EP3195430A1

EP3195430A1 - Q-switched co2laser material machining system comprising acousto-optic modulators

Info

Publication number: EP3195430A1
Application number: EP15787282.1A
Authority: EP
Inventors: Gisbert Staupendahl
Original assignee: Feha Lasertec GmbH
Current assignee: Feha Lasertec GmbH
Priority date: 2014-09-18
Filing date: 2015-07-22
Publication date: 2017-07-26
Also published as: KR20170056633A; JP2017535063A; WO2016042387A1; CN107005019A; US20170310070A1; DE102014013567B3; US10224689B2

Abstract

The invention relates to a Q-switched CO₂laser material machining system comprising acousto-optic modulators (AOM) which are used inside the resonator for Q-switching the CO₂ laser as well as externally for extremely efficiently suppressing radiation feedback between the laser and the workpiece. The essential idea is to specifically take into account the frequency shift of the radiation which is diffracted on the AOM and corresponds exactly to the exciting frequency of the acoustic wave in the AOM crystal, in order to amplify radiation in the active medium. Since said frequency shift significantly reduces the amplification of the radiation, same has to be prevented during the Q-switching process; for this purpose, according to the invention, two AOMs are used which have the same exciting frequency but propagate the acoustic waves in opposite directions in the crystal. In contrast thereto, the frequency shift has an advantageous effect on the suppression of radiation feedback between the laser and the workpiece if, according to the invention, an AOM is placed between the laser output and the workpiece, said AOM having a specific minimum exciting frequency for the acoustic wave such that the wave propagating back into the laser undergoes virtually no amplification by the active medium when the beam diffracted on the AOM is used as the working beam.

Description

Q-switched C0 ₂ laser material processing system with acousto-optic modulators

Field of the invention

The invention relates to a Q-switched C0 ₂ laser material processing system with acousto-optical modulators (AOM) for beam shaping.

Prior art and background of the invention

Numerous technologically relevant

Material processing tasks can be solved very efficiently with C0 ₂ lasers of a wide variety of concrete designs. Frequently, however, these tasks are bound to pulsed radiation, such as drilling with high

Quality requirements. But here lies a certain weak point of the known commercially available C0 ₂ lasers: Their pulse intensity is considerably limited by the wavelength range of the radiation in the infrared by about 10 μτ, because there are only a limited number of optically transparent materials which are used for

Modulation, in particular the Q-switching, at the high levels required for laser material processing

average powers are suitable. In addition to mechanical switches with their known disadvantages, almost exclusively acousto-optic modulators (AOM) based on germanium and electro-optical modulators (EOM) based on CdTe are used for the Q-switching of modern C0 ₂ lasers Application, but with relatively narrow limits in terms of achievable average power in the long-standing conventional resonator design. One way out of this conflict is the Q-switched C0 ₂ laser system described in WO 2013/113306 A8, which, in principle, permits average powers of Q-switched C0 ₂ laser systems down to the kW range.

Technical problem of the invention

The aim of the invention is to provide a C0 ₂ ~ laser material processing system, on the one hand by means of

Acousto-optic modulators (AOM) Q-switched and on the other hand by means of another AOM, which is located externally, ie outside the laser resonator, extremely efficiently decoupled from radiation that is reflected from the workpiece.

Broad features of the invention and preferred

embodiments

To solve this technical problem, the invention teaches the subject matter of claim 1. Preferred

Embodiments are specified in the dependent claims.

In the context of the invention, only the use of AOM in as powerful as possible, u.a. for the

Laser material processing suitable, Q-switched C0 ₂ - viewed laser systems, with the external, ie Beam shaping taking place outside the laser resonator, in particular the isolation of the laser from radiation reflected from the workpiece, is also included. in the

Center of the invention is a factor that i.a. is neglected, namely the frequency shift of the diffracted at the AOM beam, which has its cause in the diffraction on a moving grid and the frequency with which this running grid is generated. If one uses the diffracted beam, which is often useful or even necessary for reasons explained below, this fact has a decisive influence on the effect of the amplifying active medium on the radiation with positive and negative aspects. To understand the solution according to the invention, the relationship between the spectral width of the gain profile of the active medium and the influence of the radiation frequency in the diffracted beam of an AOM must be considered in more detail. This will also be described in more detail with reference to the figures showing merely exemplary embodiments

explained which are referred to in detail below.

