A neodymium-doped fiber laser capable of suppressing ASE in the 1060 nm band

Abstract

The utility model discloses a kind of neodymium-doped fiber lasers capable of inhibiting 1060nm waveband ASE, and the laser includes master oscillator and power amplifier.Master oscillator includes linear resonant cavity by first reflection grating, first neodymium-doped fiber and second reflection grating, and its reflection center wavelength is located 890~935nm waveband;First filter grating is equipped in resonant cavity, and it forms inhibition band at 1060±15nm, and forms passband in 890~935nm waveband.Power amplifier includes second neodymium-doped fiber, second filter grating and cladding light filter, and second filter grating has same spectral characteristics with first filter grating.The utility model carries out double spectral inhibition to 1060nm waveband ASE in oscillation and amplification whole process, effectively solve the gain competition problem between it and 920nm laser, ensure the stable oscillation and efficient amplification of 920nm waveband laser, simultaneously have the advantages of compact structure, output spectrum purity is high and work reliable.

Description

Technical Field

[0001] This invention belongs to the field of fiber lasers, and particularly relates to a neodymium-doped fiber laser capable of suppressing ASE in the 1060 nm band. Background Technology

[0002] Fiber lasers, with their advantages of high output efficiency, compact structure, and good beam quality, are playing an increasingly important role in industrial processing and defense. Laser wavelength is a key factor determining its application scenarios and technical solutions. Among them, 920 nm lasers have significant application value in biological detection and terahertz generation, and can also be used as pump sources to increase the output power of kilowatt-level lasers in the 1 μm band.

[0003] Currently, the generation of 920 nm lasers mainly relies on Ti:sapphire solid-state lasers, but this approach is bulky, environmentally sensitive, and unsuitable for system integration and portable applications. In recent years, achieving 920 nm laser output using neodymium-doped fiber has become an important research direction. However, under 808 nm pumping, neodymium-doped fiber simultaneously generates amplified spontaneous emission (ASE) in three bands: 920 nm, 1060 nm, and 1310 nm. Among these, ASE in the 1310 nm band is easily lost, while ASE in the 920 nm and 1060 nm bands is readily formed. To establish 920 nm laser oscillation in this system, ASE in the 1060 nm band must be effectively suppressed; otherwise, severe gain competition will occur between the two, making it difficult for the 920 nm laser to oscillate.

[0004] Currently, common methods for suppressing 1060 nm ASE include bending optical fibers, introducing spatial filtering devices, and designing specially structured optical fibers. However, while bending optical fibers and spatial filtering devices suppress 1060 nm ASE, they also introduce additional losses to the 920 nm laser, and the use of spatial devices reduces system integration; while the design and fabrication costs of specially structured optical fibers are usually high. Therefore, there is an urgent need for a technical solution that can effectively suppress 1060 nm ASE at a low cost. Utility Model Content

[0005] The purpose of this invention is to provide a neodymium-doped fiber laser that can suppress ASE in the 1060 nm band, so as to solve the technical problem that the gain competition caused by ASE in the 1060 nm band in neodymium-doped fiber lasers makes it difficult to start oscillation in the 920 nm band.

[0006] To achieve the above objectives, the specific technical solution of this utility model is as follows: A neodymium-doped fiber laser capable of suppressing ASE (associated acoustic emission) in the 1060 nm band is disclosed. The laser includes a master oscillator and a power amplifier. The master oscillator includes a linear fiber resonant cavity defined by a first reflection grating, a first neodymium-doped fiber, and a second reflection grating. The reflection center wavelengths of the first and second reflection gratings are set in the 890–935 nm band. A first pump combiner is provided on the input side of the first neodymium-doped fiber, and the pump port of the first pump combiner is connected to a first pump source in the 808 nm band. The output side of the second reflection grating is connected to the input of the power amplifier via an isolator. At least one first filter grating is provided in the linear fiber resonant cavity. The transmission spectrum of the first filter grating forms a suppression band at 1060 ± 15 nm and a passband in the 890–935 nm band.

[0007] Therefore, this invention sets up a first filter grating in the linear fiber resonator, utilizing its spectral characteristics to form a suppression band in the 1060 nm band to introduce high loss, while maintaining a passband in the 920 nm band to maintain low loss. Combined with the gratings at both ends of the resonator whose reflection center wavelength is located in the 920 nm band, a selective amplification environment is constructed, so that the pump energy is directed to the oscillation and amplification of the 920 nm laser. This fundamentally breaks the gain competition balance between the 1060 nm band ASE and the 920 nm band laser, solving the technical problem that the gain competition caused by the 1060 nm band ASE in neodymium-doped fiber laser makes it difficult to start oscillation in the 920 nm band.

