Energy transmission fiber optic components and fiber laser systems

Abstract

The present application discloses an energy transmission fiber assembly and an optical fiber laser system. The energy transmission fiber assembly includes a passive optical fiber, a stripping component, and an end cap. The input end of the passive optical fiber is used to connect to the optical path of the output end of the laser and to transmit the laser beam outputted from the output end of the laser. The passive optical fiber includes an amplifying section, a transmission section, and a contraction section sequentially connected from the input end to the output end of the passive optical fiber. The amplifying section is used to amplify the spot of the laser beam, and the contraction section is used to contract the spot of the laser beam. The input end of the stripping component is connected to the optical path of the output end of the passive optical fiber, and the stripping component is used to strip the ultra-high-order mode light in the laser beam. The end cap has an input end connected to the optical path of the output end of the stripping component. The energy transmission fiber assembly provided in the embodiment of the present application can solve the problem that the optical fiber laser system is easily unstable or even damaged when the energy transmission fiber assembly transmits the laser beam through a double-tapered passive optical fiber.

Description

Technical Field

[0001] The present application relates to the field of laser technology, and in particular to an energy transmission fiber optic component and a fiber laser system. Background Art

[0002] With the rapid development of domestic fiber laser system technology, the application scenarios of fiber laser systems are becoming more and more extensive. Among them, the length of the energy transmission fiber component used to transmit the laser beam in the fiber laser system is usually designed to be longer, so that the fiber laser system can process large-format and thick plates. However, as the power of the fiber laser system increases, the stimulated Raman scattering (SRS) in the energy transmission fiber component will increase significantly, thereby affecting the stability of the fiber laser system. In particular, when the ratio of the laser energy of the fiber laser system to the stimulated Raman scattering energy in the energy transmission fiber component is similar (for example, the deterioration exceeds 15dB), the fiber laser system is in a state of collapse at any time.

[0003] To address the significant increase in stimulated Raman scattering (SRS) caused by the growth of power-transmitting fiber components, a bi-tapered fiber was proposed in Volume 49, Issue 24 of the journal "China Laser." This method effectively suppresses SRS and maintains laser beam quality while increasing the length of the power-transmitting fiber. A Chinese patent publication (CN109928614A) also mentions a method for manufacturing a tapered fiber using a tapered fiber preparation method.

[0004] However, when applying bi-tapered optical fibers to fiber laser systems, researchers discovered that bi-tapered optical fibers could still adversely affect the stability of the fiber laser system during the transmission of laser beams, and could even cause irreversible damage to the system. Summary of the Invention

[0005] The embodiments of the present application provide an energy transmission fiber assembly and an optical fiber laser system, which are intended to solve the problem that the optical fiber laser system is easily unstable or even damaged when the energy transmission fiber assembly transmits a laser beam through a double-tapered passive optical fiber.

[0006] The present invention provides an optical fiber assembly for transmitting energy, the optical fiber assembly comprising:

[0007] A passive optical fiber, wherein the input end of the passive optical fiber is used to be connected to the optical path of the output end of the laser and to transmit the laser beam outputted from the output end of the laser. The passive optical fiber comprises an amplifying section, a transmission section, and a contraction section sequentially connected from the input end to the output end of the passive optical fiber. The amplifying section is used to amplify the spot of the laser beam, and the contraction section is used to contract the spot of the laser beam.

[0008] a stripping component, wherein an input end of the stripping component is optically connected to an output end of the passive optical fiber, and the stripping component is used to strip ultra-high-order mode light in the laser beam;

[0009] An end cap, wherein the input end of the end cap is optically connected to the output end of the stripping component.

[0010] In some embodiments, the end surface of the output end of the end cap is provided with a multi-layer first anti-reflection film;

[0011] The energy transmission optical fiber assembly also includes a window, which is arranged on the optical path of the output end of the end cap; the surface of the window facing the end cap is provided with multiple layers of second anti-reflection film, and the surface of the window away from the end cap is provided with multiple layers of third anti-reflection film.

[0012] In some embodiments, the number of layers of the first antireflection film is greater than or equal to 4; the number of layers of the second antireflection film is greater than or equal to 4; and the number of layers of the third antireflection film is greater than or equal to 4.

[0013] In some embodiments, in the direction from the input end to the output end of the passive optical fiber, the diameter of the amplifying section gradually increases, and the diameter of the contracting section gradually decreases;

[0014] The ratio of the maximum diameter to the minimum diameter of the enlarged section is greater than or equal to 1.2; the ratio of the maximum diameter to the minimum diameter of the enlarged section is less than or equal to 1.5; and / or,

[0015] The ratio of the maximum diameter to the minimum diameter of the contraction section is greater than or equal to 1.2; the ratio of the maximum diameter to the minimum diameter of the contraction section is less than or equal to 1.5.

[0016] In some embodiments, the mode stripping component includes a filter mode optical fiber and a mode stripper provided on the filter mode optical fiber. The input end of the filter mode optical fiber is optically connected to the output end of the passive optical fiber, and the output end of the filter mode optical fiber is optically connected to the end cap. The filter mode optical fiber is used to convert the ultra-high-order mode light in the laser beam into cladding light, and the mode stripper is used to strip the cladding light.

[0017] In some embodiments, the passive optical fiber includes a first fiber core and a first cladding disposed on the outer circumference of the first fiber core; the filter mode optical fiber includes a second fiber core and a second cladding disposed on the outer circumference of the second fiber core; the numerical aperture (NA) of the first fiber core is greater than or equal to the numerical aperture (NA) of the second fiber core.

[0018] In some embodiments, the first cladding includes a first inner cladding, a first middle cladding, and a first outer cladding sequentially distributed in a direction away from the first fiber core, and the refractive indices of the first middle cladding, the first inner cladding, and the first outer cladding gradually decrease; the refractive indices of the first fiber core, the first inner cladding, and the first outer cladding gradually decrease; and / or,

[0019] The second cladding includes a second inner cladding, a second middle cladding and a second outer cladding distributed in sequence in a direction away from the second fiber core; the refractive index of the second middle cladding, the second inner cladding and the second outer cladding gradually decreases; the refractive index of the second fiber core, the second inner cladding and the second outer cladding gradually decreases.

[0020] In some embodiments, the diameter of the first fiber core is greater than or equal to 10 μm; the numerical aperture (NA) of the first fiber core is greater than or equal to 0.065; and / or,

[0021] The numerical aperture (NA) of the first fiber core is greater than or equal to 0.12 and less than or equal to 0.23; the numerical aperture (NA) of the first middle cladding is greater than or equal to 0.3 and less than or equal to 0.46.

