Method for amplifying ultrashort laser pulses and method for designing an amplification system
By compensating for the nonlinear effects caused by dynamic amplification and bandwidth amplification during the amplification of ultrashort laser pulses, and by utilizing additional phase contribution and spectral adjustment, the problem of pulse shape change was solved, and high-quality laser pulse amplification was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2021-02-09
- Publication Date
- 2026-03-27
AI Technical Summary
During the amplification of ultrashort laser pulses, the nonlinear effects caused by dynamic amplification and bandwidth amplification lead to changes in pulse shape and degradation of pulse quality. In particular, when the pulse power of the laser pulse approaches or exceeds the damage threshold of the amplifier stage, the nonlinear phase change affects the quality of the compressed laser pulse.
Phase and spectral adjustments are made by imparting additional phase contributions to the laser pulse and/or altering the spectrum to compensate for nonlinear effects caused by dynamic amplification and bandwidth amplification, especially before or after compression. This is achieved using devices such as electro-optic modulators, spectral filters, and optical fibers for phase and spectral adjustment.
High-quality ultrashort laser pulses can be obtained by neutralizing dynamic amplification and/or bandwidth amplification effects through appropriate, quasi-complementary influences on the laser pulse, especially by reducing or avoiding pulse quality degradation after compression through additional phase contributions and/or spectral changes.
Smart Images
Figure CN115088144B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present invention relates to a method for amplifying ultrashort laser pulses and a method for designing an amplification system. BACKGROUND
[0002] Ultrashort laser pulses are usually amplified by means of the so-called CPA (English: Chirped Pulse Amplification) technique, wherein an ultrashort laser pulse, in particular generated by a laser pulse source, in particular an ultrashort pulse laser also referred to as seed laser, is temporally stretched, wherein a temporally stretched laser pulse is obtained. This temporally stretched laser pulse is then amplified, in particular in at least one amplifier stage or an amplification chain consisting of multiple amplification stages, wherein an amplified temporally stretched laser pulse is obtained. Here, the temporal stretching of the laser pulse is in particular used to avoid that the pulse power of the laser pulse exceeds a damage threshold or a destruction threshold of at least one amplifier stage and to reduce unwanted nonlinear processes / effects. Subsequently, the amplified temporally stretched laser pulse is again temporally compressed, as a result of which an amplified ultrashort laser pulse is finally obtained. Here, a dynamic amplification also referred to as Gain-Dynamik, can lead to a change in the pulse shape of the laser pulse, in particular due to saturation of the amplification. In particular, this problem arises as soon as the operation of at least one amplification stage is sufficiently close to or above its saturation. In addition, the spectral dependence of the amplification, i.e. the bandwidth amplification can also contribute to the change in the pulse shape. In addition, the inventors have recognized that due to the dynamic amplification and / or due to the bandwidth amplification, in addition to the nonlinear effects in at least one amplifier stage or amplifier chain (often also referred to as amplification system), a change in the phase (hereinafter also referred to as nonlinear phase) occurs. This change in the nonlinear phase (hereinafter also referred to as amplification phase contribution and can be a dynamic amplification phase contribution, a bandwidth amplification phase contribution, or a combination of a dynamic amplification phase contribution and a bandwidth amplification phase contribution) influences the pulse quality of the compressed laser pulse, that is to say ultimately the quality of the useful beam obtained. SUMMARY
[0003] The present invention is based on the object of developing a method for amplifying ultrashort laser pulses and a method for designing an amplification system, wherein at least the above-mentioned disadvantages are reduced.
[0004] This object is achieved by the present technical teaching provided, in particular the teaching of the independent claims and the technical teaching of the embodiments disclosed in the dependent claims and the description.
[0005] This object is achieved, inter alia, by developing a method for amplifying an ultrashort laser pulse, wherein at least one amplification phase contribution selected from the group consisting of a dynamic amplification phase contribution, a bandwidth amplification phase contribution, and a combination of a dynamic amplification phase contribution and a bandwidth amplification phase contribution is compensated for by imparting an additional phase contribution on the laser pulse prior to compression in such a way that the at least one amplification phase contribution is compensated for after compression. Alternatively or additionally, the spectrum of the laser pulse is changed in such a way that the at least one amplification phase contribution is compensated for after compression. By means of the additional phase contribution and / or the spectrum change of the laser pulse, the method presented here enables compensation of the at least one amplification phase contribution in such a way that a deterioration of the pulse quality after compression is reduced, preferably avoided. In this way, a high-quality, ultrashort, amplified laser pulse can be obtained, which can be used in an improved manner, preferably without restrictions, for desired applications, whether for material processing (e.g. laser cutting, laser welding or laser polishing, in particular micro material processing, frequency conversion) or for scientific purposes (e.g. pumping of an OPCPA or spectroscopy).
[0006] In particular, it is recognized according to the present application that the effects of dynamic amplification and / or bandwidth amplification, as well as nonlinear effects occurring in the amplification system, can be neutralized by suitable, quasi-complementary influences on the laser pulse, in particular in such a way that the deformations ultimately produced in the amplification process ultimately result in a pulse shape that can be well compressed despite the nonlinearities occurring therein. This can be achieved by an additional phase contribution and / or by changing the spectrum of the laser pulse. In particular, the additional phase contribution can be designed in such a way that at least one amplification phase contribution is pre-compensated for by the nonlinearities occurring. Alternatively or additionally, in particular spectral filtering and / or spectral shaping can be carried out in such a way that a nonlinear phase is produced here from the pulse shape, which can be well compressed together with the remaining phase contributions. In comparison with the additional phase contribution, the spectrum change of the laser pulse contributes to an improved pulse quality over a greater range of pulse energies, since the additional phase contribution requires nonlinear effects in order to be compensated for. However, these only occur at high pulse energies. Accordingly, in the case of too low a pulse energy for the nonlinear effects to occur to a sufficient extent, the compressed laser pulse imparted with the additional phase contribution will have a deteriorated pulse quality after compression. In contrast, changing the spectrum does not immediately lead to a phase change, so this process is also suitable for lower pulse energies.
[0007] Here, an ultrashort laser pulse is understood to be a laser pulse whose temporal bandwidth is in the range of ps to fs, in particular. Preferably, the temporal pulse width of the compressed ultrashort laser pulse is at most 10 ps, preferably a few hundred fs or less.
[0008] A dynamic amplification phase contribution is understood to be a change in the nonlinear phase of the laser pulse which is derived by dynamic amplification, in particular in at least one amplifier stage or amplifier chain, and by nonlinear effects. Here, this can be a temporal phase contribution and / or a spectral phase contribution.
