DE102018109405B3 - Pulse length adjusting unit, laser system and method for pulse length adjustment of a laser pulse - Google Patents

Abstract

A pulse width adjusting unit (7, 7 ') for a pulsed laser beam (5) having a spectral width comprises a first and a second dispersive element (11A, 11B) for generating angular dispersion in an angular dispersion range bounded by the dispersive elements (11A, 11B) ( 13). In the angular dispersion region (13), individual spectral components of the laser beam (5) are assigned optical paths (13A, 13B) which extend at least in sections at an angle to one another. Furthermore, the pulse length adjusting unit (7, 7 ') comprises a first and a second 3-area reflector (9A, 9B), wherein each of the 3-area reflectors (9A, 9B) in the beam path between the first and the second dispersive element (9 11A, 11B) and having three reflecting surfaces (R1, R2, R3). The laser beam (5) is reflected by each of the three-surface reflectors (9A, 9B) by three successive reflections of the laser beam (5) on the respective three reflection surfaces (R1, R2, R3), wherein a directional deflection and a beam offset occur ,

Description

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 pulses. 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 leads to a divergence of the spectral components, so that in particular for short and ultrashort laser pulses with pulse durations in the ps range and shorter usually a dispersion adjustment of the optical path is made. Optical structures that counteract 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) that use a fanning of the spectral components of the laser pulse in a deflection direction of the gratings or prisms, referred to herein as angular dispersion, to produce different optical path lengths.

Furthermore, amplified pulses can lead to high intensities, which include nonlinear effects such as self-focusing, e.g. in the amplifier laser medium can cause. Such non-linear optical effects can adversely affect the beam and pulse quality and accordingly the overall 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-matching 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 adjusting units include e.g. Grid pair or prism pair-based span units (in short: grid or prism stretchers) comprising e.g. to produce a pulse compressor unit used opposite angular dispersion, for example, with an integrated lens system.

The fundamental parameter in grating or prism compressors and grating or prism stretchers is the extent of spectral fanning. This depends e.g. from the lattice constants of the grid used or the refractive index of the prism used and from 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 as a result of the angular dispersion. In lattice compressors or stretchers, in particular, the phase accumulated by the diffraction contributes to the dispersion. Generally, 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 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 time stretched (e.g., in a fiber-based straightener or in a grating spacer), amplified in a fiber amplifier unit, and then time compressed (e.g., in a lattice compressor). Similar constructions for generating (ultra-) short pulses may e.g. in machine tools based on disk laser systems. Typically, very precise and technically sophisticated compression is required to reverse the dispersive divergence of the spectral components.

The prior art discloses various approaches to precise dispersion control, for example in lattice compressors. For example, disclose WO 2015/117128 A1 and US Pat. No. 7,822,347 B1 Concepts where the change in pulse duration is controlled by the grating pitch of the harvester or compressor and additionally fine-tuned using a chirped FBG (Fiber Bragg Grating). Further approaches are off US 7,729,045 B2 . US 8,077,749 B2 as well as out US 8,780,440 B2 known. Further, on the application DE 10 2016 110 947 A1 by 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 at e.g. Provide grating pair and prism pair-based pulse length adjusting units, wherein the beam quality of the output beam is maintained. A further aspect of the invention is based on the object of enabling a dispersion adjustment in the case of such pulse length adaptation units, which has the least possible effect on the beam quality and the beam path after the dispersion adaptation 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 given in the subclaims.

In one aspect, a pulse width modulating unit for a pulsed laser beam having a spectral width includes first and second dispersive elements for producing angular dispersion in an angular dispersion range defined by the dispersive elements. In the angular dispersion region, individual spectral components of the laser beam are assigned optical paths which extend 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 directional deflection in the range of 150 ° to 210 ° and a beam offset occur. In such directional deflection, rotation about the beam axis of the laser beam may be e.g. at an angle in the range of 150 ° to 210 °. Substantially complete reversal of direction may occur when using a corner cube reflector. Further, directional deflections in the range of 160 ° to 200 ° or in the range of 170 ° to 190 ° can be used to provide, in particular, substantially back reflection type reflectors.

In a further aspect, a laser system has a laser pulse source for generating spectrally broad laser pulses and at least one pulse length adaptation unit 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 adjusting 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 adjusted 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.

In some embodiments of the pulse length adjusting unit, at least one of the 3-plane reflectors has three mutually fixed reflecting surfaces which form an optical reflector unit and are arranged relative to each other such that the laser beam experiences three successive reflections at the three reflecting 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 °. Furthermore, the beam axis sections can be skewed to one another, the skewed arrangement being such that a displacement of one of the two laser beams in the direction of the distance of the laser beams leads to intersecting beams in an angle range of 0 ° to 30 °.

In some embodiments of the pulse length adjusting unit, at least one of the 3-surface reflectors has reflecting surfaces extending in pairs substantially orthogonal to each other. In this case, at least one of the 3-surface reflectors can be formed as a prism modified on a side surface, which has a beam inlet and outlet surface, a reflective planar side surface and a region designed as a reflective roof edge prism. Optionally, it may further comprise upper and lower sides extending substantially along the deflection direction. Further, the modified prism may be formed as a rectangular prism and two reflective side surfaces of the roof edge prism are formed perpendicular to each other and perpendicular to the plane side surface.

In some embodiments of the pulse length adjusting unit, as many reflecting surfaces as possible, i.e., for example, the flat 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 antireflective to reduce the losses during passage. Furthermore, these surfaces, in particular the reflection surfaces, may be phase-influencing (e.g., acting similar to a λ / 4 plate or a λ / 2 plate) to affect polarization.

