DE102017114399A1 - DYNAMIC SEEDING OF LASER AMPLIFIER SYSTEMS - Google Patents

Abstract

A laser amplifier system (1) comprises a seed laser pulse source unit (3) for providing at least two seed pulse trains for a subsequent amplification, wherein seed pulses (3 ') of the at least two seed pulse train have a seed pulse duration (T, TA, TB ) and within a range during the seed pulse duration (T, TA, TB) varying and adjustable in their seed amplitude (A). The laser amplifier system (1) further comprises an amplifier stage and in particular a gain chain (5) of (for example fiber) amplifier stages (5A, 5B, 5C), which output an output pulse train (5 '). The laser amplifier system (1) is designed so that an amplitude characteristic of an output pulse (5 ') of the output pulse train is due to contributions from at least two seed pulses (3').

Description

The present invention relates to laser amplifier systems, in particular for generating high power laser pulses. Furthermore, the invention relates to a method for dynamically seeding a laser amplifier system, such as a fiber laser amplifier system.

When amplifying pulses in laser amplifier systems, it is possible to achieve outputs which can lead to a pulse shape change due to saturation of the amplification. For example, the pulse shape of a nanosecond pulse may change during amplification in a high gain fiber laser amplifier system when the fiber laser amplifier system is operated sufficiently near or above saturation. Pulse shape changes may make it difficult to achieve a pulse shape desired by the user, or in extreme cases may also result in the destruction of optical components such as a fiber due to excessive pulse peak power.

It is known that via a compensation in the seed pulse form, a defined pulse shape can be achieved at the output of a laser amplifier system, in particular at high output powers. The compensation in the seed pulse form can be made by controlling a seed laser. For example, For example, the energization of a diode laser acting as a seed laser (also referred to herein as a seed diode) can be varied. The achievable dynamics when driving a seed diode is limited, for example, by reaching the laser threshold. At the top, a maximum amplitude is e.g. is limited by a damage threshold of the semiconductor structure and / or by thermal effects in the semiconductor structure of the underlying laser diode structure. Furthermore, pulse shaping, e.g. a pulse pruning, with a control intervention e.g. between two stages of an amplifier chain by means of e.g. acousto-optic modulators (AOM, AOD, AOTF, ...), electro-optic modulators (EOM, Pockels cells, ...) or mechanical switches. The trimming of the pulses often takes place late in an amplifier chain, which can result in high power losses.

It is an object of this disclosure to provide a pulse shaping of a seed laser pulse that enables efficient amplification.

At least one of these objects is achieved by a laser amplifier system according to claim 1, by a laser amplifier system according to claim 5, by a method for grounding a gain chain according to claim 16 and by a method for selecting a gain chain according to claim 18. Further developments are given in the subclaims.

In one aspect, a laser amplifier system includes a seeded laser pulse source unit for providing at least two seed pulse trains for subsequent amplification, seed pulses of the at least two seed pulse trains having a respective seed pulse duration and a range varying within a range during the respective seed pulse duration and have adjustable seed amplitude in their course. Furthermore, a laser amplifier system comprises at least one amplifier stage for amplifying the at least two seed pulse trains and for outputting an output pulse train with output pulses having an output pulse duration. The at least two seed pulse sequences are coupled into the amplifier stage in such a way that an amplitude characteristic of an output pulse of the output pulse sequence goes back to contributions from at least two seed pulses, which are each assigned to one of the at least two seed pulse sequences.

In a further aspect, a laser amplifier system comprises a seed laser pulse source unit for providing at least two seed pulse trains for subsequent amplification, seed pulses of the at least two seed pulse trains having a respective seed pulse duration and one within a range during the respective seed pulse duration have varying and adjustable in their course seed amplitude. Furthermore, the laser amplifier system comprises a gain chain comprising a sequence of at least two gain stages coupled in series, the gain in the gain stages being sequential to form intermediate pulses associated with the gain stages, and the gain chain outputting an output pulse sequence having output pulse duration output pulses, wherein an amplitude characteristic an output pulse of the output pulse train to contributions of at least two seed pulses, each associated with one of the at least two seed pulse sequences, goes back.

In a further aspect, a method of generating a train of amplified output pulses comprises the steps of providing at least two seed pulse trains for subsequent amplification, seed pulses of the at least two seed pulse trains each having a seed pulse duration and a seed pulse duration, respectively Range during the seed pulse duration varying and adjustable in their seed amplitude, and amplifying the seed pulses in an amplifier stage, so that there is an output pulse train with output pulse duration having output pulses, wherein the at least two seed pulse trains in the amplifier stage be coupled an amplitude characteristic of an output pulse of the output pulse train is due to contributions from at least two seed pulses, which are each assigned to one of the at least two seed pulse sequences.

In a further aspect, a method of generating a train of amplified output pulses comprises the steps of providing at least two seed pulse trains for subsequent amplification, seed pulses of the at least two seed pulse trains each having a seed pulse duration and a seed pulse duration, respectively Range during the seed pulse duration varying and adjustable in their seed amplitude, and amplifying the seed pulses in sequentially arranged amplifier stages to form the amplifier stages associated intermediate pulses, so that there is an output pulse train having output pulse duration output pulses, wherein an amplitude curve an output pulse of the output pulse train to contributions of at least two seed pulses, each associated with one of the at least two seed pulse sequences, goes back.

In some embodiments, the seed laser pulse source unit may be configured to provide at least two sub-seed pulse trains to be amplified, the sub-pulses of which have a partial pulse duration. The seed laser pulse source unit comprises e.g. at least one laser pulse source, e.g. an adjustable energizable laser diode. At least one of the partial pulse durations may be shorter than an output pulse duration of the output pulses. In each case one of the at least two partial seed pulse sequences to be amplified can deliver one of the at least two contributions from at least two seed pulses and the at least two contributions can be jointly supplied to one of the amplifier stages for the formation of one of the intermediate pulses.

In some embodiments, the laser amplifier system, and in particular the control of the seed laser pulse source unit, may be configured such that the at least two seed pulses, which contribute to the amplitude characteristic of an output pulse, are temporally spaced, temporally adjoined, or overlapping in time.

