WO2021077396A1 - Tunable optical filtering device - Google Patents

Abstract

Disclosed is a tunable optical filtering device, comprising a transparent fixed substrate provided with a first mirror face and a transparent thin-film substrate provided with a second mirror face, wherein on the transparent fixed substrate, a spacer layer is arranged around the outside of the first mirror face; the face of the spacer layer away from the transparent fixed substrate is provided with a piezoelectric actuator; and the transparent thin-film substrate is erected on the piezoelectric actuator to form a cavity body between the first mirror face and the second mirror face, such that the piezoelectric actuator can drive the second mirror face to move relative to the first mirror face. By means of the piezoelectric actuator, the transparent thin-film substrate can perform displacement relative to the transparent fixed substrate, such that an intrinsic effect and a pull-in effect caused by capacitor driving can be completely avoided, thereby expanding the movable range of the transparent thin-film substrate and the spectrum-tunable range of a Fabry-Perot cavity. In addition, the tunable filtering device produced and manufactured by means of a micromachining process has a simple structure, the process is mature, both mass production and miniaturization can be realized, and the cost can be reduced.

Description

Adjustable optical filter device Technical field

The invention relates to the field of filters, in particular to a tunable optical filter device.

Background technique

The Fabry-Perot interference filter is composed of two flat plates placed in parallel. In order to improve the reflectivity of the end face, a multilayer dielectric film or a metal film is plated on the two flat plates. If the interval between two parallel planes is fixed (usually using quartz or Invar as the interval), the instrument becomes an F-P etalon; if the interval between the two parallel planes can be changed, the instrument becomes an F-P interferometer. Compared with the Michelson interferometer, the F-P interferometer based on multi-beam interference produces much sharper fringes. Therefore Fabry-Perot cavity (Fabry-Perot cavity) has been widely used in spectral fine structure analysis, laser resonant cavity, optical filter and so on.

Fabry-Perot cavity is used in optical filters. Under normal incidence, if the optical thickness of the cavity length is an integer multiple of the half wavelength of the incident light, the light at this wavelength can be transmitted through with low loss, while the wavelength that does not meet this condition is Reflected to achieve the filtering function. Tunable filter devices (FPI) based on Fabry-Perot (Fabry-Perot cavity) interference can be applied to miniature spectrometers and miniature or even miniature hyperspectral cameras. In the field of visible-near infrared (400-1000nm) hyperspectral imaging, compared to other solutions, the Fabry-Perot cavity provides the simplest system structure and optical path, so it can greatly reduce the cost, volume and cost of hyperspectral cameras. Power consumption.

FPI devices in the visible-near infrared range usually use optical glass (such as synthetic quartz glass) as a substrate, and form a mirror chip through optical and semiconductor processing, and then assemble two mirror chips and an external piezoelectric actuator to form a Fabry -Perot cavity module, by adjusting the driving voltage of the piezoelectric actuator, the relative position between the two mirror chips can be adjusted, so as to realize the light of different bands on the gating spectrum. Usually devices need to use very thick glass as a substrate to reduce deformation, resulting in difficulties in mirror processing and an increase in the volume of the system, and it is also difficult to achieve mass production in module assembly methods.

Fabry-Perot cavity devices made by micromachining can further realize miniaturization, mass production and cost reduction. The main manufacturing methods are body craft type and surface craft type. The essential feature of the two processes is to form a cantilever beam structure on the substrate of the mirror structure itself, or the mirror film itself is the elastic support of the device. However, the current micro-machined Fabry-Perot cavity devices all adopt the capacitive drive mode. The advantage of the capacitive drive is that the structure is relatively simple, but it will be restricted by problems such as pull-in, which may lead to film displacement. Less than 1/3 of the gap. Integrating the piezoelectric film with the movable mirror can realize the mirror displacement in the positive and negative directions and the required driving voltage is usually smaller than that of the capacitor drive, and the voltage signal is not directly loaded on the movable film spring structure when the piezoelectric film is driven Therefore, the pull-in effect caused by the capacitor drive can be completely avoided, thereby increasing the movable range of the film, that is, the adjustable spectral range of the Fabry-Perot cavity can be expanded accordingly.