In some embodiments of the pulse length adaptation unit, at least one of the three-surface reflectors is designed as a mirror unit which has three mirrors which are fixed in space (in other words spatially fixed, in particular as a component or made of glued or welded 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 retardation plate for influencing the phase, in particular for influencing the polarization, preferably for polarization compensation, for example a λ / 4 plate, λ / 2 plate or a combination of multiple retardation plates, which lies between the first dispersive element and the first 3-plane reflector in the beam path of an incident on the first 3-surface reflector laser beam is arranged.

In some embodiments of the pulse length adjusting unit, the reflecting surfaces or the beam inlet and outlet surface are phase-influencing, for 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 reflection element can cause a return of the optical path through the dispersive elements and the 3-surface reflectors. The reflection element is optionally a roof edge mirror or a deflection prism. In some embodiments, the reflective element may provide back reflection of the optical paths parallel to a deflection plane associated with a direction of deflection of the dispersive element. In general, the return may optionally result in a return path to an inverted 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 further offset can be generated vertically or horizontally.

In some embodiments, the pulse length adjustment unit further comprises a second retardation plate for phase influencing, in particular for influencing the polarization, preferably for polarization compensation, for example a λ / 4 plate, λ / 2 plate or a combination of multiple retardation plates, which is arranged between the first 3 area Reflector and the first dispersive element in the beam path of the first 3-plane reflector emerging laser beam 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 about 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-plane reflector and the 3-faces Reflectors are arranged with respect to the deflection 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 again in the deflection of the first dispersive element and the laser beam after the second 3-plane reflector is offset with respect to the laser beam before the first reflection at the first 3-plane reflector in the deflection direction.

In some embodiments of the pulse length adjusting unit, the 3-plane reflectors are identically formed, but are arranged in the order of the reflections on the reflection surfaces inverted in the beam path between the dispersive element.

In some embodiments, the pulse length adjusting unit further comprises a translation 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 the second dispersive element. The translation device may optionally be configured to displace one of the 3-plane reflectors along a beam axis section 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 receive one of the 3- To move surface reflectors such that the entrance angle and / or the entry position of the optical paths with respect to a first reflective of the three reflection surfaces of the moving 3-surface reflector and the exit angle are maintained.

In some embodiments, the pulse length adjusting unit further comprises a control device for driving the translating device, wherein the control device is designed 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 pulse power parameter and / or adjusting a pulse energy parameter by shifting 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. In each case one of the focusing elements is arranged between the first dispersive element and the first 3-area reflector and between the second 3-area reflector and the second dispersive element.

In some embodiments, the pulse length adjusting unit further comprises an optical element transmitting the electromagnetic beam in the angular dispersion range, causing an incident angle-dependent parallel displacement 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 adjustment unit can have an adjustment device for aligning the optical element, wherein the adjustment device can be controlled in particular for changing the parallel offset of the individual spectral components.

In some embodiments, the laser system further comprises a control device and a positioning unit, on which one of the three-surface reflectors is arranged, and which is in communication with the control device for controlling translational movements of the three-surface reflector. The positioning unit may e.g. a translation device for displacing the 3-plane reflector optionally along a beam axis of an incident laser beam. Furthermore, the laser system can optionally have a pulse duration measuring device for outputting a pulse duration-dependent measuring signal to the control device for activating 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, such that the beam cross-section of the laser beam prior to the first reflection at a e.g. first corner cube reflector is deformed in the deflection direction.

Generally, the reflection surfaces may be sized and arranged in the deflection direction such that the laser beam is reflected as a whole from 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 affect the offset. For example, a first angle adjusting device configured to align one of the 3-plane reflectors about the normal direction to adjust an offset component of the beam displacement in the deflection plane may be provided. Alternatively or additionally, a second Winkeleinstellvorrichtung, which is designed to align the 3-plane reflector with respect to the deflection plane for adjusting an offset component of the beam offset in the normal direction, are provided.

The embodiments disclosed herein may include i.a. have the following advantages:

The use of 3-surface reflectors, for example an angle reflector with three (spatially) mutually fixed reflecting surfaces (in the case of 90 ° angles between each two surfaces known as a so-called corner-cube reflector, here also as a 3-surface reflector Retroreflector) can simplify the construction of dispersion adjustment units, since it eliminates degrees of freedom, for example present at plan deflecting mirrors. If the surfaces of the 3-plane reflector are not perpendicular to each other, then an appropriate positioning of a subsequent 3-plane reflector at a correspondingly adapted angle. Thus, in particular the adjustment of grating or prism stretchers or grating 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 to 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 moves less on, for example, the second grating, so that in particular the angle remains the same and thus less influence of the dispersion by thermal-mechanical changes 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 for the pulse length adjustment. For example, the rotation of a 3-area reflector can be actively readjusted or varied by means of a motor 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, angular variations in the beam path.

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

• 1 eine schematische Aufsicht auf ein Lasersystem mit einer auf einem Paar von corner-cube-Reflektoren basierenden Pulslängenanpassungseinheit zur Pulsdauerkomprimierung (Kompressor),
• 2 eine schematische Perspektivansicht auf die Pulslängenanpassungseinheit der 1,
• 3 eine schematische Perspektivansicht auf den Strahlengang zwischen zwei corner-cube-Reflektoren einer allgemein einsetzbaren Weglängenanpassungseinheit,
• 4 eine schematische Darstellung einer auf einem Paar von corner-cube-Reflektoren basierenden Pulslängenanpassungseinheit zur Pulsdauerstreckung (Strecker) und
• 5 eine schematische Perspektivansicht auf eine Pulslängenanpassungseinheit mit Polarisationsanpassung beispielhaft für ein 3-Flächen-Reflektor mit nicht-orthogonal angeordneten, reflektierenden Flächen.

