Single-mode hollow-core anti-resonance optical fiber for transmitting high-power laser

Abstract

The invention relates to a single-mode hollow-core anti-resonance optical fiber for transmitting high-power laser, the single-mode hollow-core anti-resonance optical fiber comprises a cladding layer and a fiber core which are sequentially arranged from outside to inside, the cladding layer comprises an outer cladding layer and an inner cladding layer, the inner cladding layer comprises a plurality of anti-resonance layer units, each anti-resonance layer unit comprises a first anti-resonance layer, a second anti-resonance layer and a thin wall, the first anti-resonance layer and the second anti-resonance layer are tangent in an area close to the outer cladding layer, a tangent point at the tangent position is cut off and is connected through a thin wall, and the tail end of the thin wall is connected with the outer cladding layer. Compared with the prior art, the invention has the advantages of low fundamental mode transmission loss, high single-mode performance, wide spectral bandwidth, high damage threshold, low nonlinear coefficient and the like.

Description

Technical Field

[0001] The invention relates to an anti-resonance optical fiber, in particular to a single-mode hollow-core anti-resonance optical fiber for transmitting high-power laser. Background Art

[0002] High-power lasers refer to lasers ranging from several kilowatts to megawatts, which are widely used in industrial fields such as laser cutting, laser marking and laser grinding, as well as in the military field. Among them, high-power single-mode lasers perform well in industrial applications, especially in cutting, welding, marking, etc. Their high-quality laser beams can achieve precise processing and efficient processing of materials, improving the efficiency and quality of industrial production. For example, in metal cutting, high-power single-mode lasers can provide high-precision and high-speed processing methods; in laser welding, high-power single-mode lasers are widely used in the automotive, aviation and electronics industries due to their precision and flexibility.

[0003] There are some inherent defects when solid-core optical fiber transmits high-power single-mode lasers. During the high-power laser transmission process, the optical fiber may be damaged due to excessive laser power, resulting in reduced transmission performance or optical fiber breakage; and due to factors such as optical fiber loss and dispersion, its transmission distance will be limited. The use of hollow-core optical fiber can solve these problems well.

[0004] Hollow-core antiresonant fiber is an important research direction in fiber optics. With its specific microstructure design, it can confine light in the fiber core and reduce the overlap of the light field and the quartz area. Compared with traditional solid-core fiber, hollow-core fiber overcomes intrinsic losses such as material and scattering, and in principle can achieve ultra-low loss light transmission; in addition, it also has the advantages of low latency, low dispersion, low nonlinearity, high optical damage threshold, anti-interference and high flexibility of being able to be filled with liquid or gas. It has broad application prospects in the fields of high-power pulsed laser transmission, ultrafast optics and nonlinear optics, and promotes the rapid development of fiber optics.

[0005] By designing and optimizing the microstructure in the cladding of hollow-core antiresonant fibers, the restrictive loss in the fiber can be reduced. In addition, due to its simple cladding structure, the internal structure and specific dimensions of the hollow-core antiresonant fiber can be flexibly designed according to a specific transmission wavelength and practical application requirements.

[0006] Hollow-core optical fiber has been rapidly developed due to its excellent characteristics such as low delay, low loss, low dispersion and high damage threshold. Although the loss of hollow-core antiresonant optical fiber has been as low as 0.08dB / km, the characteristic of maintaining single-mode transmission is not obvious.

[0007] After searching, Chinese patent publication number CN119247539A discloses a high single-mode low-loss hollow-core anti-resonant optical fiber, which specifically discloses an outer cladding and an inner cladding, wherein the inner cladding is composed of nested structural units, which are arranged along the circumference of the inner wall of the outer cladding and connected to the inner wall of the outer cladding, and the central cavity covered by the inner cladding forms a fiber core, and the nested structural unit includes two layers of nested glass tubes with different radii, including an outer nested glass tube and an inner nested glass tube. However, the existing patent has problems such as high loss.

[0008] Therefore, how to design a hollow-core antiresonant optical fiber that can maintain single-mode characteristics while maintaining low loss, so as to achieve the transmission of high-power single-mode laser, becomes a technical problem that needs to be solved. Summary of the invention

[0009] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a single-mode hollow-core anti-resonant optical fiber for transmitting high-power lasers with low fundamental mode transmission loss, wide spectral bandwidth, high damage threshold, good single-mode characteristics and low nonlinearity.

