A MEMS fiber Fabry - Perot sensor, manufacturing device and manufacturing method

Abstract

The present invention relates to a MEMS fiber optic Fabry-Perot sensor, a manufacturing device thereof, and a manufacturing method. The sensor includes an optical fiber, a large hole, a small hole, a reflective layer, and a sensitive diaphragm. The reflective layer is fabricated on the sensitive diaphragm. The sensitive diaphragm is located at the bottom of the small hole. The small hole is located at the bottom of the large hole. The bottom of the large hole is fixed to the end face of the optical fiber and is coaxially arranged. Compared with the prior art, the present invention has the advantages of greatly simplifying the subsequent packaging steps, improving the construction efficiency of the Fabry-Perot cavity, accurately controlling the cavity length of the Fabry-Perot cavity, greatly increasing the finesse of Fabry-Perot interference, reducing the loss of the Fabry-Perot cavity, and improving the interference quality of the Fabry-Perot cavity, etc.

Description

Technical Field

[0001] The present invention relates to the field of fiber optic sensing, and more particularly to a MEMS fiber optic Fabry-Perot sensor, a manufacturing device thereof, and a manufacturing method. Background Art

[0002] Optical fiber sensors are a new type of sensors gradually formed with the development of optical fiber and optical fiber communication technologies. They have the characteristics of high sensitivity, light weight, good stability, anti-electromagnetic interference, fast response speed, long transmission distance, etc., and are favored by researchers at home and abroad. Nanoimprint technology was proposed by Stephen Chou of Princeton University in the United States. This technology combines modern microelectronic processes and material technologies to complete the transfer of patterns through contact imprinting. The process of nanoimprint technology is roughly divided into three steps: 1. Fabrication and processing of the imprint mold; 2. Imprinting; 3. Post-processing. Among them, the imprint mold is the core of this technology. The fabrication of the imprint mold mostly uses Micro-Electro-Mechanical System (MEMS) processes, which are developed on semiconductor manufacturing technologies and integrate technologies such as lithography, etching, thin film deposition, and silicon and non-silicon microfabrication. It is a revolutionary new technology and is widely used in high-tech industries. The fiber optic Fabry-Perot sensor based on nanoimprint technology not only has many advantages of optical fiber sensors, but also has the characteristics of a large material selection range, easy construction, and batch repeatable preparation, which is conducive to reducing the manufacturing cost of fiber optic Fabry-Perot sensors and promoting the vigorous development of sensing technologies.

[0003] In 2003, Bing Yu et al. proposed an optical fiber Fabry - Perot sensor based on MEMS technology (J. Appl. Opt., 2003, Vol. 42, pp. 3241 - 3250). A Fabry - Perot cavity was formed by bonding an optical fiber and a sensitive diaphragm made of fused silica material with a fused silica sleeve. However, it has a relatively large volume, low sensitivity, and a relatively low construction efficiency of the Fabry - Perot cavity. In 2013, Jun Ma et al. proposed an optical fiber Fabry - Perot sensor based on multi - layer graphene (IEEE Photon. Technol. Lett., 2013, Vol. 25(10), pp. 932 - 935). The implementation method was to bond multi - layer graphene to a zirconia sleeve that had already fixed the optical fiber to form a Fabry - Perot cavity. Although using multi - layer graphene to make the sensitive diaphragm significantly improved the sensitivity of the sensor, the bonding of the sensitive diaphragm was relatively difficult, and the cavity length of the Fabry - Perot cavity was not easy to control. In 2016, Bin Liu et al. proposed an optical fiber Fabry - Perot sensor based on MEMS technology (J. Microelectron. Eng., 2016, vol. 166, pp. 50 - 54.). A silver film with a complete circular structure was used as the sensitive diaphragm of the sensor, and a glass sleeve was used to bond the optical fiber and the sensitive diaphragm to form a Fabry - Perot cavity. The cavity length was determined by the distance between the end face of the optical fiber and the diaphragm, which was not conducive to the precise control of the cavity length. In 2018, Wenjun Ni proposed an optical fiber Fabry - Perot sensor based on ultrathin graphene film (Opt. Express, 2018, vol. 26, pp. 20758 - 20767.). The reflective end face was composed of the end face of the optical fiber and the graphene film. The implementation method was to first combine the graphene film and the ceramic sleeve in deionized water, and then fix the ceramic sleeve and the optical fiber with epoxy glue. Although using ultrathin graphene to make the sensitive diaphragm significantly improved the signal - to - noise ratio of the sensor, the bonding of the sensitive diaphragm and the ceramic sleeve was relatively difficult, and the diaphragm was pre - bent in the solution, reducing the flatness of the Fabry - Perot cavity, making it difficult to control the subsequent Fabry - Perot cavity length. In summary, in the related research, the construction link of the Fabry - Perot cavity was processed later when designing the sensitive diaphragm. The control of the Fabry - Perot cavity length was relatively difficult, and the construction efficiency was relatively low. Summary of the Invention

