CN113260897A

CN113260897A - Adjustable optical filter device

Info

Publication number: CN113260897A
Application number: CN201980087770.5A
Authority: CN
Inventors: 郭斌
Original assignee: Shenzhen Haippi Nanooptical Technology Co ltd
Current assignee: Shenzhen Haippi Nanooptical Technology Co ltd
Priority date: 2019-10-25
Filing date: 2019-10-25
Publication date: 2021-08-13
Also published as: WO2021077396A1

Abstract

The embodiment of the application discloses adjustable optical filter, including the transparent fixed substrate that is provided with first mirror surface and the transparent film substrate that is provided with the second mirror surface, be provided with the wall around the outside that is located first mirror surface on transparent fixed substrate, be provided with piezoelectric actuator in the one side of wall of keeping away from transparent fixed substrate, transparent film substrate erects on piezoelectric actuator in order to form the cavity between first mirror surface and second mirror surface to make piezoelectric actuator can drive the second mirror surface and remove for first mirror surface. The piezoelectric actuator can make the transparent film substrate generate displacement relative to the transparent fixed substrate, and can completely avoid the intrinsic effect and the attraction effect caused by capacitance driving, thereby improving the movable range of the transparent film substrate and expanding the spectrum adjustable range of the Fabry-Perot cavity. In addition, the adjustable optical filter produced and manufactured by the micromachining process has a simple structure and a mature process, can realize batch and miniaturization and reduces the cost.

Description

Adjustable optical filter device

Technical Field

The invention relates to the field of filters, in particular to an adjustable optical filter device.

Background

A Fabry-Perot interference filter consists of two planar plates placed in parallel. In order to improve the end face reflectivity, a plurality of layers of dielectric films or metal films are plated on the two plane plates. If the separation of the two parallel planes is constant (usually quartz or invar is used as the separation), the instrument becomes an F-P etalon; if the separation between the two parallel planes can be varied, the instrument becomes an F-P interferometer. The F-P interferometer based on multi-beam interference produces much finer and sharper fringes compared to the Michelson interferometer. Therefore, the Fabry-Perot cavity (Fabry-Perot cavity) is widely applied to the aspects of spectral fine structure analysis, laser resonant cavity, optical filter and the like.

The Fabry-Perot cavity is applied to an optical filter, and if the optical thickness of the cavity length is integral multiple of half wavelength of incident light under normal incidence, light at the wavelength can be transmitted with low loss, while the wavelength which does not meet the condition is reflected, so that the function of filtering is realized. Tunable FPIs based on Fabry-Perot (Fabry-Perot cavity) interference can be applied in micro spectrometers and small and even mini hyperspectral cameras. In the field of visible light-near infrared (400-.

In a FPI device in the visible-near infrared range, optical glass (e.g., synthetic quartz glass) is usually used as a substrate, mirror chips are formed through optical and semiconductor processing, then two mirror chips and an external piezoelectric actuator are assembled to form a fabry-perot cavity module, and by adjusting the driving voltage of the piezoelectric actuator, the relative position between the two mirror chips can be adjusted, thereby realizing the gating of light in different bands on the spectrum. In general, the device needs to use very thick glass as a substrate to reduce deformation, resulting in difficulty in mirror finishing and increase in system volume, and the module assembly method is difficult to realize mass production.

The Fabry-Perot cavity device manufactured by micromachining (micromechining) can further realize miniaturization, mass production and cost reduction. The main manufacturing method is a body process type and a surface process type. The essential characteristic of both processes is that a cantilever beam structure is formed on the substrate of the mirror structure itself, or the mirror film itself is the elastic support of the device. However, the existing micro-machined fabry-perot cavity device adopts a capacitance driving mode, and the capacitance driving has the advantage of relatively simple structure, but is limited by problems such as Pull-in (Pull-in) and the like, so that the displacement of the thin film is required to be smaller than 1/3 of the gap. The piezoelectric film and the movable mirror are integrated, mirror displacement in positive and negative directions can be realized, the required driving voltage is usually small relative to that of capacitor driving, and a voltage signal is not directly loaded on a movable film spring structure when the piezoelectric film is driven, so that the attraction effect caused by the capacitor driving can be completely avoided, the movable range of the film is further improved, and the spectrum adjustable range of the Fabry-Perot cavity can be correspondingly expanded.

In summary, there are some key problems with the current fabry-perot cavity devices in the visible-near infrared range that limit the commercial application of the technology itself, such as:

1. the large-size Fabry-Perot cavity device has the problems of large volume, manual assembly, mismatching of an external piezoelectric actuator and a mirror chip and the like.