In some embodiments, the laser amplifier system, and in particular the control of the seed laser pulse source unit, may be configured such that the at least two seed pulses that contribute to the amplitude response of an output pulse are spaced apart in time, temporally adjoin one another or overlap in time. Thus, seed pulses may e.g. with a time offset smaller than the seed pulse duration, spaced apart. Furthermore, the laser amplifier system, and in particular the control of the seed laser pulse source unit, be designed such that at least one seed pulse, which contributes to the amplitude characteristic of an output pulse, is temporally spaced with respect to an intermediate pulse, temporally adjoined thereto or temporally overlapped with this. Thus, e.g. the at least one seed pulse having a time offset smaller than the seed pulse duration (T) is spaced from the intermediate pulse.

Furthermore, a temporal segment of the output pulses may be due to at least one seed laser pulse source whose seed pulses have passed through all amplifier stages of the amplification chain. Alternatively or additionally, the seed pulses contributing to the amplitude characteristic of an output pulse of one of the at least two seed pulse sequences may represent partial pulses of a sub-seed pulse sequence to be amplified whose partial pulse duration is shorter than the output pulse duration of the output pulses.

In some embodiments, the laser amplifier system may include an optical delay unit for generating a laser pulse time offset between pulses contributing to the amplitude characteristic of an output pulse, in particular seed pulses or split pulses, a split unit for dividing a laser pulse into two or more split pulses, a combiner unit for combining the Partial pulses, such as an X: (100-X) (fiber) combiner, and / or an attenuation unit for reducing the amplitude of laser pulses, sub-pulses and / or intermediate pulses. The optical delay unit may e.g. generate a laser pulse time offset between a seed pulse of one of the at least two seed pulse trains and an intermediate pulse or between seed pulses of different ones of the at least two seed pulse trains

In some developments, the laser amplifier system may have at least one pulse-shaping device for changing the amplitude of one of the intermediate pulses. The pulse-shaping device may in particular be designed as an amplitude-changing unit arranged between two adjacent amplifier stages, for example as an acousto-optical modulator or an electro-optical modulator. Alternatively or additionally, at least one pulse-shaping device may be provided following the amplification for changing the amplitude of the output pulses of the output pulse train.

In some embodiments, the seed laser pulse source unit may include at least one laser pulse source in the form of an adjustable energizable laser diode, and optionally for each of the at least two seed pulse trains, a separate laser pulse source.

In some embodiments, the laser amplifier system may further comprise a drive unit, which is designed for setting the seed pulse shape, in particular for driving a seed source, a combination unit and / or a pulse-shaping device. For example, the drive unit may be designed to derive the seed pulse profile from a target pulse profile, in particular a target amplitude characteristic of one of the output pulses, and the seed pulse form, in particular the contributions from the at least two seed pulses and / or the circumcision of the amplitude at least one of the associated intermediate pulses to adjust accordingly. Furthermore, the drive unit may be designed to control the intensity of the pulse-shaping device during material processing, in particular during the beam guidance around a curved path, in order to reduce the output pulses.

Further, in some embodiments of the methods, an amplitude characteristic of one of the output pulses may be due to a truncation of the amplitude of at least one seed pulse / intermediate pulse. Furthermore, the amplitude curves of the seed pulses and optionally the truncation of the amplitude of at least one associated intermediate pulse can be adapted to each other such that a dynamic range after amplification is available which is greater than the dynamic range of a single seed pulse.

In some embodiments of the method, at least one seed pulse sequence can be coupled into the amplifier stage in such a way and, optionally, at least one seed pulse sequence can be coupled into a subsequent amplifier stage in such a way that an intermediate pulse to be amplified is formed, whose amplitude profile depends on contributions from at least two seed pulses. Pulses, each associated with one of the at least two seed pulse sequences, goes back.

The pulsed multi-site interventions proposed herein in a laser amplifier system provide a high dynamic range that can enable achievement of a target pulse shape at the output of the laser amplifier system, particularly at the end of a high gain amplifier chain.

In contrast to a purely temporal pulse shaping between two stages, which basically requires that a significant power component of the pulse is attenuated and thus lost, the herein disclosed highly dynamic Seeden of (eg fiber) lasers can be in principle at least partially lossless and significantly more efficient and allow an increased dynamic range. Thus, a combination of the concepts disclosed herein with known technologies may enable pulse control to an unprecedented extent.

This is usually exemplified by (laser) pulses. In this case, a pulse may inter alia include a burst pulse sequence as a "burst pulse". Correspondingly, a pulse below its Pulse envelope covers the Burstpulsfolge. Furthermore, a seed pulse train generally comprises one or more pulses.

• 1 eine schematische Darstellung eines Lasersystems mit mehreren Verstärkerstufen,
• 2 eine schematische Darstellung einer für eine hohe Verstärkung gewünschte Seed-Pulsform mit hoher Amplitudendynamik,
• 3 eine schematische Darstellung einer real beispielsweise mit einer Laserdiode und Diodenstrommodulation erreichbaren Pulsform,
• 4A und 4B schematische Darstellungen von mittels Teilpuls-Kombination erreichbaren Pulsformen,
• 5 eine schematische Darstellung eines kaskadierten Teilpuls-basierten Seed-Konzepts mit mehreren Eingriffsorten in einem Laserverstärkersystem,
• 6 und 7 schematische Darstellungen zur Teilpuls-Kombination zur Seed-Puls-Erzeugung,
• 8 eine schematische Darstellung zur Teilpuls-Erzeugung und Teilpuls-Kombination basierend auf einer einzigen Laserpulsquelle,
• 9 eine schematische Darstellung zur Erreichen der gewünschten Zielpulsform mittels Amplitudenbeschneidung an mehreren Eingriffsorten in einem Laserverstärkersystem und
• 10 eine schematische Darstellung zur Verdeutlichung einer Amplitudenbeschneidung.

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

• 1 a schematic representation of a laser system with multiple amplifier stages,
• 2 a schematic representation of a desired for a high gain seed pulse shape with high amplitude dynamics,
• 3 a schematic representation of a real reachable for example with a laser diode and Diodenstromodulation pulse shape,
• 4A and 4B schematic representations of achievable by means of partial pulse combination pulse shapes,
• 5 1 a schematic representation of a cascaded partial pulse-based seed concept with a plurality of intervention modes in a laser amplifier system,
• 6 and 7 schematic representations of the partial pulse combination for seed pulse generation,
• 8th a schematic representation of the partial pulse generation and partial pulse combination based on a single laser pulse source,
• 9 a schematic representation of the achievement of the desired target pulse shape by means of amplitude truncation at multiple intervention sites in a laser amplifier system and
• 10 a schematic representation to illustrate an amplitude truncation.

