A Polarization-Controlled Coherent Perfect Absorber Based on Multilayer Metamaterials

Abstract

The present invention provides a polarization-controlled coherent perfect absorber based on multi-layer metamaterials, which includes two layers of metal asymmetric split ring resonators and a dielectric layer between the two layers of asymmetric split ring resonators. The two layers of metal asymmetric split ring resonators with a periodic structure are composed of an inverted V-shaped metal wire and a U-shaped metal wire. The two layers of metal asymmetric split ring resonator structures are the same and are symmetrically arranged along the dielectric layer. Signal light and control light with the same polarization angle, amplitude, and frequency propagate towards each other along a direction perpendicular to the metamaterial layer. The operation of the present invention is simple. By adjusting the polarization directions of the control light and the signal light, the phase of the control light, the structure, size parameters, and material properties of the metamaterials, the absorption magnitude of light with a specific frequency can be controlled. The present invention also has the advantages of simple structure, convenient operation, and high efficiency.

Description

Technical Field

[0001] The present invention relates to a polarization-controlled coherent perfect absorber based on multi-layer metamaterials, belonging to the fields of metamaterials and absorbers. Background Art

[0002] With the continuous development of contemporary science and technology, wave absorption technology plays an important role in many applications, such as photodetectors, electromagnetic stealth, bolometers, and optical switches. Due to the perfect absorption characteristics of metamaterials having advantages incomparable to those of traditional electromagnetic materials, researchers have devoted a great deal of effort to metamaterial perfect absorbers.

[0003] Metamaterials are a class of artificial composite materials with periodic unit structures possessing extraordinary electromagnetic properties. By artificially adjusting the geometric parameters of the unit structures, electromagnetic functions far exceeding those of natural materials can be achieved. The electromagnetic response of metamaterials is determined not only by the materials they are composed of, but also by the microstructure and arrangement of their resonant units. In 2008, N.I. Landy et al. proposed a metamaterial perfect absorber, whose structure consists of two metamaterial resonators, which are respectively coupled to the electric field and the magnetic field to absorb all incident radiation within a single unit layer. Different from traditional absorbers, the metamaterial is composed only of metal elements, and the peak absorption rate is greater than 88% at 11.5 GHz. Since then, researchers have designed perfect absorbers with various different structures, and the research frequency band has been extended from the microwave band to the THz band, the near-infrared band, and the visible light band. Currently, more and more researchers are focusing their research on multi-band or broadband metamaterial absorbers. In 2010, Tao et al. demonstrated a dual-band metamaterial absorber. The dual-band absorber consists of a dual-band electric field-coupled resonator and a metal ground plane, separated by a dielectric spacer. The fine-tuning of the two absorption resonances is achieved by separately adjusting the geometry of each ELC resonator. Experiments showed two different absorption peaks of 0.85 at 1.4 terahertz band and 0.94 at 3.0 terahertz band. Ying et al. reported a three-band ideal metamaterial absorber based on a copper-dielectric-copper three-layer nanostructure. The top metal thin film structure consists of a ring and four pairs of capacitor plates, with a frequency selection effect, allowing the absorber to resonate in the near-infrared range. Theoretical studies showed that the absorptions of the three absorption peaks (872.54 nm, 1008.69 nm, and 1138.62 nm) were 87.1%, 99.9%, and 99.6% respectively. The average absorption was 95.53%, including two perfect absorption peaks. Chowdhary et al. reported a super-wideband perfect metamaterial absorber, including a two-dimensional array of a semi-ellipsoidal metal-dielectric multi-layer structure. Theoretically proven, at normal incidence, within the spectral range of 300 to 4500 nm, we believe an unprecedented average absorbance of approximately 99% was achieved using 20 pairs of molybdenum-germanium metal-dielectric layers, with tungsten as the ground metal placed on a silicon substrate. Nie et al. studied the multi-band coherent perfect absorption of a simple double-layer asymmetric split-ring metamaterial. When the phase difference between the signal wave and the control wave was 0 degrees, the absorption rate reached 98% at 5.37 GHz; when the phase difference between the two waves was 180 degrees, the absorption rates at 4.95 GHz and 5.84 GHz were 97.53% and 90.50% respectively.

