GLASS ELEMENT WITH STRUCTURED WALL AND METHOD FOR THE PRODUCTION THEREOF

Abstract

A panel-shaped glass element is provided that includes vitreous material having a thermal expansion coefficient of less than 10×10.sup.-6 K.sup.-1 as well as two opposing surfaces. The glass element furthermore has at least one recess which runs through the glass of the glass element and has a recess wall which runs around the recess and adjoins the two opposing surfaces. The recess wall has a structure with a multiplicity of mutually adjacent rounded dome-shaped depressions. A roughness of the recess wall is formed by these depressions as well as the ridges enclosing the depressions. The recess wall has a mean roughness value (Ra) which is less than 5 .Math.m.

Claims

1. A panel-shaped glass element, comprising: a vitreous material having a thickness defined between two opposing surfaces, the vitreous material having a thermal expansion coefficient of less than 10×10.sup.-6 K.sup.-1; a recess defined through the thickness of vitreous material so that the recess has a recess wall that adjoins the two opposing surfaces; and a plurality of depressions defined in the recess wall such that the recess wall has a mean roughness value that is at least 50 nm and less than 5 .Math.m, wherein each of the plurality of depressions have a rounded dome-shape hollow and a ridge enclosing the rounded dome-shape hollow.

2. The panel-shaped glass element of claim 1, wherein the recess has a recess depth that is transverse to at least one of the two opposing surfaces.

3. The panel-shaped glass element of claim 1, wherein the recess has a recess depth that is perpendicular to at least one of the two opposing surfaces.

4. The panel-shaped glass element of claim 1, wherein the mean roughness value is less than 1 .Math.m.

5. The panel-shaped glass element of claim 1, wherein the plurality of depressions have a depth that is less than 10 .Math.m, the depth being defined by a difference between a center of the rounded dome-shape hollow and an average peak of the ridge.

6. The panel-shaped glass element of claim 1, wherein the rounded dome-shape hollow has a diameter that is less than 20 .Math.m.

7. The panel-shaped glass element of claim 1, further comprising an outer wall that runs around the thickness of the vitreous material and connects the two opposing surfaces to one another, the outer wall having a plurality of second depressions, wherein each of the plurality of second depressions have a second rounded dome-shape hollow and a second ridge enclosing the second rounded dome-shape hollow.

8. The panel-shaped glass element of claim 7, wherein the outer wall has a second mean roughness value that is more than 0.2 .Math.m.

9. The panel-shaped glass element of claim 7, further comprising a transmission of visible light in a wavelength range of between 300 nm and 1000 nm that is more than 80% for light having a direction oriented parallel to at least one of the two opposing surfaces.

10. The panel-shaped glass element of claim 9, wherein the transmission is more than 90%.

11. The panel-shaped glass element of claim 7, wherein the mean roughness value is configured anisotropically and the anisotropy is expressed as a parameter A, with A being a square of a quotient, the quotient being formed from an average value of the mean roughness value of three 30 .Math.m wide measurement bands oriented parallel to the outer wall and the average value of the mean roughness values of three 30 .Math.m wide measurement bands which are oriented perpendicularly to the outer wall, the anisotropy being less than 1.

12. The panel-shaped glass element of claim 7, wherein the mean roughness value is configured anisotropically and the anisotropy is expressed as a parameter A, with A being a square of a quotient, the quotient being formed from an average value of the mean roughness value of three 30 .Math.m wide measurement bands oriented parallel to the outer wall and the average value of the mean roughness values of three 30 .Math.m wide measurement bands which are oriented perpendicularly to the outer wall, the anisotropy more than 1.

13. The panel-shaped glass element of claim 7, wherein the recess wall and/or the outer wall has a roughness that is direction-dependent either transverse to the thickness or parallel to the thickness.

14. The panel-shaped glass element of claim 1, wherein the vitreous material comprises glass having a constituent selected from a group consisting of: an SiO.sub.2 fraction of at least 30 wt%, an SiO.sub.2 fraction of at least 50 wt%, an SiO.sub.2 fraction of at least 80 wt%, and a TiO.sub.2 fraction of at most 10 wt%.

15. The panel-shaped glass element of claim 1, wherein the panel-shaped glass element os configured for a field of use selected from a group consisting of: camera imaging, 3D camera imaging, pressure sensing, packaging of electro-optical components, biotechnology, diagnosis, and medical technology.

