Nanosecond pulse fiber laser

Abstract

The utility model provides a nanosecond pulse fiber laser. The nanosecond pulse fiber laser comprises a seed source module, a first-stage amplification module, a second-stage amplification module and a third-stage amplification module. The seed source module is used for outputting seed light, the input end of the first-stage amplification module is connected with the seed source module, the input end of the second-stage amplification module is connected with the output end of the first-stage amplification module, and the input end of the third-stage amplification module is connected with the output end of the second-stage amplification module. The seed source module comprises a directly modulated semiconductor laser diode and a first online isolator, the output end of the semiconductor laser diode is connected with the input end of the first online isolator, the input end of the primary amplification module is connected with the output end of the first online isolator, and the output end of the first online isolator is used for outputting seed light. The nanosecond pulse fiber laser provided by the utility model can solve the technical problem that the tuning frequency range is limited in the prior art.

Description

Technical Field

[0001] The present application belongs to the technical field of fiber lasers, and more specifically, relates to a nanosecond pulse fiber laser. Background Art

[0002] Nanosecond pulsed fiber lasers have the advantages of excellent output beam quality, compact structure and high flexibility, and therefore have developed very rapidly.

[0003] In related technologies, nanosecond pulsed fiber lasers use Q-switching technology to generate seed light, which is then amplified by an amplification module to the target performance index.

[0004] However, nanosecond pulse fiber lasers using Q-switched technology have a technical problem of limited tuning frequency range. Utility Model Content

[0005] The purpose of the embodiments of the present application is to provide a nanosecond pulse fiber laser to solve the technical problem of limited tuning frequency range existing in the related art.

[0006] To achieve the above objectives, the technical solution adopted in this application is:

[0007] A nanosecond pulse fiber laser is provided, comprising a seed source module, a first-stage amplification module, a second-stage amplification module, and a third-stage amplification module. The seed source module is configured to output seed light; the input of the first-stage amplification module is connected to the seed source module, the input of the second-stage amplification module is connected to the output of the first-stage amplification module, and the input of the third-stage amplification module is connected to the output of the second-stage amplification module. The seed source module comprises a directly modulated semiconductor laser diode and a first in-line isolator; the output of the semiconductor laser diode is connected to the input of the first in-line isolator, the input of the first-stage amplification module is connected to the output of the first in-line isolator, and the output of the first in-line isolator is configured to output seed light.

[0008] Through this technical solution, the first-stage amplification module performs the first amplification of the seed light, the second-stage amplification module performs the second amplification, and the third-stage amplification module performs the third amplification, thus achieving the target performance indicators. Furthermore, the seed source module utilizes a directly modulated semiconductor laser diode as the light source, which increases the tuning frequency range and allows for tunable pulse width.

[0009] Therefore, the nanosecond pulse fiber laser provided in this application can solve the technical problem of limited tuning frequency range existing in related technologies.

[0010] In some embodiments, the seed source module further includes a fiber Bragg grating (FBG), wherein the output of the semiconductor laser diode is connected to the input of the FBG, which is then connected to the input of the first in-line isolator. The FBG is a weakly reflective FBG. The seed source module includes a FBG between the semiconductor laser diode and the first in-line isolator to form a resonant cavity for filtering, thereby reducing the linewidth of the seed light.

[0011] In some embodiments, the central wavelength of the semiconductor laser diode is 1064 nm, and / or the line width of the semiconductor laser diode is less than 15 nm, and / or the output fiber of the semiconductor laser diode is a PM980 fiber.

[0012] In some embodiments, the central wavelength of the fiber Bragg grating is 1064 nm, and / or the line width of the fiber Bragg grating is less than 1 nm, and / or the output fiber of the fiber Bragg grating is PM980 fiber, and / or the reflectivity of the fiber Bragg grating is less than 5%.

[0013] In some embodiments, the central wavelength of the first in-line isolator is 1059 nm, and / or the operating bandwidth of the first in-line isolator is 16 nm, and / or the input fiber of the first in-line isolator is Hi1060 fiber, and / or the output fiber of the first in-line isolator is 10 / 125 single-clad fiber.

[0014] In some embodiments, the first-stage amplification module further includes a first pump laser, a first photodetector, and a first beam combiner, a first gain fiber, a second online isolator, and a coupler connected in sequence, wherein the input end of the first beam combiner is connected to the output end of the first online isolator, the output end of the first pump laser is connected to the input end of the first beam combiner, the input end of the first beam combiner is used to receive the seed light and the pump light output by the first pump laser, the first output end of the coupler is connected to the input end of the second-stage amplification module, and the second output end of the coupler is connected to the first photodetector.

