CN110873909A - An ultra-broadband polarization-insensitive absorber in all ultraviolet-mid-infrared bands - Google Patents

Abstract

The invention provides an ultra-broadband polarization-insensitive absorber in the full ultraviolet-mid-infrared band, comprising a substrate and a metamaterial unit structure arranged on the substrate in a periodic arrangement, and the metamaterial unit structure includes sequentially arranged metamaterial unit structures. The multi-layer dielectric/metal film and the single-layer dielectric film/metal also include an outer dielectric cylindrical ring arranged on the outer layer of the multi-layer dielectric/metal film, and the height of the outer dielectric cylindrical ring is smaller than that of the multi-layer dielectric cylindrical ring. Height of layer dielectric/metal film. The absorber of the invention has a frequency band of 200-2000 nm, covers all ultraviolet, visible light, near-infrared and mid-infrared wavebands, the average absorption rate is as high as 94.3%, the absorption rate is as high as 99.89%, and it is insensitive to polarized light and low in cost. , can be used for solar energy harvesting and UV protection.

Description

An ultra-broadband polarization-insensitive absorber in all ultraviolet-mid-infrared bands

technical field

The invention relates to the technical field of metamaterials and electromagnetic functions, in particular to an ultra-broadband polarization-insensitive absorber in the full ultraviolet-mid-infrared band.

Background technique

The global energy crisis and air pollution problems have become increasingly prominent. As an ideal clean energy, solar energy has attracted the attention of many countries. The energy spectrum of sunlight radiated to the ground is mainly composed of three bands: ultraviolet (9%), visible light (46%) and infrared (45%). Traditional solar photovoltaic cells can only absorb energy in the visible light band and the absorption rate is not high, so that the energy in the solar spectrum is not effectively absorbed. At the same time, photovoltaic solar cells are easily affected by weather conditions such as four seasons, cloudy day and night, especially in dark weather and night, traditional photovoltaic cells almost lose their function. Therefore, there is a need for a high-absorption, broadband solar energy collection technology that can absorb light in the ultraviolet to infrared wavelengths with high efficiency.

At present, in order to achieve broadband absorption, relevant technical personnel have done some research, and most optical perfect absorbers need relatively complex structures. With the rapid development of micro- and nano-scale processing technology, technicians have proposed and fabricated a variety of metamaterial structures to achieve wide-spectrum absorption, and relevant researchers in the field have done a lot of research on their properties. However, the existing metamaterial structures mainly have three problems: 1. The absorption rate of simple metamaterial structures is low, and they are sensitive to oblique incident light, so they cannot achieve broadband spectral absorption; 2. In order to ensure high absorption rate, Metamaterial structures require sophisticated structural design, which increases the difficulty of process realization, high fabrication costs, and limits the promotion of absorbers; 3. Most metamaterial structures use high-conductivity metal materials such as precious metals gold/silver, which is a serious problem. The application of other materials in the absorber is restricted, which increases the production cost and is not suitable for promotion of processing and production.

SUMMARY OF THE INVENTION

The present invention aims to solve the above problems, and provides an ultra-broadband polarization insensitive absorber with high absorption rate, wider absorption frequency band covered, and better incident angle insensitivity in the full ultraviolet-mid-infrared wavelength band.

For achieving the above object, the present invention provides the following scheme:

An ultra-broadband polarization-insensitive absorber in the full ultraviolet-mid-infrared band, comprising a substrate and a metamaterial unit structure arranged on the substrate in a periodic arrangement, the metamaterial unit structure comprising sequentially arranged multilayer media/ A metal film and a single-layer dielectric film/metal, further comprising an outer dielectric cylindrical ring disposed on the outer layer of the multilayer dielectric/metal film, and the height of the outer dielectric cylindrical ring is smaller than that of the multilayer dielectric/metal height of the membrane.

Preferably, the material of the substrate is iron, aluminum or copper.

Preferably, the thickness of the substrate is 180-220 mm.

