Back-driving tunable FP filter

Abstract

The present invention provides a reverse-driven tunable F-P filter and a preparation method thereof, wherein the filter comprises a static mirror, a moving mirror, a supporting bridge pier, a microbridge, an electrode supporting structure and a top electrode; wherein the supporting bridge pier is prepared on the static mirror, and a cavity is formed between the supporting bridge pier and the static mirror; the moving mirror is located in the cavity, and an F-P resonant cavity is formed between the moving mirror and the static mirror, and a first stopper is prepared on the static mirror to prevent the moving mirror from contacting the static mirror; the microbridge comprises a central part and an edge part, wherein the central part is prepared on the side of the moving mirror facing away from the static mirror, and the central part acts as a bottom electrode for adsorption with the top electrode; the edge part is prepared on the top of the supporting bridge pier, and the electrode supporting structure is supported between the edge part and the top electrode. The present invention can determine the minimum cavity length by using a reverse driving method, and drives the moving mirror in the opposite direction of the static mirror, thereby overcoming the problem of adsorption instability in principle, thereby expanding the spectral detection range by increasing the cavity length tuning range.

Description

Technical Field

[0001] The present invention relates to the technical field of filters, and in particular to a reverse-driven tunable FP filter. Background Art

[0002] The spectrometer detects the composition of the material by detecting the emission or absorption spectrum of the object being measured. Its non-contact rapid measurement characteristics are increasingly attracting widespread attention. Limited by the large size and high cost of traditional spectrometers, micro-spectrometers are currently attracting more and more attention from scientific researchers. At present, the core filter devices of micro-spectrometers are mainly realized through four technical routes: dispersion type, narrowband filtering type, Fourier transform type and computational spectroscopy type. However, dispersion type and Fourier transform type filter devices are restricted by resolution, and the miniaturization target is subject to theoretical limitations; computational spectroscopy type filter devices require a large number of complex calculations and cannot achieve fast real-time measurement. Narrowband filtering type filter devices circumvent the problems encountered by the above technical routes. It is easier to achieve miniaturization goals and the post-processing algorithm is relatively simple, making it the most widely used filter element in miniaturized filter elements. Among them, FP filter (hereinafter referred to as "FPI"), as a planar filter element, has a more mature manufacturing process, structural design and preparation process, so it has become the main filter structure choice in narrowband filter devices.

[0003] At present, FPI filter components are mainly driven in the forward direction. The driving principle is as follows: Figure 1 As shown in the figure, by applying electrostatic force between the moving mirror and the static mirror, the moving mirror is brought closer to the static mirror, thereby adjusting the cavity length. However, due to the attraction effect generated by the electrostatic force adsorption, the cavity length tuning range will be greatly affected. If the upper and lower electrodes are adsorbed together, the moving mirror surface and the static mirror surface will be locked, resulting in device failure. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and propose a reverse-driven tunable FP filter, which adopts a reverse-driven method to solve the small-distance cavity length tuning that cannot be achieved under forward-driven tuning, thereby expanding the cavity length tuning range and avoiding the upper and lower electrodes from being adsorbed together.

[0005] To achieve the above object, the present invention adopts the following specific technical solutions:

[0006] The reverse-driven tunable FP filter provided by the present invention comprises a static mirror, a dynamic mirror, a supporting bridge pier, a microbridge, an electrode supporting structure and a top electrode; wherein the supporting bridge pier is prepared on the static mirror, and a cavity is formed between the supporting bridge pier and the static mirror; the dynamic mirror is located in the cavity, and an FP resonant cavity is formed between the dynamic mirror and the static mirror, and a first stopper is prepared on the static mirror to prevent the dynamic mirror from contacting the static mirror; the microbridge comprises a central part and an edge part, wherein the central part is prepared on the side of the dynamic mirror facing away from the static mirror, and the central part acts as a bottom electrode for adsorption with the top electrode; the edge part is prepared on the top of the supporting bridge pier, and the electrode supporting structure is supported between the edge part and the top electrode.

[0007] Preferably, the edge portion is a cantilever beam uniformly distributed along the circumference of the central portion.

[0008] Preferably, the cantilever beam is a straight structure or a bent structure.

[0009] Preferably, the central portion is a circular structure or a polygonal structure.

