Amplifier structure with high light beam quality

Abstract

The invention provides an amplifier structure with high light beam quality, and belongs to the technical field of light path packaging structures. Comprising a beam combining unit used for combining trunk input light and bypass pump light and then outputting the combined light; the input end of the at least one amplification unit is connected with the output end of the beam combining unit through a light path, and the output end of the at least one amplification unit is connected with the input end of the cladding light stripping unit through a light path; the output end of the cladding light stripping unit is in light path connection with the input end of at least one output unit, and the output end of the output unit outputs an amplified laser beam; each amplification unit comprises a first passive optical fiber section, a second passive optical fiber section and an active optical fiber, one end of the first passive optical fiber section is connected with the output end of the beam combining unit, and one end of the second passive optical fiber section is connected with the input end of the cladding light stripping unit; a passive optical fiber is arranged between the other end of the first passive optical fiber section and the other end of the second passive optical fiber section; and at least one tapering section is arranged on the active optical fiber.

Description

Technical Field

[0001] The invention relates to the technical field of optical path packaging structures, and in particular to an amplifier structure with high light beam quality. Background Art

[0002] Conventional 30 / 250 fiber fusion splicing and 50 / 400 fiber fusion splicing sometimes use direct fusion splicing, which has poor splicing effect, serious beam quality degradation, and when the external return light is strong, heat accumulation is easy to occur at the cladding docking 400-250 position, thus causing fiber fuse phenomenon, that is, after a strong laser beam is incident from one end of the fiber, the other end burns. In order to optimize the beam quality of the laser output, reverse pumping is usually selected, but the beam combiner itself will cause degradation to the beam transmission and is difficult to control.

[0003] Based on the above defects, it is very necessary to propose an amplifier structure with high beam quality, which can avoid fiber melting by slowing down the change trend between the cladding and the core, and at the same time improve the influence of the combiner on signal injection and improve the light output quality of the laser. Summary of the invention

[0004] In view of this, the present invention proposes an amplifier structure with high beam quality that improves the degradation of the injected beam, adopts a specific winding structure to sequentially transition optical fibers with different core diameters to achieve maximum control of the beam quality, and improves the degradation of the laser M2 caused by the core diameter change by tapering.

[0005] The present invention provides an amplifier structure with high beam quality, comprising a beam combining unit, at least one amplifying unit, a cladding light stripping unit and an output unit;

[0006] A beam combining unit is used to combine the main input light and the bypass pump light and then output them; the input end of at least one amplifying unit is optically connected to the output end of the beam combining unit, and the output end of at least one amplifying unit is optically connected to the input end of the cladding light stripping unit; the output end of the cladding light stripping unit is optically connected to the input end of at least one output unit, and the output end of the output unit outputs the amplified laser beam;

[0007] Among them, at least one amplification unit includes a first passive optical fiber segment, a second passive optical fiber segment and an active optical fiber, one end of the first passive optical fiber segment is connected to the output optical path of the beam combining unit, and one end of the second passive optical fiber segment is connected to the input optical path of the cladding light stripping unit; a passive optical fiber is arranged between the other end of the first passive optical fiber segment and the other end of the second passive optical fiber segment; and at least one tapered segment is arranged on the active optical fiber.

[0008] On the basis of the above technical scheme, preferably, the number of amplifying units is two or three; in the amplifying unit close to the head end of the beam combining unit, the first passive optical fiber segment is optically connected to the output end of the beam combining unit and one end of the active optical fiber of the current amplifying unit, and the second passive optical fiber segment is optically connected to the other end of the active optical fiber and one end of the first passive optical fiber segment of the subsequent amplifying unit; in the amplifying unit close to the end of the cladding light stripping unit, the second passive optical fiber segment is optically connected to one end of the active optical fiber of the current amplifying unit and the input end of the cladding light stripping unit.

[0009] Preferably, the first passive optical fiber segment, the second passive optical fiber segment and the active optical fiber in at least one amplifying unit all have a coiled structure.

