Metasurface structure and refractive index detector

Abstract

The invention discloses a metasurface structure and a refractive index detector, the metasurface structure is simple in structure, and only comprises a substrate and a nano column array arranged on the first surface of the substrate, and the direction angle of each nano column in the nano column array is limited; according to the metasurface structure, the spatial refractive index information can be obtained by reading the focal position information on the focal plane, and the metasurface structure is used for detecting the refractive index. According to the metasurface structure, the size is only dozens of microns, the detection range is free, the result of the metasurface structure can be clearly presented on a focal plane, a complex spectrum analysis and calculation module does not need to be arranged, and the metasurface structure has important reference significance for miniaturization development of a refractive index detector.

Description

Technical Field

[0001] The present invention belongs to the technical field of detection equipment, and in particular relates to a metasurface structure and a refractive index detector. Background Art

[0002] Refractive index is an important physical parameter when light propagates in different media. Different materials have different refractive indices. By selecting appropriate materials and adjusting the refractive index, the propagation path, focusing ability and dispersion effect of light can be controlled and changed, which is crucial for the design and manufacture of optical devices (such as lenses, prisms, optical fibers, etc.).

[0003] In optical measurement and optical sensors, monitoring the change of refractive index is an important application direction. For example, refractive index sensors can be used to measure the concentration of liquids, the pressure of gases, temperature changes, etc. These sensors have a wide range of applications in scientific research, industrial control, and biomedicine. In summary, the refractive index is an important parameter for the interaction between light and matter, and is of great significance for understanding the propagation behavior of light, the properties of optical materials, and optical measurement and sensor applications. Therefore, the development of refractive index detection tools has broad research prospects.

[0004] Optical sensing technology is one of the mainstream technologies in the field of sensing and detection. Among them, optical refractive index sensors have the advantages of high safety, high accuracy, anti-electromagnetic interference, fast response speed and imaging, which can meet the needs of real-time sensing and label-free detection in practical applications. The basic principle of optical refractive index sensing is that when the incident electromagnetic wave passes through materials with different refractive indices in the detection area, its corresponding resonant frequency, intensity, phase and other characteristics will change. Therefore, by monitoring the change of a certain characteristic quantity of light during propagation, the change of external refractive index can be sensed.

[0005] At present, the widely used refractive index detectors include traditional refractive index detectors based on the principle of light refraction, air refractive index detectors, core-shell fiber refractive index sensors, etc. However, their structures are often complex and have a large volume. In the pursuit of device miniaturization and integration today, traditional bulky refractive index detectors are gradually replaced by nanophotonic structures, such as metasurfaces, photonic crystals, plasma structures, etc. These structures can be highly integrated with other functional modules, such as light sources, light detectors, temperature sensors, etc., with their millimeter and micrometer sizes. And these micro materials and structures are highly sensitive to external refractive index changes, most of which sense the refractive index through resonance peak shifts. In addition, they have the characteristics of rapid response to refractive index changes and show high advantages. These characteristics have important applications in the fields of optical fiber communication, medical biotechnology, and environmental monitoring. However, the detection results of most refractive index sensors based on nanophotonic materials are not intuitive and require specific analysis components, such as fiber couplers, spectrometers, photodetectors, etc. At the same time, the detection range of these sensors is usually limited. In addition, these devices also require complex materials and manufacturing processes.

[0006] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0007] The purpose of the present invention is to provide a metasurface structure and a refractive index detector. The metasurface structure is simple and lightweight, the detection range can be freely set, and the results can be clearly presented on the focal plane. It does not need to be equipped with complex spectral analysis and calculation modules, which has important reference significance for the miniaturization development of refractive index detectors.

[0008] In order to achieve the above object, a technical solution provided by a specific embodiment of the present invention is as follows:

[0009] A metasurface structure, comprising:

[0010] a substrate having a first surface;

[0011] A nanocolumn array is formed on the first surface of the substrate, wherein the nanocolumn array is composed of a plurality of nanocolumns arranged at different direction angles;

[0012] A coordinate system is established with the geometric center of the substrate as the origin, and the orientation angle of the nanorods satisfies the following conditions:

[0013]

[0014] Wherein, θ(x,y) represents the orientation angle of each nanocolumn of the metasurface structure; x is the x-axis coordinate of different nanocolumns, and y is the y-axis coordinate of different nanocolumns; λ is the working wavelength of the metasurface structure; N is the number of focal points; f is the focal length of the metasurface structure; f Dj is the distance from each focus to the origin; x j is the x-axis coordinate of different foci, y j is the y-axis coordinate of different foci; n j is the spatial refractive index corresponding to each focus;

[0015] Under the condition of left-handed polarized light incidence, the metasurface structure can form focal points at different positions on its focal plane according to different spatial refractive indices.

