Composite hollow core optical fiber and method for manufacturing thereof

Abstract

This invention relates to a composite hollow-core optical fiber and its fabrication method. The fabrication method includes: arranging multiple tubular elements circumferentially on the inner wall of the cladding to obtain a hollow-core optical fiber; sintering a graded-index multimode fiber of a predetermined length at one end of the hollow-core optical fiber, wherein the cladding of the hollow-core optical fiber and the graded-index multimode fiber are coaxial, the inner diameter of the cladding of the hollow-core optical fiber is less than or equal to the inner diameter of the cladding of the graded-index multimode fiber, and the outer diameter of the cladding of the hollow-core optical fiber is greater than the outer diameter of the cladding of the graded-index multimode fiber; and fabricating a droplet lens at the end of the graded-index multimode fiber away from the hollow-core optical fiber, wherein the diameter of the droplet lens is greater than or equal to the inner diameter of the cladding of the graded-index multimode fiber, thus obtaining a composite hollow-core optical fiber. Based on the composite hollow-core optical fiber and its fabrication method provided by this invention, miniaturization of the optical fiber focusing port can be achieved, ensuring flexible transmission of ultrafast lasers, and enabling its use in medical and extremely confined laser processing applications.

Description

Technical Field

[0001] This invention belongs to the field of communication engineering technology, specifically relating to a composite hollow optical fiber and its preparation method. Background Technology

[0002] Hollow-core optical fibers are used to transmit optical energy. The core of a hollow-core fiber is air. Because the refractive index of air is lower than that of the cladding medium, total internal reflection is not possible. Therefore, a specially designed cladding structure is required to transmit light in the hollow core. When light is incident on the interface between the core and the cladding, it is strongly scattered by the periodically arranged air holes in the cladding. This multiple scattering produces coherence, allowing light waves with specific wavelengths and incident angles to return to the core and continue propagating. Using this structure, light can be guided and propagated even when the refractive index of the core is lower than that of the cladding.

[0003] In existing technologies, in order to adapt hollow optical fibers to different application scenarios, different gas media are usually filled or vacuuming is performed to meet the actual application requirements. Specifically, during the filling or vacuuming process, filling / vacuuming devices need to be set at both ends of the hollow optical fiber, and an additional optical energy output head needs to be set at the output end of the hollow optical fiber. This results in a complex structure and large volume at the output end, which seriously restricts its versatility and applicability. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention provides a composite hollow-core optical fiber and its fabrication method. The technical problem to be solved by this invention is achieved through the following technical solution:

[0005] In a first aspect, the present invention provides a composite hollow-core optical fiber, characterized in that it comprises: a hollow-core optical fiber, and a graded-index multimode optical fiber disposed at one end of the hollow-core optical fiber, wherein a droplet lens is disposed at the end of the graded-index multimode optical fiber away from the hollow-core optical fiber; wherein the inner diameter of the cladding of the hollow-core optical fiber is less than or equal to the inner diameter of the cladding of the graded-index multimode optical fiber, the outer diameter of the cladding of the hollow-core optical fiber is greater than the outer diameter of the cladding of the graded-index multimode optical fiber, and the diameter of the droplet lens is greater than or equal to the inner diameter of the cladding of the graded-index multimode optical fiber, and less than the outer diameter of the cladding of the graded-index multimode optical fiber.

[0006] In some embodiments, the droplet lens is conical in shape.

[0007] In some embodiments, the focusing distance of the droplet lens is expressed as:

[0008] ;

[0009] in, It is the focusing distance of the droplet lens. It is the mode field radius of the graded-index multimode fiber. It is the wavelength of the laser. It is the radius of curvature of the droplet lens. The wavelength of the graded-index multimode fiber in the laser is... The nominal refractive index below.

[0010] In some embodiments, the droplet lens is made of silicon dioxide.

[0011] In some embodiments, the inner cladding diameter of the hollow fiber ranges from 10 μm to 60 μm, and the outer cladding diameter of the hollow fiber ranges from 200 μm to 500 μm.

