A hollow-core optical fiber for carbon dioxide laser transmission based on antiresonance structure

Abstract

The present invention discloses a hollow-core optical fiber for carbon dioxide laser transmission based on an antiresonance structure, which belongs to the technical field of mid-infrared optical fiber laser, and includes an outer cladding, an antiresonance region and an air core region arranged in sequence from the outside to the inside; the outer cladding covers the antiresonance region and the air core region; the antiresonance region is composed of a plurality of antiresonance units; the antiresonance unit includes a large fan-shaped dielectric tube, and first, second and third type circular dielectric tubes arranged therein; the first type circular dielectric tube and the second type circular dielectric tube are externally tangent and fused, and are axially symmetrically arranged around the core; the second type circular dielectric tube and the third type circular dielectric tube are externally tangent and fused, and the third type circular dielectric tube does not contact the large fan-shaped dielectric tube. The hollow-core optical fiber of the present invention is a working band in the carbon dioxide laser band, and has the characteristics of low loss, large mode field area, anti-bending and near-zero dispersion, so that the carbon dioxide laser can achieve high-power, high-quality long-distance transmission.

Description

Technical Field

[0001] The present invention relates to the technical field of mid-infrared optical fiber lasers, and more specifically, to a hollow-core optical fiber for carbon dioxide laser transmission based on an anti-resonance structure. Background Art

[0002] The research on hollow-core optical fiber started in the 1930s. Due to its high loss and multi-mode characteristics, the development and application of hollow-core optical fiber progressed very slowly. With the further development of production technology, the first hollow-core photonic crystal fiber came out in 1999, which once again attracted the attention of researchers. The microstructure cladding was introduced into the design and manufacture of hollow-core optical fiber. It is very possible to achieve low-loss hollow-core optical fiber using this method. Since 2012, hollow-core optical fiber with anti-resonant microstructure has developed rapidly, and the loss and mode characteristics of hollow-core optical fiber with this structure have been greatly improved and enhanced. At present, hollow-core optical fiber is mainly based on SiO2 and the transmission wavelength is mainly in the communication band. The loss is reduced to 0.1dB / km, which is lower than the loss limit of solid silica-based optical fiber (about 0.14dB / km).

[0003] Compared with traditional solid-core optical fibers, hollow-core optical fibers have the characteristics of high optical loss threshold, small and flat dispersion, and small waveguide nonlinear coefficient. They have natural advantages in high-power laser transmission and ultrafast laser transmission. However, the current research on hollow-core optical fibers has been mainly focused on the communication band, and there is only a small amount of research on the transmission window in the deep ultraviolet (200 nm) and mid-infrared (4μm) wavelength range. The transmission optical fiber for carbon dioxide lasers in the 10.6μm wavelength range is still based on special optical fibers (optical fibers doped with rare earth elements such as selenium, arsenic, antimony or germanium). At the same time, the current hollow-core optical fiber for carbon dioxide lasers is mainly hollow silica waveguide optical fibers produced by Polymicro Technologies (PT) under Molex. Its structure is mainly a hollow core, and the outside is wrapped with aluminum film, silver film, and silica tube in turn. It is very different from conventional hollow-core optical fibers with photonic band gaps and antiresonant microstructures. Molex's hollow-core optical fiber has a complex structure and high cost, and does not have the advantages of ultra-low loss, flat dispersion and bending resistance of anti-resonance hollow-core optical fiber or photonic bandgap hollow-core optical fiber.

