WO2019201791A1

WO2019201791A1 - Pulse length adjustment unit, laser system and method for adjusting the pulse length of a laser pulse

Info

Publication number: WO2019201791A1
Application number: PCT/EP2019/059507
Authority: WO
Inventors: Andreas Enzmann
Original assignee: Trumpf Laser Gmbh
Priority date: 2018-04-19
Filing date: 2019-04-12
Publication date: 2019-10-24
Also published as: DE102018109405B3

Abstract

A pulse length adjustment unit (7, 7') for a pulsed laser beam (5) with a spectral width comprises a first and a second dispersive element (11A, 11B) for generating angular dispersion in an angular dispersion range (13) limited by the dispersive elements (11A, 11B). In the angular dispersion range (13), optical paths (13A, 13B) are assigned to individual spectral components of the laser beam (5), at least some sections of said optical paths running at an angle to one another. The pulse length adjustment unit (7, 7') also comprises a first and second 3-surface reflector (9A, 9B), wherein each of the 3-surface reflectors (9A, 9B) is arranged in the beam path between the first and the second dispersive element (11A, 11B) and has three reflective surfaces (R1, R2, R3). The laser beam (5) is reflected by each of the 3-surface reflectors (9A, 9B) via three consecutive reflections of the laser beam (5) on the three reflective surfaces (R1, R2, R3) such that a change in direction and beam offsetting take place.

Description

Pulse length adjustment unit, laser system and

Method for pulse length adaptation of a laser pulse

The present invention relates to a unit for pulse length adjustment by adjusting the dispersion in an electromagnetic beam having a spectral width, for example, a pulsed laser beam. The unit for pulse length adaptation can be designed for example as Pulskompressoreinheit and / or as a pulse-stretching unit of a laser system.

Laser pulses have a spectral width which determines the achievable minimum duration of the laser pulse. The wider the underlying frequency spectrum, the lower the pulse duration of the laser pulse can become. However, in general, the dispersion of the material passed through and possibly a self-phase modulation at high peak powers lead to a divergence of the spectral components, so that, in particular for short and ultrashort laser pulses with pulse duration in the ps range and shorter usually, dispersion adaptation of the optical path is undertaken , Optical constructions which counteract a dispersive broadening of the pulse duration are referred to herein as pulse compressor units. Examples of such dispersion adjusting units include e.g. Grating pair or prism pair-based compressor units (short: grating or prism compressors), which use a Auffächem here called angular dispersion of the spectral components of the laser pulse in a deflection of the grating or prisms to produce unterschiedli chen optical path lengths.

Furthermore, amplified pulses can lead to high intensities, which can cause, inter alia, non-linear effects such as self-focusing, eg in the amplifier laser medium. Such non-linear optical effects can adversely affect the beam and pulse quality and accordingly the entire amplification process. Accordingly, amplifier configurations are designed such that either an actively stretched laser pulse is amplified or the pulse extension occurs during the amplification process. Optical structures of such dispersion adjusting units which cause a dispersive broadening of the pulse duration of a laser pulse are referred to herein as pulse stretching units. Examples of such dispersion adaptation units include, for example, grating pair or prism pair-based excursion units (in short: grating or prism spacers) which produce an angular dispersion opposite, for example, to a later used pulse compressor unit, for example with an integrated lens system. The basic parameter in lattice or prism compressors and grating or prism stretching is the extent of spectral fanning. This depends, for example, on the lattice constants of the grid used or the refractive index of the prism used and on the spacing of the gratings or prisms. In general, the dispersion can be set by the spacing of the gratings or prisms, which determines the path length differences produced on the basis of the angular dispersion. In lattice compressors or stretchers, in particular, the phase accumulated by the diffraction contributes to the dispersion. In general, the better the dispersion can be compensated, the closer the pulse duration can approach the spectrally achievable pulse duration.

In general, the above concepts for pulse stretching and pulse compression in the so-called CPA (chirped pulse amplification) are used to generate ultrashort pulses with high pulse energies. For example, to generate (ultra-) short pulses with a fiber laser system, typically an input laser pulse of a fiber laser is stretched in time (eg, in a fiber-based expander or in a grating spacer), amplified in a fiber gain purity, and then time compressed (eg, in a grating compressor). , Similar constructions for generating (ultra-) short pulses may e.g. in machine tools based on disk laser systems. Typically, very precise and technically demanding compression is required to reverse the dispersive divergence of the spectral components.

In the prior art, various approaches to precise dispersion control, e.g. known in lattice compressors. For example, WO 2015/117128 discloses Al and

US Pat. No. 7,822,347 B1 Concepts in which the change in the pulse duration is regulated via the grating spacing of the extensor or compressor and additionally fine-tuned by means of a "chirped" FBG (Fiber Bragg Grating). Other approaches are known from US 7,729,045 B2, US 8,077,749 B2 and US 8,780,440 B2. Further, reference is made to the application DE 10 2016 110 947 A1 of the Applicant, which discloses an approach for fine adjustment of the dispersion.

One aspect of this disclosure is based on the object of providing a structure in the case of dispersion adaptation in, for example, grating pair and prism pair-based pulse length adjusting units, in which the beam quality of the output beam is maintained. A further aspect of the invention is based on the object of providing a dispersion adjustment in the case of gene pulse length adjustment units, which has the least possible impact on the beam quality and the beam path after the dispersion adjustment unit. Furthermore, an easily controllable adjustability of the dispersion is desired.

At least one of these objects is achieved by a pulse length adjusting unit according to claim 1, by a laser system according to claim 18 and by a method according to claim 20. Further developments are specified in the subclaims.

In one aspect, a pulsed laser beam pulse length adjusting unit having a spectral width includes first and second dispersive elements for producing angular dispersion in an angular dispersion range limited by the dispersive elements. In the angular dispersion region, individual spectral components of the laser beam are assigned optical paths which run at least in sections at an angle to one another. The pulse length adjusting unit further comprises a first and a second 3-area reflector, wherein each of the 3-area reflectors is arranged in the beam path between the first and the second dispersive element. Each of the 3-surface reflectors has three reflection surfaces. The laser beam is reflected by each of the 3-plane reflectors by three successive reflections of the laser beam at the respective three reflection surfaces. At each of the 3-surface reflectors, there is a directional deflection in the range of 150 ° to 210 ° and a beam offset. With such a directional deflection, a rotation about the beam axis of the laser beam can be achieved e.g. at an angle in the range of 150 ° to 210 °. Substantially complete directional reversal can be accomplished using a comer-cube reflector. Furthermore, directional deflections can be set in the range of 160 ° to 200 ° or in the range of 170 ° to 190 °, in particular to provide substantially back reflection-type reflectors.

In a further aspect, a laser system comprises a laser pulse source for generating spectrally broad laser pulses and at least one Pulslängenanpas sungseinheit as described above for pulse compression, pulse stretching and / or pulse optimization of the spectrally wide laser pulses.

In another aspect, a method for pulse length adjustment of a laser pulse having a pulse length adjusting unit as described above is disclosed. The pulse length adjustment The detection unit has a first and a second dispersive element for generating angular dispersion and a first and a second 3-area reflector, wherein each of the 3-area reflectors is arranged in the beam path between the first and the second dispersive element. The method comprises the step of displacing the first and / or the second dispersive element to adjust the path of the optical path between the first and the second dispersive element. Optionally, the path length of the optical path between the first and the second dispersive element can be set as a function of a pulse duration-dependent measurement signal, a pulse power parameter, a peak pulse power parameter and / or a pulse energy parameter by shifting at least one of the 3-surface reflectors.

