Optical fiber polarization beam splitter

Abstract

The embodiment of the invention provides an optical fiber polarization beam splitter, and relates to the technical field of optical fiber devices, the radial section of the optical fiber polarization beam splitter is circular, and the optical fiber polarization beam splitter comprises a fiber core, an elliptical structure and six cladding structures; the section of the elliptical structure along the radial direction is an elliptical ring; on the radial cross section, the center of the elliptical ring coincides with the center of the optical fiber polarization beam splitter; the fiber core comprises a first fiber core and a second fiber core. In the radial section, the first fiber core and the second fiber core are arranged on the two sides of the long axis of the oval ring, and the first fiber core and the second fiber core are in central symmetry along the center of the oval ring. In a radial cross section, the six cladding structures are arranged around the elliptical structure along a circumferential direction. According to the optical fiber polarization beam splitter, by introducing the elliptical structure and the cladding structure, the optical fiber performance such as polarization maintaining, polarization beam splitting and single-mode output is achieved, and the requirements for the performance and stability of optical fiber devices can be better met.

Description

Technical Field

[0001] The present application relates to the technical field of optical fiber devices, and in particular to an optical fiber polarization beam splitter. Background Art

[0002] Fiber Polarization Beam Splitter (FPBS) is a fiber device that can separate the input optical signal into two mutually perpendicular polarization directions according to its polarization state and output them, or it can also be used to combine two optical signals with different polarization states into one output optical fiber. It has a wide range of applications in optical fiber communication systems, optical measurement, laser development, and optical fiber sensing technology. According to the different principles of polarization beam splitting, it can be divided into several types, such as birefringent crystal splitting type, waveguide coupled splitting type, polarization selective reflection type, and integrated optical device type. Among them, the waveguide coupled splitting type realizes the separation of polarization states through fused taper or waveguide design. It has attracted much attention due to its small size and flexible structural design, and is very suitable for the establishment of all-fiber communication and transmission systems. At present, most of the waveguide coupled splitting type optical fiber polarization beam splitters are designed based on ordinary communication optical fiber or photonic crystal fiber. Its scope of application is limited to the traditional scenario of splicing with ordinary communication optical fiber, and it is not suitable for the scenario of splicing with hollow core or all-solid core anti-resonant optical fiber. Hollow-core antiresonant fiber has attracted more and more attention because the light is confined in the air core, and has the characteristics of high fiber damage threshold and low transmission loss. It has become the most likely choice for the backbone fiber of the next generation of communication systems, and its applicable scenarios and scope of use will become larger and larger. Fully solid-core antiresonant fiber is an improvement and development of hollow-core antiresonant fiber. The introduction of low-refractive-index fiber materials in the fiber core is more conducive to the design and performance improvement of the fiber beam splitter structure. Its transmission loss is lower than that of traditional solid-core fiber, and its performance is better and easier to design. As a hot spot in the current research field of optical fibers, antiresonant fiber has attracted much attention and made breakthrough progress, but the research in the field of design of its supporting photonic devices has just started, which greatly limits the development and application of antiresonant fiber. It is urgent to study and design antiresonant fiber-type photonic devices, and the research and design of this type of polarization beam splitter is particularly urgent. In addition, the mid-infrared band is of great significance for applications in the fields of communication, medical treatment, and sensing. This not only reflects the advantages of the light in this band itself, but also contributes to the necessity of seizing technological dominance and establishing first-mover advantages. Therefore, the development of fiber photonic devices in this band is of great significance and urgency. Summary of the invention

[0003] The purpose of the embodiment of the present application is to provide a fiber polarization beam splitter, which adopts a fully solid-state anti-resonance design, which is of great significance for meeting the needs of industry development, developing fiber beam splitter technology, and improving polarization beam splitting and single-mode output characteristics. The specific technical solution is as follows:

[0004] The present application provides an optical fiber polarization beam splitter, wherein the cross section of the optical fiber polarization beam splitter along the radial direction is circular.

[0005] The optical fiber polarization beam splitter comprises: a fiber core, an elliptical structure and six cladding structures;

[0006] The radial cross section of the elliptical structure is an elliptical ring; in the radial cross section, the center of the elliptical ring coincides with the center of the optical fiber polarization beam splitter;

[0007] The fiber core includes a fiber core 1 and a fiber core 2; in a radial cross section, the fiber core 1 and the fiber core 2 are arranged on both sides of the long axis of the elliptical ring, and the fiber core 1 and the fiber core 2 are centrally symmetrical along the center of the elliptical ring;

[0008] In a radial cross section, the six cladding structures are arranged around the elliptical structure in a circumferential direction.

