3-14 [mu] m intermediate infrared multi-band absorber

Abstract

The invention discloses a 3-14 [mu] m mid-infrared multi-band absorber, which comprises a plurality of embedded absorption units, and each embedded absorption unit is provided with a titanium bottom layer located at the bottom layer and with the thickness of tmetal 2, tmetal 2 = 0.25 [mu] m, a titanium bottom layer located at the bottom layer and a titanium bottom layer located at the bottom layer and with the thickness of tmetal 2 = 0.25 [mu] m; the thickness of the silicon dielectric layer is t dielectric 1, and t dielectric 1 is equal to 0.825 mu m; the thickness of the metal cross in the middle layer is tmetal 3, and tmetal 3 is 0.15 mu m; the aluminum oxide dielectric layer is located on the surface layer, the thickness of the aluminum oxide dielectric layer is t dielectric 2, and t dielectric 2 is equal to 1.45 microns; the thickness of the metal ring positioned on the surface layer is tmetal 1, and tmetal 1 is 0.15 mu m; and the titanium bottom layer, the silicon dielectric layer, the metal cross, the aluminum oxide dielectric layer and the metal ring have the same period. According to the invention, the key frequency band of the mid-infrared spectrum area is covered, the mid-infrared multi-band perfect absorption is realized, the absorption is not sensitive to the polarization angle of the light source, and the multi-band absorption can be realized in the broadband range of 3-14 [mu] m.

Description

Technical Field

[0001] The present invention relates to the technical field of light absorbers, and more specifically to a 3-14 μm mid-infrared multi-band absorber. Background Art

[0002] In recent years, research on absorbers that absorb electromagnetic waves in specific bands has received widespread attention and developed rapidly. They have great application potential in reconnaissance, sensing, imaging and other fields. Mid-infrared lasers have a unique band that covers the atmospheric window. Absorbers covering this band have important practical value in medical operations, automobile manufacturing, fire safety and other fields. Although some progress has been made in the research of mid-infrared multi-band absorbers, they are still faced with constraints in wide-band design, material selection and preparation, design complexity and scalability, environmental influences, integration and application, which limit the scalability and practicality of the absorber.

[0003] Compared with gold, silver, copper and other metals, the dielectric constant of titanium changes slowly, which is more conducive to the realization of multi-band, but it is easy to oxidize in a heated environment. This characteristic limits the use environment of titanium absorbers. If titanium is placed in a structure with better stability, the application range of titanium structure absorbers will be expanded.

[0004] Therefore, how to provide a 3-14 μm mid-infrared multi-band absorber based on a titanium structure is a problem that technicians in this field need to solve urgently. Summary of the invention

[0005] In view of this, the present invention provides a 3-14 μm mid-infrared multi-band absorber, which covers the key frequency bands in the mid-infrared spectral region, achieves perfect mid-infrared multi-band absorption and is insensitive to the polarization angle of the light source.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] The 3-14 μm mid-infrared multi-band absorber comprises a plurality of embedded absorption units, wherein the embedded absorption units are sequentially provided with:

[0008] The titanium bottom layer at the bottom has a thickness of t 金属2 , t 金属2 =0.25μm;

[0009] The silicon dielectric layer in the middle layer has a thickness of t 介质1 , t 介质1 =0.825 μm;

[0010] The aluminum oxide dielectric layer on the surface has a thickness of t 介质2 , t 介质2 =1.45μm;

[0011] A metal cross is embedded in the silicon dielectric layer, and the thickness is t 金属3 , t 金属3 =0.15μm;

[0012] The aluminum oxide dielectric layer is embedded with a metal ring having a thickness of t 金属1 , t 金属1 =0.15μm;

[0013] The titanium bottom layer, the silicon dielectric layer, the metal cross, the aluminum oxide dielectric layer and the metal ring have the same period.

[0014] Preferably, the embedded absorption unit is in the shape of a quadrangular prism;

[0015] The titanium bottom layer, the silicon dielectric layer and the aluminum oxide dielectric layer are all quadrangular prisms, and the length and width are the same as the period.

[0016] Preferably, the inner radius r of the metal ring is 金属1 =0.4μm, outer radius R 金属1 =0.9μm;

[0017] The distance between the metal ring and the silicon dielectric layer is d 金属1 , d 金属1 =0.8125um.

[0018] Preferably, the length L1 of the metal cross is 2.8 μm, and the width L2 is 0.5 μm;

[0019] The distance between the metal cross and the titanium base layer is denoted as d1.