In some embodiments of the pulse length adjustment unit, at least one of the three-surface reflectors has three mutually fixed reflective surfaces, which form an optical reflector unit and are arranged relative to one another such that the laser beam experiences three successive reflections on the three reflective surfaces. These cause the directional deflection of the laser beam with a two-stage beam offset. Two-stage here refers to a first offset between the first two reflective surfaces and a second offset between the last two reflective surfaces. The two offsets are obviously in non-parallel directions. The beam offset is such that the laser beam incident on the at least one of the three-surface reflectors and the laser beam emerging from the at least one of the three-surface reflectors (in particular the associated beam axis sections of the central wavelength of the laser pulse) are considered to be reflected back within the scope of the design are. This is the case, for example, when the beam axis sections (with reflective surfaces oriented at 90 ° to one another) run parallel to one another. Furthermore, this is the case when the beam axis sections intersect in an intersection angle range of 0 ° to 30 °. Further, the Strahlachsenab sections can run each other skewed, the skewed arrangement is such that a displacement of one of the two laser beams in the direction of the distance of the laser beams to intersecting rays in an angle range of 0 ° to 30 ° leads.

In some embodiments of the pulse length adjusting unit, at least one of the 3-surface reflectors has reflector surfaces which extend in pairs substantially orthogonally to each other. In this case, at least one of the 3-surface reflectors may be formed as a prism modified on a side surface, which has a beam inlet and outlet surface. che, a reflective planar side surface and formed as a reflective roof edge prism area. Optionally, it may also have upper and lower sides extending substantially along the deflecting direction. Further, the modified prism may be formed as a rectangular prism and two reflective side surfaces of the roof edge prism are perpendicular to each other and formed perpendicular to the plane side surface.

In some embodiments of the pulse length adjusting unit, as many reflection surfaces as possible, that is to say, for example, the planar side surface and the side surfaces of the roof edge prism, are coated in such a reflective manner that, if possible, the spectral width of the laser beam is completely reflected. Furthermore, the jet inlet and outlet surface can be coated with anti-reflection, in order to reduce the losses during the passage. Furthermore, these surfaces, in particular the reflective surfaces, may be phase-influencing (e.g., acting similarly to a 1/4 plate or 1/2-plate) to affect the polarization.

In some embodiments of the pulse length adjustment unit, at least one of the 3-surface reflectors is designed as a mirror unit which has three spatially fixed (in other words, spatially fixed, in particular as a component or made of glued or welded surfaces) to each other Mirror surfaces form the three reflection surfaces. Optionally, two of the mirror surfaces form a roof edge mirror, in particular a 90 ° roof edge mirror.

In some embodiments, the pulse length adjusting unit further comprises a first delay plate for influencing the phase, in particular for influencing the polarization, preferably for polarization compensation, for example a 1/4 plate, 1/4 plate or a combination of a plurality of delay plates, that between the first dispersive element and the first 3-area reflector is arranged in the beam path of a laser beam incident on the first 3-area reflector.

In some embodiments of the pulse length adjustment unit, the reflection surfaces or the beam inlet and outlet surface are phase-influencing coated, example, such that the polarization after exiting the reflector is equal to the polarization of the beam entering the reflector. In some embodiments, the pulse length adjusting unit further comprises at least one reflecting element. The reflective element can cause a return of the optical path through the dispersive elements and the 3-surface reflectors. The reflective element is optionally a roof edge mirror or a deflection prism. In some embodiments, the reflection element can lead to a return reflection of the optical paths that is perpendicular to a deflection plane associated with a deflection direction of the disper-sive element. In general, feedback can optionally result in a return path to an inverse order of the reflections on the reflection surfaces with respect to the outward path. In general, multiple passes in multiple levels when using correspondingly large components are possible. For example, the reflection element can be formed as a roof edge prism and combined with another optical reflector, so that a wide rer offset can be generated vertically or horizontally.

In some embodiments, the pulse length adjusting unit further comprises a second delay plate for influencing the phase, in particular for influencing the polarization, preferably for polarization compensation, for example a 1/4 plate, 1/2 plate or a combination of multiple retardation plates, which is connected between the first 3 Surface reflector and the first dispersive element in the beam path of a laser beam emerging from the first 3-area reflector is arranged.

In some embodiments of the pulse length adjusting unit, the first dispersive element is configured to deflect the spectral components in a deflection direction around wavelength dependent angles such that the beam cross section of the laser beam is deformed in the deflection direction prior to the first reflection at the first 3-area reflector, and the third Surface reflectors are arranged with respect to the deflection direction of the first dispersive element such that the deformation of the beam cross section of the laser beam after reflection at the second 3-plane reflector is again in the deflection direction of the first dispersive element and the laser beam after the second Area reflector with respect to the La serstrahls before the first reflection on the first 3-area reflector in the deflection ver sets runs.

In some embodiments of the pulse length adjusting unit, the 3-surface reflectors are formed identically, but are in the order of the reflections on the reflection xionsflächen invertedly arranged in the beam path between the dispersive element. In some embodiments, the pulse length adjusting unit further comprises a translating device for adjusting the distance between the 3-plane reflectors, and thus for adjusting the path length of the optical path between the first and second dispersive elements. The translation device may optionally be designed to displace one of the 3-plane reflectors along a beam axis portion of the laser beam (given by the central wavelength of the laser pulse) between the 3-plane reflectors.

In some embodiments, the translation device is configured to move one of the 3-plane reflectors such that the entrance angle and / or entry position of the optical paths with respect to a first reflective one of the three reflective surfaces of the three-planar reflector and the exit angles are maintained become.

In some embodiments, the pulse length adjusting unit further comprises a control device for driving the translation device, wherein the control device is configured to determine a path length of the optical path between the first and the second dispersive element as a function of a pulse duration-dependent measuring signal, a pulse power parameter, a peak Set pulse power parameters and / or a Pulergieergiepara meters by moving at least one of the 3-plane reflectors.

In some embodiments, the pulse length adjusting unit further comprises two focusing elements forming an optical telescope arrangement, optionally lenses or mirrors. Depending Weil one of the focusing elements is disposed between the first dispersive element and the Ers th 3-surface reflector and between the second 3-plane reflector and the second dispersive element.

In some embodiments, the pulse length adjustment unit further comprises an optical element which is arranged in the angular dispersion region and transmits the electromagnetic beam to an incident angle-dependent parallel offset of the individual spectral components of the laser beam with respect to the propagation of the individual spectral components before and after the optical element. Furthermore, the pulse length adjusting unit may have an adjusting device for aligning the optical element, wherein the setting direction especially for changing the parallel offset of the individual Spektralkomponen th is controlled.

In some embodiments, the laser system further comprises a control device and a positioning unit on which one of the 3-plane reflectors is disposed and which communicates with the control device for controlling translational movements of the 3-surface reflector. a translation Vorrich device for displacement of the 3-surface reflector optionally along a beam axis of a falling laser beam. Furthermore, the laser system can optionally have a pulse duration measuring device for outputting a pulse duration-dependent measuring signal to the device for controlling the positioning unit.

In some embodiments of the pulse length adjusting unit, the first dispersive element may be configured to deflect the spectral components in a deflection direction about wavelength-dependent angles so that the beam cross-section of the laser beam, prior to the first reflection, is reflected at a e.g. first comer-cube reflector is deformed in the deflection direction.

