Method for manufacturing a light deflection structure, application of a substrate having the light deflection structure, and light deflection unit having the light deflection structure

Abstract

The present invention relates to a method for manufacturing an optical deflection structure (3), in which a matrix material (5) of a matrix (7) is irradiated with at least one pulsed laser beam, and the method has the following steps: generating a plurality of first interaction regions (9) along a first path (P1), wherein the first interaction regions (9) spatially overlap, and in the interaction regions, at least one laser beam interacts with the matrix material (5) respectively; f) generating a plurality of second interaction regions (9) along a second path (P2) offset relative to the first path and spatially overlapping with the first path (P1), wherein the second interaction regions (9) spatially overlap; thereby generating a type-II modification of the matrix material (5), wherein at least one process parameter is changed from one path (P1, P2, PN) to another path (P1, P2, PN) to produce a predetermined deflection geometry.

Description

Field of the Invention

[0001] The present invention relates to a method for manufacturing an optical deflection structure, an application of a substrate having the optical deflection structure, and an optical deflection unit having the optical deflection structure. Background Art

[0002] The optical deflection structure includes periodic material modifications, in particular refractive index modifications or scattering disturbances, such as vacancies or damage sites, in the volume or on the surface of the substrate, wherein the material modifications affect the properties of light transmitted through the substrate.

[0003] Previously, periodic material modifications were particularly used to affect the polarization properties of transmitted light. However, an optical deflection structure having a predetermined intensity and / or orientation of optical deflection is generally required. For example, in a laser disc, it is desired to couple the laser generated by stimulated emission along a determined and well-defined direction, while the undesired, spontaneously emitted light should be emitted within as wide a spatial angle range as possible. In contrast, in other elements, such as solar cells, it is necessary to capture incident light as much as possible and retain it in the component, i.e., no longer export it from the component. Summary of the Invention

[0004] The object of the present invention is to provide a method for manufacturing an optical deflection structure that at least to some extent enables targeted optical deflection. In addition, the object of the present invention is to provide an application of a substrate having the optical deflection structure and an optical deflection unit having the optical deflection structure.

[0005] This object is solved by providing the technical teachings of the present invention, in particular the teachings of the independent claims and the embodiments disclosed in the dependent claims and the description.

[0006] This task is solved in particular by providing a method for manufacturing an optical deflection structure, in which a substrate material of a substrate is irradiated with at least one pulsed laser beam, and the method has the following steps. a) Generating a plurality of first interaction regions along a first path, wherein the first interaction regions spatially overlap. b) Generating a plurality of second interaction regions along a second path that is offset relative to the first path and spatially overlaps with the first path, wherein the second interaction regions spatially overlap. Optionally, c) Generating a plurality of additional interaction regions along an additional path that is offset relative to the previously used path and spatially overlaps with the directly adjacent previously used path, wherein the additional interaction regions spatially overlap. Optionally, d) Performing step c) multiple times to obtain a predetermined number of paths, in particular until a predetermined number of paths is obtained. A type-II modification of the substrate material is produced in the overlapping interaction regions, and at least one process parameter is changed from one path to another during manufacturing to produce a predetermined deflection geometry. This particularly means that at least one process parameter is changed from one path to another in such a way that a predetermined deflection geometry is produced. By means of the method, it is possible to provide an optical deflection structure that has predetermined deflection characteristics in a defined manner for a defined wavelength of light transmitted through the substrate material.

[0007] The interaction region should be understood here in particular as the spatial region in which at least one laser beam interacts with the substrate material. The interaction should be understood here in particular as the substrate material undergoing a permanent, i.e., stable under normal conditions, in particular at 1013 mbar and 25 °C, material modification by the laser beam in the interaction region. That is to say, the interaction region is the spatial region in which the energy density or power density of the laser beam is higher than the modification threshold of the substrate material to permanently change the material.

[0008] The spatial overlap of the interaction regions should be understood here in particular as: at least the directly adjacent interaction regions overlap with each other along one path or at least in directly adjacent paths, so that in particular the laser radiation in the second interaction region overlapping with the first interaction region interacts with the material modification produced in the first interaction region or with the laser radiation in the first interaction region. The material modification or laser radiation in the first interaction region affects the action of the laser radiation in the second interaction region; conversely, the laser radiation in the second interaction region preferably affects the material modification or laser radiation in the first interaction region.