[0010] Preferably, a light-through hole is provided at the center of the central portion.

[0011] Preferably, a second stopper is prepared on the top electrode to prevent the central portion from contacting the top electrode.

[0012] The method for preparing the reverse-driven tunable FP filter provided by the present invention comprises the following steps:

[0013] S1, evaporating a first reflective film on a first substrate to form a static mirror;

[0014] S2, forming supporting bridge piers on the static mirror by using photolithography and magnetron sputtering process;

[0015] S3, coating a first sacrificial layer in the cavity formed by the supporting bridge pier and the static mirror, evaporating a second reflective film on the first sacrificial layer, and forming a second substrate on the second reflective film by a magnetron sputtering process to form a moving mirror;

[0016] S4, forming a microbridge on the moving mirror by using photolithography and magnetron sputtering process;

[0017] S5, forming an electrode support structure on the microbridge by using photolithography and magnetron sputtering processes;

[0018] S6, coating a second sacrificial layer in the cavity surrounded by the electrode support structure and the moving mirror;

[0019] S7, forming a top electrode on the second sacrificial layer by using photolithography and magnetron sputtering process;

[0020] S8. The first sacrificial layer and the second sacrificial layer are vaporized to release the space between the top electrode and the microbridge and between the moving mirror and the static mirror, thereby forming a reverse-driven tunable FP filter.

[0021] The present invention can achieve the following technical effects:

[0022] 1. Compared with the forward driving method, the reverse driving method can determine the minimum cavity length and drive the moving mirror in the opposite direction of the static mirror, thereby overcoming the problem of adsorption instability in principle, thereby expanding the spectral detection range by increasing the cavity length tuning range.

[0023] 2. The microbridge can increase the tuning range and achieve visible-infrared wide spectrum tuning in the 700nm-3μm band. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the driving principle of the forward drive mode;

[0025] Figure 2 is a schematic structural diagram of a reverse-driven tunable FP filter provided according to an embodiment of the present invention;

[0026] Figure 3 is a schematic diagram of the driving principle of the reverse driving method provided in an embodiment of the present invention;

[0027] Figure 4a-4c Schematic diagrams of the structures of three microbridges provided according to embodiments of the present invention;

[0028] Figure 5 Schematic diagram of the linear relationship between driving force and displacement of three microbridges provided according to an embodiment of the present invention.

[0029] The reference numerals therein include: static mirror 1, first substrate 1-1, first reflective film 1-2, supporting bridge pier 2, moving mirror 3, second substrate 3-1, second reflective film 3-2, microbridge 4, electrode support structure 5, top electrode 6, first stopper 7-1, second stopper 7-2. DETAILED DESCRIPTION

[0030] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same modules are represented by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, the detailed description thereof will not be repeated.

[0031] 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 accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0032] Figure 2 The structure of a back-driven tunable FP filter provided according to an embodiment of the present invention is shown.

[0033] like Figure 2 As shown, the reverse-driven tunable FP filter provided by the embodiment of the present invention includes a static mirror 1, a supporting bridge pier 2, a moving mirror 3, a microbridge 4, an electrode supporting structure 5 and a top electrode 6.

[0034] The static mirror 1 includes a first substrate 1-1 and a first reflective film 1-2. The first reflective film 1-2 is evaporated on the first substrate 1-1 to form the static mirror 1. A supporting pier 2 is prepared on the portion of the first substrate 1-1 where the first reflective film 1-2 is not evaporated. A cavity for accommodating the moving mirror 3 is formed between the supporting pier 2 and the static mirror 1.

[0035] The moving mirror 3 includes a second substrate 3-1 and a second reflective film 3-2. The second reflective film 3-2 is prepared on the second substrate 3-1 to form the moving mirror 3. The second reflective film 3-2 faces the first reflective film 1-1. The moving mirror 3 is located in a cavity surrounded by the supporting pier 2 and the static mirror 1. There is a gap between the moving mirror 3 and the static mirror 1 to form an FP resonant cavity. The distance between the moving mirror 3 and the static mirror 1 is changed by moving the moving mirror 3, thereby realizing the tunable length of the resonant cavity.

