Optical fiber end face micro-operation system and preparation method thereof

Abstract

This invention belongs to the field of femtosecond laser micro / nano fabrication technology, specifically disclosing a micro-operating system for fiber optic end faces. Its features include: an optical fiber, a Fresnel lens structure, two hydrogel grippers, and a silver nanoparticle layer. The Fresnel lens structure is directly fabricated and fixed at the center of the fiber end face; the two hydrogel grippers are directly fabricated and fixed to the fiber end face, with the two grippers located on opposite sides of the Fresnel lens structure; the silver nanoparticle layer is attached to the surface of the hydrogel grippers. This invention not only solves the technical challenge of integrating multifunctional microstructures on fiber end faces but also achieves the synergistic operation of optical focusing and mechanical clamping, providing a novel technical solution with a compact structure, integrated functions, and flexible operation for applications such as micro / nano manipulation, micro-perforation, and photothermal ablation.

Description

Technical Field

[0001] This invention belongs to the field of femtosecond laser micro-nano fabrication technology, specifically a micro-operating system for fiber end face and its fabrication method. Background Technology

[0002] As an excellent medium for optical energy transmission, optical fiber has shown broad application prospects in fields such as microfluidics, biosensing, precision medicine, and minimally invasive procedures through the integrated fabrication of its end-face micro and nanostructures. By integrating micro-optical elements and micromechanical structures into the end face of optical fibers, it is possible to achieve optical manipulation, capture, and localized micro-processing (such as ablation, perforation, and localized heating) of tiny targets. However, the cross-section of optical fiber end faces is only on the order of hundreds of micrometers, and the overall shape is slender. Due to the constraints of processing size and the special morphology of the end face, traditional micro and nano manufacturing processes (such as electron beam etching and photolithography) are difficult to apply to the precise integration and three-dimensional secondary processing of optical fiber end faces.

[0003] Existing technologies have developed fiber end-face micro-grippers based on femtosecond laser two-photon processing (see Chinese patent application CN115356815B). These technologies achieve optically driven clamping by sequentially integrating a flexible actuation structure (a composite of thermally responsive hydrogel and metal nanoparticles) and a rigid framework structure on the fiber end-face. While this technology solves the problems of fiber end-face functionalization and remote optical actuation, it still has significant limitations: First, existing solutions mostly employ a composite structure of "flexible actuation + rigid framework," relying on changes in the hydrogel volume to pull the rigid framework to achieve opening and closing. This structure is complex and has a single function, only capable of clamping and unable to achieve synergy between optical focusing and mechanical manipulation. Second, in existing technologies, metal nanoparticles are uniformly distributed within the hydrogel. Although this enables photothermal conversion, it lacks the ability to control the beam, making it impossible to simultaneously perform composite operations such as targeted heating or ablation. Third, existing gripper structures are mostly symmetrical opening and closing modes, making it difficult to achieve directional bending clamping and precise positioning of small targets.

[0004] Therefore, how to achieve a high degree of integration between optical focusing elements and mechanical clamping structures at the fiber end face, and solve the problems of difficulty in coordinating "optical control" and "mechanical control", limited space, and single function, has become a technical bottleneck that the current fiber end face micro-nano operating system urgently needs to overcome. Summary of the Invention

[0005] This invention aims to solve at least one of the technical problems existing in the prior art; Therefore, this invention proposes a micro-operating system for fiber optic endfaces and its fabrication method.

[0006] A fiber optic end-face micro-operating system, characterized in that it comprises: optical fiber; A Fresnel lens structure, which is directly machined and fixed at the center of the end face of the optical fiber; Two hydrogel grippers, directly machined and fixed to the end face of the optical fiber, are located on opposite sides of the Fresnel lens structure; and A layer of silver nanoparticles is attached to the surface of the hydrogel grippers; in: The Fresnel lens structure is used to focus the light beam introduced by the optical fiber to heat or ablate the target object. The hydrogel gripper has an asymmetric cross-linking density controlled by femtosecond laser processing parameters, which enables it to bend directionally toward the center of the optical fiber when the silver nanoparticle layer absorbs the light energy introduced by the optical fiber and generates a photothermal effect, so as to clamp or fix the target object.

