WO2014108333A1

WO2014108333A1 - Optical rotation device and associated method

Info

Publication number: WO2014108333A1
Application number: PCT/EP2014/000026
Authority: WO
Inventors: Johannes Früchtenicht
Original assignee: Universität Stuttgart
Priority date: 2013-01-09
Filing date: 2014-01-09
Publication date: 2014-07-17

Abstract

The invention relates to an optical rotation device for receiving an injected laser beam in the optical rotation device, comprising deflection devices (11, 12, 13) between which the injected laser beams (S') rotate in the optical rotation device (10), an optical element (15) with which the injected laser beam (S') interacts during at least one rotation such that a beam property of the laser beam (S') is modified and an extraction device (14, 14') for extracting the laser beam (S') after carrying out a predetermined number of rotations with the interaction with the optical element (15) in the rotation device (10).

Description

OPTICAL ROTATING DEVICE AND ASSOCIATED METHOD

description

The invention relates to an optical circulating device for receiving a laser beam coupled into the optical circulating device and to a method for adjusting at least one beam property of a laser beam. The laser pulse duration and the q-parameter of a laser beam have a significant influence on the interaction of the laser beam with matter. In material processing by means of laser radiation, e.g. different Pulse duration regimes from each other, the differences in the types of interaction with the workpiece, the quality of the produced workpiece, the achievable machining geometries, the efficiency and the damage of the material have. The different interaction regimes are each for each material to be processed at different pulse durations of the laser pulse. Thus, e.g. When drilling or producing fine holes in metals with laser pulses that have a duration of a few picoseconds, very precise machining geometries can be generated (so-called cold ablation). With laser pulses lasting a few nanoseconds, processing is more efficient and faster, but results are less accurate. There are efforts in the industry to use, in terms of productivity, different interaction regimes for processing the same location of the workpiece, staggered in time, in order to combine the respective advantages. This requires a laser with changing laser pulse duration.

Alternatively, several different laser systems with different wavelengths, beam characteristics, processing optics, and process techniques may be used. In addition to the need to provide multiple laser systems, all the above parameters have a significant impact on the interaction process and the process result. A high quality Material processing can thus be determined approximately only over lengthy comparisons of different laser systems and thus ensured.

The differences in pulse duration regime apply not only to laser material processing in production, but also generally in research, metrology and various applications in fields such as materials processing, physics, chemistry, biology and medicine.

The invention is based on the object to provide a way to individually set at least one essential beam property of a laser beam independently of a preceding and a subsequent laser pulse.

This object is solved by the subject matters of the independent claims. Preferred embodiments are subject matters of the dependent claims.

One aspect relates to an optical circulating device for receiving a coupled into the optical circulating laser beam with deflection devices, between which the coupled laser beam circulates in the optical circulating device performs. The circulating device has an optical element with which the coupled-in laser beam interacts during at least one revolution such that at least one beam property of the laser beam is changed, in particular the pulse duration of the laser beam and / or the q parameter of the laser beam. Furthermore, a decoupling device is provided for decoupling the laser beam after a predetermined number of circulations have been carried out in interaction with the optical element in the circulating device.

Such a circulating device is designed as a resonator-external optical structure and may be similar to the structure of a laser resonator. The circulating device is designed and provided to receive a laser beam of a conventional laser, wherein the laser beam may be formed in particular as a pulsed laser beam and / or pulsed maritime light. The circulating device can, for example, as a ring resonator, as a Fabry-Perot resonator or be constructed resonator similar.

One or more deflection devices serve to guide the laser beam in the circulating device. As deflection devices, for example, mirrors, reflectors, prisms or the like may be provided. After a predetermined number of revolutions of the laser beam in the circulating device, the laser beam is decoupled from the circulating device.

In at least one revolution of the coupled-in laser beam in the circulating device, the optical element interacts with the laser beam. Thus, a beam property of the laser beam is gradually modified per revolution in interaction with the optical element. In this case, the optical element can be designed so that the pulse duration, the spectral composition, the chirp and / or the q-parameter of the laser beam is modified by the interaction. The optical element may e.g. GTI mirrors, chirped mirrors, gratings, waveguides, prism pairs, free air propagation (e.g., to alter the q parameter), a nonlinear element, particularly a self-phase modulation (SPM) element, and / or dispersive transmission bodies. The optical element may in particular comprise a plurality of components.