[0004] The above-mentioned metamaterial-based perfect absorber has a fixed operating frequency band and cannot dynamically adjust its operating frequency band. The polarization-controlled coherent perfect absorber based on multi-layered metamaterials is due to the coupling effect in the multi-layered metamaterials, which leads to mode hybridization, thus generating multiple electric resonances and magnetic resonances. By adjusting the polarization and phase of the incident light, the operating band and absorption intensity can be dynamically regulated. Compared with previous works, the absorber designed by us can change the operating frequency of the absorber by adjusting the polarization. The polarization-controlled coherent perfect absorber is simple in structure, convenient to operate, high in efficiency compared with traditional absorbers, and can dynamically adjust the absorption rate and operating frequency, thus having great potential application value. Summary of the Invention

[0005] The object of the present invention is to utilize the resonance characteristics of metamaterials and the coupling effect of multi-layered metamaterials to design a polarization-controlled coherent perfect absorber based on multi-layered metamaterials. This kind of metamaterial absorber can achieve selective absorption of light with different frequencies and polarizations in the optical band. The polarization-controlled coherent perfect absorber based on multi-layered metamaterials is composed of the unit structures of multi-layered metamaterials, and has the characteristics of simple structure, convenient operation and high efficiency, and can dynamically adjust the absorption rate and operating frequency, thus having great potential application value.

[0006] The object of the present invention is achieved as follows:

[0007] The polarization-controlled coherent perfect absorber based on multi-layered metamaterials is composed of two layers of metamaterials and the dielectric layer between the two layers of ring metamaterials. The two layers of metamaterials have the same structure and are symmetrically arranged on both sides of the dielectric layer. Each metamaterial is an asymmetric split ring resonator structure in a periodic array. The asymmetric split ring resonator structure is composed of an inverted V-shaped metal wire and a U-shaped metal wire. Signal light and control light with the same polarization angle, amplitude and frequency propagate in opposite directions along the direction perpendicular to the metamaterial layer.

[0008] The present invention also includes the following structural features:

[0009] The material of the asymmetric split ring resonator structure is gold, and its dielectric constant is derived from the Drude model.

[0010] The thickness of the asymmetric split ring resonator structure is on the order of nanometers.

[0011] The material of the dielectric layer is silica material or glass, and its thickness is on the order of hundreds of nanometers.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0013] The present invention is simple in structure and convenient to manufacture, and can be processed by using the mature focused ion beam (FIB) milling technology. Traditional wave-absorbing materials require complex processes and are expensive.

[0014] The present invention has the characteristics of selective coherent perfect absorption. This structure can achieve selective perfect absorption of light at specific frequencies within the optical band, and by adjusting the polarization states of the signal light and the control light, the light absorption rate at specific frequencies can be controlled. It has broad development and application prospects in the fields of photodetectors, thermal emitters, photovoltaics, optical communications, etc.

[0015] The operation of the present invention is simple. By adjusting the polarization directions of the control light and the signal light, the phase of the control light, the structure, size parameters, and material properties of the metamaterial, the absorption magnitude of light at specific frequencies can be controlled.

[0016] The present invention also has the advantages of being portable, lightweight, and easy to integrate. Compared with traditional wave-absorbing materials, the present invention has a small thickness, is lightweight, and is easy to conform.

[0017] Compared with the patent of a polarization-controllable multi-band metamaterial coherent absorption device by Shi Jinhui of Harbin Engineering University, the operating frequency band of the device is in the optical band, and the structure of the asymmetric split ring resonator is different. Description of the Drawings

[0018] Figure 1 is a schematic diagram of the basic structural unit of a polarization-controlled coherent perfect absorber based on multi-layer metamaterials.

[0019] Figure 2 is a view of the basic structural unit of a polarization-controlled coherent perfect absorber based on multi-layer metamaterials.

[0020] Figure 3 、 Figure 4 is the working principle diagram of a polarization-controlled coherent perfect absorber based on multi-layer metamaterials.

[0021] Figure 5 is the simulation result of X polarization (solid line) and Y polarization (dashed line) when the phase difference between the control light and the signal light is 0 degrees during the operation of a polarization-controlled coherent perfect absorber based on multi-layer metamaterials.

