In-line cylindrical ultra-wideband absorber

Abstract

This invention discloses an ultrawideband absorber with an embedded cylinder. The absorber uses SiO2 as a substrate, with Ti layer placed above it as a transition layer. The surface of the Ti layer has periodically arranged absorption units, each including a frustum formed by a dielectric layer. The side length of the base of each frustum is consistent with the array period P. A cylindrical inlay is embedded at the central axis of the dielectric layer frustum, with its bottom tangent to the bottom surface of the dielectric layer and a metal layer on top. The top of the inlay protrudes h3 relative to the top surface of the dielectric layer. This protrusion introduces additional electromagnetic resonance, supplementing the absorption intensity in the short-wave infrared band and complementing the long-wave absorption of the dielectric layer, thus broadening the effective absorption bandwidth and enhancing electromagnetic field localization. The inlay acts as a support structure, providing a certain height to the metal layer, which facilitates light absorption by the high-loss metal layer during multiple round trips. The average absorption rate reaches 98% in the incident wavelength range of 1100nm to 3400nm, and achieves 99.7% absorption near 2500nm, independent of polarization.

Description

Technical Field

[0001] This invention discloses a microwave absorbing device, and more particularly relates to an ultrawideband absorber with an embedded cylinder. Background Technology

[0002] Metasurfaces are two-dimensional planar structures constructed from subwavelength micro / nano resonant / absorption units. These specially designed nanomaterials can precisely control electromagnetic wave characteristics and frequency response range, making them a research hotspot in many fields such as optics and electromagnetics.

[0003] Metasurface material absorbers generally consist of two main parts: a top resonant structure and a bottom substrate. Their absorption range can be adjusted by changing the horizontal or vertical arrangement of the resonant structure, the material composition, and the shape and pattern of each unit within the resonant structure. For example, in 2008, the Rephaeli team at Stanford University introduced a pyramid structure into the design of a solar metasurface material absorber, achieving ideal and perfect absorption within the solar radiation spectrum (Rephaeli E, Fan S. Tungsten black absorber for solar light with wide angular operation range [J]. Applied Physics Letters, 2008, 92(211107):2008.). In 2021, Piao et al. designed a three-layer pyramid structure perfect absorber consisting of titanium nitride, a dielectric film, and a titanium nitride bottom layer. This device can achieve near-total absorption in the 300~2500nm spectral range, with an average absorption rate of over 99% (Ultra-broadband perfect absorber based on nanoarray of titanium nitride truncated pyramids for solar energy harvesting [J]. Physica E: Low-dimensional Systems and Nanostructures, 2021, 134.). CN 120491228 A discloses an ultra-wideband high-efficiency absorber, and CN 120802414 A discloses an absorber containing an inlay.

[0004] All of the above solutions can improve absorption bandwidth and absorption rate, but the resonant structure is more complex, which increases the difficulty of fabrication. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to propose an ultrawideband absorber with a simplified structure and an embedded cylinder, which can achieve high absorption efficiency in the short-wave infrared to mid-wave infrared spectral range, while having complete polarization insensitivity.

[0006] Technical Solution: The present invention discloses an ultrawideband absorber with an embedded cylinder, comprising a substrate layer formed by a bottom layer of SiO2 and a transition layer of Ti, and absorption units periodically arranged on the surface of the transition layer Ti. The absorption unit comprises a frustum-shaped dielectric layer, an inlay passing through the dielectric layer along the axial direction of the dielectric layer, and a metal layer disposed on top of the inlay. The bottom edge length of the dielectric layer is not greater than the period P of the absorption unit. The outer diameter r of the circumscribed circle of the inlay is smaller than the top edge length a of the dielectric layer, and the top surface of the inlay protrudes h3 relative to the top surface of the dielectric layer. The metal layer is frustum-shaped, and the bottom edge length b of the metal layer is smaller than the bottom edge length of the dielectric layer and larger than the outer diameter r of the inlay.

[0007] The invention features a tapered structure that is wider at the bottom and narrower at the top, achieving continuous impedance matching and minimizing reflection while maximizing transmission and absorption. The absorption unit consists of only three parts, greatly simplifying its structure. The inlay protrudes slightly from the dielectric layer, introducing additional electromagnetic resonance to supplement the absorption intensity in the short-wave infrared band. This complements the long-wave absorption of the dielectric layer, broadening the effective absorption bandwidth and enhancing the localization of the electromagnetic field. The inlay also serves as a support structure, giving the metal layer a certain height, which is beneficial for the continuous absorption of light by the high-loss metal layer during multiple round trips.