[0009] The substrate material is especially transparent or translucent. The substrate material is in particular transparent or translucent to the pulsed laser radiation used for manufacturing the light deflection structure. The substrate material is especially not only transparent or translucent to the pulsed laser radiation used for manufacturing the light deflection structure but also to at least one target wavelength of the light that is to be deflected in a defined manner through the manufactured light deflection structure. Transparent should in particular be understood to mean that the transmittance of radiation of a wavelength determined in the case of cw radiation in the substrate material is greater than 80%, preferably greater than 85%, preferably greater than 90%.

[0010] It is possible that the method is carried out with exactly one pulsed laser beam, in particular with one pulsed laser beam per interaction region or with one pulsed laser beam that is suitably distributed over different interaction regions. Then, preferably by means of suitable focusing, the energy density (fluence), i.e., in particular the areal energy density, in the interaction region is ensured to be greater than the modification threshold of the substrate material.

[0011] Alternatively, it is also possible to use multiple pulsed laser beams, in particular two pulsed laser beams per interaction region, for example in such a way that the pulsed laser beams are in corresponding overlapping interaction regions. The energy density is then greater than the modification threshold just at the overlap of the laser beams, where the individual laser beams themselves do not provide an energy density greater than the modification threshold.

[0012] It is also possible to generate multiple laser beams by splitting the pulsed laser beam generated by the laser source in a suitable manner into multiple sub-laser beams. This is also referred to as multiplexing.

[0013] The light deflection structure is preferably generated in the substrate material, i.e., in the volume of the substrate material. Particularly preferably, a three-dimensional light deflection structure is generated in the volume of the substrate material. Correspondingly preferably, the different paths are not arranged only in a plane in the substrate material but are rather three-dimensionally distributed in the volume.

[0014] Alternatively or additionally, it is possible that the light deflection structure is generated on the surface of the substrate material. Then the individual paths extend at least partially or completely along the surface of the substrate.

[0015] Preferably, a silicate-containing material, in particular silicate, fused quartz or borosilicate, is used as the substrate material. The substrate can in particular be glass, especially quartz glass, especially borosilicate glass. However, it is also possible that the substrate is a polymer, ceramic, especially a semiconductor or crystal comprising Si and / or GaAs.

[0016] The spatial overlap of two paths in particular means that the interaction regions of the two paths overlap spatially.

[0017] The offset of one path relative to another path, in particular, means that one path, especially the center-of-gravity line or the center line of a path, is vertically spaced from the center-of-gravity line or the center line of another path.

[0018] Type II modification (Typ II-Modifikation) should in particular be understood as a material modification of a matrix material, which is produced based on a self-organization effect caused by multiple irradiations of the same site (so the interaction regions and paths overlap spatially). In particular, the previously irradiated site optically interacts with the laser beam when the same site is irradiated again; preferably, the previously irradiated site is used as a grating. An anisotropic structure is formed here, which has a directional deflection effect due to its anisotropy. The characteristic of Type II modification is in particular that the effective refractive index is different laterally. Therefore, the changed properties are in particular the same as those of a uniaxial optical crystal. Thus, generating a Type II modification especially means that at least one process parameter, in particular at least one radiation parameter of at least one laser beam and / or at least one arrangement parameter of the arrangement of the interaction region, is selected in such a way that a Type II modification is formed. Generating a Type II modification is especially based on an optical effect rather than a thermal effect.

[0019] Changing at least one process parameter from one path to another path in particular means selecting different values of at least one process parameter for at least two paths. In particular, the value or setting of at least one process parameter preferably changes between manufacturing the previous path and manufacturing the next path. It is possible to change more than one process parameter or all process parameters. It is also possible to implement the following embodiment of the method, in which all process parameters of multiple paths remain constant, where at least one process parameter of at least one additional path or multiple additional paths is changed. In particular, it is also possible to produce groups of paths with constant process parameters, where at least one process parameter is changed between different groups of paths. However, preferably, at least one process parameter different from the directly adjacent, in particular the previously used and / or subsequently produced, path is selected for each path. It is possible to always change the same process parameter or the same multiple process parameters from one path to another path. It is also possible to change different process parameters from one path to another path.

[0020] A predetermined deflection geometry should in particular be understood as that the optical deflection structure is designed geometrically in space such that light of a determined wavelength is deflected to a determined spatial angle range with a defined intensity.

