Laser system and method for providing pulsed laser beam arranged for interaction with target material

Abstract

The present application relates to a laser system for providing a pulsed laser beam arranged for interaction with a target material, the laser system comprises a laser beam source for providing a pulsed input laser beam, a target region for arranging a target material, a beam deflection device which deflects and / or splits the input laser beam and provides at least one pulsed laser beam, and a control device which controls and / or regulates the position of the at least one laser beam relative to the target region, the position of the laser beam being directed towards the target region in a first operating mode, and the position of the laser beam being directed towards the target region in a second operating mode. The position of the laser beam misses the target area. The pulsed laser beam provided in the second operating mode is positioned symmetrically with respect to the temporal averaging and / or spatial averaging with respect to the pulsed laser beam formed in the first operating mode.

Description

Technical Field

[0001] The present application relates to a laser system and method for providing a pulsed laser beam configured to interact with a target material. Background Art

[0002] WO 2014 / 044392 A1 discloses an EUV radiation generating device, comprising: a vacuum chamber, in which a target material can be arranged at a target position for generating EUV radiation, and a beam guiding chamber for guiding a laser beam from a driver laser device in the direction of the target position. An intermediate chamber is provided, which is arranged between the vacuum chamber and the beam guiding chamber, a first window hermetically closing the intermediate chamber for the laser beam to enter from the beam guiding chamber, and a second window hermetically closing the intermediate chamber for the laser beam to exit into the vacuum chamber.

[0003] DE 10 2020 200 798 A1 discloses a method for laser material processing by means of a processing laser beam, wherein a first laser beam and / or a second laser beam is generated from an input laser beam, the first laser beam is coupled into at least a first fiber core of a multi-core optical fiber, and the second laser beam is coupled into at least a second fiber core of the multi-core optical fiber. The first and second laser beams are coupled out of the multi-core optical fiber individually or together as a processing laser beam, and the ratio of the laser power between the first and second laser beams is varied with a modulation frequency between 1 Hz and 100 kHz. Summary of the invention

[0004] The object of the present application is to provide a laser system and a method of the type mentioned in the introduction, by means of which a pulsed laser beam with high average power provided for interaction with a target material can be generated and at the same time controllable interaction of the laser pulses of the pulsed laser beam with the target material can be achieved.

[0005] According to the application, this object is achieved in the following manner: the laser system comprises: a beam deflection device; a control device assigned to the beam deflection device; a laser beam source for providing a pulsed input laser beam for coupling into the beam deflection device; and a target area for arranging a target material, wherein the pulsed input laser beam can be deflected and / or split by means of the beam deflection device, and at least one pulsed laser beam emitted from the beam deflection device is provided based on the pulsed input laser beam by means of the beam deflection device, wherein the control device is designed to control and / or regulate the position of the at least one pulsed laser beam relative to the target area by actuating the beam deflection device, wherein the control device has a first operating mode, in which the position of the at least one pulsed laser beam is selected so that it is directed toward the target area to interact with the target material arranged in the target area, and wherein the control device has a second operating mode, in which the position of the at least one pulsed laser beam is selected so that it misses the target area.

[0006] By selecting the first operating mode and the second operating mode, it is possible to control whether the pulsed laser beam strikes or does not strike the target material arranged in the target area, i.e., whether the laser pulses assigned to the pulsed laser beam interact with the target material. This makes it possible, for example, to control the generation of secondary radiation and, in particular, the average dose (Dosis) and / or intensity of the generated secondary radiation in a simple manner.

[0007] In the solution according to the present application, the pulsed laser beam is deflected and / or directed in a first operating mode so that it strikes a target material arranged in the target region, and in a second operating mode so that it does not strike the target material, i.e., the pulsed laser beam is deflected in this case so that it passes by the target material or misses the target material. Thus, no technical intervention in the laser beam source itself is required to control the interaction between the existing pulsed laser beam and the target material. In particular, it is not necessary to control the laser pulses of the input laser beam or pulsed laser beam provided by means of the laser beam source in terms of time in order to prevent the interaction with the target material in an appropriate manner.

[0008] By means of the provided beam deflection device, the position and / or the pointing and / or the orientation of the at least one pulsed laser beam relative to the target area and the target material arranged therein can be controlled in a simple time-dependent manner by actuation via the control device. In addition, a possible splitting of the input laser beam can be controlled thereby to provide one or more (or more than two) pulsed laser beams emerging from the beam deflection device.

[0009] In particular, the first operating mode and the second operating mode can be set and / or selected on the control device. It can be provided that the control device has an input for receiving a control signal, wherein the first operating mode or the second operating mode is selected by means of the control signal.

[0010] The position of the at least one pulsed laser beam relative to the target region is to be understood in particular to mean the position of a focal region and / or a focal cross section of the at least one pulsed laser beam relative to the target region.

[0011] The pulsed laser beam that can be provided is particularly suitable and / or designed for interaction with the target material.

[0012] In particular, it can be provided that the laser system is suitable and / or designed for generating secondary radiation by interaction of a pulsed laser beam with a target material. It can be provided in particular that the pulsed laser beam is directed at the target material in a first operating mode so that the laser pulses of the pulsed laser beam interact with the target material and thereby generate secondary radiation. Alternatively or additionally, the laser system can be suitable and / or designed for preparing and / or pre-treating the target material by interaction of a pulsed laser beam with the target material. In particular, the target material is introduced into a certain form and / or a certain state by interaction of the laser pulses of the pulsed laser beam in the first operating mode, which enables particularly efficient generation of secondary radiation by interaction with further laser pulses in a subsequent process. For example, the preparation of the target material is performed with laser pulses of a first laser beam source, and the subsequent generation of the secondary radiation is then performed by interaction with further laser pulses of a second laser beam source. The second laser beam source then has in particular a higher average power than the first laser beam source.

[0013] Furthermore, the laser system can also be used to diagnose the quality of the mentioned preparation and / or pretreatment of the target material.

[0014] The at least one pulsed laser beam misses the target area and / or the target material arranged therein in the second operating mode, which is understood to mean that the at least one pulsed laser beam does not interact or does not significantly interact with the target material, so that, for example, depending on the application of the laser system, no secondary radiation is generated or the generated secondary radiation is below a threshold intensity or the target material is not prepared or sufficient preparation of the target material is not carried out.