[0012] In a second aspect, the present invention provides a method for fabricating a composite hollow optical fiber, the method being used to fabricate the composite hollow optical fiber described in the first aspect above; the method comprising: arranging a plurality of tubular elements along the circumference of the cladding on the inner wall of the cladding to obtain a hollow optical fiber; sintering a graded-index multimode fiber of a predetermined length at one end of the hollow optical fiber, wherein the cladding of the hollow optical fiber and the graded-index multimode fiber are coaxial, the inner diameter of the cladding of the hollow optical fiber is less than or equal to the inner diameter of the cladding of the graded-index multimode fiber, and the outer diameter of the cladding of the hollow optical fiber is greater than the outer diameter of the cladding of the graded-index multimode fiber; and fabricating a drop lens at the end of the graded-index multimode fiber away from the hollow optical fiber to obtain a composite hollow optical fiber, wherein the diameter of the drop lens is greater than or equal to the inner diameter of the cladding of the graded-index multimode fiber and smaller than the outer diameter of the cladding of the graded-index multimode fiber.

[0013] In some embodiments, the plurality of tubular elements are made of pure quartz, and the cladding of the hollow optical fiber is made of acrylate.

[0014] In some embodiments, the diameter of each tubular element is 14 μm to 40 μm.

[0015] In some embodiments, the method further includes: evacuating or gasifying the end of the hollow fiber that is away from the graded-index multimode fiber.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] To address the problem that the complex and large output structure of existing hollow optical fibers severely restricts their versatility and applicability, this invention provides a composite hollow optical fiber and its fabrication method. This composite hollow optical fiber incorporates a graded-index multimode fiber at one end of the hollow optical fiber as a gain lens, and a droplet lens at the output end of the graded-index multimode fiber to focus the transmitted light. The outer diameter of the cladding of the graded-index multimode fiber is smaller than that of the hollow optical fiber, enabling miniaturization of the fiber focusing port and ensuring flexible transmission of ultrafast lasers. This allows for applications in medical and extremely confined laser processing. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a composite hollow optical fiber provided in an embodiment of the present invention.

[0019] Figure 2 This is a schematic diagram showing the relationship between the focusing distance of the droplet lens and the mode field radius of the graded refractive index multimode fiber provided in this embodiment of the invention;

[0020] Figure 3 This is a focusing schematic diagram of the composite hollow optical fiber provided in an embodiment of the present invention;

[0021] Figure 4 This is a schematic flowchart of a method for preparing a composite hollow optical fiber according to an embodiment of the present invention;

[0022] Figure 5 This is a schematic diagram illustrating the fabrication of a composite hollow optical fiber according to an embodiment of the present invention.

[0023] Figure label:

[0024] 1: Hollow-core optical fiber; 2: Graded-index multimode optical fiber; 3: Drop lens. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0026] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0027] Although the invention has been described herein in conjunction with various embodiments, those skilled in the art will understand and implement other variations of the disclosed embodiments by reviewing the accompanying drawings, disclosure, and appended claims in carrying out the claimed invention. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality. A single processor or other unit can implement several functions listed in the claims. While different dependent claims may recite certain measures, this does not mean that these measures cannot be combined to produce good results.

[0028] The composite hollow-core optical fiber and its fabrication method provided by embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In one possible application scenario, the composite hollow-core optical fiber provided by the present invention can be used in ultrafast lasers to transmit ultrafast laser light.

[0029] Example 1

[0030] Figure 1 This is a schematic diagram of a composite hollow optical fiber provided in an embodiment of the present invention. Figure 1 As shown, the composite hollow fiber is characterized by comprising: a hollow fiber 1, and a graded-index multimode fiber 2 disposed at one end of the hollow fiber 1, wherein a drop lens 3 is disposed at the end of the graded-index multimode fiber 2 away from the hollow fiber 1; wherein the inner diameter of the cladding of the hollow fiber 1 is less than or equal to the inner diameter of the cladding of the graded-index multimode fiber 2, the outer diameter of the cladding of the hollow fiber 1 is greater than the outer diameter of the cladding of the graded-index multimode fiber 2, and the diameter of the drop lens 3 is greater than or equal to the inner diameter of the cladding of the graded-index multimode fiber 2, and less than the outer diameter of the cladding of the graded-index multimode fiber 2.