[0015] In some embodiments, the output power of the first pump laser is greater than 10 W, the central wavelength of the first pump laser is 915 nm, and the output fiber of the first pump laser is a 105 / 125 multimode fiber; and / or, the pump fiber and the signal fiber of the first combiner are arranged at the input end of the first combiner, the output end of the first pump laser is connected to the pump fiber of the first combiner, the signal fiber of the first combiner is connected to the output end of the first in-line isolator, the signal fiber of the first combiner is a 10 / 125 double-clad fiber, and the pump fiber of the first combiner is a 105 / 125 multimode fiber.

[0016] In some embodiments, the secondary amplification module includes a red light laser, a second pump laser, and a wavelength division multiplexer, a first mode field adapter, a second gain fiber, a second combiner, and a third online isolator connected in sequence. The input end of the wavelength division multiplexer is connected to the output end of the primary amplification module, the output end of the red light laser is connected to the input end of the wavelength division multiplexer, the input end of the wavelength division multiplexer is used to receive the optical signal output by the primary amplification module and the red light output by the red light laser, the output end of the second pump laser is connected to the output end of the second combiner, and the input end of the tertiary amplification module is connected to the output end of the third online isolator.

[0017] In some embodiments, the output fiber of the red laser is a Hi1060 fiber, and the output power of the red laser is 60 mW; and / or, the input end of the wavelength division multiplexer is provided with a signal port and a red light port, the signal port of the wavelength division multiplexer is connected to the output end of the first-stage amplification module, the red light port of the wavelength division multiplexer is connected to the output end of the red laser, the optical fiber of the signal port is a 10 / 125 single-clad optical fiber, and the optical fiber of the red light port is a Hi1060 optical fiber; and / or, the output power of the second pump laser is greater than 30 W, the central wavelength of the second pump laser is 915 nm, and the second pump laser The output fiber of the optical device is a 105 / 125 multimode fiber; and / or, the signal fiber of the second combiner is arranged at the input end of the second combiner, the pump fiber and the output fiber of the second combiner are arranged at the output end of the second combiner, the output end of the second pump laser is connected to the pump fiber of the second combiner, the signal fiber of the second combiner is connected to the output end of the second gain fiber, the output fiber of the second combiner is connected to the input end of the third in-line isolator, the signal fiber and the output fiber of the second combiner are 20 / 125 double-clad fibers, and the pump fiber of the second combiner is a 105 / 125 multimode fiber.

[0018] In some embodiments, the three-stage amplification module includes a second photodetector, a third pump laser, and a second mode field adapter, a third gain fiber, and an integrated output isolator connected in sequence. The input end of the second mode field adapter is connected to the output end of the two-stage amplification module, the output end of the integrated output isolator forms the output end of the three-stage amplification module, the output end of the third pump laser is connected to the input end of the integrated output isolator, and the second photodetector is arranged at the detection hole on the integrated output isolator.

[0019] In some embodiments, the output power of the third pump laser is greater than 450 W, the central wavelength of the third pump laser is 976 nm, and the output fiber of the third pump laser is a 200 / 220 multimode fiber; and / or, the signal fiber and the third pump fiber of the integrated output isolator are arranged at the input end of the integrated output isolator, the signal fiber of the integrated output isolator is connected to the output end of the third gain fiber, the pump fiber of the integrated output isolator is connected to the output end of the third pump laser, the signal fiber of the integrated output isolator is a 30 / 250 double-clad fiber, and the pump fiber of the integrated output isolator is a 200 / 220 multimode fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0021] Figure 1 A schematic diagram of the structure of a nanosecond pulsed fiber laser provided in an embodiment of the present application;

[0022] Figure 2 A schematic diagram of the structure of the seed source module provided in an embodiment of the present application;

[0023] Figure 3 A schematic structural diagram of a first-stage amplification module provided in an embodiment of the present application;

[0024] Figure 4 A schematic structural diagram of a secondary amplification module provided in an embodiment of the present application;

[0025] Figure 5 This is a schematic structural diagram of the three-stage amplification module provided in an embodiment of the present application.

[0026] Among them, the reference numerals in the figures are:

[0027] 10-seed source module; 11-semiconductor laser diode; 12-fiber Bragg grating; 13-first online isolator; 20-first stage amplification module; 21-first pump laser; 22-first combiner; 23-first gain fiber; 24-second online isolator; 25-coupler; 26-first photodetector; 30-second stage amplification module; 31-red laser; 32-wavelength division multiplexer; 33-first mode field adapter; 34-second gain fiber; 35-second combiner; 36-second pump laser; 37-third online isolator; 40-third stage amplification module; 41-second mode field adapter; 42-third gain fiber; 43-third pump laser; 44-integrated output isolator; 45-second photodetector. DETAILED DESCRIPTION

[0028] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, this application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0029] It should be noted that when an element is referred to as being “fixed on” or “disposed on” another element, it may be directly on the other element or indirectly on the other element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or indirectly connected to the other element.

