Hollow-core polarization maintaining optical fiber with double rings and double arcs in orthogonal direction of inner cladding area

Abstract

The invention provides a hollow-core polarization-maintaining optical fiber with double rings and double arcs in the orthogonal direction of an inner cladding region, and belongs to the technical field of optical communication and laser photoelectron. The hollow-core polarization-maintaining optical 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 comprises an annular anti-resonance layer and a negative-curvature arc-shaped anti-resonance layer; and the high effective refractive index cladding region comprises regular hexagonal air holes which are strictly and periodically arranged. Through the design of the band gap cladding and the anti-resonance cladding, the transmission loss can be reduced to below 10dB / km, and through the double-ring double-arc double rotational symmetry, the birefringence can reach 2 * 10 <-4 >. Compared with the existing hollow-core polarization-maintaining photonic band gap optical fiber, the optical fiber has the advantages of low transmission loss, high birefringence, bending resistance and single-mode transmission, and has huge application value in miniaturized optical fiber sensing, optical fiber communication and high-energy laser transmission systems.

Description

Technical Field

[0001] The 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 an 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. published a hollow core polarization-maintaining fiber titled "Single-polarization single-mode hollow core photonic bandgap fiber for gyroscope applications" at the SPIE International Conference on Optical Fibre Sensors (OFS24). The fiber achieves single polarization transmission characteristics by changing the duty cycle of the horizontal air holes in the hollow core photonic bandgap fiber and filtering out the polarization mode. It 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 modes and one polarization fundamental mode with the slab mode, thereby improving the corresponding high-order mode and polarization fundamental mode losses. The goal achieved is also single-polarization fundamental mode transmission characteristics, and it is also 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 improve the asymmetry of the structure and achieve high birefringence. The birefringence can reach 10 -3It can achieve single-mode characteristics and high birefringence characteristics within the wavelength range of 200nm, but the curved thin wall has weak constraint on the core mode. Even with the help of the 7cell small fiber core to ensure single-mode transmission, the mode field intensity at the curved 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 belongs to a high birefringence polarization-maintaining optical fiber, so as 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 an 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 materials arranged periodically in accordance with 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 regular hexagonal air hole as the center; a line in the approximately regular hexagonal region The sides of the two layers are placed horizontally, and a rectangular coordinate system is established with the center of the approximate 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, the annular antiresonance layer and the negative curvature arc-shaped antiresonance layer are made of a high refractive index material, the double annular antiresonance layers are each inscribed in the approximate 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, and the double negative curvature arc-shaped antiresonance layers are each inscribed in the approximate 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 approximately rounded, 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 4.3-4.4 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.

[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-shaped anti-resonance layer is 13 μm, two ends of the negative curvature arc-shaped anti-resonance layer are connected to 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 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] Beneficial effects of the present invention: The optical fiber solves the problems of high surface scattering loss, inability to bend and low birefringence in the prior art. It has the advantages of ultra-low nonlinearity, material absorption, Rayleigh scattering, and ultra-high damage threshold. The existence of the double-ring double-arc anti-resonance structure greatly enhances the ability to limit light waves, mainly limiting the light waves to be transmitted in the fiber core, and greatly reducing the existence of surface modes, so that the transmission loss is low and it has good anti-bending characteristics.

[0017] Additional aspects and advantages of the present invention will be given in part in the following description, which will become obvious from the following description, or may be learned through 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 accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying 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 described in 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 having double rings and double arcs in orthogonal directions in the inner cladding region described in 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 anti-resonance layer; 5-negative curvature arc anti-resonance layer; 6-regular hexagonal air hole. DETAILED DESCRIPTION

[0022] The embodiments of the present invention are described in detail below, and 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 with the same or similar functions. The embodiments described below by the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0023] It should be understood by those skilled in the art 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 that 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 features, integers, steps, operations, elements and / or components, but does not exclude 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, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", 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 one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples, unless they are contradictory.

[0027] In the description of this specification, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and 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. indicate orientations or positional relationships based on the orientations or positional relationships 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 referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present technology.

[0029] Unless otherwise clearly specified or limited, the terms "installed", "connected", "connected", and "set" should be understood in a broad sense, for example, they can be fixedly connected or set, or detachably connected or set, or integrally connected or set. For ordinary technicians in this field, the specific meanings of the above terms in this technology can be understood according to 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, and 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 double rings and double arcs in the orthogonal direction of the inner cladding region of the 19-cell hollow-core photonic bandgap optical fiber. Relying on the double rings and double arcs with strong core mode constraint, a larger 19-cell core can be used, effectively reducing the mode field intensity at the introduced double rings and double arcs, thereby effectively reducing the surface scattering loss, greatly improving the single-mode and anti-bending characteristics, and realizing long-distance low-loss transmission. Moreover, through the optimization of the double ring and double arc structural parameters, the geometric asymmetry is effectively increased, and the high birefringence is achieved, thereby becoming a high-performance hollow-core polarization-maintaining optical fiber. Therefore, the hollow-core polarization-maintaining optical fiber with double rings and double arcs in the orthogonal direction of the inner cladding region has great application potential in optical fiber communication systems, optical fiber sensing systems, and especially 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 double rings and double arcs in orthogonal directions in the inner cladding region is provided, comprising a low effective refractive index region 1 (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 (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 materials 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 from the above triangular lattice, and then extracting two adjacent circles of regular hexagonal air holes with the regular hexagonal air hole as the center. domain; placing one side of the above-mentioned approximately regular hexagonal region in the horizontal direction, and taking the center of the approximately regular hexagonal region as the origin of the rectangular coordinate system to establish a 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 high refractive index material, the double 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, 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 placed 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 4.6μm, 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 between the negative curvature arc anti-resonance layer and the origin of the rectangular coordinate system is 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 double rings and double arcs in orthogonal directions in the inner cladding region comprises 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 materials arranged periodically according to a triangular lattice; the low effective refractive index region is an approximate regular hexagonal region formed by extracting a regular hexagonal air hole 6 from the triangular lattice and then extracting two adjacent circles of regular hexagonal air holes with the regular hexagonal air hole 6 as the center; one side of the approximate regular hexagonal region Placed horizontally, and taking the center of the approximately regular hexagonal region as the origin of the rectangular coordinate system to establish a 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 high refractive index material, the double 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, 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 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, 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 4.4μm, 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 connected to 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 double rings and double arcs in the orthogonal directions of 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 the 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 existence of the double-ring double-arc anti-resonance structure greatly enhances the ability to limit light waves, and mainly limits the light waves to be transmitted in the core. At the same time, the existence of surface modes is greatly reduced, so that its transmission loss is low and it has good anti-bending characteristics. The hollow-core polarization-maintaining optical fiber with such excellent transmission performance is of great significance in the fields of optical fiber sensing, optical fiber communication, and high-energy laser transmission, especially in the application of optical fiber gyroscopes.

[0044] Although the above describes the specific implementation mode 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 without creative work on the basis of the technical solution disclosed in the present invention 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 materials 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 by taking 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, the annular antiresonance layer and the negative curvature arc-shaped antiresonance layer are made of high refractive index material, the double annular antiresonance layers are each inscribed in an 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, and the double negative curvature arc-shaped antiresonance layers are each inscribed in an 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.

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 holes in the high effective refractive index cladding region are approximately regular hexagonal air holes, each corner of the approximately regular hexagonal air holes is approximately rounded, 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 holes 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 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.

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, 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.

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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