[0007] Preferably, the optical fiber is a multimode optical fiber.

[0008] Preferably, the Fresnel lens structure includes a circular phase structure at the top and a support structure at the bottom; the phase of the circular phase structure is formed by superimposing the Fresnel lens phase and the Bessel light phase, and is used to convert the incident beam into a Bessel beam; the support structure is a hollow columnar structure with windows on its sidewalls for accelerating development.

[0009] Preferably, the hydrogel grippers are made of a thermally responsive hydrogel material, and the two hydrogel grippers are elongated and their dimensions are adapted to be symmetrically arranged on the end face of the optical fiber.

[0010] Preferably, the thermoresponsive hydrogel material is poly(N-isopropylacrylamide) (PNIPAM).

[0011] Preferably, the asymmetric crosslinking density of the hydrogel grippers is achieved by adjusting the scanning area and number of scans during femtosecond laser processing, so that the left gripper and the right gripper have different crosslinking densities, thereby producing different degrees of shrinkage under photothermal stimulation and achieving directional bending towards the center of the optical fiber.

[0012] Preferably, the silver nanoparticle layer is generated in situ on the surface of the hydrogel gripper by reducing the silver ammonia solution with a femtosecond laser.

[0013] This invention also proposes a method for fabricating a micro-operating system on an optical fiber end face, comprising the following steps: Step 1: Fix the fiber end face; Step 2: Using a femtosecond laser processing system, a Fresnel lens structure is fabricated at the center of the end face of the optical fiber; Step 3: Using a femtosecond laser processing system, hydrogel grippers are processed on both sides of the Fresnel lens structure. By adjusting the parameters during femtosecond laser processing, the hydrogel grippers are made to have an asymmetric cross-linking density, thereby enabling them to bend directionally towards the center of the optical fiber under photothermal stimulation. Step 4: Form a layer of silver nanoparticles with photothermal conversion capability on the surface of the hydrogel gripper.

[0014] Preferably, the method for fixing the fiber end face in step one is as follows: insert the fiber into the ceramic ferrule and fix the fiber end face onto the substrate using photoresist.

[0015] Preferably, after step two and before step three, a step of developing the processed fiber end face is included to remove the unprocessed photoresist material and obtain a clear Fresnel lens structure; after step three and before step four, a step of developing the processed fiber end face is included to remove the unprocessed hydrogel material.

[0016] The beneficial effects of this invention are: This invention integrates a Fresnel lens structure with hydrogel grippers on the end face of a single optical fiber. The photothermal effect of the silver nanoparticle layer drives the hydrogel grippers to bend and hold the target object in a specific direction. Simultaneously, the Fresnel lens converts the incident light beam into a Bessel beam and focuses it, achieving targeted heating or ablation of the held target. This composite function of "first clamping and fixing, then precise manipulation" solves the technical challenge of coordinating "optical control" and "mechanical control" in traditional solutions, significantly improving the precision and flexibility of composite manipulation of small objects and overcoming the limitation of only being able to perform a single clamping operation in the prior art.

[0017] This invention achieves asymmetric cross-linking density in the hydrogel grippers on both sides by controlling the scanning area and number of scans during femtosecond laser processing. This results in varying degrees of contraction under photothermal stimulation, enabling directional bending towards the center of the optical fiber. Compared to the complex structures in existing technologies that rely on rigid skeletons for opening and closing, this application achieves reliable clamping and fixation without a rigid skeleton. The structure is more compact, and the directional bending mode is more conducive to the precise positioning and flexible grasping of small targets (such as cells and particles), avoiding mechanical damage to the target object.

[0018] All functional structures of this invention (Fresnel lens, hydrogel gripper, silver nanoparticle layer) are directly fabricated and fixed to the fiber end face, with an overall size on the order of hundreds of micrometers, making full use of the limited space of the fiber end face. Compared with existing technologies that require complex rigid-flexible composite structures, this invention achieves multifunctional integration on a single fiber end face, making it particularly suitable for minimally invasive procedures in space-constrained environments such as small cavities within biological bodies.

