A laser amplifier and laser

Abstract

The embodiment of the application relates to the technical field of laser equipment, and discloses a laser amplifier and a laser device, the laser amplifier comprising: a slab crystal assembly and a mirror; the slab crystal assembly is used for making a seed light beam incident to the slab crystal assembly to perform forward zigzag transmission to perform first round amplification and then emit; the mirror is arranged on one side of the slab crystal assembly, a reflecting surface of the mirror is configured as an ellipsoidal surface, and the mirror is used for reflecting the seed light beam emitted after the first round amplification back to the slab crystal assembly; and the slab crystal assembly is further used for making the seed light beam reflected by the mirror perform reverse zigzag transmission to perform second round amplification and then emit from the slab crystal assembly. Through the above mode, the embodiment of the application meets the miniaturization requirement of the laser amplifier, and obtains a laser beam with higher gain.

Description

Technical Field

[0001] This application relates to the field of laser equipment technology, specifically to a laser amplifier and a laser. Background Technology

[0002] A laser amplifier is a device that amplifies the energy (power) of light using stimulated emission. Existing laser amplifiers consist of a plate-shaped crystal and two planar mirrors. Within the plate-shaped crystal, a large number of particles transition from low to high energy levels under the influence of pump light. The seed beam, acting as an optical signal, excites the high-energy particles within the plate-shaped crystal to emit a laser beam with the same frequency and phase as the seed beam, thereby amplifying the power of the seed beam.

[0003] In existing technologies, to achieve higher gain, the length of the plate crystal in a laser amplifier is typically increased. This allows for a greater number of zigzag transmission channels for the seed beam within the plate crystal, resulting in a higher-power seed beam. However, this increase in the size of the plate crystal leads to a larger laser amplifier, which fails to meet the miniaturization requirements of laser amplifiers. Summary of the Invention

[0004] In view of the above problems, embodiments of this application provide a laser amplifier and a laser that, while meeting the miniaturization requirements of the laser amplifier, achieve a higher gain laser beam.

[0005] According to one aspect of the embodiments of this application, a laser amplifier is provided, the laser amplifier including: a slab crystal assembly and a reflector; the slab crystal assembly is used to incident a seed beam onto the slab crystal assembly for forward zigzag transmission to perform a first round of amplification before exiting; the reflector is disposed on one side of the slab crystal assembly, the reflecting surface of the reflector being configured as an ellipsoid, the reflector being used to reflect the seed beam exiting after the first round of amplification back to the slab crystal assembly; the slab crystal assembly is further used to cause the seed beam reflected by the reflector to perform reverse zigzag transmission to perform a second round of amplification before exiting from the slab crystal assembly.

[0006] In one alternative approach, the seed beam is incident on the slab crystal assembly via a first point for a first round of amplification, and after a second round of amplification, exits the slab crystal assembly and passes through a second point, which is located on the same side as the first point or on the side of the slab crystal assembly opposite to the first point.

[0007] In one alternative configuration, the first point and the second point are respectively the first focus and the second focus of the ellipsoid; the slab crystal assembly is used to cause the waist of the seed beam to pass through the first focus and then be incident on the slab crystal assembly for forward zigzag transmission to perform a first round of amplification before exiting; the slab crystal assembly is also used to cause the waist of the seed beam reflected by the mirror to undergo reverse zigzag transmission to perform a second round of amplification before exiting the slab crystal assembly and passing through the second focus.

[0008] In one alternative embodiment, the slab crystal assembly includes a slab crystal, a first reflecting unit, and a second reflecting unit. The slab crystal has a first side and a second side, and is used to amplify a seed beam transmitted therein. The first reflecting unit and the second reflecting unit are respectively disposed on the first and second sides of the slab crystal. The first reflecting unit is used to reflect the seed beam emitted from the first side of the slab crystal back to the slab crystal, and the second reflecting unit is used to reflect the seed beam emitted from the second side of the slab crystal back to the slab crystal. A mirror is disposed on one side of the slab crystal and is used to reflect the seed beam emitted after the first amplification back to the slab crystal. The reflecting unit in the first and second reflecting units that is located on the same side as the mirror is configured to not interfere with the position of the mirror, so as to reflect the seed beam incident on it.

[0009] In one alternative embodiment, the first and second reflecting units are plane mirrors or reflective films coated on slab crystals.

[0010] In one alternative approach, the seed beam passes through a first focal point and is incident on a first side surface of the slab crystal, the first side surface being a vertical surface and the second side surface being an inclined surface; the slab crystal also includes a first end surface and a second end surface opposite to each other, the seed beam propagating from the first end surface to the second end surface during the first round of amplification, the reflector being close to the second end surface, and the distance between the inclined surface and the vertical surface gradually increasing from the first end surface to the second end surface.

[0011] In one alternative approach, the seed beam is incident at a preset angle toward the second end face at an angle.

[0012] In one alternative approach, the major axis 2a of the reflector satisfies: 2a = L tot +L′ tot +L0+L′0; where L tot L′ is the total passage length of the seed beam during the first round of amplification within the lath crystal. tot L0 is the total passage length of the seed beam during the second round of amplification within the slab crystal. L0 is the distance between the first focal point and the incident point of the seed beam at the first focal point on the first side of the slab crystal. L′0 is the distance between the exit point of the seed beam after the second round of amplification from the second side of the slab crystal and the second focal point.

[0013] In one alternative, the distance between the first and second end faces of the slab crystal is configured such that when the seed beam is incident from a position on the vertical plane adjacent to the first end face, it can exit from the vertical plane or the inclined plane adjacent to the second end face to the reflector.

[0014] According to another aspect of the embodiments of this application, a laser is provided, the laser comprising: a seed source device, a pumping device, and a laser amplifier provided in the above embodiments; the seed source device is disposed on one side of a slab crystal assembly for inputting a seed beam into the slab crystal assembly; the pumping device is disposed on both sides of the slab crystal assembly for inputting pump light into the slab crystal assembly; and the laser amplifier is used to amplify the seed beam based on the energy provided by the pump light.

[0015] In a laser amplifier, the seed beam is propagated in a forward zigzag pattern within a slab crystal assembly, enabling the assembly to amplify the seed beam in the first stage. An ellipsoidal mirror reflects this amplified seed beam back into the slab crystal assembly, allowing it to undergo a reverse zigzag pattern for a second stage of amplification. This two-stage amplification of the seed beam within the slab crystal assembly achieves a higher-gain laser beam without increasing the amplifier's size, meeting miniaturization requirements and reducing production costs. Furthermore, the focusing effect of the ellipsoidal mirror reduces the size of the seed beam during the second stage of amplification, resulting in a smaller final output seed beam and improved beam quality.

