High-reflection-light-resistant laser and manufacturing method thereof

Abstract

The invention relates to the technical field of light transmission, in particular to a high-return-light-resistant laser and a manufacturing method thereof.The high-return-light-resistant laser is characterized in that a red light unit and a laser unit are coupled through a red light optical fiber and a main optical fiber, the red light optical fiber is an optical fiber with the gradually-changed refractive index, and the main optical fiber is an optical fiber with the gradually-changed refractive index; the red light signal can be transmitted to the main optical fiber through the design of gradually changing the refractive index, and is transmitted in the forward direction along the laser unit; the refractive index of the red light optical fiber is set to be smaller than the refractive index of the main optical fiber, due to the fact that the refractive indexes of the red light optical fiber and the main optical fiber are different, the return light can be totally reflected at the coupling position of the main optical fiber and the red light optical fiber, and therefore the return light is effectively limited in the main optical fiber, and the return light is reversely transmitted along the main optical fiber. And the risk that the red light diode in the red light unit is damaged by the return light is reduced.

Description

Technical Field

[0001] The present invention relates to the field of optical transmission technology, and in particular to a laser capable of resisting high-return light and a manufacturing method thereof. Background Art

[0002] As the application of fiber lasers continues to expand, the demand for laser stability is also increasing. Different versions of lasers will be used for the diversity of application scenarios. For the cutting and processing of certain metal materials, such as copper, aluminum and other metal materials, these materials have a high surface reflectivity to the laser of the fiber laser. The laser reflected by the surface can be reversely coupled to the core or cladding of the fiber laser. This part of the reverse laser can be amplified and transmitted to the indication light path when passing through the gain fiber of the fiber laser; in addition, due to the incomplete reflection of the high-reflection grating in the resonant cavity light path or the Raman laser generated by the system, it will be transmitted back through the core to the indication light path. The laser transmitted in the reverse direction along the core can cause serious damage to the red light diode in the indication light path, which can ultimately have a serious impact on the reliability and stability of the fiber laser.

[0003] Existing technologies for combating backlight generally include: the first method is to pass red light indicator light through a stripper, then coil the optical fiber, squeeze the backlight originally in the core into the cladding, and remove the backlight through a stripper; the second method is to remove the cladding light through spatial coupling, and use a spatial alignment scheme to process the cladding light. Since the divergence angle of the backlight is large, the red light passes through a focusing mirror and the backlight passes through a collimating mirror, and the backlight will be further reduced at this time.

[0004] The defects of the prior art are:

[0005] 1. Reducing the cladding light by coiling will cause part of the red light to be stripped off, and the coil cannot solve the problem of the return light propagating in the fiber core returning to the semiconductor, thus causing damage to the red light diode.

[0006] 2. The spatial coupling method is expensive, and the high power of the returned light will cause the lens to heat up, causing the red light to weaken and even cause the lens to burn.

[0007] In view of this, overcoming the defects of the prior art is an urgent problem to be solved in the field of this technology. Summary of the invention

[0008] The technical problem to be solved by the present invention is how to attenuate the returned light to reduce the risk of damage to the red light diode in the high-power laser caused by the returned light.

[0009] The present invention adopts the following technical solution:

[0010] In a first aspect, a laser resistant to high-return light is provided, comprising: a laser unit 1, a red light unit 2, a main optical fiber 3 and a red light optical fiber 4, wherein the output end of the red light unit 2 is coupled with one end of the red light optical fiber 4, and the other end of the red light optical fiber 4 is coupled with the side of the main optical fiber 3; the output end of the main optical fiber 3 is coupled with the input end of the laser unit 1;

[0011] The red light unit 2 is used to emit a red light signal, and the red light optical fiber 4 is used to receive the red light signal and transmit the red light signal to the main optical fiber 3;

[0012] The refractive index of the red light optical fiber 4 is lower than that of the main optical fiber 3 , so that the return light from the output end of the main optical fiber 3 is transmitted in the reverse direction along the main optical fiber 3 .

[0013] Preferably, the refractive index of the core of the red light optical fiber 4 gradually decreases as its core radius increases until it matches the refractive index of its cladding.

[0014] Preferably, the red light unit 2 comprises a red light diode 20, a stripper 21 and an output optical fiber 22 coupled in sequence along the optical path, and the output optical fiber 22 is fused with one end of the red light optical fiber 4;

[0015] The red light diode 20 is used to generate the red light signal, and the stripper 21 is used to perform mode field adaptation and mode stripping on the optical fiber through which the red light signal flows, so as to perform mode matching with the output optical fiber 22;

[0016] The output optical fiber 22 is used to transmit the red light signal to the red light optical fiber 4 .

[0017] Preferably, the stripper 21 comprises a mode field adapter 210 and a red light mode stripper 211 coupled in sequence;

[0018] The mode field adapter 210 is used to perform mode matching between the output pigtail of the red light diode 20 and the output optical fiber 22 , and the red light mode stripper 211 is used to set the stripping area in the mode matching area to reduce the transmission loss of the red light signal.

