A metamaterial electromagnetic wave absorber with polarization selection in the long-wave infrared band

Abstract

The present invention discloses a metamaterial electromagnetic wave absorber with polarization selectivity in the long-wave infrared band, relating to the technical field of metamaterial electromagnetic wave absorbers. The metamaterial electromagnetic wave absorber comprises a unit structure, wherein the unit structure is provided in n groups, and the n groups of unit structures constitute a periodic metamaterial electromagnetic wave absorber; the unit structure comprises a metal grating layer and an MIM structure, wherein the metal grating layer is provided at a central position above the MIM structure. Through the above-mentioned method, the present invention has an average absorption rate of up to 95.7% in the 8-14um band under the incidence of TM electromagnetic waves. When applied to infrared detectors, it can significantly improve the detection capability of long-wave infrared detection. When applied to TE electromagnetic waves, the absorption rate is lower than an average of 1.7%. The selective absorption performance of TM and TE polarized electromagnetic waves enables it to be applied to polarized light detection in the 8-14um band. By introducing a polarization dimension in addition to the intensity dimension, the contrast between different targets can be effectively enhanced. The metamaterial electromagnetic wave absorber is suitable for application scenarios where the temperature difference between targets is small and the polarization difference is obvious.

Description

Technical Field

[0001] The present invention relates to the technical field of metamaterial electromagnetic wave absorbers, and in particular to a metamaterial electromagnetic wave absorber with polarization selection in the long-wave infrared band. Background Art

[0002] The 8-14μm band of electromagnetic waves is an important atmospheric transparent window in the infrared band and can be used in infrared detection, infrared imaging and other fields. Therefore, improving the absorption rate of the detector in the 8-14μm band has important practical application value.

[0003] In some applications requiring polarized light detection, metamaterial absorbers are designed to selectively absorb electromagnetic waves polarized in a specific direction. Such polarization-selective absorbers should maximize absorption of electromagnetic waves with a specific polarization direction while minimizing absorption of waves with an orthogonal polarization direction. Such polarization-selective absorbers have important practical applications in polarization detection, such as identifying artificial infrared camouflage targets and detecting light reflected from liquid surfaces.

[0004] Existing metamaterial electromagnetic wave absorber designs generally design a resonant structure of different sizes so that the resonance peaks are distributed in different positions. This method can broaden the absorption bandwidth. Alternatively, multiple different types of resonant structures can be designed to achieve the superposition of the resonance peak positions of different resonance types, thereby broadening the absorption bandwidth. Metamaterial absorbers designed using these two approaches can achieve ultra-wideband absorption, but they have the disadvantages of complex structure and high manufacturing difficulty. At the same time, the vast majority of existing metamaterial absorbers are designed to achieve polarization-insensitive absorption, while absorbers used in polarization absorption scenarios have not received much attention. Existing metamaterial absorbers do not have a significant difference in absorption performance in two mutually perpendicular polarization directions. Polarization absorption application scenarios require the maximum possible absorption of electromagnetic waves in a certain polarization direction and the minimum possible absorption of electromagnetic waves in the orthogonal polarization direction. Existing designs do not fully consider the needs of this application scenario.

[0005] Based on this, the present invention designs a metamaterial electromagnetic wave absorber with polarization selection in the long-wave infrared band to solve the above problems. Summary of the Invention

[0006] In view of the above-mentioned shortcomings of the prior art, the present invention provides a metamaterial electromagnetic wave absorber with polarization selection in the long-wave infrared band.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0008] A metamaterial electromagnetic wave absorber with polarization selection in the long-wave infrared band, comprising a unit structure, wherein the unit structure is provided in n groups, and the n groups of unit structures constitute a periodic metamaterial electromagnetic wave absorber;

[0009] The unit structure includes a metal grating layer and a MIM structure, and the metal grating layer is arranged at a central position above the MIM structure.

[0010] Furthermore, the period of the n groups of unit structures constituting the metamaterial electromagnetic wave absorber is 2600 nm.

[0011] Furthermore, the material of the metal grating layer is aluminum.

[0012] Furthermore, the thickness of the metal grating layer is 2200 nm and the width is 1560 nm.

[0013] Furthermore, the MIM structure includes a MIM structure upper metal titanium layer, a MIM structure intermediate dielectric zinc sulfide layer and a MIM structure bottom metal titanium layer, wherein the MIM structure upper metal titanium layer is arranged above the MIM structure intermediate dielectric zinc sulfide layer, and the MIM structure intermediate dielectric zinc sulfide layer is arranged above the MIM structure bottom metal titanium layer.

[0014] Furthermore, the thickness of the metal titanium layer on the MIM structure is 5 nm.

[0015] Furthermore, the thickness of the intermediate dielectric zinc sulfide layer of the MIM structure is 350 nm.

[0016] Furthermore, the thickness of the bottom metal titanium layer of the MIM structure is 70 nm.

