Optical fiber mode detection device and laser output device

Abstract

The application discloses a kind of optical fiber mode detection device and laser output device, it is related to optical fiber technical field, wherein, optical fiber mode detection device includes base, double-clad fiber and detection component, double-clad fiber is set on base, double-clad fiber is formed with detection area, multiple stripping areas are equipped in detection area, the diameter of multiple stripping areas successively decreases along the axial direction of double-clad fiber, to respectively strip out different mode light waves, detection component includes the optical power meter being set on base, optical power meter is set corresponding detection area, to detect the power of stripping light, by setting base, to install double-clad fiber with detection device, and by setting multiple stripping areas in detection area, to strip out different mode light in double-clad fiber, simultaneously by setting optical power meter, to respectively detect the power of stripping light in different stripping areas, to obtain the power of each mode light in optical fiber, to determine the proportion of each mode of optical fiber.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical fiber technology, in particular to an optical fiber mode detection device and a laser output device. BACKGROUND

[0002] High-power fiber lasers generally use master oscillator power amplifier technology to amplify seed light in gain fiber by pump light to realize high-power output. In the amplification process, the fundamental mode and the high-order mode are amplified at the same time, and the two will compete for the upper level particle number, and the mode instability phenomenon will occur with the increase of the internal thermal effect of the gain fiber. However, in the multimode fiber, the fundamental mode and the high-order mode will be output from the fiber core at the same time, so how to determine the proportion of each mode in the output process is of great significance to the study of the laser. SUMMARY

[0003] The main purpose of the present application is to provide an optical fiber mode detection device and a laser output device, which aims to solve the problem of how to determine the proportion of each mode in the output process.

[0004] To achieve the above purpose, the optical fiber mode detection device provided by the present application comprises:

[0005] a base;

[0006] a double-clad fiber disposed on the base, the double-clad fiber being formed with a detection area, the detection area being provided with a plurality of stripped light areas, the diameters of the cores of the plurality of stripped light areas being sequentially reduced along the axial direction of the double-clad fiber to strip out light of different modes respectively;

[0007] a detection assembly comprising an optical power meter disposed on the base, the optical power meter being arranged corresponding to the detection area to detect the power of the stripped light.

[0008] In an embodiment, the stripped light area comprises a tapered region and a tapered waist region, the tapered region having a first end with a larger diameter and a second end with a smaller diameter, the first end being used for inputting light waves, and the second end being connected to the tapered waist region, the tapered waist region being used to strip out light of different modes.

[0009] In an embodiment, the length of the tapered region and / or the tapered waist region is L, wherein L>10mm.

[0010] In an embodiment, the plurality of stripped light areas are continuously arranged along the axial direction of the double-clad fiber.

[0011] In an embodiment, the plurality of stripped light areas are arranged at intervals along the axial direction of the double-clad fiber.

[0012] In an embodiment, the fiber mode detection device further comprises a cylindrical mirror arranged on the double-clad fiber, the cylindrical mirror is arranged corresponding to the detection area, and a light transmission hole is arranged on the cylindrical mirror.

[0013] The optical power meter is arranged corresponding to the light transmission hole.

[0014] In an embodiment, the fiber mode detection device further comprises a lens arranged on the base, the lens is arranged between the light transmission hole and the optical power meter.

[0015] In an embodiment, the optical power meter is movably arranged on the base along the axial direction of the double-clad fiber.

[0016] In addition, the application further provides a laser output device, which comprises a laser, an output head and a fiber structure, the input end of the double-clad fiber is connected with the laser, the output end of the double-clad fiber is connected with the output head, the double-clad fiber is formed with a detection area, a plurality of stripping areas are arranged in the detection area, and the diameters of the plurality of stripping areas are sequentially reduced along the light wave propagation direction to strip out light waves of different modes respectively.

[0017] In an embodiment, the double-clad fiber is detachably connected with the laser and the output head.

