Laser resonant cavity capable of directly generating special light beam mode and application thereof

Abstract

The invention relates to a laser resonant cavity capable of directly generating a special light beam mode and application thereof. The laser resonant cavity comprises a total reflection cavity mirror and an output cavity mirror which are arranged at an interval, the total reflection cavity mirror and the output cavity mirror are coaxially arranged along an optical axis to form a negative-branch confocal unstable cavity; the inner mirror surface of the total reflection cavity mirror is designed into a curved surface A, the curved surface A is formed by rotating a curve with the curvature radius of RA around the optical axis by a circle, the inner mirror surface of the output cavity mirror is designed into a curved surface B, and the curved surface B is formed by rotating a curve with the curvature radius of RB around the optical axis by a circle; and the center of the output cavity mirror is provided with a laser output port. An existing thought of obtaining a special light beam mode through extra-cavity shaping is overturned, the special light beam mode can be directly output through optimization design of structures and parameters of the total reflection cavity mirror and the output cavity mirror, and therefore the urgent requirements for special light beams in the current fields of laser drilling, cutting, welding, cladding and the like are met.

Description

Technical field:

[0001] The invention relates to the technical field of lasers, and in particular to a laser resonant cavity for directly generating a special light beam mode and applications thereof. Background technology:

[0002] Carbon dioxide lasers have the advantages of high power, efficient energy conversion, high beam quality, rich spectrum lines and tunability, so they are widely used in national economy and national defense, such as welding, cutting, drilling, communications, laser-induced chemical reactions, and surgical operations.

[0003] As the demand for laser output modes in related fields such as laser drilling, cutting, welding, and cladding continues to increase. At present, the Gaussian beam output by the RF slab carbon dioxide laser is not enough to meet the application requirements. The lateral light field distribution intensity of the Gaussian beam is strong in the center and gradually weakens on both sides, with obvious "two wings". This uneven energy distribution will cause the temperature in the center area to be too high, causing local overheating of the workpiece. At the same time, the heat-affected zone is large, the processing quality and precision are limited, and the excessive concentration of central energy will easily damage the optical device. Therefore, some special beam modes are usually used in the field of industrial processing, such as annular beams or flat-top beams. The center of the annular beam has low intensity or almost no light intensity, and a concentric ring-shaped high-intensity area is formed around it; the flat-top beam has a flat and stable energy distribution, and its energy is mainly concentrated in the top area, without obvious "two wings".

[0004] The most commonly used technology to generate annular beams or flat-top beams in the existing CO2 laser field is beam shaping, that is, to perform extracavity shaping transformation on the Gaussian beam through a specific optical element or system to obtain special beam mode distributions such as flat-top beams or annular beams. However, the existing extracavity shaping transformation method requires complex optical design and precision machining, which is costly, and introduces more additional optical losses during the shaping process, which greatly affects the output power and efficiency of the laser.

[0005] It should be noted that the above contents belong to the technical knowledge of the inventor and do not necessarily constitute prior art. Summary of the invention:

[0006] The purpose of the present invention is to solve the problems existing in the prior art, to provide a laser resonant cavity and its application for directly generating a special beam mode, to overturn the existing design concept of obtaining a special beam mode by extra-cavity shaping, and to realize the direct output of a ring beam by the laser resonant cavity through improved design of a total reflection cavity mirror and an output cavity mirror.

[0007] The present invention achieves the above-mentioned purpose by adopting the following technical solutions:

[0008] A laser resonant cavity that directly generates a special beam mode comprises a total reflection cavity mirror and an output cavity mirror that are arranged at intervals; the total reflection cavity mirror and the output cavity mirror are coaxially arranged along the optical axis to form a negative branch confocal unstable cavity; the inner mirror surface of the total reflection cavity mirror is designed to be a curved surface A, and the curved surface A is composed of a curvature radius of R A The curve is formed by rotating one circle around the optical axis, and the inner mirror surface of the output cavity mirror is designed to be a curved surface B, and the curved surface B is formed by a curvature radius of R B The curve is formed by rotating one circle around the optical axis; a laser output port is arranged at the center of the output cavity mirror.