The optical element can be designed to set the diameter, the focal distance, the focus diameter and / or the divergence of the laser beam.

The circulating device thus serves to vary and set a beam property of the laser beam, in particular of a laser pulse. This can be used either to adjust the jet property directly or to compensate for fluctuations elsewhere in this jet property.

The optical element can be designed to influence the q-parameter of the laser beam. For this purpose, the optical element may be formed, for example, as a lens or as a curved mirror. With the circulating device, a jet property of the laser beam can be controlled / adjusted in accordance with the number of revolutions performed in the circulating device in interaction with the optical element. The thus adjustable or adjustable beam properties are thus discrete values. The number of different selectable beam property values corresponds to the number of maximum predetermined rotations that the laser beam can make in the orbiting device in interaction with the optical element. The decoupling mechanism is designed so switchable that when switching or activating the Auskoppelmechnismus the laser beam is coupled out of the circulating device. In this case, the switching time at which the coupling-out mechanism is switched determines or determines after how many revolutions the laser beam is coupled out. If the coupled-in laser beam interacts with the optical element, for example during each revolution, the switching of the coupling-out mechanism makes it possible to regulate or control how much the beam property of the laser beam is changed by interaction with the optical element. The decoupling mechanism may comprise, for example, an electro-optic modulator (EOM) (eg a Pockels and / or Kerr cell) and / or an acousto-optic modulator (AOM), and / or realized by mechanical movement of an optical component such as a glass or crystal body.

The circulating device is designed so that a laser beam performs a specific, specifically for each laser pulse independently of the preceding and the subsequent laser pulse individually adjustable number of cycles under interaction with the optical element in the circulating device. At a definable, controllable time, the laser beam is decoupled from the circulating device. This makes it possible that a beam property of the laser beam can be adjusted specifically.

The circulating device can in particular for modifying ultra short or short-pulsed laser radiation in the ns, ps, and / or fs range can be used. The circulating device may be completely static, so be formed without moving components and optics. As a result, a high switching speed can be achieved.

According to an embodiment, the optical element is arranged in the optical circulating device in such a way that the coupled-in laser beam interacts with the optical element during each rotation, whereby a beam property of the laser beam is changed. The total number of rotations that the laser beam makes in the optical circulator determines how much the beam property of the laser beam is changed in this embodiment.

According to one embodiment, an adjusting device of the optical circulating device is designed to set the number of revolutions at which the coupled-in laser beam interacts with the optical element. By controlling the setting device can be adjusted how many rotations the laser beam performs in interaction with the optical element and how many rotations the laser beam without interacting with the optical element performs. The interaction can be switched on and / or off for each circulation. The adjustment device can have, for example, an EOM and / or AOM with which the activation and / or deactivation of the interaction can be controlled. The interaction can take place, for example, as a function of the polarization of the laser beam, which can be influenced by the adjustment device. For this purpose, the portion of the circulating device in which the optical element is located may be formed as a polarization-dependent section of the circulating device. In particular, it can be adjusted with the adjusting device that the coupled-in laser beam interacts with the optical element during each revolution. According to one embodiment, the decoupling device of the optical circulating device has a Pockels cell and a polarization beam splitter. By controlling the Pockels cell, the polarization of the laser beam can be adjusted be that the laser beam is coupled out via the polarization beam splitter from the circulating device. A Pockels cell as a switching element has the advantage that it has a high switching speed and the beam quality has little effect. Thus, the number of revolutions, which performs the laser beam in the circulating device, can be adjusted quickly and accurately. A circuit of the Pockels cell takes place at a pre-definable or predetermined switching time, which corresponds to a predeterminable / predetermined number of revolutions in the circulating device. A Pockels cell is an electro-optical switch that is usually based on the Pockels effect, which is an electro-optic effect. If an electric field is applied to such a Pockels cell, it has different refractive indices for the E field components of the radiation flowing through it (birefringence). By controlling a Pockels cell thus the polarization of the light flowing through them can be influenced or adjusted, in particular the polarization direction of linearly polarized light can be switched so. Pockels cells regularly have a birefringent crystal. A Pockels cell in the sense of the present application may be based on a linear or non-linear electro-optical effect. Pockels cells are electrically switchable very quickly, so that for decoupling, for example, the polarization of the laser beam in the circulating device can be modified so that the laser beam is coupled out at a polarization beam splitter after a predetermined number of cycles from the circulating device. According to one embodiment, the decoupling device can be switched with a frequency in the MHz range. Thus, the circulating device can be used for setting and influencing beam properties of laser pulses, which are generated, for example, with high pulse repetition rates in the range between 10 Hz to 100 MHz. Even beam properties of such fast successive laser pulses can be set with the circulating device with single pulse precision. In particular, the time between repetitions, in which the laser beams are coupled as laser pulses in the circulating device, be greater than the orbital period of a Laser beam in the circulating device multiplied by the maximum number of cycles provided in order to separate the individual laser beams well. According to one embodiment, by interaction with the optical element, the pulse duration of the laser beam and / or the q-parameter of the laser beam are variable in dependence on the number of cycles performed in the circulating device in interaction with the optical element. These beam properties can be further changed per cycle. Depending on the design of the circulating device as many adjustment levels of the beam properties of the laser beam can be provided as circulations are individually adjustable. With a high number of adjustable circulations, the adjustment of the beam properties is thus quasi-continuous, preferably with about 20 to 100, about 80 to 300, about 280 to about 500 or about 20 to about 500 different adjustment stages. To allow a high number of cycles, the circulating device should be designed as low loss. If no compensation of the losses by an amplifier integrated in the circulation device (eg a gain medium) takes place, a maximum number of revolutions of 100 to be carried out in the circulation device should generally not be exceeded.