[0010] Further preferably, the winding structures of the first passive optical fiber segment, the second passive optical fiber segment and the active optical fiber each include a first arc segment, a second arc segment, a third arc segment and a fourth arc segment; the first arc segment and the second arc segment are symmetrically arranged, and both the first arc segment and the second arc segment are provided with openings; the third arc segment and the fourth arc segment are respectively arranged between the first arc segment and the second arc segment, the third arc segment is respectively arranged tangent to one end of the openings of the first arc segment and the second arc segment, and the fourth arc segment is respectively arranged tangent to the other end of the openings of the first arc segment and the second arc segment; the centers of the third arc segment and the fourth arc segment are both far away from the openings.

[0011] More preferably, the radii of the first arc segment and the second arc segment are the same, and the distance between the centers of the first arc segment and the second arc segment is greater than the radius of the first arc segment; and the center angles of the third arc segment and the fourth arc segment do not exceed 90°.

[0012] Still further preferably, the active optical fiber comprises a first active segment, a second active segment and a first tapered segment, the first active segment and the second active segment have different diameters, one end of the first active segment is fused to one end of the first passive optical fiber segment away from the beam combining unit, and the other end of the first active segment is optically connected to one end of the first tapered segment; one end of the second active segment is optically connected to the other end of the first tapered segment, and the other end of the second active segment is optically connected to one end of the second passive optical fiber segment away from the cladding light stripping unit; the diameter of the first active segment is the same as the diameter of the small diameter end of the first tapered segment, and the diameter of the second active segment is the same as the diameter of the large diameter end of the first tapered segment.

[0013] More preferably, it also includes a second tapered section, which is arranged between one end of the second active section away from the first active section and one end of the second passive optical fiber section away from the first tapered section; one end of the second tapered section is optically connected to the second active section, and the other end of the second tapered section is optically connected to the input end of the second passive optical fiber section, and the diameter of the large diameter end of the second tapered section is the same as the diameter of the second active section, and the small diameter end of the second tapered section is the same as the diameter of the second passive optical fiber section.

[0014] Further preferably, in each amplification unit, the energies of the first active segments and the second active segments that transition and amplify along the laser output direction are E1, E2, …, E n respectively; the core diameters of the first active segments and the second active segments that extend along the laser output optical path direction in each amplification unit are R1, R2, R3, …, R n-1 , R n , satisfying i = 1, 2, …, n, E max is the maximum output energy of the laser.

[0015] Further preferably, the lengths of the first active segments and the second active segments sequentially arranged along the laser output optical path direction are L1, L2, …, L m respectively; the absorption coefficients of the first active segments and the second active segments sequentially arranged along the laser output optical path direction are η1, η2, …, ηm respectively, satisfying 14 dB < L1η1 + L2η2 + … + L m η m < 20 dB.

[0016] Further preferably, the taper region lengths of the first tapered segments and the second tapered segments along the laser output direction are d1, d2, …, d k-1 , d k , j = 1, 2, …, k, j < n; the taper region lengths of each tapered segment satisfy the following relationship:

[0017] An amplifier structure with high beam quality provided by the present invention has the following beneficial effects compared with the prior art:

[0018] (1) The main part of the present invention combines active fiber segments and passive fibers with different core diameters, and controls the beam quality to the greatest extent through the amplification ratios of the fibers with different core diameters. At the same time, from the perspectives of improving the degradation of the injected beam of the combiner and improving the numerical aperture of the fiber, the structure of the internal devices of the amplifier is improved, thereby improving the beam quality of the laser output;

[0019] (2) By means of tapering, the change trend between the core and the cladding is slowed down. The external return light will gradually be transmitted to the middle region of the cladding during the return process, and by limiting the taper region length of the taper, it is also possible to protect the beam quality from sudden deterioration, thereby being beneficial to improving the beam quality of the laser output. Description of the Drawings

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 A structural block diagram of an amplifier structure with high beam quality according to the present invention;

[0022] Figure 2 A schematic diagram of the internal structure of an amplifier unit of an amplifier structure with high beam quality according to the present invention;

[0023] Figure 3 An embodiment of an amplifying unit of an amplifier structure with high beam quality of the present invention;

[0024] Figure 4 The present invention is a schematic diagram of a winding structure of a first passive optical fiber segment, a second passive optical fiber segment or a passive optical fiber of an amplifier structure with high beam quality.