[0009] A bandwidth amplification phase contribution is understood to be a change in the nonlinear phase of the laser pulse which is derived by amplification of the amplification medium, i.e. the spectral dependence of the amplification, in at least one amplifier stage, or in at least one amplifier in an amplifier chain, and by nonlinear effects. Here, this can be a temporal phase contribution and / or a spectral phase contribution.
[0010] Now, an amplification phase contribution is understood to be, in particular, a dynamic amplification phase contribution, or a bandwidth amplification phase contribution, or a combination of a dynamic amplification phase contribution and a bandwidth amplification phase contribution.
[0011] Correspondingly, an additional phase contribution is understood to be, in particular, a phase change of the laser pulse which is induced in a targeted manner, the purpose of which is to compensate for the amplification phase contribution. The additional phase contribution can be a temporal and / or a spectral phase contribution.
[0012] It is thus possible to compensate only for the dynamic amplification phase contribution. Alternatively, it is possible to compensate only for the bandwidth amplification phase contribution. However, it is also possible to compensate not only for the dynamic amplification phase contribution but also for the bandwidth amplification phase contribution - or a combination thereof.
[0013] Depending on the specific design of the amplification system and the ultrashort laser pulse, the dynamic amplification phase contribution can dominate, but the bandwidth amplification phase contribution can also dominate. It is thus optionally possible, in particular in limiting cases, to compensate for only one of the two contributions in order to obtain an amplified ultrashort laser pulse having a high pulse quality. However, it is also possible to compensate for both contributions in order to ensure a high pulse quality of the amplified ultrashort laser pulse.
[0014] Here, a nonlinear effect is understood to be, in particular, an effect which depends on the intensity of the laser pulse, in particular an effect which occurs at high intensities. These effects are referred to as nonlinear effects because these effects include the square of the electric field strength of the laser pulse.
[0015] Dynamic amplification is understood to mean, inter alia, that, in particular when high pulse energies are to be extracted, i.e. when high energies are to be called upon from at least one amplifier stage, the time-stretched laser pulse to be amplified and thus simultaneously its frequency components experience different amplification at the beginning of the time pulse than at the end of the time pulse, since the population inversion of the amplifying medium is changed by the energy extraction. Since the time-stretched pulse is stretched by a so-called chirp, it has different frequency components at the beginning of the time pulse than at the end of the time pulse. As a result, in particular the frequency components at the beginning of the time pulse are amplified more than at the end of the time pulse, resulting in a pulse deformation. The deformation of the time-stretched pulse also influences the compressed pulse shape due to nonlinear effects and ultimately leads to a deteriorated compression, i.e. a pulse deformation and / or a pulse duration extension compared to the time width of an undisturbed compressed laser pulse.
[0016] Bandwidth amplification is understood to mean, inter alia, that the amplification, i.e. in particular the gain of an amplifier or amplifier chain, has a spectral dependence and a limited bandwidth. This leads to a spectral deformation of the laser pulse, in particular in the case of a non-optimal matching of the bandwidth amplification to the spectrum of the laser pulse to be amplified, which likewise leads to a deformation of the time-stretched laser pulse and also influences the compressed time pulse shape due to nonlinear effects. This can lead to a deteriorated compression, i.e. a pulse deformation or a pulse duration extension relative to the time width of an optimally amplified laser pulse, in particular in the case of an unchanged or only slightly changed spectrum due to the bandwidth amplification.
[0017] Amplification phase contribution is compensated for in particular means that the Strehl ratio of the laser pulse, due to the possibly remaining residual components of the amplification phase contribution, is not more than 5% smaller than in the case of a complete avoidance or complete compensation of the amplification phase contribution. Thus, the amplification phase contribution, or the influence or effect of the amplification phase contribution, does not need to be compensated for to be in particular 100%, but a compensation within the above-mentioned range is sufficient. However, advantageously, the amplification phase contribution is compensated for to a greater extent, so that, correspondingly, the Strehl ratio is less than 5%, in particular less than 2%, preferably less than 1%, compared to the case without amplification phase contribution. In the present application, the Strehl ratio, also referred to as Strehl number, is understood to mean the ratio of the pulse peak power to the theoretical pulse peak power of a Fourier-limited, i.e. perfectly compressed, pulse. Thus, the Strehl ratio of a perfect compression system is 1.
[0018] The compensated amplification phase contribution thus means, inter alia, that the influence or effect of the amplification phase contribution on the amplified ultrashort laser pulse is compensated for, in particular by optimizing the Strehl ratio.
[0019] In a preferred embodiment, the spectrum of the laser pulse is changed before amplifying the time-stretched laser pulse such that the amplification phase contribution is compensated after compression.
[0020] In another preferred embodiment, the spectrum of the laser pulse is changed while amplifying the time-stretched laser pulse such that the amplification phase contribution is compensated after compression.
[0021] In another preferred embodiment, the spectrum of the laser pulse is changed after amplifying the time-stretched laser pulse such that the amplification phase contribution is compensated after compression.
[0022] In another preferred embodiment, the spectrum of the laser pulse is changed before and after amplifying the time-stretched laser pulse such that the amplification phase contribution is compensated after compression.
[0023] In another preferred embodiment, the spectrum of the laser pulse is changed before and during amplifying the time-stretched laser pulse such that the amplification phase contribution is compensated after compression.
[0024] In another preferred embodiment, the spectrum of the laser pulse is changed during and after amplifying the time-stretched laser pulse such that the amplification phase contribution is compensated after compression.
[0025] In another preferred embodiment, the spectrum of the laser pulse is changed before, during and after amplifying the time-stretched laser pulse such that the amplification phase contribution is compensated after compression.
[0026] According to an extension of the application, at least one step selected from imparting an additional phase contribution and changing the spectrum of the laser pulse is performed when time-stretching the ultra-short laser pulse. Alternatively or additionally, the at least one step is performed before stretching the ultra-short laser pulse. Alternatively or additionally, the at least one step is performed after stretching the ultra-short laser pulse and before amplifying the time-stretched laser pulse. Alternatively or additionally, the at least one step is performed while amplifying the time-stretched laser pulse. This allows to exert an influence on the laser pulse in a desired manner before compressing the laser pulse such that, at the latest after compression, or already before compression, and possibly by compression, at least one amplification phase contribution is compensated due to the respective influence by the at least one step.
[0027] According to a preferred configuration, the at least one step is in particular changing the spectrum of the laser pulse.
