduced into the sample structures formed during the first processing step. When a component comes into frictional contact with the processed sample, the lubricant within the structures comes into tribological contact with the component, improving the friction properties of the sample. This allows for longer use of the processed sample.

[0058] In a further embodiment of the invention, the second optical processing device is designed as a heating device. Alternatively, the heating device can be designed as a separate component from the optical processing devices.

[0059] The beam splitting means is preferably designed to split the laser beam incident on the optical device into at least three partial beams, wherein a third optical processing device for processing the sample in a third processing step is assigned to the third partial beam in such a way that the third partial beam, after passing through the third optical processing device, can be aligned with the sample in such a way in order to process the sample in the third processing step in a third processing area, wherein the third processing step takes place before the first processing step, wherein the power density of the third partial beam directed onto the sample is lower than the power density of the first partial beam directed onto the sample. Two beam splitters can be provided to split the laser beam into at least three partial beams.In particular, it can be provided that the second beam splitter is assigned to the third partial beam and / or the third optical processing device. The third processing step can be designed for pretreating the sample, in particular for thermal pretreatment thereof, and in particular can comprise leveling topographical irregularities, for example by melting effects. The third processing step can provide for smoothing the surface structure of the sample and / or pretreating it before the first processing step. The power density of the first partial beam directed at the sample can be the greatest compared to the power densities of the other partial beams directed at the sample. The power density of the first partial beam directed at the sample can be at least a factor of 100 greater than the power density of the third partial beam directed at the sample.The power density of the third partial beam directed at the sample can be substantially equal to the power density of the second partial beam directed at the sample. The third processing area can at least partially overlap the first processing area and / or the second processing area. The optical device according to the invention can be configured for use with the optical system.

[0060] The optical system can provide that the first partial beam has ultrashort pulses, wherein the laser is designed as an ultrashort pulse laser. In particular, it can be provided that the temporal pulse duration of the first partial beam is at most 15 ps. This ensures that thermal effects during processing of the sample in the first processing step are prevented as far as possible, which improves the manufacturing quality of the sample processing. In addition, the formation of melting and thermally induced material damage, in particular stress cracks, is largely prevented. It is known that with shorter pulse durations thermal effects are increasingly neglected, so that the sample can be increasingly processed mechanically. This effect is also referred to as cold ablation.From this point of view, it can be provided that the temporal pulse duration of the first partial beam is at most 10 ps, ​​so that even fewer thermal effects occur. In addition, the precision of the processing of the sample is improved. For the same reason, it can be provided that the temporal pulse duration of the first partial beam is at most 1 ps, whereby an even better processing quality of the sample processed after the first processing step can be achieved. Preferably, a temporal pulse duration of between 100 fs and 15 ps, in particular between 100 fs and 1 ps, is provided for the first partial beam.

[0061] Furthermore, the power of the first partial beam can be between 1 W and 5 kW, in particular between 1 W and 500 W, and / or the energy of the pulses of the first partial beam can be between 10 pj and 200 mJ, in particular between 10 pj and 100 mJ. When processing the sample in the first processing step, the first partial beam can have a beam diameter of between 2 pm and 6 pm. When processing the sample in the first processing step, between 2 and 1000 individual pulses can be superimposed within the first processing area in order to obtain high structural aspect ratios through correspondingly high material removal.

[0062] In a further embodiment of the invention, the first partial beam can have pulse durations of greater than 1 ns, in particular greater than 10 ns. Should unwanted surface artifacts arise due to melting effects, these can be eliminated in the second processing step by processing the sample using the second optical processing device.

[0063] The laser may comprise at least one component from the following group, in particular be configured as a member of the following group: In particular, diode-pumped solid-state lasers, for example Nd:YAG lasers, disk lasers, fiber lasers. The beam profile of the laser may be substantially Gaussian and / or rectangular, at least in sections; the latter is also referred to as a "top hat" profile.

[0064] The second partial beam has, in particular, a pulse duration of at least 10 ns, in particular at least 100 ns. As a result, surface artifacts, which may have arisen in particular due to processing of the sample during the first processing step with ultrashort pulses, can be processed comparatively thermally without the surface topography of the sample resulting from the first processing step being significantly impaired. In a further development of the invention, the optical system has, in particular, only a single laser, to which, in particular, a single optical device according to the invention is assigned.