Aspects disclosed herein are based, in part, on the recognition that pulse circumcision at the end of an amplification process may be inefficient because, depending on the pulse shape, a high power component may be lost through pulse shaping. Furthermore, a decoupled high (loss) power is safe, and thus consuming to dissipate. Furthermore, modulation of laser pulses at very high powers can be technically difficult to implement.

The aspects disclosed herein are further based in part upon the recognition that large (exponential) amplification may require controlling the pulse shape (of a single pulse or a burst pulse train) in a high dynamic gain process. For pulse shaping with high dynamics, pulse-forming interventions can be made which adapt the shape of a pulse underlying the amplification to a stepped amplification process. In this case, the shaping interventions can be made at at least two different locations within an amplifier chain and / or by means of two or more different approaches. The starting point is in each case a pulse formation of a seed pulse of a seed laser pulse source. This first shaping intervention provides seed pulses in a seed pulse train having a seed pulse duration and a seed amplitude varying within a range during the seed pulse duration and adjustable in course. This can be done for example by an adjustable, for example, increasing, energization of a (seed) laser diode. In general, the seed pulse can be designed as a single pulse or as a burst pulse train.

Since the dynamics of the seed laser pulse source, in the above example, the region in which the current can be made limited due to the already mentioned laser threshold and maximum amplitude of a seed diode, it is proposed herein, with a second shaping engagement (in general with other shaping interventions) to extend the limit in the control of the dynamic range of the pulse amplitude of a seed pulse. In each individual case, the shaping interventions can be simulated using analytical models such as the Frantz-Nodvik equation or other numerical approaches, and the shaping interventions can be adapted accordingly. Additionally or alternatively, the shaping interventions may be performed by measuring pulse parameters and corresponding iterative enhancements of the interventions.

In some embodiments, a single output pulse of a laser amplifier system may be due to a plurality of (directly adjacent and overlapping) subpulses (as a single pulse or as a burst pulse train). Moreover, in order to further increase the dynamics, the partial pulses may also be applied at different locations of the amplifier chain, e.g. between adjacent amplifier stages. Alternatively or additionally, an amplitude adjustment can also be made between different amplifier stages. As a result, the total power losses can be minimized or at least reduced.

In some embodiments described below, e.g. a pulse is preformed by modulating the current of a laser diode. Before the subsequent amplifier stage and / or between two successive amplifier stages, the pulse (as a single pulse or as a burst pulse sequence) can also be shaped by an optical modulator. As a result, pulse deformations that occur during the amplification process, for example due to the saturation of the gain, are precompensated or corrected in between. Since such interventions occur in a low power range of the amplification process, they are accompanied by lower losses.

The above mentioned and e.g. Based on the Frantz-Nodvik equation based analytical models may allow, with regard to the desired target pulse shape or in knowledge of parameter changes in the laser system seed pulse shapes, possibly specially required combination of multiple sub-pulses and / or trimming the amplitude to determine adjust. Such control concepts can also be implemented by means of a control of e.g. During the operation of a laser system, in particular in real time or in the setting of an operating mode, control units which are involved with seed diodes are made.

Many applications of short-pulse lasers, for example in the nano- and picosecond range, can benefit from such control over the pulse shape at the output of a laser system or an amplifier stage. In the following, various measures for pulse shaping will be explained in more detail by way of example in connection with the figures.

1 shows a multi-stage laser amplifier system 1 with a seed laser pulse source unit 3 , an amplification chain 5 and an (optional) final amplifier stage 7 , The various units and their components can be used, for example, via fiber couplers / combiners (as an example of a fiber-specific (pulse) combiner unit 9A) , Fiber spliced sections 9B , Transport fiber sections (for example, between the units / components by lines 9C indicated) and / or free jet sections 9D be connected to each other. Although the gain chain 5 described below is based primarily on fiber laser amplifier stages, laser amplifier stages may generally include (Rod-type) fiber, rod, slab, and / or disk laser amplifier stages, among others.

The seed laser pulse source unit 3 includes one or more seed lasers 3A . 3B . 3C (Seed sources) for providing at least one seed pulse train with seed pulses 3 ' for a subsequent reinforcement. To be exemplary in 1 shown three seed lasers. Examples of seed lasers include DFB, DBR or Fabry-Perot laser diodes as well as mode-locked ultrashort pulse (UKP) laser or microchip laser. Furthermore, the seed laser pulse source unit comprises 3 a (diode) drive unit 11 for adjusting the seed pulse shape (s). The drive unit 11 is shown via dotted control connections with the example, three seed lasers 3A . 3B . 3C connected. For example, the controller may adjust the modulation of the current (ie, energization) of the seed diode (s) to the subsequent gain. Furthermore, the seed performance of one or more seed lasers 3A . 3B . 3C be set with a attenuator. By way of example, an attenuation unit 4 in the beam path of the seed laser 3B schematically drawn and with the control unit 11 connected. Furthermore, the drive unit 11 generally to an adaptation of parameters of the seed laser pulse source unit 3 (generally the laser amplifier system 1 ) to a specific application of the generated laser beam.

For example, the gain chain 5 may be a sequence of fiber amplifier stages 5A . 5B which are embodied, for example, as cocurrently or countercurrently pumped, cored or shell-pumped fiber amplifiers. Exemplary is in 1 a pumping diode 6 shown which split in their performance and the amplifiers 5A and 5B backward-propagating (counter-rotating) is supplied. The drive unit 11 in this example also serves to set the pumping diode 6 , In the fiber amplifier stages 5A . 5B becomes the injected seed pulse 3 ' sequentially with formation of the fiber amplifier stages 5A . 5B associated intermediate pulses 3 ' amplified or pre-amplified for the final amplifier stage 7. To clarify that other amplifier systems can be used as amplifier stages, for example, an amplifier stage 5C not formed as a fiber amplifier stage.

The amplification chain 5 may further comprise modulators 13 . 15 Have (eg amplitude modulators such as acousto-optic modulators or electro-optical modulators or spectral shaping units such as spatial light modulators (Spatial Light Modulator, SLM)) for additional temporal or spectral pulse shaping or power stabilization. One or more monitoring units 17 also serve to stabilize the performance and / or the monitoring of the pulse shape. The modulators 13 . 15 and the monitoring units 17 For example, are also from the drive unit 11 controlled or give data to this. Through the power monitoring 17, for example, the seed laser 3A . 3B . 3C (Seed power), the pumping diode 6 (Pump power) and the modulators 13 . 15 (Amplitude modulation / spectral shaping) with the aim of stabilization or adaptation of the driving unit 11 be controlled.

