Intermediate infrared laser and intermediate infrared laser system based on praseodymium-doped indium fluoride optical fiber
By using a cascade transition mechanism of praseodymium doped indium fluoride fiber and Pr3+ ions in mid-infrared lasers, the problem of difficulty in generating a 4-5 μm wavelength laser in the prior art is solved, and efficient and fully fiberized laser output is achieved.
Patent Information
- Application Number
- CN202510379082.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-28
- Publication Date
- 2025-07-01
AI Technical Summary
The existing mid-infrared fiber lasers are difficult to effectively generate lasers of 4 to 5 μm wavelengths, and are limited by the rare earth ion species and the transmission range of ZrF4 glass, and the prior art is complex or cannot be fully fiberized.
Praseodymium fluoride fiber is used as the gain medium, and the two transition processes of Pr3+ ions, 3H6→3H5 and 3H4 are used to generate laser light at a wavelength of 4 to 5 μm through 2μm pumping light, combining high reflectivity and low reflectivity fiber Bragg gratings to optimize the resonant cavity structure.
It has achieved efficient production of mid-infrared lasers with wavelengths of 4 to 5 μm, and has a fully fiberized structure for practical application.
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Figure CN120237513A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of laser technology, and particularly to a mid-infrared laser and a mid-infrared laser system based on praseodymium-doped indium fluoride fiber. Background Art
[0002] An optical fiber laser refers to a laser that uses a rare-earth element-doped glass optical fiber as a gain medium. However, according to different wavelengths, the existing optical fiber lasers can achieve the following wavelengths: near-infrared wavelengths (such as 900 - 940 nm, 978 - 1120 nm, etc.), 1.5 μm wavelength, 2.0 μm wavelength, 2.8 μm wavelength, 3.0 - 3.8 μm wavelength, visible and ultraviolet wavelengths (such as 450 - 470 nm, 225 - 235 nm, etc.).
[0003] However, most of the mid-infrared fiber lasers currently being intensively researched and developed in the domestic and foreign scientific research and industrial circles are based on rare-earth-doped ZBLAN fibers. Their wavelengths are restricted by the types of rare-earth ions and the transmission range of ZrF4 glass, and are concentrated between 2.7 and 3.5 μm. In the fields of industry, environmental protection, etc., there are many application requirements for lasers with longer wavelengths. In particular, some functions of mid-infrared lasers with wavelengths of 4 - 5 μm are of great significance for greenhouse gas detection and infrared countermeasure research.
[0004] Therefore, there is an urgent need for an optical fiber laser that can generate mid-infrared lasers with wavelengths of 4 - 5 μm. Summary of the Invention
[0005] The present invention provides a mid-infrared laser and a mid-infrared laser system based on praseodymium-doped indium fluoride fiber, which can generate mid-infrared lasers with wavelengths of 4 - 5 μm.
[0006] According to a first aspect of the present invention, there is provided a mid-infrared laser based on praseodymium-doped indium fluoride fiber, comprising: a pump laser for outputting pump light; an isolator, one end of which is connected to the pump laser; a butt-jointed first fiber jumper plug and second fiber jumper plug, one end of the first fiber jumper plug being further connected to the isolator; a signal light high-reflectivity fiber Bragg grating connected to one end of the second fiber jumper plug; a praseodymium-doped fiber connected to the signal light high-reflectivity fiber Bragg grating; a signal light low-reflectivity fiber Bragg grating connected to the praseodymium-doped fiber; and a pump light high-reflectivity fiber Bragg grating connected to one end of the signal light low-reflectivity fiber Bragg grating.
[0007] Further, the pump laser includes: a high-reflectivity fiber grating; a semiconductor laser pump for generating initial pump light; a beam combiner, one end of the beam combiner being connected to the high-reflectivity fiber grating and the semiconductor laser pump; a thulium-doped fiber connected to the other end of the beam combiner; a low-reflectivity fiber grating connected to the other end of the thulium-doped fiber; and a thin-film optical stripper connected to the other end of the low-reflectivity fiber grating.