[0015] The at least one pulsed laser beam irradiates the target area and / or the target material arranged therein in the first operating mode, which is understood to mean that the at least one pulsed laser beam interacts with the target material so that, for example, depending on the application of the laser system, secondary radiation with an intensity above a threshold is generated or preparation or sufficient preparation of the target material is carried out.

[0016] In particular, the control device has no further operating states (apart from the inactive state) besides the first operating state and the second operating state.

[0017] The laser beam source comprises in particular a seed laser, for example a diode laser.

[0018] The laser beam source comprises in particular a laser amplifier and / or a laser amplifier chain. The laser amplifier is preferably Yb- or Nd-doped. For example, Yb:Glas, Yb:YAG or Nd:YAG amplifiers are used as laser amplifiers. The laser amplifiers used can be implemented in particular in the geometry of an optical fiber, a rod, a plate or a disk.

[0019] Preferably, in the first operating mode, exactly one pulsed laser beam is provided from the beam deflection device, which is directed toward the target area and / or the target material. In particular, in this case, a plurality of pulsed laser beams are not provided simultaneously from the beam deflection device, but rather the exactly one pulsed laser beam is provided at a specific time.

[0020] In particular, it can be provided that in the second operating mode, exactly one pulsed laser beam emitted from the beam deflection device is provided which misses the target area. In particular, in this case, a plurality of pulsed laser beams emitted from the beam deflection device are not provided simultaneously, but rather the exactly one pulsed laser beam is provided at a specific time.

[0021] It can be advantageous if, in the temporally successive second operating mode(s), the position of the precisely one pulsed laser beam is deflected alternately toward a first side and toward a second side opposite the first side with reference to the target region. This makes it possible, for example, to achieve a symmetrical arrangement of the pulsed laser beams provided in the successive second operating modes with respect to the pulsed laser beam provided in the first operating mode, in terms of a temporal average. This in turn makes it possible to achieve a simplified and less disruptive stabilization of the pointing and / or positioning of the pulsed laser beam emitted by the beam deflection device.

[0022] For the same reasons, it can be advantageous if, in a second, temporally subsequent operating mode, the position of the precisely one pulsed laser beam is deflected alternately in a first direction and in a second direction opposite to the first direction with reference to the target region.

[0023] The second operating mode that is successive in time is particularly understood to mean that the second operating mode is first selected at a determined time point and then again at a later time point, wherein a determined time period of the first operating mode is selected between these two time points. Here, for example, the following sequence is obtained: first operating mode (time point t1) – second operating mode (time point t2) – first operating mode (time point t3) – second operating mode (time point t4), etc., where t1 < t2 < t3 < t4. The successive second operating mode can be understood, for example, as the second operating mode at time points t2 and t4, i.e., two second operating modes that are successively selected in time.

[0024] It can be expedient that, in the second operating mode, two or more pulsed laser beams emitted from the beam deflection device are provided, and the two or more pulsed laser beams are emitted from the beam deflection device simultaneously. Thereby, for example, an approximately symmetric arrangement of the pulsed laser beams provided in the second operating mode with respect to the pulsed laser beams provided in the first operating mode can be achieved in terms of spatial averaging. Thereby, a simplified and less interference-prone stabilization of the pointing and / or positioning of the pulsed laser beams emitted from the beam deflection device can be achieved again.

[0025] Here, for example, the pulsed laser beams provided in the second operating mode are positioned and / or pointed symmetrically in space with respect to the pulsed laser beams provided in the first operating mode. For example, the pulsed laser beams provided in the second operating mode are deflected with respect to the target area towards a first side and / or a first direction, and another pulsed laser beam provided in the second operating mode is deflected with respect to the target area towards a second side opposite to the first side and / or a second direction opposite to the first direction. Thereby, in particular, a simplified and less interference-prone stabilization of the pointing and / or positioning of the pulsed laser beams emitted from the beam deflection device can be achieved. In particular, the advantages in terms of using a beam tracker for stabilization are obtained here, where, for example, false feedback signals can be reduced or avoided.

[0026] For the same reason, it can be advantageous that the pulsed laser beams provided in the second operating mode are positioned symmetrically with respect to the pulsed laser beams formed in the first operating mode in terms of time and / or spatial averaging. For example, there is a plane symmetry and / or point symmetry of the pulsed laser beams provided in the second operating mode with respect to the pulsed laser beams provided in the first operating mode.

[0027] In particular, it can be provided that the position of the center point of the beam cross section of the at least one pulsed laser beam in the target region in the first operating mode is spaced apart from the position of the center point of the at least one pulsed laser beam in the second operating mode by at least the diameter of the beam cross section. In the case of the simultaneous presence of a plurality of pulsed laser beams, the corresponding positions of the center points of all pulsed laser beams present in the first operating mode are spaced apart from the corresponding positions of the center points of all pulsed laser beams present in the second operating mode by at least the diameter of the beam cross section of the corresponding pulsed laser beam.

[0028] In particular, it can be provided that the beam deflection device comprises an acousto-optic deflector and / or an acousto-optic modulator or is designed as an acousto-optic deflector or an acousto-optic modulator. As a result, the position of the at least one pulsed laser beam relative to the target area can be varied with high temporal dynamics.

[0029] In the context of the present document, the at least one pulsed laser beam is to be understood in principle as a working laser beam, which is provided by deflecting and / or splitting an input laser beam by means of a beam deflection device and which, depending on the positioning and / or splitting, can be used in the selected operating mode for an adequate interaction with the target material according to the intended application. In the case of an acousto-optic deflector or modulator, in particular the first diffraction order is used as the working laser beam. The other diffraction orders are not used and therefore do not belong to the term "pulsed laser beam".

[0030] In particular, the beam deflection device is controlled by the control device in a first operating mode with a control voltage having a constant carrier frequency. In particular, the spectrum of the control voltage has the carrier frequency as the only frequency. As a result, in particular a single pulsed laser beam directed onto the target area is emitted from the beam deflection device.

