Multifunctional terahertz metamaterial device

Abstract

The invention discloses a multifunctional terahertz metamaterial device, which belongs to the technical field of terahertz devices and comprises a plurality of unit structures with two-dimensional periodicity. The unit structure comprises a GST225 pattern layer, a first dielectric layer, a GST225 pattern-free layer, a polarization conversion metal layer, a second dielectric layer and a metal backboard layer which are sequentially connected from top to bottom. According to the multifunctional terahertz metamaterial device, by changing the phase change characteristics of GST225 in the GST225 pattern layer and the GST225 pattern-free layer, switching between functions of a multifunctional multi-band polarization converter and a double-frequency wave absorber can be achieved. The problem that an existing terahertz device is single in function is solved.

Description

Technical Field

[0001] This invention belongs to the field of terahertz device technology, and particularly relates to a multifunctional terahertz metamaterial device. Background Technology

[0002] Terahertz (THz) waves, also known as submillimeter waves, have a frequency range of 0.1-10 THz. In both long and short wavebands, terahertz waves overlap with millimeter waves and infrared waves, thus possessing characteristics of both electronics and photonics. Terahertz waves occupy a unique position in the electromagnetic spectrum, exhibiting high penetration, low energy, and sensitivity to organic macromolecules. They can be widely used in fields such as security detection, wireless communication, and biomedical sensing. However, terahertz waves rarely interact strongly with natural materials, meaning that the necessary equipment for terahertz wave generation cannot be manufactured using natural materials.

[0003] To overcome this limitation, current research has begun to apply metamaterials to design terahertz devices. Metamaterials are materials composed of periodically arranged subwavelength metasurface structural units with a thickness of only a few hundred nanometers. By adjusting the size and shape of the unit structure, electromagnetic waves can be controlled to adjust their propagation direction, amplitude, and other characteristics.

[0004] However, the current terahertz devices have limited functionality and operate in a limited number of frequency bands, which restricts the application of terahertz metamaterial devices. Summary of the Invention

[0005] To address the aforementioned shortcomings in the prior art, this invention provides a multifunctional terahertz metamaterial device, which solves the problem of the limited functionality of existing terahertz devices.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: The present invention provides a multifunctional terahertz metamaterial device comprising several unit structures with two-dimensional periodicity; The unit structure includes, from top to bottom, a GST225 patterned layer, a first dielectric layer, a GST225 unpatterned layer, a polarization conversion metal layer, a second dielectric layer, and a metal backplate layer. The multifunctional terahertz metamaterial device can switch between the functions of a multifunctional multi-band polarization converter and a dual-frequency absorber by changing the phase transition characteristics of GST225 in the patterned and unpatterned GST225 layers.

[0007] Furthermore, the GST225 in the patterned layer and the unpatterned layer undergoes a reversible phase transition between crystalline and amorphous states under external temperature stimulation; When GST225 in the patterned layer and the unpatterned layer is in an amorphous state, the multifunctional terahertz metamaterial device acts as a multifunctional multi-band polarization converter. When the GST225 in the patterned and unpatterned layers is in a crystalline state, the multifunctional terahertz metamaterial device acts as a dual-frequency absorber.

[0008] Furthermore, the pattern in the GST225 pattern layer includes an open square outer ring, a circular middle ring, and a circular inner ring. The geometric centers of the open square outer ring, the circular middle ring, and the circular inner ring are all located at the center of the GST225 pattern layer, and the inner radius of the circular inner ring is... The value range is 2~6μm, and the outer radius is... The value range is 5~10μm, and the inner radius of the circular inner ring is... The value range is 12~18μm, and the outer radius is... The value range is 15~20μm, and the side length of the outer ring of the open square is... The value range is 45~49.5μm, and the ring width is... The value ranges from 2 to 5.5 μm, and the aperture spacing is... The value range is 8~14μm; The thickness of the GST225 pattern layer It is 0.3μm.

[0009] Furthermore, both the first dielectric layer and the second dielectric layer employ... The dielectric constant is 3.75, and the thickness of the first dielectric layer is... The thickness of the second dielectric layer All are 15μm.

[0010] Furthermore, the GST225 patternless layer serves as a function switching layer, and its size is the same as that of the first dielectric layer and the second dielectric layer; the thickness of the GST225 patternless layer... It is 0.3μm.

[0011] Furthermore, the polarization conversion metal layer consists of two completely symmetrical metal structures at a 135° angle to the horizontal plane, wherein the axisymmetric spacing between the two metal structures is... The diameter is 4 μm, and each metal structure consists of three semi-circular arched metals, wherein the inner radius of each semi-circular arched metal is 4 μm. The value range is 3~8μm, and the outer radius is... The value range is 9~11μm.

[0012] Furthermore, the metal backplate layer serves as the reflective backplate of the converter, and its size is the same as that of the first dielectric layer and the second dielectric layer.

[0013] Furthermore, the periodic arrangement of the unit structure adopts a square cell arrangement; the length and width of the unit structure are both periodic. Furthermore, they are arranged periodically in both length and width directions.

