Device and method for generating a laser pulse by means of cavity dumping

Abstract

The invention relates to a device (10) for generating a laser pulse by means of cavity dumping having the features of claim 1, and to a method for generating a laser pulse by means of cavity dumping having the features of the additional independent claim.

Description

[0001] 2022P00174WO 18.11.2025

[0002] Title: Device and method for generating a

[0003] Laser pulses via cavity dumping

[0004] Description

[0005] The invention relates to a device for generating a laser pulse by means of cavity dumping with features of claim 1 and a method for generating a laser pulse by means of cavity dumping with features of the dependent claim.

[0006] Cavity dumping generates high-intensity laser pulses by controlled discharge of energy stored in an optical resonator. This technique is widely used in fields such as laser spectroscopy, materials processing, and medicine because it enables the controlled emission of short, high-energy light pulses. Typically, the resonator discharge is achieved using electro-optic or acousto-optic modulators, which allow for rapid and precise switching of the degree of extraction from the cavity. A disadvantage of this technique is that the temporal and spatial distribution of the field within the resonator is modulated in steps. This leads to different laser pulse shapes, pulse lengths, and jitter of the extracted laser pulse, depending on the extraction time.

[0007] The task is therefore to provide a device and a method for generating a laser pulse by means of cavity dumping, whereby the above disadvantages are eliminated or at least reduced.

[0008] The above problem is solved by a device for generating a laser pulse by means of cavity dumping with the features of claim 1.

[0009] The device comprises a resonator for generating and amplifying a laser beam. The resonator includes at least two mirrors. The laser beam is reflected within the resonator by means of the mirrors.

[0010] The resonator can be designed as a linear resonator or as a ring resonator.

[0011] In the case of a linear resonator, the device can include two mirrors, with the laser beam being reflected back and forth between the two mirrors (inside the resonator).

[0012] In the case of a ring resonator, the device can comprise at least two, and in particular more than two, mirrors, wherein the laser beam is reflected or deflected within the resonator by means of the mirrors, in particular in a ring-like manner and / or in the form of a circuit. The device includes an output coupling device. The output coupling device is configured to couple the laser beam out of the resonator. The output coupling device can be designed as a polarizer or an aperture, e.g., a mirror with an opening or an edge.

[0013] The device includes an optical switch. The optical switch is configured to modulate the laser beam in order to couple it out of the resonator via the coupling device.

[0014] The device includes a switching unit. The switching unit is configured to generate a control signal for the optical switch. The optical switch can be designed as an electro-optic switch or as an acousto-optic switch. The control signal is designed as a high-voltage signal (e.g., in the case of an electro-optic switch) or a high-frequency signal (e.g., in the case of an acousto-optic switch). The control signal can be a square pulse. The control signal has an input edge and an output edge. The input edge has a first switching time. The first switching time is longer than one revolution of the resonator. The output edge has a second switching time. The second switching time is shorter than the first switching time.

[0015] This allows for different laser pulse shapes, avoids variations in laser pulse length, and eliminates jitter in the coupled-out laser pulse. In the prior art, the switching time of the coupled-out edge is used to adjust the pulse duration for a given resonator length. Surprisingly, it has been shown that by changing the coupled-in edge, particularly by slowing it down, i.e., before a laser pulse is generated, the pulse characteristics (pulse duration, pulse duration stability, amplitude stability, and / or energy stability, etc.) of the subsequently generated laser pulse can be (positively) influenced.

[0016] Before the resonator closes, it can be filled with spontaneously emitted photons from the laser medium during cavity dumping. These photons can provide the starting energy for pulse generation via cavity dumping. However, the photon distribution is not constant, particularly along the resonator axis. Depending on the location of the laser medium or the optical switch, the photon density can exhibit discrete jumps along the resonator axis in the propagation direction. If the resonator is now closed quickly (the initial switching time is shorter than the resonator rotation time), this non-constant photon density is amplified, especially up to the point of output coupling. The internal field in the resonator thus acquires a temporal modulation that depends on the resonator rotation time. The resulting pulse shape of the output laser pulse can depend on the phase relationship between the output coupling time and the resonator rotation time.When the output coupling time is changed, the pulse shapes repeat themselves, particularly at periodic intervals with the resonator rotation time as the period interval.