In summary, the current Fabry-Perot cavity devices in the visible-near-infrared range have some key problems that limit the commercial application of the technology itself, such as:

1. Large-size Fabry-Perot cavity devices have problems such as large volume, manual assembly and mismatch of external piezoelectric actuators and mirror chips.

2. The micro-machined Fabry-Perot cavity device has problems such as capacitive drive and the inability to isolate the elastic structure from the mirror surface, which leads to intrinsic stress and pull-in effect, which limits the application range of this type of device.

Summary of the invention

In view of the above-mentioned problems, the embodiments of the present application provide a tunable optical filter device, including a transparent fixed substrate provided with a first mirror surface and a transparent film substrate provided with a second mirror surface, on the transparent fixed substrate A spacer layer is arranged around the outer periphery of the first mirror surface, and a piezoelectric actuator is arranged on the side of the spacer layer away from the transparent fixed substrate. The transparent film substrate is erected on the piezoelectric actuator to connect the first mirror surface and the second mirror surface. A cavity is formed between, so that the piezoelectric actuator can drive the second mirror surface to move relative to the first mirror surface.

In some embodiments, the edge of the transparent film substrate is connected with a piezoelectric actuator to form a movable optical film. Therefore, a certain voltage can be applied to the piezoelectric actuator to drive the transparent film substrate to move in the positive and negative directions, thereby forming a movable optical film.

In some embodiments, the spacer layer is made of a sacrificial material, and the sacrificed portion of the spacer layer forms a cavity. The Fabry-Perot cavity can be formed by etching the sacrificial material.

In some embodiments, the piezoelectric actuator is partially suspended on the surface of the spacer layer. Since the spacer layer is partially sacrificed, the piezoelectric actuator is arranged on the surface of the spacer layer and is in a partially suspended state, which is more conducive to driving the transparent film substrate to move.

In some embodiments, the edge of the transparent film substrate is mounted on the suspended part of the piezoelectric actuator. Therefore, the movement range of the transparent film substrate can be expanded.

In some embodiments, the transparent film substrate and/or the suspension part of the piezoelectric actuator is provided with perforations for etching the sacrificial material. The sacrificial material is corroded by setting perforations, and the process is mature and simple.

In some embodiments, the piezoelectric actuator is disposed on the spacer layer by deposition or bonding. The method of deposition or bonding is simple and easy to process.

In some embodiments, the piezoelectric actuator includes a piezoelectric film structure and electrodes on the upper and lower surfaces of the piezoelectric film structure. The piezoelectric actuator can be driven to drive the transparent film substrate to move by applying voltage on the upper and lower surfaces of the piezoelectric film structure.

In some embodiments, the material of the transparent film substrate includes alumina. Alumina facilitates micromachining to make the substrate into a thin film, and has high transparency.

In some embodiments, the first mirror surface and the second mirror surface include a silver layer or a distributed Bragg reflector formed by superimposing silicon, silicon dioxide, and silicon. The first mirror surface, the second mirror surface, and the cavity in the middle form a Fabry-Perot cavity. Therefore, a silver layer or a distributed Bragg reflector formed by superimposing silicon, silicon dioxide and silicon is selected to reflect light.

In some embodiments, the material of the transparent fixed substrate includes glass or aluminum oxide. The use of glass or alumina as the transparent fixed substrate is beneficial for micro-processing in industry.

The embodiment of the present application discloses a tunable optical filter device, which includes a transparent fixed substrate provided with a first mirror surface and a transparent film substrate provided with a second mirror surface. The transparent fixed substrate is located outside the first mirror surface. A spacer layer is arranged around the spacer layer, and a piezoelectric actuator is arranged on the side of the spacer layer away from the transparent fixed substrate. The transparent film substrate is erected on the piezoelectric actuator to form a cavity between the first mirror surface and the second mirror surface, Thus, the piezoelectric actuator can drive the second mirror surface to move relative to the first mirror surface. The piezoelectric actuator can cause the transparent film substrate to be displaced relative to the transparent fixed substrate. The voltage applied to the piezoelectric actuator is not directly applied to the movable optical film structure, so it can completely avoid the drive caused by the capacitor. The pull-in effect improves the movable range of the transparent film substrate and expands the adjustable spectrum range of the Fabry-Perot cavity. In addition, the Fabry-Perot cavity is formed by micromachining and sacrificial layer corrosion, the manufacturing process is simple, the cost is reduced, and industrial mass production can be realized.