[0004] Carbon dioxide lasers are widely used in marking, cutting, engraving and other processing. Therefore, how to effectively reduce the loss of carbon dioxide lasers during the transmission process has a good guarantee for high-precision processing and cutting. At the same time, hollow-core optical fibers for carbon dioxide laser transmission are extremely scarce in recent years. From the perspective of ultra-low loss, flat dispersion and anti-bending characteristics achieved by hollow-core optical fibers in the communication band, expanding hollow-core optical fibers to various bands to achieve the above-mentioned good characteristics has good development prospects. Summary of the invention

[0005] In view of the shortcomings of existing research on optical fiber technology in the mid-infrared band, the present invention proposes a hollow-core optical fiber for carbon dioxide laser transmission based on an anti-resonance structure. The anti-resonance region adopts a nested design to allow light to propagate in the core as much as possible, so that the designed optical fiber can enable carbon dioxide laser to achieve light wave transmission with the characteristics of low loss, large mode field area, anti-bending and near-zero dispersion.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a hollow core optical fiber for carbon dioxide laser transmission based on an anti-resonance structure, comprising an outer cladding, an anti-resonance region and an air core region from outside to inside;

[0008] The outer cladding covers the anti-resonance region and the air core region;

[0009] The anti-resonance region includes at least four anti-resonance units with the same structure; the anti-resonance unit is a nested cladding tube structure, and the nested cladding tube structure is a double-layer structure, including a large fan-shaped dielectric tube and a first type of circular dielectric tube, a second type of circular dielectric tube and a third type of circular dielectric tube arranged therein;

[0010] The large sector-shaped dielectric tube is a large circular dielectric tube; the large circular dielectric tube intersects with the circular arc boundary of the anti-resonance region and cuts off the portion exceeding the boundary;

[0011] The first type of circular dielectric tube is inscribed and fused with the arc boundary of the anti-resonance region; the first type of circular dielectric tube is inscribed and fused with the second type of circular dielectric tube, and the first type of circular dielectric tube and the second type of circular dielectric tube are axially symmetrically arranged around the core of the hollow-core optical fiber, and neither of them contacts the large fan-shaped dielectric tube;

[0012] The second type of circular medium tube and the third type of circular medium tube are externally cut and welded; the third type of circular medium tube does not contact the large sector-shaped medium tube;

[0013] The anti-resonance unit is in an axisymmetric structure relative to the symmetry axis of the large fan-shaped dielectric tube, and the large fan-shaped dielectric tubes of each anti-resonance unit are not in contact with each other;

[0014] The air core region is composed of a plurality of anti-resonance units uniformly distributed in the anti-resonance region, and is the light guiding region of the hollow core optical fiber.

[0015] Preferably, the number of the anti-resonance units is 4 to 10.

[0016] Preferably, the material of the outer cladding layer and the various dielectric tube materials of the anti-resonance unit in the anti-resonance region are any one of fluoride, sulfide, selenide, silver halide and telluride.

[0017] Preferably, the outer cladding is a cylindrical tube, the outer radius of the cylindrical tube is 240-260 μm, and the inner radius is 215-235 μm.

[0018] Preferably, the thicknesses of the large sector-shaped medium tube, the first type of circular medium tube, the second type of circular medium tube and the third type of circular medium tube are all the same.

[0019] Preferably, the ratio between the radius of the first type of circular dielectric tube and the radius of the large fan-shaped dielectric tube in the anti-resonance unit is 0.1-0.4;

[0020] The ratio between the radius of the second type of circular medium tube and the radius of the first type of circular medium tube is 0.6 to 0.9;

[0021] The ratio between the radius of the third type of circular medium tube and the radius of the second type of circular medium tube is 1-1.5.

[0022] Preferably, the radius of the large fan-shaped medium tube is 90-130 µm; the radius of the first type of circular medium tube is 20-40 µm; the radius of the second type of circular medium tube is 15-35 µm; and the radius of the third type of circular medium tube is 25-45 µm.

[0023] Preferably, the angle between the line formed by the intersection of the large sector-shaped dielectric tube and the anti-resonance boundary and the center of the large sector-shaped dielectric tube and the symmetry axis of the anti-resonance unit is 60°~70°;

[0024] The angle between the line between the intersection of the first type of circular dielectric tube and the second type of circular dielectric tube and the center of the fiber core and the symmetry axis of the anti-resonance unit is 8°~15°;

[0025] The angle between the line between the centers of the second type of circular dielectric tube and the third type of circular dielectric tube and the symmetry axis of the anti-resonance unit is It is 28°~35°.