[0008] Furthermore, the first filter grating has a suppression degree of ≥30 dB for 1060±15 nm and an insertion loss of ≤0.2 dB for the 890~935 nm passband.

[0009] Furthermore, the first filter gratings are spaced apart along the optical path direction of the linear fiber resonator, and the spacing between two adjacent first filter gratings is 90 cm to 110 cm, ensuring that the 1060 nm band ASE is continuously and sufficiently depleted during the accumulation process, thereby improving the reliability of the overall suppression effect.

[0010] Furthermore, the bandwidth of the first reflective grating is 2 nm to 3 nm, and the bandwidth of the second reflective grating is 0.2 nm to 0.5 nm. The wider bandwidth of the first reflective grating is beneficial for capturing a wider range of spontaneous emission light and injecting energy, facilitating rapid laser oscillation; the narrower bandwidth of the second reflective grating can precisely lock the final output laser wavelength, ensuring the spectral purity and stability of the output laser.

[0011] Furthermore, the first reflective grating has a reflectivity of ≥99.9% for signal light between 919 nm and 922 nm, while the second reflective grating has a reflectivity of ≤14% for signal light between 920 nm and 920.3 nm. The high reflectivity of the first reflective grating forms a strong feedback end of the resonant cavity, providing a strong foundation for laser oscillation; the low reflectivity of the second reflective grating forms the output end, allowing sufficient laser energy to be efficiently coupled and output while ensuring that the laser can start oscillating, and then sent to the subsequent power amplifier, realizing efficient energy transfer between the oscillator and the amplifier.

[0012] Furthermore, the power amplifier includes a second neodymium-doped fiber, a second filter grating, and a cladding optical filter sequentially coupled along the optical path. The input side of the second neodymium-doped fiber is provided with a second pump combiner. The pump port of the second pump combiner is connected to a second pump source in the 808 nm band. The signal port of the second pump combiner is connected to the output side of the isolator. The transmission spectrum of the second filter grating forms a suppression band at 1060±15 nm and a passband in the 890~935 nm band.

[0013] Therefore, by setting a second filter grating inside the power amplifier, this utility model actively filters out the 1060 nm band ASE newly generated by the second neodymium-doped fiber under high-power pump when amplifying the pure seed light output from the main oscillator. This forms a "dual suppression" mechanism that runs through the entire process of main oscillation and power amplification, effectively preventing energy competition and efficiency degradation during amplification. At the same time, by introducing a cladding light filter, harmful stray light accumulated in the system is eliminated, jointly ensuring the conversion efficiency, spectral purity, and long-term operational reliability of the laser when achieving high-power output.

[0014] Furthermore, the second filter grating has a suppression degree of ≥30 dB for 1060±15 nm and an insertion loss of ≤0.05 dB for the 890~935 nm passband.

[0015] Furthermore, the second filter gratings are spaced apart along the optical path direction, and the spacing between two adjacent second filter gratings is 90 cm to 110 cm.

[0016] Furthermore, the first reflection grating is a chirped fiber Bragg grating, the second reflection grating is a fiber Bragg grating, and both the first and second filtering gratings are long-period fiber gratings. The chirped fiber Bragg grating provides a wider reflection bandwidth, efficiently capturing spontaneous emission light to promote rapid laser oscillation; the fiber Bragg grating utilizes its narrow bandwidth and precise reflectivity to rigorously filter and lock specific wavelengths to achieve pure laser output; the long-period fiber grating can couple light of specific wavelengths from the fiber core to the cladding loss, thereby achieving efficient filtering of amplified spontaneous emission in non-target wavelength bands.

[0017] In addition, the output end of the cladding optical filter is connected to an optical fiber output head, which is preferably a QBH type standard optical fiber connector.

[0018] This utility model has the following advantages: 1. By setting filter gratings with specific spectral characteristics in the resonant cavity and amplifier, a dual suppression mechanism is constructed, which directionally and greatly suppresses ASE in the 1060 nm band, ensuring stable oscillation of the 920 nm laser.

[0019] 2. The filter grating has low loss in the target band. Combined with optimized grating parameters, it maximizes the pump energy conversion efficiency and precisely locks the output wavelength, ensuring the output of high-power, high-purity laser. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the neodymium-doped fiber laser structure of this utility model. Figure 2 This is a schematic diagram of the main oscillator structure of this utility model; Figure 3 This is a schematic diagram of the power amplifier structure of this utility model.