As is well known, in Bragg diffraction on the current grating in the AOM, the frequency _f0M at which this grating is generated by the transducer _imposes additive or subtractive on the frequency f of the lightwave impinging on the AOM, depending on the running direction of the grating, so that for the resulting Frequency f _{B of} the diffracted wave is: fß = f -tfflOM · How does this frequency-shifted wave interact with the active medium, ie how does the shift affect the gain? In the C0 ₂ laser, it is mainly two line broadening mechanisms that determine the gain profile g (f - f ₀ ), the Doppler broadening and the

Pressure broadening.

The Doppler broadening as inhomogeneous

Line broadening yields a Gaussian profile for the gain profile g (f - f ₀ ) according to the function g (f - fo) _G = (irIn 2) _f -exp [- In 2]

with the resonance frequency f ₀ and the half-value width Af. FIG. 1 illustrates how the gain decreases relative to the maximum value at f = f ₀ with increasing frequency shift with respect to the resonance frequency. If f _Ä0 and Af are of the same order of magnitude, this fact gets decisive

Meaning for the function of the laser system.

The pressure broadening as a homogeneous line broadening results in the gain profile of a Lorentz profile according to the function

As shown in FIG. 2, the gain reduction here has a very similar behavior as in the case of Doppler broadening, when again f _A0 M and Δί are of the same order of magnitude. It should be noted that for low pressure C0 ₂ - Laser to about 30 mbar Doppler broadening is dominant, with medium and high pressure lasers above 100 mbar pressure broadening plays an increasing role. In any case, it can be assumed that at the typical AOM frequencies in the range 40 MHz and more, the resulting frequency shift of the diffracted

Radiation bundle significantly reduces the gain of this bundle in the active medium. A simple one

Consideration should illustrate this.

Assuming lossless amplification in an active medium of length z, if a power Po enters the medium with the gain g in the case of

Small signal gain the power P (g) at the output according to

P (g) = P ₀ exp (gz). The relative gain P (g) / Po is shown in FIG. 3 as a function of the product gz. Since the small signal amplification is typically in the range 10 ⁴ to 10 ⁶ in high-power C0 ₂ lasers, it can immediately be seen that relatively small reductions in the gz (z is assumed to be constant) by, for example, a factor of 2 from 10 to 5 to a decrease in gain by two

Orders of magnitude from 10 ⁴ to 10 ² lead. Such

Decreasing g by a factor of 2, however, already results in frequency shifts of the radiation interacting with the active medium from the resonance frequency f ₀ by Af / 2 (see FIGS. 1 and 2). In the case of typical low-pressure C0 ₂ laser is the

Doppler broadening and thus Δί of the gain profile at about 60 MHz, i. a frequency shift of 30 MHz (the usual frequency ranges of AOM are 40 MHz and more) already reduces g by a factor of 2 and thus the small-signal amplification of the active medium by a factor of about 100.

The following explains the importance of using AOM in a C0 ₂ laser material processing system. Following the aim of the invention, two cases with completely different requirements must be distinguished. For the sake of illustration, FIGS. 5 and 9 can be used.

1. The Use of AOM for Q-Switching of the C0 ₂ Laser In general, the simplest variant is used, in which the AOM for the Q-switching between the active medium and a resonator end mirror is arranged and the undiffracted, transmitted beam is fed back. It fails, however, if, first, the

Diffraction efficiency of the AOM is not sufficiently high and / or secondly, the gain of the active medium is so high that complete suppression of the laser function in the desired pulse pauses by activation of the AOM, i.

