Optical fiber, preparation method thereof and all-optical-fiber phase delayer

Abstract

The invention discloses an optical fiber, a preparation method thereof and an all-optical-fiber phase delayer, and belongs to the technical field of optical fibers. The optical fiber comprises a fiber core and a cladding, the cladding comprises a plurality of air holes which surround the circumference of the fiber core and are periodically distributed, the fiber core is located in the center of the cladding, and each air hole extends in the axial direction of the optical fiber and penetrates through the two ends of the optical fiber; the inner walls of part of the air holes are provided with transition metal chalcogenide layers serving as first air holes, and the rest air holes serve as second air holes; the number of the first air holes is at least two, and the first air holes are symmetrically distributed in the two sides of the fiber core with the fiber core as the symmetry center. Through the arrangement, the birefringence effect is introduced and enhanced, controllable birefringence and beat-length optimization can be achieved, compared with a traditional optical fiber delayer manufacturing process, the length dependence of polarization regulation and control is reduced, integration with an optical fiber system is easy, and the optical fiber environment stability is better.

Description

Technical Field

[0001] This application relates to the field of optical fiber technology, and more specifically, to an optical fiber, a method for fabricating the same, and an all-fiber phase delayer. Background Technology

[0002] In all-fiber systems, polarization state manipulation is a key technology for realizing various optical applications, such as mode-locked fiber lasers, optical communication, and quantum information processing. Currently, a section of birefringent fiber (such as polarization-maintaining fiber) is typically used as a phase delayer to manipulate the polarization state of the all-fiber system. The birefringence effect in the fiber is usually introduced by designing the fiber geometry or by introducing asymmetric stress.

[0003] However, the aforementioned optical fibers have the following problems: 1. Due to the sensitivity of geometric and stress birefringence to the external environment, the performance of traditional optical fiber phase delayers is easily affected by temperature changes, mechanical deformation, etc., leading to instability in polarization control; 2. The manufacturing process of this type of optical fiber is complex, involving fine structural design and material processing, which not only results in high cost but also makes it difficult to apply on a large scale in actual production; 3. Geometric or stress-based birefringent fibers usually have extremely short beat lengths (millimeter level), which greatly increases the difficulty of precise cutting and splicing operations during integration with all-fiber systems. Summary of the Invention

[0004] This application provides an optical fiber, a method for fabricating the same, and an all-fiber phase delayer to improve at least one of the aforementioned technical problems.

[0005] The embodiments of this application are implemented as follows:

[0006] In a first aspect, this application provides an optical fiber including a core and a cladding, the cladding including a plurality of circumferentially and periodically distributed air holes surrounding the core, the core being located at the center of the cladding, and each air hole extending along the axial direction of the optical fiber and penetrating both ends of the optical fiber.

[0007] Among them, some air holes have a transition metal chalcogenide layer on their inner wall as first air holes, and the remaining air holes are used as second air holes.

[0008] The number of first air holes is at least two, and the first air holes are symmetrically distributed on both sides of the fiber core with the fiber core as the center of symmetry.

[0009] The optical fiber provided in this application introduces and enhances the birefringence effect by generating a transition metal chalcogenide layer on the inner wall of the first air hole in the optical fiber, thereby changing the propagation speed of the orthogonal polarization mode. This not only enables controllable birefringence and beat length optimization, but also reduces the length dependence of polarization modulation compared to traditional optical fiber delayer manufacturing processes, making it easier to integrate with optical fiber systems, while also providing better stability in the optical fiber environment.

[0010] In a second aspect, this application provides a method for fabricating an optical fiber, which includes the following steps:

[0011] A bare optical fiber is obtained, which includes a core and a cladding. The cladding includes a plurality of air holes that are circumferentially distributed and periodically arranged around the core. The core is located at the center of the cladding. Each air hole extends along the axial direction of the optical fiber and passes through both ends of the optical fiber. Some of the air holes serve as target air holes for coating, and the remaining air holes serve as second air holes. There are at least two target air holes, which are symmetrically distributed on both sides of the core with the core as the center of symmetry.

[0012] A metal mask is physically adsorbed onto both ends of a bare optical fiber to block the second air hole, exposing the target air hole and obtaining a sealed optical fiber;

[0013] One end of the fiber is placed in an aqueous solution of a transition metal source, so that the transition metal source solution is adsorbed into the target air hole, thus obtaining a wetted fiber.

[0014] A chemical vapor deposition reaction is carried out using a sulfur source and a transition metal source impregnated in an optical fiber as raw materials to grow a transition metal chalcogenide layer on the inner wall of the target air hole to form the first air hole, while simultaneously decomposing the metal mask to obtain the optical fiber.

