A method for transferring metal nanofilm on optical fiber end face

Abstract

The present invention relates to the technical field of optical fiber device preparation, and specifically to a method for transferring a metal nanofilm on the end face of an optical fiber. The method comprises the following steps: providing a substrate, forming a metal nanofilm and a water-soluble support layer on the surface of the substrate; separating the substrate; installing an optical fiber insert at one end of the pretreated optical fiber, transferring the water-soluble support layer combined with the metal nanofilm to the end face of the optical fiber, so that the metal nanofilm contacts the end face of the optical fiber; coating ultraviolet curing glue, and placing it in water after curing to remove the water-soluble support layer; cutting and shaping, so that the metal nanofilm is tightly combined with the optical fiber insert and the end face of the optical fiber through electrostatic adsorption. The present invention introduces a water-soluble support layer to improve the flatness and uniformity of the metal nanofilm on the end face of the optical fiber while improving the preparation efficiency, thereby solving the problems of low efficiency, poor precision, easy contamination and damage to the film in the existing method for transferring micro-nanostructures on the end face of the optical fiber.

Description

Technical Field

[0001] The invention relates to the technical field of optical fiber device preparation, and in particular to a method for transferring a metal nano film on an optical fiber end face. Background Art

[0002] Fiber optic devices have the advantages of miniaturization, easy networking and multiplexing, corrosion resistance, and resistance to electromagnetic interference. They are widely used in optoelectronic fields such as optical communications, optical sensing, and optical regulation. At present, fiber end face devices use the fiber end face as a microscopic platform for the interaction between light and matter, combining the two major technical advantages of fiber photonics and planar micro-nano processing technology. By integrating a variety of materials and various ingenious functional structures into the fiber end face, combining the mature basic conditions of the fiber optic network, and empowering the existing fiber optic devices and fiber optic networks, the functionalized devices of the fiber end face are widely used in optical sensing, optical communications, optical regulation, and imaging. Although the combination of fiber end face and micro-nano processing technology is of great significance, the small space of the fiber end face greatly increases the technical difficulty of micro-nano processing.

[0003] At present, the methods for processing micro-nano structures on the end faces of optical fibers that have been realized by research teams at home and abroad mainly include the following: self-assembly method for modifying the end faces of optical fibers; technology for patterning the end faces of optical fibers using semiconductor micro-nano processing technologies such as electron beams; and technology for transferring micro-nano structures processed on planar substrates to the end faces of optical fibers. Among the mainstream micro-nano processing technologies for the end faces of optical fibers, the technology for transferring micro-nano structures processed on planar substrates to the end faces of optical fibers is compatible with existing semiconductor micro-nano processing technologies, while also having the advantages of large-scale processing to improve production efficiency and reduce costs. The micro-nano structures realized by this type of processing technology are usually first completed on a planar substrate and then transferred to the end face of the optical fiber. Therefore, in theory, any structure that can be prepared on a planar substrate can be integrated on the end face of the optical fiber.

[0004] At present, the technologies for transferring micro-nano structures on the end face of optical fiber mainly include: physical contact transfer, manual transfer, nano-cutting transfer and adhesive transfer. Although these technologies can realize the transfer of micro-nano structures, they still have certain limitations in the actual processing process, such as the inability to control the accuracy of sample transfer position, especially for the transfer of small-area micro-nano structures.

[0005] Patent application document CN104345358A discloses a method for making a metal micro-nano structure on the end face of an optical fiber using a peel-and-stick method. The method mainly uses an adhesive to bond the end face of the optical fiber and the metal micro-nano structure. However, this configuration of the adhesive may cause the adhesive to cover or contaminate the metal micro-nano structure, affecting the overall performance of the optical fiber device. In particular, in the adhesive bonding transfer technology, the metal micro-nano structure can only be made with the adhesive as the substrate, and the optical response and application performance of the metal micro-nano structure are restricted by the physical and chemical properties of the adhesive.

