A topological insulator core optical fiber and a method of manufacturing the same

Abstract

The application discloses a topological insulator fiber core optical fiber and a preparation method thereof. The optical fiber comprises a fiber core (with a non-zero topological Chern number C≠0) composed of a topological insulator material (Bi2Se3, Bi2Te3 or Sb2Te3), a cladding layer, a transition layer and a coating layer. The transition layer is arranged between the fiber core and the cladding layer, and is used for reducing interface stress and scattering loss. An electrode structure is arranged in the fiber core or the periphery of the fiber core, and is used for adjusting the topological Chern number through an external electric field. The preparation method comprises the steps of fiber core preform preparation, transition layer deposition, cladding layer preparation, optical fiber drawing, coating layer preparation and electrode preparation. The application realizes topologically protected optical fiber transmission, and the optical signal is protected by the topological Chern number in the fiber core, has the outstanding advantages of low transmission loss, bending resistance and adjustable Chern number, and can be applied to optical communication, optical storage and quantum information transmission scenes.

Description

Technical Field

[0001] This invention relates to the fields of optical fiber manufacturing technology and topological photonics technology, specifically to a topologically insulated fiber core and its fabrication method. This invention can be applied to fields such as optical communication, optical storage, quantum information transmission, and fiber optic sensing, and is particularly suitable for applications requiring topological protection for optical signal transmission and storage. Background Technology

[0002] Optical fiber is the fundamental transmission medium for optical communication and optical information processing. Traditional optical fibers consist of a quartz glass core and a cladding, with optical signals propagating within the core through total internal reflection. However, traditional optical fibers are sensitive to bending loss, manufacturing defects, and environmental disturbances, which can easily affect signal transmission quality. Topological insulators are a new class of quantum materials with nontrivial topological states. Their bulk states are insulating while their surface states are conductive. The surface states are topologically protected and immune to defects and perturbations. In recent years, researchers have begun to explore the application of topological insulator materials in optoelectronic devices. Existing topological insulator fiber technologies mainly suffer from the following problems: (i) Incompatibility between topological insulator materials and optical fiber fabrication processes Topological insulator materials (such as Bi₂Se₃ and Bi₂Te₃) have significant differences in processing temperature and material compatibility with traditional silica optical fiber fabrication processes (such as MCVD and OVD). Current technologies make it difficult to directly integrate topological insulator materials into optical fiber structures. (ii) The interface quality between the core and the cladding is difficult to control. The interface between the topological insulator core and the quartz cladding has problems such as thermal expansion coefficient mismatch and large refractive index difference, which leads to large interface scattering loss and affects the quality of optical signal transmission. (iii) Verification of transmission characteristics lacking topology protection Current research on topological insulator optical fibers mainly focuses on material preparation and basic transmission characteristic testing, and quantitative characterization methods and stability criteria for topological protection transmission performance have not yet been established. (iv) Lack of topological Chern number control methods Existing topological insulator fibers lack the design to respond to external fields (electric fields, magnetic fields, etc.), and cannot achieve active control of the topological Chern number, which limits their application in tunable optical devices and information storage. To address the above problems, this invention provides a topological insulator core optical fiber and its preparation method. Summary of the Invention

