Laser system and method of providing a pulsed laser beam intended to interact with a target material

Abstract

The invention relates to a laser system for providing a pulsed laser beam intended for interaction with a target material, comprising a laser beam source for providing a pulsed input laser beam, a target area for the arrangement of the target material, a beam deflection device that deflects and / or splits the input laser beam and provides at least one pulsed laser beam, and a control device that controls and / or regulates a position of the at least one laser beam relative to the target area, wherein in a first operating mode the position of the laser beam is directed towards the target area, and in a second operating mode the position of the laser beam misses the target area. Pulsed laser beams provided in the second operating mode are symmetrically positioned, on a temporal or spatial mean, with respect to the pulsed laser beams formed in the first operating mode.

Description

[0001] Laser system and method for providing a pulsed laser beam intended for interaction with a target material

[0002] The invention relates to a laser system and a method for providing a pulsed laser beam intended for interaction with a target material.

[0003] WO 2014 / 044392 A1 discloses an EUV radiation generation device comprising a vacuum chamber in which a target material can be arranged at a target position to generate EUV radiation, and a beam guidance chamber for guiding a laser beam from a driver laser device toward the target position. An intermediate chamber is provided, which is arranged between the vacuum chamber and the beam guidance chamber, a first window, which seals the intermediate chamber in a gas-tight manner, for the entry of the laser beam from the beam guidance chamber, and a second window, which seals the intermediate chamber in a gas-tight manner, for the exit of the laser beam into the vacuum chamber.

[0004] DE 10 2020 200 798 A1 discloses a method for laser material processing using a processing laser beam, wherein a first laser beam, which is coupled into at least a first fiber core of an optical multi-core fiber, and / or a second laser beam, which is coupled into at least a second fiber core of the multi-core fiber, are generated from an input laser beam. The first and second laser beams are coupled out of the multi-core fiber, either individually or jointly, as a processing laser beam, and the laser power ratio between the first and second laser beams is varied at a modulation frequency between 1 Hz and 100 kHz.

[0005] The invention is based on the object of providing a laser system and method as mentioned above, by means of which a pulsed laser beam intended for interaction with the target material can be generated with a high average power and at the same time enables controllability with regard to the interaction of the laser pulses of the pulsed laser beam with the target material.

[0006] This object is achieved according to the invention in that the laser system comprises a beam deflection device, a control device associated with 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 the target material, wherein the pulsed input laser beam is deflectable and / or splittable by means of the beam deflection device and at least one pulsed laser beam emerging from the beam deflection device is provided by means of the beam deflection device based on the pulsed input laser beam, wherein the control device is configured to control and / or regulate a position of the at least one pulsed laser beam relative to the target area by controlling 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 such that it is directed towards the target area in order to interact with a 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.

[0007] By selecting the first operating mode and the second operating mode, it is possible to control whether the pulsed laser beam impinges on the target material arranged in the target area, i.e., whether laser pulses associated with the pulsed laser beam interact with the target material. This allows, for example, the generation of secondary radiation and, in particular, the average dose and / or intensity of the generated secondary radiation to be controlled in a technically simple manner.

[0008] In the solution according to the invention, the pulsed laser beam is deflected and / or aligned in the first operating mode such that it hits the target material arranged in the target area, and in the second operating mode such that it does not hit the target material, i.e., the pulsed laser beam is "deflected" or "shot past" the target material in this case. 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, no temporal control of laser pulses of the input laser beam or pulsed laser beam provided by the laser beam source is required to specifically prevent interaction with the target material.

[0009] By means of the provided beam deflection device, the position and / or orientation and / or alignment of the at least one pulsed laser beam relative to the target area and the target material arranged therein can be controlled in a technically simple, time-dependent manner by means of the control device. Furthermore, this allows for the control of any splitting of the input laser beam to provide either one or more pulsed laser beams exiting the beam deflection device.

[0010] In particular, the first operating mode and the second operating mode can be set and / or selected on the control device. The control device may have 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.

[0011] The position of the at least one pulsed laser beam relative to the target area is to be understood in particular as a position of a focused area and / or a focused cross-section of the at least one pulsed laser beam relative to the target area.

[0012] The pulsed laser beam that can be provided is particularly suitable and / or configured to interact with the target material.

[0013] In particular, it can be provided that the laser system is suitable and / or configured to generate secondary radiation through interaction of the pulsed laser beam with the target material. It can then be provided, in particular, that the pulsed laser beam is directed at the target material in the first operating mode, so that laser pulses of the pulsed laser beam interact with the target material, thereby generating secondary radiation. Alternatively or additionally, the laser system can be suitable and / or configured to prepare and / or preprocess the target material through interaction of the pulsed laser beam with the target material.In particular, in the first operating mode, the target material is then brought into a specific shape and / or state by the interaction of laser pulses of the pulsed laser beam, which subsequently enables the generation of secondary radiation through interaction with further laser pulses particularly efficiently. For example, the preparation of the target material is carried out with laser pulses from a first laser beam source, and the subsequent generation of secondary radiation is then carried out by interaction with further laser pulses from a second laser beam source. The second laser beam source then has, in particular, a higher average power than the first laser beam source.

