A mid-infrared multi-wavelength active-passive hybrid modulation all-fiber laser

Abstract

This invention discloses a mid-infrared multi-wavelength active-passive hybrid modulation all-fiber laser, comprising a cascaded 976nm laser pump source, a 976nm laser pump source pigtail, a pump coupling device, an isolator, a first fiber grating, an erbium-doped active fiber, a second fiber grating, a thulium-doped active fiber, a third fiber grating, a fourth fiber grating, a fifth fiber grating, a dysprosium-InF-doped active fiber, a sixth fiber grating, a seventh fiber grating, a praseodymium-doped active fiber, an eighth fiber grating, a ninth fiber grating, and a tenth fiber grating, and a laser output point. The first and third fiber gratings constitute a first resonant cavity; the straight-cut end faces of the second and sixth fiber gratings constitute a second resonant cavity; the fourth and tenth fiber gratings constitute a third resonant cavity; the fifth and ninth fiber gratings constitute a fourth resonant cavity; and the seventh and eighth fiber gratings constitute a fifth resonant cavity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mid-infrared fiber laser, in particular to a kind of mid-infrared multi-wavelength active-passive hybrid modulation all-fiber laser. BACKGROUND

[0002] In recent years, mid-infrared multi-wavelength fiber laser has advantages in laser scalpel, laser spectroscopy, infrared countermeasure and other aspects, but in 3-5 μm mid-infrared wavelength region, it is difficult to realize multi-wavelength high-power Q-switched narrow pulse laser output by a fiber laser or even a laser based on one kind of fiber. The existing technology mainly includes active Q-switching and passive Q-switching. Active Q-switching refers to the technology of adding external control devices such as electro-optic Q-switching and acousto-optic Q-switching to laser resonant cavity to adjust the loss in the cavity and realize Q-switched laser output. Passive Q-switching mainly refers to the technology of periodically adjusting the loss in the cavity by adding real saturable absorber in the cavity to realize Q-switched laser output. However, the current various modulation elements have different defects, and it is difficult to realize stable high-power tunable pulse laser output.

[0003] In summary, the traditional mid-infrared multi-wavelength fiber laser has the problem of being unable to realize stable multi-wavelength high-power Q-switched narrow pulse laser output. SUMMARY

[0004] Therefore, the present application provides a kind of mid-infrared multi-wavelength active-passive hybrid modulation all-fiber laser, by improving the structure of laser and corresponding optical path, the problem of being unable to realize stable multi-wavelength high-power Q-switched narrow pulse laser output of traditional mid-infrared multi-wavelength fiber laser is solved.

[0005] To solve the above problems, the technical scheme of the present application is to adopt a kind of mid-infrared multi-wavelength active-passive hybrid modulation all-fiber laser, comprising: 976nm laser pump source, 976nm laser pump source tail fiber, pump coupling device, isolator, first fiber grating, erbium-doped active optical fiber, second fiber grating, thulium-doped active optical fiber, third fiber grating, fourth fiber grating, fifth fiber grating, dysprosium-doped:InF active optical fiber, sixth fiber grating, seventh fiber grating, praseodymium-doped active optical fiber, eighth fiber grating, ninth fiber grating and tenth fiber grating and laser output point are cascaded in turn, wherein, the first fiber grating and the third fiber grating constitute a first resonant cavity, for outputting 1.5 μm laser;The straight cut end face of the second fiber grating and the sixth fiber grating constitutes a second resonant cavity, for outputting 1.7 μm laser;The fourth fiber grating and the tenth fiber grating constitute a third resonant cavity, for outputting 4.3 μm laser;The fifth fiber grating and the ninth fiber grating constitute a fourth resonant cavity, for outputting 3 μm laser;The seventh fiber grating and the eighth fiber grating constitute a fifth resonant cavity, for outputting 4.8 μm laser.

[0006] Optionally, the first fiber grating and the third fiber grating are Bragg diffraction gratings etched on ordinary optical fiber, and have high reflectivity to 1.5 μm wavelength, and the high reflectivity is reflectivity≥95%.

[0007] Optionally, the second fiber grating is a Bragg diffraction grating etched on ordinary optical fiber, and has high reflectivity to 1.7 μm wavelength, and the sixth fiber grating is a Bragg diffraction grating etched on fluoride optical fiber, and has high reflectivity to 1.7 μm wavelength, and the high reflectivity is reflectivity≥95%.

