Beam shaping system and method based on fast and slow axis independent shaping and focal point separation

Abstract

The application discloses a light beam shaping system and method based on fast-slow axis independent shaping and focal point separation. The light beam shaping system comprises a light emitting unit strip, a first lens group, a light guide pipe, a second lens group, a third lens group, a fourth lens group and a slab crystal which are sequentially arranged along a light beam transmission direction. The light emitting unit strip is used for outputting a light beam diverging along fast and slow axes. The light beam shaping method comprises the following steps: step one, establishing a three-dimensional coordinate system of fast axis-slow axis-light beam transmission direction, so as to obtain the focal point positions of the light beam in the fast axis direction and the slow axis direction and the sizes of the light spot formed by the cross section of the light beam in the fast axis direction and the slow axis direction. In the application, the first lens group, the light guide pipe, the second lens group, the third lens group and the fourth lens group are matched, so that the fast axis Gaussian distribution and the slow axis flat top distribution are realized, and the focal points of the light beam in the fast axis direction and the slow axis direction are separated in the light beam transmission direction.

Description

Technical Field

[0001] This invention relates to the field of laser amplifier technology, and more specifically to a beam shaping system and method based on independent fast and slow axis shaping and focus separation. Background Technology

[0002] The Innoslab slab amplifier, with its excellent surface area-to-volume ratio, results in one-dimensional heat conduction, high heat dissipation efficiency, and a high degree of overlap between the pump and signal beams. This ensures near-diffraction-limited beam quality and extremely high energy extraction efficiency, giving it a significant advantage in the high-power laser field. Its excellent heat dissipation capabilities and ease of matching pump and seed beam modes make it a promising candidate to simultaneously achieve high average power, high repetition rate, and high beam quality laser output. The pump beam shaping system, using Yb:YAG as the gain medium, is a key component of this system. It needs to simultaneously meet three core objectives: ensuring that the pump light intensity within the slab crystal exceeds the material's saturation intensity; achieving a uniform flat-top distribution of light intensity along the slow axis (horizontal) of the slab crystal to optimize thermal management and gain uniformity; and maintaining a Gaussian distribution along the fast axis (vertical) to match the seed beam mode.

[0003] Regarding this requirement, in existing technologies such as Figure 1 and Figure 2 The paper discloses an independent beam shaping scheme that uses different focal length lens combinations for the fast and slow axes to adapt to the large differences in divergence characteristics between the two.

[0004] The above beam shaping scheme can independently shape the fast and slow axes. However, in the actual construction of the pump beam shaping system, this beam shaping scheme has obvious shortcomings, as follows.

[0005] First, during the assembly and adjustment process, since the beams on the fast and slow axes are shaped using the same lens group, if the assembly and adjustment precision of the lens group is insufficient, it is difficult to simultaneously ensure that the slab crystal can form a uniform flat-top light intensity distribution in the slow axis direction and maintain the required Gaussian distribution in the fast axis direction. This is because during the assembly and adjustment process, the distribution of the Gaussian beam is prone to "bifuzzing" distortion, that is, there will be a "concave" in the middle of the Gaussian beam, or the size of the Gaussian beam will become wider due to the influence of the assembly and adjustment precision, thereby affecting the pumping efficiency and the uniformity of gain.

[0006] Secondly, existing beam shaping schemes are detailed in the accompanying diagram of the prior art. Figure 2To meet the high power density required for pump light, the fast axis size is typically designed within the range of 0.2–0.3 mm. In practical systems, the light emitted from the bar strip is essentially parallel to the beam direction after passing through the built-in fast axis collimating lens. However, this design makes it difficult to precisely match the fast axis size with actual application conditions, which in turn makes it impossible to determine the fast axis size of the beam from the front face to the rear face of the slab crystal (because the beam size varies greatly inside the slab crystal, resulting in significant changes in the beam profile).

[0007] Therefore, how to overcome the shortcomings of the existing technology is the subject of this invention. Summary of the Invention

[0008] The purpose of this invention is to provide a beam shaping system and method based on independent fast and slow axis shaping and focus separation.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A beam shaping system based on independent fast and slow axis shaping and focus separation includes a light-emitting unit strip, a first lens group, a light guide tube, a second lens group, a third lens group, a fourth lens group, and a slab crystal arranged sequentially along the beam transmission direction.

[0011] The light-emitting unit strip is used to output a light beam that diverges along the fast and slow axes;

[0012] The first lens group is used to focus the light beam into the light guide tube and homogenize the light beam in the slow axis direction within the light guide tube;

[0013] The second lens group is used to collimate the beam in the slow axis direction, so that the beam is output parallel in the slow axis direction;

[0014] The fourth lens group is used to refocus the aligned beam in the slow axis direction;

[0015] The third lens group is located between the second lens group and the fourth lens group. The third lens group is configured to perform beam contraction processing on the light beam passing through the second lens group in order to control the focal position of the light beam in the fast axis direction, so that the focal position in the fast axis direction is located before the focal position in the slow axis direction in the light beam transmission direction.

[0016] The slab crystal is configured to be pumped by a beam passing through a fourth lens group;

[0017] In use, the first lens group, the second lens group, and the fourth lens group constitute a slow-axis shaping system to focus the light beam into the slab crystal with a target set length in the slow-axis direction. The third lens group performs focus reduction processing on the light beam in the fast-axis direction, so that the focal point in the fast-axis direction is located before the focal point in the slow-axis direction in the light beam transmission direction. This allows the size of the light beam transmitted from the input end to the output end of the slab crystal in the fast-axis direction to vary within a set range, thereby achieving a uniform distribution of the light beam.

[0018] In the above scheme, the goal of fast-axis Gaussian distribution and slow-axis flat-top distribution can be achieved by cooperating the first lens group, the light guide tube, the second lens group, the third lens group and the fourth lens group. At the same time, the focal points of the beam in the fast axis direction and the slow axis direction can be separated from the beam transmission direction.

