Optical fiber end face microstructure precision packaging method based on double-layer PDMS mold

Abstract

The invention discloses an optical fiber end face microstructure precise packaging method based on a double-layer PDMS mold. The method comprises the following steps that 1, a micro-groove mold is prepared on a silicon wafer through the photoetching technology, a PDMS bottom layer with a micro-groove is obtained through transfer printing, a micro-cylinder mold is prepared on the silicon wafer through the photoetching technology, and a PDMS top layer with a through hole is obtained through transfer printing; step 2, concentrically aligning and bonding the PDMS top layer with the through hole and the PDMS bottom layer with the micro groove under a microscope to form a composite die with a guide hole-micro cavity structure; and step 3, filling the cavity with ultraviolet curing resin, vertically inserting the optical fiber into the top guide hole and abutting against the bottom groove, and demolding after ultraviolet curing to realize precise integration of the microstructure on the end face of the optical fiber. According to the method, a double-layer PDMS composite mold is prepared by using a soft lithography technology, and blind-mating self-alignment packaging of the optical fiber is realized through physical limiting.

Description

Technical Field

[0001] This invention belongs to the field of fiber optic sensing and relates to a precision packaging method for microstructures on the end face of an optical fiber. Background Technology

[0002] In the field of fiber optic sensing, to endow optical fibers with specific sensing functions (such as Fabry-Perot interferometers and surface plasmon resonance), it is usually necessary to integrate micron-scale polymer structures or thin films on the end face of single-mode optical fibers. Currently, the fabrication of fiber end face microstructures mainly relies on active alignment technology using precision displacement stages or direct photolithography. However, existing fabrication methods have significant limitations: 1. Direct dip coating: It is difficult to precisely control the thickness and flatness of the coating, resulting in poor repeatability; 2. Active alignment imprinting: It requires expensive high-precision three-dimensional displacement platforms and microscopic vision systems, places extremely high demands on operators, and can only fabricate one fiber at a time, making mass production difficult; 3. Direct photolithography: It requires coating the fiber end face with resin and performing extremely difficult end face exposure, resulting in a complex process. Therefore, there is an urgent need for a fiber end face encapsulation method that does not require expensive alignment equipment, can control resin thickness with high precision at low cost, and has self-alignment capabilities. Summary of the Invention

[0003] This invention provides a precision packaging method for fiber end face microstructure based on a dual-layer PDMS mold. The method uses soft lithography to prepare a dual-layer PDMS composite mold and achieves blind insertion self-alignment packaging of the fiber through physical positioning.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] A precision packaging method for fiber optic end-face microstructures based on a dual-layer PDMS mold includes the following steps:

[0006] Step 1, Mold Preparation:

[0007] Step 1-1, Microstructure shaping layer (bottom layer) preparation: Microgroove molds are prepared on silicon wafers using photolithography, and PDMS bottom layer with microgrooves is transferred to define the shape and thickness of the polymer at the fiber end face. The diameter of the microgrooves is 80~120μm, not exceeding the diameter of the fiber cladding, and the depth is 0.5~50μm.

[0008] Step 1-2, Fabrication of fiber guide layer (top layer): A micro cylindrical mold is fabricated on a silicon wafer using photolithography, and a PDMS top layer with through holes is transferred to it. The diameter of the through holes is slightly larger than the diameter of the single-mode fiber cladding, serving as a physical guide for fiber insertion. The diameter of the through holes is 128~132μm, and the diameter of the single-mode fiber cladding is 125.0±0.7μm.

[0009] Step 2, Double-layer mold bonding:

[0010] The PDMS top layer with through holes and the PDMS bottom layer with microgrooves are concentrically aligned and bonded under a microscope to form a composite mold with a guide hole-microcavity structure.

[0011] Step 3, blind-insertion packaging:

[0012] A UV-curable resin is filled into the cavity. An optical fiber is vertically inserted through a top-layer guide hole, pressing against a bottom-layer groove. After UV curing, the fiber is demolded, achieving precise integration of the microstructure on the fiber end face. The UV-curable resin is OrmoComp, using Micro-Resist Technology. The UV curing light source wavelength is 300-400 nm, optimally 365 nm, and the exposure dose is 500-1000 mJ / cm². 2 If it is a handheld UV lamp, the intensity is 20mW / cm². 2 The irradiation time is 25~50 seconds, and after UV curing, it is baked at 140~160℃ for 1~3 hours.

[0013] Compared with the prior art, the present invention has the following advantages:

[0014] 1. Achieve self-alignment and precise thickness control: By using pre-prepared PDMS guide holes and microgrooves, the lateral displacement and longitudinal depth of the optical fiber are limited. This eliminates the need for a high-precision displacement stage during packaging to ensure that the center of the microstructure is aligned with the fiber core, and the thickness is strictly determined by the photoresist thickness (e.g., precisely controlled at 1.6μm).

[0015] 2. Reduced equipment threshold and cost: The high-precision alignment process is transferred to the mold preparation stage (completed in one go), and only simple plugging and unplugging operations are required in the subsequent fiber optic packaging stage, which greatly reduces the requirements for the operating environment and equipment.

[0016] 3. Protecting the fiber end face: PDMS material is elastic, and the fiber makes soft contact with the mold when inserted, avoiding damage to the fiber end face that may be caused by hard contact. At the same time, the elastic seal helps to reduce resin leakage. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the photolithography process.

[0018] Figure 2 This is a schematic diagram of the fabrication process for a double-layer PDMS mold.