16. A method for producing a panel-shaped glass element, comprising: providing a vitreous material having a thickness defined between two opposing surfaces, the vitreous material having a thermal expansion coefficient of less than 10×10.sup.-6 K.sup.-1; directing a laser beam of an ultrashort-pulse laser onto one of the two opposing surfaces through focusing optics in order to form an elongate focus in the vitreous material until a plurality of filamentary channels are generated in the thickness by incident energy of the laser beam, the plurality of filamentary channels having a depth that runs transverse to the thickness and being arranged at a distance from one another; exposing the vitreous material to an etchant that erodes the vitreous material to widen the plurality of filamentary to define a recess through the thickness of vitreous material with a recess wall adjoining the two opposing surfaces and with a plurality of depressions in the recess wall, wherein each of the plurality of depressions have a rounded dome-shape hollow and a ridge enclosing the rounded dome-shape hollow; and adjusting parameters of the laser beam so that the recess wall has a mean roughness value that is at least 50 nm and less than 5 .Math.m.

17. The method of claim 16, wherein the distance between the plurality of filamentary channels is more than 1 .Math.m and less than 20 .Math.m.

18. The method of claim 16, wherein the distance between the plurality of filamentary channels is more than 3 .Math.m and less than 10 .Math.m.

19. The method of claim 16, further comprising controlling the laser beam to provide a laser pulse that is divided into a multiplicity of individual pulses with a multiplicity of more than 1 and less than 10.

20. The method of claim 16, further comprising controlling the laser beam to provide a pulse duration that is less than 15 ps.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The invention will be explained in more detail below with the aid of the appended figures. In the figures, references which are the same respectively denote elements that are the same or correspond to one another.

[0054] FIG. 1 shows a schematic representation of the generation of damage in the laser element by a laser;

[0055] FIG. 2 shows a schematic representation of a glass element having a plurality of damages;

[0056] FIG. 3 shows a schematic representation of a process of etching the glass element;

[0057] FIG. 4 shows a schematic representation of the glass element after the etching process and the separation of a part in order to generate the recess;

[0058] FIG. 5 shows an electron microscopy image of a recess wall of a glass element;

[0059] FIG. 6 shows measurement results of the roughness of the recess wall as a function of the pulse duration;

[0060] FIG. 7 shows measurement results of the roughness of the recess wall as a function of the burst;

[0061] FIG. 8 shows measurement results of the roughness of the recess wall as a function of the pitch;

[0062] FIG. 9 shows a surface measurement result of the recess wall having strong isotropy with a pulse duration of 1 ps;

[0063] FIG. 10 shows a surface measurement result of the recess wall having strong isotropy parallel to the laser with a pulse duration of 10 ps;

[0064] FIG. 11 shows a surface measurement result of the recess wall having strong isotropy perpendicularly to the laser with a pulse duration of 10 ps;

[0065] FIG. 12 shows a surface measurement result of the recess wall without significant isotropy with a pulse duration of 10 ps;

[0066] FIG. 13 shows a schematic representation of a transmission measurement of the recess wall; and

[0067] FIG. 14 shows measurement results of a reflection measurement on the recess wall.

DETAILED DESCRIPTION

[0068] FIG. 1 schematically shows a glass element 1 having two surfaces 2, which are arranged opposite one another so that the volume of the glass element is arranged between the surfaces, as well as a thickness D which defines a spacing of the two surfaces 2. The surfaces may in this case be arranged parallel to one another. The glass element 1 furthermore extends in a longitudinal direction L and a transverse direction Q. The glass element 1 preferably also has at least one outer face 4, which ideally encloses the glass element 1, in particular fully, and the height of which corresponds to the thickness D of the glass element 1. The thickness D of the glass element 1 and the height of the side face 4 in this case ideally extend in the longitudinal direction L, and the surfaces of the glass element may extend in the transverse direction.

[0069] In a first method step, damages, particularly in the form of channels 16, or channel-shaped damages 16, are generated in the volume of the glass element 1 by a laser 101, preferably an ultrashort-pulse laser 101. For this purpose, the laser beam 100 is focused and directed onto a surface 2 of the glass element by means of focusing optics 102, for example a lens having uncorrected spherical aberrations, or a lens system which has an increased spherical aberration as the overall effect of the individual elements. By the focusing, in particular elongate focusing of the laser beam 100, onto a region inside the volume of the glass element 1, the consequently incident energy of the laser beam 100 ensures that filamentary damage is generated, and in particular also widened to form a channel 16, for example by using the burst mode in which a plurality of individual pulses in the form of a pulse packet generate the damages, or channels 16.

