Fiber laser based on long-period fiber grating
By introducing long-period fiber grating filtering technology into fiber lasers, the problems of ASE and self-excited output in high-power ytterbium-doped fiber lasers are solved, and the high-power output of pure spectroscopy and the safety of optical systems are improved.
Patent Information
- Application Number
- CN202422073011.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-26
- Publication Date
- 2025-08-08
- Estimated Expiration
- 2034-08-26
AI Technical Summary
The prior art is difficult to effectively suppress ASE and self-excitation output of <1030 nm in high-power ytterbium-doped fiber lasers, resulting in safety hazards and reduced optical efficiency of the optical system.
The long-period fiber grating filtering technology is used to use the filtering effect of the long-period fiber grating to suppress 1030nm ASE and self-excited output. Through the filtering effect of the long-period fiber grating, the loss is increased and the gain of 1030nm is reduced, and the spectral components are purified.
Effective suppression of 1030nm ASE and self-excitation is achieved, and a high power <1030nm doped ytterbium-doped laser with pure spectra is obtained, which improves the safety and optical efficiency of the optical system.
Smart Images
Figure CN223206619U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to a fiber laser based on a long-period fiber grating. Background Art
[0002] With the use of co-band pumping technology in fiber laser technology, the risks of fiber melting and transverse mode instability caused by fiber thermal problems can be greatly reduced by using a pump light source with low photon loss. Therefore, co-band pumping technology has become a reliable technology for achieving high-power, high-brightness single-fiber output of tens of thousands of watts. The light source used for co-band pumping technology of high-power ytterbium-doped fiber lasers is generally obtained by combining ytterbium-doped gain fiber with resonant cavity or mopa amplification. Given the absorption spectrum of ytterbium-doped fiber, the laser wavelength of the co-band pump light source should be less than 1030nm. However, this wavelength is also within the absorption spectrum of ytterbium-doped fiber, indicating strong reabsorption. For the 1030nm wavelength, which is the emission peak and has a low reabsorption effect, the laser oscillation threshold of lasers with a center wavelength less than 1030nm is higher, making it more difficult to form laser oscillation. Therefore, high-power ytterbium-doped fiber lasers with a center wavelength less than 1030nm are generally accompanied by ASE or self-excited output of lasers with a wavelength of 1030nm.
[0003] To achieve high-brightness, high-power single-fiber ytterbium-doped laser output, co-band pumping technology generally requires a high-brightness, high-power co-band pump laser source. "High brightness" can improve the pump light injection capability, while "high power" can increase the upper limit of the output power of a single-fiber amplification based on co-band pumping technology. As a typical co-band pump source for the commonly used ytterbium-doped 1080nm fiber laser, a 1018nm wavelength light source is generally obtained by pumping a high-absorption ytterbium-doped fiber at 915nm, 940nm, or 976nm. However, because 1018nm is located in the strong absorption band of the ytterbium-doped active fiber, it is more difficult to obtain gain compared to the 1030nm wavelength located in the strong emission peak band of the ytterbium-doped active fiber. As a result, 1030nm ASE and self-oscillation are very likely to occur in the 1018nm light source system based on the ytterbium-doped fiber, which will limit the acquisition of high-power, high-brightness laser at 1018nm and may also cause certain damage to the optical system. Existing solutions typically involve shortening the active fiber or increasing the reflectivity of the low-reflection grating. While shortening the active fiber suppresses ASE and self-oscillation, it also reduces the absorption of the pump laser, ultimately reducing optical efficiency. Increasing the reflectivity of the low-reflection grating increases the laser energy density within the cavity, potentially heating the active fiber due to 1018nm reabsorption, and potentially causing nonlinear effects, potentially jeopardizing the safety of the optical system. Utility Model Content
[0004] The purpose of this utility model is to provide a fiber laser based on a long-period fiber grating. In order to obtain a purer spectrum of <1030nm laser light and effectively suppress 1030nm ASE or self-excitation, the filtering effect of the long-period fiber grating is utilized to filter the 1030nm ASE, increase the loss and reduce the 1030nm gain, thereby purifying the spectral components and obtaining a high-power ytterbium-doped in-band pump laser with a central wavelength of <1030nm and a pure spectrum.