[0028] According to a further preferred embodiment, at least one of the steps is to impart an additional phase contribution. The additional phase contribution is preferably imparted to the laser pulse during the temporal stretching or during the amplification, in particular by an electro-optical modulator, preferably a Pockels cell, arranged in the amplifier chain. However, the following preferred configuration is also possible: wherein the additional phase contribution is imparted to the laser pulse after the amplification, in particular by a volume Bragg grating (VBG).
[0029] According to an extension of the application, an additional phase contribution is imparted to the laser pulse by using a stretcher for the temporal stretching of the ultrashort laser pulse, to which an appropriately matched, wavelength-dependent propagation time variation is written or applied to the stretcher. Thus, while the temporal stretching is carried out in the stretcher, the additional phase contribution can be easily imparted to the laser pulse.
[0030] According to an extension of the application, an appropriately matched, wavelength-dependent propagation time variation is statically written or dynamically applied to the stretcher. Thus, a correspondingly suitably configured stretcher can be preferably statically coordinated with the additional phase contribution, in particular by a correspondingly written grating pitch. However, a variably matched stretcher can also be used, in particular a thermally modifiable stretcher or a stretcher which is modifiable in a tension-dependent manner according to a mechanical tension acting on the stretcher. In the latter case, the material of the stretcher can in particular be stretched by applying a tensile stress and preferably changing the tensile stress in a parameter-dependent manner, in particular in dependence on the additional phase contribution to be imparted. In particular, an optical fiber which can be mechanically stretched in a corresponding manner can be used as a stretcher. In the case of a thermally modifiable stretcher, a temperature profile can preferably be applied, in particular by at least one Peltier element, preferably by a plurality of Peltier elements which can in particular be arranged distributed over the length of the stretcher. Here, the relative distance of the individual Bragg elements of the stretcher from one another can be changed by an appropriate local temperature variation.
[0031] According to an extension of the application, the spectrum of the laser pulse is changed by using a stretcher for the temporal stretching of the ultrashort laser pulse, which is written or applied with a spectral filter. In particular, an optical fiber with a reflection grating in which a reflection curve is written can be used as a stretcher. Thus, the change of the spectrum can be carried out in a particularly compact and installation space-saving manner, while the temporal stretching is carried out.
[0032] Alternatively or additionally, the spectrum of the laser pulse is changed, preferably by filtering the laser pulse, by a spectral filter which is arranged in front of the stretcher or behind the stretcher in the propagation direction of the laser pulse. This is a particularly simple and flexibly adjustable implementation of the spectral change.
[0033] Alternatively or additionally, the spectrum of the laser pulse is changed, preferably by guiding the laser pulse, in the propagation direction of the laser pulse, through an optical fiber in front of or behind the stretcher, wherein a spectral filter is written into the optical fiber. Thus, in particular, the optical fiber used for beam guidance can additionally be used in any case to change the spectrum of the laser pulse.
[0034] Alternatively or additionally, the spectrum of the laser pulse is changed, preferably by spectral filtering and / or spectral shaping of the laser pulse before or during the laser pulse's passage through an amplifier in which or behind which self-phase modulation occurs. Self-phase modulation is a main source of nonlinear phase contributions, wherein self-phase modulation occurs in particular within or behind the last amplifier, in particular the main amplifier, of the amplifier chain. However, whether self-phase modulation occurs also depends on the spatial width of the laser pulse and the geometric design of the amplifier medium, wherein, depending on the structure type of the amplifier, self-phase modulation can also occur in front of the last amplifier or the main amplifier in the propagation direction, but in particular also in front of or behind a preamplifier. The spectral filtering and / or spectral shaping of the laser pulse preferably takes place before or during the laser pulse's experience of self-phase modulation, in particular the first self-phase modulation.
[0035] In particular, the spectrum of the laser pulse is changed, preferably by filtering and / or shaping, which is complementary or oppositely matched to at least one effect or a combination of effects of the selected active amplification and bandwidth amplification. For this purpose, in particular a separate transmissive filter or a transmissive filter written into an optical fiber can be used. In a stretcher which works in a reflective manner, a reflectivity can also be matched regionally in correspondence with the desired spectral filtering. Correspondingly, in the case of a stretcher which works in a transmissive manner, a transmissivity can be correspondingly matched. According to a further preferred configuration, a temporally arranged pulse attenuator, in particular an acousto-optic modulator or an electro-optic modulator, in particular a Pockels cell, is used as an alternative or supplement to the spectral change of the laser pulse. A spectral influence can thereby be achieved, since the laser pulse is preferably chirped, so that the various frequency or wavelength components of the laser pulse can be processed separately in time.
[0036] According to an embodiment of the application, the time-stretched laser pulse is amplified by an amplifier chain having a plurality of amplifiers. The spectrum of the laser pulse is changed by the laser pulse passing through at least one of the plurality of amplifiers of the amplifier chain, the bandwidth amplification of which is suitably matched in order to at least partially compensate for the at least one amplification phase contribution. Advantageously, the amplification phase contribution can be compensated for by suitably matching the bandwidth amplification, in particular at least for one of the amplifiers of the amplifier chain. By means of the matched bandwidth amplification, the spectrum of the laser pulse is changed, in particular spectrally shaped, during amplification in such a way that the at least one amplification phase contribution is at least partially compensated for. Preferably, the amplifier chain can comprise a plurality of amplifiers whose bandwidth amplification is suitably matched.
[0037] According to an embodiment of the application, for the change of the spectrum of the laser pulse, at least one of the plurality of amplifiers is used, the bandwidth amplification of which is suitably matched by the amplifier having a suitably matched doping. Here, the doping can be matched in particular by selecting at least one doping element or a combination of doping elements, and / or by suitably selecting the doping amount and / or the doping density, i.e. in particular the respective number and / or number density of extrinsic atoms.
[0038] Alternatively or additionally, the bandwidth amplification of at least one of the amplifiers is suitably matched by the amplifier having a suitably matched path length, in particular a suitably matched fiber length, for the laser pulse within the amplifier. For a given amplifier energy efficiency (Ausbeute), the population inversion in the amplifier depends on the path length of the laser pulse through the amplifier, in particular the fiber length of the amplifier configured as a fiber amplifier. Here, with a fixed energy efficiency and an increased path length or fiber length, this can in particular lead to a lower population inversion and thus to a spectral shift and / or deformation of the amplified laser pulse. By way of example, a red shift can occur in the case of a ytterbium-doped amplifier medium. Thus, the spectrum of the laser pulse can be suitably changed by matching the path length, in particular the fiber length, in order to at least partially compensate for the at least one amplification phase contribution.