[0036] A first stopper 7-1 is prepared on the first reflective film 1-2. The first stopper 7-1 plays a blocking role to prevent the moving mirror 3 from contacting the static mirror 1, so that there is a gap between the moving mirror 3 and the static mirror 1. The height of the first stopper 7-1 is the minimum cavity length of the resonant cavity.

[0037] The microbridge 4 includes a central portion and an edge portion. The central portion is prepared on a side of the second substrate 3 - 1 away from the second reflective film 3 - 2 , and the edge portion is prepared on the top of the supporting pier 2 .

[0038] Figure 3 The driving principle of the reverse driving method provided by the embodiment of the present invention is shown.

[0039] like Figure 3 As shown, the central part of the microbridge 4 acts as a bottom electrode for adsorption with the top electrode 6. When an electrostatic force is applied between the central part and the top electrode 6 to make the moving mirror 3 move closer to the top electrode 6, the edge part applies a force in the opposite direction to the moving mirror 3 to prevent the moving mirror 3 and the top electrode 6 from being attracted together.

[0040] When the moving mirror 3 moves away from the static mirror 1 while approaching the top electrode 6, the cavity length of the resonant cavity gradually increases, thereby increasing the tuning range and achieving visible-infrared wide spectrum tuning in the 700nm-3μm band.

[0041] The bottom end of the electrode support structure 5 is supported on the edge part of the micro-bridge 4, and the top end of the electrode support structure 5 is supported on the bottom of the top electrode 6. The electrode support structure 5 serves two functions. One is to support the top electrode 6, and the other is to fix the edge part of the micro-bridge 4 to prevent displacement of the edge part of the micro-bridge 4.

[0042] A second stop block 7-2 is prepared on the top electrode 6, and the second stop block 7-2 can prevent the central part of the micro-bridge 4 from being attracted to the top electrode 6.

[0043] The edge part of the micro-bridge 4 is a cantilever beam uniformly distributed circumferentially along the central part, and the cantilever beam is a straight structure or a bent structure.

[0044] The central part of the micro-bridge 4 is a circular structure or a polygonal structure, and a light through hole is provided at the center position of the central part.

[0045] Figure 4a-4c The structures of three micro-bridges provided according to an embodiment of the present invention are shown.

[0046] As Figure 4a-4c shown, the central part of the first micro-bridge structure is a circular structure, and the edge part is a straight structure; the central part of the second micro-bridge structure is a square structure, and the edge part is a straight structure; the central part of the third micro-bridge structure is a square structure, and the edge part is a bent structure.

[0047] Figure 5 The linear relationship between the driving force and the displacement of three micro-bridges provided according to an embodiment of the present invention is shown.

[0048] As Figure 5 shown, under the same displacement, compared with the first micro-bridge structure and the second micro-bridge structure, the third micro-bridge structure requires a greater driving force, and stress analysis also shows that the stress it receives is greater. Therefore, the micro-bridge 4 of the present invention preferably adopts the third micro-bridge structure, and the horizontal plane projection of the third micro-bridge structure is similar to a "卍" structure.

[0049] The present invention uses a reverse driving method to drive the moving mirror in the opposite direction of the static mirror, thereby overcoming the problem of adsorption instability in principle, and expanding the spectral detection range by increasing the cavity length tuning range.

[0050] By using Comsol software to simulate the forward driving mode, the existence of pull-in instability is determined, and through the simulation of the reverse driving method, it can be found that compared with the forward driving method, the relationship between the voltage and the displacement of the cantilever beam tends to be a linear relationship, thus verifying the feasibility of the reverse driving method. Mechanical and parallelism analyses are carried out for different micro-bridge structures, and the excellent characteristics of the "卍" - shaped micro-bridge structure are determined, thereby determining the design structure of the micro-bridge.

[0051] The present invention can also prepare a plurality of moving mirrors 3, each of which is connected to the supporting bridge pier 2 via a microbridge 4, so that the reverse-driven tunable FP filter becomes an array structure, realizing multi-light simultaneous output.

[0052] The array structure can improve the space utilization rate on the basis of increasing the tuning range and the mirror tuning stability, thereby ensuring the high flux of light. Compared with the traditional single-channel FPI filter, the array structure design greatly improves the spectrum acquisition efficiency and reduces the response time by 89% compared with the single-channel FPI filter.