[0008] Further, the reflectivity of the high-reflectivity fiber grating is 90% - 100%; the reflectivity of the low-reflectivity fiber grating is 10% - 30%.
[0009] Further, the initial pump light generated by the semiconductor laser pump has a wavelength of 793 nm, and the pump light output by the pump laser has a wavelength of 2 μm.
[0010] Further, the first fiber jumper plug and the second fiber jumper plug are made of ceramic material, and the inner diameter of the first fiber jumper plug matches the diameter of the fluoride fiber, and the inner diameter of the second fiber jumper plug matches the diameter of the quartz fiber.
[0011] Further, the mid-infrared laser based on praseodymium-doped indium fluoride fiber passes through 3 H6→ 3 H5 and 3 H5→ 3 H4 two transitions for cascading to generate a laser with a wavelength of 4 - 5 μm.
[0012] According to the second aspect of the present invention, the present invention also provides a mid-infrared laser system including the mid-infrared laser based on praseodymium-doped indium fluoride fiber described in any one of the above.
[0013] Through one embodiment or multiple embodiments in the above embodiments of the present invention, at least the following technical effects can be achieved:
[0014] In the technical solution disclosed by the present invention, when using praseodymium-doped fiber as the gain medium and generating laser in the mid-infrared laser based on praseodymium-doped indium fluoride fiber, Pr 3+ ions undergo transitions, thereby generating a continuous-wave signal light with a wavelength of 4 - 5 μm. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The following combines the drawings and describes the specific embodiments of the present invention in detail, and the technical solutions and other beneficial effects of the present invention will be obvious.
[0016] Figure 1 It is a schematic structural diagram of the mid-infrared laser based on praseodymium-doped indium fluoride fiber provided by the embodiment of the present invention;
[0017] Figure 2 The energy level structure diagram of Pr3+ ions for the mid-infrared laser based on praseodymium-doped indium fluoride fiber provided by the embodiment of the present invention;
[0018] Figure 3 The structural schematic diagram of the pump laser for the mid-infrared laser based on praseodymium-doped indium fluoride fiber provided by the embodiment of the present invention.
[0019] Reference numerals:
[0020] 1, pump laser; 2, isolator; 3, first fiber jumper plug; 4, second fiber jumper plug; 5, signal light high reflectivity fiber Bragg grating; 6, praseodymium-doped fiber; 7, signal light low reflectivity fiber Bragg grating; 8, pump light high reflectivity fiber Bragg grating; 11, high reflectivity fiber grating; 12, semiconductor laser pump; 13, beam combiner; 14, thulium-doped fiber; 15, low reflectivity fiber grating; 16, cladding light stripper. Detailed implementation manners
[0021] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the protection scope of the present invention.
[0022] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the term "and / or" in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article generally represents an "or" relationship between the associated objects before and after without special instructions.
[0023] A fiber laser refers to a laser using a glass fiber doped with rare earth elements as the gain medium. However, according to different wavelengths, the existing fiber lasers can achieve the following wavelengths: near-infrared wavelengths (such as 900 - 940 nm, 978 - 1120 nm, etc.), 1.5 μm wavelength, 2.0 μm wavelength, 2.8 μm wavelength, 3.0 - 3.8 μm wavelength, visible and ultraviolet wavelengths (such as 450 - 470 nm, 225 - 235 nm, etc.).
[0024] However, most of the mid-infrared fiber lasers that are currently the focus of research and development in the domestic and international scientific research and industrial communities are based on rare-earth-doped ZBLAN fibers. Their wavelengths are restricted by the types of rare-earth ions and the transmission range of ZrF4 glass, and are concentrated between 2.7 and 3.5 μm. In the fields of industry, environmental protection, etc., there are many application requirements for lasers with longer wavelengths. In particular, some functions of mid-infrared lasers with wavelengths of 4-5 μm are of great significance for greenhouse gas detection and infrared countermeasure research.