[0021] The markings in the diagram are as follows: 1. Master oscillator; 11. First pump source; 12. First pump combiner; 13. First reflection grating; 14. First neodymium-doped fiber; 15. First filter grating; 16. Second reflection grating; 17. Isolator; 2. Power amplifier; 21. Second pump source; 22. Second pump combiner; 23. Second neodymium-doped fiber; 24. Second filter grating; 25. Cladding optical filter; 26. Fiber optic output head. Detailed Implementation

[0022] To better understand the purpose, structure, and function of this utility model, a more detailed description of this utility model is provided below with reference to the accompanying drawings.

[0023] like Figure 1 and Figure 2 As shown, a neodymium-doped fiber laser capable of suppressing ASE in the 1060 nm band according to this invention includes a master oscillator 1 and a power amplifier 2. The master oscillator 1 includes a linear fiber resonant cavity defined by a first reflection grating 13, a first neodymium-doped fiber 14, and a second reflection grating 16. At least one first filter grating 15 is provided within the linear fiber resonant cavity. A first pump combiner 12 is provided on the input side of the first neodymium-doped fiber 14, and the pump port of the first pump combiner 12 is connected to a first pump source 11 in the 808 nm band. The output side of the second reflection grating 16 is connected to the input end of the power amplifier 2 via an isolator 17.

[0024] Specifically, the first reflection grating 13 of this invention is a chirped fiber Bragg grating, and the second reflection grating 16 is a fiber Bragg grating. The reflection center wavelengths of the first reflection grating 13 and the second reflection grating 16 are set in the 890–935 nm band. The bandwidth of the first reflection grating 13 is 2 nm, and the bandwidth of the second reflection grating 16 is 0.2 nm. The reflectivity of the first reflection grating 13 for signal light between 919 nm and 922 nm is ≥99.9%, and the reflectivity of the second reflection grating 16 for signal light between 920 nm and 920.3 nm is ≤14%.

[0025] The first filter grating 15 is a long-period fiber grating, and the first filter gratings 15 are spaced apart along the optical path direction of the linear fiber resonator, with a spacing of 100 cm between two adjacent first filter gratings 15. The transmission spectrum of the first filter grating 15 forms a suppression band at 1060±15 nm and a passband in the 890–935 nm band. The suppression degree of the first filter grating 15 at 1060±15 nm is ≥30 dB, and the insertion loss in the 890–935 nm passband is ≤0.2 dB.

[0026] Based on this, the 808 nm pump light emitted from the first pump source 11 enters the first neodymium-doped fiber 14 via the first pump combiner 12, generating an ASE (laser optics) containing 920 nm and 1060 nm wavelengths. The first reflection grating 13 utilizes its wide bandwidth and high reflectivity to form strong feedback for the 920 nm wavelength light; the second reflection grating 16 utilizes its narrow bandwidth and specific reflectivity to precisely filter and output the laser wavelength. Simultaneously, the first filter gratings 15, spaced apart within the cavity, suppress the 1060 nm ASE by ≥30 dB, coupling it from the fiber core to the cladding loss, while introducing only ≤0.2 dB of loss for the 920 nm signal light. This design creates a spectral environment within the cavity that is conducive to 920 nm laser oscillation while strongly suppressing 1060 nm ASE, thus solving the gain competition problem at the oscillation source.

[0027] like Figure 1 and Figure 3 As shown, the power amplifier 2 includes a second neodymium-doped fiber 23, a second filter grating 24, and a cladding optical filter 25, which are sequentially coupled along the optical path. A second pump combiner 22 is provided on the input side of the second neodymium-doped fiber 23. The pump port of the second pump combiner 22 is connected to a second pump source 21 in the 808 nm band. The signal port of the second pump combiner 22 is connected to the output side of the isolator 17. An optical fiber output head 26 is connected to the output end of the cladding optical filter 25.

[0028] Specifically, the second filter grating 24 of this invention is a long-period fiber grating. The second filter gratings 24 are spaced apart along the optical path, with a spacing of 100 cm between adjacent second filter gratings 24. The transmission spectrum of the second filter grating 24 forms a suppression band at 1060±15 nm and a passband in the 890–935 nm band. The suppression degree of the second filter grating 24 at 1060±15 nm is ≥30 dB, and the insertion loss in the 890–935 nm passband is ≤0.05 dB. The fiber optic output head 26 is a QBH type standard fiber optic connector.

[0029] Based on this, the pure 920 nm seed light from the master oscillator 1 enters the power amplifier 2 through the isolator 17, and is injected into the second neodymium-doped fiber 23 together with the pump light from the second pump source 21 for power amplification. During the amplification process, the second filter grating 24, which is set at intervals, continuously filters out the newly generated 1060 nm band ASE in the second neodymium-doped fiber 23 with a suppression degree of ≥30 dB, while controlling the additional loss to the 920 nm signal light to an extremely low level of ≤0.05 dB, thereby maintaining high spectral purity and high conversion efficiency during the amplification stage. Subsequently, the cladding light filter 25 removes the residual stray light in the fiber cladding, and finally outputs high-quality laser light through the fiber output head 26.