[0005] To solve the above problems, the utility model provides a fiber laser based on long-period fiber grating, comprising a pump source, a first beam combiner, a second beam combiner, an active fiber, a high-reflection grating, a low-reflection grating, and a long-period fiber grating, characterized in that: the pump fiber of the first beam combiner is connected to the pump source, multiple pump fibers of the first beam combiner are connected to multiple pump light sources, and the output fiber of the first beam combiner is connected to the first end of the high-reflection grating; the second end of the high-reflection grating is connected to the first end of the active fiber, the second end of the active fiber is connected to the first end of the long-period fiber grating, and the second end of the long-period fiber grating is connected to the first end of the low-reflection grating; the pump fiber of the second beam combiner is connected to the pump source, the first end of the central fiber of the second beam combiner is connected to the second end of the low-reflection grating, and the second end of the central fiber of the second beam combiner outputs the laser in the resonant cavity, and uses the long-period fiber grating for filtering. The long-period fiber grating is used for ASE of the laser and suppression of self-excitation.
[0006] Preferably, the long-period grating has a central wavelength of 1030 nm and a bandwidth greater than 3 nm.
[0007] Preferably, it further comprises a stripper and an output device, the second end of the central fiber of the second combiner is connected to the first side of the stripper, the second side of the stripper is connected to the first side of the output device, and the second side of the output device is used to output laser.
[0008] Preferably, the laser output by the resonant cavity is an ytterbium-doped fiber in-band pump laser with a central wavelength less than 1030 nm.
[0009] Preferably, the resonant cavity outputs a 1018 nm fiber laser output greater than 600 W.
[0010] Preferably, the pump source adopts multiple pump light sources, including forward pump light sources and reverse pump light sources; the pump source is composed of multiple semiconductor laser diode fiber-coupled output pump light sources with pump light working wavelengths of 915nm, 940nm or 976nm, wherein the output power of a single pump light source output fiber is ≥200W.
[0011] Preferably, the first beam combiner adopts a forward 3*1 pump beam combiner, and the second beam combiner adopts a reverse (2+1)*1 beam combiner.
[0012] Preferably, the long-period fiber grating is obtained by etching the fiber core point by point with an ultraviolet laser. The core etching obtains the characteristic of high transparency for 1018 nm transmission in the core and coupling lasers of other wavelengths transmitted in the core into the cladding.
[0013] Preferably, the active optical fiber length is greater than 4m, the central wavelength of the high-reflection grating is 1018nm, the reflection bandwidth is 3nm, and the reflectivity is ≥99.5%, which is obtained by combining a mask with a femtosecond laser fiber core etching; the central wavelength of the low-reflection grating is 1018nm, the reflection bandwidth is 1nm, and the reflectivity is 15%-5%. Relative to the 1018nm laser, the 1030nm spectral component suppression ratio is more than 60dB.
[0014] Preferably, the fiber parameters of the pump fibers of the first and second combiners are 105 / 125 / 0.22, and the fiber parameters of the central output fiber are 20 / 130 / 0.08; the output fiber type is 20 / 130 / 0.08, and the internal stripper can strip the cladding light.
[0015] The beneficial effect of this utility model lies in effectively suppressing 1030nm ASE by utilizing the filtering effect of a long-period fiber grating (LPFG). This patented method can achieve the suppression of 1030nm ASE and self-excitation. By using a LPFG to suppress ASE and self-excitation, the LPFG 7 has a central wavelength of 1030nm and a bandwidth greater than 3nm, resulting in a higher suppression capability for ASE and self-excitation. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 It is a structural diagram of the present utility model.
[0017] Figure 2 This is a schematic diagram of the long-period fiber grating of the present invention. DETAILED DESCRIPTION
[0018] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.