[0015] The fabrication method provided in this application uses a metal mask to selectively plug the optical fiber end face, enabling the selective adsorption of the transition metal source solution into the target air hole. Then, a chemical vapor deposition reaction is used to grow a transition metal chalcogenide layer on the inner wall of the target air hole to form the first air hole. The above-mentioned fabrication method has the advantages of low fabrication difficulty and the introduction of the transition metal chalcogenide layer into the optical fiber through the inner wall of the first air hole, which changes the propagation speed of the orthogonal polarization mode, thereby introducing and enhancing the birefringence effect. This not only enables controllable birefringence and beat length optimization, but also reduces the length dependence of polarization control compared to traditional optical fiber delayer manufacturing processes, making it easier to integrate with optical fiber systems, while also improving the stability of the optical fiber environment.

[0016] In a third aspect, this application provides an all-fiber phase delayer, which is made from the optical fiber provided in the first aspect of this application or from the optical fiber prepared by the preparation method provided in the second aspect of this application. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the end face of the MoS2 composite optical fiber provided in Embodiment 1 of this application;

[0019] Figure 2 A schematic diagram of the preparation process of the third product provided in Example 1 of this application;

[0020] Figure 3 This is a schematic diagram of the end face of the fiber optic cable provided in Embodiment 1 of this application;

[0021] Figure 4 This is a comparison diagram of the MoS2 composite optical fiber and the bare optical fiber in Embodiment 1 of this application;

[0022] Figure 5 This is a schematic diagram of the optical path system shown in Experimental Example 1;

[0023] Figure 6 Schematic diagrams of 1 / 4, 1 / 2, and 3 / 4 waveplates fabricated from the MoS2 composite optical fiber prepared in Example 1.

[0024] Icons: 10-MoS2 composite optical fiber; 11-fiber core; 12-first air hole; 13-transition metal chalcogenide layer; 14-second air hole; 21-first silicon wafer; 22-patterned gold plating layer; 23-PMMA layer; 24-pyrolysis tape; 25-second silicon wafer; 26-PPC layer; 27-mask area; 28-target air hole. Detailed Implementation

[0025] The embodiments of this application will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of this application. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0026] The following provides a detailed description of the optical fiber, its fabrication method, and the all-fiber phase delay device according to embodiments of this application:

[0027] The first aspect of this application provides an optical fiber, which includes a core and a cladding. The cladding includes a plurality of air holes that are circumferentially distributed and periodically arranged around the core. The core is located at the center of the cladding. Each air hole extends along the axial direction of the optical fiber and passes through both ends of the optical fiber.

[0028] Among them, some air holes have a transition metal chalcogenide layer on their inner wall as first air holes, and the remaining air holes are used as second air holes.

[0029] The number of first air holes is at least two, and the first air holes are symmetrically distributed on both sides of the fiber core with the fiber core as the center of symmetry.

[0030] It is understandable that the fiber core is the solid region located at the center of the optical fiber.

[0031] The cladding in this application includes a plurality of air holes that are circumferentially and periodically distributed around the fiber core. For example, the plurality of air holes can be arranged periodically in a regular hexagonal pattern, that is, the cladding has a multi-layer (e.g., 2 layers, at least 4 layers, generally 5 to 9 layers) air hole structure from the inside (the side closer to the fiber core) outward. The plurality of air holes are rotationally symmetrical about the fiber core, and the center distance between any two adjacent air holes is the same. The shape and size of the plurality of air holes are all the same, for example, all are circular.

[0032] A transition metal chalcogenide layer is set on the inner wall of a portion of the air holes as the first air hole, and the first air holes are symmetrically distributed on both sides of the fiber core with the fiber core as the center of symmetry. That is, by introducing the transition metal chalcogenide layer, the structural symmetry of the fiber can be effectively broken without destroying the intrinsic transmission mode of the fiber, so that the first air hole does not have rotational symmetry. Then, the propagation speed of the orthogonal polarization mode is changed by the transition metal chalcogenide layer, thereby introducing and enhancing the birefringence effect. At the same time, the above setting can not only achieve controllable birefringence and beat length optimization, but also reduce the length dependence of polarization control compared with traditional fiber delayer manufacturing process, making it easier to integrate with fiber optic systems. Moreover, the fiber environmental stability is better, effectively reducing the impact of external factors (such as temperature, humidity and mechanical deformation) on performance. The two-dimensional material fiber phase delayer made from this fiber has extremely high reliability and stability under complex conditions.

[0033] In other words, this application provides a novel technical approach for introducing birefringence effects into optical fibers, expanding the application potential of all-fiber phase delayers under harsh conditions and complex operating scenarios.