According to one embodiment, the optical element is designed as a dispersive element for compressing and / or extending the laser pulse duration of the laser beam. Thus, a laser pulse can be individually changed, in particular stretched and / or compressed, to obtain different selectable laser pulses, e.g. can be used for laser material processing. The laser pulse can thus be brought to a desired pulse length.

According to one embodiment, the optical element is designed as a nonlinear medium, in particular as a component for self-phase modulation (SPM). By interacting with an SPM, the laser beam is spectrally symmetrically extended by new frequency components. According to one embodiment, the deflecting devices are arranged so that the beam axis of the laser beam coincides with the orbital axis of the laser beam in the previous circulation during each revolution. The deflection devices are adjusted in such a way (exactly) that the beam axes of the laser beams coincide with each revolution. Thus, the geometric beam position, and in particular the propagation axis, is maintained at each revolution, while only the tunable beam property of the laser beam changes.

According to one embodiment, the circulating device is designed to influence a secondary light pulse for a laser amplifier. Thus, with an adjustable pulse duration, the seed pulse can thus be brought or changed to a desired pulse length. The pre-circuit of the circulating device in front of the amplifier resonator of the laser amplifier has the advantage that caused by the circulating device losses occur on the laser beam before the power build-up in the laser. Thus, these losses can be compensated in the construction of the laser power in a downstream laser amplifier. This embodiment may comprise the circulating device and a downstream in the beam path laser amplifier, in which the decoupled from the circulating device laser pulse is coupled as a seed light.

Alternatively, the circulating device may be configured to receive a laser beam that has been decoupled from a laser resonator. Thus, the circulating device for adjusting a laser beam is used, which is coupled out of a laser amplifier. This embodiment may comprise the circulating device and a laser amplifier arranged upstream in the beam path, wherein the laser pulse coupled out of the laser amplifier is coupled into the circulating device.

According to one embodiment, the decoupling device is also designed as a coupling device for coupling the laser pulse, which can be realized, for example, by the decoupling mechanism having a thin-film polarizer (TFP) beam splitter. According to one embodiment, the deflection device has two, three or four mirrors and / or prisms. Thus, the circulating device can be linearly stretched, triangular or square. Alternatively, the circulating device can also comprise significantly more mirrors, lenses and / or curved mirrors and / or have irregular geometries.

One aspect relates to a method for adjusting at least one beam property of a laser beam with the steps:

Coupling a laser beam into a circulating device,

Deflecting the coupled-in laser beam for a predetermined number of revolutions in the optical circulating device,

Interaction of the coupled laser beam in at least one circulation with an optical element such that at least one beam property of the laser beam is changed and

Decoupling the laser beam from the circulating device after a predetermined number of circulations in the circulating device in interaction with the optical element. The method can be carried out in particular with a previously described optical circulating device.

The invention will be described in more detail with reference to embodiments shown in FIGS.