[0026] Preferably, the air core region is an air hole surrounded by a plurality of anti-resonance units; the radius of the air hole is 40-60 µm.

[0027] Preferably, in the anti-resonance region, gas is filled between the large fan-shaped dielectric tube and the first type circular dielectric tube, between the first type circular dielectric tube and the second type circular dielectric tube, between the second type circular dielectric tube and the third type circular dielectric tube, and in the air core region, and the refractive index of the gas is 1.

[0028] By adopting the above technical solution, the present invention has the following beneficial effects:

[0029] Compared with the existing common solid optical fibers, the hollow-core optical fiber designed based on the anti-resonance structure of the present invention can well achieve the advantages of low loss, near-zero dispersion and anti-bending, and the use of a nested structure makes it have good structural adjustability. In terms of the design of the hollow-core optical fiber, the present invention is designed for the 9~11.05µm band as the transmission band of the optical fiber. The anti-resonance region is reasonably nested to allow light to propagate in the core as much as possible, so that the designed optical fiber is at least one order of magnitude lower than the minimum loss of the existing solid optical fiber in theoretical calculations, and fills the gap in the design of hollow-core optical fibers in the 10µm range. At the same time, by adjusting the size of various dielectric tubes in the anti-resonance region, and then adjusting the size of the air core, through a reasonable cladding region design, the optical fiber can be effectively customized for a specific wavelength range. Experiments have shown that lower restrictive losses (as low as 10) can be obtained through the above-mentioned adjustment or optimization methods. -3 dB / km), larger mode area (4620µm 2 above) and near-zero flat dispersion over a wider wavelength range (stable at -3.63×10 -7 ~2.75×10 -7 ps / (nm·km)). The present invention only uses a common circular nested double-layer structure in design, and the optical fiber structure is simple and easy to produce and prepare. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of the overall structure of a hollow-core optical fiber for carbon dioxide laser transmission based on an anti-resonance structure provided in an embodiment of the present invention;

[0031] Figure 2 A diagram showing the mode field distribution and height expression of the fundamental mode at 10.6 μm provided by an embodiment of the present invention;

[0032] Figure 3 The electric field mode contour distribution diagram of the fundamental mode at 10.6µm provided in an embodiment of the present invention;

[0033] Figure 4 is a graph showing the relationship between the limiting loss of the fundamental mode and the wavelength according to an embodiment of the present invention;

[0034] Figure 5 is a graph showing the relationship between the effective mode field area of ​​the fundamental mode and the wavelength according to an embodiment of the present invention;

[0035] Figure 6 is a graph showing the relationship between the dispersion of the fundamental mode and the wavelength of an embodiment of the present invention;

[0036] Figure 7 is a graph showing the relationship between the mode field distribution of the fundamental mode at 10.6 μm and the bending radius of an embodiment of the present invention;

[0037] Figure 8 FIG. 4 is a graph showing the relationship between the bending restriction loss of the fundamental mode at 10.6 μm and the wavelength according to an embodiment of the present invention. DETAILED DESCRIPTION

[0038] 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.

[0039] The present invention provides a hollow-core optical fiber for carbon dioxide laser transmission based on an anti-resonance structure, wherein the hollow-core optical fiber is sequentially provided with three layers from the outside to the inside, namely, an outer cladding region, an anti-resonance region and an air core region; Figure 1 , from inside to outside are the air core areas of the optical fiber, that is, Figure 1 The air core 1, the anti-resonance region composed of at least four anti-resonance units with the same structure and the optical fiber outer cladding 6.