[0070] So that the surface of the recess 10 to be generated can be structured optimally in a later method step, it may be advantageous to adjust particular laser parameters deliberately so that the surfaces of the damages and/or channels are so to speak already pretreated during the generation of the latter. For this purpose, for example, at least one of the following parameters may be adjusted precisely: the pulse durations of the laser beams 100, which preferably lie in the range of picoseconds or femtoseconds, the number of individual pulses in a pulse packet, or in the burst, the spacing of the emitted laser beams 100 relative to one another, that is to say the spacing of the damages/channels 16 generated, the energy of the laser, or the frequency. Without restriction to this embodiment, the frequency of a pulse packet may for example be 12 ns — 48 ns, preferably about 20 ns, in which case the pulse energy may be at least 200 microjoules and the burst energy may correspondingly be at least 400 microjoules. By corresponding selection of particular values of these parameters, the roughness of the recess wall 11 of the recess 10 to be generated may already be deliberately adjusted in advance.

[0071] Preferably, as shown in FIG. 2, in further steps a plurality of channels 16 are generated, these ideally being arranged next to one another in such a way that a multiplicity of channels 16 constitutes a perforation and this perforation, or this multiplicity of channels 16, forms outlines of a structure 17. In the best case, a structure 17 generated in such a way corresponds to a shape of a recess 10 to be generated. In other words, a spacing 18 and a number of the channels 16 are selected in such a way that outlines of recesses to be generated are formed. The spacing 18 of the channels 16 in this case corresponds to the pitch of the laser, that is to say the spacing 18 of the laser beams 100 to be emitted.

[0072] FIG. 3 shows a further step. After a multiplicity of channels 16 have been generated in the glass element 1 by means of the laser 101, the glass element 1 preferably structured by the channels is placed in an etchant 200. For this purpose, the glass element is preferably arranged releasably on holders 50, in which case the glass element 1 may only rest on the holders 50 or may be or have been fixed thereon. The glass element 1 is in this case held by the holders 50, and in particular immersed, in an etchant 200, preferably an etching solution, which is preferably arranged in a container 202. Ideally, for this purpose the container 202 consists of a material which is substantially resistant to the etchant 200. This means that the material of the container 202 is substantially resistant so that the etchant 200 attacks, or erodes, the material of the container only to a very small extent, or that the ions and atoms of the material of the container 202 in contact with the etchant 200 substantially remain in the volume of the container 202, so that the composition of the etchant 200 ideally remains unchanged by contact with the container 202. It is, however, also conceivable that the composition of the etchant 200 is influenced by contact with the container, and in particular the etching ability of the etchant 200 can be modified by container constituents released from the container 202, and the erosion rate of the erosion 70 of the glass element can thereby be modified in a desired direction. The erosion rate may, however, also be modified by a by physical and/or mechanically induced movement of the etchant 200, in particular stirring, for example by magnetic stirrers, or by local temperature variations. Preferably, the etchant 200 is brought to a temperature of between 40° C. and 150° C. in order to achieve an optimal erosion rate.

[0073] Preferably, an acidic or alkaline solution is used as the etchant 200, and in particular an alkaline solution, for example KOH. Ideally, a basic etchant 200 having a pH > 12, for example a KOH solution having a concentration > 4 mol/l, preferably > 5 mol/l, particularly preferably > 6 mol/l, but < 30 mol/l is used. Without restriction to this embodiment, the etching is preferably carried out with a temperature of the etchant > 70° C., preferably > 80° C., particularly preferably > 90° C., and especially about 100° C., or at a temperature below 160° C.

[0074] The erosion 70, or an erosion rate, may for example be adjusted by the duration for which the glass element 1 is exposed to the etchant 200. For this purpose, the desired erosion 70 is increased when the glass element 1 remains in the etchant 200 for longer. In order to bring the channel wall, or wall of the channels 16, pre-structured by the laser 100 to its target structure, or the desired roughness of the recess 10 or recess wall 11 to be generated, an erosion rate of less than 5 .Math.m/h is optimal. In particular, the desired mean roughness values may also be achieved by means of the total etching duration. For this purpose, it is favorable for the etching duration to be at least 12 hours. The erosion may, however, also vary and be for example 34 .Math.m with an etching duration of 16 hours, 63 .Math.m with 30 hours and 97 .Math.m with 48 hours.

