WO2004068651A2

WO2004068651A2 - Laser system

Info

Publication number: WO2004068651A2
Application number: PCT/EP2004/000672
Authority: WO
Inventors: Angelika Beyertt; Adolf Giesen; Detlef Nickel
Original assignee: Forschungsgesellschaft Für Strahlwerkzeuge-Fgsw -Mbh
Priority date: 2003-01-30
Filing date: 2004-01-27
Publication date: 2004-08-12
Also published as: WO2004068651A3; DE10304399A1

Abstract

The invention relates to a laser system for generating laser pulses, comprising a seed laser and a regenerative amplifier, in which an amplifier laser pulse generated from a seed laser pulse of the seed laser can be amplified by multiple revolutions. The regenerative amplifier comprises a resonator, a controllable coupling element, which is placed inside the resonator, and comprises a solid disc, which is also situated inside the resonator and which is provided with a laser-active medium. The aim of the invention is to improve a laser system of the aforementioned type so that extracted laser pulses can be generated as easily as possible in picoseconds or in the span of subpicoseconds. To this end, the invention provides that at least one dispersion compensation element, which is passed through by the multiply revolving amplifier laser pulse during each revolution. In order to generate extracted laser pulses in the span of fewer than five picoseconds in the resonator, at least one dispersion compensation element, which is passed through by the multiply revolving amplifier laser pulse during each revolution, is provided with a negative dispersion which counteracts an increase in the pulse duration by positively dispersing components of the regenerative amplifier.

Description

laser system

The invention relates to a laser system for generating laser pulses, comprising a seed laser and a regenerative amplifier, in which an amplifier laser pulse generated from a seed laser pulse of the seed laser can be amplified by multiple rotations, the regenerative amplifier having a resonator and an in Controllable coupling element arranged in the resonator and a solid-state disk with laser-active medium arranged in the resonator.

The problem with such laser systems is that, due to components with positive dispersion, seed laser pulses in the picosecond or sub-picosecond range do not lead to decoupled laser pulses in the picosecond or sub-picosecond range, but rather, due to the positive dispersion of the components increasing the pulse duration, the laser pulses decoupled from the regenerative amplifier Have range of picoseconds and possibly more, which can only be returned to the picosecond or sub-picosecond range by an additional element with a strong negative dispersion.

The invention is therefore based on the object of improving a laser system of the generic type in such a way that outcoupled laser pulses in the picosecond or sub-picosecond range can be generated as simply as possible. This object is achieved according to the invention in a laser system of the type described in the introduction in that at least one dispersion compensation element with negative dispersion penetrated by the multiple revolving amplifier laser pulse in each revolution is provided in the resonator for generating outcoupled laser pulses in the region of less than five picoseconds, one of which is provided counteracts pulse duration increase by positive dispersion of components of the regenerative amplifier.

The advantage of the solution according to the invention is thus to be seen in the fact that the at least one dispersion compensation element provided directly in the resonator makes it possible to compensate for the effect of the positive dispersion which increases or lengthens the pulse duration, so that the decoupled laser pulse itself already exists in the picosecond or sub-picosecond range and thus has the desired short pulse duration.

Even if a subsequent compensation of the increase in the pulse duration of the outcoupled laser pulse is possible in the known solutions, this pulse duration compensation is extremely complex and sensitive with regard to the required optical elements and in particular also the adjustment thereof.

Moreover, if the total pulse duration increase accumulated in the course of the large number of rounds of the amplifier laser pulse is compensated for by positive dispersion, there is the problem that it can fluctuate from the out-coupled laser pulse to the out-coupled laser pulse, especially if the number of rounds of the individual laser pulses is not constant. In contrast, in the solution according to the invention there is the advantage that the positive dispersion causing a pulse duration increase in the amplifier laser pulse in each revolution can also be compensated for in the revolution itself, so that with each revolution the pulse duration increase occurring during this revolution can also be counteracted by positive dispersion and thus the required negative dispersion of the at least one dispersion compensation element does not have to be so large that it compensates for the sum of the pulse duration increases occurring in all round trips, but only has to be so large that it counteracts the pulse duration increase occurring during each round trip by positive dispersion of the amplifier laser pulse ,

Thus, with the large number of revolutions of the amplifier laser pulse in the regenerative amplifier, a serious increase in the pulse duration due to positive dispersion does not build up, which - even if it can be compensated - does not have to be compensated for with complex measures.