Resulting output pulses 5 ' the reinforcement chain 5 can be used directly, for example, for material processing. Alternatively, the resulting output pulses 5 ' the gain chain 5 also as seed pulses of the final amplifier stage 7 for generating power amplifier pulses 7 ' be supplied. The final amplifier stage 7 is for example one designed as a main amplifier and in 1 schematically indicated amplifier with a disc-shaped laser-active medium.

The thus amplified power amplifier pulses 7 ' or also the output coil 5 ' For example, they can be used in machine tools for laser cutting, laser welding and for material processing, such as micromaterial processing, or for frequency conversion. They can also be used for scientific purposes, such as pumping OPCPA, as well as in spectroscopy.

The amplification-related pulse deformations mentioned at the outset can arise in the fibers used in the amplification chain 5 with correspondingly high amplification (and corresponding inversion). Accordingly, the original seed pulse shape may increase during amplification in the (fiber) amplifier stages 5A . 5B . 5C through saturation effects. For example, the front part of the seed pulse or the first pulses of a burst pulse train may experience a significantly increased gain over the back part, as in FIG 1 regarding the seed pulse 3 ' and the intermediate pulse 3 ' indicated schematically. It is in the exemplary representation of the 1 (as well as in the exemplary representations of 5 and 8th ) the pulse shape over the propagation direction indicated schematically, in contrast to the temporal representation in the 2 to 4B ,

The drive unit 11 may according to the concepts disclosed herein for adjusting seed pulse shape (s), in particular for driving a seed source, a combining unit and / or pulse-shaping device ( 15 . 60 ) be formed. Furthermore, the drive unit 11 optionally be designed to derive a seed pulse course from a target pulse course. In particular, a target amplitude characteristic of one of the output pulses can be derived. Accordingly, the drive unit 11 set the seed pulse shape (s), in particular the contributions from the at least two seed pulses and / or the truncation of the amplitude of at least one of the associated intermediate pulses. The derivative may be based, for example, on the already mentioned algorithms and based on measured power values. Of course, a drive unit can also be constructed from a plurality of individual drive units.

It is noted that in some amplifier configurations, the effect of the amplification process on the pulse shape may be substantially negligible, for example, if the aforementioned saturation is not achieved. This may be the case, for example, in a correspondingly designed disk amplifier (wherein in general a pulse shape change may also occur in a disk amplifier). In a case with negligible pulse shape change, the target pulse shape is essentially already the output pulse shape of the gain chain 5 and not just the pulse shape after the final amplifier stage 7 , The pulse shape after the final amplifier stage 7 can, for example, in its form almost identical to the output pulse shape of the gain chain 5 be, albeit intensified. For example, it can only have changes that are negligible for the subsequent station, for example, a material processing device. This is in the determination of the target pulse shape and the corresponding control of the seed diodes and / or modulator (s) of the drive unit 11 to take into account.

For example, a - as in 1 Example indicated - rectangular pulse with pulse durations in the nano- or picosecond range as a target pulse shape for a laser processing process are needed. Other examples include a plateau pulse with or without rising and / or falling edge, generally trapezoidal or any pulse shapes. If, for example, a rectangular pulse of approximately 250 ns pulse duration is present at the end of the amplifier chain 5, a seed pulse shape is needed which precompensates the disproportionate amplification of the front region, for example by an exponential increase in amplitude.

In 2 is an exponential increase of the amplitude A with increasing time t schematically for an "ideal" seed pulse (eg for a rectangular output pulse) with a pulse duration T shown. For such an increase in amplitude, the seed laser diode would be operated with, for example, an exponentially increasing current.

However, the laser threshold and maximum amplitude mentioned at the outset limit the dynamic range of a seed laser diode between minimum and maximum current (or between minimum and maximum seed pulse amplitude).

In 3 By way of example, a realizable increase in the amplitude A of a seed pulse with time t is shown schematically for a laser diode. It can be seen that the laser threshold of the laser diode can form a plateau P with low amplitude (just above the laser threshold) in the front pulse part. Furthermore, a usable maximum amplitude Amax of the seed pulse is limited, for example, by a damage threshold of the semiconductor structure and / or by thermal effects in the semiconductor structure of the laser diode.

Consequently, in view of the realizable increase in amplitude, the pulse shaping encounters limits of the dynamic range of the possible activation of the laser diode. For the above-mentioned modulation of the energization of laser diodes may not be sufficient to compensate in advance for a deformation of the seed pulses during the amplification process in such a way that the target pulse shape adjusts itself after the amplification. This can occur in addition to the already mentioned case in which the amplifier system has a gain that is too high in terms of deformation, even if the target pulse form itself should have a high (not precompensatable) dynamic. Also, pulse forming devices such as e.g. An AOM can be limited in its dynamic range.

The concepts described herein may allow for a desired target pulse shape for a e.g. subsequent laser processing operation also in such cases, e.g. at high laser powers after the amplification process. The proposed pulse shaping with high dynamics is performed by shaping interventions at at least two different points of a gain process. In addition to shaping the seed pulse - e.g. For example, a pulse can be preformed by modulating the diode current - at least one other shaping intervention is made.

The further shaping intervention may further comprise the concept that a seed pulse to be amplified is built up from a plurality of partial pulses. For example, multiple sub-pulses may be different (eg, via the attenuation unit 4 in FIG 1 reduced) dynamic ranges are used. As a further shaping intervention, in addition or as an alternative, partial pulses of partial seed pulse sequences can be introduced into the amplification process at different points of the amplifier chain 5. For example, as in 1 shown, the introduction of the laser pulses of the seed laser 3C in front of the fiber amplifier stage 5B respectively. Alternatively or additionally, laser pulses may follow a fiber amplifier stage, eg after the fiber amplifier stage 5B to be introduced.

A basic idea here is that a cascaded arrangement of partial pulse seed sources is responsible for temporally successive segments of a seed pulse, the pulse durations of the segments usually being shorter than the pulse duration of the output pulses. For example, in the above example, partial pulses / intermediate pulses with pulse durations in the range of 10% to 90% of, for example, 250 ns can be combined. In general, shorter or longer pulse durations of eg 50 ns or 10 μs can also be used Partial pulses / intermediate pulses are combined. In this case, partial pulse seed sources can each be designed as a single seed diode (as described below in order to simplify the description in FIGS 5 to 7 converted) or go back to a common (seed) seed diode (see 8th ).