[0019] Preferably, the laser unit 1 comprises a forward beam combiner 10, a high reflection grating 11, a gain fiber 12, a low reflection grating 13, a reverse beam combiner 14 and an output head 15 which are sequentially coupled along the forward transmission direction of the red light signal; the forward beam combiner 10 is connected to at least one forward pump diode 16, and the reverse beam combiner 14 is connected to at least one reverse pump diode 17;

[0020] The forward combiner 10 is used to couple the first pump light emitted by the forward pump diode 16 into the gain fiber 12; the reverse combiner 14 is used to couple the second pump light output by the reverse pump diode 17 into the gain fiber 12;

[0021] The gain optical fiber 12 is used to obtain gain through the excitation of the first pump light and the second pump light, and to form a resonant structure through a grating pair composed of the high-reflection grating 11 and the low-reflection grating 13, so as to realize oscillation amplification of the laser to output the excitation light;

[0022] The excitation light outputs forward excitation light through the low-reflection grating 13 , and the forward excitation light is output through the output head 15 .

[0023] Preferably, a laser stripper 30 is provided at the rear end of the fusion joint between the red light optical fiber 4 and the main optical fiber 3 on the main optical fiber 3, and the laser stripper 30 is used to guide the return light into the corresponding heat dissipation device.

[0024] In a second aspect, a method for manufacturing a laser resistant to high-return light is provided, which is used to manufacture the laser resistant to high-return light as described in the first aspect, comprising:

[0025] coupling the output end of the red light unit 2 with one end of the red light optical fiber 4;

[0026] Processing the red light optical fiber 4 so that the refractive index of the red light optical fiber 4 is lower than the refractive index of the main optical fiber 3, and coupling the other end of the red light optical fiber 4 with the side of the main optical fiber 3;

[0027] The output end of the main optical fiber 3 is coupled to the input end of the laser unit 1 .

[0028] Preferably, making the refractive index of the red light optical fiber 4 lower than the refractive index of the main light optical fiber 3, and coupling the other end of the red light optical fiber 4 with the side surface of the main light optical fiber 3 comprises:

[0029] Performing heat treatment on the red light optical fiber 4 so that the numerical aperture of the red light optical fiber 4 is lower than the numerical aperture of the main optical fiber 3;

[0030] Stripping off the coating layer of the red light optical fiber 4 to expose its cladding, and cutting the end of the red light optical fiber 4 flat;

[0031] Performing a core expansion process on the core of the red light optical fiber 4 to make its refractive index lower than the refractive index of the main optical fiber 3, and heating and melting the red light optical fiber 4 to form a taper;

[0032] The coating layer of the main optical fiber 3 is stripped off, and the red optical fiber 4 after heating, melting and taper is fused with the cladding of the main optical fiber 3 to couple the red optical fiber 4 to the main optical fiber 3 .

[0033] Preferably, the calculation formula of the numerical aperture NA of the optical fiber is:

[0034]

[0035] Where n1 is the refractive index of the optical fiber core, and n2 is the refractive index of the optical fiber cladding.

[0036] Preferably, a red light stripper 211 is coupled to the red light unit 2, a laser stripper 30 is coupled to the main optical fiber 3, and the manufacturing method further includes:

[0037] Corrosion or etching is performed starting from the surface of the red light optical fiber 4 until the cladding at a preset position on the red light optical fiber 4 is removed to form a red light stripper 211;

[0038] Corrosion or etching is performed starting from the surface of the main optical fiber 3 until the core at a preset position on the main optical fiber 3 is removed to form a laser stripper 30;

[0039] The portion of the red light optical fiber 4 where the red light mode stripper 211 is located and the portion of the main optical fiber 3 where the laser mode stripper 30 is located are integrated in the device housing.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The present invention couples the red light unit 2 and the laser unit 1 through a red light fiber 4 and a main optical fiber 3, wherein the red light fiber 4 adopts an optical fiber with a gradient refractive index, and can transmit the red light signal to the main optical fiber 3 through a gradient refractive index design, and transmit it forward along the laser unit 1; the refractive index of the red light fiber 4 is set to be smaller than the refractive index of the main optical fiber 3, and since the refractive index of the red light fiber 4 is different from that of the main optical fiber 3, the returned light will be totally reflected at the coupling point between the main optical fiber 3 and the red light fiber 4, thereby being effectively confined in the main optical fiber 3, so that the returned light is transmitted in the reverse direction along the main optical fiber 3, reducing the risk of the returned light damaging the red light diode 20 in the red light unit 2. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0043] Figure 1 1 is a schematic structural diagram of a laser resistant to high-return light provided by an embodiment of the present invention;

[0044] Figure 2 is another structural schematic diagram of a laser resistant to high-return light provided by an embodiment of the present invention;

[0045] Figure 3 It is a structural schematic diagram of a red light unit of a laser resistant to high-return light provided by an embodiment of the present invention;

[0046] Figure 4 1 is a schematic structural diagram of a laser unit of a laser resistant to high-return light provided by an embodiment of the present invention;

[0047] Figure 5 It is a structural schematic diagram of a laser stripper for a laser that is resistant to high-return light provided by an embodiment of the present invention;