[0025] Reference numerals: 1, beam combining unit; 2, amplifying unit; 3, cladding light stripping unit; 4, output unit; 21, first passive optical fiber segment; 22, second passive optical fiber segment; 23, active optical fiber; 231, first active segment; 232, second active segment; 233, first tapered segment; 234, second tapered segment;

[0026] 100, first arc segment; 200, second arc segment; 300, third arc segment; 400, fourth arc segment. DETAILED DESCRIPTION

[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Active gain fibers with different core diameters can be directly spliced. On the one hand, the splicing effect is poor, the beam quality is seriously degraded, and the fiber may melt. In view of this, if Figure 1 and Figure 2 As shown, the present invention provides an amplifier structure with high beam quality, comprising a beam combining unit 1, at least one amplifying unit 2, a cladding light stripping unit 3 and an output unit 4;

[0029] The beam combining unit 1 is used to combine the main input light and the bypass pump light and then output them; the input end of at least one amplifying unit 2 is optically connected to the output end of the beam combining unit 1, and the output end of at least one amplifying unit 2 is optically connected to the input end of the cladding light stripping unit 3; the output end of the cladding light stripping unit 3 is optically connected to the input end of at least one output unit 4, and the output end of the output unit 4 outputs the amplified laser beam; in order to improve the problem of beam quality degradation, the suitable unit 1 of the present invention adopts a forward pumping method to improve the influence of the beam combining unit on signal injection.

[0030] Among them, at least one amplification unit 2 includes a first passive optical fiber segment 21, a second passive optical fiber segment 22 and an active optical fiber 23, one end of the first passive optical fiber segment 21 is connected to the output optical path of the beam combining unit, and one end of the second passive optical fiber segment 22 is connected to the input optical path of the cladding light stripping unit 3; an active optical fiber 23 is arranged between the other end of the first passive optical fiber segment 21 and the other end of the second passive optical fiber segment 22; and at least one tapered segment is arranged on the active optical fiber 23.

[0031] During the amplification process of the amplification unit 2, the maximum control of the beam quality is achieved by using optical fiber transitions with different core diameters, but a tapered section is used to improve the degradation of the laser output beam M2 caused by the core diameter change and eliminate the fiber melting phenomenon.

[0032] like Figure 1 Combination Figure 2 As shown, specifically, the number of the amplifying units 2 is two or three; in the amplifying unit 2 near the head end of the beam combining unit 1, the first passive optical fiber segment 21 is optically connected to the output end of the beam combining unit 1 and one end of the active optical fiber 23 of the current amplifying unit 2, respectively, and the second passive optical fiber segment 22 is optically connected to the other end of the active optical fiber 23 and one end of the first passive optical fiber segment 21 of the subsequent amplifying unit 2; in the amplifying unit 2 near the end of the cladding light stripping unit 3, the second passive optical fiber segment 22 is optically connected to one end of the active optical fiber 23 of the current amplifying unit 2 and the input end of the cladding light stripping unit 3.

[0033] The multiple amplifying units 2 of the present solution are cascaded in sequence, and each amplifying unit 2 has a first passive optical fiber segment 21 , a second passive optical fiber segment 22 and an active optical fiber 23 arranged in sequence.

[0034] like Figure 4 As shown, the first passive fiber segment 21, the second passive fiber segment 22 and the active fiber 23 in at least one amplifying unit 2 all have a coiled structure. The winding method of the coiled structure can also improve the beam quality degradation introduced by the beam combining unit 1.