[0034] In summary, the optical fiber provided in this application, by setting a transition metal chalcogenide layer in the inner wall of the first air hole in the optical fiber, changes the propagation speed of the orthogonal polarization mode, thereby introducing and enhancing the birefringence effect. This not only enables controllable birefringence and beat length optimization, but also reduces the length dependence of polarization modulation compared to traditional optical fiber delayer manufacturing processes, making it easier to integrate with optical fiber systems, while also providing better stability in the optical fiber environment.

[0035] In some embodiments, the number of first air holes is at least four, and the first air holes are arranged sequentially from the inside to the outside along the radial direction of the optical fiber.

[0036] In this configuration, the innermost first air hole is positioned adjacent to the fiber core; or...

[0037] There are 1-2 second air holes between the innermost first air hole and the fiber core.

[0038] It is understandable that, since the first air holes are symmetrically distributed on both sides of the fiber core with the fiber core as the center of symmetry, the number of the first air holes is an even number.

[0039] When the number of first air holes is at least 4, the first air hole located on the innermost side is positioned adjacent to the fiber core, or the first air hole located on the innermost side is spaced apart from the fiber core by 1-2 second air holes.

[0040] In some embodiments, the number of first air holes is two;

[0041] Each first air hole is disposed adjacent to the fiber core; or...

[0042] There are 1-2 second air holes between each first air hole and the fiber core.

[0043] In some embodiments, the end face of the optical fiber has X-axis and Y-axis directions that are perpendicular to each other and intersect the fiber core, and a plurality of first air holes are arranged at intervals along the X-axis or Y-axis directions.

[0044] The above-mentioned structure is simple, easy to prepare, and has excellent birefringence.

[0045] Optionally, the optical fiber is a photonic crystal fiber.

[0046] Alternatively, the optical fiber may be made of quartz or quartz polymer.

[0047] It should be noted that the thickness of the transition metal chalcogenide layer can be a single layer or a few layers, for example, the thickness of the transition metal chalcogenide layer can be 1-5 layers.

[0048] In some embodiments, the transition metal chalcogenide layer is a single layer.

[0049] By using a single-layer transition metal chalcogenide, the atomically thin two-dimensional material does not introduce additional optical loss and has good flexibility. On the other hand, the atomically thin two-dimensional material has a high refractive index. Introducing the two-dimensional material into the inner wall of the first air hole can effectively break the structural symmetry of the optical fiber without destroying the intrinsic transmission mode of the optical fiber, thereby significantly enhancing the birefringence effect.

[0050] Optionally, the composition of the transition metal chalcogenide layer includes MoS2, MoSe2, MoTe2, WS2, WSe2, WTe2, MoS x Se 2-x MoS x Te 2-x MoTex Se 2-x WS x Se 2-x WS x Te 2-x ,WTe x Se 2-x At least one of them, where 0 < x < 2.

[0051] A second aspect of this application provides a method for fabricating an optical fiber, comprising the following steps:

[0052] A bare optical fiber is obtained, which includes a core and a cladding. The cladding includes a plurality of air holes that are circumferentially distributed and periodically arranged around the core. The core is located at the center of the cladding. Each air hole extends along the axial direction of the optical fiber and passes through both ends of the optical fiber. Some of the air holes serve as target air holes for coating, and the remaining air holes serve as second air holes. There are at least two target air holes, which are symmetrically distributed on both sides of the core with the core as the center of symmetry.

[0053] A metal mask is physically adsorbed onto both ends of a bare optical fiber to block the second air hole, exposing the target air hole and obtaining a sealed optical fiber;

[0054] One end of the fiber is placed in an aqueous solution of a transition metal source, so that the transition metal source solution is adsorbed into the target air hole, thus obtaining a wetted fiber.

[0055] A chemical vapor deposition reaction is carried out using a sulfur source and a transition metal source impregnated in an optical fiber as raw materials to grow a transition metal chalcogenide layer on the inner wall of the target air hole to form the first air hole, while simultaneously decomposing the metal mask.

[0056] The fabrication method provided in this application uses a metal mask to selectively plug the optical fiber end face, enabling the selective adsorption of the transition metal source solution into the target air hole. Then, a chemical vapor deposition reaction is used to grow a transition metal chalcogenide layer on the inner wall of the target air hole to form the first air hole. The above-mentioned fabrication method has the advantages of low fabrication difficulty and the introduction of the transition metal chalcogenide layer through the inner wall of the first air hole into the fabricated optical fiber, which changes the propagation speed of the orthogonal polarization mode, thereby introducing and enhancing the birefringence effect. This not only enables controllable birefringence and beat length optimization, but also reduces the length dependence of polarization control compared to traditional optical fiber delayer manufacturing processes, making it easier to integrate with optical fiber systems, while also improving the stability of the optical fiber environment.

