All-fiber laser

Abstract

The invention provides an all-fiber laser, and relates to the technical field of fiber lasers, the all-fiber laser comprises a laser seed source, a laser amplifier, a polarization compensator and an end cap, linear polarization fiber laser output by the laser seed source is output through the end cap after being subjected to optical power amplification through the laser amplifier stage, and in the process, the polarization compensator is output through the end cap. A polarization compensator is arranged between the laser seed source and the end cap, and is used for compensating elliptical polarization components generated by welding points among the laser seed source, the laser amplifier, the polarization compensator and the end cap due to countershaft errors or optical fiber mechanical stress, so that the elliptical polarization components are effectively converted into linearly polarized light; the depolarization compensation of the high-efficiency and high-compactness all-fiber laser is realized, so that the polarization extinction ratio of laser output by the end cap is effectively increased.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber laser technology, and in particular to an all-optical fiber laser. Background Art

[0002] Fiber lasers are lasers that use optical fiber as a gain medium, among which the most widely used gain fiber is rare-earth-doped fiber. By using gain fibers doped with different rare earth elements, the operating wavelength of fiber lasers can cover a wide range from ultraviolet to mid-infrared. Fiber lasers have distinct advantages such as simple and compact structure, maintenance-free, low energy consumption, high conversion efficiency, high stability, and high beam quality, so they are widely used in communications, medicine, military, and material processing. However, the fusion joints between the various optical fiber devices in the fiber laser link of the fiber laser will produce elliptical polarization components due to the axis angle error and the mechanical stress of the fiber, which will affect the polarization extinction ratio of the output laser of the all-fiber laser. Summary of the invention

[0003] The present invention provides an all-fiber laser, which is used to solve the technical problem that the fusion points of the connection parts between various optical fiber devices in the optical fiber laser link will generate elliptical polarization components due to axis angle errors and optical fiber mechanical stress, thereby affecting the polarization extinction ratio of the laser output by the all-fiber laser.

[0004] In order to solve the above technical problems, the following technical solutions are proposed:

[0005] The present application provides an all-fiber laser, comprising:

[0006] A laser seed source, used for outputting linearly polarized laser;

[0007] A laser amplifier connected to the output end of the laser device source and used to amplify the power of the linearly polarized laser output by the laser seed source;

[0008] a polarization compensator, the polarization compensator being connected to an output end of the laser amplifier;

[0009] An end cap, connected to an output end of the polarization compensator, for outputting laser light;

[0010] The polarization compensator is used to compensate for the polarization component, which is generated by the axis angle error and mechanical stress of the connection part between the laser seed source, the laser amplifier, the polarization compensator and the end cap.

[0011] In some embodiments, the polarization component is connected between the laser seed source, the laser amplifier, the polarization compensator, and the end cap through a polarization-maintaining optical fiber.

[0012] In some embodiments, the polarization compensator is a quarter wave plate.

[0013] In some embodiments, the quarter wave plate is a birefringent polarization-maintaining fiber.

[0014] In some embodiments, the axis-to-axis angle of the connection portion between the 1 / 4 wave plate and the end cap is the axis-to-axis angle corresponding to the maximum value of the polarization extinction ratio of the end output laser being measured.

[0015] In some embodiments, the quarter wave plate is made of a crystal material or an organic film material, and the quarter wave plate is disposed on the receiving end of the end cap by gluing or coating.

[0016] In some embodiments, the quarter wave plate is made of quartz, calcite, perovskite, polyester film, or polypropylene film.

[0017] In some embodiments, the axis-to-axis angle of the connection portion between the 1 / 4 wave plate and the laser amplifier is the axis-to-axis angle corresponding to the maximum value of the polarization extinction ratio of the end output laser being measured.

[0018] In some embodiments, the laser amplifier includes a laser pre-amplifier and a laser main amplifier, the laser pre-amplifier and the laser main amplifier are connected to the laser seed source in sequence, and the 1 / 4 wave plate is connected to the output end of the laser main amplifier.