[0040] In the present invention, the optical fiber outer cladding 6 is a cylindrical tube with a certain thickness, covering the anti-resonance region and the air core region, and is used to protect the anti-resonance region and the air core region.

[0041] In the present invention, the air core 1 is an air region, which is composed of a plurality of anti-resonance units uniformly distributed in the anti-resonance region and is the main light-guiding region of the hollow-core optical fiber.

[0042] Specifically, the air core 1 is essentially an air hole surrounded by a number of anti-resonance units; the radius (R) of the air hole is 40~60µm.

[0043] See also Figure 1In the present invention, the anti-resonance unit is a nested cladding tube structure, which is a double-layer structure, including a large fan-shaped dielectric tube 2 and a first type of circular dielectric tube 5, a second type of circular dielectric tube 4 and a third type of circular dielectric tube 3 arranged inside it; wherein the large fan-shaped dielectric tube 2 is formed by a large circular dielectric tube and the arc boundary of the anti-resonance region intersecting and cutting off the part exceeding the boundary; the first type of circular dielectric tube 5 and the arc boundary of the anti-resonance region are inscribed and fused; the first type of circular dielectric tube 5 and the second type of circular dielectric tube 4 are externally cut and fused, the first type of circular dielectric tube 5 and the second type of circular dielectric tube 4 are axially symmetrically arranged around the core of the hollow-core optical fiber, and neither of them contacts the inner wall of the large fan-shaped dielectric tube 2; the second type of circular dielectric tube 4 and the third type of circular dielectric tube 3 are externally cut and fused; the third type of circular dielectric tube 3 does not contact the large fan-shaped dielectric tube 2, and a certain distance should be maintained (but the distance cannot be too large). The design of multiple types of circular dielectric tubes is to reduce the cladding mode in the core and to concentrate the light in the core area as much as possible.

[0044] The anti-resonance unit is an axisymmetric structure about the symmetry axis of the large sector-shaped dielectric tube 2, and the large sector-shaped dielectric tubes 2 of each anti-resonance unit are not in contact with each other. Figure 1 , defines the radius formed by the intersection of the large sector-shaped circular dielectric tube and the antiresonance boundary and the center of the large sector-shaped circular dielectric tube , and the angle between it and the symmetry axis of the anti-resonance unit is The angle between the distance between the intersection of the first type of circular dielectric tube 5 and the second type of circular dielectric tube 4 and the center of the fiber core and the symmetry axis of the anti-resonance unit is ; The angle between the distance between the centers of the second type of circular dielectric tube and the third type of circular dielectric tube and the symmetry axis of the anti-resonance unit is . You can adjust the parameters , and Optimize fiber performance.

[0045] It should be noted that the wall thickness and other parameters of the hollow-core antiresonant optical fiber need to meet the antiresonance conditions. As long as the antiresonance conditions are met, the glass wall reflection is maximum and the transmission is minimum, and most of the light is reflected back into the core to form an optical waveguide. According to the principle of antiresonance reflection, the nested structure can further effectively reduce the leakage loss of the optical fiber by adding additional layers of antiresonance glass walls. The thickness of each type of dielectric tube of the antiresonance unit (including: large fan-shaped dielectric tube 2, first type circular dielectric tube 5, second type circular dielectric tube 4 and third type circular dielectric tube 3) is the same and meets the following requirements:

[0046] ;

[0047] in, Indicates the thickness of the medium tube, represents the designed operating wavelength, and are the refractive index of the dielectric tube material and the refractive index of air, respectively. is an integer.

[0048] In some embodiments, the number of anti-resonance units is 4-10.

[0049] In some embodiments, size tuning can be performed within the following ranges:

[0050] The ratio between the radius of the first type of circular dielectric tube 5 and the radius of the large fan-shaped dielectric tube 2 in the anti-resonance unit 0.1~0.4;

[0051] The ratio between the radius of the second type of circular medium tube 4 and the radius of the first type of circular medium tube 5 0.6~0.9;

[0052] The ratio between the radius of the third type circular medium tube 3 and the radius of the second type circular medium tube 4 It is 1~1.5.