[0017] Beneficial effects

[0018] Compared with the known public technology, the technical solution provided by the present invention has the following beneficial effects:

[0019] 1. The present invention has an average absorption rate of up to 95.7% in the 8-14um band under the incidence of TM electromagnetic waves. When applied to infrared detectors, it can greatly improve the detection capability of long-wave infrared detection. Under the incidence of TE electromagnetic waves, the absorption rate is lower than the average 1.7%. The selective absorption performance of TM and TE polarized electromagnetic waves enables it to be used in polarized light detection in the 8-14um band. By introducing the polarization dimension in addition to the intensity dimension, it can effectively enhance the contrast between different targets. It is suitable for application scenarios with small temperature differences and obvious polarization differences between targets, and is suitable for typical application scenarios such as liquid surface reflection infrared detection and artificial infrared camouflage target recognition. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0021] Figure 1 Schematic diagram of the unit structure of the present invention;

[0022] Figure 2 It is a schematic diagram of the overall structure of the present invention;

[0023] Figure 3 This is the absorption curve of the present invention under two different polarized light incidents: TM and TE;

[0024] Figure 4 The absorption spectra of the present invention at different incident angles under TM incidence;

[0025] Figure 5 This is the absorption spectrum of the present invention at different incident angles under TE incidence.

[0026] The numbers in the figure represent:

[0027] 1. Metal grating layer; 2. Metal titanium layer on the MIM structure; 3. Zinc sulfide layer in the middle of the MIM structure; 4. Metal titanium layer at the bottom of the MIM structure. DETAILED DESCRIPTION

[0028] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying 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 making any creative efforts shall fall within the scope of protection of the present invention.

[0029] The present invention will be further described below with reference to the embodiments.

[0030] Example 1

[0031] like Figure 1 and 2 As shown, a metamaterial electromagnetic wave absorber with polarization selection in the long-wave infrared band includes a unit structure (such as Figure 1 As shown), the unit structure is provided with n groups, and the n groups of unit structures constitute a periodic metamaterial electromagnetic wave absorber (as shown Figure 2 shown);

[0032] The period of the n groups of unit structures constituting the metamaterial electromagnetic wave absorber is 2600 nm;

[0033] The unit structure includes a metal grating layer 1 and a MIM structure, wherein the metal grating layer 1 is arranged at a central position above the MIM structure.

[0034] The material of the metal grating layer 1 is aluminum.

[0035] The metal grating layer 1 has a thickness of 2200 nm and a width of 1560 nm.

[0036] The MIM structure includes a MIM upper metal titanium layer 2, a MIM intermediate dielectric zinc sulfide layer 3 and a MIM bottom metal titanium layer 4. The MIM upper metal titanium layer 2 is arranged above the MIM intermediate dielectric zinc sulfide layer 3, and the MIM intermediate dielectric zinc sulfide layer 3 is arranged above the MIM bottom metal titanium layer 4.

[0037] The thickness of the metal titanium layer 2 on the MIM structure is 5 nm.

[0038] The thickness of the intermediate dielectric zinc sulfide layer 3 of the MIM structure is 350 nm.

[0039] The thickness of the bottom metal titanium layer 4 of the MIM structure is 70 nm.

[0040] Guided by impedance matching theory and other electromagnetic theories, and in order to achieve the goal of maximizing the absorption of electromagnetic waves in a certain polarization direction while minimizing the absorption of electromagnetic waves in the orthogonal polarization direction in infrared polarization detection and infrared polarization imaging applications, a metamaterial electromagnetic wave absorber structure with a metal grating added on top of a MIM structure was selected. Using electromagnetic field numerical simulation software, the geometric parameters of the structure were scanned within an appropriate range to determine the materials and geometric dimensions of the metal grating layer 1, the titanium layer 2 on the MIM structure, the zinc sulfide layer 3 in the middle of the MIM structure, and the titanium layer 4 at the bottom of the MIM structure.

[0041] When metamaterials interact with electromagnetic waves, they experience reflection, transmission, and absorption, the sum of which equals the total energy of the incident electromagnetic wave: A = 1-RT, where A is the absorptivity of the metamaterial, R is the reflectivity, and T is the transmittance. Therefore, in MIM-based absorber designs, the thickness of the underlying metal is typically much greater than its skin depth, resulting in a transmittance of approximately zero. Therefore, the device's absorptivity is expressed as A = 1-R.

[0042] The equivalent impedance Z of the entire metamaterial absorber as a homogeneous medium can be expressed as:

[0043]

[0044] S 11is the real part of the reflection coefficient obtained by simulation; S 21 is the imaginary part of the transmission coefficient obtained by simulation.

[0045] The impedance Z0 of free space can be expressed as:

[0046]

[0047] ε is the dielectric constant of free space, μ is the magnetic permeability of free space;

[0048] According to the Fresnel formula, the reflection coefficient R can be expressed as:

[0049]

[0050] The geometric parameters of the designed structure are controlled so that when Z=Z0, the reflection coefficient of the metamaterial absorber is 0, thereby achieving maximum absorption. It is determined that the best polarization-selective absorption performance can be obtained when the period is 2600nm, the metal grating width is 1560nm, and the thickness of each layer from top to bottom is 2200nm, 5nm, 350nm, and 70nm. The geometric dimensions of the metal grating layer 1, the metal titanium layer 2 on the MIM structure, the zinc sulfide layer 3 in the middle of the MIM structure, and the metal titanium layer 4 at the bottom of the MIM structure are determined.