[0075] Ideally, the erosion 70 and the etching duration are selected in such a way that the material is eroded between neighboring channels to such an extent that the channels join up, and in particular a continuous opening is generated by the joining up of the channels 16, such as is shown by way of example schematically in FIG. 4. Without restriction to the example shown in FIG. 4, the continuous opening may also assume any other shape and/or outline. What is important, however, is that a large opening is generated by the merging of the channels 16 in the glass element 1, in which case an inner part 20 of the glass element 1 that was previously enclosed by channels is exposed by the channel merging, and in particular may be dissolved or removed. In the course of this, the recess 10 having a recess wall 11 is generated.

[0076] Ideally, the recess wall 11 has a uniform structure, in particular with a deliberately adjusted roughness, or mean roughness value. It may, however, also be advantageous for the recess wall 11 to be configured anisotropically, for example by deliberate adjustment of the erosion rate, particularly in a form such that intermediate regions between the channels are eroded only incompletely, or partially, so that the recess wall 11 comprises such intermediate regions 30 as well as channel regions 31. By the alternation of the intermediate regions 30 and the channel regions 31, grooves that preferably form an anisotropic, or direction-dependent, roughness of the recess wall 11 may be formed on the recess wall 11.

[0077] In order to be able to adjust the structure, or the roughness, of the recess wall optimally, it may be assumed that at least one of the following relationships exists:

[00001]$\text{burst}\times \text{pulse duration}\text{=}\text{constant}$

[00002]$\text{pitch}/\text{erosion}\text{=}\text{constant}$

[0078] In view of these relationships, it is clear that the laser parameters, and in particular the pitch and the burst, or the number of individual pulses of a pulse packet, have a considerable influence on the roughness of the recess wall.

[0079] FIG. 5 shows an electron microscopy image of a channel section 31 of the recess wall 11. A multiplicity of dome-shaped depressions 12, which are distributed over the recess wall 11, may be seen clearly. The depressions 12 are in this case arranged in such a way that they adjoin one another, the depressions 12 ideally each being enclosed by a ridge 13, which for example can impede crack growth. As may be seen in the image, the depressions 12 form concave curves, the curvature of which runs in the direction of the glass volume, and in particular the ridges 13 therefore lie higher in relation to a central face than, for example, depression hollows 14. The depression hollows 14 in this case essentially form a lowest point of the depressions in relation to the ridges 13, and the ridges 13 form a highest point, or a highest line. In proportion to the curves, or curvatures, the ridges 13 are however configured only narrowly.

[0080] The depth of the dome-shaped depressions may in this case lie between 10 .Math.m and 0.1 .Math.m, a depth of between 0.2 .Math.m and 2 .Math.m being preferred since the depth substantially determines the roughness of the recess wall 11, and in particular corresponds to a difference between a center of the depression hollow 14 and the ridge 13 enclosing the depression. This means that the depth of the depressions 12 substantially determines the mean roughness value (Ra) of the recess wall 11. Other factors, for example the grooves and/or intermediate regions 30, also make a contribution to the mean roughness value (Ra). In the best case, the mean roughness value (Ra) lies between 0.2 .Math.m and 4.5 .Math.m.

[0081] Furthermore, the depressions 12 have a cross section 15 which is preferably between 5 .Math.m and 30 .Math.m in size, in particular between 10 .Math.m and 20 .Math.m. The cross section 15, or the shape, of the depressions 12 may in this case be configured polygonally. The ridges 13 in this case form boundary lines between the depressions 12, it also being possible for the ridges 13 to also be angled by the polygonal shape of the depressions 12. Ideally, the depressions 12 are formed during the etching process in such a way that they form a space-saving cross section 15, for example having a number of vertices which is between 5 and 8, and preferably precisely 6, since this shape offers the mathematically smallest outline with at the same time the greatest spatial content, that is to say it most closely resembles a circular shape. In particular, a uniform and regular roughness may be adjusted in this way, and the glass element may therefore be adapted particularly accurately to the intended application.