Preferably, the multi-layer dielectric/metal film and the single-layer dielectric film/metal have a cross-shaped structure.

Preferably, the multilayer dielectric/metal films are alternately arranged dielectric strips and metal films, and the thickness of the dielectric strips is greater than the thickness of the metal films;

Preferably, the single-layer dielectric film/metal is a dielectric film and a metal strip arranged in sequence, and the thickness of the metal strip is greater than the thickness of the dielectric film.

Preferably, the arm length of the multilayer dielectric/metal film is 80-120 nm, and the arm width is 55-100 nm; the thickness of the dielectric strip is 140-150 nm, and the thickness of the metal film is 10-15 nm;

Preferably, the arm length of the dielectric film is 80-120 nm, the arm width is 55-100 nm, and the thickness is 10-15 nm; the arm length of the metal strip is 26-36 nm, the arm width is 22-32 nm, and the thickness is 40 nm ~60nm.

Preferably, the material of the dielectric strip is silicon, silicon dioxide, silicon nitride, aluminum oxide or magnesium fluoride, and the material of the two metal films adjacent to the dielectric strip is different from that of gold or silver, respectively. , and iron, aluminium or copper;

Preferably, the material of the dielectric film is silicon, silicon dioxide, silicon nitride, aluminum oxide or magnesium fluoride, and the material of the metal strip is iron, aluminum or copper.

Preferably, the material of the outer dielectric cylindrical ring is silicon, silicon dioxide, silicon nitride, aluminum oxide or magnesium fluoride, the inner radius is 110-170 nm, the outer radius is 130-190 nm, and the height is 540-705 nm .

Preferably, the array period of the metamaterial unit structure is 260-380 nm.

The invention provides an ultra-broadband polarization-insensitive absorber in the full ultraviolet-mid-infrared band, which is used in solar energy capture and ultraviolet protection.

The present invention can achieve the following beneficial effects:

1. The absorber of the present invention is symmetrical about the xoz plane and the yoz plane as a whole, so that the absorber is not sensitive to the polarization of incident light; the multi-layer dielectric/metal film structure is adopted, and the slow wave effect generated by the multi-layer dielectric/metal structure is used to widen the The absorption bandwidth of the absorber; the top layer adopts a single-layer dielectric film/metal structure, which excites localized surface plasmon (LSP) modes in the ultraviolet to visible region, thereby enhancing the absorption rate.

2. The outer dielectric cylindrical ring provided by the present invention has a height lower than that of the multi-layer dielectric/metal film structure, and is easily coupled with the multi-layer dielectric/metal film structure, and at the same time excites surface plasmon resonance (SPR), The absorption bandwidth of the absorber is increased.

3. The present invention adopts the multi-layer dielectric/metal film structure of the cross-shaped structure, which is easy to excite the electric dipole resonance and the magnetic dipole resonance, so that the electric field strength and magnetic field strength increase, and more electromagnetic waves can be captured by the structure. , thereby increasing the absorption rate.

4. The frequency band of the absorber of the present invention is 200-2000 nm, covering all ultraviolet, visible, near-infrared and mid-infrared bands, the average absorption rate is as high as 94.3%, and the maximum absorption rate is as high as 99.89%.

5. The absorber provided by the present invention has excellent absorption performance, simple structure, low manufacturing cost, strong practicability, high flexibility, and is favorable for popularization and application.

Description of drawings

1 is a schematic structural diagram of an ultra-broadband polarization-insensitive absorber in the full ultraviolet-mid-infrared band of a preferred embodiment of the present invention;

Fig. 2 is the schematic diagram of the metamaterial unit structure of the preferred embodiment of the present invention;

3 is a top view and a side view of a metamaterial unit structure according to a preferred embodiment of the present invention;

4 is a top view of a silicon cylindrical ring according to a preferred embodiment of the present invention;

5 is a schematic structural diagram of a multi-layer dielectric/metal film and a single-layer dielectric film/metal according to a preferred embodiment of the present invention;

