A high-power supercontinuum system based on tapered fiber amplification structure

Abstract

The present invention provides a high-power supercontinuum system based on a tapered fiber amplification structure, comprising a nanosecond pulse seed source and an amplification unit, wherein the nanosecond pulse seed source is connected to the amplification unit; the amplification unit comprises a pre-amplification stage and a main amplification stage, wherein the pre-amplification stage is formed by cascading more than two amplification units, wherein the core cladding sizes of the gain fibers in each amplification unit in the pre-amplification stage are different from each other, and the output end of the pre-amplification stage is connected to the main amplification stage, wherein the main amplification stage uses a tapered gain fiber as the last stage of the main amplification. The present invention further improves the output power and beam quality of the output supercontinuum by optimizing the spatial structure of the gain fiber of the main amplification stage.

Description

Technical Field

[0001] The invention mainly relates to the technical field of optical fiber lasers, in particular to a high-power supercontinuum system based on a tapered optical fiber amplification structure. Background Art

[0002] High-power near-infrared supercontinuum light sources have broad application prospects in optoelectronic countermeasures, optical coherence tomography, and hyperspectral lidar. The principle of generating supercontinuum is to pump a high nonlinear medium with a high peak pulse, and broaden the spectrum under the action of nonlinearity. In recent years, some new methods for generating high-power supercontinuum light sources have emerged, which has promoted the further development of high-power supercontinuum light sources.

[0003] In order to increase the average power of the supercontinuum output, the pulse must have high average power in addition to high peak power. Therefore, most conventional amplification methods for seed pulses are based on a master oscillator power amplifier (MOPA) structure. This scheme is based on low average power pulse seed light, and then uses doped gain fibers with gradually increasing core sizes to amplify it step by step. High-power supercontinuum laser light sources based on MOPA structures usually first use a multi-stage fiber amplifier to amplify the pulse seed power, and then pump a section of nonlinear fiber to generate a supercontinuum, such as photonic crystal fiber, single-mode fiber, etc.

[0004] However, in order to increase the nonlinearity, the nonlinear optical fiber used has a small core diameter and cannot withstand higher power. Therefore, in order to obtain a high-power near-infrared supercontinuum, a method is proposed to use a fiber amplifier to directly output the supercontinuum. This method does not have the problem of difficult fusion of the pump fiber and the nonlinear fiber. Single-wavelength fiber lasers based on fiber amplifiers have already exceeded 10 kW, so the solution based on direct supercontinuum output of fiber amplifiers has great potential in terms of power improvement. However, due to the nonlinear suppression of the gain fiber in the fiber amplifier and the increase in high-order modes caused by the increase in core diameter, it leads to problems such as low output power efficiency and poor beam quality.

[0005] In summary, in the existing schemes for directly generating supercontinuum spectrum based on fiber amplifier structure, there are problems of low output power and poor beam quality. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention proposes a high-power supercontinuum system based on a tapered fiber amplification structure. Starting from the method of generating a high-power supercontinuum by a master oscillator power amplification structure, the present invention directly obtains a high-power near-infrared supercontinuum by optimizing the scheme.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] The present invention provides a high-power supercontinuum spectrum system based on a tapered optical fiber amplification structure, comprising a nanosecond pulse seed source and an amplification unit, wherein the nanosecond pulse seed source is connected to the amplification unit, and the nanosecond pulse seed source is a nanosecond pulse seed source whose pulse and repetition frequency can be modulated;

[0009] The amplification unit comprises a pre-amplification stage and a main amplification stage. The pre-amplification stage is formed by cascading more than two amplification units. The core cladding sizes of the gain optical fibers in each amplification unit in the pre-amplification stage are different from each other. The output end of the pre-amplification stage is connected to the main amplification stage. The main amplification stage adopts a tapered gain optical fiber as the last stage of main amplification.

[0010] Preferably, the pre-amplification stage comprises a first-stage amplification unit, a second-stage amplification unit, ..., an N-stage amplification unit, wherein the core diameter of the amplification gain fiber in the n+1-stage amplification unit is greater than the core diameter of the amplification gain fiber in the n-stage amplification unit, n=1, ..., N-1. Preferably, the pre-amplification stage comprises a first-stage amplification unit, a second-stage amplification unit, and a third-stage amplification unit. Preferably, the first-stage amplification gain fiber in the first-stage amplification unit uses a 6 / 125 ytterbium-doped fiber, the second-stage amplification gain fiber in the second-stage amplification unit uses a 10 / 125 ytterbium-doped fiber, and the third-stage amplification gain fiber in the third-stage amplification unit uses a 20 / 130 ytterbium-doped fiber.