[0019] Unlike existing technologies, this application enables the beam to be distributed as a flat-top beam within the lath crystal along the slow axis, and the beam shape is not easily deformed during assembly. In the fast axis direction, the beam is distributed as a Gaussian beam within the lath crystal, and the beam size remains almost unchanged. Furthermore, the shape of the fast-axis beam is not easily deformed during assembly. At the same time, the focal point in the fast axis direction is ahead of the focal point in the slow axis direction. This design minimizes the mutual influence between the flat-top beam in the slow axis and the Gaussian beam in the fast axis. If an assembly error occurs during the assembly process, the original state can be restored in a short time.

[0020] In a further technical solution, the first lens group is a spherical cylindrical lens group;

[0021] The second lens group, the third lens group, and the fourth lens group are respectively an aspherical cylindrical lens group, a spherical cylindrical lens group, and an aspherical cylindrical lens group.

[0022] The above design not only effectively improves the stability and reliability of the beam shaping system, but also significantly reduces the difficulty of beam shaping system assembly and adjustment and the cost of subsequent maintenance.

[0023] In a further technical solution, the target length is set to 10mm.

[0024] With the above design, the slow-axis spot can be precisely controlled within the target length of 10mm, ensuring that the beam uniformly covers the effective gain area of ​​the slab crystal, maximizing energy utilization and laser output stability.

[0025] In a further technical solution, the light-emitting unit strip includes multiple horizontally arrayed laser diodes;

[0026] The output power of the light-emitting unit strip is 200W, the output center wavelength is 938.5nm, and the wavelength deviation is ±2nm.

[0027] The length of each light-emitting unit strip is 10mm, and the total length of the array is 47.5mm.

[0028] The above design allows the entire beam shaping system to be applied to high-power laser amplifiers. Furthermore, by using a horizontal array of laser diodes as the pump source, the fast and slow axes of the beam can be processed separately.

[0029] This invention also discloses a beam shaping method based on independent fast and slow axis shaping and focus separation, for use in a beam shaping system based on independent fast and slow axis shaping and focus separation. The beam shaping method includes:

[0030] Step 1: Establish a three-dimensional coordinate system of fast axis-slow axis-beam propagation direction to obtain the focal position of the beam in the fast axis and slow axis directions, as well as the size of the spot formed by the beam cross-section in the fast axis and slow axis directions.

[0031] In this system, the end face of the slab crystal perpendicular to the beam propagation direction is used as a reference. The direction of the slow axis is the pump line direction, and the beam propagation direction is the pump direction. The direction of the fast axis is perpendicular to the direction of the slow axis. The beam propagation direction is perpendicular to the plane containing the fast axis and the slow axis. The origin of the three-dimensional coordinate system of the fast axis, slow axis, and beam propagation direction is defined on the common geometric central axis of the first lens group, the second lens group, the third lens group, the fourth lens group, and the slab crystal.

[0032] Step 2: Using the first lens group, focus the light beam emitted by the light-emitting unit strip so that the size of the light spot formed by the light beam in the slow axis direction is focused to a first set length.

[0033] Step 3: Pass the light beam through the light guide tube to homogenize the light beam in the slow axis direction, and then guide the homogenized light beam into the second lens group for collimation, so that the light beam is output parallel in the slow axis direction.

[0034] Step 4: Use the third lens group to perform beam contraction processing on the beam in the fast axis direction, so that the focal point in the fast axis direction is located before the focal point in the slow axis direction in the beam transmission direction. This separates the focal points in the fast axis direction from those in the slow axis direction in the beam transmission direction, and makes the spot size of the beam transmitted from the input end to the output end of the slab crystal in the fast axis direction vary within a set range to achieve uniform beam distribution.

[0035] The beam transmission direction is perpendicular to the plane containing the fast axis and the slow axis;

[0036] Step 5: Use the fourth lens group to refocus the beam that has been collimated in the slow axis direction, so that the size of the spot formed by the beam output in parallel in the slow axis direction is focused to the target set length.

[0037] Step 6: Pump the slab crystal using the beam passing through the fourth lens group.

[0038] In the above scheme, independent control of the fast axis and slow axis can ensure that the beam in the fast axis direction maintains a Gaussian distribution and the beam in the slow axis direction maintains a flat-top distribution. Combined with homogenization and collimation control in the slow axis direction, the pump light is ensured to be transmitted stably and uniformly in the slab crystal.

[0039] In a further technical solution, the light spot formed by the beam in the slow axis direction has a first set length of 6-12 mm when focused.

[0040] The above design allows for a more compact beam shaping system.

[0041] In a further technical solution, the first set length of the light spot formed by the beam in the slow axis direction is 9mm, and the height of the second lens group is 76mm.

[0042] The above design improves the compactness of the beam shaping system and optimizes the optical path layout, effectively reducing the sensitivity of the beam shaping system to installation errors.

[0043] In a further technical solution, the size of the slab crystal is 10mm × 1mm × 10mm;

[0044] On a lath crystal, the size of the spot formed by the cross-section of the beam in the fast axis direction is 0.2-0.24 mm;

[0045] On a lath crystal, the size of the light spot formed by the cross section of the light beam in the slow axis direction is 10 mm.

[0046] With the above design, the light spot in the fast axis direction can always maintain a Gaussian distribution pattern throughout the entire 10mm working length inside the lath crystal; at the same time, the size of the light spot in the fast axis direction is strictly limited to fluctuate within a very small range of 0.2mm to 0.24mm.

[0047] In a further technical solution, the divergence angle of the light beam in the slow axis direction is 8°, and the divergence angle of the light beam in the fast axis direction is 46°.

[0048] In a further technical solution, the beam shaping system also includes a fast-axis collimating lens positioned on the fast axis.

[0049] The above design reduces the difficulty of fast-axis alignment. The fast-axis collimating lens setting allows the divergence angle variation of the fast axis to be controlled within 0.4°.