[0016] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0017] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0018] Figure 1 This is a schematic diagram of an existing laser amplifier.

[0019] Figure 2 This is a schematic diagram of the structure of a laser amplifier provided in an embodiment of the present invention;

[0020] Figure 3 This is a schematic diagram of the transmission path of the seed beams at different angles within the slab crystal assembly provided in the embodiment of the present invention during the first round of amplification.

[0021] Figure 4 A graph showing the functional relationship between the lateral offset of the seed beam in the slab crystal assembly and the incident angle offset, provided in an embodiment of the present invention;

[0022] Figure 5 A graph showing the functional relationship between the lateral offset of the seed beam at different incident angles in the slab crystal assembly and the number of channels of the seed beam in the slab crystal assembly, provided for embodiments of the present invention;

[0023] Figure 6 A graph showing the functional relationship between the total lateral offset of the seed beam in the slab crystal assembly and the incident angle offset, provided in an embodiment of the present invention;

[0024] Figure 7 This is a schematic diagram of the structure of a laser amplifier provided in an embodiment of the present invention;

[0025] Figure 8 A schematic diagram of the transmission path of seed beams at different angles on the reflector of an ellipsoidal surface, provided in an embodiment of the present invention;

[0026] Figure 9 This is a schematic diagram showing the lateral shift of the seed beam during amplification in both existing and present laser amplifiers.

[0027] Figure 10 This is a schematic diagram of the structure of a laser amplifier provided in an embodiment of the present invention;

[0028] Figure 11 This is a schematic diagram of the structure of a laser amplifier provided in an embodiment of the present invention;

[0029] Figure 12 A schematic diagram of the transmission path of the seed beam in the lath crystal during the first round of amplification provided in an embodiment of the present invention;

[0030] Figure 13 This is a schematic diagram of the structure of a laser provided in an embodiment of the present invention.

[0031] The reference numerals in the detailed embodiments are as follows:

[0032] 100. Existing laser amplifier; 110. Plate-shaped crystal; 120. Plane mirror;

[0033] 200, Laser amplifier; 210, Slab crystal assembly; 211, Slab crystal; 2111, First side surface; 2112, Second side surface; 2113, First end face; 2114, Second end face; 212, First reflecting unit; 213, Second reflecting unit; 220, Reflector; 221, First focal point; 222, Second focal point;

[0034] 1000, Laser; 300, Seed source device; 400, Pumping device;

[0035] A. First point; B. Second point. Detailed Implementation

[0036] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0038] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0039] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0040] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists, A and B exist simultaneously, and B exists. In addition, the character " / " in this document generally indicates that the related objects before and after it have an "or" relationship.

[0041] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple groups" refers to two or more (including two groups), and "multiple pieces" refers to two or more (including two pieces).

[0042] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0043] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0044] A laser amplifier is a device that amplifies the energy (power) of light using stimulated emission. By employing a laser amplifier, high laser energy or power can be obtained while maintaining laser quality, reducing damage to optical components.

[0045] Figure 1 A schematic diagram of the structure of a conventional laser amplifier 100 is shown in the figure. · "Indicates that the y-axis direction is perpendicular to the paper and outwards, such as Figure 1As shown, the existing laser amplifier 100 consists of a plate-shaped crystal 110 and two planar mirrors 120 respectively disposed on both sides of the plate-shaped crystal 110. Pump light is incident from both sides of the plate-shaped crystal 110 along the z-axis, causing a large number of particles within the plate-shaped crystal 110 to transition from low energy levels to high energy levels under the influence of the pump light, thereby achieving energy transfer between the pump beam and the particles within the plate-shaped crystal 110. When a seed beam is incident from one side of the plate-shaped crystal 110 along the z-axis, and this seed beam travels in a zigzag pattern within the plate-shaped crystal 110 under the reflection of the two planar mirrors 120, and overlaps with the pump beam within the same plate-shaped crystal 110, the seed beam, as an optical signal, can excite the high-energy particles within the plate-shaped crystal 110 to emit a laser beam with the same frequency and phase as the seed beam, thereby achieving power amplification of the seed beam.

[0046] In the prior art, to obtain higher gain, the length of the plate-shaped crystal 110 of the existing laser amplifier 100 is generally increased. Figure 1 The length of the plate crystal 110 (along the x-axis) increases the number of zigzag transmission channels for the seed beam within the plate crystal 110, resulting in a higher-power seed beam. However, this increases several issues. First, the increased length of the plate crystal 110 leads to a larger size for the existing laser amplifier 100, failing to meet miniaturization requirements and increasing production costs. Second, due to the divergence angle of the seed beam, its size (i.e., beam diameter) increases with the number of travel channels within the plate crystal 110, making the seed beam size larger than the thickness of the plate crystal 110. Figure 1 The dimension along the y-axis, thus making the lateral dimension of the seed beam output after power amplification ( Figure 1 The dimension along the x-axis is much larger than the longitudinal dimension. Figure 1 The dimension along the y-axis causes the seed beam to exhibit higher-order modes, reducing the beam quality of the seed beam.

[0047] Based on this, this application provides a laser amplifier that uses an ellipsoidal mirror to reflect the seed beam, which has undergone a first round of amplification within a slab crystal, back into the slab crystal. This allows the seed beam to undergo a second round of amplification within the slab crystal before being output. The focusing effect of the ellipsoidal mirror reduces the size of the seed beam reflected back into the slab crystal, resulting in a higher gain and a smaller seed beam. In this way, using a single laser amplifier achieves the effect of cascading two laser amplifiers, effectively amplifying the gain from the first laser amplifier through the second. This achieves a higher gain laser beam without increasing the size of the laser amplifier, meeting the miniaturization requirements of laser amplifiers and reducing production costs. Furthermore, the smaller size of the seed beam reflected back into the slab crystal ensures the quality of the final higher-gain seed beam output.

[0048] The laser amplifiers provided in this application include, but are not limited to, those used in laser measurement, lidar, and laser communication.