Fig. 6 is the ultra-broadband absorber reflectivity simulation diagram of the ultra-broadband polarization-insensitive absorber of the full ultraviolet-mid-infrared waveband of the preferred embodiment of the present invention;

7 is a simulation diagram of an ultra-broadband absorber absorption rate of an ultra-broadband polarization-insensitive absorber in the full ultraviolet-mid-infrared band according to a preferred embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. . Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Example 1:

As shown in FIGS. 1 to 5 , an ultra-broadband polarization-insensitive absorber in the full ultraviolet-mid-infrared band includes a substrate 1 and a metamaterial unit structure arranged on the substrate 1 and arranged periodically. Among them, the metamaterial unit structure includes a multi-layer dielectric/metal film 2 and a single-layer dielectric film/metal 3 arranged in sequence, and also includes an outer dielectric cylindrical ring 4 arranged on the outer layer of the multi-layer dielectric/metal film 2. The height of the multilayer dielectric cylindrical ring 4 is smaller than the height of the multilayer dielectric/metal film 2 . Among them, the material of the substrate 1 is metal iron, and the substrate 1 is coated with a sufficiently thick metal iron film, so that the transmittance becomes 0, and the incident wave will enter the absorber to the maximum extent and be absorbed and lost, so the thickness of the substrate 1 is designed to be Hd =200mm. The multi-layer dielectric/metal film 2 is composed of alternately arranged dielectric strips 21 and metal films 22 in a cross-shaped structure, and there are six layers of dielectric strips 21 and metal films 22 in total. Among them, the material of the dielectric strip 21 is silicon, and the material of the metal film 22 is gold and iron alternately arranged, that is, the structure of the multilayer dielectric/metal film 2 is silicon strip, gold film, silicon strip, iron film, Silicon strip, gold film, silicon strip, iron film, silicon strip, gold film, silicon strip, iron film. Dielectric strip 21 and metal film 22 have the same arm length and arm width, arm length L1=94.5nm, arm width W1=82nm, dielectric strip 21 thickness H1=145nm, metal film 2 thickness H2=10nm. The invention adopts the multi-layer dielectric/metal film structure of the cross-shaped structure, which is easy to excite the electric dipole resonance and the magnetic dipole resonance, so that the electric field strength and the magnetic field strength are increased, and more electromagnetic waves can be captured by the structure, thereby The absorption rate is increased; at the same time, the slow wave effect produced by the multilayer dielectric/metal structure broadens the absorption bandwidth of the absorber. The single-layer dielectric film/metal 3 is composed of a cross-shaped dielectric film 31 and metal strips 32 arranged in sequence from bottom to top. The dielectric film 31 is made of silicon, and the metal strip 32 is made of iron. The arm length and arm width of the dielectric film 31 are equal to those of the dielectric strip 21 and the metal film 22, and the thickness is thinner as H3=10nm; the arm length and arm width of the metal strip 32 are smaller, respectively: L2=31.5nm, W2= 27nm, thickness H4=50nm. Because the dielectric film 31 is thinner and the arm length and width of the metal strip 32 are smaller, it is easier to excite the localized surface plasmon (LSP) mode in the ultraviolet to visible light region, thereby enhancing the structural absorptivity. The material of the outer dielectric cylindrical ring 4 is silicon, the inner radius of the cylindrical ring is r=142nm, the outer radius is R=162nm, and the height is Hr=610nm. The multi-layered cruciform structure of the inner layer produces the coupling effect and simultaneously excites surface plasmon resonance (SPR), which increases the bandwidth of the absorber. The array period of the metamaterial unit structure is 324 nm, the dimension length of the substrate 1 of the unit structure is L=324 nm, and the width is W=324 nm.

