Laser systems and methods for providing processing laser pulses for interaction with a target, and related computer program products.

Abstract

The present invention relates to a laser system (1) for providing processing laser pulses (2, 2') for interaction with targets (3) that periodically pass through a target region (4) or periodically pass through successively with respect to periodic errors, wherein the laser system comprises a laser pulse emitting device (6) for emitting processing laser pulses (2, 2'), wherein at least one processing laser pulse (2, 2') is assigned to each target (3); and a control device (7) which controls the laser pulse output device (6) and is configured to set the output timing of the processing laser pulses (2, 2') such that the processing laser pulses hit the targets (3) in the target region (4) in order to interact with the targets (3) as an ON processing laser pulse (2), or that the processing laser pulses (2') move away from the targets (3) in the target region (4) in order not to interact with the targets (3).

Description

Technical Field

[0001] The present invention relates to a laser system and method for providing a processing laser pulse for interaction with a target that periodically passes through a target area one after another or passes through it one after another periodically excluding periodic errors, and a related computer program product.

[0002] US2022 / 0317576A1 describes a laser system for generating secondary radiation, in which a laser pulse hits a stream of targets that are substantially evenly spaced to generate secondary radiation. Based on the detected target positions and trajectories, a trigger signal is generated that requests a laser pulse to interact with the target.

[0003] A method according to DE102014017568A1 for generating amplified output laser pulses at individually specified times is known, which is achieved by a free trigger using a pulse picker. For this purpose, a high-power ps laser is used, which consists of a mode-locked seeder, a pulse picker, an amplifier, a modulator, and optionally a frequency conversion unit having a pulse repetition rate of about 10 MHz. The pulse picker consists of a modulator and a driver, using which at least three levels can be set according to the specifications of different pulse amplitudes downstream of the pulse picker. If the time interval between two required pulses is greater than the reciprocal of the nominal pulse repetition rate, the driver switches to an intermediate level, and as a result, the pulse picker allows a passing pulse of a predetermined low amplitude to condition the gain of the laser medium for a certain laser parameter.

[0004] Finally, DE102017210272B3 also discloses a pulse-on-demand (POD) laser system for generating amplified laser pulses at individually specified times. For example, if laser pulses with different pulse energies are required, the corresponding energy reduction is achieved by time-adjusted partial outcoupling with respect to the immediately preceding input laser pulse or an inserted preceding sacrificial laser pulse, respectively, as a function of its known pulse interval. [Background technology]

[0005] The object of the present invention is to provide the above-described laser system and method that enables the generation of processing laser pulses intended for interaction with a target, and at the same time enables controllability regarding the interaction between the processing laser pulses and the target.

[0006] Summary of the Invention This objective is achieved by a laser system for providing processing laser pulses for interaction with targets that periodically pass through a target region one after another, or periodically pass through a target region one after another with respect to periodic errors, comprising a laser pulse emitting device for emitting processing laser pulses, wherein at least one processing laser pulse is assigned to each target; and a control device for controlling the laser pulse emitting device and configuring the emission time of the processing laser pulses such that the processing laser pulses either hit a target in the target region in order to interact with the target as an ON processing pulse, or move away from the target in the target region in time in order not to interact with the target as an OFF processing laser pulse.

[0007] According to the present invention, the ON processing laser pulse strikes a target positioned in the target region, while the OFF processing laser pulse temporally moves away from the target within the target region. The processing laser pulse can be driven by an external control signal according to a pulse-on-demand (POD) scheme. The splitting into processing laser pulses and intermediate laser pulses means that less laser power needs to be held in reserve compared to the prior art. The target passes through the target region in the form of a target stream with low time jitter.

[0008] Preferably, the pulse energy of the ON processing laser pulse deviates from the average pulse energy by less than 3%, specifically less than 1%, such that the ON processing laser pulse has the same or substantially the same pulse energy for interaction with the target.