[0031] For example, the beam deflection device is controlled by means of the control device in the second operating mode with a control voltage having a frequency reduced relative to the carrier frequency or having a frequency increased relative to the carrier frequency. In particular, the idealized spectrum of the control voltage then has a single frequency, which is a reduced or increased frequency. As a result, in particular, a single pulsed laser beam is emitted from the beam deflection device, which is deflected in such a way that it misses the target area.

[0032] The increased frequency and the reduced frequency are, for example, symmetrical with respect to the carrier frequency.

[0033] For example, the beam deflection device is actuated by means of the control device in the second operating mode with a control voltage having a superposition of two or more frequencies, wherein these frequencies are different from the carrier frequency. In particular, the spectrum of the control voltage then has two or more frequencies that are different from the carrier frequency, but in particular not the carrier frequency itself. As a result, in particular two or more pulsed laser beams are emitted simultaneously from the beam deflection device, which are deflected in such a way that they miss the target area.

[0034] The two or more frequencies are, for example, symmetrical about the carrier frequency.

[0035] It can be provided that the beam deflection device is actuated by means of the control device in the second operating mode with a control voltage which has a beat frequency of (a plurality of) signals which have a frequency which is reduced relative to the carrier frequency and a frequency which is increased relative to the carrier frequency.

[0036] In particular, it can be provided that in the first operating mode, the laser pulses of the at least one pulsed laser beam are introduced into the target region in such a way that they are synchronized in time with the target material introduced into the target region, so that in the first operating mode an interaction of one or more laser pulses with the target material in the target region takes place. The coupling of the target material into the target region can, for example, be somewhat irregular or error-prone in time, wherein a corresponding jitter can be, for example, + / -1 μs. By means of the mentioned synchronization, it can be ensured in the first operating mode that an adequate interaction of the laser pulses of the pulsed laser beam with the target material actually takes place, depending on the application.

[0037] For example, the laser pulses of the input laser beam or of the at least one pulsed laser beam provided by means of a laser beam source are staggered in time and / or output in a corrected manner so that in a first operating mode the laser pulses strike a target material arranged in the target area and compensate for temporal irregularities in the coupling of the target material into the target area.

[0038] The laser beam source is designed in particular to provide laser pulses of a pulsed input laser beam and / or a pulsed laser beam with a constant energy mean value, wherein the energy of the laser pulses deviates from the energy mean value by less than 2% and in particular by less than 1% during operation of the laser system. The energy mean value is understood in particular to be a predetermined desired value for the energy of the laser pulses.

[0039] The laser beam source is designed in particular to provide laser pulses of a pulsed input laser beam and / or a pulsed laser beam with a constant pulse repetition rate mean value, wherein the pulse repetition rate of the provided laser pulses deviates from the constant pulse repetition rate mean value by less than 20% and in particular by less than 15% during operation of the laser system. In the context of the deviation, in particular time corrections can be made, which may be necessary for the aforementioned synchronization of the laser pulses with the target material. The pulse repetition rate mean value is to be understood in particular as a constant desired value of the pulse repetition rate, from which corresponding deviations may occur for the aforementioned synchronization of the laser pulses.

[0040] In particular, the laser system comprises a supply device for supplying the target material into the target region. For example, the target material is introduced into the target region in the form of individual units and / or droplets by means of the supply device. In particular, the target material is supplied such that it is positioned in the target region at a (with error) point in time or within a time window. In principle, it is also possible that the target material is introduced into the target region in the form of a material stream, in particular a continuous material stream, by means of the supply device.

[0041] In particular, it can be provided that the feeding device is designed to introduce the target material into the target area at a speed of at least 50 m / s and / or at most 200 m / s and preferably at least 60 m / s and / or at most 130 m / s. The target material can especially pass through the target area at a speed in the range mentioned.

[0042] In particular, it can be provided that the target material is introduced into the target region at an at least approximately constant speed and / or at an at least approximately constant clock rate during operation of the laser system.

[0043] In particular, the target material moves through the target region with a direction of movement which is directed at least approximately parallel to the direction of gravity.

[0044] It may be expedient for the laser system to include a target material detection device for detecting a target material in the target region, wherein the target material detection device is designed in particular to output a control signal to the laser beam source and / or to a control device associated with the beam deflection device when a target material is detected in the target region. In this way, in particular in the first operating mode, a temporal synchronization of the laser pulses of the pulsed laser beam with the target material arranged in the target region can be achieved. Furthermore, in this way, depending on the application, the first operating mode or the second operating mode can be selected based on whether a target material is present in the target region.

[0045] It may be advantageous if the laser system has a beam detection device for detecting the orientation and / or position of the pulsed laser beam emitted by the beam deflection device. In particular, the position of the at least one pulsed laser beam can be adjusted thereby. For example, the orientation and / or position of the at least one pulsed laser beam can be stabilized by means of the beam detection device. For this purpose, the laser system may have a corresponding device for stabilizing the orientation and / or position. Furthermore, the position of the at least one pulsed laser beam can be adjusted thereby in the first operating mode and / or in the second operating mode by means of a control device assigned to the beam deflection device.

[0046] According to the present application, a method for providing a pulsed laser beam configured to interact with a target material is provided, in which method the target material is arranged or is arranged in a target area, a pulsed input laser beam is provided by means of a laser beam source, the pulsed input laser beam is coupled into a beam deflection device, wherein the pulsed input laser beam can be deflected and / or split by means of the beam deflection device, and at least one pulsed laser beam emitted from the beam deflection device is provided based on the pulsed input laser beam by means of the beam deflection device, wherein the position of the pulsed laser beam emitted from the beam deflection device relative to the target area is controlled and / or adjusted by actuating the beam deflection device by means of a control device, wherein the control device has a first operating mode, in which the position of the at least one pulsed laser beam is selected such that it is directed toward the target area and interacts with the target material arranged in the target area, and wherein the control device has a second operating mode, in which the position of the at least one pulsed laser beam is selected such that it misses the target area.

[0047] The method according to the present application has, in particular, one or more further features and / or advantages of the laser system according to the present application. Advantageous embodiments have already been explained in conjunction with the laser system.