[0039] According to an embodiment of the application, when amplifying the time-stretched laser pulse, at least 30%, preferably at least 50%, preferably at least 70%, preferably at least 90%, preferably more than 90% of the energy stored in the amplifier is called upon for amplifying the time-stretched laser pulse by means of the amplifier. The above-mentioned effects of dynamic amplification are in particular obtained in said range of amplification. In the amplifier, in particular in at least one amplifier stage or amplifier chain, energy is stored, in particular in the form of a population inversion, by optical pumping, in particular by means of a pump lamp, a pump diode or a pump laser source, wherein the population inversion is removed by the laser pulse passing through the amplifier, by means of which the stored energy is called upon.
[0040] According to an extended arrangement of the application, the B-integral for the laser pulse is greater than 3 rad after amplification. In particular in said range of the B-integral, the effects described here occur. In particular, the B-integral for the laser pulse is greater than 3 rad after passing through at least one amplifier stage, in particular an amplifier chain, in particular the entire amplifier chain. Here, the B-integral is a measure for the nonlinear phase shift of the laser pulse in the amplification system. It is defined as
[0041]
[0042] where I(z) is the light intensity along the beam axis (z direction) of the laser beam; z is the beam propagation direction, thus the position in the propagation direction, n2is the nonlinear refractive index, which quantifies the Kerr nonlinearity. Thus, n2I(z) is the nonlinear variation of the refractive index, wherein it can be easily seen that the B-integral states the total axial nonlinear phase shift accumulated when passing through the propagation path, in particular the amplifier chain here.
[0043] According to an extended arrangement of the application, at least one property of the compressor for the time-stretched laser pulse of the compression amplification is changed in order to at least partially compensate for the at least one amplification phase contribution. In this way, the compressor can also advantageously contribute to the compensation of the amplification phase contribution. In a preferred embodiment, in order to at least partially compensate for the at least one amplification phase contribution, the grating spacing of the compressor is changed, in particular by a mechanical extension or compression of the compressor, or a thermal application, in particular heating or cooling. It is also possible that the grating spacing is not constant along the extension of the compressor, but changes, for example linearly, quadratically or in any other or higher order function, for example by an inhomogeneous compression, stretching and / or thermal application of the compressor.
[0044] The object is also achieved by developing a method for designing an amplification system for amplifying ultrashort laser pulses, the method comprising the steps of determining at least one amplification phase contribution and providing at least one compensation element, the at least one amplification phase contribution being selected from the group consisting of a dynamic amplification phase contribution, a bandwidth amplification phase contribution, and a combination of a dynamic amplification phase contribution and a bandwidth amplification phase contribution, the dynamic amplification phase contribution being derived in the amplification system for an ultrashort laser pulse passing through the amplification system as a nonlinear phase change due to a dynamic amplification of the amplification system, the bandwidth amplification phase contribution being derived in the amplification system for an ultrashort laser pulse passing through the amplification system as a nonlinear phase change due to a bandwidth amplification of the amplification system; the at least one compensation element being arranged to compensate for the determined amplification phase contribution. In particular, the at least one compensation element is coordinated with the determined amplification phase contribution, almost complementarily or oppositely in effect. In particular, the compensation element is selected and configured such that it imparts an additional phase contribution to the laser pulse and / or changes the spectrum of the laser pulse, so that the amplification phase contribution and / or its effect on the amplified ultrashort laser pulse is compensated. In particular, the compensation element is arranged to compensate for the amplification phase contribution in the method for amplifying ultrashort laser pulses according to the invention or in one of the above-mentioned embodiments of the method for amplifying ultrashort laser pulses. In connection with the method for designing an amplification system, in particular the advantages already explained in connection with the method for amplifying ultrashort laser pulses are derived.
[0045] In particular, determining the amplification phase contribution means detecting the amplification phase contribution directly or indirectly. If the amplification phase contribution is detected directly, the value of the amplification phase contribution is obtained directly, in particular by determining or measuring the amplification phase contribution, by calculating the amplification phase contribution from at least one other measured variable, or by simulation. If the amplification phase contribution is detected indirectly, the effect of the amplification phase contribution on the amplified ultrashort laser pulse is determined, wherein this effect is used as a measure for the amplification phase contribution, in particular indirectly. In particular, the value of the amplification phase contribution is not obtained here as such.
[0046] According to an expansion of the application, the amplification phase contribution occurring in the amplification system is determined, preferably measured, in such a way that it is determined, preferably measured, by means of a phase measurement, in particular by means of Frequency Resolved Optical Gating (FROG) or Spectral Phase Interferometry for Direct Electric-field Reconstruction (SPIDER). Alternatively or additionally, the amplification phase contribution is preferably calculated from the measured spectrum. Alternatively or additionally, the amplification phase contribution is preferably calculated from a measurement in time, in particular a measured temporal pulse shape. The amplification phase contribution, in particular the dynamic amplification phase contribution or dynamic gain, and the bandwidth amplification phase contribution, can be measured relatively easily in time. In particular in the case of temporally stretched pulses (for example on the ns scale), the temporal pulse shape can be measured by means of, for example, a photodiode, and the spectrum or the nonlinear phase can be calculated therefrom, preferably by means of a known stretching factor and / or knowledge of the CPA system. Alternatively or additionally, the amplification phase contribution is preferably determined, in particular calculated, by means of a simulation, in particular a numerical simulation. The methods mentioned here enable the amplification phase contribution to be determined particularly precisely and meaningfully.
[0047] According to an embodiment of the application, the at least one additional phase contribution of the laser pulse and / or the spectrum of the laser pulse is set by means of a dynamic, in particular a steerable modulator, in particular a steerable spatial light modulator (SLM), an acousto-optic modulator, an electro-optic modulator and / or a steerable stretcher, wherein at least one measurement variable on the amplified ultrashort laser pulse is measured. The step is then repeated with a changed additional phase contribution of the laser pulse and / or spectrum, wherein the at least one measurement variable is optimized depending on the additional phase contribution of the laser pulse and / or spectrum. The change of the additional phase contribution of the laser pulse and / or spectrum is repeated, in particular iterated, until an optimum of the at least one measurement variable is found. Thus, in particular, an optimum of the at least one measurement variable is sought as a function of the additional phase contribution of the laser pulse and / or spectrum, and the corresponding assigned settings or steering of the steerable modulator and / or steerable stretcher are memorized, in particular stored. The optimum of the at least one measurement variable is in particular to be understood as meaning that the respective Strehl ratio of the amplified ultrashort laser pulse in relation to the at least one measurement variable is less than 5% compared to the case without the amplifying phase contribution. The optical configuration of the compensation element is determined by the optimization of the at least one measurement variable, in particular such that the compensation element provides an additional phase contribution and / or spectrum which is assigned to the optimum of the at least one measurement variable. In particular, the optical configuration of the compensation element then corresponds to the memorized, in particular stored, settings or steering of the steerable modulator and / or steerable stretcher.
