All-fiber flat ultraviolet to mid-infrared supercontinuum laser based on a single seed source

Abstract

The application discloses a single-seed-source-based all-fiber flat ultraviolet-mid-infrared supercontinuum laser, which comprises a seed laser, two-stage ytterbium-erbium-doped fiber amplifiers, a high-nonlinear fiber NL-1550, a large-mode-field ytterbium-erbium-doped fiber amplifier, a large-mode-field ytterbium-doped fiber amplifier, a photonic crystal fiber and a passive fluorine-doped fiber which are connected in sequence; wherein the seed laser outputs seed pulse laser of 1.55 mu m, and finally outputs supercontinuum laser with a spectral range of 370-4500 nm, covering ultraviolet-mid-infrared bands. The application adopts an all-fiber structure, has high stability and portability, reduces the loss in the process of light transmission and the system complexity, realizes double-wavelength pumping through a seed source, and realizes super-flat spectral output covering ultraviolet to mid-infrared through a multi-stage amplification structure and a multi-stage nonlinear medium structure.

Description

Technical Field

[0001] This invention relates to the field of supercontinuum lasers, and more particularly to an all-fiber flat ultraviolet-mid-infrared supercontinuum laser based on a single seed source. Background Technology

[0002] Supercontinuum generation refers to the phenomenon where a high-intensity laser pumps a nonlinear medium, resulting in a significant spectral broadening under the combined effects of dispersion and nonlinearity. The mid-infrared supercontinuum covers the characteristic absorption lines of numerous molecules and has wide applications in frequency metrology, molecular spectroscopy, biomedicine, hyperspectral imaging, and national defense. All-fiber supercontinuum lasers possess advantages such as high spatial coherence, good stability, and portable structure, making them one of the hot topics in international supercontinuum light source research. However, existing schemes for generating supercontinuum light sources still have several defects and shortcomings:

[0003] (1) All-fiber design: In existing supercontinuum light sources, some systems rely on free-space optical elements, resulting in low energy conversion efficiency of the pump laser and high system complexity and instability. The all-fiber structure can efficiently absorb and convert the energy of the pump laser, which can significantly improve the stability and anti-interference capability of the system.

[0004] (2) Spectral coverage: The spectral range of existing supercontinuum light sources is limited, and most of them can only cover the visible to near-infrared band or the near-infrared to mid-infrared band, failing to achieve full-band spectral coverage from ultraviolet to mid-infrared.

[0005] (3) Spectral flatness: Most traditional technologies for generating supercontinuum lasers at home and abroad use a single wavelength to pump a nonlinear medium structure, which has problems such as obvious residual pump peaks or significant decrease in spectral brightness in certain wavelength ranges, resulting in poor overall spectral flatness.

[0006] (4) Number of seed sources: Some existing technologies use two seed sources, which are pre-amplified and main-amplified before being coupled into the optical fiber through a wavelength division multiplexer. However, in some applications with high requirements for optical coherence, such as coherent optical communication and holographic imaging, this may have a certain impact on system performance and imaging quality. At the same time, the method of amplifying and coupling the light through two seed sources may introduce more inhomogeneities and losses during the amplification process, affecting the flatness and intensity of the supercontinuum. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide an all-fiber flat ultraviolet-mid-infrared supercontinuum laser based on a single seed source.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] A first aspect of the present invention provides an all-fiber flat ultraviolet-mid-infrared supercontinuum laser based on a single seed source, comprising a seed laser, two stages of ytterbium-erbium-doped fiber amplifiers, a highly nonlinear fiber NL-1550, a large-mode-field ytterbium-erbium-doped fiber amplifier, a large-mode-field ytterbium-doped fiber amplifier, a photonic crystal fiber, and a passive fluoride fiber connected in sequence.