[0048] The method according to the application can be carried out in particular with the aid of a laser system according to the application. In particular, the method according to the application can be carried out with the aid of a laser system according to the application.

[0049] A laser system for providing a laser beam having a focal region with a non-rotationally symmetrical cross section, the laser system comprising a beam deflection device, a control device assigned to the beam deflection device, and a laser beam source for providing an input laser beam for coupling into the beam deflection device, wherein the beam deflection device comprises an acousto-optic deflector and / or an acousto-optic modulator, and wherein the control device is designed to control the beam deflection device so that the input laser beam is simultaneously split by means of the beam deflection device into at least two laser beams emitted from the beam deflection device and the corresponding beam cross sections of the emitted laser beams overlap at least in sections so that a focal region with a non-rotationally symmetrical cross section is formed.

[0050] In particular, the laser beam emerging from the beam deflection device is focused by means of focusing optics, wherein the emerging laser beams overlap at least in sections in a focusing plane associated with the focusing optics to form a focusing region having a rotationally non-symmetrical cross section there.

[0051] A non-rotationally symmetrical cross section is to be understood as meaning, in particular, an elliptical cross section and / or an elongated cross section and / or a cross section with a primary direction and / or a non-point-symmetrical cross section.

[0052] In particular, the beam deflection device is actuated by means of the control device with a control voltage which has a superposition and / or a beat frequency of a signal containing two or more frequencies.

[0053] A focal region is to be understood in particular to mean a spatially continuous radiation region in which the radiation intensity is above a certain threshold intensity.

[0054] A method for providing a laser beam having a focal region with a non-rotationally symmetric cross section, in which an input laser beam is provided by means of a laser beam source and the input laser beam is coupled into a beam deflection device, wherein the beam deflection device comprises an acousto-optic deflector and / or an acousto-optic modulator, and wherein a control device controls the beam deflection device so that the input laser beam is simultaneously split by means of the beam deflection device into at least two laser beams emitted from the beam deflection device and the corresponding beam cross sections of the emitted laser beams overlap at least in sections in the focal region, so that a focal region with a non-rotationally symmetric cross section is formed.

[0055] In particular, the expression “at least approximately” is generally understood to mean a deviation of at most 10%, ie the actual value deviates from the ideal value by at most 10%.

[0056] The following description of the preferred embodiments is used to explain the present application in detail in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The accompanying drawings show:

[0058] Figure 1 One embodiment of a laser system is shown;

[0059] Figure 2 shows a cross section of a provided pulsed laser beam, wherein the positioning of the pulsed laser beam relative to the target material is shown in different operating modes;

[0060] Figure 3 A diagram showing different frequencies of a control voltage for driving a beam deflection device of a laser system, wherein the power is plotted as a function of the corresponding frequency;

[0061] Figure 4shows cross sections of the provided laser beams, wherein corresponding beam cross sections of the laser beams overlap one another and form a focal region;

[0062] Figure 5 shows an example of positioning of a provided pulsed laser beam relative to a target material as a function of time; and

[0063] Figure 6 A second example of the positioning of the provided pulsed laser beam relative to the target material is shown as a function of time. DETAILED DESCRIPTION

[0064] Identical or functionally equivalent elements are provided with the same reference symbols in all figures.

[0065] One embodiment of a laser system is Figure 1 1 and denoted there by 100. The laser system 100 comprises a laser beam source 102, by means of which a pulsed input laser beam 103 is provided during operation of the laser system 100. It is provided that at least one pulsed laser beam 104 based on the input laser beam 103 is formed and directed to a target material 106. By the interaction of laser pulses 108 assigned to the input laser beam 103 or the pulsed laser beam 104 with the target material 106, secondary radiation 110 can be generated. Alternatively or additionally, the target material 106 can be prepared for generating secondary radiation by the interaction.

[0066] To generate the secondary radiation, the laser beam source 102 can be designed, for example, as a CO2 laser which, during operation of the laser system 100 , has an average power of 1 kW or more.

[0067] If the laser system 100 is to be used for preparing a target material 108, the laser beam source 102 can be designed, for example, as an Nd:YAG laser or a Yb-YAG laser. The average power in this case is, for example, between 500 W and 800 W. The input laser beam 103 and / or the pulsed laser beam 104 provided by means of the laser beam source 102 then have, for example, laser pulses 108 with a pulse repetition rate in the kilohertz range, for example in the range of 40 kilohertz to 100 kilohertz. The pulse duration of each of the laser pulses 108 is in particular in the nanosecond range, for example in the range of 1 nanosecond to 500 nanoseconds, in particular in the range of 5 nanoseconds to 20 nanoseconds.

[0068] In principle, the laser system 100 may have a plurality of laser beam sources 102 , for example one for generating the secondary radiation 110 and another one for preparing the target material 106 .

[0069] The laser beam source 102 can, for example, have a laser beam source control device 109, by means of which the output of laser pulses 108 by the laser beam source 102 can be triggered and / or controlled at a specific time. For example, it can be provided that the laser beam source 102 outputs one or more laser pulses 108 when the control device 109 receives a corresponding control signal. As a result, laser pulses 108 can be requested expediently at specific times and / or the laser pulses 108 outputted can be regularly staggered in time relative to one another by the laser beam source 102. This can be achieved, for example, by means of the pulse-on-demand principle.

[0070] The secondary radiation 110 that can be provided by the interaction of the target material 106 with the laser pulses 108 of the laser beam 104 is, for example, EUV radiation. The target material 106 is, for example, tin or comprises tin.

[0071] The laser system 100 has a target region 112 in which a target material 106 can be arranged in order to impinge upon the target material with the laser beam 104. It is provided that, during operation of the laser system 100, the target material 106 is introduced into the target region 112 and there brought into interaction with the laser pulses 108. In particular, the pulsed laser beam 104 directed toward the target material 106 is focused onto the target material 106 and / or the target region 112. For this purpose, for example, focusing optics 113 may be provided.

[0072] In particular, it can be provided that the target region 112 is designed and / or positioned in a liquid-tight and / or gas-tight chamber 114. In the chamber 114, for example, a vacuum is formed.

