A sleeve and a light homogenizing device

Abstract

This invention provides a sleeve and a beam homogenizing device, relating to the technical field of lasers. The sleeve is fitted onto the outside of a crystal rod. The inner wall of the sleeve cavity includes a plurality of reflective planes connected sequentially from end to end in the circumferential direction, and adjacent reflective planes are connected by a rounded corner, which protrudes in a direction away from the center of the sleeve. The number of reflective planes is odd. The center line of the rounded corner passes through and is perpendicular to a reflective plane opposite to it.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lasers, in particular to a sleeve and a light homogenizing device. BACKGROUND

[0002] With the development of high-power laser technology, lasers are increasingly widely used in industrial processing, medical and cosmetic treatment, scientific research and other fields. As a core component of the laser, the performance of the pump module directly affects the output quality of the laser. In the prior art, the end-pumped structure is widely used due to its high energy conversion efficiency, and its typical structure includes a glass sleeve, a plurality of lasers surrounding the outer side of the sleeve in the circumferential direction, and a gain medium (usually a Nd:YAG or Nd:YVO4 laser crystal rod) coaxially arranged at the center position inside the sleeve.

[0003] The working principle of such a pump module is that the pump light emitted by the laser enters the inner cavity through the glass sleeve and is finally absorbed by the central gain medium after multiple total reflections on the inner wall of the sleeve. The sleeve not only plays a protective role in this process, but also undertakes the function of homogenizing the light field. However, due to the limitations of the geometric shape and optical properties of the existing sleeve, the pump light is difficult to achieve ideal uniform distribution during transmission, resulting in the formation of a Gaussian-type light spot at the end face of the gain medium, as shown in FIG. 1. Such uneven pump distribution can cause problems such as thermal lens effect and thermal-induced birefringence, thereby affecting the beam quality and output power stability of the laser. Figure 1 SUMMARY

[0004] The purpose of the present application is to provide a sleeve and a light homogenizing device to alleviate the problem that it is difficult for laser to form a homogenized light spot in the crystal rod, which further leads to the formation of a Gaussian-type light spot at the end face of the gain medium, and such uneven pump distribution can cause problems such as thermal lens effect and thermal-induced birefringence.

[0005] In a first aspect, the present application provides a sleeve, which is sleeved on the outside of a crystal rod, and the inner wall of the sleeve cavity includes a plurality of reflection planes connected in sequence along the circumferential direction, and adjacent two reflection planes are connected by a round corner, and the round corner protrudes in a direction away from the center of the sleeve.

[0006] The number of reflection planes is odd; and the center line of the round corner passes through and is perpendicular to the reflection plane opposite to it.

[0007] Further, the ratio of the circumferential length of the reflection plane to the radius of the crystal rod is not greater than 2.

[0008] ​Further, when the number of the reflection planes is three, the ratio of the circumferential length of the reflection planes to the radius of the crystal rod is in the range of 0.725-2;

[0009] Or, when the number of the reflection planes is five, the ratio of the circumferential length of the reflection planes to the radius of the crystal rod is in the range of 1.45-1.975;

[0010] Or, when the number of the reflection planes is seven, the ratio of the circumferential length of the reflection planes to the radius of the crystal rod is in the range of 1.125-1.425.

[0011] Further, the ratio of the radius of the circular corner to the radius of the crystal rod is greater than or equal to 1:1.86.

[0012] Further, when the number of the reflection planes is three, the ratio of the radius of the circular corner to the radius of the crystal rod is 1:1.86;

[0013] Or, when the number of the reflection planes is five, the ratio of the radius of the circular corner to the radius of the crystal rod is 1:4.7;

[0014] Or, when the number of the reflection planes is seven, the ratio of the radius of the circular corner to the radius of the crystal rod is 1:8.89.

[0015] In the second aspect, the application provides a light homogenizing device, which comprises the sleeve.

[0016] The light homogenizing device further comprises a crystal rod and a plurality of lasers.

[0017] The crystal rod is arranged at the center of the inner cavity of the sleeve, and the crystal rod is coaxially arranged with the sleeve.