[0018] In the technical scheme of the application, the base is arranged to mount the double-clad fiber and the detection device, the plurality of stripping areas are arranged in the detection area to strip out light waves of different modes in the double-clad fiber, and the optical power meter is arranged to detect the power of the stripped light in different stripping areas to obtain the power of light of each mode in the fiber and determine the proportion of each mode of the fiber. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical scheme in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only show some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of the drawings shown.

[0020] Figure 1 The structural schematic diagram of an embodiment of the fiber mode detection device provided by the application;

[0021] Figure 2 The structural schematic diagram of an embodiment of the double-clad fiber in the application; Figure 1

[0022] Figure 3 The structural schematic diagram of an embodiment of the double-clad fiber in the application;​Figure 1 Structure diagram of another embodiment of the double-clad fiber in the application;

[0023] Figure 4 Structure block diagram of an embodiment of the laser output device provided by the application.

[0024] Explanation of reference numerals:

[0025] 100, fiber mode detection device; 1, double-clad fiber; 11, detection area; 12, stripping area; 121, taper area; 122, tapered waist area; 2, detection assembly; 21, optical power meter; 3, cylindrical mirror; 31, light transmission hole; 4, lens;

[0026] 200, laser output device.

[0027] The implementation, functional features and advantages of the application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the application.

[0029] It should be noted that if the embodiments of the application involve directionality indications (such as up, down, left, right, front, back, etc.), the directionality indications are only used to explain the relative position relationship, movement condition, etc. between components in a certain posture, and if the certain posture changes, the directionality indications also change accordingly.

[0030] In addition, if the embodiments of the application involve descriptions such as “first”, “second”, etc., the descriptions of “first”, “second”, etc. are only for description purposes, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by “first” and “second” can explicitly or implicitly include at least one of the features. In addition, “and / or” or “and / or” appearing throughout the text means that the three parallel solutions are included, for example, “A and / or B” includes A solution, or B solution, or A and B solutions are satisfied at the same time. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the fact that a person of ordinary skill in the art can realize it, and when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, and is not within the protection scope of the application.

[0031] High-power fiber lasers generally use master oscillator power amplifier technology to amplify seed light in gain fiber by pump light to realize high-power output. In the amplification process, the fundamental mode and the high-order mode are amplified at the same time, and the two will compete for the upper level particle number, and the mode instability phenomenon will occur with the increase of the internal thermal effect of the gain fiber. However, in the multimode fiber, the fundamental mode and the high-order mode will be output from the core at the same time, so how to determine the proportion of each mode in the output process is of great significance to the study of the laser.

[0032] Based on this, the present application provides a kind of optical fiber mode detection device, to solve how to determine the proportion of each mode in the output process problem. Wherein, Figures 1 to 3 The structural diagram of the optical fiber mode detection device provided by the present application, Figure 4 The structural block diagram of the laser output device provided by the present application.

[0033] Please refer to Figures 1 to 3 In an embodiment of the present application, the optical fiber mode detection device 100 includes a base (not shown in the figure), a double-clad fiber 1 and a detection assembly 2, the double-clad fiber 1 is arranged on the base, the double-clad fiber 1 is formed with a detection area 11, a plurality of stripping areas 12 are arranged in the detection area 11, the diameters of the plurality of stripping areas 12 are sequentially reduced along the axial direction of the double-clad fiber 1, to strip out light of different modes respectively, the detection assembly 2 includes a light power meter 21 arranged on the base, the light power meter 21 is arranged corresponding to the detection area 11, to detect the power of the stripped light.

[0034] In the technical scheme of the present application, the base is arranged to mount the double-clad fiber 1 and the detection device, and a plurality of stripping areas 12 are arranged in the detection area 11 to strip out light of different modes in the double-clad fiber 1, and the light power meter 21 is arranged to detect the power of the stripped light of different stripping areas 12 respectively, to obtain the power of light of each mode in the optical fiber, and to determine the proportion of each mode of the optical fiber.