[0049] Please see Figure 2 , Figure 2 A schematic diagram of a laser amplifier provided in an embodiment of the present invention is shown. The laser amplifier 200 includes a slab crystal assembly 210 and a reflector 220. The slab crystal assembly 210 is used to direct a seed beam into the slab crystal assembly 210 for forward zigzag transmission to perform a first round of amplification before exiting. The reflector 220 is disposed on one side of the slab crystal assembly 210, and the reflecting surface of the reflector 220 is configured as an ellipsoid. The reflector 220 is used to reflect the seed beam exiting after the first round of amplification back to the slab crystal assembly 210. The slab crystal assembly 210 is also used to direct the seed beam reflected by the reflector 220 for reverse zigzag transmission to perform a second round of amplification before exiting from the slab crystal assembly 210.

[0050] In the figure, the solid arrows represent the seed beams that undergo the first round of amplification, the dashed arrows represent the seed beams that undergo the second round of amplification, the x-axis is the length direction of the slab crystal assembly, and the z-axis is the width direction of the slab crystal assembly.

[0051] Specifically, the slat crystal assembly 210 can be a cuboid or a prism with one side of the seed beam incident being a vertical plane and the other side being an inclined plane, with an acute angle between the two sides. Furthermore, both sides of the slat crystal assembly 210 have reflective media so that the seed beam, after entering the slat crystal assembly 210, is reflected back and forth inside the slat crystal assembly 210. It should be noted that the slat crystal assembly 210 does not have reflective media at the seed beam incident and exit points.

[0052] First, it should be noted that the pump light is incident from both sides of the slab crystal assembly 210 along its width, causing a large number of particles within the slab crystal assembly 210 to transition to higher energy levels. Then, during the process of the seed beam being incident from one side of the slab crystal assembly 210 along its width, to ensure that the seed beam propagates in a forward zigzag pattern within the slab crystal assembly 210, specifically, when the slab crystal assembly 210 is a cuboid, the angle θ between the seed beam and the side of the slab crystal assembly 210 needs to be set to an acute angle. When the slab crystal assembly 210 is a prism with one side of the seed beam incident being a vertical plane and the other side being an inclined plane, the angle θ between the seed beam and the side of the slab crystal assembly 210 can be set to a right angle or an acute angle. When the seed beam is incident on the slab crystal assembly 210, and the seed beam is reflected in a forward zigzag pattern within the slab crystal assembly 210 by the reflective medium on both sides of the slab crystal assembly 210, the high-energy particles within the slab crystal assembly 210 are excited to emit a laser beam with the same frequency and phase as the seed beam, thereby achieving the first round of amplification of the seed beam.

[0053] The reflecting surface of the reflector 220 is configured as an ellipsoid, meaning its shape is the same as a local area of ​​an ellipsoidal reflector. This allows it to reflect light beams emitted onto its surface and to converge the reflected beams. By placing the reflector 220 on one side of the slab crystal assembly 210 and positioning it at a point where the seed beam, after initial amplification, can exit from the slab crystal assembly 210 and be projected onto it, the reflector 220 can reflect the seed beam back into the slab crystal assembly 210. Furthermore, the seed beam reflected back into the slab crystal assembly 210 undergoes a reverse zigzag transmission within the slab crystal assembly 210. Furthermore, as the seed beam gradually increases in size during the first round of amplification within the slab crystal assembly 210 until it reaches its maximum size upon exiting the reflector 220, when the reflector 220 reflects the seed beam after the first round of amplification, the size of the seed beam reflected back to the slab crystal assembly 210 is smaller than the size of the seed beam incident on the reflector 220 due to the converging effect of the reflector 220.

[0054] During the reverse zigzag transmission of the seed beam reflected back into the slab crystal assembly 210 by the reflector 220, the high-energy particles within the slab crystal assembly 210 are again excited to emit a laser beam with the same frequency and phase as the seed beam, thus achieving a second round of amplification of the seed beam. Furthermore, due to the focusing effect of the reflector 220 on the seed beam during the reflection of the first-round amplified seed beam, the size of the seed beam undergoing the second round of amplification is reduced, thereby reducing the size of the final higher-gain output seed beam.

[0055] In the laser amplifier 200, the seed beam is propagated in a forward zigzag pattern within the slab crystal assembly 210, enabling the slab crystal assembly 210 to perform a first-round amplification of the seed beam. The first-round amplified seed beam emitted from the slab crystal assembly 210 is then reflected back into the slab crystal assembly 210 via an ellipsoidal reflector 220, allowing the reflected seed beam to undergo a reverse zigzag pattern within the slab crystal assembly 210, thus enabling the slab crystal assembly 210 to perform a second-round amplification of the seed beam. In this way, the seed beam undergoes two rounds of amplification within the slab crystal assembly 210, achieving a higher-gain laser beam without increasing the size of the laser amplifier 200, meeting the miniaturization requirements of the laser amplifier, and reducing the production cost of the laser amplifier 200. Furthermore, due to the focusing effect of the ellipsoidal reflector 220, the size of the seed beam undergoing the second-round amplification is reduced, resulting in a smaller final output seed beam and improved beam quality.

[0056] In some embodiments, the seed beam is incident on the slab crystal assembly at a first point for a first round of amplification, and after a second round of amplification, exits the slab crystal assembly and passes through a second point, which is located on the same side as the first point.

[0057] Since the seed beam output after two rounds of amplification by the laser amplifier needs to undergo a series of processes such as collimation and beam expansion, after the seed beam after the second round of amplification is emitted from the slab crystal assembly, it is usually necessary to reflect the seed beam through a plane mirror to change the transmission path of the seed beam in order to perform subsequent processing on the seed beam.

[0058] When the second point and the first point are set on the same side of the slab crystal assembly, the angle between the transmission path of the seed beam incident on the slab crystal assembly through the first point and the transmission path of the seed beam exiting the slab crystal assembly to the second point may be small. In this case, the plane mirror needs to be installed at a greater distance from the slab crystal assembly in order to reflect the seed beam after final amplification, rather than the incident seed beam.

[0059] To make the optical components inside the laser of the laser amplifier 200 more compact, this application further proposes an embodiment, please refer to [further details]. Figure 2 As shown in the figure, the seed beam is incident on the slab crystal assembly 210 through the first point A for the first round of amplification, and then for the second round of amplification. After exiting the slab crystal assembly 210, it passes through the second point B, which is located on the side of the slab crystal assembly 210 away from the first point A.