[0009] In a preferred embodiment of the present invention, the laser pulse emission device comprises a laser beam source driven by a control device to generate an input laser pulse (seed laser pulse), and an optical amplifier for amplifying the input laser pulse into a processing laser pulse and, if necessary, further input laser pulses into an intermediate laser pulse existing between the two processing laser pulses. After amplifying the ON processing laser pulse to a specified pulse energy, the optical amplifier requires a gain-related minimum time period to provide the same specified pulse energy for the immediately following ON processing pulse. This gain-related minimum time period is required by the inversion structure and is necessary for amplification in the optical amplifier. The minimum possible time for the target is preferably equal to or at most greater than the gain-related minimum time period. The control device is also configured to specifically set the emission time and / or pulse energy of the input laser pulses underlying the OFF processing laser pulse and the intermediate laser pulse, and thereby the energy stored in the optical amplifier such that the ON processing laser pulse has the same specified pulse energy in either case.

[0010] To stabilize the pulse energy of the target processing laser pulse, the extractable energy of the amplifier system can be adjusted by an additional, internally switchable intermediate laser pulse (pulse on demand). The seed energy of the intermediate laser pulse can be selected to increase as the pulse interval between the two processing laser pulses increases. To dissipate as little energy as possible, the seed energy of the triggered processing laser pulse can also be reduced as the pulse interval between the two processing laser pulses decreases. In either case, by triggering the processing laser pulse and the intermediate laser pulse using separate energy compensation schemes, specified energy stability can be ensured with respect to an external reference event (target) that repeats at a period prone to errors. An external control signal requests a laser pulse for the reference event and controls whether the laser pulses should be triggered before, simultaneously with, or after the relevant reference event, respectively.

[0011] Preferably, if the current ON processing laser pulse follows immediately after the ON processing laser pulse, the control device is configured to drive the laser beam source to emit an input laser pulse that forms the basis of the current ON processing laser pulse; if the time interval between these two processing laser pulses is greater than the gain-related minimum time period, to emit a further input laser pulse that is amplified in the optical amplifier into an intermediate laser pulse between these two processing laser pulses; and to set the emission time and pulse energy of the further input laser pulse, and thereby the energy stored in the optical amplifier for the current ON processing laser pulse so that the current ON processing laser pulse has a specified pulse energy.

[0012] Preferably, if the current OFF processing laser pulse follows immediately after the ON processing laser pulse, the control device is configured to drive the laser beam source to emit the underlying input laser pulse for the current OFF processing laser pulse, and the time interval between the current OFF processing laser pulse and the ON processing laser pulse is specifically smaller than the gain-related minimum time period. In this case, the control device can advantageously be configured to set the energy of the current OFF processing laser pulse via the energy of the underlying input laser pulse so that the ON processing laser pulse or OFF processing laser pulse that follows immediately after the current OFF processing laser pulse can again reach a specified pulse energy after the gain-related minimum time period.

[0013] Preferably, if the current OFF processing laser pulse follows immediately after the OFF processing laser pulse, the control device is configured to drive the laser beam source to emit an input laser pulse that underlies the current OFF processing pulse, and, if the time interval between these two processing laser pulses is greater than the gain-related minimum time period, to emit a further input laser pulse that is amplified in the optical amplifier into an intermediate laser pulse between these two processing laser pulses.

[0014] Preferably, if the current ON processing laser pulse follows immediately after the OFF processing laser pulse, the control device is configured to drive the laser beam source to emit an input laser pulse that forms the basis of the current ON processing pulse; if the time interval between these two processing laser pulses is greater than the gain-related minimum time period, to emit a further input laser pulse that is amplified in the optical amplifier into an intermediate laser pulse between these two processing laser pulses; and to set the emission time and pulse energy of the further input laser pulse, and thereby the energy stored in the optical amplifier for the current ON processing laser pulse so that the current ON processing laser pulse has a specified pulse energy.

[0015] The pulse energy of the OFF processing laser pulse and / or intermediate laser pulse is advantageously at most equal to the specified pulse energy of the ON processing laser pulse.

[0016] Preferably, the OFF processing laser pulse arrives in the target region at least a minimum time interval earlier than the target in question, to ensure that no interaction occurs between the OFF processing laser pulse and the target. This minimum time interval is greater than the minimum possible period of the target.

[0017] Specifically, the control device is configured to emit an intermediate laser pulse at least a second minimum time period before the processing laser pulse that immediately follows.

[0018] Preferably, the laser beam source is configured to provide an input laser pulse having a constant pulse energy.