[0011] Preferably, the tapered gain fiber used in the main amplifier stage is a tapered ytterbium-doped fiber, and the tapered gain fiber comprises a thin section, a tapered transition section and a thick section, the end of the thin section serves as the input end, and the end of the thick section serves as the output end.

[0012] The scheme of directly generating supercontinuum spectrum based on the existing fiber amplifier structure has the problems of low output power and poor beam quality.

[0013] Because the supercontinuum spectrum needs to be generated under high nonlinearity, the present invention uses a pulse seed source with adjustable pulse width and repetition rate. By controlling the repetition rate, the peak power can be increased, and the nonlinear effect can be increased to generate the supercontinuum spectrum.

[0014] Furthermore, the present invention further improves the output power and beam quality of the output supercontinuum by optimizing the spatial structure of the gain optical fiber of the main amplifier stage.

[0015] The present invention can perfectly solve the problems of beam quality and output power efficiency by designing a tapered gain fiber of sufficient length as the main amplifier stage. The thin section and the tapered transition section are used to maintain the beam quality and optimize the spectrum, and the thick section is used to suppress nonlinearity and improve the output power. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] 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.

[0017] Figure 1 is a schematic structural diagram of a high-power supercontinuum system based on a tapered optical fiber amplification structure provided in one embodiment;

[0018] Figure 2 is a schematic diagram of the structure of a tapered gain fiber;

[0019] Figure 3 This is a schematic structural diagram of a beam quality test optical path of a high-power supercontinuum system based on a tapered fiber amplification structure provided in an embodiment;

[0020] Figure 4 1 is a spectrum diagram and a beam quality diagram obtained at a maximum output power of 1066 W according to an embodiment, wherein (a) is a spectrum diagram obtained at a maximum output power of 1066 W, and its spectral range is 1000-1650 nm, (b) is a beam quality diagram of the output spectrum measured at a wavelength of 1000 nm when the maximum output power is 1066 W, (c) is a beam quality diagram of the output spectrum measured at a wavelength of 1064 nm when the maximum output power is 1066 W, and (d) is a beam quality diagram of the output spectrum measured at a wavelength of 1100 nm when the maximum output power is 1066 W;

[0021] Description of the figure:

[0022] 1. Nanosecond pulse seed source; 2. First isolator; 3. First pump source; 4. First combiner; 5. First-stage amplification gain fiber; 6. Second isolator; 7. Second pump source; 8. Second combiner; 9. Second-stage amplification gain fiber; 10. Third isolator; 11. Third pump source; 12. Fourth pump source; 13. Third combiner; 14. Third-stage amplification gain fiber; 15. Fourth isolator; 16. Fifth pump source; 17. Sixth pump source; 18. Fourth combiner; 19. Tapered gain fiber; 20. Laser output end; 21. Spectroscope; 22. Filter; 23. Beam quality analyzer; 19-1. Thin section; 19-2. Tapered transition section; 19-3. Thick section. DETAILED DESCRIPTION

[0023] 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.

[0024] The present invention provides a high-power supercontinuum spectrum system based on a tapered fiber amplification structure, comprising a nanosecond pulse seed source and an amplification unit, wherein the nanosecond pulse seed source 1 is connected to the amplification unit; the nanosecond pulse seed source 1 is a nanosecond pulse seed source in which both pulse and repetition frequency can be modulated, wherein the adjustable repetition frequency can be used to increase the peak power, thereby increasing the nonlinear effect to generate a supercontinuum spectrum. The amplification unit comprises a pre-amplification stage and a main amplification stage, wherein the pre-amplification stage is formed by cascading more than two amplification units, wherein the core cladding sizes of the gain optical fibers in each amplification unit in the pre-amplification stage are different from each other, and the output end of the pre-amplification stage is connected to the main amplification stage, wherein the main amplification stage uses a tapered gain optical fiber as the last stage of main amplification. The pre-amplification stage comprises a first-stage amplification unit, a second-stage amplification unit, ..., an N-stage amplification unit, wherein the core diameter of the amplification gain optical fiber in the n+1-stage amplification unit is greater than the core diameter of the amplification gain optical fiber in the n-stage amplification unit, n=1, ..., N-1.