[0019] In some embodiments, the connection portion between the laser pre-amplifier and the laser main amplifier is connected by a 45° axial connection of the birefringence main axis.

[0020] Beneficial effects: The present application provides an all-fiber laser, which relates to the field of fiber laser technology, including a laser seed source, a laser amplifier, a polarization compensator and an end cap. The linearly polarized fiber laser output by the laser seed source is amplified by a laser amplifier stage and then output through the end cap. During this process, a polarization compensator is provided between the laser seed source and the end cap. The axial errors of various fusion points among the laser seed source, the laser amplifier, the polarization compensator and the end cap or the elliptical polarization components generated by the mechanical stress of the optical fiber are compensated by the polarization compensator, so that the elliptical polarization components are effectively converted into linearly polarized light, thereby realizing the depolarization compensation of the high-efficiency and high-compact all-fiber laser, thereby effectively increasing the polarization extinction ratio of the laser output from the end cap. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A structural framework diagram of an all-fiber laser provided by an embodiment of the present invention;

[0022] Figure 2 A schematic diagram of the polarization state conversion when the laser passes through the polarization compensator provided by an embodiment of the present invention;

[0023] Figure 3 A schematic diagram of the laser polarization states at the input and output ends of the depolarization compensation end cap provided in an embodiment of the present invention;

[0024] Figure 4 A schematic diagram of the end cap structure when a quarter wave plate of a crystal or organic film provided in an embodiment of the present invention is connected to the end cap by gluing or coating.

[0025] Description of Reference Numerals

[0026] 1. Laser seed source; 2. Polarization compensator; 3. End cap; 4. Laser pre-amplifier; 5. Laser main amplifier; 6. Polarization extinction ratio test assembly; 7. Polarization-maintaining optical fiber; 8. First fusion point; 9. Second fusion point; 10. Third fusion point. DETAILED DESCRIPTION

[0027] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0029] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0030] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0031] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0032] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0033] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0034] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0035] Fiber lasers are lasers that use optical fiber as a gain medium, among which the most widely used gain fiber is rare-earth-doped fiber. By using gain fibers doped with different rare earth elements, the operating wavelength of fiber lasers can cover a wide range from ultraviolet to mid-infrared. Fiber lasers have distinct advantages such as simple and compact structure, maintenance-free, low energy consumption, high conversion efficiency, high stability, and high beam quality, so they are widely used in communications, medicine, military, and material processing. However, the fusion points of the connections between the various optical fiber devices in the fiber laser link will produce elliptical polarization components due to the axis angle error and the mechanical stress of the fiber, which will affect the polarization extinction ratio of the output laser of the all-fiber laser.

[0036] In order to solve the technical problem that the fusion joints of the connection parts between the various optical fiber devices in the optical fiber laser link will generate elliptical polarization components due to the axis angle error and the mechanical stress of the optical fiber, thereby affecting the polarization extinction ratio of the laser output by the all-fiber laser, the present application provides an all-fiber laser, which can effectively convert the elliptical polarization components generated by the axis angle error and the mechanical stress of the optical fiber at the fusion joints of the connection parts between the various optical fiber devices into linear polarized light through the polarization compensator 2, thereby achieving the technical effect of online depolarization compensation of the high-efficiency and high-compact all-fiber laser.

[0037] Please refer to Figure 1 , Figure 1 A structural framework diagram of an all-fiber laser provided in an embodiment of the present application, the all-fiber laser includes a laser seed source 1, a laser amplifier, a polarization compensator 2 and an end cap 3, wherein the laser seed source 1 is used to output linearly polarized laser; the laser amplifier is connected to the output end of the laser device source, and is used to amplify the power of the linearly polarized laser output by the laser seed source 1; the polarization compensator 2 is connected to the output end of the laser amplifier; it is used to compensate for the polarization component caused by the axial angle error and mechanical stress of the connection part between the laser seed source 1, the laser amplifier, the polarization compensator 2 and the end cap 3; the end cap 3 is connected to the output end of the polarization compensator 2, and is used to output laser.