[0014] Furthermore, the laser system can also be used to diagnose the quality of the preparation and / or pre-processing of the target material.

[0015] The fact that the at least one pulsed laser beam misses the target area and / or the target material arranged therein in the second operating mode means that the at least one pulsed laser beam does not interact or does not interact significantly with the target material, so that, for example, depending on the application of the laser system, no secondary radiation or secondary radiation below a threshold intensity is generated or no or insufficient preparation of the target material takes place.

[0016] The fact that the at least one pulsed laser beam impinges on the target area and / or the target material arranged therein in the first operating mode means 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 above the threshold intensity is generated or a preparation or sufficient preparation of the target material takes place. In particular, the control device has no further operating state (apart from a deactivated state) besides the first operating state and the second operating state.

[0017] The laser beam source comprises in particular a seed laser, such as a diode laser.

[0018] In particular, the laser beam source comprises a laser amplifier and / or a chain of laser amplifiers. The laser amplifier(s) are preferably Yb- or Nd-doped. For example, Yb:glass, Yb:YAG, or Nd:YAG amplifiers are used as laser amplifiers. In particular, the laser amplifiers used can be implemented in fiber, rod, slab, or disk geometries.

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

[0021] It can be advantageous if the position of exactly one pulsed laser beam is deflected alternately toward a first side and toward a second side opposite the first side of the target area in successive second operating modes. This makes it possible, for example, to achieve a symmetrical arrangement of the pulsed laser beams provided in successive second operating modes with respect to the pulsed laser beam provided in the first operating mode, averaged over time. This, in turn, allows for simplified and low-interference stabilization of the orientation and / or positioning of pulsed laser beams emerging from the beam deflection device.

[0022] For the same reason, it may be advantageous if the position of exactly one pulsed laser beam is deflected in temporally successive second operating modes alternately with respect to the target area in a first direction and in a second direction opposite to the first direction.

[0023] Temporarily successive second operating modes are understood in particular to mean that the second operating mode is first selected at a specific point in time and then again at a later point in time, with the first operating mode being selected for a specific period between these two points in time. This then results, for example, in a sequence of first operating mode (time ti) - second operating mode (time tz) - first operating mode (time ts) - second operating mode (time t4), etc., where ti < t2 < t3 < t4. Successive second operating modes are understood, for example, to mean those at times t2 and t4, i.e. two second operating modes selected one after the other.

[0024] It may be advantageous if, in the second operating mode, two or more pulsed laser beams are provided from the beam deflection device, which exit from the beam deflection device simultaneously. This makes it possible, for example, to achieve a spatially symmetrical arrangement of the pulsed laser beams provided in the second operating mode with respect to the pulsed laser beam provided in the first operating mode. This, in turn, allows for simplified and low-interference stabilization of the orientation and / or positioning of the pulsed laser beams exiting the beam deflection device.

[0025] For example, the pulsed laser beams provided in the second operating mode are then spatially symmetrically positioned and / or oriented with respect to the pulsed laser beam provided in the first operating mode. For example, one of the pulsed laser beams provided in the second operating mode is deflected to a first side and / or first direction with respect to the target area, and another of the pulsed laser beams provided in the second operating mode is deflected to a second side opposite the first side and / or a second direction opposite the first direction with respect to the target area. This makes it possible, in particular, to achieve a simplified and low-interference stabilization of the orientation and / or positioning of pulsed laser beams emerging from the beam deflection device. This results in particular in advantages when using a beam tracker for stabilization, for exampleerroneous feedback signals can be reduced or avoided.

[0026] For the same reason, it may be advantageous if the pulsed laser beams provided in the second operating mode are positioned symmetrically, on average, in time and / or space, with respect to the pulsed laser beams formed in the first operating mode. For example, the plane symmetry and / or point symmetry of the pulsed laser beams provided in the second operating mode is point-symmetric with respect to the pulsed laser beams provided in the first operating mode.

[0027] In particular, it can be provided that a position of a center point of a beam cross-section of the at least one pulsed laser beam in the target area in the first operating mode is spaced from the position of the center point of the at least one pulsed laser beam in the second operating mode by at least one diameter of the beam cross-section. In the case of multiple pulsed laser beams present simultaneously, the respective positions of the centers of all pulsed laser beams present in the first operating mode are spaced from the respective positions of the centers of all pulsed laser beams present in the second operating mode by at least one diameter of the beam cross-section of the respective pulsed laser beams.

[0028] In particular, the beam deflection device may comprise an acousto-optical deflector and / or an acousto-optical modulator, or be designed as an acousto-optical deflector or an acousto-optical modulator. This allows the position of the at least one pulsed laser beam relative to the target area to be varied with high temporal dynamics.

[0029] For the purposes of these documents, the at least one pulsed laser beam is generally understood to mean a useful laser beam, which is provided by deflecting and / or splitting the input laser beam using the beam deflection device and, depending on the positioning and / or splitting according to the selected operating mode, can be used for sufficient interaction with the target material according to the intended application. In the case of an acousto-optical deflector or modulator, the first diffraction order in particular is used as the useful laser beam. Other diffraction orders are not used and are therefore not covered by the term "pulsed laser beam."

