Composite hollow-core optical fiber and preparation method thereof

Abstract

The invention relates to a composite hollow-core optical fiber and a preparation method thereof, and the preparation method comprises the steps: arranging a plurality of tubular elements on the inner wall of a cladding in the circumferential direction of the cladding, and obtaining a hollow-core optical fiber; one end of the hollow-core optical fiber is sintered with a preset length of graded-index multimode optical fiber, the cladding of the hollow-core optical fiber and the cladding of the graded-index multimode optical fiber are coaxial, and the inner diameter of the cladding of the hollow-core optical fiber is smaller than or equal to that 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 that of the cladding of the gradient refractive index multimode optical fiber; a drop lens is prepared at the end, away from the hollow-core optical fiber, of the graded-index multimode optical fiber, the diameter of the drop lens is larger than or equal to the inner diameter of the cladding of the graded-index multimode optical fiber, and the composite hollow-core optical fiber is obtained. Based on the composite hollow-core optical fiber and the preparation method thereof provided by the invention, miniaturization of an optical fiber focusing port can be realized, flexible transmission of ultrafast laser is ensured, and the composite hollow-core optical fiber can be used for medical treatment and laser processing at extremely narrow positions.

Description

Technical Field

[0001] The invention belongs to the technical field of communication engineering, and in particular relates to a composite hollow-core optical fiber and a preparation method thereof. Background Art

[0002] Hollow-core optical fibers are used to transmit light energy. The core of a hollow-core optical fiber is air. Since the refractive index of air is lower than that of the cladding medium, it does not meet the conditions for total reflection. 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 that meet specific wavelengths and incident angles to return to the core layer and continue to propagate. With this structure, light can be guided and propagated even when the refractive index of the core layer is lower than that of the cladding.

[0003] In the existing related technologies, in order to make hollow-core optical fibers adapt to different application scenarios, they are usually filled with different gas media or evacuated to meet actual applications. Specifically, during the filling or vacuuming process, it is necessary to set filling / vacuuming devices at both ends of the hollow-core optical fiber and set an additional light energy output head at the output end of the hollow-core optical fiber. This will cause the structure of its output end to be complex and large in size, which seriously restricts its versatility and applicability. Summary of the invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides a composite hollow core optical fiber and a preparation method thereof. The technical problem to be solved by the present invention is achieved by the following technical solutions:

[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 arranged at one end of the hollow-core optical fiber, wherein a drop lens is arranged 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 drop lens is greater than or equal to the inner diameter of the cladding of the graded-index multimode optical fiber, and is smaller than the outer diameter of the cladding of the graded-index multimode optical fiber.

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

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

[0008]

[0009] Among them, Z LFis the focusing distance of the drop lens, W0 is the mode field radius of the gradient index multimode fiber, λ is the wavelength of the laser, R OSC is the radius of curvature of the drop lens, and n is the refractive index of the gradient-index multimode optical fiber.

[0010] In some embodiments, the material of the drop lens is silicon dioxide.

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

[0012] In a second aspect, the present invention provides a method for preparing a composite hollow-core optical fiber, the preparation method is used to prepare the composite hollow-core optical fiber described in the first aspect above; the preparation method comprises: arranging a plurality of tubular elements on the inner wall of the cladding along the circumference of the cladding to obtain a hollow-core optical fiber; sintering a preset length of a graded-index multimode optical fiber at one end of the hollow-core optical fiber, wherein the hollow-core optical fiber and the cladding of the graded-index multimode optical 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 optical 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 optical fiber; preparing a drop lens at the end of the graded-index multimode optical fiber away from the hollow-core optical fiber to obtain a composite hollow-core 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 optical fiber and less than the outer diameter of the cladding of the graded-index multimode optical fiber.

[0013] In some embodiments, the material of the plurality of tubular elements is pure silica, and the material of the cladding of the hollow core optical fiber is acrylate.