[0020] Preferably, the material of the metal cross and the metal ring is titanium.

[0021] Preferably, the plurality of embedded absorption units are arranged in an array and are located in the same plane.

[0022] Preferably, t 金属1 :t 介质1 :t 介质2 :t 金属3 :t 金属2 =0.6:3.3:5.8:0.6:1.

[0023] Preferably, the material of the aluminum oxide dielectric layer is aluminum oxide.

[0024] Preferably, the period p=5 μm.

[0025] As can be seen from the above technical solutions, compared with the prior art, the present invention discloses a 3-14μm mid-infrared multi-band absorber. This structure not only ensures high absorption but also makes up for the defect that metal Ti is prone to oxidation in a heating environment. Moreover, the aluminum oxide on the top of the absorber plays a role in inducing resonance and can effectively prevent the oxidation of metal Ti. Embedding the metal Ti ring into the aluminum oxide dielectric layer further enhances the structural stability. By reasonably designing the size and layout of the metal cross, surface plasmon resonance can be effectively excited and the light absorption effect can be enhanced. The embedded composite structure absorber of the present invention can achieve multi-band absorption in a wide band range of 3-14μm, covering the key frequency bands in the mid-infrared spectral region, enabling the absorber to meet the absorption requirements in different frequency bands and improving the adaptability and performance in different application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the provided drawings.

[0027] Figure 1 Schematic three-dimensional structure diagram of the embedded absorption unit of the present invention;

[0028] Figure 2 Top view of the embedded absorption unit of the present invention;

[0029] Figure 3 Side view of the embedded absorption unit of the present invention;

[0030] Figure 4 Schematic diagram of the arrangement of multiple embedded absorption units of the present invention;

[0031] Figure 5 Schematic diagram of the absorption spectrum of the absorber of the present invention;

[0032] Figure 6 Electric field distribution of the x-y plane where the cross is located at (a) 3.58μm (b) 4.56μm (c) 8.26μm (d) 11.25μm;

[0033] Figure 7 Electric field vector diagram of the x-y plane where the cross is located at (a) 3.58μm (b) 4.56μm (c) 8.26μm (d) 11.25μm;

[0034] Figure 8The electric field distribution of the ring in the xy plane at (a) 3.58μm (b) 4.56μm (c) 8.26μm (d) 11.25μm;

[0035] Fig. 9 The electric field vector diagram of the xy plane where the ring is located at (a) 3.58μm (b) 4.56μm (c) 8.26μm (d) 11.25μm;

[0036] Fig.10 The effect of the cross height on the absorption performance of the absorber;

[0037] Fig.11 The effect of the cross thickness on the absorption performance of the absorber;

[0038] Fig.12 The effect of L1 length on the absorption performance of the absorber;

[0039] Fig.13 The effect of L2 length on the absorption performance of the absorber;

[0040] Fig.14 The absorption characteristics of the absorber are related to (a) the incident angle of the unpolarized wave and (b) the polarization angle. DETAILED DESCRIPTION

[0041] 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.

[0042] The embodiment of the present invention discloses a 3-14 μm mid-infrared multi-band absorber, such as Figure 1 , Figure 2 and Figure 3 As shown, it comprises a plurality of embedded absorption units, and the embedded absorption units are arranged in sequence from the bottom layer to the surface layer:

[0043] The titanium bottom layer 1 at the bottom layer has a thickness of t 金属2 , t 金属2 =0.25μm;

[0044] The silicon dielectric layer 2 in the middle layer has a thickness of t 介质1 , t 介质1 =0.825 μm;

[0045] The metal cross 3 in the middle layer has a thickness of t 金属3 , t 金属3 =0.15 μm, wherein the metal cross 3 is embedded in the silicon dielectric layer 2;

[0046] The aluminum oxide dielectric layer 4 located on the surface has a thickness of t 介质2 , t 介质2 =1.45μm;

[0047] The metal ring 5 located on the surface has a thickness of t 金属1 , t 金属1 =0.15 μm, the metal ring 5 is embedded in the alumina dielectric layer 4;

[0048] The titanium bottom layer 1, the silicon dielectric layer 2, the metal cross 3, the aluminum oxide dielectric layer 4 and the metal ring 5 have the same period, that is, the absorber of the entire structure is arranged periodically in the x and y directions according to the size of the period p.