[0021] The multiple first, multiple second, and at least multiple others can be different in number, however, it is also possible that at least two of them mean the same number.

[0022] According to an improved embodiment of the present invention, the pulsed laser beam has a temporal pulse width of at least 100 fs up to a maximum of 5 ps. Thus, the pulsed laser beam in particular comprises ultrashort laser pulses.

[0023] According to an improved embodiment of the present invention, the induced grating period of the optical deflection structure is modulated by changing at least one process parameter. In this way, a so-called chirp is generated in the optical deflection structure, thereby achieving a wider deflection distribution and / or scattering angle distribution. The chirped structure with a variable period, in particular a grating, can be generated by a constant or variable orientation.

[0024] According to an improved embodiment of the present invention, a plurality of nano-grating layers are successively generated in the substrate. Thereby, the deflection effect can be enhanced.

[0025] According to an improved embodiment of the present invention, at least one process parameter is changed within at least one path selected from the first path, the second path, and optionally an additional path according to one of steps c) and d) to produce a predetermined deflection geometry. Thus, the optical deflection structure can be modified more subtly. In this way, in particular, the induced grating period of the optical deflection structure can be changed, in particular modulated, within the path. In particular, a 2D-matched structure can be produced, wherein, in particular, the grating period is changed within the path, in particular by means of the variable pulse energy and / or variable feed rate of the laser spot of at least one laser beam per unit time relative to the substrate, and also the grating period is changed from one path to another in the same or other way, thereby obtaining a two-dimensional chirped grating that deflects or scatters light components with different incident angles at the same exit angle, or vice versa depending on the application. Similarly, the diffraction response can be designed to increase or decrease continuously by changing, in particular, process parameters, especially the pulse repetition rate, along the path such that grating formation is suppressed, wherein, thereby, the chirped grating from one path to another is changed along the feed with respect to the efficiency of the grating.

[0026] Alternatively, at least one process parameter is preferably kept constant within each path and is only changed from one path to another. Particularly preferably, all process parameters are kept constant within the same path.

[0027] According to an improved embodiment of the present invention, a diffraction deflection geometry is generated. Preferably, the period of the optical deflection structure is in particular selected to be greater than or approximately equal to the following wavelength at which the deflection structure is to function in a specified manner. The deflection structure then has a diffraction effect for this wavelength.

[0028] Alternatively, a scattering deflection geometry is preferably generated. For this purpose, the period of the light deflection structure is preferably chosen to be less than the wavelength at which the light deflection structure is to operate in a defined manner. The substrate is an effective medium with a refractive index difference, which results in anisotropic scattering of light of the defined wavelength.

[0029] Accordingly, deflection should generally be understood as a change in the propagation direction of light, where the term "deflection" particularly includes diffraction or scattering.

[0030] The light deflection structure proposed here can in particular achieve local light deflection.

[0031] According to an improvement of the invention, at least one of the paths selected from the first path, the second path, and optionally a further path according to one of steps c) and d) extends along a straight line. This is a particularly simple design of the method.

[0032] Alternatively or additionally, it is possible that at least one of the paths selected from the first path, the second path, and optionally a further path according to one of steps c) and d) has at least locally a finite curvature. The path can also be curved as a whole. Here, a more flexible and more accurately adapted light deflection structure and deflection geometry can also be generated. That the curvature is finite means that the curvature is greater than zero, i.e., the curvature does not vanish. The curvature can be constant along the path or at least locally variable.

[0033] At least one process parameter is in particular selected from at least one radiation parameter of at least one laser beam and at least one arrangement parameter of the arrangement of the interaction region. The arrangement parameter here particularly refers to the spatial geometric arrangement of the interaction region or the generation of the spatial geometric arrangement of the interaction region. As will also be explained below, different interaction regions can be generated simultaneously or successively in time, where the different interaction regions are generated successively in time in particular by shifting the focal region or the laser spot of at least one laser beam relative to the substrate. In the latter case, the arrangement parameter is in particular the shift parameter of the relative shift of the laser beam relative to the substrate.

[0034] Regarding the relative shift here and below or only the shift of the laser beam relative to the substrate, this should in no way be understood restrictively as the laser beam shifting and the substrate remaining spatially stationary. Rather, it is possible that the laser beam remains spatially stationary while the substrate shifts. It is also possible that both the laser beam and the substrate shift. However, a particularly preferred design due to its particularly easy implementation is that the substrate remains spatially stationary while the laser beam shifts.