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. From the figures show:

• 1 a schematic plan view of a laser system with a on a pair of corner-cube reflectors based pulse length adjustment unit for pulse duration compression (compressor),
• 2 a schematic perspective view of the pulse length adjusting unit of 1 .
• 3 3 is a schematic perspective view of the beam path between two corner cube reflectors of a general-purpose path length adaptation unit;
• 4 a schematic representation of a based on a pair of corner-cube reflectors pulse length adjustment unit for pulse duration stretching (Strecker) and
• 5 a schematic perspective view of a pulse width adjusting unit with polarization adjustment, for example, for a 3-plane reflector with non-orthogonally arranged reflecting 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 changing 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 upon the insight that alignment changes of the path-length changing components can cause angular errors on the second grid. 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 reflection with respect to an axis, a (perfect) space inversion, which corresponds to a 180 ° rotation for a transverse beam profile, can be used with a corner-cube reflector as an example. Area retroreflectors are achieved. A corner cube reflector reflects a laser beam at three mutually orthogonal surfaces (corresponding to the three sides of a cube corner), wherein at an incidence of the laser beam on one of the three reflection surfaces with distance to the intersection and the intersection lines of the three surfaces, a parallel beam offset and a space inversion of the laser beam takes place. Thus, in the propagation direction, the spectral distribution remains the same for a spectrally split beam (eg after diffraction at the grating), for example on the left side in the propagation direction the longer wavelength spectral range and in the propagation direction on the right side the shorter wavelength spectral range.

An exemplary embodiment of a corner cube reflector is a modified one Rectangular prism, which provides one of the three reflective surfaces on one of the Ankathetenseiten and provides with a provided on the other Ankathetenseite 90 ° roof edge structure, the remaining two of the three orthogonal mutually arranged reflecting surfaces.

The properties of the corner-cube reflectors, and generally of 3-area retroreflectors, make the beam path length change invariant to angular errors. Thus, due to the (retro) reflector property, angular adjustment degrees of freedom can be dispensed with. Since at very high compression levels, the angular sensitivity and the adjustment resolution can be particularly sensitive, the optical arrangements disclosed herein can significantly reduce the influence of angular errors and even eliminate them altogether.

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 angle tilting in all three axes of the incident beam or the 3D retroreflector itself is compensated by the operation of the 3-area retroreflector, so that the output beam undergoes substantially no angular changes despite, for example, tilting the 3-area retroreflector. That is, the output beam is always 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 substantially 180 degrees and the beam experiences a lateral offset each time. 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 of the pulse length adjusting unit, by setting the distance between the 3-plane reflectors, the path length, and thus the spectral broadening of the laser pulse, a dispersion adjustment can be made.

In a further embodiment of the pulse length adaptation unit, the variability of the lateral offset can furthermore be used selectively to vary the pulse length. Thus, the lateral offset can be influenced by a specific angular tilting of the 3-area reflector, whereby the propagation length between the dispersive elements is changed.

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, e.g. tipped around the hypotenuse of the underlying triangular shape of the rectangular prism. This is preferably aligned substantially parallel to the deflection / spectral fanning of the laser beam. This type of tilt can be used to adjust the vertical distance of the two laterally offset and horizontally superimposed input and output beams. However, such a tilt can not only be used to adjust 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 of rotation perpendicular to the spectral fan-out plane (also referred to herein as the yaw axis of the 3-plane reflector) has a greater influence 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 accurate pulse length adjustment.

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

The angular stability with regard to grating compressors makes it possible to provide pulse lengths of, for example, 300 fs over a long period of time, without these being prolonged by changes in the adjustment to ps pulses. The latter can easily be caused, for example, by setting movements of optical elements (eg flat deflection mirrors) in state of the art compressors thermal-mechanical misalignment of example adjusting screws are generated.

The following is in conjunction with the 1 and 2 a pulse length adjustment in a ultrashort pulse system 1 described for pulse duration compression. The ultrashort pulse system 1 is exemplary of pulsed laser systems, which usually make a dispersion adjustment.

The ultrashort pulse system 1 is in 1 shown schematically. It includes a laser pulse source 3 for generating a laser beam 5 from spectrally wide laser pulses and a pulse length adjustment unit 7 for pulse duration compression of the laser pulses. A long (in the case of use as a pulse compressor non-compressed) laser pulse 5A is schematically indicated for the input beam. As explained below, the pulse length adjusting unit comprises 7 two specially arranged folding elements: a first corner-cube reflector 9A and a second corner-cube reflector 9B, which together form a path length adjusting unit. With reference to 4 For example, a similarly constructed pulse length adjusting unit for pulse stretching in the laser pulse source 3 be integrated.