[0038] Specifically, in the present embodiment, polarization components are sequentially connected in series by means of axial fusion among the laser seed source 1, the laser amplifier, the polarization compensator 2, and the end cap 3, thereby forming an all-fiber laser link. In the process of sequentially fusion-fusing the above-mentioned optical fiber devices such as the laser seed source 1, the laser amplifier, the polarization compensator 2, and the end cap 3, each fusion point among the laser seed source 1, the laser amplifier, the polarization compensator 2, and the end cap 3 may cause the linearly polarized laser to have an elliptical polarization component due to the influence of the axial error of the fusion point or the mechanical stress of the optical fiber, thereby affecting the polarization extinction ratio of the laser output from the end cap 3. In the present embodiment, by providing a polarization compensator 2 capable of compensating for the elliptical polarization component in the all-fiber laser link, the elliptical polarization component is effectively converted into linearly polarized light, thereby realizing the depolarization compensation of the highly efficient and compact all-fiber laser, thereby effectively increasing the polarization extinction ratio of the laser output from the end cap 3.

[0039] Furthermore, in the present embodiment, the polarization components of the laser seed source 1, the laser amplifier, the polarization compensator 2, and the end cap 3 are connected by a polarization-maintaining optical fiber 7. The polarization-maintaining optical fiber 7 enables the linearly polarized laser output by the laser seed source 1 to maintain the polarization state of the light beam during the laser output process, thereby ensuring the stability and consistency of the polarization direction of the light beam. Secondly, the polarization-maintaining optical fiber also has good stability and is not easily affected by the external environment, so that the all-fiber laser can maintain the polarization maintenance and output power stability of the light beam during long-term use, thereby providing a reliable guarantee for long-term and continuous use.

[0040] For further information, please refer to Figure 2 In this embodiment, the polarization compensator 2 is a 1 / 4 wave plate, and the 1 / 4 wave plate enables the laser emitted by the laser seed source 1 to convert the elliptically polarized component into a linearly polarized laser after passing through the polarization compensator 2.

[0041] Furthermore, in the present embodiment, the quarter wave plate is made of birefringent polarization-maintaining optical fiber. The quarter wave plate made of birefringent polarization-maintaining optical fiber can utilize the birefringence characteristics of the optical fiber itself to achieve stable phase delay while maintaining high compatibility and low loss of the optical fiber system. Secondly, the quarter wave plate made of birefringent polarization-maintaining optical fiber has strong resistance to external mechanical interference (such as vibration and impact) and is suitable for use in dynamic environments.

[0042] Furthermore, in this embodiment, the axis-to-axis angle of the connection portion between the quarter wave plate and the end cap 3 is the axis-to-axis angle corresponding to the maximum value of the polarization extinction ratio of the end output laser light.

[0043] For details, please refer to Figure 3In this embodiment, a polarization extinction ratio test component 6 is built behind the end cap 3, and the polarization extinction ratio test component 6 monitors the polarization extinction ratio test value of the laser output by the end cap 3 in real time. When the 1 / 4 wave plate and the end cap 3 are connected, the 1 / 4 wave plate 1 and the end cap 3 pigtails are subjected to conventional stripping, coating, cutting and other treatments, and the optical fiber displacement control is adjusted manually or automatically to achieve the alignment of the optical fiber cladding or core to be melted on both sides; then the laser seed source 1 is controlled to output linearly polarized laser under the state of outputting milliwatt laser, and the angle of the optical fiber to be melted on both sides is continuously changed. At this time, the polarization extinction ratio test component 6 monitors the polarization extinction ratio test value of the laser output by the end cap 3 in real time, and the polarization extinction ratio test value monitored by the polarization extinction ratio test component 6 is screened, and the corresponding axis angle when the polarization extinction ratio display value reaches the maximum is selected. After the axis angle corresponding to the polarization extinction ratio display value reaches the maximum is screened, the optical fiber is fused, and then the fusion between the 1 / 4 wave plate and the end cap 3 is completed. In this embodiment, the above method can effectively convert the elliptical polarization component generated by the axis angle error and the mechanical stress of the optical fiber at the first fusion point 8 (i.e., the connection portion between the 1 / 4 wave plate and the end cap 3) in the polarization-maintaining optical fiber laser link into linearly polarized light, thereby realizing online depolarization compensation of a highly efficient and compact all-fiber laser, thereby increasing the polarization extinction ratio of the output laser of the end cap 3.