[0049] This structure exhibits very perfect absorption performance in the entire 3-14μm mid-infrared band, with the highest, lowest and average absorption rates being 98.4%, 95.5% and 97.1% respectively.

[0050] The present structure is insensitive to changes in the polarization angle of the light source, and the absorption rate remains at a similar level regardless of the polarization direction of the light.

[0051] Furthermore, the embedded absorption unit is in the form of a quadrangular prism;

[0052] The titanium bottom layer 1, the silicon dielectric layer 2 and the aluminum oxide dielectric layer 4 are all quadrangular prisms, and the length and width are the same as the period.

[0053] The inner radius r of the metal ring 5 金属1 =0.4μm, outer radius R 金属1 =0.9μm;

[0054] The distance between the metal ring 5 and the silicon dielectric layer 2 is d 金属1 , d 金属1 =0.8125um.

[0055] The length L1 of the metal cross 3 is 2.8 μm, and the width L2 is 0.5 μm;

[0056] The distance between the metal cross 3 and the titanium base layer 1 is denoted as d1.

[0057] The material of the metal cross 3 and the metal ring 5 is titanium.

[0058] Multiple embedded absorption units are arranged in an array and located in the same plane, such as Figure 4 shown.

[0059] t 金属1 :t 介质1 :t 介质2 :t 金属3 :t 金属2=0.6:3.3:5.8:0.6:1.

[0060] In the simulation setting, the plane wave was incident vertically, the polarization direction of the electromagnetic wave was set to the x direction, the wavelength range to be solved was set to 3-14μm, the electric field direction of the electromagnetic wave was along the negative direction of the y axis, the magnetic field direction was along the negative direction of the x axis, and the wave vector was along the negative direction of the z axis. In order to simulate the periodic structure, the boundary conditions of the x-axis and y-axis were set to periodic boundary conditions to simulate the infinitely repeated unit structure. The boundary condition in the z-axis direction used the PML (Perfectly Matched Layer) perfect absorption boundary condition to effectively absorb the reflection and radiation of the incident wave, using the formula: A = 1-TR. The optical parameters of both Si and Al2O3 materials were taken from Palik's data, and the dielectric constant of Ti was used using the Drude Lorentz model.

[0061] like Figure 5 As shown in the figure, this absorber realizes the design of a four-band perfect absorber with an average absorption rate of 97.1%. The design of this multi-band absorber successfully achieves high absorption rates in different wavelength ranges. By rationally designing the structural parameters and material selection of the absorber, the absorber has a high absorption capacity for light of a specific wavelength. This multi-band perfect absorber can be applied in various fields, such as optical sensing, light detection, and thermal radiation control.

[0062] In order to observe the electric field changes of the multi-band absorber at the four peaks more intuitively, a simulation was performed and the electric field intensity and electric field vector distribution diagrams in the horizontal direction of the cross and the ring were drawn. Figure 6 and Figure 8 It can be seen that the electric field strength of the absorber's ring and cross shows different characteristics at different absorption peaks. Figure 7 and Fig. 9 It shows that under the action of the incident wave, the charges inside the absorber move, thus forming an electric field distribution diagram. This shows that the charges inside the metal in the absorber resonate under the excitation of the incident wave. Figure 6 and Figure 8 The following conclusions can be drawn from the observation results:

[0063] (1) The absorption peaks at 3.58μm and 4.56μm are mainly caused by the intrinsic absorption of the material, which means that the energy at these two wavelengths is mainly absorbed by the absorber material; (2) The absorption peaks at 8.26μm and 11.25μm are mainly caused by surface plasmons, which means that the energy at these two wavelengths is mainly concentrated on the surface area of ​​the absorber and has no direct relationship with the absorption of the material itself. In addition, the observation Figure 6In parts (c) and (d), we can see that the resonance strength of the two pillars in the metal cross is not the same. Figure 8 In (c) and (d), the electric field intensity in the x direction is significantly higher than that in the y direction. This is because the polarization direction of the incident wave is in the x direction, which makes the structure of the metal cross more sensitive to the electric field in the x direction.