[0022] In some embodiments, the passive optical fiber further includes an input section, wherein the input section, the amplification section, the transmission section, and the contraction section are integrally formed and optically connected in sequence along the input end to the output end of the passive optical fiber, and the diameter of the input section is smaller than the diameter of the transmission section;

[0023] Wherein, the passive optical fiber further includes an output section, one end of the output section is optically connected to the end of the contraction section away from the transmission section, and the output section and the contraction section are integrally formed, and the diameter of the output section is smaller than the diameter of the transmission section; the input end of the filter mode optical fiber is optically connected to the end of the output section away from the contraction section; or,

[0024] The input end of the filter mode optical fiber is optically connected to an end of the contraction section away from the transmission section, and the filter mode optical fiber and the contraction section are integrally formed, and the diameter of the filter mode optical fiber is smaller than the diameter of the transmission section.

[0025] The present application also provides a fiber laser system, comprising:

[0026] a laser for generating a laser beam;

[0027] An energy transmission optical fiber assembly, wherein the energy transmission optical fiber assembly is the energy transmission optical fiber assembly described above, and the energy transmission optical fiber assembly comprises:

[0028] A passive optical fiber, wherein the input end of the passive optical fiber is optically connected to the output end of the laser and is used to transmit the laser beam output by the output end of the laser. The passive optical fiber includes an amplifying section, a transmission section, and a contraction section sequentially connected from the input end to the output end of the passive optical fiber. The amplifying section is used to amplify the spot of the laser beam, and the contraction section is used to contract the spot of the laser beam.

[0029] a stripping component, wherein an input end of the stripping component is optically connected to an output end of the passive optical fiber, and the stripping component is used to strip ultra-high-order mode light in the laser beam;

[0030] An end cap, wherein the input end of the end cap is optically connected to the output end of the stripping component.

[0031] The energy transmission fiber optic assembly provided in the embodiment of the present application is provided with an amplifying section for amplifying the light spot of the laser beam at the input end of the passive optical fiber to reduce the energy density of the laser beam, so that the laser beam can be transmitted over a long distance in the transmission section with a lower energy density. Then, a contraction section for contracting the light spot of the laser beam is provided at the output end of the passive optical fiber to contract the light spot of the laser beam, so as to increase the energy density of the laser beam, thereby achieving long-distance transmission of the laser beam through the energy transmission fiber optic assembly while reducing stimulated Raman scattering (SRS) in the energy transmission fiber optic assembly. That is, while the length of the energy transmission fiber optic assembly is increased, the beam quality of the laser beam transmitted by the energy transmission fiber optic assembly remains basically unchanged.

[0032] Moreover, the passive optical fiber of the energy transmission fiber assembly is not affected by whether the fiber core is doped with photosensitive substances. Therefore, it can be applied to many different types of fiber laser systems and has extremely high compatibility.

[0033] On this basis, the energy transmission optical fiber assembly provided in the embodiment of the present application connects the input end of the stripping component to the output optical path of the passive optical fiber, and connects the input end of the end cap to the output optical path of the stripping component, so that the ultra-high-order mode light (light that has not converged after the divergence angle is greater than or equal to 0.125 radians) excited in the laser beam transmitted by the passive optical fiber can be stripped off by the stripping component, so that the laser beam stripped of the ultra-high-order mode light is converted into spatial light and emitted at the output end of the end cap. Through experimental testing, although the stripping component will cause part of the energy loss of the laser beam after stripping the ultra-high-order mode light, the energy loss is very small, less than 1% of the energy of the laser beam, and the stability of the laser system will be greatly enhanced. Therefore, it is possible to avoid the problem that the ultra-high-order mode light in the laser beam affects the stability of the laser beam, thereby affecting the stability of the laser system. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The following detailed description of the specific embodiments of the present application in conjunction with the accompanying drawings will make the technical solutions and other beneficial effects of the present application apparent.

[0035] Figure 1 A schematic structural diagram of an embodiment of a fiber laser system provided in an embodiment of the present application;

[0036] Figure 2 A schematic structural diagram of an embodiment of an energy transmission optical fiber assembly provided in an embodiment of the present application;

[0037] Figure 3 Schematic diagram of the internal optical path transmission of the energy transmission fiber optic assembly and the filter mode fiber provided in the embodiment of the present application;

[0038] Figure 4 A radial cross-sectional view and internal optical path transmission diagram of the passive optical fiber provided in an embodiment of the present application;

[0039] Figure 5 A cross-sectional view of an embodiment of a filter mode optical fiber provided in an embodiment of the present application;

[0040] Figure 6 A schematic diagram of the optical path of the laser from the thin section to the thick section of the fiber core provided in an embodiment of the present application;

[0041] Figure 7 A schematic diagram of the optical path of the laser from the thick section to the thin section of the fiber core provided in an embodiment of the present application;

[0042] Figure 8 A schematic diagram of the optical path within the passive optical fiber provided in an embodiment of the present application;

[0043] Figure 9 This is a comparison chart of the laser divergence angle output by a 30KW 100μm fiber laser using a 30m power transmission fiber assembly and the divergence angle output directly using a double-tapered fiber in the embodiment of this application;

[0044] Figure 10 This is a comparison chart of the Raman heat dissipation light reflectivity of the fiber laser after adopting the passive optical fiber in the embodiment of this application;

[0045] Figure 11 This is a diagram of the nonlinear effect of a 30KW 100μm fiber laser at full power output when the length of the energy transmission fiber assembly is 20 meters in the embodiment of the present application;

[0046] Figure 12 This is a diagram of the nonlinear effect of a 30KW 100μm fiber laser at full power output when the length of the energy transmission fiber assembly is 30 meters in the embodiment of the present application;

[0047] Figure 13This is a test diagram of the beam quality of a 30KW 100μm fiber laser at full power output when the energy transmission fiber assembly is 20 meters long in the embodiment of the present application;

[0048] Figure 14 This is a test diagram of the beam quality of a 30KW 100μm fiber laser at full power output when the length of the energy transmission fiber assembly in the embodiment of the present application is 30 meters.

[0049] Fiber laser system 100; laser 110; power transmission fiber assembly 120; tapered change region 1200; thin section 1201; thick section 1202; passive fiber 121; input section 1211; amplification section 1212; transmission section 1213; contraction section 1214; output section 1215; first fiber core 1216; first cladding 1217; first inner cladding 1218; first middle cladding 1219; first outer cladding 1220; mode stripping component 123; mode filter fiber 1231; second fiber core 1232; second cladding 1233; second inner cladding 1234; second middle cladding 1235; second outer cladding 1236; mode stripper 1237; end cap 125; window 126. DETAILED DESCRIPTION

[0050] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0051] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the said features. In the description of the present application, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0052] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections, electrical connections, or mutual communication; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to internal communication between two components or the interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0053] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0054] The disclosure below provides many different embodiments or examples for realizing different structures of the present application. In order to simplify the disclosure of the present application, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present application. In addition, the present application may repeat reference numbers and / or reference letters in different examples, and such repetition is for the purpose of simplicity and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present application provides examples of various specific processes and materials, but those of ordinary skill in the art will appreciate the application of other processes and / or the use of other materials.