[0057] It should be noted that the number of target air holes is even and at least two.

[0058] For example, when the number of target air holes is at least four, the target air holes are arranged sequentially from the inside to the outside along the radial direction of the optical fiber. The innermost target air hole is arranged adjacent to the fiber core; or, the innermost target air hole is spaced apart from the fiber core by one or two second air holes.

[0059] For example, when there are two target air holes; each target air hole is arranged adjacent to the fiber core; or each target air hole is spaced 1-2 second air holes from the fiber core.

[0060] For example, the end face of the optical fiber has mutually perpendicular X-axis and Y-axis directions that intersect the fiber core, and multiple target air holes are arranged at intervals along the X-axis or Y-axis direction. The patterned metal coating is made of materials including, but not limited to, gold, copper, etc. The thickness of the patterned metal coating is, for example, 50-100 nm.

[0061] For example, the patterned metal plating is made of gold.

[0062] It should be noted that the chemical vapor deposition reaction using sulfur source and transition metal source in impregnated optical fiber as raw materials can refer to relevant technologies. For example, the chemical vapor deposition reaction using sulfur source and transition metal source in impregnated optical fiber as raw materials includes, but is not limited to: setting a first temperature zone and a second temperature zone sequentially along the airflow direction of the protective gas in a tube furnace; placing the chalcogen material in the first temperature zone and placing the impregnated optical fiber in the second temperature zone. Then, the tube furnace is evacuated until the gas pressure inside the tube furnace is lower than 0.1 Pa, and then the protective gas is introduced to maintain the pressure inside the tube at 50-300 Pa. Next, the second temperature zone is first heated to 120℃-150℃ and then dried at low pressure for 30 min; then the second temperature zone is heated to 750-1500℃ and kept constant, while the first temperature zone is controlled at 130℃-300℃ for sulfur growth. (III) After the growth is completed, the heating power is turned off, the protective gas flow rate is kept constant, and the temperature is cooled to room temperature. The protective atmosphere is an inert atmosphere, including but not limited to argon or nitrogen atmosphere.

[0063] Optionally, the distance between the immersion optical fiber and the sulfur source is controlled between 15-20 cm.

[0064] In some embodiments, the step of physically adsorbing a metal mask onto both ends of a bare optical fiber to seal the second air hole includes:

[0065] A patterned metal coating is formed on the surface of a first hard substrate. The patterned metal coating has an exposed area corresponding to a target air hole and a mask area corresponding to a second air hole. A low-melting-point polymer layer is formed on the side of the patterned metal coating away from the first hard substrate. The first hard substrate is peeled off to form a first film layer.

[0066] The patterned metal coating of the first film layer is attached to the second hard substrate. The low-melting-point polymer layer is removed by heat treatment. A high-melting-point polymer layer is formed on the side of the patterned metal coating layer away from the second hard substrate. The adhesion of the high-melting-point polymer layer is less than that of the low-melting-point polymer layer. The second hard substrate is then peeled off to form the second film layer.

[0067] The two ends of the bare optical fiber are respectively bonded to a patterned metal coating of a second film layer. The high-melting-point polymer layer is removed by heat treatment at 150℃-300℃ for 2min-5min, so that the mask area is physically adsorbed onto the two ends of the bare optical fiber to form a metal mask, thus obtaining the sealed optical fiber.

[0068] It is understandable that, due to the small diameter of the optical fiber, the methods for forming a patterned metal coating on the surface of the first rigid substrate include, but are not limited to, electron beam evaporation, vacuum evaporation, or electroplating. Electron beam evaporation can be selected, which can effectively improve the preparation efficiency and reduce the preparation difficulty. However, the bonding force between the patterned metal coating formed by the above methods and the first rigid substrate is relatively large. Therefore, a low-melting-point polymer layer with high adhesion is used as a support layer to enable it to be stably bonded to the patterned metal coating. At the same time, it is convenient for the patterned metal coating to exist on the low-melting-point polymer layer after the first rigid substrate is peeled off, forming the first film layer.

[0069] However, since the low-melting-point polymer layer in the first film layer covers the exposed area of ​​the patterned metal coating, it is necessary to remove at least this part of the low-melting-point polymer layer through heat treatment. If the first film layer is directly transferred to both ends of the bare optical fiber, the low-melting-point polymer layer is likely to remain and the amount of residue is large, which will affect the growth and purity of the subsequent transition metal chalcogenide layer. Therefore, it is chosen to re-attach the patterned metal coating of the first film layer to the surface of the second rigid substrate, remove the low-melting-point polymer layer, and then form a high-melting-point polymer layer with weak adhesion on the surface as a support layer. The second rigid substrate is then peeled off to form the second film layer.

