3-5 μm mid-wave infrared broadband perfect absorber

Abstract

This invention relates to an embedded absorber primarily targeting light in the spectral range of 3 to 5 micrometers. The absorber comprises multiple embedded absorption units, each containing a bottom titanium substrate with a thickness of t. 金属2 =0.2μm; the silicon dielectric layer located in the middle layer has a thickness of: t 介质1 =0.5-0.65μm; the thickness of the metal ring in the middle layer is: t 金属1 =0.05-0.2μm; the alumina dielectric layer located on the surface has a thickness of: t 介质2 =0.5-0.8μm; the inner and outer radii of the ring are r and r, respectively. 金属1 and R 金属1 The period is p, and the distance between the ring and the substrate is d. 金属1 ;r 金属1 =0.5-0.65μm, R 金属1 =0.75-0.9μm, d 金属1 =0.075-0.3375μm, p=1.8μm. t 金属1 :t 介质1 :t 介质2 :t 金属2 = (0.25-1):(2.5-3.25):(2.5-4):1; The embedded absorption unit is a quadrangular prism; the metal material of the middle layer is arranged in a ring; all structures have the same period. This structure can effectively absorb mid-wave infrared light.

Description

Technical Field

[0001] This invention relates to the field of light absorber technology; specifically, it relates to an embedded light absorber that primarily absorbs light in the spectral range of 3 to 5 micrometers. Background Technology

[0002] In recent years, research on absorbers that absorb electromagnetic waves in specific bands has received widespread attention and rapid development. They have enormous application potential in reconnaissance, sensing, and imaging. The mid-infrared band is a highly transparent atmospheric window within the electromagnetic spectrum, and absorbers covering this band have significant practical value in night vision reconnaissance, weapon aiming, and fire safety. Although the design principle of plasmon resonance can induce localized surface plasmon resonances on micro- and nano-sized metal surfaces, the resulting narrow bandwidth prevents effective utilization of light energy across a wide spectral range, limiting the absorption's application in infrared imaging and electromagnetic stealth. Therefore, achieving near-perfect absorption in the broadband mid-infrared remains a significant challenge.

[0003] Common methods for achieving broadband absorption include using high-loss metallic materials and grating array structures. Compared to metals such as gold, silver, and copper, titanium's dielectric constant changes slowly, making it more suitable for broadband absorption. However, it is prone to oxidation under heating conditions, which limits the application environment of titanium absorbers. Placing titanium in a more stable structure would expand the application range of titanium structure absorbers. Summary of the Invention

[0004] The purpose of this invention is to provide an embedded absorber with high absorption, covering the entire mid-wave infrared absorption band and being insensitive to the incident angle of the incident light.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] An embedded light absorber comprises multiple embedded absorption units, which include:

[0007] The bottom layer is a titanium metal substrate with a thickness of t. 金属2 ;t 金属2 =0.2μm;

[0008] The silicon dielectric layer located in the middle layer has a thickness of t. 介质1 ;t 介质1 =0.5-0.65μm;

[0009] The intermediate layer is a titanium ring with a thickness of t. 金属1 ;t 金属1 =0.05-0.2μm;

[0010] The alumina dielectric layer located on the surface has a thickness of t. 介质2 ;t 介质2 =0.5-0.8μm;

[0011] The inner and outer radii of the annulus are r and r, respectively. 金属1 and R 金属1 The period is p, and the distance between the ring and the substrate is d. 金属1 ;r 金属1 =0.5-0.65μm, R 金属1 =0.75-0.9μm, d 金属1 =0.075-0.3375μm, p=1.8μm.

[0012] t 金属1 :t 介质1 :t 介质2 :t 金属2 = (0.25-1): (2.5-3.25): (2.5-4): 1.

[0013] The device has a titanium substrate at the bottom, a titanium ring embedded in a silicon dielectric layer in the middle, and is covered by an aluminum oxide dielectric layer at the top.

[0014] This invention proposes a metal ring-embedded three-layer absorber. This structure ensures high absorption while compensating for the susceptibility of titanium to oxidation under heating conditions. Furthermore, the alumina at the top of the absorber induces resonance and effectively prevents titanium oxidation. Embedding the titanium ring into dielectric silicon further enhances the structural stability. Surface plasmon resonance (SPR) excited by the substrate and the embedded metal surface enables the absorber to exhibit high absorption performance in the mid-infrared band. Moreover, the two different dielectrics induce two resonant absorption peaks at different locations; the combined effect of these two mechanisms allows the overall structure to achieve broadband perfect absorption.