[0018] The lasers emit laser beams towards the circular corner, so that the laser beams pass through the sleeve and irradiate on the crystal rod.

[0019] Further, the divergence angle of the laser beams is set to be tangent to the crystal rod after passing through the circular corner.

[0020] Further, the reflection plane directly opposite to the circular corner is a first reflection plane, and the two reflection planes adjacent to the first reflection plane are a second reflection plane and a third reflection plane.

[0021] The two edge rays of the laser beams tangent to the crystal rod are incident on the second reflection plane and the third reflection plane respectively, and are reflected by the second reflection plane and the third reflection plane respectively and then enter the crystal rod.

[0022] Further, the radial distance between the outer wall of the crystal rod and the center point of the round corner is L2;

[0023] The radial distance between the outer wall of the crystal rod and the reflection plane is L1;

[0024] The value range of L2 / L1 is 1.45-2.7.

[0025] Further, when the number of the reflection planes is seven, the circumferential length of the reflection plane is 2.25mm;

[0026] The outer diameter of the sleeve is 9mm;

[0027] The diameter of the crystal rod is 4mm;

[0028] L1=3.4mm;

[0029] L2=3.77mm;

[0030] The radial distance between the laser and the center point of the round corner is 4.5mm;

[0031] The divergence angles of the fast axis and the slow axis of the laser are 70° and 10° respectively.

[0032] The present application has at least the following advantages or beneficial effects:

[0033] The sleeve provided by the present application is sleeved on the outside of the crystal rod, the inner wall of the lumen of the sleeve comprises a plurality of reflection planes connected in sequence in the circumferential direction, and two adjacent reflection planes are connected by a round corner, and the round corner protrudes in the direction away from the center of the sleeve; the number of the reflection planes is odd; the center line of the round corner passes through and is perpendicular to the reflection plane opposite to it.

[0034] The laser emitted by the laser passes through the sleeve and is irradiated to the round corner of the inner wall of the sleeve, the laser converges after passing through the round corner, and the laser is directly injected into the crystal rod inside the sleeve. The reflection plane can reflect the laser that does not enter the crystal rod and inject it into the crystal rod, so that all the laser is irradiated into the crystal rod, plays a homogenizing role, and converts Gaussian light into flat-top light. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the specific embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0036] Figure 1Light field distribution diagram of the crystal rod of the light homogenizing device with a cylindrical sleeve in the prior art;

[0037] Figure 2 Schematic diagram of the light homogenizing device provided by the embodiment of the present application;

[0038] Figure 3 Light field distribution diagram of the crystal rod of the light homogenizing device provided by the embodiment of the present application;

[0039] Figure 4 Optical simulation diagram of the light homogenizing device without the round corner in the sleeve in the comparative scheme;

[0040] Figure 5 Flare uniform distribution diagram of the light homogenizing device without the round corner in the sleeve in the comparative scheme;

[0041] Figure 6 Energy distribution diagram of the light homogenizing device without the round corner in the sleeve in the comparative scheme.

[0042] Legend: 1-sleeve; 11-reflective plane; 12-round corner; 2-crystal rod; 3-laser. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0044] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without making creative efforts fall within the scope of protection of the present application.

[0045] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0046] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention 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, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0047] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0048] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; 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; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0049] like Figure 1 As shown, the sleeve 1 provided by the present invention is sleeved on the outside of the crystal rod 2, and the two can be coaxially arranged. The cross-section of the outer wall of the sleeve 1 is circular. The inner wall of the sleeve 1 includes a plurality of reflective planes 11 connected sequentially from end to end along the circumference. The number of reflective planes 11 is odd, such as three, five or seven, so that the plurality of reflective planes 11 roughly form a triangle, pentagon or heptagon.