[0048] Figure 6 It is a schematic flow chart of a method for manufacturing a laser resistant to high-return light provided by an embodiment of the present invention;

[0049] Figure 7 It is another schematic flow chart of a method for manufacturing a laser resistant to high-return light provided by an embodiment of the present invention;

[0050] Figure 8 It is a structural schematic diagram of a red light stripper and a laser stripper for a laser that is resistant to high-return light provided by an embodiment of the present invention;

[0051] Fig. 9 It is a schematic structural diagram of an integrated arrangement of a red light stripper and a laser stripper for a laser that is resistant to high-return light provided by an embodiment of the present invention;

[0052] Fig.10 The present invention is a schematic diagram of the positions of a red light stripper and a laser stripper of a laser resistant to high-return light provided by an embodiment of the present invention after being integrated in the laser.

[0053] In all drawings, like reference numerals refer to like structures, wherein:

[0054] Laser unit 1, forward combiner 10, high reflection grating 11, gain fiber 12, low reflection grating 13, reverse combiner 14, output head 15, forward pump diode 16, reverse pump diode 17, red light unit 2, red light diode 20, stripper 21, mode field adapter 210, red light mode stripper 211, output fiber 22, main fiber 3, laser mode stripper 30, red light fiber 4. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0056] Unless the context requires otherwise, throughout the specification and claims, the term "including" is to be interpreted as open inclusion, that is, "including, but not limited to". In the description of the specification, the terms "one embodiment", "some embodiments", "exemplary embodiments", "examples", "specific examples" or "some examples" and the like are intended to indicate that specific features, structures, materials or characteristics associated with the embodiment or example are included in at least one embodiment or example of the present disclosure. The schematic representation of the above terms does not necessarily refer to the same embodiment or example. In addition, the specific features, structures, materials or characteristics may be included in any one or more embodiments or examples in any appropriate manner, that is, although they may be carried in the embodiments or examples of the above terms due to reasons such as the order and position of appearance, it is not limited to that they can be carried in combination by one embodiment or example.

[0057] In the description of the present invention, the terms "first" and "second" are used only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present disclosure, unless otherwise specified, the meaning of "multiple" is two or more. In addition, for example, the same type of nouns may be described as two independent individuals by adding "A" and "B" at the end. In this case, the corresponding features defined as "A" and "B" are only used to distinguish the same type of individuals for description purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features.

[0058] When describing some embodiments, the expressions "coupling", "coupling" and "connection" and their derivatives may be used. For example, when describing some embodiments, the term "connection" may be used to indicate that two or more components are in direct physical or electrical contact with each other. For another example, when describing some embodiments, the term "coupling" may be used to indicate that two or more components are in direct physical or electrical contact. However, the terms "connection" or "coupling" may also refer to two or more components that are not in direct contact with each other, but still cooperate or interact with each other, such as "optical path coupling", "wireless connection", etc. The embodiments disclosed herein are not necessarily limited to the contents of the present invention.

[0059] In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0060] Embodiment 1:

[0061] In lasers, the main reasons for the generation of return light include the following four aspects: (1) The laser and pump light are bidirectional transmissions. The grating mainly reflects the laser light of 1080nm±2nm in the fiber core. However, as the power increases in the laser, the loss of the active fiber and the passive fiber causes laser scattering. A portion of the laser light exceeding 1080nm will leak from the high-reflection grating to the cladding, forming return light. (2) In order to control the Raman of the entire machine, backward pumping is generally used. A portion of the pump light that is not absorbed will be transmitted along the cladding of the active fiber to form return light. (3) The active fiber generally used in the laser is very long. The active fiber will be coiled along a certain bending radius. In high-power fiber lasers, a portion of the laser mode is poor. The bending angle and the fiber transmission angle do not meet the total reflection conditions, and overflow from the core to the cladding. This type of laser and pump light will also pass through the high-reflection grating in the core, forming return light. (4) When cutting high-reflection materials, a portion of the laser light will return to the resonant cavity along the core, forming return light.

[0062] However, in traditional lasers, a red diode is usually placed at the front end of the laser. The red light signal generated by the red diode is emitted together with the laser light generated after the pump light excites the gain fiber, which is used to indicate the role of the light. Therefore, the return light generated in the above four cases will be reflected back to the red diode along the optical path, causing damage to the red diode.