The laser pulse source 3 may be formed for example as a laser oscillator or laser oscillator-amplifier combination. In the ultrashort pulse system 1 For example, laser pulses with spectral widths of, for example, 1 nm and greater and pulse energies of, for example, 0.1 .mu.J and greater are generated. These become the pulse length adjustment unit 7 fed. The spectral width of the laser pulses necessitates a dispersion adaptation of the beam path in order to provide a specific pulse shape (intensity profile) of the laser pulses at a target location with a desired, for example the shortest possible or a pulse duration adapted to a processing method. The concepts described herein can be used in particular in ultrashort pulse systems which provide pulse durations of, for example, a few 100 fs for material processing. The applications of such laser systems include glass cutting (eg, cutting displays and medical devices), labeling, medical applications such as eye surgery, drilling of, for example, injectors, and conducting scientific experiments.

The pulse length adjusting unit 7 is exemplary constructed as a folded grid compressor. The grid compressor comprises a pair of dispersive elements in the form of a first grid 11A and a second grid 11B , the two interaction areas of the grid 11A . 11B deploy with the laser beam. The spectrally dependent diffraction conditions produce an angular dispersion after the first grating 11A , That is, in an angular dispersion range 13 between the dispersive elements (grid 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 1 are the grids 11A . 11B parallel aligned transmission grating. Alternatively, for example, reflection grids, prisms or grisms can be used.

For a folding of the beam path, the lattice compressor further comprises a reflector element 15 , which is designed for example as (deflecting) roof edge prism or roof mirror. Thus, an optical way 16A and an optical return path 16B provided by the grid compressor, which are offset from one another in sections in height. After the double pass through the grating arrangement, the height offset allows separation of the compressed laser pulses from the coupled-in laser pulses on a scraper mirror 17 for outputting an output beam 19 , An example of the case of use as a pulse compressor is a short (compressed) laser pulse 19A schematically for the output beam 19 in 1 shown. The reflector element 15 allows, together with the special arrangement of the corner-cube reflectors 9A, 9B, substantially the same optical conditions for the way out 16A and the way back 16B of the laser beam through the grating arrangement.

In the supervision of the 1 will only be the way 16A by way of example with reference to two optical paths 13A . 13B in the angular dispersion range 13 for spectral components with a longer (dashed line: λ> λ ₀ ) and a shorter (solid line: λ <λ ₀ ) wavelength with respect to a central wavelength λ _{0 of} the laser pulse plotted. It should be noted that the optical path of the center wavelength λ ₀ usually defines the beam axis of the laser beam.

In 1 are exemplary beam axis sections 20A . 20B . 20C indicated by arrows, wherein the beam axis and thus the beam axis sections are given by the beam path of a central wavelength. Since the reflecting surfaces of the corner-cube reflectors 9A, 9B are aligned orthogonal to each other, the beam axis sections extend 20A . 20B the rays entering the corner cube reflectors 9A, 9B are parallel to the respective beam axis sections 20B . 20C the rays emerging from the corner cube reflectors 9A, 9B. In other words, the beam axis section run 20A and the beam axis section 20B or the beam axis section 20B and the beam axis section 20C Ideal training at no angle to each other. at Ideally designed corner-cube 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 an alignment / parallelization of the optical paths 13A . 13B causes, before this on the reflector element 15 to meet.

In the in 2 shown perspective view of the pulse length adjusting unit 7 you can see different parts of the way 16A and the way back 16B of the laser beam. Due to the spectral fanning, the laser beam points in the deflection direction of the grating 7A an elliptically indicated beam profile. The different sections extend in height (ie, perpendicular to the fanning plane) offset from one another. The one from the laser pulse source 3 (not in 2 shown) emitted laser beam 5 is below the output beam 19 , The corner cube reflectors 9A, 9B each cause an offset in height, so that between the corner cube reflectors 9A, 9B, the optical way 16A above the optical return path 16B runs.

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

In the embodiment shown by way of example, each of the corner cube reflectors 9A, 9B is designed as a rectangular prism, wherein the rectangular prisms are modified such that on one side of the rectangle not a plane surface but a 90 ° rotated (90 °) Dachkantenprismabereich is provided. Thus, for this example of a 3-surface reflector 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 jet inlet and outlet surface runs 21 along the hypotenuse of the triangular basic shape of the rectangular prism. A 90 ° angle of the basic shape of a right triangle is in 1 for corner cube reflector 9B indicated. The jet inlet and jet exit surface 21 is essentially formed as a rectangle whose long side extends along the deflection plane. Furthermore, the modified rectangular prisms comprise upper and lower sides extending substantially in the deflection direction 23 , which are not irradiated and do not serve as reflection surfaces.

The construction of the modified rectangular prisms and the resulting beam guidance are described below by way of example at the first corner-cube reflector 9A.

As in 2 As shown, the fanned-out laser beam on the way down on a (left) half of the beam entrance and exit surface 21 of the first corner-cube reflector 9A, and it turns 180 ° on top of the other (right) half of the beam entrance and exit surfaces 21 out. For this reversal of the direction of the laser beam, the rectangular prism comprises three reflection surfaces (coated, for example, with broadband reflection) R1 . R2 . R3 ,

The reflection surfaces R1 and R2 (Also referred to herein as lower and upper (roof edge) reflecting surfaces) are formed by the roof edge prism area, wherein the reflecting surfaces of the roof edge prism area are formed perpendicular to each other (see also the 2 for the corner cube reflector 9B indicated 90 ° angle). In the illustrated orientation of the corner-cube reflector 9A, the reflective surfaces are substantially each at a 45 ° angle to the deflection plane. The spectrally fanned out incident laser beam is from the lower reflection surface R1 on the upper reflection surface R2 distracted. In 1 and 2 is the elliptical impact area 22A on the reflection surface R2 indicated. From there, the laser beam is projected onto the upper half of the, as a reflection surface R3 acting side surface of the modified rectangular prism further. From the reflection surface R3 The laser beam is opposite to the original direction of propagation, spatially offset and cross-section in the beam cross-section rotated by 180 ° through the upper (right) area of the beam inlet and outlet surface 21 decoupled from the rectangular prism.

