WO2023050884A1 - 超表面及具有其的指纹识别装置 - Google Patents

超表面及具有其的指纹识别装置 Download PDF

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WO2023050884A1
WO2023050884A1 PCT/CN2022/098342 CN2022098342W WO2023050884A1 WO 2023050884 A1 WO2023050884 A1 WO 2023050884A1 CN 2022098342 W CN2022098342 W CN 2022098342W WO 2023050884 A1 WO2023050884 A1 WO 2023050884A1
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medium
metasurface
equal
array
optical detector
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PCT/CN2022/098342
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English (en)
French (fr)
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郝成龙
谭凤泽
朱健
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深圳迈塔兰斯科技有限公司
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Publication of WO2023050884A1 publication Critical patent/WO2023050884A1/zh

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses

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  • the present application relates to the technical field of metamaterials, in particular, to a metasurface.
  • Angle selection refers to changing the transmittance at different incident angles so that incident light within a specific incident angle range can pass through.
  • Angular selection has important applications in light-emitting diodes (LED, Light Emitting Diode) and laser directional emission.
  • the angle selection is mainly realized through the diaphragm, that is, the diaphragm is set on the incident light path, and only the incident light within a specific incident angle range can pass through the window of the diaphragm, and the light outside the specific incident angle range is blocked by the diaphragm. .
  • Apertures are mainly used in traditional optical systems, but the processing technology of micron-sized apertures is complicated, which is not conducive to the miniaturization of optical components.
  • the embodiment of this application provides the following technical solutions:
  • an embodiment of the present application provides a metasurface, the metasurface includes a substrate, a first medium, and a second medium;
  • the first medium is a subwavelength structure, and the first medium is distributed in an array on one side of the substrate;
  • the second medium is filled between the first mediums
  • the included angle between the normal of the interface between the first medium and the second medium and the normal of the substrate surface is not equal to 0°.
  • cross-sections of the first medium at any two positions on the height axis of the sub-wavelength structure have similar figures.
  • the metasurface further includes a third medium
  • the third medium is arranged in the first medium; the height of the third medium is less than or equal to the height of the first medium.
  • the array comprises a plurality of superstructure units
  • the plurality of superstructure units are close-packable figures filling the surface of the substrate, and the first medium is arranged at the vertices and/or central positions of the close-packable figures.
  • the absolute value of the difference between the refractive index of the second medium and the refractive index of the first medium is greater than or equal to 0.5.
  • the second medium includes a material transparent to the target wavelength band.
  • the second medium includes air.
  • the height of the first medium is greater than or equal to 300 nanometers and less than or equal to 2000 nanometers.
  • the minimum distance between any two adjacent first media is greater than or equal to 80 nanometers.
  • the critical angle ⁇ c of the metasurface is less than or equal to 40°.
  • the maximum aspect ratio of the first medium is less than or equal to 20;
  • the maximum aspect ratio is equal to the ratio of the height of the first medium to the minimum diameter of the first medium.
  • the first medium includes titanium oxide, silicon nitride, fused silica, aluminum oxide, gallium nitride, gallium phosphide, amorphous silicon, crystalline silicon and hydrogenated amorphous silicon.
  • the embodiment of the present application provides a fingerprint identification device, the fingerprint identification device includes a metasurface array and an optical detector;
  • the metasurface array is arranged opposite to the photosensitive surface of the optical detector
  • One side of the metasurface array is provided with the above-mentioned metasurface.
  • the distance from any metasurface in the metasurface array to the detection unit mapped to the metasurface is equal to the back focus of the metasurface.
  • the metasurfaces in the metasurface array are in a one-to-one mapping relationship with the detection units of the optical detector.
  • the sum of the thickness of the metasurface array, the thickness of the optical detector, and the distance between the metasurface array and the optical detector is less than or equal to 500 microns.
  • the fingerprint identification device also includes an optical detector cover
  • the thickness of the optical detector cover is equal to the distance from the metasurface array to the optical detector.
  • an embodiment of the present application further provides an electronic device, which is characterized in that the electronic device includes the above-mentioned fingerprint identification device.
  • the embodiment of the present application provides a metasurface, by making the angle between the normal line of the interface between the first medium and the second medium and the normal line of the substrate surface not equal to 0°, the angle selection and phase control of the incident light are realized, The process difficulty of the angle selection element is reduced, and the miniaturization of the optical element is promoted.
  • the present application also provides a fingerprint recognition device including the metasurface, and the metasurface provided by the embodiment of the present application realizes small size, no crosstalk, high recognition accuracy and high resolution.
  • Fig. 1 shows a schematic diagram of an optional structure of a metasurface provided by an embodiment of the present application
  • Fig. 2 shows another optional structural schematic diagram of the metasurface provided by the embodiment of the present application
  • Fig. 3 shows another optional structural schematic diagram of the metasurface provided by the embodiment of the present application.
  • Fig. 4 shows a kind of optional schematic structural diagram of the superstructure unit that the embodiment of the present application provides
  • Fig. 5 shows another optional structural schematic diagram of the superstructure unit provided by the embodiment of the present application.
  • Fig. 6 shows another optional structural schematic diagram of the metasurface provided by the embodiment of the present application.
  • Fig. 7 shows another optional structural schematic diagram of the metasurface provided by the embodiment of the present application.