It has previously been assumed that the laser system according to the invention operates in the range of less than five picoseconds. The advantages of the system according to the invention become particularly clear when it is intended for generating laser pulses in the sub-picosecond range, since even in the sub-picosecond range, even a small amount of dispersion leads to a time widening of the laser pulses in the resonator in the case of a large number of circulations of a laser pulse to be amplified, which leads them out of the sub-picosecond range. It is particularly favorable in the solution according to the invention if the at least one dispersion compensation element essentially compensates for a positive dispersion of optical resonator components in each revolution of the amplifier laser pulse in the resonator, so that an increase in pulse duration can be substantially avoided with each revolution and thus the increase in the pulse duration of the decoupled Laser pulse is essentially independent of the number of revolutions in the resonator of the regenerative amplifier.

Thus, even with a variation in the energy of the outcoupled laser pulses, it can be assumed that they have essentially the same pulse duration.

It is particularly advantageous in the solution according to the invention if the at least one dispersion compensation element essentially compensates for a positive dispersion of the controllable coupling element.

With regard to the formation of the dispersion compensation element itself, no further details have so far been given.

For example, it would be conceivable to use grating pairs as the dispersion compensation elements.

However, grid pairs in particular have high optical losses.

For this reason, it is particularly advantageous if the at least one dispersion compensation element is designed as an interferometer. Such interferometers are preferably Gires Tournois interferometers, which are known from the literature.

It is particularly favorable, in particular in order to achieve the necessary resonator length with an inexpensive compact construction of the resonator, if the at least one dispersion compensation element works in reflection.

As an alternative to providing an interferometer as a dispersion compensation element, it is also possible to use a pair of prisms as a dispersion compensation element.

The pair of prisms is preferably formed from Brewster prisms which have particularly low optical losses.

In the context of the invention, it is also possible, in particular in the case of a plurality of dispersion compensation elements, to use both interferometers and prism pairs as dispersion compensation elements in the same regenerative amplifier.

In order to be able to manufacture and use the dispersion compensation elements as simply as possible, provision is preferably made for the dispersion compensation elements to be arranged in the resonator at a plurality of points in the radiation profile.

This has the advantage that when the dispersion compensation elements are manufactured, their negative dispersion does not have to be matched exactly to the positive dispersion occurring in the resonator, but rather a coordination can be achieved by using several dispersion compensation elements with either identical or different negative dispersion in coordination with the positive dispersion of the other resonator components.

Thus, the tuning can be set, for example, by selecting the number and the corresponding negative dispersion of the dispersion compensation elements, for example instead of conventional reflectors, the reflectors already present in the resonator, for example those without dispersion, possibly using reflectors with a suitable negative dispersion, which in this case are then act as dispersion compensation elements, can be replaced.

In laser systems for the generation of laser pulses in the picosecond and sub-picosecond range, in particular in the production of laser pulses with high energy in the sub-picosecond range, it is usually necessary to provide pulse duration-increasing elements with positive dispersion in front of the resonator in order to avoid high intensity maxima which damage the could lead optical components.

Due to the use of a cooled solid-state disk, diameters of the radiation field in the resonator can be realized, which allow the laser system to be essentially free of positive dispersion elements arranged in front of the resonator for increasing the pulse duration, so that the laser amplifier pulses circulating in the resonator also have pulse durations which are in the order of magnitude of the coupled-in seed laser pulse, in particular are essentially identical to it.

In particular, a polarization-rotating coupling element, preferably a Pockels cell, is provided as the controllable coupling element.

In order to prevent the outcoupled laser pulse from acting back on the seed laser, an optical isolator is preferably provided following the seed laser, in particular between the seed laser and the regenerative amplifier.

Furthermore, it is preferably provided that a mode adaptation unit is arranged between the seed laser and the regenerative amplifier, which allows the mode of the seed laser to be adapted to the mode of the regenerative amplifier, in particular the resonator thereof.

A pulse separator is preferably provided between the seed laser and the regenerative amplifier in order to be able to advantageously couple the outcoupled laser pulse and, in particular, to largely avoid a reaction on the seed laser.

Such a pulse separator can be arranged particularly favorably between the mode adaptation device and the regenerative amplifier, so that the decoupled laser pulse emerges directly with the mode of the amplifier laser pulse in the resonator and no longer runs over the mode adaptation device and undergoes a change in it. In this solution, the optical isolator, which represents additional protection for the seed laser against any retroactive laser pulses, is preferably also provided between the mode adaptation device and the seed laser.