[0044] Another feasible embodiment is also proposed in this application, please refer to Figure 4 In this embodiment, the 1 / 4 wave plate can be made of materials such as crystal materials or organic film materials, and the 1 / 4 wave plate is set at the receiving end of the end cap 3 by gluing or coating. In this embodiment, setting the 1 / 4 wave plate in the end cap 3 can not only more easily achieve precise control of the 1 / 4 wave plate, but also is easier to achieve than the 1 / 4 wave plate made of birefringent polarization-maintaining optical fiber.

[0045] In this embodiment, the quarter wave plate can be made of one of quartz, calcite, perovskite, polyester film, and polypropylene film.

[0046] Among them, the 1 / 4 wave plate made of quartz has high transparency in the visible light and ultraviolet light bands, which is very suitable for optical systems that require high light transmittance. Secondly, quartz has a high hardness and has relatively good wear resistance and corrosion resistance. The 1 / 4 wave plate made of calcite has a high birefringence characteristic and can produce a large phase delay, which is very suitable for applications that require high phase delay scenes. The 1 / 4 wave plate of perovskite has achromatic characteristics and can achieve achromatic polarization modulation in a wide wavelength range. The 1 / 4 wave plate made of polyester film and polypropylene film not only has good flexibility, but also has a low manufacturing cost.

[0047] It can be seen that 1 / 4 wave plates made of different materials have their own advantages in optical properties, mechanical properties, chemical stability, etc. Therefore, 1 / 4 wave plates made of suitable materials can be selected according to actual needs to meet the use of different application scenarios.

[0048] Furthermore, since in this embodiment the quarter wave plate is directly disposed at the receiving end of the end cap 3 by gluing or coating, in this embodiment, the polarization extinction ratio of the output laser at the end can be maximized by adjusting the axial angle of the connection portion between the quarter wave plate and the laser amplifier.

[0049] Specifically, when connecting the 1 / 4 wave plate and the laser amplifier, the pigtails of the 1 / 4 wave plate and the laser amplifier are subjected to conventional stripping, coating, cutting and other processing, and the fiber displacement control is adjusted manually or automatically to achieve alignment of the cladding or core of the optical fibers to be melted on both sides; then the laser seed source 1 is controlled to output linearly polarized laser under the state of outputting milliwatt-level laser, and the angle of the optical fibers to be melted on both sides is continuously changed, at which time the polarization extinction ratio test component 6 monitors the polarization extinction ratio test value of the laser output by the end cap 3 in real time, and the polarization extinction ratio test value monitored by the polarization extinction ratio test component 6 is screened, and the corresponding axis angle when the polarization extinction ratio display value reaches the maximum is selected, and after the axis angle corresponding to the polarization extinction ratio display value reaches the maximum is screened, the optical fiber is fused, and then the fusion between the 1 / 4 wave plate and the laser amplifier is completed, and a third fusion point 10 is formed.

[0050] Furthermore, in this embodiment, the laser amplifier includes a laser preamplifier 4 and a laser main amplifier 5, which are connected to the laser seed source 1 in sequence, and a quarter wave plate is connected to the output end of the laser main amplifier 5. The laser preamplifier 4 is used to preliminarily amplify the low-power laser output by the laser seed source 1, and to increase the power of the laser output by the laser seed source 1 to a level suitable for injection into the main amplifier, while the laser main amplifier 5 further amplifies the laser output by the laser preamplifier 4 to the required high power level.

[0051] Furthermore, in this embodiment, the connection portion between the laser pre-amplifier 4 and the laser main amplifier 5 (ie, the second fusion point 9) is connected by a 45° axial connection of the birefringence main axis.