[0008] Optionally, the fourth fiber grating and the tenth fiber grating are Bragg diffraction gratings etched on fluoride optical fiber, wherein the fourth fiber grating has high reflectivity to 4.3 μm wavelength, and the tenth fiber grating has low reflectivity to 4.3 μm wavelength, and the high reflectivity is reflectivity≥95%, and the low reflectivity is 40%-50%.

[0009] Optionally, the fifth fiber grating and the ninth fiber grating are Bragg diffraction gratings etched on fluoride optical fiber, wherein the fifth fiber grating has high reflectivity to 3 μm wavelength, and the ninth fiber grating has low reflectivity to 3 μm wavelength, and the high reflectivity is reflectivity≥95%, and the low reflectivity is 40%-50%.

[0010] Optionally, the seventh fiber grating and the eighth fiber grating are Bragg diffraction gratings etched on fluoride fiber, wherein the seventh fiber grating has high reflectivity to 4.8 m wavelength, the eighth fiber grating has low reflectivity to 4.8 m wavelength, the high reflectivity is reflectivity ≥ 95%, and the low reflectivity is 40%-50%.

[0011] Optionally, a first fiber fusion point is arranged between the 976 nm laser pump source tail fiber and the pump coupling device, a second fiber fusion point is arranged between the pump coupling device and the isolator, a third fiber fusion point is arranged between the isolator and the first fiber grating, a fourth fiber fusion point is arranged between the first fiber grating and the erbium-doped active fiber, a fifth fiber fusion point is arranged between the erbium-doped active fiber and the second fiber grating, a sixth fiber fusion point is arranged between the second fiber grating and the thulium-doped active fiber, a seventh fiber fusion point is arranged between the thulium-doped active fiber and the third fiber grating, an eighth fiber fusion point is arranged between the third fiber grating and the fourth fiber grating, a ninth fiber fusion point is arranged between the fifth fiber grating and the dysprosium:InF active fiber, a tenth fiber fusion point is arranged between the dysprosium:InF active fiber and the sixth fiber grating, an eleventh fiber fusion point is arranged between the seventh fiber grating and the praseodymium-doped active fiber, and a twelfth fiber fusion point is arranged between the praseodymium-doped active fiber and the eighth fiber grating.

[0012] Optionally, the 976 nm laser pump source, the 976 nm laser pump source tail fiber, the first fiber fusion point, the pump coupling device, the second fiber fusion point, the isolator, the third fiber fusion point, the first fiber grating, the fourth fiber fusion point, the erbium-doped active fiber, the fifth fiber fusion point, the second fiber grating, the sixth fiber fusion point, the thulium-doped active fiber, the seventh fiber fusion point, the third fiber grating, and the eighth fiber fusion point are sequentially cascaded and are electrically connected to each other through ordinary optical fiber.

[0013] Optionally, the eighth fiber fusion point, the fourth fiber grating, the fifth fiber grating, the ninth fiber fusion point, the dysprosium:InF active fiber, the tenth fiber fusion point, the sixth fiber grating, the seventh fiber grating, the eleventh fiber fusion point, the praseodymium-doped active fiber, the twelfth fiber fusion point, the eighth fiber grating, the ninth fiber grating, and the tenth fiber grating, and the laser output point are sequentially cascaded and are electrically connected to each other through fluoride fiber.

[0014] The primary improvement of the present application is to provide a mid-infrared multi-wavelength active-passive hybrid modulation all-fiber laser, by constructing a resonant cavity composed of five pairs of optical fiber gratings with different reflectivity, so that the overall optical path can realize the operation of pump light pulse through the saturable absorption process of pump light, and can realize the operation of narrow pulse of doped fiber laser based on gain switching effect, effectively improving the stability of the optical path. At the same time, the doped fiber used in the present application acts as both a passive Q-switch element in the previous resonant cavity and a gain medium in the subsequent resonant cavity, without the need for additional Q-switch devices. By multiplexing the doped fiber, the complexity of the optical path structure is effectively reduced, further improving the stability of the optical path, and solving the problem of the traditional mid-infrared multi-wavelength fiber laser that cannot realize stable multi-wavelength high-power Q-switched narrow pulse laser output. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a simplified structure connection diagram of the mid-infrared multi-wavelength active-passive hybrid modulation all-fiber laser of the present application;

[0016] Figure 2 is an energy level transition diagram of the Er 3+ of the present application;

[0017] Figure 3 is an energy level transition diagram of the Tm 3+ of the present application;

[0018] Figure 4 is an energy level transition diagram of the Dy 3+ of the present application;

[0019] Figure 5 is an energy level transition diagram of the Pr 3+ of the present application. DETAILED DESCRIPTION

[0020] In order for those skilled in the art to better understand the technical solutions of the present application, the present application will be further described in detail below in conjunction with the drawings and specific embodiments.