[0022] Figure 6 is the simulation result of X polarization (solid line) and Y polarization (dashed line) when the phase difference between the control light and the signal light is 180 degrees during the operation of a polarization-controlled coherent perfect absorber based on multi-layer metamaterials.

[0023] In the figure: 1. Dielectric layer, 2. Metal wire, 3. Metal wire, 4. Signal light, 5. Control light, 6. Signal light, 7. Control light Detailed Embodiments

[0024] The present invention will be further described below in conjunction with specific embodiments. The present invention will be further described in detail below in conjunction with the drawings and specific examples.

[0025] Combined with Figures 1 to 6 , the present invention adopts a multi-layer asymmetric split-ring metamaterial, and realizes polarization-controlled coherent absorption of light in multiple frequency bands in the optical band. The polarization-controlled coherent perfect absorber based on the multi-layer metamaterial is composed of two layers of metal asymmetric split rings and a dielectric layer between the two layers of asymmetric split rings. The two layers of metal asymmetric split rings are composed of an inverted V-shaped metal wire and a U-shaped metal wire. The two layers of metal asymmetric split ring structures are the same and symmetrically arranged along the dielectric layer. Signal light and control light with the same polarization angle, amplitude and frequency propagate towards each other along the direction perpendicular to the metamaterial layer. Polarization-controlled coherent absorption is achieved by changing the polarization angles and phase differences of the signal light and the control light.

[0026] The thickness of the asymmetric split-ring structure is on the order of nanometers, and the material used for the unit structure is a noble metal material; the material of the unit structure is gold.

[0027] The dielectric layer is made of silica material or glass, and the thickness is on the order of hundreds of nanometers.

[0028] The coherent perfect absorption is achieved by adjusting the phase of the control light to adjust the absorption intensity at a specific frequency, and the phase of the control light source is from 0 to 2π.

[0029] The metamaterial absorber is sensitive to the polarization direction of the incident wave. By switching the polarization direction, the switching of the working frequency and the change of the absorption efficiency can be realized.

[0030] The polarization-controlled coherent perfect absorber of the multi-layer metamaterial has its working band in the optical band.

[0031] The polarization-controlled coherent perfect absorption is achieved by the interaction between the signal light and the control light in the metamaterial and by adjusting the polarization angles of the two beams of light. The two beams of light propagate towards each other along the direction perpendicular to the metamaterial. By adjusting the phase of the control light source, the phase difference between the control light source and the signal light source can be changed, so that the interaction between the metamaterial and the light in a specific band can be suppressed or enhanced, and multi-band polarization-controlled coherent perfect absorption can be realized. Examples show that when the phase difference is 0 degrees, when the polarization state is switched from X to Y, the working frequency of coherent absorption is switched from 357 THz to about 326 THz. When the phase difference is 180 degrees, when the polarization state is switched from X to Y, the working frequencies of coherent absorption are switched from 158 and 487 THz to about 254 and 405 THz.

[0032] The technical solution adopted by the present invention is a polarization-controlled coherent perfect absorber based on a multi-layer metamaterial, which consists of a multi-layer metamaterial structure. A signal light beam and a control light beam are incident perpendicularly onto the metamaterial from both sides of the metamaterial at a certain wavelength. The two light beams have the same polarization angle, amplitude, and frequency. By adjusting the polarization angle and phase difference of the signal light and the control light, and modulating the size and structure of the metamaterial as needed, polarization-controlled coherent perfect absorption is achieved.

[0033] The polarization-controlled coherent perfect absorber of the multi-layer metamaterial consists of two layers of metamaterials and a dielectric layer. The dielectric layer is located between the two layers of metamaterials. The metamaterial is an asymmetric split-ring structure, and each asymmetric split-ring is composed of an inverted V-shaped metal wire and a U-shaped metal wire. Each layer of the metamaterial is composed of periodically arranged metamaterial unit structures. The unit structures of the two layers of metamaterials are exactly the same, and there is structural asymmetry in the unit structure. This structure does not undergo polarization polarization and orthogonal polarization transmission. Each unit of the split-ring structure is composed of an inverted V-shaped metal wire and a U-shaped metal wire. The periodic split-ring structure is etched on both sides of the substrate and periodically extended along the X and Y directions. The material of the metal wire of the metamaterial is gold, and the dielectric constant is derived from the Drude model. The dielectric material of the metamaterial usually uses silicon dioxide, glass, etc., and the thickness is on the order of hundreds of nanometers.