[0009] In a possible implementation manner, the six cladding structures each include a cladding tube and a nested tube;

[0010] The nested tube is concentrically nested in the cladding tube; the cross sections of the nested tube and the cladding tube are both circular rings.

[0011] In a possible implementation manner, the six cladding structures include four cladding ones and two cladding twos;

[0012] In a radial cross section, the four cladding layers 1 are centrally symmetrical along the center of the elliptical ring, and the distance from the common center of each cladding layer 1 to the major axis of the elliptical ring is the same;

[0013] In the radial cross section, the line between the centers of the two cladding layers 2 is perpendicular to the major axis of the elliptical ring, and the distance from the common center of each cladding layer 2 to the center of the elliptical ring is the same.

[0014] In a possible implementation manner, a radial cross-section diameter of the optical fiber polarization beam splitter is 100 μm.

[0015] In a possible implementation manner, the wall thickness of the elliptical ring is 0.5 μm, the semi-major axis of the inner ellipse is 18 μm, and the semi-minor axis is 1 μm.

[0016] In a possible implementation, the wall thickness of the cladding tube is 0.5 μm, and the inner radius is 11.6 μm;

[0017] The wall thickness of the nested tube is 0.5 μm, and the inner radius is 0.3 μm.

[0018] In a possible implementation manner, the common center of each cladding layer 1 has the same distance from the major axis of the elliptical ring of 15 μm, and the same distance from the minor axis of the elliptical ring of 20 μm;

[0019] The distance between the common center of each cladding layer 2 and the center of the elliptical ring is 30 μm.

[0020] In a possible implementation, the elliptical structure is an elliptical tube, and the material of the elliptical tube, the cladding tube and the nested tube are all chalcogenide glass As2Se3.

[0021] In a possible implementation, the length of the optical fiber polarization beam splitter is 5 cm.

[0022] In a possible implementation, the wavelength of the incident light of the optical fiber polarization beam splitter is 2.955 μm to 3.045 μm.

[0023] Beneficial effects of the embodiments of the present application:

[0024] The embodiment of the present application provides a fiber polarization beam splitter, the cross section of the fiber polarization beam splitter along the radial direction is circular, and the fiber polarization beam splitter includes: a core, an elliptical structure and six cladding structures; the cross section of the elliptical structure along the radial direction is an elliptical ring; on the radial cross section, the center of the elliptical ring coincides with the center of the fiber polarization beam splitter; the core includes core one and core two; on the radial cross section, the core one and the core two are arranged on both sides of the long axis of the elliptical ring, and the core one and the core two are centrally symmetrical along the center of the elliptical ring; on the radial cross section, the six cladding structures are arranged around the elliptical structure along the circumferential direction. The fiber polarization beam splitter provided in the present application can achieve optical fiber performances such as polarization maintenance, polarization splitting and single-mode output by introducing an elliptical structure and a cladding structure, and can better meet the requirements for the performance and stability of optical fiber devices in practical applications. At the same time, the structural design of the all-solid-state anti-resonant optical fiber is not only more flexible, but also conducive to the development of different types of optical fiber devices. The fiber polarization beam splitter provided in the present application realizes polarization splitting of light in the 3-micron band through the innovative design of the optical fiber structure. It is suitable for connection and function realization with all current types of optical fibers, including ordinary communication optical fibers, photonic crystal fibers, hollow-core antiresonant fibers and improved all-solid-core antiresonant fibers. It is the development and improvement of existing beam splitter design technology, and is of great significance in helping to build a closed loop of the next-generation hollow-core fiber-based communication system.

[0025] Of course, implementing any product or method of the present application does not necessarily require achieving all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other embodiments can also be obtained based on these drawings.

[0027] Figure 1 A schematic diagram of the structure of a fiber polarization beam splitter provided in an embodiment of the present application;

[0028] Figure 2 A curve diagram showing the relationship between the normalized output power of the core 1 and the core 2 of the optical fiber polarization beam splitter proposed in the present application and the propagation length;

[0029] Figure 3 A curve diagram showing the relationship between the polarization extinction ratio of the optical fiber polarization beam splitter proposed in this application and the propagation length;

[0030] Figure 4 A curve diagram showing the relationship between the polarization extinction ratio of the optical fiber polarization beam splitter proposed in this application and the wavelength at an optical fiber length of 5 cm;

[0031] Figure 5 This is a schematic diagram of the relationship between the high-order mode extinction ratio and wavelength of the optical fiber polarization beam splitter proposed in this application at an optical fiber length of 5 cm. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field based on the present application belong to the scope of protection of the present application.