[0035] According to an improved embodiment of the present invention, at least one process parameter is selected from the group consisting of: the spectrum of the laser beam, the pulse energy of the laser beam, the energy density of the laser beam, the temporal pulse width of the laser beam, the temporal pulse shape of the laser beam, the spatial pulse shape of the laser beam, the radiation dynamic characteristics of the laser beam, the polarization of the laser beam, in particular the polarization direction, the pulse repetition rate of the laser beam, the micro-pulse repetition rate of the laser beam, the focus size of the laser beam, in particular the focus diameter or the laser spot diameter, the focus cross-sectional shape of the laser beam, the focus profile of the laser beam, the feed rate of the laser spot of at least one laser beam per unit time relative to the substrate, the number of pulses per laser spot or per unit length, and the overlap amount between adjacent interaction regions.

[0036] The temporal pulse shape of the laser beam should in particular be understood as the envelope shape of the temporal intensity curve of the laser pulse. In contrast, the radiation dynamic characteristics of the laser beam should be understood as the temporal structure of the intensity curve within the pulse, and thus to a certain extent as the temporal microstructure of the laser pulse. This particularly includes whether the laser pulse has a continuous temporal pulse shape or is composed of a burst or multiple bursts of pulses and thus forms a pulse sequence.

[0037] The pulse repetition rate should in particular be understood as the macro-pulse repetition rate, i.e., the repetition rate of individual laser pulses or pulse sequences. In contrast, the micro-pulse repetition rate should be understood as the repetition rate of individual micro-pulses or bursts within a laser pulse or pulse sequence.

[0038] The focus size should in particular be understood as the spot size of the laser beam, in particular the characteristic extension or length of the laser spot in a plane perpendicular to the propagation direction, or the area of the laser spot in said plane. In the case of a Gaussian beam, the laser spot (or simply the spot) is defined as twice the beam waist radius R, which is obtained by dividing the peak wavelength λ by the sum of pi and the numerical aperture NA of the laser system (R = λ / (π*NA)).

[0039] The focus cross-sectional shape should in particular be understood as the cross-sectional shape of the laser spot. The focus profile should in particular be understood as the profile of the laser spot, especially in the focal plane. Here, the profile is in particular the spatial intensity curve, i.e., especially the intensity curve in the focal plane or on the surface of the spot.

[0040] The number of pulses per laser spot must be greater than 1 to obtain a type II modification (e.g., self-organized nanostructures, nanogratings, or periodically arranged interferences). Here, the number of pulses per laser spot is obtained by multiplying the spot size by the pulse repetition rate and dividing by the feed rate. Thus, the pulse rate per laser spot ultimately corresponds to the number of pulses per unit length, where this number of pulses per unit length must be chosen such that more than one pulse is incident in the feed direction over the length extension of the laser spot.

[0041] If the interaction regions are generated not sequentially in time but simultaneously, the number of pulses per laser spot or the number of pulses per unit length corresponds in particular to the amount of overlap of directly adjacent interaction regions.

[0042] According to an improvement of the invention, it is provided that the wavelength of the laser beam, in particular the peak wavelength, is at least 200 nm to a maximum of 5000 nm.

[0043] Alternatively or additionally, the pulse repetition rate is preferably at least 1 Hz to a maximum of 5 MHz, preferably to a maximum of 4 MHz, preferably to a maximum of 3 MHz, preferably to a maximum of 2 MHz, preferably to a maximum of 1 MHz.

[0044] Alternatively or additionally, the micro-pulse repetition rate is preferably at least 1 MHz to a maximum of 50 GHz.

[0045] Alternatively or additionally, the temporal pulse width is preferably at least 100 fs to a maximum of 5 ps.

[0046] Alternatively or additionally, the energy density is preferably greater than 0.01 J / cm 2 , in particular for glass, in particular fused silica as the substrate, preferably greater than 0.1 J / cm 2 , preferably greater than 1 J / cm 2 . The modification threshold in the volume of the substrate material is typically greater than 0.1 J / cm 2 , and if necessary also greater than 1 J / cm 2 . On the surface of the substrate material, the modification threshold is reduced in contrast and is typically greater than 0.01 J / cm 2 , and if necessary also greater than 0.1 J / cm 2 . The energy density used is preferably chosen to be greater than the corresponding relevant value of the modification threshold.