[0015] Preferably, the metal substrate has a thickness of 0.2 μm; the silicon dielectric layer has a thickness of 0.6 μm; the alumina dielectric layer has a thickness of 0.6 μm; the metal ring has a thickness of 0.15 μm; the inner radius of the ring is 0.6 μm; the outer radius of the ring is 0.9 μm; and the distance between the ring and the substrate is 0.175.

[0016] This structure exhibits excellent absorption performance across the entire 3-5 μm mid-infrared band, with maximum, minimum, and average absorptivity of 99.91%, 93.91%, and 98.57%, respectively. The absorption coefficient is expressed as A = 1 - RT.

[0017] This structure is also insensitive to the incident angle of the incident light. When the incident angle of the incident light reaches 60°, the average absorption rate is still as high as 93.55%.

[0018] The beneficial effects of the present invention are as follows: the structure of the present invention can effectively absorb light in the spectral range of 3 micrometers to 5 micrometers. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a unit structure according to the present invention;

[0020] Figure 2 This is a schematic diagram of the absorption spectrum of the absorber in this invention;

[0021] Figure 3 The electric field distribution of the XZ cross section at a wavelength of 3μm in this invention;

[0022] Figure 4 The magnetic field distribution of the XZ cross section at a wavelength of 3μm in this invention;

[0023] Figure 5 The electric field distribution of the XZ cross section at a wavelength of 4μm in this invention;

[0024] Figure 6 The magnetic field distribution of the XZ cross section at a wavelength of 4μm in this invention;

[0025] Figure 7 The electric field distribution of the XZ cross section at a wavelength of 5 μm in this invention;

[0026] Figure 8 The magnetic field distribution of the XZ cross section at a wavelength of 5 μm in this invention;

[0027] Figure 9 To investigate the effect of thickness on the absorption properties of the alumina medium;

[0028] Figure 10 To alter the effect of thickness on the absorption properties of dielectric silicon;

[0029] Figure 11 To change the effect of ring height on absorption performance;

[0030] Figure 12 To change the effect of the ring thickness on absorption performance;

[0031] Figure 13 To change the effect of the inner radius of the ring on absorption performance;

[0032] Figure 14 To change the effect of the outer radius of the ring on absorption performance;

[0033] Figure 15 The effect of the incident angle of light on the absorption performance of the structure; Figure 16 This is a three-dimensional diagram of the unit structure. Detailed Implementation

[0034] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0035] Example: This invention relates to an embedded absorber with high absorption, covering the entire mid-infrared absorption band and insensitive to the incident light angle. In the simulation, periodic boundary conditions are used in the x and y directions, and a PML boundary is used in the z direction. The plane wave is incident perpendicularly from the negative z-axis. Monitors are placed below the substrate and behind the light source to monitor the transmittance and reflectance of the structure. The absorptivity is calculated using the formula: A = 1 - TR. The optical parameters of both silicon and alumina are taken from Palik's data, and the dielectric constant of titanium is modeled using the Drud-Lorentz model.

[0036] like Figure 1 (a) shows a three-dimensional view of the unit structure. The bottom is a titanium substrate, the middle is a silicon dielectric layer with a titanium ring embedded in it, and the top is covered by an aluminum oxide dielectric layer. A top view is shown below. Figure 1 As shown in (b), the side view is as follows Figure 1 As shown in (c).

[0037] like Figure 2 As shown, the reflectivity and transmittance are almost zero. In the 3-5μm range, the absorption intensity is at least 93.91%, and the average absorption rate is as high as 98.57%, completely covering the 3-5μm mid-wave infrared atmospheric transparency window, achieving perfect absorption.