[0070] Since the two ends of the bare optical fiber are respectively bonded to a patterned metal coating of a second film layer, in order to make the patterned metal coating and the bare optical fiber physically adhere tightly, it is necessary to keep it at 150℃-300℃ for 2min-5min. It is understandable that the decomposition temperature of the high melting point polymer layer is greater than the holding temperature for making the patterned metal coating and the bare optical fiber physically adhere tightly.

[0071] After the patterned metal coating and the bare optical fiber are physically bonded together, the high-melting-point polymer layer is removed. Due to the material properties of the high-melting-point polymer layer and the low adhesion between it and the patterned metal coating, it is easy to remove through heat treatment, resulting in a sealed optical fiber with good sealing effect and high purity.

[0072] In other words, the above-mentioned sealing method is simple to operate. It can not only quickly achieve the physical adsorption of metal masks onto both ends of bare optical fibers to selectively seal the second air holes, thereby effectively improving the fiber fabrication efficiency, but also is easy to remove, avoiding the introduction of impurities during the fabrication process.

[0073] The first hard substrate and the second hard substrate include, but are not limited to, double-polished alumina wafers, double-polished fused silica wafers, or magnesium oxide wafers.

[0074] In some embodiments, the material of the low-melting-point polymer layer includes polymethyl methacrylate or polypropylene carbonate, and the material of the high-melting-point polymer layer includes polypropylene carbonate.

[0075] Among them, polymethyl methacrylate or polypropylene carbonate has high adhesion and is easy to form a thick coating, providing excellent support and facilitating the complete peeling of the patterned metal plating from the surface of the first hard substrate.

[0076] Polypropylene carbonate has a high melting point, which helps it maintain its integrity at the temperature where patterned metal coatings and bare optical fibers are physically adsorbed tightly, and it is easy to remove in subsequent heat treatment.

[0077] Optionally, the steps of removing the low-melting-point polymer layer by heat treatment and removing the high-melting-point polymer layer by heat treatment respectively include:

[0078] Soak in acetone for 2-4 hours, dry at room temperature, and then place in an inert atmosphere and an inert pressure of 30-50 Pa in the furnace cavity. Anneal at 400-420℃ for 3-5 hours.

[0079] Under the above conditions, it is beneficial to remove both low-melting-point polymer layers and high-melting-point polymer layers.

[0080] For example, the pressure inside the furnace cavity is any one of 30 Pa, 35 Pa, 40 Pa, 45 Pa, 50 Pa, or between any two of these values. For example, the annealing temperature is any one of 400°C, 405°C, 410°C, 415°C, 420°C, or between any two of these values, and the annealing time is any one of 3 h, 4 h, 5 h, or between any two of these values.

[0081] Optionally, the temperature is increased to the annealing temperature at a heating rate of 5-15℃ / min.

[0082] For example, the heating rate is any one of 5°C / min, 7°C / min, 10°C / min, 13°C / min, 15°C / min, or between any two of these values.

[0083] In some embodiments, the transition metal source includes at least one of Na₂MoO₄, K₂MoO₄, Na₂WO₄, and K₂WO₄; and / or,

[0084] The sulfur source includes at least one of elemental sulfur, elemental selenium, and elemental tellurium; and / or,

[0085] The transition metal chalcogenide layer is a single layer.

[0086] Optionally, the concentration of the transition metal source in the aqueous solution is 5-150 mg / ml.

[0087] The third aspect of this application provides an all-fiber phase delayer, which is fabricated from the optical fiber provided in the first aspect of this application or from the optical fiber prepared by the method provided in the second aspect of this application.

[0088] Among them, the all-fiber phase delayer includes polarizers, etc.

[0089] It should be noted that before fabricating an all-fiber phase delay device, it is necessary to test and obtain the polarization beat length of the fiber, and then cut the fiber to a certain length to realize phase delay devices with different polarization modulation functions.

[0090] The methods for testing the polarization beat length of optical fibers include: 1. Selecting a stable light source and adjusting the polarization state of the incident light using a polarization control device. Measuring the Stokes vector of the incident light using a polarization analyzer. 2. Placing the optical fiber in the optical path. After the incident light passes through the fiber, the polarization state of the light changes. Measuring the Stokes vector of the outgoing light using a polarization analyzer and fitting the phase delay of the incident light. 3. Performing a truncation test on the optical fiber and measuring the change in phase delay with fiber length to obtain the polarization beat length of the fabricated optical fiber.

[0091] In the method of testing the polarization beat length of the optical fiber, a Solvay TLX1 laser was selected as the stable light source. The polarization analyzer was a Solvay PAX1000IR2 / M.

[0092] The optical fiber, its fabrication method, and the all-fiber phase delay device of this application are further described in detail below with reference to embodiments.