[0065] The optical system preferably has a first laser, a second laser and an optical device according to the invention which is assigned to both lasers. The laser beam of the first laser and the laser beam of the second laser can be aligned with the optical device. The optical beam path of the first laser can at least partially overlap with the optical beam path of the second laser, in particular in a partial region of the optical device. The laser beam of the first laser and / or the laser beam of the second laser can be activated and / or deactivated in a user-defined manner, for example by means of user-actuable beam blocking means which, for example, have tilting mirrors.The optical device can have a first power density changing means associated with the first laser and / or a second power density changing means associated with the second laser, wherein the first power density changing means can be configured to complement the second power density changing means. For example, the first power density changing means can have a pulse compressor and / or the second power density changing means can have a pulse expander. The first optical processing device and / or the second optical processing device can be associated with the first laser and the second laser, resulting in a space-saving design.In this case, the power density of the first partial beam passing through the first optical processing device, which partial beam can be assigned to the first laser or the second laser, can be greater than the power density of the second partial beam passing through the second optical processing device, which partial beam can be assigned to the first laser or the second laser.

[0066] The method can provide for the partial beam not currently used for processing the sample to be blocked in a user-defined manner, in particular with the aid of a beam blocker.

[0067] The method according to the invention preferably uses an optical device according to the invention, in particular an optical system according to the invention.

[0068] Preferably, the sample is moved between the first and second processing steps to enable efficient processing of the sample. This eliminates the need to move optical components, thus avoiding the risk of their deterioration. The movement of the sample between the first and second processing steps can be over a distance of 1 mm to 20 mm to achieve a space-saving setup.

[0069] Preferably, the sample is structured in the first processing step, in particular by means of at least two partial beams, most preferably periodically and / or interferometrically. Alternatively or additionally, the sample may be topographically smoothed, melted, and / or flattened in the second processing step.

[0070] Preferably, a lubricant, in particular one containing fat, is applied to the sample before the second processing step, in particular by means of a lubricating device, wherein heat is applied to the lubricant, in particular after the application of the lubricant, in particular during the second processing step. This can occur, in particular, due to the interaction of the second partial beam with the sample after passing through the second optical processing device during the second processing step.

[0071] The method can provide that before the first processing step the sample is processed with laser radiation in a third processing step, wherein in particular it is provided that the laser beam is split into at least three partial beams by the beam splitter, wherein the third partial beam passes through a third optical processing device and is then aligned with the sample in such a way that the sample is processed in a third processing step in a third processing area, wherein the third processing area at least partially overlaps with the first processing area and / or with the second processing area, wherein the power density of the third partial beam directed at the sample is smaller than the power density of the first partial beam directed at the sample.In this respect, the third processing step can represent a type of pretreatment of the sample, as already explained above in connection with the corresponding device-related developments of the invention. All statements regarding the device-related developments of the invention apply accordingly to the corresponding method-related developments.

[0072] Preferably, the sample has been processed by means of an optical system according to the invention and / or by means of a method according to the invention.

[0073] Further advantages and features emerge from the claims and the following description, in which exemplary embodiments of the invention are explained in detail with reference to the drawings. In the drawings:

[0074] Fig. 1 shows an embodiment of an optical system according to the invention with an optical device according to the invention in a schematic representation,

[0075] Fig. 2 representations of a sample structured with the optical system according to Fig. 1,

[0076] Fig. 3 shows a further embodiment of the optical system according to the invention with an optical device according to the invention, Fig. 4 shows representations of a sample structured with the optical system according to Fig. 3,

[0077] Fig. 5 shows a further embodiment of the optical system according to the invention with an optical device according to the invention,

[0078] Fig. 6 Representations of a sample structured with the optical system according to Fig. 5,

[0079] Fig. 7 shows a further embodiment of the optical system according to the invention with an optical device according to the invention,

[0080] Fig. 8 Representations of a sample structured with the optical system according to Fig. 7,

[0081] Fig. 9 shows a further embodiment of the optical system according to the invention with an optical device according to the invention,

[0082] Fig. 10 Representations of a sample structured with the optical system according to Fig. 9,

[0083] Fig. 11 shows a further embodiment of the optical system according to the invention with an optical device according to the invention,

[0084] Fig. 12 shows representations of a sample structured with the optical system according to Fig. 11, Fig. 13 shows a further embodiment of the optical system according to the invention with an optical device according to the invention and

[0085] Fig. 14 Representations of a sample structured with the optical system according to Fig. 13.