[0021] As Figure 1As shown, a kind of mid-infrared multi-wavelength active-passive hybrid modulation all-fiber laser, comprising: 976nm laser pump source 1, 976nm laser pump source tail fiber 2, pump coupling device 4, isolator 6, first fiber grating 8, erbium-doped active optical fiber 10, second fiber grating 12, thulium-doped active optical fiber 14, third fiber grating 16, fourth fiber grating 19, fifth fiber grating 20, dysprosium-doped: InF active optical fiber 22, sixth fiber grating 24, seventh fiber grating 25, praseodymium-doped active optical fiber 27, eighth fiber grating 29, ninth fiber grating 30 and tenth fiber grating 31 and laser output point 33 are sequentially cascaded, wherein the first fiber grating 8 and the third fiber grating 16 constitute a first resonant cavity for outputting 1.5 μm laser;The straight cut end face of the second fiber grating 12 and the sixth fiber grating 24 constitutes a second resonant cavity for outputting 1.7 μm laser;The fourth fiber grating 19 and the tenth fiber grating 31 constitute a third resonant cavity for outputting 4.3 μm laser;The fifth fiber grating 20 and the ninth fiber grating 30 constitute a fourth resonant cavity for outputting 3 μm laser;The seventh fiber grating 25 and the eighth fiber grating 29 constitute a fifth resonant cavity for outputting 4.8 μm laser.

[0022] Further, the first fiber grating 8 and the third fiber grating 16 are Bragg diffraction gratings etched on ordinary optical fiber, which have high reflectivity for 1.5 μm wavelength, and the high reflectivity is reflectivity ≥95%.

[0023] Further, the second fiber grating 12 is a Bragg diffraction grating etched on ordinary optical fiber, which has high reflectivity for 1.7 μm wavelength, and the sixth fiber grating 24 is a Bragg diffraction grating etched on fluoride optical fiber, which has high reflectivity for 1.7 μm wavelength, and the high reflectivity is reflectivity ≥95%. Wherein, the ordinary optical fiber can be quartz optical fiber.

[0024] Further, the fourth fiber grating 19 and the tenth fiber grating 31 are Bragg diffraction gratings etched on fluoride optical fiber, wherein the fourth fiber grating 19 has high reflectivity for 4.3 μm wavelength, and the tenth fiber grating 31 has low reflectivity for 4.3 μm wavelength, and the high reflectivity is reflectivity ≥95%, and the low reflectivity is 40%-50%.

[0025] Further, the fifth fiber grating 20 and the ninth fiber grating 30 are Bragg diffraction gratings etched on fluoride optical fiber, wherein the fifth fiber grating 20 has high reflectivity for 3 μm wavelength, and the ninth fiber grating 30 has low reflectivity for 3 μm wavelength, and the high reflectivity is reflectivity ≥95%, and the low reflectivity is 40%-50%.

[0026] Furthermore, the seventh fiber grating 25 and the eighth fiber grating 29 are Bragg diffraction gratings etched on fluoride optical fibers. The seventh fiber grating 25 has high reflectivity for a wavelength of 4.8 μm, and the eighth fiber grating 29 has low reflectivity for a wavelength of 4.8 μm. The high reflectivity is ≥95%, and the low reflectivity is 40%-50%.