[0073] In order to supply the target material 106 to the target region 112, the laser system 100 may have a supply device 116, by means of which the introduction of the target material 106 into the target region 112 may be controlled and / or regulated. For example, the target material 106 may be discharged by means of the supply device 116 in such a way that it passes through the target region 112 at a specific, in particular regular, point in time and / or is positioned in the target region 112 at a specific, in particular regular, point in time.

[0074] The target material 106 is introduced into the target region, for example, at a speed of between 60 m / s and 120 m / s, wherein the target material 106 is in this case present, in particular, in the form of individual droplets which successively pass through the target region.

[0075] In terms of technical details, the coupling of the target material 106 into the target area 112 for generating secondary radiation can be found in the scientific publication “Light sources for high-volume manufacturing EUV lithography: technogy, performance, and power scaling”, I. Fomenkov et al., Advanced Optical Technologies 6(3):173-186, DOI:10.1515 / aot-2017-0029.

[0076] The target material 106 can be provided, for example, in the form of individual elements and / or droplets by means of a supply device 116, which respectively pass through the target region 112 one after the other at a certain point in time. In the example shown, the direction of gravity points in the negative y direction, so that the target material 106 output by means of the supply device 116 passes through the target region 112 from top to bottom (i.e., in the negative y direction).

[0077] It can be provided that the laser system 100 has a target material detection device 118, by means of which it can be detected whether the target material 106 is arranged in the target area 112 at a certain point in time. The target material detection device 118 includes, for example, a camera device to detect the target material 106 in the target area 112, for example by means of image recognition.

[0078] The laser system 100 comprises a beam deflection device 120 into which the input laser beam 103 is coupled. The pulsed laser beam formed by means of the beam deflection device 120 based on the input laser beam 103 and emerging from the beam deflection device 120 is referred to as pulsed laser beam 104.

[0079] The beam deflection device 120 is suitable for deflecting and / or splitting the input laser beam 103. In principle, a pulsed laser beam 104 can be emitted from the beam deflection device 120 or multiple pulsed laser beams 104 can be emitted from the beam deflection device 120 at the same time. The beam deflection device 120 can be used to adjust the orientation and / or position of a pulsed laser beam 104 or multiple pulsed laser beams 104 relative to the target area 112.

[0080] In press Figure 1In the embodiment of the invention, the beam deflection device 120 is an acousto-optic modulator and / or an acousto-optic deflector or comprises an acousto-optic modulator and / or an acousto-optic deflector. In the example shown, the pulsed laser beam 104 impinging on the beam deflection device 120 is split into a plurality of sub-beams of different diffraction orders by means of the beam deflection device 120, wherein the sub-beam of order 1 is used as a working laser beam or the pulsed laser beam 104 for loading the target material 106. Typically, the sub-beam of order 1 used has a beam intensity of more than 90% of the laser beam 104 originally impinging on the beam deflection device 120. The sub-beam of order 0, which is marked with 104a, is not used like the other sub-beams of the other orders and is guided, for example, into a beam trap 122.

[0081] In order to control the beam deflection device 120, the laser system 100 includes a control device 124, which is, for example, operatively connected to the beam deflection device 120 for signals or integrated into the beam deflection device 120. By controlling the beam deflection device 120 by means of the control device 124, the pulsed laser beam 104 can be displaced relative to the target area 112, that is, the orientation and / or position of the beam relative to the target area 112 can be adjusted.

[0082] It can be provided that the laser system has a beam detection device 125 (in Figure 1 The beam detection device 125 is used to detect the orientation and / or position of the pulsed laser beam 104 emitted from the beam deflection device 120. The beam detection device 125 comprises in particular a plurality of detectors and / or cameras, by means of which the orientation and / or position can be detected. The beam detection device 125 is, for example, a beam tracker or comprises a beam tracker.

[0083] In particular, a stabilization of the pointing and / or positioning of the pulsed laser beam 124 can be performed with the aid of the beam detection device 125. To this end, the laser system 100 can have a device (not shown) for stabilizing the pointing and / or positioning of the pulsed laser beam 124, which receives information about the pointing and / or positioning of the pulsed laser beam 124 from the beam detection device 125 and performs stabilization based on this information.

[0084] In addition, the beam detection device 125 can be connected to the control device 124 in a signal-effective manner to transmit information about the direction and / or position of the pulsed laser beam 104 emitted from the beam deflection device 120 to the control device 124. In this way, it is particularly possible to adjust the direction and / or position of the pulsed laser beam 104 by means of the control device 124 or the beam deflection device 120.

[0085] It is provided that the control device 124 has a first operating mode, in which the beam deflection device 120 is controlled so that the pulsed laser beam 104 emitted therefrom is directed toward the target region 112 and the laser pulses 108 are emitted to the target region 112 and / or to the target material 106 arranged in the target region 112. In this case, the laser pulses 108 of the pulsed laser beam 104 can interact with the target material 106 arranged in the target region 112.

[0086] In the first operating mode, the pulsed laser beam 104 coupled out of the beam deflection device 120 is Figure 1 It is additionally marked with 104-b1.

[0087] Furthermore, the control device 124 has a second operating mode in which the beam deflection device 120 is controlled so that the pulsed laser beam 104 emitted therefrom misses the target region. In this case, the laser pulses 108 do not or approximately do not strike the target region 112 and / or do not or approximately do not strike the target material 106 arranged in the target region 112. In this case, the laser pulses 108 may not interact with the target material or may interact only slightly with the target material. In this case, depending on the application, no secondary radiation 110 is generated or the generated secondary radiation 110 is present only below a threshold intensity, or no sufficient interaction occurs for preparing the target material.

[0088] In principle, there are several possibilities for how to deflect pulsed laser beam 104 by means of beam deflection device 120 to miss target region 112 . Thus, in the second operating mode, several variants can be provided with regard to the orientation and / or position of pulsed laser beam 104 relative to target region 112 .

[0089] As in Figure 1 As briefly shown in , two different variants can be set, for example, wherein, in a first variant of the second operating mode, the pulsed laser beam 104 is deflected, for example, in a first direction to miss the target area 112 and miss the target material 106 located therein (pulsed laser beam 104-b2'), and, in a second variant, the pulsed laser beam 104 is deflected, for example, in a second direction different from the first direction to miss the target area 112 and miss the target material 106 located therein (pulsed laser beam 104-b2"). In principle, it is possible to set another variant of the second operating mode, in which the pulsed laser beam 104 is deflected in different directions to miss the target area 112 and / or the target material 106.