[0050] Due to the application of the above-mentioned solution, the technical solution of this application has the following advantages and effects compared with the prior art:

[0051] In this invention, the fast-axis Gaussian distribution and the slow-axis flat-top distribution can be achieved through the cooperation of the first lens group, the light guide tube, the second lens group, the third lens group, and the fourth lens group. At the same time, the focal points of the beam in the fast-axis direction and the slow-axis direction can be separated from the beam transmission direction.

[0052] Specifically, in use, the first lens group, the second lens group, and the fourth lens group constitute a slow-axis shaping system to focus the light beam into the slab crystal with a target-set spot length in the slow-axis direction. The third lens group performs focus reduction processing on the light beam in the fast-axis direction, so that the focal point in the fast-axis direction is located before the focal point in the slow-axis direction in the light beam transmission direction. This allows the spot size of the light beam transmitted from the input end to the output end of the slab crystal in the fast-axis direction to vary within a set range, thereby achieving a uniform distribution of the light beam. In this way, the goal of achieving a Gaussian distribution in the fast-axis direction and a flat-top distribution in the slow-axis direction within the effective gain region of the slab crystal is achieved.

[0053] Unlike existing technologies, this application enables the beam to be distributed as a flat-top beam within the slab crystal along the slow axis, and the beam shape is not easily deformed during assembly. In the fast axis direction, the beam is distributed as a Gaussian beam within the slab crystal, and the beam size remains almost unchanged. Furthermore, the shape of the fast-axis beam is not easily deformed during assembly. At the same time, the focal point in the fast axis direction is ahead of the focal point in the slow axis direction. This design minimizes the mutual influence between the flat-top beam in the slow axis and the Gaussian beam in the fast axis. Moreover, if an assembly error occurs during the assembly process, the original state can be restored in a short time.

[0054] Meanwhile, the third lens group performs focus reduction on the fast-axis beam, and the fast-axis focus is located before the slow-axis focus. The core function of this design is to ensure that the fast-axis beam is in a collimated transmission state within the effective area of ​​the crystal. Combined with the effect of keeping the size of the fast-axis spot consistent from the input end to the output end, the beam will not diverge significantly during transmission. Attached Figure Description

[0055] Figure 1 This is a schematic diagram of beam transmission in the slow axis direction of a beam shaping system in the prior art;

[0056] Figure 2 This is a schematic diagram of beam transmission in the fast axis direction of a beam shaping system in the prior art;

[0057] Figure 3 This is a schematic diagram of beam transmission in the fast axis direction of the beam shaping system in an embodiment of the present invention;

[0058] Figure 4 This is a schematic diagram of beam transmission in the slow axis direction of the beam shaping system in an embodiment of the present invention;

[0059] Figure 5 This is a schematic diagram showing the focal points of the laser beam at the laser diode in the fast axis direction and the focal points in the slow axis direction in an embodiment of the present invention;

[0060] Figure 6 This is a schematic diagram of the principle when multiple laser diodes in the light-emitting unit strip in an embodiment of the present invention emit light beams;

[0061] Figure 7 This is a schematic diagram of the light intensity distribution of the beam on the front end face of the lath crystal in the slow axis direction in an embodiment of the present invention;

[0062] Figure 8 This is a schematic diagram of the light intensity distribution of the beam in the slow axis direction in the middle region of the lath crystal in an embodiment of the present invention;

[0063] Figure 9 This is a schematic diagram of the light intensity distribution of the beam on the slow axis direction at the rear end face of the lath crystal in an embodiment of the present invention;

[0064] Figure 10 This is a schematic diagram of the light intensity distribution of the beam on the front end face of the slab crystal in the fast axis direction in an embodiment of the present invention;

[0065] Figure 11 This is a schematic diagram of the light intensity distribution of the beam in the fast axis direction in the middle region of the lath crystal in an embodiment of the present invention;

[0066] Figure 12 This is a schematic diagram of the light intensity distribution of the beam on the fast axis direction at the rear end face of the lath crystal in an embodiment of the present invention;

[0067] Figure 13 This is a schematic diagram of the light intensity distribution of a beam on a lath crystal along the fast axis in an embodiment of the present invention, where the intensity is low at both ends and high in the middle.

[0068] Figure 14 This is a schematic diagram of the light intensity distribution of a beam on a lath crystal along the fast axis direction, showing a central depression in an embodiment of the present invention.

[0069] Figure 15 This is a schematic diagram illustrating an intermediate distortion in the intensity distribution of a beam along the fast axis on a lath crystal, as described in an embodiment of the present invention.

[0070] In the above diagram: 1. Light-emitting unit strip;

[0071] 2. First lens group;

[0072] 3. Light guide tube;

[0073] 4. Second lens group;

[0074] 5. Third lens group;

[0075] 6. Fourth lens group;

[0076] 7. Lath crystals;

[0077] 8. Fast axis;

[0078] 9. Slow axis;

[0079] 10. Beam of light. Detailed Implementation

[0080] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0081] The terms "first," "second," etc., used in this article do not specifically refer to order or sequence, nor are they intended to limit this case; they are merely used to distinguish components or operations described using the same technical terms.

[0082] The terms "connection" or "positioning" as used in this article can refer to two or more components or devices making direct physical contact with each other, or making indirect physical contact with each other, or to two or more components or devices operating or moving with each other.

[0083] The terms “include,” “including,” and “have” used in this article are all open-ended, meaning they include but are not limited to.

[0084] Unless otherwise specified, the terms used herein generally have their ordinary meaning in the context of the art, the subject matter, and the specific context. Certain terms used to describe this case will be discussed below or elsewhere in this specification to provide additional guidance to those skilled in the art in describing this case.

[0085] The terms “front,” “back,” “up,” “down,” “left,” and “right” used in this article are directional terms. In this case, they are only used to describe the positional relationship between the structures and are not intended to limit the specific direction of the protection scheme or its actual implementation.

[0086] The terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the scope of this work. Singular forms such as “a,” “this,” “this,” “the,” and “the” as used herein also include plural forms.