[0004] In order to overcome the defects in fabricating fiber optic Fabry-Perot sensors by using traditional processing methods, such as only preparing diaphragms singularly while neglecting the Fabry-Perot cavity, low finesse of the Fabry-Perot cavity, large overall size of the sensor, small array density when forming an array, difficult assembly of the Fabry-Perot cavity, difficult precise control of the Fabry-Perot cavity length, and high cost of the sensor. The present invention provides a MEMS fiber optic Fabry-Perot sensor, a manufacturing device, and a manufacturing method. The imprint mold is prepared by using MEMS technology, and the sensitive diaphragm and the Fabry-Perot cavity step of the sensitive structure are prepared by using nanoimprint technology. The sensitive structure can be completed by a single imprint of the imprint mold, aiming to simplify the processing technology, reduce the processing cost and difficulty of the chip, process sensitive structures that are difficult to process by traditional methods, and reduce the assembly difficulty of the Fabry-Perot cavity.

[0005] The object of the present invention can be achieved by the following technical solutions:

[0006] According to one aspect of the present invention, there is provided a MEMS fiber optic Fabry-Perot sensor, including an optical fiber, a large hole, a small hole, a reflective layer, and a sensitive diaphragm. The reflective layer is fabricated on the sensitive diaphragm. The sensitive diaphragm is located at the bottom of the small hole. The small hole is located at the bottom of the large hole. The bottom of the large hole is fixed to the end face of the optical fiber and is coaxially arranged.

[0007] As a preferred technical solution, the optical fiber is a single-mode optical fiber or a multi-mode optical fiber.

[0008] As a preferred technical solution, the reflective layer is a reflective layer fabricated from materials such as gold, silver, or aluminum through a deposition process.

[0009] According to another aspect of the present invention, there is provided a manufacturing device for the MEMS fiber optic Fabry-Perot sensor, including a substrate, a bottom mask, a top mask, positioning small holes, positioning large holes, a substrate, and a thin film;

[0010] The top mask is fabricated on the bottom mask. The bottom mask is fabricated on the substrate. The positioning small holes and the positioning large holes are both located on the substrate. The positioning large holes and the positioning small holes are coaxially arranged. The thin film is fabricated on the substrate.

[0011] As a preferred technical solution, the sensitive diaphragm, the large hole, and the small hole are components integrally fabricated on the thin film by using nanoimprint technology.

[0012] As a preferred technical solution, the thin film is a thin film fabricated from photoresist, PMMA, or PDMS.

[0013] As a preferred technical solution, the top mask is a mask fabricated from photoresist.

[0014] As a preferred technical solution, the bottom mask is a mask fabricated from aluminum, chromium, or silicon oxide.

[0015] As a preferred technical solution, the substrate is made of silicon, silicon oxide or silicon nitride; the substrate is made of silicon, silicon oxide or silicon nitride.