[0008] Preferably, the dielectric layer is Ge, and the inlay material is Pt. Ge's high refractive index and high infrared loss are key to achieving broadband strong absorption in the mid-to-long-wave infrared band, while Pt can significantly improve the absorption rate and also has the advantages of reducing costs, improving process compatibility, high temperature resistance, oxidation resistance, and long-term stability.

[0009] Preferably, the metal layer is made of Cu. Compared to the precious metal Cu, Cu has extremely low cost, moderate optical properties and stability, and superior overall performance.

[0010] Preferably, the dielectric layer and the inlay are regular square frustums, the base side of the dielectric layer is equal to P, and the inlay is a cylinder. Regular square frustums possess good orthogonal symmetry, enabling consistent electromagnetic responses of x- and y-polarized light, ensuring polarization independence, reducing coaxial alignment difficulty and process precision requirements, and improving yield.

[0011] Preferably, to ensure an absorption rate of not less than 90% in the 1000~3400nm range, the top surface of the inlay protrudes by h3 = 200~315nm relative to the top surface of the dielectric layer. More preferably, the transition layer Ti has a height h1 = 430~450 nm and a period P = 330~350 nm, the dielectric layer h2 ≥ 208 nm and a = 100~160 nm, the inlay a > r ≥ 20 nm, and the metal layer h4 ≥ 30 nm, r < d < b ≤ 230 nm.

[0012] Preferably, in order to achieve an absorption rate of not less than 95%, the period P = 335~350nm, a = 140~160nm, the inlay h3 = 248~308nm, r = 25~60nm, the metal layer h4 ≥ 70nm, b = 160~220nm, and d = 65~200nm.

[0013] Preferably, to avoid interference or advanced diffraction caused by excessive overall device height, the dielectric layer h2 = 208~225nm and h4 = 80~185nm. More preferably, the transition layer Ti height h1 = 435~445nm, period P = 335~345nm, dielectric layer a = 145~155nm, inlay h3 = 268~303nm, r = 30~50nm, metal layer h4 = 85~120nm, b = 170~210nm, d = 95~150nm. Most preferably, the period P = 340±3nm, the transition layer Ti height h1 = 440±2nm, dielectric layer h2 = 210±2nm, a = 150±3nm, inlay r = 35±3nm, h3 = 278±5nm, metal layer b = 196±3nm, d = 140±3nm, and h4 = 100±2nm.

[0014] The aforementioned ultra-wideband absorber can be used for solar energy collection, optical sensing, stealth materials, and thermal emitter fabrication.

[0015] Beneficial Effects: Compared with the prior art, the present invention has the following significant advantages: 1. The absorber structure of the present invention has a reasonable layout design, which facilitates precise alignment. The overall structure is simple, easy to manufacture, and cost-controllable. Its high-efficiency absorption region with an absorption rate of not less than 90% covers the working wavelength range of 1000~3400nm, exhibiting excellent broadband absorption characteristics. At the same time, it maintains a high degree of insensitivity to the polarization state of incident light. In the range of 1100nm to 3400nm, it achieves a theoretical average absorption rate of 98%, and in the range of 2100nm to 3000nm, the average absorption rate is as high as 99%, with the highest absorption rate of 99.7% when the wavelength is around 2500nm; 2. It has excellent material compatibility, stable working performance, and long service life; 3. It provides an innovative technical solution for the research and development of ideal solar thermal absorbers and the breakthrough of solar thermal-photovoltaic conversion technology, playing an indispensable role in the field of renewable energy (especially in the areas of solar thermal-photovoltaic conversion and efficient utilization of solar thermal energy); 4. It has broad application potential and development prospects in multiple fields such as solar energy collection, optical sensing, stealth technology, and thermal emitters. Attached Figure Description

[0016] Figure 1 The following diagrams illustrate the structure and characterization of the absorber: (a) is an overall schematic diagram of the structural unit; (b) is a cross-sectional schematic diagram of one period cut along the X-axis in this invention; (c) is a schematic diagram of the incident angle of light in this invention (5×5 period); and (d) is an absorption spectrum of the absorber in the 1000nm to 3500nm band under TM and TE waves.

[0017] Figure 2 The results show the effect of only the Ti layer on the absorption performance of the absorber;

[0018] Figure 3 To incorporate the results on the effect of Ge on the absorption performance of the absorber into the existing results;

[0019] Figure 4 The results show the effect of adding Pt to the existing structure on the absorption performance of the absorber.

[0020] Figure 5 The results show the effect of adding Cu to the existing structure on the absorption performance of the absorber.

[0021] Figure 6 The results show the effect of different P values ​​on the absorption performance of the absorber.