[0086] Fig. 1 shows a schematic structure of an optical system 1 according to the invention with an optical device 2 according to the invention for processing a sample 3 in two processing steps. For this purpose, the optical system 1 has a laser 4 which, in the exemplary embodiment shown, is designed as an ultrashort pulse laser and emits a pulsed laser beam 5 with a pulse duration of 15 ps. The laser beam 5 of the laser 4 is aligned with the optical device 2 in such a way that the laser beam 5 strikes a beam splitter 6 of the optical device 2, so that the laser beam is or will be split into two partial beams 7, 8. According to Fig. 1, the first partial beam 7 is reflected by the beam splitter 6 in the direction of a first optical processing device 9 which is assigned to the first partial beam 7 and is shown schematically in Fig. 1. The first optical processing device 9 has as optical deflection means 10 a in Fig.1, for splitting the first partial beam 7 into two further partial beams 11, 12. The further partial beams 11, 12 are focused in the direction of the sample 3 by a lens (not shown in FIG. 1) as a component of the optical deflection means 10 in such a way that the further partial beams 11, 12 interfere with one another in a first processing region 13 on the surface 14 of the sample 3, as a result of which the sample 3 is processed, in particular structured, in the first processing step 13 by the first partial beam 7 in the form of the further partial beams 11, 12. The optical deflection means 10 of the first optical processing device 9 is thus designed for the interferometric structuring of the sample 3. For processing, the sample 3 is mechanically fed to the interference region of the further partial beams 11, 12, for example by means of a lens (not shown in FIG. 1 conveyor belt not shown.Due to the interferometric processing of the sample 3 in the first processing step, the sample 3 is processed flat and provided with a periodic structure 15 which has linear depressions 16 aligned parallel to one another. The depressions 16 are arranged offset from one another perpendicular to their direction of extension. The structure 15 has a rectangular depression 17 with rounded corners surrounding the linear depressions 16. The width, the depth and the position of the depressions 16, 17 can be adjusted in a user-defined manner via a user-defined manipulation of the first partial beam 7, as can the position and the size of the first processing area 13 of the sample 3.

[0087] The part of the laser beam 5 which passes through the beam splitter 6 is the second partial beam 8, the intensity of which, due to the design of the beam splitter 6 in the present exemplary embodiment, does not correspond to the intensity of the first partial beam 7, but rather only 30% of this. In this respect, the beam splitter 6 is designed as a power density changing means 18. Already after leaving the beam splitter 6, the power density of the second partial beam 8 is therefore lower than the power density of the first partial beam 7. After the beam splitter 6, the second partial beam 8 strikes a partially reflecting mirror 19, although only the reflected partial beam 8 is shown in Fig. 1. The partially reflecting mirror 19 is designed such that 99% of the intensity of the incident second partial beam 8 is reflected and the remaining 1% passes through the partially reflecting mirror 19. The beam passing through the mirror 19, shown in Fig.The part of the second partial beam 8 not shown in Fig. 1 strikes a power measuring device not shown in Fig. 1 which is designed to determine the intensity of the partial beam striking it. On this basis, and based on the known intensity distribution ratios of the mirror 19 and the beam splitter 5, conclusions can be drawn about the intensities of the second partial beam 8, the portion thereof reflected by the mirror 19, the first partial beam 7 and also the laser beam 5 as a whole. The part of the second partial beam 8 passing through the mirror 19 also strikes a beam profile measuring device not shown in Fig. 1 which is designed to characterize the beam shape and in this way enables a characterization of the beam shapes of the first partial beam 7, the second partial beam 8 and the laser beam 5.

[0088] The part of the second partial beam 8 reflected by the mirror 19 is directed towards a second optical processing device 20 which, in Fig. 1, is arranged offset to the right from the first optical processing device 9. The second optical processing device 20 has a further optical deflection means 21, not shown in Fig. 1, which in the present embodiment is designed as a polygon scanner which has a mirror provided with a galvanometer and which can be rotated by means of the latter, so that the second partial beam 8, after being reflected by this mirror, passes through the second optical processing device 20 in such a way that the second partial beam 8 is deflected in the direction of the sample 3 and strikes it, since the sample 3 was fed to the second optical processing device 20 after the first processing step.With the aid of the second optical processing device 20, the second partial beam 8 is guided along the sample 3 in a user-defined movement, so that the sample 3 is processed in a second processing step. The sample 3 is processed in a second processing area 22 which at least partially overlaps with the first processing area 13. Due to the lower power density compared to the first partial beam 7, which is expressed in particular in a lower peak power density, the processing of the sample 3 takes place in particular in that surface artifacts which were formed as a result of the first processing step are removed by the second processing step. The surface 14 of the sample 3 is smoothed in the process. This significantly improves the quality of the processing of the sample 3. The movement of the sample 3 is illustrated by an arrow pointing to the right.