[0033] First, the professional terms that may be used in the embodiments of the present application are explained:

[0034] Optical fiber, full name optical fiber, is a medium that uses the principle of total reflection of light to transmit optical signals in thin and long transparent fibers. Optical fiber is mainly composed of core, cladding and coating. The core is the core part of the optical fiber, usually made of high-purity silica or other transparent materials, responsible for transmitting optical signals; the cladding is tightly wrapped around the outside of the core, and its refractive index is slightly lower than that of the core, ensuring that the optical signal is totally reflected at the interface between the core and the cladding without leaking to the outside world; the coating is located on the outermost layer, mainly to protect and enhance the flexibility of the optical fiber, and prevent the optical fiber from being damaged during bending or pulling.

[0035] Fiber polarization beam splitter is an optical device used to couple orthogonal linear polarization light in one fiber to two optical fibers for output, or to couple two orthogonal polarization light beams input from polarization-maintaining fiber branches to a single-mode output fiber. Its working principle is to split the incident light so that the outgoing light is output from two vibration directions, one perpendicular to the incident plane and the other parallel to the incident plane. Application scenarios of fiber polarization beam splitters include: Polarization multiplexer / demultiplexer: In fiber-optic communication, polarization beam splitters are used to separate or combine optical signals of different polarization states to achieve information transmission and processing. In optical amplifiers, polarization beam splitters can improve the extinction ratio and stability of the system. Fiber sensing: In fiber-optic sensing applications, polarization beam splitters are used to detect and measure various physical quantities, such as temperature, strain, etc. Optical transmission: In long-distance optical transmission, polarization beam splitters are used to improve the stability and reliability of signals. The characteristics of fiber polarization beam splitters include: Low insertion loss: Low insertion loss to ensure signal integrity. High extinction ratio: It can effectively eliminate unwanted polarized light and improve the signal-to-noise ratio of the system. High stability and reliability: The structure is stable and can work reliably in various environments.

[0036] Infrared light refers to electromagnetic waves with wavelengths between 0.7 microns and 25 microns. According to the wavelength range, it can be divided into near infrared, mid-infrared and far infrared. Among them, mid-infrared light (wavelength range 2.5 microns to 5 microns) has important applications in spectroscopy, especially in materials research, environmental monitoring, safety detection, fire warning and other fields. The mid-infrared band is located in the absorption window of the atmosphere, and the transmittance of most wavelengths is above 60%, which enables mid-infrared band lasers to achieve long-distance transmission in the atmosphere, and has important application value in remote sensing, detection and other fields. Concentration area of ​​thermal radiation energy: At room temperature, blackbody radiation is mainly concentrated in the range of 4 microns to 20 microns, with a peak value near 10 microns. When the temperature rises, the energy of blackbody radiation gradually concentrates in the mid-infrared band, which makes the detection of blackbody radiation in the mid-infrared band an important technology.

[0037] Dual-core fiber refers to an optical fiber with two cores in the same cladding. Each core is an independent optical waveguide, which is equivalent to integrating two single-core optical fibers in a dual-core fiber. This type of optical fiber has a special refractive index distribution, which breaks the refractive index distribution structure of conventional optical fibers. It is usually used as an optical transmission medium and to construct new optical devices. Structure and characteristics: The transmission characteristics of dual-core optical fiber depend not only on parameters such as the cladding refractive index, the core refractive index, the core radius, and the wavelength of the transmitted light, but also on the distance between the two cores. Changing the distance between the two cores will affect the energy distribution between the two cores. In addition, the birefringence effect of dual-core optical fiber also needs special analysis, and its waveguide structure does not have circular symmetry. The application scenarios of dual-core optical fiber include: high-speed data transmission between servers within the data center: in situations where multiple channels of data need to be transmitted simultaneously, dual-core optical fiber jumpers can provide higher bandwidth and more stable transmission performance. Application scenarios requiring two-way communication: dual-core optical fiber jumpers have advantages in saving space and reducing wiring complexity, and are suitable for systems requiring two-way communication.