[0030] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this 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 a limitation on this application.

[0031] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0032] Nanosecond pulsed fiber lasers have the advantages of excellent output beam quality, compact structure, and high flexibility, and therefore have developed rapidly. In related technologies, nanosecond pulsed fiber lasers use Q-switching technology to generate seed light, which is then amplified to the target performance index through an amplifier module. However, nanosecond pulsed fiber lasers using Q-switching technology have the technical problem of limited tuning frequency range.

[0033] Please also refer to Figures 1 to 5 , the nanosecond pulse fiber laser provided in the embodiments of the present application is now described.

[0034] See also Figure 1 The nanosecond pulse fiber laser provided in the embodiment of the present application includes a seed source module 10, a first-stage amplification module 20, a second-stage amplification module 30, and a third-stage amplification module 40. The seed source module 10 can output seed light, the input end of the first-stage amplification module 20 is connected to the seed source module 10, the first-stage amplification module 20 can amplify the seed light for the first time, the input end of the second-stage amplification module 30 is connected to the output end of the first-stage amplification module 20, the second-stage amplification module 30 can amplify the seed light after the first amplification for the second time, the input end of the third-stage amplification module 40 is connected to the output end of the second-stage amplification module 30, the third-stage amplification module 40 can amplify the seed light after the second amplification for the third time, and the output end of the third-stage amplification module 40 is used to output the amplified seed light.

[0035] See also Figure 2 In some embodiments, the seed source module 10 includes a directly modulated semiconductor laser diode 11 and a first online isolator 13. The output end of the semiconductor laser diode 11 is connected to the input end of the first online isolator 13. The input end of the first-stage amplification module 20 is connected to the output end of the first online isolator 13. The output end of the first online isolator 13 is used to output seed light.

[0036] The semiconductor laser diode 11 can be directly modulated, enabling a more flexible frequency tuning range, thereby resolving the technical issue of a limited tuning frequency range. Furthermore, the pulse width of the semiconductor laser diode 11 is tunable, enabling the output of a corresponding optical signal as required, thereby meeting diverse application market demands.

[0037] Exemplarily, the semiconductor laser diode 11 can be a commercial superluminescent diode (SLD), which has the advantages of high power, wide spectrum, small ripple, and good temperature stability. Exemplarily, the center wavelength of the semiconductor laser diode 11 can be 1064nm. Exemplarily, the line width of the semiconductor laser diode 11 is less than 15nm. Exemplarily, the output fiber of the semiconductor laser diode 11 is a PM980 fiber. Exemplarily, the output state of the semiconductor laser diode 11 is pulsed. Exemplarily, the pulse width range of the semiconductor laser diode 11 can be 6ns-500ns, and can have a wide tuning range. Exemplarily, the repetition frequency of the semiconductor laser diode 11 can be 1kHz-4000kHz.

[0038] Exemplarily, the central wavelength of the first in-line isolator 13 can be 1059 nm. Exemplarily, the operating bandwidth of the first in-line isolator 13 can be 16 nm. Exemplarily, the input optical fiber of the first in-line isolator 13 can be Hi1060 optical fiber. Exemplarily, the output optical fiber of the first in-line isolator 13 can be 10 / 125 single-clad optical fiber. In addition, the optical fiber of the main optical path of the first-stage amplification module 20 is a 10 / 125 optical fiber. In this way, the specifications of the output optical fiber of the seed source module 10 are the same as the specifications of the optical fiber of the main optical path of the first-stage amplification module 20, which facilitates the connection between the seed source module 10 and the first-stage amplification module 20.

[0039] Exemplarily, the first in-line isolator 13 can withstand an average power of 300 mW. The average power withstand of the first in-line isolator 13 is greater than the output power of the semiconductor laser diode 11, and the average power withstand of the first in-line isolator 13 can match that of the semiconductor laser diode 11. Exemplarily, the insertion loss of the first in-line isolator 13 is less than 3 dB. Exemplarily, the isolation of the first in-line isolator 13 is greater than 25 dB.

[0040] In some embodiments, the seed source module 10 further includes a fiber Bragg grating 12. The output end of the semiconductor laser diode 11 is connected to the input end of the fiber Bragg grating 12, which is also connected to the input end of the first in-line isolator 13. The fiber Bragg grating 12 is a weakly reflective fiber Bragg grating 12. The seed source module 10 sets the fiber Bragg grating 12 between the semiconductor laser diode 11 and the first in-line isolator 13 to form a resonant cavity for filtering, thereby reducing the linewidth of the seed light.