[0090] For example, if the target material 106 is fed by the feeding device 116 as in Figure 1As shown in FIG, , laser beam 104-b2 is supplied to target region 112 from top to bottom (i.e., in the negative y direction), then laser beam 104-b2′ is spatially deflected behind target material 106 with reference to the direction of movement of target material 106 so as to miss target material 106, i.e., when target material 106 is positioned in target region 112, laser beam 104-b2′ is behind target material 106. Laser beam 104-b2″ is spatially deflected in front of target material 106 so as to miss target material 106, i.e., when target material 106 is positioned in target region 112, laser beam 104-b2″ is in front of target material 106.

[0091] Obviously, pulsed laser beam 104 can also be deflected in a direction pointing transversely or perpendicularly to the direction of movement of target material 106, for example, in order to miss target material 106. In principle, pulsed laser beam 104 can be deflected in any arbitrary direction pointing perpendicularly to beam propagation direction 126 of pulsed laser beam 104 for this purpose.

[0092] Figure 2 The positioning of pulsed laser beams 104-b1, 104-b2' and 104-b2" relative to the target area 112 and the target material 106 in a cross-sectional plane is shown, wherein the cross-sectional plane is pointed perpendicular to the beam propagation direction 126 of the pulsed laser beam 104-b1 irradiated to the target area 112 and the target material 106 is positioned on the cross-sectional plane (in the example shown, the beam propagation direction 126 is parallel to the z-direction and the cross-sectional plane is pointed parallel to the xy plane).

[0093] The corresponding beam cross sections of the laser beams 104-b1, 104-b2' and 104-b2" are Figure 2 In particular, the laser beams 104 - b1 , 104 - b2 ′ and 104 - b2 ″ are focused at the height of the target region 112 and / or the target material 106 with reference to the beam propagation direction 126 .

[0094] The pulsed laser beams 104-b2' and 104-b2" provided in the second operating mode preferably extend symmetrically with respect to the symmetry plane. In particular, the pulsed laser beam 104-b1 formed in the first operating mode is located in the symmetry plane (in Figure 1 In the example shown, the symmetry plane is parallel to the beam propagation direction 126 and / or points parallel to the xz plane).

[0095] In particular, corresponding center points 128 of the beam cross sections of pulsed laser beams 104 - b2 ′ and 104 - b2 ″ are arranged point-symmetrically with respect to the position of target material 106 and / or with respect to the center point of the beam cross section of pulsed laser beam 104 - b1 formed in the first operating mode.

[0096] In a further variant of the second operating mode, it can be provided that the input laser beam 103 coupled into the beam deflection device 120 is simultaneously split into two or more deflected sub-beams by means of the beam deflection device 120. For example, the pulsed laser beam 104 is split into two or more deflected sub-beams by means of the beam deflection device 120 as in Figure 1 As schematically shown in FIG. 1 , the laser beam is split into two pulsed laser beams 104 - b2 ′ and 104 - b2 ″. In this case, the two pulsed laser beams each have, for example, approximately half the intensity of the pulsed laser beam 104 - b1 formed in the first operating mode and directed toward the target area 112 .

[0097] In the example shown, the beam deflection device 120, which is designed as an acousto-optic modulator and / or an acousto-optic deflector, is controlled by a control device 124 using a control voltage. The control voltage has a defined frequency and / or a defined frequency spectrum. The control voltage is, for example, a sinusoidal voltage or includes a sinusoidal voltage.

[0098] In a first operating mode, the beam deflection device 120 is actuated at a certain carrier frequency f0 ( Figure 3 ) is performed to achieve the laser beam 104-b1 irradiating the target material 106. The carrier frequency f0 is, for example, 80 MHz.

[0099] In the second operating mode, the frequency of the voltage is increased or decreased relative to the carrier frequency f0 to realize the pulsed laser beams 104-b2' and 104-b2", For example, in order to realize the pulsed laser beam 104-b2', the beam deflection device 120 is operated at a frequency f0 reduced relative to the carrier frequency f0. - Control, and, in order to realize the pulsed laser beam 104-b2", the beam deflection device 120 is driven at a frequency f increased relative to the carrier frequency f0. + Control.

[0100] For example, the reduced frequency f - and the increased frequency f + Symmetrical distribution about the carrier frequency f0. The reduced frequency f - For example, the frequency f is 79 MHz and the increased frequency f + For example, 81 MHz.

[0101] In the case of the aforementioned further variant of the second operating mode, the input laser beam 103 is simultaneously split into two or more deflected sub-beams by means of a beam deflection device 120, wherein the beam deflection device 120 is actuated by means of a voltage whose spectrum has two or more frequencies. For example, the voltage includes a superposition and / or a beat frequency of signals having two or more frequencies.

[0102] In order to simultaneously deflect the incident pulsed laser beam 104 into the pulsed laser beam 104 - b2 ′ and the pulsed laser beam 104 - b2 ″, the beam deflection device 120 is controlled by means of the control device 124 , for example, with a voltage having a reduced frequency f - and the increased frequency f + superposition of signals.

[0103] In an alternative embodiment of the laser system, which is denoted by 100' at the end, the laser system comprises a laser beam source 102, a beam deflection device 120, a control device 124 and in particular focusing optics 113, wherein the beam deflection device 120 is designed as an acousto-optic deflector and / or an acousto-optic modulator. In this embodiment, an input laser beam 103 is provided by means of the laser beam source 102, which does not necessarily have to be a pulsed laser beam.

[0104] The beam deflection device 120 is controlled by means of a control device 124 with a voltage having a superposition and / or beat frequency of two or more frequencies. The frequency assigned to the voltage is selected so that the corresponding focused beam cross sections of the formed pulsed laser beams 104-b2' and 104-b2" overlap at least in sections ( Figure 4 ). As a result, a focusing region 129 is formed with a non-rotationally symmetrical cross section (with respect to a cross-sectional plane pointing perpendicularly to the beam propagation direction 126). This can be important, for example, for applications in the processing of transparent materials. The focusing region has, for example, an elliptical cross section.