[0051] At the same time, the material of the metal grating layer 1 is determined to be aluminum, the material of the metal titanium layer 2 on the MIM structure and the metal titanium layer 4 on the bottom of the MIM structure are determined to be titanium, and the material of the zinc sulfide layer 3 in the middle of the MIM structure is determined to be zinc sulfide. The metal grating layer 1 of the unit structure realizes the requirement of polarization-selective absorption of incident light, and the MIM structure realizes the requirement of maximizing the absorption of incident light. The metal of the metal titanium layer 2 on the MIM structure and the metal titanium layer 4 on the bottom of the MIM structure in the MIM structure is selected from titanium to maximize the absorption of incident electromagnetic waves by utilizing the high loss of titanium while reducing the thickness of the structure. The zinc sulfide layer 3 in the middle of the MIM structure is selected from zinc sulfide. Zinc sulfide is a high refractive index medium that increases the interaction time between light and the metamaterial electromagnetic wave absorber. Zinc sulfide is also a lossless medium that facilitates the destructive interference of surface plasmon resonances excited at the upper and lower dielectric-metal interfaces of the MIM structure to form a resonant cavity resonance mode. Metal grating layer 1 is made of aluminum, a highly conductive metal. Aluminum metal gratings transmit TM incident electromagnetic waves to a high degree while reflecting TE incident electromagnetic waves to the greatest extent, enabling polarization-selective absorption. Under TM polarized light, the resonant cavity resonance modes generated in the MIM structure resonate with the surface plasmon resonance modes and localized surface plasmon resonance modes generated in the metal grating, broadening the absorption bandwidth and achieving higher absorption.

[0052] Figure 3This is the absorption rate curve of the present invention for TM and TE polarized electromagnetic waves. In the long-wave infrared band of 8-14um, the average absorption rate for TM polarized electromagnetic waves can be greater than 95.7%, and the average absorption rate for TE polarized electromagnetic waves is less than 1.7%, which proves that the metamaterial polarization absorber we designed has broadband ultra-high absorption performance and excellent polarization-selective absorption performance.

[0053] Figure 4 It is the absorption rate at different incident angles when the electromagnetic wave is incident in TM polarization mode.

[0054] Figure 5 It is the absorption rate at different incident angles when the electromagnetic wave is incident in TE polarization mode.

[0055] Figure 4 、 Figure 5 The results demonstrate that the present invention exhibits excellent polarization-selective absorption performance in the 8-14 μm band over a wide range of incident angles. The metamaterial absorber possesses ultra-broadband, polarization-selective, and wide-angle absorption characteristics, making it suitable for applications in infrared polarization detection and imaging.

[0056] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A metamaterial electromagnetic wave absorber with polarization selectivity in the long-wave infrared band, comprising a unit structure, characterized in that: The unit structures are provided in n groups, and the n groups of unit structures constitute a periodic metamaterial electromagnetic wave absorber; The unit structure comprises a metal grating layer (1) and a MIM structure, wherein the metal grating layer (1) is arranged at a central position above the MIM structure; The MIM structure comprises a MIM structure upper metal titanium layer (2), a MIM structure intermediate dielectric zinc sulfide layer (3), and a MIM structure bottom metal titanium layer (4); the MIM structure upper metal titanium layer (2) is arranged above the MIM structure intermediate dielectric zinc sulfide layer (3), and the MIM structure intermediate dielectric zinc sulfide layer (3) is arranged above the MIM structure bottom metal titanium layer (4).

2. The metamaterial electromagnetic wave absorber with polarization selection in the long-wave infrared band according to claim 1, characterized in that: The period of the n groups of unit structures constituting the metamaterial electromagnetic wave absorber is 2600 nm.

3. The metamaterial electromagnetic wave absorber with polarization selection in the long-wave infrared band according to claim 2, characterized in that: The material of the metal grating layer (1) is aluminum.

4. The metamaterial electromagnetic wave absorber with polarization selection in the long-wave infrared band according to claim 3, characterized in that: The metal grating layer (1) has a thickness of 2200 nm and a width of 1560 nm.

5. The metamaterial electromagnetic wave absorber with polarization selection in the long-wave infrared band according to claim 1, characterized in that: The thickness of the metal titanium layer (2) on the MIM structure is 5 nm.

6. The metamaterial electromagnetic wave absorber with polarization selection in the long-wave infrared band according to claim 1, characterized in that: The thickness of the intermediate medium zinc sulfide layer (3) of the MIM structure is 350 nm.

7. The metamaterial electromagnetic wave absorber with polarization selection in the long-wave infrared band according to claim 1, characterized in that: The thickness of the bottom metal titanium layer (4) of the MIM structure is 70 nm.

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