[0055] The embodiments of the present application provide an energy transmission fiber assembly and a fiber laser system, which are described in detail below.

[0056] First, an embodiment of the present application provides an energy transmission optical fiber assembly.

[0057] Figure 1 A schematic structural diagram of an embodiment of a fiber laser system provided in an embodiment of the present application. Figure 2 This is a schematic diagram of the structure of an embodiment of the energy transmission optical fiber assembly provided in the embodiment of the present application. Figure 1As shown, the fiber laser system 100 includes a laser 110 and a power transmission fiber assembly 120. The laser 110 is used to generate a laser beam. The input end of the power transmission fiber assembly 120 is optically connected to the output end of the laser 110, so that the power transmission fiber receives the laser beam output from the output end of the laser 110 and outputs the laser beam from the output end of the power transmission fiber assembly 120.

[0058] It should be noted that the input end of the energy transmission fiber optic component 120 is connected to the optical path of the output end of the laser 110. The input end of the energy transmission fiber optic component 120 can be directly connected to the output end of the laser 110, or the input end of the energy transmission fiber optic component 120 can be located in the optical path of the output end of the laser 110. It is only necessary to ensure that the laser beam output from the output end of the laser 110 can enter the energy transmission fiber optic component 120 from the input end of the energy transmission fiber optic component 120.

[0059] In some embodiments, as Figure 2 and Figure 3 As shown, the energy transmission fiber optic assembly 120 includes a passive optical fiber 121. The input end of the passive optical fiber 121 is used to be connected to the output end optical path of the laser 110 of the fiber laser system 100, and is used to transmit the laser beam output from the output end of the laser 110. The laser beam output from the output end of the laser 110 can enter the passive optical fiber 121 from the input end of the passive optical fiber 121 and be output from the output end of the passive optical fiber 121.

[0060] As the power of the laser 110 increases, or as the length of the passive fiber 121 increases, stimulated Raman scattering (SRS) within the passive fiber 121 of the power delivery fiber assembly 120 increases significantly, thereby affecting the stability of the fiber laser system 100. In particular, when the ratio of the laser energy of the laser 110 to the stimulated Raman scattering energy within the power delivery fiber assembly 120 is close (e.g., a deterioration of less than 15 dB), the fiber laser system 100 is at risk of collapse.

[0061] In order to avoid the above problems, in some embodiments, as Figure 2 and Figure 3 As shown, the passive optical fiber 121 can include an amplifying section 1212, a transmission section 1213 and a contraction section 1214 connected in sequence from the input end to the output end of the passive optical fiber 121, the amplifying section 1212 is used to amplify the spot of the laser beam, and the contraction section 1214 is used to contract the spot of the laser beam.

[0062] The energy transmission fiber optic assembly 120 provided in the embodiment of the present application is provided with an amplifying section 1212 for amplifying the light spot of the laser beam at the input end of the passive optical fiber 121, so as to reduce the energy density of the laser beam, so that the laser beam can be transmitted over a long distance in the transmission section 1213 with a lower energy density. Then, a contraction section 1214 for contracting the light spot of the laser beam is provided at the output end of the passive optical fiber 121, so as to contract the light spot of the laser beam output from the output end of the transmission section 1213, so as to increase the energy density of the laser beam, thereby achieving long-distance transmission of the laser beam through the energy transmission fiber optic assembly 120 while reducing stimulated Raman scattering (SRS) in the energy transmission fiber optic assembly 120, that is, while the length of the energy transmission fiber optic assembly 120 is increased, the beam quality of the laser beam transmitted by the energy transmission fiber optic assembly 120 remains basically unchanged.

[0063] Moreover, the passive optical fiber 121 of the energy transmission optical fiber assembly 120 provided in the embodiment of the present application is not affected by whether the core is doped with photosensitivity. Therefore, it can be applied to a variety of different types of optical fiber laser systems 100 and has extremely high compatibility.

[0064] In the embodiment of the present application, an amplifying section 1212 for amplifying the spot of the laser beam is provided at the input end of the passive optical fiber 121 of the power transmission optical fiber assembly 120, and a contraction section 1214 for contracting the spot of the laser beam is provided at the output end of the passive optical fiber 121. The principle of achieving long-distance transmission of the laser beam while reducing stimulated Raman scattering (SRS) within the power transmission optical fiber assembly 120 is as follows:

[0065] The brightness formula of the laser beam (1) is as follows:

[0066] Brightness = P / (Ω·s) (1);

[0067] Where Brightness is the brightness of the laser beam, P is the total power of the laser beam, Ω is the three-dimensional divergence angle of the laser beam, and S is the area of ​​the laser beam.

[0068] According to the law of conservation of brightness and the brightness formula of a laser beam, in an ideal homogeneous medium, if there is no energy loss, the three-dimensional divergence angle and area of ​​the laser beam remain essentially unchanged. However, most laser beams are Gaussian beams or near-Gaussian beams, which are usually expressed by the beam parameter product (BPP) or beam quality (M2). This is the following formula (2):

[0069] BPP=θ*w (2);

[0070] Where BPP is the beam parameter product of the laser beam, θ is the laser beam divergence angle (half angle), and w is the beam waist radius of the laser beam. As can be seen from formula (2), the smaller the BPP, the higher the beam quality. The beam quality (M2) and the beam parameter product (BPP) can be converted to each other according to the following formula (3):

[0071] M 2 =(BPP*π) / λ (3);

[0072] Among them, M 2 The values ​​are normalized BPP values ​​for a diffraction-limited beam with a specific wavelength, where λ is the wavelength of the laser beam.

[0073] According to the law of conservation of brightness and the above formulas (1)-(3), when a laser beam is transmitted in a homogeneous medium, there is no energy loss and its brightness remains unchanged. Simply put, in a spatial beam, when there is no energy loss, any lens (ideal lens) transformation does not change the brightness of the beam. In other words, the M2 (or BPP) of a laser beam does not change with lens transformation.

[0074] For waveguide structures, especially optical fibers, the theory is still applicable, provided that the adiabatic conditions are met. Figure 6 As shown, when the laser beam propagates from thin segment 1201 to thick segment 1202 in the fiber core, the beam parameter product BPP1 of the laser beam in thin segment 1201 is equal to w1*θ1. The variation range of the tapered region 1200 of the core supports adiabatic properties. Simply put, the curvature of the tapered region 1200 is small, which does not cause additional mode excitation and leakage. In other words, when there is no power loss, the beam parameter product BPP2 of the laser beam output from thick segment 1202 is equal to w2*θ2=BPP1. In other words, when the laser beam propagates from thin segment 1201 to thick segment 1202 in the fiber core, the input and output brightness remain unchanged.