[0022] Figure 7 The effect of different h1 values ​​on the absorption performance of the absorber;

[0023] Figure 8 The effect of different h2 values ​​on the absorption performance of the absorber;

[0024] Figure 9 The effect of different h3 values ​​on the absorption performance of the absorber;

[0025] Figure 10 The effect of different h4 values ​​on the absorption performance of the absorber;

[0026] Figure 11 The effect of different values ​​of a on the absorption performance of the absorber;

[0027] Figure 12 The results show the effect of different r values ​​on the absorption performance of the absorber.

[0028] Figure 13 The results show the effect of different b values ​​on the absorption performance of the absorber.

[0029] Figure 14 The results show the effect of different d values ​​on the absorption performance of the absorber. Detailed Implementation

[0030] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0031] like Figure 1 Parts (a) and (b) show an overall schematic diagram and cross-sectional view of an absorber containing an inlay. The absorption structure unit uses SiO2 as a substrate for easy compatibility with semiconductor processes. A titanium (Ti) nanorectangular array is mounted on the SiO2 substrate, with its side length consistent with the array period P and a height of h1. A truncated pyramid made of Ge is mounted on the Ti nanorectangular array, with its base side length consistent with the array period P, its top side length a, and a height of h2. A cylinder made of Pt is embedded at the central axis of the Ge truncated pyramid, its bottom tangent to the contact surface between Ti and Ge, with a radius of r and a height of h2+h3. The bottom surface of a truncated pyramid made of Cu is tangent to the top surface of the Pt cylinder, with a base side length b, a top side length d, and a height of h4. During testing, light is shone vertically downwards along the Z-axis, as shown... Figure 1 The direction of the arrow in part (c).

[0032] like Figure 1 As shown in section (d), a comprehensive analysis and comparison of the absorption rates of TM and TE waves shows that the structure is completely insensitive to polarization in the wavelength range of 1000nm to 3500nm. This is because the Cu, Pt, and Ge material systems are all isotropic materials, and the material structures formed by them have rotational symmetry and polarization independence characteristics. Therefore, the absorption rate curves of TE and TM waves completely coincide, which is a typical isotropic metamaterial perfect absorber.

[0033] Next, we explored the variation of the allowable range of parameter errors in the absorption performance during actual manufacturing. We used the controlled variable method to change each geometric parameter in turn and studied the influence of different geometric parameters on the working performance of the absorber.

[0034] After optimizing the parameters, the optimal parameters were obtained as follows: P=340nm, h1=440nm, h2=210nm, h3=278nm, h4=100nm, a=150nm, b=196nm, d=140nm, and r=35nm. Here, we define the region with an absorbance higher than 90% as the high-efficiency absorption region. The proposed DUHA's high-efficiency absorption range covers from 1000nm to 3400nm, approximately 2400nm.

[0035] Figure 2 , Figure 3 , Figure 4 and Figure 5 The influence of the presence of each layer on the absorption performance of the absorber was demonstrated, based on... Figure 2 It can be seen that the absorption rate is poor when the structure consists only of a Ti substrate. However, after adding Ge truncated pyramids to the Ti substrate, as... Figure 3 The absorption rate curve increases significantly in the range of 1250nm to 3250nm. Figure 4 The results were obtained by embedding Pt cylinders within Ge frustums. The graph shows that the average absorption rate is higher after adding the Pt cylinders than... Figure 3 Finally, by adding Cu frustums to the top surface of the Pt cylinder, an average absorption rate of 98% can be achieved in the range of 1100nm to 3400nm, and an average absorption rate as high as 99% in the range of 2100nm to 3000nm. The highest absorption rate of 99.7% is achieved when the wavelength is around 2500nm.

[0036] To determine the effect of changing the array period P on the absorber's absorptivity, while keeping other simulation parameters constant, the range of P was set from 300 nm to 200 nm, with a simulation step size of 20 nm. The resulting absorptivity curve is shown below. Figure 6 As shown in the figure, the optimal value P=340nm can balance high absorbance and ultra-wideband absorption. When the value of P becomes larger or smaller relative to the optimal parameter, although the absorbance does not change significantly in the range of 2000nm to 3000nm, the absorbance effect is much lower than the optimal parameter in the wavelength range of 1100 to 1500nm. Therefore, P=340nm is selected in the following simulation experiments.