In general, the reflection surfaces may be dimensioned and arranged in the deflection direction so that the laser beam is reflected as a whole by each of the reflection surfaces, and in particular that all the spectral components are reflected by the reflection surfaces in the same order.

In some embodiments of the pulse length adjusting unit, a deflecting direction of the dispersive elements may be associated with a deflecting plane having a normal direction. The pulse length adjusting unit may further include one or more angle adjusting devices that influence the offset. For example, a first Winkeleinstell Vorrich device, which is designed to align one of the 3-surface reflectors to the normal direction for a position of an offset component of the beam offset in the deflection plane, are seen before. Alternatively or additionally, a second angle adjustment device, which is designed to align the 3-surface reflector with respect to the deflection plane for setting an offset component of the beam offset in the normal direction, may be provided. The embodiments disclosed herein may include, but are not limited to:

The use of 3-plane reflectors, for example an angle reflector with three (spatially) fixed reflective surfaces (in the case of 90 ° angles between each two surfaces known as a comer-cube reflector; Area retroreflector) can simplify the construction of dispersion adjustment units, since degrees of freedom omitted, for example present at plan deflecting mirrors.

If the surfaces of the 3-area reflector are not perpendicular to each other, then a corresponding positioning of a subsequent 3-area reflector shall be carried out at a correspondingly adjusted angle. Thus, in particular, the adjustment of grid or prism stretchers or lattice or prism compressors is simplified. This is based inter alia on the fact that an angle invariance in the setting of an optical path is possible. The invariance against angular errors can reduce or even avoid astigmatism and / or out-of-roundness of the beam profile.

In other words, the arrangements described herein can compensate for mechanical tolerances since degrees of freedom in the folding are eliminated, which makes CPA systems more robust and cost effective. In the more stable systems, the laser beam travels less to e.g. the second grating, so that in particular the angle remains the same and thus less influence on the dispersion by thermal-mechanical Variegated ments of the components can occur.

If in the concepts disclosed herein, the 3-plane reflectors are rotated only by a relatively small angle, highly dynamic drives can be used ver for pulse width adjustment. For example, the rotation of a 3-area reflector can be actively readjusted or varied by means of a Mo gate or piezoelectric element.

Furthermore, in the case of a lattice compressor, the beam quality is very sensitive to the alignment of the lattice structures. Therefore, adjusting the pulse duration in such prior art systems requires a complex grid holder that would allow the grid to translate very accurately without affecting the orientation of the grid structure. The structures disclosed herein reduce the effect on errors or changes in alignment. The disclosed herein optical arrangements generally allow a length adjustment in the beam path of a laser system in which occur during the adjustment as few, preferably no given, angular variations in the beam path.

In general, the concepts proposed herein allow to reduce the space required for a dispersion adjusting unit.

Herein, concepts are disclosed that allow to at least partially improve aspects of the prior art. In particular, further features and their expediencies emerge from the following description of embodiments with reference to the figures. The figures show:

1 shows a schematic plan view of a laser system with a pulse length adaptation unit based on a pair of comer-cube reflectors for pulse duration compression (compressor),

FIG. 2 is a schematic perspective view of the pulse length adjusting unit of FIG

Fig. 1,

3 is a schematic perspective view of the beam path between two corner-cube reflectors of a generally usable Weglängenanpassungsein unit,

4 is a schematic illustration of a pair of comer-cube

Reflector based pulse length adjustment unit for pulse duration stretching (Strecker) and

Fig. 5 is a schematic perspective view of a pulse length adjusting unit with

Polarization adjustment by way of example for a 3-surface reflector with non-orthogonal reflective surfaces.

As explained above, in CPA systems, the degree of compression of the laser pulses can be realized over the distance between two diffraction gratings (or prisms). It is known to use path length varying components such as folding mirrors or rectangular prisms to modify the propagation length between the two gratings.

The aspects described herein are based, in part, on the recognition that alignment changes of the path length varying components angle errors on the second grid can cause. It has been found that these, when passing through a CPA system, cause astigmatism that can adversely affect beam quality.

The inventors have now recognized that a path length change can be implemented with a pair of 3-area (retro) reflectors. An example of a 3-area retroreflector is a rectangular prism, to each of which one of the two Ankatheten a 90 ° - roof edge prism is provided.

In contrast to roof prisms, which reflect a laser beam with a beam offset and a mirroring with respect to an axis, a (perfect) space inversion, which corresponds to a 180 ° rotation for a transverse beam profile, can be compared with a comercube reflector as an example. Area retroreflectors are achieved. A comer-cube reflector reflects a laser beam to three mutually orthogonal surfaces arranged (corresponding to the three sides of a cube corner), with an incidence of the laser beam on one of the three reflection surfaces with distance to the intersection and the Schnittli lines of the three surfaces a parallel Beam offset and a space inversion of the laser beam takes place. Thus, as seen in the propagation direction in a spectrally split beam (eg., After diffraction at the grating), the spectral distribution remains the same, for example, on the left side seen in the propagation direction of the long-wave spectral range and in Propaga tion direction on the right side of the shorter wavelength spectral range.

An exemplary embodiment of a comer-cube reflector is a modified right eckprisma, which provides one of the three reflection surfaces on one of the Ankathetenseiten and provides with a provided on the other Ankathetenseite 90 ° roof edge structure, the two remaining three of the three mutually orthogonal reflection surfaces.

The properties of the comer-cube reflectors, and generally of 3-area retroreflectors, make the beam path length change invariant to angle errors. Thus, because of the (retro) reflector property, angular adjustment degrees of freedom can be omitted. Since the sensitivity of the angle and the adjustment resolution can be particularly sensitive in the case of very large degrees of compression, the optical arrangements disclosed herein can significantly reduce the influence of angular errors and, under certain circumstances, even completely eliminate them. As will be explained below in connection with the figures, it is proposed herein, in an exemplary embodiment of a pulse length adjustment unit, to provide two 3-area retroreflectors between two dispersive elements, such as optical grids, prisms or grisms of a compressor or extender. An angular tilting in all three axes of the incident beam or the 3D retroreflector itself is compensated by the radio tion of the 3-area retroreflector, so that the output beam undergoes substantially no changes in angle despite, for example, tilting the 3-area retroreflector. That is, the output beam always runs substantially parallel to the input beam.

However, by the operation of the 3-area retroreflector after each 3-area retroreflector, the beam profile is rotated by substantially 180 ° and the beam learns Weil each a lateral offset. By using two 3-area retroreflectors, the image is rotated twice by substantially 180 ° so that there is effectively no change in the beam at the output of the second 3-area retroreflector.

In one embodiment, the pulse length adjustment unit can be made by adjusting the distance between the 3-plane reflectors, the path length, and thus the spectral expansion to the fiber pulse, a dispersion adjustment.

In a further embodiment of the pulse length adaptation unit, furthermore, the variability of the lateral offset can be used specifically for varying the pulse length. Thus, the Fateralversatz be influenced by a targeted Winkelverkippung the 3-plane reflector be, whereby the propagation length is changed between the dispersive elements.