Switching on high diffraction losses becomes impossible. This situation is quickly reached, considering the huge small signal amplifications mentioned above, which already occur after a few tens of ps with continuous pumping of the active medium, if no inversion degradation

he follows. As a result, the occurrence is statistical Radiation peaks in the actual pulse break (see Fig. 4), a controlled Q-switching is not possible.

To adjust the contrast ratio "On" - "Off" of the

It makes sense to use the diffracted beam of the AOM for the feedback because it disappears completely when the AOM is deactivated, a parasitic oscillation of the laser is reliably suppressed even with very high population inversions. But this seemingly simple solution has a big problem, namely the one above

discussed frequency shift of the diffracted beam! If one takes as a typical example diffraction on one

current grid generated at 40 MHz,

shifts the radiation frequency by exactly this 40 MHz in a diffraction process. Since the grid in the

If feedback is passed twice in the same direction, the result is a frequency shift of even 80 MHz. The

Doppler width of the gain profile of a low-pressure C0 ₂ - laser is only about 60 MHz, ie the diffracted and returning back to the active medium radiation finds a very low gain before (see Fig. 1) and is therefore only very weak amplified (see Figure 3), an efficient laser function is not possible.

The solution to this problem according to the invention consists in the use of an AOM tandem, ie a first AOM divides the incoming beam into transmitted and diffracted portions, a second AOM positioned directly behind it is arranged such that firstly the diffracted portion returns to the optimum Bragg angle secondly, and secondly, the effective direction of the Grid running in the two AOM is exactly opposite, so that the effective frequency shift of the above

For example, once +40 MHz and once -40 MHz, so in the sum is 0. The returning beam finds analogous conditions and the feedback beam, which diffracts four times in total, comes along

Frequency shift 0 back into the active medium, finds optimal gain and normal laser function is possible.

This principle even works if you go to

Simplification of the control only with an AOM the

Modulates power and runs the second AOM continuously, i. The latter serves practically only to compensate for the frequency shift of the first AOM, with which the actual Q-switching is performed. The use of an AOM tandem according to the invention therefore firstly ensures complete suppression of parasitic feedbacks in the laser and secondly completely free

Controllability of the pulse parameters within the scope of the AOM switching times.

2. AOM insert for highly efficient suppression of the radiation feedback workpiece laser

A second critical point for a Q-switched C0 ₂ laser is in any case the radiation feedback from the workpiece into the laser. This can reach considerable values, especially in highly reflective materials such as copper or aluminum and flat workpiece surfaces, which far exceed 10% of on the workpiece may be falling radiation power. The usual method for the solution of the consequent problems, ie the realization of a clean laser function with

"Laser-based" wavefront formation, which is determined by the selected resonator configuration is the

Integration of a combination of ATFR mirror (Absorbing Thin Film Reflector) and λ / 4 phase shift mirror into the beam path between laser output and workpiece.

This even has a double function, in addition to the

Radiation decoupling the often desired circular

Polarization of the current to the workpiece radiation is generated. This form of decoupling is e.g. in cw operation of the laser, in which continuously reduces the inversion and maintained at a relatively low level, completely sufficient. But you work with it

Quit, rise in the pulse breaks

Occupancy inversion and thus gain by orders of magnitude, the small signal gain reaches the above values and even the smallest feedback

Radiation amounts are sufficient to become parasitic

Oscillations of the laser lead and the

Sensitive to disturbing quality control process. Here fails the said system, since even with optimal adjustment certain radiation components, which may well be in the percent range of radiation to the workpiece, run back into the laser. The sequence illustrates e.g. Fig. 4: While the left image without workpiece, ie without

Radiation feedback, a clean pulse generation of the Q-switched laser shows results when introducing a workpiece, so with a more or less large radiation feedback, shown in the right image Situation, that after the momentum impulse and a certain pause, in which the inversion until the

building critical value, parasitic oscillations

begin, which make the desired laser function impossible.