[0038] All-solid-state antiresonant fiber is an optical fiber with an all-solid-state antiresonant structure, which has the advantages of large-mode field single-mode transmission and filtering characteristics. This optical fiber is prepared by punching-tube combined with high-temperature drawing technology, which can effectively suppress high-order modes and amplify spontaneous radiation within a specific wavelength range, thereby improving the performance and application range of the optical fiber. Characteristics and applications include: Large-mode field single-mode transmission: All-solid-state antiresonant fiber has an ultra-high high-order mode suppression ratio and is suitable for single-mode transmission systems, high-power fiber lasers and amplifiers. Filtering characteristics: By fusing all-solid-state antiresonant fiber in the amplifier, Yb 3+ Amplified spontaneous emission of ions (ytterbium ions). Preparation method, including: all-solid-state antiresonant optical fiber is prepared by punching-tube combined with high-temperature drawing technology. This technical route not only achieves low-cost and efficient preparation, but also can further optimize the transmission band and filtering range of the optical fiber through thermal annealing treatment.

[0039] Chalcogenide glass is a glass material with sulfide, selenide, antimonide as the main components, and sometimes also includes oxides. It is an amorphous material formed by combining chalcogenide elements (such as sulfur, selenium, tellurium) with other metal elements (such as gallium, germanium, etc.). Chalcogenide glass is black in color and has excellent mid- and far-infrared transmittance. It is widely used in infrared night vision, infrared temperature measurement, infrared thermal imaging and other fields. Composition and preparation method: The main components of chalcogenide glass include chalcogenide elements such as sulfur, selenium, tellurium, and metal elements such as gallium and germanium. Its preparation method usually adopts vacuum melting technology to melt high-purity raw materials at high temperature in a vacuum environment and quickly form them. This preparation method makes chalcogenide glass have excellent temperature viscosity characteristics, which is suitable for precision molding production of optical components with complex surfaces. Chalcogenide glass has the following main characteristics: Optical properties: Chalcogenide glass has high transmittance in the mid-wave and long-wave infrared bands, and the transmission band can cover three atmospheric windows of 1~3um, 3~5um and 8~12um. Its far-infrared transmittance is greater than 64% (wavelength 8μm~12μm), and the transmittance after coating can reach more than 95%. The refractive index of chalcogenide glass is as high as 1.7-2.4, and the temperature coefficient of refractive index is small, which is suitable for thermal defocus adjustment and chromatic aberration correction of infrared thermal imaging systems. Physical properties: Chalcogenide glass has a high density (such as the density of IRG101 is 3.20g / cm³), and has good thermal and chemical stability, and can maintain image stability in the temperature range of -40℃~70℃. Processing method: Chalcogenide glass is produced by melt quenching method, which has high production efficiency, short cycle and low cost. Its processing efficiency is more than 10 times higher than that of traditional diamond turning, and it is suitable for mass production of complex surface optical components. Chalcogenide glass is widely used in infrared optical systems, such as infrared night vision, infrared temperature measurement and infrared thermal imaging. Due to its excellent performance and low-cost production method, chalcogenide glass has been widely used in the manufacture of infrared lenses, especially in security, automotive and industrial vision.

[0040] In the existing technology, mid-infrared fiber technology has important applications in the generation and transmission of mid-infrared lasers, biomedical monitoring, environmental monitoring and other fields, and with the continuous development of technology, its application prospects will be broader. Chalcogenide glass is currently the most widely studied mid-infrared fiber material. Chalcogenide fiber performs well in supercontinuum generation, laser damage threshold control, and absorption loss and scattering loss suppression. Hollow-core antiresonant fiber is considered to be an ideal mid-infrared fiber due to its low loss and wide bandwidth. However, due to the viscosity-temperature characteristics of chalcogenide glass and the hollow core structure of the fiber, it is challenging to prepare high-quality chalcogenide hollow-core antiresonant fiber. In order to construct a structurally stable antiresonant fiber, considering the difference in refractive index between chalcogenide glasses, two or more chalcogenide glasses can be selected as fiber materials to design all-solid-state antiresonant fibers and fiber devices. Fiber polarization beam splitter is a fiber device that can separate the input optical signal into two mutually perpendicular polarization directions according to its polarization state. It has a wide range of applications in optical communications, lasers, fiber optic sensing technology and other fields. At present, most of the fiber polarization beam splitters used in the mid-infrared band are designed based on traditional solid-core communication optical fibers and photonic crystal fibers. The structural design of all-solid-state antiresonant optical fibers is more flexible, which is conducive to the development of different types of optical fiber devices. By introducing different cladding structures, optical fiber performance such as polarization maintenance, polarization splitting and single-mode output can be achieved. At the same time, the all-solid-state optical fiber structure can better meet the requirements for the performance and stability of optical fiber devices in practical applications. From the perspective of practical applications, there is an urgent need to develop high-performance mid-infrared all-solid-state antiresonant optical fibers and optical fiber devices, and to promote the development of mid-infrared all-solid-state antiresonant optical fibers and related technologies. Therefore, the present application provides a mid-infrared dual-core all-solid-state antiresonant optical fiber polarization beam splitter, and provides new ideas for the development of mid-infrared all-solid-state antiresonant optical fibers and their devices.