[0016] In one or more embodiments of the present invention, different focal points on the focal plane of the metasurface structure are arranged in a circular ring, and the horizontal coordinate x of each focal point is j =rsin[(j-1)2π / N], the ordinate y of each focus j =-rcos[(j-1)2π / N], where r is the radius of the ring formed by all the focal points on the focal plane of the metasurface structure.

[0017] In one or more embodiments of the present invention, the spatial refractive index n corresponding to each focus j =n1+(j-1)Δn, where n1 represents the initial refractive index, one of all the foci is defined as the first focus, and the initial refractive index is the spatial refractive index corresponding to the first focus; Δn is the difference in refractive indices represented by adjacent foci.

[0018] In one or more embodiments of the present invention, the operating wavelength λ of the metasurface structure satisfies: 0.38um<λ<0.74um.

[0019] In one or more embodiments of the present invention, the focal length f of the metasurface structure satisfies: 5um<f<60um.

[0020] In one or more embodiments of the present invention, the metasurface structure is a geometric phase metasurface structure.

[0021] In one or more embodiments of the present invention, the nanorod array is formed by a periodic arrangement of a number of nanorods with different orientation angles, and the period T satisfies 0.3um<T<0.5um.

[0022] In one or more embodiments of the present invention, the nanocolumn is a rectangular column, and the length L, width W, and height H of the nanocolumn respectively satisfy: 0.15um<L<0.3um, 0.06um<W<0.1um, 0.2um<H<0.6um.

[0023] In one or more embodiments of the present invention, the material of the nanorods includes a metal plasma material.

[0024] In one or more embodiments of the present invention, the substrate is a rectangular column, and the side length A and thickness H of the substrate satisfy: 10um<A<50um, 2um<H<100um; and / or,

[0025] The substrate has a second surface opposite to the first surface, and the second surface is a polished surface; and / or,

[0026] The material of the substrate includes glass; and / or,

[0027] The material of the substrate is a material with high transmittance in the wavelength range of 0.38um to 0.74um.

[0028] Compared with the prior art, the metasurface structure of the present invention has a simple structure and can obtain spatial refractive index information by reading the focus position information on the focal plane.

[0029] The metasurface structure of the present invention can freely set the detection range of the spatial refractive index, and the result can be clearly presented on the focal plane without the need for complex spectral analysis and calculation modules, which has important reference significance for the miniaturization development of refractive index detectors. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 A schematic diagram of the structure of a super surface structure in one embodiment of the present invention;

[0032] Figure 2 A schematic diagram of a nanocolumn structure of a super surface structure in one embodiment of the present invention;

[0033] Figure 3 A schematic diagram of a nano-pillar array of a super surface structure in one embodiment of the present invention;

[0034] Figure 4 1 is a diagram of the light intensity at the focal plane of the metasurface structure at different spatial refractive indices in one embodiment of the present invention. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0036] As mentioned in the background, the detection results of most refractive index sensors based on nanophotonic materials are not intuitive and require specific analysis components, such as fiber couplers, spectrometers, photodetectors, etc. At the same time, the detection range of these sensors is usually limited. In addition, these devices also require complex materials and manufacturing processes.

[0037] In response to these problems, the present invention proposes a metasurface structure and a metasurface structure, wherein the metasurface structure is simple in structure, and only includes a substrate and a nanocolumn array arranged on the first surface of the substrate. By defining various corresponding relationships between the direction angle of each nanocolumn in the nanocolumn array and the focal position and the spatial refractive index, the metasurface structure of the present invention can obtain spatial refractive index information by reading the focal position information on the focal plane. The metasurface structure of the present invention is only a few tens of microns in size, has a free detection range, and its results can be clearly presented on the focal plane. It does not need to be equipped with a complex spectral analysis and calculation module, which has important reference significance for the miniaturization development of refractive index detectors.

