Single polarization laser and its preparation device and preparation method

Abstract

The present invention relates to a single polarization laser and a preparation device and method thereof. The preparation device of the single polarization laser comprises a second pump source, a second wavelength division multiplexer connected to the second pump source, an isolator connected to the second wavelength division multiplexer, a coupler connected to the isolator, a spectrum analyzer and a photodetector connected to the coupler, a spectrum analyzer connected to the photodetector, and a polishing mechanism. The preparation device of the single polarization laser polishes the side of a phase-shifted fiber Bragg grating through the polishing mechanism, observes the changes of the laser spectrum displayed on the spectrum analyzer and the laser beat frequency signal recorded by the spectrum analyzer, controls the thickness of the phase-shifted fiber Bragg grating, and enables the phase-shifted fiber Bragg grating to realize single polarization laser output. The single polarization laser has a simple manufacturing process, high production efficiency, and low production cost, and can realize large-scale production.

Description

Technical Field

[0001] The present invention relates to the field of laser technology, in particular to a single polarization laser and a preparation device and method thereof. Background Art

[0002] Compared to traditional semiconductor lasers, fiber lasers offer advantages such as excellent fiber coupling, narrow linewidth, wavelength selectivity, and high power. They are widely used in optical communications, sensing, spectroscopy, and other fields. Single-polarization fiber lasers, in particular, have high requirements for the polarization characteristics of the output laser in many fields, such as fiber gyroscopes, fiber sensing, nonlinear frequency conversion, and coherent beam combining. A single-polarization laser is one that outputs laser light in only one polarization state.

[0003] Traditional methods for producing single-polarization lasers include: doped polarization-maintaining fiber, polarization controller, and polarization-splitting reflective cavity. All of these methods suffer from complex structures and high production costs. Summary of the Invention

[0004] Based on this, it is necessary to provide a single polarization laser and a manufacturing device and method thereof.

[0005] A single polarization laser is characterized by comprising a first pump source, a first wavelength division multiplexer and a phase-shifted fiber Bragg grating connected in sequence.

[0006] The single polarization laser has a simple structure and is easy to use, and the wavelength of the emitted single polarization laser is stable.

[0007] In one embodiment, the phase-shifted fiber Bragg grating is a D-type active phase-shifted fiber Bragg grating.

[0008] A single-polarization laser manufacturing device, used for polishing a phase-shifted fiber Bragg grating; characterized in that the single-polarization laser manufacturing device includes a second pump source, a second wavelength division multiplexer connected to the second pump source, an isolator connected to the second wavelength division multiplexer, a coupler connected to the isolator, a spectrum analyzer and a photodetector connected to the coupler, a spectrum analyzer connected to the photodetector, and a polishing mechanism; the second wavelength division multiplexer is also used to connect to the phase-shifted fiber Bragg grating.

[0009] The above-mentioned single-polarization laser preparation device has a simple structure. By polishing the side of the phase-shifted fiber Bragg grating, observing the changes in the laser spectrum displayed on the spectrum analyzer and the laser beat frequency signal recorded by the spectrum analyzer, the thickness of the phase-shifted fiber Bragg grating is controlled, so that the phase-shifted fiber Bragg grating can achieve single-polarization laser output. The single-polarization laser production process is simple, the production efficiency is high, and the production cost is low, and large-scale production can be achieved.

[0010] In one embodiment, the second pump source is a 980 nm pump laser.

[0011] In one embodiment, the second wavelength division multiplexer is a three-port wavelength division multiplexer.

[0012] In one embodiment, the second wavelength division multiplexer is provided with an input end, a first output end and a second output end; the input end is connected to the second pump source, the first output end is used to connect to a phase-shifted fiber Bragg grating, and the second output end is connected to the isolator.

[0013] In one embodiment, the isolator is a polarization-dependent optical isolator.

[0014] In one embodiment, the coupler is a 3dB coupler.

[0015] In one embodiment, the spectrum analyzer is a real-time spectrum analyzer or a swept-tuned spectrum analyzer.

[0016] In one embodiment, the photodetector is a high-speed photodetector.

[0017] In one embodiment, the spectrum analyzer is one of a diffraction grating spectrometer, a prism spectrometer, an interference spectrometer and a micro spectrometer.