[0031] Here, the inner cladding diameter of hollow fiber 1 ranges from 10μm to 60μm, and the outer cladding diameter ranges from 200μm to 500μm. It should be understood that the outer cladding diameter of hollow fiber 1 can be set according to actual requirements.

[0032] Here, graded-index multimode fiber 2 can be used as a gain lens. Graded-index multimode fiber 2 is a multimode fiber with a graded-index profile. Its basic structure consists of a composite material composed of multiple layers, including a multilayer vacuum film, an outer refractive index layer, a dielectric layer, an inner refractive index layer, and a support layer. The refractive index of the graded-index multimode fiber can gradually change along the fiber core axis, and it can transmit multiple different modes simultaneously. Compared to traditional single-mode fiber, multimode graded-index multimode fiber has a larger bandwidth and lower dispersion. Here, the inner diameter of the cladding of hollow-core fiber 1 is less than or equal to the inner diameter of the cladding of graded-index multimode fiber 2, ensuring that the transmitted light completely enters the graded-index multimode fiber. The outer diameter of the cladding of hollow-core fiber 1 is greater than the outer diameter of the cladding of graded-index multimode fiber 2. Compared to conventional, bulky, and complex optical output heads, this design occupies less space, has a simpler structure, and offers superior transmission performance.

[0033] Here, the droplet lens 3 is conical in shape. Furthermore, the material of the droplet lens 3 is silicon dioxide. When fabricating the droplet lens 3, the focusing distance of the droplet lens 3 needs to be determined according to actual requirements. The focusing position is changed by controlling the curvature of the droplet lens 3. Then, based on the focusing distance of the droplet lens 3, the diameter of the bottom of the droplet lens 3 (the connection point with the graded-index multimode fiber) is controlled.

[0034] Figure 2 This is a schematic diagram illustrating the relationship between the focusing distance of the droplet lens and the mode field radius of the graded-index multimode fiber provided in this embodiment of the invention. Figure 2 As shown, in one possible implementation, the focusing distance of the droplet lens 3 is expressed as:

[0035] ;

[0036] in, This is the focusing distance of lens 3. It is the mode field radius of graded-index multimode fiber 2. It is the wavelength of the laser. It is the radius of curvature of lens 3. Graded-index multimode fiber 2 is used in lasers at wavelengths... The nominal refractive index below.

[0037] and then, Figure 3 This is a focusing schematic diagram of the composite hollow-core optical fiber provided in an embodiment of the present invention. Figure 3 As shown, the light is focused once in the graded refractive index multimode fiber 2, and then focused a second time in the drop lens 3 before being output.

[0038] Example 2

[0039] Figure 4This is a schematic flowchart of a method for preparing a composite hollow optical fiber according to an embodiment of the present invention. Figure 5 This is a schematic diagram illustrating the fabrication of a composite hollow optical fiber according to an embodiment of the present invention. Figure 4 and Figure 5 As shown, the preparation method includes:

[0040] S1. Multiple tubular elements are arranged along the circumference of the cladding on the inner wall of the cladding to obtain hollow fiber 1.

[0041] Here, the material of multiple tubular elements is pure silica, and the cladding material of hollow fiber 1 is acrylate. Furthermore, the inner diameter of the cladding of hollow fiber 1 ranges from 7μm to 9μm, and the outer diameter ranges from 200μm to 500μm. The diameter of each tubular element is 14μm to 40μm.

[0042] S2. A graded-index multimode fiber 2 of a predetermined length is sintered at one end of the hollow fiber 1, wherein the cladding of the hollow fiber 1 and the graded-index multimode fiber 2 are coaxial, the inner diameter of the cladding of the hollow fiber 1 is less than or equal to the inner diameter of the cladding of the graded-index multimode fiber 2, and the outer diameter of the cladding of the hollow fiber 1 is greater than the outer diameter of the cladding of the graded-index multimode fiber 2.