[0047] Alternatively or additionally, it is provided that the feed of the laser spot relative to the substrate per unit time is preferably at least 0.01 mm / s to a maximum of 1000 mm / s, preferably to a maximum of 500 mm / s.

[0048] Alternatively or additionally, it is proposed that the number of pulses per unit length is preferably greater than one pulse per μm (1 / μm), where the term "pulse" also includes pulse sequences herein.

[0049] According to an improvement of the present invention, the interaction region is generated at least simultaneously along a path selected from the first path, the second path, and optionally another path according to one of steps c) and d). This can in particular be carried out by means of a spatio-temporally shaped excitation beam and / or by means of a phase mask.

[0050] Alternatively, the interaction region is preferably generated sequentially in time at least along a path selected from the first path, the second path, and optionally another path according to one of steps c) and d), in particular by shifting the focal region or laser spot of at least one laser beam relative to the substrate. Writing the light deflection structure into the substrate is then carried out point by point, in particular by scanning with a laser beam.

[0051] Preferably, the interaction region is generated simultaneously or sequentially in time along all paths.

[0052] Preferably, steps a) to d) are carried out simultaneously or sequentially in time overall. That is to say, in particular, it is possible that steps a) to d) are carried out simultaneously, in particular by means of a spatio-temporally shaped excitation beam and / or by means of a phase mask. It is also possible that a plurality of laser beams offset from each other are shifted along the path simultaneously, in particular at least one laser beam for each path is shifted along the path simultaneously. In the case of simultaneous execution of the steps, the term "previously used path" in step c) refers to the previously mentioned path, however, the path is generated simultaneously with the corresponding other path. In this regard, the term "multiple implementations" in step d) also relates to, straightforwardly speaking, generating a plurality of other paths.

[0053] The shift of the focal region or laser spot relative to the substrate can be carried out perpendicular to the propagation direction of the laser beam and / or parallel to the propagation direction of the laser beam. It is only important that the following region of the laser beam is shifted relative to the substrate, in which a permanent material modification is achieved.

[0054] According to an improvement of the present invention, a predetermined temporal form is applied to a single pulse of at least one laser beam. The temporal form of the laser beam or laser pulse, in particular a single pulse, can additionally influence the generated light deflection structure.

[0055] According to a further development of the invention, it is provided that after step b), the substrate is at least partially heated in order to change the produced type II modification. In particular, the substrate is heated at least partially in such a way that the produced type II modification is changed in a predetermined manner. By means of such subsequent heating of the substrate, defects can be repaired and, for example, the optical properties of the initiated periodic material modification can be changed. Heating the substrate at least partially after step b) comprises optionally heating the substrate after step c) or after step d). In particular, the substrate is heated accordingly at the end of the production process, i.e. after all interaction regions have been produced.

[0056] The substrate is preferably heated to a temperature T which is suitable for:

[0057] 0.5T g <T<1.2T g ,

[0058] Among them, T g is the transition temperature of the matrix. The transition temperature is in particular 10 12 The temperature at which the viscosity is in Pas.

[0059] The object is also achieved by providing a use of a substrate having a light-deflecting structure, wherein the light-deflecting structure is produced by the method according to the invention or one of the above-described embodiments of the method, wherein the substrate is used as an optical fiber, a laser disc, a glass display or a solar cell. In particular, the advantages described in conjunction with the light-deflecting structure are obtained here.

[0060] In particular, when the substrate is used as a laser disc, the light deflection structure can be used to couple out the desired, stimulated and enhanced laser light from the laser disc in a defined direction. Alternatively, the light deflection structure can be provided to couple out the undesired, spontaneously emitted and enhanced light from the laser disc in a manner that is scattered as widely as possible, in particular at different angles depending on the wavelength, so as to reduce the thermal load on the surrounding area caused by the spontaneous emission.

[0061] If the substrate is used as a solar cell, the light-redirecting structure can in particular help to retain the light incident on the solar cell in said solar cell and thus increase the efficiency and yield of the solar cell.