[0050] The ratio of the circumferential length of the reflecting plane 11 to the radius of the crystal rod 2 is no greater than 2. Specifically, in this embodiment, the diameter of the crystal rod is 4 mm. The circumferential length of any one of the reflecting planes 11 ranges from 1.45 mm to 4 mm. All reflecting planes 11 have the same circumferential length, or at least two reflecting planes 11 have different circumferential lengths. The fact that all reflecting planes 11 have the same circumferential length, combined with the transition fillet 12, allows the cross-section of the inner wall of the sleeve 1 to have a regular shape, such as approximately triangular, pentagonal, or heptagonal. This ensures that the light emitted by the lasers uniformly arranged at various positions on the outside of the sleeve 1 follows approximately the same path within the sleeve 1, thus ensuring that the amount of light incident on the crystal rod 2 from all directions is approximately the same.

[0051] In one embodiment, when the number of reflective planes 11 is three, the ratio of the circumferential length of the reflective plane 11 to the radius of the crystal rod 2 ranges from 0.725 to 2; or, when the number of reflective planes 11 is five, the ratio of the circumferential length of the reflective plane 11 to the radius of the crystal rod 2 ranges from 1.45 to 1.975; or, when the number of reflective planes 11 is seven, the ratio of the circumferential length of the reflective plane 11 to the radius of the crystal rod 2 ranges from 1.125 to 1.425.

[0052] When there are three reflective planes 11, the circumferential length of the reflective plane 11 is 1.45 mm - 4 mm. When there are five reflective planes 11, the circumferential length of the reflective plane 11 is 2.9 mm - 3.95 mm. When there are seven reflective planes 11, the circumferential length of the reflective plane 11 is 2.25 mm - 2.85 mm.

[0053] Two adjacent reflective planes 11 are connected by a fillet 12, and the fillet 12 protrudes in a direction away from the center of the sleeve 1. The center line of the fillet 12 ( Figure 2 The dotted line in the image passes through and is perpendicular to a reflection plane 11 opposite to it (i.e., each rounded corner 12 is provided with a unique corresponding reflection plane 11, and the center line of the rounded corner 12 is perpendicular to the reflection plane 11 provided with it). The two edges (i.e. edge rays) of the laser emitted from the center of the rounded corner 12 are tangent to the two outer walls of the crystal rod 2, and are directed toward two spaced reflection planes 11 (i.e., the second reflection plane and the third reflection plane). The reflection planes 11 reflect the laser back into the crystal rod 2.

[0054] In one embodiment, the ratio of the radius of curvature of the fillet 12 to the radius of the crystal rod 2 is greater than or equal to 1:1.86.

[0055] In one embodiment, when the number of reflective planes 11 is three, the ratio of the radius of curvature of the fillet 12 to the radius of the crystal rod 2 is 1:1.86; or, when the number of reflective planes 11 is five, the ratio of the radius of curvature of the fillet 12 to the radius of the crystal rod 2 is 1:4.7; or, when the number of reflective planes 11 is seven, the ratio of the radius of curvature of the fillet 12 to the radius of the crystal rod 2 is 1:8.89.

[0056] This application employs a combined design of a reflective plane 11 and a rounded corner 12, which significantly increases the adjustment range of the rounded corner 12. With a crystal rod 2 diameter of 4mm, the radius of curvature of the rounded corner 12 ranges from 0.2mm to 3mm, with a minimum adjustable value of 0.2mm. In existing sleeve 1 designs, the inner wall is circular, and the minimum radius of curvature is limited to the same as that of the crystal rod 2 (i.e., 2mm), restricting further miniaturization. In contrast, the sleeve 1 design in this embodiment allows for a wider range of control over the radius of curvature, thereby overcoming the aforementioned limitations.

[0057] When there are three reflective planes 11, the radius of curvature of the fillet 12 ranges from 1.3 mm to 3 mm; when there are five reflective planes 11, the radius of curvature of the fillet 12 ranges from 0.5 mm to 1.2 mm; when there are seven reflective planes 11, the radius of curvature of the fillet 12 ranges from 0.2 mm to 0.7 mm.

[0058] The sleeve 1 can be made of a material with a higher refractive index than quartz, preferably sapphire.

