A hollow-core antiresonant optical fiber with high extinction ratio and large energy transmission

Abstract

The invention discloses a hollow-core anti-resonance optical fiber with high extinction ratio and large energy transmission, belonging to the field of optical fiber communication technology; the hollow-core anti-resonance optical fiber includes: an outer cladding, an inner cladding and an air core region from outside to inside; the inner cladding includes a plurality of anti-resonance units uniformly distributed in the circumferential direction; the anti-resonance unit includes a first-class circular dielectric tube, an elliptical dielectric tube, a second-class circular dielectric tube and a third-class circular dielectric tube; the elliptical dielectric tube is located in the first-class circular dielectric tube and is internally fused to each other; the second-class circular dielectric tube is located in the elliptical dielectric tube and is internally fused to each other; and the first-class circular dielectric tube and the second-class circular dielectric tube are coaxial; the third-class circular dielectric tube is arranged outside the first-class circular dielectric tube and is externally fused to each other; the third-class circular dielectric tube is externally fused to the first-class circular dielectric tube in the adjacent anti-resonance unit. The hollow-core anti-resonance optical fiber can have low restrictive loss in a large wavelength range and a large mode field area in the near-infrared band.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fiber communication, and in particular relates to a hollow-core anti-resonance optical fiber with high extinction ratio and large energy transmission. Background Art

[0002] Near-infrared light is an electromagnetic wave between visible light and mid-infrared light. According to the definition of ASTM (American Society for Testing and Materials), it refers to electromagnetic waves with a wavelength range of 780 to 2526 nm. With the development of near-infrared long waves in medicine and industry, the demand for near-infrared optical fibers is gradually increasing.

[0003] Existing optical fibers in this band have high losses. Solid-core optical fibers are mostly made of arsenic-sulfide materials with low thermal damage thresholds, while traditional hollow-core optical fibers are mostly metal dielectric film structures with complex manufacturing processes and poor chemical stability. In recent years, hollow-core antiresonant optical fibers have become a research hotspot for near-infrared long-wave transmission due to their simple preparation process, low loss, high thermal damage threshold of quartz substrate materials, and low cost.

[0004] At present, most of the research on hollow-core antiresonant optical fibers is focused on the mid-infrared band and the communication wavelength of 1.55μm, and there are few studies on the performance near 1μm. The structure of general antiresonant optical fibers has relatively good performance in the mid-infrared band and the communication wavelength of 1.55μm, but often performs poorly in the near-infrared band. At present, the laser power of fiber laser systems in the one-micron band is already greater than 1kW, so the optical fiber corresponding to this band should also have low loss in order to transmit large energy. In the patent literature of recent years, the performance of restrictive loss, mode field area and high-order mode extinction ratio in the 1μm band needs to be improved. Summary of the invention

[0005] In view of the deficiencies of the prior art, the purpose of the present invention is to provide a hollow-core anti-resonant optical fiber with high extinction ratio and large energy transmission, which solves the problems in the prior art.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A hollow-core anti-resonance optical fiber with high extinction ratio and large energy transmission, which comprises, from outside to inside, an outer cladding, an inner cladding and an air core region; the inner cladding comprises a plurality of anti-resonance units uniformly distributed in the circumferential direction; the air core region is composed of a plurality of anti-resonance units;

[0008] The anti-resonance unit includes a first type of circular dielectric tube, an elliptical dielectric tube, a second type of circular dielectric tube and a third type of circular dielectric tube; the elliptical dielectric tube is located inside the first type of circular dielectric tube, and the tubes are internally fused to each other; the second type of circular dielectric tube is located inside the elliptical dielectric tube, and the tubes are internally fused to each other; and the first type of circular dielectric tube and the second type of circular dielectric tube are coaxial; the third type of circular dielectric tube is arranged outside the first type of circular dielectric tube, and the tubes are externally fused to each other; and the third type of circular dielectric tube is externally fused to the first type of circular dielectric tube in the adjacent anti-resonance unit.

