Multi-mode polarization sensitive infrared band metamaterial absorber based on chain type structure

Abstract

The invention discloses a multi-mode polarization sensitive infrared band metamaterial absorber based on a chain type structure, and relates to the field of broadband response multi-mode polarization sensitive absorption. The metamaterial absorber comprises a metal resonator, a dielectric layer and a metal reflecting layer which are sequentially arranged from top to bottom, the metal resonator and the metal reflecting layer form a resonant cavity; the resonant cavity is used for capturing incident light; the metal resonator comprises a plurality of resonance units; the resonance units are periodically arranged; each resonance unit comprises a plurality of resonance groups which are connected in sequence; each resonance group comprises a middle metal block, a first metal block, a second metal block, a third metal block and a fourth metal block; the first metal block and the third metal block are arranged on one side of the middle metal block and are in contact connection with one side of the middle metal block; and the second metal block and the fourth metal block are arranged on the other side of the middle metal block and are in contact connection with the other side of the middle metal block. According to the invention, multi-mode broadband polarization absorption response can be realized in a medium-long wave infrared range.

Description

Technical Field

[0001] The present invention relates to the technical field of broadband response multi-mode polarization-sensitive absorption, and in particular to a multi-mode polarization-sensitive infrared band metamaterial absorber based on a chain-type structure. Background Art

[0002] Polarization of light has extremely wide and important applications in the fields of detection, sensing and imaging. It greatly improves the detection capability and accuracy in these fields by providing additional spatial dimension information. By utilizing the polarization characteristics of light, targets in complex environments can be accurately identified and the detection accuracy of research targets can be improved. Metamaterial polarization absorbers can be used in infrared polarization detection and imaging technology, and play an important role in industrial detection, biomedicine, modern military, aviation, navigation and other fields, and are receiving more and more attention.

[0003] Metamaterials are artificial composite materials with special physical properties, such as negative dielectric constant and negative magnetic permeability, which are not found in natural materials. Since Landy et al. proposed a perfect single-frequency metamaterial absorber in 2008, metamaterial absorbers have gradually developed. The absorption frequency of metamaterial absorbers has developed from single frequency to multi-frequency, and the absorption bandwidth has developed from narrow band to broadband, which has undergone rapid development. With the development of infrared detection and the actual production needs for device diversification and functionalization, the requirements for metamaterial absorbers have also changed from polarization-independent to polarization-dependent. However, our research on polarization-sensitive absorbers is still incomplete and there is still a lot of room for development. Compared with traditional polarization-insensitive metasurface absorbers, polarization-sensitive absorbers can obtain more phase and polarization information. Polarization-sensitive absorbers play an important role in optical imaging and detection. For example, polarization-sensitive photodetectors can be used to measure the polarization state of light, thereby improving the contrast and recognition probability of imaging. By obtaining the polarization characteristics of the target, the contrast between the target and the background can be significantly enhanced, solving the problem of target detection in complex backgrounds. Summary of the invention

[0004] The purpose of the present invention is to provide a multi-mode polarization-sensitive infrared band metamaterial absorber based on a chain-type structure, which can solve the problems of existing polarization-sensitive absorbers such as difficult processing, complex structure and low efficiency, and can achieve good polarization-selective absorption in the mid-wave infrared and long-wave infrared.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A multi-mode polarization-sensitive infrared band metamaterial absorber based on a chain-type structure, the metamaterial absorber comprising a metal resonator, a dielectric layer and a metal reflective layer arranged in sequence from top to bottom;

[0007] The metal resonator and the metal reflective layer form a resonant cavity; the resonant cavity is used to capture incident light;

[0008] The metal resonator includes a plurality of resonance units; each of the resonance units is arranged periodically; each of the resonance units includes a plurality of resonance groups connected in sequence; each of the resonance groups includes a middle metal block, a first metal block, a second metal block, a third metal block and a fourth metal block;

[0009] The first metal block and the third metal block are both arranged on one side of the intermediate metal block and are both in contact and connected with one side of the intermediate metal block; the second metal block and the fourth metal block are arranged on the other side of the intermediate metal block and are in contact and connected with the other side of the intermediate metal block.