  • Fig. 8 shows another optional structural schematic diagram of the metasurface provided by the embodiment of the present application.
  • Fig. 9 shows another optional structural schematic diagram of the metasurface provided by the embodiment of the present application.
  • Figure 10 shows the transmittance of the metasurface provided by the embodiment of the present application to incident light at different angles
  • Figure 11 shows the control of the phase length of the incident light by the side length of the metasurface nanoprism provided by the embodiment of the present application
  • FIG. 12 shows an optional structural schematic diagram of a fingerprint identification device provided by an embodiment of the present application.
  • Figure 13 shows the point spread function of a single metasurface in the fingerprint identification device provided by the embodiment of the present application when the incident angle is 0°;
  • FIG. 14 shows the point spread function of a single metasurface in the fingerprint identification device provided by the embodiment of the present application when the incident angle is 6°;
  • the embodiment of the present application provides a metasurface.
  • the metasurface includes a substrate 1 , a first medium 2 and a second medium 3 .
  • the first medium 2 is a sub-wavelength structure, and the first medium 2 is distributed on one side of the substrate 1 in an array; the second medium 3 is filled between the first medium 2; the separation of the first medium 1 and the second medium 3
  • the angle between the normal of the interface and the normal of the surface of the substrate 1 is not equal to 0°.
  • the incident light can be incident from the side of the substrate 1 provided with the first medium 2 , or can be incident from the other side of the substrate 1 .
  • the incident angle of the incident light is greater than the critical angle ⁇ c , the transmittance of the metasurface provided by the embodiment of the present application decreases to zero.
  • the incident angle is less than or equal to the critical angle ⁇ c , the metasurface has high transmittance, and the phase of the incident light is adjusted to cover 2 ⁇ by the first medium 2 .
  • Subwavelength structures refer to structures whose characteristic size is equivalent to (or slightly larger than) or smaller than the working wavelength, and can directly regulate the phase, amplitude and polarization of light, usually on the order of nanometers (such as tens to hundreds of nanometers).
  • the working wavelengths include infrared wavelengths, visible light wavelengths and ultraviolet wavelengths.
  • the first medium 2 has high transmittance in the working wavelength band.
  • the first medium 2 has a transparency of at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, or at least about 95% in the working wavelength band.
  • the first medium 2 includes titanium oxide, silicon nitride, fused silica, aluminum oxide, gallium nitride, gallium phosphide, amorphous silicon, crystalline silicon, and hydrogenated amorphous silicon.
  • the second medium 3 is a filling medium between the first medium 2 .
  • the second medium 3 includes a material transparent to the target wavelength band.
  • the second medium 3 has at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 85%, at least about 90%, or at least about 95% in the working band. % transmittance.
  • the second medium 3 can be a fluid, such as air; the second medium 3 can also be non-fluid.
  • the second medium 3 includes polymethyl methacrylate (PMMA, polymethyl methacrylate) or photoresist (such as SU-8 type photoresist).
  • the second medium 3 is a fluid other than air
  • other structures with high light transmittance can be used for encapsulation.
  • the second medium 3 can also protect the first medium 2 .
  • the angle between the normal of the interface between the first medium 1 and the second medium 3 and the normal of the surface of the substrate 1 is larger than 0° and smaller than 90°. It should be noted that the absolute value of the difference between the refractive index of the second medium 3 and the refractive index of the first medium 2 is greater than or equal to 0.5, so as to reduce the reflection loss of light.
  • the array of the first medium 2 includes a plurality of superstructure units, as shown in FIGS.
  • the first medium 2 is provided at the vertices and/or the center of the close-packable figure.
  • close-packable figures include squares and regular hexagons.
  • the metasurface can modulate incident light through superstructure units.
  • the metasurface modulates the incident light by changing the period of the superstructure unit.
  • the minimum distance between any two adjacent first media 2 is greater than or equal to 80 nanometers.
  • the first medium 2 is a sub-wavelength structure.
  • cross-sections at any two positions on the height axis of the sub-wavelength structure are similar figures.
  • the similarity ratio of any two similar figures can be equal to 1, or greater than 1 or less than 1. That is to say, if any two positions on the height axis of the subwavelength structure are cross-sectional along a direction perpendicular to the height axis, the obtained cross-sectional shapes are similar figures, and the cross-sectional areas may be the same or different.
  • the above-mentioned similar figure, that is, the cross-sectional shape of the first medium 2 is obtained from the basic figure or similar figures of multiple basic figures through Boolean operations.
  • Basic graphics include circles, ellipses, and polygons.
  • the structure of the first medium 2 includes nano-cone, nano-ellipse cone, nano-pyramid, nano-cylinder, nano-ellipse cylinder, nano-prism, nano-cone, nano-ellipse cone, nano-pyramid, nano-cone, nano-ellipse or nano-prism One or more and combinations of more in Taichung.
  • the nano-column or nano-prism can form an inclination through the action of airflow or other fluids, so that the angle between the normal line of the interface between the first medium 2 and the second medium 3 and the normal line of the surface of the substrate 1 is not equal to 0° .
  • the structure of the first medium 2 includes nano-truncated cones, wherein the cross-sectional area of the nano-truncated cones varies along the direction of the height axis.