[0037] To determine the effect of varying Ti height on the absorber's absorptivity, other simulation parameters were kept constant, and the range of h1 was set from 400 nm to 480 nm, with a simulation step size of 20 nm. The resulting absorptivity curve is shown below. Figure 7As shown, when the parameter values ​​change relative to the optimal parameters, it is obvious that except for the range of 2000nm-2500nm where the absorbance variation is not significant, the absorbance curves with parameters different from the optimal parameters are much lower than the absorbance curves with the optimal parameters in other bands. Therefore, in the following simulation experiments, h1=440nm is selected.

[0038] To determine the effect of varying Ge truncated pyramid height on the absorber's absorptivity, other simulation parameters were kept constant, and the range of h2 was set from 200 nm to 220 nm, with a simulation step size of 5 nm. The resulting absorptivity curve is shown below. Figure 8 As shown in the figure, the absorbance curve decreases significantly when the parameter is below 210 nm, while the three curves almost completely overlap when the parameter is above 210 nm. Therefore, it can be concluded that variations in h2 within a certain range have little impact on the overall absorbance of the structure. To facilitate subsequent experiments and considering the need to minimize interference between adjacent structures and higher-order diffraction, the overall height of the structure should not be too high; we set h2 = 210 nm.

[0039] To determine the effect of varying Pt cylinder height on the absorber's absorptivity, other simulation parameters were kept constant, and the range of h3 was set from 198 to 358 nm, with a simulation step size of 40 nm. The resulting absorptivity curve is shown below. Figure 9 As shown in the figure, when h3 is 238 nm, the absorbance still remains within 90%, but the fluctuation range increases, the average absorbance decreases, and when h3 decreases to a certain extent, the structural absorbance decreases significantly in the short-wavelength band. When h3 is greater than 278 nm, the overall absorption effect decreases, and the absorption effect in the short-wavelength band is lower than the optimal parameter. To facilitate subsequent experiments and considering the need to reduce interference between adjacent structures and higher-order diffraction, the overall height of the structure should not be too high. Therefore, h3 = 278 nm is chosen for the following simulation experiments.

[0040] To determine the effect of changing the Cu frustum height on the absorber's absorptivity, while keeping other simulation parameters constant, the range of h4 was set from 20 nm to 180 nm, with a simulation step size of 40 nm. The resulting absorptivity curve is shown below. Figure 10 As shown in the figure, when the value of h4 is less than 100 nm, the absorption rate is less than 90% in the range of 1500 nm to 2000 nm; when the value of h4 is greater than 100 nm, the absorption rate decreases significantly in the range of 1000 nm to 1500 nm. Furthermore, to reduce interference between adjacent structures and higher-order diffraction, the overall height of the structure should not be too high. Considering all these factors, h4 = 100 nm will be chosen for the following simulation experiments.

[0041] To determine the effect of varying the surface edge length of the Ge prism on the absorber's absorptivity, while keeping other simulation parameters constant, the range of 'a' was set from 110 nm to 190 nm, with a simulation step size of 20 nm. The resulting absorptivity curve is shown below. Figure 11 As shown in the figure, when the parameter value is lower than the optimal parameter, the absorption rate is far below 90% in the wavelength range of 1000nm to 1500nm; when the parameter value is higher than the optimal parameter, extremely poor absorption rate occurs in the range of 1500nm to 3000nm. Therefore, in the following simulation experiment, a = 150nm is chosen.

[0042] To determine the effect of the Pt cylinder radius on the absorber's absorptivity, keeping other simulation parameters constant, the range of r was set from 110 nm to 190 nm, with a simulation step size of 20 nm. The resulting absorptivity curve is shown below. Figure 12 As shown in the figure, when the parameter is less than the optimal parameter, the absorption rate curve decreases to varying degrees with the change of wavelength, and the absorption bandwidth also narrows to varying degrees. When the parameter is greater than the optimal parameter, the average absorption rate is 97.46%, while the average absorption rate of the optimal parameter is 97.54%. Therefore, in the following simulation experiment, r = 35 nm is selected.

[0043] To determine the effect of the lower surface of the Cu frustum on the absorber's absorptivity, keeping other simulation parameters constant, the range of b was set from 116 nm to 276 nm, with a simulation step size of 40 nm. The resulting absorptivity curve is shown below. Figure 13 As shown in the figure, when the parameters are less than the optimal parameters, the average absorptivity is 95.89% when b=116nm; 96.61% when b=156nm; and 97.50% when b=196nm. When the parameters are greater than the optimal parameters, the absorptivity decreases significantly between 1000 and 2000 nm, completely failing to meet the requirements of the absorber. Therefore, b=196nm was chosen for the following simulation experiments.