[0018] In one embodiment, the polishing mechanism includes two brackets, a displacement platform located between the two brackets, a rolling wheel mounted on the displacement platform, sandpaper wrapped around the rolling wheel, a drive assembly for driving the rolling wheel to rotate, and a control system electrically connecting the displacement platform and the drive assembly; the two ends of the phase-shifted fiber Bragg grating are respectively fixed to the two brackets via single-mode optical fibers, and one end of the phase-shifted fiber Bragg grating is connected to the second wavelength division multiplexer via a single-mode optical fiber.

[0019] In one embodiment, the displacement platform is an X, Y, and Z three-axis precision electric displacement platform.

[0020] In one embodiment, the rolling wheel is a steel roller with adjustable diameter.

[0021] In one embodiment, the bracket is further provided with an adjustable clamp, and the clamp is used to clamp and fix the single-mode optical fiber on the bracket.

[0022] In one embodiment, the clamp is a non-rotating clamp or a rotating clamp.

[0023] In one embodiment, the bracket is a square bracket or a triangular bracket.

[0024] In one embodiment, the polishing mechanism further includes a tension adjustment component located between the two brackets, for adjusting the tensile tension of the phase-shifted fiber Bragg grating.

[0025] In one embodiment, the tension adjustment assembly includes a positioning rod, a pulley arranged on the positioning rod, and a weight. The positioning rod is arranged near one of the brackets. The single-mode optical fiber at one end of the phase-shifted fiber Bragg grating is fixed to the bracket after passing through the winding pulley, and the weight is suspended on the single-mode optical fiber between the positioning rod and the bracket.

[0026] In one embodiment, the pulley is a steel pulley.

[0027] In one embodiment, the weight is a hook-type weight.

[0028] In one embodiment, the driving assembly includes a motor mounted on the displacement platform, a driving wheel connected to the motor, and a transmission belt sleeved on the driving wheel and the rolling wheel, and the motor is electrically connected to the control system.

[0029] In one embodiment, the driving wheel is a steel roller.

[0030] A method for preparing a single-polarization laser comprises the following steps:

[0031] a. Providing a single polarization laser preparation apparatus, comprising a second pump source, a second wavelength division multiplexer connected to the second pump source, an isolator connected to the second wavelength division multiplexer, a coupler connected to the isolator, a spectrum analyzer and a photodetector connected to the coupler, a spectrum analyzer connected to the photodetector, and a polishing mechanism;

[0032] b. The phase-shifted fiber Bragg grating is fixed to the polishing mechanism, and one end of the phase-shifted fiber Bragg grating is connected to the second wavelength division multiplexer;

[0033] c. The pump light generated by the second pump source is input to the phase-shifted fiber Bragg grating via the second wavelength division multiplexer, the phase-shifted fiber Bragg grating is lased to generate laser light, and the spectrum analyzer begins to record the spectrum of the laser light, and the spectrum analyzer begins to record the beat frequency signal of the laser light;

[0034] d. Start the polishing mechanism, the polishing mechanism polishes the side of the phase-shifted fiber Bragg grating;

[0035] e. As the thickness of the phase-shifted fiber Bragg grating changes, the laser spectrum displayed on the spectrum analyzer and the laser beat signal recorded by the spectrum analyzer also change continuously; until the beat signal displayed on the spectrum analyzer disappears and the spectrum analyzer still displays the laser spectrum, then the laser output by the phase-shifted fiber Bragg grating is a single-polarized laser, the polishing mechanism is turned off, and the polishing is completed.

[0036] The method for preparing a single-polarization laser of the present invention polishes the side of a phase-shifted fiber Bragg grating by a polishing mechanism, observes changes in the laser spectrum displayed on a spectrum analyzer and the laser beat frequency signal recorded by the spectrum analyzer, and controls the thickness of the phase-shifted fiber Bragg grating so that the phase-shifted fiber Bragg grating achieves single-polarization laser output. The single-polarization laser has a simple manufacturing process, high production efficiency, and low production cost, and can be produced on a large scale.