[0019] This invention utilizes optical fibers to guide light energy, which is then efficiently converted into photothermal energy through a silver nanoparticle layer to drive the movement of a hydrogel gripper, achieving remote active optical manipulation. Employing thermoresponsive hydrogel materials such as PNIPAM, it exhibits excellent biocompatibility, and the optical driving method avoids the negative impacts of temperature manipulation on biological tissues, making it of significant application value in precision medicine and single-cell manipulation.

[0020] This invention employs femtosecond laser micro / nano fabrication technology to directly reduce silver nanoparticles in situ on the surface of hydrogel grippers by controlling laser parameters, achieving precise integration of functional materials and microstructures. The fabrication process eliminates the need to remove the optical fiber from the ceramic ferrule; a clear structure can be obtained through a simple development step. The operation is controllable, with high processing precision and good repeatability, making it suitable for batch fabrication in complex micromanipulation scenarios.

[0021] In summary, this invention not only solves the technical challenge of integrating multifunctional microstructures on the fiber end face, but also achieves the synergistic operation of optical focusing and mechanical clamping, providing a novel technical solution with compact structure, integrated functions, and flexible operation for applications such as micro-nano manipulation, micro-perforation, and photothermal ablation. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the femtosecond laser processing system used in this invention; the system includes a femtosecond laser processing main component, an image acquisition module, a manual input module, and a sample to be processed; Figure 2 This is a schematic diagram of a ceramic ferrule-optical fiber-photoresist sample. The diagram shows the optical fiber, photoresist, ceramic ferrule, and the cover glass substrate at the bottom, demonstrating the method of fixing the optical fiber end face. Figure 3 This is a schematic diagram of a Fresnel lens structure located at the end face of an optical fiber; the diagram shows the Fresnel lens fabricated and fixed at the center of the end face of the optical fiber, including the circular phase structure at the top and the support structure at the bottom; Figure 4 A schematic diagram of the front view and phase diagram of a Fresnel lens structure located at the end face of an optical fiber; Figure 5 This is a schematic diagram of a composite structure located at the end face of an optical fiber; the diagram shows a composite structure with hydrogel grippers fabricated on both sides of the Fresnel lens structure; Figure 6 This is a frontal schematic of the composite structure located on the fiber end face; the figure shows two hydrogel grippers symmetrically arranged on both sides of the Fresnel lens structure, and the distance from the center of the gripper to the center of the fiber end face is marked (25μm). Figure 7 This is a schematic diagram of a micro-operating system located at the end face of an optical fiber; the figure shows the complete micro-operating system after a layer of silver nanoparticles has been formed on the surface of the hydrogel grippers; Figure 8 This is a schematic diagram of the deformation of a miniature operating system located at the end face of an optical fiber; the diagram shows the state in which the hydrogel grippers bend towards the center of the optical fiber under the drive of photothermal effect after the optical fiber is illuminated, thereby clamping the target object. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the specific embodiments of this invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the scope of protection of this invention.

[0025] This invention provides a micro-operating system for fiber optic end faces, which highly integrates optical focusing and mechanical clamping functions into the end face of a single fiber. The system utilizes femtosecond laser micro-nano fabrication technology to directly fabricate a Fresnel lens structure at the center of the fiber end face, and then fabricates hydrogel grippers with asymmetric cross-linking density on both sides of the lens. Finally, a silver nanoparticle layer is restored in situ on the gripper surface. During operation, light energy is introduced through the fiber, causing the silver nanoparticle layer to generate a photothermal effect, driving the hydrogel grippers to bend directionally towards the center of the fiber to clamp the target object. Simultaneously, the Fresnel lens at the center focuses the beam, allowing for heating or ablation of the clamped target object. This solves the problems of difficulty in coordinating "optical control" and "mechanical control," space constraints, and limited functionality in traditional solutions.

[0026] Example 1

[0027] This embodiment provides a micro operating system for fiber optic endfaces, the specific structure of which is as follows.

[0028] like Figures 5 to 8 As shown, the fiber end face micro-operating system includes: a fiber, a Fresnel lens structure, two hydrogel grippers, and a silver nanoparticle layer.