[0062] Finally, the object is achieved by providing a light deflection unit having a light deflection structure which is produced using the method according to the invention or one of the above-mentioned embodiments of the method. In conjunction with the light deflection unit, in particular the advantages already mentioned above are achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] This task will be described in detail below with the aid of the accompanying drawings.

[0064] Figure 1 Schematic diagrams showing two embodiments of a light deflection structure

[0065] Figure 2 Exemplarily shows the correlation between the period of the light deflection structure generated in a determined matrix material and the number of pulses of each laser spot, and

[0066] Figure 3 Exemplarily shows the correlation between the period of the light deflection structure generated in a determined matrix material and the wavelength of the laser beam used for manufacturing. Detailed description of the specific implementation

[0067] Figure 1 In a), a schematic diagram of a first embodiment of a light deflection unit 1 having a first embodiment of a light deflection structure 3 is shown. The light deflection structure is generated in a matrix material 5 of a matrix 7 by means of at least one pulsed laser beam in particular by the following method, which method includes the following steps: generating a plurality of first interaction regions 9, and only two of the interaction regions are schematically marked for better clarity and provided with corresponding reference numerals. Here, the interaction regions 9 are generated along a first path P1, where the interaction regions overlap spatially, i.e., step a).

[0068] The light deflection structure 3 is manufactured in particular as a nanograting, the grating ridges of which are Figure 1 shown as black lines in

[0069] Step b): Generating a plurality of second interaction regions 9 along a second path P2, where the second interaction regions 9 overlap spatially, and where the second path P2 is offset relative to the first path P1, yet overlaps spatially with the first path P1, which is indicated here by overlapping braces. This particularly means that the interaction regions of the plurality of second interaction regions 9 arranged along the second path P2 overlap with the interaction regions 9 of the plurality of first interaction regions 9 arranged along the first path P1.

[0070] Optionally, a plurality of additional interaction regions 9 are generated along an additional path PN that is offset relative to the previously used paths P1, P2 and overlaps spatially with the directly adjacent previously used path PN-1, where the additional interaction regions 9 overlap spatially. Specifically, a plurality of third interaction regions 9 are generated here in such a way that they overlap spatially along a third path P3, which is offset relative to the first path P1 and the second path P2, yet overlaps with the second path P2, i.e., step c).

[0071] Step d): This step c) can be carried out multiple times until a predetermined number of paths is obtained.

[0072] Within the framework of the method, a type-II modification in the matrix material 5 is generated.

[0073] At least one process parameter is changed from one path to another to generate a predefined deflection geometry. It is also possible that, when generating at least one path, at least one process parameter is changed within the path to generate a predefined deflection geometry.

[0074] The deflection geometry can be a diffraction deflection geometry or a scattering deflection geometry.

[0075] In the embodiment shown here, the paths P1, P2, P3 extend along a straight line. However, it is also possible that at least one of the paths extends along a curved line, in particular along an arc. Different geometries can also be achieved for different paths.

[0076] At least one process parameter is preferably selected from the group consisting of: the spectrum of the laser beam, the pulse energy of the laser beam, the energy density of the laser beam, the temporal pulse width of the laser beam, the temporal pulse shape of the laser beam, the spatial pulse shape of the laser beam, the radiation dynamic characteristics of the laser beam, the polarization of the laser beam, in particular the polarization direction, the pulse repetition rate, the micro-pulse repetition rate, the focus size or the laser spot size, in particular the focus diameter or the laser spot diameter, the focus cross-sectional shape or the laser spot cross-sectional shape, the focus profile or the laser spot profile, the feed rate of the laser spot per unit time relative to the matrix 7, the number of pulses per laser spot on the matrix 7 or the number of pulses per unit length, and the amount of overlap of the interaction regions 9 directly adjacent to each other.

[0077] In the embodiment shown here, the polarization direction, schematically indicated by the double arrow DP here, is changed as a process parameter from one path to another.

[0078] Preferably, the interaction regions 9 are generated at least along the paths simultaneously or sequentially in time, in particular by shifting the focus region or the laser spot of at least one laser beam relative to the matrix 7.

[0079] The different paths can also be scanned simultaneously by a plurality of laser beams offset from each other, wherein in particular at least one laser beam is used for each path.

[0080] Preferably, a predefined temporal form is applied to the individual pulses of at least one laser beam.

[0081] Preferably, after step b), in particular after all the interaction regions 9 have been generated along all the paths P1, P2, PN, the matrix 7 is heated at least locally to change the generated type-II modification.