[0010] Optionally, the first metal block of the resonance group is connected to the third metal block of the adjacent resonance group; the second metal block of the resonance group is connected to the fourth metal block of the adjacent resonance group; the first metal block, the second metal block, the third metal block and the fourth metal block of each resonance group are connected to the middle metal block.

[0011] Optionally, the dielectric layer is made of germanium.

[0012] Optionally, the dielectric layer has a thickness of 0.4 micrometer to 0.6 micrometer.

[0013] Optionally, the material of the metal reflective layer is a metal material or a metal compound material.

[0014] Optionally, the metal reflective layer has a thickness of 0.4 microns.

[0015] Optionally, the material of the metal reflective layer includes titanium, silver, aluminum, gold, iron and nickel, and corresponding metal compounds.

[0016] Optionally, the first metal block, the second metal block, the third metal block and the fourth metal block have the same size.

[0017] Optionally, the resonance units are periodically arranged on the upper surface of the dielectric layer.

[0018] Optionally, the thickness of the metal resonator is 0.1 micrometer.

[0019] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0020] The present invention discloses a multi-mode polarization-sensitive infrared band metamaterial absorber based on a chain-type structure, wherein a metal resonator is composed of a chain-type metal unit structure and has polarization characteristics; the metal unit structure includes two groups of metal blocks of different sizes, wherein the middle metal block is surrounded by four metal blocks, which are periodically arranged in a chain-type structure. The present invention realizes polarization-selective absorption of TE polarized light and TM polarized light in the mid-wave infrared and long-wave infrared bands, respectively, and not only has high polarization sensitivity, but can realize multi-mode broadband polarization absorption response in the mid- and long-wave infrared range, and has incident angle stability, which can enable the absorber to achieve efficient absorption in a wide range of incident angles of 0 to 60 degrees, and has a simple structure and is easy to process. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] 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 will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 It is a schematic diagram of each layer of the unit structure of the multi-mode polarization-sensitive infrared band metamaterial absorber based on a chain-type structure of the present invention;

[0023] Figure 2 It is a schematic plan view of the top metal structure of the multi-mode polarization-sensitive infrared band metamaterial absorber based on a chain-type structure of the present invention;

[0024] Figure 3 It is a three-dimensional schematic diagram of the multi-mode polarization-sensitive infrared band metamaterial absorber based on a chain-type structure of the present invention.

[0025] Figure 4 The absorption spectrum of the multi-mode polarization-sensitive infrared band metamaterial absorber based on the chain-type structure of the present invention;

[0026] Figure 5 Absorption spectra of the chain-structured multi-mode polarization-sensitive infrared band metamaterial absorber at different polarization angles of the present invention;

[0027] Figure 6 The absorption spectra of the chain-structured multi-mode polarization-sensitive infrared band metamaterial absorber under different incident angles of the present invention.

[0028] Description of the accompanying drawings:

[0029] Metal resonator—1, dielectric layer—2, metal reflective layer—3, middle metal block—4, first metal block—5, second metal block—6, third metal block—7, fourth metal block—8. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions 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 are within the scope of protection of the present invention.

[0031] The purpose of the present invention is to provide a multi-mode polarization-sensitive infrared band metamaterial absorber based on a chain-type structure, aiming to achieve multi-mode broadband polarization absorption response in the mid- and long-wave infrared range.

[0032] The present invention realizes polarization selective absorption of TE polarized light and TM polarized light in the mid-wave infrared and long-wave infrared bands, respectively. When different polarized lights are incident, they interact with the horizontal and vertical unit structures, stimulate polarization coupling at different wavelengths, and generate absorption peaks. Through reasonable design, multiple absorption modes work together to realize broadband polarization selective absorption in the target band, which is of great significance to the development of infrared detection systems.

