An all-fiber polarization-maintaining vortex optical amplification system

Abstract

The present invention provides an all-fiber polarization-maintaining vortex light amplification system, including a polarization-maintaining seed laser output system, a polarization-maintaining mode conversion device, a fiber polarization controller, a mode matcher, a pump signal combiner, a laser diode light source group, a few-mode polarization-maintaining ytterbium-doped fiber, a cladding mode filter, and a water-cooling plate. The present invention realizes high-power and high-stability vortex light beam output with an all-fiber structure, controls the laser mode field of the incident laser through the fiber polarization controller, and makes the eigenvector mode superposition generate a vortex light field; at the same time, the present invention adopts a few-mode polarization-maintaining ytterbium-doped fiber to output the amplified high-power vortex light field, and the few-mode polarization-maintaining ytterbium-doped fiber can reduce the crosstalk between modes, solve the degradation problem of polarization purity and mode purity in the power amplification process, and thus realize high-power vortex light field output.

Description

Technical Field

[0001] The invention relates to the technical field of optical fiber lasers, and in particular to an all-fiber polarization-maintaining vortex light amplification system. Background Art

[0002] The vortex beam has a spiral phase wavefront with a phase singularity in the middle. Its light field is distributed in a circular hollow. At the same time, each photon carries orbital angular momentum. The phase increases by 2π every time the beam moves forward for one cycle. l ,in l is the topological charge number, which can be any integer in theory. Due to its special phase and intensity distribution, it can carry infinite-dimensional spiral topological charge information and keep the central light intensity at zero at all times. Vortex beams are widely used in large-capacity optical communications, frequency shifting, optical manipulation and other fields.

[0003] At present, there are two main ways to generate vortex light fields. One is to generate them using spatial structures, such as metasurfaces, spatial light modulators, spiral phase plates, etc. There are many types of vortex light fields that can be generated in free space, but spatial structures are not conducive to integration, and the power level is relatively limited. The other is to generate them directly in optical fibers, which can use long-period fiber gratings, photon lanterns, acoustic fiber gratings, etc. to directly achieve all-fiber vortex light field output, but due to its manufacturing process, the fiber mode conversion device has limited power tolerance. In order to achieve higher power vortex light field output, the high-purity seed vortex light field needs to be further amplified.

[0004] Optical fiber has waveguide mode stability and can generate and transmit vortex beams. Fiber lasers have the advantages of compact structure, convenient thermal management, and high efficiency. All-fiber systems are conducive to achieving high-power and high-stability vortex beam output. Vortex light fields can be generated by the superposition of intrinsic vector modes in optical fibers, and the polarization state of optical fibers has a great influence on the purity of vortex light fields. Therefore, a solution is urgently needed to solve the problem of degradation of polarization purity and mode purity during power amplification. Summary of the invention

[0005] In view of the defects in the prior art, the present invention provides an all-fiber polarization-maintaining vortex light amplification system.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] The present invention provides an all-fiber polarization-maintaining vortex optical amplification system, comprising a polarization-maintaining seed laser output system, a polarization-maintaining mode conversion device, a fiber polarization controller, a mode matcher, a pump signal combiner, a laser diode light source group, a few-mode polarization-maintaining ytterbium-doped optical fiber, a cladding mode filter, and a water cooling plate;

[0008] The input end of the polarization-maintaining mode conversion device is connected to the output end of the polarization-maintaining seed laser output system, and is used to convert the single-mode polarization-maintaining laser into a high-mode order polarization-maintaining laser;

[0009] The input end of the optical fiber polarization controller is connected to the output end of the polarization-maintaining mode conversion device, and is used to control the laser mode field vibration state of the output laser of the polarization-maintaining mode conversion device, and adjust the optical fiber polarization controller according to the output light spot to make different vector modes produce phase difference, thereby superimposing and generating a vortex beam with a phase singularity;

[0010] The input end of the mode matcher is connected to the output end of the optical fiber polarization controller, and is used to reduce the mode field mismatch when the output laser of the optical fiber polarization controller enters the pump signal combiner, so as to ensure that the mode of the high-order mode seed laser does not degenerate when entering the pump signal combiner;