[0059] The laser emitted by the laser passes through the sleeve 1 and illuminates the rounded corner 12 on the inner wall of the sleeve 1. After passing through the rounded corner 12, the laser beam converges and directly enters the crystal rod 2 inside the sleeve 1. The reflecting plane 11 reflects any laser beam that does not enter the crystal rod 2 and directs it into the crystal rod 2, thus ensuring that all the laser beam illuminates the crystal rod 2, achieving a homogenization effect and converting the Gaussian light into a flat-top light, such as... Figure 3 As shown.

[0060] Furthermore, if only reflective planes 11 are provided in the sleeve 1, and the reflective planes 11 are not connected by fillets 12, the sleeve 1 without fillets 12 (e.g., a quartz tube) approximates a prism. When light enters the cooling medium (which is placed between the crystal rod 2 and the sleeve 1) from the sleeve 1, it satisfies Snell's law of refraction. That is, when the incident light rays exit from the high refractive index quartz into the low refractive index cooling medium, the light rays will be refracted to the sides deviating from the center of the crystal rod 2, resulting in no light rays entering the center of the crystal rod 2. Ultimately, the absorption distribution will show a situation where there is no light in the center, such as... Figures 4-6 As shown.

[0061] The light homogenizing device provided by the present invention includes the aforementioned sleeve 1; the light homogenizing device also includes a crystal rod 2 and a plurality of lasers 3; the crystal rod 2 is disposed at the center of the inner cavity of the sleeve 1, and the crystal rod 2 is coaxially disposed with the sleeve 1; the lasers 3 emit lasers toward the rounded corner 12 so that the lasers pass through the sleeve 1 and irradiate the crystal rod 2.

[0062] Cooling media with a refractive index higher than water, such as coolant, inert gas, or nitrogen, can be introduced into the space between the sleeve 1 and the crystal rod 2 to achieve heat dissipation.

[0063] Preferably, the doping concentration of the crystal rod 2 is 0.6%.

[0064] The line connecting the axis of the laser emitted by laser 3 and the center of the crystal rod passes through the center of the rounded corner. The divergence angle of the laser is set such that the edge ray of the laser after passing through the rounded corner 12 is tangent to the crystal rod 2. This ensures that all the light emitted by the laser enters the crystal rod uniformly, and that all areas of the crystal rod 2 are completely covered by the laser, maximizing laser utilization.

[0065] To further increase utilization, the reflecting plane 11 directly opposite the rounded corner 12 is designated as the first reflecting plane, and the two reflecting planes 11 adjacent to the first reflecting plane are designated as the second and third reflecting planes. Two edge rays of the laser tangent to the crystal rod 2 are respectively irradiated onto the second and third reflecting planes and reflected into the crystal rod 2. Since the edge rays enter the crystal rod 2 after only one reflection, the light loss is low, and most of the light enters the crystal rod 2, thus improving utilization.

[0066] To achieve tangency, the radial distance between the outer wall of the crystal rod 2 and the center point of the fillet 12 is L2; ​​the radial distance between the outer wall of the crystal rod 2 and the reflecting plane 11 is L1; the value range of L2 / L1 is 1.45-2.7. In the verified scheme, the following parameters can achieve tangency: the number of reflecting planes 11 is seven, the circumferential length of the reflecting planes 11 is 2.25 mm; the outer diameter of the sleeve 1 is 9 mm; the diameter of the crystal rod 2 is 4 mm; L1 = 3.4 mm; the value range of L2 is 3.77 mm. The radial distance between the laser 3 and the center point of the fillet 12 is 4.5 mm; the divergence angles of the fast axis and slow axis of the laser 3 are 70° and 10°, respectively.