[0025] Reference Figure 2 , is a schematic diagram of the structure of a tapered gain fiber. The tapered gain fiber used in the main amplifier stage is a tapered ytterbium-doped fiber. The tapered gain fiber 19 includes a thin segment 19-1, a tapered transition segment 19-2 and a thick segment 19-3. The end of the thin segment 19-1 serves as the input end of the tapered gain fiber, and the end of the thick segment 19-3 serves as the output end of the tapered gain fiber. The present invention can improve the output power and beam quality of the output supercontinuum spectrum by optimizing the core diameter of the amplification gain fiber of each stage of the pre-amplification stage and optimizing the spatial structure of the gain fiber of the main amplifier stage.

[0026] Reference Figure 1 In one embodiment, a high-power supercontinuum system based on a tapered fiber amplification structure is provided, including a nanosecond pulse seed source and an amplification unit, wherein the amplification unit includes a pre-amplification stage and a main amplification stage, and the pre-amplification stage is formed by cascading three amplification units.

[0027] Reference Figure 1, is a schematic diagram of the structure of a nanosecond pulse seed source 1 and a pre-amplifier stage in an embodiment, wherein the pre-amplifier stage includes a first-stage amplification unit, a second-stage amplification unit, and a third-stage amplification unit, which are connected in sequence, wherein the core cladding sizes of the first-stage amplification gain fiber 5, the second-stage amplification gain fiber 9, and the third-stage amplification gain fiber 14 in the first-stage amplification unit, the second-stage amplification unit, and the third-stage amplification unit are different from each other. The pump sources connected to the first-stage amplification unit and the second-stage amplification unit are both single-mode pump sources, and the pump source connected to the third-stage amplification unit is a single-mode pump source.

[0028] Specifically, Figure 1 The laser beam generator comprises a nanosecond pulse seed source 1, a first isolator 2, a first pump source 3, a first combiner 4, a first-stage amplification gain fiber 5, a second isolator 6, a second pump source 7, a second combiner 8, a second-stage amplification gain fiber 9, a third isolator 10, a third pump source 11, a fourth pump source 12, a third combiner 13, a third-stage amplification gain fiber 14, a fourth isolator 15, a fifth pump source 16, a sixth pump source 17, a fourth combiner 18, a tapered gain fiber 19, and a laser output end 20. The first pump source 3 is a continuous light LD with a central wavelength of 976nm and a maximum output power of 400mw, and the output fiber pigtail is 105 / 125 microns; the second pump source 7 is a continuous light LD with a central wavelength of 976nm and a maximum output power of 28W, and the output fiber pigtail is 105 / 125; the third pump source 11 is a continuous light LD with a central wavelength of 976nm and a maximum output power of 130W, and the output fiber pigtail is 105 / 125; the fourth pump source 12 is a continuous light LD with a central wavelength of 976nm and a maximum output power of 130W, and the output fiber pigtail is 105 / 125; the fifth pump source 16 is a continuous light LD with a central wavelength of 976nm and a maximum output power of 800W, and the output fiber pigtail is 220 / 242; the sixth pump source 17 is a continuous light LD with a central wavelength of 976nm and a maximum output power of 800W, and the output fiber pigtail is 220 / 242. The fifth pump source 16 and the sixth pump source 17 are two pump sources of the main amplifier stage, and the pump power of the main amplifier stage is 1366W.

