A high beam quality amplifier structure

Abstract

This invention proposes a high beam quality amplifier structure, belonging to the field of optical path packaging structure technology; it includes a beam combining unit for combining trunk input light and bypass pump light for output; the input end of at least one amplification unit is optically connected to the output end of the beam combining unit, and the output end of at least one amplification unit is optically connected to the input end of a cladding stripping unit; the output end of the cladding 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; each of the at least one amplification unit includes a first passive fiber segment, a second passive fiber segment, and an active fiber, one end of the first passive fiber segment is connected to the output end of the beam combining unit, and one end of the second passive fiber segment is connected to the input end of the cladding stripping unit; a passive fiber is disposed between the other ends of the first and second passive fiber segments; and at least one tapered section is disposed on the active fiber.

Description

Technical Field

[0001] This invention relates to the field of optical path packaging structure technology, and in particular to an amplifier structure with high beam quality. Background Technology

[0002] Conventional 30 / 250 fiber fusion splicing to 50 / 400 fiber sometimes uses direct fusion splicing. This method results in poor splicing performance, severe beam quality degradation, and, when external backlight is strong, heat accumulation easily occurs at the cladding splice position between 400-250, leading to fiber fuse—the phenomenon where a strong laser beam incident on one end of the fiber causes the other end to melt. To optimize the laser output beam quality, reverse pumping is usually chosen; however, the combiner itself degrades beam transmission and is difficult to control.

[0003] Based on the aforementioned shortcomings, it is essential to propose a high beam quality amplifier structure that mitigates the change trend between the cladding and the fiber core, avoids fiber melting, and improves the influence of the combiner on signal injection, thereby enhancing the output quality of the laser. Summary of the Invention

[0004] In view of this, the present invention proposes a high beam quality amplifier structure that improves injection beam degradation, achieves maximum beam quality control by sequentially transitioning optical fibers of different core diameters with a specific winding structure, and improves laser M2 degradation caused by core diameter changes by tapering.

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

[0006] A beam combining unit is used to combine the trunk input light and the bypass pump light and output them; the input end of at least one amplification unit is connected to the output end of the beam combining unit, and the output end of at least one amplification unit is connected to the input end of the cladding stripping unit; the output end of the cladding stripping unit is 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] Each amplification unit includes a first passive fiber segment, a second passive fiber segment, and an active fiber. One end of the first passive fiber segment is connected to the output optical path of the bundle combining unit, and one end of the second passive fiber segment is connected to the input optical path of the cladding optical stripping unit. A passive fiber is disposed between the other end of the first passive fiber segment and the other end of the second passive fiber segment. At least one tapered segment is disposed on the active fiber.

[0008] Based on the above technical solutions, preferably, the number of amplification units is two or three; in the amplification unit near the beginning of the bundle combining unit, the first passive fiber segment is connected to the output end of the bundle combining unit and one end of the active fiber of the current amplification unit, respectively, and the second passive fiber segment is connected to the other end of the active fiber and one end of the first passive fiber segment of the next stage amplification unit, respectively; in the amplification unit near the end of the cladding light stripping unit, the second passive fiber segment is connected to one end of the active fiber of the current amplification unit and the input end of the cladding light stripping unit, respectively.

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

[0010] In a further preferred embodiment, the coiled structure of the first passive optical fiber segment, the second passive optical fiber segment, and the active optical fiber all 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 an opening; 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 tangent to one end of the opening of the first arc segment and the second arc segment, and the fourth arc segment is tangent to the other end of the opening 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 opening.

[0011] More preferably, the first arc segment and the second arc segment have the same radius, 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; the central angle of the third arc segment and the fourth arc segment does not exceed 90°.

[0012] In a further preferred embodiment, the active optical fiber includes 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 the end of the first passive optical fiber segment furthest from the 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 the end of the second passive optical fiber segment furthest from the cladding optical 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] A further preferred embodiment includes a second tapered section, which is disposed between the end of the second active section away from the first active section and the end of the second passive optical fiber section away from the first tapered section; one end of the second tapered section is connected to the optical path of the second active section, and the other end of the second tapered section is connected to the optical path of 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 diameter of 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 are transitionally amplified 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 respectively, and satisfy 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 arranged in sequence 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 arranged in sequence along the laser output optical path direction are η1, η2, …, ηm respectively, and satisfy 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 respectively, 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 optical fiber segments with different core diameters and passive optical fibers, and controls the beam quality to the greatest extent through the amplification ratios of optical fibers with different core diameters. At the same time, from the perspectives of improving the deterioration of the injected beam of the combiner and improving the numerical aperture of the optical 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 changing trend of the fiber core and the cladding is slowed down, and the external reflected light will gradually be transmitted to the middle area of the cladding during the return process. Moreover, by limiting the taper region length of the taper, the beam quality can be protected from sudden deterioration, which is beneficial to improving the beam quality of the laser output. Description of the Drawings

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

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

[0022] Figure 2 This is a schematic diagram of the internal structure of the amplification unit of the high beam quality amplifier structure of the present invention;

[0023] Figure 3 This is an embodiment of the amplification unit of the high beam quality amplifier structure of the present invention;

[0024] Figure 4 This is a schematic diagram of the first passive fiber segment, the second passive fiber segment, or the coiled structure of a high beam quality amplifier structure according to the present invention.