[0019] To enable the individual setting of the pulse energy of the input pulse, and thereby the pulse energies of the processing laser pulse and the intermediate laser pulse, an optical modulator driven by a control device is preferably located upstream of the optical amplifier, and the modulator modulates the input laser pulse energy accordingly, for example, by modulating the amplitude or trimming the pulse edge. The optical modulator may be, for example, an AOM (acousto-optic modulator) or an EOM (electro-optic modulator). The system may also include an amplifier chain or frequency converter downstream of the optical amplifier, and a device for setting the pulse energy may be located upstream of the amplifier, or actually between the amplifiers.

[0020] Particularly preferably, the laser system includes a pulse picker (e.g., AOM or EOM) positioned between the optical amplifier and the target region and driven by a control device to extract intermediate laser pulses from the further beam path of the processing laser pulse. This ensures that intermediate laser pulses do not accidentally strike the target. Preferably, the extracted intermediate laser pulses are removed internally, for example, by a beam trap. Alternatively, the input laser pulses underlying the intermediate laser pulses can have different wavelengths. After being amplified by a broadband optical amplifier, the intermediate laser pulses are extracted using a pulse picker embodied as a spectral filter. Intermediate laser pulses with suitable polarization can also be triggered, and these intermediate laser pulses are then extracted downstream of the optical amplifier using a pulse picker embodied as a polarization filter.

[0021] More preferably, the control device is configured to emit at least one intermediate pulse when the time interval between the next emitting processing laser pulse and the previous processing laser pulse is greater than a specified maximum duration, which can be, for example, twice the minimum time period. In this case, the control device triggers an intermediate laser pulse, for example, after the gain-related minimum time period, having the energy of the ON processing laser pulse and preventing excess energy from accumulating in the optical amplifier. For longer time intervals between two processing laser pulses, multiple intermediate laser pulses are inserted accordingly, in any case, for example, at intervals of the gain-related minimum time period, thereby preventing excess energy from accumulating in the optical amplifier.

[0022] Preferably, each target is assigned a control signal that can determine the time of arrival of the target in the target area, and the control device is configured to emit ON or OFF processing laser pulses based on each control signal.

[0023] In a further embodiment, the present invention also provides a method for providing a processing laser pulse for interaction with a target that periodically passes through a target region in succession, or periodically passes through a target in succession with respect to a periodic error, the method steps being as follows: - The step of emitting at least one processing laser pulse to each target, - The process includes setting the emission time of at least one processing laser pulse using a control device such that the processing laser pulse either strikes the target in the target region to interact with the target as an ON processing laser pulse, or temporally moves away from the target in the target region to not interact with the target as an OFF processing laser pulse.

[0024] Preferably, the ON processing laser pulse or OFF processing laser pulse is emitted based on a control signal assigned to the target, and the arrival time of each target in the target area can be determined from this control signal.

[0025] Finally, the present invention also relates to a control program product having coding means adapted to carry out all steps of the method according to the present invention when the program is executed on a control device for a laser system according to the present invention.

[0026] Further advantages of the present invention will become apparent from the specification and drawings. Similarly, the features mentioned above and those further described can be used individually or together in any desired combination. The illustrated and described embodiments should not be understood as an exhaustive list, but rather as illustrative examples illustrating the present invention. [Brief explanation of the drawing]

[0027] [Figure 1] Figure 1 shows an exemplary embodiment of a laser system according to the present invention for providing processing laser pulses for interaction with a target that is periodically emitted. [Figure 2]Figures 2a to 2d show an exemplary temporal representation of the time-dependent energy control of the laser system according to the present invention when switching between a processing laser pulse that strikes the target and a processing laser pulse that temporally moves away from the target.

[0028] The laser system 1 shown in Figure 1 plays the role of providing processing laser pulses 2, 2' for interaction with the target 3, and the processing laser pulses 2, 2' have a period t p Periodically, or with a periodic error Δt p Except for one instance, the stream passes through the target region 4 sequentially, i.e., in the form of a target stream with low time jitter.

[0029] The interaction between the processing laser pulse 2 and the target 3 within the target region 4 can generate secondary radiation 5 (e.g., EUV radiation). For example, the target material may be tin or contain tin.