[0035] The winding structures of the first passive optical fiber segment 21, the second passive optical fiber segment 22 and the active optical fiber 23 all include a first arc segment 100, a second arc segment 200, a third arc segment 300 and a fourth arc segment 400; the first arc segment 100 and the second arc segment 200 are symmetrically arranged, and both the first arc segment 100 and the second arc segment 200 are provided with openings; the third arc segment 300 and the fourth arc segment 400 are respectively arranged between the first arc segment 100 and the second arc segment 200, the third arc segment 300 is respectively tangent to one end of the opening of the first arc segment 100 and the second arc segment 200, and the fourth arc segment 400 is respectively tangent to the other end of the opening of the first arc segment 100 and the second arc segment 200; the centers of the third arc segment 300 and the fourth arc segment 400 are both far away from the openings.

[0036] The radius of the first arc segment 100 and the second arc segment 200 is the same, and the center distance between the first arc segment 100 and the second arc segment 200 is greater than the radius of the first arc segment 100; the center angle of the third arc segment 300 and the fourth arc segment 400 does not exceed 90°.

[0037] Depend on Figure 4 It can be seen that the first arc segment 100 and the second arc segment 200 are dashed lines in the figure, and the third arc segment 300 and the fourth arc segment 400 are dotted lines in the figure. By means of the winding method of the optical fiber similar to the "8" shape, a specific spatial structure is formed to improve the degradation of the beam quality introduced by the beam combining unit 1, and the end of the coiled optical fiber can be led out from any position of the "8" shape.

[0038] like Figure 2 As shown, the active optical fiber 23 includes a first active segment 231, a second active segment 232 and a first tapered segment 233. The diameters of the first active segment 231 and the second active segment 232 are different. One end of the first active segment 231 is fused with one end of the first passive optical fiber segment 21 away from the beam combining unit 1, and the other end of the first active segment 231 is optically connected to one end of the first tapered segment 233; one end of the second active segment 232 is optically connected to the other end of the first tapered segment 233, and the other end of the second active segment 232 is optically connected to one end of the second passive optical fiber segment 22 away from the cladding light stripping unit 3; the diameter of the first active segment 231 is the same as the diameter of the small diameter end of the first tapered segment 233, and the diameter of the second active segment 232 is the same as the diameter of the large diameter end of the first tapered segment 233.

[0039] As a further improvement of the present embodiment, it further includes a second tapered section 234, which is arranged between one end of the second active section 232 away from the first active section 231 and one end of the second passive optical fiber section 22 away from the first tapered section 233; one end of the second tapered section 234 is optically connected to the second active section 232, and the other end of the second tapered section 234 is optically connected to the input end of the second passive optical fiber section 22, and the diameter of the large diameter end of the second tapered section 234 is the same as the diameter of the second active section 232, and the small diameter end of the second tapered section 234 is the same as the diameter of the second passive optical fiber section 22.

[0040] like Figure 2 Combination Figure 3 As shown, the first passive optical fiber segment 21 and the second passive optical fiber segment 22 are both 30 / 250GDF active optical fibers, the first active segment 231 is a 30 / 250Yb passive optical fiber, and the second active segment 232 is a 50 / 400Yb passive optical fiber. Since the first active segment 231 and the first passive optical fiber segment 21 have the same core diameter, they can be directly fused. However, the core diameters of the first active segment 231 and the second active segment 232 are different. In order to improve the degradation of beam quality and fiber melting caused by direct fusion, the first tapered segment 233 is introduced to form a smooth transition between the first active segment 231 and the second active segment 232 with different core diameters. Similarly, the core diameter of the second active segment 232 is also different from the core diameter of the second passive optical fiber segment 22. In order to improve the degradation of beam quality and fiber melting caused by direct fusion, the second tapered segment 234 is further introduced to achieve a smooth transition of different core diameters. Of course, the tapered section is only a suitable transition structure when the core diameter difference is not large. If the core diameter difference is large, it may be necessary to insert an amplification unit 2 in the middle to slow down the amplitude of the core diameter jump and smoothly realize the embedding of the first tapered section and / or the second tapered section.