2. The micromechanical Fabry-Perot cavity device has the problems of capacitance drive, incapability of isolating an elastic structure from a mirror surface and the like, so that intrinsic stress and an attraction effect are caused, and the application range of the device is limited.

Disclosure of Invention

In view of the above existing problems, an embodiment of the present application provides an adjustable optical filter device, including a transparent fixed substrate provided with a first mirror surface and a transparent thin film substrate provided with a second mirror surface, a spacer layer is provided on the transparent fixed substrate around the outside of the first mirror surface, a piezoelectric actuator is provided on one surface of the spacer layer away from the transparent fixed substrate, the transparent thin 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 drive the second mirror surface to move relative to the first mirror surface.

In some embodiments, the edge of the transparent film substrate is coupled to a piezoelectric actuator to form a movable optical film. Therefore, the transparent film substrate can be driven to move in the positive and negative directions by applying a certain voltage on the piezoelectric actuator, so that the movable optical film is formed.

In some embodiments, the spacer layer is made of a sacrificial material, and the sacrificial portion of the spacer layer forms the cavity. A fabry-perot cavity may be formed by etching a sacrificial material.

In some embodiments, the piezoelectric actuator is partially suspended from the spacer layer surface. Because 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, and the transparent film substrate is more favorably driven to move.

In some embodiments, the edge of the transparent film substrate rides on the suspended portion of the piezoelectric actuator. The moving range of the transparent thin film substrate can be expanded.

In some embodiments, the transparent membrane substrate and/or the suspended portion of the piezoelectric actuator is provided with perforations to erode the sacrificial material. The sacrificial material is corroded by the through holes, so that the process is mature and simple.

In some embodiments, the piezoelectric actuator is disposed on the spacer layer by deposition or bonding. The deposition or bonding mode has simple process and convenient processing.

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

In some embodiments, the material of the transparent thin film substrate includes aluminum oxide. The aluminum oxide is convenient for micro-processing to make the substrate into a film and has high transparency.

In some embodiments, the first mirror and the second mirror comprise silver layers or distributed bragg reflectors formed by stacking silicon, silicon dioxide and silicon. The first mirror, the second mirror and the middle cavity form a Fabry-Perot cavity, so that a silver layer or a distributed Bragg reflector formed by overlapping silicon, silicon dioxide and silicon is selected to reflect light.

In some embodiments, the material of the transparent mounting substrate comprises glass or alumina. The transparent fixed substrate is made of glass or alumina, which is beneficial to industrial micro-processing.

The embodiment of the application discloses adjustable optical filter, including the transparent fixed substrate that is provided with first mirror surface and the transparent film substrate that is provided with the second mirror surface, be provided with the wall around the outside that is located first mirror surface on transparent fixed substrate, be provided with piezoelectric actuator in the one side of wall of keeping away from transparent fixed substrate, transparent film substrate erects on piezoelectric actuator in order to form the cavity between first mirror surface and second mirror surface to make piezoelectric actuator can drive the second mirror surface and remove for first mirror surface. The transparent film substrate can generate displacement relative to the transparent fixed substrate through the piezoelectric actuator, and the voltage applied to the piezoelectric actuator is not directly loaded on the movable optical film structure, so that the attraction effect caused by capacitance driving can be completely avoided, the movable range of the transparent film substrate is improved, and the spectrum adjustable range of the Fabry-Perot cavity is expanded. In addition, the Fabry-Perot cavity is formed by micromachining and corroding the sacrificial layer, the manufacturing process is simple, the cost is reduced, and industrial mass production can be realized.

Drawings

The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments and together with the description serve to explain the principles of the invention. Other embodiments and many of the intended advantages of embodiments will be readily appreciated as they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding similar parts.

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

fig. 2 is a schematic cross-sectional view ii of a tunable optical filter device according to an embodiment of the present application.

Detailed Description

The present application will be described in further detail with reference to the following drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and not restrictive of the invention. It should be noted that, for convenience of description, only the portions related to the related invention are shown in the drawings.

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.

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 having a first mirror 111 and a transparent thin film substrate 102 having a second mirror 112, wherein the first mirror 111 and the second mirror 112 are disposed opposite to each other, a spacer layer 301 is disposed on the transparent fixed substrate 101 and around the first mirror 111, a piezoelectric actuator 121 is disposed on a side of the spacer layer 301 away from the transparent fixed substrate 101, and the transparent thin film substrate 102 is mounted on the piezoelectric actuator 121 to form a cavity between the first mirror 111 and the second mirror 112, i.e., to form a Fabry-Perot cavity, such that the piezoelectric actuator 121 can drive the second mirror 112 to move relative to the first mirror 111, thereby changing a relative distance between the Fabry-Perot cavity and implementing a tunable filtering function The method is mature, can realize batch production, and is convenient to popularize and apply to various small-sized hyperspectral optical equipment.

