Hollow-core polarization-maintaining optical fiber with double rings and double arcs in orthogonal directions in the inner cladding region

Abstract

The present invention provides a hollow-core polarization-maintaining optical fiber with dual rings and dual arcs in orthogonal directions in the inner cladding region, belonging to the fields of optical communications and laser optoelectronics. The fiber comprises a low effective refractive index region, a high effective refractive index cladding region, and a high effective refractive index inner cladding region. The high effective refractive index inner cladding region includes a ring-shaped antiresonant layer and a negative curvature arc-shaped antiresonant layer. The high effective refractive index cladding region includes a strictly periodic arrangement of regular hexagonal air holes. Through the design of the bandgap cladding and antiresonant cladding, the transmission loss can be reduced to below 10dB / km. Through the double rotational symmetry of the dual rings and dual arcs, the birefringence can be as high as 2×10 ‑4 Compared with the existing hollow-core polarization-maintaining photonic bandgap fiber, the optical fiber of the present invention has the advantages of low transmission loss, high birefringence, bending resistance and single-mode transmission, and has great application value in miniaturized optical fiber sensing, optical fiber communication and high-energy laser transmission systems.

Description

Technical Field

[0001] The present invention relates to the field of optical communication and laser optoelectronic technology, and in particular to a hollow-core polarization-maintaining optical fiber with double rings and double arcs in orthogonal directions in the inner cladding region, which belongs to a high-birefringence polarization-maintaining optical fiber. Background Art

[0002] Polarization-maintaining optical fiber is a basic component of coherent application systems and is widely used in defense industry, aerospace, Internet, industrial processing, medical and other fields.

[0003] In 2015, the V. et al. presented a hollow-core polarization-maintaining fiber at the SPIE International Conference on Optical Fibre Sensors (OFS24) titled "Single-polarization single-mode hollow core photonic bandgap fiber for gyroscope applications." By varying the duty cycle of the horizontal air holes in the hollow-core photonic bandgap fiber, the polarization mode is filtered out to achieve single-polarization transmission characteristics. This fiber is a single-polarization-maintaining fiber, not a high-birefringence polarization-maintaining fiber. In September 2021, Song Ningfang and others from the Beijing University of Aeronautics and Astronautics published a hollow-core polarization-maintaining fiber titled "Single-polarization single-mode hollow-core photonic-bandgap fiber with thin slab waveguide" in the journal Optics Express, Volume 29, Issue 19, Pages 30371-30383. A slab waveguide structure was added in a certain direction in the core of the hollow-core photonic bandgap fiber to couple its high-order mode and a polarization fundamental mode with the slab mode, thereby improving the corresponding high-order mode and polarization fundamental mode losses. The goal achieved was also single-polarization fundamental mode transmission characteristics, and it was not a high-birefringence polarization-maintaining fiber. In August 2021, Guo Yuru et al. from Beijing Jiaotong University published a hollow-core polarization-maintaining fiber with high birefringence and wide single-mode bandwidth in the journal Results in Physics, Vol. 29, p. 104725. The fiber introduces a pair of curved thin walls into the core of a 7-cell hollow-core photonic bandgap fiber to increase the asymmetry of the structure and achieve high birefringence, with a birefringence of up to 10 -3It is of the order of magnitude and can achieve single-mode characteristics and high birefringence characteristics within the wavelength range of 200nm. However, the arc-shaped thin wall has weak constraint on the core mode. Even with the help of a 7-cell small fiber core to ensure single-mode transmission, the mode field intensity at the arc-shaped thin wall is still too large, resulting in large surface scattering loss, inability to achieve long-distance transmission, and poor anti-bending characteristics. Summary of the Invention

[0004] The object of the present invention is to provide a hollow-core polarization-maintaining optical fiber having double rings and double arcs in orthogonal directions in the inner cladding region, which is a high-birefringence polarization-maintaining optical fiber, to solve at least one technical problem existing in the above-mentioned background technology.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides a hollow-core polarization-maintaining optical fiber with double rings and double arcs in orthogonal directions in the inner cladding region, comprising a low effective refractive index region, a high effective refractive index inner cladding region, and a high effective refractive index cladding region; the high effective refractive index cladding region is composed of regular hexagonal air holes formed by thin walls of high refractive index material and arranged periodically in a triangular lattice structure; the low effective refractive index region is an approximately regular hexagonal region formed by first extracting a regular hexagonal air hole from the triangular lattice structure, and then extracting two adjacent regular hexagonal air holes around the triangular lattice structure; a line in the approximately regular hexagonal region The sides of the anti-resonance layer are placed horizontally, and a rectangular coordinate system is established with the center of the approximately regular hexagonal region as the origin; the high effective refractive index inner cladding region is composed of a ring-shaped anti-resonance layer and a negative curvature arc-shaped anti-resonance layer, and the ring-shaped anti-resonance layer and the negative curvature arc-shaped anti-resonance layer are made of a high refractive index material; the double ring-shaped anti-resonance layers are each inscribed in the approximately regular hexagonal region of the low effective refractive index region and are symmetrically placed about the horizontal axis and the vertical axis of the rectangular coordinate system; the double negative curvature arc-shaped anti-resonance layers are each inscribed in the approximately regular hexagonal region of the low effective refractive index region and are symmetrically placed about the horizontal axis and the vertical axis of the rectangular coordinate system.