[0025] However, generating 4-5 μm lasers with fiber lasers has some technical difficulties:
[0026] 1) The ZBLAN fiber with the most mature manufacturing process has relatively high absorption losses in the wavelength region above 4 μm;
[0027] 2) There is a lack of a suitable rare-earth ion transition mechanism because the energy difference between the energy levels corresponding to wavelengths of 4-5 μm is only 2000-2500 cm -1 , and the upper-level lifetime is very short, making it difficult to achieve population inversion. Using soft glass materials with lower phonon energies, such as InF3 glass and chalcogenide glass, can solve the absorption loss problem, but the transition mechanism problem is more difficult to solve because the rare-earth ion transition process that can generate photons with wavelengths above 4 μm has either too high a quantum deficit or too high a threshold power when applied to lasers. Another technical route is to use soliton self-frequency shift and supercontinuum generation to extend mid-infrared laser pulses with a wavelength of 3 μm to 4-5 μm through nonlinear effects. The structure of such systems is very complex and cannot be fully fiberized.
[0028] To solve at least one of the above problems, an embodiment of the present application provides a mid-infrared laser based on praseodymium-doped indium fluoride fiber, which can generate mid-infrared laser with a wavelength of 4-5 μm.
[0029] Figure 1 The mid-infrared laser based on praseodymium-doped indium fluoride fiber provided by the embodiment of the present invention is shown, including: a pump laser 1, an isolator 2, a first fiber jumper plug 3, a second fiber jumper plug 4, a signal light high-reflectivity fiber Bragg grating 5, a praseodymium-doped fiber 6, and a signal light low-reflectivity fiber Bragg grating 7; wherein, the pump laser 1 is used to output pump light; one end of the isolator 2 is connected to the pump laser 1; the first fiber jumper plug 3 and the second fiber jumper plug 4 are butted and fixed to each other, and one end of the first fiber jumper plug 3 is also connected to the isolator 2; the signal light high-reflectivity fiber Bragg grating 5 is connected to one end of the second fiber jumper plug 4; the praseodymium-doped fiber 6 is connected to the signal light high-reflectivity fiber Bragg grating 5; the signal light low-reflectivity fiber Bragg grating 7 is connected to the praseodymium-doped fiber 6.
[0030] In this embodiment, the praseodymium-doped fiber 6 is a praseodymium-doped indium fluoride fiber, i.e., Pr3 + :InF3 fiber, and the wavelength of the pump light generated by the pump laser 1 is 2 μm.
[0031] The mid-infrared laser based on the praseodymium-doped indium fluoride fiber provided in this embodiment has a luminescence mechanism of using a 2-μm wavelength pump to pump Pr 3+ ions, and through two transition processes of Pr 3+ ions 3 H6→ 3 H5 and 3 H5→ 3 H4 cascades to generate 4-5 μm laser.
[0032] Specifically, as Figure 2 shown, Figure 2 shows the energy level structure diagram of Pr 3+ ions during the generation of 4-5 μm laser by the mid-infrared laser based on the praseodymium-doped indium fluoride fiber. Among them, the 2-μm pump light pumps Pr 3+ ions to 3 F2 through the ground-state absorption process (GSA, Ground-State Absorption), and then quickly migrates to 3 H6 through multi-phonon relaxation (MR, Multi-phononRelaxation). Since 3 the energy difference between F2 and 3 H6 is extremely small, they can be regarded as the same energy level (referred to as the "thermal coupling energy level") for processing. Ions at this energy level follow the Boltzmann distribution [7] between 3 F2 and 3 H6. Spectroscopic studies have shown that in the InF3 medium, the 3+ energy difference between the 3 H6 energy level and 3 the H5 energy level of Pr 3 ions and the 3 energy difference between the H5 energy level and 3 the H4 energy level are extremely close (the difference between the two is less than the average energy of a single phonon in the InF3 medium), and almost show a resonant relationship. Therefore, 3 H6→ 3 H5 and 3 H5→ 3 H4 two radiative transition processes (Laser) have a large overlap in the emission cross-section spectrum, and can generate laser of the same wavelength (its wavelength is 4-5 μm), and these two transition processes are in a cascade relationship ( 3 the upper energy level of the H5→ 3 H4 transition is3 the lower energy level of the H5 transition), i.e., 3 H5 → 3 the laser corresponding to the H4 transition and 3 H6 → 3 the laser corresponding to the H5 transition have a mutually promoting effect (because the former consumes the population of the latter's lower energy level, which helps the latter achieve population inversion, while the latter provides particles for the upper energy level of the former). This project utilizes 3 H6 → 3 H5 and 3 H5 → 3 H4 to generate a laser with a wavelength of 4 - 5 μm through these two transition processes together.