The inventive solution to this problem is again based on the frequency shift of the diffracted beam in an AOM. This time this effect is used to a positive effect in the following way. Immediately after the laser output, an AOM is arranged so that the linearly polarized radiation is optimally diffracted. This diffracted radiation component, which again has the described frequency shift, is sent to the workpiece for processing. It should be noted that

Frequency shifts of eligible

Magnitude does not affect the

Have material processing itself. Reverberated

Radiation components (reflected or scattered) hit the AOM a second time, the frequency shift

doubles up. Now occurs this frequency

modified beam into the active medium, is his

Effect on the population inversion quasi zero, since it is practically not reinforced. Specifically, this means with the parameters mentioned above 40 MHz and Af = 60 MHz that returns to the resonator

Radiation amplified by more than 4 orders of magnitude less than resonant radiation of frequency f ₀ .Zur

Illustrating the huge difference to

classical decoupling, let's review the amplified power P (g): P (g) = P ₀ x exp (gz)

l l

"ATFR + λ / 4" "AOM"

In the decoupling variant "ATFR + λ / 4-phase shifter", the parameter P _{0 is} influenced and P (g) is proportional to the change of P _0. In contrast, in the solution according to the invention, the changes in the g go into the

Exponential function, so that even comparatively small reductions in g make up several orders of magnitude in gain.

The specifics of AOM deployment in a C0 ₂ laser material processing system in accordance with the invention will now be described with reference to two embodiments disclosed in the

The following drawings are shown schematically, will be explained in more detail. These show: FIG. 1: Relative gain as a function of

Frequency shift for Gaussian profile

Figure 2: Relative gain as a function of

Frequency shift for Lorentz profile

Figure 3: Relative gain in the active medium as

Function of g z

FIG. 4: For radiation feedback of workpiece - laser:

Left without, right with workpiece Figure 5: C0 ₂ laser with AOM Q-switching

FIG. 6: The function of an AOM tandem for the Q-switching FIG. 7: For suppressing the radiation feedback

Workpiece laser by means of AOM

FIG. 8: Complete decoupling by means of AOM, ATFR and λ / 4

- Phase shifter

FIG. 9: AOM insert in a C0 ₂ laser according to FIG

Patent WO 2013/113306 A8

FIG. 10: Example for suppressing the

Radiation feedback workpiece laser by means of

AOM at 4 partial beams

Fig. 5 shows schematically a first embodiment, which is based on the basic structure of a conventional

Q-switched C0 ₂ laser, for which a linear arrangement of the resonator "100% end-mirror - active medium - good-humidification element - decoupling plate" is typical The illustration shows the unit for feedback I, which is arranged at the one end of the active medium and the adjoining, highly schematic unit II, which shows the beam guidance from the laser to the workpiece As noted above, when using an AOM as a Q-switching element, two problems are encountered

transmitted beam, so the 0th order back. Then it will not be possible with a powerful laser be suppressed, the laser function at maximum population inversion, since the diffraction efficiency of conventional AOM for C0 ₂ laser is little more than 90% and thus the maximum losses introduced are not high enough. Or one couples the diffracted beam, ie the 1st order of diffraction back to the problem of the frequency shift and the resulting drastically reduced gain.

The problem is solved according to the invention by the tandem arrangement of two AOMs shown in FIG. 5 and explained in more detail in their function in FIG

Q-switching element. In this case, the jet 8 coming from the direction of the active medium 1 drops to a first AOM 2 which, when a corresponding switching voltage is applied, deflects this beam into the 1st Bragg diffraction order.