[0006] Therefore, the high-precision, high-efficiency, and high-quality transfer method of metal nanostructures on the end face of optical fiber is still one of the bottlenecks in the development of micro-nano optical fiber devices. It is urgent to provide a transfer method that is simple to operate, highly firm, and free of adhesive residues to prepare metal nanofilm optical fiber probe devices and explore their application performance in optical sensing and other aspects. Summary of the invention

[0007] In order to solve the problems of low efficiency, poor precision, easy contamination and damage to the film in the existing method of transferring micro-nano structure on the end face of optical fiber, the purpose of the present invention is to provide a method for transferring metal nano film on the end face of optical fiber.

[0008] The present invention mainly utilizes the water-soluble support layer as an auxiliary structure in the transfer process, simplifies the preparation process, and improves the preparation efficiency. At the same time, the method can also achieve a stable combination of the metal nanofilm and the optical fiber end face, providing new possibilities for the development of optical sensing and optical communication fields.

[0009] To achieve the above objectives, the technical solution of the present invention is as follows.

[0010] The present invention provides a method for transferring a metal nanofilm on an optical fiber end face, comprising the following steps:

[0011] Providing a substrate, and forming a metal nanofilm on the surface of the substrate;

[0012] A water-soluble support layer is formed by coating the side of the substrate surface where the metal nanofilm is formed;

[0013] separating the substrate to obtain a water-soluble support layer combined with a metal nanofilm;

[0014] Installing an optical fiber insert at one end of the pre-treated optical fiber, transferring the water-soluble support layer combined with the metal nanofilm to the end face of the optical fiber, so that the metal nanofilm contacts the end face of the optical fiber;

[0015] Coating ultraviolet curing glue around the optical fiber core in contact with the metal nanofilm, and after curing, immersing it in water to remove the water-soluble support layer;

[0016] The metal nanofilm is cut and shaped, and the metal nanofilm is tightly combined with the optical fiber ferrule and the optical fiber end face through electrostatic adsorption.

[0017] The present invention introduces a water-soluble support layer to support and assist the transfer of the metal nanofilm during the preparation and transfer process, and can protect the metal nanofilm during the transfer and subsequent processing to prevent the metal nanofilm from being contaminated or damaged; it also helps to simplify subsequent processing steps and improve preparation efficiency.

[0018] The method of the present invention can improve the position accuracy and preparation efficiency of the metal nanofilm on the end face of the optical fiber, and solve the problem of adhesive residue; the method of the present invention can expand the types of metal nanofilm support substrates, no longer limited to adhesives. At the same time, for different purposes, different types of metal nanofilms can be transferred and different types of optical fibers or optical fiber ferrules can be used as substrates, which can be widely used in optical sensing, optical communication and other fields.

[0019] Preferably, the area of ​​the metal nanofilm is larger than the end surface area of ​​the optical fiber plug; the area of ​​the water-soluble support layer is larger than the end surface area of ​​the optical fiber plug. Therefore, it is convenient to apply UV curing glue later to fix the water-soluble support layer combined with the metal nanofilm on the end surface of the optical fiber plug. At the same time, it is convenient to support, assist transfer and protect the metal nanofilm during the preparation and transfer process to prevent the metal nanofilm from being contaminated or damaged.

[0020] Preferably, the material of the water-soluble support layer is polyvinyl pyrrolidone K30 (other water-soluble materials with certain bonding ability may also be used). Polyvinyl pyrrolidone K30, referred to as PVP-K30, is a water-soluble polymer compound. As the water in the solution evaporates, PVP-K30 will gradually solidify. The solidification time of the PVP-K30 solution is related to the ambient temperature and humidity. At room temperature, the solidification time is 2 to 3 hours. The dissolution time of polyvinyl pyrrolidone K30 is related to the thickness of PVP-K30 and the ambient temperature. It takes 10 to 30 minutes to dissolve millimeter-thick PVP-K30 at room temperature.

[0021] Further preferably, a water-soluble support layer is formed by coating on the side of the substrate on which the metal nanofilm is formed, and the specific operation is:

[0022] A polyvinyl pyrrolidone K30 solution is coated on the side of the substrate surface where the metal nanofilm is formed, and after drying, a water-soluble support layer is formed;

[0023] The polyvinyl pyrrolidone K30 solution is obtained by mixing polyvinyl pyrrolidone K30 and water in a mass ratio of 3 to 5:10.