[0011] The input end of the pump signal combiner is connected to the output end of the mode matcher, and the input end of the pump signal combiner is also connected to a laser diode light source group, and the laser diode light source group provides a pump source for the all-fiber polarization-maintaining vortex light amplification system;

[0012] The input end of the few-mode polarization-maintaining ytterbium-doped optical fiber is connected to the output end of the pump signal combiner to provide gain for the all-fiber polarization-maintaining vortex optical amplification system; the fiber winding diameter of the few-mode polarization-maintaining ytterbium-doped optical fiber is greater than 30 cm to avoid high-order mode field power loss and mode degradation caused by excessive bending;

[0013] The water cooling plate is used to place the few-mode polarization-maintaining ytterbium-doped optical fiber to dissipate the heat generated during the laser amplification process;

[0014] The input end of the cladding mode filter is connected to the output end of the few-mode polarization-maintaining ytterbium-doped optical fiber to achieve cladding light filtering;

[0015] After the cladding light is filtered out, the laser is output through the output end of the cladding mode filter.

[0016] Furthermore, the polarization-maintaining seed laser output system is a combination of a polarization-maintaining single-mode seed laser or a non-polarization-maintaining single-mode seed laser and a polarization-maintaining laser conversion device.

[0017] Furthermore, the non-polarization-maintaining single-mode seed laser is a light source that stably outputs single-mode laser light, including but not limited to a laser oscillator, a laser amplifier, a random Raman fiber laser, and an amplified spontaneous emission light source.

[0018] Furthermore, the polarization-maintaining laser conversion device is used to convert the non-polarization-maintaining single-mode seed laser into a polarization-maintaining laser, and includes a fiber polarizer and a polarization beam splitter.

[0019] Furthermore, the laser output from the cladding filter is output through an output end cap, and the output end cap is coated with an output wavelength anti-reflection film to avoid the generation of back-propagating return light.

[0020] Furthermore, the polarization-maintaining mode conversion device includes but is not limited to a polarization-maintaining long-period fiber grating and a polarization-maintaining acoustic fiber grating.

[0021] Furthermore, the optical fiber polarization controller includes a three-ring polarization controller, a squeeze polarization controller, and an electric polarization controller.

[0022] Furthermore, the laser diode light source group is a pump light source with an output wavelength of 915nm or 976nm.

[0023] Furthermore, the few-mode polarization-maintaining ytterbium-doped optical fiber includes but is not limited to ytterbium-doped optical fiber with a core diameter of 15 / 130 and an NA of 0.08, ytterbium-doped optical fiber with a core diameter of 20 / 130 and an NA of 0.08, ytterbium-doped optical fiber with a core diameter of 25 / 250 and an NA of 0.065, and ytterbium-doped optical fiber with a core diameter of 20 / 400 and an NA of 0.065.

[0024] Furthermore, it also includes a polarization-maintaining single-mode amplifier for increasing the output optical power of the polarization-maintaining seed laser output system.

[0025] Compared with the prior art, the technical effects that the present invention can produce are:

[0026] The present invention realizes high-power and high-stability vortex light beam output with an all-fiber structure, and controls the laser mode field of the incident laser through a fiber polarization controller, so that the eigenvector mode is superimposed to generate a vortex light field; at the same time, the present invention adopts a few-mode polarization-maintaining ytterbium-doped fiber to output the amplified high-power vortex light field. The few-mode polarization-maintaining ytterbium-doped fiber can reduce the crosstalk between modes, solve the degradation problem of polarization purity and mode purity in the power amplification process, and thus realize high-power vortex light field output.