Description of the drawings

The drawings are included to provide a further understanding of the embodiments and the drawings are incorporated into this specification and constitute a part of this specification. The drawings illustrate the embodiments and together with the description serve to explain the principle of the present invention. It will be easy to recognize the other embodiments and the many expected advantages of the embodiments because they become better understood by quoting the following detailed description. The elements of the drawings are not necessarily in proportion to each other. The same reference numerals refer to corresponding similar parts.

FIG. 1 is a schematic cross-sectional view I of the tunable optical filter device according to the embodiment of the application;

2 is a schematic cross-sectional view II of the tunable optical filter device according to the embodiment of the application.

Detailed ways

The application will be further described in detail below with reference to the drawings and embodiments. It can be understood that the specific embodiments described here are only used to explain the related invention, but not to limit the invention. In addition, it should be noted that, for ease of description, only the parts related to the relevant invention are shown in the drawings.

It should be noted that the embodiments in this application and the features in the embodiments can be combined with each other if there is no conflict. Hereinafter, the application will be described in detail with reference to the drawings and in conjunction with the embodiments.

Fig. 1 shows a cross-sectional view of a tunable optical filter device according to one of the embodiments of the present invention. As shown in FIG. 1, the tunable optical filter device includes a transparent fixed substrate 101 provided with a first mirror surface 111 and a transparent film substrate 102 provided with a second mirror surface 112, wherein the first mirror surface 111 and the second mirror surface 112 are opposite to each other. A spacer layer 301 is arranged on the transparent fixed substrate 101 outside the first mirror surface 111, a piezoelectric actuator 121 is arranged on the side of the spacer layer 301 away from the transparent fixed substrate 101, and the transparent film substrate 102 is erected On the piezoelectric actuator 121, a cavity is formed between the first mirror surface 111 and the second mirror surface 112, that is, a Fabry-Perot cavity is formed, so that the piezoelectric actuator 121 can drive the second mirror surface 112 relative to The first mirror 111 moves to change the relative distance of the Fabry-Perot cavity to realize the adjustable filtering function. The result of the whole device is relatively simple, the cost is low, and the processing technology is very simple and mature, which can realize mass production and is convenient Popularize and apply to various small-scale hyperspectral optical equipment.

In a specific embodiment, the edge of the transparent film substrate 102 is connected with the piezoelectric actuator 121 to form a movable optical film. By applying a certain voltage to the piezoelectric actuator 121, the transparent film substrate 102 can be driven to move in the positive and negative directions. The transparent film substrate 102 and the piezoelectric actuator 121 are always in a connected state, and the second mirror 112 is connected to the transparent film substrate 102, so the transparent film substrate 102 is driven to move by the piezoelectric actuator 121, so the first mirror can be controlled The distance between 111 and the second mirror 112, that is, the gap of the Fabry-Perot cavity is adjusted to realize the function of adjustable optical filtering.