[0060] Specifically, by placing the first point A on one side of the slab crystal assembly 210 and the second point B on the other side, the transmission paths of the seed beam incident from the first point A to the slab crystal assembly 210 and exiting from the slab crystal assembly 210 to the second point B are located on opposite sides of the slab crystal assembly 210. This avoids overlapping transmission paths or interference caused by excessively small angles between the transmission paths. In this configuration, by simply installing the plane mirror at a relatively small distance from the slab crystal assembly 210, the seed beam, after being amplified in the second round, can be reflected by the plane mirror after exiting the slab crystal assembly 210, thereby altering the transmission path of the seed beam for subsequent laser processing. This method allows for a more compact arrangement between the slab crystal assembly 210 and the plane mirror, resulting in a more compact internal optical element within the laser and a reduced overall laser size.

[0061] Taking a prism with one side of the slab crystal assembly 210 being a vertical plane and the other side being an inclined plane, and the included angle between the two sides being an acute angle, as an example, please refer to... Figure 3 , Figure 3 This diagram illustrates the transmission path of seed beams at different incident angles within a slab crystal assembly during the first round of amplification. The slab crystal assembly 210 in the diagram is compared to... Figure 2 Rotate 90° counterclockwise. As shown in the figure, the solid line represents the transmission path of the seed beam with an incident angle of α, and the dashed line represents the transmission path of the seed beam with an incident angle of α1. Specifically, the incident angle of the seed beam is α, which is the angle between the seed beam and the normal to the vertical plane perpendicular to the slab crystal assembly 210; the angle between the inclined plane of the slab crystal assembly 210 and its vertical plane is β; the width of the slab crystal assembly 210 is L; and the passage length of the seed beam within the slab crystal assembly 210 when it passes through the slab crystal assembly 210 for the i-th (channel number) time is L. i For example, in the figure, L1, L2, L3, and L4 represent the passing length of the seed beam when the number of channels is 1, 2, 3, and 4, respectively; when the incident angle of the seed beam changes from α to α1, that is, when the incident angle shift is Δα, the lateral shift of the seed beam in the i-th time within the slab crystal assembly 210 is ΔL. i (Offset along the x-axis), that is, the lateral offset of the seed beam within the slab crystal assembly 210 when the number of channels is i is ΔL. i For example, when the number of channels is 1, the lateral offset is ΔL2, and when the number of channels is 4, the lateral offset is ΔL4.

[0062] When i is odd, the lateral offset ΔL of the seed beam i The relationship between Δα and Δα is:

[0063] ΔL i =Li ×tan[α+iβ]×Δα, where i=1,3,5,7,….

[0064] When i is even, the lateral offset ΔL of the seed beam i The relationship between Δα and Δα is:

[0065] ΔL i =L i ×tan[α+(i-1)β]×Δα, where i=1,3,5,7,….

[0066] For example, with α = 0.2 rad (radians), L = 10 mm, and β = 0.01 rad, please refer to [link / reference]. Figure 4 , Figure 4 A graph showing the functional relationship between the lateral offset of the seed beam within the slab crystal assembly and the incident angle offset is presented. The horizontal axis represents the incident angle offset (rad), and the vertical axis represents the lateral offset (mm). Lines ΔL1, ΔL2, ΔL3, ΔL4, ΔL5, and ΔL6 represent the lateral offsets of the seed beam within the slab crystal assembly 210 during its 1st to 6th passes, respectively. Figure 4 As shown, the lateral offset ΔL i It increases linearly with the incident angle shift Δα. Next, please refer to... Figure 5 , Figure 5 A graph showing the functional relationship between the lateral offset of the seed beam at different incident angles within the slab crystal assembly and the number of channels the seed beam passes through within the slab crystal assembly is illustrated. The horizontal axis represents the number of channels i, and the vertical axis represents the lateral offset (mm). Lines 0.005, 0.01, 0.015, and 0.02 represent the lateral offsets of the seed beams at incident angle offsets Δα of 0.005, 0.01, 0.015, and 0.02 within the slab crystal assembly 210 during their 1st to 6th passes through the assembly 210, respectively. Figure 5 As shown, the lateral offset ΔL i The number of channels, i, increases non-linearly. Further details can be found in the following section. Figure 6 , Figure 6 The graph shows the relationship between the total lateral offset of the seed beam in the slab crystal assembly and the incident angle offset. The horizontal axis represents the incident angle offset (rad), and the vertical axis represents the total lateral offset (mm). Figure 6 As shown, the total lateral offset ΔL i It increases linearly with the incident angle offset Δα.

[0067] In summary, the lateral offset (offset along the x-axis) of the seed beam during the first amplification process within the slab crystal assembly 210 is proportional to the angle offset of the seed beam's first incident angle on the side of the slab crystal assembly 210 (the angle between the seed beam and the incident side of the seed beam on the slab crystal assembly 210). Therefore, when the seed beam undergoes positive zigzag transmission within the slab crystal assembly 210, any small angular offset of the seed beam's first incident angle on the slab crystal assembly 210 will significantly affect the total transmission length of the seed beam within the slab crystal assembly 210. The significant impact is the lateral offset (offset along the x-axis), which causes a deviation in the position of the seed beam emitted from the slab crystal assembly 210 after the second round of amplification. This results in the final output seed beam not being accurately reflected by the plane mirror for subsequent laser processing. Furthermore, it can also easily cause the position of the seed beam emitted from the slab crystal assembly 210 after the first round of amplification to change, preventing the seed beam from being emitted onto the mirror 220. Consequently, the mirror 220 cannot reflect the seed beam back into the slab crystal assembly 210 for the second round of amplification.

[0068] To reduce the lateral offset (offset along the x-axis) of the seed beam during amplification within the slab crystal assembly 210 caused by the offset of the seed beam incident angle, this application further proposes an implementation method, please refer to... Figure 2 And see Figure 7 , Figure 7 A schematic diagram of the laser amplifier provided in an embodiment of the present invention is shown. As shown in the figure, point A and point B are the first focal point 221 and the second focal point 222 of the ellipsoid, respectively. The slab crystal assembly 210 is used to allow the beam waist of the seed beam to pass through the first focal point 221 and then enter the slab crystal assembly 210 for forward zigzag transmission to perform a first round of amplification before exiting. The slab crystal assembly 210 is also used to allow the beam waist of the seed beam reflected by the mirror 220 to undergo reverse zigzag transmission for a second round of amplification before exiting the slab crystal assembly 210 and passing through the second focal point 222.