  • the structure of the first medium 2 includes nano-prisms, wherein the cross-sectional area of the nano-prisms varies along the direction of the height axis.
  • the change of the above-mentioned cross-sectional area along the height axis may be an increase or a decrease.
  • the shape of the height-axis cross-section of the nanoprisms includes polygons, the result of Boolean operations between polygons and polygons, circles, or ellipses, such as the quadrilateral shown in FIG. 7 .
  • the height of the first medium 2 is greater than or equal to 300 nanometers and less than or equal to 2000 nanometers.
  • the maximum aspect ratio of the first medium 2 is less than or equal to 20, and the maximum aspect ratio is equal to the ratio of the height of the first medium 2 to the minimum diameter of the first medium 2 .
  • the maximum period of the section perpendicular to the height axis of the first medium 2 is less than or equal to 260 nanometers, so as to optimize the regulation of the phase of the incident light by the sub-wavelength structure of the first medium 2 . It should be noted that the specific structure and characteristic size of the first medium 2 need to be selected according to the required critical angle.
  • the metasurface provided in the embodiment of the present application further includes a third medium 4, wherein the third medium 4 is arranged inside the first medium 2, and the third medium 4 The height of the medium 4 is less than or equal to the height of the first medium 2 .
  • the third medium 4 includes a material with high transmittance in the target wavelength band, so as to participate in the phase adjustment of the incident light.
  • the first medium 2 is equivalent to a hollow structure, such as a hollow nano-circular truncated or hollow nano-prism.
  • the height axis section of the structure of the third medium 4 may or may not be similar to the height axis section of the structure of the first medium 2 .
  • the height axes of the structure of the third medium 4 and the structure of the first medium 2 may be parallel or non-parallel.
  • the angle formed by the normal of the interface between the third medium 4 and the first medium 2 and the normal of the surface of the base 1 is not equal to 0°, so as to further select the angle.
  • FIG. 9 shows that the structure of the metasurface provided by the embodiment of the present application including the third medium 4 includes prisms.
  • the embodiment of the present application provides a metasurface, which includes a substrate 1, a first medium 2 and a second medium 3.
  • the first medium 2 is a nanoprism, and the first medium 2 is distributed on one side of the substrate 1 in a regular hexagonal array; the second medium 3 is air, and the second medium 3 is filled between the first medium 2; The included angle between the normal of the interface between the first medium 1 and the second medium 3 and the normal of the surface of the substrate 1 is not equal to 0°.
  • the incident light can be incident from the side of the substrate 1 provided with the first medium 2 , or can be incident from the other side of the substrate 1 .
  • the incident angle of the incident light is greater than the critical angle ⁇ c , the transmittance of the metasurface provided by the embodiment of the present application decreases to zero.
  • the incident angle is less than or equal to the critical angle ⁇ c , the metasurface has high transmittance.
  • the critical angle ⁇ c is less than or equal to 40°.
  • FIG. 10 shows the transmittance of the metasurface provided by the embodiment of the present application to incident light at different angles. It can be concluded from Fig. 10 that when the incident angle is greater than 40°, the transmittance of the metasurface drops to 0.
  • the cross section of the nanoprism is set as a square.
  • FIG. 11 shows that when the critical angle ⁇ c is 6°, the metasurface provided by the embodiment of the present application can adjust the phase of the incident light by changing the side length of the nanoprism. It can be seen from FIG. 11 that when the period of the nanoprism (ie, the length of the base and side) is less than or equal to 260 nanometers, the phase of the incident light of the metasurface provided by the embodiment of the present application covers 2 ⁇ .
  • the metasurface provided by the embodiment of the present application can reduce the light transmittance of the incident angle exceeding the critical angle to 0 through the fact that the normal line of the interface between the first medium and the second medium is not parallel to the normal line of the base surface.
  • the phase is adjusted.
  • the metasurface can be mass-produced through a photolithography process, which reduces the complexity of the processing process of the angle selection device and promotes the miniaturization of optical components.
  • the embodiment of the present application also provides a fingerprint recognition device, as shown in FIG. 12 , the device includes a metasurface array 5 and an optical detector 6;
  • the metasurface array 5 is arranged opposite to the photosensitive surface of the optical detector 6;
  • the metasurface array 5 includes a plurality of metasurfaces provided in any one of the above embodiments.
  • the fingerprint detection light reflected by the fingerprint is projected onto the photosensitive surface of the optical detector 6 through the metasurface array 5, thereby forming an electrical signal of the fingerprint image.
  • the metasurface array 5 is used to select the angle of the incident fingerprint detection light, and only the fingerprint detection light whose incident angle is within the range of the critical angle ⁇ c can be projected onto the optical detector 6 . Therefore, the light reflected by the fingerprints in different regions is projected to different regions on the photosensitive surface of the optical detector 6 after being angularly selected by the metasurfaces at different positions in the metasurface array 5, thereby avoiding the crosstalk of the fingerprint detection light and improving the The accuracy and resolution of the fingerprint identification device.
  • the metasurfaces in the metasurface array 5 are in one-to-one correspondence with the detection units on the optical detector 6 .
  • the light source for the fingerprint detection light includes an infrared light source or an organic light-emitting diode (OLED, Organic Light-Emitting Diode) pixel.