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

[0031] For example, the beam deflection device is controlled by means of the control device in the second operating mode with a control voltage which has a frequency which is reduced compared to the carrier frequency or a frequency which is increased compared to the carrier frequency.

[0032] In particular, an idealized frequency spectrum of the control voltage then exhibits a single frequency, which is the reduced or increased frequency. As a result, a single pulsed laser beam emerges from the beam deflection device, which is deflected in such a way that it misses the target area.

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

[0034] For example, the two or more frequencies are symmetrical with respect to the carrier frequency.

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

[0036] In particular, it can be provided that, in the first operating mode, laser pulses of the at least one pulsed laser beam are introduced into the target area in such a way that they are temporally synchronized with a target material introduced into the target area, so that, in the first operating mode, an interaction of one or more laser pulses with the target material in the target area takes place. For example, a coupling of target material into the target area can be slightly irregular or error-prone in terms of time, in which case a corresponding jitter can amount to, for example, + / - 1 ps. By means of the aforementioned synchronization, it can be ensured in the first operating mode that, depending on the application, a sufficient interaction between laser pulses of the pulsed laser beam and the target material actually takes place.

[0037] For example, laser pulses of the input laser beam or of the at least one pulsed laser beam provided by the laser beam source are emitted in a temporally offset and / or corrected manner such that they hit target material arranged in the target area in the first operating mode and temporal irregularities in the coupling of the target material into the target area are compensated.

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

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

[0040] In particular, the laser system comprises a feed device for feeding target material into the target area. For example, the target material is introduced into the target area by means of the feed device in the form of individual units and / or drops. In particular, the target material is then fed in such a way that it is positioned in the target area at a (faulty) point in time or within a time window. It is also possible in principle for the target material to be introduced into the target area by means of the feed device in the form of a material stream, and in particular a continuous material stream. In particular, it can be provided that the feed device is configured 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.In particular, the target material can pass through the target area at a speed in the mentioned ranges.

[0041] In particular, it can be provided that the target material is introduced into the target area during operation of the laser system at an at least approximately constant speed and / or at an at least approximately constant clock rate.

[0042] In particular, the target material passes through the target area with a direction of movement that is at least approximately parallel to the direction of gravity.

[0043] It may be advantageous for the laser system to include a target material detection device for detecting target material within the target area. The target material detection device is configured, in particular, to output a control signal to the laser beam source and / or to the control device associated with the beam deflection device upon detection of target material in the target area. This allows, particularly in the first operating mode, a temporal synchronization of laser pulses of the pulsed laser beam with the target material arranged in the target area to be achieved. Furthermore, depending on the application, the first or second operating mode can be selected based on the presence of target material in the target area.

[0044] It may be advantageous if the laser system has a beam detection device for detecting an orientation and / or a position of pulsed laser beams emerging from the beam deflection device. This allows, in particular, the position of the at least one pulsed laser beam to be controlled. For example, the beam detection device can be used to stabilize the orientation and / or position of the at least one pulsed laser beam. The laser system can have a corresponding device for stabilizing the orientation and / or position for this purpose. Furthermore, the position of the at least one pulsed laser beam can be controlled in the first operating mode and / or second operating mode by means of the control device assigned to the beam deflection device.

[0045] According to the invention, a method as mentioned above for providing a pulsed laser beam intended for interaction with a target material is provided, in which 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 is deflectable and / or splittable by means of the beam deflection device, and at least one pulsed laser beam emerging from the beam deflection device is provided by means of the beam deflection device based on the pulsed input laser beam, wherein a position of the pulsed laser beam emerging from the beam deflection device relative to the target area is controlled and / or regulated by controlling 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 towards 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.

[0046] The method according to the invention has, in particular, one or more further features and / or advantages of the laser system according to the invention. Advantageous embodiments have already been explained in connection with the laser system.

[0047] The method according to the invention can be carried out in particular by means of the laser system according to the invention. In particular, the method according to the invention is carried out by means of the laser system according to the invention.

[0048] A laser system for providing a laser beam with a focus zone having a non-rotationally symmetric cross-section comprises a beam deflection device, a control device associated with 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-optical deflector and / or an acousto-optical modulator and wherein the control device is configured to control the beam deflection device in such a way that the input laser beam is split by means of the beam deflection device simultaneously into at least two laser beams emerging from the beam deflection device and respective beam cross sections of the emerging laser beams overlap at least in sections in such a way that a focus zone with a non-rotationally symmetric cross-section is formed.

[0049] In particular, the laser beams emerging from the beam deflection device are focused by means of a focusing optics, wherein the emerging laser beams overlap at least partially in a focal plane assigned to the focusing optics in order to form the focus zone with a non-rotationally symmetric cross-section.

[0050] A non-rotationally symmetric cross-section is understood to mean, in particular, an elliptical cross-section and / or an elongated cross-section and / or a cross-section with a preferred direction and / or a non-point-symmetric cross-section.