[0043] Here, after the graded refractive index multimode fiber 2 is sintered at one end of the hollow fiber 1, the end of the hollow fiber 1 away from the graded refractive index multimode fiber 2 is subjected to vacuuming or gas filling treatment.

[0044] S3. A drop lens 3 is prepared at the end of the graded-index multimode fiber 2 that is away from the hollow fiber 1 to obtain a composite hollow fiber. The diameter of the drop lens 3 is greater than or equal to the inner diameter of the cladding of the graded-index multimode fiber 2.

[0045] To address the problem that the complex and large output structure of existing hollow optical fibers severely restricts their versatility and applicability, this invention provides a composite hollow optical fiber and its fabrication method. This composite hollow optical fiber incorporates a graded-index multimode fiber at one end of the hollow optical fiber as a gain lens, and a droplet lens at the output end of the graded-index multimode fiber to focus the transmitted light. The outer diameter of the cladding of the graded-index multimode fiber is smaller than that of the hollow optical fiber, enabling miniaturization of the fiber focusing port and ensuring flexible transmission of ultrafast lasers. This allows for applications in medical and extremely confined laser processing.

[0046] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A composite hollow optical fiber, characterized in that, include: A hollow-core optical fiber and a graded-index multimode optical fiber disposed at one end of the hollow-core optical fiber, wherein a droplet lens is disposed at the end of the graded-index multimode optical fiber away from the hollow-core optical fiber; wherein the inner diameter of the cladding of the hollow-core optical fiber is less than or equal to the inner diameter of the cladding of the graded-index multimode optical fiber, the outer diameter of the cladding of the hollow-core optical fiber is greater than the outer diameter of the cladding of the graded-index multimode optical fiber, and the diameter of the droplet lens is greater than or equal to the inner diameter of the cladding of the graded-index multimode optical fiber, and less than the outer diameter of the cladding of the graded-index multimode optical fiber. The droplet lens is conical in shape. The focusing distance of the droplet lens is expressed as: ； in, It is the focusing distance of the droplet lens. It is the mode field radius of the graded-index multimode fiber. It is the wavelength of the laser. It is the radius of curvature of the droplet lens. The wavelength of the graded-index multimode fiber in the laser is... The nominal refractive index below.

2. The composite hollow optical fiber according to claim 1, characterized in that, The material of the droplet lens is silicon dioxide.

3. The composite hollow optical fiber according to claim 1, characterized in that, The inner cladding diameter of the hollow fiber ranges from 10μm to 60μm, and the outer cladding diameter ranges from 200μm to 500μm.

4. A method for preparing a composite hollow optical fiber, characterized in that, The preparation method is used to prepare the composite hollow-core optical fiber according to any one of claims 1 to 3; the preparation method includes: A plurality of tubular elements are arranged circumferentially on the inner wall of the cladding to obtain a hollow optical fiber; A graded-index multimode fiber of a predetermined length is sintered at one end of the hollow-core fiber, wherein the cladding of the hollow-core fiber and the graded-index multimode fiber are coaxial, the inner diameter of the cladding of the hollow-core fiber is less than or equal to the inner diameter of the cladding of the graded-index multimode fiber, and the outer diameter of the cladding of the hollow-core fiber is greater than the outer diameter of the cladding of the graded-index multimode fiber. A droplet lens is prepared at the end of the graded-index multimode fiber away from the hollow fiber to obtain a composite hollow fiber, wherein the diameter of the droplet lens is greater than or equal to the inner diameter of the cladding of the graded-index multimode fiber, and smaller than the outer diameter of the cladding of the graded-index multimode fiber.

5. The method for preparing composite hollow optical fiber according to claim 4, characterized in that, The material of the plurality of tubular elements is pure quartz, and the cladding material of the hollow optical fiber is acrylate.

6. The method for preparing composite hollow optical fiber according to claim 4, characterized in that, The diameter of each tubular element is 14μm to 40μm.

7. The method for preparing composite hollow optical fiber according to claim 4, characterized in that, The method further includes: The end of the hollow optical fiber furthest from the graded-index multimode optical fiber is subjected to vacuuming or gas filling treatment.

Images