[0009] The laser resonant cavity is axially symmetrically distributed along two sides of the optical axis, and a negative-branch unstable cavity structure is formed on each side.

[0010] The outer mirror surface of the output cavity mirror is chamfered corresponding to the laser output port.

[0011] The surfaces of the curved surface A and the curved surface B are plated with a high-reflection film, and the reflectivity of the high-reflection film is greater than 99.9%.

[0012] The curved surface A and the curved surface B are spherical surfaces.

[0013] The total reflection cavity mirror and the output cavity mirror are designed to be circular, the laser output port is designed to be circular, and the correspondingly formed laser resonant cavity is a circular laser resonant cavity.

[0014] The total reflection cavity mirror and the output cavity mirror are designed to be in a bar shape, and the laser output port is designed to be in a bar shape, and the correspondingly formed laser resonant cavity is a bar-shaped laser resonant cavity.

[0015] Application of laser resonators that directly generate special beam modes, such as the application of circular laser resonators in waveguide gas lasers, glass tube gas lasers or rod-shaped solid lasers as mentioned above; application of strip-shaped laser resonators in solid-state slab lasers or radio frequency slab carbon dioxide lasers as mentioned above.

[0016] The present invention adopts the above method to bring the following beneficial effects:

[0017] By improving and optimizing the structure of the total reflection cavity mirror and the output cavity mirror, it is possible to directly generate a special mode laser intensity distribution by adjusting the corresponding parameters, without the need for complex external optical path shaping, with high integration and easy adjustment. At the same time, the size of the minimum intensity point at the center of the annular beam distribution can be adjusted according to the application scenario. This solution can be applied to medium and high power lasers to meet the urgent needs of special beams such as annular beams or flat-top beams in the current fields of laser drilling, cutting, welding, cladding, etc. Description of the drawings:

[0018] Figure 1 Schematic diagram of the optical path of the laser resonant cavity of the present invention;

[0019] Figure 2 This is a front view of the total reflection cavity mirror of Example 1 of the present invention;

[0020] Figure 3 for Figure 2 AA section view in the figure;

[0021] Figure 4 Outputting the main view of the cavity mirror in Example 1 of the present invention;

[0022] Figure 5 for Figure 4 BB section view;

[0023] Figure 6 is a stereoscopic diagram of a total reflection cavity mirror according to embodiment 2 of the present invention;

[0024] Figure 7 This is a front view of the total reflection cavity mirror of Example 2 of the present invention;

[0025] Figure 8 for Figure 7 CC section view;

[0026] Fig. 9 Outputting a stereoscopic image of the cavity mirror in Example 2 of the present invention;

[0027] Fig.10 Outputting the main view of the cavity mirror in Example 2 of the present invention;

[0028] Fig.11 for Fig.10 DD section view in;

[0029] Fig.12 This is a schematic diagram of a circular laser resonant cavity directly outputting an annular light beam according to Embodiment 1 of the present invention;

[0030] Fig.13 This is a schematic diagram of a strip-shaped laser resonant cavity directly outputting a ring-shaped light beam according to Embodiment 2 of the present invention;

[0031] In the figure, 1. total reflection cavity mirror, 2. output cavity mirror, 3. optical axis, 4. curved surface A, 5. curved surface B, 6. laser output port, 7. chamfer. Specific implementation method:

[0032] In order to more clearly illustrate the overall concept of the present invention, a detailed description is given below in an exemplary manner in conjunction with the accompanying drawings.