[0052] Specifically, the main limiting factor for further improvement of the power of high-power narrow-linewidth linearly polarized fiber lasers is the stimulated Brillouin scattering effect. From the perspective of the generation mechanism, stimulated Brillouin scattering is due to the excitation of backward Stokes light after the transmission of high-intensity signal light. The backward Stokes light interferes with the forward signal light and generates acoustic waves. The acoustic wave field further excites the backward transmitted Stokes light to grow exponentially. It can be seen that the stimulated Brillouin scattering effect is closely related to the polarization direction of the laser in the amplifier. When the signal light (i.e., the pump light of stimulated ignoring scattering) and the Stokes light are in the same polarization state, the Brillouin gain is maximum; when the signal light (i.e., the pump light of stimulated ignoring scattering) and the Stokes light are orthogonal linear polarizations, the Brillouin gain is zero. Therefore, the stimulated Brillouin scattering effect of the polarization-maintaining system is the strongest, and it is particularly difficult to obtain high-power narrow-linewidth linearly polarized laser output. The linearly polarized signal light of the laser pre-amplifier stage is incident at 45 degrees into the main amplifier stage of the fiber laser, which will effectively increase the stimulated Brillouin threshold.

[0053] However, after the laser output by the laser pre-amplifier 4 passes through the connection between the laser pre-amplifier 4 and the laser main amplifier 5, the polarization state of the linearly polarized light will not be maintained in the laser main amplifier stage. Therefore, in order to solve the above problem, in this embodiment, the axis angle of the connection between the 1 / 4 wave plate and the laser main amplifier 5 can be adjusted to achieve depolarization compensation of stimulated Brillouin scattering suppression. In this embodiment, on the basis of improving the problem of polarization extinction ratio, the power increase limitation caused by nonlinear effects is also solved.

[0054] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. An all-fiber laser, characterized in that: include: A laser seed source, used for outputting linearly polarized laser; A laser amplifier, connected to the output end of the laser seed source, and used to amplify the power of the linearly polarized laser output by the laser seed source; An end cap, the end cap being connected to the output end of the laser amplifier and used for outputting laser; A polarization compensator, the polarization compensator being disposed between the laser seed source and the end cap; The polarization compensator is used to compensate for the polarization component, which is generated by the axis angle error and mechanical stress of the connection part between the laser seed source, the laser amplifier, the polarization compensator and the end cap.

2. The all-fiber laser according to claim 1, characterized in that: The polarization component is that the laser seed source, the laser amplifier, the polarization compensator, and the end cap are connected through a polarization-maintaining optical fiber.

3. The all-fiber laser according to claim 1, characterized in that: The polarization compensator is a 1 / 4 wave plate.

4. The all-fiber laser according to claim 3, characterized in that: The quarter wave plate is a birefringent polarization-maintaining optical fiber.

5. The all-fiber laser according to claim 3, characterized in that: The axis-to-axis angle of the connection portion between the 1 / 4 wave plate and the end cap is the axis-to-axis angle corresponding to the maximum value of the polarization extinction ratio of the end output laser being measured.

6. The all-fiber laser according to claim 3, characterized in that: The 1 / 4 wave plate is made of a crystal material or an organic film material, and the 1 / 4 wave plate is arranged on the receiving end of the end cap by gluing or coating.

7. The all-fiber laser according to claim 6, characterized in that: The 1 / 4 wave plate is made of quartz, calcite, perovskite, polyester film, or polypropylene film.

8. The all-fiber laser according to claim 6, characterized in that: The axis-to-axis angle of the connection portion between the 1 / 4 wave plate and the laser amplifier is the axis-to-axis angle corresponding to the maximum value of the polarization extinction ratio of the end output laser light.

9. The all-fiber laser according to claim 8, characterized in that: The laser amplifier comprises a laser pre-amplifier and a laser main amplifier, the laser pre-amplifier and the laser main amplifier are connected to the laser seed source in sequence, and the 1 / 4 wave plate is arranged between the laser seed source and the end cap.

10. The all-fiber laser according to claim 9, characterized in that: The connection portion between the laser pre-amplifier and the laser main amplifier is connected by a 45° axial connection of the birefringence main axis.

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