[0033] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] Example 1

[0035] like Figure 1 , Figure 2 and Figure 3 As shown, the multi-mode polarization-sensitive infrared band metamaterial absorber based on a chain-type structure in this embodiment includes:

[0036] The metal resonator 1, the dielectric layer 2 and the metal reflective layer 3 are arranged in sequence from top to bottom.

[0037] The metal resonator 1 and the metal reflective layer 3 form a resonant cavity; the resonant cavity is used to capture incident light.

[0038] The metal resonator 1 includes multiple resonance units; each of the resonance units is arranged periodically; each of the resonance units includes multiple resonance groups connected in sequence; each of the resonance groups includes a middle metal block 4, a first metal block 5, a second metal block 6, a third metal block 7 and a fourth metal block 8.

[0039] The first metal block 5 and the third metal block 7 are both arranged on one side of the intermediate metal block 4 and are both in contact and connected with one side of the intermediate metal block 4; the second metal block 6 and the fourth metal block 8 are arranged on the other side of the intermediate metal block 4 and are in contact and connected with the other side of the intermediate metal block 4.

[0040] Specifically, the middle metal block 4, the first metal block 5, the second metal block 6, the third metal block 7 and the fourth metal block 8 are all rectangular parallelepiped structures. The lower surfaces of the middle metal block 4, the first metal block 5, the second metal block 6, the third metal block 7 and the fourth metal block 8 are in contact with the upper surface of the dielectric layer 2; the right sides of the first metal block 5 and the second metal block 6 are in contact with the left side of the middle metal block 4, and the first metal block 5 and the second metal block 6 are not in contact; the left sides of the second metal block 6 and the fourth metal block 8 are connected to the right side of the middle metal block 4, and the second metal block 6 and the fourth metal block 8 are not in contact; the other two opposite sides of the middle metal block 4 are not in contact with the first metal block 5, the second metal block 6, the third metal block 7 and the fourth metal block 8. Each of the resonant units is periodically arranged on the upper surface of the dielectric layer 2. The first metal block 5 of the resonance group is connected to the third metal block 7 of the adjacent resonance group; the second metal block 6 of the resonance group is connected to the fourth metal block 8 of the adjacent resonance group; the first metal block 5, the second metal block 6, the third metal block 7 and the fourth metal block 8 of each resonance group are connected to the middle metal block 4. The first metal block 5, the second metal block 6, the third metal block 7 and the fourth metal block 8 have the same size.

[0041] Among them, the upper layer is a chain-type metal resonator 1; the middle is a dielectric layer 2; the bottom is a metal reflective layer 3; the chain-type metal resonator 1 is a periodic unit structure composed of two groups of metal blocks of different sizes; the two groups of metal blocks are: the first group is a middle metal block 4; the second group includes a first metal block 5, a second metal block 6, a third metal block 7 and a fourth metal block 8; the periodic structure includes: an middle metal block 4 and four surrounding metal blocks (a first metal block 5, a second metal block 6, a third metal block 7 and a fourth metal block 8), the four surrounding metal blocks have the same size, are respectively connected to the middle metal block 4, and are periodically arranged to form a grating-like structure.

[0042] Electromagnetic radiation is incident from the upper chain-type metal resonator 1 , and the upper chain-type metal resonator 1 and the bottom metal reflective layer 3 form a resonant cavity to capture the incident light and realize polarization selective absorption.

[0043] The material of the upper chain-type metal resonator 1 is metal or metal compound material, and the material of the metal resonator 1 includes: titanium, silver, aluminum, gold, iron or nickel, or their metal compounds. The thickness h1 of the chain-type metal resonator 1 is 0.05 micrometers to 0.15 micrometers. The overlap spacing Δl is 0.1 micrometers to 1.1 micrometers; P x and P yRespectively represent the period of the unit structure in the x direction and the y direction, the period in the x direction is 1 micron to 1.5 microns, and the period in the y direction is 2.8 microns. Among them, the overlapping spacing is the length of the first metal block 5, the second metal block 6, the third metal block 7 or the fourth metal block 8 contacting and connecting with the side of the middle metal block 4, and the length of the first metal block 5, the second metal block 6, the third metal block 7 or the fourth metal block 8 contacting and connecting with the side of the middle metal block 4 is the same.