[0089] Fig. 2 shows three representations of the nature of the surface 14 of the sample 3 before the first processing step (left), after the first processing step (center) and after the second processing step (right). Before the first processing step, the surface 14 of the sample 3 facing the optical system is therefore essentially flat. After the first processing step, after the surface 14 of the sample 3 has been structured by the first optical processing device 9 with the interfering partial beams 11, 12, its surface 14 has the structure 15 shown in the center of Fig. 2. The structure 15 contains the already mentioned linear, periodically arranged depressions 16 with a further, rectangular depression 17 enclosing these, which characterizes the first processing region 13 of the sample 3.After the second processing step, the sample 3 was processed by the second optical processing device 20 using the second partial beam 8 in the second processing region 22, wherein the second processing region 22 overlaps with the first processing region 13, but is not identical thereto. In the present exemplary embodiment, the second processing region 22 is arranged offset to the bottom left, starting from the first optical processing region 13. The second processing step does not provide for any periodic structuring of the sample 3, which is illustrated in Fig. 2 in the right-hand illustration by the filled-in second processing region 22.In the overlapping region 23 of the two processing regions 13, 22, the second processing step processes the periodic structure 15 itself, which was formed as a result of the first processing step, and which is thereby smoothed and no longer contains any undesired surface artifacts.

[0090] Fig. 3 shows a further embodiment of the optical system 1, wherein a dot-dashed line denotes the optical device 2. The optical system 1 according to Fig. 3 largely corresponds to the optical system 1 according to Fig. 1, in particular with regard to the laser 4, the beam splitter 6, the mirror 19 and the second optical processing device 20. In contrast to the embodiment in Fig. 1, the first optical processing device 9 according to Fig. 3 is not designed for interferometric processing of the sample 3 as part of the first processing step, but nevertheless has a beam splitter (not shown in Fig. 3) for splitting the first partial beam as a component of the deflection means 10. The partial beams 11 generated thereby are deflected by the beam splitter 6 shown in Fig.3, deflection means 10, not shown, are aligned onto the sample 3 after passing through the first optical processing device 9, the deflection means 10 being designed as a polygon scanner. The partial beams 11 of the first partial beam 7 are aligned onto the sample 3 by the deflection means 10 in such a way that the sample 3 is thereby structured within the scope of the first processing step in the first processing region 13. This is also referred to as “multi-beam processing” or “multi-beam direct laser writing”. Within the scope of the first processing step, the sample 3 is structured which essentially corresponds to the structuring according to the embodiment according to Fig. 1. The sample 3 is provided for processing within the scope of the first processing step in the position shown in Fig. 3 below the first optical processing device 9.

[0091] After the first processing step, the sample 3 is fed to a lubricating device 24, shown in dashed lines in Fig. 3, of the optical device 2, which is designed to dispense a grease-containing lubricant onto the sample 3 processed after the first processing step. After the sample 3 has been arranged in the position shown in Fig. 3 below the lubricating device 24, the lubricant, which in the present embodiment is cooking oil, is applied to the sample 3 so that the lubricant gets into the depressions 16, 17 of the sample 3 and wets essentially the entire surface 14 of the sample 3 as evenly as possible. This is due, for example, to capillary forces which develop in the microstructure area as a result of the processing of the sample 3 and draw the lubricant into the depressions 16, 17. The lubricant remains there, at least temporarily.The lubricant forms an approximately flat layer on the sample 3 with a thickness of 100 nm, which corresponds to the distance from a non-machined area of ​​the surface 14 of the sample 3 to the surface of the layer of lubricant.

[0092] The sample 3 is then fed to the second optical processing device 20 and processed with it, as was already explained in connection with the embodiment according to Fig. 1. It is important here that the second partial beam 8 also has a lower power density than the first partial beam 7, so that during the second processing step, in which the sample 3 is processed with the second partial beam 8, there is an essentially thermal interaction between the second partial beam 8 and the sample 3 and thus also with the applied lubricant. The second optical processing device 20 is therefore designed as a heating device 25.The temperature applied to the lubricant in this way is selected in particular such that it is below the smoke point of the lubricant, in this case the cooking oil, but is still sufficiently high to cause, for example, polymerization, oxidation and hydrolysis of the lubricant. Decomposition products of these reactions are stored in the depressions 16, 17, also referred to as microcavities, of the structured sample 3 and adhere particularly well due to the surface 14 of the sample 3 being enlarged by the structuring and form a friction-reducing layer or film, which is also referred to as a "tribo-film". This layer, in combination with the structuring of the sample 3 in the micrometer range, improves the non-stick properties and also improves the corrosion properties of the sample 3.