[0041] Here, 30 / 250GDF is just an example. The first passive fiber segment 21 and the second passive fiber segment 22 are passively doped with germanium, and the first active segment 231 and the second active segment 232 are both actively doped with ytterbium. The core diameter is not necessarily 30 or 50 microns in the embodiment, but can also be other sizes. The content in this embodiment is not considered to be a limitation of the solution.

[0042] In order to limit the length of the winding mode of each first passive optical fiber segment 21 and the second passive optical fiber segment 22, better realize high-quality laser output control, and control the generation of transverse mode in the amplification process to the greatest extent, the energy of the transition amplification of each first active segment 231 and the second active segment 232 along the laser output direction in each amplification unit 2 is E1, E2, ..., E n; The core diameters of the first active section 231 and the second active section 232 of each amplification unit 2 extending along the laser output optical path direction are R1, R2, R3, …, R n-1 、R n , satisfying i = 1, 2, …, n, E max is the maximum output energy of the laser.

[0043] Let the lengths of the first active sections 231 and the second active sections 232 sequentially arranged along the laser output optical path direction be L1, L2, …, L m , in unit of m; the absorption coefficients of the first active sections 231 and the second active sections 232 sequentially arranged along the laser output optical path direction are η1, η2, …, ηm, satisfying 14dB < L1η1 + L2η2 + … + L m η m < 20dB. The unit of the absorption coefficient is dB / m.

[0044] Theoretically, the longer the length of the tapered section is, the better. However, considering the energy limitation problem, the length of the tapered region has a certain limit. If the tapered region is too small, the optimization requirement of the beam quality cannot be met. Therefore, let the tapered region lengths of the first tapered sections 233 and the second tapered sections 234 along the laser output direction be d1, d2, …, d k-1 、d k , j = 1, 2, …, k, j < n; the tapered region lengths of each tapered section satisfy the following relationship:

[0045] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An amplifier structure with high beam quality, characterized in that: It comprises a beam combining unit (1), at least one amplifying unit (2), a cladding light stripping unit (3) and an output unit (4); A beam combining unit (1) is used to combine the main input light and the bypass pump light and then output them; the input end of at least one amplifying unit (2) is optically connected to the output end of the beam combining unit (1), and the output end of at least one amplifying unit (2) is optically connected to the input end of the cladding light stripping unit (3); the output end of the cladding light stripping unit (3) is optically connected to the input end of at least one output unit (4), and the output end of the output unit (4) outputs the amplified laser beam; Wherein, at least one amplification unit (2) comprises a first passive optical fiber segment (21), a second passive optical fiber segment (22) and an active optical fiber (23); one end of the first passive optical fiber segment (21) is connected to the output optical path of the beam combining unit, and one end of the second passive optical fiber segment (22) is connected to the input optical path of the cladding light stripping unit (3); an active optical fiber (23) is arranged between the other end of the first passive optical fiber segment (21) and the other end of the second passive optical fiber segment (22); and at least one tapered segment is arranged on the active optical fiber (23).

2. The amplifier structure with high beam quality according to claim 1, characterized in that: The number of the amplifying units (2) is two or three; in the amplifying unit (2) close to the head end of the beam combining unit (1), the first passive optical fiber segment (21) is optically connected to the output end of the beam combining unit (1) and one end of the active optical fiber (23) of the current amplifying unit (2), and the second passive optical fiber segment (22) is optically connected to the other end of the active optical fiber (23) and one end of the first passive optical fiber segment (21) of the next-stage amplifying unit (2); in the amplifying unit (2) close to the end of the cladding light stripping unit (3), the second passive optical fiber segment (22) is optically connected to one end of the active optical fiber (23) of the current amplifying unit (2) and the input end of the cladding light stripping unit (3).