[0007] Optionally, the regular hexagonal air hole in the high effective refractive index cladding region is an approximately regular hexagonal air hole, each corner of the approximately regular hexagonal air hole is an approximately rounded corner, and the ratio of the diameter of the inscribed circle of the approximately rounded corner to the diameter of the inscribed circle of the approximately regular hexagonal air hole is 0.35 to 0.66.

[0008] Optionally, the center distance between adjacent approximately regular hexagonal air holes is 4.3 to 4.4 μm or 4.6 to 4.9 μm, and the ratio of the diameter of the inscribed circle of the approximately regular hexagonal air hole to the center distance between adjacent approximately regular hexagonal air holes is 0.976 to 0.984.

[0009] Optionally, the thickness of the negative curvature arc-shaped anti-resonance layer and the thickness of the annular anti-resonance layer are 0.43-0.48 μm; the radius of the annular anti-resonance layer is 2.8 μm-3.1 μm, and the annular anti-resonance layer is tangent to the inner wall of the approximately regular hexagonal region.

[0010] Optionally, the radius of the negative curvature arc anti-resonance layer is 13 μm, two ends of the negative curvature arc anti-resonance layer are connected to the inner wall of the approximately regular hexagonal region, and the distance between the negative curvature arc anti-resonance layer and the origin of the rectangular coordinate system is approximately equal to and does not exceed 4.6 μm.

[0011] Optionally, the high refractive index material is high-purity quartz glass, soft glass or polymer, and the area outside the high refractive index material is vacuum, gas or liquid.

[0012] Optionally, the soft glass is soda-lime silicate glass, soda-aluminum silicate glass or soda-borosilicate glass.

[0013] Optionally, the polymer is a photosensitive resin, polyethylene, polyvinyl chloride, phenolic resin, epoxy resin, unsaturated polyester resin, polymethyl acrylate, polycarbonate, styrene-butadiene rubber, butadiene rubber, isoprene rubber or ethylene-propylene rubber.

[0014] Optionally, the gas is air, hydrogen, methane, carbon monoxide, chlorine, ammonia, nitrogen or carbon dioxide.

[0015] Optionally, the liquid is water, ethanol, carbon tetrachloride, benzene, ethyl acetate or octane.

[0016] The present invention addresses the existing problems of high surface scattering loss, inability to bend, and low birefringence. This optical fiber offers advantages such as ultra-low nonlinearity, material absorption, and Rayleigh scattering, as well as an ultra-high damage threshold. The dual-ring, dual-arc antiresonant structure significantly enhances lightwave confinement, confining it primarily to the fiber core while significantly reducing the presence of surface modes. This results in low transmission loss and excellent bending resistance.

[0017] Additional aspects and advantages of the present invention will be set forth in part in the following description, will become apparent from the following description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 This is a schematic diagram of the end face structure of a hollow-core polarization-maintaining optical fiber having double rings and double arcs in orthogonal directions in the inner cladding region according to Example 1 of the present invention.

[0020] Figure 2This is a schematic diagram of the end face structure of a hollow-core polarization-maintaining optical fiber with double rings and double arcs in orthogonal directions in the inner cladding region according to Example 2 of the present invention.

[0021] Among them: 1- low effective refractive index region; 2- high effective refractive index cladding region; 3- high effective refractive index inner cladding region; 4- annular antiresonance layer; 5- negative curvature arc antiresonance layer; 6- regular hexagonal air hole. DETAILED DESCRIPTION

[0022] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0023] Those skilled in the art will understand that unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which this invention belongs.

[0024] It should also be understood that terms, such as those defined in commonly used dictionaries, should be understood to have a meaning consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless as defined herein.

[0025] Those skilled in the art will appreciate that, unless otherwise stated, the singular forms "a," "an," "said," and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the stated features, integers, steps, operations, elements, and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, and / or groups thereof.