Correspondingly, the first corner-cube reflector 9A effects first parallel offsets dependent on the entrance angle and on the entry position for all optical paths V1 in which all parallel offsets of the spectral components result in a rotation of the laser beam through 180 ° about the beam axis of the laser beam.

For adjusting the entry angle, the entry position and the distance from the first grid 11A is the first corner-cube reflector 9A on a positioning unit 25 arranged, the translation and / or rotation axes has. For controlling the positioning unit 25 can the laser system 1 Further, a control device 27 and a pulse duration measuring device 29 have, via control lines 31 with each other and with the ultrashort pulse system 1 are connected. The control device 27 For example, it is designed to be path lengths of the optical path between the first and the second dispersive element 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 set.

For example, the pulse duration measuring device 29 designed to output a pulse duration-dependent measurement signal (eg an autocorrelation signal). As in 1 is indicated schematically, the pulse duration measuring device 29 one on a slide 30 tapped (non-transmitted) portion of the output beam 19 fed. The pulse duration measuring device 29 derives therefrom the pulse duration-dependent measurement signal and gives it to the control device 27 from. The control device 27 in turn gives a control signal generated therefrom to the positioning unit 25 for moving or aligning, such as twisting or tilting, of the positioning unit 25 mounted corner cube reflector off. The control device 27 For example, it uses an optimization algorithm to look for one or both corner-cube reflectors 9A . 9B to vary the angular position and / or the distance from the dispersive elements for pulse duration shortening and to make a corresponding adjustment with regard to a shortest pulse duration or a pulse duration (or pulse shape) required for a specific application in material processing.

A major change in the optical paths between the grids 11A . 11B can eg by a translation of the first corner cube reflector 9A be made. For this purpose, the positioning unit 25 a translation device for adjusting the distance between the corner cube reflectors 9A . 9B include. The translation device may optionally, as in 1 schematic with double arrows 33A . 33B hinted at moving one of the corner cube reflectors 9A . 9B along a beam axis of the laser beam between the corner cube reflectors 9A . 9B be educated.

In particular, the translation device can be designed to be one of the corner cube 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 of the three reflecting surfaces R1 . R2 . R3 moving corner cube reflector 9A . 9B - in 1 the reflection surface R1 moving corner cube reflector 9A - is / will be maintained.

The translation device may, for example, a motorized and / or displaceable via a piezoelectric actuator element of the corner-cube reflector 9A be, 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 corner-cube reflector 9A the optical paths 13A . 13B between the reflective surfaces R1 . R2 . R3 and thus also changes the path length differences between the spectral components. Accordingly, such rotation also affects the dispersion characteristics of the pulse length adjusting unit 7 and the pulse duration of the laser pulses in the output beam 19 can eg by the rotation of the first corner-cube reflector 9A be set.

This results in two possible rotational movements, which have different effects on the beam path in the corner-cube reflector.

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

The positioning unit 25 may include a first angle adjusting device for aligning the corner cube reflector 9A is formed around the normal direction n. Turn the corner cube reflector 9A around the normal direction n become the offset components of the beam offsets V1 set in the deflection plane. Such Winkeleinstellvorrichtungen are in the 1 and 2 schematically by axes of rotation 35A . 35B for the corner cube reflectors 9A . 9B indicated.

Alternatively or additionally, the positioning unit 25 a second angle adjustment device. This is designed to align the corner cube reflector with respect to the deflection plane. The wide Winkeleinstellvorrichtung thus allows the adjustment of the offset components of the beam offsets V1 in the normal direction n. Such Winkeleinstellvorrichtungen are in 2 schematically by axes of rotation 37A . 37B for the corner cube reflectors 9A . 9B indicated.

The Winkeleinstellvorrichtungen can, for example, motorized and / or piezoelectric elements rotatable brackets of the corner-cube reflector 9A . 9B be, which allow one, in particular stepless, adjustment of the rotation angle. The Winkeleinstellvorrichtungen and the control device thus allow adjustment, in particular control, the pulse duration by an actively controlled, in particular controlled, alignment of the respective corner cube reflector 9A . 9B ,

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

At each of the corner cube reflectors 9A . 9B is - regardless of entrance angle, entry position and distance from the first grid 11A - The reflected back 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 mount of corner-cube reflectors serving as folding mirrors.

It should be noted that due to the angle of incidence on the reflective surfaces of the corner-cube reflector 9A the polarization of the back-reflected beam can be influenced. The Indian 5 The design shown may counteract such changes in polarization by providing, for example, λ / 4 plates, λ / 2 plates (alternatively or additionally by providing a correspondingly reflective coating).

As in 1 The laser beam passes through the reflection surfaces R1 . R2 . R3 the second corner cube reflector 9B in reverse order. That is, the (now considerably further) fanned laser beam occurs on the way up on a (right) half of the beam inlet and outlet surface 21 the second corner cube reflector 9B on. Because the second corner cube reflector 9B regarding the first corner cube reflector 9A rotated in the deflection plane by 180 °, this entry position corresponds to the exit position of the first corner cube reflector 9A ,

For the (second) direction reversal of the laser beam comprises the rectangular prism of the second corner cube reflector 9B also three reflective coated reflective surfaces R1 . R2 . R3 , The reflection surfaces R1 and R2 are also formed here by a roof edge prism area, wherein the reflection surfaces of the roof edge prism area are aligned perpendicular to each other and each again substantially at a 45 ° angle to the deflection plane.