[0075] Likewise, if Figure 7 As shown, the brightness conservation law is still satisfied when the laser beam is transmitted in the reverse direction. When the laser beam propagates from the thick core segment 1202 to the thin core segment 1201 in the fiber core, the beam parameter product BPP2 of the laser beam in the thick core segment 1202 is equal to w2*θ2. The range of variation of the tapered core region 1200 supports adiabatic properties. Simply put, the curvature of the tapered core region 1200 is small, which does not cause additional mode excitation and leakage. In other words, when there is no power loss, the beam parameter product BPP1 of the laser beam output from the thin core segment 1201 is equal to w1*θ1. This means that when the laser beam propagates from the thick core segment 1202 to the thin core segment 1201 in the fiber core, the input and output brightness remain unchanged.

[0076] Therefore, if Figure 8 As shown, the beam parameter product BPP1=w1*θ1 of the laser beam in the amplification section 1212 and the contraction section 1214 of the passive optical fiber 121 is equal to the beam parameter product BPP2=w2*θ2 of the laser beam in the transmission section 1213 of the passive optical fiber 121, that is, the brightness of the laser beam remains unchanged when it is transmitted from the input end to the output end of the passive optical fiber 121.

[0077] The Raman threshold of the optical fiber can be calculated using the following formula (4):

[0078] P th =16·A eff / (g r ·L eff ) (4);

[0079] Among them, P th is the fiber Raman threshold, A eff is the fiber mode field area, g r is the fiber Raman gain coefficient, L eff is the effective length of the optical fiber.

[0080] Since the energy transmission fiber assembly 120 in the embodiment of the application does not need to consider energy amplification and its own loss is relatively small, the energy loss can be ignored. Therefore, according to formula (4), the larger the effective mode field area, the higher the stimulated Raman scattering threshold, which can suppress the stimulated Raman scattering effect in long-distance laser transmission. In order to increase the Raman threshold while maintaining the same transmission length, the effective mode field area can only be increased. According to the conclusion in the previous article: when the laser beam passes through the tapered change region 1200 of the optical fiber, the brightness of the laser beam remains unchanged. Therefore, the power density can be reduced by increasing the effective mode field area while maintaining the brightness unchanged.

[0081] Therefore, the energy transmission fiber optic component 120 provided in the embodiment of the present application can effectively reduce the energy density in the transmission section 1213 of the passive optical fiber 121 by setting an amplification section 1212 at the input end of the passive optical fiber 121 and setting a contraction section 1214 at the output end of the passive optical fiber 121, so as to achieve the effect of long-distance transmission of the laser beam by the passive optical fiber 121 and keep the beam quality of the laser beam basically unchanged.

[0082] Although an amplifying section 1212 for amplifying the laser beam spot is provided at the input end of the passive optical fiber 121 of the power transmission fiber assembly 120, and a contracting section 1214 for contracting the laser beam spot is provided at the output end of the passive optical fiber 121, thereby enabling long-distance transmission of the laser beam through the power transmission fiber assembly 120 while reducing stimulated Raman scattering (SRS) within the power transmission fiber assembly 120, when researchers use the power transmission fiber assembly 120 including the passive optical fiber 121 in the fiber laser system 100, the laser beam of the power transmission fiber assembly 120 may suffer from poor stability, or even cause irreversible damage to the fiber laser system 100.

[0083] After repeated experiments and in-depth research by R&D personnel, it was found that the reason for the poor stability of the laser beam of the energy transmission fiber optic assembly 120 is that when the amplifying section 1212 and the contracting section 1214 of the passive optical fiber 121 amplify and contract the light spot of the laser beam, due to the self-structure, internal stress, environmental interference and other factors of the amplifying section 1212 and the contracting section 1214 of the passive optical fiber 121, the thermal insulation of the amplifying section 1212 and the contracting section 1214 of the passive optical fiber 121 will be broken, which is equivalent to two fixed disturbances, causing ultra-high-order mode light to be excited in the laser beam. The ultra-high-order mode will affect the stability of the laser beam, and thus affect the stability of the laser system, and even cause irreversible damage to the fiber laser system 100.

[0084] Among them, ultra-high-order mode light refers to light that has not converged after the divergence angle is greater than or equal to 0.125 radians (rad). Figure 9 As shown, when the stripping component 123 is not connected to the output optical path of the passive optical fiber 121, the divergence angle of the laser beam is 0.138 rad ( Figure 9 Therefore, ultra-high-order mode light will be generated.

[0085] In order to avoid the above problems and improve the stability of the laser beam transmitted by the energy transmission fiber assembly 120, in the embodiment of the present application, Figure 2 and Figure 3 As shown, the power transmission fiber assembly 120 also includes a stripping component 123 and an end cap 125. The input end of the stripping component 123 is optically connected to the output end of the passive optical fiber 121. The stripping component 123 is used to strip ultra-high-order mode light from the laser beam. The input end of the end cap 125 is optically connected to the output end of the stripping component 123.

[0086] The energy transmission fiber assembly 120 provided in the embodiment of the present application connects the input end of the stripping component 123 to the optical path of the output end of the passive optical fiber 121, and connects the input end of the end cap 125 to the optical path of the output end of the stripping component 123. This allows the stripping component 123 to strip the ultra-high-order mode light excited in the laser beam transmitted by the passive optical fiber 121. This allows the laser beam stripped of the ultra-high-order mode light to be converted into spatial light and emitted at the output end of the end cap 125. This reduces the probability of the high-energy-density laser beam being directly output from the output end of the stripping component 123 and damaging the stripping component 123. Experimental testing has shown that although the stripping of the ultra-high-order mode light by the stripping component 123 results in a partial energy loss in the laser beam, the energy loss is minimal, less than 1% of the laser beam energy, and the stability of the laser system is significantly enhanced. Therefore, the problem of ultra-high-order mode light in the laser beam affecting the stability of the laser beam and thus the stability of the laser system can be avoided.

[0087] like Figure 9 As shown, the energy transmission fiber assembly 120 provided in the embodiment of the present application can achieve convergence of the laser beam divergence angle at 0.123 radians (rad) by connecting the mode filter component to the output optical path of the passive optical fiber 121 ( Figure 9 When the mode filter component is not connected to the output optical path of the passive optical fiber 121, the divergence angle of the laser beam is 0.138 rad ( Figure 9 Therefore, ultra-high-order mode light will be generated.

[0088] In some embodiments, the end surface of the output end of end cap 125 is provided with multiple layers of first anti-reflection coating (not shown). By providing multiple layers of first anti-reflection coating on the end surface of the output end of end cap 125, the transmittance of the laser beam and Raman scattered light at the output end of end cap 125 can be increased, while the reflectivity of the end surface of the output end of end cap 125 to the laser beam and Raman scattered light can be reduced, thereby further suppressing stimulated Raman scattering (SRS). The number of layers of first anti-reflection coating provided on the end surface of the output end of end cap 125 is preferably greater than or equal to four to maximize the transmittance of the laser beam at the output end of end cap 125.