[0063] In order to reduce the risk of the reflected light damaging the red light diode, this embodiment provides a laser that is resistant to high reflected light, such as Figure 1 and Figure 2 As shown, it includes: a laser unit 1, a red light unit 2, a main optical fiber 3 and a red light optical fiber 4, the output end of the red light unit 2 is coupled with one end of the red light optical fiber 4, and the other end of the red light optical fiber 4 is coupled with the side of the main optical fiber 3; the output end of the main optical fiber 3 is coupled with the input end of the laser unit 1; the red light unit 2 is used to emit a red light signal, and the red light optical fiber 4 is used to receive the red light signal and transmit the red light signal to the main optical fiber 3; the refractive index of the red light optical fiber 4 is lower than the refractive index of the main optical fiber 3, so that the return light from the output end of the main optical fiber 3 is transmitted in the reverse direction along the main optical fiber 3. In one embodiment, the red light optical fiber 4 can be the pigtail of the red light unit 2, which is directly coupled with the main optical fiber 3. At the same time, the red light optical fiber 4 can also be a separate optical fiber, one end of which is first coupled with the side of the main optical fiber 3, and then the other end is coupled with the output optical fiber 22 of the red light unit 2 (such as Figure 3) is coupled. Accordingly, for the convenience of distinguishing the description, the main optical fiber 3 can be coupled with the red light optical fiber 4 as a separate optical fiber and then coupled with the input end of the laser unit 1 (see the following description for details), or it can be directly coupled with the red light optical fiber 4 as a part of the laser unit 1. In this embodiment, the red light optical fiber 4 and the main optical fiber 3 are described as separate optical fibers. It is worth noting that the coupling here can be the fusion splicing of optical fibers by melting means. The specific fusion splicing techniques include side fusion splicing and end fusion splicing, which are not described in detail in this embodiment.

[0064] In order to resist high return light, the present embodiment uses a red light unit 2, a red light optical fiber 4 and a main optical fiber 3. The red light unit 2 generates a red light signal, and the red light optical fiber 4 is used to receive and transmit the red light signal to the main optical fiber 3. By setting the refractive index of the red light optical fiber 4 to be lower than the refractive index of the main optical fiber 3, the return light from the output end of the main optical fiber 3 will be transmitted in the reverse direction along the main optical fiber 3, and will not be reflected back to the red light unit 2 through the red light optical fiber 4, thereby reducing the risk of damage to the red light diode 20 in the red light unit 2.

[0065] In order to transmit the red light signal generated by the red light unit 2 to the main optical fiber 3, in one embodiment, the red light optical fiber 4 can use a transition optical fiber with a gradient refractive index, that is, the refractive index of the core in the red light optical fiber 4 gradually decreases as its core radius increases until it matches the refractive index of its cladding. Due to the large divergence angle of the red light signal, in a multimode optical fiber, the optical signal propagates at multiple different incident angles, and these incident angles depend on the wavefront shape of the red light signal. Due to the change in the core refractive index of the red light optical fiber 4, the red light signals at different incident angles will have different transmission paths and speeds. This difference will cause the transmission time of the red light signal in the red light optical fiber 4 to be different, thereby causing modal dispersion. The gradient refractive index optical fiber reduces the rate of change of the refractive index by making its core refractive index decrease as the radius increases, thereby reducing the modal dispersion, thereby improving the transmission quality of the red light signal, and can better transmit the red light signal to the main optical fiber 3.

[0066] Next, the specific structures of the red light unit 2 and the laser unit 1 will be described.

[0067] In one embodiment, Figure 3As shown, the red light unit 2 includes a red light diode 20, a stripper 21 and an output optical fiber 22 coupled in sequence along the optical path, and the output optical fiber 22 is fused with one end of the red light optical fiber 4; the red light diode 20 is used to generate the red light signal, and the stripper 21 is used to perform mode field adaptation and mode stripping on the optical fiber through which the red light signal flows, so as to perform mode matching with the output optical fiber 22; the output optical fiber 22 is used to transmit the red light signal to the red light optical fiber 4.

[0068] In one embodiment, the red optical fiber 4 and the output optical fiber 22 are different optical fibers, and the output optical fiber 22 is coupled to the red optical fiber 4. In other embodiments, the output optical fiber 22 may not be provided, but the red optical fiber 4 is directly coupled to the stripper 21, depending on the actual situation.

[0069] Generally, the stripper 21 is subjected to roughening and etching operations. When the red light signal is output from the red light diode 20, it is easy to cause the red light signal to escape from the stripper 21. To solve this problem, in one embodiment, as shown in FIG. Figure 3 As shown, the stripper 21 includes a mode field adapter 210 and a red light mode stripper 211 coupled in sequence; the mode field adapter 210 is used to mode match the output pigtail of the red light diode 20 and the output optical fiber 22, and the red light mode stripper 211 is used to set the stripping area in the mode matching area to reduce the transmission loss of the red light signal.

[0070] Specifically, the function of the mode field adapter 210 is to perform mode matching between the output pigtail of the red light diode 20 and the output optical fiber 22 (which may also be the red light optical fiber 4). The design of the mode field adapter 210 is to enable the optical mode of the red light signal output from the red light diode 20 to be adapted to the mode of the output optical fiber 22, thereby reducing the loss and modal dispersion of the red light signal at the connection. In one embodiment, the mode field adapter 210 is generally implemented by using components such as a lens or an optical fiber coupler, and more specific explanation is not given in this embodiment.

[0071] The purpose of the red light mode stripper 211 is to set the stripping area in the mode matching area selected by the mode field adapter 210, so as to reduce the transmission loss caused by the mismatch of the optical mode during the stripping process. The red light mode stripper 211 is used to cut a part of the optical fiber to reduce the reflection and echo of the red light signal, thereby improving the performance of the system. By setting the stripping area of ​​the red light mode stripper 211 in the mode matching area, it can be ensured that the red light mode stripper 211 will not destroy the optical mode during the stripping process, thereby reducing the transmission loss of the red light signal.