[0030] The laser system 1 includes a laser pulse emitting device 6 for generating processing laser pulses 2, 2', and a control device 7 that can trigger and / or control the emission of processing laser pulses 2, 2' by the laser pulse emitting device 6 at a specific time. For example, when the control device 7 receives a corresponding control signal, the laser pulse emitting device 6 may be made to emit processing laser pulses 2, 2' as a single laser pulse or in the form of laser pulse packets (laser bursts). This makes it possible to specifically request processing laser pulses 2, 2' having individual pulse energies at a given time, which can be achieved to some extent using, for example, the known pulse-on-demand concept.

[0031] As shown in Figure 1, the laser pulse emission device 6 comprises, for example, a laser beam source 8 driven by a control device 7 for generating an input laser pulse 9 having a constant pulse energy, and an optical amplifier 10 for amplifying the input laser pulse 9 into processing laser pulses 2, 2', and, if necessary, for amplifying further input laser pulses 9 into intermediate laser pulses 11, the intermediate laser pulses 11 can be extracted from the further beam path of the processing laser pulses 2, 2' using an optional pulse picker 16, and therefore do not reach the target region 4. The pulse picker 16 is positioned between the optical amplifier 10 and the target region 4 and is driven by the control device 7 to deflect the intermediate laser pulses 11 from the beam path of the processing laser pulses 2, 2', and to feed them to, for example, a beam trap 17. This ensures that the intermediate laser pulses 11 do not accidentally hit the target 3. Preferably, the pulse picker 16 is an AOM or EOM.

[0032] The input laser pulse 9 has a specified pulse energy E nom When a processing laser pulse 2, 2' having the same specified pulse energy E is amplified, the optical amplifier 10 amplifies the processing pulse 2, 2' that immediately follows with the same specified pulse energy E. nom To provide a new inversion structure, the gain-related minimum time period T min This requires the minimum possible period t of target 3. p -Δt p The minimum time period T related to gain is min That concludes the explanation. The input laser pulse 9 that forms the basis of the processing laser pulse and the intermediate laser pulses 2, 2', and 11 can be either a single laser pulse or a laser pulse packet (laser burst).

[0033] The laser pulse emission device 6 optionally has an optical modulator 12 arranged upstream of an optical amplifier 10 for individually setting the pulse energy of the input laser pulse 9 in order to set the pulse energies of the machining laser pulses and the intermediate laser pulses 2, 2', 11 accordingly. The optical modulator 12 is driven by a control device 7 to set the desired pulse energy of the input laser pulse 9, in any case, for example, by modulating the amplitude or trimming the pulse edges, and can take the form of, for example, an AOM or an EOM.

[0034] To feed the target 3 into the target area 4, the laser system 1 can have a target emission device 13 that emits the target 3 so that the target 3 passes through the target area 4 periodically one after another with a period t p ±Δt p For example, the target 3 can be emitted by the target emission device 13 in the form of individual droplets in the direction of gravity, i.e., downward in FIG. 1, and can pass through the target area 4 from top to bottom. A target detection device (for example, a camera) 14 can be additionally arranged downstream of the target emission device 13, and the target detection device detects the emitted target 3 and specifically its target shape, for example, using image recognition, at least in the target area 4, and distributes a corresponding external control signal 15 to the control device 7. The control signal can be used to determine the respective arrival times of the target 3 in the target area 4. Based on the control signal 15, the control device 7 then controls the laser pulse emission device 6 to emit the machining laser pulses 2, 2'. However, if the time interval between the emitted machining laser pulses 2, 2' and the previous machining laser pulses 2, 2' is greater than the gain-related minimum time period T min For example, 2*T min up to an amount greater than the specified maximum duration, the control device 7 preferably triggers an intermediate laser pulse 11 that has the energy of the ON machining laser pulse 2 after the gain-related minimum time period T min and prevents excessive energy from being accumulated in the optical amplifier 10. n*T minFor longer time intervals between two processing laser pulses (n≧2), an additional n-1 intermediate pulse 11 is given to prevent excessive energy from accumulating in the optical amplifier 10. min They are inserted at intervals of [number].

[0035] For technical details regarding the internal coupling of target 3 to target region 4 for generating secondary radiation 5, please refer to the scientific publication "Light sources for high-volume manufacturing EUV lithograghy ​​technology, performance, and power scaling," I. Formenkov et al., Advanced Optical Technologies 6(3):173-186, DOI:10.1515 / aot-2017-0029.