[0087] See Figure 3 - Figure 15 As shown, the beam shaping system based on independent fast and slow axis shaping and focus separation includes a light-emitting unit strip 1, a first lens group 2, a light guide tube 3, a second lens group 4, a third lens group 5, a fourth lens group 6, and a slab crystal 7 arranged sequentially along the beam 10 transmission direction.

[0088] The light-emitting unit 1 is used to output a light beam 10 that diverges along the fast and slow axes;

[0089] The first lens group 2 is used to focus the light beam 10 into the light guide tube 3 and homogenize the light beam 10 in the slow axis 9 direction within the light guide tube 3;

[0090] The second lens group 4 is used to collimate the beam 10 in the slow axis 9 direction, so that the beam 10 is output parallel in the slow axis 9 direction;

[0091] The fourth lens group 6 is used to refocus the aligned beam 10 in the slow axis 9 direction;

[0092] The third lens group 5 is located between the second lens group 4 and the fourth lens group 6. The third lens group 5 is configured to perform beam contraction processing on the light beam 10 passing through the second lens group 4, so as to control the focal position of the light beam 10 in the fast axis 8 direction, so that the focal position in the fast axis 8 direction is located before the focal position in the slow axis 9 direction in the transmission direction of the light beam 10.

[0093] The slab crystal 7 is configured to be pumped by a beam 10 passing through the fourth lens group 6;

[0094] In use, the first lens group 2, the second lens group 4, and the fourth lens group 6 constitute a slow-axis shaping system, so that the beam 10 is focused into the slab crystal 7 with a target set length of light spot in the slow-axis 9 direction. The third lens group 5 performs focus reduction processing on the beam 10 in the fast-axis 8 direction, so that the focal point in the fast-axis 8 direction is located before the focal point in the slow-axis 9 direction in the beam 10 transmission direction. This allows the size of the light spot transmitted from the input end to the output end of the slab crystal 7 in the fast-axis 8 direction to change within a set range, thereby achieving a uniform distribution of the beam.

[0095] In this invention, the light-emitting unit strip 1 is used to output a light beam 10 with a significant divergence difference along the fast axis 8 and the slow axis 9, and the divergence angle in the direction of the fast axis 8 is greater than the emission angle in the direction of the slow axis 9.

[0096] The light-emitting unit bar 1 refers to the bar bar.

[0097] In this invention, the slab crystal 7 is pumped by a beam 10 through a fourth lens group 6. This beam shaping system is sequentially composed of a first lens group 2, a light guide tube 3, a second lens group 4, a third lens group 5, and a fourth lens group 6. The combined action of all optical elements results in a Gaussian distribution of the beam along the fast axis 8 and a flat-top distribution along the slow axis 9. As the final component of the system, the fourth lens group 6 is responsible for precisely guiding the beam 10 into the effective gain region of the slab crystal 7 (the effective gain region refers to the volume region within the slab crystal that truly contributes to the output laser and produces net optical amplification) to complete the pumping. Within this region, the spot size along the fast axis 8 is controlled between 0.2 mm and 0.24 mm, while the spot size along the slow axis 9 covers the entire length of the slab crystal 7, thereby ensuring stable stimulated emission amplification within this core region.

[0098] The slab crystal 7, as the gain medium, is doped with activating ions and is the core carrier for realizing laser amplification.

[0099] In this invention, the spot size in the fast axis 8 and slow axis 9 directions refers to the size of the spot formed by the cross section of the beam 10 in the fast axis 8 and slow axis 9 directions.

[0100] In this invention, such as Figure 1 and Figure 2 It is known that the beam shaping system in the prior art includes, from left to right, a first cylindrical lens group, a light guide tube 3, a second cylindrical lens group, a spherical mirror, a dichroic mirror, and a gain medium (equivalent to the slab crystal 7 of this application).

[0101] In this invention, the goal of Gaussian distribution on the fast axis 8 and flat-top distribution on the slow axis 9 can be achieved through the cooperation of the first lens group 2, the light guide tube 3, the second lens group 4, the third lens group 5, and the fourth lens group 6. At the same time, the focal points of the beam 10 on the fast axis 8 and the slow axis 9 can be separated from the beam 10 transmission direction.

[0102] Specifically, in use, the first lens group 2, the second lens group 4, and the fourth lens group 6 constitute a slow-axis shaping system to focus the beam 10 into the slab crystal 7 with a target set length of light spot in the slow-axis 9 direction. The third lens group 5 performs focus reduction processing on the beam 10 in the fast-axis 8 direction, so that the focal point in the fast-axis 8 direction is located before the focal point in the slow-axis 9 direction in the beam 10 transmission direction. This allows the size of the light spot transmitted from the input end to the output end of the slab crystal 7 in the fast-axis 8 direction to change within a set range, thereby achieving a uniform distribution of the beam. In this way, the goal of Gaussian distribution in the fast-axis 8 and flat-top distribution in the slow-axis 9 within the effective gain region of the slab crystal 7 is achieved.

[0103] Unlike existing technologies, this application enables the beam 10 to be distributed as a flat-top beam 10 within the slab crystal 7 along the slow axis 9 direction. During assembly and adjustment, the shape of the beam 10 along the slow axis 9 direction is not easily deformed, while along the fast axis 8 direction, it is distributed as a Gaussian beam within the slab crystal 7. The size of the beam 10 remains almost unchanged, and the shape of the beam 10 along the fast axis 8 direction is not easily deformed during assembly and adjustment. At the same time, the focal point along the fast axis 8 direction is ahead of the focal point along the slow axis 9 direction. This design minimizes the mutual influence between the flat-top beam 10 along the slow axis 9 and the Gaussian beam along the fast axis 8. If an assembly and adjustment error occurs during the assembly and adjustment process, the original state can be restored in a short time.