In particular, the pulse separator is constructed so that it has a polarizer and an optical rotator.

The polarizer is preferably designed as a thin-film polarizer.

With regard to the repetition rate of the outcoupled laser pulses, no further details have been given in connection with the previous exemplary embodiments. An advantageous exemplary embodiment provides that the laser system generates outcoupled laser pulses with a repetition rate of several kilohertz.

This laser system is particularly advantageous when it generates outcoupled laser pulses with a repetition rate of more than five kilohertz.

With regard to the number of revolutions of the amplifier laser pulses in the resonator, no further details have so far been given.

The laser system according to the invention is particularly suitable for all those applications in which a high number of revolutions in the resonator is required for amplification.

It is preferably provided in the laser system according to the invention that the decoupling element can be controlled by a control such that the Amplifier laser pulses are only decoupled from the resonator after at least twenty revolutions, even better only after at least fifty revolutions, and even better only after more than one hundred revolutions.

In connection with the previous explanation of the individual embodiments of the laser system according to the invention, no further specification of the laser-active medium has been discussed.

It has proven to be particularly advantageous if materials are provided as the laser-active medium for the solid-state disk, which have a reinforcement of at least 5% per double passage through the solid-state disk with a maximum thickness of the solid disk and their optical bandwidth Generation of amplifier laser pulses shorter than ten picoseconds allowed.

In order not to destroy the laser-active medium, it is preferably provided in a further exemplary embodiment of the solution according to the invention that in the laser-active medium the maximum energy density per amplifier laser pulse is less than one hundred millijoules per square centimeter, even better less than fifty millijoules per square centimeter and even better less than thirty Is millijoules per square centimeter, so that high powers have the consequence that these are to be distributed over a large cross section of an amplifier radiation field.

Further features and advantages of the invention are the subject of the following description and the drawing of an exemplary embodiment. Show in the drawing

Fig. 1 is a schematic representation of a first embodiment of the laser system according to the invention in plan view and

FIG. 2 shows a schematic illustration of a second exemplary embodiment of the laser system according to the invention similar to FIG. 1.

An embodiment of a laser system according to the invention, shown in FIG. 1, comprises a seed laser 10, which is preferably designed as a diode-pumped ytterbium glass laser oscillator or ytterbium tungsten laser oscillator and is passively mode-locked.

The mode coupling is preferably carried out by a saturable semiconductor absorber mirror.

The seed laser 10 operates, for example, with a repetition rate of more than 20 MHz, and generates seed laser pulses 20 limited by the time bandwidth with a pulse duration of approximately 300 femtoseconds.

The wavelengths of the seed laser 10 are in the range of, for example, 1000 to 1100 nanometers with pulse energies in the order of 1 nanojoule. Following the seed laser 10, an optical isolator, designated as a whole by 12, is provided, which is designed as a Faraday isolator 14, which prevents reflected laser pulses from acting back on the seed laser 10 and disturbing it.

In addition, a λ / 2 plate 16 is provided for polarization rotation.

The seed laser pulse 20 leaving the seed laser 10 is preferably coupled into the optical isolator 12 by deflecting mirrors 22 and 24 and passes through it.

In addition, a photodiode 26 and a spectrometer 28 are provided for monitoring the function of the seed laser 10, with which a laser pulse 30 coupled out parasitically to the seed laser pulse 20 can be analyzed.

The laser system is preferably triggered by means of the photodiode 26.

In order to select the seed laser pulses 20 actually used for amplification and to suppress the other seed laser pulses 20 from the multiplicity of seed laser pulses 20 generated by the seed laser 10, a pulse selector 32 is preferably provided, which in particular includes a Pockels cell 34 comprises a polarizer 36, the Pockels cell being driven accordingly for pulse selection. After passing through the optical isolator 12, the seed laser pulse 20 decoupled from the seed laser 10 passes through a mode adaptation unit 40, preferably designed as a telescope with, for example, three telescope mirrors 42, 44, 46, with which an adaptation to a mode described in detail below Resonators 50 takes place.

Before entering the resonator, the seed laser pulse 20 passes through a pulse separator 52, comprising a thin-film polarizer 54, a Faraday rotator 56 and a λ / 2 plate 58, which serve to separate the seed laser pulse 20 entering the resonator 50 from one Laser pulse 70 decoupled from the resonator 50 later, as described in detail below.