[0033] In this embodiment, the central operating wavelength of the isolator 2 is the same as the wavelength of the pump laser, and it can block the residual pump light returning from the resonator of the Pr3 + :InF3 fiber laser (i.e., the mid-infrared laser based on praseodymium-doped indium fluoride fiber provided in this embodiment).
[0034] In some embodiments, the length of the praseodymium-doped fiber 6 is less than the length of the thulium-doped fiber 14, and the mid-infrared laser based on praseodymium-doped indium fluoride fiber further includes: a high-reflectivity fiber Bragg grating 8 for pump light, connected to one end of the low-reflectivity fiber Bragg grating 7 for signal light.
[0035] In this embodiment, the Pr3 + :InF3 fiber has a short length, which can reduce the manufacturing cost of the mid-infrared laser based on praseodymium-doped indium fluoride fiber. Also, due to this situation, even in the case of core pumping, a large part of the 2-μm pump light cannot be absorbed by the fiber. And at the end of the Pr3 + :InF3 fiber (i.e., the output end of the resonator), a high-reflectivity chirped grating with a central reflection wavelength corresponding to the pump light wavelength (i.e., the high-reflectivity fiber Bragg grating for pump light) is inscribed. Therefore, the residual pump light can be reflected back into the resonator for reuse, thereby improving the pump utilization efficiency.
[0036] In some embodiments, the pump laser 1 includes: a high-reflectivity fiber grating 11; a semiconductor laser pump 12 for generating initial pump light; a beam combiner 13, one end of the beam combiner 13 is connected to the high-reflectivity fiber grating 11 and the semiconductor laser pump 12; a thulium-doped fiber 14, connected to the other end of the beam combiner 13; a low-reflectivity fiber grating 15, connected to the other end of the thulium-doped fiber 14; a cladding light stripper 16, connected to the other end of the low-reflectivity fiber grating 15.
[0037] Among them, the reflectivity of the high-reflectivity fiber grating 11 is 90% to 100%; the reflectivity of the low-reflectivity fiber grating 15 is 10% to 30%; the initial pump light generated by the semiconductor laser pump 12 has a wavelength of 793 nm, and the pump light wavelength output by the pump laser 1 is 2 μm.
[0038] In this embodiment, the semiconductor laser pump 12 uses a 793 nm semiconductor diode pump, and its specific wavelength is determined by the high-reflectivity fiber grating 11. The output wavelength of the pump laser 1 can be changed by replacing the high-reflectivity fiber grating 11.
[0039] In some embodiments, the first fiber jumper plug 3 and the second fiber jumper plug 4 are made of ceramic material, and the inner diameter of the first fiber jumper plug 3 matches the diameter of the fluoride fiber, and the inner diameter of the second fiber jumper plug 4 matches the diameter of the quartz fiber.
[0040] In this embodiment, at the output fiber of the 2 μm pump laser and one end of the Pr3 + :InF3 fiber, a jumper end is made with a ceramic ferrule each. The ferrules are specially customized (the inner diameters respectively match the diameters of the fluoride fiber and the quartz fiber), and their end faces are processed with abrasive paper. The two jumper ends are fixed tightly together with fasteners, and the 2 μm pump light enters the core of the Pr3 + :InF3 fiber through the butt joint of the jumper ends.
[0041] In summary, for the mid-infrared laser based on praseodymium-doped indium fluoride fiber provided by the embodiments of the present application, the resonant cavity reflector needs to have a relatively high reflectivity to achieve high-efficiency 4 - 5 μm laser generation within a reasonable power range, and at the same time, the pump light also needs to have a relatively high utilization rate. That is, the reflectivity of the signal light grating at the pump injection end of the resonant cavity is 95% - 100%, the reflectivity of the signal light grating at the output end is 80% - 90%, and the reflectivity of the pump light grating at the output end is 80% - 100%. The relatively high reflectivity of the resonant cavity also helps to suppress 3 H6→ 3 H5 and 3 H5→ 3 H4 problems of generating lasers with different wavelengths in the two transitions.