[0017] The non-constant power density at the beginning of pulse build-up can lead to a further effect. Both effects (pulse shape and jitter) are a consequence of this. The power density at a location in the resonator may not increase strictly monotonically during pulse build-up, but may be superimposed with an oscillation (with the resonator rotation time as the period). With light-triggered pulse extraction of cavity dumping, this can lead to an increase in the temporal jitter of the pulse extraction and a deterioration of energy stability.

[0018] If an optical switch is used whose first switching edge is larger, or whose first switching time of the drive signal is longer, than the resonator rotation time, the differences in photon density along the resonator axis can be reduced before the resonator closes. As a result, a significantly more constant photon density can be amplified, which can lead to a constant pulse shape. In particular, there is no longer any dependence on the phase relationship of the output coupling time with respect to the resonator rotation time. The power density in the resonator can increase strictly monotonically during pulse build-up. The switching time of the output coupling edge of the drive signal can remain unchanged and can be adapted to the desired pulse duration.

[0019] Alternatively, this effect can be used to implement a beam source with a controllable pulse shape. Different pulse shapes can be selectively set by slightly altering the amplification time, on the order of approximately half a resonator revolution. The influence on other pulse parameters, such as the pulse energy, can be minimal, since the amplification during a single resonator revolution is small compared to the total amplification (amplification typically occurs over approximately 100 resonator revolutions). Additionally, a modulated switching signal around the time the resonator closes could be used to selectively modify the power density distribution, thereby increasing (or decreasing) the effect.

[0020] According to a further development of the device, the first switching time of the coupled edge can be in a range of 50 to 100 ns (nanoseconds).

[0021] This allows for an optimal duration of the coupling edge.

[0022] According to a further development of the device, the coupling edge can be stepped. The coupling edge can have at least one step, and in particular two steps. This can correspond, for example, to the switching on of the positive and negative poles of the applied high voltage. The individual steps of the coupled edge can each have a duration that is shorter than the rotation period of the resonator.

[0023] This allows the coupling edge to be implemented as flexibly as possible.

[0024] According to a further development of the device, the coupling edge can exhibit a delay. The sum of the delay with a first time duration and / or a

[0025] (2n — 1) The second time period can be multiplied by the orbital period of the

[0026] Two resonators correspond to this. Here, n can be an integer and positive (n = 1, 2, 3, 4, 5, ...). This allows the control signal to be further optimized.

[0027] According to a further development of the device, the second switching time can be in a range of 5 to 10 ns.

[0028] This allows the decoupling flank to be implemented using simple means.

[0029] According to a further development of the device, the optical switch can be arranged inside the resonator.

[0030] This allows for the simplest and most efficient modification of the laser beam in the resonator to be implemented using simple means.

[0031] According to a further development of the device, the optical switch can be configured as a Rockels cell. The optical switch can include at least one additional waveplate. It is also conceivable that the optical switch can be configured without an additional waveplate.

[0032] This allows the optical switch to be implemented using simple means.

[0033] According to a further development of the device, the device can include a control unit. The control unit can be configured to control the switching device. The control unit can be configured to generate a TTL (transistor-to-transistor logic) signal. The control unit can be provided for specifying the modulation for the optical switch. The switching device can be configured to convert the TTL signal into the control signal.

[0034] This allows the switching device to be controlled using simple means.

[0035] According to a further development of the device, the switching device and / or the control device can comprise a full bridge or be designed as a full bridge. In this context, "full bridge" refers to an electrical bridge circuit, H-circuit, or H-bridge.

[0036] In a switching device designed as a full bridge, another way to achieve a slow closing of the resonator can be implemented. This is done by delaying the trigger signals of the two half-bridges of the full bridge relative to each other by a specific time.