[0044] Specifically, the metal resonator 1 is formed by periodically arranging metal unit structures, and the thickness h1 of the metal resonator 1 is 0.1 micrometers. Figure 2 As shown, the metal structure unit is a resonance group, and the metal structure unit is composed of four equal-sized metal blocks connected to an intermediate metal block 4, the width w1 of the intermediate metal block 4 is 0.3 microns to 0.5 microns, the length l1 of the intermediate metal block 4 is 1 micron to 2.8 microns, the width w2 of the four equal-sized metal blocks (the first metal block 5, the second metal block 6, the third metal block 7 and the fourth metal block 8) is 0.08 microns to 0.12 microns, the length l2 / 2 of the four equal-sized metal blocks is 0.9 microns to 1.1 microns, and the value range of l2 is 1.8 microns to 2.2 microns. After periodic arrangement, as shown in FIG. Figure 3 As shown, a grating chain-like structure is formed. By adjusting the parameters, the absorption wavelength is changed to achieve absorption of the target band. Specifically, by changing the length and width of the middle metal block, the length and width of the surrounding metal blocks, the thickness of the dielectric layer 2, and the period P of the minimum unit x and P y The size of the grating can be adjusted to achieve the redshift or blueshift of the target absorption band to change the absorption wavelength. Although the ordinary grating structure can achieve polarization absorption, the absorption band is narrow. This grating-like chain structure can achieve polarization absorption and obtain a higher absorption bandwidth through the diversified design in the x direction.

[0045] The bottom is a metal reflective layer 3, which plays a reflective role and forms a resonant cavity with the upper metal resonator 1 to capture the incident light. Therefore, the thickness of the bottom metal layer should be increased to be greater than the skin depth of the metal to reduce the transmission of light and thus enhance absorption.

[0046] The material of the bottom metal reflective layer 3 is a metal or metal compound material, and the material of the metal reflective layer 3 includes: titanium, silver, aluminum, gold, iron or nickel, or their metal compounds. The thickness of the metal reflective layer 3 is greater than the skin depth of the selected material.

[0047] Preferably, the thickness h3 of the metal reflective layer 3 is 0.4 micrometers. The metal reflective layer 3 is a titanium metal layer.

[0048] The material of the intermediate dielectric layer 2 is germanium. The dielectric layer 2 provides a sufficient real part of the refractive index for the metamaterial absorber, and the thickness h2 of the dielectric layer 2 is 0.4 micrometers to 0.6 micrometers.

[0049] Figure 4 The absorption spectra of the polarization sensitive absorber proposed in this embodiment under TM and TE polarized light incidence are shown. Figure 4 It can be seen that the resonant wavelengths of the absorber are located at 6.09μm, 8.6μm and 10.32μm, and the peak absorption rates are 94.8%, 99.3% and 99.9% respectively. The absorber has an average absorption rate of 96.68% in the wavelength range of 8μm to 11μm, and can work in a part of the long-wave infrared atmospheric window range. The absorption spectrum width of TM polarized light is 3μm. For TE polarized light, the average absorption rate can reach 90.37% in the mid-wave infrared wavelength range of 5.85μm-6.8μm, and the absorption spectrum width is 0.95μm.

[0050] Figure 5 The polarization characteristics of the metamaterial absorber under different polarization angles are shown. It can be seen that as the polarization angle increases, the absorption mode of the absorber gradually changes from TM dual-mode broadband absorption to TE single-mode absorption. The average absorption rate of the TM mode gradually decreases, and the average absorption rate of the TE mode gradually increases. Therefore, the absorber has excellent polarization sensitivity.