[0010] The seed laser outputs a 1.55 μm seed pulse laser. Two stages of ytterbium-erbium-doped fiber amplifiers amplify and broaden the seed pulse laser to generate a supercontinuum laser covering 1.5–2.3 μm. The supercontinuum laser pumps the highly nonlinear fiber NL-1550 to obtain a flat supercontinuum laser covering 0.9–2.9 μm. The flat supercontinuum laser is amplified at 1.5 μm and 1.06 μm by large-mode-field ytterbium-erbium-doped fiber amplifiers and large-mode-field ytterbium-doped fiber amplifiers, respectively. The flat supercontinuum lasers amplified at these two locations are extended to the ultraviolet band of 370 nm by photonic crystal fiber and to the mid-infrared band of 4500 nm by passive fluoride fiber. The final output is a supercontinuum laser covering the ultraviolet-mid-infrared band with a spectral range of 370–4500 nm.

[0011] Furthermore, a first optical isolator is provided between the seed laser and the two-stage ytterbium-doped fiber amplifier.

[0012] Furthermore, the two-stage ytterbium-doped fiber amplifier includes a first-stage ytterbium-doped fiber amplifier, a second-stage ytterbium-doped fiber amplifier, and a single-mode fiber connected in sequence.

[0013] The first-stage ytterbium-doped fiber amplifier includes a first single-mode double-clad Er 3+ / Yb 3+ The system comprises a doped optical fiber, a first 976 / 1550nm beam combiner, and a first 976nm multimode semiconductor laser with a maximum output power of 5W; wherein the first 976 / 1550nm beam combiner is used to couple the seed pulse laser output from the seed laser and the pump light output from the first 976nm multimode semiconductor laser to a first single-mode double-clad Er 3+ / Yb 3+ Doped optical fibers;

[0014] The second-stage ytterbium-doped fiber amplifier includes a second single-mode double-clad Er 3+ / Yb 3+The system comprises a ytterbium-doped fiber, a second 976 / 1550nm beam combiner, and a second 976nm multimode semiconductor laser with a maximum output power of 10W. The second 976 / 1550nm beam combiner couples the extended seed pulse laser output from the first-stage ytterbium-doped fiber amplifier and the pump light output from the second 976nm multimode semiconductor laser to a second single-mode double-clad Ernst laser. 3+ / Yb 3+ Doped optical fibers have an extended spectral range of 1.5–2 μm;

[0015] The nonlinearity of single-mode fiber further shifts the operating frequency to 2.3 μm, generating a supercontinuum laser covering 1.5–2.3 μm.

[0016] Furthermore, a second optical isolator is provided between the first-stage erbium-doped fiber amplifier and the second-stage erbium-doped fiber amplifier;

[0017] A third optical isolator is provided between the second-stage ytterbium-doped fiber amplifier and the single-mode fiber.

[0018] Furthermore, the large-mode-field ytterbium-doped fiber amplifier includes a large-mode-field double-clad Erbium fiber amplifier. 3+ / Yb 3+ The system comprises a doped fiber, a third 976 / 1550nm beam combiner, and two third 976nm multimode semiconductor lasers with a maximum output power of 30W. The third 976 / 1550nm beam combiner couples the 0.9–2.9 μm flat supercontinuum laser output from the highly nonlinear NL-1550 fiber and the pump light from the two third 976nm multimode semiconductor lasers to a large-mode-field double-clad Er... 3+ / Yb 3+ Doped optical fibers amplify the 1.5μm region of a flat supercontinuum laser.

[0019] The large-mode-field ytterbium-doped fiber amplifier includes a large-mode-field double-clad Yb fiber amplifier directly cascaded with the large-mode-field ytterbium-erbium-doped fiber amplifier. 3+ Doped optical fibers amplify the 1.06 μm region of a flat supercontinuum laser.

[0020] Furthermore, a mode field adapter is provided between the large mode field ytterbium-doped fiber amplifier and the photonic crystal fiber.

[0021] Furthermore, the passive fluoride optical fiber is an indium fluoride optical fiber.