[0024] Preferably, the substrate is a continuous and flat substrate or a substrate with a micro-nano structure; the structure of the metal nanofilm is the same as the surface structure of the substrate.

[0025] Further preferably, the substrate having the micro-nano structure is processed to form a nanopore array structure on the surface of the substrate.

[0026] Preferably, a metal nanofilm is formed on the surface of the substrate, and the specific operation is:

[0027] The metal nanofilm is deposited on the surface of the substrate by using the resistance thermal evaporation method.

[0028] Further preferably, the process parameters of resistance thermal evaporation are: the pressure in the vacuum chamber is 8 to 9×10 -4 Pa, the deposition rate of the metal nanofilm is The thickness of the metal nanofilm is 50 to 100 nm.

[0029] Preferably, the pre-processed optical fiber is to make the end face of the optical fiber flat and smooth.

[0030] The specific process of flattening and smoothing is: remove the optical fiber coating, clean the outside of the optical fiber with ethanol after stripping the coating, cut the optical fiber, and obtain a flat and smooth optical fiber end face. The concentration of ethanol is ≥99.5%. Cutting the optical fiber can be done with a cutting knife or a ruby ​​scribing pen.

[0031] Preferably, before the metal nanofilm is brought into contact with the end face of the optical fiber, ensure that the end face of the optical fiber and the end face of the optical fiber ferrule are located on the same plane. This facilitates the subsequent coating of UV curing adhesive to fix the water-soluble support layer combined with the metal nanofilm on the end face of the optical fiber ferrule. It can also ensure that the metal nanofilm is tightly combined with the optical fiber ferrule and the end face of the optical fiber through electrostatic adsorption.

[0032] Preferably, the outer diameter of the optical fiber matches the inner diameter of the optical fiber ferrule.

[0033] Preferably, the optical fiber ferrule is a SMA905 optical fiber ferrule. A suitable optical fiber ferrule can also be selected according to actual needs.

[0034] Preferably, the UV curing adhesive is NOA61. NOA61 is cured by irradiating a UV lamp with a wavelength of 365 nm for 5 to 10 seconds.

[0035] Preferably, the substrate is a silicon substrate. Of course, a suitable substrate can also be selected according to actual needs.

[0036] Beneficial effects of the present invention:

[0037] 1. The present invention can quickly and accurately transfer the metal nanofilm to the optical fiber end face by introducing a water-soluble support layer, and can improve the flatness and uniformity of the metal nanofilm on the optical fiber end face during the preparation and transfer process; and effectively enhance the firmness of the metal nanofilm on the optical fiber end face by fixing with ultraviolet curing glue and electrostatic adsorption.

[0038] 2. The method of the present invention is highly practical and has stable production repeatability. It can mass-produce high-quality optical fiber end metal nanofilm devices with high flatness, high firmness and no adhesive residue, meeting the development requirements of optical fiber devices for the interaction between strong light and matter. At the same time, different types of metal nanofilms can be transferred and different types of optical fibers or optical fiber ferrules can be used as substrates for different purposes, which can be widely used in optical sensing, optical communication and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A flow chart of a method for transferring a metal nanofilm on an optical fiber end face provided in one embodiment of the present invention.

[0040] Figure 2 This is an optical micrograph of an optical fiber ceramic ferrule with a continuous gold nanofilm bonded to the end face according to Example 1 of the present invention.

[0041] Figure 3 The optical micrograph (a) of the optical fiber ceramic ferrule with the gold nano-hole array film bonded to the end face and the scanning electron micrograph (b) of the gold nano-hole array film according to Example 2 of the present invention.

[0042] Figure 4 The reflection spectra of the optical fiber probe with the gold nano-circular hole array film bonded to the end face according to Example 2 of the present invention to salt solutions of different concentrations.

[0043] Figure 5 This is the curve of the characteristic wavelength of the gold nanocircular hole array changing with the refractive index of the salt solution. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0045] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present invention.