[0053] The angle between the line formed by the intersection of the large sector-shaped dielectric tube 2 and the antiresonance boundary and the center of the large sector-shaped dielectric tube 2 and the symmetry axis of the antiresonance unit is 60°~70°;

[0054] The angle between the line between the intersection of the first type of circular dielectric tube 5 and the second type of circular dielectric tube 4 and the center of the fiber core and the symmetry axis of the anti-resonance unit 8°~15°;

[0055] The angle between the line between the centers of the second type of circular dielectric tube 4 and the third type of circular dielectric tube 3 and the symmetry axis of the anti-resonance unit is It is 28°~35°.

[0056] In some embodiments, size tuning can be performed within the following ranges:

[0057] The radius of the large sector-shaped medium tube 2 is 90~130µm;

[0058] The radius of the first type of circular medium tube 5 is 20~40µm;

[0059] The radius of the second type of circular medium tube 4 is 15~35µm;

[0060] The radius of the third type of circular medium tube 3 is 25~45µm.

[0061] In some embodiments, the optical fiber outer cladding 6 is a cylindrical tube with a certain thickness, an outer radius of which is 240-260 μm and an inner radius of which is 215-235 μm.

[0062] In some embodiments, the material of the outer cladding of the optical fiber and the materials of various dielectric tubes of the anti-resonance unit in the anti-resonance region are fluoride, sulfide, selenide, silver halide or telluride, etc.

[0063] In some embodiments, the space between the large fan-shaped dielectric tube 2 and the first type circular dielectric tube 5, between the first type circular dielectric tube 5 and the second type circular dielectric tube 4, between the second type circular dielectric tube 4 and the third type circular dielectric tube 3, the air core region and other internal spaces in the anti-resonance region are filled with gas with a refractive index of 1.

[0064] The design advantages of the present invention are described below by the following embodiments:

[0065] Figure 1 The figure shows the overall structure of a hollow-core fiber for a carbon dioxide laser based on an anti-resonance structure, which includes, from the inside to the outside, the air core 1 of the optical fiber, the large fan-shaped dielectric tube 2, the first type of circular dielectric tube 5, the second type of circular dielectric tube 4, the third type of circular dielectric tube 3 and the outer cladding 6 of the optical fiber. Among them, the outer cladding 6 of the optical fiber is a cylindrical tube with a certain thickness, made of fluoride (ZBLAN) glass, with an outer radius of 250µm and an inner radius of 230µm; the radius (R) of the air core 1 is 50µm, and it is a "negative curvature" core structure. The research shows that the "negative curvature" core structure can well reduce the restrictive loss in the core region. The anti-resonance region is composed of 4 anti-resonance units. Each anti-resonance unit is composed of a large fan-shaped dielectric tube 2 and the first type of circular dielectric tube 5, the second type of circular dielectric tube 4 and the third type of circular dielectric tube 3 nested in each other. The large sector-shaped dielectric tube is formed by intersecting a large circular dielectric tube and the arc boundary of the anti-resonance region and cutting off the part beyond the boundary; the first type of circular dielectric tube and the arc boundary of the anti-resonance region are inscribed and welded; the first type of circular dielectric tube and the second type of circular dielectric tube are inscribed and welded. The thickness T2 of each type of dielectric tube is the same and is 3.1079µm; the radius of the large sector-shaped dielectric tube 2 is is 110µm, the angle between the radius formed by the intersection of the large sector-shaped dielectric tube 2 and the antiresonance boundary and the center of the large sector-shaped dielectric tube 2 and the symmetry axis of the antiresonance unit is is 64.417°; the radius of the first type of circular medium tube 5 and the radius of the second type of circular medium tube 4 The angles between the intersection of the first type of circular dielectric tube 5 and the second type of circular dielectric tube 4 and the center of the fiber core and the symmetry axis of the anti-resonance unit are 35µm and 25µm respectively. The radius of the third type of circular medium tube 3 is 12°. is 30 μm, and the angle between the distance between the centers of the second type circular dielectric tube 4 and the third type circular dielectric tube 3 and the symmetry axis of the anti-resonance unit is It is 33.59°.