The absorber structure in this embodiment is simulated and calculated by the software FDTD Solutions to the absorption rate of the absorber. In the case of vertical incidence, its reflection spectrum is shown in Figure 6, and its absorption spectrum is shown in Figure 7. The formula for calculating the absorption rate is: A=1-R-T, where R is the reflectivity and T is the transmittance. By reasonably optimizing the structural parameters and materials of the absorber, the impedance of the absorber at the set specific frequency is matched with the impedance of the free space (that is, the effective permittivity of the absorber is equal to the effective permeability). At this time, since the electromagnetic wave completely enters the absorber and is hardly reflected, the reflectivity R is close to zero, as shown in Figure 6; secondly, the metal reflective layer makes the electromagnetic wave impermeable to the material, so that the transmittance T is also zero; in this way Electromagnetic waves are completely confined inside the device, resulting in nearly 100% perfect absorption. The simulation results show that the design shows good characteristics. As shown in Figure 7, the average absorption rate of the absorber is 94.3%, the frequency band width reaches 1800nm (the wavelength range is 200nm-2000nm), and the maximum absorption rate is as high as 99.89%.

Example 2:

The structure of the ultra-broadband polarization-insensitive absorber in the full ultraviolet-mid-infrared band of this embodiment is similar to that of the first embodiment, the difference is that the thickness of the substrate 1 is Hd=210mm; the multilayer dielectric/metal film 2 has a total of eight dielectric strips 21 and metal film 22, that is, the structure of the multilayer dielectric/metal film 2 is silicon strip, gold film, silicon strip, iron film, silicon strip, gold film, silicon strip, iron film, silicon strip, gold film from bottom to top film, silicon strip, iron film, silicon strip, gold film, silicon strip, iron film; arm length L1=100nm, arm width W1=70nm of dielectric strip 21 and metal film 22, thickness H1=150nm of dielectric strip 21, metal The thickness of the film 2 is H2=15 nm. The arm length and arm width of the dielectric film 31 are equal to those of the dielectric strip 21 and the metal film 22, and the thickness is thinner as H3=15nm; the arm length and arm width of the metal strip 32 are smaller, respectively: L2=35nm, W2=30nm, Thickness H4=55nm. The inner radius of the outer dielectric cylindrical ring 4 is r=165 nm, the outer radius R=185 nm, and the height Hr=700 nm. The array period of the metamaterial unit structure is 370 nm, the dimension length of the substrate 1 of the unit structure is L=370 nm, and the width is W=370 nm.

The absorber structure in this embodiment is simulated and calculated by the software FDTD Solutions to the absorber absorption rate. In the case of vertical incidence, the average absorption rate of the absorber is 92.3%, and the frequency band width reaches 1800nm (the wavelength range is 200nm～2000nm), The maximum absorption rate is as high as 99.32%.

Example 3:

The structure of the ultra-broadband polarization-insensitive absorber in the full ultraviolet-mid-infrared band of this embodiment is similar to that of Embodiment 1, except that the material of the substrate 1 is aluminum, and the thickness is Hd=180mm; the multilayer dielectric/metal film 2 has a common Four layers, wherein the material of the dielectric strip 21 is silicon dioxide, and the material of the metal film 22 is silver and aluminum alternately arranged, that is, the structure of the multi-layer dielectric/metal film 2 is silicon dioxide strip and silver film from bottom to top. , silicon dioxide strip, aluminum film, silicon dioxide strip, silver film, silicon dioxide strip, aluminum film; the arm length L1=85nm of the dielectric strip 21 and the metal film 22, the arm width W1=60nm, the thickness of the dielectric strip 21 H1=140 nm, and the thickness of the metal film 2 is H2=12 nm. In the single-layer dielectric film/metal 3, the material of the dielectric film 31 is silicon dioxide, and the material of the metal strip 32 is aluminum; the arm length and width of the dielectric film 31 are equal to those of the dielectric strip 21 and the metal film 22, and the thickness is thinner is H3=12nm; the arm length and arm width of the metal strip 32 are smaller respectively: L2=30nm, W2=23nm, and thickness H4=40nm. The inner radius of the outer dielectric cylindrical ring 4 is r=110 nm, the outer radius R=135 nm, and the height Hr=540 nm. The array period of the metamaterial unit structure is 260 nm, the dimension length of the substrate 1 of the unit structure is L=260 nm, and the width is W=260 nm.