[0064] During the optimization process, when any of the following parameters are changed, the other parameters remain unchanged. Fig.10 As shown in the figure, as the height of the cross increases, the absorption peak blue-shifts. At the same time, the absorptivity also increases. This shows that the change in the height of the cross has a significant effect on the absorption performance of light in a specific wavelength range; Fig.11 In the figure, as the thickness of the cross increases, the absorptivity decreases gradually. This may be because the increased thickness of the cross leads to an increase in the light transmission path, allowing part of the light to pass through the absorber instead of being completely absorbed. Therefore, as the thickness of the cross increases, the amount of light that is not absorbed increases, resulting in a decrease in the absorptivity; Fig.12 It can be seen that as the length of L1 increases, the absorptivity gradually increases. This shows that the change in the length of L1 has a significant effect on the light absorption effect within a specific wavelength range; Fig.13 It can be seen that the change of L2 not only affects the absorption rate of the absorption peak at 8.26μm, but also affects the absorption valley in the range of 8.26μm to 11.25μm. As the length of L2 changes, the absorption rate shows an upward or downward trend in this range. For the above preferred data: t 介质1 =0.825μm; t 介质2 =1.45μm; t 金属1 =0.15μm; t 金属2 =0.25μm; t 金属3 =0.15μm; r 金属1 =0.4μm, R 金属1 =0.9μm, d 金属1 =0.8125μm; L1=2.8μm, L2=0.5μm.

[0065] like Fig.14As shown in part (a), when the incident angle of the light source changes from 0° to 60°, the position of the absorption peak at 3.58μm remains almost unchanged, and the absorptivity gradually decreases with the increase of the incident angle. The position of the absorption peak at 4.56μm gradually splits into two absorption peaks as the incident angle increases, and the absorption peak at the longer wavelength is coupled with the absorption peak at 5.45μm. The position of the absorption peak at 8.26μm has a blue shift, and gradually tends to couple with the absorption peak at 5.45μm. The absorption peak at 11.25μm has almost no change in position as the incident angle increases, but the absorptivity gradually decreases. On the other hand, part (b) shows the effect of the polarization angle of the light source on the absorptivity. According to the results in the figure, it can be observed that the absorptivity is insensitive to changes in the polarization angle of the light source, that is, regardless of the polarization direction of the light, the absorptivity remains at a similar level. This may be because the absorber structure has similar absorption characteristics for light with different polarization directions.

[0066] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0067] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. 3-14μm mid-infrared multi-band absorber, characterized in that: It comprises a plurality of embedded absorption units, wherein the embedded absorption units are sequentially provided with: The titanium bottom layer at the bottom has a thickness of t 金属2 , t 金属2 =0.25μm; The silicon dielectric layer in the middle layer has a thickness of t 介质1 , t 介质1 =0.825 μm; The aluminum oxide dielectric layer on the surface has a thickness of t 介质2 , t 介质2 =1.45μm; A metal cross is embedded in the silicon dielectric layer, and the thickness is t 金属3 , t 金属3 =0.15 μm; The aluminum oxide dielectric layer is embedded with a metal ring having a thickness of t 金属1 , t 金属1 =0.15 μm; The titanium bottom layer, the silicon dielectric layer, the metal cross, the aluminum oxide dielectric layer and the metal ring have the same period.

2. The 3-14 μm mid-infrared multi-band absorber according to claim 1, characterized in that: The embedded absorption unit is in the form of a quadrangular prism; The titanium bottom layer, the silicon dielectric layer and the aluminum oxide dielectric layer are all quadrangular prisms, and the length and width are the same as the period.

3. The 3-14 μm mid-infrared multi-band absorber according to claim 1, characterized in that: The inner radius r of the metal ring 金属1 =0.4μm, outer radius R 金属1 =0.9μm; The distance between the metal ring and the silicon dielectric layer is d 金属1 , d 金属1 =0.8125um.

4. The 3-14 μm mid-infrared multi-band absorber according to claim 1, characterized in that: The metal cross has a length L1 = 2.8 μm and a width L2 = 0.5 μm; The distance between the metal cross and the titanium bottom layer is expressed as d1, d1 = 0.125 um.

5. The 3-14 μm mid-infrared multi-band absorber according to claim 1, characterized in that: The metal cross and the metal ring are made of titanium.

6. The 3-14 μm mid-infrared multi-band absorber according to claim 1, characterized in that: The plurality of embedded absorption units are arranged in an array and are located in the same plane.

7. The 3-14 μm mid-infrared multi-band absorber according to claim 1, characterized in that: t 金属1 :t 介质1 :t 介质2 :t 金属3 :t 金属2 =0.6:3.3:5.8:0.6:1。 8. The 3-14 μm mid-infrared multi-band absorber according to claim 1, characterized in that: The material of the aluminum oxide dielectric layer is aluminum oxide.

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