[0027] Furthermore, to facilitate understanding of the technical solution of this application, as follows: Figures 2-5 As shown, the energy level transition process involved in the technical solution claimed in this application is illustrated: from Er 3+ Based on the energy levels, the 976nm pump light puts the object in the ground state. 4 I 15 / 2 Electrons absorb pump photons and transition to... 4 I 11 / 2 Then quickly from 4 I 11 / 2 nonradiative transition from energy level to excited state 4 I 13 / 2 Energy levels. Through stimulated emission, electrons transition from an excited state to the ground state ( 4 I 13 / 2 → 4 I 15 / 2 This generates a 1.5μm wavelength laser. (The text abruptly ends here, likely due to an incomplete sentence or a formatting error.) 3+ Based on the energy levels, the 1.5μm wavelength laser, acting as a new pump light, puts the object in the ground state. 3 H6's electrons absorb and pump photons, transitioning to... 3 H4, through stimulated emission, electrons transition from the excited state to the ground state. 3 H4→ 3 H6) generates a 1.7μm wavelength laser. (Dy) 3+ According to the energy levels, in a dysprosium-doped InF3 cascade laser system, a 1.7 μm pump light causes stimulated absorption by ions in the ground state. 6 H 11 / 2 energy level, 6 H 11 / 2 The non-radiative decay of energy level ions will cause 6 H 13 / 2 There will also be a large number of ions in the energy level. During the 1.7 μm ESA process, some of these ions will absorb photons and be excited to [a specific energy level]. 6 F 9 / 2 , 6 H 7 / 2 energy levels 6 F 9 / 2 and 6 H 7 / 2 Since the resonance of thermal coupling can be considered as an energy level, the coupling... 6 F 9 / 2 , 6H 7 / 2 Energy levels and 6 F 11 / 2 , 6 H 9 / 2 The multiphonon relaxation process at energy levels is very intense, and a large number of ions will pass through the multiphonon relaxation process from 6 F 9 / 2 , 6 H 7 / 2 Energy level 6 F 11 / 2 , 6 H 9 / 2 The energy level returns to the 4.3 μm upper laser energy level. 6 H 11 / 2 Simultaneously, the 3μm stimulated emission process established in the system ( 6 H 13 / 2 → 6 H 15 / 2 This generates a 3μm wavelength laser, while simultaneously reducing the laser's lower energy level. 6 H 13 / 2 The ion number density, the 3μm stimulated emission process, and the 1.7μm ESA process can promote 6 H 11 / 2 and 6 H 13 / 2 An energy level undergoes a population inversion, resulting in an energy level transition. 6 H 11 / 2 → 6 H 13 / 2 This generates a 4.3μm wavelength laser. (Produced by Pr) 3+ Based on the energy levels, the 4.3 μm pump light causes the ions in the ground state to undergo excited absorption. 3 At the H5 energy level, through stimulated emission, electrons transition from the excited state to the ground state. 3 H5→ 3 H4) generates 4.8μm wavelength laser light.

[0028] Further, the first optical fiber fusion joint 3 is arranged between the 976 nm laser pump source tail fiber 2 and the pump coupling device 4, the second optical fiber fusion joint 5 is arranged between the pump coupling device 4 and the isolator 6, the third optical fiber fusion joint 7 is arranged between the isolator 6 and the first fiber grating 8, the fourth optical fiber fusion joint 9 is arranged between the first fiber grating 8 and the erbium-doped active optical fiber 10, the fifth optical fiber fusion joint 11 is arranged between the erbium-doped active optical fiber 10 and the second fiber grating 12, the sixth optical fiber fusion joint 13 is arranged between the second fiber grating 12 and the thulium-doped active optical fiber 14, the seventh optical fiber fusion joint 15 is arranged between the thulium-doped active optical fiber 14 and the third fiber grating 16, the eighth optical fiber fusion joint 17 is arranged between the third fiber grating 16 and the fourth fiber grating 19, the ninth optical fiber fusion joint 21 is arranged between the fifth fiber grating 20 and the dysprosium:InF active optical fiber 22, the tenth optical fiber fusion joint 23 is arranged between the dysprosium:InF active optical fiber 22 and the sixth fiber grating 24, the eleventh optical fiber fusion joint 26 is arranged between the seventh fiber grating 25 and the praseodymium-doped active optical fiber 27, and the twelfth optical fiber fusion joint 28 is arranged between the praseodymium-doped active optical fiber 27 and the eighth fiber grating 29.