[0046] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0047] The end face of an optical fiber is a microscopic platform for the interaction between light and matter. The micro-nano structures on it have an important impact on optoelectronic fields such as optical communications, optical sensing, and optical regulation. At present, in the mainstream micro-nano processing technology of the end face of an optical fiber, the technology of transferring the micro-nano structure processed in a plane to the end face of an optical fiber is compatible with the existing semiconductor micro-nano processing technology, while also having the advantages of large-scale processing to improve production efficiency and reduce costs. The micro-nano structures realized by this processing technology are usually completed on a planar substrate first, and then transferred to the end face of the optical fiber. Therefore, in theory, any structure that can be prepared on a planar substrate can be integrated on the end face of the optical fiber.

[0048] For example, prior art 1: CN104345358A discloses a method for making a metal micro-nano structure on the end face of an optical fiber using a peel-and-stick method, which mainly involves preparing a metal micro-nano structure on the surface of a substrate, applying an adhesive on the end face of the optical fiber or the surface of the metal micro-nano structure, and bonding the optical fiber end face and the metal micro-nano structure with the adhesive. After the adhesive is cured, the substrate is separated to obtain the result. This method mainly uses an adhesive to bond the end face of the optical fiber and the metal micro-nano structure. However, this bonding method may cover or contaminate the metal micro-nano structure, affecting the overall performance of the optical fiber device. In addition, in the adhesive bonding transfer technology, the manufactured metal micro-nano structure can only be based on the adhesive, and the optical response and application performance of the metal micro-nano structure are restricted by the physical and chemical properties of the adhesive.

[0049] Based on this, the present invention can quickly and accurately transfer the metal nanofilm to the optical fiber end face by introducing a water-soluble support layer, and can improve the flatness and uniformity of the metal nanofilm on the optical fiber end face during the preparation and transfer process; through UV curing glue fixation and electrostatic adsorption, the firmness of the metal nanofilm on the optical fiber end face is effectively enhanced, solving the problems of low efficiency, poor precision, easy contamination and damage to the film in the existing optical fiber end face micro-nanostructure transfer method. The present invention has high process stability, wide applicability of metal film and optical fiber types, and the prepared optical fiber end face metal nanofilm has the advantages of good uniformity, high firmness, no adhesive residue, etc. The related optical fiber devices can be widely used in optical sensing, optical communication and other fields.

[0050] In the following embodiments of the present invention, the function of the water-soluble support layer is:

[0051] First, it supports the metal nanofilm during the transfer process to ensure the integrity and flatness of the metal nanofilm structure. Since the metal nanofilm is very thin and fragile, a stable support is needed to prevent it from being damaged or deformed during the transfer process.

[0052] Secondly, it protects the metal nanofilm during the transfer and subsequent processing to prevent the metal nanofilm from being contaminated or damaged.

[0053] Third, it plays an auxiliary role in the transfer process. By coating the water-soluble support layer on the metal nanofilm, the metal nanofilm can be more easily separated from the substrate surface and accurately transferred to the end face of the optical fiber without damaging the metal nanofilm.

[0054] Fourth, the use of a water-soluble support layer can simplify subsequent processing steps and improve preparation efficiency. After the metal nanofilm is transferred to the end face of the optical fiber, it is coated with UV curable glue and cured, and then the entire structure is immersed in water. The water-soluble support layer will dissolve in the water, making it easy to remove the water-soluble support layer, leaving the metal nanofilm tightly attached to the end face of the optical fiber.

[0055] In summary, the present invention mainly utilizes the water-soluble support layer to play multiple roles in the process of preparing the metal nanofilm on the end face of the optical fiber, such as supporting, protecting, assisting transfer and simplifying subsequent treatment.

[0056] The method of the present invention can improve the position accuracy and preparation efficiency of the metal nanofilm on the end face of the optical fiber, and at the same time can expand the types of metal nanofilm supporting substrates, no longer limited to adhesives; the method of the present invention can be used to efficiently prepare metal nanofilms on the end face of optical fiber with high flatness, high firmness and no adhesive residue, meeting the requirements for the development of optical fiber devices for the interaction between strong light and matter.

[0057] The present invention can flexibly select different types of metal nanofilms (for example, continuous and flat nano-thickness films and nano-structured films with artificial units) and different types of optical fibers (for example, solid optical fibers, hollow-core optical fibers, single-mode optical fibers, multi-mode optical fibers) and optical fiber ferrules as substrates according to different uses, and can be widely used in optical sensing, optical communication and other fields.