After passing through the pulse separator 52, the seed laser pulse 20 is coupled into the resonator 50 via an adjusting unit 66, comprising, for example, two mirrors 62 and 64, with the penetration of a thin-film polarizer 68 belonging to the resonator 50, via which the seed laser pulse is coupled 20 takes place in the resonator 50, the seed laser pulse 20 circulating several times as an amplifier laser pulse 60 in the resonator 50 and being amplified until the amplifier laser pulse 60 is decoupled as a laser pulse 70 from the resonator 50.

The resonator 50 comprises a first end mirror 72, a second end mirror 74 and a laser-active medium 76 in the form of a thin disk, which can be cooled by a cooling device 78, as described, for example, in European Patent 0 632 551, to which reference is hereby made.

Furthermore, a Pockels cell 80 is arranged in the resonator 50 between the thin-film polarizer 68 and the first end mirror 72 as a coupling element and can be controlled by a control 82, for example a so-called push / pull circuit, the control 82 generating a trigger signal from one of the end mirrors 74 assigned photodiode 75 and preferably also the photodiode 26.

The Pockels cell 80 is further combined with a so-called λ / 4 plate 84.

A seed laser pulse 20, which is coupled in via the coupling / decoupling element 68 of the resonator 50, propagates in the resonator 50 as an amplifier laser pulse 60 and first penetrates the λ / 4 plate 84 and the Pockels cell 80 until it hits the first end mirror 72 , which is designed as a reflecting end mirror of the resonator 50.

Thus, the amplifier laser pulse 60 is reflected at the first end mirror 72, passes through the Pockels cell 80 and the λ / 4 plate 84 again and is thereby, when this amplifier laser pulse 60 is to be amplified in the resonator 50, by the coupling / decoupling element 68 not transmitted again as a decoupled laser pulse 70 in the direction of the pulse separator 52, but reflected to a deflecting mirror 86, reflected by the latter to a deflecting mirror 88 and then penetrating, for example, a λ / 2 plate 90 provided for polarization rotation.

After passing through the λ / 2 plate 90, the amplifier laser pulse 60 strikes the laser-active medium 76, which in turn is provided on the back with a reflector 92, which again amplifies the laser pulse 60 on a deflecting mirror 94 and on a deflecting mirror 96, which in turn deflects onto a deflecting mirror 98, from which the amplifier laser pulse 60 then strikes the second end mirror 74 and is reflected back by the latter.

Due to the action of the reflector 92, the amplifier laser pulse 60 was amplified twice by the laser-active medium 76 before it reached the second end mirror 74.

In the case of a renewed back reflection, there is a renewed reflection at the deflection mirrors 98, 96 and 94 until the amplifier laser pulse 60 passes through the laser-active medium 76 twice again, then hits the deflection mirrors 88 and 86 again via the polarization-rotating element 90 and then hits the Coupling / decoupling element 68, which reflects the amplifying laser pulse 60, which has now been amplified four times by the laser-active medium 76, back to the λ / 4 plate 84 and the Pockels cell 80 until this amplifying laser pulse 60 hits the first end mirror 72 again , The resonator 50 together with the laser-active medium 76 thus acts as a regenerative amplifier 100 for amplifying the incoming seed laser pulse 20.

The Pockels cell 80 is now controlled by the control unit 82 in such a way that the originally coupled seed laser pulse 20 passes through the resonator 50 more than about 100 times, even better more than about 150 times and more, and is thereby amplified.

Since the individual elements of the resonator 50, in particular the Pockels cell 80, have a positive dispersion with regard to the group speed, each time the amplifier laser pulse passes through the resonator 50, the amplifier laser pulse 60 is widened in time, all of which until the amplifier is finally decoupled. Laser pulse can be a multiple of the pulse duration of the seed laser pulse 20. For example, the pulse duration can be broadened by a factor of 10 or more.

For this reason, dispersion compensation elements penetrated by the rotating amplifier laser pulse 60 are provided directly in the resonator 50, which have a negative dispersion compensating for a positive dispersion of the individual elements of the resonator 50, in particular a dispersion of the Pockels cell 80. Such dispersion compensation elements are, for example, the first end mirror 72, the deflection element 86 and the deflection element 98, which are designed as so-called Gires Tournois interferometer mirrors, which together allow compensation of the positive dispersion generated by the Pockels cell.