[0072] In one embodiment, Figure 4As shown, the laser unit 1 includes a forward combiner 10, a high reflection grating 11, a gain fiber 12, a low reflection grating 13, a reverse combiner 14 and an output head 15 which are sequentially coupled along the forward transmission direction of the red light signal; the forward combiner 10 is connected to at least one forward pump diode 16, and the reverse combiner 14 is connected to at least one reverse pump diode 17; the forward combiner 10 is used to couple the first pump light emitted by the forward pump diode 16 into the gain fiber 12; the reverse combiner 14 is used to couple the second pump light output by the reverse pump diode 17 into the gain fiber 12; the gain fiber 12 is used to obtain gain through the excitation of the first pump light and the second pump light, and to form a resonant structure through the grating pair composed of the high reflection grating 11 and the low reflection grating 13, so as to realize the oscillation amplification of the laser to output the excitation light; the excitation light outputs the forward excitation light through the low reflection grating 13, and the forward excitation light is output through the output head 15.

[0073] Among them, the function of the forward combiner 10 is to couple the first pump light emitted by the forward pump diode 16 into the gain fiber 12. The first pump light is used to excite the light of the gain fiber 12. The gain fiber 12 contains optical fibers doped with rare earth elements. These elements can absorb the energy of the pump light and convert it into the energy of the laser beam. The length and doping concentration of the gain fiber 12 determine the gain characteristics and wavelength of the laser, which are not specifically limited in this embodiment. The forward combiner 10 usually includes a fiber coupler, a lens or other optical elements to ensure efficient coupling of the first pump light. The function of the reverse combiner 14 is to couple the second pump light output by the reverse pump diode 17 into the gain fiber 12. This structure allows the use of pump light in two directions at the same time to improve the efficiency and gain of the laser.

[0074] The high-reflection grating 11 is used to reflect most of the laser beam, and only a small part of the beam is transmitted. In this way, the laser beam is reflected back and forth in the gain fiber 12, and is amplified each time it passes through the gain fiber 12. The high-reflection grating 11 is usually tightly coupled with the end of the gain fiber 12 to form a resonant cavity. The low-reflection grating 13 is usually located at the output end of the laser, and its function is to allow a part of the laser beam to be output from the resonant cavity. The reflectivity of the low-reflection grating 13 is lower than that of the high-reflection grating 11, so it only reflects a small part of the beam and allows most of the beam to pass.

[0075] The output head 15 is the output part of the laser, which usually contains a fiber coupler and other optical components to ensure that the laser beam can be efficiently output from the laser and transmitted to where it is needed. The entire laser unit 1 is designed to obtain gain through the excitation of pump light and amplify and output the laser beam using the resonant structure composed of grating pairs. This structure can generate optical signals with specific wavelengths and intensities, which are suitable for various application scenarios.

[0076] In one embodiment, when the reflected light is relatively large, it may affect other components in the laser and cause damage. Figure 5 As shown, a laser stripper 30 is provided at the rear end of the fusion joint between the red light fiber 4 and the main optical fiber 3 on the main optical fiber 3, and the laser stripper 30 is used to guide the return light into the corresponding heat dissipation device. Figure 5 To the left of the middle weld.

[0077] Specifically, the laser stripper 30 may be a through-core stripper (i.e., the corrosion depth penetrates from the cladding of the main optical fiber 3 to the core of the main optical fiber 3). With such a design, the laser stripper 30 may guide the return light from the output end of the main optical fiber 3 through the device housing into the corresponding heat dissipation device for heat dissipation, thereby preventing other devices from being damaged by the return light. The heat dissipation device may be a water cooling plate.

[0078] In this embodiment, the red light unit 2 and the laser unit 1 are coupled via a red light fiber 4 and a main light fiber 3, wherein the red light fiber 4 is a fiber with a gradient refractive index, and the red light signal can be transmitted to the main light fiber 3 through a gradient refractive index design, and transmitted forward along the laser unit 1; the refractive index of the red light fiber 4 is set to be smaller than the refractive index of the main light fiber 3. Since the refractive index of the red light fiber 4 is different from that of the main light fiber 3, the returned light will be totally reflected at the coupling point between the main light fiber 3 and the red light fiber 4, thereby being effectively confined within the main light fiber 3, so that the returned light is transmitted in the reverse direction along the main light fiber 3, thereby reducing the risk of the returned light damaging the red light diode 20 in the red light unit 2.

[0079] Embodiment 2:

[0080] In Example 1, a laser resistant to high light reflection is proposed. In this example, a method for manufacturing a laser resistant to high light reflection is proposed. Figure 6 As shown, the manufacturing method comprises:

[0081] Step 101 : coupling the output end of the red light unit 2 with one end of the red light optical fiber 4 .

[0082] Among them, the red light unit 2 includes a red light diode 20, a stripper 21 and an output optical fiber 22 coupled in sequence along the optical path, and the output optical fiber 22 is fused with one end of the red light optical fiber 4; the red light diode 20 is used to generate the red light signal, and the stripper 21 is used to perform mode field adaptation and mode stripping on the optical fiber through which the red light signal flows, so as to perform mode matching with the output optical fiber 22; the output optical fiber 22 is used to transmit the red light signal to the red light optical fiber 4.