3. The amplifier structure with high beam quality according to claim 2, characterized in that: The first passive optical fiber segment (21), the second passive optical fiber segment (22) and the active optical fiber (23) in at least one amplification unit (2) all have a coiled structure.

4. The amplifier structure with high beam quality according to claim 3, characterized in that: The coiled structures of the first passive optical fiber segment (21), the second passive optical fiber segment (22) and the active optical fiber (23) all include a first arc segment (100), a second arc segment (200), a third arc segment (300) and a fourth arc segment (400); the first arc segment (100) and the second arc segment (200) are symmetrically arranged, and the first arc segment (100) and the second arc segment (200) are both provided with openings; the third arc segment (300) and the fourth arc segment (400) are symmetrically arranged. The segments (400) are respectively arranged between the first arc segment (100) and the second arc segment (200); the third arc segment (300) is respectively arranged tangent to one end of the opening of the first arc segment (100) and the second arc segment (200); the fourth arc segment (400) is respectively arranged tangent to the other end of the opening of the first arc segment (100) and the second arc segment (200); and the centers of the third arc segment (300) and the fourth arc segment (400) are both far away from the opening.

5. The amplifier structure with high beam quality according to claim 4, characterized in that: The radii of the first arc segment (100) and the second arc segment (200) are the same, and the distance between the centers of the first arc segment (100) and the second arc segment (200) is greater than the radius of the first arc segment (100); and the center angles of the third arc segment (300) and the fourth arc segment (400) do not exceed 90°.

6. The amplifier structure with high beam quality according to claim 5, characterized in that: The active optical fiber (23) comprises a first active section (231), a second active section (232) and a first tapered section (233); the first active section (231) and the second active section (232) have different diameters; one end of the first active section (231) is fused to one end of the first passive optical fiber section (21) away from the beam combining unit (1); the other end of the first active section (231) is optically connected to one end of the first tapered section (233); one end of the second active section (232) is optically connected to the other end of the first tapered section (233); the other end of the second active section (232) is optically connected to one end of the second passive optical fiber section (22) away from the cladding light stripping unit (3); the diameter of the first active section (231) is the same as the diameter of the small diameter end of the first tapered section (233); the diameter of the second active section (232) is the same as the diameter of the large diameter end of the first tapered section (233).

7. The amplifier structure with high beam quality according to claim 6, characterized in that: The optical fiber optical fiber further comprises a second tapered section (234), which is arranged between an end of the second active section (232) away from the first active section (231) and an end of the second passive optical fiber section (22) away from the first tapered section (233); one end of the second tapered section (234) is optically connected to the second active section (232), and the other end of the second tapered section (234) is optically connected to the input end of the second passive optical fiber section (22); the diameter of the large diameter end of the second tapered section (234) is the same as the diameter of the second active section (232), and the small diameter end of the second tapered section (234) is the same as the diameter of the second passive optical fiber section (22).

8. The amplifier structure with high beam quality according to claim 7, characterized in that: The energy of transition amplification of each first active section (231) and second active section (232) along the laser output direction in each amplifying unit (2) is sequentially E1, E2, ..., E n The core diameters of the first active section (231) and the second active section (232) of each amplifying unit (2) extending along the laser output optical path are R1, R2, R3, ..., R n-1 , R n ,satisfy E max is the maximum output energy of the laser.

9. The amplifier structure with high beam quality according to claim 8, characterized in that: The lengths of the first active segments (231) and the second active segments (232) sequentially arranged along the laser output optical path are L1, L2, ..., L m The absorption coefficients of the first active segments (231) and the second active segments (232) sequentially arranged along the laser output optical path are η1, η2, ..., η m , satisfying 14dB<L1η1+L2η2+…+L m η m <20dB.

10. The amplifier structure with high beam quality according to claim 8, characterized in that: Let the taper region lengths of the first tapered segments (233) and the second tapered segments (234) along the laser output direction be d1, d2, …, d k-1 、d k , where j = 1, 2, …, k, j < n; the taper region lengths of the tapered segments satisfy the following relationship:

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