[0093] Example 1

[0094] Please see Figure 1 The MoS2 composite optical fiber 10 includes a core 11 and a cladding. The cladding includes two layers of air holes that are circumferentially distributed in a regular hexagonal pattern around the core 11. The core 11 is located at the center of the cladding. Each air hole extends along the axial direction of the optical fiber and passes through both ends of the optical fiber.

[0095] The inner walls of four air holes are provided with a transition metal chalcogenide layer 13 as first air holes 12, and the remaining air holes are used as second air holes 14. The end face of the MoS2 composite optical fiber 10 has a square shape with the X-axis and Y-axis perpendicular to each other and intersecting the fiber core 11. The four first air holes 12 are all located in the X-axis direction, and the four first air holes 12 are symmetrically distributed on both sides of the fiber core 11 with the fiber core 11 as the center of symmetry.

[0096] In the above-mentioned method for fabricating MoS2 composite optical fiber 10, the bare optical fiber selected is a photonic crystal fiber, which includes a core 11 and a cladding. The cladding includes two layers of air holes that are circumferentially distributed in a regular hexagonal pattern around the core 11. The core 11 is located at the center of the cladding. Each air hole extends along the axial direction of the optical fiber and passes through both ends of the optical fiber. Four of the air holes are designated as target air holes 28, and the remaining air holes are designated as second air holes 14. The end face of the bare optical fiber has a square shape that is perpendicular to each other and intersects the X-axis and Y-axis of the core 11. The four target air holes 28 and the core 11 are all located in the X-axis direction, and the four target air holes 28 are symmetrically distributed on both sides of the core 11 with the core 11 as the center of symmetry.

[0097] Please see Figure 2 The steps of the MoS2 composite optical fiber fabrication method include:

[0098] A patterned gold plating layer 22 is prepared on the surface of the first silicon wafer 21 by electron beam evaporation. The patterned gold plating layer 22 has an exposed area corresponding to the target air hole 28 and a mask area 27 corresponding to the second air hole 14. Polymethyl methacrylate (PMMA) is coated on the side of the patterned gold plating layer 22 away from the first silicon wafer 21 by spin coating, and then dried on a heating table at 120°C to form a PMMA layer 23. The patterned gold plating layer 22 is peeled off from the surface of the first silicon wafer 21 in water by using thermal release tape 24 to bond it to the PMMA layer 23, and the patterned gold plating layer 22 / PMMA layer 23 / thermal release tape 24 are obtained as the first product.

[0099] The first product is transferred to the surface of the second silicon wafer 25, so that the patterned gold plating layer 22 adheres to the surface of the second silicon wafer 25. The thermal release adhesive is removed, and then the wafer is immersed in acetone for 3 hours. After drying at room temperature, the wafer is placed in the furnace chamber of a tube furnace. The furnace chamber pressure is evacuated to a level of 3 Pa, and then a protective gas is introduced to maintain the furnace chamber pressure at 50 Pa. The temperature is controlled to rise at a rate of 10 °C / min to 410 °C, and the wafer is held for annealing for 4 hours. The PMMA layer 23 is then removed to obtain the stacked second silicon wafer 25 / patterned gold plating layer 22, which is the second product.

[0100] Polypropylene carbonate (PPC) was uniformly spin-coated onto the surface of the patterned gold plating layer 22 of the second product using a spin-coating method. The mixture was then placed on a heating stage at 150°C for heating, allowing the PPC to diffuse throughout the entire interface. The assembly was then cooled to 30°C to form a PPC layer 26. The patterned gold plating layer 22 was peeled off from the surface of the second silicon wafer 25 in water using a thermal release adhesive tape 24 bonded to the PPC layer 26, resulting in a stacked patterned gold plating layer 22 / PPC layer 26 as the third product.

[0101] like Figure 3 As shown, the two ends of the bare optical fiber are respectively bonded to a patterned gold plating layer 22 of a third product, so that the mask area 27 blocks the second air hole 14 and the exposed area exposes the target air hole 28. The fiber is kept at 200℃ for 5 min, then immersed in acetone for 3 h, dried at room temperature, and placed in a tube furnace. The vacuum is evacuated until the gas pressure inside the tube furnace is as low as 3 Pa, then a protective gas is introduced to maintain the pressure inside the tube at 50 Pa. The heating rate is controlled at 10℃ / min to raise the temperature to 410℃, and the fiber is held for annealing for 4 h. The PPC layer 26 is then removed to obtain the sealed optical fiber.

[0102] One end of the fiber was placed in a 70 mg / ml Na2MoO4 aqueous solution. The Na2MoO4 aqueous solution was drawn into the target air hole 28 by capillary action to obtain the fiber wetted.