[0027] Since the temperature rise will aggravate the mode coupling in the optical fiber, resulting in the reduction of mode purity, the thermally induced mode instability may occur at higher temperatures, causing the mode to change continuously. Therefore, the present invention places the few-mode polarization-maintaining ytterbium-doped optical fiber on a water-cooled plate to dissipate the heat generated during the laser amplification process, thereby ensuring the normal operation of the few-mode polarization-maintaining ytterbium-doped optical fiber and reducing the influence of the thermal effect on the few-mode polarization-maintaining ytterbium-doped optical fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0029] Figure 1 This is a schematic diagram of an all-fiber polarization-maintaining vortex light amplification system;

[0030] Figure 2 A schematic diagram of an all-fiber polarization-maintaining vortex light amplification system provided in Example 1;

[0031] Figure 3 A schematic diagram of an all-fiber polarization-maintaining vortex light amplification system provided in Example 2;

[0032] Figure 4 A schematic diagram of an all-fiber polarization-maintaining vortex light amplification system provided in Example 3;

[0033] Figure 5 A diagram showing the simultaneous detection results of the output end pump power, the output signal light power, and the vortex beam focusing spot after the seed vortex laser with a topological charge of +1 provided in Example 1 is amplified, wherein ①, ②, and ③ are the vortex beam focusing spots corresponding to low pump power, medium pump power, and maximum pump power, respectively;

[0034] Figure 6 A diagram showing the simultaneous detection results of the output end pump power, the output signal light power, and the vortex beam focusing spot after the seed vortex laser with a topological charge of -1 provided in Example 1 is amplified, wherein ①, ②, and ③ are the vortex beam focusing spots corresponding to low pump power, medium pump power, and maximum pump power, respectively;

[0035] Figure 7 A diagram showing the detection results of the input end pump power and the output signal optical power after the seed vortex laser amplification with a topological charge of +1 provided in Example 2;

[0036] Figure 8 A diagram showing the detection results of the input end pump power and the output signal optical power after the seed vortex laser amplification with a topological charge of +1 provided in Example 4;

[0037] Fig. 9 The optical spectra corresponding to the output powers of 1 W, 7 W, 22 W, 36 W and 51 W provided in one embodiment, and the focusing spot diagrams of the vortex beams with the topological charges of +1 and -1;

[0038] Fig.10 A schematic diagram of the decomposition of a 50W vortex light mode with a topological charge of +1 and -1 is provided in an embodiment, wherein Fig.10 (a) is the focusing spot diagram of the vortex beam before amplification with a topological charge of +1. Fig.10 (b) is the focusing spot diagram of the amplified vortex beam with a topological charge of +1. Fig.10 (c) is the proportion of each mode of the amplified vortex beam with a topological charge of +1. Fig.10 (d) is the focusing spot diagram of the vortex beam before amplification with a topological charge of -1. Fig.10 (e) is the focusing spot diagram of the amplified vortex beam with a topological charge of -1. Fig.10 (f) is a diagram showing the proportion of each mode in the amplified vortex beam with a topological charge of -1.

[0039] Figure annotation:

[0040] 1. Polarization-maintaining seed laser output system; 11. Non-polarization-maintaining single-mode seed laser; 12. Polarization-maintaining laser conversion device; 2. Polarization-maintaining mode conversion device; 3. Fiber polarization controller; 4. Mode matcher; 5. Pump signal combiner; 51. Forward Pump signal combiner; 52, backward Pump signal combiner; 6. Laser diode light source group; 61. First laser diode light source group; 62. Second laser diode light source group; 7. Few-mode polarization-maintaining ytterbium-doped optical fiber; 8. Cladding mode filter; 9. Output end cap; 10. Polarization-maintaining single-mode amplifier. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] Reference Figure 1 The present invention provides an all-fiber polarization-maintaining vortex optical amplification system, comprising a polarization-maintaining seed laser output system 1, a polarization-maintaining mode conversion device 2, a fiber polarization controller 3, a mode matcher 4, a pump signal combiner 5, a laser diode light source group 6, a few-mode polarization-maintaining ytterbium-doped fiber 7, a cladding mode filter 8, an output end cap 9, and a water-cooled plate;

[0043] The input end of the polarization-maintaining mode conversion device 2 is connected to the output end of the polarization-maintaining seed laser output system 1, and is used to convert the single-mode polarization-maintaining laser into a high-order mode polarization-maintaining laser;

