Optical fiber mode detection device and laser output device

Abstract

The invention discloses an optical fiber mode detection device and a laser output device.The optical fiber mode detection device comprises a base, a double-clad optical fiber and a detection assembly, the double-clad optical fiber is arranged on the base, a detection area is formed on the double-clad optical fiber, a plurality of light stripping areas are arranged in the detection area, and the detection assembly is arranged on the base. The diameters of the multiple light stripping areas are sequentially reduced in the axial direction of the double-clad optical fiber, the multiple light stripping areas are used for stripping light waves in different modes, the detection assembly comprises an optical power meter arranged on the base, and the optical power meter is arranged corresponding to the detection area and used for detecting the power of stripping light. A detection area is arranged in the double-clad optical fiber, a plurality of light stripping areas are arranged in the detection area to strip light in different modes in the double-clad optical fiber, and meanwhile, an optical power meter is arranged to detect the power of the stripping light in the different light stripping areas so as to obtain the power of the light in each mode in the optical fiber, so that the proportion of each mode of the optical fiber is determined.

Description

Technical Field

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

[0002] High-power fiber lasers generally use master oscillator power amplification technology to achieve high-power output by amplifying seed light in the gain fiber through pump light. During the amplification process, the fundamental mode and the higher-order mode are amplified at the same time, and the two will compete for the number of upper energy level particles. As the thermal effect inside the gain fiber increases, mode instability occurs. However, in multimode optical fibers, the fundamental mode and higher-order modes are 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 for laser research. Summary of the invention

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

[0004] To achieve the above object, the optical fiber mode detection device proposed in the present invention comprises:

[0005] Base;

[0006] A double-clad optical fiber is arranged on the base, wherein the double-clad optical fiber forms a detection area, wherein a plurality of stripping areas are arranged in the detection area, and the diameters of the plurality of stripping areas are successively reduced along the axial direction of the double-clad optical fiber, so as to strip out light of different modes respectively;

[0007] The detection component comprises an optical power meter arranged on the base, wherein the optical power meter is arranged corresponding to the detection area and is used for detecting the power of the stripping light.

[0008] In one embodiment, the stripping zone includes a tapered zone and a tapered waist zone, the tapered zone has a first end with a larger diameter and a second end with a smaller diameter, the first end is used for light wave input, the second end is connected to the waist zone, and the tapered waist zone is used to strip out light of different modes.

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

[0010] In one embodiment, a plurality of the stripping regions are continuously arranged along the axial direction of the double-clad optical fiber.

[0011] In one embodiment, a plurality of the stripping regions are spaced apart along the axial direction of the double-clad optical fiber.

[0012] In one embodiment, the optical fiber mode detection device further comprises a cylindrical reflector disposed on the double-clad optical fiber, the cylindrical reflector being disposed corresponding to the detection area and having a light-transmitting hole thereon;

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

[0014] In one embodiment, the optical fiber mode detection device further includes a lens disposed on the base, and the lens is located between the light transmission hole and the optical power meter.

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

[0016] In addition, the present invention also provides a laser output device, which includes a laser, an output head and an optical fiber structure. 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. The double-clad optical fiber forms a detection area, and a plurality of stripping areas are arranged in the detection area. The diameters of the plurality of stripping areas decrease successively along the propagation direction of the light wave, so as to strip out light waves of different modes respectively.

[0017] In one embodiment, the double-clad optical fiber is detachably connected to the laser and the output head.

[0018] In the technical solution of the present invention, the base is provided to install the double-clad optical fiber and the detection device, and a plurality of stripping zones are provided in the detection area to strip light of different modes in the double-clad optical fiber. At the same time, the optical power meter is provided to detect the power of the stripped light in different stripping zones respectively, so as to obtain the power of each mode of light in the optical fiber, thereby determining the proportion of each mode of the optical fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] 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 the structures shown in these drawings without paying creative work.

[0020] Figure 1 A schematic structural diagram of an embodiment of an optical fiber mode detection device provided by the present invention;

[0021] Figure 2 for Figure 1 A schematic structural diagram of an embodiment of a double-clad optical fiber;

[0022] Figure 3 for Figure 1 A schematic structural diagram of another embodiment of a double-clad optical fiber;

[0023] Figure 4 This is a structural block diagram of an embodiment of a laser output device provided by the present invention.