[0067] To achieve proper matching between the sleeve 1 and the crystal rod, ensuring sufficient laser incidence into the crystal rod, the ratio of the radius of curvature of the fillet 12 to the radius of the crystal rod 2 is set to be greater than or equal to 1:1.86. In other feasible implementations, when the number of reflecting planes 11 is three, the ratio of the radius of curvature of the fillet 12 to the radius of the crystal rod 2 is 1:1.86. When the number of reflecting planes 11 is five, the ratio of the radius of curvature of the fillet 12 to the radius of the crystal rod 2 is 1:4.7. In this embodiment, when the number of reflecting planes 11 is seven, the ratio of the radius of curvature of the fillet 12 to the radius of the crystal rod 2 is 1:8.89.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A light homogenizing device, characterized in that, The uniform light device comprises a sleeve (1) sleeved on the outside of a crystal rod (2), the inner wall of the sleeve (1) comprises a plurality of reflection planes (11) connected in sequence along the circumference, and two adjacent reflection planes (11) are connected by a round corner (12) which protrudes towards the direction away from the center of the sleeve (1); The number of the reflection planes (11) is odd; the center line of the round corner (12) passes through and is perpendicular to the reflection plane (11) opposite to it; The uniform light device further comprises the crystal rod (2) and a plurality of lasers (3); The crystal rod (2) is arranged at the center position of the inner cavity of the sleeve (1), and the crystal rod (2) is coaxially arranged with the sleeve (1); The lasers (3) emit laser beams towards the round corner (12) so that the laser beams pass through the sleeve (1) and irradiate on the crystal rod (2); The divergence angle of the laser beams is set to be tangent to the crystal rod (2) after passing through the round corner (12).

2. The light uniformizing device according to claim 1, characterized in that The ratio of the circumferential length of the reflection plane (11) to the radius of the crystal rod (2) is not greater than 2.

3. The light uniformizing device according to claim 2, characterized in that When the number of the reflection planes (11) is three, the ratio of the circumferential length of the reflection plane (11) to the radius of the crystal rod (2) is in the range of 0.725-2; Or, when the number of the reflection planes (11) is five, the ratio of the circumferential length of the reflection plane (11) to the radius of the crystal rod (2) is in the range of 1.45-1.975; Or, when the number of the reflection planes (11) is seven, the ratio of the circumferential length of the reflection plane (11) to the radius of the crystal rod (2) is in the range of 1.125-1.

425.

4. The light homogenizing device according to any of claims 1 to 3, characterized in that The ratio of the curvature radius of the round corner (12) to the radius of the crystal rod (2) is greater than or equal to 1:1.

86.

5. The light homogenizing device of claim 4, wherein When the number of the reflection planes (11) is three, the ratio of the curvature radius of the round corner (12) to the radius of the crystal rod (2) is 1:1.86; Or, when the number of the reflection planes (11) is five, the ratio of the curvature radius of the round corner (12) to the radius of the crystal rod (2) is 1:4.7; Or, when the number of the reflection planes (11) is seven, the ratio of the curvature radius of the round corner (12) to the radius of the crystal rod (2) is 1:8.

89.

6. The light uniformizing device according to claim 1, characterized in that The reflection plane (11) directly opposite to the round corner (12) is a first reflection plane, and the two reflection planes (11) adjacent to the first reflection plane are a second reflection plane and a third reflection plane; Two edge light rays of the laser beam tangent to the crystal rod (2) are incident on the second reflection plane and the third reflection plane respectively, and are reflected by the second reflection plane and the third reflection plane respectively and then enter the crystal rod (2).

7. The light uniformizing device according to claim 1 or 6, characterized in that The radial distance between the outer wall of the crystal rod (2) and the center point of the round corner (12) is L2; The radial distance between the outer wall of the crystal rod (2) and the reflection plane (11) is L1; The value range of L2 / L1 is 1.45-2.

7.

8. The light uniformizing device according to claim 1 or 6, characterized by The radial distance between the outer wall of the crystal rod (2) and the center point of the round corner (12) is L2; The radial distance between the outer wall of the crystal rod (2) and the reflection plane (11) is L1; When the number of the reflection planes (11) is seven, the circumferential length of the reflection plane (11) is 2.25 mm; The outer diameter of the sleeve (1) is 9 mm; The diameter of the crystal rod (2) is 4 mm; L1=3.4 mm; L2=3.77 mm; The radial distance between the laser (3) and the center point of the round corner (12) is 4.5 mm; The divergence angles of the fast axis and the slow axis of the laser (3) are 70° and 10°, respectively.

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