[0037] In one embodiment, the beat frequency signal on the spectrum analyzer satisfies the formula:

[0038]

[0039] B=|n x -n y |

[0040] f x and f y are the frequencies corresponding to two mutually perpendicular polarization states;

[0041] n x and n y are the refractive indices corresponding to two mutually perpendicular polarization states;

[0042] n0 is the average refractive index;

[0043] c is the speed of light;

[0044] λ is the central wavelength of the laser;

[0045] B is called birefringence;

[0046] The magnitude of the birefringence B can be determined by changes in the beat frequency signal on the spectrum analyzer. As the thickness of the phase-shifted fiber Bragg grating changes, the birefringence B continuously changes. When the beat frequency signal is displayed on the spectrum analyzer, it indicates that the laser light output by the phase-shifted fiber Bragg grating has two polarization states. When the beat frequency signal displayed on the spectrum analyzer disappears and the spectrum is still displayed on the spectrometer, it indicates that the laser light output by the phase-shifted fiber Bragg grating has only one polarization state, thereby achieving single-polarization laser output.

[0047] In one embodiment, the polished phase-shifted fiber Bragg grating is a phase-shifted fiber Bragg grating. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 Schematic diagram of the structure of a single polarization laser according to a preferred embodiment of the present invention;

[0049] Figure 2 A three-dimensional image of a phase-shifted fiber Bragg grating for a single-polarization laser;

[0050] Figure 3 Schematic diagram of the structure of a device for preparing a single-polarization laser according to a preferred embodiment of the present invention.

[0051] The meanings of the reference numerals in the accompanying drawings are:

[0052] A first pump source 101, a first wavelength division multiplexer 102, a laser output end 104, and a phase-shifted fiber Bragg grating 103;

[0053] Phase-shifted fiber Bragg grating 100;

[0054] A second pump source 10, a second wavelength division multiplexer 20, an input end 21, a first output end 22, a second output end 23, an isolator 30, a coupler 40, a spectrum analyzer 50, a photodetector 60, and a spectrum analyzer 70;

[0055] Polishing mechanism 80 , bracket 81 , tension adjustment assembly 82 , positioning rod 820 , pulley 821 , weight 822 , displacement platform 83 , rolling wheel 84 , motor 85 , driving wheel 86 , transmission belt 87 , single-mode optical fiber 88 . DETAILED DESCRIPTION

[0056] To facilitate understanding of the present invention, the present invention will be described more fully below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0057] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0058] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. Conversely, when an element is referred to as being "directly on" another element, there is no intermediate element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only.

[0059] Please refer to Figure 1 and Figure 2 , a single-polarization laser according to a preferred embodiment of the present invention, comprises a first pump source 101, a first wavelength division multiplexer 102, and a phase-shifted fiber Bragg grating 103, connected in sequence. The first pump source 101 provides pump energy for the phase-shifted fiber Bragg grating 103 to generate laser light. The first wavelength division multiplexer 102 is provided with a laser output terminal 104 for outputting the single-polarization fiber laser light emitted by the phase-shifted fiber Bragg grating 103. Specifically, the pump light emitted by the first pump source 101 passes through the first wavelength division multiplexer 102 and enters the phase-shifted fiber Bragg grating 103, where it is excited to generate single-polarization fiber laser light. The single-polarization fiber laser light returns to the first wavelength division multiplexer 102 and is then output to the outside world from the laser output terminal 104. In other embodiments, the single-polarization fiber laser light can also be output directly from the phase-shifted fiber Bragg grating 103 to the outside world. The phase-shifted fiber Bragg grating 103 is a D-type active phase-shifted fiber Bragg grating.

[0060] Please refer to Figure 3 This single-polarization laser manufacturing apparatus, a preferred embodiment of the present invention, is used to polish a phase-shifted fiber Bragg grating (FBG) 100. The phase of the phase-shifted fiber Bragg grating (FBG) 100 is π, and the phase-shifted fiber Bragg grating (FBG) 100 is manufactured using an active optical fiber through a blocked phase mask scanning method. The blocked phase mask scanning method involves side-scanning an ultraviolet excimer laser through a phase mask blocked by a block. The single-polarization laser manufacturing apparatus includes a second pump source 10, a second wavelength division multiplexer 20 connected to the second pump source 10, an isolator 30 connected to the second wavelength division multiplexer 20, a coupler 40 connected to the isolator 30, a spectrum analyzer 50 and a photodetector 60 connected to the coupler 40, a spectrum analyzer 70 connected to the photodetector 60, and a polishing mechanism 80. The second wavelength division multiplexer 20 is also used to connect to the phase-shifted fiber Bragg grating 100.