[0038] The metasurface structure of the present invention constructs a nanocolumn array on the first surface of the substrate and defines various corresponding relationships between the direction angles of the nanocolumns in the nanocolumn array and the focal position and the spatial refractive index. It can focus the incident light on different focal points according to the different spatial refractive indices. Therefore, it is only necessary to observe the focal position on the focal plane to infer the spatial refractive index at this time.

[0039] like Figure 1 As shown, a super surface structure in an embodiment of the present invention includes a substrate 10 and a nanorod array 20 formed on the surface of the substrate 10. The nanorod array 20 is composed of a plurality of nanorods 21 arranged at different direction angles.

[0040] With the geometric center of the substrate as the origin, a coordinate system is established, and the orientation angle of the nanorod 21 satisfies the following conditions:

[0041]

[0042] Wherein, θ(x, y) represents the direction angle of each nanocolumn 21 of the metasurface structure; x is the x-axis coordinate of different nanocolumns 21, and y is the y-axis coordinate of different nanocolumns 21; λ is the working wavelength of the metasurface structure; N is the number of focal points; f is the focal length of the metasurface structure; f Dj is the distance from each focus to the origin; x j is the x-axis coordinate of different foci, y j is the y-axis coordinate of different foci; n j is the spatial refractive index corresponding to each focus.

[0043] When the orientation angle of each nanorod in the nanorod array 20 satisfies the above conditions, the metasurface structure formed can form different focal points on its focal plane according to different spatial refractive indices under the condition of left-handed polarized light incidence, and the different focal points formed on the focal plane are arranged in a circular ring. Each focal position corresponds to a spatial refractive index. The horizontal coordinate x of each focal point is j =rsin[(j-1)2π / N], the ordinate y of each focus j =-rcos[(j-1)2π / N], where r is the radius of the ring formed by all the focal points on the focal plane of the metasurface structure.

[0044] The spatial refractive index n corresponding to each focus j =n1+(j-1)Δn, where n1 represents the initial refractive index, one of all the foci is defined as the first focus, and the initial refractive index is the spatial refractive index corresponding to the first focus; Δn is the difference in refractive indices represented by adjacent foci.

[0045] Furthermore, the material of the substrate 10 should meet the following conditions: high transmittance in the wavelength range of 0.38um to 0.74um. The material of the substrate 10 is selected with reference to the working wavelength range to ensure the highest possible transmittance. Preferably, the material of the substrate 10 includes glass.

[0046] The substrate 10 is a cubic rectangular column having a side length A and a thickness H. The side length A and the thickness H of the substrate 10 satisfy: 10um<A<50um, 2um<H<100um.

[0047] In a specific embodiment, the side length A and thickness H of the substrate 10 satisfy: A=30 um, H=5 um.

[0048] The substrate 10 has a first surface and a second surface opposite to each other in the thickness direction thereof. The second surface of the substrate 10 is polished to form a smooth polished surface.

[0049] Further, the nanocolumn array 20 is formed on the first surface of the substrate 10. The nanocolumns 21 in the nanocolumn array 20 are arranged periodically, and the period T satisfies: 0.3um<T<0.5um. The material of the nanocolumns 21 in the nanocolumn array 20 includes metal plasma, and the selection of the metal plasma material refers to the working wavelength range to ensure the highest possible transmittance. Preferably, the metal plasma material is gold.

[0050] refer to Figure 2 As shown, preferably, the nanocolumn 21 is a rectangular column, and the nanocolumn 21 has a length L, a width W, and a height H. The length L, width W, and height H of the nanocolumn 21 respectively satisfy: 0.15um<L<0.3um, 0.06um<W<0.1um, and 0.2um<H<0.6um.

[0051] In a specific embodiment, the length L, width W, and height H of the nanorod 21 respectively satisfy: L=0.2 um, W=0.08 um, H=0.4 um; and the period T of the nanorod 21 satisfies: T=0.3 um.

[0052] Furthermore, the operating wavelength λ of the metasurface structure satisfies: 0.38um<λ<0.74um.

[0053] Furthermore, the focal length f of the metasurface structure satisfies: 5um<f<60um.

[0054] In a specific embodiment, the number of focal points N is 8; the radius of the ring surrounded by all focal points on the focal plane is r = 3um; the initial refractive index n1 = 1.00, and the difference in refractive index represented by adjacent focal points Δn = 0.03; the working wavelength λ of the metasurface structure is 0.48um, and the focal length f = 30um.