[0044] The input end of the optical fiber polarization controller 3 is connected to the output end of the polarization-maintaining mode conversion device 2, and is used to control the laser mode field vibration state of the output laser of the polarization-maintaining mode conversion device 2, and adjust the optical fiber polarization controller according to the output light spot, so that different vector modes produce phase differences, and then superimpose to generate a vortex beam with a phase singularity;

[0045] The input end of the mode matcher 4 is connected to the output end of the optical fiber polarization controller 3, and is used to reduce the mode field mismatch when the output laser of the optical fiber polarization controller 3 enters the pump signal combiner 5, and ensure that the mode of the high-order mode seed laser does not degenerate when entering the pump signal combiner;

[0046] The input end of the pump signal combiner 5 is connected to the output end of the mode matcher 4, and the input end of the pump signal combiner 5 is also connected to a laser diode light source group 6, and the laser diode light source group 6 provides a pump source for the all-fiber polarization-maintaining vortex light amplification system;

[0047] The input end of the few-mode polarization-maintaining ytterbium-doped optical fiber 7 is connected to the output end of the pump signal combiner 5 to provide gain for the all-fiber polarization-maintaining vortex optical amplification system; the fiber winding diameter of the few-mode polarization-maintaining ytterbium-doped optical fiber 7 is greater than 30 cm to avoid high-order mode field power loss and mode degradation caused by excessive bending;

[0048] The water cooling plate is used to place the few-mode polarization-maintaining ytterbium-doped optical fiber 7 to dissipate the heat generated during the laser amplification process;

[0049] The input end of the cladding mode filter 8 is connected to the output end of the few-mode polarization-maintaining ytterbium-doped optical fiber 7 to achieve cladding light filtering;

[0050] After the cladding light is filtered out, the laser is output through the output end of the cladding mode filter 8.

[0051] The polarization-maintaining seed laser output system 1 is a combination of a polarization-maintaining single-mode seed laser or a non-polarization-maintaining single-mode seed laser 11 and a polarization-maintaining laser conversion device 12 .

[0052] The polarization-maintaining seed laser can be connected to a polarization-maintaining isolator or a circulator to protect the seed laser and prevent the backward return light generated in the subsequent amplification process from damaging the seed laser.

[0053] The non-polarization-maintaining single-mode seed laser 11 is a light source that stably outputs single-mode laser light, including but not limited to a laser oscillator, a laser amplifier, a random Raman fiber laser, and an amplified spontaneous emission light source.

[0054] The polarization-maintaining laser conversion device 12 is used to convert the non-polarization-maintaining single-mode seed laser into a polarization-maintaining laser, and includes a fiber polarizer and a polarization beam splitter.

[0055] An isolator or a circulator is further arranged between the non-polarization-maintaining single-mode seed laser 11 and the polarization-maintaining laser conversion device 12 to protect the seed light source.

[0056] The laser outputted by the cladding filter 8 is outputted through the output end cap 9, and the output end cap 9 is plated with an output wavelength anti-reflection film to avoid the generation of backward return light.

[0057] The polarization-maintaining mode conversion device 2 includes but is not limited to a polarization-maintaining long-period fiber grating and a polarization-maintaining acoustic fiber grating, which can convert a single-mode polarization-maintaining laser into an LP laser. 11 LP 21 Mode and other high-order mode polarization-maintaining lasers.

[0058] The input optical fiber of the mode matcher 4 is the same polarization-maintaining optical fiber as the polarization-maintaining mode conversion device 2 and the optical fiber polarization controller 3 , and the output optical fiber of the mode matcher 4 is the same as the input optical fiber of the pump signal combiner 5 .

[0059] The optical fiber polarization controller 3 includes a three-ring polarization controller, a squeeze polarization controller, and an electric polarization controller.

[0060] The laser diode light source group 6 is a pump light source with an output wavelength of 915 nm or 976 nm.