[0089] Because the Raman effect is similar to laser amplification, when the seed Raman light aggregated from the transmitted laser is low (the proportion of Raman components in the signal light is low), the Raman gain in the energy transmission fiber assembly 120 is similar to stimulated emission amplification, and the efficiency is low. However, when the neutron Raman light is high, an effect similar to laser amplification occurs, at which point the efficiency is higher, and the Raman light is rapidly amplified. The wavelength of the anti-reflection coating on the end face of the output end of the conventional end cap 125 is generally only targeted at the wavelength of the laser beam and does not involve the Raman wavelength. In other words, the anti-reflection coating on the end face of the output end of the conventional end cap 125 generally only increases the transmittance of the laser beam and does not increase the transmittance of the Raman heat dissipation light.

[0090] The energy transmission fiber assembly 120 proposed in this application is capable of simultaneously achieving low reflectivity of the laser beam and Raman heat dissipation light by providing a multi-layer first anti-reflection film on the end face of the output end of the end cap 125, thereby further suppressing stimulated Raman scattering (SRS).

[0091] like Figure 2 and Figure 3 As shown, the power transmission fiber assembly 120 further includes a window 126, which is disposed in the optical path of the output end of the end cap 125. Thus, the window 126 can protect the end cap 125 and allow the laser beam and Raman scattered light output from the output end of the end cap 125 to pass through the window 126.

[0092] In some embodiments, a multi-layer second anti-reflection film (not shown) is provided on the surface of the window 126 facing the end cap 125 to increase the transmittance of the laser beam and Raman scattered light on the surface of the window 126 facing the end cap 125, thereby further suppressing stimulated Raman scattering (SRS). The number of layers of the second anti-reflection film provided on the surface of the window 126 facing the end cap 125 is greater than or equal to 4, so as to maximize the transmittance of the laser beam and Raman scattered light on the surface of the window 126 facing the end cap 125.

[0093] Similarly, a multi-layer third anti-reflection film (not shown) is provided on the surface of the window 126 facing away from the end cap 125 to increase the transmittance of the laser beam and Raman scattered light on the surface of the window 126 facing away from the end cap 125, thereby further suppressing stimulated Raman scattering (SRS). The number of layers of the third anti-reflection film provided on the surface of the window 126 facing away from the end cap 125 is greater than or equal to four, so as to maximize the transmittance of the laser beam and Raman scattered light on the surface of the window 126 facing away from the end cap 125.

[0094] In a preferred embodiment, the number of layers of the first anti-reflection film provided on the end face of the output end of the end cap 125 is greater than or equal to 4, the number of layers of the second anti-reflection film provided on the surface of the window 126 facing the end cap 125 is greater than or equal to 4, and the number of layers of the third anti-reflection film provided on the surface of the window 126 facing away from the end cap 125 is greater than or equal to 4, then the overall reflectivity of the end cap 125 and the window 126 to the laser beam and Raman scattered light is less than 0.2%, thereby suppressing stimulated Raman scattering (SRS) to the greatest extent.

[0095] Of course, it is also possible to apply multiple layers of the first antireflection film only to the end surface of the output end of the end cap 125. Alternatively, it is also possible to apply multiple layers of the second antireflection film only to the surface of the window 126 facing the end cap 125. Alternatively, it is also possible to apply multiple layers of the third antireflection film only to the surface of the window 126 facing away from the end cap 125. Furthermore, the materials of the first, second, and third antireflection films can be the same or different, as long as they can improve the transmittance of the laser beam and Raman scattered light.

[0096] In some embodiments, as Figure 2 and Figure 3 As shown, in the direction from the input end to the output end of the passive optical fiber 121, the diameter of the amplifying section 1212 gradually increases, so that when the laser beam passes through the amplifying section 1212 along the direction from the input end to the output end of the passive optical fiber 121, the amplifying section 1212 can amplify the light spot of the laser beam.

[0097] The ratio of the maximum diameter to the minimum diameter of the amplifying section 1212 is greater than or equal to 1.2. This ensures that the energy density of the laser beam is sufficiently low when the laser beam spot, after being amplified by the amplifying section 1212, enters the transmission section 1213, thereby reducing stimulated Raman scattering (SRS) of the laser beam during transmission in the transmission section 1213. Furthermore, the ratio of the maximum diameter to the minimum diameter of the amplifying section 1212 is less than or equal to 1.5 to avoid excessively increasing the ratio of the maximum diameter to the minimum diameter of the amplifying section 1212, which would significantly reduce the thermal insulation properties of the amplifying section 1212 and thereby increase ultra-high-order mode light.

[0098] In a preferred embodiment, the ratio of the maximum diameter to the minimum diameter of the amplifying section 1212 is between 1.2 and 1.5. This ensures that the laser beam spot, after amplification by the amplifying section 1212, has a low energy density in the transmission section 1213. This also ensures the thermal insulation of the amplifying section 1212 and prevents the generation of excessive ultra-high-order mode light. The ratio of the maximum diameter to the minimum diameter of the amplifying section 1212 can be 1.3, 1.4, or other values, depending on actual circumstances. For example, if the amplifying section 1212 is 4 meters long, the ratio of the maximum diameter to the minimum diameter of the amplifying section 1212 is 1.5.

[0099] Continue to refer to Figure 2 and Figure 3 In the direction from the input end to the output end of the passive optical fiber 121, the diameter of the contraction section 1214 gradually decreases, so that when the laser beam passes through the contraction section 1214 along the direction from the input end to the output end of the passive optical fiber 121, the contraction section 1214 can contract the spot of the laser beam.

[0100] The ratio of the maximum diameter to the minimum diameter of the contraction section 1214 is greater than or equal to 1.2 to prevent the laser beam spot from being too small and the energy density from being too high after contraction by the contraction section 1214, which could affect the stability of the laser system. Furthermore, the ratio of the maximum diameter to the minimum diameter of the contraction section 1214 is less than or equal to 1.5 to prevent an excessive decrease in the thermal insulation of the contraction section 1214, which could lead to an increase in ultra-high-order mode light.

[0101] In a preferred embodiment, the ratio of the maximum diameter to the minimum diameter of the contraction section 1214 is between 1.2 and 1.5. This ensures that the energy density of the laser beam is not excessively high after the laser beam spot is contracted by the contraction section 1214. Furthermore, the thermal insulation of the contraction section 1214 is ensured to prevent the generation of excessive ultra-high-order mode light. The ratio of the maximum diameter to the minimum diameter of the contraction section 1214 can be 1.3, 1.4, or other values, depending on the actual situation. For example, if the length of the contraction section 1214 is 4 meters, the ratio of the maximum diameter to the minimum diameter of the contraction section 1214 is 1.5.