[0055] Embodiment 1:

[0056] In this embodiment, the relevant parameters of the super surface structure are shown in Table 1: (Table 1, unit um)

[0057] Table 1

[0058] L W H T A H N r <![CDATA[n1]]> Δn λ f 0.2 0.08 0.4 0.3 30 5 8 3 1.00 0.03 0.48 30

[0059] The final constructed metasurface structure is as follows Figure 3 shown.

[0060] In this embodiment, under the incident 480nm left-handed polarized light, the focal plane light intensity diagrams under different spatial refractive indices are as follows: Figure 4 shown.

[0061] from Figure 4It can be seen that when the spatial refractive index changes, the focal position of the light beam will also change, and these focal positions are arranged in a ring. Therefore, in actual use of the metasurface structure of the present invention, it is only necessary to observe the position of the focal point on the ring to know the spatial refractive index at this time.

[0062] The present invention also provides a refractive index detector, comprising the above-mentioned metasurface structure.

[0063] Compared with the prior art, the metasurface structure of the present invention has a simple structure and can obtain spatial refractive index information by reading the focus position information on the focal plane.

[0064] The metasurface structure of the present invention has a spatial refractive index detection range that can be freely set, and the results can be clearly presented on the focal plane without the need for complex spectral analysis and calculation modules, which has important reference significance for the miniaturization development of refractive index detectors.

[0065] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0066] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A super surface structure, characterized in that: include: a substrate having a first surface; A nanocolumn array is formed on the first surface of the substrate, wherein the nanocolumn array is composed of a plurality of nanocolumns arranged at different direction angles; A coordinate system is established with the geometric center of the substrate as the origin, and the orientation angle of the nanorods satisfies the following conditions: Wherein, θ(x,y) represents the orientation angle of each nanocolumn of the metasurface structure; x is the x-axis coordinate of different nanocolumns, and y is the y-axis coordinate of different nanocolumns; λ is the working wavelength of the metasurface structure; N is the number of focal points; f is the focal length of the metasurface structure; f Dj is the distance from each focus to the origin; x j is the x-axis coordinate of different foci, y j is the y-axis coordinate of different foci; n j is the spatial refractive index corresponding to each focus; Under the condition of left-handed polarized light incidence, the metasurface structure can form focal points at different positions on its focal plane according to different spatial refractive indices.

2. The supersurface structure according to claim 1, characterized in that: The different focal points on the focal plane of the metasurface structure are arranged in a circular ring, and the abscissa x of each focal point is j =rsin[(j-1)2π / N], the ordinate y of each focus j =-rcos[(j-1)2π / N], where r is the radius of the ring formed by all the focal points on the focal plane of the metasurface structure.

3. The super surface structure according to claim 2, characterized in that: The spatial refractive index n corresponding to each focus j =n1+(j-1)Δn, where n1 represents the initial refractive index, one of all the foci is defined as the first focus, and the initial refractive index is the spatial refractive index corresponding to the first focus; Δn is the difference in refractive indices represented by adjacent foci.

4. The supersurface structure according to claim 1, characterized in that: The working wavelength λ of the metasurface structure satisfies: 0.38um<λ<0.74um.

5. The supersurface structure according to claim 1, characterized in that: The focal length f of the metasurface structure satisfies: 5um<f<60um.

6. The supersurface structure according to claim 1, characterized in that: The metasurface structure is a geometric phase metasurface structure.

7. The super surface structure according to claim 1, characterized in that: The nanorod array is formed by periodically arranging a number of nanorods with different orientation angles, and the period T satisfies 0.3um<T<0.5um; and / or, The length L, width W and height H of the nanocolumn respectively satisfy: 0.15um<L<0.3um, 0.06um<W<0.1um, 0.2um<H<0.6um.

8. The supersurface structure according to claim 1, characterized in that: The material of the nanorods includes metal plasma material.

9. The supersurface structure according to claim 1, characterized in that: The substrate is a rectangular column, and the side length A and thickness H of the substrate satisfy: 10um<A<50um, 2um<H<100um; and / or, The substrate has a second surface opposite to the first surface, and the second surface is a polished surface; and / or, The material of the substrate includes glass; and / or, The material of the substrate is a material with high transmittance in the wavelength range of 0.38um to 0.74um.

10. A refractive index detector, characterized in that: Comprising a super surface structure as described in any one of claims 1-9.

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