[0016] According to another aspect of the present invention, there is provided a method for manufacturing the MEMS fiber optic Fabry-Perot sensor, including the following steps:

[0017] Step 1: Prepare two layers of masks on the substrate of the imprint mold, namely the bottom mask and the top mask;

[0018] Step 2: Etch positioning holes on the substrate by ICP;

[0019] Step 3: Remove the top mask of the substrate, and etch positioning large holes on the substrate by ICP;

[0020] Step 4: Remove the bottom mask to obtain the imprint mold;

[0021] Step 5: Make a thin film on the substrate by a deposition process;

[0022] Step 6: Based on the nanoimprint technology, use the imprint mold obtained in Step 4 to imprint a sensitive structure on the thin film;

[0023] Step 7: Remove the substrate to form a sensitive diaphragm, large holes and small holes;

[0024] Step 8: Make a reflective film on the sensitive diaphragm by the MEMS thin film deposition process to form a reflective layer;

[0025] Step 9: Directly bond the optical fiber to the large hole, and ensure that the optical fiber is centered with the sensitive diaphragm to form a complete fiber optic Fabry-Perot sensor.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] (1) The integrated structure of the sensitive diaphragm and the Fabry-Perot cavity step can greatly simplify the subsequent packaging steps, improve the construction efficiency of the Fabry-Perot cavity, accurately control the cavity length of the Fabry-Perot cavity, significantly increase the finesse of Fabry-Perot interference, reduce the loss of the Fabry-Perot cavity, and improve the interference quality of the Fabry-Perot cavity.

[0028] (2) The production of the imprint mold mainly uses the MEMS process, which can break through the thickness limitation of the traditional processing method when processing sensitive structures, significantly reduce the thickness and manufacturing difficulty of sensitive structures, and realize high-fidelity production of sensitive diaphragms and Fabry-Perot cavity steps.

[0029] (3) The fabrication of the sensitive structure mainly adopts nanoimprint technology, which has the characteristics of low cost, short processing cycle, mature process, small size, etc. The sensitive diaphragm has the characteristics of small size, low cost, simple assembly, etc. The present invention will promote the application and popularization of fiber optic Fabry-Perot sensors in more fields. Brief Description of the Drawings

[0030] Figure 1 It is a schematic structural diagram of the MEMS fiber optic Fabry-Perot sensor of the present invention;

[0031] Figure 2 It is a schematic diagram of preparing two layers of masks on the substrate of the imprint mold of the present invention;

[0032] Figure 3 It is a schematic diagram of etching positioning small holes on the substrate by ICP according to the present invention;

[0033] Figure 4 It is a schematic diagram of etching positioning large holes on the substrate by ICP according to the present invention;

[0034] Figure 5 It is a schematic diagram of removing the bottom mask to obtain the imprint mold according to the present invention;

[0035] Figure 6 It is a schematic diagram of fabricating a thin film on the substrate according to the present invention;

[0036] Figure 7 It is a schematic diagram of imprinting the sensitive structure on the thin film by the imprint mold according to the present invention;

[0037] Figure 8 It is a schematic diagram of forming the sensitive diaphragm, large holes and small holes according to the present invention;

[0038] Figure 9 It is a schematic diagram of fabricating a reflective film on the sensitive diaphragm according to the present invention;

[0039] Figure 10 It is a schematic diagram of directly bonding the optical fiber to the large hole according to the present invention;

[0040] Figure 11 It is a process flow chart of the present invention. Detailed Embodiments

[0041] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0042] The present invention proposes a sensitive structure of a MEMS optical fiber Fabry-Perot sensor and a manufacturing method thereof. The sensitive structure consists of a sensitive diaphragm and a Fabry-Perot cavity step. When performing nanoimprinting processing, the sensitive structure is formed in one step, and there is no need to construct the Fabry-Perot cavity in subsequent steps. This design method can greatly simplify the processing and subsequent packaging processes of the sensitive structure. A nanoimprint mold is prepared by using MEMS technology, and the diaphragm and the Fabry-Perot cavity step of the sensitive structure are prepared by using nanoimprinting technology. The two are combined to prepare the MEMS optical fiber Fabry-Perot sensitive structure. By means of the nanoimprint mold, the pattern is transferred to the polymer film, and the sensitive diaphragm and the Fabry-Perot cavity step of the sensor sensitive structure can be constructed synchronously, while it is difficult to construct the two synchronously by using traditional processing methods.