The absorber structure in this embodiment is simulated and calculated by the software FDTD Solutions to the absorber absorption rate. In the case of vertical incidence, the average absorption rate of the absorber is 90.5%, and the frequency band width reaches 1800nm (the wavelength range is 200nm～2000nm), The maximum absorption rate is as high as 99.22%.

Example 4:

The ultra-broadband polarization-insensitive absorber in the full ultraviolet-mid-infrared waveband of this embodiment is similar in structure to that of Embodiment 1, except that the material of the substrate 1 is copper, and the thickness Hd=190mm; , the dielectric strip 21 is made of magnesium fluoride, and the metal film 22 is made of gold and copper alternately, that is, the structure of the multi-layer dielectric/metal film 2 is magnesium fluoride strips, gold films, and magnesium fluoride from bottom to top. strip, copper film, magnesium fluoride strip, gold film, magnesium fluoride strip, copper film, magnesium fluoride strip, gold film, magnesium fluoride strip, copper film; arm length L1=105nm of dielectric strip 21 and metal film 22 , the arm width W1=88nm, the thickness of the dielectric strip 21 is H1=142nm, and the thickness of the metal film 2 is H2=13nm. In the single-layer dielectric film/metal 3, the material of the dielectric film 31 is magnesium fluoride, and the material of the metal strip 32 is copper; the arm length and width of the dielectric film 31 are equal to those of the dielectric strip 21 and the metal film 22, and the thickness is thinner is H3=13nm; the arm length and arm width of the metal strip 32 are smaller respectively: L2=28.5nm, W2=25nm, and thickness H4=45nm. The inner radius of the outer dielectric cylindrical ring 4 is r=128 nm, the outer radius R=150 nm, and the height Hr=650 nm. The array period of the metamaterial unit structure is 300 nm, the dimension length of the substrate 1 of the unit structure is L=300 nm, and the width is W=300 nm.

The absorber structure in this embodiment is simulated and calculated by the software FDTD Solutions to the absorber absorption rate. In the case of vertical incidence, the average absorption rate of the absorber is 92.4%, and the frequency bandwidth reaches 1800nm (the wavelength range is 200nm～2000nm), The maximum absorption rate is as high as 99.38%.

Example 5:

The structure of the ultra-broadband polarization-insensitive absorber in the full ultraviolet-mid-infrared band of this embodiment is similar to that of Embodiment 1, except that the thickness of the substrate 1 is Hd=220mm; the multilayer dielectric/metal film 2 has four layers in total, wherein , the dielectric strip 21 is made of silicon nitride, and the metal film 22 is made of gold and iron alternately, that is, the structure of the multilayer dielectric/metal film 2 is silicon strips, gold films, silicon strips, and iron films from bottom to top. , silicon strip, gold film, silicon strip, iron film; arm length L1=115.5nm of dielectric strip 21 and metal film 22, arm width W1=95nm, thickness H1=148nm of dielectric strip 21, thickness H2=14nm of metal film 2 . In the single-layer dielectric film/metal 3, the material of the dielectric film 31 is silicon nitride, the arm length and width of the dielectric film 31 are equal to those of the dielectric strip 21 and the metal film 22, and the thickness is thinner as H3=14nm; the metal strip 32 The smaller arm length and arm width are: L2=26nm, W2=22nm, and thickness H4=60nm. The inner radius r=150nm, the outer radius R=174nm, and the height Hr=560nm of the outer dielectric cylindrical ring 4 . The array period of the metamaterial unit structure is 348 nm, the dimension length of the substrate 1 of the unit structure is L=348 nm, and the width is W=348 nm.

The absorber structure in this embodiment is simulated and calculated by the software FDTD Solutions to the absorber absorption rate. In the case of vertical incidence, the average absorption rate of the absorber is 91.8%, and the frequency bandwidth reaches 1800nm (the wavelength range is 200nm～2000nm), The maximum absorption rate is as high as 99.45%.