With regard to the angle tilting of the 3-area reflector, the pulse length adaptation has two different sensitivities:

Tilting can be done around the opening side of the 3-plane reflector, for example, the long front side of a modified rectangular prism. In the case of a quasi-symmetrical structure, for example, the hypotenuse of the underlying triangular shape of the rectangular prism is tilted. This is preferably aligned substantially parallel to the deflection / spectral fanning of the fiber beam. This type of tilting can be used to adjust the vertical distance between the two laterally offset and horizontally superimposed input and output beams. However, such a tilt can not only be used for adjusting the vertical separation distance of a reflected laser beam, but it can also be used to search the pulse length minimum. This tilting has only a small influence on the path length between the two 3-area reflectors. Thus, a fine adjustment of the pulse length can be made by such a tilt.

In contrast to the preceding tilting, a rotation about an axis perpendicular to the spectral fanning plane extending axis of rotation (also referred to herein as yaw axis of the 3-surface reflector) has a greater impact on the path length and thus on the pulse duration. If a 3-area reflector varies in accordance with the yaw angle, it may be possible to dispense with further dispersion adjustment options, such as those using a plane-parallel plate.

Such angular adjustments of the tilt and / or rotation can be made, for example, via a motorized eccentric drive, galvo drive and / or piezoelectric actuator with a high angular resolution for precise pulse length adaptation.

Advantageously, the absolute angle settings required for such a fine adjustment can be significantly lower than, for example, upon rotation of a plane-parallel plate, as described in the aforementioned application DE 10 2016 110 947 of the applicant.

The angular stability with respect to grid compressors allows pulse lengths of e.g. 300 fs over a long period of time without being prolonged by changes in the adjustment to ps pulses. The latter can easily be achieved in the prior art compressors, e.g. be caused by setting movements of optical elements (for example, planar deflection mirror), which are produced by thermal-mechanical maladjustment of, for example, adjusting screws.

Hereinafter, a pulse length adjustment in egg nem Ultrakurzpulssystem 1 for pulse duration compression is described in conjunction with Figures 1 and 2. The ultrashort pulse system 1 is exemplary of pulsed laser systems, which usually carry out a dispersion adaptation. The ultrashort pulse system 1 is shown schematically in FIG. It comprises a laser pulse source 3 for generating a laser beam 5 from spectrally wide laser pulses and a pulse length adaptation unit 7 for pulse duration compression of the laser pulses. A long (not compressed for the Lall of use as Pulskompressor) laser pulse 5 A is schematically indicated for the input beam. As explained below, the pulse length adjusting unit 7 comprises two specially arranged charging elements: a first comer-cube reflector 9A and a second comer-cube reflector 9B, which together form a path length adjusting unit. With reference to FIG. 4, for example, a similarly constructed pulse length adjusting unit for pulse stretching in the laser pulse source 3 may be integrated.

The laser pulse source 3 may be formed, for example, as a laser oscillator or laser oscillator amplifier combination. In ultrashort pulse system 1, laser pulses with spectral widths of e.g. 1 nm and larger and pulse energies of e.g. 0.1 pJ and larger generated. These are supplied to the pulse length adjusting unit 7. The spectral width of the laser pulses be dingt the need for a dispersion adjustment of the beam path to provide at a destination a specific pulse shape (intensity curve) of the laser pulses with a desired, for example, the shortest possible or adapted to a machining process, pulse duration. The concepts described herein can be used in particular in ultra-short pulse systems which have pulse durations of e.g. some 100 fs for material processing. The fields of application of such laser systems include glass cutting (e.g., cutting displays and medical devices), labeling, medical applications, e.g. Eye operations, drilling of, for example, injectors and conducting scientific experiments.

The pulse length adjusting unit 7 is constructed by way of example as a folded grid compressor. The lattice compressor comprises a pair of dispersive elements in the form of a first lattice l lA and a second lattice 11B, the two interaction regions of the lattices 11A,

11B with the laser beam. The spectrally dependent diffraction conditions produce an angular dispersion after the first grating 11A. That is to say, in an angular dispersion region 13 between the dispersive elements (lattice 11A and 11B), the optical paths for the individual spectral components in a deflection plane (here in the plane of the drawing) extend at least partially at an angle to one another. In Fig. 1, the grids 11A, 11B are parallel aligned transmission grating. Alternatively, for example reflection grids, prisms or grisms can be used.

For a folding of the beam path of the lattice compressor further comprises a reflector element 15, which is formed for example as (deflecting) roof edge prism or as a roof mirror. Thus, an optical way L6A and an optical return path 16B are provided by the grid compressor, which are offset from each other in sections in height. After the double pass through the grating arrangement, the height offset enables a separation of the compressed laser pulses from the coupled-in laser pulses on a scraper mirror 17 to output an output beam 19. By way of example, in the case of use as a pulse compressor, a short (compressed) laser pulse 19A is schematic for the output beam 19 shown in Fig. 1. The reflector element 15, together with the special arrangement of the comer-cube reflectors 9A, 9B, permits substantially the same optical conditions for the outgoing path 16A and the return path 16B of the laser beam to be present through the grid array.

In the plan view of FIG. 1, only the way 16A is exemplified by two optical paths 13A, 13B in the angular dispersion range 13 for spectral components with a longer (dashed line: l lo) and a shorter (solid line: l <lo) wavelength - Delayed a central wavelength lo of the laser pulse drawn. It should be noted that the optical path of the central wavelength lo usually defines the beam axis of the laser beam.

In Fig. 1 by way of example beam axis sections 20 A, 20 B, 20 C indicated by arrows, where in the beam axis and thus the beam axis sections are given by the beam path of a ZENTRA len wavelength. Since the reflecting surfaces of the comer-cube reflectors 9A, 9B are orthogonal to each other, the beam axis portions 20A, 20B of the comer-cube reflectors 9A, 9B are parallel to the respective beam axis portions 20B, 20C of the comer cube reflectors 9A, 9B from passing beams. In other words, the beam axis section 20A and the beam axis section 20B and the beam axis section 20B and the beam axis section 20C are not at an angle to each other when ideally formed. Ideally designed comercube reflectors generally apply to all spectral components. In contrast, the optical paths of the different wavelengths fanned out, ie, at an angle to each other. It can be seen that the second grid 11B effects alignment / parallelization of the optical paths 13A, 13B before they strike the reflector element 15.

In the perspective view of the pulse length adjusting unit 7 shown in Fig. 2, various portions of the outgoing path 16A and the return path 16B of the laser beam can be seen. Due to the spectral fanning in the deflection direction of the grating 7A, the laser beam has an elliptically indicated beam profile. The various sections are vertically offset (i.e. perpendicular to the fanning plane). The laser beam 5 emitted by the laser pulse source 3 (not shown in FIG. 2) lies below the output beam 19. The comer-cube reflectors 9A, 9B each cause an offset in the height, so that between the comer-cube reflectors 9A, 9B, the optical path 16A extends above the optical return path 16B.

In the exemplary embodiment shown in FIGS. 1 and 2, the pulse length adjusting unit 7 includes the first comer-cube reflector 9A and the second comer-cube reflector 9B. As discussed below, the comer-cube reflectors allow multiple approaches to adjusting dispersion in the lattice compressor.

In the embodiment shown by way of example, each of the comer-cube reflectors 9A, 9B is designed as a rectangular prism, the rectangular prisms being modified in such a way that on one side of the rectangle it is not a plane surface but a 90 ° -rotated (90 °) Roof edge prism is provided. Thus, for this example of a 3-surface Refelktors three spatially fixed to each other arranged reflective surfaces.