  • the metasurface array 5 is coaxially opposite to the optical detector 6 .
  • the exit angle of the light leaving the metasurface is changed accordingly, so that the metasurface array 5 and the optical detector 6 can be misplaced and opposite to each other.
  • the distance from any metasurface in the metasurface array 5 to the detection unit mapped to the metasurface is equal to the back focus of the metasurface.
  • the first medium 2 of the metasurface is located on the side of the substrate 1 away from the optical detector 6 .
  • the first medium 2 of the metasurface is located on the side of the substrate 1 facing the optical detector 6 .
  • the orientation of the first medium 2 to the optical detector 6 is beneficial to reduce wear of the first medium 2 .
  • the fact that the first medium 2 faces away from the optical detector 6 is beneficial to avoid collision between the first medium 2 and the optical detector 6 .
  • the fingerprint recognition device further includes an optical detector cover plate 7 ; the thickness of the optical detector 7 is equal to the distance from the metasurface array 5 to the optical detector 6 .
  • the optical detector cover 7 is used to protect the photosensitive surface of the optical detector 6 .
  • the optical detector cover plate 7 is made of a material with high transmittance to the fingerprint detection light.
  • the material of the optical detector cover plate 7 includes titanium oxide, silicon nitride, fused silica, aluminum oxide, gallium nitride, gallium phosphide, amorphous silicon, crystalline silicon and hydrogenated amorphous silicon.
  • the fingerprint identification device provided by the embodiment of the present application includes a surface array 5 and an optical detector 6; the metasurface array 5 is arranged opposite to the photosensitive surface of the optical detector 6; the metasurface array 5 includes a plurality of any of the above-mentioned A metasurface is provided in one embodiment.
  • the parameters of the fingerprint identification device are shown in Table 1.
  • the F number is the ratio of the focal length of a single metasurface to the circumcircle diameter of a single metasurface.
  • the point spread function of a single metasurface in the metasurface array 5 is shown in Fig. 13 and Fig. 14 . Wherein, Fig. 13 shows the point spread function of a single metasurface when the incident angle is 0°; Fig. 14 shows the point spread function of a single metasurface when the incident angle is 6°.
  • the thickness of the fingerprint identification device is less than or equal to 500 microns. That is, the sum of the thickness of the metasurface array 5 , the thickness of the optical detector 6 and the distance between the metasurface array 5 and the optical detector 6 is less than or equal to 500 micrometers. Preferably, the thickness of the fingerprint recognition device is less than or equal to 100 microns.
  • the fingerprint identification device uses a metasurface to replace the lens of a traditional fingerprint identification device, and realizes angular selection. It not only reduces the size of the fingerprint identification device, but also improves the identification accuracy and resolution of the fingerprint identification device by selecting the angle.
  • an embodiment of the present application further provides an electronic device, including the fingerprint identification device provided in any one of the foregoing embodiments.
  • an embodiment of the present application provides a mobile phone, including a screen and the fingerprint recognition device provided in any one of the above embodiments; the fingerprint recognition device is arranged under the screen.
  • the electronic device provided by the embodiment of the present application adopts the fingerprint identification device provided by the embodiment of the present application, which saves the space inside the electronic device and improves the space utilization rate of the electronic device.
  • the embodiment of the present application provides a metasurface, by making the angle between the normal line of the interface between the first medium and the second medium and the normal line of the substrate surface not equal to 0° to realize the angular selection of the incident light and phase regulation, which reduces the difficulty of the processing technology of the angle selection element and promotes the miniaturization of the optical element.
  • the present application also provides a fingerprint recognition device including the metasurface, and the metasurface provided by the embodiment of the present application realizes small size, no crosstalk, high recognition accuracy and high resolution.