Referring to 2 becomes the first corner cube reflector 9A Thus, the incoming laser beam is first of the upper half of the plan, as a reflection surface R3 acting side surface of the modified rectangular prism in the deflection plane on the upper reflection surface R2 and from there to the lower reflection surface R1 distracted. In 2 one recognizes correspondingly larger elliptical impact areas 22B on the reflection surfaces R3 and R2 , being on the reflection surface R3 the impact areas 22B are indicated by way and way back.

At the reflection surface R1 the laser beam is directed against the propagation direction between the corner cube reflectors 9A . 9B and thus parallel to the laser beam, as seen from the first grid 7A was deflected, through the lower portion of the jet inlet and outlet surface 21 output. In this case, the beam components in turn experience the entry angle and the entry position dependent spatial parallel offsets V2 by which the laser beam is rotated by 180 ° around the beam axis.

The further fanned due to the subsequent propagation laser beam thus thus meets in an orientation and angular distribution on the second grid 7B as if the laser beam directly from the first grid 7A would come. At the grid 7B In turn, the laser beam is diffracted to face with parallel rays on the reflector element 15 hold true.

In alternative arrangements of the two 3-area reflectors they can be nested in particular staircase in height.

In addition, the previously described pulse length adjustment unit can be equipped with further measures for fine-tuning the dispersion. With reference to the aforementioned German patent application DE 10 2016 110 947 A1 the applicant show the 1 and 2 Dashed a plane-parallel glass plate 39 , which are in the angular dispersion range 13 is arranged. The glass plate 39 can be about a rotation axis 41 , which is parallel to the normal n, are rotated to the angle of incidence of the laser beam on the glass plate 39 to set the pulse duration setting. 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 rotation angle).

3 generally shows a path length adjusting unit 43 which includes two corner cube reflectors and can be used, for example, in pulse length adjusting units such as compressor units or rack units. The path length adjustment unit 43 can for an incident laser beam 45A provide variably adjustable path lengths, wherein the exiting laser beam 45B parallel to the incident in the Y direction laser beam 45A extends and is offset in the X direction, but otherwise the beam profile of the incident laser beam 45A (except, for example, a propagation-induced widening or rejuvenation of the beam).

The course of the laser beam in the path length adjustment unit 43 is through a central optical path 47 , which corresponds to the beam axis, and optical paths 47A . 47B clarified.

In the exemplary embodiment of the 3 are the corner cube reflectors as mirror units 49A . 49B formed, of which only the reflection surfaces (hereinafter referred to as mirror surfaces) are schematically sketched. Each of the mirror units 49A . 49B includes three mirror surfaces 49-1 . 49-2 . 49-3 wherein each of the mirror surfaces is 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 reflection surfaces in the 1 and 2 are the mirror surfaces 49-1 . 49-2 . 49-3 arranged such that the incident laser beam 45A first on the plane perpendicular to the XY plane mirror surface 49-1 (corresponding R3 in 1 ), from there on the lower mirror surface 49-2 (corresponding to R2 in 1 ) of the roof edge formation is reflected and then from this to the upper mirror surface 49-3 (corresponding to R1 in 1 ) of the roof edge formation is deflected. Accordingly, the laser beam with a height offset in the Z direction with respect to the incident laser beam to the second mirror unit 47B , This corresponds to the first mirror unit 47A , but is rotated by 180 ° around the Z-axis. The mirror surfaces 49-1 . 49-2 . 49-3 the second mirror unit 47B are done in reverse order so that at the end there is only a beam offset in the X-direction.

Referring to the previous discussion of 1 and 2 one recognizes that each of the individual optical paths 47 . 47A . 47B by the successive reflections on the three mirror surfaces in each mirror unit 49A . 49B experiences its own parallel offset. The parallel offsets are such that the entire beam profile in addition to a directional deflection and an offset in the X and Y directions undergoes a 180 ° rotation. Because the second mirror unit 49B causes a corresponding offset in (-Y) direction, but otherwise causes a further rotation by 180 ° (or -180 °), represents the path length adjustment unit 43 a compact unit with the path lengths to be traversed by shifting or, as previously discussed, aligning the mirror unit 49A . 49B coarse and fine can be adjusted.

4 FIG. 12 shows an exemplary implementation of the dispersion adjustment concepts disclosed herein in a pulse length adjusting unit configured as a grating spacer. FIG 7 ' with a path length adjustment unit 51 , the two corner cube reflectors 9A . 9B includes. Unlike in the 1 and 2 shown compressor are in 4 exemplary two prisms 53A . 53B used as dispersive elements. Alternatively, for example, reflection grids or grisms can be used. In the beam path between the two prisms 53A . 53B are the two corner cube reflectors 9A . 9B arranged for path length adjustment.

In order to achieve inverted angular dispersion contributions, in the exemplary prism extender a lens system (eg a telescope arrangement) in the beam path between the two prisms 53A . 53B intended. Exemplary is in 4 a telescope arrangement 55 with two lenses 55A . 55B shown. The telescope arrangement 55 causes an image of the first prism 53A such that the fanned-out spectral components follow the lens system at the second prism 53B converge.

As in 1 is the pulse length adjusting unit 7 ' with a reflector element 15 folded to a way out and a way back through the prisms 53A . 53B to provide in a structure.