In general, the modified rectangular prisms each comprise a beam entry and exit surface 21 (front surface). In this case, the beam inlet and outlet surface 21 runs along the hypotenuse of the triangular basic shape of the rectangular prism. A 90 ° angle of the basic shape of a right triangle is indicated in Fig. 1 for comer-cube reflector 9B. The jet inlet and outlet surface 21 is substantially formed as a rectangle, the long side of which extends along the deflection plane. Furthermore, the modified right corner prisms extend substantially in the deflection extending upper and lower sides 23, which are not irradiated and also do not serve as reflection surfaces. The structure of the modified rectangular prisms and the resulting beam guidance are described below by way of example on the first comer-cube reflector 9 A.

As shown in Fig. 2, the fanned-out laser beam on the downside occurs on a (left) half of the beam entrance and exit surface 21 of the first comer-cube reflector 9A and it rotates 180 ° on top of the other (right) half of Beam inlet and Strahlaus exit surface 21 from. For this directional reversal of the laser beam, the rectangular prism comprises three reflective surfaces Rl, R2, R3 (coated, for example, with broadband reflection).

The reflection surfaces R 1 and R 2 (also referred to herein as lower and upper (roof edge) reflection surfaces) are formed by the roof edge prism region, wherein the reflection surfaces of the roof edge prism region are formed perpendicular to one another (see also FIG. 2 for the comer cube). Reflector 9B indicated 90 ° angle). In the illustrated alignment of the comer-cube reflector 9A, the reflection surfaces are substantially each at a 45 ° angle to the deflection plane. The spectrally fanned-in incident La serstrahl is deflected from the lower reflection surface Rl on the upper reflection surface R2. In FIGS. 1 and 2, the elliptical impingement region 22A on the reflection surface R2 is indicated. From there, the laser beam is deflected to the upper half of the plane surface R3 acting as surface reflection surface of the modified rectangular prism. From the reflection surface R3, the laser beam is contrary to the original propagation direction, spatially offset and rotated in the beam cross section by 180 ° through the upper (right) Be rich the beam inlet and exit surface 21 coupled out of the rectangular prism.

Correspondingly, the first comer-cube reflector 9A effects first parallel offsets V 1 for all optical paths from the entry angle and the entry position, all parallel offsets of the spectral components resulting in a 180 ° rotation of the laser beam about the beam axis of the laser beam.

For adjusting the entrance angle, the entry position and the distance from the first grid llA, the first comer-cube reflector 9A is arranged on a positioning unit 25 having translation and / or rotation axes. In order to control the positioning unit 25, the laser system 1 may further comprise a control device 27 and a pulse duration measuring device 29 which, via control lines 31, communicate with one another and with the ultrashort pulse signal. System 1 are connected. The control device 27 is designed, for example, to set path lengths of the optical path between the first and the second dispersive element as a function of a pulse duration-dependent measuring signal, a pulse power parameter, a peak pulse power parameter and / or a pulse energy parameter.

For example, the pulse duration measuring device 29 is configured to output a pulse duration dependent measurement signal (e.g., an autocorrelation signal). As is indicated schematically in FIG. 1, the pulse duration measuring device 29 is supplied with a portion of the output beam 19 tapped at a wafer 30 (non-transmitted). The pulse duration measuring device 29 derives therefrom the pulse duration-dependent measuring signal and outputs it to the control device 27. The control device 27 in turn outputs a control signal generated therefrom to the positioning unit 25 for shifting or aligning, such as twisting or tilting, the comer-cube reflector supported by the positioning unit 25. For example, the controller 27 uses an optimization algorithm to vary the angular position and / or distance from the dispersive elements for pulse duration shortening for one or both comer-cube reflectors 9A, 9B and for a shortest pulse duration or one for a particular application During the processing of the material, the pulse duration (or pulse shape) required for it is set accordingly.

A larger change of the optical paths between the gratings 11A, 11B may e.g. by a translation of the first comer-cube reflector 9A. For this purpose, the positioning unit 25 may comprise a translation device for adjusting the distance between the comer-cube reflectors 9A, 9B. The translating device can optionally, as indicated schematically in FIG. 1 by double arrows 33A, 33B, be designed to displace one of the corner-cube reflectors 9A, 9B along a beam axis of the laser beam between the comer cube reflectors 9A, 9B.

In particular, the translation device can be designed to move one of the comer-cube reflectors 9A, 9B in such a way that the entry angle and / or the entry position of the optical paths 13A, 13B with respect to a first reflecting of the three reflection surfaces Rl, R2, R3 of the moving comer-cube reflector 9A, 9B - in Fig. 1, the reflection surface Rl of the moving comer-cube reflector 9A - - will be maintained /. The translation device may be, for example, a motorized and / or displaceable via a piezoelectric actuator zel of the comer-cube reflector 9A, whereby a, in particular stepless, position adjustment is implemented along a translation axis. The translation device and the control device thus permit adjustment, in particular regulation, of the pulse duration by means of an actively controlled, in particular controlled, distance adjustment.

The inventors have also recognized that rotation of, for example, the first comerube reflector 9A also changes the optical paths 13A, 13B between the reflection surfaces R1, R2, R3 and thus also the path length differences between the spectral components. Accordingly, such a rotation also influences the dispersion characteristics of the pulse length adjusting unit 7 and the pulse duration of the laser pulses in the output beam 19 can be e.g. by the rotation of the first comer-cube reflector 9A.

This results in two possible rotational movements, which have different effects on the Strah lengang effect in comer-cube reflector.

In Fig. 1, the deflection direction through the grids 7A, 7B a deflection plane (here the character plane of Fig. 1) associated with a normal direction n.

The positioning unit 25 may include a first angle adjusting device configured to align the comer-cube reflector 9A with the normal direction n. By rotating the comer-cube reflector 9A in the normal direction n, the offset components of the beam offsets V 1 in the deflection plane are adjusted. Such winch leinstellvorrichtungen are indicated schematically in Figures 1 and 2 by axes of rotation 35A, 35B for the comer-cube reflectors 9A, 9B.

Alternatively or additionally, the positioning unit 25 may comprise a second angle adjusting device. This is designed to align the comer-cube reflector with respect to the deflection bene. The wide angle adjusting device thus allows the Ver set components of the beam offset V 1 in the normal direction n. Such Winkeleinstell- devices are indicated in Fig. 2 schematically by axes of rotation 37A, 37B for the comer-cube reflectors 9A, 9B. The angle adjusting devices may be, for example, motorized and / or piezoelectric elements rotatable holders of the comer-cube reflector 9A, 9B, which allow a, in particular stepless, adjustment of the angle of rotation. The angle adjusting devices and the control device thus permit adjustment, in particular regulation, of the pulse duration by an actively controlled, in particular controlled, alignment of the respective comer cube reflector 9A, 9B.

If at least one of the comer-cube reflectors 9A, 9B is rotatably mounted about the normal direction n and / or with respect to the deflection plane for adjusting the offset components, the entrance angle and the entry position of the optical paths 13A, 13B can be the first one of the three Reflection surfaces and the exit angle and the exit position of the optical paths 13A, 13B are adjusted with respect to a last reflective of the three reflection surfaces.

In each of the comer-cube reflectors 9A, 9B - regardless of Eintritswinkel, a tread position and distance from the first grid 11 A - the back-reflected laser beam parallel to the incident beam. Accordingly, the degrees of freedom in the beam guidance of the pulse length adjusting units disclosed herein are reduced and the optical beam path is less sensitive to changes (such as thermal changes) in the retention of the comer-cube reflectors serving as folding mirrors.