Such Gires Tournois interferometer mirrors are for example from the article by F. Gires and P. Tournois, Comt. Rend. Acad. Be. (Paris) 258, 6112 (1964).

Depending on the dispersion of the other components of the resonator 50, there is now the possibility of providing dispersion compensation elements in a corresponding number and with a corresponding dispersion, which allow the dispersion of the amplifier laser pulse 60 circulating in the resonator 50 to be compensated for directly with each revolution, so that essentially the pulse duration of the seed laser pulse 20 can be maintained.

After the resonator 50 has been run through several times, the corresponding activation of the Pockels cell 80 via the coupling / decoupling element 68 decouples the amplifier laser pulse 60 in the form of the decoupled laser pulse 70, which then passes through the adjusting device 66 and the pulse separator 52 and through the thin-film polarizer 54 thereof is reflected and thus strikes a substrate 110, for example for material processing.

The Pockels cell 80 is preferably operated with cycles whose frequency is several kilohertz, preferably between 1 and 10 kHz or even possibly even more in order to obtain a high repetition rate of the outcoupled laser pulse 70.

In principle, all materials are suitable as laser-active medium for the solid-state disk 76 which, with a maximum thickness of the solid-state disk of 0.5 mm, have a reinforcement of at least 5% per double passage through the reinforcing material, that is to say through the solid-state disk, and the bandwidth of the generation of laser pulses shorter than 10 picoseconds allowed.

The laser active medium 76 in the form of a disc less than 0.5 mm thick is preferably Yb-KYW, but there are also similar materials, such as Yb: KGW or Yb: YAG or Yb doped sesquioxides e.g. Lutetium oxide, or semiconductor materials are suitable.

The thickness of the disk of the laser-active medium is, for example, approximately in the order of magnitude of less than 300 μm and in particular is in the order of approximately 100 μm, and the doping of the laser-active medium is, for example, less than 20%, preferably in the order of approximately 10% ,

In order to prevent destruction of the laser-active medium, the energy density per amplifier laser pulse in the regenerative amplifier 100 is advantageously less than 100 millijoules per square centimeter, even better less than 50 millijoules per square centimeter. With regard to the mode in which the resonator 50 is operated, nothing has been explained in detail so far. The resonator 50 preferably operates in TEMoo mode and the mode adaptation device 40 is set such that it converts a radiation field of the seed laser pulse 20 to a radiation field corresponding to the TEMoo mode of the resonator 50.

In contrast to conventional femtosecond laser systems comprising an element arranged in front of the regenerative amplifier and a pulse duration-compressing element provided after passing through the regenerative amplifier, in particular a grating, with an increase in pulse duration and a subsequent pulse duration compression taking place by a factor of approximately 10 ⁴ , this provides Laser system according to the invention picosecond pulses without the integration of elements that increase the pulse duration. This means that this technology, which destabilizes the radiation field and increases the cost of the laser system, can be dispensed with.

In a second exemplary embodiment of a laser system according to the invention, shown in FIG. 2, all those elements which are identical to the first laser system are provided with the same reference numerals, so that with regard to the description thereof, reference is made in full to the explanations for the first exemplary embodiment.

In the second exemplary embodiment, a pair of prisms, comprising two prisms 122 and 124, is provided as the dispersion compensation element 120, wherein the pair of prisms 120 is preferably arranged between the deflecting mirror 94 and the end mirror 74.

The pair of prisms 120 can be designed in such a way that it itself has such a large negative dispersion that the positive dispersion of the Pockels cell 80 is essentially compensated for every revolution, so that it is not necessary to include the first end mirror 72 and the deflecting element 86 to train as dispersion compensation elements. Rather, they can be designed as conventional optical components.

However, it is also conceivable to provide additional dispersion compensation elements in addition to the pair of prisms 120, provided that the negative dispersion of the pair of prisms 120 is not sufficient to compensate for the positive dispersion of the Pockels cell 80. In this case, a further pair of prisms can be provided or the end mirror 72 or the deflection element 86 can also be used as a Gires Tournois interferometer mirror with negative dispersion.

Otherwise, the second exemplary embodiment according to FIG. 2 functions in the same way as the first exemplary embodiment, so that with regard to its function, reference is also made in full to the first exemplary embodiment according to FIG. 1.