[0041] Exemplarily, the fiber Bragg grating 12 can be a commercial fiber Bragg grating 12. Exemplarily, the central wavelength of the fiber Bragg grating 12 can be 1064 nm. Exemplarily, the reflectivity of the fiber Bragg grating 12 is less than 5%. Exemplarily, the linewidth of the fiber Bragg grating 12 is less than 1 nm. Exemplarily, the fiber of the fiber Bragg grating 12 is PM980 fiber, and the specifications of the fiber Bragg grating 12 are consistent with those of the output fiber of the semiconductor laser diode 11, and can be directly connected.

[0042] It should be noted that when the input optical fiber of the first online isolator 13 is Hi1060 optical fiber, although the specifications of the input optical fiber of the first online isolator 13 are inconsistent with those of the optical fiber of the fiber Bragg grating 12, the specifications of the Hi1060 optical fiber and the PM980 optical fiber are similar, for example, the mode field diameter (MFD) and numerical aperture (NA) are consistent, and the input optical fiber of the first online isolator 13 can be directly connected to the fiber Bragg grating 12.

[0043] See also Figure 3 In some embodiments, the primary amplification module 20 is provided with a first photodetector 26, which is used to detect the optical signal output by the primary amplification module 20. Thus, the first photodetector 26 can detect the optical path of the nanosecond pulse fiber laser, thereby determining the operating status of the nanosecond pulse fiber laser based on the detection results. The nanosecond pulse fiber laser can also be adjusted based on the detection results, which helps protect the optical path system of the nanosecond pulse fiber laser and thus improves its performance.

[0044] For example, the nanosecond pulse fiber laser provided in the embodiment of the present application may also include a controller, which is electrically connected to the first photodetector 26. The first photodetector 26 may also be electrically connected to the seed source module 10. The controller can obtain information detected by the first photodetector 26, so that the seed source module 10 can be controlled according to the information detected by the first photodetector 26, thereby adjusting the nanosecond pulse fiber laser.

[0045] Exemplarily, the first photodetector 26 is a commercial fiber-coupled photodetector, and the optical fiber of the first photodetector 26 may be a Hi1060 optical fiber.

[0046] Please continue reading Figure 3In some embodiments, the first-stage amplification module 20 further includes a coupler 25. The input end of the coupler 25 is used to receive an optical signal. The first output end of the coupler 25 is connected to the input end of the second-stage amplification module 30. The second output end of the coupler 25 is connected to the first photodetector 26. In this way, the first photodetector 26 can receive the optical signal from the coupler 25, thereby detecting the operating status of the optical path of the nanosecond pulse fiber laser.

[0047] For example, the splitting ratio of coupler 25 can be 1:1000, or in other words, the coupling ratio of coupler 25 is 999:1. Thus, of the optical signal received by coupler 25, 999‰ of the power is transmitted to the input of secondary amplification module 30, and 1‰ of the power is transmitted to first photodetector 26. The first photodetector 26 can detect the operating status of the optical path of the nanosecond pulse fiber laser using this smaller power ratio.

[0048] For example, the coupler 25 may be able to withstand an average power of 2 W and may be used in the first-stage amplification module 20 .

[0049] Exemplarily, the optical fiber at the input end of the coupler 25 can be a 10 / 125 single-clad optical fiber. Exemplarily, the optical fiber at the first output end of the coupler 25 can be a 10 / 125 single-clad optical fiber. Exemplarily, the optical fiber at the second output end of the coupler 25 can be a 10 / 125 single-clad optical fiber.

[0050] Please continue reading Figure 3 In some embodiments, the first-stage amplification module 20 further includes a first pump laser 21 and a first combiner 22, a first gain fiber 23, and a second online isolator 24 connected in sequence. The input end of the first combiner 22 is connected to the seed source module 10, and the output end of the first pump laser 21 is connected to the input end of the first combiner 22. The input end of the first combiner 22 is used to receive the seed light and the pump light output by the first pump laser 21. The output end of the second online isolator 24 is connected to the input end of the coupler 25. The first output end of the coupler 25 forms the output end of the first-stage amplification module 20.

[0051] The output power of the first pump laser 21 is greater than 10 W, the central wavelength of the first pump laser 21 is 915 nm, and the output fiber of the first pump laser 21 is a 105 / 125 multimode fiber. The first pump laser 21 can provide pump excitation for the first gain fiber 23. Exemplarily, the first gain fiber 23 is an ytterbium-doped fiber. Exemplarily, the first gain fiber 23 is an ytterbium-doped 10 / 125 double-clad fiber. The fiber length of the first gain fiber 23 is determined by the actual absorption coefficient of the fiber.

[0052] Exemplarily, the pump fiber and signal fiber of the first beam combiner 22 are disposed at the input end of the first beam combiner 22. The output end of the first pump laser 21 is connected to the pump fiber of the first beam combiner 22, and the signal fiber of the first beam combiner 22 is connected to the output end of the first in-line isolator 13. Exemplarily, the signal fiber of the first beam combiner 22 is a 10 / 125 double-clad fiber, and the pump fiber of the first beam combiner 22 is a 105 / 125 multimode fiber. The pump light coupling efficiency of the first beam combiner 22 is greater than 95%, the signal light power tolerance is greater than 1 W, and the pump light power tolerance is greater than 10 W.