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Abstract

本申请实施例提供了一种超表面及具有其的指纹识别装置，属于超材料技术领域。该表面包括基底、第一介质和第二介质；其中，所述第一介质为亚波长结构，且所述第一介质呈阵列分布于所述基底的一侧；所述第二介质填充于所述第一介质之间；所述第一介质与所述第二介质的分界面的法线与所述基底表面的法线夹角不等于0°。通过本申请实施例提供的超表面，实现了对入射光的角向选择和相位调控，减小了指纹识别装置的体积。

Description

超表面及具有其的指纹识别装置 技术领域
本申请涉及超材料技术领域，具体而言，涉及一种超表面。
背景技术
角向选择是指对改变不同入射角下的透射率，使特定入射角范围内的入射光可以透过。角向选择在发光二极管(LED，Light Emitting Diode)和激光定向发射上有重要应用。
相关技术中主要通过光阑实现角向选择，即在入射光路上设置光阑，只有特定入射角范围内的入射光可以透过光阑的窗口，特定入射角范围外的光线则被光阑遮挡。
光阑主要应用于传统光学系统，但是微米级尺寸的光阑加工工艺复杂，不利于光学元件的小型化。
发明内容
为解决现有存在的技术问题，克服光阑对光学元件小型化的限制，实现对入射光的角向选择及相位调控，本申请实施例提供了以下技术方案：
一方面，本申请实施例提供了一种超表面，所述超表面包括基底、第一介质和第二介质；
其中，所述第一介质为亚波长结构，且所述第一介质呈阵列分布于所述基底的一侧；
所述第二介质填充于所述第一介质之间；
所述第一介质与所述第二介质的分界面的法线与所述基底表面 的法线夹角不等于0°。
可选地，所述第一介质在所述亚波长结构的高度轴上任意两个位置上的截面为相似图形。
可选地，所述超表面还包括第三介质；
所述第三介质设置于所述第一介质内；所述第三介质的高度小于或等于所述第一介质的高度。
可选地，所述阵列包括多个超结构单元；
所述多个超结构单元为填充所述基底表面的可密堆积图形，所述可密堆积图形的顶点位置和/或中心位置设置有所述第一介质。
可选地，所述第二介质的折射率与所述第一介质的折射率差值的绝对值大于或等于0.5。
可选地，所述第二介质包括对目标波段透明的材料。
可选地，所述第二介质包括空气。
可选地，所述第一介质的高度大于或等于300纳米且小于或等于2000纳米。
可选地，任意相邻两个所述第一介质之间的最小间距大于或等于80纳米。
可选地，所述超表面的临界角θ c小于或等于40°。
可选地，所述第一介质的最大深宽比小于或等于20；
所述最大深宽比等于所述第一介质的高度与所述第一介质的最小直径的比值。
可选地，所述第一介质包括氧化钛、氮化硅、熔融石英、氧化铝、氮化镓、磷化镓、非晶硅、晶体硅和氢化非晶硅。
第二方面，本申请实施例提供了一种指纹识别装置，所述指纹识别装置包括超表面阵列和光学探测器；
所述超表面阵列与所述光学探测器的感光面相对设置；
所述超表面阵列的一侧设置有上述的超表面。
可选地，所述超表面阵列中的任一超表面到与所述超表面映射的探测单元的距离等于所述超表面的后焦距。
可选地，所述超表面阵列中的超表面与所述光学探测器的探测单元成一一映射的关系。
可选地，所述超表面阵列的厚度、所述光学探测器的厚度以及所述超表面阵列与所述光学探测器之间距离的和小于或等于500微米。
可选地，所述指纹识别装置还包括光学探测器盖板；
所述光学探测器盖板的厚度等于所述超表面阵列到所述光学探测器的距离。
第三方面，本申请实施例还提供了一种电子设备，其特征在于，所述电子设备包括上述的指纹识别装置。
本申请提供的技术方案至少取得了以下有益效果：
本申请实施例提供了一种超表面，通过使第一介质和第二介质的分界面法线与基底表面法线夹角不等于0°，实现了对入射光的角向选择和相位调控，降低了角向选择元件的加工工艺难度，促进了光学元件的小型化。本申请还提供了包括该超表面的指纹识别装置，通过本申请实施例提供的超表面实现了体积小、无串扰、识别精度高及分辨率高。
附图说明
为了更清楚地说明本申请实施例或背景技术中的技术方案，下面将对本申请实施例或背景技术中所需要使用的附图进行说明。
图1示出了本申请实施例提供超表面的一种可选的结构示意图；
图2示出了本申请实施例提供超表面的又一种可选的结构示意图；
图3示出了本申请实施例提供超表面的再一种可选的结构示意图；
图4示出了本申请实施例提供的超结构单元的一种可选的结构示 意图；
图5示出了本申请实施例提供的超结构单元的又一种可选的结构示意图；
图6示出了本申请实施例提供的超表面的又一种可选的结构示意图；
图7示出了本申请实施例提供的超表面的又一种可选的结构示意图；
图8示出了本申请实施例提供的超表面的又一种可选的结构示意图；
图9示出了本申请实施例提供的超表面的又一种可选的结构示意图；
图10示出了本申请实施例提供的超表面对不同角度的入射光的透过率；
图11示出了本申请实施例提供的超表面纳米棱台的边长对入射光的相位的调控；
图12示出了本申请实施例提供的指纹识别装置的一种可选的结构示意图；
图13示出了入射角为0°时本申请实施例提供的指纹识别装置中单个超表面的点扩散函数；
图14示出了入射角为6°时本申请实施例提供的指纹识别装置中单个超表面的点扩散函数；。
图中附图标记分别表示：