[0105] The laser system 100 works as follows:

[0106] During operation of the laser system 100, a pulsed laser beam 104 is provided by means of a laser beam source 102 and a beam deflection device 120. In order to generate secondary radiation 110 and / or to prepare a target material 106 so that secondary radiation 110 can be generated by the target material 106, the pulsed laser beam 104 is brought into interaction with the target material 106, i.e. the target material 106 is acted upon by laser pulses 108.

[0107] For this purpose, the beam deflection device 120 is controlled in a first operating mode by means of the control device 124 so that in particular exactly one pulsed laser beam, for example the pulsed laser beam 104-b1, is generated, which is directed toward the target region 112. The laser pulses 108 assigned to the laser beam 104-b1 strike the target region 112 and are introduced into the target region 112 in such a way that the laser pulses 108 are synchronized in time with the target material 106 introduced into the target region 112. As a result, an interaction of one or more laser pulses 108 with the target material 106 located in the target region 112 occurs.

[0108] The presence of the target material 106 in the target region 112 can be detected, for example, by means of a target material detection device 118. The target material detection device 118 can, for example, output a control signal to the laser beam source control device 109 when the target material 106 is present in the target region, and the laser beam source control device 109 then controls the laser beam source 102 to output the laser pulse 108 at a certain time point or to stagger the output laser pulse 108 in time. The output of the laser pulse 108 at a predetermined time point can be realized, for example, by means of a pulse-on-demand method. In this way, for example, irregularities in the coupling of the target material 106 into the target region 112 can be compensated and it can be ensured that in the first operating mode, the laser pulse 108 actually strikes the target material 106 that is in the target region 112 in a certain time window for generating the secondary radiation 110 and / or for preparing the target material 106.

[0109] The coupling of target material 106 into target region 112 and the repetition rate of laser pulses 108 can be coordinated and / or synchronized with one another in particular, so that in a first operating mode, laser pulses 108 strike target material 106 when target material 106 is positioned in the target region within a certain time window. Typically present (small) temporal irregularities in the coupling of target material 106 into target region 112 can be compensated for by temporal staggering of laser pulses 108 emitted by laser source 102, as described.

[0110] In order to vary the intensity and / or dose of the generated secondary radiation 110, for example, provision can be made to temporarily stop the interaction of the laser pulse 108 with the target material 106 arranged in the target region 112. This can reduce the intensity of the output secondary radiation 110, for example, on average over time.

[0111] To this end, the beam deflection device 120 is controlled in a second operating mode by means of the control device 124, thereby forming a pulsed laser beam 104-b2' and / or 104-b2". which misses the target area 112 and the target material 106. The corresponding laser pulses 108 of the pulsed laser beams 104-b2', 104-b2" are not used or are essentially not used to generate secondary radiation 110 or to prepare the target material 108.

[0112] exist Figure 5 and Figure 6 In the example shown in FIG. 1 , the beam deflection device 120 is controlled by means of the control device 124 in a first operating mode and in a second operating mode alternately in time ( Figure 5 and Figure 6 ).

[0113] In press Figure 5In the example shown, in a second operating mode that is successive in time, the pulsed laser beam is alternately deflected toward different sides with respect to the target area 112 and / or the target material 106, i.e., pulsed laser beams 104-b2' and 104-b2" are alternately formed in a second operating mode that is successive in time. The pulsed laser beams 104-b2' and 104-b2" in the second operating mode are thus positioned symmetrically with respect to the pulsed laser beam 104-b1 in the first operating mode in terms of a temporal average in the example shown.

[0114] For example, in Figure 5 In the example shown, the pulsed laser beam 104 - b2 ′, 104 - b2 ″ in the second operating mode is deflected alternately toward a first side 130a and toward a second side 130b opposite the first side 130a with respect to the position of the target region 112 and / or the target material 106 .

[0115] Instead, press Figure 6 In the example of FIG. 1 , the pulsed laser beam is simultaneously split into two pulsed laser beams 104 - b2 ′ and 104 - b2 ″ in the second operating mode. The simultaneously formed laser beams 104 - b2 ′ and 104 - b2 ″ are positioned symmetrically with respect to the pulsed laser beam 104 - b1 in the first operating mode.

[0116] Reference numerals

[0117] f0 carrier frequency

[0118] f - Reduced frequency

[0119] f + Increased frequency

[0120] 100, 100' laser system

[0121] 102 Laser beam source

[0122] 103 Pulse input laser beam

[0123] 104 Pulsed laser beam

[0124] 104-b1 Pulsed laser beam (first operating mode)

[0125] 104-b2' Pulsed laser beam (second operating mode)

[0126] 104-b2" pulsed laser beam (second operating mode)

[0127] 104a Level 0 sub-beam

[0128] 106 Target Materials

[0129] 108 laser pulses

[0130] 109 Laser beam source control device

[0131] 110 Secondary Radiation

[0132] 112 Target Area

[0133] 113 Focusing light

[0134] 114 cavity

[0135] 116 Feeding device

[0136] 118 Target material detection device

[0137] 120 Beam deflection device

[0138] 122 Beam Trap

[0139] 124 Control Device

[0140] 125 Beam Detection Device

[0141] 126 Beam propagation direction

[0142] 128 Center Point

[0143] 129 Focus Area

[0144] 130a First side

[0145] 130b Second side

Claims

1. A laser system for providing a pulsed laser beam (104) configured to interact with a target material (106), the laser system comprising: A beam deflection device (120); a control device (124) assigned to the beam deflection device (120); a laser beam source (102) for providing a pulsed input laser beam (103) for coupling into a beam deflection device (120); and, a target area (112) for arranging a target material (106), The pulsed input laser beam (103) can be deflected and / or split by means of a beam deflection device (120), and at least one pulsed laser beam (104) emerging from the beam deflection device (120) is provided based on the pulsed input laser beam (103) by means of the beam deflection device (120). wherein the control device (124) is designed to control and / or regulate the position of the at least one pulsed laser beam (104) relative to the target area (112) by actuating the beam deflection device (120), wherein the control device (124) has a first operating mode in which the position of the at least one pulsed laser beam (104) is selected such that the at least one pulsed laser beam is directed toward a target area (112) to interact with a target material (106) arranged in the target area (112), and wherein the control device (124) has a second operating mode, in which the position of the at least one pulsed laser beam (104) is selected such that the at least one pulsed laser beam misses the target area (112), The invention is characterized in that the pulsed laser beam (104; 104-b2', 104-b2") provided in the second operating mode is positioned symmetrically in terms of the temporal average and / or in terms of the spatial average with respect to the pulsed laser beam (104; 104-b1) formed in the first operating mode.