[0061] The few-mode polarization-maintaining ytterbium-doped optical fiber 7 includes an ytterbium-doped optical fiber with a core diameter of 15 / 130 and an NA of 0.08, an ytterbium-doped optical fiber with a core diameter of 20 / 130 and an NA of 0.08, an ytterbium-doped optical fiber with a core diameter of 25 / 250 and an NA of 0.065, and an ytterbium-doped optical fiber with a core diameter of 20 / 400 and an NA of 0.065. The ytterbium-doped optical fiber with a core diameter of 15 / 130 and an NA of 0.08 has a V value of about 3.54 at a wavelength of 1064nm, and can transmit the fundamental mode and LP 11 mode, and a vortex light field with a topological charge of ±1; the Yb-doped fiber with a core diameter of 20 / 130 and an NA of 0.08 has a V value of about 4.72 at a wavelength of 1064nm, which can transmit the fundamental mode and LP 11 LP 21 mode, and vortex light fields with topological charges of ±1 and ±2; the Yb-doped fiber with a core diameter of 25 / 250 and NA of 0.065 has a V value of about 4.80 at a wavelength of 1064nm, which can transmit the fundamental mode and LP 02 LP 11 LP 21 mode, and vortex light fields with topological charges of ±1 and ±2; the Yb-doped fiber with a core diameter of 20 / 400 and NA of 0.065 has a V value of about 3.84 at a wavelength of 1064nm, which can transmit the fundamental mode and LP 11 LP 21 modes, and vortex light fields with topological charges of ±1 and ±2.

[0062] The number of modes supported by the few-mode polarization-maintaining ytterbium-doped optical fiber 7 for transmission and amplification is related to the numerical aperture NA in the core diameter, the core radius a and the laser wavelength λ, and the number of modes supported by the optical fiber. V is the normalized frequency, and the V value is calculated according to the following formula:

[0063] ;

[0064] The number of vector modes supported by ytterbium-doped fiber is about V 2 / 2, where the V value needs to be between 2.405 and 5.7 to ensure that the ytterbium-doped fiber has a few-mode output. At the same time, the larger the core diameter of the ytterbium-doped fiber, the stronger the power carrying capacity of the ytterbium-doped fiber.

[0065] Embodiment 1:

[0066] Reference Figure 2 Embodiment 1 provides an all-fiber polarization-maintaining vortex optical amplification system, including a non-polarization-maintaining single-mode seed laser 11, a polarization-maintaining laser conversion device 12, a polarization-maintaining mode conversion device 2, a fiber polarization controller 3, a mode matcher 4, a pump signal combiner 5, a laser diode light source group 6, a few-mode polarization-maintaining ytterbium-doped fiber 7, a cladding mode filter 8, an output end cap 9, and a water-cooled plate;

[0067] The non-polarization-maintaining single-mode seed laser 11 is a light source for stably outputting single-mode laser light, and the output power is 3 watts. The polarization-maintaining laser conversion device 12 is a fiber polarizer, and the power loss after passing through the fiber polarizer 12 is normal. The pump signal combiner 5 is Pump signal combiner, few-mode polarization-maintaining ytterbium-doped fiber 7 is a ytterbium-doped fiber with a core diameter of 15 / 130 and NA of 0.08. Its V value at a wavelength of 1064nm is about 3.54, which can transmit fundamental mode and LP 11 mode, and a vortex light field with a topological charge of ±1; the few-mode polarization-maintaining ytterbium-doped optical fiber 7 is placed on a water-cooled plate.

[0068] Reference Figure 5 , Figure 5 The results of simultaneous detection of the output end pump power, output signal light power, and vortex beam focusing spot of the seed vortex laser with a topological charge of +1 after amplification provided in Example 1, wherein ①, ②, and ③ are the vortex beam focusing spots corresponding to low pump power, medium pump power, and maximum pump power, respectively; Figure 6 , Figure 6 The results of simultaneous detection of the output end pump power, output signal light power, and vortex beam focus spot of the seed vortex laser with a topological charge of -1 after amplification provided in Example 1, where ①, ②, and ③ are the vortex beam focus spots corresponding to low pump power, medium pump power, and highest pump power, respectively. Figure 4 , Figure 5It can be seen that the present invention amplifies low-power vortex seed light to the order of tens of watts.