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

[0015] In some embodiments, the method further comprises: performing a vacuum or gasification treatment on an end of the hollow-core optical fiber away from the gradient-index multimode optical fiber.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] Aiming at the problem that the output end of the existing hollow-core optical fiber has a complex structure and a large volume, which seriously restricts its versatility and applicability, the present invention provides a composite hollow-core optical fiber and a preparation method thereof. The composite hollow-core optical fiber is provided with a gradient-index multimode optical fiber at one end of the hollow-core optical fiber as a gain lens, and a drop lens is provided at the output end of the gradient-index multimode optical fiber to focus the transmitted light. The outer diameter of the cladding of the gradient-index multimode optical fiber is smaller than the outer diameter of the cladding of the hollow-core optical fiber, so that the miniaturization of the optical fiber focusing port can be achieved, and the flexible transmission of ultrafast lasers can be ensured. The composite hollow-core optical fiber can be used for medical treatment and laser processing at extremely narrow positions. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0019] Figure 2 It is a schematic diagram of the relationship between the focusing distance of the drop lens and the mode field radius of the gradient refractive index multimode optical fiber provided in an embodiment of the present invention;

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

[0021] Figure 4 It is a schematic diagram of a process of preparing a composite hollow-core optical fiber provided by an embodiment of the present invention;

[0022] Figure 5 It is a schematic diagram of preparing a composite hollow core optical fiber provided in an embodiment of the present invention.

[0023] Reference numerals:

[0024] 1: Hollow core fiber; 2: Graded-index multimode fiber; 3: Drop lens. DETAILED DESCRIPTION

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

[0026] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification.

[0027] Although the present invention is described herein in conjunction with various embodiments, in the process of implementing the claimed invention, those skilled in the art may understand and implement other variations of the disclosed embodiments by viewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "one" or "an" does not exclude multiple situations. A single processor or other unit may implement several functions listed in the claims. Certain measures are recorded in different dependent claims, but this does not mean that these measures cannot be combined to produce good results.

[0028] Now, in conjunction with the accompanying drawings, a composite hollow core optical fiber and a preparation method thereof provided by an embodiment of the present invention are described in detail. In a possible application scenario, the composite hollow core optical fiber provided by the present invention can be used in an ultrafast laser to transmit ultrafast laser.

[0029] Embodiment 1

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

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

[0032] Here, the gradient refractive index multimode optical fiber 2 can be used as a gain lens. The gradient refractive index multimode optical fiber 2 is a multimode optical fiber with a gradient refractive index profile, and its basic structure is composed of a composite body composed of multiple layers such as a multilayer vacuum film, an outer layer of a refractive index agent, a dielectric layer, an inner layer of a refractive index agent and a support layer. The refractive index of the gradient refractive index multimode optical fiber can be gradient along the core axis, and multiple different modes can be transmitted simultaneously. Compared with traditional single-mode optical fibers, multimode gradient refractive index multimode optical fibers have a larger bandwidth and lower dispersion. Here, the inner diameter of the cladding of the hollow-core optical fiber 1 is less than or equal to the inner diameter of the cladding of the gradient refractive index multimode optical fiber 2, which can ensure that the transmitted light completely enters the gradient refractive index multimode optical fiber, and the outer diameter of the cladding of the hollow-core optical fiber 1 is greater than the outer diameter of the cladding of the gradient refractive index multimode optical fiber 2. Compared with the conventional light energy output head with a large body and complex structure, it occupies a smaller volume and has a simpler structure, and has better transmission performance.

[0033] Here, the shape of the drop lens 3 is conical. And the material of the drop lens 3 is silicon dioxide. When preparing the drop lens 3, it is necessary to determine the focusing distance of the drop lens 3 according to actual needs, and change the focusing position by controlling the curvature of the drop lens 3, and then control the diameter of the bottom of the drop lens 3 (the connection with the gradient refractive index multimode optical fiber) according to the focusing distance of the drop lens 3.

[0034] Figure 2 FIG. 1 is a schematic diagram showing the relationship between the focusing distance of the drop lens and the mode field radius of the gradient refractive index multimode optical fiber provided by an embodiment of the present invention. Figure 2 As shown, in a possible implementation, the focusing distance of the drop lens 3 is expressed as:

[0035]

[0036] Among them, Z LF is the focusing distance of the drop lens 3, W0 is the mode field radius of the graded-index multimode fiber 2, λ is the wavelength of the laser, R OSC is the radius of curvature of the drop lens 3 , and n is the refractive index of the graded-index multimode optical fiber 2 .

[0037] and then, Figure 3 FIG. 1 is a schematic diagram of focusing of a composite hollow core optical fiber provided by an embodiment of the present invention. Figure 3 As shown, the light is focused once in the graded-index multimode optical fiber 2, and then enters the drop lens 3 for secondary focusing, and then is output.