[0082] FIG. 6 shows graphically depicted measurement values of the mean roughness value (Ra) on the recess wall 11 which were produced by the above-described combination of the introduction of damages 16 with a laser and the subsequent widening of the damages by etching to form channels 16. The mean roughness values (Ra) generated by the aforementioned process are represented in the graph as a function of various laser parameters. The mean roughness values (Ra) are plotted on the ordinate, the number of individual pulses of a burst, or pulse packet, lying on the abscissa. The size or diameter of the measurement points in this case represents the pitch or spacing of the pulses and channels. Furthermore, roughness measurement values of a roughness that was generated with a pulse duration of 1 ps are shown on the righthand side, and those which were generated with a pulse duration of 10 ps are shown on the lefthand side. The distribution of the mean roughness values (Ra) illustrates the dependency of the roughness on pulse duration, pulse number and the spacing of the pulses.

[0083] As the graph shows, lower mean roughness values (Ra), or a smoother surface of the recess wall 11, are generated with a short pulse duration of, for example, 1 ps than is the case for example with a longer pulse duration, for example 10 ps. In particular, the graph also shows that with a lower pulse duration, both the pitch and preferably also the burst or the individual pulse number have less influence than with a higher pulse duration. The measured mean roughness values (Ra) are therefore particularly high, for instance in the range of between 1 .Math.m and 2 .Math.m, with a higher pulse duration of about 10 ps, in particular with a high pitch and a high burst, while the mean roughness values (Ra) for a low pulse duration are less than 1 .Math.m, independently of the pitch and burst. This means that a particularly low roughness of the recess wall 11 may be achieved with a low pulse duration.

[0084] FIGS. 7 and 8 show graphically depicted measurement values of the mean roughness value (Ra) of the recess wall 11. However, the mean roughness values (Ra) are plotted as a function of the burst, that is to say the number of individual pulses (in FIG. 7 plotted on the abscissa; in FIG. 8 plotted on the ordinate) and the pitch, that is to say the spacing of the pulse packets (in FIG. 7 plotted on the ordinate; in FIG. 8 plotted on the abscissa). In both figures, measurement values of a roughness that was generated with a 10 ps pulse duration are represented. Lines connecting the measurement points in this case indicate the glass erosion which was eroded during the etching process. FIGS. 7 and 8 illustrate the dependency of the generatable roughness of the recess wall 11 and/or outer wall 11 on the pitch and burst. It is clear here that the roughness, or the measured mean roughness values (Ra), are particularly high, for example in the range of 3 .Math.m or more, particularly with a high pitch beyond for example 12 .Math.m and a high burst beyond for example 7. On the other hand, beyond a pitch above 6 .Math.m the measured mean roughness values (Ra) are relatively high, for example more than 1.5 .Math.m, even with a very low burst of between 1 and 2. Since the measurement value curves run substantially parallel and for the most part lie above one another, it may be deduced therefrom that the erosion has only a small influence on the generated roughness of the recess wall 11 and/or of the outer walls 4. Essentially, the roughness of the recess wall 11 and/or of the outer walls 4 may be adjusted by the selection of the laser parameters, in particular pulse duration, pitch and burst.

[0085] It is therefore apparent that particularly rough recess walls 11 and/or outer walls 4 may be generated with a parameter field that provides at least one of the following parameters, preferably a combination of the following parameters: long pulse durations, for example more than 1, preferably more than 3, preferably more than 5, a high number of individual pulses of a pulse packet (burst), for example 7 or more, a large pitch, for example 10 .Math.m or more.

[0086] On the other hand, particularly smooth recess walls 11 and/or outer walls 4, in particular ones having a low roughness value, may be generated with a parameter field that provides at least one of the following parameters, preferably a combination of the following parameters:

[0087] short pulse durations, for example less than 5, preferably less than 3, preferably less than 1, a number of individual pulses of a pulse packet (burst) of between 2 and 7, a low pitch, for example less than 15 .Math.m.

[0088] In a development of the method, however, it is provided that for the separation of one or more inner parts 20, at least a low pitch, that is to say spatial distance between two points of impact of the laser beam 100 on the glass element 1, or between at least two channels 16, is at most 6 .Math.m, preferably at most 4.5 .Math.m, and/or the erosion is more than 34 .Math.m. In particular, a low pitch or a combination of high pitch and high erosion is advantageous in order to separate at least one inner part 20 so as to widen the channels during the etching process to such an extent that they join up. This may be carried out with a sufficiently high erosion.