[0069] The ellipsoidal reflector 220 is characterized in that light emitted from or passing through any focal point is reflected by the ellipsoidal reflector 220 and converges to another focal point. Please refer to [link to details]. Figure 8Figure 8 shows a schematic diagram of the transmission path of seed beams at different angles through a reflector on an ellipsoidal surface. Solid and dashed lines represent the transmission paths of seed beams at different incident angles, respectively. As shown, the reflector 220 on the ellipsoidal surface has a first focus 221 and a second focus 222, which are equidistantly distributed on both sides of the major axis of the reflector 220. When a seed beam is incident on the reflecting surface of the reflector 220 through the first focus 221, the reflecting surface of the reflector 220 reflects the seed beam to the second focus 222. Furthermore, when the angle at which the seed beam is incident from the first focus 221 changes, the angle at which the seed beam reflected by the reflecting surface of the reflector exits through the second focus 222 also changes, but it always passes through the second focus 222. Also, d1 + d2 = d1' + d2', and (d1 + d2) is equal to the major axis of the reflector 220.

[0070] Specifically, the seed beam has a waist and a divergence angle. The waist refers to the parallel portion of the seed beam, and the divergence angle is the angle between the non-parallel and parallel beams. After the seed beam is emitted, due to the divergence angle, the distance between the non-parallel and parallel beams in the seed beam increases. The laser cross-sectional area affected by the divergence angle increases as the transmission distance of the seed beam increases. However, the laser cross-sectional area affected by the waist of the seed beam does not change with the transmission distance.

[0071] Therefore, after the waist of the seed beam passes through the first focal point 221 of the ellipsoidal reflector 220, it enters the slab crystal assembly 210 and is transmitted in a positive zigzag pattern within the slab crystal assembly 210 for the first round of amplification. Then, the seed beam after the first amplification exits from the slab crystal assembly 210 and is reflected back into the slab crystal assembly 210 by the reflector 220. After the seed beam is reflected back into the slab crystal assembly 210 by the reflector 220, it is transmitted in a reverse zigzag pattern within the slab crystal assembly 210 for the second round of amplification. The waist of the seed beam exiting from the slab crystal assembly 210 after the second round of amplification will pass through the second focal point 222 of the reflector 220. This can eliminate the lateral offset of the final output seed beam caused by the incident angle offset when the seed beam first enters the slab crystal assembly 210, thereby improving the reliability of the laser amplifier 200.

[0072] Taking a prism with one side of the slab crystal assembly 210 being a vertical plane and the other side being an inclined plane, and the included angle between the two sides being an acute angle, as an example, please refer to [link to relevant documentation]. Figure 9 , Figure 9The diagram illustrates the lateral offset of the seed beam amplified in both a conventional laser amplifier and the laser amplifier of this embodiment. The horizontal axis represents the number of zigzag channels, and the vertical axis represents the lateral offset (mm). Line 10 represents the lateral offset of the seed beam amplified in the conventional laser amplifier 100, and line 20 represents the lateral offset of the seed beam amplified in the laser amplifier 200. As shown, when the number of zigzag channels for the seed beam is 16, the lateral offset of the seed beam in the conventional laser amplifier 100 increases with the increase of the number of zigzag channels. However, the lateral offset of the seed beam in the laser amplifier 200 gradually increases during the number of zigzag channels from 1 to 8, gradually decreases during the number of zigzag channels from 9 to 16, and decreases to 0 when the number of zigzag channels is 16. Therefore, the laser amplifier 200 can compensate for the lateral offset of the final output seed beam caused by changes in the incident angle of the seed beam.

[0073] Furthermore, due to the divergence angle of the seed beam, its size gradually increases as it travels from the first focal point 221 to the reflector 220, reaching its maximum size upon reaching the reflector 220. After the reflector 220 reflects the seed beam, its waist is focused onto the second focal point 222 after a second round of amplification. This causes the seed beam's size to gradually decrease as it travels from the reflector 220 to the second focal point 222, ensuring that its size at the second focal point 222 is the same as its size at the first focal point 221. Consequently, the final output seed beam exhibits both high gain and higher beam quality.

[0074] By incidenting the seed beam waist into the slab crystal assembly 210 after passing through the first focal point 221 for a first round of amplification before exiting, and by reflecting the seed beam waist reflected by the mirror 220 back into the slab crystal assembly 210 for a second round of amplification before exiting through the second focal point 222, the influence of the incident angle shift caused by the first incident of the seed beam into the slab crystal assembly 210 on the seed beam deviation can be avoided. Furthermore, the beam quality of the seed beam output after the second round of amplification can also be improved.

[0075] To ensure the secondary amplification of the seed beam by the laser amplifier 200, this application further proposes an implementation method, please refer to [link to implementation details]. Figure 10 , Figure 10A schematic diagram of the structure of a laser amplifier provided in an embodiment of the present invention is shown. As shown in the figure, the slab crystal assembly 210 includes a slab crystal 211, a first reflecting unit 212, and a second reflecting unit 213. The slab crystal 211 has a first side surface 2111 and a second side surface 2112, and is used to amplify the seed beam transmitted therein. The first reflecting unit 212 and the second reflecting unit 213 are respectively disposed on the first side and the second side of the slab crystal 211. The first reflecting unit 212 is used to reflect the seed beam emitted from the first side surface 2111 of the slab crystal 211 back to the slab crystal 211, and the second reflecting unit 213 is used to reflect the seed beam emitted from the second side surface 2112 of the slab crystal 211 back to the slab crystal 211. A reflector 220 is disposed on one side of the slab crystal 211 (the first side in this embodiment) and is used to reflect the seed beam emitted after the first round of amplification back to the slab crystal 211. In this configuration, the reflection units in the first reflection unit 212 and the second reflection unit 213 located on the same side as the reflector 220 are configured to not interfere with the position of the reflector 220, so as to reflect the seed beam incident upon them respectively. The first reflection unit 212 and the second reflection unit 213 function similarly to the reflective medium described above.

[0076] Specifically, the first reflective unit 212 and the second reflective unit 213 can be respectively disposed on the first side and the second side of the slab crystal 211, and can be disposed separately from the first side and the second side, or can be respectively attached to the first side 2111 and the second side 2112 of the slab crystal 211.

[0077] In some preferred embodiments, the first reflecting unit 212 and the second reflecting unit 213 can be soldered to the slab crystal 211, respectively. This ensures that during the first and second rounds of amplification of the seed beam within the slab crystal assembly 210, the transmission path of the seed beam is entirely within the slab crystal 211. This avoids the seed beam from transmitting in the space between the first reflecting unit 212 and the second reflecting unit 213 and the slab crystal 211, thereby reducing the total transmission length of the seed beam, reducing the size of the seed beam, and ultimately improving the beam quality of the final output seed beam.