[0051] In particular, the beam deflection device is controlled by means of the control device with a control voltage which has a superposition and / or beat of signals with two or more frequencies.

[0052] A focus zone is understood to be a spatially contiguous radiation area in which a radiation intensity lies above a certain threshold intensity.In a method for providing a laser beam with a focus zone which has a non-rotationally symmetrical cross-section, 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-optical deflector and / or an acousto-optical modulator and wherein the control device controls the beam deflection device in such a way that the input laser beam is split by means of the beam deflection device simultaneously into at least two laser beams emerging from the beam deflection device and respective beam cross sections of the emerging laser beams overlap at least partially in the focus zone in such a way that a focus zone with a non-rotationally symmetrical cross-section is formed.

[0053] In particular, the statement "at least approximately" is generally understood to mean a deviation of no more than 10%, i.e. that an actual value deviates from an ideal value by no more than 10%.

[0054] The following description of preferred embodiments, taken in conjunction with the drawings, serves to further explain the invention. They show:

[0055] Fig. 1 shows an embodiment of a laser system;

[0056] Fig. 2 shows a cross section of provided pulsed laser beams, illustrating a positioning of the pulsed laser beams relative to a target material in different operating modes;

[0057] Fig. 3 shows a representation of different frequencies of a control voltage used to control a beam deflection device of the laser system, with power plotted as a function of the respective frequency; Fig. 4 shows a cross-section of provided laser beams, with respective beam cross-sections of the laser beams overlapping and forming a focus zone;

[0058] Fig. 5 shows a first example of a positioning of provided pulsed laser beams as a function of time relative to the target material; and

[0059] Fig. 6 shows a second example of positioning of provided pulsed laser beams as a function of time relative to the target material.

[0060] Identical or functionally equivalent elements are provided with the same reference numerals in all figures.

[0061] An embodiment of a laser system is shown in Fig. 1 and designated therein 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 onto a target material 106. Secondary radiation 110 can be generated through the interaction of the input laser beam 103 or laser pulses 108 associated with the pulsed laser beam 104 with the target material 106. Alternatively or additionally, the interaction can prepare the target material 106 for the generation of secondary radiation.

[0062] To generate secondary radiation, the laser beam source 102 can be designed, for example, as a CO2 laser, which has an average power of 1 kW or more during operation of the laser system 100.

[0063] If the laser system 100 is to be used to prepare the target material 108, the laser beam source 102 can be designed, for example, as an Nd:YAG laser or 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 pulsed laser beam 104 provided by the laser beam source 102 then has, for example, laser pulses 108 with a pulse repetition rate in the kHz range, such as in the range between 40 kHz and 100 kHz. A respective pulse duration of the laser pulses 108 is in particular in the ns range, for example in the range from 1 ns to 500 ns, in particular in the range from 5 ns to 20 ns.

[0064] In principle, the laser system 100 can have several laser beam sources 102, e.g. one for generating secondary radiation 110 and another for preparing the target material 108.

[0065] The laser beam source 102 can, for example, have a laser beam source control device 109, by means of which the emission of laser pulses 108 by the laser beam source 102 can be triggered and / or controlled at specific times. For example, it can be provided that the laser beam source 102 emits one or more laser pulses 108 when the control device 109 receives a corresponding control signal. This allows laser pulses 108 to be specifically requested at specific times and / or laser pulses 108 regularly emitted by the laser beam source 102 to be staggered in time. This can be implemented, for example, using pulse-on-demand concepts.

[0066] 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. For example, the target material 106 is or comprises tin.

[0067] The laser system 100 has a target area 112 in which the target material 106 can be arranged in order to impinge upon it with the laser beam 104. During operation of the laser system 100, the target material 106 is introduced into the target area 112 and there interacts with the laser pulses 108. In particular, the pulsed laser beam 104 directed onto the target material 106 is focused onto the target material 106 and / or the target area 112. For this purpose, focusing optics 113 can be provided, for example. In particular, it can be provided that the target area 112 is formed and / or positioned in a fluid-tight and / or gas-tight chamber 114. A vacuum is formed in the chamber 114, for example.

[0068] To supply the target material 106 to the target area 112, the laser system 100 can have a supply device 116, by means of which the introduction of the target material 106 into the target area 112 can be controlled and / or regulated. For example, the target material 106 can be delivered by means of the supply device 116 such that it passes through the target area 112 at specific, in particular regular, times and / or is positioned in the target area 112 at specific, in particular regular, times.

[0069] For example, the target material 106 is introduced into the target area at a speed between 60 m / s and 120 m / s, wherein the target material 106 in this case is in particular in the form of individual drops which pass through the target area one after the other.

[0070] For the technical details concerning the coupling of target material 106 into the target area 112 for generating secondary radiation, reference is made to the scientific publication "Light sources for high-volume manufacturing EUV lithography: technology, performance, and power scaling", I. Fomenkov et al., Advanced Optical Technologies 6(3): 173-186, DOI: 10.1515 / aot-2017-0029.