[0026] In the description of this specification, reference to the terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" 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. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine and integrate different embodiments or examples described in this specification, as well as features of different embodiments or examples, unless otherwise inconsistent.

[0027] In the description of this specification, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0028] In the description of this specification, the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings. They are only for the convenience of describing the present technology and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, they should not be understood as limiting the present technology.

[0029] Unless otherwise specified or limited, the terms "installed," "connected," "connected," and "disposed" should be understood broadly. For example, they may refer to fixed connection or disposition, detachable connection or disposition, or integral connection or disposition. Those skilled in the art will understand the specific meanings of these terms in this technology based on specific circumstances.

[0030] To facilitate understanding of the present invention, the present invention is further explained below with reference to specific embodiments in conjunction with the accompanying drawings. However, the specific embodiments do not constitute a limitation on the embodiments of the present invention.

[0031] Those skilled in the art should understand that the drawings are merely schematic diagrams of embodiments, and the components in the drawings are not necessarily necessary for implementing the present invention.

[0032] The present invention introduces dual loops and dual arcs in orthogonal directions within the inner cladding region of a 19-cell hollow-core photonic bandgap fiber. The strong core mode confinement of the dual loops and dual arcs enables the use of a larger 19-cell core, effectively reducing the mode field intensity at the introduced dual loops and dual arcs, thereby effectively reducing surface scattering losses, significantly improving single-mode and bend resistance, and enabling long-distance, low-loss transmission. Furthermore, through optimization of the dual loop and dual arc structural parameters, the geometric asymmetry is effectively increased, achieving high birefringence and resulting in a high-performance hollow-core polarization-maintaining fiber. Therefore, hollow-core polarization-maintaining fibers with dual loops and dual arcs in orthogonal directions within the inner cladding region have great potential for application in optical fiber communication systems, optical fiber sensing systems, and particularly miniaturized optical fiber gyroscope systems.

[0033] Example 1

[0034] like Figure 1As shown, in this embodiment 1, a hollow-core polarization-maintaining optical fiber with two rings and two arcs in orthogonal directions in the inner cladding region is provided, comprising a low effective refractive index region 1 (a regular hexagonal dotted frame region in the figure), a high effective refractive index inner cladding region 2, and a high effective refractive index cladding region 3 (a circular dotted frame region with a larger radius in the figure); the high effective refractive index cladding region is composed of regular hexagonal air holes 6 formed by thin walls of high refractive index material and arranged periodically in a triangular lattice; the low effective refractive index region is an approximately regular hexagonal region formed by extracting a regular hexagonal air hole from the above triangular lattice and then extracting two adjacent regular hexagonal air holes around the regular hexagonal air hole. domain; one side of the above-mentioned approximately regular hexagonal region is placed horizontally, and a rectangular coordinate system is established with the center of the approximately regular hexagonal region as the origin of the rectangular coordinate system; the high effective refractive index inner cladding region is composed of a ring-shaped antiresonance layer 4 and a negative curvature arc-shaped antiresonance layer 5, the ring-shaped antiresonance layer and the negative curvature arc-shaped antiresonance layer are made of a high refractive index material, the double ring-shaped antiresonance layers are each inscribed in the approximately regular hexagonal region of the low effective refractive index region and are symmetrically arranged about the horizontal axis and the vertical axis of the rectangular coordinate system, and the double negative curvature arc-shaped antiresonance layers are each inscribed in the approximately regular hexagonal region of the low effective refractive index region and are symmetrically arranged about the horizontal axis and the vertical axis of the rectangular coordinate system.

[0035] The regular hexagonal air hole in the high effective refractive index cladding region is an approximately regular hexagonal air hole, each corner of the approximately regular hexagonal air hole is an approximately rounded corner, and the diameter of the inscribed circle of the approximately rounded corner is d c The ratio of the diameter D of the inscribed circle of the approximately regular hexagon to the center distance Λ of adjacent approximately regular hexagonal air holes is 0.6, the center distance Λ of adjacent approximately regular hexagonal air holes is 4.6 μm, and the ratio of the diameter D of the inscribed circle of the approximately regular hexagonal air holes to the center distance Λ of adjacent approximately regular hexagonal air holes is 0.982.

[0036] The thickness of the negative curvature arc anti-resonance layer and the thickness t of the annular anti-resonance layer are 0.46 μm; the radius R1 of the annular anti-resonance layer is 3 μm, and the annular anti-resonance layer is tangent to the inner wall of the approximately regular hexagonal region; the radius of the negative curvature arc anti-resonance layer is 13 μm, and both ends of the negative curvature arc anti-resonance layer are connected to the inner wall of the approximately regular hexagonal region, and the distance r from the origin of the rectangular coordinate system to the negative curvature arc anti-resonance layer is 13 μm. x Equal to 4.5μm.