[0024] Description of Figure Numbers:

[0025] 100. Optical fiber mode detection device; 1. Double-clad optical fiber; 11. Detection area; 12. Stripping area; 121. Taper area; 122. Taper waist area; 2. Detection component; 21. Optical power meter; 3. Cylindrical reflector; 31. Light transmission hole; 4. Lens;

[0026] 200. Laser output device.

[0027] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in 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.

[0029] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0030] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of the features. In addition, if "and / or" or "and / or" appears in the full text, its meaning includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or solutions that satisfy both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0031] High-power fiber lasers generally use master oscillator power amplification technology to achieve high-power output by amplifying seed light in the gain fiber through pump light. During the amplification process, the fundamental mode and the higher-order mode are amplified at the same time, and the two will compete for the number of upper energy level particles. As the thermal effect inside the gain fiber increases, mode instability occurs. However, in multimode optical fibers, the fundamental mode and higher-order modes are 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 for laser research.

[0032] Based on this, the present invention provides a fiber mode detection device, which aims to solve the problem of how to determine the proportion of each mode in the output process. Figures 1 to 3 A schematic diagram of the structure of the optical fiber mode detection device provided by the present invention, Figure 4 This is a structural block diagram of the laser output device provided by the present invention.

[0033] See also Figures 1 to 3 In one embodiment of the present invention, the optical fiber mode detection device 100 includes a base (not shown in the figure), a double-clad optical fiber 1 and a detection component 2, wherein the double-clad optical fiber 1 is arranged on the base, and the double-clad optical fiber 1 forms a detection area 11, wherein the detection area 11 is provided with a plurality of stripping areas 12, and the diameters of the plurality of stripping areas 12 decrease successively along the axial direction of the double-clad optical fiber 1, so as to strip out light of different modes respectively, and the detection component 2 includes an optical power meter 21 arranged on the base, and the optical power meter 21 is arranged corresponding to the detection area 11, so as to detect the power of the stripping light.

[0034] In the technical solution of the present invention, the base is provided to install the double-clad optical fiber 1 and the detection device, and a plurality of stripping zones 12 are provided in the detection area 11 to strip light of different modes in the double-clad optical fiber 1. At the same time, the optical power meter 21 is provided to detect the power of the stripped light in different stripping zones 12 respectively, so as to obtain the power of light of each mode in the optical fiber, thereby determining the proportion of each mode of the optical fiber.

[0035] It should be noted that in a multimode optical fiber, light usually has multiple specific modes of propagation. Specifically, taking the laser wavelength of 1.08um, the core diameter of the double-clad optical fiber 1 of 30um, the cladding diameter of 600um, the numerical aperture of 0.065, and the core of the double-clad optical fiber 1 containing a total of 6 modes, namely LP01, LP02, LP11, LP12, LP21, and LP31, as an example, when the core diameter is 29um, the LP12 mode in the optical fiber does not meet the waveguide transmission conditions and will be stripped out of the double-clad optical fiber 1; when the core diameter is 26um, the LP31 mode in the optical fiber does not meet the waveguide transmission conditions and will be stripped out of the double-clad optical fiber 1; when the core diameter is 20um, the LP02 and LP21 modes in the optical fiber do not meet the waveguide transmission conditions and will be stripped out of the double-clad optical fiber 1; when the core diameter is 12um, the LP11 mode in the optical fiber does not meet the waveguide transmission conditions and will be stripped out of the double-clad optical fiber 1. Furthermore, the fundamental mode is always present in the double-clad optical fiber 1. After stripping the LP11 mode, the power of the fundamental mode can be directly tested at the output end of the double-clad optical fiber 1 to obtain the modal power of the fundamental mode. Among them, LP stands for 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 optical fibers. Each mode corresponds to a specific electromagnetic field distribution. Specifically, the first number (such as 0, 1, 2, 3, etc.) represents the radial mode, that is, the number of times the light intensity distribution changes along the radial direction of the optical fiber minus one. For example, the LP0x mode means that the light intensity is evenly distributed throughout the core diameter, while LP1x, LP2x, etc. indicate that there are more radial intensity changes; the second number (such as 1, 2, etc.) represents the angular mode, which reflects the change of the light intensity distribution along the circumferential direction. For the same radial mode, different angular modes mean different modes of rotational symmetry around the optical fiber axis.