[0071] For example, target material 106 can be provided by the feed device 116 in the form of individual elements and / or drops, each of which passes through the target area 112 at specific times. In the example shown, the direction of gravity is oriented in the negative y-direction, so that target material 106 delivered by the feed device 116 passes through the target area 112 from top to bottom (i.e., in the negative y-direction).

[0072] 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 a target material 106 is arranged in the target area 112 at a specific time. The target material detection device 118 comprises, for example, a camera to detect the target material 106 in the target area 112, for example by means of image recognition.

[0073] The laser system 100 comprises a beam deflection device 120 into which the input laser beam 103 is coupled. The pulsed laser beams formed by the beam deflection device 120 based on the input laser beam 103 and exiting the beam deflection device 120 are referred to as pulsed laser beams 104.

[0074] The beam deflection device 120 is suitable for deflecting and / or splitting the input laser beam 103. Consequently, in principle, one pulsed laser beam 104 or several pulsed laser beams 104 can emerge from the beam deflection device 120 simultaneously. The beam deflection device 120 can be used to adjust the alignment and / or position of the pulsed laser beam 104 or the pulsed laser beams 104 relative to the target area 112.

[0075] In the embodiment according to Fig. 1, the beam deflection device 120 is or comprises an acousto-optical modulator and / or an acousto-optical deflector. In the example shown, the pulsed laser beam 104 incident on the beam deflection device 120 is split by the beam deflection device 120 into several partial beams of different diffraction orders, with the first-order partial beam being used as the useful laser beam or pulsed laser beam 104 for impinging on the target material 106. Typically, the first-order partial beam used has more than 90% of the beam intensity of the laser beam 104 originally incident on the beam deflection device 120. The partial beam 0, designated 104a.

[0076] Order, as well as the partial beams of other orders, are not used and are guided, for example, into a beam trap 122.

[0077] To control the beam deflection device 120, the laser system 100 comprises a control device 124, which is, for example, connected to the beam deflection device 120 for signal transmission or is 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, i.e., the orientation and / or position of this beam relative to the target area 112 can be adjusted.

[0078] The laser system may include a beam detection device 125 (indicated in Fig. 1) for detecting an orientation and / or a position of pulsed laser beams 104 emerging 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. For example, the beam detection device 125 is or comprises a beam tracker.

[0079] In particular, the orientation and / or positioning of the pulsed laser beams 124 can be stabilized by means of the beam detection device 125. For this purpose, the laser system 100 can have a device for stabilizing the orientation and / or positioning of the pulsed laser beams 124 (not shown), which receives information regarding the orientation and / or positioning of the pulsed laser beams 124 from the beam detection device 125 and performs the stabilization based on this information.

[0080] Furthermore, the beam detection device 125 can be connected to the control device 124 in a signal-effective manner in order to transmit information regarding the orientation and / or positioning of pulsed laser beams 104 emerging from the beam deflection device 120. This allows, in particular, a control of the orientation and / or positioning of the pulsed laser beams 104 by means of the control device 124 or the beam deflection device 120.

[0081] It is provided that the control device 124 has a first operating mode in which the beam deflection device 120 is controlled such that the pulsed laser beam 104 emerging from it is directed toward the target area 112, and the laser pulses 108 strike the target area 112 and / or a target material 106 arranged therein. In this case, the laser pulses 108 of the pulsed laser beam 104 can interact with the target material 106 arranged in the target area 112.

[0082] The pulsed laser beam 104 coupled out of the beam deflection device 120 in this first operating mode is additionally designated 104-bl in Fig. 1.

[0083] Furthermore, the control device 124 has a second operating mode in which the beam deflection device 120 is controlled such that the pulsed laser beam 104 emerging from it misses the target area. In this case, the target area 112 and / or a target material 106 arranged therein are not hit or almost not hit by the laser pulses 108. In this case, the laser pulses 108 cannot interact with the target material or can only interact very slightly. In this case, depending on the application, no secondary radiation 110 is generated, or any secondary radiation 110 generated is only below a threshold intensity, or there is insufficient interaction to prepare the target material.

[0084] In principle, there are a multitude of ways in which the pulsed laser beam 104 is deflected by the beam deflection device 120 in order to miss the target area 112. In the second operating mode, therefore, several variants can be provided with regard to the orientation and / or position of the pulsed laser beam 104 relative to the target area 112.

[0085] As indicated in Fig. 1, for example, two different variants can be provided, wherein in a first variant of the second operating mode, the pulsed laser beam 104 is deflected, for example, in a first direction in order to miss the target area 112 and the target material 106 located therein (pulsed laser beam 104-b2'), and in a second variant, it is deflected in a second direction different from the first direction in order to miss the target area 112 and the target material 106 located therein (pulsed laser beam 104-b2"). It is fundamentally possible to provide further variants of the second operating mode in which the pulsed laser beam 104 is deflected in different directions in order to miss the target area 112 and / or the target material 106.