In general, an amplified output pulse is then based on the amplification of at least two seed pulses of different seed pulse sequences.

The 4A and 4B illustrate the partial pulse approach in the generation of pulse shapes (a single pulse or a pulse envelope of a burst pulse train) with high dynamics. 4A schematically shows a superposition of contributions from two sub-pulses 21A . 21B (With partial pulse durations TA, TB of, for example, each approximately half the pulse duration T), each one as in 3 have shown amplitude curve, wherein the associated amplitude curves have different lower limits (plateau amplitudes) and upper limits (maximum amplitudes). The partial pulse 21A In the lower amplitude range, essentially a time-advanced segment of the seed pulse forms and the partial pulse in the higher amplitude range essentially forms a segment of the seed pulse following in time.

Combine more and more partial pulses - eg shows 4B a combination of four partial pulses with partial pulse durations Ti - can be found in the 2 approximate the "ideal" amplitude curve shown. In the example shown, a first subpulse seed source controls the amplitude of a first subpulse / segment and an Nth subpulse seed source controls the amplitude of an Nth subpulse / segment. In this case, the time duration of the N segments, ie the partial pulse duration of the partial pulses, can be (substantially) the same or they can be at least partially different.

Furthermore, contributions from subpulse seed sources may overlap in time. For example, a first partial pulse seed source can radiate from beginning to end, and a second partial pulse seed source is switched on from an adjustable point in time.

In some embodiments, as already associated with 1 Thus, the sequential amplification itself can be used to increase the dynamics of the pulse amplitudes of the sub-pulse seed sources.

The following embodiments are explained by way of example for seed diodes as seed lasers and fiber amplifier stages as amplifier stage. However, other types of seed lasers and amplifier stages, such as those already mentioned, may be used depending on the amplifier system.

5 shows, as a further exemplary embodiment, an amplifier chain 20 which is repeatedly grounded via the amplification process after several (eg fiber) amplifier stages. By way of example, a first seed diode controls 23A the amplitude of the (temporally) first partial pulse of a partial seed pulse train 23A ' , a seed diode 23B that of the second partial pulse of a partial seed pulse train 23B ' , ... and a seed diode 23N that of the Nth subpulse. In general, a seed laser can also control one or more subsequent partial pulses.

After the first seed diode 23A there is a first amplifier stage 25A (For example, a fiber amplifier stage), in which the first partial pulse of the partial seed pulse train 23A ' is coupled to the gain. The amplified first partial pulse / intermediate pulse is via a combiner (combiner unit 9A) (eg in the free jet or fiber-coupled) with the second (not yet amplified) partial pulse of the part-seed pulse train 23B ' merged, so that the resulting pulse, for example, a longer pulse duration (for example, the sum of the pulse durations of the first and the second partial pulse) has. In general, the subpulses / intermediate pulses can be temporally spaced apart from one another, in particular with a time offset which is smaller than the seed pulse duration, can be combined, join in time with one another or overlap in time (merge into one another).

Each subpulse can be assigned a time range (for example, a segment) of the output pulse ultimately leaving the amplifier chain 5 '. The high dynamics of such an assignment is based on the use of the sequence of amplifier stages 25A . 25B ... 25N back. It should be noted here that the time position of a time range (segment) does not have to correspond to the position of the associated seed diode in the sequential structure. Rather, they can differ from each other. Depending on the target pulse shape, a partial pulse for a corresponding time range is introduced into the amplification process. Usually, partial pulses are introduced into the cascade earlier for more intensified time ranges, as partial pulses for less strongly amplified time ranges of the output laser pulse. In 4B For example, four partial pulses are shown, which are amplified corresponding to four segments of the generated output pulse. That is, the amplified output pulse generally comprises electromagnetic radiation due to the four seed pulses, thus based on the amplification of four seed pulses of different seed pulse sequences.

In the embodiment according to 6 is the high dynamics via a combination unit 9A generated. For example, if one goes from two (or more) equally strong seed diodes 33A . 33B (as an example of a seed laser), one channel may be the combiner unit 9A for example, the partial pulse of the seed diode 33A transmit to 90%, with the other channel of the combining unit 31 the partial pulse of the seed diode 33B only 10% transmitted. A temporal offset and / or overlap of the partial pulses can be achieved by controlling the seed diodes 33A . 33B respectively. A correspondingly resulting combined laser pulse is fed to an amplifier stage 35. Analogously, more than two seed diodes can be combined with corresponding selectable ratios, offsets and / or overlaps, in particular spaced from each other in time, adjoin one another in terms of time or overlapping in time. For example, at least two of the seed pulses may be spaced apart with a time offset less than the seed pulse duration.

The embodiment according to 6 (As well as the embodiments of the following figures), for example, in the cascade of 5 at one or more of the seed diodes 23A ,... to get integrated.

In the embodiment according to 7 becomes a unit 41 when combining two (or more) partial pulses of two seed lasers 43A . 43B used. The unit 41 For example, acts uniformly over the pulse duration on the amplitude profile of one of the partial pulses. For example, one indicates the seed laser 43A associated optical arm an amplifier or a Abschwächeinheit as a unit 41 on, so that eg in a combination unit 9A Equally combined partial pulses cover different, possibly adjustable, amplitude ranges. Thus, an increased amplitude dynamics is generated, which in the subsequent amplification in an amplifier stage 45 can be used for precompensation. The timing of the seed laser 43A . 43B in turn, can be done according to the affected segment (by far, overlapping, merging, etc.).

In further embodiments, multiple sub-pulses may be generated with only one seed laser. As exemplified in 8th can be shown first with a splitter 51 a seed pulse of a seed diode 53 in two optical arms associated with each other 53A . 53B spreading partial pulses are optically split. Based on part-seed pulse trains thus formed 53A ' . 53B ' Then, the desired amplitude dynamics is generated, so that an output pulse (its electromagnetic radiation) goes back to at least two seed pulses of different (partial) seed pulse sequences.

For example, in 8th in the optical arm 53A a partial pulse (eg as in 7 with the unit 41 ) attenuated or amplified. The other optical arm 53B indicates a delay, for example over a fiber link 57 (or a free jet propagation) on. Subsequently, both sub-pulses are again corresponding to the affected segments at a distance, overlapping, merge into one another, etc. in a combination unit 9A combined (weighted or weighted) and fed to an amplifier stage 55.