[0009] Furthermore, the first type of circular medium tube, the elliptical medium tube, the second type of circular medium tube and the third type of circular medium tube have the same thickness and satisfy:

[0010]

[0011] Wherein, t is the thickness, λ is the designed working wavelength, n1 is the refractive index of the cladding tube material, n0 is the refractive index of air, and m is a positive integer.

[0012] Furthermore, the number of the anti-resonance units is 4-6.

[0013] Furthermore, the radius of the first type of circular medium tube is 35-55 μm; the major semi-axis of the elliptical medium tube is 35-55 μm, the minor semi-axis is 10-30 μm, and the radius of the second type of circular medium tube is 10-30 μm.

[0014] Furthermore, the ratio of the major axis to the minor axis of the elliptical medium tube is 1-3.

[0015] Furthermore, the radius of the air core region is 20-40 μm.

[0016] Furthermore, the outer cladding is quartz glass.

[0017] Furthermore, the materials of the first type of circular dielectric tube, the elliptical dielectric tube, the second type of circular dielectric tube and the third type of circular dielectric tube are all quartz glass.

[0018] Furthermore, the outer cladding, the interior of the first type circular dielectric tube, the elliptical dielectric tube, the second type circular dielectric tube and the third type circular dielectric tube, and the air core region are all provided with a medium; and the refractive index of the medium is 1.

[0019] A night vision device comprises the above-mentioned hollow-core anti-resonance optical fiber with high extinction ratio and large energy transmission.

[0020] Beneficial effects of the present invention:

[0021] The anti-resonant hollow-core optical fiber proposed in the present invention can achieve lower leakage loss. In this optical fiber structure, a smaller cladding tube is nested in the cladding tube surrounding the hollow core, which can provide stronger light confinement in the core, so that the hollow-core anti-resonant optical fiber has low limiting loss in the 0.8-1.3μm band and 1500μm 2 It has a larger mode field area than the above, and has good single-mode characteristics near 1μm, and a simple structure, which meets the needs of optical communication and fiber optic sensing. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 This is a schematic diagram of the hollow core anti-resonant optical fiber structure of the present invention.

[0024] Figure 2 It is an enlarged view of the local details of the nested structure in the hollow-core antiresonant optical fiber of the present invention;

[0025] Figure 3 It is a diagram of the mode field distribution and height expression of the fundamental mode of the present invention;

[0026] Figure 4 The high-order mode LP of the present invention 11 Mode field distribution diagram of

[0027] Figure 5 It is a schematic diagram of the variation of limiting loss of the fundamental mode and the higher-order mode with wavelength in the present invention;

[0028] Figure 6 is a schematic diagram of the variation of the high-order mode extinction ratio with wavelength in the present invention;

[0029] Figure 7 It is a schematic diagram of the change of mode field area with wavelength in the present invention.

[0030] In the figure: 1-air core region, 2-first type circular dielectric tube, 3-elliptical dielectric tube, 4-second type circular dielectric tube, 5-third type circular dielectric tube, 6-outer cladding. DETAILED DESCRIPTION

[0031] 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.

[0032] like Figure 1 As shown, a hollow-core anti-resonance optical fiber with high extinction ratio and large energy transmission comprises, from outside to inside, an outer cladding 6, an inner cladding and an air core region 1; the inner cladding is uniformly distributed with anti-resonance units in a circular pattern; the air core region 1 is composed of a plurality of anti-resonance units;

[0033] like Figure 2 As shown, the anti-resonance unit includes a first type of circular dielectric tube 2, an elliptical dielectric tube 3, a second type of circular dielectric tube 4 and a third type of circular dielectric tube 5; the elliptical dielectric tube 3 is located in the first type of circular dielectric tube 2, and they are internally fused to each other; the second type of circular dielectric tube 4 is located in the elliptical dielectric tube 3, and they are internally fused to each other, and the first type of circular dielectric tube 2 and the second type of circular dielectric tube 4 are coaxial; the third type of circular dielectric tube 5 is arranged outside the first type of circular dielectric tube 2; the first type of circular dielectric tube 2 and the third type of circular dielectric tube 5 are externally tangent and fused to the surface; and the third type of circular dielectric tube 5 is also externally tangent and fused to the first type of circular dielectric tube 2 in the adjacent anti-resonance unit;