[0036] Figures 2a to 2d illustrate an exemplary representation of the time-dependent energy control of the laser system 1 when switching between a processing laser pulse 2 that hits the target 3 within the target region 4 and a processing laser pulse 2' that moves away from the target 3 within the target region 4 in time.

[0037] Figure 2a shows the target 3 emitted by the target emission device 13, which are time t i-1 , t i , t i+1 , t i+2 and t i+3 It is positioned in the target region 4. A target 3 used to generate secondary radiation 5 is called an ON target, and a target 3 that is not used to generate secondary radiation 5 (for example, because the period error is too large, the target shape is not optimal, or to modulate the power of the secondary radiation source, or to omit the processing pulse) is called an OFF target.

[0038] As shown in Figure 2b, each target 3 is assigned processing pulses 2 and 2'. The processing pulse that hits the assigned ON target 3 within the target region 4 in order to interact with the ON target 3 is called the ON processing laser pulse 2, and the processing laser pulse that is temporally out of sync with the assigned OFF target 3 within the target region 4 in order not to interact with the OFF target 3 is called the OFF processing laser pulse 2'. The ON processing pulse 2 interacts with the ON target 3 within the target region 4, time t i-1 , t i and t i+3 In this case, as requested by the control device 7, in either case the same specified pulse energy E nom The pulse energy of the ON processing laser pulse 2 preferably deviates by less than 3%, specifically less than 1%, from the specified average pulse energy. On the other hand, the OFF processing pulse 2' is at least a minimum time interval Δt1 earlier than when the associated OFF target 3 is positioned in the target region 4, i.e., in this case, time t i+1 -Δt1, t i+2 At -Δt1, where the specified pulse energy E of the ON processing pulse 2. nom The following are individually configurable pulse energies, as required by the control device 7. The minimum time interval Δt1 is selected so that no interaction occurs between the OFF processing laser pulse 2' and the OFF target 3.

[0039] As shown in Figure 2c, the control device 7, if necessary, in any case at least a second minimum time interval Δt2 before the ON processing laser pulse or OFF processing laser pulse 2, 2', i.e., in this case, time t i -Δt², t i+2 -Δt1-Δt2 and t i+3 At -Δt2, where the specified pulse energy E of the ON processing pulse 2. nomAn intermediate laser pulse 11 having individually configurable pulse energies should be requested as follows: The time and pulse energy of the OFF processing laser pulse 2' and the intermediate laser pulse 11 are, on the one hand, within the optical amplifier 10, in either case, the same specified pulse energy E as the ON processing laser pulse 2'. nom To amplify the energy, the optical amplifier 10 is selected to retain as little energy as possible, while ensuring that the energy E stored in the optical amplifier 10 for the ON processing laser pulse 2 is always the same.

[0040] Figure 2d shows the relevant time profile of the energy E stored in the optical amplifier 10. In this case, the control device 7 controls the emission time and / or pulse energy of the input laser pulse 9 that underlies the OFF processing laser pulse 2' and the intermediate laser pulse 11, as described below, and thereby the ON processing laser pulse 2, in either case, the same specified pulse energy E. nom The energy E stored in the optical amplifier 10 is set to have the following characteristics.

[0041] 1. Current ON processing laser pulse 2 (here, time t) i ) ON processing laser pulse 2 (here time t i-1 If it follows immediately after: The control device 7 controls the time t of the ON target 3. i At pulse energy E nom A current ON processing laser pulse 2 is required, and in this case, the time interval between the two ON processing laser pulses 2 is the minimum time period T without gain. min If it is greater than, that is, t i -t i-1 >T min In this case, time t iAt -Δt2, an intermediate laser pulse 11 is requested between these two processing laser pulses. The requested time and pulse energy of the intermediate laser pulse 11 are reduced due to the amplification of the intermediate laser pulse 11. The energy E stored in the optical amplifier 10 is equal to the current ON processing laser pulse 2's specified pulse energy E. nom The control device 7 sets the signal to rise again to the extent of time t1, which is amplified to the desired level. The time interval between the two ON processing laser pulses 2 is the minimum time period T without gain. min If equal to, that is, t i -t i-1 =T min In this case, the intermediate laser pulse 11 does not need to be requested by the control device 7. On the other hand, the minimum time period T without gain. min The time interval between two ON processing laser pulses 2 is smaller than t i -t i-1 <T min This is unacceptable and not permitted by the control device 7, or is evaluated as an OFF processing laser pulse, and the pulse energy is as described in section 2 below, for a minimum time period T min It is set as a function of the interval from.