[0048] By means of the method described here, the optical configuration of the compensation element can be reliably and at the same time easily determined. This can be carried out not only in real experiments, but also by simulation, in particular by numerical simulation.
[0049] In order to determine the influence of the set additional phase contribution and / or the set spectrum, the phase of the amplified ultrashort laser pulse or of the amplified ultrashort laser pulse is preferably measured. Here, in particular, the amplified ultrashort laser pulse is quantified after compression by means of the at least one measurement variable. The associated measurement can in particular be a measurement for reconstructing the electric field, a self-correlation measurement or a power measurement after frequency conversion. In particular, it is then possible to infer from the at least one measurement variable about the Strehl ratio.
[0050] Preferably, an LCD (liquid crystal display) or a similar device is used as a steerable spatial light modulator. Preferably, a thermally variable stretcher or a stretcher which can be set by means of a variable tension load is used as a steerable stretcher.
[0051] According to an embodiment of the application, the determined optical configuration of the compensation element is transferred to a permanent optical structure by means of which the compensation element is provided. In this way, a compensation element which is easy to use and permanently durable can be obtained, which is coordinated with the amplification phase contribution in a precisely matched manner. In particular, the remembered, in particular stored, settings or manipulations of the assignable modulator as the optimum measurement variable can be transferred to a solid, permanent structure, for example a mirror, a grating or any other optical element, for example an optical fiber or the like. In particular, the optical element is configured in such a way that it achieves the same effect on the laser pulse as the remembered, in particular stored, settings or manipulations of the assignable modulator.
[0052] Correspondingly, the static stretcher can be designed in such a way that its influence on the laser pulse corresponds to the influence of the corresponding remembered, in particular stored, settings or manipulations of the assignable stretcher. By way of example, the corresponding structure can be statically written into the stretcher.
[0053] In the case of a compensation element configured as an amplifier, the determined optical configuration of the compensation element can also be transferred to a permanent optical structure in that the doping within the amplifier and / or the path length for the laser pulse is selected in correspondence with the determined optical configuration.
[0054] According to an embodiment of the application, a compensation element is used which is selected from the group consisting of: a stretcher for temporally stretching the laser pulse; an optical fiber for conducting the laser pulse; a filter, in particular a spectral filter, in particular a reflective filter or a transmissive filter; a mirror; a grating, in particular a volume Bragg grating; an amplifier, in particular a preamplifier or a main amplifier, for amplifying the laser pulse; an electro-optical modulator (EOM); a Pockels cell; an acousto-optical modulator (AOM); and a combination of at least two of the aforementioned elements.
[0055] According to an embodiment of the application, an amplifier is used as a compensation element, the bandwidth amplification of which is matched in order to at least partially compensate at least one determined amplification phase contribution. Matching the bandwidth amplification of the amplifier comprises: selecting an amplifier having a corresponding bandwidth amplification; in turn, this comprises, in particular, replacing a first amplifier having a first, less well-matched bandwidth amplification previously used with a second amplifier having a second, better-matched bandwidth amplification.
[0056] In a preferred configuration, the bandwidth amplification of the amplifier used as a compensation element is matched by changing the doping of the amplifier. In particular, different doping elements or different combinations of doping elements are preferably used. Alternatively or additionally, the number and / or the number density of foreign atoms is changed.
[0057] Alternatively or additionally, preferably the path length within the amplifier for the laser pulse, in particular the fiber length of an amplifier configured as a fiber amplifier, is changed to match the bandwidth amplification.
[0058] In particular, the optical configuration for the compensation element, which is determined as described above, can be permanently transferred into the optical structure of the amplifier by correspondingly matching or selecting the doping and / or the path length, in particular the fiber length, of the amplifier.
[0059] Alternatively, the respective matching design of the amplifier can also be determined by configuring the respective laser system with different amplifiers in various variants, wherein the amplifiers with different designs are tested in connection with the laser system, in particular with regard to their doping and / or their path length for the laser pulse. An optimization can then be performed on the quality of the compressed laser pulse, wherein the amplifier that is considered to be the best with regard to the quality of the compressed laser pulse, i.e. the amplifier with the best doping and / or the best path length within the amplifier for the laser pulse, is selected from the various amplifiers.
[0060] Alternatively, a suitable configuration of the bandwidth amplification, in particular the doping and / or the path length within the amplifier for the laser pulse, can also be obtained by calculation or simulation.
[0061] The application also comprises an amplification system which is provided for carrying out the method for amplifying ultrashort laser pulses according to the application or one of the preferred embodiments of the method for amplifying ultrashort laser pulses described above. Here, the amplification system in particular comprises a stretcher for temporally stretching the ultrashort laser pulse, and also at least one amplifier stage for amplifying the temporally stretched laser pulse, and also at least one compressor for compressing the amplified temporally stretched laser pulse. The amplification system also comprises at least one compensation element which is provided and arranged for imparting an additional phase contribution on the laser pulse and / or for changing the spectrum of the laser pulse in such a way that the at least one amplification phase contribution is compensated behind the compressor in the direction of propagation. In particular, the advantages already explained in connection with the method are obtained in connection with the amplification system.
[0062] In general, laser systems for generating ultrashort laser pulses are designed such that significant nonlinearities occur at the end of the final amplifier stage, i.e. when the pulse energy is at its maximum. Due to the nonlinearities, the pulse acquires an additional phase, the shape of which is given by the pulse shape, which in turn is determined by the stretching and the spectrum of the laser pulse. Good pulse quality can be achieved if the entire phase of the laser pulse can be compensated by stretching, dispersion and nonlinearities in a compressor of the laser system. In particular, the phase caused by the nonlinearities also needs to be compensated, which can exhibit a profile that is difficult to compensate with a compressor, in particular due to dynamic amplification and / or bandwidth amplification. Good pulse quality can then only be achieved if either the phase in the laser system, in particular the phase of the stretcher, is designed such that the phase is pre-compensated by the nonlinearities, or the laser system is designed, for example by a spectral filter or by a suitable matching of the amplifiers, such that the pulse shape generates a nonlinear phase which can be well compressed together with the remaining phase contributions.