[0051] Figure 6 The absorption spectra of the polarization-sensitive absorber proposed in this embodiment at different incident angles are shown. In fact, objects at room temperature will emit infrared radiation in various random directions. Therefore, it is particularly important for the metamaterial absorber to be designed so that it can maintain high-efficiency absorption at different incident angles. In the case of oblique incidence, the incident angle of the present invention increases from 0° to 60°, with each 10° being a step. It is found that the average absorption rate of the absorber is between 89.14% and 96.68% in the range of incident angles of 0 to 60°. In general, for polarized incidence of 8μm-11μm TM light, the average absorption rate of the absorber in a wide range of incident angles of 0 to 60° can reach 95.2%. As the incident angle increases, the absorption peak remains almost unchanged, and excellent absorption characteristics can be maintained in a large angle range, showing good incident angle stability.

[0052] The beneficial effects of the present invention are:

[0053] The present invention realizes polarization selective absorption of TE polarized light and TM polarized light in the mid-wave infrared and long-wave infrared bands, respectively. Compared with the traditional metamaterial absorber, the absorber not only has good broadband response performance and incident angle stability, but also has polarization sensitivity, concentrated heat distribution, simple structure, low processing difficulty, and can achieve the change of the target band by adjusting the size. It shows excellent absorption performance in the mid-wave infrared and long-wave infrared, which is of great significance to infrared filtering and infrared detection.

[0054] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0055] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A multi-mode polarization-sensitive infrared band metamaterial absorber based on a chain-type structure, characterized in that: The metamaterial absorber comprises a metal resonator, a dielectric layer and a metal reflective layer arranged in sequence from top to bottom; The metal resonator and the metal reflective layer form a resonant cavity; the resonant cavity is used to capture incident light; The metal resonator includes a plurality of resonance units; each of the resonance units is arranged periodically; each of the resonance units includes a plurality of resonance groups connected in sequence; each of the resonance groups includes a middle metal block, a first metal block, a second metal block, a third metal block and a fourth metal block; The first metal block and the third metal block are both arranged on one side of the intermediate metal block and are both in contact and connected with one side of the intermediate metal block; the second metal block and the fourth metal block are arranged on the other side of the intermediate metal block and are in contact and connected with the other side of the intermediate metal block.

2. The multi-mode polarization-sensitive infrared band metamaterial absorber based on a chain-type structure according to claim 1 is characterized in that: The first metal block of the resonance group is connected to the third metal block of the adjacent resonance group; the second metal block of the resonance group is connected to the fourth metal block of the adjacent resonance group; the first metal block, the second metal block, the third metal block and the fourth metal block of each resonance group are connected to the middle metal block.

3. The multi-mode polarization-sensitive infrared band metamaterial absorber based on a chain-type structure according to claim 1 is characterized in that: The dielectric layer is made of germanium.

4. The multi-mode polarization-sensitive infrared band metamaterial absorber based on a chain-type structure according to claim 1, characterized in that: The thickness of the dielectric layer is 0.4 micrometer to 0.6 micrometer.

5. The multi-mode polarization-sensitive infrared band metamaterial absorber based on a chain-type structure according to claim 1, characterized in that: The material of the metal reflective layer is a metal material or a metal compound material.

6. The multi-mode polarization-sensitive infrared band metamaterial absorber based on a chain-type structure according to claim 1, characterized in that: The thickness of the metal reflective layer is 0.4 micrometers.

7. The multi-mode polarization-sensitive infrared band metamaterial absorber based on a chain-type structure according to claim 1, characterized in that: The material of the metal reflective layer includes titanium, silver, aluminum, gold, iron and nickel, and corresponding metal compounds.

8. The multi-mode polarization-sensitive infrared band metamaterial absorber based on a chain-type structure according to claim 1, characterized in that: The first metal block, the second metal block, the third metal block and the fourth metal block have the same size.

9. The multi-mode polarization-sensitive infrared band metamaterial absorber based on a chain-type structure according to claim 8, characterized in that: The resonant units are periodically arranged on the upper surface of the dielectric layer.

10. The multi-mode polarization-sensitive infrared band metamaterial absorber based on a chain-type structure according to claim 1, characterized in that: The thickness of the metal resonator is 0.1 micrometer.

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