[0102] In some embodiments, as Figure 2 and Figure 3 As shown, the mode stripping component 123 includes a filter mode fiber 1231 and a mode stripper 1237 disposed on the filter mode fiber 1231. The input end of the filter mode fiber 1231 is optically connected to the output end of the passive optical fiber 121, and the output end of the filter mode fiber 1231 is optically connected to the end cap 125. The filter mode fiber 1231 is used to convert ultra-high-order mode light in the laser beam into cladding light, and the mode stripper 1237 is used to strip the cladding light. Thus, after the ultra-high-order mode light is converted into cladding light by the filter mode fiber 1231 of the mode stripping component 123, the cladding light is stripped by the mode stripper 1237, thereby improving the stability of the laser beam.

[0103] Specifically, the passive optical fiber 121 further includes an input section 1211. The input section 1211, amplifying section 1212, transmission section 1213, and contraction section 1214 of the passive optical fiber 121 are optically connected in sequence from the input end to the output end of the passive optical fiber 121. The diameter of the input section 1211 is smaller than the diameter of the transmission section 1213. The end of the input section 1211 remote from the amplifying section 1212 serves as the input end of the passive optical fiber 121. A laser beam enters the input section 1211 from the end of the input end remote from the amplifying section 1212, amplifies the light spot in the amplifying section 1212, enters the transmission section 1213, and then contracts the laser beam spot in the contraction section 1214.

[0104] The input section 1211, amplification section 1212, transmission section 1213, and contraction section 1214 of the passive optical fiber 121 are integrally formed. Thus, the passive optical fiber 121 can be straightened in an integrated manner using a drawing tower, or by straightening one end of a standard optical fiber using a taper machine.

[0105] Passive optical fiber 121 also includes an output section 1215. One end of output section 1215 is optically connected to the end of contraction section 1214, distal from transmission section 1213. The diameter of output section 1215 is smaller than that of transmission section 1213. The end of output section 1215 distal from contraction section 1214 serves as the output end of passive optical fiber 121. After the laser beam narrows its spot in contraction section 1214, it enters output section 1215 and is output from the end of output section 1215 distal from contraction section 1214.

[0106] The output section 1215 and the contraction section 1214 are integrally formed. Thus, the passive optical fiber 121 can be formed by straightening the fiber using a drawing tower, or by straightening one end of a standard optical fiber using a taper machine.

[0107] In some embodiments, the input end of the filter mode fiber 1231 is optically connected to the end of the output section 1215 away from the contraction section 1214. Specifically, the input end of the filter mode fiber 1231 is fused to the end of the output section 1215 away from the contraction section 1214, thereby optically connecting the input end of the filter mode fiber 1231 to the end of the output section 1215 away from the contraction section 1214. This can change the numerical aperture (NA) of the filter mode fiber 1231, thereby improving the filtering effect on ultra-high-order mode light.

[0108] In some embodiments, as Figure 4 and Figure 5As shown, the passive optical fiber 121 includes a first core 1216 and a first cladding 1217 disposed on the outer circumference of the first core 1216. The filter mode optical fiber 1231 includes a second core 1232 and a second cladding 1233 disposed on the outer circumference of the second core 1232. The numerical aperture (NA) of the first core 1216 is greater than or equal to the numerical aperture (NA) of the second core 1232. This utilizes the mismatch between the numerical aperture (NA) of the first core 1216 of the passive optical fiber 121 and the numerical aperture (NA) of the second core 1232 of the filter mode optical fiber 1231 to enhance the filter mode optical fiber 1231's ability to filter ultra-high-order mode light.

[0109] In other embodiments, the input end of the filter mode fiber 1231 is optically connected to the end of the contraction section 1214 away from the transmission section 1213, and the filter mode fiber 1231 and the contraction section 1214 are integrally formed, with the diameter of the filter mode fiber 1231 being smaller than the diameter of the transmission section 1213. Thus, the filter mode fiber 1231 and the passive optical fiber 121 can be formed by straightening them together using a draw tower, or by straightening one end of a standard optical fiber using a taper machine. This makes processing more convenient, and there is no fusion splice between the filter mode fiber 1231 and the passive optical fiber 121, further improving the optical performance of the power transmission optical fiber assembly 120.

[0110] In some embodiments, as Figure 4 As shown, the first cladding 1217 of the passive optical fiber 121 includes a first inner cladding 1218, a first middle cladding 1219 and a first outer cladding 1220, which are sequentially distributed in a direction away from the first core 1216. The refractive indices of the first middle cladding 1219, the first inner cladding 1218 and the first outer cladding 1220 gradually decrease. The refractive indices of the first core 1216, the first inner cladding 1218 and the first outer cladding 1220 gradually decrease, so as to confine the laser beam to the first core 1216 and the second middle cladding 1235 for transmission.

[0111] Specifically, the numerical aperture (NA) of the first fiber core 1216 is greater than or equal to 0.12 and less than or equal to 0.23. The numerical aperture (NA) of the first middle cladding 1219 is greater than or equal to 0.3 and less than or equal to 0.46, so as to confine the laser beam to be transmitted within the first fiber core 1216 and the second middle cladding 1235.

[0112] In some embodiments, as Figure 5As shown, the second cladding 1233 includes a second inner cladding 1234, a second middle cladding 1235, and a second outer cladding 1236, which are sequentially distributed away from the second core 1232. The refractive indices of the second middle cladding 1235, the second inner cladding 1234, and the second outer cladding 1236 gradually decrease. The gradually decreasing refractive indices of the second core 1232, the second inner cladding 1234, and the second outer cladding 1236 confine the laser beam to the second core 1232 and the second middle cladding 1235 for transmission.

[0113] Furthermore, by making the first cladding 1217 of the passive optical fiber 121 include a first inner cladding 1218, a first middle cladding 1219, and a first outer cladding 1220, and making the second cladding 1233 of the filter mode optical fiber 1231 include a second inner cladding 1234, a second middle cladding 1235, and a second outer cladding 1236, the refractive indexes of the first core 1216 of the passive optical fiber 121 and the second core 1232 of the filter mode optical fiber 1231 can be made the same or close. After being fused with the second core 1232 of the filter mode optical fiber 1231, no Fresnel reflection will be caused, so as to avoid the Fresnel reflection at the fusion point between the first core 1216 of the passive optical fiber 121 and the second core 1232 of the filter mode optical fiber 1231, which will cause losses to the fiber laser system 100. At the same time, the Raman scattered light reflected at the fusion point between the first core 1216 of the passive optical fiber 121 and the second core 1232 of the filter mode optical fiber 1231 is avoided to further increase the stimulated Raman scattering problem of the entire system.