[0044] To determine the effect of the upper surface of the Cu prism on the absorber's absorptivity, keeping other simulation parameters constant, the range of d was set from 60 nm to 220 nm, with a simulation step size of 40 nm. The resulting absorptivity curve is shown below. Figure 14 As shown in the figure, when the parameter is less than the optimal parameter, the average absorbance is calculated to be 96.87% when d=60nm, 97.50% when d=100nm, and 97.54% when d is the optimal parameter. When the parameter is greater than the optimal parameter, the absorption curve decreases in the range of 1000nm to 1500nm, and the decrease becomes more significant with increasing parameter. Therefore, d=140nm.

[0045] Taking all factors into consideration, the absorption structure unit P=340nm of the absorber is periodically arranged on the SiO2 substrate as a titanium (Ti) nanorectangular array, with its side length consistent with the array period P and a height h1=440nm. On the Ti nanorectangular array are truncated pyramids made of Ge, with the bottom side length consistent with the array period P, the top side length a=150nm, and a height h2=210nm. A Pt cylinder is embedded at the central axis of the Ge truncated pyramid, its bottom tangent to the Ti and Ge interface, with a radius r=35nm and a height h2+h3=488nm. A Cu truncated pyramid has its bottom tangent to the bottom of the Pt cylinder, with a bottom side length b=196nm, a top side length d=140nm, and a height h4=100nm. The incident wavelength is [wavelength value missing]. Here, we define the region with an absorptivity higher than 90% as the high-efficiency absorption region. The proposed DUHA has an efficient absorption range from 1000 nm to 3400 nm, approximately 2400 nm.

Claims

1. An ultrawideband absorber, comprising a substrate layer formed of a bottom SiO2 layer and a transition layer Ti, and absorber units periodically arranged on the surface of the transition layer Ti, characterized in that, The absorption unit includes a frustum-shaped dielectric layer, an inlay passing through the dielectric layer along its axial direction, and a metal layer disposed on the top surface of the inlay; the bottom edge length of the dielectric layer is not greater than the period P of the absorption unit; the bottom surface of the inlay is tangent to the bottom surface of the dielectric layer, the outer diameter r of the circumscribed circle of the inlay is smaller than the top edge length a of the dielectric layer, and the top surface of the inlay protrudes h3 relative to the top surface of the dielectric layer; the metal layer is frustum-shaped, the bottom edge length b of the metal layer is smaller than the bottom edge length of the dielectric layer, and larger than the outer diameter r of the inlay.

2. The ultra-wideband absorber according to claim 1, characterized in that, The dielectric layer is Ge, and the inlay material is Pt.

3. The ultra-wideband absorber according to claim 1, characterized in that, The metal layer is made of Cu.

4. The ultra-wideband absorber according to any one of claims 1 to 3, characterized in that, The dielectric layer and the metal layer are regular square frustums, the inlay is a cylinder, and the base side length of the dielectric layer is equal to P.

5. The ultra-wideband absorber according to claim 4, characterized in that, The top surface of the inlay protrudes h3 = 215 ~ 315 nm relative to the top surface of the dielectric layer.

6. The ultra-wideband absorber according to claim 5, characterized in that, The transition layer Ti has a height h1 = 430 ~ 450 nm and a period P = 330 ~ 350 nm. The dielectric layer h2 ≥ 208 nm and a = 100 ~ 160 nm. The inlay a > r ≥ 20 nm. The metal layer h4 ≥ 30 nm and r < d < b ≤ 230 nm.

7. The ultra-wideband absorber according to claim 4, characterized in that, Period P = 335~350nm, a = 140~160nm, inlay h3 = 248~308nm, r = 25~60nm, metal layer h4 ≥ 70nm, b = 160~220nm, d = 65~200nm.

8. The ultra-wideband absorber according to claim 4, characterized in that, The dielectric layer has a wavelength of h2 = 208~225 nm and a wavelength of h4 = 80~185 nm.

9. The ultra-wideband absorber according to claim 4, characterized in that, The transition layer Ti has a height h1 = 435~445 nm and a period P = 335~345 nm. The dielectric layer a = 145~155 nm. The inlay h3 = 268~303 nm and r = 30~50 nm. The metal layer h4 = 85~120 nm, b = 170~210 nm, and d = 95~150 nm.

10. The ultra-wideband absorber according to claim 4, characterized in that, Period P = 340 ± 3 nm, transition layer Ti height h1 = 440 ± 2 nm, dielectric layer h2 = 210 ± 2 nm, a = 150 ± 3 nm, inlay r = 35 ± 3 nm, h3 = 278 ± 5 nm, metal layer b = 196 ± 3 nm, d = 140 ± 3 nm, h4 = 100 ± 2 nm.

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