In a particular embodiment, the edge of the transparent film substrate 102 is coupled to a piezoelectric actuator 121 to form a movable optical film. The transparent thin film substrate 102 can be driven to move in the positive and negative directions by applying a certain voltage to the piezoelectric actuator 121. The transparent film substrate 102 and the piezoelectric actuator 121 are always in a connected state, and the second mirror 112 is connected with the transparent film substrate 102, so that the piezoelectric actuator 121 drives the transparent film substrate 102 to move, and thus the distance between the first mirror 111 and the second mirror 112 can be controlled, that is, the gap of the fabry-perot cavity is adjusted, thereby realizing the function of tunable optical filtering.

In a specific embodiment, the transparent thin film substrate 102 and the movable optical thin film formed by the piezoelectric actuator 121 are disposed on the side of the spacer layer 301 remote from the transparent fixed substrate 101. The spacer layer 301 is made of a sacrificial material, and the sacrificial portion of the spacer layer 301 forms a cavity. Therefore, the sacrificial material is etched to leave a portion of the spacer layer 301, which is not etched, to support the transparent thin film substrate 102 and the transparent fixed substrate 101 to form the fabry-perot cavity. The first mirror 111 and the second mirror 112 can have relatively parallel surfaces when being processed by adopting a process of corroding the spacing layer 301, the first mirror 111 is deposited on the transparent fixed substrate 101, the spacing layer 121 is arranged on the transparent fixed substrate 101, the second mirror 112, the piezoelectric actuator 301 and the transparent thin film substrate 102 are deposited, and finally, the spacing layer 301 is corroded to form a Fabry-Perot cavity between the first mirror 111 and the second mirror 112. In a preferred embodiment, the sacrificial material is eroded by providing perforations 103 in the suspended portion of the transparent membrane substrate 102 and/or piezoelectric actuator 301. In alternative embodiments, the sacrificial material may be etched in other ways. The whole process is simple and convenient, and the adopted technology is the mature technology in the current micro machining (micromachining) manufacturing process, so that the whole device is suitable for industrial mass production, and the miniaturization can be further realized and the cost can be reduced by the micromachining mode.

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 thin film structure 1211, and an electrode 1212 and an electrode 1213 disposed on the upper and lower surfaces of the piezoelectric thin film structure 1211, wherein the material of the piezoelectric thin film structure 1211 may be a lead zirconate titanate thin film, an aluminum nitride thin film, or a zinc oxide thin film. The lead zirconate titanate film as a ferroelectric film has higher piezoelectric, dielectric and heat release performances compared with a non-ferroelectric film (such as an aluminum nitride film or a zinc oxide film), and a piezoelectric film material meeting the requirements of various parameters can be selected according to specific application occasions in practical application scenes so as to meet the use requirements under different conditions. In this case, the voltage is applied to the

electrodes

1212 and 1213 of the piezoelectric actuator 121 without applying a voltage to the movable optical film structure, so that a pull-in effect caused by capacitance driving can be avoided, thereby improving the movable range of the optical film, i.e., the tunable range of the spectrum of the fabry-perot cavity can be correspondingly expanded.

In a preferred embodiment, the piezoelectric actuator 121 is partially suspended from the surface of the spacer layer 301 after the portion of the spacer layer 301 is sacrificed. When the piezoelectric actuator 121 is disposed on the surface of the spacer layer 301 and in a partially suspended state, it is more beneficial to drive the transparent thin film substrate 102 to move. The edge of the transparent film substrate 102 is mounted on the suspended portion of the piezoelectric actuator 301, that is, the edge of the transparent film substrate 102 is disposed on the other side of the suspended portion of the piezoelectric actuator 301 away from the cavity. In this case, the transparent thin film substrate 102 can be driven to move by applying a certain range of voltage to the piezoelectric actuator 301, and compared with the case that the other piezoelectric actuator 301 is not suspended, the movable range of the transparent thin film substrate 102 in this case is obviously improved, so that the spectral tunable range of the fabry-perot cavity is further expanded. In addition, at this time, the piezoelectric actuator 121 and the second mirror 112 are respectively located at two sides of the transparent film substrate 102, that is, the piezoelectric actuator 121 and the second mirror 112 are separately disposed, so that intrinsic stress and attraction effect can be reduced.