[0030] Therefore, by setting a first filter grating in the resonant cavity of the main oscillator and a second filter grating in the power amplifier, this invention forms a dual suppression mechanism for the 1060 nm band ASE throughout the entire oscillation and amplification process. This efficiently and selectively eliminates the gain competition between the ASE in this band and the 920 nm target laser, ensuring the stable start-up and efficient amplification of the 920 nm laser, and ultimately achieving reliable output of high-power, high-spectral-purity laser.

[0031] It is understood that this utility model has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of this utility model. Furthermore, under the teachings of this utility model, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of this utility model. Therefore, this utility model is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of this utility model.

Claims

1. A neodymium-doped fiber laser capable of suppressing ASE in the 1060 nm band, comprising a master oscillator (1) and a power amplifier (2); characterized in that: The main oscillator (1) includes a linear fiber resonant cavity defined by a first reflective grating (13), a first neodymium-doped fiber (14), and a second reflective grating (16). The reflection center wavelengths of the first reflective grating (13) and the second reflective grating (16) are set in the 890-935 nm band. A first pump combiner (12) is provided on the input side of the first neodymium-doped fiber (14). The pump port of the first pump combiner (12) is connected to a first pump source (11) in the 808 nm band. The output side of the second reflective grating (16) is connected to the input end of the power amplifier (2) via an isolator (17). At least one first filter grating (15) is provided in the linear fiber resonant cavity. The transmission spectrum of the first filter grating (15) forms a suppression band at 1060±15 nm and a passband in the 890-935 nm band.

2. The neodymium-doped fiber laser capable of suppressing ASE in the 1060 nm band according to claim 1, characterized in that, The first filter grating (15) has a suppression degree of ≥30 dB for 1060±15 nm and an insertion loss of ≤0.2 dB for the 890~935 nm passband.

3. The neodymium-doped fiber laser capable of suppressing ASE in the 1060 nm band according to claim 1, characterized in that, The first filter grating (15) is arranged at intervals along the optical path direction of the linear fiber resonator, and the spacing between two adjacent first filter gratings (15) is 90 cm to 110 cm.

4. The neodymium-doped fiber laser capable of suppressing ASE in the 1060 nm band according to claim 1, characterized in that, The bandwidth of the first reflective grating (13) is 2 nm to 3 nm, and the bandwidth of the second reflective grating (16) is 0.2 nm to 0.5 nm.

5. The neodymium-doped fiber laser capable of suppressing ASE in the 1060 nm band according to claim 1, characterized in that, The first reflective grating (13) has a reflectivity of ≥99.9% for signal light between 919 nm and 922 nm, and the second reflective grating (16) has a reflectivity of ≤14% for signal light between 920 nm and 920.3 nm.

6. The neodymium-doped fiber laser capable of suppressing ASE in the 1060 nm band according to claim 1, characterized in that, The power amplifier (2) includes a second neodymium-doped fiber (23), a second filter grating (24) and a cladding optical filter (25) coupled sequentially along the optical path. The input side of the second neodymium-doped fiber (23) is provided with a second pump combiner (22). The pump port of the second pump combiner (22) is connected to a second pump source (21) in the 808 nm band. The signal port of the second pump combiner (22) is connected to the output side of the isolator (17). The transmission spectrum of the second filter grating (24) forms a suppression band at 1060±15 nm and a passband in the 890~935 nm band.

7. The neodymium-doped fiber laser capable of suppressing ASE in the 1060 nm band according to claim 6, characterized in that, The second filter grating (24) has a suppression degree of ≥30 dB for 1060±15 nm and an insertion loss of ≤0.05 dB for the 890~935 nm passband.

8. The neodymium-doped fiber laser capable of suppressing ASE in the 1060 nm band according to claim 6, characterized in that, The second filter grating (24) is spaced apart along the optical path direction, and the spacing between two adjacent second filter gratings (24) is 90 cm to 110 cm.

9. The neodymium-doped fiber laser capable of suppressing ASE in the 1060 nm band according to claim 6, characterized in that, The first reflective grating (13) is a chirped fiber Bragg grating, the second reflective grating (16) is a fiber Bragg grating, and the first filter grating (15) and the second filter grating (24) are both long-period fiber gratings.

10. The neodymium-doped fiber laser capable of suppressing ASE in the 1060 nm band according to claim 6, characterized in that, The output end of the cladding optical filter (25) is connected to an optical fiber output head (26).

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