[0003] (a) Purpose of the invention This invention aims to solve the technical problems in existing topological insulator fiber technology, such as material and process incompatibility, difficulty in controlling interface quality, lack of topological protection verification, and lack of Chern number control methods, and provides a topological insulator core fiber and its preparation method. (II) Technical Solution This invention provides a topologically insulator-core optical fiber, characterized in that it comprises: A fiber core is made of a topological insulator material having a non-zero topological Chern number C≠0; A cladding layer is formed around the periphery of the fiber core, and the refractive index of the cladding layer is lower than that of the fiber core. A transition layer is disposed between the fiber core and the cladding to reduce interfacial stress and scattering loss; A coating layer is applied to the periphery of the outer layer. The topological insulator material includes at least one of Bi2Se3, Bi2Te3 or Sb2Te3, or a ternary alloy system thereof. The diameter of the fiber core is 5μm–50μm. The cladding material is quartz glass or polymer material, and the cladding diameter is 80μm–250μm. The transition layer is made of a material with a refractive index between that of the core and the cladding, and the thickness of the transition layer is 50nm–500nm. The coating is made of polymer material and has a diameter of 150μm–400μm. The topological Chern number C of the topological insulator core optical fiber is determined by the following relationship: Where F is the Berry curvature and S is the closed surface of the Brillouin zone. The projection angle θ of the topological insulator core optical fiber is defined as: Where β_r and β_s satisfy the projection constraint: β_r² + β_s² = 1. The topology protection bandwidth σ_θ of the topology insulator core optical fiber is determined by the following relationship: Where w is the interlayer coupling strength, ħ is the reduced Planck constant, v_F is the Fermi velocity, ΔS = h / 2 is the minimum action quantum, L_w is the characteristic length, and h is the Planck constant. The core of the topological insulator fiber is provided with an electrode structure for applying an external electric field to control the topological Chern number of the topological insulator material. The electrode structure is a pair of parallel electrodes extending along the fiber axial direction, or a ring electrode surrounding the fiber core. This invention also provides a method for preparing a topological insulator core optical fiber, characterized by comprising the following steps: Step 1: Preparation of topological insulator core preforms A core preform of a topological insulator material (at least one of Bi₂Se₃, Bi₂Te₃, or Sb₂Te₃) is prepared using at least one of chemical vapor transport, molecular beam epitaxy, or hot pressing sintering. The diameter of the core preform is 5 mm–20 mm. Step 2: Prepare the transition layer A transition layer material is deposited on the outer surface of the fiber core preform. The transition layer material is at least one of GeO2, Al2O3, or TiO2. The deposition method includes at least one of chemical vapor deposition, sol-gel method, or sputtering method. The thickness of the transition layer is 50 nm–500 nm. Step 3: Prepare the cladding A cladding layer is prepared around the transition layer. When the cladding material is quartz glass, the cladding material is deposited using at least one of external vapor deposition, axial vapor deposition, or plasma-enhanced chemical vapor deposition. When the cladding material is a polymer, the cladding layer is prepared using coating or injection molding methods. Step 4: Fiber drawing The core-transition layer-cladding composite preform prepared in step 3 was drawn on an optical fiber drawing tower. The drawing temperature was determined based on the core and cladding materials, and the drawing speed was 1 m / min–20 m / min. The core and cladding diameters were monitored in real time during the drawing process, and dimensional uniformity was maintained through feedback control. Step 5: Coating preparation A polymer coating layer is applied to the surface of the drawn optical fiber. The coating material is at least one of acrylate or polyimide. The coating layer thickness is 10 μm–100 μm. Step 6: Electrode preparation An electrode structure is fabricated in or around the fiber core. The electrode structure is fabricated using at least one of the following methods: - embedding metal electrode wires during the fabrication of the fiber core preform; - depositing a thin metal film electrode around the fiber core; - forming conductive channels in the cladding. Step 7: Topological Chern Number Verification By measuring the transmission spectrum, electrical transport properties, or magnetic transport properties of the topological insulator core optical fiber, it is verified whether the topological Chern number C of the topological insulator material is non-zero. When C≠0, it is confirmed that the optical fiber has topological protection capability. (III) Beneficial Effects Topology-protected optical transmission: The fiber core is made of a topological insulator material. When the optical signal is transmitted in the fiber core, it is protected by the topological Chern number and is immune to bending, defects and environmental disturbances. Interface optimization design: The transition layer effectively reduces the thermal expansion coefficient mismatch and scattering loss between the fiber core and cladding, improving transmission quality. Adjustable Chern number: The built-in electrode structure supports active adjustment of the topology Chern number via an external electric field, expanding fiber optic functionality. Fabrication process compatibility: The fabrication method is compatible with existing optical fiber drawing processes, enabling large-scale production. Topological protection verification: The topological Chern number state can be quantitatively verified through transmission spectroscopy and transport property measurements. Diverse structural designs: Supports various topological insulator materials and electrode structure designs. Attached Figure Description