[0037] A delay can be useful in this context, whereby the sum of the delay with an initial duration and / or a

[0038] (2n — 1) second time period which is - - times (with n=1 , 2 , 3 , ... ) the

[0039] 2

[0040] The resonator rotation time corresponds to the differences in the power density distribution along the resonator axis that are still present after the closing of the first half-bridge can be compensated for by the delayed closing of the resonator with the second half-bridge.

[0041] This time delay can be implemented using a delay circuit in the control electronics. Alternatively, both half-bridges can be driven with the same trigger signal, whereby the time delay can be achieved by using different lengths of control lines.

[0042] This allows the switching device and / or the control device to be implemented using simple means.

[0043] The above problem is further solved by a method for generating a laser pulse by cavity dumping with the features of the dependent claim. The method comprises the following steps:

[0044] Providing a laser beam in a resonator.

[0045] Modulating the laser beam using an optical switch to couple it out of the resonator.

[0046] Generating a control signal and controlling the optical switch using the control signal, wherein the control signal has an input edge and an output edge, the input edge having a first switching time that is longer than one revolution of the resonator. The second revolution time can be in the range of 50 to 100 ns. The output edge has a second switching time that is shorter than the first switching time.

[0047] This allows a laser pulse to be generated that is coupled out of the resonator, whereby pulse shape instabilities and / or jitter in the laser pulse can be avoided or at least reduced.

[0048] According to a further development of the method, the coupling edge can be step-shaped. This allows the control signal to be implemented as flexibly as possible.

[0049] According to a further development of the procedure, the procedure can include the following step:

[0050] Delaying the coupling edge by means of a delay, where the sum of the delay with a first

[0051] (2n — 1)

[0052] duration and / or a second duration multiplied by - - times

[0053] 2 corresponds to the orbital period of the resonator, where n is an integer and positive (n = 1 , 2 , 3 , 4 , 5 , ... ).

[0054] This allows the control signal to be further optimized.

[0055] According to a further development of the procedure, the procedure can include the following step:

[0056] Arranging the optical switch inside the resonator.

[0057] This makes it possible to modulate the laser beam using simple means.

[0058] According to a further development of the procedure, the process can include the following steps:

[0059] Generating the control signal using a switching device.

[0060] Controlling the switching device using a TTL signal.

[0061] This allows the switching device to be controlled using simple means. According to a further development of the method, a device as described above can be used to carry out the method.

[0062] Regarding the advantages achievable with this method, reference is made to the relevant explanations concerning the device. The measures described in connection with the device and / or those explained below can be used to further develop the method.

[0063] Further features, details and advantages of the invention will become apparent from the wording of the claims and from the following description of exemplary embodiments with reference to the drawings. The drawings show:

[0064] Fig. 1 shows a schematic representation of a device for generating a laser pulse by means of cavity dumping.

[0065] Fig. 2 shows a schematic diagram of a control signal of the device according to Figure 1 according to a first embodiment and

[0066] Fig. 3 shows a schematic diagram of the control signal of the device according to Figure 1 according to a second embodiment.

[0067] In the following description and in the figures, corresponding components and elements are designated by the same reference symbols. For clarity, not all reference symbols are shown in every figure. Figure 1 shows a schematic representation of the device 10 for generating a laser pulse by cavity dumping.

[0068] The device 10 comprises a resonator 12. The resonator 12 is configured to generate and amplify a laser beam 14. The device 10 comprises at least two mirrors 16, 18. The laser beam 12 is reflected in the resonator 12 by means of the mirrors 16, 18.

[0069] The resonator 12 can be configured as a linear resonator or as a ring resonator. In this case, the resonator 12 is configured as a linear resonator. The resonator 12 comprises a first mirror 16 and a second mirror 18. The laser beam 14 is reflected back and forth between the two mirrors 16 and 18.

[0070] The device 10 comprises a coupling device 20. The coupling device 20 is configured to couple the laser beam 14 out of the resonator 12. The coupling device 20 is configured here as a polarizer or an aperture, e.g., a mirror with an opening or an edge. The laser beam or laser pulse 13 coupled out of the resonator 12 by means of the coupling device 20 is shown in Figure 1 by means of an arrow.