In addition, one or more pulse shaping devices (modulators) may be used for timing pulse shaping between amplifier stages.

9 shows similar 5 an amplifier chain 20 ' that is a cascade of amplifier stages 61 having. Injected seed pulses of a laser, for example a seed laser diode 63 , be in the amplifier stages 61 sequentially with training from the amplifier stages 61 amplified associated intermediate pulses. The amplifier chain 20A outputs correspondingly amplified output pulses, each based on a coupled seed pulse, which - as explained below - was amplified and modulated in amplitude.

Between successive amplifier stages 61 can pulse-shaping devices 60 be provided for changing the amplitude of an associated intermediate pulse. For example, the pulse-shaping device 60 a unit for changing the amplitude, ie the amplitude curve during the pulse duration of the intermediate pulse. It is designed, for example, as an optical modulator, for example as an acousto-optical modulator or electro-optical modulator, which is designed to decouple energy during the pulse duration of the intermediate pulse, so that the pulse shape changes, in particular the amplitude in the corresponding temporal range / Segment reduced.

In 10 is the concept of truncating the amplitude of intermediate pulses with an amplitude curve 71 clarified. For example, an acousto-optic modulator is controlled in such a way that the front side of the intermediate pulse (small t-values) experiences losses which decrease with increasing t-values. In this way, the amplification can be formed in such a way that the amplification takes place quasi with an amplitude characteristic which corresponds to the "ideal" amplitude characteristic 73 (similar 2 ) is approximated.

The intermediate pulses may further (as previously explained) before or after the pulse-shaping device 60 be supplemented with other sub-pulses to the desired Reach dynamic range. Accordingly, then amplified output pulses, generally their electromagnetic radiation in each case go back to several coupled seed pulses and thus each of the output pulses based on the gain of several seed pulses. Moreover, the pulse-shaping device 61 For example, be used for ASE suppression.

In this way, pulse deformations may be corrected, for example, due to the saturation of the gain before or between the fiber amplifier stages 61.

Looking back on 1 It will be appreciated that the structure illustrated therein schematically illustrates the weighted combining of (sub) pulses of the seed sources 3A . 3B shows. Furthermore, the structure comprises an injection of further partial pulses of the seed source 3C in front of the amplifier stage 5B as well as, for example, an amplitude adjustment before the amplifier stages 5B and 5C ,

With regard to the various concepts disclosed herein, e.g. a fiber-seed laser are used, the (possibly stretched) seed pulses are divided and at least one side given to a delay unit, which delays the split seed pulses to each other. The divided and possibly delayed seed pulses may optionally additionally or alternatively be modulated with a modulator in the respective branch in their energy and subsequently recombined. In addition, a modulator for merging may be provided to clip the correspondingly composed pulse. Thereafter, a series of further amplifiers, e.g. Fiber, rod, slab, disk-based, can form an amplifier chain. Between these amplifiers a supplementary pulse shaping as shown in the examples of fiber amplifier chains can be made.

With regard to the initially mentioned seed source of a UKP laser, the seed pulse sequence can have an envelope whose amplitude profile can be adjusted in accordance with the concepts disclosed herein. Furthermore, UKP seed pulses may be closer together than the seed clock dictates. This is in the determination of the target pulse shape and the corresponding control of the seed diodes and / or modulator (s) of the drive unit 11 For example, to consider a reduction in the repetition rate.

The concepts disclosed herein further allow the output pulse (e.g., with powers in the W range) coming from the (e.g., fiber-based) amplifier chain to be used as an input pulse for e.g. Insert a disk laser multiplex amplifier system with one or more (disk laser) amplifier stages. The high power laser beam (e.g., in the kW range) ultimately provided by the laser assembly is then applied to the particular application, for example, a laser processing application.

In some applications, it may be advantageous to modulate the laser beam with high power, for example on a workpiece to be machined, quickly in the performance, in particular to interrupt the irradiation. For this purpose, external, the laser beam generating laser assembly downstream, modulators, etc. can be used. These allow the laser arrangement to be operated at a fixed (the "optimal") operating point and thus at constant and known beam parameters. However, such modulators are costly and z.T. complex in the implementation, since they and possibly subsequent structures the z.T. to handle (dissipate) very high decoupled power.

In some embodiments, an external modulator may be provided prior to laser processing to adjust the output power to processing histories. For example, according to a (e.g., crystal-based) power amplifier, the output pulse may be cropped by an external modulator without appreciably changing the pulse shape (a single pulse or a pulse envelope in burst pulse sequences). This can e.g. desired when turning around a curve in material processing, e.g. a curve intersects, e.g. to keep the introduced energy constant.

Using the concepts disclosed herein, alternatively or in addition to an external modulator, the power of the input pulses may be varied for a main amplifier following a gain chain, eg for the disk multiplex amplifier. That is, for example, the output pulses of the amplifier chain 5 in 1 For example, the peak pulse power extracted from the gain chain or the repetition rate are adjusted. The procedure using highly dynamic seedling will be explained below as an example for the disk multiplex amplifier as the main amplifier. The procedure can be transferred to a wide variety of main amplifier systems and amplifier chains. As noted, other active medium amplifier systems such as a slab or a rod-type fiber can also be used with respect to the concepts disclosed herein.

After a change in the coupled-in output pulses of the amplifier chain 5, the power extraction from the laser disk of the disk multiplex amplifier also changes. This can result in a change in the gain in the main amplifier, a change in the gain from the laser disk, and a change (typically in the millisecond range) in thermal stresses, e.g., after a short time (typically in the range of microseconds). lead the laser disc.

To compensate for these two aspects, the pump power for the disk multiplex amplifier can be changed in a modulation of the supplied pulse power such that the dissipated power and thus the thermal lens, which arises in the laser disk, remains constant to a first approximation.

Further, the change in the gain of the disk multiplex amplifier may be compensated via a dynamic change in the input pulse power, or the change may be limited by an effect limiting the maximum gain (e.g., cross-ASE, auxiliary resonator or controlled pump power in the main amplifier).

The change in pump power in the main amplifier can be e.g. either controlled or regulated. For the latter case, a measurement may be made of the disk power or other parameter describing the thermal lens (e.g., disk temperature). For example, For example, the beam parameters of the laser beam or of an auxiliary laser beam, which propagates collinearly to the laser beam, can be measured and used as a control signal. Appropriate modeling can be used, e.g. Depending on the laser configuration, heat generation may increase or decrease with reduced input pulse power and constant pump power.