[0089] FIGS. 6 to 8 thus illustrate that through the behavior of the glass material, or of the thermal expansion coefficient, the selected laser parameters have a crucial influence on the roughness of the recess wall 11. A glass that has a thermal expansion coefficient of less than 10×10.sup.-6 K.sup.-1 is in this case purposely selected in order to be able to adjust the roughness in the best possible way. It may furthermore be advantageous for the thermal expansion coefficient to be more than 0.1×10.sup.-6 K.sup.-1, preferably more than 1×10.sup.-6 K.sup.-1, particularly preferably more than 2×10.sup.-6 K.sup.-1, so that the glass has an expansion ability that is sufficient to induce a reaction to the energy of the laser. Without restriction to the proposed embodiments, glasses which have an SiO.sub.2 fraction of between 30 wt% and 80 wt% and/or a TiO.sub.2 fraction of at most 10 wt% in particular are suitable in respect of processability.

[0090] FIGS. 9 to 12 show surface measurements of the recess wall 11 having a direction-dependent roughness after erosion of 10 .Math.m in the etching bath with a measurement region about 800 .Math.m wide and about 750 .Math.m high. In this case, the measurement region width runs parallel to the surface 2 of the glass element and the measurement height runs perpendicularly to the surface of the glass element 1, and in particular parallel to the laser beam 100. On the scale at the right edge of the image, the roughness or depth (in .Math.m) of the depressions 12 relative to a central face of the recess wall 11 may be read.

[0091] FIGS. 9 and 10 depict recess walls 11 having a roughness that runs anisotropically, and particularly in the form of strips parallel to the laser beam, or perpendicularly/transversely to the surface 2 of the glass element 1. The factor A of the anisotropy is in this case preferably more than 1. This anisotropy is particularly pronounced with a short pulse duration of about 1 ps, a low burst of 2 and a pitch of 10 .Math.m, as represented in FIG. 9. The dome-shaped depressions 12 can be seen only with difficulty, but are evidently pronounced in the manner of a grid, or arranged with respect to one another in a similar way to a grid, in particular arranged above one another in the direction of the laser beam, in such a way that an arrangement of the depressions 12 form strips that run perpendicularly/transversely to the surface 2 of the glass element. The depressions 12 in this case show a round, sometimes circular cross section.

[0092] The situation is different with a recess wall 11 that was produced with 10 ps, a burst of 1 and a pitch of 10 .Math.m, as depicted in FIG. 10. As in FIG. 9, the roughness is configured anisotropically and runs in particular parallel to the laser beam, or perpendicularly/transversely to the surface 2 of the glass element 1. The individual depressions 12, however, are in this case configured rather vermiformly, they the vermiform shape preferably extending along a direction which runs parallel to the laser beam 100 and/or perpendicularly/transversely to the surface 2 of the glass element 1. In the context of the invention, vermiform is intended to mean that the ridges 13 form a nonuniform height around a depression 12 and regionally have a height which may correspond to the depth of the depression, or at least is much less than the height of a majority of the ridge 13 enclosing the depression. When there are two or more mutually adjacent depressions having such small heights of at least one region of the ridge 13, the depressions 12 appear with an approximately uniform depth in the measurement image, so that the vermiform shape consisting of a concatenation of individual depressions 12 results. It is evident overall that when using a pulse duration of 10 ps (FIG. 10; mean roughness value of 0.50 .Math.m), the recess wall 11 is configured much more coarsely, and therefore in a more matt fashion, or more roughly, than when using a pulse duration of 1 ps (FIG. 9; mean roughness value of 0.38 .Math.m). The mean roughness value (Ra) may therefore be adjusted particularly accurately by varying the pulse duration.

[0093] FIG. 11 depicts a recess wall 11 having a roughness which is configured anisotropically, preferably in the form of strips that run transversely to the laser beam 100 and/or parallel to the surface 2 of the glass element 1. The factor A of the anisotropy is in this case preferably less than 1. The recess wall 11 in this case shows essentially two regions which run in the form of strips, the depressions 12 of each region preferably having a uniform depth so that the regions essentially differ by the depth of the depressions. This leads to relatively uniform gray values of the measurement results or mean roughness values (Ra) of each region.