[0010] The purpose of the present invention can be achieved by the following technical solutions:

[0011] According to one aspect of the present invention, a single-mode hollow-core antiresonant optical fiber for transmitting high-power laser light is provided, comprising a cladding and a core arranged in sequence from the outside to the inside, wherein the cladding comprises an outer cladding and an inner cladding, wherein the inner cladding comprises a plurality of antiresonant layer units, wherein each of the antiresonant layer units comprises a first antiresonant layer, a second antiresonant layer and a thin wall, wherein the first antiresonant layer and the second antiresonant layer are tangent to each other near the outer cladding region, the tangent point at the tangent point is cut off and connected with a thin wall, and the end of the thin wall is connected to the outer cladding.

[0012] As a preferred technical solution, there are five anti-resonance layer units, and the intervals between adjacent anti-resonance layer units are equal.

[0013] As a preferred technical solution, the cut width a of the first anti-resonance layer and the second anti-resonance layer is 7.5-8.5 μm.

[0014] As a preferred technical solution, the length L of the thin wall is 3.5-4.5 μm.

[0015] As a preferred technical solution, the thickness t of the first anti-resonance layer, the second anti-resonance layer and the thin wall is consistent, and t and the transmission wavelength meet the condition

[0016]

[0017] Where n is the refractive index of silica glass, λ is the transmission wavelength, and m is a positive integer.

[0018] As a preferred technical solution, the thickness t is 0.75-0.85 μm.

[0019] As a preferred technical solution, the second anti-resonance layer is nested in the first anti-resonance layer.

[0020] As a preferred technical solution, the diameter c of the first anti-resonance layer is 16-17 μm, and the diameter b of the second anti-resonance layer is 7.8-8.5 μm.

[0021] As a preferred technical solution, the diameter d of the outer cladding is 110-150 μm.

[0022] As a preferred technical solution, the fiber core radius r is 13.5-14.5 μm.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] 1) The present invention cuts off the connection point between the first anti-resonance layer and the second anti-resonance layer, and uses a thin wall to support each unit anti-resonance layer. Cutting off the connection point can further reduce the restrictive loss, and can make the high-order mode leak easily, so that the optical fiber maintains good single-mode characteristics; and the optical fiber structure is simple and easy to process and manufacture;

[0025] 2) The hollow-core antiresonant optical fiber of the present invention can realize low-loss transmission of high-power laser. In the transmission wavelength range of 1010-1130nm, the total loss of the fundamental mode is less than 0.4dB / km, the total loss of the high-order mode is greater than 560dB / km, and the suppression ratio of the high-order mode is greater than 2000; the 1010-1130nm band includes the wavelengths of 1064nm and 1080nm of high-power lasers commonly used in the existing industry, so the hollow-core optical fiber of the present invention has great application prospects in the industrial field.

[0026] 3) The total fundamental mode loss of the hollow core antiresonant optical fiber of the present invention at 1064nm and 1080nm is 0.25dB / km and 0.24dB / km respectively. The high-order mode suppression ratios are 2391 and 2645 respectively; therefore, the hollow core antiresonant optical fiber of the present invention can transmit lasers of 1064nm and 1080nm wavelengths with low loss and can maintain good single-mode characteristics.

[0027] 4) The hollow-core antiresonant optical fiber of the present invention has good tuning characteristics. By further optimizing its structure, the loss can be further reduced and the single-mode characteristics can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the cross-sectional structure of an optical fiber in an embodiment of the present invention.

[0029] Figure 2This is a fundamental mode electric field distribution diagram in an implementation case of the present invention.

[0030] Figure 3 This is a high-order mode electric field distribution diagram in an implementation case of the present invention.

[0031] Figure 4 This is a graph showing how fundamental mode loss varies with transmission wavelength in an implementation example of the present invention.

[0032] Figure 5 This is a graph showing how the high-order mode loss varies with the transmission wavelength in an implementation example of the present invention.

[0033] Figure 6 This is a graph showing how the high-order mode suppression ratio varies with the transmission wavelength in an implementation example of the present invention.