[0022] The beneficial effects of this invention are:

[0023] In an exemplary embodiment of the present invention, an all-fiber structure is adopted, which has high stability and portability, and reduces the loss and system complexity during optical transmission; dual-wavelength pumping is achieved through a seed source, and an ultra-flat spectral output covering the ultraviolet to mid-infrared is achieved through a cascaded multi-stage amplification structure and a multi-stage nonlinear dielectric structure. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of an all-fiber flat ultraviolet-mid-infrared supercontinuum laser based on a single seed source provided in an exemplary embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of the structure of an all-fiber flat ultraviolet-mid-infrared supercontinuum laser based on a single seed source, provided in another exemplary embodiment of the present invention. Detailed Implementation

[0026] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] In the description of this invention, it should be noted that the directions or positional relationships indicated by terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0028] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0029] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0030] See Figure 1 , Figure 1The diagram illustrates the structure of an all-fiber flat ultraviolet-mid-infrared supercontinuum laser based on a single seed source, provided in an exemplary embodiment of the present invention. The laser includes a seed laser, two stages of erbium-doped ytterbium fiber amplifiers (EYDFAs), a highly nonlinear fiber NL-1550, a large-mode-field erbium-doped ytterbium fiber amplifier (LMA-EYDFA), a large-mode-field ytterbium-doped fiber amplifier (LMA-YDFA), a photonic crystal fiber (PCF), and a passive fluoride fiber (InF3) connected in sequence.

[0031] The seed laser outputs a 1.55 μm seed pulse laser. Two stages of ytterbium-erbium-doped fiber amplifiers amplify and broaden the seed pulse laser to generate a supercontinuum laser covering 1.5–2.3 μm. The supercontinuum laser pumps the highly nonlinear fiber NL-1550 to obtain a flat supercontinuum laser covering 0.9–2.9 μm. The flat supercontinuum laser is amplified at 1.5 μm and 1.06 μm by large-mode-field ytterbium-erbium-doped fiber amplifiers and large-mode-field ytterbium-doped fiber amplifiers, respectively. The flat supercontinuum lasers amplified at these two locations are extended to the ultraviolet band of 370 nm by photonic crystal fiber and to the mid-infrared band of 4500 nm by passive fluoride fiber. The final output is a supercontinuum laser covering the ultraviolet-mid-infrared band with a spectral range of 370–4500 nm.

[0032] Specifically, in this exemplary embodiment, the following advantages are included:

[0033] (1) All-fiber design: This exemplary embodiment adopts an all-fiber structure, which is compact, highly stable and portable. Compared with the structure of spatial optical transmission, the all-fiber structure can efficiently absorb and convert the energy of the pump laser, reduce the loss of optical signal during transmission, reduce the complexity and cost of the system, and improve the overall system performance.

[0034] (2) Spectral Coverage and Spectral Flatness: This exemplary embodiment employs a seed source cascaded with a multi-stage amplifier and a multi-stage nonlinear dielectric structure to achieve dual-wavelength pumping. Thanks to the high peak power pulse of the pump source and the full coverage of the zero-dispersion point of the nonlinear dielectric, this exemplary embodiment can achieve flat spectral output over a wide wavelength range covering the ultraviolet to mid-infrared range. This effectively improves the problem of limited spectral range and obvious residual pump spikes caused by using a single wavelength to pump the nonlinear dielectric in traditional technical solutions, and significantly improves spectral flatness.

[0035] (3) Number of Seed Sources: This exemplary embodiment uses a single seed source for time-domain synchronization, and cascades active fiber after pre-spreading using NL-1550 fiber to achieve dual-wavelength synchronous amplification. Compared to a structure using two independent seed sources, this exemplary embodiment can control the time synchronization of light of different wavelengths, thereby improving the coherence and stability of the supercontinuum. In some applications with high requirements for optical coherence, such as coherent optical communication and holographic imaging, this exemplary embodiment can provide a higher quality light source, which helps to improve system performance and imaging quality. This exemplary embodiment achieves dual-wavelength synchronous amplification by cascading active fiber after pre-spreading using NL-1550 fiber. This design can more effectively utilize the nonlinear effects of optical fibers to achieve more uniform and efficient dual-wavelength synchronous amplification.

[0036] In summary, this exemplary embodiment employs an all-fiber structure, which offers high stability and portability, while reducing losses and system complexity during optical transmission. Dual-wavelength pumping is achieved through a single seed source, and an ultra-flat spectral output covering the ultraviolet to mid-infrared range is realized through cascaded multi-stage amplification structures and multi-stage nonlinear dielectric structures.