In a specific embodiment, the movable optical film formed by the transparent film substrate 102 and the piezoelectric actuator 121 is disposed on the side of the spacer layer 301 away from the transparent fixed substrate 101. The spacer layer 301 is made of a sacrificial material, and the sacrificed portion of the spacer layer 301 forms a cavity. Therefore, in the process, the sacrificial material can be etched to leave a part of the spacer layer 301 that is not etched to support the transparent film substrate 102 and the transparent fixed substrate 101 to form a Fabry-Perot cavity. The process of etching the spacer layer 301 can make the first mirror surface 111 and the second mirror surface 112 have relatively parallel surfaces during processing. The first mirror surface 111 is deposited on the transparent fixed substrate 101 and the spacer layer 121 is then deposited. The mirror 112, the piezoelectric actuator 301 and the transparent film substrate 102, and finally the spacer layer 301 is etched to form a Fabry-Perot cavity between the first mirror 111 and the second mirror 112. In a preferred embodiment, a through hole 103 is provided on the suspended portion of the transparent film substrate 102 and/or the piezoelectric actuator 301 to corrode the sacrificial material. In other optional embodiments, other methods may also be used to corrode the sacrificial material. The whole process is simple and convenient, and it adopts the very mature technology in the current micromachining manufacturing process, so the whole device is suitable for mass production in industry, and the production through micromachining can further realize miniaturization and reduce costs.

In a preferred embodiment, the piezoelectric actuator 121 is disposed on the spacer layer 301 by deposition or bonding. The piezoelectric actuator 121 specifically includes a piezoelectric film structure 1211 and electrodes 1212 and 1213 arranged on the upper and lower surfaces of the piezoelectric film structure 1211. The material of the piezoelectric film structure 1211 can be lead zirconate titanate film, nitride Aluminum film or zinc oxide film. As a ferroelectric film, lead zirconate titanate film has higher piezoelectric, dielectric and heat release properties than non-ferroelectric films (such as aluminum nitride film or zinc oxide film). In actual application scenarios, it can be based on specific Select piezoelectric film materials that meet the requirements of various parameters in the application to meet the requirements of use under different conditions. In this case, voltage is applied to the electrodes 1212 and 1213 of the piezoelectric actuator 121, and there is no need to apply voltage to the movable optical film structure, so the pull-in effect caused by the capacitor drive can be avoided, thereby improving the optical film The movable range of the Fabry-Perot cavity can be expanded accordingly.

In a preferred embodiment, after the spacer layer 301 is partially sacrificed, the piezoelectric actuator 121 is partially suspended on the surface of the spacer layer 301. When the piezoelectric actuator 121 is arranged on the surface of the spacer layer 301 and is in a partially suspended state, it is more advantageous to drive the transparent film substrate 102 to move. The edge of the transparent film substrate 102 is mounted on the suspended part of the piezoelectric actuator 301, that is, the edge of the transparent film substrate 102 is arranged on the other side of the suspended part of the piezoelectric actuator 301 away from the cavity. In this case, applying a certain range of voltage to the piezoelectric actuator 301 can drive the transparent film substrate 102 to move, and compared to other piezoelectric actuators 301 that are not suspended, in this case the transparent film The movable range of the substrate 102 is significantly improved, thereby further expanding the spectral adjustable range of the Fabry-Perot cavity. In addition, the piezoelectric actuator 121 and the second mirror 112 are respectively located on both sides of the transparent film substrate 102 at this time, which is to separate the piezoelectric actuator 121 and the second mirror 112, which can reduce the intrinsic stress and absorption.合 effect.

In a specific embodiment, as shown in FIG. 1, the first mirror surface 111 and the second mirror surface 112 may be silver layers. As shown in FIG. 2, the first mirror surface 111 and the second mirror surface 112 may also be made of silicon, Distributed Bragg reflector formed by superposition of silicon and silicon. The first mirror surface 111, the second mirror surface 112 and the cavity in the middle form a Fabry-Perot cavity. Therefore, a silver layer or a distributed layer formed by superimposing silicon, silicon dioxide and silicon is selected in the Fabry-Perot cavity. The Bragg reflector reflects the light, and it can also be other reflective materials. Specifically, the appropriate mirror material can be selected according to the actual needs of hyperspectral imaging to achieve the best filtering effect.

In a preferred embodiment, the material of the transparent film substrate 102 includes alumina. Using alumina as the substrate can ensure the transmittance of visible light-near infrared light (400-1000nm). It should be realized that other materials other than alumina, such as silicon or zinc selenide, can also be used to achieve the technical effects of the present invention. On the other hand, alumina is easy to process, and the substrate can be made into a very thin film, which can further miniaturize the device and expand the moving range of the movable film. The material of the transparent fixed substrate 101 includes glass or alumina. Glass or alumina is convenient for micro-processing in industrial production. In other optional embodiments, the transparent fixed substrate 101 can also be selected from other materials to also achieve the technical effects of the present invention.