[0058] The following is a description of the method for transferring the metal nanofilm on the end face of an optical fiber according to the present invention by means of specific embodiments. The methods described in the following embodiments are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0059] Example 1

[0060] like Figure 1 A method for transferring a metal nanofilm on the end face of an optical fiber is disclosed, wherein a 50 nm thick continuous gold nanofilm on a silicon wafer is transferred to the end face of an optical fiber, wherein the optical fiber used is a multimode quartz optical fiber with a core diameter of 105 μm and a cladding diameter of 125 μm. The specific transfer method comprises the following steps:

[0061] (1) Coating: A gold film is deposited on a silicon wafer using the resistance thermal evaporation method. The pressure in the vacuum chamber is 9×10 - 4 Pa, the gold film deposition rate is The film thickness is 50 nm; a 50 nm thick continuous gold nanofilm, referred to as gold film, is obtained.

[0062] (2) Glue coating: Coat a polyvinyl pyrrolidone K30 (PVP-K30) solution on a 50 nm thick gold film. PVP-K30 is a water-soluble polymer compound. As the water in the solution evaporates, PVP-K30 will gradually solidify. The PVP-K30 solution is obtained by mixing PVP-K30 and water at a mass ratio of 4:10. The area coated with the PVP-K30 solution should be larger than the end face area of ​​the optical fiber ferrule to facilitate the subsequent coating of UV-curing glue to fix the PVP-K30 and the gold film on the top of the optical fiber ferrule.

[0063] (3) Peeling: After the PVP-K30 solution solidifies, the PVP-K30 combined with a 50 nm thick gold film (referred to as gold film / PVP-K30) is peeled off from the silicon wafer; the solidification time of the PVP-K30 solution is related to the ambient temperature and humidity. At room temperature, the solidification time is 2 to 3 hours; when peeling off the solidified PVP-K30, you can first use a blade to gently scratch around the PVP-K30 to facilitate the peeling of the gold film.

[0064] (4) Removing the optical fiber coating: Use Miller pliers to strip the coating of a multimode quartz optical fiber of appropriate length; after stripping the coating, wipe and clean the side wall of the optical fiber with 99.5% anhydrous ethanol.

[0065] (5) Preparation of fiber end face: Use a cutting knife or ruby ​​​​scribber pen to cut and remove the coating of the multimode quartz fiber, and check the quality of the fiber end face under an optical microscope and a fiber end face detector to obtain a flat and smooth fiber end face. Install the processed fiber into the SMA905 fiber ferrule, ensuring that the fiber end face and the ferrule end face are on the same horizontal plane. The outer diameter of the SMA905 fiber ferrule is 3.17mm and the inner diameter is 126μm.

[0066] (6) Transfer: Fix the fiber ferrule in the fiber fixture on the three-dimensional translation stage, with the fiber end facing up, and use tweezers to transfer the gold film / PVP-K30 to the end of the ferrule, ensuring that one side of the gold film is in contact with the end of the ferrule. To facilitate the curing of the glue, install a metal plate on another three-dimensional translation stage, adjust the height of the plate, and gently press the gold film / PVP-K30 on the end of the fiber ferrule to fix it, which is convenient for the subsequent coating of UV curing glue.

[0067] (7) Fixation: UV curing glue is applied to the outer surface of the optical fiber ferrule in contact with the gold film. The UV curing glue is NOA61. To prevent the UV curing glue from diffusing to the center of the ferrule and contaminating the optical fiber end face and the gold film, only a small amount of UV curing glue is applied and immediately irradiated with a 365nm wavelength UV lamp for 5 to 10 seconds.

[0068] (8) Dissolution: Immerse the gold film / PVP-K30 and the ferrule fixed by UV curing glue into water. After the PVP-K30 is completely dissolved, the gold film will naturally bond tightly to the ferrule and the end face of the optical fiber due to electrostatic adsorption. The dissolution time of PVP-K30 is related to its thickness and ambient temperature. It takes 10 to 30 minutes to dissolve millimeter-level thick PVP-K30 at room temperature. To avoid PVP-K30 residue, immerse the optical fiber ferrule combined with the gold film in clean water for secondary dissolution and cleaning. Finally, a fiber optic ceramic ferrule with a continuous gold nanofilm on the end face is obtained.