1-基底；2-第一介质；3-第二介质；4-第三介质；5-超表面阵列；6-光学探测器；7-光学探测器盖板。
具体实施方式
为了便于理解本申请，下面将参照相关附图对本申请进行更全面的描述。附图中给出了本申请的首选实施例。但是，本申请可以以许多不同的形式来实现，并不限于本文所描述的实施例。相反地，提供 这些实施例的目的是使对本申请的公开内容更加透彻全面。
需要说明的是，当一个元件被认为是“连接”另一个元件，它可以是直接连接到另一个元件并与之结合为一体，或者可能同时存在居中元件。本文所使用的术语“安装”、“一端”、“另一端”以及类似的表述只是为了说明的目的。
除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同。本文中在本申请的说明书中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请。本文所使用的术语“及/或”包括一个或多个相关的所列项目的任意的和所有的组合。
本申请实施例提供了一种超表面，如图1至图3所示，该超表面包括基底1、第一介质2和第二介质3。
其中，第一介质2为亚波长结构，且第一介质2呈阵列分布于基底1的一侧；第二介质3填充于第一介质2之间；第一介质1与第二介质3的分界面的法线与基底1表面的法线夹角不等于0°。
入射光线可以从基底1设置有第一介质2的一侧射入，也可以从基底1的另一侧射入。当入射光线的入射角大于临界角θ c时，本申请实施例提供的超表面透过率降为0。当入射角小于等于临界角θ c时，该超表面具有高透过率，且入射光的相位被第一介质2调控为覆盖2π。
亚波长结构是指特征尺寸与工作波长相当(或略大于)或更小的结构，可直接调控光的相位、幅度和偏振等特性，通常为纳米量级(例如几十到几百纳米)。示例性地，工作波长包括红外线波长、可见光波长和紫外线波长。第一介质2在工作波段具有高透过率。例如第一介质2在工作波段具有至少大约40％、至少大约50％、至少大约60％、至少大约70％、至少大约80％、至少大约85％、至少大约90％或至少大约95％的透过率。示例性地，第一介质2包括氧化钛、氮化硅、熔融石英、氧化铝、氮化镓、磷化镓、非晶硅、晶体硅和氢化非晶硅。
第二介质3为第一介质2之间的填充介质。可选地，第二介质3包括对目标波段透明的材料。示例性地，第二介质3在工作波段具有 至少大约40％、至少大约50％、至少大约60％、至少大约70％、至少大约80％、至少大约85％、至少大约90％或至少大约95％的透过率。优选地，第二介质3可以是流体，例如空气；第二介质3也可以是非流体。示例性地，第二介质3包括聚甲基丙烯酸甲酯(PMMA，polymethyl methacrylate)或光刻胶(例如SU-8型光刻胶)。当第二介质3为非空气的流体时，可采用其他高透光率的结构封装。第二介质3还可以起到保护第一介质2的作用。可选地，第一介质1与第二介质3的分界面的法线与基底1表面的法线夹角大于0°小于90°。需要说明的是，第二介质3的折射率与第一介质2的折射率差值的绝对值大于或等于0.5，以降低光线的反射损失。
在一种可选的实施方式中，第一介质2的阵列包括多个超结构单元，如图4至图5所示，多个超结构单元为填充基底1表面的可密堆积图形，每个可密堆积图形的顶点位置和/或中心位置设置有第一介质2。示例性地，可密堆积图形包括正方形和正六边形。本申请一些实施例中，该超表面可以通过超结构单元来调制入射光。示例性地，该超表面通过改变超结构单元的周期调制入射光。优选地，任意两个相邻的第一介质2之间的最小间距大于或等于80纳米。
第一介质2中为亚波长结构，本申请可选的实施例中，该亚波长结构的高度轴上任意两个位置上的截面为相似图形。任意两个相似图形的相似比可以等于1，也可以大于1或小于1。也就是说，在该亚波长结构的高度轴上任意两个位置沿垂直于高度轴的方向截面，所得的截面形状是相似图形，截面面积可以相同也可以不同。进一步地，上述相似图形，即第一介质2的截面形状由基础图形或多个基础图形的相似图形通过布尔运算得到。基础图形包括圆、椭圆和多边形。可选地，第一介质2的结构包括纳米圆锥、纳米椭圆锥、纳米棱锥、纳米圆柱、纳米椭圆柱、纳米棱柱、纳米圆锥、纳米椭圆锥、纳米棱锥、纳米圆台、纳米椭圆台或纳米棱台中的一种或多种及多种的组合。可选地，纳米圆柱或纳米棱柱可以通过气流或其他流体的作用，形成倾斜，使第一介质2与第二介质3的分界面的法线和基底1表面的法线 夹角不等于0°。
示例性地，如图6所示，第一介质2的结构包括纳米圆台，其中纳米圆台的截面面积沿高度轴方向变化。示例性地，如图7所示，第一介质2的结构包括纳米棱台，其中纳米棱台的截面面积沿高度轴方向变化。上述截面面积沿高度轴变化可以是增加，也可以是减少。纳米棱台的高度轴截面形状包括多边形、多边形与多边形、圆形或椭圆形的布尔运算结果，例如图7中示出的四边形。
更进一步地，第一介质2的高度大于或等于300纳米且小于或等于2000纳米。优选地，第一介质2的最大深宽比小于或等于20，最大深宽比等于第一介质2的高度与第一介质2的最小直径的比值。
在本申请一些的实施例中，第一介质2垂直于高度轴截面的最大周期小于或等于260纳米，以优化第一介质2的亚波长结构对入射光相位的调控。需要说明的是，第一介质2的具体结构和特征尺寸需要根据所需临界角的大小选择。