It should be noted that, due to the angle of incidence on the reflecting surfaces of the comer-cube reflector 9A, the polarization of the back-reflected beam can be influenced. The construction shown in Fig. 5 can provide such changes in polarization by providing e.g. ¼ plates, ½ plates (alternatively or additionally by viewing a correspondingly reflective coating).

As shown in Fig. 1, the laser beam passes through the reflection surfaces Rl, R2, R3 of the second comer-cube reflector 9B in an inverted order. That is, the (now much further) on fanned laser beam enters the way up on a (right) half of the beam inlet and outlet surface 21 of the second comer-cube reflector 9B. Since the second comerube reflector 9B is rotated by 180 ° with respect to the first comer-cube reflector 9A in the deflection plane, this entry position corresponds to the exit position from the first comerube reflector 9A. For the (second) direction reversal of the laser beam, the rectangular prism of the second comer-cube reflector 9B also comprises three reflection-coated reflective surfaces Rl, R2, R3. The reflection surfaces R 1 and R 2 are also formed here by a roof edge prism region, wherein the reflection surfaces of the roof edge prism region are oriented perpendicular to one another and each again substantially at a 45 ° angle to the deflection plane.

With reference to FIG. 2, the laser beam coming from the first comer-cube reflector 9A will thus first of the upper half of the plan, acting as a reflection surface R3 side surface of the modified rectangular prism in the deflection plane on the upper surface Reflexionsflä R2 and from there on the lower reflection surface Rl deflected. In Fig. 2 can be seen accordingly larger elliptical Auftreffbereiche 22 B on the reflection surfaces R 3 and R 2, wherein on the reflection surface R 3 Auftreffbereiche 22 B of outward and return are hinted Tet.

At the reflection surface Rl, the laser beam is emitted counter to the direction of propagation between the comer-cube reflectors 9A, 9B and thus parallel to the laser beam, as it was deflected by the first grating 7A, through the lower portion of the beam inlet and outlet surface 21. In this case, the beam components in turn learn from the entry angle and from the entry position dependent spatial parallel displacements V2, by which the laser beam is rotated by 180 ° about the beam axis.

The laser beam fanned further due to the subsequent propagation thus impinges on the second grating 7B in an orientation and angular distribution, as if the laser beam were coming directly from the first grating 7A. At the grating 7B, the laser beam is in turn diffracted to strike the reflector element 15 with parallel rays.

In alternative arrangements of the two 3-area reflectors, these can be nested, in particular stairs, in height.

In addition, the previously described pulse length adjustment unit can be equipped with further measures for fine tuning of the dispersion. Referring to the aforementioned German patent application DE 10 2016 110 947 Al the applicant show Figures 1 and 2 in dashed lines a plane-parallel glass plate 39, which is arranged in the angular dispersion 13 area. The glass plate 39 can be rotated about an axis of rotation 41, which runs parallel to the Norma len, to adjust the angle of incidence of the laser beam on the glass plate 39 for pulse width adjustment. The possible variation of the pulse duration depends, inter alia, on the thickness and the material of the glass plate (for a given adjustment range of the angle of rotation).

Fig. 3 generally shows a path length adjusting unit 43 comprising two comer-cube reflectors and e.g. can be used in pulse length adjustment units such as compressor units or track purity. The path length adjusting unit 43 can provide 45 A variably adjustable path lengths for einfal loin laser beam, wherein the exiting laser beam 45 B parallel to the incident in the Y direction laser beam 45 A and is offset in the X direction, but otherwise the beam profile of the incident laser beam 45 A has (except, for example, a propagation-induced widening or rejünung the beam).

The course of the laser beam in the path length adjusting unit 43 is illustrated by a central optical path 47 corresponding to the beam axis and optical paths 47A, 47B.

In the exemplary embodiment of Fig. 3, the comer-cube reflectors gel units as Spie 49 A, 49 B are formed, of which only the reflection surfaces (hereinafter referred to as mirror surfaces) are schematically outlined. Each of the mirror units 49A, 49B comprises three mirror surfaces 49-1, 49-2, 49-3, each of the mirror surfaces being arranged perpendicular to the other two mirror surfaces. The mirror surfaces 49-2, 49-3 form a roof edge formation and are optionally formed by a roof edge mirror.

In contrast to the arrangement of the reflective surfaces in Figures 1 and 2, the mirror surfaces 49-1, 49-2, 49-3 are arranged such that the incident laser beam 45 A first on the aligned perpendicular to the XY plane mirror surface 49-1 (Fig. corresponding to R3 in FIG. 1), from there to the lower mirror surface 49-2 (corresponding to R2 in FIG. 1) the Dachkantenforma tion is reflected and then from this to the upper mirror surface 49-3 (corresponding to Rl in Fig. 1) the roof edge formation is deflected. Accordingly, the laser beam extends with a height offset in the Z direction with respect to the incident laser beam to the second mirror. gel unit 47B. This corresponds to the first mirror unit 47A, but is rotated by 180 ° about the Z axis. The mirror surfaces 49-1, 49-2, 49-3 of the second mirror unit 47B are passed in the reverse order, so that only one beam offset in the X direction results at the end.

With reference to the preceding discussion of FIGS. 1 and 2, it can be seen that each of the individual optical paths 47, 47A, 47B experiences its own parallel offset as a result of the successive reflections on the three mirror surfaces in each mirror unit 49A, 49B. The parallel offsets are such that the entire beam profile undergoes a 180 ° turn in addition to a directional deflection and an offset in the X and Y directions. Since the second mirror unit 49B causes a corresponding offset in (-Y) direction, but otherwise causes a further rotation through 180 ° (or -180 °), the Weglängenanpassungs- unit 43 is a compact unit, with the path lengths to be traversed By moving or as previously discussed aligning the mirror unit 49A, 49B coarse and finely adjusted who can.

FIG. 4 shows an exemplary implementation of the dispersion adaptation concepts disclosed herein in a grid length-configured pulse length adjusting unit 7 'having a path length adjusting unit 51 comprising two comer-cube reflectors 9A, 9B. In contrast to the compressor shown in FIGS. 1 and 2, two prisms 53A, 53B are used as dispersive elements in FIG. 4 by way of example. Alternatively, e.g. Reflection gratings or grisms are used. In the beam path between the two prisms 53A, 53B, the two comer-cube reflectors 9A, 9B are arranged for path length adaptation.

In order to achieve inverted angular dispersion contributions, a lens system (eg a telescope arrangement) is provided in the exemplary prism stringer in the beam path between the two prisms 53A, 53B. By way of example, FIG. 4 shows a telescope arrangement 55 with two ones 55A, 55B. The telescope arrangement 55 effects a mapping of the first prism 53A so that the fanned-out spectral components after the lens system converge at the second prism 53B. As in Fig. 1, the pulse length adjusting unit 7 'is folded with a reflector element 15 to provide a way out and a return path through the prisms 53A, 53B in a structure.

In contrast to the compressor arrangement of FIG. 1, the two comer-cube reflectors 9A, 9B are arranged in a spectrally fanned-out but collimated region of the angular dispersion region 13. That is, similar to the illustration in FIG. 3, the optical paths of the various spectral components are substantially parallel through the path length adjusting unit 51.