[0034] Among them, the first type of circular medium tube 2, the elliptical medium tube 3, the second type of circular medium tube 4 and the third type of circular medium tube 5 have the same thickness, satisfying:

[0035]

[0036] Wherein, t is the thickness, λ is the designed working wavelength, n1 is the refractive index of the cladding tube material, n0 is the refractive index of air, and m is a positive integer; in this embodiment, the thickness t is 1.19 μm.

[0037] In this embodiment, the number of anti-resonance units is 4; in other embodiments, the number of anti-resonance units may be 4-6.

[0038] In this embodiment, the radius of the air core region 1 is 30 μm, the radius of the first type circular dielectric tube 2 is R=45 μm, and the ratio of the major axis to the minor axis of the elliptical dielectric tube 3 is is 2.25, the radius of the second type circular medium tube 4 is a=20μm, and the third type circular medium tube 5 is just tangent to the two adjacent first type circular medium tubes 2, so r is calculated to be about 8.033;

[0039] In other embodiments, the radius of the air core region 1 is 20-40 μm, the radius of the first type circular medium tube 2 is 35-55 μm; the long semi-axis of the elliptical medium tube 3 is 35-55 μm, the short semi-axis is 10-30 μm, and the ratio of the long axis to the short axis of the elliptical medium tube 3 is 1-3; the radius of the second type of circular medium tube 4 is 10-30 μm.

[0040] In this embodiment, the outer cladding 6 is made of quartz glass with a thickness of 30 μm; the materials of the first type circular dielectric tube 2 , the elliptical dielectric tube 3 , the second type circular dielectric tube 4 and the third type circular dielectric tube 5 are also quartz glass.

[0041] The outer cladding 6, the interior of the first type circular dielectric tube 2, the elliptical dielectric tube 3, the second type circular dielectric tube 4 and the third type circular dielectric tube 5 and the air core region 1 are all provided with medium; the medium is air, and the refractive index is 1.

[0042] from Figure 3 It can be seen from the mode field distribution diagram of the fundamental mode that the energy of the hollow-core antiresonant optical fiber in this embodiment is concentrated in the core region during transmission, indicating that the light is confined in the core region.

[0043] Figure 4 What is calculated is a typical high-order mode in hollow-core antiresonant optical fiber - LP11 mode, which is a kind of high-order mode. Under the condition of constant fundamental mode loss, the greater the high-order mode loss, the greater the high-order mode extinction ratio and the better the single-mode characteristics. Figure 4 This indicates that a clear high-order mode exists in some wavelength bands of the optical fiber of the present invention.

[0044] Figure 5 Schematic diagram of the variation of limiting loss of the fundamental mode and the high-order mode with wavelength in this embodiment. Figure 5 It can be seen that the limiting loss of the fundamental mode of this embodiment is at a relatively low level under the condition of incident wavelength of 0.8-1.3 μm, which is 10 -5 dB / km, while existing fiber optic simulations are generally below 10 -3 It is about 2 orders of magnitude lower than the existing photonic crystal fiber.

[0045] Figure 6It is a schematic diagram of the variation of the high-order mode extinction ratio with wavelength in this embodiment; the high-order mode extinction ratio is defined as the ratio of the minimum high-order mode loss to the fundamental mode loss in the optical fiber. The larger the value of the high-order mode extinction ratio, the faster the core high-order mode energy decays than the core fundamental mode energy per unit length, which can effectively filter out unnecessary high-order modes and ensure the high purity of the optical fiber fundamental mode. Therefore, the maximum value of 1968.6 is reached when the wavelength of light is 1μm, and the high-order mode extinction ratio also exceeds 1000 at 1.15μm. Therefore, the designed optical fiber working conditions are mainly at a wavelength of 1μm, so the single-mode characteristics of the optical fiber under working conditions are very excellent.