[0093] Fig. 4 shows the condition of the surface 14 of the sample 3 before the first processing step (left), after the first processing step (middle) and after the second processing step (right), wherein the lubricant applied to the sample 3 is not shown, so that Fig. 4 essentially corresponds to Fig. 2.

[0094] Fig. 5 shows a further embodiment of the optical system 1 with the optical device 2, the optical system 1 largely corresponding to the embodiment according to Fig. 1. In particular, the first optical processing device 9 is designed for the interferometric processing of the sample 3 in the first processing step, as was already explained in connection with Fig. 1. Unlike in Fig. 1, in Fig. 5 the mirror 19 is not partially transparent but reflects the second partial beam 8 incident on it completely in the direction of the second optical processing device 20.

[0095] Between the beam splitter 6, which is still designed as a power density changing means 18, and the mirror 19, a further power density changing means 18 of the optical device 2 is arranged in the form of a pulse duration modulation means 26, which in the present embodiment is a pulse expander 26 and increases the temporal pulse duration of the second laser beam 8 guided through the pulse expander 26, whereby the power density of the second partial beam 8 is reduced compared to the power density of the first partial beam 7. After the pulse expander 26, the second partial beam 8 strikes the already mentioned, fully reflecting mirror 19, from where the second partial beam 8 is guided in the direction of the second optical processing device 20 and passes through this. The second optical processing device 20 is similar to the design according to Fig.1, so that the second partial beam 8 emerging therefrom is guided in the direction of the sample 3 and processes this as part of the second processing step as already described. Fig. 6 shows, similar to Fig. 1 and Fig. 3, the condition of the sample 3 before the first processing step (left), after the first processing step (center) and after the second processing step (right).

[0096] Fig. 7 shows a further embodiment of the optical system 1, which comprises a first laser 4, a second laser 27 and an optical device 2. The first laser 4 is arranged on the right in Fig. 7 and emits a first laser beam 5 onto a first beam splitter 6 of the optical device 2, which, as already described, is designed to split the first laser beam 5 into a first partial beam 7 transmitted by the beam splitter 6 and a second partial beam 8 reflected by the beam splitter 6. The first partial beam 7 passes through a first power density changing means, which is designed as a pulse duration modulation means in the form of a pulse compressor 27, so that the temporal pulse duration of the first partial beam 7 is shortened compared to the temporal pulse duration of the second partial beam 8. The first partial beam 7 is then, similar to the embodiment according to Fig.5 is completely reflected at a first mirror 19 and then passes through the first optical processing device 9 in order to interferometrically structure the sample 3 in the first processing step as part of the first processing step, as already explained above. The second partial beam 8 passes through the second optical processing device 20 for processing the sample 3 in the second processing step, the sample 3 being moved between the first processing step and the second processing step.

[0097] In addition to the first laser 4, the optical system 1 has the second laser 28, which is arranged top right in Fig. 7 and which emits a second laser beam 29 in the direction of a second beam splitter 30 as a component of the optical device 2. The beam splitter 30 is designed to split the second laser beam 29 into a third partial beam 31 and a fourth partial beam 32. The third partial beam 31 is reflected by the beam splitter 30 in the direction of the first optical processing device 9, so that after passing through the sample 3, the sample is interferometrically structured in the first processing step, similar to the first partial beam 7 of the first laser 4. The fourth partial beam 32 passes through the beam splitter 30 in transmission and then the already described pulse expander 26 as the pulse duration modulation means.The fourth partial beam 31 is then completely reflected by a second mirror 33 in the direction of the second optical processing device 20, after passing through which the fourth partial beam 32 is deflected in the direction of the sample 3 in order to process it as part of the second processing step. Due to the pulse expander 26, the power density of the third partial beam 31 directed at the sample after passing through the first optical processing device 9 is greater than the power density of the fourth partial beam 31 directed at the sample.