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

The above in connection with the 1 to 3 Explanations to the beam path explained are corresponding to the course of the laser beam through the path length adjustment unit 51 transferable. In particular, the adjustment options described above with respect to the compressor arrangement (translation, alignment, in particular rotation about one or two axes) can generally be applied to straighteners and, in particular, to the stretching arrangement of FIGS 4 transfer.

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

5 shows a schematic perspective view of a pulse length adjusting unit 61 that exemplifies two 3-area reflectors 63A . 63B based on non-orthogonal reflective surfaces. Optical elements and the portions of the beam path, as in connection with z. B. the 1 and 2 have been explained, are provided with the same reference numerals.

Accordingly, a laser beam spreads 5 that of a first grid 11A spectrally expanded, along a way 16A through the pulse length adjusting unit 61 out. The way goes in 5 between the first grid 11A and the 3-area reflector 63A below a return route 16B , between the first 3-area reflector 63A and the second 3-area reflector 63A above the return route 16B and between a second grid, which together with a back reflector in 5 not shown (see eg. 1 ) again below the return route 16B , To clarify, the ray of the way out became 16A pulled through and the beam of the return path 16B shown in dashed lines.

Because the reflective surfaces of the 3-surface reflectors 63A . 63B are aligned non-orthogonal to each other, run beam axis sections 65A . 65B in the 3-area reflectors 63A . 63B entering beams (the beam axis and thus the beam axis sections are again given by the beam path of a central wavelength) not parallel to the corresponding beam axis sections 65B . 65C the one from the 3-area reflectors 63A . 63B emerging rays. In other words, the beam axis section run 65A and the beam axis section 65B or the beam axis section 65B and the beam axis section 65C at an angle to each other (for example, the angle is spanned primarily parallel to the splitting plane) or the respective beam axis sections are skewed.

It also recognizes a rotatably held glass plate 39 included in the pulse length adjustment unit 61 between the first grid 11A and the first 3-area reflector 63A Optionally for additional pulse length adjustment can be provided.

Furthermore, in 5 a first retardation plate 67A for polarization compensation (eg, a λ / 4 plate, a λ / 2 plate, generally a combination of multiple retardation plates may be provided) between the first grid 11A and the first 3-area reflector 63A arranged. When using 3-surface reflectors, the reflections on the surfaces of the 3-surface reflectors, to which the laser beam 5 with different angles of incidence / incidence orientation that affect polarization. This applies to both 3-plane reflectors with orthogonal and non-orthogonal reflective surfaces. The use of the λ / 4 plate 67A now acts such a polarization error of the 3-surface reflectors 63A . 63B opposite. In particular, a phase offset between the S and P polarization components is compensated.

In the folded structure of 5 can be a second delay tile 67B for influencing the phase and preferably for polarization compensation (usually a corresponding λ / 4 plate, λ / 2 plate or a corresponding combination of several retardation plates) at the end of the return path 16B be provided, for example, between the first 3-area reflector 63A and the first grid 11A , Accordingly, the incident laser beam 5 and the outgoing laser beam 19 a substantially similar polarization.

Alternatively or in addition to the use of retardation plates, one or more of the reflective surfaces may be coated with a corresponding coating 69 be provided to influence the polarization of the incoming and outgoing beam. The coating 69 For example, it is designed in such a way that the polarization is rotated into the polarization required for the grating. For this example, metallic coatings (such as gold or silver coatings) for generating a desired phase jump (eg λ / 4) can be used.

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

Other configurations of pulse length adjusting units, as they play in the 1 . 2 . 4 and 5 include non-folded assemblies with two sequentially irradiated pairs of dispersive elements, so that the way-out and return paths are not as in FIG 2 or 4 in a structure but implemented 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 from 200 nm to 10 μm, depending on the application). However, application of the concepts disclosed herein is generally applicable to electromagnetic radiation having a spectral width.

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 pointed out that all features disclosed in the description and / or the claims are considered separate and independent of each other for the purpose of original disclosure as well as for the purpose of limiting the claimed invention independently of the feature combinations in the embodiments and / or the claims should. 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 (20)