A disadvantage of the procedure described above is that the laser gain, in particular the laser gain over the pulse duration, can not be kept constant, so that when the input pulse power changes, corresponding pulse peaks can occur. Such pulse overshoots can be suppressed, for example, by suitable adaptation of the input pulse energy, and in particular by adaptation of the amplitude profile of the injected output pulses by means of the dynamic seed concepts disclosed herein.

1. (1) Die Ausgangsleistung der Laseranordnung wird über die Eingangspulserzeugung des Scheibenmultipassverstärkers nach unten moduliert, beispielsweise um die halbe Ausgangsleistung zu erhalten.
2. (2) Die Sättigung des Scheibenmultipassverstärkers ändert sich und die Scheibe wird z.B. wärmer, da das Inversionsniveau steigt. Gleichzeit steigt die Verstärkung des Scheibenmultipassverstärkers.
3. (3) Die Pumpleistung wird reduziert, so dass die Verstärkung zurückgeht.
4. (4) Die Eingangspulsenergie muss wieder etwas angehoben werden, um eine konstante Ausgangsenergie nach dem Scheibenmultipassverstärker beizubehalten.
5. (5) Es ergibt sich eine bessere Sättigung und die Laserscheibe wird kälter. Entsprechend wird die Pumpleistung für den Scheibenmultipassverstärker erhöht, die Eingangspulsenergie ist wieder zu reduzieren und so fort.

An example flow may summarize the following steps:

1. (1) The output power of the laser array is modulated down through the input pulse generation of the disk multiplex amplifier, for example, to obtain half the output power.
2. (2) The saturation of the disk multiplex amplifier changes and the disk becomes warmer, for example, as the inversion level increases. At the same time, the gain of the disk multiplex amplifier increases.
3. (3) The pump power is reduced so that the gain decreases.
4. (4) The input pulse power must be raised again slightly to maintain a constant output power after the disc multiplex amplifier.
5. (5) There is better saturation and the laser disc gets colder. Accordingly, the pump power for the disk multiplex amplifier is increased, the input power is to be reduced again and so forth.

Whenever pulse peaks are to be expected within the scope of a step taken, the amplitude characteristic of the output pulses of the amplification chain coupled into the main amplifier can be adapted accordingly. In addition, the beam caustics may change due to the modulation, so that the output beam size may also have to be adapted, whereby the changes may be based on different time scales. It will be appreciated that the amplitude adjustment to the respective target amplitude curve is generally a complex control process, e.g. can be parameterized via a suitable model.

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

Claims (20)