[0036] In one embodiment of the present invention, see Figure 2 and Figure 3 The stripping area 12 includes a tapered area 121 and a tapered waist area 122. The tapered area 121 has a first end with a larger diameter and a second end with a smaller diameter. The first end is used for light wave input, and the second end is connected to the waist area.

[0037] Since the transmission of laser in the core of optical fiber needs to meet certain waveguide conditions, different modes need to meet different conditions. If a specific mode needs to be detected, it is necessary to calculate the core size of the mode that does not meet the core transmission requirements through the optical fiber parameters. To this end, the tapered area 121 is set so that the optical fiber core can be tapered to a specific diameter, and the tapered waist area 122 is set so that the light of the corresponding mode does not meet the transmission conditions, so that the mode can be stripped from the cladding into space.

[0038] It can be understood that, in the axial cross section along the double-clad optical fiber 1, the tapered area 121 is arranged in an isosceles trapezoidal shape, and the tapered waist area 122 is arranged in an equal diameter. Further, in order to enable the tapered waist area 122 to strip off a specific mode of light, it is necessary to process the cladding of the tapered waist area 122, wherein there are multiple methods for processing the cladding of the tapered waist area 122. In this embodiment, the tapered waist area 122 is processed by etching. Specifically, the etching process can be performed by chemical corrosion or carbon dioxide, etc.

[0039] Furthermore, since the shorter the tapered area 121 and the tapered waist area 122 are, the easier it is for the corresponding mode of light to be lost during propagation, in this embodiment, the length of the tapered area 121 and / or the tapered waist area 122 is L, where L>10mm, so that the tapered length of the stripping area 12 satisfies the adiabatic tapering to avoid loss of the corresponding mode of light during propagation.

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

[0041] In one embodiment of the present invention, see Figure 2 , multiple stripping zones 12 are continuously arranged along the axial direction of the double-clad optical fiber 1. Since the tapered waist zone 122 needs to transition through the tapered zone 121, the smaller the diameter of the tapered waist zone 122 in the stripping zone 12, the longer the length of the corresponding tapered zone 121 in the stripping zone 12. Therefore, multiple stripping zones 12 are continuously arranged, which can not only make the multiple stripping zones 12 have a smooth transition, which helps to reduce the length of the tapered zone 121 between two adjacent tapered waist zones 122, but also make two adjacent tapered waist zones 122 share one tapered zone 121, which helps to reduce the number of tapered zones 121, thereby greatly reducing the length of the detection area 11, which is beneficial to reducing the volume of the optical fiber mode detection device 100.

[0042] In one embodiment of the present invention, see Figure 3The plurality of stripping zones 12 are arranged at intervals along the axial direction of the double-clad optical fiber 1. Although the plurality of stripping zones 12 are arranged continuously, which can reduce the length of the detection area 11, the manufacturing difficulty and cost are relatively high. Therefore, the plurality of stripping zones 12 are arranged at intervals to isolate the plurality of stripping zones 12 so as to form a plurality of stripping zones 12 respectively, which 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 one embodiment of the present invention, see Figure 1 The optical fiber mode detection device 100 also includes a cylindrical reflector 3 disposed on the double-clad optical fiber 1. The cylindrical reflector 3 is disposed corresponding to the detection area 11 and is provided with a light-transmitting hole 31. The optical power meter 21 is disposed corresponding to the light-transmitting hole 31. Since conventional strippers are non-directional, the light will be scattered along the circumference of the double cladding. Therefore, the cylindrical reflector 3 is disposed to gather the stripping light at the scattered location, and the light-transmitting hole 31 is disposed to allow the gathered stripping light to be directed to a designated area, thereby helping to improve the detection accuracy of the detection component 2. Of course, in other embodiments, a directional stripper may also be used to strip the laser from the cladding unidirectionally, and the present invention is not limited to this.

[0044] It is understandable that the light-transmitting hole 31 can have various shapes, such as circular, strip-shaped, etc., and the present invention is not limited to this. Specifically, in this embodiment, the light-transmitting hole 31 is arranged in a strip shape to match the double-clad optical fiber 1 so that the light-transmitting hole 31 can transmit more stripping light.