[0053] For example, the input fiber of the second inline isolator 24 can be a 10 / 125 single-clad fiber. For example, the output fiber of the second inline isolator 24 can be a 10 / 125 single-clad fiber. It is understood that maintaining consistent fiber specifications in the first-stage amplification module 20 facilitates optical signal transmission.

[0054] Exemplarily, the center wavelength of the second in-line isolator 24 is 1062 nm. Exemplarily, the operating bandwidth of the second in-line isolator 24 is 20 nm. Exemplarily, the average power withstand of the second in-line isolator 24 is 2 W. Exemplarily, the insertion loss of the second in-line isolator 24 is less than 1.5 dB. Exemplarily, the isolation of the second in-line isolator 24 is greater than 25 dB.

[0055] See also Figure 4 In some embodiments, the secondary amplification module 30 includes a red laser 31, a second pump laser 36, and a wavelength division multiplexer 32, a first mode field adapter 33, a second gain fiber 34, a second combiner 35 and a third online isolator 37 connected in sequence.

[0056] Among them, the input end of the wavelength division multiplexer 32 is connected to the output end of the first-stage amplification module 20, the output end of the red light laser 31 is connected to the input end of the wavelength division multiplexer 32, the input end of the wavelength division multiplexer 32 is used to receive the optical signal output by the first-stage amplification module 20 and the red light output by the red light laser 31, the output end of the second pump laser 36 is connected to the output end of the second combiner 35, and the input end of the third-stage amplification module 40 is connected to the output end of the third online isolator 37.

[0057] Exemplarily, the red laser 31 is a commercial red laser diode. Exemplarily, the output fiber of the red laser 31 is a Hi1060 fiber, and the output power of the red laser 31 is greater than 60 mW.

[0058] In some embodiments, the input end of the wavelength division multiplexer 32 is provided with a signal port and a red light port. The signal port of the wavelength division multiplexer 32 is connected to the output end of the first-stage amplifier module 20 (the first output end of the coupler 25), and the red light port of the wavelength division multiplexer 32 is connected to the output end of the red light laser 31 (the output optical fiber of the red light laser 31). The optical fiber of the signal port is a 10 / 125 single-clad optical fiber, and the optical fiber of the red light port is a Hi1060 optical fiber. The optical fiber of the signal port of the wavelength division multiplexer 32 and the optical fiber of the first output end of the coupler 25 have the same specifications and can be directly connected. The optical fiber of the red light port of the wavelength division multiplexer 32 and the optical fiber of the output optical fiber of the red light laser 31 have the same specifications and can be directly connected. In this way, the wavelength division multiplexer 32 can receive the optical signal output by the first-stage amplifier module 20 and the optical signal output by the red light laser 31.

[0059] Exemplarily, the wavelength division multiplexer 32 can withstand an average power greater than 2W.

[0060] For example, the second gain fiber 34 may be an ytterbium-doped fiber. For example, the second gain fiber 34 may be an ytterbium-doped 20 / 125 double-clad fiber.

[0061] It is understood that the second pump laser 36 can provide pump excitation for the second gain fiber 34. Exemplarily, the output power of the second pump laser 36 is greater than 30 W. Exemplarily, the central wavelength of the second pump laser 36 is 915 nm. Exemplarily, the output fiber of the second pump laser 36 is a 105 / 125 multimode fiber.

[0062] Exemplarily, the signal fiber of the second combiner 35 is arranged at the input end of the second combiner 35, the pump fiber and the output fiber of the second combiner 35 are arranged at the output end of the second combiner 35, the output end of the second pump laser 36 is connected to the pump fiber of the second combiner 35, the signal fiber of the second combiner 35 is connected to the output end of the second gain fiber 34, the output fiber of the second combiner 35 is connected to the input end of the third online isolator 37, and the output end of the third online isolator 37 forms the output end of the secondary amplification module 30.

[0063] The signal fiber of the second combiner 35 can be a 20 / 125 double-clad fiber, the output fiber of the second combiner 35 can be a 20 / 125 double-clad fiber, and the pump fiber of the second combiner 35 can be a 105 / 125 multimode fiber. Exemplarily, the pump light coupling efficiency of the second combiner 35 is greater than 95%. Exemplarily, the signal light power of the second combiner 35 can withstand greater than 10 W. Exemplarily, the pump light power of the second combiner 35 can withstand greater than 30 W.