[0043] Embodiment 1

[0044] The structure of the optical fiber Fabry-Perot sensor proposed by the present invention is shown in Figure 1 , and its device and structure mainly include an optical fiber 1, a large hole 2, a small hole 3, a reflective layer 4, and a sensitive diaphragm 5. The manufacturing device of the sensor includes a substrate 6, a bottom mask 7, a top mask 8, a positioning small hole 9, a positioning large hole 10, a substrate 11, and a thin film 12;

[0045] The reflective layer 4 is fabricated on the sensitive diaphragm 5. The sensitive diaphragm 5 is located at the bottom of the small hole 3. The small hole 3 is located at the bottom of the large hole 2. The bottom of the large hole 2 is fixed to the end face of the optical fiber 1 and is coaxial.

[0046] The top mask 8 is fabricated on the bottom mask 7. The bottom mask 7 is fabricated on the substrate 6. The positioning small hole 9 is located on the substrate 6. The positioning large hole 10 is located on the substrate 6 and is coaxial with the positioning small hole 9.

[0047] The thin film 12 is fabricated on the substrate 11.

[0048] Furthermore, the optical fiber 1 is a single-mode optical fiber (central wavelength: 1550 nm) and is connected to the large hole 2 through an adhesive process.

[0049] Furthermore, the sensitive diaphragm 5, the small hole 3, and the large hole 2 are integrally fabricated on the thin film 12 by using nanoimprinting technology, and the base material of the thin film is selected as photoresist.

[0050] Furthermore, the reflective layer 4 is fabricated through a deposition process, and the material is selected as gold.

[0051] Furthermore, the substrate 6 is prepared by using MEMS technology, and the material is selected as silicon.

[0052] Furthermore, the thin film 12 is coated on the substrate 11, and the material of the substrate 11 is selected as silicon.

[0053] The basic working principle is as follows: The light generated by the light source enters Fiber 1 through the fiber optic circulator. Part of the light is reflected back into the fiber by the end face of Fiber 1, and the other part of the light passes through the fiber and is reflected by the reflective layer 4 and then re-enters the fiber. These two parts of the light beams converge and interfere, and then enter the backend detection system through the fiber optic circulator. The interference signal is related to the cavity length of the Fabry-Perot cavity formed by the end face of Fiber 1 and the reflective layer 4. When the acoustic wave causes the diaphragm 5 of the sensitive structure to deform axially, it causes a change in the cavity length of the Fabry-Perot cavity, thereby causing a change in the interference signal. The information of the acoustic wave can be obtained by demodulating the interference signal.

[0054] Refer to Figure 11 , the fabrication process of the sensitive structure of the MEMS fiber optic Fabry-Perot sensor proposed in this embodiment includes the following basic steps:

[0055] Step 1: Refer to Figure 2 , prepare two layers of masks on the substrate 6 of the imprint mold. The material of the bottom mask 7 is selected as aluminum, the material of the top mask 8 is selected as photoresist, and the material of the imprint mold substrate 6 is selected as silicon;

[0056] Step 2: Refer to Figure 3 , etch positioning holes 9 on the substrate 6 of the imprint mold through ICP;

[0057] Step 3: Refer to Figure 4 , remove the top mask 8 of the imprint mold substrate, and etch positioning large holes 10 on the substrate 6 of the imprint mold through ICP;

[0058] Step 4: Refer to Figure 5 , remove the bottom mask 7 of the imprint mold substrate to obtain the imprint mold;

[0059] Step 5: Refer to Figure 6 , select silicon as the substrate 11 (substrate thickness: 50 μm), and spin-coat a certain thickness of photoresist (thickness: 15 μm) on the top layer of the substrate 11, and heat the photoresist to make it soft;