The explanations on the beam path explained above in connection with FIGS. 1 to 3 can be transmitted to the course of the laser beam by the path length adaptation unit 51. In particular, the setting options (translation, alignment, in particular rotation about one or two axes) described above with regard to the compressor assembly can be generally transferred to straighteners and in particular to the stretching arrangement of FIG. 4.

Furthermore, a plane-parallel plate 39 can also be provided in the straightener as a further optical element before or after the telescope arrangement 55 in the angular dispersion region in order to provide a further adaptation possibility of the dispersion.

5 shows a schematic perspective view of a pulse length adjusting unit 61, which is based, for example, on two 3-area reflectors 63A, 63B with non-orthogonal reflecting surfaces. Optical elements and the sections of the beam path, as in connexion with z. B. Figures 1 and 2 have been explained, are provided with the same reference characters.

Accordingly, a laser beam 5, which has been spectrally expanded by a first grating 11A, propagates along a forward path 16A through the pulse length adjusting unit 61. Since in Fig. 5 the path between the first grid l lA and the 3-surface reflector 63 A below a return path 16B, between the first 3-surface reflector 63 A and the second 3-surface reflector 63 A above the Return path 16B and between a second grid, which is not shown together with a back reflector in Fig. 5 (see, eg. Fig. 1) again below the return path 16B. For clarity, the beam of the way away 16A was pulled through and the beam of the return path 16B shown in phantom.

Since the reflective surfaces of the 3-surface reflectors 63A, 63B are aligned non-orthogonal to each other, beam axis portions 65A, 65B of the 3-surface reflectors 63A, 63B entering rays (the beam axis and thus the Strahlach senabschnitte again through the beam path of a central wavelength) are not parallel to the respective beam axis sections 65B, 65C of the beams emerging from the 3-surface reflectors 63A, 63B. In other words, the beam axis section 65 A and the beam axis section 65 B or the beam axis section 65 B and the beam axis section 65 C at an angle to each other (for example, the angle is spanned primarily parallel to the splitting plane) or the respective Strahlachsenabschnit te are skewed.

It can also be seen a rotatably supported glass plate 39, the unit 61 in the Pulslängenanpassungsein between the first l lA and the first 3-area reflector 63 A can optionally be provided for additional pulse length adjustment.

5, a first retardation chip 67A for polarization compensation (for example, a 1/4 plate, a 1/2 plate, generally a combination of multiple delay plates can be provided) between the first grid 1 IA and the first 3 Surface reflector 63 A arranged. When using 3-surface reflectors, the reflections on the surfaces of the 3-surface reflectors to which the laser beam 5 with different incident angles / incidence orientations affect the polarization. This applies to both 3-surface reflectors with orthogonal and non-orthogonal reflective surfaces. The use of the I / 4 plate 67A now counteracts such a polarization error of the 3-surface reflectors 63A, 63B. In particular, a phase offset between the S and P polarization components is compensated.

In the folded structure of Fig. 5, a second retardation plate 67B for Pha senbeeinflussung and preferably for polarization compensation (usually a corre sponding l / 4 plate, ½ platelets or a corresponding combination of multiple delay ing plate provided at the end of the return path 16B be, for example, between the first 3-area reflector 63 A and the first grid 11A. Accordingly, the incident laser beam 5 and the outgoing laser beam 19 has a substantially similar polarization.

Alternatively or in addition to the use of retardation plates, one or more of the reflection surfaces may be provided with a corresponding coating 69 for influencing the polarization of the incoming and outgoing beam. The coating 69 is e.g. designed such that the polarization is rotated in the polarization required for the grid. For this, e.g. metallic coatings (such as gold or silver coatings) can be used to produce a desired phase jump (e.g., 1/4).

By changing the distance between the 3-plane reflectors 63A, 63B, the optical path length between the dispersive elements, and thus the angular dispersion occurring, can be set.

Further configurations of pulse-length adjusting units, as have been shown by way of example in FIGS. 1, 2, 4 and 5, comprise unfolded arrangements with two pairs of dispersive elements irradiated sequentially, so that the way-out and the return path do not occur as in FIG 4 are implemented in a structure but in separate pulse length adjusting units. Furthermore, straightener and compressor arrangements can be matched with respect to the dispersive elements.

The exemplary embodiments have been described with reference to laser light, in particular in the extended spectral range of ultrashort pulse lasers (usually in the wavelength range of 200 nm to 10 pm, depending on the application). However, application of the concepts disclosed herein is generally applicable to spectral width electromagnetic radiation.

The embodiments of pulse length adjusting unit described herein can be used as described in single or multiple passes and / or find application in oscillator systems with free-jet compressors and / or stretchers.

It is explicitly emphasized that all features disclosed in the description and / or the claims are considered separate and independent of each other for the purpose of the original disclosure. tion as well as for the purpose of limiting the claimed invention, regardless of the combinations of features in the embodiments and / or the claims to be considered. It is explicitly stated that all range indications or indications of groups of units disclose every possible intermediate value or subgroup of units for the purpose of the original disclosure as well as for the purpose of restricting the claimed invention, in particular also as the limit of a range indication.

Claims

claims

A pulse width adjusting unit (7, 7 ') for a pulsed laser beam (5) having a spectral width, with

a first and a second dispersive element (11A, 53A, 11B, 53B) for generating angular dispersion in one of the dispersive elements (11A, 53A, 11B,

53B) limited angle dispersion range (13), wherein in the angular dispersion region (13) of individual spectral components of the laser beam (5) optical paths (13A, 13B) are associated, which extend at least in sections at an angle to each other, and

a first and a second 3-surface reflector (9A, 9B), wherein each of the 3-surface reflectors (9A, 9B) in the beam path between the first and the second disper-sive element (11A, 53A, 11B, 53B) arranged and three reflecting surfaces (Rl, R2, R3) and the laser beam (5) of each of the 3-surface reflectors (9A, 9B) by three successive reflections of the laser beam (5) at the respective three reflection surfaces (Rl, R2, R3) is reflected, wherein at each of the 3-surface reflectors (9A, 9B), a directional deflection in the range of 150 ° to 210 ° and a beam offset occur.

Second pulse length adjusting unit (7, 7 ') according to claim 1, wherein at least one of the 3-surface reflectors (9A, 9B) has three mutually fixed reflective surfaces, which form an optical reflector unit and are arranged to each other that the laser beam (5) undergoes three successive reflections on the three reflective surfaces causing the directional deflection of the laser beam (5) with a two-stage beam offset, the beam offset being such as to be incident on the at least one of the 3-plane reflectors (9A, 9B). incident laser beam and the at least one of the 3-surface reflectors (9A, 9B) emerging laser beam parallel to each other, intersect in a cutting angle range of 0 ° to 30 ° or skewed to each other, the skewed arrangement is such that a Displacement of one of the two laser beams in the direction of the distance of the laser beams to intersecting beams an angle range of 0 ° to 30 ° leads.

3. pulse length adjustment unit (7, 7 ') according to any one of the preceding claims, wherein at least one of the 3-surface reflectors (9A, 9B) in pairs substantially orthogonal mutually extending reflective surfaces.

4. pulse length adjusting unit (7, 7 ') according to claim 3, wherein at least one of the 3-surface reflectors (9A, 9B) is formed as a prism modified on a side surface having a beam inlet and outlet surface (21), a reflective plane Side surface (R3), designed as a reflective roof edge prism region and optionally substantially along the deflection extending upper and lower sides (23), and

wherein optionally the modified prism is formed as a rectangular prism and two reflective side surfaces (Rl, R2) of the roof edge prism perpendicular to each other and perpendicular to the plane right side surface are formed.