[0104] Meanwhile, the third lens group 5 performs focus reduction processing on the beam 10 in the direction of fast axis 8, and the focal point in the direction of fast axis 8 is located before the focal point in the direction of slow axis 9. The core function of this design is to ensure that the beam 10 in the direction of fast axis 8 is in a collimated transmission state within the effective area of ​​the slab crystal 7 and presents a Gaussian profile. Combined with the effect that the size of the beam spot in the direction of fast axis 8 remains consistent from the input end to the output end (in practice, it should be basically consistent because there will be slight changes), it shows that the beam 10 does not diverge significantly during transmission.

[0105] Preferably, the first lens group 2 is a spherical cylindrical lens group;

[0106] The second lens group 4, the third lens group 5, and the fourth lens group 6 are respectively an aspherical cylindrical lens group, a spherical cylindrical lens group, and an aspherical cylindrical lens group.

[0107] The above design not only effectively improves the stability and reliability of the beam shaping system, but also significantly reduces the difficulty of assembly and adjustment and the cost of subsequent maintenance. Through the appropriate combination of spherical and aspherical cylindrical lens groups, the beam distribution characteristics along the fast and slow axes are further optimized, enabling uniform flat-top output in the slow axis (9th direction) while maintaining the compactness and transmission consistency of the Gaussian beam in the fast axis (8th direction).

[0108] Preferably, the target length is set to 10 mm.

[0109] With the above design, the slow axis 9 spot is precisely controlled within the target setting length of 10mm, which ensures that the beam 10 uniformly covers the effective gain area of ​​the slab crystal 7, maximizing energy utilization and laser output stability.

[0110] It is important to note that, such as Figure 3 and Figure 4As shown, when viewed from left to right, the fourth lens group 6 is the second aspherical cylindrical lens group, with its cylindrical direction parallel to the slow axis 9. Its function is to precisely focus the parallel beam 10 along the slow axis 9 to the desired target length (10mm). At the focal point, the beam 10 is a flat-top beam 10 along the slow axis 9. A slab crystal 7Yb:YAG with dimensions of 10mm × 1mm × 10mm is placed here. When the 10mm wide flat-top beam 10 along the slow axis 9 is incident on the side of the slab crystal 7, the beam 10 is transmitted along the length of the slab crystal 7 inside the slab crystal 7, and will continuously undergo total internal reflection along the slow axis 9. This transmission mechanism ensures that the beam 10 is in the same plane along the slow axis 9 (the plane formed by the fast axis 8 and the slow axis 9, as shown in the image). Figure 5 As shown in the figure, the light intensity distribution remains basically unchanged.

[0111] In this invention, such as Figure 5 The laser diodes shown are in a horizontal position. In practice, there are also vertical configurations. The specific configuration should be adjusted according to the position of the slab crystal.

[0112] Preferably, the light-emitting unit strip 1 includes a plurality of horizontally arrayed laser diodes (meaning that each light-emitting unit strip 1 includes a plurality of horizontally arrayed laser diodes).

[0113] Each light-emitting unit strip 1 has an output power of 200 W, an output center wavelength of 938.5 nm, and a wavelength deviation of ±2 nm;

[0114] Each light-emitting unit strip 1 is 10mm long, and the total array length is 47.5mm.

[0115] With the above design, the entire beam shaping system can be applied to high-power laser amplifiers. For example, four light-emitting unit strips 1 with a total power of 800W can be used, which is sufficient to drive Yb:YAG slab crystals to achieve efficient laser amplification.

[0116] This invention also discloses a beam shaping method based on independent fast and slow axis shaping and focus separation, for use in a beam shaping system based on independent fast and slow axis shaping and focus separation. The beam shaping method includes:

[0117] Step 1: Establish a three-dimensional coordinate system with fast axis 8, slow axis 9, and beam 10 transmission direction to obtain the focal position of beam 10 in the fast axis 8 and slow axis 9 directions, as well as the size of the light spot formed by the cross section of beam 10 in the fast axis 8 and slow axis 9 directions.

[0118] In this system, the end face of the slab crystal 7 perpendicular to the direction of beam 10 is used as a reference. The direction of the slow axis 9 is the pump line direction, and the direction of beam transmission is the pump direction. The direction of the fast axis 8 is perpendicular to the direction of the slow axis 9, and the direction of beam transmission is perpendicular to the plane containing the fast axis 8 and the slow axis 9. The origin of the three-dimensional coordinate system of the fast axis 8, the slow axis 9, and the direction of beam 10 transmission is defined on the common geometric central axis of the first lens group 2, the second lens group 4, the third lens group 5, the fourth lens group 6, and the slab crystal 7.

[0119] The pump direction here is the emission direction of beam 10, and the pump direction is from left to right, for example... Figure 6 The straight line in the middle extends perpendicularly to the right end face of the light-emitting unit strip 1. The pump line direction lies in the plane formed by the fast axis 8 and the slow axis 9; for example, the pump line direction lies in the plane formed by the fast axis 8 and the slow axis 9. Figure 6 The light-emitting unit 1 is located in a plane parallel to the right end face of the light-emitting unit.

[0120] Note that the pump direction is the direction in which the pump moves forward, and the pump line direction refers to the direction in which the line is located, that is, the direction in which the multiple light-emitting unit strips 1 are arranged in the three-dimensional coordinate system of fast axis 8 - slow axis 9 - beam 10 transmission direction.

[0121] Step 2: Using the first lens group 2, focus the light beam 10 emitted by the light-emitting unit strip 1 so that the size of the light spot formed by the light beam 10 in the slow axis 9 direction is focused to a first set length.

[0122] Step 3: Pass the light beam 10 through the light guide tube 3 to homogenize the light beam 10 in the slow axis 9 direction, and then guide the homogenized light beam 10 into the second lens group 4 for collimation, so that the light beam 10 is output parallel in the slow axis 9 direction.

[0123] Step 4: Use the third lens group 5 to perform beam reduction processing on the beam 10 in the fast axis 8 direction, so that the focal point in the fast axis 8 direction is located before the focal point in the slow axis 9 direction in the beam 10 transmission direction. This separates the focal points of the beam 10 in the fast axis 8 direction from those in the slow axis 9 direction in the beam 10 transmission direction. It also changes the spot size of the beam 10 in the fast axis 8 direction from the input end to the output end of the slab crystal 7 within a set range to achieve uniform beam distribution (in practice, the set range is controlled according to the requirements, and the main purpose is to achieve uniform beam distribution).