[0060] Step 6: Refer to Figure 7 , based on the nanoimprint technology, use the imprint mold obtained in Step 4 to imprint the sensitive structure on the photoresist;

[0061] Step 7: Refer to Figure 8 , remove the substrate 11 to form the sensitive diaphragm 5, small holes 3, and large holes 2;

[0062] Step 8: Refer to Figure 9 , sputter a 20-nm-thick gold film on the sensitive diaphragm 5 through the MEMS thin film deposition process to form the reflective layer 4;

[0063] Step 9: Refer to Figure 10, the optical fiber 1 is directly bonded to the large hole 2 and the center alignment between the optical fiber and the sensitive diaphragm 5 is ensured to form a complete fiber Fabry-Perot sensor.

[0064] Embodiment 2

[0065] The structure of the fiber Fabry-Perot sensor proposed by the present invention is referred to Figure 1 , and its device and structure mainly include an optical fiber 1, a large hole 2, a small hole 3, a reflective layer 4, and a sensitive diaphragm 5. The manufacturing device of the sensor mainly includes a substrate 6, a bottom mask 7, a top mask 8, a positioning small hole 9, a positioning large hole 10, a substrate 11, and a thin film 12;

[0066] The reflective layer 4 is fabricated on the sensitive diaphragm 5. The sensitive diaphragm 5 is located at the bottom of the small hole 3. The small hole 3 is located at the bottom of the large hole 2. The bottom of the large hole 2 is fixed to the end face of the optical fiber 1 and is coaxial.

[0067] The top mask 8 is fabricated on the bottom mask 7. The bottom mask 7 is fabricated on the substrate 6. The positioning small hole 9 is located on the substrate 6. The positioning large hole 10 is located on the substrate 6 and is coaxial with the positioning small hole 9.

[0068] The thin film 12 is fabricated on the substrate 11.

[0069] Furthermore, the optical fiber 1 is a single-mode optical fiber (central wavelength: 1550 nm) and is connected to the large hole 2 through a bonding process.

[0070] Furthermore, the sensitive diaphragm 5, the small hole 3, and the large hole 2 are integrally fabricated on the thin film 12 through a nanoimprinting technique, and the thin film matrix material is selected as PMMA.

[0071] Furthermore, the reflective layer 4 is fabricated through a deposition process, and the material can be selected as silver.

[0072] Furthermore, the substrate 6 is prepared through a MEMS process, and the material is selected as silicon oxide.

[0073] Furthermore, the thin film 12 is coated on the substrate 11, and the substrate 11 material is selected as silicon oxide.

[0074] The basic working principle is as follows: The light generated by the light source enters the optical fiber 1 through the optical fiber circulator. Part of the light is reflected back into the optical fiber by the end face of the optical fiber 1, and the other part of the light passes through the optical fiber and is reflected back into the optical fiber by the reflective layer 4. These two parts of the light beams converge and interfere and then enter the backend detection system through the optical fiber circulator. The interference signal is related to the cavity length of the Fabry-Perot cavity formed by the end face of the optical fiber 1 and the reflective layer 4. When the acoustic wave causes the diaphragm 5 of the sensitive structure to deform axially, it causes a change in the cavity length of the Fabry-Perot cavity, thereby causing a change in the interference signal. The information of the acoustic wave can be obtained by demodulating the interference signal.

[0075] Refer toFigure 11 , the manufacturing process of the sensitive structure of the MEMS fiber optic Fabry-Perot sensor proposed in this embodiment includes the following basic steps:

[0076] Step 1: Refer to Figure 2 , prepare two layers of masks on the substrate 6 of the imprint mold. The material of the bottom mask 7 is selected as metal chromium, the material of the top mask 8 is selected as photoresist, and the material of the imprint mold substrate 6 is selected as silicon oxide;

[0077] Step 2: Refer to Figure 3 , etch positioning holes 9 on the substrate 6 of the imprint mold through ICP;