This beam 9 falls on a second AOM 3, which generates the diffracted beam 10 when the switching voltage is applied. After partial reflection at the adjusted

Auscooppelplatte the beam runs back exactly (rays 11, 12 and 13) and provides the feedback that is required for the laser function. Crucial to the proper functioning of this AOM tandem are two factors: First, both AOMs must be exactly the same

Have excitation frequency for the diffraction grating and

second, the directions of movement of both grids

be opposite. The concept of exactly the same

Excitation frequency refers in particular

Frequencies whose difference is at most 100 ppm (relative to the higher frequency), in particular not more than 10 ppm,

preferably not more than 1 ppm or 0.1 ppm. Then the resulting frequency shift is the feedback one Beam 0 as needed. The respective back and forth shifts of the frequencies by 5f as well as the

successive decrease of the power P of the beams 8 - 13 by the diffraction at the AOM make the assigned representations of the qualitative dependences g (f) and P as a function of f clear.

As already explained above, there is a further latent threat to the proper Q-switching operation of the considered CC> 2 laser in the feedback of radiation from the workpiece to be machined into the laser. To their extremely efficient suppression according to the invention, a third AOM 5 immediately after

Laser output coupling 4 arranged. In the beam path to the workpiece can still optionally a unit 6 for further beam shaping, in particular for generating the desired for many applications circular polarization of the radiation on the workpiece 7 and for compensation (eg by means of cylindrical lenses) often typical for AOM slightly elliptical distortion of the beam, to get integrated.

Figures 7 and 8 illustrate the suppression of the radiation feedback again in detail. Fig. 7 focuses on the effect of the frequency shift according to the invention. The decoupled beam 16 falls on the third AOM 5, which sends the diffracted and frequency-shifted by 5f beam 17 on the workpiece upon application of the switching voltage. The thrown back from there

(reflected or scattered) radiation 18 is diffracted a second time in the AOM 5 and suffers a second Frequency shift, so that ultimately the 25f frequency-shifted beam 19 in the direction of coupling plate

4 of the laser is running. Analogously to FIG. 5, the qualitative dependencies g (f) and P were also indicated in FIG. 6 as a function of f. According to the invention, the AOM 5 must be selected such that the double frequency shift 25f is at least of the order of the half-width Δί of the gain profile. Here, the term "order of magnitude" denotes that the ratio 2δί / Δί should preferably be in the range from 1:10 to 100: 1, in particular from 1: 1 and / or to 10: 1.

An essential factor of the arrangement according to the invention is the fact that the usual conversion of the linearly polarized radiation of the laser in circular

polarized by a rear AOM 5 arranged λ / 4 phase shifter is easily possible. It is also possible to additionally introduce the classical decoupling beyond this into the beam path by means of a combination of "ATFR mirror - λ / 4 phase shifter." Such a "complete version" is illustrated in FIG

5 diffracted beam 22 with vertical linear polarization 23 passes through the polarization-dependent absorber 20 (in practice ATFR) virtually lossless and is then in the λ / 4-phase shifter 21 in the beam 24 with circular

Polarization 25 transformed. After interaction with the workpiece 7, a certain proportion 26 of this circularly polarized radiation travels back towards the laser. When passing through the λ / 4-phase shifter 21, it is in a beam 27 with linear horizontal polarization 28th

transformed when interacting with the polarization-dependent absorber is largely destroyed. A now already very much weakened residual beam 29 then hits again on the AOM 5 and in the sum of the summarized below again loss processes for the to be destroyed returning beam results in an extremely good decoupling of the laser of this

Radiation:

1. As shown above, the AOM 5 shifts the diffracted beam frequency by 5f from the workpiece

thus returning radiation by 25f. What was detrimental to the QoS AOM is here

Giant advantage - the radiation returning to the laser is only minimally amplified.

2. The decoupling effect of the combination "ATFR mirror - λ / 4-phase shifter" remains fully preserved.

3. A third decoupling effect comes thereby

concluded that the returning radiation through the

Phase shifter is polarized perpendicular to the outgoing polarity and therefore diffracted by the AOM 5 only ineffective, d. H. less radiation is going towards the laser. The combination of these three effects, which are purely stationary and do not require any special timing of the AOM 5, leads to the arrangement according to the invention reducing the return radiation by many

Magnitudes weakens, so that even with maximum gain in the active medium and at maximum feedback (z. B. by highly reflective metals such as copper) no parasitic oscillations occur.