[0069] Embodiment 2:

[0070] Reference Figure 3 Embodiment 2 provides an all-fiber polarization-maintaining vortex optical amplification system, comprising a polarization-maintaining seed laser output system 1, a polarization-maintaining mode conversion device 2, a fiber polarization controller 3, a mode matcher 4, a pump signal combiner 5, a laser diode light source group 6, a few-mode polarization-maintaining ytterbium-doped fiber 7, a cladding mode filter 8, an output end cap 9, a polarization-maintaining single-mode amplifier 10, and a water-cooled plate;

[0071] The polarization-maintaining seed laser output system 1 is a polarization-maintaining single-mode seed laser, and the pump signal combiner 5 is Pump signal combiner 51; the few-mode polarization-maintaining ytterbium-doped fiber 7 is a ytterbium-doped fiber with a core diameter of 20 / 400 and an NA of 0.065, and its V value at a wavelength of 1064nm is about 3.84, which can transmit LP 11 LP 21 modes, and vortex light fields with topological charges of ±1 and ±2.

[0072] The input end of the polarization-maintaining single-mode amplifier 10 is connected to the output end of the polarization-maintaining seed laser output system 1. The polarization-maintaining single-mode amplifier 10 is used to increase the output optical power of the polarization-maintaining seed laser output system 1, so that the output power of the seed light is increased to 10-50 watts; the input end of the polarization-maintaining mode conversion device 2 is connected to the output end of the polarization-maintaining single-mode amplifier 10, the input end of the optical fiber polarization controller 3 is connected to the output end of the polarization-maintaining mode conversion device 2, and the input end of the mode matcher 4 is connected to the output end of the optical fiber polarization controller 3; the forward The input end of the pump signal combiner 51 is connected to the output end of the mode matcher 4, and the forward The input end of the pump signal combiner 51 is also connected to the laser diode light source group 6; the input end of the few-mode polarization-maintaining ytterbium-doped optical fiber 7 is connected to the forward The output end of the pump signal combiner 51 is connected, the input end of the cladding filter 8 is connected to the output end of the few-mode polarization-maintaining ytterbium-doped fiber 7, the output end of the cladding filter 8 is connected to the output end cap 9, and the few-mode polarization-maintaining ytterbium-doped fiber 7 is placed on a water-cooled plate.

[0073] Reference Figure 7 , Figure 7 This is a diagram showing the detection results of the output end pump power and output signal optical power after the seed vortex laser amplification with a topological charge of +1 provided in Example 2. Under the condition of single laser diode pump injection, the maximum output power is 550 watts.

[0074] Embodiment 3:

[0075] Reference Figure 4Embodiment 3 provides an all-fiber polarization-maintaining vortex optical amplification system, including a polarization-maintaining seed laser output system 1, a polarization-maintaining mode conversion device 2, a fiber polarization controller 3, a mode matcher 4, a pump signal combiner 5, a laser diode light source group 6, a few-mode polarization-maintaining ytterbium-doped fiber 7, a cladding mode filter 8, an output end cap 9, a polarization-maintaining single-mode amplifier 10, and a water-cooled plate;

[0076] The polarization-maintaining seed laser output system 1 is a polarization-maintaining single-mode seed laser, and the pump signal combiner 5 includes a forward Pump signal combiner 51 and backward Pump signal combiner 52; laser diode light source group 6 includes a first laser diode light source group 61 and a second laser diode light source group 62; the few-mode polarization-maintaining ytterbium-doped fiber 7 is a ytterbium-doped fiber with a core diameter of 20 / 400 and an NA of 0.065, and its V value at a wavelength of 1064nm is about 3.84, which can transmit LP 11 LP 21 modes, and vortex light fields with topological charges of ±1 and ±2.