[0064] Exemplarily, the input fiber of the third in-line isolator 37 is a 20 / 125 single-clad fiber. Exemplarily, the output fiber of the second in-line isolator 24 is a 20 / 125 single-clad fiber. Exemplarily, the center wavelength of the third in-line isolator 37 is 1062 nm. Exemplarily, the operating bandwidth of the third in-line isolator 37 is 20 nm. Exemplarily, the average power withstand of the third in-line isolator 37 is 10 W. Exemplarily, the insertion loss of the third in-line isolator 37 is less than 1 dB. Exemplarily, the isolation of the third in-line isolator 37 is greater than 25 dB.

[0065] It is understood that the 20 / 125 fiber specifications used to transmit optical signals in the main optical path of the secondary amplifier module 30, which are used by the second gain fiber 34, the second combiner 35, and the third in-line isolator 37, can be directly connected. Therefore, the fiber specifications of the main optical path of the secondary amplifier module 30 are 20 / 125 fiber. The optical fiber at the output end of the primary amplifier module 20 and the optical fiber at the output end of the wavelength division multiplexer 32 are 10 / 125 single-clad fiber. The specifications of the output fiber of the primary amplifier module 20 are different from those of the main optical path of the secondary amplifier module 30. The primary amplifier module 20 and the secondary amplifier module 30 use optical fibers of different specifications as the optical fibers for the main optical path to accommodate the specifications of their respective optical devices, but there is a mode field mismatch, which can easily affect optical signal transmission.

[0066] Please continue reading Figure 4 In some embodiments, the optical fiber at the input end of the first mode field adapter 33 is a 10 / 125 single-clad optical fiber, which has the same specifications as the optical fiber at the output end of the wavelength division multiplexer 32. The optical fiber at the output end of the first mode field adapter 33 is a 20 / 130 single-clad optical fiber, which has the same specifications as the second gain fiber 34. Exemplarily, the first mode field adapter 33 can withstand an average power greater than 2W.

[0067] The optical fiber at the input end of the first mode field adapter 33 is connected to the optical fiber at the output end of the wavelength division multiplexer 32, and the optical fiber at the output end of the first mode field adapter 33 is connected to the input end of the second gain fiber 34, so that the first-stage amplification module 20 and the second-stage amplification module 30 can be connected through the wavelength division multiplexer 32 and the first mode field adapter 33 without affecting the transmission of optical signals.

[0068] See also Figure 5In some embodiments, the three-stage amplification module 40 is provided with a second photodetector 45, which is used to detect the optical signal output by the three-stage amplification module 40. In this way, the second photodetector 45 can detect the optical path of the nanosecond pulse fiber laser, thereby determining the operating status of the nanosecond pulse fiber laser based on the detection results. The nanosecond pulse fiber laser can also be adjusted based on the detection results, which is beneficial for protecting the optical path system of the nanosecond pulse fiber laser and thus improving its performance.

[0069] For example, the controller can be electrically connected to the second photodetector 45, and the second photodetector 45 can also be electrically connected to the seed source module 10. The controller can obtain the information detected by the second photodetector 45, so that the seed source module 10 can be controlled according to the information detected by the second photodetector 45, thereby adjusting the nanosecond pulse fiber laser.

[0070] Exemplarily, the second photodetector 45 is a free-space photodetector. Exemplarily, the second photodetector 45 is a commercial free-space photodetector.

[0071] In some embodiments, the three-stage amplification module 40 also includes a third pump laser 43 and a second mode field adapter 41, a third gain fiber 42 and an integrated output isolator 44 connected in sequence. The input end of the second mode field adapter 41 is connected to the output end of the two-stage amplification module 30, the output end of the integrated output isolator 44 forms the output end of the three-stage amplification module 40, the output end of the third pump laser 43 is connected to the input end of the integrated output isolator 44, and the second photodetector 45 is arranged at the detection hole on the integrated output isolator 44.

[0072] It can be understood that the integrated output isolator 44 integrates the function of the combiner.

[0073] Among them, the signal fiber of the integrated output isolator 44 and the pump fiber of the integrated output isolator 44 are arranged at the input end of the integrated output isolator 44, the signal fiber of the integrated output isolator 44 is connected to the third gain fiber 42, and the output end of the third pump laser 43 is connected to the pump fiber of the integrated output isolator 44.

[0074] For example, the third gain fiber 42 may be an ytterbium-doped fiber. For example, the third gain fiber 42 may be an ytterbium-doped 30 / 250 double-clad fiber.

[0075] It is understood that the third pump laser 43 can provide pump excitation to the third gain fiber 42. Exemplarily, the output power of the third pump laser 43 is greater than 450 W. Exemplarily, the central wavelength of the third pump laser 43 is 976 nm. Exemplarily, the output fiber of the third pump laser 43 is a 200 / 220 multimode fiber.