Show it:

FIG. 1 is a schematic representation of an optical circulating device which is similar to a ring resonator;

FIG. 2 shows in a diagram the dependence of the pulse duration on the number of cycles performed in the circulating device, 3A shows a diagram of the temporal pulse progression of a laser pulse when coupled into a circulating device, FIG. 3B shows a diagram of the temporal pulse progression of a laser pulse after the first circulation in the circulating device,

FIG. 3C shows a diagram of the temporal pulse progression of a laser pulse after the hundredth revolution in the circulating device and FIG

FIGS. 4A and 4B are diagrams showing the beam radius in focus and the focal position of a light beam when using recirculating devices for setting the q-parameter of the light beam. Figure 1 shows a schematic representation of an optical circulating device 0, as an optical structure, which is externally formed by a laser resonator as an independent module. The optical circulating device 10 is designed substantially as a quadrangular optical structure that can be traversed by a laser beam. The quadrangular structure may e.g. be arranged horizontally and has at its four Umlaufeckpunkten three deflection devices 11, 12 and 13, which may be formed as a deflection mirror or deflection prism, and a coupling-out device 14, which, for. as a polarization beam splitter, e.g. as a TFP (thin film polarizer) may be formed. The circulating device 10 shown in Figure 1 is an exemplary embodiment. Other circulating devices according to the invention may additionally or alternatively comprise lenses and / or curved mirrors and be arranged in different geometries (for example a substantially triangular, pentagonal or linear structure).

The decoupling device 14 further comprises a switching element 14 ', which is formed, for example, as a Pockels cell. The combination of a Pockels cell as a switching element 14 'together with a thin film polarizer (TFP) as decoupling device 14 serves as a switching element for coupling out a laser beam from the circulating device. In the beam path of the optical circulating device 10, an optical element 15 is further arranged, which interacts with a coupled into the circulating device 10 laser beam at each revolution. The optical element 15 may be formed, for example, as a GTI mirror (with anomalous dispersion), as a chirped mirror (with anomalous dispersion), as a lattice, as a prism pair, as a non-linear element or as a dispersive transmission element. The optical element 15 may further comprise a medium of normal chromatic dispersion, such as an undoped YAG rod with Brewster ends or AR coatings on its facets. By grid pairs as the optical element 15, a high dispersion can be achieved. The optical element 15 may alternatively or additionally be designed such that it interacts with the coupled-in laser beam with each revolution in such a way that it alters and / or influences the q-parameter of the laser beam.

In the beam path of the circulating device 10, a plurality of different or identical optical elements 15 of the aforementioned type can be arranged.

At the decoupling device 14, a laser beam S can be coupled into the circulating device 10. The decoupling device 14 is thus at the same time formed as a coupling device. If the decoupling device 14 is designed as a polarization beam splitter, only laser radiation of a first polarization is coupled into the circulating device. The coupled laser beam S 'passes through the circulating device 10, wherein it is deflected at the highly reflective deflecting devices 11, 12 and 13 in each case by 90 °. By controlling a Pockels cell as a switching element 14 'is controlled whether the injected laser beam S' is reflected back on the Auskoppelmechanismus 14 for another circulation in the circulating device 10 or on Auskoppelmechanismus 14 from the circulating device as decoupled Laser beam S "is decoupled.

During the first revolution, the Pockels cell can be switched to a λ / 2 voltage, so that the coupled-in laser beam S 'at the Pockels cell is repolarized to a second polarization. The re-polarized laser beam S 'is reflected at the thin-film polarizer and remains in the circulating device 10. After the first revolution, the Pockel cell is turned off and causes no polarization change in the following rounds of the coupled laser beam S'. The coupled laser beam S 'now circulates the circulating device 10 until a λ / 2 voltage is again applied to the Pockels cell and the laser beam S' is coupled out of the circulating device 10 at the thin-film polarizer 14. The mechanism for coupling and uncoupling the laser beam into and out of the optical circulating device is similar to the coupling mechanism of a regenerative laser amplifier.

This can be controlled by the switching of the switching element, the number of revolutions, which remains the coupled laser beam S 'in the circulating device 10. Depending on the number of revolutions performed in the circulating device 10, the laser beam S 'is caused to interact with the optical element 15 by e.g. added a different degrees of dispersion.

The circulating device 10 may incorporate other optical components, such as e.g. a compensation gain medium for compensating for a loss when circulating in the circulating device 10. The circulating device 10 may be formed in particular also gain medium free.