[0124] The transmission direction of the light beam 10 is perpendicular to the plane containing the fast axis 8 and the slow axis 9;

[0125] Step 5: Use the fourth lens group 6 to refocus the beam 10 that has been collimated in the slow axis 9 direction, so that the size of the light spot formed by the beam 10 that is output in parallel in the slow axis 9 direction is focused to the target set length.

[0126] Step 6: Pump the slab crystal 7 using the beam 10 passing through the fourth lens group 6.

[0127] In this invention, the independent adjustment of the fast axis 8 and the slow axis 9 can ensure that the beam 10 in the direction of the fast axis 8 maintains a Gaussian distribution and the beam 10 in the direction of the slow axis 9 maintains a flat-top distribution. Combined with the homogenization and collimation control in the direction of the slow axis 9, the pump light is ensured to be transmitted stably and uniformly in the slab crystal 7.

[0128] Specifically, in the slow axis 9 direction, the first lens group 2 (spherical cylindrical lens group) is used to focus the beam 10 into the light guide tube 3, so that the beam 10 is homogenized in the slow axis 9 direction. After the beam 10 is emitted from the light guide tube 3, the second lens group 4 (aspherical cylindrical lens group) is used to shape the beam 10 into a parallel beam 10 in the slow axis 9 direction. Then, the fourth lens group 6 (aspherical cylindrical lens group) is used to focus the spot size of the beam 10 in the slow axis 9 direction to the target set length. Finally, between the two aspherical cylindrical lens groups, the third lens group 5 (spherical cylindrical lens group) is inserted for shaping the beam 10 in the fast axis 8 direction.

[0129] At this point, the third lens group 5 can perform beam contraction processing on the focal point in the fast axis 8 direction, thereby setting the focal point of beam 10 in the fast axis 8 direction in front of the focal point in the slow axis 9 direction. This effectively isolates the shaping optical paths of fast axis 8 and slow axis 9 (the shaping optical paths of fast axis 8 and slow axis 9 refer to the independent beam 10 shaping, focusing, and transmission paths of fast axis 8 and slow axis 9), reducing mutual interference and ensuring the dimensional stability of the Gaussian beam of fast axis 8 within the gain region of the slab crystal 7.

[0130] Preferably, the light spot formed by the beam 10 in the slow axis 9 direction has a first set length of 6-12 mm for focusing.

[0131] The above design allows for a more compact beam shaping system.

[0132] Preferably, the first set length of the light spot formed by the beam 10 in the slow axis 9 direction is 9 mm, and the height of the second lens group 4 is 76 mm.

[0133] The above design improves the compactness of the beam shaping system and optimizes the optical path layout, effectively reducing the system's sensitivity to installation errors. With a first set length of 9mm for the beam spot formed along the slow axis 9 and a matching height of 76mm for the second lens group 4, the beam spot control precision along the slow axis 9 is improved, further enhancing the stability and pumping efficiency of the beam shaping system and ensuring that the output beam 10 meets the application requirements of high-power lasers. Matching the target set length with the cross-section of the slab crystal 7, and through secondary focusing achieved by the fourth lens group 6, the beam spot size along the slow axis 9 is precisely controlled at 10mm, ensuring a high degree of fit between the pump beam spot and the cross-section of the slab crystal 7. This design effectively controls the beam to remain flat-topped along the slow axis 9 while reducing the risk of thermal stress distortion.

[0134] It is important to note that the reason why the beam 10 is focused to 9mm in the slow axis 9 direction is that when the focused beam spot is too small, the divergence angle of the beam 10 at the exit of the light guide tube 3 on the slow axis 9 will increase significantly. This forces the optical elements used for collimating and focusing the beam 10 in the slow axis 9 direction to be designed to be larger. That is, when the divergence angle is large, the size of the entire lens group must be made very large (far greater than 76mm, because the current theory is 100mm and above). However, this will increase the cost of the laser and impair the compactness of the beam shaping system, and greatly increase the requirements for assembly and adjustment accuracy.

[0135] Furthermore, when the focused spot size is too large, a very long light guide tube 3 is required to achieve sufficient homogenization, which also leads to a large size and reduced compactness of the beam shaping system. Therefore, choosing a focused spot size of 9mm for the beam 10 along the slow axis 9 is the balance point found in this scheme between homogenization effect, subsequent optical element size, and light guide tube 3 length.

[0136] At this size, the light guide tube 3 outlet can achieve a good flat-top distribution along the slow axis 9. At this point, by monitoring the intensity distribution of the beam 10 at the light guide tube 3 outlet along the slow axis 9, the success of the initial assembly and adjustment can be visually determined. The observed flat-top distribution is an important indicator of successful assembly and adjustment.

[0137] Simultaneously, a second lens group 4 (aspherical cylindrical lens group) is placed immediately behind the exit of the light guide tube 3, with its cylindrical surface direction parallel to the slow axis 9. It can collimate the homogenized beam 10 emitted from the light guide tube 3 along the slow axis 9, forming a parallel beam 10 along the slow axis 9. To improve the compactness of the beam shaping system, the height of the second lens group 4 is set to 76mm, which is a significant size optimization for a high-power linear array pumped beam shaping system. Current theoretical specifications would require a height of 100mm or more.

[0138] Preferably, the size of the lath crystal 7 is 10mm × 1mm × 10mm;

[0139] On the lath crystal 7, the size of the light spot formed by the cross section of the beam 10 in the fast axis 8 direction is 0.2-0.24 mm;

[0140] On the lath crystal 7, the size of the light spot formed by the cross section of the beam 10 in the slow axis 9 direction is 10 mm.