[0098] In the embodiment of Fig. 7, the sample 3 is not processed simultaneously by both lasers 4, 28. Rather, the optical system 1 shown there is functionally divided in such a way that the first beam splitter 6, the first power density changing means, thus the pulse compressor 27, and the first mirror 19 are assigned to the first laser 4, while the second beam splitter 30, the second power density changing means, thus the pulse expander 26, and the second mirror 33 are assigned to the second laser 28. These assignments are indicated by the two dashed rectangles in Fig. 7. The first optical processing device 9 and the second optical processing device 20 are used jointly by both laser beams 5, 29, wherein the respective unused laser beam is blocked in a user-defined manner by a beam blocking means not shown in Fig. 7.Regardless of whether the first laser 4 or the second laser 28 is used to process the sample 3, the sample 3 is structured in the first processing step by means of the first optical processing device 9 interferometrically with a partial beam 7, 31 which has a greater power density than the other partial beam 8, 31 passing through the second optical processing device.

[0099] Fig. 8 illustrates, similar to Fig. 6, the surface of the sample before the first processing step (left), after the first processing step (centre) and after the second processing step.

[0100] Fig. 9 shows a further embodiment of the optical system 1, which is essentially similar to the embodiment according to Fig. 7, wherein, however, the first optical processing device 9 is not designed for interferometric processing of the sample 3 as in Fig. 7, but for "multi-beam direct laser writing", as has already been explained in connection with Fig. 3.

[0101] Fig. 11 shows a further embodiment of the optical system 1 which corresponds in many ways to the optical system 1 in Fig. 7, but which, in contrast, first processes the sample 3 in a third processing step before the first processing step takes place as already described. Similar to the optical system 1 according to Fig. 7, the first laser 4 emits the first laser beam 5 which strikes the beam splitter 6, the second partial beam 8 reflected thereby passing through the optical processing device 20 and processing the sample 3 in the second processing region 22 as part of the second processing step. The partial beam 34 passing through the beam splitter 6 strikes a further beam splitter 35 assigned to it, the partial beam 7 of which passing through this beam splitter, as already described in connection with Fig.7, after the pulse compressor 27, the mirror and the first optical processing device in the form of the two - interfering - partial beams 11, 12, the sample 3 is interferometrically processed in the first processing area 13 as part of the first processing step. The partial beam 36 reflected at the beam splitter 35, which does not pass through the pulse compressor 27 due to the arrangement of the beam splitter 35 upstream of the latter, is directed by a mirror 37 through a third optical processing device 38, which in the exemplary embodiment shown is designed essentially analogously to the second optical processing device 20. After passing through the third optical processing device 38, the partial beam 36 is directed onto the sample 3 by a deflection means 39 assigned to it in such a way that the sample is thus - first - processed in a third processing area 40 as part of the third processing step.The sample 3 is then processed in the first processing step and subsequently in the second processing step, as already described. Since in the exemplary embodiment shown the third optical processing device 38 is designed essentially similarly to the second optical processing device 20, the power density of the third partial beam 36 directed at the sample 3, in particular its peak power density, is essentially equal to the power density of the second partial beam 8 directed at the sample 3, which passes through the second optical processing device 20. In addition, the power density of the third partial beam 36 directed at the sample 3 is smaller than the power density of the first partial beam 7 directed at the sample 3.

[0102] 7, the sample 3 can be processed not only by means of the first laser 4 but also by means of the second laser 5, the laser beam 29 of which strikes the beam splitter 30 in the manner already described. The partial beam 31 reflected by the latter passes through the first optical processing device 9 and processes the sample 3 in the form of partial beams 11, 12 interferometrically as part of the first processing step in the first processing area 13. The partial beam passing through the beam splitter 30 passes through the pulse expander 26 and then strikes a further beam splitter 40, the partial beam 32 passing through this being directed by the mirror 33 onto the second optical processing device 20, as already described in connection with FIG. 7, and after passing through the second optical processing device, the sample is processed as part of the second processing step in the second processing area 22.The partial beam 42 reflected by the beam splitter 41 is directed by two mirrors 43, 44 onto the third optical processing device 37 and, after passing through the third optical processing device 37, strikes the sample 3, which is then processed in the third processing area 40 as part of the third processing step. The beam path assigned to the second laser 28 is covered in perspective by the beam path assigned to the first laser 4, as already shown in Fig. 7.

[0103] In any case, similar to the beam path of the first laser 4, the power density of the third partial beam 36 assigned to the second laser 28 and directed onto the sample 3 is approximately equal to the power density of the second partial beam 32 assigned to the second laser 28 and directed onto the sample 3 and smaller than the power density of the first partial beam 31 assigned to the second laser 28 and directed onto the sample 3.