Regardless of this systemic decoupling according to the invention, of course, the AOM

Function as Fast Switch with switching times less than 1 fully utilized, i. with appropriate control of virtually every single pulse coming from the laser

Desire to be influenced.

In the embodiment described above, the two AOM for Q-switching directly to the resonator-internal radiation field with its always present

Performance over the decoupled

Laser power exposed. Such laser systems are limited to average output powers of a few hundred watts because of the relatively low radiation load of germanium. As noted above, this provides

Principle of the laser according to WO 2013/113306 A8 a way out of this dilemma and allows medium

Output power up to the kW range. The in

However, the problem area described above also remains fully valid for this type of laser, and in order to make full use of its potential possibilities, the solutions according to the invention are particularly useful.

This situation will be briefly discussed in a second embodiment. Fig. 9 shows the principal difference from the first embodiment. It consists here above all in the changed outcoupling of the

Laser beam over a thin film polarizer (thin film Polarizer - TFP) 30. The TFP 30 shares the weak

Elliptically polarized, coming from the active medium radiation into a powerful, perpendicular to

Drawing plane polarized beam that is decoupled, and a relatively weak, in the plane of the drawing

polarized beam fed back on. As a result, the radiation load on the responsible for the Q-switching AOM tandem 2, 3, even at relatively high output power is relatively low. The effects of units I and II are otherwise the same as described above. Only the coupling-out plate 4 is here replaced by a 100% end mirror 46. In this illustration, it should be noted that because of the

Polarization dependence of the AOM function of the third AOM 5 real by 90 ° to rotate about the beam axis is off

For clarity, it was omitted in Fig. 9.

With respect to this second embodiment, the following aspect will be discussed. As mentioned, the laser of FIG. 9 is typically characterized by relatively high average powers. If you now assign the external AOM 5 directly to the laser output, the usable average power would be due to the relatively low

Radiation resistance of the germanium crystal

severely limited, the benefits of the laser could not be fully exploited. Here is an often used in practice arrangement variant to, with

High power lasers work as efficiently as possible - the defined beam splitting. ZnSe-based beam splitters are loadable up to the kW range and therefore suitable, for example, a beam of the middle

Power 1.2 kW divided by a splitter cascade into 4 partial beams of 300 W, which are well tolerated by an AOM (see Fig. 10). This requires z. B. in the variant shown in Fig. 10 three

Beam splitter 32, 33 and 34, preferably with a

Divisor ratio of 50:50, and three

Deflection mirror 35, 36 and 37. Each sub-beam 38 to 41 then receives its own AOM 42 to 45. A prerequisite for the use of this method is, of course, that the respective desired application with the partial beams is feasible.

LIST OF REFERENCE NUMBERS

1 active medium

2 First AOM

3 Second AOM

4 coupling plate

5 Third AOM

6 beam forming unit

7 workpiece

8 back-coupling beam

9 beam after diffraction at the first AOM

10 beam after diffraction at the second AOM

11 Beam reflected at output plate

12 Return beam after diffraction at the second AOM

13 Return beam after diffraction at the first AOM

14 Direction of the 0th diffraction order of the first AOM

15 direction of the 0th diffraction order of the second AOM 16 decoupled laser beam

17 laser beam after diffraction at the third AOM

18 Radiation reflected back from the workpiece

19 Radiation reflected back from the workpiece after diffraction at the third AOM

20 polarization-dependent absorber (ATFR)

21 λ / 4-phase shifter

22 Beam diffracted at the third AOM

23 Horizontal polarization direction

24 Beam impinging on workpiece

25 circular polarization

26 Radiation reflected back from the workpiece

27 Radiation reflected back from the workpiece after passing the λ / 4 phase shifter

28 Vertical polarization direction

29 Ray strongly weakened by ATFR

30 thin film polarizer (TFP)