在本申请又一种可选的实施方式中，如图8所示，本申请实施例提供的超表面还包括第三介质4，其中第三介质4设置于第一介质2内部，且第三介质4的高度小于或等于第一介质2的高度。
第三介质4包括目标波段高透过率的材料，以参与对入射光的相位调控。示例性地，当第三介质4为空气时，第一介质2相当于空心结构，例如空心纳米圆台或空心纳米棱台。
可选地，第三介质4结构的高度轴截面与第一介质2结构的高度轴截面可以是相似图形，也可以不是相似图形。第三介质4的结构与第一介质2的结构的高度轴可以平行，也可以不平行。可选地，第三介质4与第一介质2的分界面的法线与基地1表面的法线所成夹角不等于0°，以进一步进行角向选择。图9示出了本申请实施例提供的超表面包括第三介质4的结构包括棱柱。
示例性地，本申请实施例提供了一种超表面，该超表面包括基底 1、第一介质2和第二介质3。
其中，第一介质2为纳米棱台，并且第一介质2呈正六边形阵列分布于基底1的一侧；第二介质3为空气，第二介质3填充于第一介质2之间；第一介质1与第二介质3的分界面的法线与基底1表面的法线夹角不等于0°。
入射光线可以从基底1设置有第一介质2的一侧射入，也可以从基底1的另一侧射入。当入射光线的入射角大于临界角θ c时，本申请实施例提供的超表面透过率降为0。当入射角小于等于临界角θ c时，该超表面具有高透过率。
可选地，临界角θ c小于或等于40°。图10示出了，本申请实施例提供的超表面对不同角度的入射光的透过率。由图10可以得出，当入射角大于40°时，该超表面的透过率降为0。
示例性地，将纳米棱台的截面设置为正方形。图11示出了本申请实施例提供的超表面在临界角θ c为6°时，通过改变纳米棱台的边长对入射光的相位进行调控。由图11可得，当纳米棱台的周期(即底边边长)小于或等于260纳米时，本申请实施例提供的超表面的入射光的相位覆盖2π。
本申请实施例提供的超表面，通过第一介质与第二介质分界面的法线与基地表面法线不平行实现了将入射角超过临界角的光线透过率降为0，并对入射光的相位进行调控。该超表面可以通过光刻工艺批量生产，降低了角向选择器件的加工工艺复杂度，促进了光学元件的小型化。
另一方面，本申请实施例还提供了一种指纹识别装置，如图12所示，该装置包括超表面阵列5和光学探测器6；
超表面阵列5与光学探测器6的感光面相对设置；
超表面阵列5包括多个上述任一实施例中提供的超表面。
指纹反射的指纹检测光通过超表面阵列5投射到光学探测器6的感光面上，从而形成指纹图像电信号。超表面阵列5用于对入射的指 纹检测光进行角向选择，只有入射角在临界角θ c范围内的指纹检测光可以投射到光学探测器6上。因此，不同区域的指纹反射的光线，经过超表面阵列5中不同位置的超表面进行角向选择后投射到光学探测器6的感光面上不同的区域，从而避免了指纹检测光的串扰，提高了该指纹识别装置的精度和分辨率。
示例性地，指纹不同区域对应超表面阵列上不同的超表面，指纹上任一区域反射的指纹检测光射入其他区域对应的超表面时，若入射角大于临界角θ c透过率降为0，则该入射光不能投射到其他区域对应的光学探测器6上。优选地，超表面阵列5中的超表面与光学探测器6上的探测单元成一一对应。可选地，指纹检测光的光源包括红外光源或有机发光二极管(OLED，Oganic Light-Emitting Diode)像素。
优选地，超表面阵列5与光学探测器6同轴相对。在本申请一些实施例中，通过改变临界角θ c，使光线离开超表面的出射角随之改变，从而可以使超表面阵列5和光学探测器6错位相对。
本申请示例性的实施例中，超表面阵列5中任一超表面到与该超表面映射的探测单元的距离等于该超表面的后焦距。可选地，超表面的第一介质2位于基底1背离光学探测器6的一侧。优选地，超表面的第一介质2位于基底1朝向光学探测器6的一侧。第一介质2朝向光学探测器6有利于减少第一介质2的磨损。第一介质2背向光学探测器6有利于避免第一介质2与光学探测器6相撞。
在一种可选的实施方式中，如图12所示，该指纹识别装置还包括光学探测器盖板7；该光学探测器7的厚度等于超表面阵列5到光学探测器6的距离。该光学探测器盖板7用于保护光学探测器6的感光面。该光学探测器盖板7采用对指纹检测光高透过率的材质。示例性地，光学探测器盖板7的材质包括氧化钛、氮化硅、熔融石英、氧化铝、氮化镓、磷化镓、非晶硅、晶体硅和氢化非晶硅。
在示例的实施例中，本申请实施例提供的指纹识别装置包括表面阵列5和光学探测器6；超表面阵列5与光学探测器6的感光面相对 设置；超表面阵列5包括多个上述任一实施例中提供的超表面。该指纹识别装置的参数如表1所示。表1中，F数为单个超表面的焦距与单个超表面的外接圆直径的比值。超表面阵列5中单个超表面的点扩散函数如图13和图14所示。其中，图13示出了入射角为0°时，单个超表面的点扩散函数；图14示出了入射角为6°时，单个超表面的点扩散函数。
表1
光学参数 值
超表面对角线 40.415μm
入射光临界角θ c 6°
焦距(石英玻璃中) 50μm
F数(F#) 1.24
色差属性 无色差
可选地，本申请实施例提供的指纹识别装置的厚度小于或等于500微米。即，超表面阵列5的厚度、光学探测器6的厚度以及超表面阵列5与光学探测器6之间距离的和小于或等于500微米。优选地，该指纹识别装置的厚度小于或等于100微米。