[0034] Figure 7 This is a graph showing the variation of the nonlinear coefficient with the transmission wavelength in an implementation example of the present invention.

[0035] Among them, 1 is the outer cladding, 2 is the second anti-resonance layer, 3 is the first anti-resonance layer, 4 is the core, and 5 is the thin wall. DETAILED DESCRIPTION

[0036] 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 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 should fall within the scope of protection of the present invention.

[0037] Example

[0038] like Figure 1 As shown, a single-mode hollow-core antiresonant optical fiber for transmitting high-power lasers includes a high-refractive-index cladding and a low-refractive-index core 4 arranged in sequence from the outside to the inside, wherein the cladding includes an outer cladding 1 and an inner cladding, wherein the outer cladding covers the inner cladding and the core, and the material is silica glass with a refractive index of n.

[0039] The inner cladding includes a plurality of anti-resonance layer units, each of which includes a first anti-resonance layer 3, a second anti-resonance layer 2 and a thin wall 5. The wall thickness of the anti-resonance layer is t and the material is silicon dioxide glass with a refractive index of n.

[0040] The diameter of the first antiresonance layer 3 of the hollow-core antiresonance optical fiber is c, the diameter of the second antiresonance layer 2 is b, the second antiresonance layer 2 is nested in the first antiresonance layer 3, the first antiresonance layer 3 and the second antiresonance layer 2 are tangent to each other in a region close to the outer cladding 1, the tangent points at the tangent points are cut off and connected with a thin wall 5, the end of the thin wall 5 is connected to the outer cladding 1 to support the antiresonance layer.

[0041] The above design method can further reduce the restrictive loss of the fundamental mode, while also increasing the leakage loss of the higher-order mode, maintaining good single-mode characteristics. Through theoretical simulation, in the 1010-1130nm band, the fundamental mode loss is as low as 0.4dB / km, the higher-order mode loss is higher than 560dB / km, the higher-order mode suppression ratio is higher than 2000, and has a very low nonlinear coefficient.

[0042] There are five anti-resonance layer units, and the intervals between adjacent anti-resonance layer units are equal.

[0043] The thickness t of the first anti-resonance layer 3, the second anti-resonance layer 2 and the thin wall 5 is consistent, and t and the transmission wavelength meet the condition

[0044]

[0045] Where n is the refractive index of silica glass, λ is the transmission wavelength, m is a positive integer, and in the present invention, the value of m is 2, and the value of t is 0.75-0.85 μm. .

[0046] like Figure 1 As shown, the cut width a of the first antiresonance layer 3 and the second antiresonance layer 2 is 7.5-8.5 μm. The length L of the thin wall 5 is 3.5-4.5 μm. The thickness t is 0.75-0.85 μm. The diameter c of the first antiresonance layer 3 is 16-17 μm, and the diameter b of the second antiresonance layer 2 is 7.8-8.5 μm. The diameter d of the outer cladding 1 is 110-150 μm. The radius r of the core 4 is 13.5-14.5 μm.

[0047] The specific manufacturing process of the inner cladding of this embodiment is as follows: first, the second antiresonance layer 2 is nested in the first antiresonance layer 3, and the second antiresonance layer 2 is tangent to the first antiresonance layer 3 in the area close to the outer cladding 1; then, the connection point between the first antiresonance layer 3 and the second antiresonance layer 2 is cut off.

[0048] The matrix material of the hollow core anti-resonance optical fiber is silica glass, and its refractive index n is 1.4517-1.448. The core of the hollow core anti-resonance optical fiber is air, and its refractive index is 1.

[0049] In the hollow core antiresonant optical fiber, the electric field distribution of the fundamental mode is as follows: Figure 2 As shown in Figure 1, it can be seen that the electric field of the fundamental mode is confined in the fiber core and has very small transmission loss. The electric field distribution of the higher-order mode is shown in Figure 1. Figure 3 As shown, it can be seen that a part of the electric field of the high-order mode is leaked through the first anti-resonance layer, causing the high-order mode to be leaked.