[0094] FIG. 12 shows a recess wall 11 having a mean roughness value of 1.05 .Math.m, which was generated with a pulse duration of 10 ps, a burst of 2 and a pitch of 3 .Math.m. In this example, the dome-shaped depressions 12 are distributed substantially homogeneously over the recess wall 11 so that only a very low anisotropy, or even no anisotropy, is formed. The cross section of the depressions 12, which are preferably configured roundly to ovally, is also relatively similarly pronounced, so that a uniform structure is formed on the recess wall 11.

[0095] FIGS. 13 and 14 schematically show a layout of transmission measurements and measurement results of reflection measurements. The glass element may advantageously be configured transparently, in particular allowing transmission of visible light, or in general light which lies in the wavelength range of between 300 nm and 1000 nm. The structuring, generated by the method presented above, of the recess wall 11 and/or outer wall 4 have advantageous light-shaping properties in order to suppress, for example, speckle effects in the case of laser diodes or other interference effects. For this purpose, the depressions 12, or the structure of the wall, may for example be configured homogeneously or anisotropically, in particular according to the forms represented in FIGS. 9-12, in order to influence the light passing through. Preferably, the glass element 1 is capable of letting light pass through both the recess wall 11 and/or outer wall 4 and through the surfaces 2 of the glass element, so that electromagnetic waves can be emitted or received through the glass element 1.

[0096] Particularly advantageously, the wall 11, 4, especially in the case of a roughness adjusted by the aforementioned method of 0.5 .Math.m (Ra), and the volume of the glass element 1 are capable of transmitting more than 90% of the light in the wavelength range between 300 nm and 1000 nm. If the wall 11, 4 is intended to have a lower transmission, however, the mean roughness value (Ra) may for example be adjusted to a value of 1.4 .Math.m, so that for example only just over 86% of the light is transmitted and more light in the wavelength range of between 300 nm and 1000 nm is reflected.

[0097] It was possible to demonstrate this inter alia by the measurement layout schematically shown in FIG. 13. It was possible to measure the transmission by means of an Ulbricht sphere 81, or an integrating sphere 81, and a light beam 80, for example a light beam 80 having a wavelength of 690 nm. In this case, the light beam 80 traveled through approximately a 10 mm volume of the glass element 1, an outer wall 4, which may be specially polished, and passed or was guided through the recess wall 11. The recess wall 11 is in this case arranged in such a way that it is arranged at or directly before the entry position of the Ulbricht sphere 81. In this way, the light beam can be scattered on the wall 11, 4 and all angles can be recorded by means of the Ulbricht sphere 81. In order to be able to determine the transmission of the wall 11, 4 independently of the volume of the glass element 1, and/or of another wall, it is also conceivable to subtract a transmission fraction of the volume of the glass element 1 and/or of a polished wall from the measurement result of the transmission. In order to be able to determine the transmission fraction of the volume of the glass element 1 and/or of the further wall, the transmission of the glass element may for example be measured in such a way that the light is guided through the surface 2 of the glass element 1, or by means of reflection measurements the degree of light reflection of a wall is determined, and this may subsequently be subtracted from the overall measurement result of the transmission measurements.

[0098] FIG. 14 shows the results of a reflection measurement. By means of a light waveguide, or a fiber sampler, light was directed onto the wall 11, 4 and the light reflected by the wall 11, 4 in the wavelength range of between 300 nm and 1000 nm was recorded. Advantageously, the recorded measurement results make it clear that the degree of reflection can be adjusted by the roughness of the wall 11, 4, or a desired reflectance may be adjusted with the aid of the roughness. It is found that, for example, the reflection of the light in the case of a rough wall 11, for example with a mean roughness value of 1.4 .Math.m, is much less than with a less rough or even smooth wall 11, 4, for example having a mean roughness value of 0.5 .Math.m.

TABLE-US-00001 LIST OF REFERENCES 1 panel-shaped glass element 2 surfaces 4 outer wall 10 recess 11 recess wall 12 dome-shaped depressions 13 ridges 14 depression hollow 15 cross section 16 channel/damages 17 structure 18 vertices 20 inner part 30 intermediate regions 31 channel regions 50 holders 70 erosion 80 light beam 81 Ulbricht sphere/integrating sphere 90 rough wall 91 smooth wall 100 laser beam 101 laser/ultrashort-pulse laser 102 focusing optics 200 etchant 202 container L longitudinal direction Q transverse direction D thickness of the glass element