[0029] The pulse width of the nanosecond pulse seed source 1 is set to 4.8 ns, the repetition rate is set to 7.5 MHz, and the central wavelength is 1064 nm. The output end of the nanosecond pulse seed source 1 is connected to the first end of the first isolator 2, the second end of the first isolator 2 is connected to the signal input arm of the first beam combiner 4, the first pump source 3 is connected to the pump input arm of the first beam combiner 4, the beam combining end of the first beam combiner 4 is connected to the first end of the first-stage amplification gain fiber 5, the second end of the first-stage amplification gain fiber 5 is connected to the first end of the second isolator 6, the second end of the second isolator 6 is connected to the signal input arm of the second beam combiner 8, the second pump source 7 is connected to the pump input arm of the second beam combiner 8, the beam combining end of the second beam combiner 8 is connected to the first end of the second-stage amplification gain fiber 9, and the second end of the second-stage amplification gain fiber 9 is connected to the first end of the third isolator 10. The second end of the third isolator 10 is connected to the signal input arm of the third beam combiner 13, the third pump source 11 and the fourth pump source 12 are respectively connected to the pump input arm of the third beam combiner 13, the beam combining end of the third beam combiner 13 is connected to the first end of the third-stage amplification gain fiber 14, the second end of the third-stage amplification gain fiber 14 is connected to the first end of the fourth isolator 15, the second end of the fourth isolator 15 is connected to the signal input arm of the fourth beam combiner 18, the fifth pump source 16 and the sixth pump source 17 are respectively connected to the pump input arm of the fourth beam combiner 18, the beam combining end of the fourth beam combiner is connected to the thin end of the tapered gain fiber 19, and the thick end of the tapered gain fiber 19 is connected to the laser output end 20. The function of each isolator is to prevent the return light from returning. The laser output end 20 can be output by cutting the optical fiber at an angle, and the angle is preferably 8 degrees or 9 degrees, which can effectively prevent the return light and prevent the end face from overheating. The laser output end 20 can also use an optical fiber end cap, and output by using an optical fiber end cap.

[0030] In this embodiment, the first-stage amplification gain fiber 5 in the first-stage amplification unit uses 6 / 125 ytterbium-doped fiber (i.e., the core diameter is 6μm, and the cladding diameter is 125μm), the second-stage amplification gain fiber 9 in the second-stage amplification unit uses 10 / 125 ytterbium-doped fiber (i.e., the core diameter is 10μm, and the cladding diameter is 125μm), and the third-stage amplification gain fiber 14 in the third-stage amplification unit uses 20 / 130 ytterbium-doped fiber (i.e., the core diameter is 20μm, and the cladding diameter is 130μm). The output beam quality of the nanosecond pulse seed source 1 is 1.01, and the output power is 43.3 mw. The structure in which the core of the amplification gain fiber of each stage of the amplification unit is amplified step by step, that is, the core size of the amplification stage is increased step by step, which can effectively increase the output power. In this way, the power of the output beam after passing through the three-stage amplification unit is 91.5 W. Refer to Figure 2, is a schematic diagram of the structure of a tapered gain fiber. The tapered gain fiber used in the main amplifier stage is a tapered ytterbium-doped fiber. The tapered gain fiber includes a thin segment 19-1, a tapered transition segment 19-2, and a thick segment 19-3. The end of the thin segment is used as the input end, and the end of the thick segment is used as the output end. Specifically, the length of the tapered gain fiber used in the main amplifier stage in this embodiment is 25 meters, of which the length of the thin segment is 7 meters, the length of the tapered transition segment is 10 meters, and the length of the thick segment is 6 meters. The specific parameter design is shown in Table 1:

[0031] Table 1

[0032]

[0033] The core diameter of the thin segment is 20.03μm, and the core diameter of the thick segment is 29.94μm. The core diameter of the tapered transition section linearly transitions from 20.03μm in the thin segment to 29.94μm in the thick segment. Similarly, the cladding diameter of the thin segment is 400.79μm, and the cladding diameter of the thick segment is 595.37μm. The cladding diameter linearly transitions from 400.79μm in the thin segment to 595.37μm in the thick segment.

[0034] The nanosecond pulse seed source 1 described in this embodiment is a commercial electrically modulated seed source, the pulse width of the nanosecond pulse seed source 1 is set to 4.8 ns, the repetition rate is set to 7.5MHz, the central wavelength is 1064 nm, and under the pumping condition of 1366W, the power of the output beam after first passing through the three-stage amplification unit in the pre-amplification stage is 91.5 W. After the output beam of the pre-amplification stage is amplified by the main amplification stage, an output power of 1066 W, a slope efficiency of 75.7%, and a high-power near-infrared supercontinuum with an output spectrum range of 1000-1650 nm are obtained. It can be seen that the present invention proposes the optimization design of the core diameter of the amplification gain optical fiber of each stage of the amplification unit of the pre-amplification stage and the optimization design of the spatial structure of the gain optical fiber of the main amplification stage, specifically, the structure of the core of the amplification gain optical fiber of each stage of the amplification unit of the amplification stage is adopted, that is, the core size of the amplification stage is increased step by step, which can effectively improve the output power and beam quality of the output supercontinuum.