[0078] Step 3: Refer to Figure 4 , remove the top mask 8 of the imprint mold substrate, and etch positioning large holes 10 on the substrate 6 of the imprint mold through ICP;

[0079] Step 4: Refer to Figure 5 , remove the bottom mask 7 of the imprint mold substrate to obtain the imprint mold;

[0080] Step 5: Refer to Figure 6 , select silicon oxide as the substrate 11 (substrate thickness: 50 μm), and spin-coat a certain thickness of PMMA (thickness: 15 μm) on the top layer of the substrate 11, and heat the PMMA to make it soft;

[0081] Step 6: Refer to Figure 7 , based on the nanoimprint technology, use the imprint mold obtained in Step 4 to imprint a sensitive structure on the PMMA;

[0082] Step 7: Refer to Figure 8 , remove the substrate 11 to form a sensitive diaphragm 5, small holes 3, and large holes 2;

[0083] Step 8: Refer to Figure 9 , sputter a 20-nm-thick silver film on the sensitive diaphragm 5 through the MEMS thin film deposition process to form a reflective layer 4;

[0084] Step 9: Refer to Figure 10 , directly bond the optical fiber 1 to the large hole 2 and ensure the center alignment of the optical fiber and the sensitive diaphragm 5 to form a complete fiber optic Fabry-Perot sensor.

[0085] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A manufacturing method for a MEMS fiber Fabry - Perot sensor, characterized in that, The sensor includes an optical fiber (1), a large hole (2), a small hole (3), a reflective layer (4), and a sensitive diaphragm (5). The reflective layer (4) is fabricated on the sensitive diaphragm (5). The sensitive diaphragm (5) is located at the bottom of the small hole (3). The small hole (3) is located at the bottom of the large hole (2). The bottom of the large hole (2) is fixed to the end face of the optical fiber (1) and is coaxially arranged. The sensitive diaphragm (5), the large hole (2), and the small hole (3) are components integrally fabricated on a thin film (12) by nanoimprint technology. The fabrication method includes the following steps: Step 1: Prepare two layers of masks on the substrate (6) of the imprint mold, namely, a bottom mask (7) and a top mask (8). Step 2: Etch positioning small holes (9) on the substrate (6) by ICP. Step 3: Remove the top mask (8) of the substrate (6), and etch positioning large holes (10) on the substrate (6) by ICP. Step 4: Remove the bottom mask (7) to obtain the imprint mold. Step 5: Fabricate a thin film (12) on the substrate (11) by a deposition process. Step 6: Based on nanoimprint technology, use the imprint mold obtained in Step 4 to imprint a sensitive structure on the thin film (12). Step 7: Remove the substrate (11) to form the sensitive diaphragm (5), the large hole (2), and the small hole (3). Step 8: Fabricate a reflective film on the sensitive diaphragm (5) by MEMS thin film deposition process to form the reflective layer (4). Step 9: Directly bond the optical fiber (1) to the large hole (2), and ensure that the center of the optical fiber (1) is aligned with the sensitive diaphragm (5) to form a complete fiber Fabry-Perot sensor.

2. The manufacturing method according to claim 1, characterized in that, The optical fiber (1) is a single-mode optical fiber or a multi-mode optical fiber.

3. The manufacturing method according to claim 1, characterized in that, The reflective layer (4) is a reflective layer fabricated by a deposition process using gold, silver, or aluminum material.

4. The manufacturing method according to claim 1, characterized in that, The thin film (12) is a thin film fabricated by photoresist, PMMA, or PDMS.

5. The manufacturing method according to claim 1, characterized in that, The top mask (8) is a mask fabricated by photoresist.

6. The manufacturing method according to claim 1, characterized in that, The bottom mask (7) is a mask fabricated by aluminum, chromium, or silicon oxide.

7. The manufacturing method according to claim 1, characterized in that The substrate (6) is a substrate fabricated by silicon, silicon oxide, or silicon nitride; the substrate (11) is a substrate fabricated by silicon, silicon oxide, or silicon nitride.

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