31 laser beam

32, 33, 34 beam splitter

35, 36, 37 deflection mirror

38, 39, 40, 41 partial beams

42, 43, 44, 45 Acousto-optic modulators f Radiation frequency

fo resonance frequency of the active medium

f _B Frequency of the diffracted wave

fAOM Frequency of the sound wave in the Ge crystal

g gain of the active medium

P radiation power

Po radiation power at the entrance of the active medium

P (g) Radiation power as a function of gain z length of the active medium

AOM acousto-optic modulator

ATFR AbsorbingThin Film Reflector

cw Continuous radiation ("continuouswave")

EOM electro-optical modulator

TFP Thin Film Polarizer

Af frequency half width of the gain

5f frequency shift of the diffracted beam λ wavelength

Claims

claims

Q-switched C0 ₂ laser system, in particular C0 ₂ - laser material processing system, with AJustooptic modulators (AOM) for beam shaping, characterized in that a) for the Q-switching two successively and preferably near a Resonatorendspiegel (46) or a laser output plate (4) arranged AOM ( 2, 3), by the same excitation frequencies and

opposite propagation directions of

are arranged in the crystal, are arranged with the proviso that one on the first AOM (2) incoming beam (8) diffracted, a resulting diffracted beam (9) on the second AOM (3) diffracted again and this from the twice diffraction resulting bundles (10) after reflection at the Resonatorendspiegel (46) or the

Laser output plate (4) ^{■ is} thrown back into itself and fed back as a bundle (11), (12) and (13) after each diffraction again at the two AOM (2) and (3) in an active medium (1) and thus

Laser function is realized when a corresponding switching voltage to the two AOM (2) and (3) applies and when switching off this voltage, the laser function is interrupted and b) a product produced in this way and by means of a

Decoupling element (4, 30) coupled out laser beam

(16) before its application, preferably for

Laser material processing, by a third AOM (5) is sent, the outside of the resonator and preferably immediately behind the decoupling element

(4, 30) is arranged, wherein the application of the by means of a corresponding switching voltage at the third AOM (5) diffracted beam (17) is used and the excitation frequency of the acoustic wave in the crystal of this third AOM (5) at least on the order of the frequency Half width of the gain profile of the active medium (1), preferably between 40 and 100 MHz, is located.

Q-switched C0 ₂ laser material processing system according to claim 1, characterized in that only the first (2) or the second (3) AOM for

Power modulation / Q-switching of the laser is used by appropriate variable control of the switching voltage and the other AOM operates with a constant switching voltage.

Q-switched C0 ₂ laser material processing system according to claim 1, characterized in that the first (2) or the second (3) AOM for Q-switching of the laser is used by variable control of the switching voltage and the other AOM is so controlled that freely selectable individual pulses or pulse groups be selected and / or the performance

Q-switched radiation is varied

Q-switched C0 ₂ laser material processing system according to any one of claims 1-3, characterized in that the external third AOM (5) is controlled so that the radiation pulses generated by the laser in their performance to the respective application

be adapted, in particular, the performance curve within the pulses, especially the peak power of Q-switching peak, is largely freely selectable.

Q-switched C0 ₂ laser material processing system according to one of claims 1 - 4, characterized in that between the third AOM (5) and the workpiece (7) a combination of ATFR mirror (20) and λ / 4 phase shifter (21) becomes.

Q-switched C0 ₂ laser material processing system according to one of claims 1 - 4, characterized in that between the third AOM (5) and the workpiece (7) in the beam-shaping unit (6) optical

Elements, preferably cylindrical lenses, for

Compensation of the AOM (5) caused

Beam deformations are arranged. Q-switched C0 ₂ laser material processing system according to one of claims 1 - 3, characterized in that the external third AOM (5) is replaced by an AOM cascade of two or more AOM and the decoupled laser beam (16) by beam splitter and deflection mirror so in Split two or more subbeams that each AOM with one of the

Sub-beams is applied.