[0077] The input end of the polarization-maintaining single-mode amplifier 10 is connected to the output end of the polarization-maintaining seed laser output system 1. The polarization-maintaining single-mode amplifier 10 is used to increase the output optical power of the polarization-maintaining seed laser output system 1, so that the output power of the seed light is increased to 10-50 watts; the input end of the polarization-maintaining mode conversion device 2 is connected to the output end of the polarization-maintaining single-mode amplifier 10, the input end of the optical fiber polarization controller 3 is connected to the output end of the polarization-maintaining mode conversion device 2, and the input end of the mode matcher 4 is connected to the output end of the optical fiber polarization controller 3; the forward The input end of the pump signal combiner 51 is connected to the output end of the mode matcher 4, and the forward The input end of the pump signal combiner 51 is also connected to the first laser diode light source group 61; the input end of the few-mode polarization-maintaining ytterbium-doped optical fiber 7 is connected to the forward The output end of the pump signal combiner 51 is connected to the The input end of the pump signal combiner 52 is connected to the output end of the few-mode polarization-maintaining ytterbium-doped fiber 7, and the reverse The input end of the pump signal combiner 52 is also connected to the second laser diode light source group 62; the input end of the cladding filter 8 is connected to the rear The output ends of the pump signal combiner 52 are connected, the output end of the cladding filter 8 is connected to the output end cap 9, and the few-mode polarization-maintaining ytterbium-doped optical fiber 7 is placed on a water-cooled plate.

[0078] Embodiment 4:

[0079] On the basis of Example 3, the number of pump laser diodes is further increased to improve the pump power. The fiber winding diameter of the few-mode polarization-maintaining ytterbium-doped fiber is 90 cm, and the temperature of the water cooling plate is controlled at 20° C. Figure 8 , Figure 8 The output end pump power and output signal optical power detection result diagram of the seed vortex laser with a topological charge of +1 after amplification provided in Example 4, from Figure 8 It can be seen from the figure that when the pump power is 1242W, the output power is 899W. It can be seen from the figure that the output power does not have an obvious power hysteresis effect, which shows that the present invention can achieve high-power vortex light field output with stable mode and high purity.

[0080] By further increasing the number of pump laser diodes and improving the pump power, the vortex seed light can be amplified to the kilowatt level.

[0081] In one embodiment, referring to Fig. 9 As can be seen from the figure, when the output power is 1W, 7W, 22W, 36W, and 51W, vortex beam focusing spots with topological charges of +1 and -1 are generated, indicating that the present invention achieves vortex beam output; and interference fringes are generated in the vortex beam focusing spots, and phase singularities exist.

[0082] In one embodiment, referring to Fig.10 As can be seen from the figure, for a vortex beam with a topological charge of +1, after amplification, the content of the output vortex beam with a topological charge of +1 is 0.8947, and the content of the topological charge of -1 is 0.0639. 01 The content of the vortex beam with a topological charge of -1 is 0.0414; for the vortex beam with a topological charge of -1, after amplification, the content of the output vortex beam with a topological charge of +1 is 0.0401, and the content of the topological charge of -1 is 0.9025. 01 The content of is 0.0574; for the vortex beam output by the present invention, the purity of the output vortex beam can be guaranteed to be about 90%. This shows that the present invention can solve the problem of mode purity degradation in the power amplification process and can ensure the output of a high-purity vortex beam.

[0083] Matters not covered by the present invention are known technologies.

[0084] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above 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.