[0029] The optical fiber is a multimode fiber with a total diameter of 125 μm and a light-transmitting portion diameter of 50 μm. The Fresnel lens structure is directly fabricated and fixed at the center of the end face of the optical fiber. Two hydrogel grippers are directly fabricated and fixed to the end face of the optical fiber, and are located on both sides of the Fresnel lens structure, arranged symmetrically. The silver nanoparticle layer is attached to the surface of the hydrogel grippers.

[0030] The Fresnel lens structure is used to focus the light beam guided by the optical fiber to heat or ablate the target object. Specifically, such as... Figure 3 and Figure 4 As shown, the Fresnel lens structure consists of a circular phase structure at the top and a support structure at the bottom. The circular phase structure has a diameter of 35 μm and a focal length of 34 μm. Its phase is formed by superimposing the Fresnel lens phase (focal length 34 μm) and the Bessel light phase (radial wavenumber kr = 2π / 40 μm⁻¹, order n = 0), and is used to convert the incident beam into a Bessel beam. The support structure is a hollow columnar structure with a height of 12 μm, an outer diameter of 35 μm, and a wall thickness of 2 μm. It has 3 μm × 6 μm rectangular windows at a distance of 3 μm from the bottom surface along four orthogonal directions. This window design increases the contact area between the support structure and the developer, thereby accelerating the development process.

[0031] The hydrogel grippers are made of a thermally responsive hydrogel material. The hydrogel material is prepared by dissolving 400 mg of isopropylacrylamide, 60 mg of crosslinking agent N,N-methylenebisacrylamide, and 15 mg of photoinitiator diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide in 500 μL of ethylene glycol, then adding 300 μL of triethanolamine, and sonicating in a 40°C water bath for 30-40 minutes until completely dissolved, yielding a hydrogel solution suitable for femtosecond laser processing. Each gripper has dimensions of 50 μm in length, 10 μm in width, and 10 μm in height. The two hydrogel grippers have an asymmetric crosslinking density controlled by femtosecond laser processing parameters. Specifically, the left and right grippers have different crosslinking densities; for example, by adjusting the scanning area and number of scans during femtosecond laser processing, the crosslinking density of one gripper can be made higher than that of the other. This asymmetric structure causes the grippers to contract to different degrees on both sides when stimulated by light and heat, resulting in directional bending towards the center of the optical fiber to clamp or fix the target object.

[0032] The silver nanoparticle layer is generated in situ on the surface of the hydrogel gripper by reducing a silver ammonia solution with a femtosecond laser. This silver nanoparticle layer can efficiently absorb light energy introduced by the optical fiber and generate a photothermal effect, providing a driving force for the directional bending of the hydrogel gripper.

[0033] Example 2 This embodiment provides a method for fabricating a micro-operating system for the fiber optic end face as described in Embodiment 1. This method is based on a process combining femtosecond laser processing with photoresist, hydrogel, and nano-silver reduction technologies to achieve integrated fabrication of multifunctional microstructures for the fiber optic end face. Figure 1 As shown, the femtosecond laser processing system used in this invention includes a femtosecond laser processing component, an image acquisition component, a manual input module, and a sample to be processed. Specifically, it includes the following steps: Step 1: Fixing the fiber end face Fix the fiber end face. The specific operation is as follows: Add 5μL of SZ2080 photoresist to the cover glass slide, insert one end of the ceramic ferrule into the photoresist, and slowly push the multimode fiber into the photoresist. Place the cover glass slide on a baking plate and heat at 100℃ for 35 minutes to solidify the photoresist, thereby fixing the fiber end face onto the substrate.

[0034] Step 2: Fabrication of Fresnel lens structure A Fresnel lens structure was fabricated at the center of the end face of the optical fiber using a femtosecond laser processing system. The femtosecond laser processing system was turned on, and the laser power was adjusted to 27.5mW. The laser scanning speed was set to 100mm / s, the number of scans to 1000, and the laser parameters were set to a pulse width of 400fs, a wavelength of 808nm, and a repetition frequency of 1MHz via the manual input module. The pre-written Fresnel lens structure fabrication program was input into the femtosecond laser processing system. The phase design of the Fresnel lens used the formula phlens=−π / (λf)(x²+y²), which represents the secondary phase distribution required for spherical wave focusing. A hollow cylindrical substrate structure was placed below the lens. The ceramic ferrule-optical fiber-photoresist sample prepared in step one was then placed at the workpiece location, and the processing was started. Figure 2 As shown.