[0004] Figure 1 This is a schematic diagram of the cross-sectional structure of a topological insulator fiber core provided in an embodiment of the present invention. Figure 2 A flowchart illustrating the fabrication method of a topological insulator core optical fiber provided in an embodiment of the present invention. Figure 3 This is a schematic diagram of the cross-section of a topological insulator fiber core containing an electrode structure, provided as an embodiment of the present invention. Figure 4 This is a schematic diagram illustrating the topological Chern number verification and control provided in an embodiment of the present invention. Detailed Implementation

[0005] Example 1: Fabrication of Bi2Se3 topological insulator core optical fiber Step 1: Preparation of Bi2Se3 core preforms A chemical vapor deposition (CVD) method was employed, using high-purity Bi and Se as raw materials. The mixture was prepared at a stoichiometric ratio of Bi:Se = 2:3, sealed in a vacuum quartz tube, and placed in a dual-temperature zone tube furnace. The source zone temperature was 750°C, the growth zone temperature was 600°C, and the growth time was 72 hours. This yielded Bi₂Se₃ single-crystal fiber core preforms with a diameter of 10 mm. Step 2: Prepare the transition layer A TiO2 transition layer with a thickness of 200 nm was deposited on the surface of a Bi2Se3 fiber core preform using a sol-gel method. The refractive index of the transition layer is between that of Bi2Se3 (approximately n≈3.5) and quartz (n≈1.45), effectively reducing interface scattering. Step 3: Prepare the cladding A quartz glass cladding layer was deposited around the transition layer using an external vapor deposition method. The deposition temperature was 1200°C–1400°C, and the cladding thickness allowed the composite preform to reach a diameter of 30 mm. Step 4: Fiber drawing The composite preform was placed in an optical fiber drawing tower, and the drawing temperature was 1100°C–1200°C, with a drawing speed of 5 m / min. During the drawing process, the core diameter (target 10 μm) and cladding diameter (target 125 μm) were monitored in real time. Step 5: Coating preparation An acrylic coating layer with a thickness of 50 μm was applied to the surface of the drawn optical fiber. The coating was then cured using UV curing. Step 6: Topological Chern Number Verification The transmission spectrum and electrical transport properties of the fabricated optical fiber were measured to confirm that the topological Chern number C≠0. The resistivity-temperature curve of the fiber core was measured at room temperature, and the insulator-metal transition characteristics were observed. Example 2: Topological insulator core optical fiber with electrode structure Step 1: Prepare a fiber core preform containing electrodes During the fabrication of the Bi2Te3 fiber core preform, two gold wire electrodes were embedded parallel to each other in the center of the preform, with a spacing of 100 μm between the electrodes. The electrode material was high-purity gold wire with a diameter of 50 μm. Steps 2 to 5: (Same as the process in Example 1) Step 6: Electrode lead-out Electrodes were led out at both ends of the optical fiber and connected to an external voltage source. The Chern number of the fiber core was controlled by applying an electric field (0–10V). Experiments showed that when a voltage of 5V was applied, the change in Chern number ΔC ≥ 0.05. Example 3: Verification of Topology Protection Transmission Performance Step 1: Fabrication of topological insulator core optical fiber Bi2Se3 topological insulator core optical fiber with a length of 10m was prepared using the method in Example 1. Step 2: Transmission Loss Measurement The transmission loss of optical fiber was measured using the truncation method. At a wavelength of 1550 nm, the transmission loss of the topologically insulated fiber core was 0.5 dB / m, which is 67% lower than that of the non-topologically insulated fiber core of the same size (approximately 1.5 dB / m). Step 3: Bending Loss Test Bending loss tests were conducted by winding optical fibers around bending rods of different diameters. When the bending radius was ≥10mm, the bending loss of the topological insulated core fiber was ≤0.1dB, which is much lower than the loss of conventional optical fibers at the same bending radius (about 3dB), verifying the effectiveness of topological protection. Terminology Explanation