[0029] Further, the first optical fiber fusion joint 3 is arranged between the 976 nm laser pump source tail fiber 2 and the pump coupling device 4, the second optical fiber fusion joint 5 is arranged between the pump coupling device 4 and the isolator 6, the third optical fiber fusion joint 7 is arranged between the isolator 6 and the first fiber grating 8, the fourth optical fiber fusion joint 9 is arranged between the first fiber grating 8 and the erbium-doped active optical fiber 10, the fifth optical fiber fusion joint 11 is arranged between the erbium-doped active optical fiber 10 and the second fiber grating 12, the sixth optical fiber fusion joint 13 is arranged between the second fiber grating 12 and the thulium-doped active optical fiber 14, the seventh optical fiber fusion joint 15 is arranged between the thulium-doped active optical fiber 14 and the third fiber grating 16, the eighth optical fiber fusion joint 17 is arranged between the third fiber grating 16 and the fourth fiber grating 19, the ninth optical fiber fusion joint 21 is arranged between the fifth fiber grating 20 and the dysprosium:InF active optical fiber 22, the tenth optical fiber fusion joint 23 is arranged between the dysprosium:InF active optical fiber 22 and the sixth fiber grating 24, the eleventh optical fiber fusion joint 26 is arranged between the seventh fiber grating 25 and the praseodymium-doped active optical fiber 27, and the twelfth optical fiber fusion joint 28 is arranged between the praseodymium-doped active optical fiber 27 and the eighth fiber grating 29.

[0030] Further, the first optical fiber fusion joint 3 is arranged between the 976 nm laser pump source tail fiber 2 and the pump coupling device 4, the second optical fiber fusion joint 5 is arranged between the pump coupling device 4 and the isolator 6, the third optical fiber fusion joint 7 is arranged between the isolator 6 and the first fiber grating 8, the fourth optical fiber fusion joint 9 is arranged between the first fiber grating 8 and the erbium-doped active optical fiber 10, the fifth optical fiber fusion joint 11 is arranged between the erbium-doped active optical fiber 10 and the second fiber grating 12, the sixth optical fiber fusion joint 13 is arranged between the second fiber grating 12 and the thulium-doped active optical fiber 14, the seventh optical fiber fusion joint 15 is arranged between the thulium-doped active optical fiber 14 and the third fiber grating 16, the eighth optical fiber fusion joint 17 is arranged between the third fiber grating 16 and the fourth fiber grating 19, the ninth optical fiber fusion joint 21 is arranged between the fifth fiber grating 20 and the dysprosium:InF active optical fiber 22, the tenth optical fiber fusion joint 23 is arranged between the dysprosium:InF active optical fiber 22 and the sixth fiber grating 24, the eleventh optical fiber fusion joint 26 is arranged between the seventh fiber grating 25 and the praseodymium-doped active optical fiber 27, and the twelfth optical fiber fusion joint 28 is arranged between the praseodymium-doped active optical fiber 27 and the eighth fiber grating 29.