[0037] The high refractive index material is high-purity quartz glass with a purity of 99.999%, and the area outside the high refractive index material is air.

[0038] Example 2

[0039] like Figure 2As shown, in this embodiment 2, a hollow-core polarization-maintaining optical fiber with two rings and two arcs in orthogonal directions in the inner cladding region includes a low effective refractive index region 1, a high effective refractive index inner cladding region 2, and a high effective refractive index cladding region 3. The high effective refractive index cladding region is composed of regular hexagonal air holes formed by thin walls of high refractive index material and arranged periodically according to a triangular lattice; the low effective refractive index region is an approximately regular hexagonal region formed by extracting a regular hexagonal air hole 6 from the triangular lattice and then extracting two adjacent regular hexagonal air holes around the triangular lattice; one side of the approximately regular hexagonal region is formed by extracting a regular hexagonal air hole 6 from the triangular lattice and then extracting two adjacent regular hexagonal air holes around the triangular lattice; The device is placed horizontally, and a rectangular coordinate system is established with the center of the approximately regular hexagonal region as the origin of the rectangular coordinate system. The high effective refractive index inner cladding region is composed of an annular antiresonance layer 4 and a negative curvature arc-shaped antiresonance layer 5. The annular antiresonance layer and the negative curvature arc-shaped antiresonance layer are made of a high refractive index material. The dual annular antiresonance layers are each inscribed in the approximately regular hexagonal region of the low effective refractive index region and are symmetrically placed about the horizontal axis and the vertical axis of the rectangular coordinate system. The dual negative curvature arc-shaped antiresonance layers are each inscribed in the approximately regular hexagonal region of the low effective refractive index region and are symmetrically placed about the horizontal axis and the vertical axis of the rectangular coordinate system.

[0040] The regular hexagonal air hole in the high effective refractive index cladding region is approximately a regular hexagon, and each corner of the approximately regular hexagon is approximately rounded, and the diameter of the inscribed circle of the approximately rounded corner is d c The ratio of the diameter D of the inscribed circle of the approximate regular hexagon to the center distance Λ of adjacent approximate regular hexagons is 0.4, the center distance Λ of adjacent approximate regular hexagons is 4.4 μm, and the ratio of the diameter D of the inscribed circle of the approximate regular hexagon to the center distance Λ of adjacent approximate regular hexagons is 0.978.

[0041] The thickness of the negative curvature arc-shaped anti-resonance layer and the thickness t of the annular anti-resonance layer are 0.44 μm, the radius R1 of the annular anti-resonance layer is 2.9 μm, and the annular anti-resonance layer is tangent to the inner wall of the approximately regular hexagonal region; the radius R2 of the negative curvature arc-shaped anti-resonance layer is 13 μm, both ends of the negative curvature arc-shaped anti-resonance layer are in contact with the inner wall of the approximately regular hexagonal region, and the distance between the negative curvature arc-shaped anti-resonance layer and the origin of the rectangular coordinate system is equal to 4.6 μm.

[0042] The high refractive index material is sodium aluminum silicate glass, and the area outside the high refractive index material is alcohol.

[0043] In summary, the hollow-core polarization-maintaining optical fiber with dual rings and dual arcs in orthogonal directions in the inner cladding region described in the embodiment of the present invention is composed of a low effective refractive index region, a high effective refractive index inner cladding region, and a high effective refractive index cladding region. This optical fiber solves the problems of high surface scattering loss, inability to bend and apply, and low birefringence in the prior art. Since this optical fiber is a hollow-core optical fiber, it has the advantages of ultra-low nonlinearity, material absorption, Rayleigh scattering, and ultra-high damage threshold. The presence of the dual-ring dual-arc anti-resonance structure greatly enhances the ability to limit light waves, mainly limiting the light waves to be transmitted in the fiber core, while greatly reducing the presence of surface modes, making its transmission loss low and having good anti-bending characteristics. Hollow-core polarization-maintaining optical fibers with such excellent transmission performance are of great significance in the fields of optical fiber sensing, optical fiber communication, and high-energy laser transmission, especially in optical fiber gyroscope applications.

[0044] Although the above describes the specific embodiments of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solutions disclosed in the present invention without the need for creative work should be included in the scope of protection of the present invention.