[0042] Therefore, for the mid-infrared laser based on praseodymium-doped indium fluoride fiber provided by the embodiments of the present application, its operating wavelength is in the 4 - 5 μm band. The light-emitting mechanism of this laser is two transition processes of Pr3 + ions 3 H6→ 3 H5 and 3 H5→ 3Cascade of H4. This laser can generate a continuous-wave signal light with a wavelength of 4 - 5 μm by pumping at a wavelength of 2 μm.
[0043] The embodiment of the present application further provides a mid-infrared laser system, including the mid-infrared laser based on praseodymium-doped indium fluoride fiber described in any of the above embodiments.
[0044] In summary, although the present invention has been disclosed above with preferred embodiments, the above preferred embodiments are not intended to limit the present invention. Those of ordinary skill in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention is subject to the scope defined by the claims.
Claims
1. A mid-infrared laser based on praseodymium-doped indium fluoride fiber, characterized in that: include: A pump laser with a wavelength of 2 μm, used to output pump light; An isolator, the central working wavelength of which is consistent with that of the pump laser, one end of which is connected to the pump laser and is used to isolate the reverse propagating residual pump light; A first optical fiber jumper plug and a second optical fiber jumper plug are connected to each other, wherein one end of the first optical fiber jumper plug is also connected to the isolator; A signal light high reflectivity fiber Bragg grating connected to one end of the second fiber jumper plug; A praseodymium-doped indium fluoride optical fiber connected to the signal light high-reflectivity fiber Bragg grating; A signal light low reflectivity fiber Bragg grating connected to the praseodymium-doped indium fluoride optical fiber; The pump light high reflectivity fiber Bragg grating is connected to one end of the signal light low reflectivity fiber Bragg grating.
2. The mid-infrared laser based on praseodymium-doped indium fluoride fiber according to claim 1, characterized in that: The pump laser comprises: High reflectivity fiber Bragg grating; Semiconductor laser pumping, used to generate initial pump light; A beam combiner, wherein two ports at one end of the beam combiner are respectively connected to the high-reflectivity fiber grating and the semiconductor laser pump; A thulium-doped optical fiber connected to the other end of the beam combiner; A low reflectivity fiber Bragg grating connected to the other end of the thulium-doped optical fiber; The cladding light stripper is connected to the other end of the low reflectivity optical fiber grating.
3. The mid-infrared laser based on praseodymium-doped indium fluoride fiber according to claim 2, characterized in that: The central wavelength of the high-reflectivity fiber Bragg grating of the pump laser is 2 μm, and the reflectivity is 90% to 100%; The central wavelength of the low-reflectivity fiber grating of the pump laser is 2 μm, and the reflectivity is 10% to 30%.
4. The mid-infrared laser based on praseodymium-doped indium fluoride fiber according to claim 2, characterized in that: The initial pump light generated by semiconductor laser pumping of the pump laser has a wavelength of 793 nm, and the pump light output by the pump laser has a wavelength of 2 μm.
5. The mid-infrared laser based on praseodymium-doped indium fluoride fiber according to claim 1, characterized in that: The first fiber jumper plug and the second fiber jumper plug are made of ceramic material, and the inner diameter of the first fiber jumper plug matches the diameter of the fluoride fiber, and the inner diameter of the second fiber jumper plug matches the diameter of the quartz fiber.
6. The mid-infrared laser based on praseodymium-doped indium fluoride fiber according to claim 1, characterized in that: The mid-infrared laser based on praseodymium-doped indium fluoride fiber is 3 H6→ 3 H5 and 3 H5→ 3 The two H4 transitions are cascaded to produce 4-5μm wavelength laser.
7. A mid-infrared laser system, characterized in that: A mid-infrared laser based on praseodymium-doped indium fluoride optical fiber as described in any one of claims 1 to 6.