Pulse length 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 an angular dispersion region (13) bounded by the dispersive elements (11A, 53A, 11B, 53B), individual spectral components being present in the angular dispersion region (13) the laser beam (5) are associated with optical paths (13A, 13B), 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 dispersive element (11A, 53A, 11B, 53B) is arranged and three reflecting surfaces (R1, R2, R3), and the laser beam (5) of each of the 3-surface reflectors (9A, 9B) is reflected by three successive reflections of the laser beam (5) on the respective three reflecting surfaces (R1, 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. Pulse length adjusting unit (7, 7 ') after Claim 1 in which 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 relative to one another so that the laser beam (5) experiences three successive reflections at the three reflective surfaces, which cause the directional deflection of the laser beam (5) with a two-stage beam offset, wherein the beam offset is such that the incident on the at least one of the 3-surface reflectors (9A, 9B) laser beam and the at least one of the 3-area Reflectors (9A, 9B) extending 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 itself cutting rays in an angle range of 0 ° to 30 ° leads. Pulse length adjusting unit (7, 7 ') according to any one of the preceding claims, wherein at least one of the 3-surface reflectors (9A, 9B) in pairs has substantially orthogonal to each other extending reflective surfaces. Pulse length adjusting unit (7, 7 ') after Claim 3 wherein at least one of the 3-surface reflectors (9A, 9B) is formed as a side face modified prism comprising a beam entrance and exit surface (21), a reflective planar side surface (R3), a roof edge prism reflective portion, and optionally has 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 (R1, R2) of the roof edge prism perpendicular to each other and perpendicular to the flat side surface. Pulse length adjusting unit (7, 7 ') after Claim 4 , wherein the planar side surface (R3) and the side surfaces (R1, R2) of the roof edge prism are reflective coated the spectral width of the laser beam and / or the phase and / or the beam inlet and outlet surface (21) is coated antireflective. Pulse length adjusting unit (7, 7 ') according to one of Claims 1 and 2 , wherein at least one of the 3-surface reflectors is formed as a mirror unit (49A, 49B) having three spatially fixed mutually arranged mirror whose mirror surfaces (49-1, 49-2, 49-3), the three reflection surfaces (R1 , R2, R3), and wherein optionally two of the mirror surfaces (49-2, 49-3) form a roof edge mirror, in particular a 90 ° roof edge mirror. Pulse length adjusting unit (7, 7 ') according to one of the preceding claims, further comprising a first phase-influencing retardation plate which is arranged between the first dispersive element (53A) and the first 3-area reflector (9A) in the beam path of a first 3-area reflector. Reflector (9A) incident laser beam is arranged. Pulse length adjusting unit (7, 7 ') according to 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 emerging from the 3-surface reflector (9A) beam is equal to the polarization of the incident in the 3-surface reflector (9A) beam. Pulse length adjusting unit (7, 7 ') according to one of the preceding claims, further comprising at least one reflection element (15), which is a return of the optical path (13A, 13B) by the dispersive elements (11A, 53A, 11B, 53B) and the 3 Surface reflectors (9A, 9B) causes, wherein the reflection element (15) is optionally formed as a roof edge mirror or deflection prism, and further optionally an inverted order of the reflections on the reflection surfaces (R1, R2, R3) in a return path (16B) in Comparison to the order of the way out (16A) is present. Pulse length adjusting unit (7, 7 ') after Claim 9 , further comprising a second phase-affecting retardation plate disposed between the first 3-plane reflector (9A) and the first dispersive element (53A) in the beam path of a laser beam emerging from the first 3-surface reflector (9A). Pulse length adjusting unit (7, 7 ') according to one of the preceding claims, wherein the first dispersive element (11A, 53A) is adapted to deflect the spectral components in a deflection direction by wavelength-dependent angles, so that the beam cross-section of the laser beam (5) before the first reflection on the first 3-plane 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 laser beam (5) after reflection on the second 3-plane reflector (9B) again in the deflection direction of the first dispersive element (11A, 53A) and the laser beam (5) after the second 3-plane reflector (9B) with respect to the laser beam (5) is offset in the deflection direction before the first reflection at the first 3-area reflector (9A). Pulse length adjusting unit (7, 7 ') according to 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 (R1, R2, R3) inverted in the beam path between the dispersive elements (11A, 53A, 11B, 53B) are arranged. Pulse length adjusting unit (7, 7 ') according to 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 (11A, 53A, 11B, 53B), wherein the translating device is optionally designed to displace one of the 3-plane reflectors (9A, 9B) along a beam axis of the laser beam (5) between the 3-plane reflectors (9A, 9B) is. Pulse length adjusting unit (7, 7 ') after Claim 13 wherein the translation device is adapted to move one of the 3-surface reflectors (9A, 9B) such that the entrance angle and / or the entry position of the optical paths (13A, 13B) relative to a first reflecting one of the three reflection surfaces (R1, R2, R3) of the moving 3-surface reflector (9A, 9B) and the exit angle are maintained. Pulse length adjusting unit (7, 7 ') according to 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 the optical path between the first and the second dispersive element (11A, 53A, 11B, 53B) in response to 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-plane reflectors (9A, 9B). 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 Surface reflector (9A) and the second 3-surface reflector (9B) and the second dispersive element (53B) are arranged. 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 an entrance angle dependent parallel displacement 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 for changing the parallel offset of the individual spectral components is controllable. Laser system (1) with a laser pulse source (3) for generating spectrally wide laser pulses and at least one pulse length adjusting unit (7, 7 ') according to one of the preceding claims Pulse compression, pulse stretching and / or pulse optimization of the spectrally wide laser pulses. Laser system (1, 1 ') after Claim 18 further comprising a control device (27), a positioning unit (25) on which one of the three-surface reflectors (9A, 9B) is arranged and which is connected to the control device (27) for controlling translational movements of the 3-surface reflector (27). 9A, 9B), the positioning unit (25) comprising a translation device for displacing the 3-plane reflector (9A, 9B) optionally along a beam axis of an incident laser beam (5), and optionally a pulse duration measuring device (29) for outputting a pulse duration-dependent measurement signal to the control device (27) for driving the positioning unit (25). Method for the pulse length adjustment of a laser pulse with a pulse length adjustment unit (7, 7 ') according to one of Claims 1 to 17 comprising first and second dispersive elements (11A, 11B) for producing angular dispersion and first and second 3-plane reflectors (9A, 9B), each of said 3-plane reflectors (9A, 9B) in Beam path between the first and the second dispersive element (11A, 53A, 11B, 53B) is arranged, with the step: shifting the first and / or the second dispersive element (11A, 53A, 11B, 53B) for adjusting the path length of the optical Way between the first and the second dispersive element (11A, 53A, 11B, 53B), wherein optionally the path length of the optical path between the first and the second dispersive element (11A, 53A, 11B, 53B) in dependence of a pulse duration-dependent measuring 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) is set.

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