[0071] The device 10 comprises an optical switch 22. The optical switch 22 is configured to modulate the laser beam 14 in order to couple it out of the resonator 12 via the coupling device 20. The optical switch 22 can be configured as an acousto-optic or an electro-optic switch.

[0072] The device 10 comprises a switching device 24.

[0073] Switching device 24 is configured to generate a control signal 26 for the optical switch 22. The control signal 26 is configured as a high-voltage signal or as a high-frequency signal. The control signal 26 has an input edge 28 and an output edge 30. The input edge 28 has a first switching time 32, which is longer than one revolution of the resonator 12 (see Figures 2 and / or 3).

[0074] The decoupling edge 30 has a second switching time 34, which is shorter than the first switching time 32.

[0075] An active medium 15 can be arranged inside the resonator 12. The active medium 15 can serve to amplify the laser beam 14.

[0076] The optical switch 22 can be arranged inside the resonator 12. The optical switch 22 can be arranged between the first mirror 16 and the second mirror 18 such that the laser beam 14 passes through the optical switch 22.

[0077] The optical switch 22 can be configured as a Rockels cell. It is also conceivable that the optical switch 22 could be configured differently.

[0078] The device 10 can include a control unit 36. The control unit 36 ​​can be configured to control the switching device 24. The control unit 36 ​​can be configured to generate a TTL signal 38.

[0079] The switching device 24 and / or the control device 36 can be configured as a bridge circuit. The switching device 24 and / or the control device 36 can comprise a full bridge or be configured as a full bridge.

[0080] Figure 2 shows a schematic diagram 40 of a control signal 26 of the device 10 according to Figure 1 according to a first embodiment. A voltage 42, in particular high voltage, (Y-axis) is plotted against time 44 (X-axis).

[0081] The first switching time 32 of the coupling edge 28 can be in a range of 50 to 100 ns .

[0082] The second switching time 34 can be shorter than the rotational time of the resonator 12. In particular, the second switching time 34 can be shorter than the first switching time 32. The second switching time 34 can be in a range of 5 to 10 ns.

[0083] Figure 3 shows a schematic diagram 40 of the control signal 26 of the device 10 according to Figure 1 according to a second embodiment. The second embodiment differs from the first embodiment shown in Figure 2 in the following ways:

[0084] The coupling flank 28 can be step-shaped.

[0085] In this case, the coupling edge 28 has a first edge 46, a plateau 48, and a second edge 50. The first edge 46 and / or the second edge 50 can each have a duration that is shorter than the rotation period of the resonator 12. The first edge 46, the plateau 48, and the second edge 50 together have a duration that corresponds to the first switching time 32. In this case, the first edge 46 has a first duration 35, and the second edge 50 has a second duration 37. The second switching time 34 can correspond to the first duration 35 and / or the second duration 37.

[0086] In the present case, the plateau 48 forms a delay 33, where a sum of the delay 33 with a first time duration (2n — 1)

[0087] 35 and / or a second duration 37 the - - times the

[0088] 2

[0089] The orbital period of resonator 12 corresponds to , where n = 1 , 2 , 3 , 4 , ... (integer and positive) .

[0090] The following describes a method for generating a laser pulse using cavity dumping, illustrated in Figures 1 to 3. The method comprises the following steps:

[0091] Providing a laser beam 14 in a resonator 12 .

[0092] Modulating the laser beam 14 by means of an optical switch 22 to couple the laser beam 14 out of the resonator 12.

[0093] Generating a control signal 26 and controlling the optical switch 22 by means of the control signal 26. The control signal 26 has an input edge 28 and an output edge 30. The input edge 28 has a first switching time 32, which is longer than one revolution of the resonator 12. The first switching time 32 can be in the range of 50 to 100 ns. The output edge 30 has a second switching time 34, which is shorter than the first switching time 32. The input edge 28 can be stepped.

[0094] The second switching time 34 can be shorter than the rotation period of resonator 12. The second switching time 34 can be in a range of 5 to 10 ns.