[0031] Further, for the purpose of understanding the technical solutions of the present application, the process of the laser from starting to emitting laser is shown as follows: after the 976nm laser pump source 1 is turned on, the generated 976nm wavelength laser enters the pump coupling device 4 through the first optical fiber fusion splice point 3, then enters the isolator 6 through the second optical fiber fusion splice point 5, is transmitted in one direction in the isolator 6, and then enters the ordinary optical fiber through the third optical fiber fusion splice point 7, is connected to the erbium-doped active optical fiber 10 through the fourth optical fiber fusion splice point 9 and the fifth optical fiber fusion splice point 11, at this time, the erbium-doped active optical fiber 10 serves as a gain medium, the first fiber grating 8 and the third fiber grating 16 form a first resonant cavity, the 976nm wavelength laser serves as pump light, the thulium-doped active optical fiber 14 is connected to the erbium-doped active optical fiber 10 through the sixth optical fiber fusion splice point 13 and the seventh optical fiber fusion splice point 15, at this time, the thulium-doped active optical fiber 14 serves as a modulation element, when the 976nm wavelength laser passes through the thulium-doped active optical fiber 14, the thulium-doped active optical fiber 14 absorbs the 976nm wavelength laser and is excited to a higher energy level, and then the thulium-doped active optical fiber 14 releases the absorbed energy in the form of 1.5μm wavelength pulse laser, the eighth optical fiber fusion splice point 17 is used for connecting the ordinary optical fiber and the fluoride optical fiber, the dysprosium-doped:InF active optical fiber 22 is connected to the ordinary optical fiber through the ninth optical fiber fusion splice point 21 and the tenth optical fiber fusion splice point 23, at this time, the thulium-doped active optical fiber 14 serves as a gain medium, the second fiber grating 12 and the sixth fiber grating 24 form a second resonant cavity, the 1.5μm wavelength pulse laser serves as pump light, and the dysprosium-doped:InF active optical fiber 22 serves as a modulation element, when the 1.5μm wavelength laser passes through the dysprosium-doped:InF active optical fiber 22, the dysprosium-doped:InF active optical fiber 22 absorbs the 1.5μm wavelength laser and is excited to a higher energy level, and then the dysprosium-doped:InF active optical fiber 22 releases the absorbed energy in the form of 2.1μm wavelength pulse laser. 4 I 15 / 2 → 4 I 11 / 2 energy level, 4 I 15 / 2 energy level, 4 I 11 / 2 energy level, 4 I 11 / 2 energy level, 4 I 13 / 2 energy level, 4 I 13 / 2 energy level, 4 I 15 / 2 energy level, 4 I 13 / 2 energy level, 4 I 13 / 2 → 4 I 15 / 2 energy level, 3 H6→ 3 H4 energy level, 3 H6 energy level, 3 H4 energy level, 3 H4 energy level, 3 H6 and 3 H4 energy level, 3 H4→3 H6) transition process occurs, generating 1.7 μm wavelength pulsed laser; dysprosium-doped: InF active fiber 22 as gain medium, fourth fiber grating 19 and tenth fiber grating 31 constituting third resonant cavity, fifth fiber grating 20 and ninth fiber grating 30 constituting fourth resonant cavity, 1.7 μm wavelength pulsed laser as pump light, through eleventh fiber fusion splicing point 26 and twelfth fiber fusion splicing point 28 accessing praseodymium-doped active fiber 27, praseodymium-doped active fiber 27 as modulation element, 1.7 μm pump light exciting ions in ground state to 6 H 11 / 2 energy level, 6 H 11 / 2 Non-radiative decay of ions in the energy level will make 6 H 13 / 2 There are also a large number of ions in the energy level, under the ESA process of 1.7 μm, a part of the ions will absorb photons to be excited to 6 F 9 / 2 , 6 H 7 / 2 energy level, 6 F 9 / 2 and 6 H 7 / 2 Because the thermal coupling resonance can be regarded as an energy level, coupling 6 F 9 / 2 , 6 H 7 / 2 Multi-phonon relaxation process of 6 F 11 / 2 , 6 H 9 / 2 energy level is very intense, a large number of ions will pass through the multi-phonon relaxation process from 6 F 9 / 2 , 6 H 7 / 2 energy level to 6 F 11 / 2 , 6 H 9 / 2 energy level back to 4.3 μm laser upper energy level 6 H 11 / 2 At the same time, the 3 μm stimulated emission process ( 6 H 13 / 2 → 6 H 15 / 2 ) is established in the system, generating 3 μm wavelength laser, at the same time, the number density of ions in the lower energy level 6 H 13 / 2 of the laser will be reduced, the 3 μm stimulated emission process and the ESA process of 1.7 μm can promote the population inversion of 6 H 11 / 2 and 6 H 13 / 2 energy level, forming energy level transition ( 6 H11 / 2 → 6 H 13 / 2 This generates a 4.3μm wavelength laser. Praseodymium-doped active fiber 27 serves as the gain medium, and the seventh fiber grating 25 and the eighth fiber grating 29 constitute the fifth resonant cavity. The 4.3μm wavelength pulsed laser is used as the pump light. When the 4.3μm wavelength laser passes through… 3 H4→ 3 The H5 energy level transition process will 3 Particles at the H4 energy level are pumped to 3 At the H5 energy level, with 3 As the number of particles in the H5 energy level increases, when 3 H4 and 3 When the H5 energy level satisfies the population inversion condition, the energy level ( 3 H5→ 3 The H4 transition process occurs, generating a 4.8μm wavelength pulsed laser. Finally, after passing through a fluoride fiber, it outputs 3μm, 4.3μm, and 4.8μm wavelength pulsed lasers through laser output point 33.

[0032] This invention constructs a resonant cavity composed of five pairs of fiber gratings with different reflectivities. This allows the overall optical path to achieve pump light pulse operation through the saturable absorption process of the pump light, and also to achieve narrow pulse operation of the doped fiber laser based on the gain switching effect, effectively improving the stability of the optical path. Simultaneously, the rare-earth-doped fiber used in this application serves as both a passive Q-switching element in the previous resonant cavity and a gain medium in the subsequent resonant cavity, eliminating the need for additional Q-switching devices. The multiplexing of the doped fiber effectively reduces the complexity of the optical path structure, further improving optical path stability. Furthermore, since the doped fiber is placed within the resonant cavity of another doped fiber laser, the pump light power density and pump rate are high, which helps overcome the reabsorption loss in the emission band of the fiber laser, achieving high-efficiency laser oscillation and output. Therefore, this invention, through active-passive hybrid modulation, gradually compresses the pulse, increases the peak power, and obtains high-energy multi-wavelength pulse output while effectively simplifying the complexity of the internal optical path of the laser.