[0041] This application provides a fiber polarization beam splitter, which can be found at Figure 1 , Figure 1 A schematic diagram of the structure of a fiber polarization beam splitter provided in an embodiment of the present application, wherein the reference numerals in the figure are as follows:

[0042] 1-fiber core one; 2-fiber core two; 3-elliptical tube; 4-cladding one; 5-cladding two; 6-nested tube; 7-cladding tube.

[0043] See also Figure 1 , the cross section of the optical fiber polarization beam splitter along the radial direction is circular;

[0044] The optical fiber polarization beam splitter comprises: a fiber core, an elliptical structure and six cladding structures;

[0045] The radial cross section of the elliptical structure is an elliptical ring; in the radial cross section, the center of the elliptical ring coincides with the center of the optical fiber polarization beam splitter;

[0046] The fiber core includes a fiber core 1 and a fiber core 2; in a radial cross section, the fiber core 1 and the fiber core 2 are arranged on both sides of the long axis of the elliptical ring, and the fiber core 1 and the fiber core 2 are centrally symmetrical along the center of the elliptical ring;

[0047] In a radial cross section, the six cladding structures are arranged around the elliptical structure in a circumferential direction.

[0048] Among them, the optical fiber polarization beam splitter described in the embodiment of the present application includes: a fiber core. The optical fiber polarization beam splitter is an optical fiber device that can separate the input optical signal into two optical signals with mutually perpendicular polarization directions according to its polarization state. Specifically, the optical fiber device can be a mid-infrared optical fiber device, which is used in the mid-infrared band. Among them, mid-infrared optical fiber technology has important applications in the fields of mid-infrared laser generation and transmission, biomedical monitoring, environmental monitoring, etc., and with the continuous development of technology, its application prospects will be broader.

[0049] Among them, the optical fiber polarization beam splitter described in the embodiment of the present application also includes: an elliptical structure, the radial cross-section of the elliptical structure is an elliptical ring, and on the radial cross-section, the center of the elliptical ring coincides with the center of the optical fiber polarization beam splitter. The center of the elliptical ring refers to the intersection of the major axis and the minor axis of the elliptical ring. In actual use, the elliptical structure is an elliptical tube. The optical fiber polarization beam splitter provided in the present application constructs a symmetrical dual-core optical fiber structure by introducing an elliptical structure. The dual core refers to the core including core 1 and core 2, and on the radial cross-section, core 1 and core 2 are arranged on both sides of the major axis of the elliptical ring, and core 1 and core 2 are centrally symmetrical along the center of the elliptical ring. When light propagates in an optical fiber, two supermodes in the same polarization direction will undergo mode coupling, and the ratio of the coupling lengths can be adjusted to achieve polarization splitting performance.

[0050] The optical fiber polarization beam splitter also includes six cladding structures. The optical fiber polarization beam splitter in the embodiment of the present application can form a hollow core anti-resonant optical fiber by introducing an elliptical structure and a cladding structure. The hollow core anti-resonant optical fiber is considered to be an ideal mid-infrared optical fiber due to its advantages such as low loss and wide bandwidth.

[0051] The optical fiber polarization beam splitter provided in the embodiment of the present application can be applied to the mid-infrared band. From the perspective of practical application, the development of high-performance mid-infrared all-solid-state anti-resonant optical fiber and optical fiber devices can promote the development of mid-infrared all-solid-state anti-resonant optical fiber and related technologies. The mid-infrared dual-core all-solid-state anti-resonant optical fiber polarization beam splitter provided in the present application can provide new ideas for the development of mid-infrared all-solid-state anti-resonant optical fiber and its devices.

[0052] It can be seen that the optical fiber polarization splitter provided in the present application can achieve optical fiber performance such as polarization maintenance, polarization splitting and single-mode output by introducing an elliptical structure and a cladding structure, thereby better meeting the requirements for optical fiber device performance and stability in practical applications.

[0053] In a possible implementation manner, the six cladding structures each include a cladding tube 7 and a nested tube 6; the nested tube 6 is concentrically nested in the cladding tube 7; and the cross-sections of the nested tube 6 and the cladding tube 7 are both circular rings.