[0019] Figure 3 This is a cross-sectional view of the mold bonding and structure;

[0020] Figure 4 This is a schematic diagram of the fiber optic blind mating and packaging process. Detailed Implementation

[0021] The technical solution of the present invention will be further described below with reference to the accompanying drawings, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0022] This invention provides a method for fabricating an optical fiber sensor with an end face integrated with a UV-curable resin microstructure having a thickness of 1.6 μm and a diameter of 80 μm. The specific implementation steps are as follows:

[0023] (1) Photolithographic fabrication of silicon-based male molds: Two silicon master molds were fabricated using a photolithography machine. Master mold A: Negative photoresist was spin-coated onto the silicon wafer, and after exposure and development, a micro-cylindrical array with a height of 1.6 μm and a diameter of 80 μm was formed, such as... Figure 1 The bottom mold is shown; Mother mold B: A thick photoresist is spin-coated onto another silicon wafer, and after exposure and development, a cylindrical array is formed with a height greater than the fiber insertion depth and a diameter slightly larger than the single-mode fiber cladding diameter (e.g., 130 μm). This array is used to create guide holes, such as... Figure 1 The top mold is shown.

[0024] (2) Transfer of the double-layer PDMS mold: After vacuum degassing, the PDMS transfer liquid is poured onto master mold A and master mold B respectively. After heating and curing, the mold is demolded to obtain a bottom layer PDMS containing microgrooves and a top layer PDMS containing micro-cylindrical through holes (the PDMS after molding needs to be cut to form through holes). The two molds are respectively as follows: Figure 2 As shown in the image.

[0025] (3) Mold alignment and bonding: The bonding surfaces of the bottom and top PDMS are processed using an oxygen plasma bonding device. Under a microscopic alignment platform, the center of the through-hole of the top PDMS is precisely aligned with the center of the groove of the bottom PDMS. After alignment, the two PDMS layers are pressed together to form an integrated fiber optic packaging mold, such as... Figure 3 As shown.

[0026] (4) Resin Filling and Fiber Insertion: Using a micro-syringe, inject UV-cured resin (OrmoComp, Microresist technology) into the guide hole of the mold until the resin fills the bottom microgroove. Insert the neatly cut single-mode fiber vertically through the guide hole of the top PDMS. Due to the guiding effect of the guide hole, the fiber will automatically align with the bottom microgroove and eventually stop on the stepped surface at the edge of the groove, such as... Figure 4 As shown.

[0027] (5) Curing and Demolding: Keep the optical fiber in a fixed position, and use an ultraviolet light source to irradiate the resin-filled area through the PDMS mold for curing (light source wavelength is 365nm; exposure dose is 1000mJ / cm). 2).like Figure 4 As shown, after curing, the optical fiber along with the resin microstructure formed on the end face is vertically pulled out from the PDMS mold, thus completing the encapsulation.

Claims

1. A method for precision packaging of fiber optic end-face microstructures based on a dual-layer PDMS mold, characterized in that... The method includes the following steps: Step 1, Mold Preparation: Step 1-1, Microstructure shaping layer preparation: Microgroove molds are prepared on silicon wafers using photolithography, and PDMS bottom layer with microgrooves is transferred to define the shape and thickness of the polymer at the fiber end face; Steps 1-2: Fabrication of fiber guide layer: Micro-cylindrical molds are fabricated on silicon wafers using photolithography, and a PDMS top layer with through holes is transferred to obtain the top layer, which serves as the physical guide for fiber insertion. Step 2, Double-layer mold bonding: The PDMS top layer with through holes and the PDMS bottom layer with microgrooves are concentrically aligned and bonded under a microscope to form a composite mold with a guide hole-microcavity structure. Step 3, blind-insertion packaging: The cavity is filled with UV-curable resin. The optical fiber is vertically inserted into the top guide hole and pressed against the bottom groove. After UV curing, the fiber is demolded to achieve precise integration of the microstructure on the end face of the optical fiber.

2. The precision packaging method for fiber optic end-face microstructures based on a dual-layer PDMS mold according to claim 1, characterized in that... In step 1-1, the diameter of the microgroove is 80~120μm and the depth is 0.5~50μm.

3. The precision packaging method for fiber optic end-face microstructures based on a dual-layer PDMS mold according to claim 1, characterized in that... In steps 1-2, the diameter of the through hole is larger than the diameter of the single-mode fiber cladding.

4. The precision packaging method for fiber optic end-face microstructures based on a dual-layer PDMS mold according to claim 3, characterized in that... The diameter of the through hole is 128~132μm, and the diameter of the single-mode fiber cladding is 125.0±0.7μm.

5. The precision packaging method for fiber optic end-face microstructures based on a dual-layer PDMS mold according to claim 1, characterized in that... In step 3, the UV-curing resin is OrmoComp or Micro resist technology.

6. The precision packaging method for fiber optic end-face microstructures based on a dual-layer PDMS mold according to claim 1, characterized in that... In step 3, the wavelength of the UV curing light source is 300~400nm, and the exposure dose is 500~1000mJ / cm. 2 .

7. The precision packaging method for fiber optic end-face microstructures based on a dual-layer PDMS mold according to claim 6, characterized in that... The wavelength of the light source for UV curing is 365nm.

8. The precision packaging method for fiber optic end-face microstructures based on a dual-layer PDMS mold according to claim 1, characterized in that... In step 3, if a handheld UV lamp is used for UV curing, its intensity is 20mW / cm², the irradiation time is 25~50 seconds, and after UV curing, it needs to be baked at 140~160℃ for 1~3 hours.

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