[0053] The above content describes in detail the structure and working principle of the reverse-driven tunable FP filter provided by the embodiment of the present invention. Corresponding to the structure, the embodiment of the present invention also provides a method for preparing the reverse-driven tunable FP filter.

[0054] A method for preparing a reverse-driven tunable FP filter comprises the following steps:

[0055] S1. Evaporating a first reflective film on a first substrate to complete the preparation of a static mirror.

[0056] S2. Form supporting bridge piers on the static mirror using photolithography and magnetron sputtering processes.

[0057] S3. Coat a first sacrificial layer in the cavity formed by the supporting bridge pier and the static mirror, evaporate a second reflective film on the first sacrificial layer, and form a second substrate on the second reflective film by a magnetron sputtering process to complete the preparation of the moving mirror.

[0058] S4. Form a microbridge on the moving mirror using photolithography and magnetron sputtering processes.

[0059] S5. Form an electrode support structure on the microbridge using photolithography and magnetron sputtering processes.

[0060] S6. Coating a second sacrificial layer in the cavity surrounded by the electrode support structure and the moving mirror.

[0061] S7. Form a top electrode on the second sacrificial layer by using photolithography and magnetron sputtering processes.

[0062] S8. The first sacrificial layer and the second sacrificial layer are vaporized to release the space between the top electrode and the microbridge and between the moving mirror and the static mirror, thereby forming a reverse-driven tunable FP filter.

[0063] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0064] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

[0065] The above specific implementations of the present invention do not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A back-driven tunable FP filter, characterized in that: It includes a stationary mirror, a movable mirror, a support pier, a micro-bridge, an electrode support structure, and a top electrode; among them, The support pier is fabricated on the stationary mirror, and a cavity is formed between the support pier and the stationary mirror; The movable mirror is located within the cavity, and an F-P resonant cavity is formed between the movable mirror and the stationary mirror. A first stop block for preventing the movable mirror from contacting the stationary mirror is fabricated on the stationary mirror; The micro-bridge includes a central part and an edge part. The central part is fabricated on the side of the movable mirror facing away from the stationary mirror, and the central part serves as a bottom electrode for generating adsorption with the top electrode; the edge part is fabricated on the top of the support pier, and the electrode support structure is supported between the edge part and the top electrode. The edge part is a cantilever beam evenly distributed circumferentially along the central part, the cantilever beam is a bent structure, and the central part is a polygonal structure, forming a "卍"-shaped micro-bridge.

2. The back-driven tunable FP filter according to claim 1, characterized in that A light passing hole is opened at the center position of the central part.

3. The back-driven tunable FP filter according to claim 1, characterized in that: A second stop block for preventing the central part from contacting the top electrode is fabricated on the top electrode.

4. The method for preparing a back-driven tunable FP filter according to any one of claims 1 to 3, characterized in that: It includes the following steps: S1. Evaporate a first reflective film on a first substrate to form a stationary mirror; S2. Use photolithography and magnetron sputtering processes to form a support pier on the stationary mirror; S3. Coat a first sacrificial layer in the cavity formed by the support pier and the stationary mirror, evaporate a second reflective film on the first sacrificial layer, and form a second substrate on the second reflective film by magnetron sputtering process to form a movable mirror; S4. Use photolithography and magnetron sputtering processes to form a micro-bridge on the movable mirror; among them, the micro-bridge includes a central part and an edge part. The central part is fabricated on the side of the movable mirror facing away from the stationary mirror, and the central part serves as a bottom electrode for generating adsorption with the top electrode; the edge part is fabricated on the top of the support pier, and the electrode support structure is supported between the edge part and the top electrode. The edge part is a cantilever beam evenly distributed circumferentially along the central part, the cantilever beam is a bent structure, and the central part is a polygonal structure, forming a "卍"-shaped micro-bridge; S5. Use photolithography and magnetron sputtering processes to form an electrode support structure on the micro-bridge; S6. Coat a second sacrificial layer in the cavity surrounded by the electrode support structure and the movable mirror; S7. Use photolithography and magnetron sputtering processes to form a top electrode on the second sacrificial layer; S8. Perform gasification treatment on the first sacrificial layer and the second sacrificial layer to release the space between the top electrode and the micro-bridge and between the movable mirror and the stationary mirror, forming a reverse drive tunable F-P filter.

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