[0054] In a possible implementation, the six cladding structures include four claddings 1 4 and two claddings 2 5; in a radial cross section, the four claddings 1 4 are centrally symmetrical along the center of the elliptical ring, and the distance from the common center of each cladding 1 4 to the major axis of the elliptical ring is the same; in a radial cross section, a line between the centers of two claddings 2 5 is perpendicular to the major axis of the elliptical ring, and the distance from the common center of each cladding 2 5 to the center of the elliptical ring is the same.

[0055] For details, see Figure 1 , Figure 1 A structural schematic diagram of an optical fiber polarization beam splitter provided in an embodiment of the present application, comprising a fiber core 1, a fiber core 2, an elliptical structure, and a cladding structure; the fiber core 1 and the fiber core 2 are symmetrical about the center of the optical fiber; the elliptical structure is an elliptical tube 3, and its cross section is an elliptical ring; the elliptical tube 3 is located at the center of the optical fiber and is located between the fiber core 1 and the fiber core 2; the long axis of the elliptical tube 3 is perpendicular to the line between the fiber core 1 and the fiber core 2; the cladding structure includes a cladding 1 4 and a cladding 2 5, and there are a total of six double-layer cladding tubes; the double-layer cladding tubes are shaped in size. The shapes are completely consistent, both consisting of a nested tube 6 and a cladding tube 7; the nested tube 6 is concentrically nested in the cladding tube 7; the cross-sections of the nested tube 6 and the cladding tube 7 are both circular rings; the cladding 1 4 includes four double-layer cladding tubes, the four double-layer cladding tubes of the cladding 1 4 are arranged around the circumference of the optical fiber center, and the vertical distances from the centers of the four double-layer cladding tubes to the long axis of the elliptical tube 3 are the same; the cladding 2 5 includes two double-layer cladding tubes, the two double-layer cladding tubes of the cladding 2 5 are symmetrical about the center of the optical fiber, and the center line of the two double-layer cladding tubes is perpendicular to the long axis of the elliptical tube 3.

[0056] The optical fiber polarization beam splitter provided in the present application introduces regularly arranged concentrically nested double-layer cladding tubes to form the cladding structure of the optical fiber. This design of concentrically nested double-layer cladding tubes can reduce optical fiber loss while achieving single-mode characteristics of the optical fiber.

[0057] In actual use, the structure of the optical fiber polarization beam splitter provided in the embodiment of the present application can be referred to the following embodiment.

[0058] In a possible implementation manner, a radial cross-section diameter of the optical fiber polarization beam splitter is 100 μm.

[0059] In a possible implementation manner, the wall thickness of the elliptical ring is 0.5 μm, the semi-major axis of the inner ellipse is 18 μm, and the semi-minor axis is 1 μm.

[0060] In a possible implementation manner, the wall thickness of the cladding tube 7 is 0.5 μm, and the inner radius is 11.6 μm; the wall thickness of the nested tube 6 is 0.5 μm, and the inner radius is 0.3 μm.

[0061] In a possible implementation, the distance from the common center of each cladding 1 4 to the major axis of the elliptical ring is 15 μm, and the distance to the minor axis of the elliptical ring is 20 μm; the distance from the common center of each cladding 2 5 to the center of the elliptical ring is 30 μm.

[0062] In a possible implementation manner, the elliptical structure is an elliptical tube 3, and the material of the elliptical tube 3, the cladding tube 7 and the nested tube 6 are all chalcogenide glass As2Se3.

[0063] Among them, chalcogenide glass is the most widely studied mid-infrared optical fiber material. Chalcogenide optical fibers perform well in supercontinuum generation, laser damage threshold control, and suppression of absorption and scattering losses. However, due to the viscosity-temperature characteristics of chalcogenide glass and the hollow core structure of the optical fiber, the preparation of high-quality chalcogenide hollow core antiresonant optical fibers is challenging. In order to construct an antiresonant optical fiber with a stable structure, the inventors selected two or more chalcogenide glasses as optical fiber materials, and designed all-solid-state antiresonant optical fibers and optical fiber devices, taking into account the difference in refractive index between chalcogenide glasses.

[0064] The wall materials of the elliptical tube 3, the nested tube 6, and the cladding tube 7 are all chalcogenide glass As2Se3, and the rest of the optical fiber parts are all chalcogenide glass As2S3. The refractive index of chalcogenide glass As2Se3 and As2S3 can be described by the Sellmeier equation.