[0063] The description of the method on the one hand and the description of the amplification system on the other hand are to be understood as complementary to each other. In particular, features of the amplification system which are explained explicitly or implicitly in connection with the method are preferably features of the amplification system, individually or in combination, of a preferred embodiment. The amplification system preferably comprises at least one feature which is determined by at least one step of one of the methods according to the application or of an embodiment of one of the methods. Similarly, method steps which are described explicitly or implicitly in connection with the amplification system are preferably individual or combined steps of one of the methods, preferably of a preferred embodiment. These are preferably characterized by at least one method step which is determined by at least one feature of the amplification system according to the application or of a preferred amplification system. BRIEF DESCRIPTION OF DRAWINGS
[0064] The application is explained in more detail below on the basis of the drawings, in which:
[0065] Figure 1 A schematic representation of an embodiment of an amplification system for carrying out an embodiment of a method for amplifying ultrashort laser pulses is shown, and
[0066] Figure 2 A schematic representation of an embodiment of a system for carrying out an embodiment of a method for designing an amplification system is shown. DETAILED DESCRIPTION
[0067] Figure 1 A schematic representation of an embodiment of an amplification system 100 for carrying out a method for amplifying ultrashort laser pulses is shown. The amplification system 100 comprises a laser pulse source 200, which is in particular configured as an ultrashort pulse laser and is provided for generating laser pulses, preferably having a temporal width in the range of ps to fs.
[0068] Furthermore, the amplification system 100 comprises a stretcher 120 which is arranged for temporally stretching the laser pulses generated by the laser pulse source 200, so that temporally stretched laser pulses are obtained. Furthermore, the amplification system 100 comprises at least one amplifier stage, here an amplifier chain with two amplifier stages, in particular a preamplifier 140 and a main amplifier 150, wherein the amplifier chain is arranged for amplifying the temporally stretched laser pulses, so that amplified and temporally stretched laser pulses are obtained. Finally, the amplifier system 100 comprises a compressor 160 which is arranged for compressing the amplified and temporally stretched laser pulses, so that finally amplified ultrashort laser pulses are obtained.
[0069] In the amplification system 100, in particular in the amplifier chain, here in the preamplifier 140 and the main amplifier 150, dynamic amplification occurs which leads to a pulse distortion of the laser pulses, in particular when a high proportion of the energy stored in the amplifier stages is called up. Alternatively or additionally, pulse distortion also occurs due to bandwidth amplification of the amplifier chain. In combination with the nonlinear effects occurring in the amplifier stages, the pulse distortion in turn leads to an amplification phase contribution, in particular a dynamic amplification phase contribution, a bandwidth amplification phase contribution, or a combination of a dynamic amplification phase contribution and a bandwidth amplification phase contribution, wherein the amplification phase contribution ultimately impairs the quality of the compressed amplified ultrashort laser pulses.
[0070] In order to reduce this negative influence, preferably to completely suppress this negative influence, the amplification system 100 here comprises at least one compensation element 130 which is arranged for compensating the amplification phase contribution, i.e. in particular the influence of the amplification phase contribution. In particular, the laser pulses are thus imparted with an additional phase contribution and / or the spectrum of the laser pulses is thus changed, in particular in the propagation direction in front of the preamplifier 140 or in front of the main amplifier 150, and / or in the propagation direction behind the preamplifier 140 or behind the main amplifier 150, and / or in the preamplifier 140 or in the main amplifier 150, in front of the compressor 160, so that the amplification phase contribution is compensated behind the compressor 160. As a result, a high-quality compressed laser pulse can be obtained. In particular, the compensation element 130 is constructed in such a way that the Strehl ratio of the laser pulses is not more than 5% smaller compared to the case in which the amplification phase contribution is completely avoided or completely compensated.
[0071] The compensation element 130 is schematically depicted here and in exemplary fashion at different positions along the propagation path. It can be arranged directly in front of the stretcher 120, directly behind the stretcher 120, directly in front of the preamplifier 140, or between the preamplifier 140 and the main amplifier 150, i.e. in particular within the amplifier chain. Arrangements behind the main amplifier 150 or behind or in the compressor 160 are also possible. Preferably, however, the matching of the spectrum is performed in front of or in the main amplifier 150. A plurality of compensation elements 130 can also be provided, which can in particular be arranged at the positions indicated here in schematic fashion.
[0072] The stretcher 120 itself can also be configured as a compensation element 130, in particular by being variably configured or by statically writing compensation properties into said stretcher.
[0073] The amplifiers of the amplifier chain, in particular the preamplifier 140 or the main amplifier 150, can also be configured as compensation elements 130, in particular by appropriately matched bandwidth amplification, in particular by appropriate selection of the doping and / or the path length for the laser pulses within the amplifier, in particular the fiber length of the amplifier.
[0074] It is also possible to vary at least one property of the compressor 160 in order to at least partially compensate for at least one amplification phase contribution. Thus, even the compressor 160, in particular in combination with a further compensation element 130, can be used as a compensation element.
[0075] In particular, the compensation element 130 is selected from the group consisting of: the stretcher 120; the optical fiber 110, in particular with a written-in fiber Bragg grating (FBG); a filter, in particular a spectral filter, in particular a reflective filter or a transmissive filter; a mirror; an electro-optical modulator (EOM); a Pockels cell; an acousto-optical modulator (AOM); a grating, in particular a bulk Bragg grating; an amplifier for amplifying laser pulses, in particular the preamplifier 140 or the main amplifier 150; and a combination of at least two of the aforementioned elements.
[0076] In particular, the imparting of the additional phase contribution and / or the changing of the spectrum can be performed while stretching the ultrashort laser pulses. Alternatively or additionally, this can be done before stretching the ultrashort laser pulses. Alternatively or additionally, this can be done after stretching the ultrashort laser pulses and before amplifying the temporally stretched laser pulses. Alternatively or additionally, this can be done while amplifying the temporally stretched laser pulses.
[0077] In particular, an additional phase contribution can be imparted to the laser pulse by using a stretcher 120 to which a suitably matched wavelength-dependent propagation time variation is written or applied, in particular for ultrashort laser pulses.
[0078] In particular, a stretcher 120 is preferably used to which a suitably matched wavelength-dependent propagation time variation is statically written or dynamically applied.
[0079] The spectrum is preferably changed by using a stretcher 120 to which a spectral filter is written or applied. Alternatively or additionally, the spectrum of the ultrashort laser pulse is changed by filtering the ultrashort laser pulse with a spectral filter in front of or behind the stretcher. Thus, the compensation element 130 can in particular be configured as a spectral filter, preferably as a reflective spectral filter (i.e. a wavelength-dependent mirror), or as a transmissive filter.