2. The laser system according to claim 1, characterized in that In a first operating mode, exactly one pulsed laser beam (104; 104-b1) is provided from the beam deflection device, which is directed toward a target area (112) and / or a target material (106).

3. The laser system according to any one of the preceding claims, characterized in that In a second operating mode, exactly one pulsed laser beam (104; 104-b2'; 104-b2") is provided which emerges from the beam deflection device (120) and misses the target area (112).

4. The laser system according to claim 3, characterized in that In a second operating mode that is sequential in time, the position of the exactly one pulsed laser beam (104; 104-b2'; 104-b2") is deflected alternately toward a first side (130a) and toward a second side (130b) opposite to the first side (130a) with reference to a target area (112), and / or the position of the exactly one pulsed laser beam is deflected alternately in a first direction and in a second direction opposite to the first direction with reference to the target area (112).

5. The laser system according to any one of the preceding claims, characterized in that In a second operating mode, two or more pulsed laser beams (104; 104-b2', 104-b2") are provided which are emitted from the beam deflection device (120), wherein the two or more pulsed laser beams are emitted from the beam deflection device (120) simultaneously.

6. The laser system according to any one of the preceding claims, characterized in that The beam deflection device (120) comprises an acousto-optic deflector and / or an acousto-optic modulator.

7. The laser system according to any one of the preceding claims, characterized in that The beam deflection device (120) is actuated by means of a control device (124) in a first operating mode with a control voltage having a constant carrier frequency (f0).

8. The laser system according to claim 7, characterized in that The beam deflection device (120) is controlled by means of a control device (124) in a second operating mode with a control voltage having a frequency (f0) which is reduced relative to the carrier frequency (f0). - ) or has a frequency (f ) increased relative to the carrier frequency (f0) + ).

9. The laser system according to claim 7 or 8, characterized in that The beam deflection device (120) is actuated by means of a control device (124) in a second operating mode with a control voltage having a superposition of two or more frequencies, wherein the frequencies are different from a carrier frequency (f0).

10. The laser system according to any one of claims 7 to 9, characterized in that The beam deflection device (120) is controlled by means of a control device (124) in a second operating mode with a control voltage comprising a frequency (f0) which is reduced relative to the carrier frequency (f0). - ) and the frequency (f + )’s beat frequency.

11. The laser system according to any one of the preceding claims, characterized in that In a first operating mode, laser pulses (108) of the at least one pulsed laser beam (104) are introduced into a target region (112) in such a way that the laser pulses are synchronized in time with a target material (106) introduced into the target region (112), so that in the first operating mode an interaction of one or more laser pulses (108) with the target material (106) in the target region (112) occurs.

12. The laser system according to any one of the preceding claims, characterized in that The laser beam source (102) is designed to provide laser pulses (108) with a constant energy average value for the pulsed input laser beam (103) and / or the at least one pulsed laser beam (104), wherein the energy of the laser pulses (108) deviates from the energy average value by less than 2% and in particular less than 1% during operation of the laser system, and / or the laser beam source (102) is designed to provide laser pulses (108) with a constant pulse repetition rate average value for the pulsed input laser beam (103) and / or the at least one pulsed laser beam (104), wherein the pulse repetition rate of the provided laser pulses (108) deviates from the constant pulse repetition rate average value by less than 20% and in particular less than 15% during operation of the laser system.

13. The laser system according to any one of the preceding claims, characterized in that A feeding device (116) is provided for feeding the target material (106) into the target area (112), and is characterized in particular in that the feeding device (116) is designed to introduce the target material (106) into the target area (112) at a speed of at least 50 m / s and / or at most 200 m / s and preferably at least 60 m / s and / or at most 130 m / s.

14. The laser system according to any one of the preceding claims, characterized in that A target material detection device (118) is provided for detecting a target material (106) in a target area (112), wherein the target material detection device (118) is particularly designed to output a control signal to a laser beam source (102) and / or to a control device (124) associated with a beam deflection device (120) when the target material (106) is detected in the target area (112), and / or, characterized in that a beam detection device (125) is provided for detecting a direction and / or a position of a pulsed laser beam (104) emitted from the beam deflection device (120).

15. A method for providing a pulsed laser beam (104), the pulsed laser beam being configured to interact with a target material (106), wherein the target material (106) is arranged or is arranged in a target area (112), a pulsed input laser beam (103) is provided by means of a laser beam source (102), the pulsed input laser beam (103) is coupled into a beam deflection device (120), wherein: A pulsed input laser beam (103) can be deflected and / or split by means of a beam deflection device (120), and at least one pulsed laser beam (104) emitted from the beam deflection device (120) is provided based on the pulsed input laser beam (103) by means of the beam deflection device (120), wherein the position of the pulsed laser beam (104) emitted from the beam deflection device (120) relative to the target area is controlled and / or adjusted by controlling the beam deflection device (120) by means of a control device (124), wherein the control device (124) has a first operating mode, in which the position of the at least one pulsed laser beam (104) is selected so that the at least one pulsed laser beam (104) The pulsed laser beam is directed toward a target area (112) and interacts with a target material (106) arranged in the target area (112), and wherein the control device (120) has a second operating mode, in which the position of the at least one pulsed laser beam (104) is selected so that the at least one pulsed laser beam misses the target area (112), characterized in that the pulsed laser beam (104; 104-b2', 104-b2") provided in the second operating mode is positioned symmetrically with respect to the pulsed laser beam (104; 104-b1) formed in the first operating mode, on average in time and / or on average in space.

Images