[0019] like Figure 1 As shown, the utility model relates to a fiber laser based on a long period fiber grating, which is used to obtain a 1018nm laser power output with an improved resonant cavity solution and suppress the generation of ASE and self-excitation.
[0020] A high-power 1018nm laser based on long-period grating self-excitation suppression includes a pump source 1, a first beam combiner 2, a second beam combiner 3, an active optical fiber 4, a high-reflection grating 5, a low-reflection grating 6, a long-period fiber grating 7, a stripper 8, and an output device 9.
[0021] from Figure 1It can be seen that the pump source 1 adopts multiple pump light sources, including a forward pump light source and a reverse pump light source; preferably, the pump source 1 is composed of a laser diode (LD) semiconductor fiber-coupled output laser pump light source with a pump light operating wavelength of 915 nm, 940 nm or 976 nm, wherein the output fiber of a single pump light source is 105 / 125 / 0.22, with an output power ≥ 200 W, and there are 5 in total, 3 forward pump sources and 2 reverse pump sources.
[0022] Preferably, the first combiner is a forward 3*1 pump combiner, preferably with pump fibers of 105 / 125 / 0.22 and central output fibers of 20 / 130 / 0.08. The pump fiber of the first combiner is connected to the pump source, multiple pump fibers of the first combiner are connected to multiple pump light sources, and the output fiber of the first combiner is connected to the first end of the high-reflection grating 5.
[0023] The second end of the high-reflection grating 5 is connected to the first end of the active fiber 4 , the second end of the active fiber 4 is connected to the first end of the long-period fiber grating, and the second end of the long-period fiber grating is connected to the first end of the low-reflection grating 6 .
[0024] Preferably, the second combiner is an inverse (2+1)*1 combiner: preferably, the pump fiber is 105 / 125 / 0.22, and the central input and output signal fibers are 20 / 130 / 0.08. The pump fiber of the second combiner is connected to the pump source, the first end of the central fiber of the second combiner is connected to the second end of the low-reflection grating 6, the second end of the central fiber of the second combiner outputs the laser light in the resonant cavity, the second end of the central fiber of the second combiner is connected to the first side of the stripper 8, the second side of the stripper is connected to the first side of the output device, and the second side of the output device is used to output the laser light.
[0025] Preferably, the active optical fiber 4 has an optical fiber type of 20 / 130 / 0.08, an absorption coefficient of ≥4dB / m@915nm, and an optical fiber length of ≥4m.
[0026] Preferably, the high-reflection grating 5 has a central wavelength of 1018 nm, a reflection bandwidth of 3 nm, and a reflectivity of ≥99.5%, and can be obtained by using a mask combined with femtosecond laser fiber core etching.
[0027] Preferably, the low-reflection grating 6 has a central wavelength of 1018 nm, a reflection bandwidth of 1 nm, and a reflectivity of 15%-5%. Preferably, the reflectivity is 10%, which can be obtained by masking combined with femtosecond laser fiber core etching.
[0028] See also Figure 2Engineers realized that due to the wide bandwidth of ASE laser at 1030nm, the bandwidth of long-period fiber grating must meet certain requirements. Preferably, the long-period fiber grating 7 has a central wavelength of 1030nm and a bandwidth of >3nm. It can be obtained by etching the fiber core point by point with ultraviolet laser. The core etching obtains its characteristics of high transparency for 1018nm transmission in the fiber core, while coupling other wavelength bands of laser transmitted in the fiber core into the cladding, thereby suppressing ASE and self-excited laser in the 1030nm band.
[0029] Preferably, the stripper 8 is of optical fiber type: 20 / 130 / 0.08, obtained by etching the optical fiber cladding by CO2 laser.
[0030] Preferably, the output device 9 is an optical fiber of type 20 / 130 / 0.08, and has an internal stripper to strip the cladding light.
[0031] This solution can achieve high-brightness 1018nm fiber laser output of >600W. Compared with 1018nm laser, the 1030nm spectral component suppression ratio can reach over 60dB.