[0037] The following preferred exemplary embodiments will be used as examples. Figure 2 Taking this as an example, the specific implementation methods and related principles of each component will be explained in detail:

[0038] More preferably, in an exemplary embodiment, a first optical isolator is provided between the seed laser and the two-stage ytterbium-doped fiber amplifier.

[0039] Specifically, in this exemplary embodiment, a 1550nm nanosecond pulsed laser is used as a seed source, and a first optical isolator (ISO) is used after the seed source to prevent harmful feedback light from damaging the laser.

[0040] More preferably, in an exemplary embodiment, the two-stage erbium-doped fiber amplifiers (EYDFAs) include a first-stage erbium-doped fiber amplifier, a second-stage erbium-doped fiber amplifier, and a single-mode fiber connected in sequence;

[0041] The first-stage ytterbium-doped fiber amplifier includes a first single-mode double-clad Er 3+ / Yb 3+ The system comprises a doped optical fiber, a first 976 / 1550nm beam combiner, and a first 976nm multimode semiconductor laser with a maximum output power of 5W; wherein the first 976 / 1550nm beam combiner is used to couple the seed pulse laser output from the seed laser and the pump light output from the first 976nm multimode semiconductor laser to a first single-mode double-clad Er 3+ / Yb 3+ Doped optical fibers;

[0042] The second-stage ytterbium-doped fiber amplifier includes a second single-mode double-clad Er 3+ / Yb 3+ The system comprises a ytterbium-doped fiber, a second 976 / 1550nm beam combiner, and a second 976nm multimode semiconductor laser with a maximum output power of 10W. The second 976 / 1550nm beam combiner couples the extended seed pulse laser output from the first-stage ytterbium-doped fiber amplifier and the pump light output from the second 976nm multimode semiconductor laser to a second single-mode double-clad Ernst laser. 3+ / Yb 3+ Doped optical fibers have an extended spectral range of 1.5–2 μm;

[0043] The nonlinearity of single-mode fiber further shifts the operating frequency to 2.3 μm, generating a supercontinuum laser covering 1.5–2.3 μm.

[0044] Specifically, in this exemplary embodiment, the first-stage ytterbium-doped erbium fiber amplifier (the first EYDFA) includes a first single-mode double-clad Er 3+ / Yb 3+ Doped optical fiber, a first 976 / 1550nm combiner, and a first 976nm multimode semiconductor laser (LD) with a maximum output power of 5W. Figure 2 The middle part is Pump1). The beam combiner is used to couple the seed pulse and pump light to Er. 3+ / Yb 3+ In the doped fiber, the LD (Light Detector) is used to provide pump light. The structure of the second-stage ytterbium-doped fiber amplifier (the second EYDFA) is similar to that of the first EYDFA, but the maximum output power of the 976nm LD is 10W. In a preferred exemplary embodiment, each EYDFA requires an optical isolator (ISO) to prevent harmful feedback light. A second optical isolator is placed between the first and second-stage ytterbium-doped fiber amplifiers; a third optical isolator is placed between the second-stage ytterbium-doped fiber amplifier and the single-mode fiber. The seed source is amplified in the two-stage EYDFAs, with most pulse energies around 1.55μm and the spectral range extended to 1.5–2μm.

[0045] By connecting a single-mode fiber (SMF) after the EYDFAs, the 1550nm laser pulse amplified by the EYDFA is decomposed into multiple ultrafast pulses. In the SMF, the frequency is shifted to 2.3μm through nonlinear effects such as self-phase modulation, modulation instability, and Raman soliton self-frequency shift, generating a supercontinuum laser with a spectral range covering 1.5 to 2.3μm. The pulse energy distribution is relatively uniform, which is beneficial for the continuous expansion of the supercontinuum.

[0046] More preferably, in an exemplary embodiment, the supercontinuum is used to pump a section of highly nonlinear fiber NL-1550, where the ZDW of the NL-1550 fiber is located at 1.55 μm. Pumping at this wavelength can generate strong nonlinear effects. Since the pump light completely covers the zero-dispersion wavelength of the NL-1550 fiber, the spectrum expands sharply towards longer wavelengths under the influence of self-phase modulation, soliton fission, and Raman soliton self-frequency shift. At the same time, due to the formation of the dispersive wave, the spectrum expands sharply towards shorter wavelengths, resulting in a flat 0.9–2.9 μm spectrum (i.e., a flat supercontinuum laser with a wavelength of 0.9–2.9 μm).