[0045] In one embodiment of the present invention, the optical fiber mode detection device 100 also includes a lens 4 arranged on the base, and the lens 4 is located between the light-transmitting hole 31 and the optical power meter 21. In this way, by setting the lens 4, the light can be converged to prevent the light from being scattered, thereby helping to improve the detection accuracy of the detection component 2.

[0046] There are many numbers of the optical power meters 21, which can be one or more, and the present invention is not limited to this. Specifically, in this embodiment, the optical power meter 21 is movably installed on the base along the axial direction of the double-clad optical fiber 1. In this way, the optical power meter 21 is movably set to enable the optical power meter 21 to detect the stripping areas 12 at different positions respectively, so as to avoid setting up multiple optical power meters 21, which helps 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 invention also provides a laser output device 200, see Figure 4The laser output device 200 includes a laser, an output head and a double-clad optical fiber 1. The input end of the double-clad optical fiber 1 is connected to the laser, and the output end of the double-clad optical fiber 1 is connected to the output head. The double-clad optical fiber 1 includes a plurality of stripping areas 12. The diameters of the plurality of stripping areas 12 decrease successively along the axial direction of the double-clad optical fiber 1 to respectively strip out different modes of light in the optical fiber. Thus, by setting a plurality of stripping areas 12 to strip the corresponding modes of light in the double-clad optical fiber 1, the laser output device 200 can select a specific mode for output, thereby helping to improve the quality of the light beam output by the laser output device 200.

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

[0049] Furthermore, the double-clad optical fiber 1 is detachably connected to the laser and the output head. Thus, a detachable connection is adopted to facilitate the disassembly and assembly of the double-clad optical fiber 1, so that the double-clad optical fiber 1 can be replaced as needed, thereby adjusting the output mode of the laser output device 200.

[0050] It is understandable that the stripping mode will be different if the diameter of the stripping area 12 in the double-clad optical fiber 1 is different, so by replacing the double-clad optical fiber 1, the stripping area 12 can be adjusted, thereby adjusting the output mode of the double-clad optical fiber 1. Furthermore, the double-clad optical fiber 1 can be connected through an optical fiber connector.

[0051] The above description is only an exemplary embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. An optical fiber mode detection device, characterized in that: include: Base; A double-clad optical fiber is provided on the base, wherein the double-clad optical fiber forms a detection area, wherein a plurality of stripping areas are provided in the detection area, wherein the diameters of the plurality of stripping areas decrease in sequence along the axial direction of the double-clad optical fiber, so as to strip out light of different modes in the optical fiber respectively; The detection component comprises an optical power meter arranged on the base, wherein the optical power meter is arranged corresponding to the detection area and is used for detecting the power of the stripping light.

2. The optical fiber mode detection device according to claim 1, characterized in that: The light stripping area includes a tapered area and a tapered 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 for light wave input, and the second end is connected to the tapered waist area. The tapered waist area is used to strip out light of different modes.

3. The optical fiber mode detection device according to claim 2, characterized in that: The length of the tapered area and / or the tapered waist area is L, wherein L>10 mm.

4. The optical fiber mode detection device according to claim 1, characterized in that: A plurality of stripping areas are continuously arranged along the axial direction of the double-clad optical fiber.

5. The optical fiber mode detection device according to claim 1, characterized in that: A plurality of stripping regions are arranged at intervals along the axial direction of the double-clad optical fiber.

6. The optical fiber mode detection device according to claim 1, characterized in that: The optical fiber mode detection device further comprises a cylindrical reflector arranged on the double-clad optical fiber, wherein the cylindrical reflector is arranged corresponding to the detection area and has a light-transmitting hole thereon; The optical power meter is arranged corresponding to the light-transmitting hole.

7. The optical fiber mode detection device according to claim 6, characterized in that: The optical fiber mode detection device also includes a lens arranged on the base, and the lens is located between the light transmission hole and the optical power meter.

8. The optical fiber mode detection device according to 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 comprises a laser, an output head and a double-clad optical fiber as claimed 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 according to claim 9, characterized in that: The double-clad optical fiber is detachably connected to the laser and the output head.

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