[0069] The fiber optic ceramic ferrule with continuous gold nanofilm on the end face prepared in Example 1 was tested for its firmness. The prepared fiber optic device was repeatedly immersed in water, and then dried and observed under an optical microscope. Figure 2 .

[0070] Figure 2 This is an optical micrograph of an optical fiber ceramic ferrule with a continuous gold nanofilm bonded to the end face according to Example 1 of the present invention.

[0071] Depend on Figure 2 It can be seen that in Example 1, there is no shedding phenomenon on the surface of the continuous gold nanofilm on the end face of the optical fiber, and the continuous gold nanofilm has high mechanical firmness.

[0072] Example 2

[0073] A method for transferring a metal nanofilm on the end face of an optical fiber, wherein a 50nm thick nanostructured gold film with a nanocircular hole array on a silicon wafer is transferred to the end face of the optical fiber, wherein the optical fiber used is a multimode quartz optical fiber with a core diameter of 200μm and a cladding diameter of 220μm. The specific transfer method includes the following steps:

[0074] (1) Nanostructure processing: Electron beam lithography is used to process a rectangular array of circular holes with a period of 700 nm and a diameter of 180 nm on a silicon wafer. The area of ​​the nano-circular hole array is 500 μm × 500 μm.

[0075] (2) Coating: A gold film is deposited on the processed silicon wafer using the resistance thermal evaporation method. The pressure in the vacuum chamber is 9×10 -4 Pa, the gold film deposition rate is The film thickness is 50 nm; a nanostructured gold film with a nanocircular hole array is obtained.

[0076] (3) Glue coating: Coat a polyvinyl pyrrolidone K30 (PVP-K30) solution on the nanostructured gold film. PVP-K30 is a water-soluble polymer compound. As the water in the solution evaporates, PVP-K30 will gradually solidify. The PVP-K30 solution is obtained by mixing PVP-K30 and water at a mass ratio of 4:10. The area coated with the PVP-K30 solution should be larger than the end face area of ​​the optical fiber ferrule, and the gold nanocircular hole array should be completely covered to facilitate the subsequent coating of UV-curable glue to fix the PVP-K30 together with the nanostructured gold film on the end face of the optical fiber ferrule.

[0077] (4) Peeling: After the PVP-K30 solution has dried and solidified, the PVP-K30 combined with the nanostructured gold film is peeled off from the silicon wafer. The solidification time of the PVP-K30 solution is related to the ambient temperature and humidity. At room temperature, the solidification time is 2 to 3 hours. When peeling off the solidified PVP-K30, you can first use a blade to gently scratch around the PVP-K30 to facilitate the peeling of the nanostructured gold film.

[0078] (5) Removing the optical fiber coating: Use Miller pliers to strip off the coating of a multimode quartz optical fiber of appropriate length. After stripping off the coating, wipe and clean the side wall of the optical fiber with 99.5% anhydrous ethanol.

[0079] (6) Preparation of fiber end face: Use a cutting knife or ruby ​​​​scribber pen to cut and remove the coating of the multimode quartz fiber, check the quality of the fiber end face under an optical microscope and a fiber end face detector, and obtain a flat and smooth fiber end face. Install the processed fiber into the SMA905 fiber ferrule, ensuring that the fiber end face and the ferrule end face are on the same horizontal plane. The outer diameter of the SMA905 fiber ferrule is 3.17mm and the inner diameter is 230μm.