[0042] 2. Current OFF processing laser pulse 2' (here, time t) i+1 -Δt1) is the ON processing laser pulse 2 (here, time t i If it follows immediately after: The control device 7 controls time t i+1 The current OFF processing laser pulse 2' is requested at -Δt1. The time interval between the current OFF processing laser pulse 2' and the previous ON processing laser pulse 2, i.e., (t i+1 -Δt1)-t i The current OFF processing laser pulse 2' has a maximum pulse energy of the specified pulse energy E. nom To amplify up to the minimum time period T with no gain minThe required time and pulse energy of the current OFF processing laser pulse 2' are preferably reduced due to the amplification of the current OFF processing laser pulse 2', the energy E stored in the optical amplifier 10, the minimum time period T without gain. min Following this, the ON or OFF processing laser pulses 2 and 2' immediately afterward have a specified pulse energy E nom The control device 7 sets the current pulse energy of the OFF processing laser pulse 2' to rise again to the extent that it is amplified. As shown, the pulse energy of the current OFF processing laser pulse 2' is equal to the specified pulse energy E of the ON processing laser pulse 2. nom It does not exceed that.

[0043] 3. Current OFF processing laser pulse 2' (here, time t i+2 -Δt1) is the OFF processing laser pulse 2' (here, time t i+ If it follows immediately after 1-Δt1): The control device 7, for example, controls time t i+2 At -Δt1, pulse energy E nom We require a current OFF processing laser pulse 2' having the following characteristics, and in this case, the time interval between these two OFF processing laser pulses is the minimum time period T without gain. min Larger than, that is, (t i+2 -Δt1)-(t i+1 -Δt1)>T min If that is the case, then here time (t i+2 At -Δt1)-Δt2, an intermediate laser pulse 11 is requested between these two processing laser pulses. The requested time and pulse energy of the intermediate laser pulse 11 are determined by the energy E stored in the optical amplifier 10, which decreases due to the amplification of the intermediate laser pulse 11, and the current OFF processing laser pulse 2' has a specified pulse energy E. nom Or, in reality, until it is amplified to a lower pulse energy, time t i+2 The control device 7 is set so that it rises again at -Δt1. As shown, the stored energy E of the intermediate laser pulse 11 before amplification is equal to the specified pulse energy E of the ON processing laser pulse 2. nom The energy level can rise to a higher level than when amplified. However, the pulse energy of the intermediate pulse 11 is the specified pulse energy E of the ON processing laser pulse 2. nom It does not exceed that.

[0044] 4. Current ON processing laser pulse 2 (here, time t) i+3 ) is OFF processing laser pulse 2' (here time t i+2 If it follows immediately after -Δt1): The control device 7 controls time t i+3 At pulse energy E nom We require a current ON processing laser pulse 2 having the following characteristics, and in this case, the time interval between these two processing laser pulses is the minimum time period T without gain. min If it is greater than, that is, (t i+3 )-(t i+2 -Δt1)>T min In this case, an intermediate laser pulse 11 is requested. The requested time and pulse energy of the intermediate laser pulse 11 are reduced due to the amplification of the intermediate laser pulse 11. The energy E stored in the optical amplifier 10 is reduced to the current ON processing laser pulse 2, which has a specified pulse energy E. nom Until it is amplified to the extent that time t i+3 The control device 7 sets the energy to rise again at the specified pulse energy E of the intermediate laser pulse 11, as shown. nom The energy level can rise to a level that is higher than when amplified. However, the pulse energy of the intermediate pulse 11 does not exceed the specified pulse energy of the ON processing laser pulse 2.