[0086] If, for example, the target material 106 is fed into the target area 112 by means of the feed device 116 as shown in Fig. 1 from top to bottom (i.e. in the negative y-direction), the laser beam 104-b2' is deflected spatially behind the target material 106 with respect to the direction of movement of the target material 106 in order to miss it, i.e. the laser beam 104-b2' is located behind the target material 106 when the latter is positioned in the target area 112. The laser beam 104-b2" is deflected spatially in front of the target material 106 in order to miss it, i.e. the laser beam 104-b2" is located in front of the target material 106 when the latter is positioned in the target area 112.

[0087] It goes without saying that the pulsed laser beam 104 could, for example, also be deflected in a direction oriented transversely or perpendicularly to the direction of movement of the target material 106 in order to miss it. In principle, the pulsed laser beam 104 can be deflected in any direction perpendicular to its beam propagation direction 126.

[0088] Fig. 2 shows the positioning of the pulsed laser beams 104-bl, 104-b2' and 104-b2" relative to the target area 112 and the target material 106 in a cross-sectional plane oriented perpendicular to the beam propagation direction 126 of the pulsed laser beam 104-bl incident on the target area 112 and positioned on the target material 106 (in the example shown, the beam propagation direction 126 is oriented parallel to the z-direction and the cross-sectional plane is oriented parallel to the xy-plane).

[0089] A respective beam cross-section of the laser beams 104-bl, 104-b2' and 104-b2" is indicated by circles in Fig. 2. In particular, the laser beams 104-bl, 104-b2' and 104-b2" are focused with respect to the beam propagation direction 126 at the level of the target area 112 and / or the target material 106.

[0090] The pulsed laser beams 104-b2' and 104-b2" provided in the second operating mode preferably extend symmetrically with respect to a plane of symmetry. In particular, the pulsed laser beam 104-bl formed in the first operating mode lies in this plane of symmetry (in the example shown in Fig. 1, the plane of symmetry is oriented parallel to the beam propagation direction 126 and / or parallel to the xz plane).

[0091] In particular, the respective centers 128 of the beam cross-sections of the pulsed laser beams 104-b2' and 104-b2" are arranged point-symmetrically with respect to a position of the target material 106 and / or point-symmetrically with respect to the center of the beam cross-section of the pulsed laser beam 104-bl formed in the first operating mode.

[0092] 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 partial beams by the beam deflection device 120. For example, the pulsed laser beam 104 is split into the two pulsed laser beams 104-b2' and 104-b2" by the beam deflection device 120, as indicated in Fig. 1. These then each have, for example, approximately half the intensity of the pulsed laser beam 104-b1 formed in the first operating mode and directed at the target area 112.

[0093] The beam deflection device 120, which in the example shown is embodied as an acousto-optic modulator and / or acousto-optic deflector, is controlled by the control device 124 using a control voltage. The control voltage has a defined frequency and / or a defined frequency spectrum. For example, the control voltage is or includes a sinusoidal voltage.

[0094] In the first operating mode, the beam deflection device 120 is controlled at a specific carrier frequency fo (Fig. 3) to generate the laser beam 104-bl impinging on the target material 106. The carrier frequency fo is, for example, 80 MHz.

[0095] In the second operating mode, to realize the pulsed laser beams 104-b2' and 104-b2", the frequency of the voltage is increased or decreased relative to the carrier frequency fo. For example, to realize the pulsed laser beam 104-b2', the beam deflection device 120 is driven at a frequency f- that is reduced relative to the carrier frequency fo, and to realize the pulsed laser beam 104-b2", the beam deflection device 120 is driven at a frequency f+ that is increased relative to the carrier frequency fo.

[0096] For example, the reduced frequency f- and the increased frequency f+ are distributed symmetrically around the carrier frequency fo. The reduced frequency f- is, for example, 79 MHz, and the increased frequency f+ is, for example, 81 MHz.

[0097] In the case of the aforementioned further variant of the second operating mode, in which the input laser beam 103 is simultaneously split into two or more deflected partial beams by means of the beam deflection device 120, the beam deflection device 120 is controlled by means of a voltage whose spectrum has two or more frequencies. For example, the voltage comprises a superposition and / or beat of signals with two or more frequencies.

[0098] For the simultaneous deflection of 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 the control device 124, for example, with a voltage which has a superposition of signals with the reduced frequency f- and the increased frequency f+.

[0099] In an alternative embodiment of a laser system, which is designated hereinafter by 100', this comprises the laser beam source 102, the beam deflection device 120, the control device 124 and in particular the focusing optics 113, wherein the beam deflection device 120 is designed as an acousto-optical deflector and / or acousto-optical modulator.

[0100] In this embodiment, the input laser beam 103, which is not necessarily a pulsed laser beam, is provided by the laser beam source 102. The beam deflection device 120 is controlled by the control device 124 with a voltage having a superposition and / or beat of two or more frequencies. The frequencies assigned to the voltage are selected such that the respective focused beam cross-sections of the formed pulsed laser beams 104-b2' and 104-b2" overlap at least in sections (Fig. 4). This forms a focus zone 129 with a non-rotationally symmetric cross-section (with respect to a cross-sectional plane oriented perpendicular to the beam propagation direction 126). This can be relevant, for example, for applications in transparent material processing. For example, the focus zone has an elliptical cross-section.