本申请实施例提供的指纹识别装置利用超表面代替传统指纹识别装置的透镜，并实现了角向选择。既缩小了指纹识别装置的尺寸，也通过角向选择提高了指纹识别装置的识别精度和分辨率。
再一方面，本申请实施例还提供了一种电子设备，包括上述任一实施例提供的指纹识别装置。
示例性地，本申请实施例提供了一种手机，包括屏幕和上述任一实施例提供的指纹识别装置；该指纹识别装置设置于屏幕下方。
本申请实施例提供的电子设备采用本申请实施例提供的指纹识 别装置，节约了电子设备内部的空间，提高了电子设备的空间利用率。
综上所述，本申请实施例提供了一种超表面，通过使第一介质和第二介质的分界面法线与基底表面法线夹角不等于0°实现了对入射光的角向选择和相位调控，降低了角向选择元件的加工工艺难度，促进了光学元件的小型化。本申请还提供了包括该超表面的指纹识别装置，通过本申请实施例提供的超表面实现了体积小、无串扰、识别精度高及分辨率高。
以上所述实施例的各技术特征可以进行任意的组合，为使描述简洁，未对上述实施例中的各个技术特征所有可能的组合都进行描述，然而，只要这些技术特征的组合不存在矛盾，都应当认为是本说明书记载的范围。以上所述，仅为本申请实施例的具体实施方式，但本申请实施例的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请实施例披露的技术范围内，可轻易想到变化或替换，都应涵盖在本申请实施例的保护范围之内。因此，本申请实施例的保护范围应以权利要求的保护范围为准。

Claims (18)

  1. 一种超表面，其特征在于，所述超表面包括基底(1)、第一介质(2)和第二介质(3)；
    其中，所述第一介质(2)为亚波长结构，且所述第一介质(2)呈阵列分布于所述基底(1)的一侧；
    所述第二介质(3)填充于所述第一介质(2)之间；
    所述第一介质(1)与所述第二介质(3)的分界面的法线与所述基底(1)表面的法线夹角不等于0°。
  2. 如权利要求1所述的超表面，其特征在于，所述第一介质(2)在所述亚波长结构的高度轴上任意两个位置上的截面为相似图形。
  3. 如权利要求2所述的超表面，其特征在于，所述超表面还包括第三介质(4)；
    所述第三介质(4)设置于所述第一介质(2)内；所述第三介质(4)的高度小于或等于所述第一介质(2)的高度。
  4. 如权利要求3所述的超表面，其特征在于，所述阵列包括多个超结构单元；
    所述多个超结构单元为填充所述基底(1)表面的可密堆积图形，所述可密堆积图形的顶点位置和/或中心位置设置有所述第一介质(2)。
  5. 如权利要求4所述的超表面，其特征在于，所述第二介质(3)的折射率与所述第一介质(2)的折射率差值的绝对值大于或等于0.5。
  6. 如权利要求1-5任一所述的超表面，其特征在于，所述第二介质(3)包括对目标波段透明的材料。
  7. 如权利要求6所述的超表面，其特征在于，所述第二介质(3) 包括空气。
  8. 如权利要求1-5任一所述的超表面，其特征在于，所述第一介质(2)的高度大于或等于300纳米且小于或等于2000纳米。
  9. 如权利要求1-5任一所述的超表面，其特征在于，任意相邻两个所述第一介质(2)之间的最小间距大于或等于80纳米。
  10. 如权利要求1-5任一所述的超表面，其特征在于，所述超表面的临界角θ c小于或等于40°。
  11. 如权利要求1-5任一所述的超表面，其特征在于，所述第一介质(2)的最大深宽比小于或等于20；
    所述最大深宽比等于所述第一介质(2)的高度与所述第一介质(2)的最小直径的比值。
  12. 如权利要求1-4任一所述的超表面，其特征在于，所述第一介质(2)包括氧化钛、氮化硅、熔融石英、氧化铝、氮化镓、磷化镓、非晶硅、晶体硅和氢化非晶硅。
  13. 一种指纹识别装置，其特征在于，所述指纹识别装置包括超表面阵列(5)和光学探测器(6)；
    所述超表面阵列(5)与所述光学探测器(6)的感光面相对设置；
    所述超表面阵列(5)包括多个如权利要求1-12任一所述的超表面。
  14. 根据权利要求13所述的指纹识别装置，其特征在于，所述 超表面阵列(5)中的任一超表面到与所述超表面映射的探测单元的距离等于所述超表面的后焦距。
  15. 根据权利要求14所述的指纹识别装置，其特征在于，所述超表面阵列(5)中的超表面与所述光学探测器(6)的探测单元成一一映射的关系。
  16. 如权利要求15所述的指纹识别装置，其特征在于，所述超表面阵列(5)的厚度、所述光学探测器(6)的厚度以及所述超表面阵列(5)与所述光学探测器(6)之间距离的和小于或等于500微米。
  17. 根据权利要求16所述的指纹识别装置，其特征在于，所述指纹识别装置还包括光学探测器盖板(7)；
    所述光学探测器盖板(7)的厚度等于所述超表面阵列(5)到所述光学探测器(6)的距离。
  18. 一种电子设备，其特征在于，所述电子设备包括如权利要求13-17任一所述的指纹识别装置。
PCT/CN2022/098342 2021-09-30 2022-06-13 超表面及具有其的指纹识别装置 WO2023050884A1 (zh)

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