[0046] Figure 7 This is a schematic diagram of the change of mode field area with wavelength in this embodiment; in high-power laser transmission, if the mode field area is small, the optical fiber will produce very high nonlinear effects, or even damage the optical fiber. Therefore, the optical fiber with a larger mode field area will have a wider range of applications. Figure 7 It can be seen that the mode field area of ​​the optical fiber is always 1700μm when the optical wavelength is 0.8-1.25μm. 2 Above, and reached a maximum value of 1762.2μm at 1.1μm 2 , optical fiber with this mode field area size can theoretically transmit high-power lasers.

[0047] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0048] The above shows and describes the basic principles, main features and advantages of the present invention. 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 to be protected.

Claims

1. A hollow-core antiresonant optical fiber with high extinction ratio and large energy transmission, characterized in that: From outside to inside, it includes: an outer cladding, an inner cladding and an air core region; the inner cladding includes a plurality of anti-resonance units uniformly distributed in the circumferential direction; the air core region is composed of a plurality of anti-resonance units; The anti-resonance unit includes a first type of circular dielectric tube, an elliptical dielectric tube, a second type of circular dielectric tube and a third type of circular dielectric tube; the elliptical dielectric tube is located inside the first type of circular dielectric tube, and the tubes are internally fused to each other; the second type of circular dielectric tube is located inside the elliptical dielectric tube, and the tubes are internally fused to each other; and the first type of circular dielectric tube and the second type of circular dielectric tube are coaxial; the third type of circular dielectric tube is arranged outside the first type of circular dielectric tube, and the tubes are externally fused to each other; and the third type of circular dielectric tube is externally fused to the first type of circular dielectric tube in the adjacent anti-resonance unit.

2. The hollow-core antiresonant optical fiber with high extinction ratio and large energy transmission according to claim 1, characterized in that: The first type of circular medium tube, the elliptical medium tube, the second type of circular medium tube and the third type of circular medium tube have the same thickness and meet the following requirements: Wherein, t is the thickness, λ is the designed working wavelength, n1 is the refractive index of the cladding tube material, n0 is the refractive index of air, and m is a positive integer.

3. The hollow-core antiresonant optical fiber with high extinction ratio and large energy transmission according to claim 1, characterized in that: The number of the anti-resonance units is 4-6.

4. The hollow-core antiresonant optical fiber with high extinction ratio and large energy transmission according to claim 1, characterized in that: The radius of the first type of circular medium tube is 35-55 μm; the major semi-axis of the elliptical medium tube is 35-55 μm, and the minor semi-axis is 10-30 μm; the radius of the second type of circular medium tube is 10-30 μm.

5. A hollow-core antiresonant optical fiber with high extinction ratio and large energy transmission according to claim 1 or 4, characterized in that: The ratio of the major axis to the minor axis of the elliptical medium tube is 1-3.

6. The hollow-core antiresonant optical fiber with high extinction ratio and large energy transmission according to claim 1, characterized in that: The radius of the air core region is 20-40 μm.

7. The hollow-core antiresonant optical fiber with high extinction ratio and large energy transmission according to claim 1, characterized in that: The outer cladding is made of quartz glass.

8. The hollow-core anti-resonant optical fiber with high extinction ratio and large energy transmission according to claim 1, characterized in that: The materials of the first type of circular dielectric tube, the elliptical dielectric tube, the second type of circular dielectric tube and the third type of circular dielectric tube are all quartz glass.

9. The hollow-core antiresonant optical fiber with high extinction ratio and large energy transmission according to claim 1, characterized in that: The outer cladding, the interior of the first type circular dielectric tube, the elliptical dielectric tube, the second type circular dielectric tube and the third type circular dielectric tube and the air core area are all provided with a medium; and the refractive index of the medium is 1.

10. A night vision device, characterized in that: A hollow-core antiresonant optical fiber with high extinction ratio and large energy transmission comprising the method described in any one of claims 1 to 9.

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