[0061] The second pump source 10 is a 980 nm pump laser, and is used to pump the phase-shifted fiber Bragg grating 100 .

[0062] The second wavelength division multiplexer 20 is a three-port wavelength division multiplexer. Specifically, the second wavelength division multiplexer 20 is provided with an input port 21, a first output port 22, and a second output port 23. The input port 21 is connected to the second pump source 10. In this embodiment, the input port 21 is a 980 nm port. The first output port 22 is used to connect to the phase-shifted fiber Bragg grating 100. That is, the pump light emitted by the second pump source 10 passes through the second wavelength division multiplexer 20 from the first output port 22 to the phase-shifted fiber Bragg grating 100, causing the phase-shifted fiber Bragg grating 100 to generate laser light. The laser light generated by the phase-shifted fiber Bragg grating 100 then returns to the second wavelength division multiplexer 20 through the first output port 22. The second output end 23 is connected to the isolator 30. The laser light generated by the phase-shifted fiber Bragg grating 100 returns from the first output end 22 to the second wavelength division multiplexer 20, and then is transmitted from the second output end 23 to the isolator 30. The laser light transmitted from the second output end 23 to the isolator 30 is unidirectional. In this embodiment, the second output end 23 is a 1550 nm port.

[0063] Laser light is transmitted through isolator 30 to coupler 40. Isolator 30 allows only unidirectional light to pass through, preventing reflected light in the optical path from interfering with the signal light. In this embodiment, isolator 30 is a polarization-dependent optical isolator. Coupler 40 is used to split and combine optical signals. After passing through coupler 40, the laser light is split into two paths: one path is transmitted to spectrum analyzer 50, and the other path is mixed in photodetector 60 to generate a beat frequency signal that is input to spectrum analyzer 70. In this embodiment, coupler 40 is a 3dB coupler.

[0064] Spectrum analyzer 50 is used to record and monitor the laser spectrum in real time. Spectrum analyzer 50 is a real-time spectrum analyzer or a scanning tuned spectrum analyzer. Photodetector 60 is a high-speed photodetector. Spectrum analyzer 70 is used to collect and record the laser beat signal in real time. Spectrum analyzer 70 is selected from the group consisting of a diffraction grating spectrometer, a prism spectrometer, an interferometer spectrometer, and a micro-spectrometer.

[0065] The polishing mechanism 80 includes two brackets 81, a tension adjustment assembly 82 and a displacement platform 83 located between the two brackets 81, a rolling wheel 84 installed on the displacement platform 83, sandpaper wrapped around the rolling wheel 84, a driving assembly that drives the rolling wheel 84 to rotate, and a control system 86 that electrically connects the displacement platform 83 and the driving assembly.

[0066] The bracket 81 is a square bracket or a triangular bracket. During polishing, the two ends of the phase-shifted fiber Bragg grating 100 are respectively fixed to the two brackets 81 via single-mode optical fibers 88. One end of the phase-shifted fiber Bragg grating 100 is connected to the second wavelength division multiplexer 20 via the single-mode optical fiber 88. Specifically, one end of the phase-shifted fiber Bragg grating 100 is connected to the first output end 22 via the single-mode optical fiber 88. The bracket 81 is also provided with an adjustable clamp for clamping and fixing the single-mode optical fiber 88 to the bracket 81. By adjusting the clamp, the fixing height of the single-mode optical fiber 88 on the bracket 81 can be adjusted. In this embodiment, the clamp is a non-rotating clamp or a rotating clamp.