[0082] The optical deflection structure 3 is preferably used as an optical fiber, a laser disc, a glass display screen or a solar cell.

[0083] Generally, the concept underlying the present invention is that periodic material modifications, in particular refractive index modifications, are generated in the volume and / or on the surface of a (semi-)transparent material by means of ultrashort laser pulses in order to influence the properties of the transmitted light and to deflect the transmitted light in a targeted manner. The geometric relationships or structural properties (e.g. period, refractive index contrast) of the induced modifications and thus the intensity and orientation of the deflection can be controlled by means of writing parameters and / or writing laser parameters, beam shaping and / or radiation dynamics.

[0084] If the ultrashort laser pulses of the writing laser are focused into the volume of a substrate, such as fused silica, the high intensity present in the focus causes non-linear absorption processes, which trigger material modifications. Writing can be carried out point by point and / or simultaneously at a plurality of position points, in particular by means of a spatio-temporally shaped excitation beam and / or by means of a phase mask.

[0085] The structure can be used to deflect diffracted or inherently scattered light into a defined angular range. Here, the orientation of the deflection can be controlled by the period of the grating, which is defined by laser parameters, such as the wavelength of the writing laser. The intensity of the diffraction efficiency can be controlled by different concepts, such as by the laser pulse energy, the feed rate and / or by means of radiation dynamics, in particular temporally, for example by means of a train of laser pulses and / or beam shaping.

[0086] Depending on the substrate material 5, the induced nanostructures can have very different structural properties. In glass, in particular, nanogratings are produced, which consist of microscopic pores with anisotropic morphology and dimensions of several hundred nanometers in length and at least ten nanometers in thickness. By irradiating with light, for example in the visible spectral range, based on the anisotropic structure, a scattering cone is generated, which is oriented corresponding to the grating orientation, i.e. always parallel to the polarization of the writing laser and thus in particular perpendicular to the grating ridges of the nanograting. Within the framework of the technical teaching presented here, this targeted scattering can in particular also be used to deflect the incident light.

[0087] If the laser-induced nanogratings are written closely adjacent to each other, in particular overlapping, the newly written gratings are arranged coherently with the orientation of the already existing gratings. In particular, self-organized structures are produced. Thus, see Figure 1 a) Regions with, for example, continuously varying nanograting orientations can be produced, and thus light can be deflected or scattered over a large angular spectrum.

[0088] Figure 1 b) shows another embodiment of the light deflection unit 1 with another embodiment of the optical deflection structure 3.

[0089] Identical and functionally identical elements are provided with the same reference signs in all the figures, and reference is accordingly made to the foregoing description in this regard.

[0090] In said another embodiment, the induced grating period is modulated, in particular, by changing at least one process parameter within each path. In particular, a so-called chirp is generated, thereby achieving a wider deflection distribution or scattering angle distribution. This can be achieved, for example, by changing process parameters such as the feed of the written laser beam, the pulse overlap, and / or the wavelength. The chirped grating can be generated with a constant or variable orientation. In addition, multiple nanograting layers arranged successively can enhance the deflection effect.

[0091] Specifically, herein, the feed of the laser spot per unit time relative to the substrate 7 and the shift speed of the laser beam, which are process parameters, are changed within each path to modulate the grating period. Herein, the acceleration of the laser beam within each path is schematically shown by an arrow. Alternatively, of course, the shift speed of the laser beam along the path can also be reduced.

[0092] Within the framework of the technical teachings proposed herein, the periodic modification is matched to the deflection geometry to be achieved. That is, the grating ridges of the nanograting can have an arbitrary angle relative to the material surface, depending on the application. In particular, the geometry of the written periodic modification is matched to the application to be achieved, and concepts such as radiation dynamic characteristics, beam shaping, multi-beam processing (multiplexing), etc. can be used to generate a large range of modified regions in the material.

[0093] Defects can be repaired by post-heating the manufactured light deflection structure 3, and for example, the optical characteristics of the induced periodic material modification can be changed.

[0094] To write the periodic material modification, different schemes can be considered: On the one hand, ultrashort laser pulses can be focused into the volume of the substrate 7 through a microscope objective, and a large area can be constructed by scanning the substrate 7 and / or the laser spot. In addition, the modified region or absorption region can be changed by beam shaping elements in the processing head, such as diffractive optical elements, spatial light modulators, or by acousto-optic deflectors. The latter can also occur highly dynamically during processing. In particular, digital optical devices or scanners with acousto-optic deflectors can be used. The time absorption dynamics can be changed by short pulse sequences, especially pulse trains.