[0078] The reflector 220 can be disposed on the first side of the slab crystal 211, on the same side as the first reflective unit 212, or it can be disposed on the second side of the slab crystal 211, on the same side as the second reflective unit 213. Figure 10In the illustrated embodiment, the reflector 220 and the first reflecting unit 212 are located on the same side (first side) of the slab crystal 211. Taking the reflector 220 being positioned on the first side of the slab crystal 211 as an example, there is no overlap between the first reflecting unit 212 and the reflector 220, and each can reflect the seed beam incident upon it, ensuring that the reflector 220 can normally reflect the seed beam after the first round of amplification back into the slab crystal 211 for the second round of amplification. The effect of the reflector 220 being positioned on the second side of the slab crystal 211 can be referenced from that of the reflector 220 being positioned on the first side of the slab crystal 211, and will not be described further here.

[0079] Specifically, when the seed beam first enters the slab crystal 211, the first reflecting unit 212 reflects the seed beam emitted from the first side 2111 back into the slab crystal 211, and the second reflecting unit 213 reflects the seed beam emitted from the second side 2112 back into the slab crystal 211. This allows the seed beam to undergo a forward zigzag transmission within the slab crystal 211 under the reflection of the first side 2111 and the second side 2112, resulting in a first round of amplification before exiting. Then, the reflector 220 reflects the seed beam emitted from it after the first round of amplification back into the slab crystal 211, and undergoes a reverse zigzag transmission within the slab crystal 211 under the reflection of the first reflecting unit 212 and the second reflecting unit 213, resulting in a second round of amplification before exiting.

[0080] By setting the first reflection unit 212 and the second reflection unit 213 on the first and second sides of the slab crystal 211 respectively, the seed beam can be transmitted in a forward zigzag pattern within the slab crystal 211 for the first round of amplification. The seed beam after the first round of amplification is reflected back into the slab crystal 211 by the reflector 220, and then transmitted in a reverse zigzag pattern within the slab crystal 211 under the reflection of the first reflection unit 212 and the second reflection unit 213 for the second round of amplification. This ensures the two-round amplification of the seed beam by the laser amplifier 200 and effectively improves the gain of the laser amplifier 200.

[0081] In order to reduce the assembly difficulty of the slab crystal assembly 210 or reduce the volume of the slab crystal assembly 210, this application further proposes an embodiment in which the first reflective unit 212 and the second reflective unit 213 are plane mirrors or reflective films coated on the slab crystal 211.

[0082] Specifically, when both the first reflecting unit 212 and the second reflecting unit 213 are planar reflectors, the installation process between the first reflecting unit 212 and the second reflecting unit 213 and the slab crystal 211 can be simplified, reducing the assembly difficulty of the slab crystal assembly 210 and improving the production efficiency of the laser amplifier 200.

[0083] When both the first reflective unit 212 and the second reflective unit 213 are reflective films coated on the slab crystal 211, the volume of the slab crystal assembly 210 can be reduced, thereby reducing the volume of the laser amplifier 200.

[0084] To reduce interference during the propagation of the seed beam within the lath crystal 211, this application further proposes an implementation method, please refer to [link to implementation details]. Figure 11 , Figure 11 A schematic diagram of the laser amplifier provided in an embodiment of the present invention is shown. As shown in the figure, the seed beam passes through the first focal point 221 and is incident on the first side surface 2111 of the slab crystal 211. The first side surface 2111 is a vertical surface, and the second side surface 2112 is an inclined surface. The slab crystal 211 also includes a first end surface 2113 and a second end surface 2114 opposite to each other. During the first round of amplification, the seed beam propagates from the first end surface 2113 to the second end surface 2114. The reflector 220 is close to the second end surface 2114, and the distance between the inclined surface and the vertical surface gradually increases from the first end surface 2113 to the second end surface 2114.

[0085] Interference is a phenomenon where two or more waves superimpose or cancel each other out when they meet in space, forming a new waveform. Since the greater the overlap between two beams, the stronger the interference effect, and in this application, during the zigzag transmission of the seed beam within the slab crystal 211 for the first round of amplification, the size of the seed beam gradually increases. Therefore, to avoid the influence of interference on the intensity of the seed beam during transmission, it is necessary to increase the angle between seed beams on adjacent paths during the zigzag transmission process to reduce the overlap between the seed beams.

[0086] Specifically, taking the first reflecting unit 212 and the second reflecting unit 213 respectively attached to the slab crystal 211 as an example, when the seed beam enters the first side surface 2111 of the slab crystal 211 after passing through the first focal point 221, under the reflection of the first reflecting unit 212 and the second reflecting unit 213, the seed beam can be transmitted in a positive zigzag pattern from the first end face 2113 to the second end face 2114 in the slab crystal 211 for the first round of amplification. When the seed beam after the first round of amplification exits the mirror 220 at a position close to the second end face 2114 of the slab crystal 211, the mirror 220 reflects the seed beam back into the slab crystal 211. Under the reflection of the first reflecting unit 212 and the second reflecting unit 213, the seed beam can be transmitted in a reverse zigzag pattern from the second end face 2114 to the first end face 2113 in the slab crystal 211 for the second round of amplification.

[0087] Specifically, when the first side surface 2111 of the slab crystal 211 is a vertical surface and the second side surface 2112 is an inclined surface, and the distance between the inclined surface and the vertical surface gradually increases from the first end surface 2113 to the second end surface 2114, the reflection angle of the seed beam can be increased when the seed beam passes through the second side surface 2112 and is reflected by the second reflection unit 213 and passes through the second side surface 2112 again. This increases the angle of the positive zigzag pattern (i.e., the angle between adjacent transmission paths) of the seed beam during the first round of amplification and transmission, thereby reducing the overlap between seed beams on adjacent paths during transmission, reducing interference between seed beams, avoiding affecting the intensity of the seed beam, and thus improving the stability of the seed beam.

[0088] To further reduce interference during the transmission of the seed beam within the slab crystal 211, this application proposes a further implementation method. Please refer to the following documentation. Figure 10 As shown in the figure, the seed beam is incident at a preset angle toward the second end face 2114.