[0045] The time interval between the emitted processing laser pulses 2, 2' and the previous processing laser pulses 2, 2' is the gain-related minimum time period T. min Larger than, for example, 2*T minIf it is an amount up to but greater than the specified maximum duration not shown in FIG. 2, the intermediate laser pulse 11, for example, the gain-related minimum time period T min After that, the intermediate laser pulse 11 has the energy of the ON processing laser pulse 2 and is triggered by the control device 7 to prevent excessive energy from being accumulated in the optical amplifier 10. n*T min In the case of a longer time interval between two processing laser pulses of n*T (n≧2), n-1 additional intermediate pulses 11 are provided in any case at intervals of T min to prevent excessive energy from being accumulated in the optical amplifier 10.

Claims

1. A laser system (1) for providing processing laser pulses (2, 2') for interaction with targets (3) that pass periodically and successively through a target region (4), or periodically and successively through a target region (3) excluding periodic errors, comprising a laser pulse emission device (6) for emitting processing laser pulses (2, 2'), wherein at least one processing laser pulse (2, 2') is assigned to each target (3), and a control device (7) for controlling the laser pulse emission device (6) and setting the emission time of the processing laser pulses (2, 2') such that the processing laser pulse (2) hits the target (3) in the target region (4) in order to interact with the target (3) as an ON processing laser pulse (2), or does not interact with the target (3) as an OFF processing laser pulse (2'), thereby moving the target (3) out of the target region (4) in time, is provided for the laser system (1).

2. The pulse energy (E) of the ON processing laser pulse (2) ｎｏｍ The laser system according to claim 1, characterized in that the pulse energy deviates by less than 3%, specifically by less than 1%, from the average pulse energy value.

3. The laser pulse emission device (6) comprises a laser beam source (8) driven by the control device (7) for generating an input laser pulse (9), and an optical amplifier (10) for amplifying the input laser pulse (9) into the processing laser pulses (2, 2') and, if necessary, for amplifying further input laser pulses (9) into an intermediate laser pulse (11) located between the two processing laser pulses, wherein the optical amplifier (10) gives the ON processing laser pulse (2) a specified pulse energy (E ｎｏｍ After being amplified, the same specified pulse energy (E) is then applied to the subsequent ON processing laser pulse (2). ｎｏｍ To provide the minimum time period related to gain (T) ｍｉｎ ) is required, and the control device (7) sets the emission time and / or pulse energy of the input laser pulse (9) which forms the basis of the OFF processing laser pulse (2') and the intermediate laser pulse (11), thereby the ON processing laser pulse (2) has the same specified pulse energy (E) in either case. ｎｏｍ The laser system according to claim 1 or 2, characterized in that it is configured to set the energy stored in the optical amplifier (10) so that it has ) and to perform .

4. When the current ON processing laser pulse (2) is immediately followed by the ON processing laser pulse (2), the control device (7) emits the input laser pulse (9) which is the basis of the current ON processing laser pulse (2), and the time interval between these two processing laser pulses is the gain-related minimum time period (T ｍｉｎ If the current ON processing laser pulse (2) is greater than the specified pulse energy (E), the optical amplifier (10) emits a further input laser pulse (9) which is amplified into an intermediate laser pulse (11) between these two processing laser pulses, and the emission time and pulse energy of the further input laser pulse (9) are such that the current ON processing laser pulse (2) has the specified pulse energy (E). ｎｏｍ The laser system according to claim 3, characterized in that the laser beam source (8) is configured to drive such that the current ON processing laser pulse (2) has the energy (E) stored in the optical amplifier (10) and to set and to perform.

5. If the current OFF processing laser pulse (2') immediately follows the ON processing laser pulse (2), the control device (7) is configured to drive the laser beam source (8) to emit the input laser pulse (9) that underlies the current OFF processing laser pulse (2'), and the time interval between the current OFF processing laser pulse (2') and the ON processing laser pulse (2) is specifically the gain-related minimum time period (T ｍｉｎ The laser system according to claim 3 or 4, characterized in that it is smaller than ).

6. The control device (7) is configured to set the energy of the current OFF machining laser pulse (2') via the energy of the underlying input laser pulse (9) such that an ON machining laser pulse or an OFF machining laser pulse (2, 2') following immediately after the current OFF machining laser pulse (2') reaches the specified pulse energy (E ｍｉｎ ), again, after the gain-related minimum time period (T ｎｏｍ ). The laser system according to claim 5, characterized in that.