[0035] Reference Figure 3 , Figure 3 is a schematic structural diagram of a beam quality test optical path of a high-power supercontinuum system based on a tapered fiber amplification structure provided in an embodiment, Figure 3The laser beam laser comprises a nanosecond pulse seed source 1, a first isolator 2, a first pump source 3, a first combiner 4, a first-stage amplification gain fiber 5, a second isolator 6, a second pump source 7, a second combiner 8, a second-stage amplification gain fiber 9, a third isolator 10, a third pump source 11, a fourth pump source 12, a third combiner 13, a third-stage amplification gain fiber 14, a fourth isolator 15, a fifth pump source 16, a sixth pump source 17, a fourth combiner 18, a tapered gain fiber 19, a laser output end 20, a spectroscope 21, a filter 22, and a beam quality analyzer 23. The output end of the nanosecond pulse seed source 1 is connected to the first end of the first isolator 2, the second end of the first isolator 2 is connected to the signal input arm of the first beam combiner 4, the first pump source 3 is connected to the pump input arm of the first beam combiner 4, the beam combining end of the first beam combiner 4 is connected to the first end of the first-stage amplification gain fiber 5, the second end of the first-stage amplification gain fiber 5 is connected to the first end of the second isolator 6, the second end of the second isolator 6 is connected to the signal input arm of the second beam combiner 8, the second pump source 7 is connected to the pump input arm of the second beam combiner 8, the beam combining end of the second beam combiner 8 is connected to the first end of the second-stage amplification gain fiber 9, and the second end of the second-stage amplification gain fiber 9 is connected to the first end of the third isolator 10. The second end of the third isolator 10 is connected to the signal input arm of the third beam combiner 13, the third pump source 11 and the fourth pump source 12 are respectively connected to the pump input arm of the third beam combiner 13, the beam combining end of the third beam combiner 13 is connected to the first end of the third-stage amplification gain fiber 14, the second end of the third-stage amplification gain fiber 14 is connected to the first end of the fourth isolator 15, the second end of the fourth isolator 15 is connected to the signal input arm of the fourth beam combiner 18, the fifth pump source 16 and the sixth pump source 17 are respectively connected to the pump input arm of the fourth beam combiner 18, the beam combining end of the fourth beam combiner is connected to the thin end of the tapered gain fiber 19, and the thick end of the tapered gain fiber 19 is connected to the laser output end 20. The laser output end 20 outputs laser light incident on the beam splitter 21, most of the power of the output laser light (i.e., signal light) is reflected and outputted by the beam splitter 21, and a small part of the power of the output laser light is transmitted to the filter 22 through the beam splitter 21, and the laser light after passing through the filter 22 is incident on the beam quality analyzer 23 for beam quality analysis. The filter 22 is determined according to the central wavelength of the light beam to be measured. For example, when measuring the quality of a 1000nm light beam, the filter 22 is a filter that only allows the 1000nm light beam to pass through. When measuring the quality of a 1064nm light beam, the filter 22 is a filter that only allows the 1064nm light beam to pass through. When measuring the quality of a 1100nm light beam, the filter 22 is a filter that only allows the 1100nm light beam to pass through.

[0036] The nanosecond pulse seed source 1 described in the present invention is a nanosecond pulse seed source whose pulse and repetition rate can be modulated. The peak power can be increased and the nonlinearity can be increased by controlling the repetition rate.