[0089] Specifically, when the first side surface 2111 of the slab crystal 211 is a vertical surface and the second side surface 2112 is an inclined surface, and the distance between the inclined surface and the vertical surface gradually increases from the first end face 2113 to the second end face 2114, the seed beam can be incident into the slab crystal 211 at an angle perpendicular to the first side surface 2111, or it can be incident into the slab crystal 211 at a preset angle towards the second end face 2114.

[0090] When the seed beam is incident obliquely into the slab crystal 211 at a preset angle toward the second end face 2114, the preset angle is the angle θ between the seed beam and the first side face 2111 of the slab crystal 211, and this angle θ is an acute angle with the opening toward the second end face 2114. In this case, when the seed beam passes through the second side face 2112 and is reflected by the second reflection unit 213 and passes through the second side face 2112 again, the reflection angle of the seed beam can be further increased, making the angle of the positive zigzag pattern of the seed beam in the first round of amplification and transmission (the angle between adjacent transmission paths) larger, further reducing the overlap between seed beams of adjacent paths during transmission, thereby making the interference effect between seed beams weaker and further improving the stability of the seed beam.

[0091] To ensure the laser amplifier 200's dual amplification function for the seed beam, this application further proposes an implementation method, please refer to the following: Figure 10 and Figure 11 and combined Figure 12 , Figure 12 This diagram illustrates the transmission path of the seed beam during the first round of amplification within a lath crystal. The lath crystal 211 in the diagram is compared to... Figure 11Rotate 90° counterclockwise and place it. As shown in the figure, the major axis 2a of the reflector 220 satisfies: 2a = L tot +L′ tot +L0+L′0. Where L tot L′ is the total passage length of the seed beam during the first round of amplification within the lath crystal 211. tot L0 is the total length through which the seed beam undergoes a second round of amplification within the slab crystal 211. L0 is the distance between the first focal point 221 and the incident point of the seed beam entering the first side surface 2111 of the slab crystal 211 via the first focal point 221. L′0 is the distance between the exit point of the seed beam after the second round of amplification from the second side surface 2112 of the slab crystal 211 and the second focal point 222.

[0092] Specifically, during the first round of amplification of the seed beam within the slab crystal 211, the seed beam passes through the slab crystal 211 1 times. The vertical distance between the inclined surface and the vertical surface of the slab crystal 211 at the location where the seed beam first incident on the slab crystal 211 is W0. The angle between the seed beam and the normal to the vertical surface of the slab crystal 211 (the dashed line perpendicular to the vertical surface in the figure) when the seed beam first passes through the slab crystal 211 is α. The angle between the inclined surface and the vertical surface of the slab crystal 211 is β. The vertical distance between the inclined surface and the vertical surface of the slab crystal 211 at the location where the seed beam first incident on the slab crystal 211 is W0. i The vertical distance between the inclined plane and the vertical plane of the lath crystal 211 at the position where the seed beam is incident on the lath crystal 211 for the i-th time is W. i-1 The length of the seed beam passing through the lath crystal 211 for the i-th time is L. i .

[0093] When i is odd, the vertical distance W between the inclined plane and the vertical plane of the lath crystal 211 at the position where the seed beam is incident on the lath crystal 211 for the i-th time is W. i for:

[0094]

[0095] The length L of the seed beam passing through the lath crystal 211 for the i-th time i for:

[0096]

[0097] Where i = 1, 3, 5, 7, ...

[0098] When i is even, the vertical distance W between the inclined plane and the vertical plane of the lath crystal 211 at the position where the seed beam is incident on the lath crystal 211 for the i-th time is...i for:

[0099] W i =W i-1 [1+tanβ×tan(α+iβ)];

[0100] The length L of the seed beam passing through the lath crystal 211 for the i-th time i for:

[0101]

[0102] Where i = 2, 4, 6, 8, ...

[0103] The total passing length L of the seed beam during the first round of amplification within the lath crystal 211 tot for:

[0104]

[0105] Where i = 1, 2, 3, 4, ...

[0106] From this, we can obtain the major axis 2a of the reflecting mirror 220:

[0107] 2a=L tot +L′ tot +L0+L′0;

[0108] The total through length L′ of the seed beam undergoing a second round of amplification within the lath crystal 211 is [not specified]. tot The calculation process can be referenced from the total passing length L during the first round of amplification of the seed beam. tot The calculation process will not be elaborated here. By calculating the major axis 2a of the reflector 220, the size parameters of the reflector 220 can be determined. Combined with the first focal point 221 and the second focal point 222, the specific position of the reflector 220 can be determined, thereby ensuring the normal reflection of the seed beam by the reflector 220, and thus ensuring the second round of amplification of the seed beam by the laser amplifier 200.

[0109] In some embodiments, the length of the slab crystal 211 can be set as the total propagation length of the seed beam during the first round of amplification within the slab crystal 211.

[0110] For details, please continue reading Figure 12 When i is odd, the propagation length D of the seed beam within the lath crystal 211 when it passes through the lath crystal 211 for the i-th time is... i for:

[0111] D i =W i-1 ×tan[α+(i-1)β];

[0112] Where i = 1, 3, 5, 7, ...

[0113] When i is even, the propagation length D of the seed beam within the lath crystal 211 when it passes through the lath crystal 211 for the i-th time is... i for:

[0114] D i =W i-1 ×tan[α+iβ];

[0115] Where i = 2, 4, 6, 8, ...

[0116] The total propagation length D of the seed beam during the first round of amplification within the lath crystal 211 tot for:

[0117]

[0118] Where i = 1, 2, 3, 4, ...

[0119] The total propagation length D of the seed beam during the first round of amplification within the lath crystal 211 was calculated. tot The length of the lath crystal 211 is set as the total propagation length D. tot This allows the length of the lath crystal 211 to be fully utilized without causing waste.

[0120] In order to reduce the volume of the slab crystal 211 and improve its utilization rate, this application further proposes an embodiment in which the distance between the first end face 2113 and the second end face 2114 of the slab crystal 211 is configured such that when the seed beam is incident from a position adjacent to the first end face 2113 on a vertical plane, it can exit from a position adjacent to the second end face 2114 on a vertical plane or an inclined plane to the reflector 220.