[0033] The above describes the mid-infrared multi-wavelength active-passive hybrid modulation all-fiber laser provided by the embodiments of the present invention. The various embodiments in the specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0034] Those skilled in the art will further appreciate that the units and algorithms described in connection with the examples disclosed herein can be embodied directly in hardware, in software, or in a combination of the two. To the extent that the above description constitutes a functional description, the functions can be embodied in software or in hardware, or in a combination of the two. To the extent that the above description constitutes a functional description, the functions can be embodied in software or in hardware, or in a combination of the two. To the extent that the above description constitutes a functional description, the functions can be embodied in software or in hardware, or in a combination of the two. To the extent that the above description constitutes a functional description, the functions can be embodied in software or in hardware, or in a combination of the two. To the extent that the above description constitutes a functional description, the functions can be embodied in software or in hardware, or in a combination of the two. To the extent that the above description constitutes a functional description, the functions can be embodied in software or in hardware, or in a combination of the two. To the extent that the above description constitutes a functional description, the functions can be embodied in software or in hardware, or in a combination of the two. To the extent that the above description constitutes a functional description, the functions can be embodied in software or in hardware, or in a combination of the two. To the extent that the above description constitutes a functional description, the functions can be embodied in software or in hardware, or in a combination of the two. To the extent that the above description constitutes a functional description, the functions can be embodied in software or in hardware, or in a combination of the two. To the extent that the above description constitutes a functional description, the functions can be embodied in software or in hardware, or in a combination of the two. To the extent that the above description constitutes a functional description, the functions can be embodied in software or in hardware, or in a combination of the two. To the extent that the above description constitutes a functional description, the functions can be embodied in software or in hardware, or in a combination of the two. To the extent that the above description constitutes a functional description, the functions can be embodied in software or in hardware, or in a combination of the two. To the extent that the above description constitutes a functional description, the functions can be embodied in software or in hardware, or in a combination of the two. To the extent that the above description constitutes a functional description, the functions can be embodied in software or in hardware, or in a combination of the two. To

Claims

1. A mid-infrared multi-wavelength actively-passively hybrid modulated all-fiber laser, characterized in that, Comprise: In turn cascaded 976nm laser pump source (1), 976nm laser pump source tail fiber (2), pump coupling device (4), isolator (6), first fiber grating (8), erbium-doped active optical fiber (10), second fiber grating (12), thulium-doped active optical fiber (14), third fiber grating (16), fourth fiber grating (19), fifth fiber grating (20), dysprosium: InF active optical fiber (22), sixth fiber grating (24), seventh fiber grating (25), praseodymium-doped active optical fiber (27), eighth fiber grating (29), ninth fiber grating (30) and tenth fiber grating (31) and laser output point (33), wherein, The first fiber grating (8) and the third fiber grating (16) constitute a first resonant cavity for outputting 1.5μm laser; wherein the erbium-doped active optical fiber (10) as a gain medium, thulium-doped active optical fiber (14) as a modulation element; The second fiber grating (12) and the straight cut end face of the sixth fiber grating (24) constitute a second resonant cavity for outputting 1.7μm laser; wherein the thulium-doped active optical fiber (14) as a gain medium, the dysprosium: InF active optical fiber (22) as a modulation element; The fourth fiber grating (19) and the tenth fiber grating (31) constitute a third resonant cavity for outputting 4.3μm laser; The fifth fiber grating (20) and the ninth fiber grating (30) constitute a fourth resonant cavity for outputting 3μm laser; The seventh fiber grating (25) and the eighth fiber grating (29) constitute a fifth resonant cavity for outputting 4.8μm laser; The final output of the laser output point (33) is a mid-infrared multi-wavelength laser of 3μm, 4.3μm and 4.8μm.

2. The hybrid mode all-fiber laser of claim 1, wherein, The first fiber grating (8) and the third fiber grating (16) are Bragg diffraction gratings etched on ordinary optical fiber, which have high reflectivity for 1.5μm wavelength, and the high reflectivity is reflectivity≥95%.