[0033] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0034] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0035] Example 1

[0036] like Figure 1-5 As shown, a laser resonant cavity that directly generates a special beam mode includes a total reflection cavity mirror 1 and an output cavity mirror 2 that are spaced apart; the total reflection cavity mirror 1 and the output cavity mirror 2 are coaxially arranged along an optical axis 3 to form a negative branch confocal unstable cavity; the inner mirror surface of the total reflection cavity mirror 1 is designed to be a curved surface A4, and the curved surface A4 is composed of a curvature radius of R A The curve is formed by rotating one circle around the optical axis 3, and the inner mirror surface of the output cavity mirror 2 is designed to be a curved surface B5, and the curved surface B5 is formed by a curvature radius R B The curve is formed by rotating one circle around the optical axis; a laser output port 6 is provided at the center of the output cavity mirror 2. It subverts the existing idea of ​​obtaining special beam modes through extra-cavity shaping. By improving and optimizing the structure of the total reflection cavity mirror and the output cavity mirror, it is possible to directly output the special mode laser intensity distribution by adjusting the corresponding parameters, without the need for complex external optical path shaping, with high integration and easy adjustment. At the same time, the size of the minimum intensity point at the center of the annular beam distribution can be adjusted according to the application scenario. This solution can be applied to medium and high power lasers to meet the urgent needs of special beams such as annular beams or flat-top beams in the current fields of laser drilling, cutting, welding, cladding, etc.

[0037] The laser resonant cavity is axially symmetrically distributed along the two sides of the optical axis 3, and a negative branch unstable cavity structure is formed on each side. The beam intensity distribution is more uniform and reasonable.

[0038] The outer mirror surface of the output cavity mirror 2 is chamfered 7 at a position corresponding to the laser output port 6 to avoid reflection on the inner wall of the laser output port 6 to interfere with normal light beam output.

[0039] The surfaces of the curved surface A4 and the curved surface B5 are coated with a high-reflection film, and the reflectivity of the high-reflection film is greater than 99.9%, providing reliable reflection.

[0040] The curved surface A4 and the curved surface B5 are spherical surfaces, which are easy to process and control and adjust.

[0041] The total reflection cavity mirror 1 and the output cavity mirror 2 are designed to be circular, and the laser output port 6 is designed to be circular, and the correspondingly formed laser resonant cavity is a circular laser resonant cavity.

[0042] Application of laser resonators that directly generate special beam modes, such as the application of circular laser resonators in waveguide gas lasers (CO2 lasers), glass tube gas lasers or rod-shaped solid-state lasers (such as Nd:YAG lasers) as mentioned above.

[0043] Example 2

[0044] The difference between this embodiment and embodiment 1 is that:

[0045] like Figure 6-11 As shown, the total reflection cavity mirror 1 and the output cavity mirror 2 are designed to be strip-shaped, the laser output port 6 is designed to be strip-shaped, and the correspondingly formed laser resonant cavity is a strip-shaped laser resonant cavity.

[0046] The application of laser resonant cavities that directly generate special beam modes, such as the application of strip laser resonant cavities in solid-state slab lasers or RF slab CO2 lasers as mentioned above. It should be noted that due to the particularity of slab structure lasers, the resonant cavity is unstable in one direction and unstable-waveguide hybrid cavity in the other direction. In addition to the characteristics of reduced central light intensity, the output beam also exhibits astigmatism. Therefore, the directly generated beam needs to undergo simple optical shaping before it can be used. This is a step that all slab structure lasers must complete.

[0047] Experimental part:

[0048] Setting: The cavity length of the laser resonant cavity is L, the intracavity magnification is M, The radius of the laser output port in the circular laser resonant cavity is r, and the length of the laser output port in the strip laser resonant cavity is a and the width is b.

[0049] like Fig.12 The following is an experiment of using a circular laser resonator to directly output a special beam mode:

[0050] Figure (a) is a special beam mode (i.e., annular beam), the left figure of Figure (a) is a schematic diagram of beam intensity distribution, and the right figure is a schematic diagram of two-dimensional beam intensity distribution. The corresponding parameters are:

[0051] L=865mm, R A =906.2mm, R B =823.8mm, M=1.1, r=4mm;

[0052] Figure (b) is a special beam mode (i.e., annular beam), and the corresponding parameters are:

[0053] L=865mm, R A =935mm, R B =795mm, M=1.18, r=6.6mm;

[0054] Figure (c) shows a special beam mode (i.e., annular beam), and the corresponding parameters are:

[0055] L=865mm, RA =1038mm, R B =692mm, M=1.5, r=14.7mm.