[0141] With the above design, the beam spot along the fast axis 8 can maintain a Gaussian distribution throughout the entire 10mm working length inside the slab crystal 7; simultaneously, the beam spot size along the fast axis 8 is strictly limited to a very small range of 0.2mm–0.24mm. This design fundamentally solves the problem of beam spot splitting or distortion due to assembly errors in the fast axis 8 in existing technologies. Furthermore, the beam spot along the fast axis 8 maintains a small size (0.2–0.24mm) and high energy density within the slab crystal 7, and remains stable over a long distance (10mm), ensuring sufficient and stable spatial overlap between the pump light and the seed light mode field. This directly improves the seed light extraction efficiency and enhances the beam quality of the output laser. At the same time, more uniform and stable pumping reduces ineffective absorption and waste heat generation, optimizing the thermal management of the beam shaping system.

[0142] Preferably, the beam 10 has a divergence angle of 8° on the slow axis 9 and a divergence angle of 46° on the fast axis 8.

[0143] Preferably, the beam shaping system further includes a fast-axis collimating lens disposed on the fast axis 8.

[0144] The above design reduces the difficulty of shaping the fast axis 8. The setting of the fast axis collimating lens allows the divergence angle variation of the fast axis 8 to be controlled within 0.4°.

[0145] Working principle: Based on the transmission direction of beam 10, multiple light-emitting unit strips 1 of the horizontal array are first used as pump light sources to separate the fast and slow axes of beam 10 for processing, thereby enabling it to be adapted to high-power laser amplifiers.

[0146] Subsequently, after the multiple light-emitting unit strips 1 in the horizontal array, a first lens group 2 (spherical cylindrical lens group) is placed to focus the light beam 10, thereby focusing the light spot formed by the light beam 10 in the slow axis 9 direction to 9mm. At the focal point, a rectangular cross-section light guide tube 3 of the same size as the light spot formed in the slow axis 9 direction is placed, and the light beam 10 in the slow axis 9 direction is homogenized by the light guide tube 3. The reason for focusing the light spot formed by the light beam 10 in the slow axis 9 direction to 9mm is that if the focused light spot is too small, it will cause the light guide tube 3 to exit at a small diameter. The divergence angle of the slow axis 9 of the beam 10 increases significantly, which forces the optical elements used for collimating and focusing the beam 10 in the slow axis 9 direction to be designed to be larger. That is, when the divergence angle is large, the size of the entire lens group must be made very large (far greater than 76mm, and the current theory is 100mm and above). However, this will increase the cost of the laser and impair the compactness of the beam shaping system, and greatly increase the requirements for assembly and adjustment accuracy. If the focused spot is too large, it will seriously weaken the homogenization effect of the light guide tube 3 and cause the light guide tube 3 to become longer, but the lens will not become larger.

[0147] Subsequently, a second lens group 4 (an aspherical cylindrical lens group) is placed immediately behind the exit of the light guide tube 3, with its cylindrical surface parallel to the slow axis 9. This collimates the homogenized beam 10 emitted from the light guide tube 3, which has a specific divergence angle along the slow axis 9, forming a parallel beam 10 along the slow axis 9. To improve the compactness of the beam shaping system, the maximum size of the lens group in this design is 76mm, a significant size optimization for a high-power linear array pumped beam shaping system, as current theoretical dimensions are 100mm and above.

[0148] Next, a second aspherical cylindrical lens group (i.e., the fourth lens group 6) is placed, its cylindrical direction also parallel to the slow axis 9. Its function is to precisely focus the parallel beam 10 in the slow axis 9 direction to the required target length (10mm). At the focal point, the beam 10 is a flat-top beam 10 in the slow axis 9 direction. Then, a slab crystal 7Yb:YAG with dimensions of 10mm×1mm×10mm is placed here. When the 10mm wide flat-top beam 10 in the slow axis 9 direction is incident on the side of the slab crystal 7, the beam 10 is transmitted along the length of the slab crystal 7 inside the slab crystal 7, and will continuously undergo total internal reflection in the slow axis 9 direction.

[0149] At this point, the beam 10 can be shaped along the fast axis 8. Specifically, a third lens group 5 (spherical cylindrical lens group) is inserted between the two aspherical cylindrical lens groups (i.e., between the second lens group 4 and the fourth lens group 6) to shape the beam 10 along the fast axis 8. The third lens group 5 can perform beam contraction on the focal point of the beam 10 along the fast axis 8, thereby setting the focal point of the beam 10 along the fast axis 8 in front of the focal point along the slow axis 9, ensuring the dimensional stability and profile stability of the Gaussian beam along the fast axis 8 within the gain region of the slab crystal 7.

[0150] Simultaneously, by setting the focal point of beam 10 in the fast axis 8 direction in front of the focal point in the slow axis 9 direction, the mutual interference of the beam 10 shaping process in the two directions is effectively reduced. More importantly, it ensures that when beam 10 reaches the focal point of slow axis 9 in the fast axis 8 direction, it is near the waist of its Gaussian beam but not at the minimum waist point. At this time, the cross-sectional size of beam 10 in the fast axis 8 direction is slightly larger than the minimum waist size. Based on the characteristic that the spot size of the Gaussian beam changes very little within the Rayleigh length range near the waist, when beam 10 subsequently illuminates the slab crystal 7 in the fast axis 8 direction, the spot size transmitted from the input end to the output end of the slab crystal 7 can be varied within a set range to achieve a uniform beam distribution.