[0034] Measure the signal light passing through the metamaterial in the propagation direction of the signal light to obtain the absorption rate of the metamaterial. In the absence of the metamaterial, the signal light and the control light propagating in opposite directions form a standing wave. A signal light source provides a signal light of a certain wavelength and propagates vertically towards the metamaterial. Another control light source provides control light, which is a coherent light with the signal light. Its amplitude, polarization state, and wavelength are the same as those of the signal light. If the electromagnetic metamaterial is placed at the node or antinode position of the standing wave, that is, the phase difference between the signal light and the control light is 0 degrees and 180 degrees. Then, by orthogonally switching the polarization states of the signal light and the control light, absorption of the signal light at different frequencies can be achieved, and the effect of multi-band perfect absorption can be achieved.

[0035] The structure of the present invention is simple, easy to manufacture, light in weight, and easy to integrate. It can achieve coherent perfect absorption of light at specific frequencies in the optical band, and has broad development and application prospects in the fields of photodetectors, thermal emitters, photovoltaics, and optical communications.

[0036] The following gives a specific embodiment of the present invention:

[0037] The present invention consists of two layers of asymmetric split-rings 2 and 3 and a dielectric layer 1. The two layers of asymmetric split-rings are periodically arranged on both sides of the dielectric layer. The thickness of the dielectric layer is on the order of hundreds of nanometers, the material is silicon dioxide, and its dielectric constant is ε silica = 2.1316, and the size of each unit is L×L nanometers. AsFigure 2 as shown Figure 1 The structure shown has asymmetric split ring resonators (SRRs) on both sides of the dielectric layer that are symmetric to each other and periodically extended along the X and Y directions, forming a periodic asymmetric split ring resonator array. Each side of the array consists of an inverted V-shaped metal wire and a U-shaped metal wire 2, 3. The material of the metal wire is gold, and its dielectric constant is derived from the Drude model. The width of the two arms of the U-shaped ring is d1, the height is D, and the overall width is l. The hypotenuse parallel width of the two arms of the V-shaped ring is d1, and the inner V-shaped height is d2. The double-layer asymmetric split ring resonators are periodically etched on both sides of the dielectric layer.

[0038] Combined with the attached Figure 3 it is further explained as follows. First, a polarization-controlled coherent perfect absorber of multi-layer metamaterials is established within the XYZ coordinate axes to form a working platform. The Z-axis is perpendicular to the surface of the metamaterials. Two beams of light, a signal light and a control light, are emitted from a signal light source and a control light source. The signal light and the control light are coherent light with the same amplitude and frequency, and their polarization directions are both in the X direction. The frequency range is set at 100 - 500 THz. The signal light and the control light propagate towards each other along the Z-axis, pass through the metamaterials, and interact with the double-layer asymmetric split ring resonators. At this time, the transmittance and reflectance are zero. Therefore, according to the absorption rate = 1 - reflectance - transmittance, the designed absorber can achieve the effect of perfect absorption.