[0076] Exemplarily, the signal fiber of the integrated output isolator 44 can be a 30 / 250 double-clad fiber. Exemplarily, the pump fiber of the integrated output isolator 44 can be a 200 / 220 multimode fiber. Exemplarily, the center wavelength of the integrated output isolator 44 is 1064 nm. Exemplarily, the integrated output isolator 44 can withstand an average power greater than 250 W. Exemplarily, the integrated output isolator 44 can withstand a pump power greater than 450 W. Exemplarily, the pump light coupling efficiency of the integrated output isolator 44 is greater than 95%. Exemplarily, the signal light insertion loss of the integrated output isolator 44 is less than 1 dB. Exemplarily, the isolation of the integrated output isolator 44 is greater than 25 dB.

[0077] The third gain fiber 42 and the signal fiber of the integrated output isolator 44 can both use 30 / 250 fiber specifications. The fiber specifications for the main optical path of the three-stage amplification module 40 are 30 / 250 fiber, while the fiber specifications for the output end of the two-stage amplification module 30 are 20 / 125 fiber. The specifications of the output fiber of the two-stage amplification module 30 differ from those of the main optical path of the three-stage amplification module 40. Although the two-stage amplification module 30 and the three-stage amplification module 40 use different fiber specifications for their main optical paths to accommodate the specifications of their respective optical components, mode field mismatch exists, which can easily affect optical signal transmission.

[0078] Please continue reading Figure 5 In some embodiments, the optical fiber at the input end of the second mode field adapter 41 is a 20 / 125 single-clad optical fiber, which has the same specifications as the optical fiber at the output end of the secondary amplification module 30. Exemplarily, the output end of the second mode field adapter 41 may be a 30 / 250 double-clad optical fiber, and the specifications of the optical fiber at the output end of the second mode field adapter 41 are consistent with those of the third gain fiber 42. Exemplarily, the second mode field adapter 41 can withstand an average power greater than 10W.

[0079] The optical fiber at the input end of the second mode field adapter 41 is connected to the optical fiber at the output end of the wavelength division multiplexer 32, and the optical fiber at the output end of the second mode field adapter 41 is connected to the input end of the third gain fiber 42, so that the secondary amplification module 30 and the tertiary amplification module 40 can be connected without affecting the transmission of optical signals.

[0080] It should be noted that, in the present application, the connections between various devices and optical fibers are all fusion-spliced ​​using an optical fiber fusion splicer.

[0081] The nanosecond pulse fiber laser provided in the embodiments of this application, achieved through a rationally designed output waveform, appropriate optical path selection, and optimized gain distribution, has the advantages of a compact optical path structure, a simple structure, and uniform output spot energy distribution, making it an ideal laser light source for laser marking and laser precision welding. The nanosecond pulse fiber laser provided in the embodiments of this application can overcome problems such as severe nonlinear effects caused by excessively high output peak power and low reliability of fiber laser systems caused by improper fiber selection.

[0082] Specifically, the nanosecond pulse fiber laser provided in the embodiment of the present application uses 915nm and 976nm multimode semiconductor lasers as pump lasers, and utilizes a three-stage amplification structure to amplify the seed light power to 250W average power, greater than 40kW peak power, and greater than 1.8mJ single pulse energy, thereby achieving nanosecond pulse laser output with high peak power, high average power, and high beam quality.

[0083] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

[0084] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A nanosecond pulse fiber laser, characterized in that: include: A seed source module, the seed source module is used to output seed light; a first-stage amplification module, wherein an input end of the first-stage amplification module is connected to the seed source module; a secondary amplification module, wherein the input end of the secondary amplification module is connected to the output end of the primary amplification module; A three-stage amplification module, wherein the input end of the three-stage amplification module is connected to the output end of the two-stage amplification module; The seed source module includes a directly modulated semiconductor laser diode and a first online isolator. The output end of the semiconductor laser diode is connected to the input end of the first online isolator. The input end of the first-stage amplification module is connected to the output end of the first online isolator. The output end of the first online isolator is used to output the seed light.

2. The nanosecond pulse fiber laser according to claim 1, wherein The seed source module further includes a fiber Bragg grating, the output end of the semiconductor laser diode is connected to the input end of the fiber Bragg grating, the output end of the fiber Bragg grating is connected to the input end of the first online isolator, and the fiber Bragg grating is a weak reflection fiber Bragg grating.

3. The nanosecond pulse fiber laser according to claim 1, wherein The central wavelength of the semiconductor laser diode is 1064 nm, and / or the linewidth of the semiconductor laser diode is less than 15 nm, and / or the output fiber of the semiconductor laser diode is a PM980 fiber, the central wavelength of the first in-line isolator is 1059 nm, and / or the operating bandwidth of the first in-line isolator is 16 nm, and / or the input fiber of the first in-line isolator is a Hi1060 fiber, and / or the output fiber of the first in-line isolator is a 10 / 125 single-clad fiber.