[0101] The Laser System 100 works as follows:

[0102] During operation of the laser system 100, the pulsed laser beam 104 is provided by the laser beam source 102 and the beam deflection device 120. In order to generate secondary radiation 110 and / or to prepare the target material 106 to generate secondary radiation 110, the pulsed laser beam 104 is brought into interaction with the target material 106, ie, the target material 106 is exposed to the laser pulses 108.

[0103] For this purpose, the beam deflection device 120 is controlled by the control device 124 in the first operating mode, so that, in particular, precisely one pulsed laser beam directed at the target area 112 is generated, for example, the pulsed laser beam 104-bl. The laser pulses 108 assigned to this laser beam 104-bl are incident on the target area 112 and are introduced into the target area 112 in such a way that they are temporally synchronized with the target material 106 introduced into the target area 112. As a result, an interaction of one or more laser pulses 108 with the target material 106 located in the target area 112 takes place.

[0104] The presence of target material 106 in the target area 112 can be detected, for example, by means of the target material detection device 118. For example, when target material 106 is present in the target area, the target material detection device 118 can transmit a control signal to the laser beam source control device 109, which then controls the laser beam source 102 to emit laser pulses 108 at a specific time or to temporally offset emitted laser pulses 108. The emission of laser pulses 108 at predetermined times can be achieved, for example, using a pulse-on-demand method.This makes it possible, for example, to compensate for irregularities in the coupling of the target material 106 into the target area 112 and to ensure that, in the case of the first operating mode, a target material 106 located in the target area 112 in a specific time window is actually hit by the laser pulses 108 to generate secondary radiation 110 and / or to prepare it.

[0105] In particular, the coupling of target material 106 into the target area 112 and the repetition rate of the laser pulses 108 can be coordinated and / or synchronized with each other such that the target material 106 is hit by the laser pulses 108 in the first operating mode if it is positioned in the target area within a specific time window. Typically present (minor) temporal irregularities in the coupling of the target material 106 into the target area 112 can be compensated for, as described, by a temporal offset of the laser pulses 108 emitted by the laser source 102.

[0106] For example, in order to vary the intensity and / or dose of the generated secondary radiation 110, it may be provided that an interaction of the laser pulses 108 with the target material 106 arranged in the target area 112 is temporarily prevented. As a result, the intensity of the emitted secondary radiation 110 can be reduced on average over time, for example.

[0107] For this purpose, the beam deflection device 120 is controlled by the control device 124 in the second operating mode, whereby the pulsed laser beams 104-b2' and / or 104-b2" are formed, which miss the target area 112 and the target material 106. The respective laser pulses 108 of these pulsed laser beams 104-b2', 104-b2" do not contribute, or do not contribute significantly, to the generation of secondary radiation 110 or to the preparation of the target material 108.

[0108] In the examples shown in Figs. 5 and 6, the beam deflection device 120 is controlled by the control device 124 alternately in time in the first operating mode and in the second operating mode (Figs. 5 and 6).

[0109] In the example according to Fig. 5, the pulsed laser beam is deflected alternately to different sides with respect to the target area 112 and / or the target material 106 in temporally successive second operating modes, ie the pulsed laser beams 104-b2' and 104-b2" are alternately formed in temporally successive second operating modes. The pulsed laser beams 104-b2' and 104-b2" in the second operating mode are therefore positioned symmetrically on average over time with respect to the pulsed laser beam 104-b1 in the first operating mode in the example shown.

[0110] For example, in the second operating mode in the example shown in Fig. 5, the pulsed laser beams 104-b2' and 104-b2" are deflected alternately to a first side 130a and to a second side 130b opposite the first side 130a with respect to a position of the target area 112 and / or the target material 106.

[0111] Alternatively, in the example according to Fig. 6, the pulsed laser beam in the second operating mode is simultaneously split into the two pulsed laser beams 104-b2' and 104-b2". These 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. List of reference symbols fo carrier frequency f- reduced frequency f+ increased frequency

[0112] 100, 100' Laser system 102 Laser beam source 103 Pulsed input laser beam 104 Pulsed laser beam 104-bl Pulsed laser beam (first operating mode) 104-b2' Pulsed laser beam (second operating mode) 104-b2" Pulsed laser beam (second operating mode) 104a 0th order partial beam 106 Target material 108 Laser pulse 109 Laser beam source control device 110 Secondary radiation 112 Target area 113 Focusing optics 114 Chamber 116 Feeding device 118 Target material detection device 120 Beam deflection device 122 Beam trap 124 Control device 125 Beam detection device 126 Beam propagation direction 128 Center point 129 Focus zone 130a First side 130b Second Page