[0065] ,

[0066] in, is the item number, and For the i The Sellmeier coefficient of the term, λ is the wavelength of light, and n(λ) is the refractive index of the material at the wavelength of light λ. For As2Se3, when =1,2,3, the parameter values ​​in the Sellmeier equation are A1=4.994871876241, A2= 0.120715248481, A3= 1.712368530625, λ1= 0.24164μm, λ2= 19μm, λ3= 0.48328μm; for As2S3, when taking =1,2, the parameter values ​​in the Sellmeier equation are A1=4.626261968807459, A2= 1.16819527529024, λ1= -0.2690645648975598μm, λ2= -31.3101221206341μm.

[0067] like Figure 2 As shown, there is a trigonometric function relationship between the normalized output power of the core light and the propagation distance. When the propagation distance is 5cm, the normalized output power of the x-polarized light of core 1 reaches the maximum, close to 1; and the normalized output power of the y-polarized light reaches the minimum, close to 0. At this time, the normalized output power of the x-polarized light of core 2 is close to 0, and the normalized output power of the y-polarized light is close to 1. The normalized output power of the polarized light in the two cores is completely opposite. This means that after the light is transmitted in the optical fiber for 5cm, core 1 only outputs x-polarized light, and core 2 only outputs y-polarized light. Combined with Figure 3 When the propagation distance is 5cm, the polarization extinction ratio of the optical fiber reaches the minimum value of -58.3dB. When the polarization extinction ratio value is lower than -20dB, it is considered that the beam splitter has good beam splitting performance, so the beam splitter has good beam splitting performance at 3μm.

[0068] The optical fiber polarization beam splitter proposed in this application is based on an all-solid-state antiresonant optical fiber design. Two chalcogenide glasses As2Se3 and As2S3 with different refractive indices and excellent performance in the mid-infrared band are selected as optical fiber materials, and light is confined to the dielectric core for transmission.

[0069] In a possible implementation, the length of the optical fiber polarization beam splitter is 5 cm. An optical fiber with a length of 5 cm can achieve polarization beam splitting and single-mode output in the wavelength range of 2.955 μm to 3.045 μm, and the high-order mode extinction ratio is higher than 1000. At a wavelength of 3 μm, the polarization extinction ratio can reach -58.3 dB. Here, the optical fiber in this application is an optical fiber polarization beam splitter.

[0070] like Figure 4As shown in the figure, when the optical fiber length is 5 cm, its polarization extinction ratio in the wavelength range of 2.955 μm to 3.045 μm is less than -20 dB. At a wavelength of 3 μm, the polarization extinction ratio can reach -58.3 dB. This shows that it has the ability of polarization beam splitting in this band. Here, the optical fiber in this application is a fiber polarization beam splitter.

[0071] like Figure 5 As shown in the figure, when the fiber length is 5cm, the mode loss and extinction ratio of the fiber in the 3μm band. There are six curves in total. The two curves in the upper part of the figure show the minimum loss of the high-order mode of the fiber and the high-order mode extinction ratio. The four curves in the lower part of the figure show the fiber loss in the x-polarization even mode, x-polarization odd mode, y-polarization even mode, and y-polarization odd mode. The directions of the arrows in the three areas A, B, and C in the figure indicate the specific vertical coordinates corresponding to each curve. It can be seen from the figure that the supermode mode loss of the optical fiber in this band (x-polarization even mode, x-polarization odd mode, y-polarization even mode, y-polarization odd mode) is less than 10 -2 dB / m, and the high-order mode extinction ratio is higher than 10 3 This shows that the optical fiber has the performance of low loss and single-mode transmission. Here, the optical fiber in this application is an optical fiber polarization beam splitter.

[0072] In a possible implementation, the wavelength of the incident light of the optical fiber polarization beam splitter is 2.955 μm to 3.045 μm.

[0073] This application proposes a dual-core all-solid-state anti-resonant fiber polarization beam splitter based on chalcogenide glass with a composite structure for use in the mid-infrared 3μm band. Two types of chalcogenide glasses with different refractive indices in the mid-infrared band are selected as optical fiber materials. A dual-core optical fiber is constructed by adding an elliptical structure to the optical fiber core position, and a concentrically nested double-layer cladding tube is introduced as the anti-resonant optical fiber cladding structure. Finally, a mid-infrared all-solid-state anti-resonant fiber polarization beam splitter with low loss, polarization splitting and single-mode output characteristics is realized.