4. The nanosecond pulse fiber laser according to claim 2, wherein: The central wavelength of the fiber Bragg grating is 1064 nm, and / or the line width of the fiber Bragg grating is less than 1 nm, and / or the output fiber of the fiber Bragg grating is PM980 fiber, and / or the reflectivity of the fiber Bragg grating is less than 5%.

5. The nanosecond pulse fiber laser according to claim 1, wherein: The first-stage amplification module also includes a first pump laser, a first photodetector, and a first beam combiner, a first gain fiber, a second online isolator, and a coupler connected in sequence. The input end of the first beam combiner is connected to the output end of the first online isolator, the output end of the first pump laser is connected to the input end of the first beam combiner, the input end of the first beam combiner is used to receive the seed light and the pump light output by the first pump laser, the first output end of the coupler is connected to the input end of the second-stage amplification module, and the second output end of the coupler is connected to the first photodetector.

6. The nanosecond pulse fiber laser according to claim 5, wherein: The output power of the first pump laser is greater than 10 W, the central wavelength of the first pump laser is 915 nm, and the output fiber of the first pump laser is a 105 / 125 multimode fiber; and / or the pump fiber and the signal fiber of the first beam combiner are arranged at the input end of the first beam combiner, the output end of the first pump laser is connected to the pump fiber of the first beam combiner, the signal fiber of the first beam combiner is connected to the output end of the first in-line isolator, the signal fiber of the first beam combiner is a 10 / 125 double-clad fiber, and the pump fiber of the first beam combiner is a 105 / 125 multimode fiber.

7. The nanosecond pulse fiber laser according to claim 1, wherein: The secondary amplification module includes a red light laser, a second pump laser, and a wavelength division multiplexer, a first mode field adapter, a second gain fiber, a second combiner, and a third online isolator connected in sequence. The input end of the wavelength division multiplexer is connected to the output end of the primary amplification module, the output end of the red light laser is connected to the input end of the wavelength division multiplexer, the input end of the wavelength division multiplexer is used to receive the optical signal output by the primary amplification module and the red light output by the red light laser, the output end of the second pump laser is connected to the output end of the second combiner, and the input end of the tertiary amplification module is connected to the output end of the third online isolator.

8. The nanosecond pulse fiber laser according to claim 7, wherein: The output optical fiber of the red laser is Hi1060 optical fiber, and the output power of the red laser is 60mW; and / or, the input end of the wavelength division multiplexer is provided with a signal port and a red light port, the signal port of the wavelength division multiplexer is connected to the output end of the first-stage amplification module, the red light port of the wavelength division multiplexer is connected to the output end of the red laser, the optical fiber of the signal port is a 10 / 125 single-clad optical fiber, and the optical fiber of the red light port is Hi1060 optical fiber; and / or, the output power of the second pump laser is greater than 30W, the central wavelength of the second pump laser is 915nm, and the output light of the second pump laser is 10 / 125 single-clad optical fiber. The fiber is a 105 / 125 multimode fiber; and / or, the signal fiber of the second beam combiner is arranged at the input end of the second beam combiner, the pump fiber and the output fiber of the second beam combiner are arranged at the output end of the second beam combiner, the output end of the second pump laser is connected to the pump fiber of the second beam combiner, the signal fiber of the second beam combiner is connected to the output end of the second gain fiber, the output fiber of the second beam combiner is connected to the input end of the third in-line isolator, the signal fiber and the output fiber of the second beam combiner are 20 / 125 double-clad fibers, and the pump fiber of the second beam combiner is a 105 / 125 multimode fiber.

9. The nanosecond pulse fiber laser according to any one of claims 1 to 8, characterized in that: The three-stage amplification module includes a second photodetector, a third pump laser, and a second mode field adapter, a third gain fiber, and an integrated output isolator connected in sequence. The input end of the second mode field adapter is connected to the output end of the two-stage amplification module, the output end of the integrated output isolator forms the output end of the three-stage amplification module, the output end of the third pump laser is connected to the input end of the integrated output isolator, and the second photodetector is arranged at the detection hole on the integrated output isolator.

10. The nanosecond pulse fiber laser according to claim 9, wherein: The output power of the third pump laser is greater than 450 W, the central wavelength of the third pump laser is 976 nm, and the output fiber of the third pump laser is a 200 / 220 multimode fiber; and / or the signal fiber and the third pump fiber of the integrated output isolator are arranged at the input end of the integrated output isolator, the signal fiber of the integrated output isolator is connected to the output end of the third gain fiber, the pump fiber of the integrated output isolator is connected to the output end of the third pump laser, the signal fiber of the integrated output isolator is a 30 / 250 double-clad fiber, and the pump fiber of the integrated output isolator is a 200 / 220 multimode fiber.

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