[0006] Terminology Meaning Topological insulators are topological materials that are insulating in their bulk states and conductive in their surface states, with the surface states being topologically protected. The topological Chern number (C) is a topological invariant describing the topological nontriviality of the band structure of a topological material. C = (1 / 2π)∮F·dS, taking integer values. The projection angle (θ) is a geometric parameter determined by structural and operational parameters, θ = arctan(β_s / β_r), where β_r² + β_s² = 1. The transition layer is an intermediate layer between the fiber core and the cladding to reduce interfacial stress and scattering loss. Chemical vapor transport (CVT) is a method for preparing materials by transporting and depositing materials through gas-phase chemical reactions. Fiber optic drawing towers are devices used to draw fiber optic preforms into thin-diameter optical fibers.

Claims

1. Claim 1 (Independent claim, structure) A topological insulator core optical fiber, characterized in that it comprises: A fiber core is made of a topological insulator material having a non-zero topological Chern number C≠0; A cladding layer is formed around the periphery of the fiber core, and the refractive index of the cladding layer is lower than that of the fiber core. A transition layer is disposed between the fiber core and the cladding to reduce interfacial stress and scattering loss; A coating layer is applied to the periphery of the outer layer.

2. Claim 2 (dependent claim) The topological insulator core optical fiber according to claim 1 is characterized in that: The topological insulator material includes at least one of Bi2Se3, Bi2Te3, or Sb2Te3.

3. Claim 3 (dependent claim) The topological insulator core optical fiber according to claim 1 is characterized in that: The diameter of the fiber core is 5μm–50μm, and the diameter of the cladding is 80μm–250μm.

4. Claim 4 (dependent claim) The topological insulator core optical fiber according to claim 1 is characterized in that: The transition layer is made of at least one of GeO2, Al2O3 or TiO2, and the thickness of the transition layer is 50nm–500nm.

5. Claim 5 (dependent claim) The topological insulator core optical fiber according to claim 1 is characterized in that: An electrode structure is provided in or around the fiber core for applying an external electric field to control the topological Chern number of the topological insulator material.

6. Claim 6 (dependent claim) The topological insulator core optical fiber according to claim 1 is characterized in that: The topological Chern number C is determined by the following relationship: Where F is the Berry curvature and S is the closed surface of the Brillouin zone.

7. Claim 7 (Independent claim, method) A method for fabricating a topologically insulator-core optical fiber, characterized by comprising the following steps: (1) Preparation of fiber core preforms of topological insulator materials; (2) A transition layer is deposited on the outer surface of the fiber core preform; (3) Prepare a cladding layer around the transition layer; (4) The composite preform prepared in step (3) is drawn on an optical fiber drawing tower; (5) Coating the surface of the drawn optical fiber with a polymer coating layer.

8. Claim 8 (dependent claim) The method according to claim 7, characterized in that: The topological insulator material mentioned in step (1) includes at least one of Bi2Se3, Bi2Te3 or Sb2Te3; the fiber core preform is prepared by at least one of chemical vapor transport, molecular beam epitaxy or hot pressing sintering.

9. Claim 9 (dependent claim) The method according to claim 7, characterized in that: The material of the transition layer in step (2) is at least one of GeO2, Al2O3 or TiO2, and the deposition method includes at least one of chemical vapor deposition, sol-gel method or sputtering method.

10. Claim 10 (dependent claim) The method according to claim 7, characterized in that: The method also includes preparing an electrode structure in or around the fiber core.

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