[0047] More preferably, in an exemplary embodiment, the large-mode-field ytterbium-doped erbium fiber amplifier includes a large-mode-field double-clad Erbium fiber amplifier. 3+ / Yb 3+ The system comprises a doped fiber, a third 976 / 1550nm beam combiner, and two third 976nm multimode semiconductor lasers with a maximum output power of 30W. The third 976 / 1550nm beam combiner couples the 0.9–2.9 μm flat supercontinuum laser output from the highly nonlinear NL-1550 fiber and the pump light from the two third 976nm multimode semiconductor lasers to a large-mode-field double-clad Er... 3+ / Yb 3+ Doped optical fibers amplify the 1.5μm region of a flat supercontinuum laser.

[0048] The large-mode-field ytterbium-doped fiber amplifier includes a large-mode-field double-clad Yb fiber amplifier directly cascaded with the large-mode-field ytterbium-erbium-doped fiber amplifier. 3+ Doped optical fibers amplify the 1.06 μm region of a flat supercontinuum laser.

[0049] Specifically, in this exemplary embodiment, a large-mode-field ytterbium-doped fiber amplifier (LMA-EYDFA) and a large-mode-field ytterbium-doped fiber amplifier (LMA-YDFA) are cascaded after NL-1550 fiber. The LMA-EYDFA includes a large-mode-field double-clad Erbium-doped fiber amplifier. 3+ / Yb 3+ The system consists of ytterbium-doped fiber, a third 976 / 1550nm beam combiner, and two third 976nm multimode semiconductor lasers with a maximum output power of 30W. A large-mode-field double-clad YbO fiber is directly cascaded after the large-mode-field ytterbium-doped fiber (LMA-EYDF). 3+ Doped fiber (LMA-YDF). LMA-EYDFA and LMA-YDFA amplify the pump light at 1.5μm and 1.06μm, respectively.

[0050] More preferably, in an exemplary embodiment, a mode field adapter is provided between the large mode field ytterbium-doped fiber amplifier and the photonic crystal fiber.

[0051] Specifically, in this exemplary embodiment, a mode field adapter (MFA) is connected after the LMA-YDF to match the mode field distribution of the optical fiber, thereby reducing loss and reflection caused by mode mismatch.

[0052] More preferably, in an exemplary embodiment, a supercontinuum amplified by a multi-stage amplifier is used as a pump source to pump a section of photonic crystal fiber (PCF). The ZDW of the PCF is located near 1 μm, and through nonlinear effects such as dispersion effect and self-phase modulation, the short-wavelength cutoff edge of the spectrum is extended to the ultraviolet band of 370 nm.

[0053] Finally, an indium fluoride fiber (InF3) is cascaded. The ZDW of InF3 is located near 1.9 μm. Under the induction of modulation instability, the pulse is decomposed into multiple ultrafast pulses. Through nonlinear effects such as self-phase modulation and stimulated Raman scattering, the spectrum broadens during pulse propagation in the anomalously dispersive fiber. The long-wavelength cutoff edge extends to the mid-infrared band of 4500 nm, and finally outputs a supercontinuum laser covering the ultraviolet-mid-infrared band with a spectral range of 370–4500 nm.

[0054] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An all-fiber flat ultraviolet-mid-infrared supercontinuum laser based on a single seed source, characterized in that: It includes a seed laser, a two-stage ytterbium-doped fiber amplifier, a highly nonlinear fiber NL-1550, a large-mode-field ytterbium-doped fiber amplifier, a large-mode-field ytterbium-doped fiber amplifier, a photonic crystal fiber, and a passive fluoride fiber, all connected in sequence. The seed laser outputs a 1.55 μm seed pulse laser. Two stages of ytterbium-erbium-doped fiber amplifiers amplify and broaden the seed pulse laser to generate a supercontinuum laser covering 1.5–2.3 μm. The supercontinuum laser pumps the highly nonlinear fiber NL-1550 to obtain a flat supercontinuum laser covering 0.9–2.9 μm. The flat supercontinuum laser is amplified at 1.5 μm and 1.06 μm by large-mode-field ytterbium-erbium-doped fiber amplifiers and large-mode-field ytterbium-doped fiber amplifiers, respectively. The flat supercontinuum lasers amplified at these two locations are extended to the ultraviolet band of 370 nm by photonic crystal fiber and to the mid-infrared band of 4500 nm by passive fluoride fiber. The final output is a supercontinuum laser covering the ultraviolet-mid-infrared band with a spectral range of 370–4500 nm.