Claims

Patent claims Laser system for providing a pulsed laser beam (104) intended for interaction with a target material (106), comprising a beam deflection device (120), a control device (124) associated with the beam deflection device (120), a laser beam source (102) for providing a pulsed input laser beam (103) for coupling into the beam deflection device (120) and a target area (112) for arranging the target material (106), wherein the pulsed input laser beam (103) is deflectable and / or splittable by means of the beam deflection device (120) and at least one pulsed laser beam (104) emerging from the beam deflection device (120) is provided by means of the beam deflection device (120) based on the pulsed input laser beam (103), wherein the control device (124) is configuredto control and / or regulate a position of the at least one pulsed laser beam (104) relative to the target area (112) by controlling 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 it is directed towards the target area (112) in order 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 it misses the target area (112), characterized in that pulsed laser beams (104; 104-b2',104-b2") are positioned symmetrically in time and / or space with respect to the pulsed laser beams (104; 104-bl) formed in the first operating mode. Laser system according to claim 1, characterized in that in the first operating mode, exactly one pulsed laser beam (104; 104-bl) emerging from the beam deflection device is provided, which is directed onto the, Target area (112) and / or the target material (106). Laser system according to one of the preceding claims, characterized in that in the second operating mode, exactly one pulsed laser beam (104; 104-b2'; 104-b2") emerging from the beam deflection device (120) is provided, which misses the target area (112). Laser system according to claim 3, characterized in that the position of exactly one pulsed laser beam (104; 104-b2'; 104-b2") is deflected in temporally successive second operating modes alternately with respect to the target area (112) toward a first side (130a) and toward a second side (130b) opposite the first side (130a), and / or is deflected alternately with respect to the target area (112) in a first direction and in a second direction opposite the first direction.Laser system according to one of the preceding claims, characterized in that in the second operating mode, two or more pulsed laser beams (104; 104-b2', 104-b2") exiting the beam deflection device (120) are provided, which exit the beam deflection device (120) simultaneously. Laser system according to one of the preceding claims, characterized in that the beam deflection device (120) comprises an acousto-optical deflector and / or an acousto-optical modulator. Laser system according to one of the preceding claims, characterized in that in the first operating mode, the beam deflection device (120) is controlled by means of the control device (124) with a control voltage having a constant carrier frequency (fo). Laser system according to claim 7, characterized in that the beam deflection device (120) is controlled by the control device (124) in the second operating mode with a control voltage having a frequency (f-) that is reduced compared to the carrier frequency (fo) or a frequency (f+) that is increased compared to the carrier frequency (fo). Laser system according to claim 7 or 8, characterized in that the beam deflection device (120) is controlled by the control device (124) in the second operating mode with a control voltage that has a superposition of two or more frequencies, these frequencies being different from the carrier frequency (fo).Laser system according to one of claims 7 to 9, characterized in that the beam deflection device (120) is controlled by the control device (124) in the second operating mode with a control voltage which has a beat of signals with a frequency (f-) that is reduced compared to the carrier frequency (fo) and a frequency (f+) that is increased compared to the carrier frequency (fo). Laser system according to one of the preceding claims, characterized in that in the first operating mode, laser pulses (108) of the at least one pulsed laser beam (104) are introduced into the target area (112) in such a way that they are synchronized in time with a target material (106) introduced into the target area (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 area (112) takes place.Laser system according to one of the preceding claims, characterized in that the laser beam source (102) is configured to provide laser pulses (108) of the pulsed input laser beam (103) and / or of the at least one pulsed laser beam (104) with a constant average energy value, wherein an energy of the laser pulses (108) during operation of the laser system differs from the average energy value by less than. 2% and in particular by less than 1%, and / or that the Laser beam source (102) is configured to provide laser pulses (108) of the pulsed input laser beam (103) and / or of the at least one pulsed laser beam (104) with a constant pulse repetition rate average, wherein a pulse repetition rate of the provided laser pulses (108) deviates from the constant pulse repetition rate average by less than 20% and in particular by less than 15% during operation of the laser system. Laser system according to one of the preceding claims, characterized by a feed device (116) for feeding target material (106) into the target area (112), and in particular characterized in that the feed 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.Laser system according to one of the preceding claims, characterized by a target material detection device (118) for detecting target material (106) within the target area (112), wherein the target material detection device (118) is in particular designed to output a control signal to the laser beam source (102) and / or to the control device (124) assigned to the beam deflection device (120) upon detection of target material (106) in the target area (112), and / or characterized by a beam detection device (125) for detecting an orientation and / or a position of pulsed laser beams (104) emerging from the beam deflection device (120).Method for providing a pulsed laser beam (104) intended for interaction with a target material (106), in which the target material (106) is 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 the pulsed input laser beam (103) is deflected by means of the. Beam deflection device (120) is deflectable and / or splittable, and at least one pulsed laser beam (104) emerging from the beam deflection device (120) is provided by means of the beam deflection device (120) based on the pulsed input laser beam (103), wherein a position of the pulsed laser beam (104) emerging from the beam deflection device (120) relative to the target area is controlled and / or regulated 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 such that it is directed towards the target area (112) and interacts with the 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 such that it misses the target area (112), characterized in that pulsed laser beams (104; 104-b2', 104-b2") provided in the second operating mode are positioned symmetrically in time and / or space with respect to the pulsed laser beams (104; 104-b1) formed in the first operating mode.

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