[0095] The procedure may include at least one or more of the following steps:

[0096] Delaying the coupling edge 28 by means of a delay 33, wherein a sum of the delay 33 with a first duration 35 and / or a second duration 37 (2n — 1) corresponds to the — - — - times the rotation period of the resonator 12, where n is an integer and positive.

[0097] Arranging the optical switch 22 inside the resonator 12 .

[0098] Generating the control signal 26 by means of a switching device 24 .

[0099] Control of the switching device 24 by means of a TTL signal 38 .

[0100] To carry out the method, a device 10 as described above can be used. The device 10 can in particular be the device 10 shown in Figure 1.

Claims

Patent claims 1. Device (10) for generating a laser pulse by cavity dumping, comprising: a resonator (12) for generating and amplifying a laser beam (14) with at least two mirrors (16, 18), wherein the laser beam (14) is reflected in the resonator (12) by means of the mirrors (16, 18), an output coupling device (20) for coupling the laser beam (14) out of the resonator (12), an optical switch (22) for modulating the laser beam (14) in order to couple it out of the resonator (12) by means of the output coupling device (20), a switching device (24) for generating a control signal (26) for the optical switch (22), wherein the control signal (26) is configured as a high-voltage signal or a high-frequency signal, wherein the control signal (26) has an input edge (28) and an output edge (28). has an edge (30), wherein the coupling edge (28) has a first switching time (32),which is longer than one revolution period of the resonator (12) and wherein the coupling edge (30) has a second switching time (34) which is shorter than the first switching time (32).

2. Device (10) according to claim 1, characterized in that the first switching time (32) of the coupling edge (28) is in a range of 50 to 100 ns.

3. Device (10) according to claim 1 or 2, characterized in that the coupling flank (28) is formed in a step shape.

4. Device (10) according to one of the preceding claims, characterized in that the coupling flank (28) has a delay (33), wherein a sum of the delay (33) with a first time duration (35) and / or a second time duration (37) corresponds to the (2n — 1) - - times the orbital period of the resonator (12) 2 corresponds to where n is an integer and positive.

5. Device according to one of the preceding claims, characterized in that the second switching time (34) is in a range of 5 to 10 ns.

6. Device (10) according to one of the preceding claims, characterized in that the optical switch (22) is arranged inside the resonator (12).

7. Device (10) according to one of the preceding claims, characterized in that the optical switch (22) is designed as a Rockels cell.

8. Device (10) according to one of the preceding claims, characterized in that the device (10) comprises a control device (36) for controlling the switching device (24), in particular wherein the control device (36) is configured to generate a TTL signal (38).

9. Device (10) according to one of the preceding claims, characterized in that the switching device (24) and / or the control device 19 (36) comprises a full bridge or is designed as a full bridge.

10. Method for generating a laser pulse using cavity dumping comprising the following steps: Providing a laser beam (14) in a resonator (12); Modulating the laser beam (14) by means of an optical switch (22) in order to couple it out of the resonator (12); Generating a control signal (26) and controlling the optical switch (22) by means of the control signal (26), wherein the control signal (26) has an input edge (28) and an output edge (30), wherein the input edge (28) has a first switching time (32) which is longer than a revolution period of the resonator (12) and is in particular in a range of 50 to 100 ns, wherein the output edge (30) has a second switching time (34) which is shorter than the first switching time (32).

11. Method according to claim 10, characterized in that the coupling flank (28) is formed in a step-like manner.

12. Method according to claim 10 or 11, characterized by the step: Delaying the coupling edge (28) by means of a delay (33) , wherein a sum of the delay (33) with a first time duration (35) (2n — 1) and / or a second time duration (37) is — - — - times corresponds to the orbital period of the resonator (12), where n is an integer and positive. 20 13. Method according to one of claims 10 to 12, characterized by the step: Arranging the optical switch (22) inside the resonator (12).

14. Method according to any one of claims 10 to 13, characterized by the steps: Generating the control signal (26) by means of a switching device (24) ; Control of the switching device (24) by means of a TTL signal (38) .

15. The method according to claim 10, characterized in that the method is carried out with a device (10) according to one of claims 1 to 9.

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