[0025] Reference numerals: 1. Bundling unit; 2. Amplification unit; 3. Cladding light stripping unit; 4. Output unit; 21. First passive fiber segment; 22. Second passive fiber segment; 23. Active 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 Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] Direct fusion splicing of active gain fibers with different core diameters results in poor splicing performance, severe beam quality degradation, and fiber melting. Therefore, if... Figure 1 and Figure 2 As shown, the present invention provides a high beam quality amplifier structure, including a beam combining unit 1, at least one amplification unit 2, a cladding light stripping unit 3, and an output unit 4;

[0029] The beam combining unit 1 is used to combine the trunk input light and the bypass pump light and output them; the input end of at least one amplification unit 2 is connected to the output end of the beam combining unit 1, and the output end of at least one amplification unit 2 is connected to the input end of the cladding light stripping unit 3; the output end of the cladding light stripping unit 3 is 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] Each amplification unit 2 includes a first passive fiber segment 21, a second passive fiber segment 22, and an active fiber 23. One end of the first passive fiber segment 21 is connected to the output optical path of the bundle combining unit, and one end of the second passive fiber segment 22 is connected to the input optical path of the cladding optical stripping unit 3. An active fiber 23 is disposed between the other end of the first passive fiber segment 21 and the other end of the second passive fiber segment 22. At least one tapered segment is disposed on the active fiber 23.

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

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

[0033] The multiple amplification units 2 in this scheme are cascaded in sequence. Each amplification 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, at least one passive fiber segment 21, a second passive fiber segment 22, and an active fiber 23 in the amplification unit 2 all have a coiled structure. The coiling method can also improve the beam quality degradation introduced by the beam combining unit 1.

[0035] 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 both the first arc segment 100 and the second arc segment 200 have 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 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 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 first arc segment 100 and the second arc segment 200 have the same radius, 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; the central angle of the third arc segment 300 and the fourth arc segment 400 does not exceed 90°.

[0037] Depend on Figure 4 As can be seen, the first arc segment 100 and the second arc segment 200 are the dashed lines in the figure, and the third arc segment 300 and the fourth arc segment 400 are the dotted lines in the figure. Through this figure-eight-shaped winding method of the optical fiber, a specific spatial structure is formed to improve the beam quality degradation introduced by the beam combining unit 1. The end of the winding optical fiber can be led out from any position of the figure-eight 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 first active segment 231 and the second active segment 232 have different diameters. One end of the first active segment 231 is fused to the end of the first passive optical fiber segment 21 away from the bundle 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 the end of the second passive optical fiber segment 22 away from the cladding optical 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 to this embodiment, a second tapered section 234 is also included. The second tapered section 234 is disposed between the end of the second active section 232 away from the first active section 231 and the 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 diameter of 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, both the first passive fiber segment 21 and the second passive fiber segment 22 are 30 / 250GDF active fibers. The first active segment 231 is a 30 / 250Yb passive fiber, and the second active segment 232 is a 50 / 400Yb passive fiber. Since the first active segment 231 and the first passive 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 beam quality degradation and fiber melting phenomenon caused by direct fusion splicing, a 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 that of the second passive fiber segment 22. In order to improve the beam quality degradation and fiber melting phenomenon caused by direct fusion splicing, a second tapered segment 234 is further introduced to achieve a smooth transition between different core diameters. Of course, the tapered section is a suitable transition structure only 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 reduce the amplitude of the core diameter jump and smoothly realize the embedding of the first tapered section and / or the second tapered section.

[0041] The 30 / 250GDF example here is merely illustrative. The first passive fiber segment 21 and the second passive fiber segment 22 are passively doped with germanium, while 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 micrometers as in the embodiment; it can be other sizes. The content of this embodiment is not intended to limit the solution.