Finally, it should be noted that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, the The technical solutions described in the foregoing embodiments can be modified, or some technical features thereof can be equivalently replaced, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included. within the protection scope of the present invention.

Claims (10)

1. The ultra-wideband polarization insensitive absorber of the full ultraviolet-mid-infrared band is characterized by comprising a substrate (1) and a metamaterial unit structure which is arranged on the substrate (1) in a periodic arrangement mode, wherein the metamaterial unit structure comprises a plurality of layers of media/metal films (2) and a single layer of media/metal (3) which are sequentially arranged, the ultra-wideband polarization insensitive absorber further comprises an outer layer dielectric cylindrical ring (4) which is arranged on the outer layer of the plurality of layers of media/metal films (2), and the height of the outer layer dielectric cylindrical ring (4) is smaller than that of the plurality of layers of media/metal films (2).

2. An ultra-wideband polarization insensitive absorber for the full ultraviolet-mid infrared band, as claimed in claim 1, characterized in that the material of the substrate (1) is iron, aluminum or copper.

3. The ultra-wideband polarization insensitive absorber of the all ultraviolet-mid infrared band as claimed in claim 2, characterized in that the thickness of the substrate (1) is 180 to 220 mm.

4. The ultra-wideband polarization insensitive absorber of the all ultraviolet-mid infrared band of claim 1, wherein the multi-layer dielectric/metal film (2) and the single-layer dielectric film/metal (3) are cross-shaped structures.

5. The ultra-wideband polarization insensitive absorber for the all ultraviolet-mid infrared band as claimed in claim 4, wherein the multi-layer dielectric/metal film (2) is an alternating arrangement of dielectric strips (21) and metal films (22), the thickness of the dielectric strips (21) being greater than the thickness of the metal films (22);

and/or the single-layer dielectric film/metal (3) is a dielectric film (31) and a metal strip (32) which are sequentially arranged, and the thickness of the metal strip (32) is larger than that of the dielectric film (31).

6. The ultra-wideband polarization insensitive absorber of the all ultraviolet-mid infrared band of claim 5, wherein the multi-layer dielectric/metal film (2) has an arm length of 80 to 120nm and an arm width of 55 to 100 nm; the thickness of the dielectric strip (21) is 140-150 nm, and the thickness of the metal film (22) is 10-15 nm;

and/or the dielectric film (31) has an arm length of 80-120 nm, an arm width of 55-100 nm and a thickness of 10-15 nm; the arm length of the metal strip (32) is 26-36 nm, the arm width is 22-32 nm, and the thickness is 40-60 nm.

7. The ultra-wideband polarization insensitive absorber for the all ultraviolet-mid infrared band as claimed in claim 5, characterized in that the material of the dielectric strip (21) is silicon, silicon dioxide, silicon nitride, aluminum oxide or magnesium fluoride, the two layers of the metal film (22) adjacent to the dielectric strip (21) are of different materials, respectively gold or silver, and iron, aluminum or copper;

and/or the dielectric film (31) is made of silicon, silicon dioxide, silicon nitride, aluminum oxide or magnesium fluoride, and the metal strip (32) is made of iron, aluminum or copper.

8. The ultra-wideband polarization insensitive absorber of the full ultraviolet-mid-infrared band as claimed in claim 1, wherein the outer layer dielectric cylindrical ring (4) is made of silicon, silicon dioxide, silicon nitride, aluminum oxide or magnesium fluoride, the inner radius is 110 to 170nm, the outer radius is 130 to 190nm, and the height is 540 to 705 nm.

9. The ultra-wideband polarization insensitive absorber for the full ultraviolet-mid infrared band of claim 1, wherein the array period of the metamaterial unit structure is 260 to 380 nm.

10. An ultra-wideband polarization insensitive absorber for the all ultraviolet-mid infrared band, as claimed in any one of claims 1 to 9, for use in solar capture and ultraviolet protection.

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