[0074] Specifically, compared with the prior art, the present application has at least the following benefits:

[0075] 1. The fiber polarization beam splitter proposed in this application is based on the design of all-solid-state anti-resonant fiber. Two chalcogenide glasses As2Se3 and As2S3 with different refractive indexes and excellent performance in the mid-infrared band are selected as fiber materials. The light is confined to the dielectric core for transmission.

[0076] 2. The optical fiber polarization beam splitter provided in this application constructs a symmetrical dual-core optical fiber structure by introducing an elliptical structure. When light propagates in the optical fiber, two supermodes with the same polarization direction will be coupled, and the ratio of the coupling lengths is adjusted to achieve polarization beam splitting performance;

[0077] 3. The optical fiber polarization beam splitter provided in the present application introduces regularly arranged concentrically nested double-layer cladding tubes to form the cladding structure of the optical fiber. This design of concentrically nested double-layer cladding tubes can reduce the optical fiber loss while achieving the single-mode characteristics of the optical fiber;

[0078] 4. The optical fiber polarization beam splitter provided in this application can simultaneously realize polarization beam splitting and single-mode output in the mid-infrared 3μm band, and the high-order mode extinction ratio is higher than 1000. At a wavelength of 3μm, the polarization extinction ratio can reach -58.3 dB.

[0079] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0080] Each embodiment in this specification is described in a related manner, and the same or similar parts between the embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0081] The above description is only a preferred embodiment of the present application and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application are included in the protection scope of the present application.

Claims

1. A fiber polarization beam splitter, characterized in that: The cross section of the optical fiber polarization beam splitter along the radial direction is circular, The optical fiber polarization beam splitter comprises: a fiber core, an elliptical structure and six cladding structures; The radial cross section of the elliptical structure is an elliptical ring; in the radial cross section, the center of the elliptical ring coincides with the center of the optical fiber polarization beam splitter; The fiber core includes a fiber core 1 and a fiber core 2; in a radial cross section, the fiber core 1 and the fiber core 2 are arranged on both sides of the long axis of the elliptical ring, and the fiber core 1 and the fiber core 2 are centrally symmetrical along the center of the elliptical ring; In the radial cross section, the six cladding structures are arranged around the elliptical structure in a circumferential direction.

2. The optical fiber polarization beam splitter according to claim 1, characterized in that: The six cladding structures each include a cladding tube and a nested tube; The nested tube is concentrically nested in the cladding tube; the cross sections of the nested tube and the cladding tube are both circular rings.

3. The optical fiber polarization beam splitter according to claim 1, characterized in that: The six cladding structures include four cladding ones and two cladding twos; In a radial cross section, the four cladding layers 1 are centrally symmetrical along the center of the elliptical ring, and the distance from the common center of each cladding layer 1 to the major axis of the elliptical ring is the same; In the radial cross section, the line between the centers of the two cladding layers 2 is perpendicular to the major axis of the elliptical ring, and the distance from the common center of each cladding layer 2 to the center of the elliptical ring is the same.

4. The optical fiber polarization beam splitter according to claim 1, characterized in that: The diameter of the radial cross section of the optical fiber polarization beam splitter is 100 μm.

5. The optical fiber polarization beam splitter according to claim 1, characterized in that: The wall thickness of the elliptical ring is 0.5 μm, the semi-major axis of the inner ellipse is 18 μm, and the semi-minor axis is 1 μm.

6. The optical fiber polarization beam splitter according to claim 2, characterized in that: The wall thickness of the cladding tube is 0.5 μm, and the inner radius is 11.6 μm; The wall thickness of the nested tubes is 0.5 μm, and the inner radius is 0.3 μm.

7. The optical fiber polarization beam splitter according to claim 3, characterized in that: The common center of each cladding layer 1 has the same distance to the major axis of the elliptical ring of 15 μm, and the same distance to the minor axis of the elliptical ring of 20 μm; The distance between the common center of each cladding layer 2 and the center of the elliptical ring is 30 μm.

8. The optical fiber polarization beam splitter according to claim 2, characterized in that: The elliptical structure is an elliptical tube, and the materials of the elliptical tube, the cladding tube and the nested tube are all chalcogenide glass As2Se3.

9. The optical fiber polarization beam splitter according to claim 1, characterized in that: The length of the optical fiber polarization beam splitter is 5 cm.

10. The optical fiber polarization beam splitter according to claim 1, characterized in that: The wavelength of the incident light of the optical fiber polarization beam splitter is 2.955 μm to 3.045 μm.

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