The tunable optical filter device of the present application is provided with a transparent fixed substrate with a first mirror surface and a transparent film substrate with a second mirror surface. A spacer layer is provided on the transparent fixed substrate around the outer periphery of the first mirror surface. The side of the layer away from the transparent fixed substrate is provided with a piezoelectric actuator, and the transparent film substrate is erected on the piezoelectric actuator to form a cavity between the first mirror surface and the second mirror surface, so that the piezoelectric actuator can be driven The second mirror surface moves relative to the first mirror surface. The piezoelectric actuator can cause the transparent film substrate to be displaced relative to the transparent fixed substrate. The voltage applied to the piezoelectric actuator is not directly applied to the movable optical film structure, so it can completely avoid the drive caused by the capacitor. Intrinsic effect and pull-in effect, thereby increasing the movable range of the transparent film substrate and expanding the adjustable range of the spectrum of the Fabry-Perot cavity. In addition, the tunable filter device manufactured by the micromachining process has a simple structure and a mature process, which can realize batch size, miniaturization and cost reduction, which is beneficial to popularize and apply to small hyperspectral optical equipment such as microspectrometers.

The specific implementation manners of this application are described above, but the protection scope of this application is not limited to this. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed in this application, and they should all be covered Within the scope of protection of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.

In the description of this application, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", etc. are based on the orientation or positional relationship shown in the drawings, and are only for It is convenient to describe the application and simplify the description, instead of indicating or implying that the device or element referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore cannot be understood as a limitation of the application. The word'comprising' does not exclude the presence of elements or steps not listed in the claims. The wording'a' or'one' in front of an element does not exclude the existence of a plurality of such elements. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used for improvement. Any reference signs in the claims should not be construed as limiting the scope.

Claims (11)

A tunable optical filter device, characterized in that it comprises a transparent fixed substrate provided with a first mirror surface and a transparent film substrate provided with a second mirror surface, and the first mirror surface is located on the transparent fixed substrate. The outer periphery is provided with a spacer layer, a piezoelectric actuator is provided on the side of the spacer layer away from the transparent fixed substrate, and the transparent film substrate is erected on the piezoelectric actuator to connect to the first A cavity is formed between the mirror surface and the second mirror surface, so that the piezoelectric actuator can drive the second mirror surface to move relative to the first mirror surface. The tunable optical filter device according to claim 1, wherein the edge of the transparent film substrate is connected with the piezoelectric actuator to form a movable optical film. The tunable optical filter device according to claim 1, wherein the spacer layer is made of a sacrificial material, and the sacrificed portion of the spacer layer forms the cavity. The tunable optical filter device according to claim 3, wherein the piezoelectric actuator is partially suspended on the surface of the spacer layer. The tunable optical filter device according to claim 4, wherein the edge of the transparent film substrate is mounted on the suspension part of the piezoelectric actuator. The tunable optical filter device according to claim 3, wherein the transparent film substrate and/or the suspension part of the piezoelectric actuator is provided with perforations to corrode the sacrificial material. The tunable optical filter device according to any one of claims 1 to 6, wherein the piezoelectric actuator is disposed on the spacer layer by deposition or bonding. The tunable optical filter device according to any one of claims 1 to 6, wherein the piezoelectric actuator comprises a piezoelectric film structure and electrodes located on the upper and lower surfaces of the piezoelectric film structure. The tunable optical filter device according to any one of claims 1 to 6, wherein the material of the transparent film substrate comprises alumina. The tunable optical filter device according to any one of claims 1-6, wherein the first mirror surface and the second mirror surface comprise a silver layer or a distribution formed by superimposing silicon, silicon dioxide and silicon. Bragg reflector. The tunable optical filter device according to any one of claims 1 to 6, wherein the material of the transparent fixed substrate comprises glass or alumina.

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