[0037] In one embodiment, based on Figure 3 In the optical path shown, the pulse width of the nanosecond pulse seed source 1 is set to 4.8 ns and the central wavelength is 1064 nm. The first-stage amplification gain fiber 5 in the first-stage amplification unit uses 6 / 125 ytterbium-doped fiber, the second-stage amplification gain fiber 9 in the second-stage amplification unit uses 10 / 125 ytterbium-doped fiber, and the third-stage amplification gain fiber 14 in the third-stage amplification unit uses 20 / 130 ytterbium-doped fiber. The output beam quality of the nanosecond pulse seed source 1 is 1.01, and the output power is 43.3mw. At the same time, the length of the tapered gain fiber used in the main amplification stage is set to 25 meters, of which the length of the thin section is 7 meters, the length of the tapered transition section is 10 meters, and the length of the thick section is 6 meters. The specific parameter design is shown in Table 2:

[0038] Table 2

[0039]

[0040] The core diameter of the thin segment is 20.03μm, and the core diameter of the thick segment is 29.94μm. The core diameter of the tapered transition section linearly transitions from 20.03μm in the thin segment to 29.94μm in the thick segment. Similarly, the cladding diameter of the thin segment is 400.79μm, and the cladding diameter of the thick segment is 595.37μm. The cladding diameter linearly transitions from 400.79μm in the thin segment to 595.37μm in the thick segment. The first pump source 3 is a continuous light LD with a central wavelength of 976nm and a maximum output power of 400mw, and the output fiber pigtail is 105 / 125 microns; the second pump source 7 is a continuous light LD with a central wavelength of 976nm and a maximum output power of 28W, and the output fiber pigtail is 105 / 125; the third pump source 11 is a continuous light LD with a central wavelength of 976nm and a maximum output power of 130W, and the output fiber pigtail is 105 / 125; the fourth pump source 12 is a continuous light LD with a central wavelength of 976nm and a maximum output power of 130W, and the output fiber pigtail is 105 / 125; the fifth pump source 16 is a continuous light LD with a central wavelength of 976nm and a maximum output power of 800W, and the output fiber pigtail is 220 / 242; the sixth pump source 17 is a continuous light LD with a central wavelength of 976nm and a maximum output power of 800W, and the output fiber pigtail is 220 / 242. The fifth pump source 16 and the sixth pump source 17 are two pump sources of the main amplifier stage, and the pump power of the main amplifier stage is 1366W. Figure 3 The high-power supercontinuum system based on the tapered fiber amplification structure outputs a high-power near-infrared supercontinuum with a spectral range of 1000-1650 nm, and the output power and spectrum of the high-power supercontinuum system based on the tapered fiber amplification structure corresponding to the nanosecond pulse seed source at different repetition rates are tested to illustrate the effectiveness of the present invention, as follows:

[0041] When the repetition rate of the nanosecond pulse seed source 1 is set to 15 MHZ and the pump power is 1366 W, the output power of the high-power supercontinuum system based on the tapered fiber amplification structure is 1250 W.

[0042] When the repetition rate of the nanosecond pulse seed source 1 is set to 10 MHZ and the pump power is 1366 W, the output power of the high-power supercontinuum system based on the tapered fiber amplification structure is 1169 W.

[0043] In addition, refer to Figure 4 , which are the spectrum diagrams and beam quality diagrams obtained at the maximum output power of 1066W, where (a) is the spectrum diagram obtained at the maximum output power of 1066W, and its spectral range is 1000-1650 nm, (b) is the beam quality diagram of the output spectrum measured at a wavelength of 1000 nm when the maximum output power is 1066W, (c) is the beam quality diagram of the output spectrum measured at a wavelength of 1064 nm when the maximum output power is 1066W, and (d) is the beam quality diagram of the output spectrum measured at a wavelength of 1100 nm when the maximum output power is 1066W. It was measured that when the repetition rate of the nanosecond pulse seed source 1 was set to 7.5 MHZ and the pump power was 1366 W, the output power of the high-power supercontinuum system based on the tapered fiber amplification structure was 1066 W. At the same time, the beam qualities of the three wavelengths of 1000 nm, 1064 nm and 1100 nm in the high-power near-infrared supercontinuum with an output spectrum range of 1000-1650 nm were measured as follows:

[0044] 1000nm:Mx 2 =2.207, My 2 =2.127;

[0045] 1064 nm: Mx 2 =2.176, My 2 =2.097;

[0046] 1100 nm: Mx 2 =1.986, My 2 =1.891.

[0047] Matters not covered by the present invention are known technologies.

[0048] 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.

[0049] 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.