[0103] A first temperature zone and a second temperature zone are sequentially set in the tubular furnace along the airflow direction of the protective gas. Sulfur powder is placed in the first temperature zone of the tubular furnace, and the impregnated optical fiber is placed in the second temperature zone of the tubular furnace. The shortest straight-line distance between the impregnated optical fiber and the sulfur source is controlled at 20 cm. After evacuating the tubular furnace to a pressure lower than 0.1 Pa, a protective gas (argon) is introduced. The second temperature zone is first heated to 110 °C and then dried under low pressure for 30 min. Then, the second temperature zone is heated to 800 °C, while the first temperature zone is controlled at 150 °C. The growth stage begins, and the growth time is 40 min. A monolayer of MoS2 is grown on the inner wall of the target air hole 28. At the same time, the gold foil is decomposed and removed during the growth process to obtain MoS2 composite optical fiber.

[0104] Figure 4 The image shows a comparison between the prepared MoS2 composite fiber and the bare fiber. The comparison shows that the MoS2 composite fiber has a slight greenish tint and no obvious difference in appearance.

[0105] Experimental Example 1

[0106] Test the beat length and polarization state conversion performance of the MoS2 composite fiber prepared in Example 1:

[0107] MoS2 composite optical fiber is fixed in such a way as Figure 5In the optical path system shown, the laser beam becomes linearly polarized light after passing through the polarizer. Then, the linearly polarized light passes through a quarter-wave plate at an angle of 45° to it to form circularly polarized light. The circularly polarized light passes through a lens and is coupled into the MoS2 composite fiber with maximum transmittance. It is emitted from the other end of the MoS2 composite fiber, and the actual polarization information at the output end of the MoS2 composite fiber is measured using a polarization measuring instrument.

[0108] The optical field at the output end of the optical fiber is measured by a beam analyzer to ensure high alignment of the beam coupled into the MoS2 composite fiber, while also ensuring the transmission of the fundamental mode in the MoS2 composite fiber.

[0109] Another beam of light is input into the polarization measuring instrument through a beam splitter, and the Stokes vector of the output light is read. The Stokes vector can be represented by a Bonga sphere, and the three coordinate axes of the Bonga sphere correspond to the three components of the Stokes vector. Any Stokes vector can be represented by a point on the Bonga sphere.

[0110] By comparing the experimentally measured Stokes vector of the output light with the theoretical output Stokes vector, the phase delay can be calculated through fitting.

[0111] A truncation test was performed on the MoS2 composite fiber. By measuring the phase delay of fibers of different lengths, the trend of phase delay variation with length was obtained, and thus the beat length of the MoS2 composite fiber was determined. Multiple measurements were taken and the average value was used to reduce errors. The final measured beat length of the MoS2 composite fiber was 7.78 cm. In other words, the MoS2 composite fiber provided in this application overcomes the technical difficulties in splicing traditional short-beat-length fibers and is easier to integrate with all-fiber systems.

[0112] Experimental Example 2

[0113] The MoS2 composite optical fibers prepared in Example 1 were cut into lengths of 2.1 cm, 4.2 cm, and 5.7 cm, respectively, and fixed to the following: Figure 5 In the optical path system shown, Figure 5 The white line represents the optical transmission path. The above optical system is used to adjust the incident light into linearly polarized light, and the actual polarization information of the output end of the MoS2 composite fiber is measured using a polarization meter.

[0114] like Figure 6 As shown, MoS2 composite optical fibers with lengths of 2.1cm, 4.2cm, and 5.7cm can be used to fabricate quarter-wave plates, half-wave plates, and three-quarter-wave plates in sequence.

[0115] In summary, the optical fiber provided in this application, by embedding a transition metal chalcogenide layer in the inner wall of the first air hole in the optical fiber, changes the propagation speed of the orthogonal polarization mode, thereby introducing and enhancing the birefringence effect. This not only enables controllable birefringence and beat length optimization, but also reduces the length dependence of polarization modulation compared to traditional optical fiber delayer manufacturing processes, making it easier to integrate with optical fiber systems, and provides better stability in the optical fiber environment.

[0116] The above are merely specific embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An optical fiber, characterized in that, The fiber includes a core and a cladding, the cladding including a plurality of air holes circumferentially and periodically distributed around the core, the core being located at the center of the cladding, and each air hole extending along the axial direction of the optical fiber and penetrating both ends of the optical fiber. Among them, some of the air holes have a transition metal chalcogenide layer on their inner walls as first air holes, and the remaining air holes are used as second air holes. The number of the first air holes is at least two, and the first air holes are symmetrically distributed on both sides of the fiber core with the fiber core as the center of symmetry.