[0035] It should be noted that in the multi-mode optical fiber, light usually exists in multiple specific modes of propagation, and specifically, with a laser wavelength of 1.08 um, a core diameter of the double-clad optical fiber 1 of 30 um, a cladding diameter of 600 um, and a numerical aperture of 0.065, the core of the double-clad optical fiber 1 contains a total of 6 modes of LP01, LP02, LP11, LP12, LP21, and LP31, and the following is described by way of example: when the core diameter is 29 um, the LP12 mode in the optical fiber does not satisfy the waveguide transmission condition and will be stripped out of the double-clad optical fiber 1; when the core diameter is 26 um, the LP31 mode in the optical fiber does not satisfy the waveguide transmission condition and will be stripped out of the double-clad optical fiber 1; when the core diameter is 20 um, the LP02 and LP21 modes in the optical fiber do not satisfy the waveguide transmission condition and will be stripped out of the double-clad optical fiber 1; and when the core diameter is 12 um, the LP11 mode in the optical fiber does not satisfy the waveguide transmission condition and will be stripped out of the double-clad optical fiber 1. Further, the fundamental mode is always present in the double-clad optical fiber 1, and the power of the fundamental mode can be directly tested at the output end of the double-clad optical fiber 1 after stripping the LP11 mode to obtain the mode power of the fundamental mode. Wherein, LP represents linear polarization mode, but more accurately, they refer to lower-order modes. These modes are mathematical descriptions of possible light wave propagation paths supported by the optical fiber. Each mode corresponds to a specific electromagnetic field distribution. Specifically, the first number (such as 0, 1, 2, 3, etc.) represents the radial mode number, which is the number of times the light intensity distribution changes along the radial direction of the fiber minus one. For example, the LP0x mode means that the light intensity is uniformly distributed throughout the core diameter, while the LP1x, LP2x, etc. indicate that there are more radial intensity variations; the second number (such as 1, 2, etc.) represents the angular mode number, which reflects the variation of light intensity distribution along the circumferential direction. For the same radial mode number, different angular mode numbers mean different modes of rotational symmetry around the fiber axis.

[0036] In an embodiment of the present application, referring to Figure 2 and Figure 3 , the light stripping area 12 includes a tapering area 121 and a tapered waist area 122, the tapering area 121 has a first end with a larger diameter and a second end with a smaller diameter, the first end is used for inputting light waves, and the second end is connected to the tapered waist area.

[0037] Since the transmission of laser in the fiber core needs to satisfy certain waveguide conditions, different modes need to satisfy different conditions, and if a specific mode needs to be detected, the fiber core size at which the mode does not satisfy the core transmission requirement needs to be calculated through the fiber parameters. To this end, the tapering area 121 is provided to enable the fiber core to be tapered to a specific diameter, and the tapered waist area 122 is provided to make the light of the corresponding mode not satisfy the transmission condition, so as to strip the mode from the cladding to the space.

[0038] It can be understood that, in the axial cross section along the double-clad fiber 1, the tapering zone 121 is arranged in the shape of an isosceles trapezoid, and the waist zone 122 is arranged in the shape of an isosceles trapezoid. Further, in order to enable the waist zone 122 to strip out light of a specific mode, the cladding of the waist zone 122 needs to be processed, and there are various processing methods for the cladding of the waist zone 122. In the embodiment, the waist zone 122 is processed by etching. Specifically, the etching processing can be performed by chemical etching or carbon dioxide.

[0039] Further, the shorter the tapering zone 121 and the waist zone 122, the more likely the corresponding mode of light to be lost during propagation. Therefore, in the embodiment, the length of the tapering zone 121 and / or the waist zone 122 is L, where L>10 mm, so that the length of the tapering zone of the light stripping zone 12 satisfies adiabatic tapering, and the corresponding mode of light will not be lost during propagation.