7. If the current OFF processing laser pulse (2') is immediately followed by the OFF processing laser pulse (2'), the control device (7) emits the input laser pulse (9) that forms the basis of the current OFF processing laser pulse (2'), and the time interval between these two processing laser pulses is the gain-related minimum time period (T ｍｉｎ The laser system according to any one of claims 3 to 6, characterized in that, if the optical amplifier (10) is greater than the following, the laser beam source (8) is configured to drive the optical amplifier (10) to emit a further input laser pulse (9) which is amplified into an intermediate laser pulse (11) between these two processing laser pulses.

8. When the current ON processing laser pulse (2) immediately follows the OFF processing laser pulse (2'), the control device (7) emits the input laser pulse (9) that forms the basis of the current ON processing laser pulse (2), and the time interval between these two processing laser pulses is the gain-related minimum time period (T ｍｉｎ If it is greater than the specified pulse energy (E), the optical amplifier (10) emits a further input laser pulse (9) which is amplified into an intermediate laser pulse (11) between these two processing laser pulses, and the emission time and pulse energy of the further input laser pulse (9) and thereby the current ON processing laser pulse (2) having the specified pulse energy (E) ｎｏｍ The laser system according to any one of claims 3 to 7, characterized in that the laser beam source (8) is driven to perform the following: setting the energy stored in the optical amplifier (10) for the current ON processing laser pulse (2) to have )

9. The pulse energy of the OFF processing laser pulse (2') and / or the intermediate laser pulse (11) is at most equal to the specified pulse energy (E) of the ON processing laser pulse (2). ｎｏｍ A laser system according to any one of claims 3 to 8, characterized in that it is at the same height as ).

10. To ensure that no interaction occurs between the OFF processing laser pulse (2') and the target (3), the associated target (3) is set to have at least a minimum time interval (Δt １ The laser system according to any one of claims 3 to 9, characterized in that it quickly reaches the target region (4).

11. The control device (7) controls at least the second minimum time period (Δt) of the processing laser pulse (2, 2') that follows immediately after. ２ The laser system according to any one of claims 3 to 10, characterized in that it is configured to emit an intermediate laser pulse (11) before the laser pulse.

12. The laser system according to any one of claims 3 to 11, characterized in that the laser beam source (8) is configured to provide the input laser pulse (9) having a constant pulse energy.

13. The laser system according to any one of claims 3 to 12, characterized in that an optical modulator (12) driven by the control device (7) is located upstream of the optical amplifier (10) to set the pulse energy of the input laser pulse (9) and thereby the pulse energy of the OFF processing laser pulse (2') and the intermediate laser pulse (11).

14. The laser system according to any one of claims 3 to 13, characterized in that a pulse picker (16) is positioned between the optical amplifier (10) and the target region (4), and extracts the intermediate laser pulse (11) from the further beam path of the processing laser pulse (2, 2').

15. The control device (7) determines that the time interval between the next processing laser pulse (2, 2') and the previous processing laser pulse (2, 2') emitted is the gain-related minimum time period (T ｍｉｎ The laser system according to any one of claims 3 to 14, characterized in that it is configured to emit at least one intermediate pulse (11) when it is greater than a specified maximum duration which is greater than ).

16. The laser system according to any one of claims 1 to 15, characterized in that each target (3) is assigned a control signal (15), and the control device (7) is configured to emit ON or OFF processing laser pulses (2, 2') based on each control signal (15).

17. A method for providing processing laser pulses (2, 2') for interaction with a target (3) that periodically passes through a target region (4) or periodically passes through a target region (3) with periodic error removed, the method comprising the following steps: - The step of emitting at least one processing laser pulse (2, 2') to each target (3), A method comprising the steps of: setting the emission time of the at least one processing laser pulse (2, 2') using a control device (7) such that the processing laser pulse strikes the target (3) in the target region (4) in order to interact with the target (3) as an ON processing laser pulse (2), or temporally moves away from the target (3) in the target region (4) in order not to interact with the target (3) as an OFF processing laser pulse (2').

18. The method according to claim 17, characterized in that the ON and OFF processing laser pulses (2, 2') are emitted in either case based on a control signal (15) assigned to the target (3).

19. A control program product comprising coding means adapted to perform all steps of the method according to claim 17 or 18 when the program is executed on a control device (7) of a laser system (1) according to any one of claims 1 to 16.

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