For many other applications, the run length through a Pockels cell should be kept as short as possible to minimize nonlinear effects and pulse broadening. In the circulating device 10, such side effects as passing through the Pockels cell can be exploited to obtain a reinforcing effect of the dispersion. The optical element 15 may alternatively or additionally be designed to influence the q parameter of the coupled-in laser beam S '. In this case, the coupled-in laser beam S 'interacts with the optical element 15 with each rotation in such a way that two decoupled laser beams S ", which have performed a different number of revolutions in the circulating device 10, have traveled two different optical distances The different optical paths mean that the real part of the q-parameter changes depending on the cycles traveled in the circulating device.

The influence on the q parameter can be significantly enhanced and / or mitigated by the use of lenses and / or curved mirrors as the optical element 15. Through the use of optical components, the imaginary part of the q-parameter can additionally be adjusted and controlled by switching the circulating device.

The optical circulating device 10 shown in FIG. 1 represents an embodiment in which the coupled-in laser beam S 'interacts with the optical element 15 during each revolution. In an alternative embodiment of a circulating device, it is possible to set by means of an adjusting device arranged in the circulating device whether one or more revolutions of the laser beam are carried out under interaction or without interaction with the optical element 15.

Figure 2 shows the operation of a circulating device with a dispersive element as the optical element 15 in a diagram. The dependency of the pulse duration on the number of round trips carried out in the circulating device is shown, wherein FIG. 2 shows the result of a numerical simulation for the pulse development.

The boundary conditions for the simulation were a seed laser with a pulse length of 100 fs and the pulse shape of a soliton (sech ² pulse) with time-bandwidth limitation used. The pulse energy is 40 nJ. In a circulating device in the form of a linear resonator 16 bounces per direction (ie 32 bounces per revolution, which corresponds to a circulation on the x-axis) are provided on the surface of a GTI with D2 = 2000 fs ² . Per circulation results in an energy loss of 0.5%. After the 100th round, the laser beam has a pulse length of 127 ps. From the start pulse length to the target pulse length at 127 ps, the pulse duration changes almost linearly as the number of revolutions increases. The spectrum and the pulse shape experience almost no change.

The associated pulse shapes are shown in FIGS. 3A to 3C. FIG. 3A shows in a diagram the temporal pulse progression of a laser pulse S during coupling into a circulating device, as it were as pulse # 0. FIG. 3B shows in a diagram the temporal pulse progression of a laser pulse S- after the first circulation in the circulating device as pulse # 1 and FIG. 3C shows in a diagram the temporal pulse progression of a laser pulse Sioo 'after the hundredth circulation in the circulating device as pulse # 100. In this case, the pulse # 0 shown in FIG. 3A has a pulse duration of 100 fs with a pulse peak power of 353 kW (40 nJ). The pulse # 1 shown in FIG. 3B has a duration of 1.29 ps with a pulse peak power of 27.3 kW (39.8 nJ). The pulse # 100 shown in Figure 3C has a duration of 127 ps with a pulse peak power of 169 W (24.2 nJ). In FIG. 3C, the two diagram axes were rescaled in comparison to the diagram axes of FIGS. 3A and 3B.

It may be disadvantageous that in successive laser pulses by the different numbers of cycles performed in the circulating device, a timing jitter arises because the laser pulses are no longer forwarded in a precisely constant repetition. This results from the different optical path length of the speed of light Revolutions of the individual laser beams. While this variation is very small, for some applications the timing jitter may be critical and compensated for by a second circulating device downstream of the first circulating device. This second circulating device does not have to have an optical element but only serves to compensate the path difference by a corresponding number of further circulations. In this case, the two circulating devices are controlled such that each laser beam has traveled the same optical path length after passing through the first and second circulating device. In an optical circulating device with an adjusting device, with which the interaction with the optical element for the individual revolutions is switched on and / or off, an optical path difference between laser beams can be compensated by a corresponding number of cycles performed without interaction with the optical element. By a second circulating device, a fine adjustment of the laser radiation can be carried out by, for example, an optical element with a lower dispersion compared to the first circulating device is arranged in the second circulating device. A second circulating device may alternatively or additionally be used to compensate for a cycle number dependent power loss. This can be effected, for example, in that the second circulating device has the same loss per revolution as the first circulating device, each laser beam executing a corresponding compensation number of circulations in the second circulating device such that after passing through the first and second circulating devices, all the laser beams are the same Have experienced loss.