[0067] The tension adjustment assembly 82 is used to adjust the tensile tension of the phase-shifted fiber Bragg grating 100. The tension adjustment assembly 82 includes a positioning rod 820, a pulley 821 mounted on the positioning rod 820, and a weight 822. In this embodiment, the pulley 821 is made of steel. The positioning rod 820 is positioned near one of the brackets 81. The single-mode optical fiber at one end of the phase-shifted fiber Bragg grating 100 is secured to the bracket 81 after being wound around the pulley 821. The weight 822 is suspended from the single-mode optical fiber 88 between the positioning rod 820 and the bracket 81. The weight of the weight 822 maintains a certain tension in the phase-shifted fiber Bragg grating 100. In this embodiment, the weight 822 is a hook-type weight, and the tensile tension of the phase-shifted fiber Bragg grating 100 can be adjusted by adjusting the mass of the weight 822.

[0068] The displacement platform 83 is a precision motorized displacement platform with three axes (X, Y, and Z). That is, the displacement platform 83 can drive the rolling wheel 84 to move in the X, Y, and Z directions. During polishing, the phase-shifted fiber Bragg grating 100 is positioned below the rolling wheel 84. The drive assembly rotates the rolling wheel 84, causing the sandpaper to polish the side of the phase-shifted fiber Bragg grating 100. In this embodiment, the rolling wheel 84 is a steel roller with an adjustable diameter. The drive assembly includes a motor 85 mounted on the displacement platform 83, a driving wheel 86 connected to the motor, and a transmission belt 87 that fits over the driving wheel 86 and the rolling wheel 84. The motor 85 is electrically connected to the control system. The motor 85 drives the driving wheel 86 to rotate, which in turn drives the rolling wheel 84 via the transmission belt 87, thereby polishing the phase-shifted fiber Bragg grating 100 with sandpaper. In this embodiment, the driving wheel 86 is a steel roller.

[0069] The preparation method of the single polarization laser is as follows:

[0070] a. A single-polarization laser preparation apparatus is provided, comprising a second pump source 10, a second wavelength division multiplexer 20 connected to the second pump source 10, an isolator 30 connected to the second wavelength division multiplexer 20, a coupler 40 connected to the isolator 30, a spectrum analyzer 50 and a photodetector 60 connected to the coupler 40, a spectrum analyzer 70 connected to the photodetector 60, and a polishing mechanism 80.

[0071] b. The phase-shifted fiber Bragg grating 100 is fixed on the polishing mechanism 80 , and one end of the phase-shifted fiber Bragg grating 100 is connected to the second wavelength division multiplexer 20 .

[0072] c. The pump light generated by the second pump source 10 is input to the phase-shifted fiber Bragg grating 100 via the second wavelength division multiplexer 20. The lasing phase-shifted fiber Bragg grating 100 generates laser light. The spectrum analyzer 50 begins to record the spectrum of the laser light, and the spectrum analyzer 70 begins to record the beat frequency signal of the laser light.

[0073] d. Start the polishing mechanism 80, the polishing mechanism 80 polishes the side of the phase-shifted fiber Bragg grating 100;

[0074] e. As the thickness of the phase-shifted fiber Bragg grating 100 changes, the laser spectrum displayed on the spectrum analyzer 50 and the laser beat signal recorded by the spectrum analyzer 70 also continuously change; until the beat signal displayed on the spectrum analyzer 70 disappears and the spectrum analyzer 50 still displays the laser spectrum, the laser output by the phase-shifted fiber Bragg grating 100 is now a single-polarization laser, and the polishing mechanism 80 is turned off, and polishing is completed.

[0075] When the second pump source 10 is pumping, the magnitude of the pump energy can be adjusted by observing the laser center wavelength displayed on the spectrum analyzer 50 .

[0076] According to the change of the beat frequency signal on the spectrum analyzer 70, the polarization state of the laser light can be determined, wherein the beat frequency signal on the spectrum analyzer 70 satisfies the formula:

[0077]

[0078] B=|n x -n y |

[0079] f x and f y are the frequencies corresponding to two mutually perpendicular polarization states;

[0080] n x and n y are the refractive indices corresponding to two mutually perpendicular polarization states;

[0081] n0 is the average refractive index;

[0082] c is the speed of light;

[0083] λ is the central wavelength of the laser;

[0084] B is called birefringence.