[0080] Alternatively or additionally, the spectrum of the laser pulse is preferably changed by guiding the ultrashort laser pulse through an optical fiber 110 in front of the stretcher 120 or behind the stretcher 120, which has a written spectral filter.
[0081] Alternatively or additionally, the laser pulse is preferably filtered and / or spectrally shaped before or during passing through an amplifier in the amplifier chain, in which or behind which self-phase modulation occurs, which can in particular be the main amplifier 150, but also the preamplifier 140, depending on the specific design of the amplifier chain and in particular of the preamplifier 140 and the main amplifier 150.
[0082] In particular, the spectrum of the temporally stretched laser pulse is preferably changed, in particular spectrally shaped, by the laser pulse passing through at least one amplifier within the amplifier chain, in particular an amplifier selected from the preamplifier 140 and the main amplifier 150, the bandwidth amplification of which is suitably matched in order to at least partially compensate for the at least one amplification phase contribution. The bandwidth amplification of the amplifier is preferably suitably matched by the amplifier having a suitably matched doping and / or a suitably matched path length for the laser pulse within the amplifier, in particular a suitably matched fiber length.
[0083] Preferably, at least 30% of the energy stored in the preamplifier 140 and / or the main amplifier 150, in particular in one of these amplifiers, is called up.
[0084] The pre-amplifier 140 and the main amplifier 150 are preferably constructed, optionally taking into account the compensation element 130 arranged in between, such that the B-integral of the laser pulse after amplification, i.e. behind the main amplifier 150 in the direction of propagation, is greater than 3 rad.
[0085] Figure 2 A schematic representation of a device is shown, which is provided for carrying out the method for designing the amplifier system 100. Identical or functionally identical elements have the same reference signs and are thus referred to the description above, respectively.
[0086] Here, in the designed amplification system 100, a manipulable modulator 300 or a manipulable stretcher 120, which can be manipulated by the computing device 500, is provided at the position where the compensation element 130 should be provided subsequently. The manipulable modulator 300 is preferably a manipulable spatial light modulator (SLM), preferably configured as an LCD. Alternatively, the manipulable modulator 300 can also be an acousto-optic modulator or an electro-optic modulator. Also here - in a similar manner as Figure 1 the compensation element 130 is provided - it is not actually necessary to provide a modulator 300 at every position where such an element is drawn using dashed lines; rather, the positions indicated with dashed lines represent those positions within the device where such a modulator 300 can be arranged. Instead of or in addition to such a light modulator 300, also a manipulable stretcher 120 can be used for temporally stretching the ultrashort laser pulse. In this respect, for its manipulation, the stretcher 120 is here also effectively connected with the computing device 500. Thus, also possible is a configuration in which only the stretcher 120 is manipulably provided and no further modulator 300 is provided. Furthermore, possible is a configuration in which the stretcher 120 is not manipulably configured and exactly one modulator 300 is provided, in particular only at one of the positions indicated here. However, it is also possible to provide a plurality of light modulators 300, wherein the stretcher 120 is not manipulably configured. Finally, a combination of a manipulable stretcher 120 with at least one modulator 300, in particular also with a plurality of modulators 300, is also possible.
[0087] In general, the amplifier system 100 is preferably designed by taking the amplification phase contribution for the amplified ultrashort laser pulse, wherein at least one compensation element 130, also possibly a corresponding matching stretcher 120, is provided, which is provided for compensating the taken amplification phase contribution.
[0088] The amplification phase contribution generated in the amplifier system 100 is preferably determined by a phase measurement, in particular by a frequency-resolved optical correlation, and / or calculated from a spectral measurement or a temporal measurement, and / or taken, in particular calculated, by means of a simulation, in particular by means of a numerical simulation.
[0089] The compensation element 130 is designed in particular by dynamically, especially by means of at least one operable modulator 300 and / or operable stretcher 120, setting at least one additional phase contribution of the laser pulse and / or the spectrum of the laser pulse. Here, at least one measurement variable is measured on the amplified ultrashort laser pulse. This is repeated—optionally multiple times—with changes to the additional phase contribution and / or spectrum of the laser pulse, wherein the at least one measurement variable is optimized depending on the additional phase contribution and / or the spectrum of the laser pulse. Here, determining the at least one measurement variable and manipulating the operable modulator 300 and / or operable stretcher 120 (i.e., setting the additional phase contribution) is preferably implemented by a computing device 500. Preferably, optimization is also performed by a computing device 500. The optimal value of the at least one measurement variable should be understood as, in particular, the corresponding Strell ratio of the amplified ultrashort laser pulse being less than 5% or less compared to the case where the amplified phase contribution is completely avoided or fully compensated. The determination of this optimal value can also be carried out iteratively, for example, in the case of FROG measurements.
[0090] In this way, the settings for the controllable modulator 300 and / or the controllable stretcher 120 are ultimately determined, wherein at least one measured variable is optimal. This corresponds to the optical configuration for determining the desired compensation element 130 in this manner.
[0091] Finally, the compensation element 130 is preferably provided by transferring the optical configuration thus obtained for the compensation element 130 to a permanent optical structure. Exemplarily, this can be embodied in, in particular, statically written into a spectral filter, volume Bragg grating, or stretcher 120 of a corresponding configuration; or in a correspondingly operable stretcher or optical modulator, in particular an electro-optic modulator or acousto-optic modulator. It is also possible to select appropriately matched bandwidth amplification for at least one amplifier, in particular a preamplifier 140 and / or a main amplifier 150, or to select the preamplifier 140 and / or the main amplifier 150 having appropriately matched bandwidth amplification. Specifically, for this purpose, appropriately matched doping and / or appropriately matched path lengths within the amplifier for the laser pulses can be selected, in particular appropriately matched fiber lengths.
Claims
1. A method for amplifying ultrashort laser pulses, the method comprising the following steps: a) Time-stretching an ultrashort laser pulse and obtaining a time-stretched laser pulse; b) Amplify the time-stretched laser pulse and obtain the amplified time-stretched laser pulse; c) Compress the amplified time-stretched laser pulse to obtain an amplified ultrashort laser pulse, wherein, At least one amplified phase contribution is compensated, the at least one amplified phase contribution being selected from the group consisting of: the dynamic amplified phase contribution of the laser pulse, the bandwidth amplified phase contribution of the laser pulse, and a combination of the dynamic amplified phase contribution and the bandwidth amplified phase contribution, wherein the dynamic amplified phase contribution is caused by the nonlinear phase change due to dynamic amplification in step b), and the bandwidth amplified phase contribution of the laser pulse is caused by the nonlinear phase change due to bandwidth amplification in step b). The method is as follows: e) The spectrum of the laser pulse is thus altered by spectral filtering and / or spectral shaping. This ensures that the at least one amplified phase contribution is compensated after step c).