A laser amplifier system (1) comprising a seed laser pulse source unit (3) for providing at least two seed pulse trains for subsequent amplification, seed pulses (3 ') of the at least two seed pulse trains having a respective seed pulse duration (T, TA, TB ) and within a range during the respective seed pulse duration (T, TA, TB) varying and adjustable in their course seed amplitude (A), and at least one amplifier stage (5A, 5B, 5C) for amplifying the at least two seed Pulse trains and to output an output pulse train with Output pulses (5 ') having an output pulse duration, the at least two seed pulse sequences being coupled into the amplifier stage (5A, 5B, 5C) in such a way that an amplitude characteristic of an output pulse (5') of the output pulse train is based on contributions from at least two seed pulses. Pulses (3 '), each associated with one of the at least two seed pulse sequences, goes back. Laser amplifier system (1) according to Claim 1 , wherein the laser amplifier system (1), and in particular the control of the seed laser pulse source unit (3), is designed such that the at least two seed pulses (3 '), which contribute to the amplitude characteristic of an output pulse (5'), with respect to each other in time are spaced, temporally adjoined, or overlapping in time, and optionally wherein the at least two seed pulses (3 ') are spaced apart with a time offset less than the seed pulse duration (T). Laser amplifier system (1) according to Claim 1 or 2 further comprising an optical delay unit (57) for generating a laser pulse time offset between the at least two seed pulses (3 ') contributing to the amplitude characteristic of an output pulse (5'). A laser amplifier system (1) according to any one of the preceding claims, wherein the amplifier stage (5A, 5B, 5C) is a fiber, rod, slab, and / or disk laser amplifier stage. Laser amplifier system (1) with a seed laser pulse source unit (3) for providing at least two seed pulse trains for a subsequent amplification, wherein seed pulses (3 ') of the at least two seed pulse trains have a respective seed pulse duration (T, TA, TB) and one within one Range during the respective seed pulse duration (T, TA, TB) varying and adjustable in their seed amplitude (A), and a gain chain (5) comprising a sequence of at least two gain stages (5A, 5B, 5C) coupled in series, the gain in the gain stages (5A, 5B, 5C) being sequentially formed by the gain stages (5A, 5B, 5C) and the amplification chain (5) outputs an output pulse train with output pulses (5 ') having an output pulse duration, wherein an amplitude characteristic of an output pulse (5 ') of the output pulse train is based on contributions from at least two seed pulses (3'), which are each assigned to one of the at least two seed pulse sequences. Laser amplifier system (1) according to Claim 5 , further comprising an optical delay unit for generating a laser pulse time offset between a seed pulse of one of the at least two seed pulse trains and an intermediate pulse (3 ") and / or an optical delay unit (57) for generating a laser pulse time offset between seed pulses different of the at least two seed pulse trains. Laser amplifier system (1) according to Claim 5 or 6 , wherein the laser amplifier system (1), and in particular the control of the seed laser pulse source unit (3), is designed such that the at least two seed pulses (3 '), which contribute to the amplitude characteristic of an output pulse (5'), temporally from each other are spaced, temporally adjoined or overlapping in time, and where optionally seed pulses having a time offset smaller than the seed pulse duration (T) are spaced apart, and / or wherein the laser amplifier system (1), and in particular the drive the seed laser pulse source unit (3) is designed such that at least one seed pulse (3 '), which contributes to the amplitude characteristic of an output pulse (5'), is temporally spaced in relation to an intermediate pulse, in time thereto or in time therewith overlaps, and optionally wherein the at least one seed pulse with a time offset that is smaller than the seed pulse duration (T), spaced from the intermediate pulse. Laser amplifier system (1) according to one of Claims 5 to 7 in which a temporal segment of the output pulses (5 ') originates from at least one seed laser pulse source whose seed pulses pass through all amplifier stages (5A, 5B, 5C) of the amplification chain (5), and / or where the amplification chain (5) is a fiber -, rod, slab, and / or disk laser amplifier stage comprises. Laser amplifier system (1) according to one of the preceding claims, wherein the seed pulses to be amplified to the amplitude characteristic of an output pulse (5 ') of one of the at least two seed pulse sequences of a sub-seed pulse sequence (23A', 23B ', 53A') are to be amplified. , 53B ') whose partial pulse duration (TA, TB) is shorter than the output pulse duration of the output pulses (5'). Laser amplifier system (1) according to one of the preceding claims, further comprising at least one splitting unit (51) for splitting a seed laser pulse, a laser pulse source in two or more pulses and / or at least one attenuation unit (4) for reducing the amplitude of laser pulses, partial pulses and / or intermediate pulses and / or at least one pulse-shaping device (15, 60) for changing the amplitude (A) of one of the seed pulses, wherein the pulse-shaping device (15, 60) is designed as an acousto-optical modulator or electro-optical modulator for a truncation of the amplitude (A) of at least one of the seed pulses in at least one temporal subregion, and / or at least one combination unit (9A), such as an X: (100 X-fiber combiner, for combining seed pulses of at least two laser pulse sources with one another or seed pulses of at least one laser pulse source with intermediate pulses (5 ') or intermediate pulses (5') with intermediate pulses (5 '). Laser amplifier system (1) according to one of the preceding claims, wherein the seed laser pulse source unit (3) has at least one laser pulse source in the form of an adjustable energizable laser diode (23A), and optionally for each of the at least two seed pulse sequences a separate laser pulse source. Laser amplifier system (1) according to one of the preceding claims, wherein the seed laser pulse source unit (3) comprises two laser pulse sources, wherein the pulses of the first laser pulse source, in particular via a attenuator or an amplifier, with the pulses of the second laser pulse source in a combination unit (9A) Create intermediate pulse train. Laser amplifier system (1) according to Claim 12 , further comprising at least one pulse-shaping device (15, 60) for changing the amplitude (A) of one of the intermediate pulses (3 "), wherein the pulse-shaping device (15, 60) as acousto-optic modulator or electro-optical modulator for a trimming of Amplitude (A) of at least one of the associated intermediate pulses (3 ") is formed in at least a temporal portion and optionally between two adjacent amplifier stages (5A, 5B, 5C) is arranged. Laser amplifier system (1) according to one of the preceding claims, further comprising a control unit (11), which is designed for setting the seed pulse shape, in particular for driving a seed source, a combination unit (9A) and / or a pulse-shaping device (15, 60) the control unit (11) is optionally designed to derive the seed pulse profile from a target pulse profile, in particular a target amplitude characteristic of one of the output pulses (5 '), and the seed pulse form, in particular the contributions from the at least two seed pulses (3 ') and / or the circumcision of the amplitude (A) at least one of the associated intermediate pulses (3 "), adjust accordingly. Laser amplifier system (1) according to one of the preceding claims, further comprising at least one pulse-shaping device following the amplification for changing the amplitude of the output pulses (5 ') of the output pulse train, wherein the pulse-shaping device is designed as an acousto-optical modulator or electro-optical modulator for a truncation of the amplitude of the output pulses (5 ') of the output pulse train and in particular after a crystal-based power amplifier to reduce the intensity of the pulse is formed without significant change in the pulse shape, said the control unit (11) is optionally designed to control the intensity of the pulse-shaping device during material processing, in particular during beam guidance around a curved path, in order to reduce the output pulses. Method for generating a sequence of amplified output pulses (5 ') Providing at least two seed pulse sequences (23A ', 23B', 53A ', 53B') for subsequent amplification, seed pulses (3 ') of the at least two seed pulse trains (23A', 23B '; 53A', 53B ') each have a seed pulse duration (T, TA, TB) and within a range during the seed pulse duration (T, TA, TB) varying and adjustable in their course seed amplitude (A), and Amplifying the seed pulses (3 ') in an amplifier stage (5A, 5B, 5C) such that an output pulse train results with output pulses (5') having an output pulse duration, wherein the at least two seed pulse trains are coupled into the amplifier stage (5A, 5B, 5C) such that an amplitude characteristic of an output pulse (5 ') of the output pulse train is based on contributions from at least two seed pulses (3'), each one of the at least two seed pulse sequences are assigned, goes back. Method according to Claim 16 wherein an amplitude characteristic of one of the output pulses (5 ') is further due to a truncation of the amplitude (A) of at least one seed pulse (3') and / or wherein the amplitude characteristics of the seed pulses (3 ') are adapted to one another such that a dynamic range after amplification is available which is greater than the dynamic range of a single seed pulse (3 '). A method of generating a train of amplified output pulses (5 ') by providing at least two seed pulse trains (23A', 23B ';53A', 53B ') for a subsequent one Amplification, wherein seed pulses (3 ') of the at least two seed pulse trains (23A', 23B ';53A', 53B ') each have a seed pulse duration (T, TA, TB) and within a range during the seed cycle. Pulse duration (T, TA, TB) varying and adjustable in their seed amplitude (A), and amplifying the seed pulses (3 ') in sequentially arranged amplifier stages (5A, 5B, 5C) to form the amplifier stages (5A , 5B, 5C) associated with intermediate pulses (3 "), so that an output pulse train with an output pulse duration output pulses (5 ') results, wherein an amplitude curve of an output pulse (5') of the output pulse train to contributions of at least two seed pulses (3 ' ), each associated with one of the at least two seed pulse sequences. Method according to one of Claims 16 to 18 , wherein at least one seed pulse sequence is coupled into the amplifier stage (5A, 5B, 5C) in such a way and wherein optionally at least one seed pulse train is coupled into a subsequent amplifier stage (5A, 5B, 5C) such that an intermediate pulse to be amplified is formed whose amplitude characteristic is due to contributions from at least two seed pulses (3 '), which are each assigned to one of the at least two seed pulse sequences. Method according to Claim 18 or 19 in which an amplitude characteristic of one of the output pulses (5 ') is also due to a truncation of the amplitude (A) of at least one intermediate pulse and / or wherein the amplitude profiles of the seed pulses (3') and optionally the truncation of the amplitude (A) of at least one associated Intermediate pulses (3 ") are adapted to one another in such a way that a dynamic range after amplification is available which is greater than the dynamic range of a single seed pulse (3 ').

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