[0085] The magnitude of birefringence B can be determined by changes in the beat signal on spectrum analyzer 70. Birefringence B continuously changes with the thickness of phase-shifted fiber Bragg grating 100. When a beat signal is displayed on spectrum analyzer 70, it indicates that the laser light output by phase-shifted fiber Bragg grating 100 has two polarization states. When the beat signal displayed on spectrum analyzer 70 disappears, but the spectrum is still displayed on the spectrometer, it indicates that the laser light output by phase-shifted fiber Bragg grating 100 has only one polarization state, thus achieving single-polarization laser output. The polished phase-shifted fiber Bragg grating 100 is a phase-shifted fiber Bragg grating, which, when combined with a wavelength division multiplexer and a pump source, forms a single-polarization laser.

[0086] The single polarization laser of the present invention has a simple structure and is easy to use, and the wavelength of the emitted single polarization laser is stable.

[0087] The single-polarization laser preparation device of the present invention has a simple structure. The side of the phase-shifted fiber Bragg grating is polished by a polishing mechanism, and the changes in the laser spectrum displayed on the spectrum analyzer and the laser beat frequency signal recorded by the spectrum analyzer are observed. The thickness of the phase-shifted fiber Bragg grating is controlled so that the phase-shifted fiber Bragg grating can achieve single-polarization laser output. The single-polarization laser production process is simple, the production efficiency is high, and the production cost is low, and large-scale production can be achieved.

[0088] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0089] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A preparation device for a single polarization laser, used for polishing a phase-shifted fiber Bragg grating of a single polarization laser, wherein the single polarization laser comprises a first pump source, a first wavelength division multiplexer and the phase-shifted fiber Bragg grating connected in sequence; characterized in that: The preparation device of the single polarization laser comprises a second pump source, a second wavelength division multiplexer connected to the second pump source, an isolator connected to the second wavelength division multiplexer, a coupler connected to the isolator, a spectrum analyzer and a photodetector connected to the coupler, a spectrum analyzer connected to the photodetector, and a polishing mechanism. The second wavelength division multiplexer is also used to connect the phase-shifted fiber Bragg grating.

2. The device for preparing a single polarization laser according to claim 1, characterized in that: The second pump source is a 980nm pump laser.

3. The device for preparing a single polarization laser according to claim 1, characterized in that: The second wavelength division multiplexer is a three-port wavelength division multiplexer.

4. The device for preparing a single polarization laser according to claim 3, characterized in that: The second wavelength division multiplexer is provided with an input end, a first output end and a second output end; the input end is connected to the second pump source, the first output end is used to connect a phase-shifted fiber Bragg grating, and the second output end is connected to the isolator.

5. The device for preparing a single polarization laser according to claim 1, characterized in that: The isolator is a polarization-dependent optical isolator.

6. The device for preparing a single polarization laser according to claim 1, characterized in that: The coupler is a 3dB coupler.

7. The device for preparing a single polarization laser according to claim 1, characterized in that: The spectrum analyzer is a real-time spectrum analyzer or a swept-tuned spectrum analyzer.

8. The device for preparing a single polarization laser according to claim 1, characterized in that: The photodetector is a high-speed photodetector.

9. The device for preparing a single polarization laser according to claim 1, characterized in that: The spectrum analyzer is one of a diffraction grating spectrometer, a prism spectrometer, an interference spectrometer and a micro spectrometer.

10. The device for preparing a single polarization laser according to claim 1, characterized in that: The polishing mechanism includes two brackets, a displacement platform located between the two brackets, a rolling wheel installed on the displacement platform, sandpaper wrapped around the rolling wheel, a driving component driving the rolling wheel to rotate, and a control system electrically connecting the displacement platform and the driving component; two ends of the phase-shifted fiber Bragg grating are respectively fixed to the two brackets through single-mode optical fibers, and one end of the phase-shifted fiber Bragg grating is connected to the second wavelength division multiplexer through a single-mode optical fiber.

11. The device for preparing a single polarization laser according to claim 10, characterized in that: The displacement platform is an X, Y, and Z three-axis precision electric displacement platform.

12. The device for preparing a single polarization laser according to claim 10, characterized in that: The rolling wheel is a steel rolling wheel with adjustable diameter.