[0066] The outer cladding material and the materials of various dielectric tubes of the antiresonance unit in the antiresonance region are all selected as ZBLAN glass, and the refractive index in the wavelength range of 9~11.05µm is 1.2916~1.377. Other materials such as sulfide, selenide, silver halide or telluride can be used as substrate materials. The space between the large fan-shaped dielectric tube and the first type of circular dielectric tube, between the first type of circular dielectric tube and the second type of circular dielectric tube, between the second type of circular dielectric tube and the third type of circular dielectric tube, the air core region and other internal spaces in the antiresonance region are filled with air, and other gases such as H2, CO2, N2 can be used as gas filling.

[0067] The hollow-core optical fiber of the carbon dioxide laser based on the anti-resonance structure designed in this embodiment is simulated and tested using the finite element simulation software COMSOL Multiphysics, and theoretical calculations are performed using the finite element method and combined with the perfect matching layer boundary absorption conditions. The mode field distribution diagram, limiting loss, effective mode field area, and dispersion variation curve of the present invention are obtained by calculation. At the same time, the anti-bending characteristics of the present invention can also be calculated based on the refractive index variation theory under bending conditions.

[0068] Figure 2 The figure shows the mode field distribution and height expression diagram of the fundamental mode at 10.6µm obtained by simulation. It can be seen from the figure that the energy of the hollow core optical fiber with an anti-resonance structure prepared in this embodiment is concentrated in the core area during light wave transmission, indicating that the light is well confined in the core area.

[0069] Figure 3 The figure shows the distribution of the electric field mode contour lines of the fundamental mode at 10.6µm obtained by simulation. It can be seen from the figure that the electric field mode contour lines of the hollow core optical fiber with an anti-resonance structure prepared in this embodiment are all concentrated in the core area during light wave transmission, indicating that the light is well confined in the core area.

[0070] Figure 4 The relationship between the limiting loss of the hollow core fiber fundamental mode and the wavelength in this embodiment is shown in the figure. It can be seen from the figure that the limiting loss of this embodiment is at a low level under the condition of an incident wavelength of 9 to 11.05 µm, and the limiting loss is approximately stable at 5.71×10 -6 ~9.31×10 -3 dB / m. It can be seen that the design structure has a lower restrictive loss in the mid-infrared band of 9~11.05µm.

[0071] Figure 5The relationship between the effective mode field area of ​​the hollow core fiber fundamental mode and the wavelength of this embodiment is shown in the figure. It can be seen from the figure that the change trend of the mode field area of ​​the optical fiber is a slow increase with the change of wavelength, and the mode field area reaches 4620µm when the wavelength of light is 9~11.05µm. 2 The mode field area of ​​the invention has reached 10 3 μm 2 It can transmit high-power and high-energy lasers and improve conversion efficiency.

[0072] Figure 6 The figure is a graph showing the relationship between the dispersion of the hollow core fiber fundamental mode and the wavelength. From the figure, we can see the dispersion of the fiber at the corresponding wavelength. In the wide band of 9~11.05µm, the value of the group velocity dispersion is still stable at -3.63×10 -7 ~2.75×10 -7 ps / (nm·km). According to the fiber dispersion, when the optical signal is transmitted in the optical fiber, the light wave will cause the pulse to expand due to the different propagation speeds, which will affect the quality of the optical fiber transmission data. Therefore, the closer the dispersion is to zero, the higher the optical fiber transmission quality.