Claims

Laser system for generating laser pulses (70) comprising a seed laser (10) and a regenerative amplifier (100), in which an amplifier laser pulse (60) generated from a seed laser pulse (20) of the seed laser (10) multiple revolutions can be amplified, the regenerative amplifier (100) comprising a resonator (50) and a controllable coupling element (80) arranged in the resonator (50) and a solid-state disk (76) with laser-active medium arranged in the resonator (50), characterized in that that in order to generate outcoupled laser pulses (70) in the region of less than five picoseconds in the resonator (50), at least one dispersion compensation element (72, 86, 98, 120) penetrated by the multiply circulating amplifier laser pulse (60) during each revolution Negative dispersion is provided, which counteracts a pulse duration increase by positive dispersion of components (80) of the regenerative amplifier (100).

Laser system according to Claim 1, characterized in that it generates outcoupled laser pulses (70) in the sub-picosecond range.

3. Laser system according to claim 1 or 2, characterized in that the at least one dispersion compensation element (72, 86, 98, 120) with each revolution of the amplifier laser pulse (60) in the resonator (50) a positive dispersion of optical resonator components (80) essentially compensated.

4. Laser system according to one of the preceding claims, characterized in that the at least one dispersion compensation element (72, 86, 98, 120) substantially compensates for a positive dispersion of the controllable coupling element (80).

5. Laser system according to one of the preceding claims, characterized in that the at least one dispersion compensation element (72, 86, 98) comprises an interferometer.

6. Laser system according to claim 4, characterized in that the at least one dispersion compensation element (72, 86, 98) is a Gires Tournois interferometer.

7. Laser system according to claim 4 or 5, characterized in that the at least one dispersion compensation element (72, 86, 98) works in reflection.

8. Laser system according to one of the preceding claims, characterized in that the at least one dispersion compensation element (120) is a pair of prisms.

9. Laser system according to claim 8, characterized in that the pair of prisms (120) is formed from Brewster prisms.

10. Laser system according to one of the preceding claims, characterized in that the dispersion compensation elements (72, 86, 98, 120) are arranged at several points in the beam path in the resonator.

11. Laser system according to one of the preceding claims, characterized in that the laser system is substantially free from elements arranged in front of the resonator (50) for increasing the pulse duration with positive dispersion.

12. Laser system according to one of the preceding claims, characterized in that the controllable coupling element is a Pockels cell (80).

13. Laser system according to one of the preceding claims, characterized in that an optical isolator (12) is provided following the seed laser (10).

14. Laser system according to one of the preceding claims, characterized in that a mode matching unit (40) is arranged between the seed laser (10) and the regenerative amplifier (100).

15. Laser system according to claim 13, characterized in that the mode adaptation unit (40) is designed as a telescope.

16. Laser system according to one of the preceding claims, characterized in that a pulse separator (52) is provided between the seed laser (10) and the regenerative amplifier (100).

17. Laser system according to claim 16, characterized in that the pulse separator (52) between, the mode matching device (40) and the regenerative amplifier (100) is arranged.

18. Laser system according to claim 16 or 17, characterized in that the pulse separator (52) has a polarizer (54) and an optical rotator (56).

19. Laser system according to claim 18, characterized in that the polarizer is a thin film polarizer (54).

20. Laser amplifier system according to one of the preceding claims, characterized in that an in / out coupling element (68) of the resonator (50) is designed as a thin film polarizer.

21. Laser system according to one of the preceding claims, characterized in that this coupled-out laser pulse (70) generates with a repetition rate of several kilohertz.

22. Laser system according to claim 21, characterized in that this coupled-out laser pulse (70) generates with a repetition rate of more than five kilohertz.

23. Laser system according to one of the preceding claims, characterized in that the decoupling element (80) can be controlled by a control (82) in such a way that the amplifier laser pulses (60) are only coupled out of the resonator (50) after at least twenty revolutions.

24. Laser system according to one of the preceding claims, characterized in that materials are provided as the laser-active medium for the solid-state disk (76), which has a gain of at least 5% per double pass at a maximum thickness of the solid-state disk (76) of 0.5 mm have through the solid-state disk (76) and whose optical bandwidth allows the generation of amplifier laser pulses (60) shorter than ten picoseconds.

25. Laser system according to one of the preceding claims, characterized in that in the laser-active medium the maximum energy density per amplifier laser puis (60) is less than one hundred millijoules per square centimeter.