5. pulse length adjusting unit (7, 7 ') according to claim 4, wherein the planar side surface (R3) and the side surfaces (Rl, R2) of the roof edge prism reflecting the spectral width of the laser beam and / or the phase are coated and / or

the jet inlet and outlet surface (21) is antireflectively coated.

6. pulse length adjustment unit (7, 7 ') according to any one of claims 1 and 2, wherein at least one of the 3-surface reflectors as a mirror unit (49A, 49B) is formed, which has three spatially fixed mutually arranged mirror whose mirror surfaces ( 49-1, 49-2, 49-3) forming the three reflecting surfaces (Rl, R2, R3), and optionally two of the Spiegelflä surfaces (49-2, 49-3) a roof edge mirror, in particular a 90 ° - roof edge mirror, form.

7. pulse length adjusting unit (7, 7 ') according to any one of the preceding claims, further comprising

a first phase-affecting retardation plate, which is arranged between the first dispersive element (53A) and the first 3-surface reflector (9A) in the beam path of a laser beam incident on the first 3-surface reflector (9A).

8. pulse length adaptation unit (7, 7 ') according to any one of the preceding claims, wherein at least one of the reflection surfaces has a coating (69) which is formed such that the polarization is influenced, and that optionally the polarization of the from the 3- surface Reflector (9A) emergent beam is equal to the polarization of the incident in the 3-surface reflector (9A) beam.

9. pulse length adjusting unit (7, 7 ') according to any one of the preceding claims, further comprising

at least one reflection element (15) which effects a return of the optical path (13A, 13B) through the dispersive elements (11A, 53A, 11B, 53B) and the 3-surface reflectors (9A, 9B), the reflection element (15 ) optionally as a roof edge mirror or deflecting prism is formed, and wherein optionally also an inverted sequence of the reflections on the reflecting surfaces (Rl, R2, R3) in a return path (16B) in comparison to the order of the way out (16A) is present.

10. pulse length adjusting unit (7, 7 ') according to claim 9, further comprising

a second phase-affecting retardation plate, which is arranged between the first 3-surface reflector (9A) and the first dispersive element (53A) in the beam path of a fiber beam exiting from the first 3-surface reflector (9A).

11. pulse length adjusting unit (7, 7 ') according to any one of the preceding claims, wherein the first dispersive element (11 A, 53 A) is adapted to deflect the spectral components in a deflection by wavelength-dependent angles, so that the beam cross section of the fiber beam (5) before the first reflection on the first 3-surface reflector (9A) is deformed in the deflection direction, and

the 3-plane reflectors (9A, 9B) are arranged with respect to the deflection direction of the first dispersive element (11A, 53A) such that the deformation of the beam cross-section of the fiber beam (5) after reflection at the second 3-plane reflector (9B) is present again in the deflection direction of the first dispersive element (11A, 53A) and the fiber beam (5) after the second 3-plane reflector (9B) with respect to the fiber beam (5) before the first re flexion on the first 3-surface reflector ( 9A) is offset in the deflection direction.

12. pulse length adjustment unit (7, 7 ') according to any one of the preceding claims, wherein the 3-surface reflectors (9A, 9B) are identical, but in the order of the reflections on the reflection surfaces (Rl, R2, R3) inverted in the beam path are arranged between the dispersive element (11A, 53A, 11B, 53B).

13. pulse length adjusting unit (7, 7 ') according to any one of the preceding claims, further comprising a translation device for adjusting the distance between the 3-surface reflectors (9A, 9B), and thus for adjusting the path length of the optical path between the first and the second dispersive element (11 A, 53 A, 11 B, 53 B), wherein the Translati Optionally onsvorrichtung for shifting one of the 3-surface reflectors (9A, 9B) along a beam axis of the laser beam (5) between the 3-surface reflectors (9A, 9B) is ausgebil det.

14. Pulse length adjusting unit (7, 7 ') according to claim 13, wherein the translation Vorrich device is adapted to one of the 3-surface reflectors (9A, 9B) to move such that the entrance angle and / or the entry position of the optical paths (13A , 13B) with respect to a first reflecting one of the three reflection surfaces (R1, R2, R3) of the moving 3-surface reflector (9A, 9B) and the exit angles.

15. Pulse length adjusting unit (7, 7 ') according to any one of claims 13 or 14, further comprising a control device (27) for driving the translation device, wherein the control device (27) is adapted to a path length of opti's path between the first and the second dispersive element (11A, 53A, 11B, 53B) as a function of a pulse duration-dependent measurement signal, a pulse power parameter, a peak pulse power parameter and / or a pulse energy parameter by shifting at least one of the 3-surface reflectors (9A, 9B) to adjust.

16. pulse length adjusting unit (7, 7 ') according to one of the preceding claims, further comprising

two focusing elements forming an optical telescope arrangement (55), optionally lenses (55A, 55B) or mirrors, each between the first dispersive element (53A) and the first 3-area reflector (9A) and the second 3-area reflector (9) 9B) and the second dispersive element (53B).

17. Pulse length adjusting unit (7, 7 ') according to one of the preceding claims, further comprising

a in the angular dispersion region (13) arranged, the electromagnetic beam transmitting optical element (39), which causes a eintrittswinkke labhängigen parallel offset of the individual spectral components of the laser beam with respect to the propagation of the individual spectral components before and after the optical element (39), and an adjusting device for aligning the optical element (39), wherein the adjusting device A for changing the parallel offset of the individual spectral components is controllable.

18. Laser system (1) with

a laser pulse source (3) for generating spectrally broad laser pulses and at least one pulse length adjusting unit (7, 7 ') according to one of the preceding claims for pulse compression, pulse stretching and / or pulse optimization of the spectrally wide laser pulses.

19. A laser system (1, G) according to claim 18, further comprising

a control device (27),

a positioning unit (25) on which one of the 3-surface reflectors (9A, 9B) is arranged and which is connected to the control device (27) for controlling Translationsbewe conditions of the 3-surface reflector (9A, 9B) wherein the positioning unit (25) comprises a translation device for displacing the 3-plane reflector (9A, 9B) optio nal along a beam axis of an incident laser beam (5), and

optionally a pulse duration measuring device (29) for outputting a pulsdauerabhängi conditions measuring signal to the control device (27) for driving the positioning unit (25).

20. A method for pulse length adjustment of a laser pulse with a Pulslängenanpas sungseinheit (7, 7) according to any one of claims 1 to 17, a first and a second disper- sives element (11 A, 11 B) for generating angular dispersion and a first and a second 3-plane reflector (9A, 9B), wherein each of the 3-plane reflectors (9A, 9B) in the beam path between the first and the second dispersive element (11A, 53 A,

11B, 53B), with the step:

Shifting the first and / or second dispersive elements (11A, 53A, 11B, 53B) to adjust the optical path path length between the first and second dispersive elements (11A, 53A, 11B, 53B), optionally the path lengths of the optical path between the first and the second dispersive element (11A, 53A, 11B, 53B) as a function of a pulse duration-dependent measurement signal, a pulse power parameter, a peak pulse power parameter and / or a pulse energy parameter by displacing at least one of the 3-surface reflectors (9A, 9B).