[0073] Figure 7 The relationship diagram of the mode field distribution of the fundamental mode of the hollow-core optical fiber of this embodiment at 10.6µm as a function of the bending radius. From the figure, it can be seen that the mode field distribution of the optical fiber changes roughly at different bending radii. When the bending radius is 1cm, the fundamental mode is destroyed and leakage of the fundamental mode occurs in the outer cladding region and the anti-resonance region; when the bending radius is 2cm, the fundamental mode characteristics are not destroyed, but it can be clearly observed that bending has a significant effect on the distribution of the fundamental mode in the core region; when the bending radius is 10cm, the effect of bending on the fundamental mode of the optical fiber is already very small. And from the effective mode refractive index, it can be seen that the effective mode refractive index of the fundamental mode of the hollow-core optical fiber designed by the present invention can quickly stabilize from 0.99812 to 0.99726 under the bending radius. Therefore, it can be seen that the present invention has good anti-bending properties.

[0074] Figure 8 The following is a graph showing the relationship between the bending restriction loss of the fundamental mode of the hollow core optical fiber of this embodiment at 10.6µm and the wavelength. From the figure, we can see that the restriction loss of the optical fiber at the corresponding bending radius is basically stable after the fundamental mode reaches 10cm when the bending radius is 1~40cm. However, there are two high loss points (18cm and 21cm). The high loss at these two points is because the light will leak out through the antiresonance tube at this bending radius, which makes the restriction loss of the fiber core very high. At other bending radii, the restriction loss of the present invention is basically stable at 10 -4 dB / m order of magnitude. It can be seen from this that the present invention has good anti-bending properties.

[0075] In summary, the present invention provides a hollow-core optical fiber based on an anti-resonance structure carbon dioxide laser, which has both low restrictive loss and wide mid-infrared transmission bandwidth, and has good near-zero dispersion characteristics in terms of dispersion, and can achieve low-loss and high-quality mid-infrared light transmission. The specific transmission wavelength is within a wide transmission wavelength range of 9 to 11.05 μm, and can achieve a minimum of 10 -6 dB / m-level restrictive loss; at the same time, the hollow-core optical fiber of the present invention also has a large effective mode field area, low dispersion (near zero dispersion) and low restrictive loss, and can perform high-power, high-quality carbon dioxide laser transmission. Therefore, the hollow-core optical fiber based on the anti-resonance structure carbon dioxide laser proposed in the present invention, on the one hand, solves the dilemma that most of the current hollow-core optical fibers are concentrated in the 1-2µm near-infrared band, while the research in the carbon dioxide laser band is extremely scarce (especially in the 10µm range); on the other hand, by using the advantages of the nested anti-resonance structure hollow-core optical fiber, it has the characteristics of a wider working band, lower restrictive loss and a larger mode field area, which greatly improves the application prospects of the invention. At the same time, it provides a new idea for broadening the working band of hollow-core optical fibers.

[0076] The basic principle, main features and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed for protection.

Claims

1. A hollow-core optical fiber for carbon dioxide laser transmission based on an anti-resonance structure, characterized in that: It includes the outer cladding, anti-resonance region and air core region from outside to inside; The outer cladding covers the anti-resonance region and the air core region; The anti-resonance region includes at least four anti-resonance units with the same structure; the anti-resonance unit is a nested cladding tube structure, and the nested cladding tube structure is a double-layer structure, including a large fan-shaped dielectric tube and a first type of circular dielectric tube, a second type of circular dielectric tube and a third type of circular dielectric tube arranged therein; The large sector-shaped dielectric tube is a large circular dielectric tube; the large circular dielectric tube intersects with the circular arc boundary of the anti-resonance region and cuts off the portion exceeding the boundary; The first type of circular dielectric tube is inscribed and fused with the arc boundary of the anti-resonance region; the first type of circular dielectric tube is inscribed and fused with the second type of circular dielectric tube, and the first type of circular dielectric tube and the second type of circular dielectric tube are axially symmetrically arranged around the core of the hollow-core optical fiber, and neither of them contacts the large fan-shaped dielectric tube; The second type of circular medium tube and the third type of circular medium tube are externally cut and welded; the third type of circular medium tube does not contact the large sector-shaped medium tube; The anti-resonance unit is in an axisymmetric structure relative to the symmetry axis of the large fan-shaped dielectric tube, and the large fan-shaped dielectric tubes of each anti-resonance unit are not in contact with each other; The air core region is composed of a plurality of anti-resonance units uniformly distributed in the anti-resonance region, and is the light guiding region of the hollow core optical fiber.