[0114] In some embodiments, the diameter of the first fiber core 1216 is greater than or equal to 10 μm, and the numerical aperture (NA) of the first fiber core 1216 is greater than or equal to 0.065. By ensuring that the diameter of the first fiber core 1216 of the passive optical fiber 121 is greater than or equal to 10 μm and the numerical aperture (NA) of the first fiber core 1216 is greater than or equal to 0.065, significant light leakage during laser beam transmission from the passive optical fiber 121 can be avoided, thereby preventing damage to the fiber laser system 100.

[0115] Specifically, the first core 1216 and first middle cladding 1219 of the passive optical fiber 121, as well as the second core 1232 and second middle cladding 1235 of the filter mode optical fiber 1231, are all made of pure silica. The first inner cladding 1218 of the passive optical fiber 121 and the first inner cladding 1218 of the filter mode optical fiber 1231 are fluorine-doped layers, which are used to confine the laser beam to propagate within the first core 1216 or the second core 1232. The first outer cladding 1220 of the passive optical fiber 121 and the second outer cladding 1236 of the filter mode optical fiber 1231 are low-refractive-index coatings, which are used to confine the cladding light of the laser beam to propagate within the first middle cladding 1219 and the second middle cladding 1235.

[0116] In some embodiments, the end face of the input end of the end cap 125 is fused to the output end of the filter mode optical fiber 1231, thereby optically connecting the input end of the end cap 125 to the output end of the stripping component 123. The power transmission fiber assembly 120 may further include a mounting base (not shown), to which the end cap 125 and the window 126 are respectively mounted, so that the window 126 is located in the optical path of the output end of the end cap 125. The mounting base is a metal output head, and the end cap 125 and the window 126 are encapsulated in the metal output head. The metal output head can be cooled using active water cooling.

[0117] A specific embodiment of the energy transmission optical fiber assembly 120 is described in detail below.

[0118] The input section 1211, amplification section 1212, contraction section 1214, and output section 1215 of the passive optical fiber 121 of the power transmission fiber assembly 120 are all 4 meters long, and the transmission section 1213 is 20 meters long. In the input section 1211 of the passive optical fiber 121, the first core 1216 has a diameter of 100 μm and a numerical aperture (NA) of 0.22. The outer diameter of the first inner cladding 1218 is 120 μm, and the outer diameter of the first middle cladding 1219 is 360 μm. In the amplification section 1212 of the passive optical fiber 121, the first core 1216 has a minimum diameter of 100 μm and a maximum diameter of 150 μm, with a numerical aperture (NA) of 0.22. The minimum outer diameter of the first middle cladding 1219 is 360 μm and a maximum outer diameter of 540 μm. In the transmission section 1213 of the passive optical fiber 121, the first core 1216 has a diameter of 150 μm and a numerical aperture (NA) of 0.22, and the outer diameter of the first middle cladding 1219 is 540 μm. In the contraction section 1214 of the passive optical fiber 121, the first core 1216 has a minimum diameter of 100 μm and a maximum diameter of 150 μm, and a numerical aperture (NA) of 0.22. The first middle cladding 1219 has a minimum outer diameter of 360 μm and a maximum outer diameter of 540 μm. In the output section 1215 of the passive optical fiber 121, the first core 1216 has a diameter of 100 μm and a numerical aperture (NA) of 0.22. The outer diameter of the first inner cladding 1218 is 120 μm, and the outer diameter of the first middle cladding 1219 is 360 μm.

[0119] The filter mode fiber 1231 of the stripping component 123 has a length of 30 cm, a second fiber core 1232 with a diameter of 100 μm, and a numerical aperture (NA) of 0.22. A stripper 1237 is integrated into the filter mode fiber 1231. One end of the filter mode fiber 1231 is fused to the output end of the passive optical fiber 121, and the other end of the filter mode fiber 1231 is fused to the end cap 125.

[0120] The passive optical fiber 121 and the filter mode optical fiber 1231 of the power transmission optical fiber assembly 120 are enclosed in a 30-meter-long metal armored tube. A portion of the fiber routing of the laser 110 is also located in the armored tube.

[0121] The laser center wavelength of the laser 110 of the fiber laser system 100 is 1070 nm-1080 nm.

[0122] like Figure 10 As shown, at the laser center wavelength of 1080nm, the reflectivity of the end cap 125 and window 126 of the conventional fiber laser system 100 for Raman scattered light (shown by the dotted line) is close to the reflectivity of the end cap 125 and window 126 of the fiber laser system 100 provided in the embodiment of the present application for Raman scattered light (shown by the solid line), both being less than 0.1%. However, at a laser wavelength of 1135nm, the reflectivity of the end cap 125 and window 126 of the fiber laser system 100 provided in the embodiment of the present application for Raman scattered light is less than or equal to 0.1%, while the reflectivity of the end cap 125 and window 126 of the conventional fiber laser system 100 for Raman scattered light exceeds 0.5%. At this point, a large amount of Raman dissipated light is reflected back into the energy-transmitting fiber assembly 120 to form Raman seeds, which are further amplified and worsen the nonlinear effects of the entire system.

[0123] Therefore, the energy transmission fiber optic assembly 120 provided in the embodiment of the present application can reduce the reflectivity of the Raman band, making it difficult for the Raman light to return and thus preventing the feedback amplification effect.

[0124] like Figures 11 to 14 As shown, when the length of the energy transmission fiber assembly 120 provided in the embodiment of the present application is 20 meters and the output power of the laser 110 is 30KW, the nonlinear effect is 19.37dB ( Figure 11 ), beam quality M2 is 10.9( Figure 13 When the length of the energy transmission optical fiber assembly 120 provided in the embodiment of the present application is extended to 30 meters, the nonlinear effect is optimized from 19.37 dB to 31.95 dB ( Figure 12 ), and the beam quality M2 is 11.1( Figure 14 ), the deterioration rate of the beam quality M2 is only 1.8%, which has no impact on practical applications.

[0125] The embodiments of the present application also propose a fiber laser system, which includes an energy transmission fiber optic component. The specific structure of the energy transmission fiber optic component refers to the above embodiments. Since the fiber laser system adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be repeated here.

[0126] The fiber laser system 100 includes a laser 110 and a power transmission fiber assembly 120. The laser 110 is used to generate laser light. The power transmission fiber assembly 120 is the power transmission fiber assembly 120 described in any of the above embodiments, or is manufactured using the method for manufacturing the power transmission fiber assembly 120 described in any of the above embodiments. The input end of the passive optical fiber 121 of the power transmission fiber assembly 120 is optically connected to the output end of the laser 110.