[0083] In one embodiment, the output end of the red light unit 2 is the output optical fiber 22. One end of the output optical fiber 22 is fused with one end of the red light optical fiber 4. The fusion of the optical fiber must be completed by a fiber fusion splicer. Before fusion, the parameters of the fusion splicer should be set. The setting parameters include the discharge voltage, discharge time, fusion temperature, etc. Normally, the parameters set at the factory are used. When fusion splicing, gently put the cut optical fiber into the V-groove of the fusion splicer. The optical fiber must not touch any object from the time it is taken out of the cutter to the time it is placed in the V-groove, and it cannot be left in the air for a long time. The length of the optical fiber placed in the V-groove cannot exceed the center line of the electrode. The two optical fibers should maintain a distance of 1 to 3 mm. Cover the protective cover and press the AUTO button of the fusion splicer to start the automatic fusion program.

[0084] During the fusion process, the fusion status can be observed through the screen of the fusion machine. The screen of the fusion machine simultaneously displays the alignment of the X-axis and Y-axis. During the alignment process of the optical fiber, it is necessary to timely observe whether the end faces of the two fiber cores are cut flat. If there is a bad end face, the fusion operation should be stopped immediately and the end face should be remade. During the fusion process, it is necessary to observe whether there are bad conditions such as too thin, too thick, virtual melting, separation, bubbles, etc. after the arc discharge, as well as the estimated loss test results after the fusion is completed. The estimated loss value should be less than 0.3dB, otherwise the end face and fusion need to be remade. After the optical fiber fusion is completed, since the coating layer of the optical fiber has been stripped off, its mechanical strength is reduced, so the joint must be protected and the hot melt tube (also called heat shrink tube) is used for sleeve connection. The hot melt tube must be inserted before the end face preparation, and it is forbidden to insert it after the optical fiber is cut. Adjust the position of the hot melt tube so that it is placed in the middle of the optical fiber joint, put it into the heater for heating, and the hot melt tube shrinks after the heat and is tightly sleeved on the fusion-jointed optical fiber to achieve the purpose of fixing the hot melt tube and protecting the optical fiber joint.

[0085] Step 102 : Process the red light optical fiber 4 so that the refractive index of the red light optical fiber 4 is lower than the refractive index of the main optical fiber 3 , and couple the other end of the red light optical fiber 4 to the side surface of the main optical fiber 3 .

[0086] In one embodiment, Figure 7 As shown, the step 102 specifically includes:

[0087] Step 1021 : heat-treating the red light optical fiber 4 to make the numerical aperture of the red light optical fiber 4 lower than the numerical aperture of the main optical fiber 3 .

[0088] Among them, heat treatment is a method of changing the physical properties of optical fiber materials. According to Example 1, the red light optical fiber 4 is a fiber with a gradient refractive index, and the red light optical fiber 4 is heated to change its refractive index distribution, thereby reducing its numerical aperture. Numerical aperture is a key characteristic of optical fiber, which is related to the coupling efficiency and modal dispersion of the optical fiber. By reducing the numerical aperture of the red light optical fiber 4, the modal mismatch when coupling with the main optical fiber 3 can be reduced, thereby improving the coupling efficiency.

[0089] Since the core refractive index of the graded-index fiber is changing, the light-collecting capabilities of different points on the core end face are different. Therefore, the concept of local numerical aperture is introduced in the graded-index fiber, which specifically refers to the numerical aperture of a point on the fiber end face, and represents the light-collecting capability of a point on the graded-index fiber end face. The calculation formula of the numerical aperture NA of the optical fiber is:

[0090]

[0091] Where n1 is the refractive index of the core of the corresponding optical fiber, and n2 is the refractive index of the cladding of the corresponding optical fiber. The local numerical aperture is related to the refractive index of the point. The larger the refractive index of the point, the larger the local numerical aperture.

[0092] Step 1022: stripping off the coating layer of the red light optical fiber 4 to expose its cladding, and cutting the end of the red light optical fiber 4 flat.

[0093] In order to better fuse with the cladding of the main optical fiber 3 and ensure good mechanical and optical contact, the outer coating material of the red optical fiber 4 is removed to expose its cladding. The end of the red optical fiber 4 is cut flat to provide a better coupling effect in subsequent operations.

[0094] Step 1023: perform core expansion processing on the core of the red light optical fiber 4 to make its refractive index lower than the refractive index of the main optical fiber 3, and heat and melt the red light optical fiber 4 to form a taper.

[0095] The core expansion process refers to increasing the diameter of the core of the red optical fiber 4, which can usually be achieved by heating and stretching the optical fiber. This can reduce the refractive index of the core of the red optical fiber 4, thereby reducing the modal mismatch with the main optical fiber 3. Heating and melting taper is an optical fiber processing technology that melts the optical fiber by heating and then stretches it into an elongated cone, thereby increasing the contact area with the cladding of the main optical fiber 3 and improving the transmission efficiency of the red light signal.