[0032] exist Figure 1 In the above text, the first end refers to the left side, and the second end refers to the right side.
[0033] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are intended solely to illustrate the principles of the present invention and should not be construed in any way as limiting the scope of protection of the present invention. Based on the explanations herein, those skilled in the art will be able to devise other specific implementations of the present invention without inventive effort, and such implementations will fall within the scope of protection of the present invention.
Claims
1. A fiber laser based on a long-period fiber grating, comprising a pump source, a first beam combiner, a second beam combiner, an active fiber, a high-reflection grating, a low-reflection grating, and a long-period fiber grating, characterized in that: The pump fiber of the first beam combiner is connected to the pump source, the multiple pump fibers of the first beam combiner are connected to the multiple pump light sources, the output fiber of the first beam combiner is connected to the first end of the high-reflection grating; the second end of the high-reflection grating is connected to the first end of the active fiber, the second end of the active fiber is connected to the first end of the long-period fiber grating, and the second end of the long-period fiber grating is connected to the first end of the low-reflection grating; the pump fiber of the second beam combiner is connected to the pump source, the first end of the central fiber of the second beam combiner is connected to the second end of the low-reflection grating, and the second end of the central fiber of the second beam combiner outputs the laser in the resonant cavity and uses the long-period fiber grating for filtering. The long-period fiber grating is used for ASE of the laser and suppression of self-excitation.
2. The fiber laser based on long-period fiber grating according to claim 1, characterized in that: The long period grating has a central wavelength of 1030 nm and a bandwidth of >3 nm.
3. The fiber laser based on long-period fiber grating according to claim 1, characterized in that: It also includes a stripper and an output device. The second end of the central fiber of the second combiner is connected to the first side of the stripper, the second side of the stripper is connected to the first side of the output device, and the second side of the output device is used to output laser.
4. The fiber laser based on long-period fiber grating according to claim 2, characterized in that: The laser output from the resonant cavity is an ytterbium-doped fiber co-band pump laser with a central wavelength less than 1030 nm.
5. The fiber laser based on long-period fiber grating according to claim 4, characterized in that: The resonant cavity output is greater than 600W of 1018nm fiber laser output.
6. The fiber laser based on long-period fiber grating according to claim 5, characterized in that: The pump source adopts multiple pump light sources, including forward pump light sources and reverse pump light sources; the pump source is composed of multiple semiconductor laser diode fiber-coupled output pump light sources with pump light working wavelengths of 915nm, 940nm or 976nm, among which the output power of a single pump light source output fiber is ≥200W.
7. The fiber laser based on long-period fiber grating according to claim 6, characterized in that: The first combiner uses a forward 3*1 pump combiner, and the second combiner uses a reverse (2+1)*1 combiner.
8. The fiber laser based on long-period fiber grating according to claim 5, characterized in that: The long-period grating is obtained by etching the optical fiber core point by point with an ultraviolet laser. The core etching obtains its characteristics of high transparency for 1018nm transmission in the core and coupling the lasers of other wavelength bands transmitted by the core into the cladding.
9. The fiber laser based on long-period fiber grating according to claim 8, characterized in that: The active optical fiber length is greater than 4m, the central wavelength of the high-reflection grating is 1018nm, the reflection bandwidth is 3nm, and the reflectivity is ≥99.5%, which is obtained by combining a mask with a femtosecond laser fiber core etching; the central wavelength of the low-reflection grating (6) is 1018nm, the reflection bandwidth is 1nm, and the reflectivity is 15%-5%. Compared with the 1018nm laser, the 1030nm spectral component suppression ratio is more than 60dB.
10. The fiber laser based on long-period fiber grating according to claim 9, characterized in that: The fiber parameters of the pump fibers of the first and second combiners are 105 / 125 / 0.22, and the fiber parameters of the central output fiber are 20 / 130 / 0.08; the output fiber type is 20 / 130 / 0.08, and it has an internal stripper to strip the cladding light.