[0056] like Fig.13 The following is an experiment of using a strip laser resonator to directly output a ring beam:

[0057] Figure (a) is a special beam mode (i.e., strip beam), and the corresponding parameters are:

[0058] L=865mm, R A =906.2mm, R B =823.8mm, M=1.1, a=13.2mm, b=5mm;

[0059] Figure (b) is a special beam mode (i.e., strip beam), and the corresponding parameters are:

[0060] L=865mm, R A =935mm, R B =795mm, M=1.18, a=13.2mm, b=5mm;

[0061] Figure (c) shows a special beam mode (i.e., a strip beam), and the corresponding parameters are:

[0062] L=865mm, R A =1038mm, R B =692mm, M=1.5, a=29.4mm, b=5mm.

[0063] It can be seen from the above experiments that the laser resonant cavity of the present application can directly output a special beam mode in the cavity by adjusting parameters.

[0064] The above specific implementation manner cannot be used as a limitation on the protection scope of the present invention. For those skilled in the art, any substitution, improvement or change made to the implementation manner of the present invention falls within the protection scope of the present invention.

[0065] The matters not described in detail in the present invention are all known technologies to those skilled in the art.

Claims

1. A laser resonant cavity that directly generates a special beam mode, comprising a total reflection cavity mirror and an output cavity mirror arranged at intervals, characterized in that: The total reflection cavity mirror and the output cavity mirror are coaxially arranged along the optical axis to form a negative branch confocal unstable cavity; the inner mirror surface of the total reflection cavity mirror is designed to be a curved surface A, and the curved surface A is composed of a curvature radius of R A The curve is formed by rotating one circle around the optical axis, and the inner mirror surface of the output cavity mirror is designed to be a curved surface B, and the curved surface B is formed by a curvature radius of R B The curve is formed by rotating one circle around the optical axis; a laser output port is arranged at the center of the output cavity mirror.

2. The laser resonant cavity for directly generating a special beam mode according to claim 1, characterized in that: The laser resonant cavity is axially symmetrically distributed along two sides of the optical axis, and a negative-branch unstable cavity structure is formed on each side.

3. The laser resonant cavity for directly generating a special beam mode according to claim 1 or 2, characterized in that: The outer mirror surface of the output cavity mirror is chamfered corresponding to the laser output port.

4. The laser resonant cavity for directly generating a special beam mode according to claim 3, characterized in that: The surfaces of the curved surface A and the curved surface B are plated with a high-reflection film, and the reflectivity of the high-reflection film is greater than 99.9%.

5. The laser resonant cavity for directly generating a special beam mode according to claim 4, characterized in that: The curved surface A and the curved surface B are spherical surfaces.

6. The laser resonant cavity for directly generating a special beam mode according to claim 5, characterized in that: The total reflection cavity mirror and the output cavity mirror are designed to be circular, the corresponding laser output port is designed to be circular, and the correspondingly formed laser resonant cavity is a circular laser resonant cavity.

7. The laser resonant cavity for directly generating a special beam mode according to claim 5, characterized in that: The total reflection cavity mirror and the output cavity mirror are designed to be in a bar shape, and the laser output port is designed to be in a bar shape, and the correspondingly formed laser resonant cavity is a bar-shaped laser resonant cavity.

8. Use of the circular laser resonant cavity as claimed in claim 6 in a waveguide gas laser, a glass tube gas laser or a rod-shaped solid laser.

9. Use of the strip laser resonant cavity as claimed in claim 7 in a solid-state slab laser or a radio frequency slab carbon dioxide laser.

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