[0080] (7) Transfer: Fix the inserted optical fiber core in the optical fiber fixture on the three-dimensional translation stage with the optical fiber end face facing up, and use tweezers to transfer the PVP-K30 combined with nanostructured gold film to the core end face, ensuring that one side of the gold film is in contact with the core end face; use a fiber optic spectrometer to measure the reflection spectrum of the nanostructured gold film on the optical fiber end face, connect the free end of the optical fiber to one end of the multimode optical fiber circulator, and the other two ends of the circulator are connected to the white light source and the optical fiber spectrometer respectively; install a metal needle on another three-dimensional translation stage, and use the metal needle to accurately move the position of the PVP-K30 combined with nanostructured gold film until the reflection spectrum curve is consistent with the theoretical curve of the nanostructured gold film, ensuring that the gold nanocircular hole array structure completely covers the optical fiber core area; move the translation stage so that the metal needle gently presses the adjusted PVP-K30 combined with nanostructured gold film to play a fixing role. During this process, monitor the reflection spectrum in real time to ensure that the curve has not changed.

[0081] (8) Fixation: UV curing glue is applied to the outer periphery of the optical fiber core in contact with the nanostructured gold film. The UV curing glue is NOA61. To prevent the UV curing glue from diffusing to the center of the core and contaminating the optical fiber end face and the nanostructured gold film, only a trace amount of UV curing glue is applied, and it is immediately irradiated with a 365nm wavelength UV lamp for 5 to 10 seconds. During this process, the optical fiber end face (especially the nanostructured gold film) is judged to be contaminated by the UV curing glue by monitoring whether the spectrum is consistent with the theoretical spectrum in real time.

[0082] (9) Dissolution: Immerse the PVP-K30 and the ferrule fixed with UV curing glue and the nanostructured gold film in water. During the dissolution of PVP-K30, the spectrum will change continuously. When the spectrum stabilizes, it means that PVP-K30 is completely dissolved. At this time, the nanostructured gold film is naturally tightly bonded to the ferrule and the end face of the optical fiber due to electrostatic adsorption. The dissolution time of PVP-K30 is related to its thickness and ambient temperature. It takes 10 to 30 minutes to dissolve PVP-K30 with a thickness of millimeters under normal temperature conditions. In order to avoid PVP-K30 residue, the optical fiber ferrule combined with the nanostructured gold film is immersed in clean water for secondary dissolution and cleaning. Finally, an optical fiber ceramic ferrule with a gold nano-circular hole array film bonded to the end face is obtained.

[0083] The fiber optic ceramic ferrule with the gold nano-circular hole array film on the end face prepared in Example 2 was tested for firmness. The prepared fiber optic device was repeatedly immersed in water, and then dried and observed under an optical microscope. Figure 3 .

[0084] Figure 3 The optical micrograph (a) of the optical fiber ceramic ferrule with the gold nano-hole array film bonded to the end face and the scanning electron micrograph (b) of the gold nano-hole array film according to Example 2 of the present invention.

[0085] Depend on Figure 3 It can be seen that there is no shedding phenomenon between the optical fiber end face and the surface of the gold nanohole array film, and the gold nanohole array film has high mechanical firmness.

[0086] Application Example 1

[0087] The optical fiber probe with integrated nanostructured gold film prepared in Example 2 was used for salinity detection.

[0088] The free end of the optical fiber probe with integrated nanostructured gold film prepared in Example 2 is connected to a multimode optical fiber circulator, and the other two ends of the circulator are connected to a white light source and an optical fiber spectrometer, respectively. The connected optical fiber probe is then immersed in the liquid to be tested.

[0089] Specifically, water and four different concentrations of salt (NaCl) solutions of 5%, 10%, 15%, and 20% were tested. Please refer to the respective reflectance spectra for details. Figure 4By matching their characteristic wavelengths with the refractive index of each solution, we can get Figure 5 Shown is a scatter plot (experimental value) of the characteristic wavelength versus the change in the solution refractive index.

[0090] Depend on Figure 4 and Figure 5 It can be seen that the characteristic wavelength changes linearly with respect to the refractive index of the solution. After linear fitting, the sensitivity of the two different characteristic wavelengths to the change of the refractive index is 404nm / RIU and 264nm / RIU respectively. This further verifies that there is a linear dependence between the characteristic spectral wavelength in the reflection spectrum and the concentration of the salt solution, and the salinity of the solution can be detected by monitoring the characteristic wavelength.