[0042] To limit the length of the coiling pattern of each first passive fiber segment 21 and second passive fiber segment 22, and to better achieve high-quality laser output control, thereby maximizing the control of transverse mode generation during amplification, the energies of the first active segment 231 and second active segment 232 along the laser output direction in each amplification unit 2 are sequentially defined as E1, E2, ..., E... n; The core diameters of the first active segment 231 and the second active segment 232 of each amplifying 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 segments 231 and the second active segments 232 sequentially arranged along the laser output optical path direction be L1, L2, …, L m , in m; the absorption coefficients of the first active segments 231 and the second active segments 232 sequentially arranged along the laser output optical path direction are η1, η2, …, ηm, satisfying 14 dB < L1η1 + L2η2 + … + L m η m < 20 dB. 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, it cannot meet the optimization requirements of the beam quality. Therefore, let the tapered 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 , j = 1, 2, …, k, j < n; the tapered region lengths of each tapered segment satisfy the following relationship:

[0045] The above is only the preferred embodiment of the present invention and is 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. A high beam quality amplifier structure, characterized in that, It includes a beam combining unit (1), at least one amplification unit (2), a cladding light stripping unit (3), and an output unit (4). A beam combining unit (1) is used to combine the trunk input light and the bypass pump light and output them; the input end of at least one amplification unit (2) is connected to the output end of the beam combining unit (1), and the output end of at least one amplification unit (2) is connected to the input end of the cladding light stripping unit (3); the output end of the cladding light stripping unit (3) is 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; At least one amplification unit (2) includes a first passive fiber segment (21), a second passive fiber segment (22), and an active fiber (23). One end of the first passive fiber segment (21) is connected to the output optical path of the bundle combining unit, and one end of the second passive fiber segment (22) is connected to the input optical path of the cladding optical stripping unit (3). An active fiber (23) is disposed between the other end of the first passive fiber segment (21) and the other end of the second passive fiber segment (22). At least one tapered segment is disposed on the active fiber (23). The number of amplification units (2) is two or three; in the amplification unit (2) near the beginning of the bundle-combining unit (1), the first passive fiber segment (21) is connected to the output end of the bundle-combining unit (1) and one end of the active fiber (23) of the current amplification unit (2), and the second passive fiber segment (22) is connected to the other end of the active fiber (23) and one end of the first passive fiber segment (21) of the next stage amplification unit (2); in the amplification unit (2) near the end of the cladding light stripping unit (3), the second passive fiber segment (22) is connected to one end of the active fiber (23) of the current amplification unit (2) and the input end of the cladding light stripping unit (3). The active optical fiber (23) includes a first active segment (231), a second active segment (232), a first tapered segment (233), and a second tapered segment (234). 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 to the end of the first passive optical fiber segment (21) away from the bundle-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 the end of the second passive optical fiber segment (22) away from the cladding optical stripping unit (3). The diameter of the first active segment (231) is different from that of the first passive optical fiber segment (232). The small diameter end of the tapered segment (233) has the same diameter, and the diameter of the second active segment (232) has the same diameter as the large diameter end of the first tapered segment (233). The second tapered segment (234) is located between the end of the second active segment (232) away from the first active segment (231) and the end of the second passive fiber segment (22) close to the first tapered segment (233). One end of the second tapered segment (234) is connected to the optical path of the second active segment (232), and the other end of the second tapered segment (234) is connected to the optical path of the input end of the second passive fiber segment (22). The large diameter end of the second tapered segment (234) has the same diameter as the second active segment (232), and the small diameter end of the second tapered segment (234) has the same diameter as the second passive fiber segment (22).

2. The high beam quality amplifier structure according to claim 1, characterized in that, At least one amplification unit (2) has a coiled structure for the first passive fiber segment (21), the second passive fiber segment (22) and the active fiber (23).

3. The high beam quality amplifier structure according to claim 2, characterized in that, The coiled structures of the first passive fiber segment (21), the second passive fiber segment (22), and the active 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 also provided with openings. The segments (400) are respectively set between the first arc segment (100) and the second arc segment (200), the third arc segment (300) is 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 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 opening.

4. The high beam quality amplifier structure according to claim 3, characterized in that, The first arc segment (100) and the second arc segment (200) have the same radius, 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); the central angle of the third arc segment (300) and the fourth arc segment (400) does not exceed 90°.

5. The high beam quality amplifier structure according to claim 1, characterized in that, Let the energy of each first active segment (231) and second active segment (232) along the laser output direction in each amplification unit (2) be successively amplified as follows: E 1. E 2、…、 E n The core diameters of the first active segment (231) and the second active segment (232) of each amplification unit (2) extending along the laser output optical path are, respectively, as follows: R 1. R 2. R 3、…, R n-1 , R n ,satisfy , , This represents the maximum output energy of the laser.

6. The high beam quality amplifier structure according to claim 5, characterized in that, Let the lengths of the first active segment (231) and the second active segment (232) arranged sequentially along the laser output optical path be respectively as follows: L 1. L 2、…、 L m The absorption coefficients of the first active segment (231) and the second active segment (232) arranged sequentially along the laser output optical path are respectively η 1. η 2、…、 η m ,satisfy .

7. The high beam quality amplifier structure according to claim 5, characterized in that, Let the lengths of the conical sections of the first tapered segment (233) and the second tapered segment (234) along the laser output direction be respectively d 1. d 2、…、 d k-1 , d k , , j < n The lengths of the conical sections of each tapered segment satisfy the following relationship: .

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