[0127] The laser system provided in the embodiment of the present application is provided with an amplifying section 1212 for amplifying the spot of the laser beam at the input end of the passive optical fiber 121 of the power transmission optical fiber assembly 120, so as to reduce the energy density of the laser beam, so that the laser beam can be transmitted over a long distance in the transmission section 1213 with a lower energy density. Then, a contraction section 1214 for contracting the spot of the laser beam is provided at the output end of the passive optical fiber 121, so as to contract the spot of the laser beam output from the output end of the transmission section 1213, so as to increase the energy density of the laser beam, thereby achieving long-distance transmission of the laser beam through the power transmission optical fiber assembly 120 while reducing stimulated Raman scattering (SRS) in the power transmission optical fiber assembly 120. That is, while the length of the power transmission optical fiber assembly 120 is increased, the beam quality of the laser beam transmitted by the power transmission optical fiber assembly 120 remains basically unchanged.

[0128] Furthermore, the passive optical fiber 121 of the energy transmission optical fiber assembly 120 is not affected by whether the core is doped with a photosensitive substance. Therefore, the passive optical fiber 121 can be applied to various types of optical fiber laser systems 100 and has extremely high compatibility.

[0129] On this basis, by connecting the input end of stripping component 123 to the optical path of the output end of passive optical fiber 121, and by connecting the input end of end cap 125 to the optical path of the output end of stripping component 123, ultra-high-order mode light (light that has not yet converged after a divergence angle greater than or equal to 0.125 radians) excited in the laser beam transmitted by passive optical fiber 121 can be stripped away by stripping component 123. The laser beam stripped of ultra-high-order mode light is then converted into spatial light and emitted at the output end of end cap 125. This prevents the ultra-high-order mode light in the laser beam from affecting the stability of the laser beam, thereby affecting the stability of the laser system.

[0130] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0131] The above is a detailed introduction to an energy transmission fiber optic component and a fiber laser system provided in the embodiments of the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the technical solutions and core ideas of the present application. Those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An energy transmission optical fiber assembly, characterized in that: The energy transmission optical fiber assembly comprises: A passive optical fiber, wherein the input end of the passive optical fiber is used to be connected to the optical path of the output end of the laser and to transmit the laser beam outputted from the output end of the laser. The passive optical fiber comprises an amplifying section, a transmission section, and a contraction section sequentially connected from the input end to the output end of the passive optical fiber. The amplifying section is used to amplify the spot of the laser beam, and the contraction section is used to contract the spot of the laser beam. a stripping component, wherein an input end of the stripping component is optically connected to an output end of the passive optical fiber, and the stripping component is used to strip ultra-high-order mode light in the laser beam; An end cap, wherein the input end of the end cap is optically connected to the output end of the stripping component.

2. The energy transmission optical fiber assembly according to claim 1, wherein: The end surface of the output end of the end cap is provided with a multi-layer first anti-reflection film; The energy transmission optical fiber assembly also includes a window, which is arranged on the optical path of the output end of the end cap; the surface of the window facing the end cap is provided with multiple layers of second anti-reflection film, and the surface of the window away from the end cap is provided with multiple layers of third anti-reflection film.

3. The energy transmission optical fiber assembly according to claim 2, wherein: The number of layers of the first antireflection film is greater than or equal to 4; the number of layers of the second antireflection film is greater than or equal to 4; and the number of layers of the third antireflection film is greater than or equal to 4.

4. The energy transmission optical fiber assembly according to any one of claims 1 to 3, wherein: In the direction from the input end to the output end of the passive optical fiber, the diameter of the amplifying section gradually increases, and the diameter of the contracting section gradually decreases; The ratio of the maximum diameter to the minimum diameter of the enlarged section is greater than or equal to 1.2; the ratio of the maximum diameter to the minimum diameter of the enlarged section is less than or equal to 1.5; and / or, The ratio of the maximum diameter to the minimum diameter of the contraction section is greater than or equal to 1.2; the ratio of the maximum diameter to the minimum diameter of the contraction section is less than or equal to 1.

5.

5. The energy transmission optical fiber assembly according to any one of claims 1 to 3, wherein: The mode stripping component includes a filter mode optical fiber and a mode stripper provided on the filter mode optical fiber. The input end of the filter mode optical fiber is optically connected to the output end of the passive optical fiber, and the output end of the filter mode optical fiber is optically connected to the end cap. The filter mode optical fiber is used to convert the ultra-high-order mode light in the laser beam into cladding light, and the mode stripper is used to strip the cladding light.

6. The energy transmission optical fiber assembly according to claim 5, wherein: The passive optical fiber includes a first fiber core and a first cladding arranged on the outer circumference of the first fiber core; the filter mode optical fiber includes a second fiber core and a second cladding arranged on the outer circumference of the second fiber core; the numerical aperture (NA) of the first fiber core is greater than or equal to the numerical aperture (NA) of the second fiber core.

7. The energy transmission optical fiber assembly according to claim 6, wherein: The first cladding includes a first inner cladding, a first middle cladding, and a first outer cladding sequentially distributed in a direction away from the first core, and the refractive indices of the first middle cladding, the first inner cladding, and the first outer cladding gradually decrease; the refractive indices of the first core, the first inner cladding, and the first outer cladding gradually decrease; and / or, The second cladding includes a second inner cladding, a second middle cladding and a second outer cladding distributed in sequence in a direction away from the second fiber core; the refractive index of the second middle cladding, the second inner cladding and the second outer cladding gradually decreases; the refractive index of the second fiber core, the second inner cladding and the second outer cladding gradually decreases.

8. The energy transmission optical fiber assembly according to claim 7, wherein: The diameter of the first fiber core is greater than or equal to 10 μm; the numerical aperture (NA) of the first fiber core is greater than or equal to 0.065; and / or, The numerical aperture (NA) of the first fiber core is greater than or equal to 0.12 and less than or equal to 0.23; the numerical aperture (NA) of the first middle cladding is greater than or equal to 0.3 and less than or equal to 0.

46.

9. The energy transmission optical fiber assembly according to claim 5, wherein: The passive optical fiber further includes an input section, wherein the input section, the amplification section, the transmission section, and the contraction section are integrally formed and optically connected in sequence along the input end to the output end of the passive optical fiber, and the diameter of the input section is smaller than the diameter of the transmission section; Wherein, the passive optical fiber further includes an output section, one end of the output section is optically connected to the end of the contraction section away from the transmission section, and the output section and the contraction section are integrally formed, and the diameter of the output section is smaller than the diameter of the transmission section; the input end of the filter mode optical fiber is optically connected to the end of the output section away from the contraction section; or, The input end of the filter mode optical fiber is optically connected to an end of the contraction section away from the transmission section, and the filter mode optical fiber and the contraction section are integrally formed, and the diameter of the filter mode optical fiber is smaller than the diameter of the transmission section.

10. A fiber laser system, characterized in that: The fiber laser system includes: a laser for generating a laser beam; An energy transmission fiber optic component, wherein the energy transmission fiber optic component is the energy transmission fiber optic component according to any one of claims 1 to 9, and the input end of the passive optical fiber of the energy transmission fiber optic component is optically connected to the output end of the laser.

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