2. The all-fiber flat ultraviolet-mid-infrared supercontinuum laser based on a single seed source according to claim 1, characterized in that: A first optical isolator is provided between the seed laser and the two-stage ytterbium-doped fiber amplifier.

3. The all-fiber flat ultraviolet-mid-infrared supercontinuum laser based on a single seed source according to claim 1, characterized in that: The two-stage ytterbium-doped fiber amplifier includes a first-stage ytterbium-doped fiber amplifier, a second-stage ytterbium-doped fiber amplifier, and a single-mode fiber connected in sequence. The first-stage ytterbium-doped fiber amplifier includes a first single-mode double-clad Er 3+ / Yb 3+ The system comprises a doped optical fiber, a first 976 / 1550nm beam combiner, and a first 976nm multimode semiconductor laser with a maximum output power of 5W; wherein the first 976 / 1550nm beam combiner is used to couple the seed pulse laser output from the seed laser and the pump light output from the first 976nm multimode semiconductor laser to a first single-mode double-clad Er 3+ / Yb 3+ Doped optical fibers; The second-stage ytterbium-doped fiber amplifier includes a second single-mode double-clad Er 3+ / Yb 3+ The system comprises a ytterbium-doped fiber, a second 976 / 1550nm beam combiner, and a second 976nm multimode semiconductor laser with a maximum output power of 10W. The second 976 / 1550nm beam combiner couples the extended seed pulse laser output from the first-stage ytterbium-doped fiber amplifier and the pump light output from the second 976nm multimode semiconductor laser to a second single-mode double-clad Ernst laser. 3+ / Yb 3+ Doped optical fibers have an extended spectral range of 1.5–2 μm; The nonlinearity of single-mode fiber further shifts the operating frequency to 2.3 μm, generating a supercontinuum laser covering 1.5–2.3 μm.

4. The all-fiber flat ultraviolet-mid-infrared supercontinuum laser based on a single seed source according to claim 3, characterized in that: A second optical isolator is provided between the first-stage erbium-doped fiber amplifier and the second-stage erbium-doped fiber amplifier. A third optical isolator is placed between the second-stage ytterbium-doped fiber amplifier and the single-mode fiber.

5. The all-fiber flat ultraviolet-mid-infrared supercontinuum laser based on a single seed source according to claim 1, characterized in that: The large-mode-field ytterbium-doped fiber amplifier includes a large-mode-field double-clad Erbium fiber amplifier. 3+ / Yb 3+ The system comprises a doped fiber, a third 976 / 1550nm beam combiner, and two third 976nm multimode semiconductor lasers with a maximum output power of 30W. The third 976 / 1550nm beam combiner couples the 0.9–2.9 μm flat supercontinuum laser output from the highly nonlinear NL-1550 fiber and the pump light from the two third 976nm multimode semiconductor lasers to a large-mode-field double-clad Er... 3+ / Yb 3+ Doped optical fibers amplify the 1.5μm region of a flat supercontinuum laser. The large-mode-field ytterbium-doped fiber amplifier includes a large-mode-field double-clad Yb fiber amplifier directly cascaded with the large-mode-field ytterbium-erbium-doped fiber amplifier. 3+ Doped optical fibers amplify the 1.06 μm region of a flat supercontinuum laser.

6. The all-fiber flat ultraviolet-mid-infrared supercontinuum laser based on a single seed source according to claim 1, characterized in that: A mode field adapter is provided between the large mode field ytterbium-doped fiber amplifier and the photonic crystal fiber.

7. The all-fiber flat ultraviolet-mid-infrared supercontinuum laser based on a single seed source according to claim 1, characterized in that: The passive fluoride optical fiber is an indium fluoride optical fiber.

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