[0104] Fig. 12 shows, in the left-hand illustration, sample 3 with a surface 14 that has not yet been processed. To the right, sample 3 was processed in the third processing step, which is illustrated by the third processing area 40. Since the power density of the laser radiation used in the third processing step essentially corresponds to that of the second processing step, the third processing step essentially involves thermal pretreatment of sample 3, which is shown by the grey area in Fig. 12. Thereafter, as already described, sample 3 is processed in the first processing step in the first processing area 13, which partially overlaps with the third processing area 40.Finally, the processing of sample 3 takes place during the second processing step in the second processing area 22, which partially overlaps the third processing area 40 and the first processing area 13. All processing areas 13, 22, 40 overlap in the overlap area 23.

[0105] The design of the optical system 1 according to Fig. 13 essentially corresponds to the optical system 1 of Fig. 11, however, in contrast to this, the processing of the sample 3 in the first processing step, similar to the embodiment of Fig. 9, is not carried out interferometrically, but by means of "multi-beam direct laser writing", which has already been described above. Fig. 14 shows the sample 3 in untreated form and after the first, second and third processing step. The representations largely correspond to those of Fig. 12, so that reference is also made to the above statements in this regard.

Claims

Patent claims 1. Optical device (2) for processing a sample (3) by means of laser radiation in at least two processing steps, with at least one beam splitter (6, 30), at least one first optical processing device (9) and at least one second optical processing device (20), wherein the at least one beam splitter (6, 30) is arranged such that a laser beam (5, 29) impinging on the optical device (2) can be split into at least two partial beams (7, 8, 31, 32), wherein the first optical processing device (9) is arranged such that a first partial beam (7, 31) after the beam splitter (6, 30) and after passing through the first optical processing device (9) can be aligned with the sample (3) in such a way as to process the sample (3) in the first processing step in a first processing area (13), wherein the second optical processing device (20) is arranged such that a second partial beam (8, 32) after the beam splitter (6, 30) and after passing through the second optical processing device (20) can be aligned with the sample (3) in such a way as to process the sample (3) in a second processing step in a second processing area (22), wherein the second processing area (22) at least partially overlaps the first processing area (13), wherein the optical device (2) has at least one power density changing means (18) which is designed such that the power density of the first partial beam (7, 31) directed onto the sample (3) is greater than the power density of the second partial beam (8, 32) directed onto the sample (3).

2. Optical device (2) according to claim 1, characterized in that the at least one power density changing means (18) is the at least one beam splitter (6, 30) and / or the at least one optical processing device (9) and / or the at least one second optical processing device (20).

3. Optical device (2) according to one of the preceding claims, characterized in that the power density changing means (18) is designed such that the peak power density of the first partial beam (7, 31) directed onto the sample (3) is greater than the peak power density of the second partial beam (8, 32) directed onto the sample (3).

4. Optical device (2) according to one of the preceding claims, characterized in that the power density changing means (18) is designed such that the power density of the first partial beam (7, 31) is at least a factor of 100 greater than the power density of the second partial beam (8, 32).

5. Optical device (2) according to one of the preceding claims, characterized in that the first optical processing device (9) for structuring the sample (3), in particular for periodic structuring ration of the sample (3) and / or that the second optical processing device (20) is designed for post-processing of the sample (3), in particular for topographically smoothing the sample (3).

6. Optical device (2) according to one of the preceding claims, characterized in that the beam splitter (6, 30) has at least one of the following components: mirror, partially transparent mirror, prism, biprism, wave plate, polarizer, power measuring device, beam profile measuring means.

7. Optical device (2) according to one of the preceding claims, characterized by at least one pulse duration modulation means (26, 27) which is designed to change the pulse duration of the partial beam (7, 32) assigned to the pulse duration modulation means (26, 27).

8. Optical device (2) according to one of the preceding claims, characterized in that at least one of the optical processing devices (9, 20) has at least one optical deflection means (10, 21) in order to direct the partial beam (7, 31, 8, 32) assigned to the optical processing device (9, 20) in the direction of the sample (3) to be processed, wherein the at least one optical deflection means (10, 21) is arranged in particular downstream of the pulse duration modulation means (26, 27).

9. Optical device (2) according to claim 8, characterized in that the at least one optical deflection means (10, 21) comprises at least one of the following components: components: laser scanner, galvanometer scanner, polygon scanner, optical focusing device.