[0095] In a first step, preferably the correlation of the periodic material modification to be produced with different process parameters of the substrate material 5 to be processed is determined and the correlation is stored as a table in the program. Then the determined diffraction or scattering or grating period can be predefined and the control parameters for processing can be retrieved from the table.

[0096] Figure 2 Exemplarily shown is the correlation of the periodic material modification to be produced with the process parameters, specifically here the correlation of the period of the produced nanogratings with the number of pulses per laser spot. Here, the period of the material modification is in particular obtained by λ / 2n, i.e., by dividing the wavelength λ of the laser beam used by twice the refractive index n of the substrate material 5.

[0097] Figure 3 Exemplarily shown is the correlation of the period of the produced material modification with the wavelength λ of the writing laser.

Claims

1. A method for manufacturing an optical deflection structure (3), wherein, Irradiating the substrate material (5) of a substrate (7) with at least one pulsed laser beam, the method having the following steps: a) Generating a plurality of first interaction regions along a first path (P1), in which the at least one laser beam interacts with the substrate material (5) respectively, wherein the first interaction regions spatially overlap; b) Generating a plurality of second interaction regions along a second path (P2) offset with respect to the first path and spatially overlapping with the first path (P1), wherein the second interaction regions spatially overlap; c) Generating a plurality of further interaction regions along a further path (PN) offset with respect to the previously used paths (P1, P2) and spatially overlapping with the directly adjacent previously used path (PN-1), wherein the further interaction regions spatially overlap; d) Repeating step c) a plurality of times to obtain a predetermined number of paths (P1, P2, PN), wherein, - generating a type-II modification of the substrate material (5), wherein, - changing at least one process parameter from one path (P1, P2, PN) to another path (P1, P2, PN) to produce a predetermined deflection geometry.

2. The method according to claim 1, characterized in that, Changing the at least one process parameter within at least one path (P1, P2, PN) selected from the first path (P1), the second path (P2), and a further path (PN) according to one of steps c) and d) to produce the predetermined deflection geometry.

3. The method according to claim 1 or 2, characterized in that, Producing a diffraction deflection geometry or a scattering deflection geometry.

4. The method according to claim 1 or 2, characterized in that, At least one path among the paths (P1, P2, PN) selected from the first path (P1), the second path (P2), and a further path (PN) according to one of steps c) and d) extends along a straight line, and / or at least one path among the paths (P1, P2, PN) selected from the first path (P1), the second path (P2), and a further path (PN) according to one of steps c) and d) has a finite curvature at least locally.

5. The method according to claim 1 or 2, characterized in that, The process parameter is selected from the group consisting of: spectrum, pulse energy, energy density, temporal pulse width, temporal pulse shape, spatial pulse shape, radiation dynamic characteristics, polarization, pulse repetition rate, micro-pulse repetition rate, focus size, focus cross-sectional shape, and focus profile, feed rate of the laser spot per unit time with respect to the substrate (7), number of pulses per laser spot, and amount of overlap of directly adjacent interaction regions with each other.

6. The method according to claim 1 or 2, characterized in that, The interaction regions are generated simultaneously or sequentially in time along at least one path (P1, P2, PN) selected from the first path (P1), the second path (P2), and a further path (PN) according to one of steps c) and d).

7. The method according to claim 1 or 2, characterized in that, Applying a predetermined temporal form to a single pulse of the at least one laser beam.

8. The method according to claim 1 or 2, characterized in that, After the step b), heat the substrate (7) at least locally to change the resulting type-II modification.

9. The method according to claim 5, characterized in that, The set for the process parameters includes the polarization direction.

10. The method according to claim 6, wherein The interaction region is produced by shifting the focal region of the at least one laser beam relative to the substrate (7).

11. Use of a substrate (7) having a light deflection structure (3) as an optical fiber, a laser disk, a glass display screen or a solar cell, the light deflection structure being manufactured by the method according to any one of claims 1 to 10.

12. A light deflection unit (1) having a light deflection structure (3) manufactured by the method according to one of claims 1 to 10.

Images