[0091] From the above analysis, it can be known that the transfer method of the metal nanofilm on the end face of the optical fiber provided by the above embodiment of the present invention can improve the position accuracy and preparation efficiency of the metal nanofilm on the end face of the optical fiber, and at the same time can expand the types of metal nanofilm supporting substrates, no longer limited to adhesives. And the transfer method provided by the above embodiment of the present invention can efficiently prepare metal nanofilms on the end face of the optical fiber with high flatness, high firmness and no adhesive residue, meeting the development requirements of optical fiber devices for the interaction between strong light and matter. At the same time, for different purposes, different types of metal nanofilms can be transferred (for example, the nano-thickness film of Example 1 and the nano-structure film of Example 2) and different types of optical fibers (for example, solid optical fiber, hollow core optical fiber, single-mode optical fiber, multi-mode optical fiber, etc.) and optical fiber ferrules are used as substrates, which can be widely used in optical sensing, optical communication and other fields.

[0092] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for transferring a metal nanofilm on the end face of an optical fiber. It is characterized in that The following steps are involved: Providing a substrate, and forming a metal nanofilm on the surface of the substrate; A water-soluble support layer is formed by coating the side of the substrate surface where the metal nanofilm is formed; separating the substrate to obtain a water-soluble support layer combined with a metal nanofilm; Installing an optical fiber insert at one end of the pre-treated optical fiber, transferring the water-soluble support layer combined with the metal nanofilm to the end face of the optical fiber, so that the metal nanofilm contacts the end face of the optical fiber; Coating ultraviolet curing glue around the optical fiber core in contact with the metal nanofilm to fix the water-soluble support layer combined with the metal nanofilm on the end face of the optical fiber core, and after curing, immersing it in water to remove the water-soluble support layer; The metal nanofilm is cut and shaped, and the metal nanofilm is tightly combined with the optical fiber ferrule and the optical fiber end face through electrostatic adsorption.

2. The method for transferring the metal nanofilm on the end face of an optical fiber according to claim 1, It is characterized in that The area of ​​the metal nano film is larger than the end surface area of ​​the optical fiber plug core; the area of ​​the water-soluble support layer is larger than the end surface area of ​​the optical fiber plug core.

3. The method for transferring the metal nanofilm on the end face of an optical fiber according to claim 1, It is characterized in that The material of the water-soluble support layer is polyvinyl pyrrolidone K30.

4. The method for transferring the metal nanofilm on the end face of an optical fiber according to claim 3, It is characterized in that The water-soluble support layer is formed by coating the side of the substrate on which the metal nanofilm is formed. The specific operation is: A polyvinyl pyrrolidone K30 solution is coated on the side of the substrate surface where the metal nanofilm is formed, and after drying, a water-soluble support layer is formed; The polyvinyl pyrrolidone K30 solution is obtained by mixing polyvinyl pyrrolidone K30 and water in a mass ratio of 3 to 5:

10.

5. The method for transferring the metal nanofilm on the end face of an optical fiber according to claim 1, It is characterized in that The substrate is a continuous and flat substrate or a substrate with a micro-nano structure; the structure of the metal nanofilm is the same as the surface structure of the substrate.

6. The method for transferring the metal nanofilm on the end face of an optical fiber according to claim 5, It is characterized in that The substrate with micro-nano structure is processed on the surface of the substrate to form a nano-hole array structure.

7. The method for transferring a metal nanofilm on an optical fiber end face according to claim 1, It is characterized in that The metal nanofilm is formed on the surface of the substrate, and the specific operation is: The metal nanofilm is deposited on the surface of the substrate by using the resistance thermal evaporation method.

8. The method for transferring a metal nanofilm on an optical fiber end face according to claim 1, It is characterized in that Pre-processing of optical fiber is to make the end face of the optical fiber flat and smooth.

9. The method for transferring a metal nanofilm on an optical fiber end face according to claim 1, It is characterized in that Before the metal nanofilm is brought into contact with the end face of the optical fiber, ensure that the end face of the optical fiber and the end face of the optical fiber ferrule are located on the same plane.

10. The method for transferring a metal nanofilm on an optical fiber end face according to claim 1, It is characterized in that The outer diameter of the optical fiber matches the inner diameter of the optical fiber ferrule.

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