10. Optical device (2) according to one of claims 8 or 9, characterized in that the at least one optical deflection means (10) comprises an optical beam splitter and a focusing means arranged downstream of the beam splitter.

11. Optical device (2) according to claim 10, characterized in that the optical deflection means (10) is designed for interferometric structuring of the sample (3).

12. Optical device (2) according to one of the preceding claims, characterized in that at least one optical processing device (9, 20) has a beam shaping means which is designed to change the beam profile of the partial beam (7, 31, 8, 32) assigned to the optical processing device (9, 20).

13. Optical device (2) according to one of the preceding claims, characterized in that the optical device (1) has a lubricating device (24) for applying a lubricant, in particular containing fat, to the sample (3), in particular after the first processing step.

14. Optical device (2) according to one of the preceding claims, characterized in that the beam splitter (6, 30, 35, 41) for splitting the laser beam (5, 29) is designed into at least three partial beams (7, 31, 8, 32, 36, 42), wherein the third partial beam (36, 42) is assigned a third optical processing device (37) for processing the sample (3) in a third processing step such that the third partial beam (36, 42), after passing through the third optical processing device (37), can be aligned with the sample (3) in such a way as to process the sample (3) in the third processing step in a third processing region (40), wherein the third processing step takes place before the first processing step, wherein the power density of the third partial beam (36, 42) directed at the sample (3) is smaller than the power density of the first partial beam (7) directed at the sample (3).

15. Optical system (1) for processing a sample (3) with at least one laser (4, 28) and with at least one optical device (2) according to one of claims 1 to 14, wherein the laser (4, 28) is designed to emit a laser beam (5, 29) which is aligned with the optical device (2) in such a way that the sample (3) can be processed in the at least two processing steps.

16. Optical system (1) according to claim 15, characterized by a first laser (4), a second laser (28) and an optical device (2) according to one of claims 1 to 14 associated with both lasers (4, 28).

17. Method for processing a sample (3) in at least two processing steps, comprising the following the steps: Providing a laser (4, 28) for emitting a laser beam (5, 29), wherein the laser beam (5, 29) impinges on a beam splitter (6, 30) in such a way that the laser beam (5, 29) is split into at least two partial beams (7, 31, 8, 32), wherein a first partial beam (7, 31) is directed onto the sample (3) after passing through a first optical processing device (9) in order to process the sample (3) in a first processing step in a first processing region (13), wherein a second partial beam (8, 32) is directed onto the sample (3) after passing through a second optical processing device (20) in order to process the sample (3) in a second processing step in a second processing region (22), wherein the second processing region (22) at least partially overlaps the first processing region (13), wherein the power density of the first partial beam directed onto the sample (3) directed partial beam (7, 31) is greater than the power density of the second partial beam (8, 32) directed onto the sample (3).

18. Method according to claim 17, characterized in that an optical device (2) according to one of claims 1 to 14, in particular an optical system (1) according to one of claims 15 or 16, is used.

19. Method according to one of claims 17 or 18, characterized in that the sample (3) is placed between the first processing step and the second processing step.

20. Method according to one of claims 17 to 19, characterized in that the sample (3) is structured in the first processing step, in particular periodically and / or interferometrically structured, and / or that the sample (3) is topographically smoothed, melted and / or flattened in the second processing step.

21. Method according to one of claims 17 to 20, characterized in that before the second processing step, a lubricant, in particular containing fat, is applied to the sample (3), in particular by means of a lubricating device (24), wherein heat is applied to the lubricant, in particular after the application of the lubricant, in particular during the second processing step.

22. Method according to one of claims 17 to 21, characterized in that before the first processing step, the sample (3) is processed with laser radiation in a third processing step, wherein it is provided in particular that the laser beam (5, 29) is split by the beam splitter (6, 30, 35, 41) into at least three partial beams (7, 31, 8, 32, 36, 42), wherein the third partial beam (36, 42) passes through a third optical processing device (37) and is then aligned with the sample (3) in such a way that the sample (3) is processed in a third processing step in a third processing area (40). wherein the third processing area (40) at least partially overlaps with the first processing area (13) and / or with the second processing area (22), wherein the power density of the third processing area (3) directed partial beam (36, 42) is smaller than the power density of the first partial beam (7, 31) directed onto the sample.

23. Sample (3) processed by means of an optical device (2) according to one of claims 1 to 14, in particular by means of an optical system (1) according to one of claims 15 or 16, and / or by means of a method according to one of claims 17 to 22.

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