[0038] Embodiment 2

[0039] Figure 4 It is a schematic flow chart of a method for preparing a composite hollow-core optical fiber provided in an embodiment of the present invention. Figure 5FIG. 1 is a schematic diagram of preparing a composite hollow core optical fiber according to an embodiment of the present invention. Figure 4 and Figure 5 As shown, the preparation method comprises:

[0040] S1. Arrange a plurality of tubular elements on the inner wall of the cladding along the circumference of the cladding to obtain a hollow-core optical fiber 1.

[0041] Here, the material of the plurality of tubular elements is pure quartz, and the material of the cladding of the hollow-core optical fiber 1 is acrylate. In addition, the value range of the inner diameter of the cladding of the hollow-core optical fiber 1 is 7 μm to 9 μm, and the value range of the outer diameter of the cladding of the hollow-core optical fiber 1 is 200 μm to 500 μm. The diameter of each tubular element is 14 μm to 40 μm.

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

[0043] Here, after the graded-index multimode optical fiber 2 is sintered at one end of the hollow-core optical fiber 1, the end of the hollow-core optical fiber 1 away from the graded-index multimode optical fiber 2 is subjected to vacuum or gasification treatment.

[0044] S3. Prepare a drop lens 3 at one end of the graded-index multimode optical fiber 2 away from the hollow-core optical fiber 1 to obtain a composite hollow-core optical fiber, wherein the diameter of the drop lens 3 is greater than or equal to the inner diameter of the cladding of the graded-index multimode optical fiber 2.

[0045] In view of the problem that the output end of the existing hollow-core optical fiber has a complex structure and a large volume, which seriously restricts its versatility and applicability, the present invention provides a composite hollow-core optical fiber and a preparation method thereof. The composite hollow-core optical fiber is provided with a gradient-index multimode optical fiber at one end of the hollow-core optical fiber as a gain lens, and a drop lens is provided at the output end of the gradient-index multimode optical fiber to focus the transmitted light. The outer diameter of the cladding of the gradient-index multimode optical fiber is smaller than the outer diameter of the cladding of the hollow-core optical fiber, so that the miniaturization of the optical fiber focusing port can be achieved, and the flexible transmission of ultrafast lasers can be ensured. The composite hollow-core optical fiber can be used for medical treatment and laser processing at extremely narrow positions.

[0046] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A composite hollow core optical fiber, characterized in that: include: A hollow-core optical fiber, and a graded-index multimode optical fiber arranged at one end of the hollow-core optical fiber, wherein a drop lens is arranged 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 drop 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.

2. The composite hollow core optical fiber according to claim 1, characterized in that: The shape of the drop lens is conical.

3. The composite hollow core optical fiber according to claim 1, characterized in that: The focusing distance of the drop lens is expressed as: Among them, Z LF is the focusing distance of the drop lens, W0 is the mode field radius of the gradient index multimode fiber, λ is the wavelength of the laser, R OSC is the radius of curvature of the drop lens, and n is the refractive index of the gradient-index multimode optical fiber.

4. The composite hollow core optical fiber according to claim 1, characterized in that: The material of the drop lens is silicon dioxide.

5. The composite hollow core optical fiber according to claim 1, characterized in that: The inner diameter of the cladding of the hollow-core optical fiber has a value range of 10 μm to 60 μm, and the outer diameter of the cladding of the hollow-core optical fiber has a value range of 200 μm to 500 μm.

6. A method for preparing a composite hollow core 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 5; the preparation method comprises: Arranging a plurality of tubular elements on the inner wall of the cladding along the circumference of the cladding to obtain a hollow core optical fiber; A graded-index multimode optical fiber of a preset length is sintered at one end of the hollow-core optical fiber, wherein the hollow-core optical fiber and the cladding of the graded-index multimode optical 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 optical 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 optical fiber; A drop lens is prepared at one end of the graded-index multimode optical fiber away from the hollow-core optical fiber to obtain a composite hollow-core 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 optical fiber and smaller than the outer diameter of the cladding of the graded-index multimode optical fiber.

7. The method for preparing a composite hollow core optical fiber according to claim 6, characterized in that: The material of the plurality of tubular elements is pure quartz, and the material of the cladding of the hollow core optical fiber is acrylate.

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

9. The method for preparing a composite hollow core optical fiber according to claim 6, characterized in that: The method further comprises: The end of the hollow-core optical fiber away from the graded-index multimode optical fiber is subjected to vacuum or gasification treatment.

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