[0040] It can be understood that the length of the tapering zone 121 and / or the waist zone 122 is L, where L>10 mm, which means that the length of the tapering zone 121 is greater than 10 mm, or the length of the waist zone 122 is greater than 10 mm, or the length of the tapering zone 121 and the length of the waist zone 122 are both greater than 10 mm.

[0041] In an embodiment of the present application, please refer to Figure 2 The plurality of light stripping zones 12 are arranged continuously along the axial direction of the double-clad fiber 1. Since the waist zone 122 needs to be transitioned by the tapering zone 121, the smaller the diameter of the waist zone 122 in the light stripping zone 12, the longer the length of the corresponding tapering zone 121 in the light stripping zone 12. Therefore, the continuous arrangement of the plurality of light stripping zones 12 can not only make the plurality of light stripping zones 12 transition smoothly and help to reduce the length of the tapering zone 121 between two adjacent waist zones 122, but also make two adjacent waist zones 122 share one tapering zone 121, which helps to reduce the number of tapering zones 121, thereby greatly reducing the length of the detection area 11 and facilitating the reduction of the volume of the fiber mode detection device 100.

[0042] In an embodiment of the present application, please refer to Figure 3The plurality of stripping areas 12 are arranged at intervals along the axial direction of the double-clad optical fiber 1. Although the plurality of stripping areas 12 are arranged continuously, the length of the detection area 11 can be shortened, but the manufacturing difficulty is relatively high and the cost is relatively high. Therefore, the plurality of stripping areas 12 are arranged at intervals, so as to isolate the plurality of stripping areas 12 and form the plurality of stripping areas 12 respectively. This is beneficial to reduce the manufacturing difficulty of the detection area 11, thereby helping to reduce the cost of the optical fiber mode detection device 100.

[0043] In an embodiment of the present application, referring to Figure 1 The optical fiber mode detection device 100 further comprises a cylindrical mirror 3 arranged on the double-clad optical fiber 1. The cylindrical mirror 3 is arranged corresponding to the detection area 11 and is provided with a light transmission hole 31. The optical power meter 21 is arranged corresponding to the light transmission hole 31. Since the conventional stripper is non-directional, the light is scattered along the circumference of the double clad. Therefore, the cylindrical mirror 3 is arranged to collect the stripped light at the scattering position. The light transmission hole 31 is arranged to enable the collected stripped light to be directed to the specified area, thereby helping to improve the detection accuracy of the detection assembly 2. Of course, in other embodiments, a directional stripper can be used to remove laser light in one direction from the cladding. The present application does not make any limitation in this regard.

[0044] It can be understood that the shape of the light transmission hole 31 can be various, such as circular, strip-shaped, etc. The present application does not make any limitation in this regard. Specifically, in the present embodiment, the light transmission hole 31 is arranged in a strip shape to adapt to the double-clad optical fiber 1, so that the light transmission hole 31 can transmit more stripped light.

[0045] In an embodiment of the present application, the optical fiber mode detection device 100 further comprises a lens 4 arranged on the base. The lens 4 is located between the light transmission hole 31 and the optical power meter 21. In this way, the lens 4 is arranged to enable the light to be converged to prevent scattering of the light, thereby helping to improve the detection accuracy of the detection assembly 2.

[0046] The number of optical power meters 21 can be one or more. The present application does not make any limitation in this regard. Specifically, in the present embodiment, the optical power meter 21 is movably mounted on the base along the axial direction of the double-clad optical fiber 1. In this way, the optical power meter 21 is movably arranged to enable the optical power meter 21 to detect the stripping area 12 at different positions respectively. This is beneficial to simplify the structure of the optical fiber mode detection device 100 and reduce the cost of the optical fiber mode detection device 100.