13. The device for preparing a single polarization laser according to claim 10, characterized in that: The bracket is also provided with an adjustable clamp, which is used to clamp and fix the single-mode optical fiber on the bracket.

14. The device for preparing a single polarization laser according to claim 13, characterized in that: The clamp is a non-rotating clamp or a rotating clamp.

15. The device for preparing a single polarization laser according to claim 13, characterized in that: The bracket is a square bracket or a tripod bracket.

16. The device for preparing a single polarization laser according to claim 12, characterized in that: The polishing mechanism further comprises a tension adjustment component located between the two brackets, for adjusting the tensile tension of the phase-shifted fiber Bragg grating.

17. The device for preparing a single polarization laser according to claim 16, characterized in that: The tension adjustment assembly includes a positioning rod, a pulley arranged on the positioning rod, and a weight. The positioning rod is arranged close to one of the brackets. The single-mode optical fiber at one end of the phase-shifted fiber Bragg grating is fixed to the bracket after being wound around the pulley, and the weight is suspended on the single-mode optical fiber between the positioning rod and the bracket.

18. The device for preparing a single polarization laser according to claim 17, characterized in that: The pulley is a steel pulley.

19. The device for preparing a single polarization laser according to claim 17, characterized in that: The weight is a hook-type weight.

20. The device for preparing a single polarization laser according to claim 10, characterized in that: The driving assembly comprises a motor mounted on the displacement platform, a driving wheel connected to the motor, and a transmission belt sleeved on the driving wheel and the rolling wheel. The motor is electrically connected to the control system.

21. The device for preparing a single polarization laser according to claim 20, characterized in that: The driving wheel is a steel roller.

22. The device for preparing a single polarization laser according to claim 21, characterized in that: The phase-shifted fiber Bragg grating is a D-type active phase-shifted fiber Bragg grating.

23. A method for preparing a single polarization laser, characterized in that: The following steps are involved: a. Providing a single polarization laser preparation device, comprising a second pump source, a second wavelength division multiplexer connected to the second pump source, an isolator connected to the second wavelength division multiplexer, a coupler connected to the isolator, a spectrum analyzer and a photodetector connected to the coupler, a spectrum analyzer connected to the photodetector, and a polishing mechanism; b. A phase-shifted fiber Bragg grating is fixed on the polishing mechanism, and one end of the phase-shifted fiber Bragg grating is connected to the second wavelength division multiplexer; c. The pump light generated by the second pump source is input to the phase-shifted fiber Bragg grating through the second wavelength division multiplexer, the phase-shifted fiber Bragg grating is lased to generate laser, and the spectrum analyzer starts to record the spectrum of the laser, and the spectrum analyzer starts to record the beat frequency signal of the laser; d. Starting the polishing mechanism, the polishing mechanism polishes the side of the phase-shifted fiber Bragg grating; e. As the thickness of the phase-shifted fiber Bragg grating changes, the laser spectrum displayed on the spectrum analyzer and the laser beat frequency signal recorded by the spectrum analyzer are also constantly changing; until the beat frequency signal displayed on the spectrum analyzer disappears, and the spectrum analyzer still displays the laser spectrum, then the laser output by the phase-shifted fiber Bragg grating is a single-polarized laser, the polishing mechanism is turned off, and the polishing is completed.

24. The method for preparing a single polarization laser according to claim 23, characterized in that: The beat frequency signal on the spectrum analyzer satisfies the formula: and are the frequencies corresponding to two mutually perpendicular polarization states; and are the refractive indices corresponding to two mutually perpendicular polarization states; is the average refractive index; c is the speed of light; is the laser center wavelength; B is called birefringence; The size of the birefringence B can be determined by the change of the beat frequency signal on the spectrum analyzer. As the thickness of the phase-shifted fiber Bragg grating changes, the birefringence B changes continuously. When the beat frequency signal is displayed on the spectrum analyzer, it means that the laser output by the phase-shifted fiber Bragg grating has two polarization states. When the beat frequency signal displayed on the spectrum analyzer disappears, and the spectrum is still displayed on the spectrum analyzer, it means that the laser output by the phase-shifted fiber Bragg grating has only one polarization state, thereby realizing single-polarization laser output.

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