[0035] Step 3: Development The processed fiber end face is developed to remove unprocessed photoresist material, obtaining a clear Fresnel lens structure. The processed sample is then removed and immersed in anhydrous ethanol for 40 minutes to remove the photoresist in the unprocessed areas, obtaining a Fresnel lens structure located at the center of the fiber end face. The entire process does not require removing the fiber from the ceramic ferrule. The resulting structure is shown below. Figure 3 and Figure 4 As shown.

[0036] Step 4: Processing the hydrogel grippers Using a femtosecond laser processing system, hydrogel grippers were fabricated on both sides of the Fresnel lens structure. An optical fiber with the Fresnel lens structure, along with its ceramic ferrule, was placed upright on a glass slide coated with 5 μL PPNIPAM hydrogel, positioned at the workpiece location. A pre-written hydrogel gripper fabrication program was input into the femtosecond laser processing system, and hydrogel grippers were fabricated on both sides of the lens structure, with the gripper center 25 μm from the center of the fiber end face. The laser power was adjusted to 75 mW, the laser scanning speed to 100 mm / s, and the number of scans to 1000. The dimensions of a single hydrogel gripper were 50 μm × 10 μm × 10 μm.

[0037] By adjusting the parameters during femtosecond laser processing, the hydrogel grippers achieve an asymmetric cross-linking density, thereby enabling them to bend directionally towards the fiber center under photothermal stimulation. Specifically, the asymmetric structure of the grippers is achieved by adjusting the processing parameters on the left and right sides: for the left gripper, the scanning area ratio of the hydrogel on the xOy plane is set to 3:7, while the scanning number ratio along the z-axis is 3:1; for the right gripper, the opposite area ratio of 7:3 and scanning number ratio of 1:3 are used. This combination of parameters results in different laser scanning numbers per unit volume on the left and right sides, thereby introducing different cross-linking densities and mechanical properties on the left and right sides, ultimately causing the grippers to undergo asymmetric deformation under photothermal stimulation, meeting the requirement of bending towards the fiber center.

[0038] Step 5: Secondary Development The processed fiber end face was developed to remove the unprocessed hydrogel material. The sample was then developed again in anhydrous ethanol for 10 minutes to remove the PNIPAM hydrogel in the unprocessed area. The structured fiber was then removed from the ceramic ferrule, resulting in the composite structure shown below. Figure 5 and Figure 6 As shown.

[0039] Step Six: Forming a Silver Nanoparticle Layer A layer of silver nanoparticles with photothermal conversion capability is formed on the surface of the hydrogel gripper. One end of the fiber ribbon structure obtained in step five is placed flat on a glass slide containing 15 μL of a silver ammonia solution with a concentration of 0.05 mol / L-0.1 mol / L, immersing the hydrogel structure in the solution. The laser power is adjusted to 3 mW, the scanning speed is set to 100 mm / s, and the number of scans is 1000. The silver nanoparticles are reduced in situ on the surface of the hydrogel gripper using a femtosecond laser. Through this step, the silver nanoparticles are reduced and attached to the surface of the hydrogel gripper, obtaining a complete fiber end-face micro-operating system, such as... Figure 7 As shown.

[0040] Example 3

[0041] This embodiment describes the working process of operating a target object using the fiber optic end-face micro-operating system described in Embodiment 1 or the system prepared by the method described in Embodiment 2.

[0042] like Figure 8As shown, the prepared fiber-optic end-face micro-operating system is brought close to the target object (such as a cell or microparticle). Continuous laser light is introduced through the fiber. The laser light is first absorbed by the silver nanoparticle layer attached to the surface of the hydrogel gripper, generating a photothermal effect and raising the local temperature. Due to its thermal response characteristics, the hydrogel gripper (PNIPAM) shrinks in volume when the temperature rises. Because the two hydrogel grippers have asymmetric cross-linking densities, they shrink to different degrees under photothermal stimulation, thereby synergistically achieving directional bending towards the center of the fiber, enabling the gripping and fixation of micron-sized targets.