[0121] Specifically, the distance between the first end face 2113 and the second end face 2114 of the slab crystal 211 is the length of the slab crystal 211. The length of the slab crystal 211 is set such that when the seed beam is incident from a position adjacent to the first end face 2113 on the vertical plane, it can exit from a position adjacent to the second end face 2114 on the vertical plane or the inclined plane to the reflector 220. That is, the length of the slab crystal 211 is set as the total propagation length D of the seed beam within the slab crystal 211. totFurthermore, when the seed beam first strikes the position of the slab crystal 211, the vertical distance between the vertical plane and the inclined plane of the slab crystal 211 is W0. By setting the length of the slab crystal 211 in the above manner, the size of the slab crystal 211 can be accurately controlled, the utilization rate of the slab crystal 211 can be improved, and thus the volume waste of the slab crystal 211 can be avoided.

[0122] According to another aspect of the embodiments of this application, a laser is also provided, which can be found in the following details. Figure 13 , Figure 13 A schematic diagram of a laser 1000 provided in an embodiment of the present invention is shown. The laser includes a seed source device 300, a pump device 400, and a laser amplifier 200 provided in the above embodiment. The seed source device 300 is disposed on one side of the slab crystal assembly 210 (the side along the z-axis in the figure) and is used to input a seed beam into the slab crystal assembly 210. The pump device 400 is disposed on both sides of the slab crystal assembly 210 (both sides along the z-axis in the figure) and is used to input pump light into the slab crystal assembly 210. The laser amplifier 200 is used to amplify the seed beam based on the energy provided by the pump light.

[0123] In the laser 1000, pump light is input to the slab crystal assembly 210 through pumping devices 400 disposed on both sides of the slab crystal assembly 210, causing a large number of particles in the slab crystal assembly 210 to transition from low energy levels to high energy levels. A seed beam is input to the slab crystal assembly 210 through a seed source device 300 disposed on one side of the slab crystal assembly 210. When the seed beam is transmitted in a forward zigzag pattern within the slab crystal assembly 210, the high-energy particles within the slab crystal assembly 210 are excited to emit a laser beam with the same frequency and phase as the seed beam, thereby achieving the first round of amplification of the seed beam. Furthermore, the seed beam emitted from the slab crystal assembly 210 after the first round of amplification is reflected back into the slab crystal assembly 210 through a reflector 220 for reverse zigzag transmission, causing the high-energy particles within the slab crystal assembly 210 to be excited again to emit a laser beam with the same frequency and phase as the seed beam, thereby achieving the second round of amplification of the seed beam.

Claims

1. A laser amplifier, characterized in that, The laser amplifier includes a slab crystal assembly and a mirror; The slab crystal assembly is used to direct the seed beam into the slab crystal assembly for positive zigzag transmission to perform a first round of amplification before exiting. The reflector is disposed on one side of the slab crystal assembly, and the reflecting surface of the reflector is configured as an ellipsoid. The reflector is used to reflect the seed beam emitted after the first amplification back to the slab crystal assembly. The slab crystal assembly is also used to transmit the seed beam reflected by the mirror in a reverse zigzag pattern for a second round of amplification before exiting from the slab crystal assembly.

2. The laser amplifier according to claim 1, characterized in that, The seed beam is incident on the slab crystal assembly at a first point for the first round of amplification, and then for the second round of amplification. After exiting the slab crystal assembly, it passes through a second point, which is located on the same side as the first point or on the side of the slab crystal assembly away from the first point.

3. The laser amplifier according to claim 2, characterized in that, The first point and the second point are the first focus and the second focus of the ellipsoid, respectively. The slab crystal assembly is used to allow the waist of the seed beam to pass through the first focal point and then be incident on the slab crystal assembly for positive zigzag transmission to perform a first round of amplification before being emitted. The slab crystal assembly is also used to cause the waist of the seed beam reflected by the mirror to be transmitted in a reverse zigzag pattern for a second round of amplification before exiting the slab crystal assembly and passing through the second focal point.

4. The laser amplifier according to claim 3, characterized in that, The slab crystal assembly includes a slab crystal, a first reflective unit, and a second reflective unit; The slab crystal has a first side and a second side, and the slab crystal is used to amplify the seed beam transmitted therein; The first reflection unit and the second reflection unit are respectively disposed on the first side and the second side of the slab crystal. The first reflection unit is used to reflect the seed beam emitted from the first side of the slab crystal back to the slab crystal, and the second reflection unit is used to reflect the seed beam emitted from the second side of the slab crystal back to the slab crystal. The reflector is disposed on one side of the slab crystal and is used to reflect the seed beam emitted after the first round of amplification back to the slab crystal. In this configuration, the first and second reflecting units located on the same side as the reflector are configured to not interfere with the position of the reflector, so as to reflect the seed beam incident on them respectively.

5. The laser amplifier according to claim 4, characterized in that, The first reflective unit and the second reflective unit are either plane mirrors or reflective films coated on the slab crystal.

6. The laser amplifier according to claim 4, characterized in that, The seed beam passes through the first focal point and is incident on the first side surface of the lath crystal. The first side surface is a vertical surface, and the second side surface is an inclined surface. The slab crystal also includes a first end face and a second end face opposite each other. The seed beam propagates from the first end face to the second end face during the first round of amplification. The reflector is close to the second end face. The distance between the inclined plane and the vertical plane gradually increases from the first end face to the second end face.

7. The laser amplifier according to claim 6, characterized in that, The seed beam is incident at a preset angle toward the second end face.

8. The laser amplifier according to claim 6, characterized in that, The major axis 2a of the reflector satisfies: 2a=L tot +L′ tot +L0+L′0; Among them, L tot L′ is the total passage length through which the seed beam undergoes its first round of amplification within the lath crystal. tot L0 is the total passage length through which the seed beam undergoes a second round of amplification within the slab crystal; L0 is the distance between the first focal point and the incident point of the seed beam incident on the first side of the slab crystal via the first focal point; and L′0 is the distance between the exit point of the seed beam after the second round of amplification from the second side of the slab crystal and the second focal point.

9. The laser amplifier according to claim 6, characterized in that, The distance between the first end face and the second end face of the lath crystal is configured such that when the seed beam is incident from a position adjacent to the first end face on the vertical plane, it can exit from a position adjacent to the second end face on the vertical plane or the inclined plane to the reflector.

10. A laser, characterized in that, The laser includes: a seed source device, a pumping device, and a laser amplifier as described in any one of claims 1-9; The seed source device is disposed on one side of the slab crystal assembly and is used to input the seed beam into the slab crystal assembly; The pumping device is disposed on both sides of the slab crystal assembly and is used to input pump light into the slab crystal assembly; The laser amplifier is used to amplify the seed beam based on the energy provided by the pump light.

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