[0050] In the hollow core antiresonant optical fiber, the fundamental mode loss varies with the transmission wavelength as follows: Figure 4 As shown in Figure 2, it can be seen that the limiting loss is very low in the anti-resonance window; the main factor affecting the total loss is the surface scattering loss; the loss of the high-order mode varies with the transmission wavelength as shown in Figure 2. Figure 5 As shown in the figure, it can be seen that the total loss of the high-order mode is mainly the limiting loss, and the minimum total loss is 560dB / km; the change of the high-order mode suppression ratio with the transmission wavelength is shown in Figure 6 As shown, it can be seen that at a wavelength of 1010-1130nm, the high-order mode suppression ratio is greater than 2000.

[0051] In the hollow core antiresonant optical fiber, the nonlinear coefficient varies with the transmission wavelength as follows: Figure 7 As shown, within the transmission wavelength range, the nonlinear coefficient decreases with the increase of wavelength. Within 1010-1130nm, the nonlinear coefficient is less than 0.00055, which is suitable for the transmission of high-power lasers.

[0052] In summary, the single-mode hollow core anti-resonant optical fiber for transmitting high-power lasers described in the present invention has a total fundamental mode transmission loss of less than 0.4 dB / km, a total high-order mode transmission loss of more than 560 dB / km, and a high-order mode suppression ratio of more than 2000 in the 1010-1130 nm band, so low-loss transmission can be achieved while maintaining good single-mode characteristics. The transmission light wavelength of 1010-1130 nm includes the laser wavelengths of 1064 nm and 1080 nm commonly used in industrial processing. According to theoretical calculations, the nonlinear coefficient is very small, so the single-mode hollow core anti-resonant optical fiber described in the present invention can be used to transmit high-power lasers.

[0053] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A single-mode hollow-core anti-resonant optical fiber for transmitting high-power laser light, comprising a cladding and a core (4) arranged in sequence from outside to inside, wherein the cladding comprises an outer cladding (1) and an inner cladding, wherein the inner cladding comprises a plurality of anti-resonant layer units, characterized in that: Each of the anti-resonance layer units comprises a first anti-resonance layer (3), a second anti-resonance layer (2) and a thin wall (5); the first anti-resonance layer (3) and the second anti-resonance layer (2) are tangent to each other in a region close to the outer cladding (1); the tangent point at the tangent point is cut off and connected with the thin wall (5); the end of the thin wall (5) is connected to the outer cladding (1).

2. A single-mode hollow-core anti-resonant optical fiber for transmitting high-power laser according to claim 1, characterized in that: There are five anti-resonance layer units, and the intervals between adjacent anti-resonance layer units are equal.

3. A single-mode hollow-core anti-resonant optical fiber for transmitting high-power laser according to claim 1, characterized in that: The cut width a of the first anti-resonance layer (3) and the second anti-resonance layer (2) is 7.5-8.5 μm.

4. The single-mode hollow-core anti-resonant optical fiber for transmitting high-power laser according to claim 1, characterized in that: The length L of the thin wall (5) is 3.5-4.5 μm.

5. The single-mode hollow-core anti-resonant optical fiber for transmitting high-power laser according to claim 1, characterized in that: The thickness t of the first anti-resonance layer (3), the second anti-resonance layer (2) and the thin wall (5) is consistent, and t and the transmission wavelength satisfy the condition Where n is the refractive index of silica glass, λ is the transmission wavelength, and m is a positive integer.

6. A single-mode hollow-core anti-resonant optical fiber for transmitting high-power laser according to claim 5, characterized in that: The thickness t is 0.75-0.85 μm.

7. The single-mode hollow-core anti-resonant optical fiber for transmitting high-power laser according to claim 1, characterized in that: The second anti-resonance layer (2) is nested in the first anti-resonance layer (3).

8. A single-mode hollow-core anti-resonant optical fiber for transmitting high-power laser according to claim 1 or 7, characterized in that: The diameter c of the first anti-resonance layer (3) is 16-17 μm, and the diameter b of the second anti-resonance layer (2) is 7.8-8.5 μm.

9. The single-mode hollow-core anti-resonant optical fiber for transmitting high-power laser according to claim 1, characterized in that: The diameter d of the outer cladding (1) is 110-150 μm.

10. The single-mode hollow-core anti-resonant optical fiber for transmitting high-power laser according to claim 1, characterized in that: The radius r of the fiber core (4) is 13.5-14.5 μm.

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