2. The method according to claim 1, characterized in that, Before step c), in step d), the laser pulse is given an additional phase contribution such that the at least one amplified phase contribution is compensated after step c).
3. The method according to claim 2, wherein, - Perform and / or when stretching the ultrashort laser pulse according to step a) - Perform and / or before stretching the ultrashort laser pulse according to step a) - Performed after stretching the ultrashort laser pulse according to step a) and before amplifying the time-stretched laser pulse according to step b) and / or - Performed while amplifying the time-stretched laser pulse according to step b). Selected from at least one step of steps d) and e).
4. The method according to claim 3, characterized in that, Step d) is performed by stretching the ultrashort laser pulse using the following stretcher (120) in step a): a properly matched, wavelength-dependent propagation time variation process is written into or applied to the stretcher for the ultrashort laser pulse.
5. The method according to claim 4, characterized in that, The appropriately matched, wavelength-dependent propagation time variation process is statically written or dynamically applied to the stretcher (120).
6. The method according to any one of the preceding claims, characterized in that, Step e) is performed in the following manner: - In step a), the following stretcher (120) is used to stretch the ultrashort laser pulse: a spectral filter is written into or applied to the stretcher, and / or - The laser pulse is filtered by a spectral filter located in front of or behind the stretcher (120), and / or - The laser pulse is guided through the following optical fiber (110) in front of or behind the stretcher (120), a spectral filter is written into the optical fiber, and / or - The laser pulse is filtered and / or spectrally shaped before or during the laser pulse passes through the following amplifier: self-phase modulation occurs in or after the amplifier.
7. The method according to any one of the preceding claims, characterized in that, In step b), the time-stretched laser pulse is amplified by an amplifier chain having a plurality of amplifiers, wherein step e) is performed by passing the laser pulse through at least one of the plurality of amplifiers within the amplifier chain, the bandwidth amplification of the at least one amplifier being appropriately matched such that at least partially compensates for the at least one amplified phase contribution.
8. The method according to claim 7, characterized in that, For step e), using at least one of the plurality of amplifiers, the bandwidth amplification of the amplifier is appropriately matched in such a way that the at least one amplifier has - Appropriately matched doping, and / or - The appropriate path length for the laser pulse within the amplifier.
9. The method according to claim 8, wherein, The path length is the fiber length.
10. The method according to any one of the preceding claims, characterized in that, In step b), at least 30% of the energy stored in the amplifier is used to amplify the time-stretched laser pulse.
11. The method according to any one of the preceding claims, characterized in that, The B-integral of the laser pulse, after being amplified in step b), is greater than 3 rad, wherein the B-integral is defined as... B = , Where I(z) is the light intensity along the beam axis of the laser beam, i.e., the z-direction; z is the position in the beam propagation direction, and therefore the position in the propagation direction; and n2 is the nonlinear refractive index.
12. The method according to any one of the preceding claims, characterized in that, At least one characteristic of the compressor (160) used in step c) to compress the amplified time-stretched laser pulse is changed in order to at least partially compensate for the at least one amplified phase contribution.
13. A method for designing an amplification system (100) for amplifying ultrashort laser pulses, the method comprising the following steps: - Calculate at least one amplification phase contribution, selected from the group consisting of: dynamic amplification phase contribution, bandwidth amplification phase contribution, and a combination of the dynamic amplification phase contribution and the bandwidth amplification phase contribution, wherein the dynamic amplification phase contribution is derived in the amplification system (100) for an ultrashort laser pulse passing through the amplification system (100) as a nonlinear phase change due to the dynamic amplification of the amplification system (100), and the bandwidth amplification phase contribution is derived in the amplification system (100) for an ultrashort laser pulse passing through the amplification system (100) as a nonlinear phase change due to the bandwidth amplification of the amplification system (100), and - Provide at least one compensation element (130), said at least one compensation element being configured to compensate at least one sought amplified phase contribution by means of the method according to any one of claims 1 to 12.
14. The method according to claim 13, characterized in that, At least one amplification phase contribution generated in the amplification system (100) - Determined by phase measurement, and / or - Calculated by spectral measurements, and / or - Calculated by time measurement, and / or - Obtained through simulation.
15. The method according to claim 14, wherein, At least one amplification phase contribution generated in the amplification system (100) is calculated by simulation.
16. The method according to any one of claims 13 to 15, characterized in that, The compensation element (130) is designed in the following way: f) Dynamically setting at least one additional phase contribution for the laser pulse and / or the spectrum of the laser pulse using a controllable spatial light modulator (300) and / or a controllable stretcher (120), wherein at least one measurement variable on the amplified ultrashort laser pulse is determined, wherein, g) Repeat step f) while changing the additional phase contribution and / or spectrum of the laser pulse, wherein the at least one measurement variable is optimized depending on the additional phase contribution and / or spectrum of the laser pulse, wherein, h) Obtain the optical configuration of the compensation element (130) by optimizing at least one measurement variable in step g).
17. The method according to claim 16, characterized in that, The compensation element (130) is provided by transferring the optical configuration for the compensation element (130) obtained in step h) onto a permanent optical structure.
18. The method according to any one of claims 13 to 17, characterized in that, The compensation element (130) is selected from the group consisting of: a stretcher (120) for time stretching the laser pulse; an optical fiber for conducting the laser pulse; a filter; a mirror; a grating; an amplifier for amplifying the laser pulse; an electro-optic modulator (EOM); a Pockels cell; an acousto-optic modulator (AOM); and a combination of at least two of the above elements.
19. The method according to claim 18, wherein, The filter is a spectral filter.
20. The method according to claim 19, wherein, The spectral filter is either a reflection filter or a transmission filter.
21. The method according to claim 18, wherein, The grating is a volume Bragg grating.
22. The method according to claim 18, wherein, The amplifier is a preamplifier (140) or a main amplifier (150).
23. The method according to any one of claims 13 to 22, characterized in that, The following amplifier is used as a compensation element (130): the bandwidth of the amplifier is matched so as to at least partially compensate for at least one of the sought amplification phase contributions.
24. The method according to claim 23, characterized in that, The bandwidth amplification of the amplifier used as a compensation element (130) is matched by: changing the amplifier's... - Doping, and / or - The path length for the laser pulse within the amplifier.
25. The method according to claim 24, wherein, The path length is the fiber length.