2. The optical fiber according to claim 1, characterized in that, The number of the first air holes is at least four, and the first air holes are arranged sequentially from the inside to the outside along the radial direction of the optical fiber; In this configuration, the innermost first air hole is disposed adjacent to the fiber core; or, One or two second air holes are spaced between the first air hole located on the innermost side and the fiber core.

3. The optical fiber according to claim 1, characterized in that, The number of the first air holes is two; In this configuration, each of the first air holes is disposed adjacent to the fiber core; or... There are 1-2 second air holes between each of the first air holes and the fiber core.

4. The optical fiber according to any one of claims 1-3, characterized in that, The end face of the optical fiber has X-axis and Y-axis directions that are perpendicular to each other and intersect the fiber core, and a plurality of first air holes are arranged at intervals along the X-axis or Y-axis directions. Optionally, the optical fiber is a photonic crystal fiber; Optionally, the optical fiber is made of quartz or quartz polymer.

5. The optical fiber according to any one of claims 1-3, characterized in that, The transition metal chalcogenide layer is a single layer; and / or, The transition metal chalcogenide layer comprises MoS2, MoSe2, MoTe2, WS2, WSe2, WTe2, MoS x Se 2-x MoS x Te 2-x MoTe x Se 2-x WS x Se 2-x WS x Te 2-x ,WTe x Se 2-x At least one of them, where 0 < x < 2.

6. A method for fabricating an optical fiber, characterized in that, Includes the following steps: A bare optical fiber is obtained, the bare optical fiber including a core and a cladding, the cladding including a plurality of air holes circumferentially and periodically distributed around the core, the core being located at the center of the cladding, each air hole extending along the axial direction of the optical fiber and penetrating both ends of the optical fiber, wherein some of the air holes serve as target air holes for coating, and the remaining air holes serve as second air holes, the number of target air holes is at least two, and the target air holes are symmetrically distributed on both sides of the core with the core as the center of symmetry; A metal mask is physically adsorbed onto both ends of the bare optical fiber to block the second air hole, exposing the target air hole, thus obtaining a sealed optical fiber; One end of the sealed optical fiber is placed in an aqueous solution of a transition metal source, so that the transition metal source solution is adsorbed into the target air hole, thereby obtaining a wetted optical fiber. A chemical vapor deposition reaction is carried out using a sulfur source and a transition metal source in the impregnated optical fiber as raw materials to grow a transition metal chalcogenide layer on the inner wall of the target air hole to form a first air hole, while the metal mask is decomposed to obtain an optical fiber.

7. The preparation method according to claim 6, characterized in that, The step of physically adsorbing the metal mask onto both ends of the bare optical fiber to seal the second air hole includes: A patterned metal coating is formed on the surface of a first hard substrate. The patterned metal coating has an exposed area corresponding to the target air hole and a mask area corresponding to the second air hole. A low-melting-point polymer layer is formed on the side of the patterned metal coating away from the first hard substrate. The first hard substrate is peeled off to form a first film layer. The patterned metal coating of the first film layer is attached to the second hard substrate. The low-melting-point polymer layer is removed by heat treatment. A high-melting-point polymer layer is formed on the side of the patterned metal coating layer away from the second hard substrate. The adhesion of the high-melting-point polymer layer is less than that of the low-melting-point polymer layer. The second hard substrate is then peeled off to form the second film layer. The two ends of the bare optical fiber are respectively bonded to the patterned metal coating of the second film layer. The high-melting-point polymer layer is removed by heat treatment at 150℃-300℃ for 2min-5min, so that the mask area is physically adsorbed on the two ends of the bare optical fiber to form the metal mask, thereby obtaining the sealed optical fiber.

8. The preparation method according to claim 7, characterized in that, The material of the low-melting-point polymer layer includes polymethyl methacrylate or polypropylene carbonate, and the material of the high-melting-point polymer layer includes polypropylene carbonate. Optionally, the steps of removing the low-melting-point polymer layer by heat treatment and removing the high-melting-point polymer layer by heat treatment respectively include: Soak in acetone for 2-4 hours, dry at room temperature, and then place in an inert atmosphere and an inert pressure of 30-50 Pa in the furnace cavity. Anneal at 400-420℃ for 3-5 hours.

9. The preparation method according to any one of claims 6-8, characterized in that, The transition metal source includes at least one of Na₂MoO₄, K₂MoO₄, Na₂WO₄, and K₂WO₄; and / or, The sulfur source includes at least one of elemental sulfur, elemental selenium, and elemental tellurium; and / or, The transition metal chalcogenide layer is a single layer.

10. An all-fiber phase delayer, characterized in that, It is made from the optical fiber as described in any one of claims 1-5, or the optical fiber prepared by the preparation method described in any one of claims 6-9.

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