[0096] Step 1024 : stripping off the coating layer of the main optical fiber 3 , and fusing the heated, fused and tapered red optical fiber 4 to the cladding of the main optical fiber 3 , so as to couple the red optical fiber 4 to the main optical fiber 3 .

[0097] Specifically, the method proposed in step 1024 is a side fusion technology, in which the red light signal is injected from the side of the main optical fiber 3 through the red optical fiber 4, rather than from the end face. The red optical fiber 4 that has been heated, melted and tapered is fused together with the cladding of the main optical fiber 3. Fusion is usually performed in a fusion splicer, which can accurately align and fuse the ends of the optical fibers to ensure a good optical connection. After the fusion is completed, the red optical fiber 4 is coupled to the main optical fiber 3.

[0098] Step 103 : coupling the output end of the main optical fiber 3 with the input end of the laser unit 1 .

[0099] In one embodiment, when the main optical fiber 3 and the laser unit 1 are integrated, the whole laser can be manufactured by coupling the red optical fiber 4 into the main optical fiber 3 mentioned in step 102. For the convenience of description, the main optical fiber 3 is a single optical fiber. Therefore, after coupling the red optical fiber 4 to the side of the main optical fiber 3, it is also necessary to connect the output end of the main optical fiber 3 to the input end of the laser unit 1 (i.e. Figure 4 The left port of the forward combiner 10 is fused.

[0100] Since the shell of the laser is limited by volume, the red light stripper 211 and the laser stripper 30 can be integrated to reduce the number of device shells to free up space for heat dissipation and other processing. In one embodiment, the manufacturing method also includes: corroding or etching from the surface of the red light optical fiber 4 until the cladding at a preset position on the red light optical fiber 4 is removed to form a red light stripper 211; wherein the red light optical fiber 4 can be processed by CO2 etching, hydrofluoric acid etching, or abrasive paste with corrosive properties, and the preset position can be determined according to actual conditions. For example, red light strippers 211 are made on both sides of the core of the red light optical fiber 4, and the red light stripper 211 on each side includes at least one removal area with a triangular cross-section (such as Figure 8 shown).

[0101] Corrosion or etching is performed starting from the surface of the main optical fiber 3 until the core at a preset position on the main optical fiber 3 is removed to form a laser stripper 30, wherein the main optical fiber 3 can be processed by CO2 etching, hydrofluoric acid etching or abrasive paste with corrosive properties, and the preset position can be determined according to actual conditions. For example, the laser stripper 30 is made at the end of the main optical fiber 3 away from the laser unit 1.

[0102] In the process of making the red light stripper 211, the cladding at the preset position will be corroded or etched, but the core of the red light optical fiber 4 will not be corroded or etched. In the process of making the laser stripper 30, the core at the preset position will be corroded or etched.

[0103] like Figure 8 As shown, a red light stripper 211 is made in the red light optical fiber 4 using a CO2 laser etcher, hydrofluoric acid etching or a special abrasive paste etching method. The CO2 laser etcher uses a laser beam to accurately remove the material of the optical fiber, the hydrofluoric acid etching uses a chemical reaction to remove the material, and the abrasive paste uses mechanical wear. The etching time is controlled to control the etching depth, ensuring that the red light stripper 211 etches to the cladding of the red light optical fiber 4 but does not touch its core, so as to obtain the red light stripper 211.

[0104] Reference Figure 8 , a laser stripper 30 is made in the main optical fiber 3. Similarly, CO2 laser etching, hydrofluoric acid etching or abrasive etching can be used to control the etching time and the etching depth so that it is corroded from the cladding of the main optical fiber 3 to the core to obtain the laser stripper 30 in the main optical fiber 3.

[0105] like Fig. 9 As shown, the red light optical fiber 4 where the red light stripper 211 is located and the main optical fiber 3 where the laser stripper 30 is located are integrated in the device housing to form an integrated device. The red light etching area of ​​the red light stripper 211 and the laser etching area of ​​the laser stripper 30 are integrated in a device housing to form a cladding mode stripper (CMS), thereby saving the volume of the laser. Fig.10 Shown is the location of the combined CMS in the entire laser.

[0106] The embodiment of the present invention can attenuate the return light at a low price, reduce the risk of damage to the red light diode 20 in the high-power laser due to the return light, and at the same time, the all-fiber structure has higher reliability. The specific structure of the laser resistant to high return light is shown in Example 1, and will not be repeated in this embodiment.

[0107] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A laser device resistant to high-return light, characterized in that: include: A laser unit (1), a red light unit (2), a main optical fiber (3) and a red light optical fiber (4), wherein the output end of the red light unit (2) is coupled to one end of the red light optical fiber (4), and the other end of the red light optical fiber (4) is coupled to the side surface of the main optical fiber (3); the output end of the main optical fiber (3) is coupled to the input end of the laser unit (1); The red light unit (2) is used to emit a red light signal, and the red light optical fiber (4) is used to receive the red light signal and transmit the red light signal to the main optical fiber (3); The refractive index of the red light optical fiber (4) is lower than the refractive index of the main optical fiber (3), so that the return light from the output end of the main optical fiber (3) is transmitted in the reverse direction along the main optical fiber (3).