[0151] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A beam shaping system based on independent fast and slow axis shaping and focus separation, characterized in that: It includes a light-emitting unit strip (1), a first lens group (2), a light guide tube (3), a second lens group (4), a third lens group (5), a fourth lens group (6), and a slab crystal (7) arranged sequentially along the transmission direction of the light beam (10); The light-emitting unit strip (1) is used to output a light beam (10) that diverges along the fast axis (8) - slow axis (9). The first lens group (2) is used to focus the light beam (10) into the light guide tube (3) and homogenize the light beam (10) in the slow axis (9) direction within the light guide tube (3); The second lens group (4) is used to collimate the beam (10) in the slow axis (9) direction, so that the beam (10) is output parallel in the slow axis (9) direction; The fourth lens group (6) is used to refocus the aligned beam (10) in the slow axis (9) direction; The third lens group (5) is located between the second lens group (4) and the fourth lens group (6). The third lens group (5) is configured to perform beam contraction processing on the beam (10) passing through the second lens group (4) to control the focal position of the beam (10) in the fast axis (8) direction, so that the focal position in the fast axis (8) direction is located before the focal position in the slow axis (9) direction in the beam (10) transmission direction. The lath crystal (7) is configured to be pumped by a beam (10) passing through the fourth lens group (6); In use, the first lens group (2), the second lens group (4) and the fourth lens group (6) constitute a slow axis shaping system so that the beam (10) is focused into the slab crystal (7) in the slow axis (9) direction with a target set length of light spot. The third lens group (5) performs focus reduction processing on the beam (10) in the fast axis (8) direction so that the focus in the fast axis (8) direction is located before the focus position in the slow axis (9) direction in the beam (10) transmission direction. This allows the light spot size of the beam (10) transmitted from the input end to the output end of the slab crystal (7) in the fast axis (8) direction to change within a set range, so as to achieve uniform distribution of the beam.

2. The beam shaping system based on independent fast and slow axis shaping and focus separation according to claim 1, characterized in that: The first lens group (2) is a spherical cylindrical lens group; The second lens group (4), the third lens group (5), and the fourth lens group (6) are respectively an aspherical cylindrical lens group, a spherical cylindrical lens group, and an aspherical cylindrical lens group.

3. The beam shaping system based on independent fast and slow axis shaping and focus separation according to claim 1, characterized in that: The target length is set to 10mm.

4. The beam shaping system based on independent fast and slow axis shaping and focus separation according to claim 1, characterized in that: The light-emitting unit strip (1) includes multiple horizontally arrayed laser diodes; The output power of the light-emitting unit strip (1) is 200W, the output center wavelength is 938.5 nm, and the wavelength deviation is ±2 nm; The length of the light-emitting unit strip (1) is 10mm, and the total length of the array is 47.5mm.

5. A beam shaping method based on independent shaping of fast and slow axes and focus separation, characterized in that: The beam shaping system based on independent fast and slow axis shaping and focus separation as described in any one of claims 1-4, the beam shaping method comprising: Step 1: Establish a three-dimensional coordinate system of fast axis (8) - slow axis (9) - beam (10) transmission direction to obtain the focal position of beam (10) in the fast axis (8) direction and slow axis (9) direction, as well as the size of the light spot formed by the cross section of beam (10) in the fast axis (8) direction and slow axis (9) direction. Among them, the end face of the slab crystal (7) perpendicular to the direction of beam (10) transmission is taken as the reference, the direction of the slow axis (9) is the direction of the pump line, and the direction of beam (10) transmission is the direction of pumping. The direction of the fast axis (8) is perpendicular to the direction of the slow axis (9), and the direction of beam (10) transmission is perpendicular to the plane where the fast axis (8) and slow axis (9) are located. The origin of the three-dimensional coordinate system of the fast axis (8) - slow axis (9) - beam (10) transmission direction is defined on the common geometric central axis of the first lens group (2), the second lens group (4), the third lens group (5), the fourth lens group (6) and the slab crystal (7). Step 2: Using the first lens group (2), focus the light beam (10) emitted by the light-emitting unit strip (1) so that the size of the light spot formed by the light beam (10) in the slow axis (9) direction is focused to the first set length; Step 3: Pass the light beam (10) through the light guide tube (3) to homogenize the light beam (10) in the slow axis (9) direction, and then guide the homogenized light beam (10) into the second lens group (4) for collimation, so that the light beam (10) is output parallel in the slow axis (9) direction; Step 4: Use the third lens group (5) to perform beam reduction processing on the beam (10) in the fast axis (8) direction, so that the focal point in the fast axis (8) direction is located before the focal point in the slow axis (9) direction in the beam transmission direction, thereby separating the focal point of the beam (10) in the fast axis (8) direction from the focal point in the slow axis (9) direction in the beam transmission direction, and making the spot size of the beam (10) transmitted from the input end to the output end of the slab crystal (7) in the fast axis (8) direction change within a set range to achieve uniform distribution of the beam; The transmission direction of the light beam (10) is perpendicular to the plane containing the fast axis (8) and the slow axis (9); Step 5: Use the fourth lens group (6) to refocus the beam (10) that has been collimated in the slow axis (9) direction, so that the size of the spot formed by the beam (10) output in parallel in the slow axis (9) direction is focused to the target set length. Step 6: Pump the slab crystal (7) using the beam (10) passing through the fourth lens group (6).

6. The beam shaping method based on independent fast and slow axis shaping and focus separation according to claim 5, characterized in that: The light spot formed by the beam (10) in the direction of the slow axis (9) has a first set length of 6-12 mm for focusing.

7. The beam shaping method based on independent fast and slow axis shaping and focus separation according to claim 6, characterized in that: The first set length of the light spot formed by the beam (10) in the slow axis (9) direction is 9 mm, and the height of the second lens group (4) is 76 mm.

8. The beam shaping method based on independent fast and slow axis shaping and focus separation according to claim 5, characterized in that: The size of the lath crystal (7) is 10mm×1mm×10mm; On the lath crystal (7), the size of the light spot formed by the cross section of the beam (10) in the fast axis (8) direction is 0.2-0.24 mm; On the lath crystal (7), the size of the light spot formed by the cross section of the beam (10) in the slow axis (9) direction is 10 mm.

9. The beam shaping method based on independent fast and slow axis shaping and focus separation according to claim 5, characterized in that: The divergence angle of the beam (10) in the slow axis (9) direction is 8°, and the divergence angle of the beam (10) in the fast axis (8) direction is 46°.

10. The beam shaping method based on independent fast and slow axis shaping and focus separation according to claim 5, characterized in that: The beam shaping system also includes a fast-axis collimating lens disposed in the fast-axis (8) direction.

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