2. The hollow-core optical fiber for carbon dioxide laser transmission based on an anti-resonance structure according to claim 1, characterized in that: The number of the anti-resonance units is 4 to 10.

3. The hollow-core optical fiber for carbon dioxide laser transmission based on an anti-resonance structure according to claim 1, characterized in that: The material of the outer cladding layer and the various dielectric tube materials of the anti-resonance unit in the anti-resonance region are any one of fluoride, sulfide, selenide, silver halide and telluride.

4. The hollow-core optical fiber for carbon dioxide laser transmission based on an anti-resonance structure according to claim 1, characterized in that: The outer cladding is a cylindrical tube, the outer radius of the cylindrical tube is 240-260 μm, and the inner radius is 215-235 μm.

5. The hollow-core optical fiber for carbon dioxide laser transmission based on an anti-resonance structure according to claim 1, characterized in that: The thicknesses of the large sector-shaped medium tube, the first type of circular medium tube, the second type of circular medium tube and the third type of circular medium tube are all the same.

6. The hollow-core optical fiber for carbon dioxide laser transmission based on an anti-resonance structure according to claim 1, characterized in that: The ratio between the radius of the first type of circular dielectric tube and the radius of the large fan-shaped dielectric tube in the anti-resonance unit is 0.1-0.4; The ratio between the radius of the second type of circular medium tube and the radius of the first type of circular medium tube is 0.6-0.9; The ratio between the radius of the third type of circular medium tube and the radius of the second type of circular medium tube is 1-1.

5.

7. The hollow-core optical fiber for carbon dioxide laser transmission based on an anti-resonance structure according to claim 1, characterized in that: The radius of the large sector-shaped medium tube is 90-130 µm; the radius of the first type of circular medium tube is 20-40 µm; The radius of the second type of circular medium tube is 15-35 µm; the radius of the third type of circular medium tube is 25-45 µm.

8. The hollow-core optical fiber for carbon dioxide laser transmission based on an anti-resonance structure according to claim 1, characterized in that: The angle between the line formed by the intersection of the large sector-shaped dielectric tube and the anti-resonance boundary and the center of the large sector-shaped dielectric tube and the symmetry axis of the anti-resonance unit is 60°~70°; The angle between the line between the intersection of the first type of circular dielectric tube and the second type of circular dielectric tube and the center of the fiber core and the symmetry axis of the anti-resonance unit is 8°~15°; The angle between the line between the centers of the second type of circular dielectric tube and the third type of circular dielectric tube and the symmetry axis of the anti-resonance unit is It is 28°~35°.

9. The hollow-core optical fiber for carbon dioxide laser transmission based on an anti-resonance structure according to claim 1, characterized in that: The air core region is an air hole surrounded by a plurality of anti-resonance units; the radius of the air hole is 40-60 μm.

10. The hollow-core optical fiber for carbon dioxide laser transmission based on an anti-resonance structure according to claim 1, characterized in that: In the anti-resonance region, gas is filled between the large fan-shaped dielectric tube and the first type circular dielectric tube, between the first type circular dielectric tube and the second type circular dielectric tube, between the second type circular dielectric tube and the third type circular dielectric tube, and in the air core region, wherein the refractive index of the gas is 1.

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