[0043] Meanwhile, the beam of light at the center of the optical fiber passes through a Fresnel lens structure, which converts the incident beam into a Bessel beam and focuses it. The focused high-energy beam can then perform targeted ablation, perforation, or localized heating on the target object held in the gripper.

[0044] Thus, this invention achieves a composite function of "first clamping and fixing, then precise operation" for micro-targets, significantly improving the precision and flexibility of composite manipulation of micro-objects.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention. The above description is merely a specific embodiment of the present invention and does not limit the scope of protection of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be covered within the scope of protection of the present invention.

[0046] The embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the embodiments above are only for helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A fiber optic end-face micro-operating system, characterized in that, include: optical fiber; A Fresnel lens structure, which is directly machined and fixed at the center of the end face of the optical fiber; Two hydrogel grippers, directly machined and fixed to the end face of the optical fiber, are located on opposite sides of the Fresnel lens structure; and A layer of silver nanoparticles is attached to the surface of the hydrogel grippers; in: The Fresnel lens structure is used to focus the light beam introduced by the optical fiber to heat or ablate the target object. The hydrogel gripper has an asymmetric cross-linking density controlled by femtosecond laser processing parameters, which enables it to bend directionally toward the center of the optical fiber when the silver nanoparticle layer absorbs the light energy introduced by the optical fiber and generates a photothermal effect, so as to clamp or fix the target object.

2. The fiber optic end-face micro-operating system according to claim 1, characterized in that, The optical fiber is a multimode optical fiber.

3. The fiber optic end-face micro-operating system according to claim 1, characterized in that, The Fresnel lens structure includes a circular phase structure at the top and a support structure at the bottom; the phase of the circular phase structure is formed by superimposing the Fresnel lens phase and the Bessel light phase, and is used to convert the incident beam into a Bessel beam; the support structure is a hollow columnar structure with windows on its sidewalls for accelerating development.

4. The fiber optic end-face micro-operating system according to claim 1, characterized in that, The hydrogel grippers are made of thermally responsive hydrogel material, and the two hydrogel grippers are elongated and their dimensions are adapted to be symmetrically arranged on the end face of the optical fiber.

5. The fiber optic end-face micro-operating system according to claim 4, characterized in that, The thermoresponsive hydrogel material is poly(N-isopropylacrylamide) (PNIPAM).

6. The fiber optic end-face micro-operating system according to claim 1, characterized in that, The asymmetric crosslinking density of the hydrogel grippers is achieved by adjusting the scanning area and number of scans during femtosecond laser processing, so that the left gripper and the right gripper have different crosslinking densities, thereby producing different degrees of shrinkage under photothermal stimulation and achieving directional bending towards the center of the optical fiber.

7. The fiber optic end-face micro-operating system according to claim 1, characterized in that, The silver nanoparticle layer is generated in situ on the surface of the hydrogel gripper by reducing silver ammonia solution with a femtosecond laser.

8. A method for fabricating a micro-operating system on an optical fiber end face, characterized in that, Includes the following steps: Step 1: Fix the fiber end face; Step 2: Using a femtosecond laser processing system, a Fresnel lens structure is fabricated at the center of the end face of the optical fiber; Step 3: Using a femtosecond laser processing system, hydrogel grippers are processed on both sides of the Fresnel lens structure. By adjusting the parameters during femtosecond laser processing, the hydrogel grippers are made to have an asymmetric cross-linking density, thereby enabling them to bend directionally towards the center of the optical fiber under photothermal stimulation. Step 4: Form a layer of silver nanoparticles with photothermal conversion capability on the surface of the hydrogel gripper.

9. The preparation method according to claim 8, characterized in that, The method for fixing the fiber end face in step one is as follows: insert the fiber into the ceramic ferrule and fix the fiber end face to the substrate using photoresist.

10. The preparation method according to claim 8, characterized in that, After step two and before step three, a development step is included to remove the unprocessed photoresist material and obtain a clear Fresnel lens structure; after step three and before step four, a development step is included to remove the unprocessed hydrogel material.

Images