[0047] In addition, the present application further provides a laser output device 200. Referring to Figure 4The laser output device 200 comprises a laser, an output head and a double-clad fiber 1, the input end of the double-clad fiber 1 is connected with the laser, the output end of the double-clad fiber 1 is connected with the output head, the double-clad fiber 1 comprises a plurality of stripping zones 12, the diameters of the plurality of stripping zones 12 are sequentially reduced along the axial direction of the double-clad fiber 1, so as to strip out the light of different modes in the fiber respectively, in this way, by arranging the plurality of stripping zones 12, the light of corresponding modes in the double-clad fiber 1 is stripped out, so that the laser output device 200 can select a specific mode for output, thereby helping to improve the beam quality of the light output by the laser output device 200.

[0048] It should be noted that the specific structure of the double-clad fiber 1 refers to the above-mentioned embodiments, since the laser output device 200 adopts all the technical solutions of the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here.

[0049] Further, the double-clad fiber 1 is detachably connected with the laser and the output head, in this way, the detachable connection is adopted to facilitate disassembly and assembly of the double-clad fiber 1, so as to facilitate replacement of the double-clad fiber 1 according to needs, thereby being able to adjust the output mode of the laser output device 200.

[0050] It can be understood that the diameters of the stripping zones 12 in the double-clad fiber 1 are different, and the corresponding stripped modes are also different, therefore, by replacing the double-clad fiber 1, the stripping zones 12 can be adjusted, thereby adjusting the output mode of the double-clad fiber 1. Further, the double-clad fiber 1 can be connected through a fiber joint.

[0051] The above-mentioned is only an exemplary embodiment of the present application, and does not limit the patent scope of the present application, any equivalent structural transformation made under the technical concept of the present application, or direct / indirect application in other related technical fields is included in the patent protection scope of the present application.

Claims

1. A fiber optic mode detection device, characterized in that, include: Base; A double-clad optical fiber includes a detection area formed on the base, and multiple stripping areas provided in the detection area. The diameter of the fiber core of the multiple stripping areas decreases sequentially along the axial direction of the double-clad optical fiber, so as to strip out different modes of light from the optical fiber respectively. The detection component includes an optical power meter disposed on the base, the optical power meter being disposed corresponding to the detection area, for detecting the power of the stripped light.

2. The fiber optic mode detection device as described in claim 1, characterized in that, The light stripping area includes a tapered area and a conical waist area. The tapered area has a first end with a larger diameter and a second end with a smaller diameter. The first end is used to input light waves, and the second end is connected to the conical waist area. The conical waist area is used to strip out different modes of light.

3. The fiber optic mode detection device as described in claim 2, characterized in that, The length of the tapered region and / or the tapered waist region is L, where L > 10 mm.

4. The fiber optic mode detection device as described in claim 1, characterized in that, Multiple stripping zones are continuously arranged along the axial direction of the double-clad optical fiber.

5. The fiber optic mode detection device as described in claim 1, characterized in that, Multiple stripping zones are spaced apart along the axial direction of the double-clad optical fiber.

6. The fiber optic mode detection device as described in claim 1, characterized in that, The fiber optic mode detection device further includes a cylindrical reflector disposed on the double-clad fiber, the cylindrical reflector being disposed corresponding to the detection area and having a light-transmitting hole thereon; The optical power meter is positioned corresponding to the light-transmitting hole.

7. The fiber optic mode detection device as described in claim 6, characterized in that, The fiber optic mode detection device also includes a lens disposed on the base, the lens being located between the light-transmitting hole and the optical power meter.

8. The fiber optic mode detection device as described in claim 1, characterized in that, The optical power meter is movably mounted on the base along the axial direction of the double-clad optical fiber.

9. A laser output device, characterized in that, It includes a laser, an output head, and a double-clad optical fiber as described in any one of claims 1 to 8, wherein the input end of the double-clad optical fiber is connected to the laser, and the output end of the double-clad optical fiber is connected to the output head.

10. The laser output device as described in claim 9, characterized in that, The double-clad optical fiber is detachably connected to the laser and the output head.

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