2. The laser device with high light return resistance according to claim 1, characterized in that: The refractive index of the core of the red light optical fiber (4) gradually decreases as its core radius increases until it matches the refractive index of its cladding.

3. The laser device with high light return resistance according to claim 1, characterized in that: The red light unit (2) comprises a red light diode (20), a stripper (21) and an output optical fiber (22) which are sequentially coupled along an optical path, and the output optical fiber (22) is fused to one end of the red light optical fiber (4); The red light diode (20) is used to generate the red light signal, and the stripper (21) is used to perform mode field adaptation and mode stripping on the optical fiber through which the red light signal flows, so as to perform mode matching with the output optical fiber (22); The output optical fiber (22) is used to transmit the red light signal to the red light optical fiber (4).

4. The laser device with high light return resistance according to claim 3, characterized in that: The stripper (21) comprises a mode field adapter (210) and a red light mode stripper (211) coupled in sequence; The mode field adapter (210) is used to perform mode matching between the output pigtail of the red light diode (20) and the output optical fiber (22), and the red light mode stripper (211) is used to set the stripping area in the mode matching area to reduce the transmission loss of the red light signal.

5. The laser device with high light return resistance according to claim 1, characterized in that: The laser unit (1) comprises a forward beam combiner (10), a high reflection grating (11), a gain optical fiber (12), a low reflection grating (13), a reverse beam combiner (14) and an output head (15) which are sequentially coupled along the forward transmission direction of the red light signal; the forward beam combiner (10) is connected to at least one forward pump diode (16), and the reverse beam combiner (14) is connected to at least one reverse pump diode (17); The forward beam combiner (10) is used to couple the first pump light emitted by the forward pump diode (16) into the gain optical fiber (12); the reverse beam combiner (14) is used to couple the second pump light output by the reverse pump diode (17) into the gain optical fiber (12); The gain optical fiber (12) is used to obtain gain through the excitation of the first pump light and the second pump light, and to form a resonant structure through a grating pair composed of the high-reflection grating (11) and the low-reflection grating (13), so as to realize oscillation amplification of laser light to output excitation light; The excitation light outputs forward excitation light through the low-reflection grating (13), and the forward excitation light is output through the output head (15).

6. The laser device with high light return resistance according to claim 1, characterized in that: A laser stripper (30) is provided at the rear end of the fusion joint between the red light optical fiber (4) and the main optical fiber (3) on the main optical fiber (3), and the laser stripper (30) is used to guide the return light into a corresponding heat dissipation device.

7. A method for manufacturing a laser resistant to high return light, characterized in that: A method for manufacturing a laser resistant to high-return light as claimed in any one of claims 1 to 6, comprising: coupling the output end of the red light unit (2) with one end of the red light optical fiber (4); The red light optical fiber (4) is processed so that the refractive index of the red light optical fiber (4) is lower than the refractive index of the main optical fiber (3), and the other end of the red light optical fiber (4) is coupled to the side surface of the main optical fiber (3); The output end of the main optical fiber (3) is coupled to the input end of the laser unit (1).

8. The method for manufacturing a laser resistant to high return light according to claim 7, characterized in that: The step of making the refractive index of the red light optical fiber (4) lower than the refractive index of the main optical fiber (3), and coupling the other end of the red light optical fiber (4) with the side surface of the main optical fiber (3) comprises: Performing heat treatment on the red light optical fiber (4) so ​​that the numerical aperture of the red light optical fiber (4) is lower than the numerical aperture of the main optical fiber (3); Stripping off the coating layer of the red light optical fiber (4) to expose its cladding, and cutting the end of the red light optical fiber (4) flat; Performing a core expansion process on the red light optical fiber (4) so ​​that its refractive index is lower than the refractive index of the main optical fiber (3), and heating and melting the red light optical fiber (4) to form a taper; The coating layer of the main optical fiber (3) is stripped off, and the red optical fiber (4) after heating, melting and taper is fused with the cladding of the main optical fiber (3) to couple the red optical fiber (4) to the main optical fiber (3).

9. The method for manufacturing a laser resistant to high return light according to claim 8, characterized in that: The calculation formula of the numerical aperture NA of optical fiber is: Among them, n1 is the refractive index of the optical fiber core, and n2 is the refractive index of the optical fiber cladding.

10. The method for manufacturing a laser resistant to high return light according to claim 7, characterized in that: A red light mode stripper (211) is coupled to the red light unit (2), a laser mode stripper (30) is coupled to the main optical fiber (3), and the manufacturing method further comprises: Carrying out corrosion or etching treatment from the surface of the red light optical fiber (4) until the cladding at a preset position on the red light optical fiber (4) is removed, so as to form a red light stripper (211); Carrying out corrosion or etching treatment from the surface of the main optical fiber (3) until the fiber core at a preset position on the main optical fiber (3) is removed, so as to form a laser stripper (30); The portion of the red light optical fiber (4) where the red light mode stripper (211) is located and the portion of the main optical fiber (3) where the laser mode stripper (30) is located are integrated in a device housing.

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