In a specific embodiment, as shown in fig. 1, the first mirror 111 and the second mirror 112 may be silver layers, and as shown in fig. 2, the first mirror 111 and the second mirror 112 may also be distributed bragg reflectors formed by stacking silicon, silicon dioxide, and silicon. The first mirror 111, the second mirror 112 and the middle cavity form a fabry-perot cavity, so that a silver layer or a distributed bragg reflector formed by silicon, silicon dioxide and silicon in a stacked manner is selected in the fabry-perot cavity to reflect light, and the fabry-perot cavity can also be made of other reflecting materials, and particularly, a proper mirror material can be selected according to the actual requirement of hyperspectral imaging, so that the optimal filtering effect is achieved.

In a preferred embodiment, the material of the transparent thin film substrate 102 comprises aluminum oxide. The transmittance of visible light-near infrared light (400-. It should be appreciated that materials other than aluminum oxide, such as silicon or zinc selenide, may also be used to achieve the technical effects of the present invention. On the other hand, alumina is easy to process, and can make the substrate into a very thin film, thereby further miniaturizing the device and enlarging the moving range of the movable film. The material of the transparent fixed substrate 101 includes glass or alumina. Glass or alumina facilitates micro-machining in industrial production, and in alternative embodiments, other materials can be selected for the transparent substrate 101 to achieve the technical effects of the present invention.

The adjustable optical filter device is provided with a transparent fixed substrate of a first mirror surface and a transparent film substrate of a second mirror surface, a spacing layer is arranged around the outer portion, located on the first mirror surface, of the transparent fixed substrate, a piezoelectric actuator is arranged on one side, far away from the transparent fixed substrate, of the spacing layer, the transparent film substrate is erected on the piezoelectric actuator to form a cavity between the first mirror surface and the second mirror surface, and therefore the piezoelectric actuator can drive the second mirror surface to move relative to the first mirror surface. The piezoelectric actuator can make the transparent film substrate generate displacement relative to the transparent fixed substrate, and the voltage applied to the piezoelectric actuator is not directly loaded on the movable optical film structure, so that the intrinsic effect and the pull-in effect caused by capacitance driving can be completely avoided, the movable range of the transparent film substrate is improved, and the spectrum adjustable range of the Fabry-Perot cavity is expanded. In addition, the adjustable optical filter produced and manufactured by the micromachining process has a simple structure and a mature process, can realize batch and miniaturization and reduce the cost, and is favorable for being popularized and applied to miniature spectrometer and other small-sized high-spectrum optical equipment.

While the present invention has been described with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

In the description of the present application, it is to be understood that the terms "upper", "lower", "inner", "outer", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are only for convenience in describing the present application and simplifying the description, and do not indicate or imply that the referred devices or elements must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present application. The word 'comprising' does not exclude the presence of elements or steps not listed in a claim. The word 'a' or 'an' preceding an element does not exclude the presence 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 to advantage. Any reference signs in the claims shall not be construed as limiting the scope.

Claims

The utility model provides an adjustable optical filter, its characterized in that, including the transparent fixed substrate that is provided with first mirror surface and the transparent film substrate that is provided with the second mirror surface transparent fixed substrate is last to be located be provided with the wall around the outside of first mirror surface the keeping away from of wall one side of transparent fixed substrate is provided with piezoelectric actuator, transparent film substrate erects on the piezoelectric actuator in order first mirror surface with form the cavity between the second mirror surface, thereby make piezoelectric actuator can drive the second mirror surface for first mirror surface removes.
A tunable optical filter device according to claim 1, wherein the edges of the transparent thin film substrate are connected to the piezoelectric actuator to form a movable optical thin film.
A tunable optical filter device according to claim 1, wherein the spacer layer is made of a sacrificial material and the sacrificial portion of the spacer layer forms the cavity.
A tunable optical filter device according to claim 3, wherein the piezoelectric actuator is partially suspended from the spacer layer surface.
A tunable optical filter device according to claim 4, wherein the edges of the transparent thin film substrate ride on the suspended portion of the piezoelectric actuator.
A tunable optical filter device according to claim 3, wherein the transparent thin film substrate and/or the suspended portion of the piezoelectric actuator is provided with perforations for corroding sacrificial material.
A tunable optical filter device according to any one of claims 1-6, wherein the piezoelectric actuator is provided on the spacer layer by deposition or bonding.
A tunable optical filter device according to any one of claims 1-6, wherein the piezoelectric actuator comprises a piezoelectric thin film structure and electrodes on both upper and lower surfaces of the piezoelectric thin film structure.
A tunable optical filter device according to any one of claims 1-6, wherein the transparent thin film substrate comprises alumina.
A tunable optical filter device according to any one of claims 1-6, wherein the first and second mirror surfaces comprise silver layers or distributed Bragg reflectors formed by the superposition of silicon, silicon dioxide and silicon.
A tunable optical filter device according to any one of claims 1-6, wherein the transparent securing substrate comprises glass or alumina.