[0038] Two unit cell structures were selected, and the electric and magnetic field distributions of the XZ cross section at three wavelengths of 3μm, 4μm, and 5μm were plotted. For example... Figure 3 and 4 As shown, the electric and magnetic fields of the 3μm incident wave are distributed in both silicon and aluminum oxide media. The electric field is mainly distributed above the metal and is uniformly distributed, while the magnetic field is mainly distributed above the metal ring. Therefore, the absorption at 3μm is mainly due to the resonance between light and structure. Figure 5 The electric field is mainly distributed at the inner edge of the upper surface of the metal ring. Figure 6 The magnetic field is confined to the upper surface of the metal ring and the upper surface of the substrate. The attenuation length of the magnetic field in the medium is much greater than that in the metal, proving that typical SPR is excited at these two locations. Furthermore, the magnetic field on the surface of the metal ring is stronger, indicating that the absorption in the 4μm wavelength band is mainly concentrated on the surface of the metal ring. Figure 7 As shown, the electric field is distributed along both the upper and lower edges of the inner side of the metal ring, with a relatively stronger electric field intensity below the ring. Figure 8 The magnetic field shown is mainly distributed on the substrate surface, and the absorption at 5 μm is mainly caused by the SPR excited by the substrate and dielectric silicon.

[0039] During the optimization process, we will discuss how any one of the following parameters changes while the other parameters remain constant. For example... Figure 9 As shown, the absorption peak undergoes a significant red shift as the thickness of the alumina gradually increases. This is because the increase in the dielectric layer thickness causes a change in the equivalent impedance of the top layer resonance relative to free space. Figure 10 In this study, variations in the thickness of the dielectric silicon only affected the absorbance in the 3-4 μm wavelength range, because the intrinsic absorption and SPR of silicon occur in this range. Figure 11 , Figure 12 , Figure 14 It can be seen that, because the titanium ring plays a crucial role in the SPR excitation process, even small changes in the height, thickness, and outer radius of the titanium ring can significantly affect the absorption rate of the entire structure; from Figure 13 It can be seen that the positions of the two absorption peaks change with the inner radius, further confirming the generation of SPR. Regarding the above optimized data: t 介质1 =0.6μm; t 介质2 =0.6μm; t 金属1 =0.15μm; d 金属1 =0.175μm; r 金属1 =0.6μm, R 金属1 =0.9μm.

[0040] like Figure 15 As shown, when the incident angle is between 0° and 30°, the two absorption peaks hardly change. When the incident angle exceeds 30°, the peak on the left gradually disappears and merges with the peak on the right into one absorption peak. This absorption peak undergoes a blue shift relative to the right peak because the two absorption peaks have hybridized. At the same time, the absorptivity to the left of the left peak and to the right of the right peak begins to decrease. However, even when the incident angle reaches 60°, the average absorptivity of the entire 3-5μm band is still as high as 93.55%, indicating that this structure has good insensitivity to the angle of incident light.

[0041] While embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations fall within the scope and spirit of the invention as set forth in the claims. Furthermore, the invention described herein may have other embodiments and can be implemented or carried out in various ways.

Claims

A 1.3-5μm mid-wave infrared broadband embedded perfect absorber, comprising multiple embedded absorption units, characterized in that: The embedded absorption unit includes: The bottom layer is a titanium metal substrate with a thickness of t. 金属2 ;t 金属2 =0.2μm; The circular embedded silicon dielectric layer in the middle layer has a thickness of t. 介质1 ;t 介质1 =0.5-0.65μm; The intermediate layer is a titanium ring with a thickness of t. 金属1 ;t 金属1 =0.05-0.2μm; The alumina dielectric layer located on the surface has a thickness of t. 介质2 ;t 介质2 =0.5-0.8μm; The embedded absorption unit is arranged in the form of a quadrangular prism. The bottom layer of titanium metal, the middle layer of silicon dielectric, and the top layer of aluminum oxide dielectric are all quadrangular prisms, while the middle layer of titanium metal is arranged in a circular ring. All structures have the same period.

2. The 3-5μm mid-wave infrared broadband embedded perfect absorber according to claim 1, characterized in that: The length and width of the titanium substrate, silicon dielectric layer, and alumina dielectric layer are all periodic p = 1.8 μm.

3. The 3-5μm mid-wave infrared broadband embedded perfect absorber according to claim 1, characterized in that: The inner radius of the titanium ring is 0.50-0.65μm, the outer radius is 0.75-0.90μm, and the period is 1.8μm.

4. The 3-5μm mid-wave infrared broadband embedded perfect absorber according to claim 1, characterized in that: The embedded absorption units are arranged in an array and located in the same plane.

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