Claims

1. A hollow-core polarization-maintaining optical fiber having double loops and double arcs in orthogonal directions in the inner cladding region, characterized in that: It includes a low effective refractive index region, a high effective refractive index inner cladding region, and a high effective refractive index cladding region; the high effective refractive index cladding region is composed of regular hexagonal air holes formed by thin walls of high refractive index material and arranged periodically according to a triangular lattice structure; the low effective refractive index region is an approximately regular hexagonal region formed by first extracting a regular hexagonal air hole from the triangular lattice structure, and then extracting two adjacent circles of regular hexagonal air holes with the hole as the center; one side of the approximately regular hexagonal region is placed horizontally, and a rectangular coordinate system is established with the center of the approximately regular hexagonal region as the origin; The high effective refractive index inner cladding region is composed of an annular antiresonance layer and a negative curvature arc-shaped antiresonance layer, which are made of high refractive index materials. The dual annular antiresonance layers are each inscribed in the approximately regular hexagonal region of the low effective refractive index region and are symmetrically arranged about the horizontal axis and the vertical axis of the rectangular coordinate system. The dual negative curvature arc-shaped antiresonance layers are each inscribed in the approximately regular hexagonal region of the low effective refractive index region and are symmetrically arranged about the horizontal axis and the vertical axis of the rectangular coordinate system.

2. The hollow-core polarization-maintaining optical fiber having double loops and double arcs in orthogonal directions in the inner cladding region according to claim 1, characterized in that: The regular hexagonal air hole in the high effective refractive index cladding region is an approximately regular hexagonal air hole, each corner of the approximately regular hexagonal air hole is an approximately rounded corner, and the ratio of the diameter of the inscribed circle of the approximately rounded corner to the diameter of the inscribed circle of the approximately regular hexagonal air hole is 0.35 to 0.

66.

3. The hollow-core polarization-maintaining optical fiber having double loops and double arcs in orthogonal directions in the inner cladding region according to claim 2, characterized in that: The center distance between adjacent approximately regular hexagonal air holes is 4.3-4.4 μm or 4.6-4.9 μm, and the ratio of the diameter of the inscribed circle of the approximately regular hexagonal air hole to the center distance between adjacent approximately regular hexagonal air holes is 0.976-0.

984.

4. The hollow-core polarization-maintaining optical fiber having double loops and double arcs in orthogonal directions in the inner cladding region according to claim 1, characterized in that: The thickness of the negative curvature arc-shaped anti-resonance layer and the annular anti-resonance layer is 0.43-0.48 μm; the radius of the annular anti-resonance layer is 2.8-3.1 μm, and the annular anti-resonance layer is tangent to the inner wall of the approximately regular hexagonal region.

5. The hollow-core polarization-maintaining optical fiber having double loops and double arcs in orthogonal directions in the inner cladding region according to claim 4, characterized in that: The radius of the negative curvature arc anti-resonance layer is 13 μm, both ends of the negative curvature arc anti-resonance layer are connected to the inner wall of the approximately regular hexagonal region, and the distance between the negative curvature arc anti-resonance layer and the origin of the rectangular coordinate system is approximately equal to and does not exceed 4.6 μm.

6. The hollow-core polarization-maintaining optical fiber having double loops and double arcs in orthogonal directions in the inner cladding region according to claim 1, characterized in that: The high refractive index material is high-purity quartz glass, soft glass or polymer, and the area outside the high refractive index material is vacuum, gas or liquid.

7. The hollow-core polarization-maintaining optical fiber having double loops and double arcs in orthogonal directions in the inner cladding region according to claim 6, characterized in that: Soft glass is soda-lime silicate glass, soda-aluminum silicate glass or soda-borosilicate glass.

8. The hollow-core polarization-maintaining optical fiber having double loops and double arcs in orthogonal directions in the inner cladding region according to claim 6, characterized in that: The polymer is photosensitive resin, polyethylene, polyvinyl chloride, phenolic resin, epoxy resin, unsaturated polyester resin, polymethyl acrylate, polycarbonate, styrene-butadiene rubber, butadiene rubber, isoprene rubber or ethylene-propylene rubber.

9. The hollow-core polarization-maintaining optical fiber having double loops and double arcs in orthogonal directions in the inner cladding region according to claim 6, characterized in that: The gas is air, hydrogen, methane, carbon monoxide, chlorine, ammonia, nitrogen or carbon dioxide.

10. The hollow-core polarization-maintaining optical fiber having double loops and double arcs in orthogonal directions in the inner cladding region according to claim 6, characterized in that: The liquid is water, ethanol, carbon tetrachloride, benzene, ethyl acetate or octane.

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