A circulation device for setting the q-parameter can be used, for example, within a telescope structure according to Kepler or Galileo. For this purpose, the circulating device is introduced between lenses and / or curved mirrors of a telescope. In this case, the circulating device can be arranged, for example, after or in front of a beam guide with a machining position-dependent variable length. The circulating device can be arranged, for example, before or after a focusing lens of the telescope.

Figures 4A and 4B show in a diagram the result of an application example of two circulating devices in a Kepler telescope. In this case, the propagation length is varied in the range of 1000 mm to 3000 mm between the two telescope lenses by means of a first circulating device, which is plotted on the y-axis in the three-dimensional diagram shown in Figure 4A. For a second orbital adjustable propagation length of 0 to 1500 mm after the telescope assembly, shown on the x-axis, the beam radius for an input beam having a predetermined q-parameter passes through a focus plotted on the z-axis.

The result is shown in the form of a diagram in FIG. 4B: The position of the focus f (in mm) shifts in this example between about 545 mm and 950 mm, while the beam radius Rs (in pm) in focus f changes less than 10% experiences. The beam radius varies between 365 pm and 405 pm. Thus, the size of the beam radius Rs in the focus f varies relatively little, although the position of the focus f shifts comparatively far by several centimeters.

LIST OF REFERENCE NUMBERS

10 circulating device

11 deflection device

12 deflection device

13 deflection device

14 decoupling device

14 'switching element

15 optical element

S external laser beam

S 'coupled laser beam

S "decoupled laser beam Focus position beam radius

Claims

Patent claims

1. Optical circulation device for receiving a laser beam coupled into the optical circulation device (10).

Deflection devices (11, 12, 13), between which the coupled laser beam (S') carries out revolutions in the optical circulation device (10),

an optical element (15) with which the coupled laser beam (S') interacts during at least one revolution in such a way that at least one beam property of the laser beam (S') is changed and

a decoupling device (14, 14') for decoupling the laser beam (S') after carrying out a predetermined number of revolutions while interacting with the optical element (15) in the circulation device (10).

2. Optical circulation device according to claim 1, wherein the optical element (15) is arranged in the optical circulation device (10) such that the coupled laser beam (S ') interacts with the optical element (15) during each revolution.

3. Optical circulation device according to claim 1 or 2, wherein an adjusting device of the optical circulation device (10) is designed to

Set the number of revolutions during which the coupled laser beam (S ') interacts with the optical element (15).

4. Optical circulation device according to at least one of the preceding claims, wherein the decoupling device (14, 14 ') has a Pockels cell (14') and a polarization beam splitter (14).

5. Optical circulation device according to at least one of the previous ones Claims, wherein the decoupling device (14, 14 ') can be switched with a frequency in the MHz range.

6. Optical circulation device according to at least one of the preceding claims, wherein by interaction with the optical element (15).

Pulse duration of the laser beam (S ') and / or the q parameter of the laser beam (S') can be changed depending on the number of revolutions carried out in the circulation device (10) in interaction with the optical element (15).

7. Optical circulation device according to at least one of the preceding claims, wherein the optical element (15) is designed as a dispersive element for compressing and / or stretching the laser pulse duration of the laser beam (S ').

8. Optical circulation device according to at least one of the preceding claims, wherein the optical element (15) is designed as a non-linear medium, in particular as SPM.

9. Optical circulation device according to at least one of the preceding claims, wherein the deflection devices (11, 12, 13) are arranged so that the beam axis of the laser beam (S ') during each revolution coincides with the beam axis of the laser beam (S') of the previous revolution . 0. Optical circulation device according to at least one of the preceding claims, wherein the circulation device

(10) is designed and provided for influencing a seed light pulse for a laser amplifier.

11. Optical circulation device according to at least one of the preceding claims, wherein the decoupling device is also designed as a coupling device for coupling in the laser pulse.

Optical circulation device according to at least one of the preceding Claims, wherein the deflection device has two, three or four mirrors and / or prisms

13. Method for adjusting at least one beam property of a laser beam with the steps:

Coupling a laser beam (S) into a circulation device (10), deflecting the coupled laser beam (S ¹ ) for a predetermined number of revolutions in the optical circulation device (10), interaction of the coupled laser beam (S ') with an optical one during at least one revolution Element (15) in such a way that at least one beam property of the laser beam (S') is changed and coupling out the laser beam (S') from the circulation device (10) after carrying out a predetermined number of revolutions in the circulation device (10) with interaction with the optical Element (15).