[0050] 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. A high-power supercontinuum system based on a tapered fiber amplification structure, characterized in that: It includes a nanosecond pulse seed source and an amplification unit, wherein the nanosecond pulse seed source is connected to the amplification unit, the nanosecond pulse seed source is a nanosecond pulse seed source whose pulse and repetition frequency can be modulated, and the pulse width of the nanosecond pulse seed source is set to 4.8 ns and the central wavelength is 1064 nm; The amplification unit comprises a pre-amplification stage and a main amplification stage, the pre-amplification stage is formed by cascading a first-stage amplification unit, a second-stage amplification unit, and a third-stage amplification unit, the core cladding sizes of the gain fibers in the amplification units in the pre-amplification stage are different from each other, the output end of the pre-amplification stage is connected to the main amplification stage, the main amplification stage uses a tapered gain fiber as the last stage of main amplification, the first-stage amplification gain fiber in the first-stage amplification unit uses a 6 / 125 ytterbium-doped fiber, the second-stage amplification gain fiber in the second-stage amplification unit uses a 10 / 125 ytterbium-doped fiber, and the third-stage amplification gain fiber in the third-stage amplification unit uses a 20 / 130 ytterbium-doped fiber; The amplification unit includes a first isolator, a first pump source, a first combiner, a first-stage amplification gain fiber, a second isolator, a second pump source, a second combiner, a second-stage amplification gain fiber, a third isolator, a third pump source, a fourth pump source, a third combiner, a third-stage amplification gain fiber, a fourth isolator, a fifth pump source, a sixth pump source, a fourth combiner, a tapered gain fiber, and a laser output end; The output end of the nanosecond pulse seed source is connected to the first end of the first isolator, the second end of the first isolator is connected to the signal input arm of the first beam combiner, the first pump source is connected to the pump input arm of the first beam combiner, the beam combining end of the first beam combiner is connected to the first end of the first-stage amplification gain fiber, the second end of the first-stage amplification gain fiber is connected to the first end of the second isolator, the second end of the second isolator is connected to the signal input arm of the second beam combiner, the second pump source is connected to the pump input arm of the second beam combiner, the beam combining end of the second beam combiner is connected to the first end of the second-stage amplification gain fiber, the second end of the second-stage amplification gain fiber is connected to the first end of the third isolator, the second end of the third isolator is connected to the signal input arm of the third beam combiner, the third pump source and the fourth pump source are respectively connected to the pump input arms of the third beam combiner, the beam combining end of the third beam combiner is connected to the first end of the third-stage amplification gain fiber, the second end of the third-stage amplification gain fiber is connected to the first end of the fourth isolator, and the second end of the fourth isolator is connected to the fourth beam combiner. The signal input arm of the fourth combiner is connected to the fifth pump source and the sixth pump source are connected to the pump input arm of the fourth combiner respectively. The combining end of the fourth combiner is connected to the thin end of the tapered gain fiber, and the thick end of the tapered gain fiber is connected to the laser output end. The tapered gain fiber used in the main amplifier stage is a tapered ytterbium-doped fiber. The tapered gain fiber includes a thin section, a tapered transition section and a thick section. The end of the thin section is used as the input end, and the end of the thick section is used as the output end. The length of the tapered gain fiber is 25 meters, of which the length of the thin section is 1.5 meters. The length of the tapered transition section is 7 meters, the length of the thick section is 10 meters, the length of the thick section is 6 meters, the core diameter of the thin section is 20.03μm, the core diameter of the thick section is 29.94μm, and the core diameter of the tapered transition section linearly transitions from 20.03μm in the thin section to 29.94μm in the thick section. Similarly, the cladding diameter of the thin section is 400.79μm, the cladding diameter of the thick section is 595.37μm, and the cladding diameter linearly transitions from 400.79μm in the thin section to 595.37μm in the thick section.

2. The high-power supercontinuum system based on a tapered fiber amplification structure according to claim 1, characterized in that: The repetition rate of the nanosecond pulse seed source is set to 7.5 MHz, and the pump power of the main amplifier stage is 1366 W.

3. The high-power supercontinuum system based on a tapered fiber amplification structure according to claim 1, characterized in that: The repetition rate of the nanosecond pulse seed source is set to 15 MHz, and the pump power of the main amplifier stage is 1366 W.

4. The high-power supercontinuum system based on a tapered fiber amplification structure according to claim 1, characterized in that: The repetition rate of the nanosecond pulse seed source is set to 10 MHz, and the pump power of the main amplifier stage is 1366W.

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