[0039] The interference of two coherent light beams with the same amplitude and propagating in opposite directions will form a standing wave. Placing the metamaterials at different positions in the standing wave can control the phase difference between the coherent waves incident on both sides of the material, thereby affecting the interaction between the wave and the metamaterials. Usually, nodes and antinodes are defined in the electric field. The node corresponds to the position where the phase difference between the two incident lights is π, and the antinode corresponds to the position where the phase difference between the two incident lights is 0. When the metamaterials are placed at the node, the magnetic field components of the two beams of light are in the same direction, and the electric field components are in the opposite direction. When the metamaterials are placed at the antinode, the magnetic field components of the two beams of light are in the opposite direction, and the electric field components are in the same direction. The simulation results show that when the phase difference is 0 degrees, as Figure 5 shown by the solid line, the absorption rate of the X-polarized light at 357 THz is 92.3%, and as Figure 5 shown by the dashed line, the absorption rate of the Y-polarized light at 326 THz is 94.4%. When the phase difference is 180 degrees, as Figure 6 shown by the solid line, the absorption rates of the X-polarized light at 158 THz and 487 THz are 99.1% and 98.3% respectively, and as Figure 6The absorption rates of the Y-polarized light at 254 THz and 405 THz shown by the dashed lines are 93.4% and 98.5% respectively. According to the above content, it can be known that by changing the polarization state of the incident light and the phase difference between the two incident lights, the operating frequency of the absorber can be adjusted, so as to achieve selective absorption. Among the above absorption peaks, 5 have an absorption rate of more than 90%, and 3 of them are more than 95%, achieving the effect of near-perfect absorption, thus realizing the polarization-controlled coherent perfect absorption of the multi-layer metamaterial.

[0040] In summary, a polarization-controlled coherent perfect absorber based on multi-layer metamaterials belongs to the fields of metamaterials and absorbers. The present invention discloses a polarization-controlled coherent perfect absorber based on multi-layer metamaterials, which is characterized in that it is composed of two layers of metal asymmetric split-ring resonators and a dielectric layer between the two layers of asymmetric split-ring resonators. The two layers of metal asymmetric split-ring resonators are composed of an inverted V-shaped metal wire and a U-shaped metal wire. The two layers of metal asymmetric split-ring resonator structures are the same and are symmetrically arranged along the dielectric layer. Signal light and control light with the same polarization angle, amplitude and frequency propagate towards each other along the direction perpendicular to the metamaterial layer. The thickness of the asymmetric split-ring resonator structure is on the order of nanometers, and the material used for the unit structure is a noble metal material; the material of the unit structure is gold. The dielectric layer is made of silica material or glass, and the thickness is on the order of hundreds of nanometers. The coherent perfect absorption is realized by adjusting the phase of the control light to adjust the absorption intensity at a specific frequency, and the phase of the control light source is from 0 to 2π. The polarization-controlled coherent perfect absorber of the multi-layer metamaterial has an operating band in the optical band.

[0041] The polarization-controlled coherent perfect absorber based on multi-layer metamaterials described in the present invention has the characteristics of simple structure, convenient operation and high efficiency, and can dynamically adjust the absorption rate and operating frequency, and has broad development and application prospects in the fields of photodetectors, thermal emitters, photovoltaics and optical communications.

Claims

1. A polarization-controlled coherent perfect absorber based on multi-layer metamaterials, the coherent perfect absorber being composed of a plurality of unit structures, and the plurality of unit structures extending along the x-direction and the y-direction, the unit structure being composed of two layers of metal asymmetric split rings and a dielectric layer between the two layers of asymmetric split rings, characterized in that: The metal asymmetric split ring resonator consists of an inverted V-shaped metal wire and a U-shaped metal wire. The metal asymmetric split ring resonators have the same structure and are symmetrically arranged along the dielectric layer. Signal light and control light with the same polarization angle, amplitude, and frequency propagate towards each other in a direction perpendicular to the metamaterial layer.

2. The polarization control coherent perfect absorber based on multi-layer metamaterials according to claim 1, characterized in that: The thickness of the asymmetric split ring resonator structure is on the order of nanometers, and the material used for the metal asymmetric split ring resonator structure is a noble metal material.

3. The polarization control coherent perfect absorber based on multi-layer metamaterials according to claim 1, characterized in that: The dielectric layer is made of silica material or glass and has a thickness on the order of hundreds of nanometers.

4. A polarization control coherent perfect absorber based on multi-layer metamaterials according to claim 1, characterized in that: The coherent perfect absorber adjusts the absorption intensity of electromagnetic waves at a specific frequency by adjusting the polarization state phase of the control light. The polarization state of the control light source is X polarization and Y polarization, and the phase of the control light source is from 0 to 2π.

5. A polarization control coherent perfect absorber based on multi-layer metamaterials according to claim 4, characterized in that: The polarization-controlled coherent perfect absorber of the multi-layer metamaterial operates in the optical band.

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