3. The hybrid mode all-fiber laser of claim 1, wherein, The second fiber grating (12) is a Bragg diffraction grating etched on ordinary optical fiber, which has high reflectivity for 1.7μm wavelength, and the sixth fiber grating (24) is a Bragg diffraction grating etched on fluoride fiber, which has high reflectivity for 1.7μm wavelength, and the high reflectivity is reflectivity≥95%.

4. The hybrid mode all-fiber laser of claim 1, wherein, The fourth fiber grating (19) and the tenth fiber grating (31) are Bragg diffraction gratings etched on fluoride fiber, wherein the fourth fiber grating (19) has high reflectivity for 4.3μm wavelength, and the tenth fiber grating (31) has low reflectivity for 4.3μm wavelength, and the high reflectivity is reflectivity≥95%, and the low reflectivity is 40%-50%.

5. The hybrid mode all-fiber laser of claim 1, wherein, The fifth fiber grating (20) and the ninth fiber grating (30) are Bragg diffraction gratings etched on fluoride fibers, wherein the fifth fiber grating (20) has high reflectivity to 3 μm wavelength, the ninth fiber grating (30) has low reflectivity to 3 μm wavelength, the high reflectivity is reflectivity ≥ 95%, and the low reflectivity is 40%-50%.

6. The hybrid mode all-fiber laser of claim 1, wherein, The seventh fiber grating (25) and the eighth fiber grating (29) are Bragg diffraction gratings etched on fluoride fibers, wherein the seventh fiber grating (25) has high reflectivity to 4.8 μm wavelength, the eighth fiber grating (29) has low reflectivity to 4.8 μm wavelength, the high reflectivity is reflectivity ≥ 95%, and the low reflectivity is 40%-50%.

7. The hybrid mode all-fiber laser of claim 1, wherein, The first fiber fusion joint (3) is arranged between the 976 nm laser pump source tail fiber (2) and the pump coupling device (4), the second fiber fusion joint (5) is arranged between the pump coupling device (4) and the isolator (6), the third fiber fusion joint (7) is arranged between the isolator (6) and the first fiber grating (8), the fourth fiber fusion joint (9) is arranged between the first fiber grating (8) and the erbium-doped active fiber (10), the fifth fiber fusion joint (11) is arranged between the erbium-doped active fiber (10) and the second fiber grating (12), the sixth fiber fusion joint (13) is arranged between the second fiber grating (12) and the thulium-doped active fiber (14), the seventh fiber fusion joint (15) is arranged between the thulium-doped active fiber (14) and the third fiber grating (16), the eighth fiber fusion joint (17) is arranged between the third fiber grating (16) and the fourth fiber grating (19), the ninth fiber fusion joint (21) is arranged between the fifth fiber grating (20) and the dysprosium-doped InF active fiber (22), the tenth fiber fusion joint (23) is arranged between the dysprosium-doped InF active fiber (22) and the sixth fiber grating (24), the eleventh fiber fusion joint (26) is arranged between the seventh fiber grating (25) and the praseodymium-doped active fiber (27), and the twelfth fiber fusion joint (28) is arranged between the praseodymium-doped active fiber (27) and the eighth fiber grating (29).

8. The hybrid mode all-fiber laser of claim 7, wherein, The 976 nm laser pump source (1), the 976 nm laser pump source tail fiber (2), the first fiber fusion joint (3), the pump coupling device (4), the second fiber fusion joint (5), the isolator (6), the third fiber fusion joint (7), the first fiber grating (8), the fourth fiber fusion joint (9), the erbium-doped active fiber (10), the fifth fiber fusion joint (11), the second fiber grating (12), the sixth fiber fusion joint (13), the thulium-doped active fiber (14), the seventh fiber fusion joint (15), the third fiber grating (16), and the eighth fiber fusion joint (17) are sequentially cascaded and are electrically connected to each other through ordinary optical fibers.

9. The hybrid mode all-fiber laser of claim 7, wherein, In the order of the eighth optical fiber splice (17), the fourth fiber grating (19), the fifth fiber grating (20), the ninth optical fiber splice (21), the dysprosium-doped: InF active optical fiber (22), the tenth optical fiber splice (23), the sixth fiber grating (24), the seventh fiber grating (25), the eleventh optical fiber splice (26), the praseodymium-doped active optical fiber (27), the twelfth optical fiber splice (28), the eighth fiber grating (29), the ninth fiber grating (30), and the tenth fiber grating (31), and the laser output point (33), are electrically connected to each other through fluoride optical fibers.

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