[0085] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

[0086] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An all-fiber polarization-maintaining vortex optical amplification system, characterized in that: It includes a polarization-maintaining seed laser output system, a polarization-maintaining mode conversion device, a fiber polarization controller, a mode matcher, a pump signal combiner, a laser diode light source group, a few-mode polarization-maintaining ytterbium-doped fiber, a cladding mode filter, and a water cooling plate; it also includes a polarization-maintaining single-mode amplifier for increasing the output optical power of the polarization-maintaining seed laser output system; The input end of the polarization-maintaining mode conversion device is connected to the output end of the polarization-maintaining seed laser output system, and is used to convert the single-mode polarization-maintaining laser into a high-order mode polarization-maintaining laser; The input end of the optical fiber polarization controller is connected to the output end of the polarization-maintaining mode conversion device, and is used to control the laser mode field vibration state of the output laser of the polarization-maintaining mode conversion device, and adjust the optical fiber polarization controller according to the output light spot to make different vector modes produce phase difference, thereby superimposing and generating a vortex beam with a phase singularity; The input end of the mode matcher is connected to the output end of the optical fiber polarization controller, and is used to reduce the mode field mismatch when the output laser of the optical fiber polarization controller enters the pump signal combiner, so as to ensure that the mode of the high-order mode seed laser does not degenerate when entering the pump signal combiner; The input end of the pump signal combiner is connected to the output end of the mode matcher, and the input end of the pump signal combiner is also connected to a laser diode light source group, and the laser diode light source group provides a pump source for the all-fiber polarization-maintaining vortex light amplification system; The input end of the few-mode polarization-maintaining ytterbium-doped optical fiber is connected to the output end of the pump signal combiner to provide gain for the all-fiber polarization-maintaining vortex optical amplification system; the fiber winding diameter of the few-mode polarization-maintaining ytterbium-doped optical fiber is greater than 30 cm to avoid high-order mode field power loss and mode degradation caused by excessive bending; The water cooling plate is used to place the few-mode polarization-maintaining ytterbium-doped optical fiber to dissipate the heat generated during the laser amplification process; The input end of the cladding mode filter is connected to the output end of the few-mode polarization-maintaining ytterbium-doped optical fiber to achieve cladding light filtering; After the cladding light is filtered out, the laser is output through the output end of the cladding mode filter.

2. The all-fiber polarization-maintaining vortex optical amplification system according to claim 1, characterized in that: The polarization-maintaining seed laser output system is a combination of a polarization-maintaining single-mode seed laser or a non-polarization-maintaining single-mode seed laser and a polarization-maintaining laser conversion device.

3. The all-fiber polarization-maintaining vortex optical amplification system according to claim 2, characterized in that: The non-polarization-maintaining single-mode seed laser is a light source that stably outputs single-mode laser light, including but not limited to a laser oscillator, a laser amplifier, a random Raman fiber laser, and an amplified spontaneous emission light source.

4. The all-fiber polarization-maintaining vortex optical amplification system according to claim 2, characterized in that: The polarization-maintaining laser conversion device is used to convert a non-polarization-maintaining single-mode seed laser into a polarization-maintaining laser, and comprises an optical fiber polarizer and a polarization beam splitter.

5. The all-fiber polarization-maintaining vortex optical amplification system according to claim 1, characterized in that: The laser output from the cladding filter is output through an output end cap, and the output end cap is coated with an output wavelength anti-reflection film to avoid the generation of back-propagating return light.

6. The all-fiber polarization-maintaining vortex optical amplification system according to claim 1, characterized in that: The polarization-maintaining mode conversion device includes, but is not limited to, a polarization-maintaining long-period fiber grating and a polarization-maintaining acoustic fiber grating.

7. The all-fiber polarization-maintaining vortex optical amplification system according to claim 1, characterized in that: The optical fiber polarization controller includes a three-ring polarization controller, a squeeze polarization controller, and an electric polarization controller.

8. The all-fiber polarization-maintaining vortex optical amplification system according to claim 1, characterized in that: The laser diode light source group is a pump light source with an output wavelength of 915nm or 976nm.

9. The all-fiber polarization-maintaining vortex optical amplification system according to claim 1, characterized in that: The few-mode polarization-maintaining ytterbium-doped optical fiber includes an ytterbium-doped optical fiber with a core diameter of 15 / 130 and an NA of 0.08, an ytterbium-doped optical fiber with a core diameter of 20 / 130 and an NA of 0.08, an ytterbium-doped optical fiber with a core diameter of 25 / 250 and an NA of 0.065, and an ytterbium-doped optical fiber with a core diameter of 20 / 400 and an NA of 0.065.

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