[0014] The beneficial effects of this invention are as follows: This invention provides a multifunctional terahertz metamaterial device that achieves multifunctional switchability of a dual-frequency line-to-line converter, a multi-frequency line-to-circular converter, and a dual-frequency absorber on a single terahertz metamaterial device through a multi-layer structure, significantly improving the functional integration on a single device; this invention achieves functional switching between the polarization converter and the absorber by controlling the phase state of the GST225, giving the device dynamic functional reconfiguration characteristics, which can significantly improve the application flexibility of the device; the multifunctional terahertz metamaterial device provided by this invention, in and Under normal incident polarization conditions, the polarization conversion rate, ellipticity, and axial ratio exhibit high consistency, indicating that the multifunctional terahertz metamaterial device provided by this scheme is polarization insensitive. Under the condition of perpendicular incident electromagnetic waves, the change in polarization angle of the multifunctional terahertz metamaterial device provided by this invention will not affect the absorption performance, that is, when the multifunctional terahertz metamaterial device exhibits the absorption function, it has good polarization angle stability.

[0015] Other advantages of the present invention will be analyzed in more detail in the following embodiments. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a side view of the unit structure of a multifunctional terahertz metamaterial device according to an embodiment of the present invention.

[0018] Figure 2 This is a schematic diagram of the GST225 patterned layer in an embodiment of the present invention.

[0019] Figure 3 This is a side view of the unit structure of a multifunctional terahertz metamaterial device according to an embodiment of the present invention.

[0020] Figure 4 This is a schematic diagram of the polarization conversion metal layer in an embodiment of the present invention.

[0021] Figure 5The figure shows the simulation results of the reflection coefficient of the multifunctional terahertz metamaterial device in the embodiment of the present invention.

[0022] Figure 6 The figure shows the simulation results of the polarization conversion rate of the multifunctional terahertz metamaterial device in the embodiment of the present invention.

[0023] Figure 7 The image shows the phase difference simulation results of the multifunctional terahertz metamaterial device in the embodiment of the present invention.

[0024] Figure 8 The figure shows the simulation results of the ellipticity of the multifunctional terahertz metamaterial device in the embodiment of the present invention.

[0025] Figure 9 The figure shows the axial ratio simulation results of the multifunctional terahertz metamaterial device in the embodiment of the present invention.

[0026] Figure 10 The figure shows the simulation results of the absorption rate of the multifunctional terahertz metamaterial device in the embodiment of the present invention.

[0027] Figure 11 The figure shows the relative impedance simulation results of the multifunctional terahertz metamaterial device in the embodiment of the present invention.

[0028] Figure 12 This is a simulation diagram of the absorption rate of the multifunctional terahertz metamaterial device under varying polarization angle in an embodiment of the present invention.

[0029] The structure consists of: 1. GST225 patterned layer; 2. First dielectric layer; 3. GST225 unpatterned layer; 4. Polarization conversion metal layer; 5. Second dielectric layer; and 6. Metal backplate layer. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0031] In one embodiment of the present invention, the present invention provides a multifunctional terahertz metamaterial device, comprising a plurality of unit structures having two-dimensional periodicity; like Figure 1The unit structure shown includes, from top to bottom, a GST225 patterned layer 1, a first dielectric layer 2, a GST225 unpatterned layer 3, a polarization conversion metal layer 4, a second dielectric layer 5, and a metal backplate layer 6 connected in sequence. The multifunctional terahertz metamaterial device can switch between the functions of a multifunctional multi-band polarization converter and a dual-frequency absorber by changing the phase transition characteristics of GST225 in the patterned layer 1 and the unpatterned layer 3 of GST225.

[0032] In this scheme, the multi-functional multi-band polarization converter includes at least a dual-frequency line-to-line converter and a multi-frequency line-to-circle converter; The GST225 in the patterned layer 1 and the unpatterned layer 3 undergoes a reversible phase transition between crystalline and amorphous states under external temperature stimulation. When the GST225 in the patterned layer 1 and the unpatterned layer 3 is in an amorphous state, the multifunctional terahertz metamaterial device acts as a multifunctional multi-band polarization converter. When the GST225 in the patterned layer 1 and the unpatterned layer 3 is in a crystalline state, the multifunctional terahertz metamaterial device acts as a dual-frequency absorber.

[0033] In this scheme, GST225 is a chalcogenide phase change material composed of germanium (Ge), antimony (Sb), and tellurium (Te) in an atomic ratio of 2:2:5. At room temperature, GST225 is amorphous. As the temperature rises to the phase transition temperature (approximately 160°C), the atoms in GST225 rearrange to form a face-centered cubic lattice structure. This crystalline state remains stable at room temperature. The abundant electron-hole pairs in the crystalline state give GST225 excellent electrical conductivity. When the crystalline GST225 undergoes a melting and quenching process, it reverts to the amorphous state. The dielectric constant of GST225 differs significantly between its amorphous and crystalline states. The dielectric constant of GST225 is described using the Drude model. The dielectric constant of GST225 is calculated as follows: , in, This indicates the angular frequency of the GST225 material in an alternating electric field. The complex permittivity of the following, Represents the high-frequency dielectric constant. Represents the imaginary unit. Indicates DC conductivity. Represents the vacuum permittivity. This represents the carrier relaxation time.

[0034] In this scheme, the Drude model parameters of the two phases of amorphous GST225 (a-GST225) and crystalline GST225 (h-GST225 with six phase angles) are shown in Table 1. Table 1. Drude model parameters for amorphous and crystalline GST225 like Figure 2 As shown, the pattern in the GST225 pattern layer 1 includes an open square outer ring, a circular middle ring, and a circular inner ring. The geometric centers of the open square outer ring, the circular middle ring, and the circular inner ring are all located at the center of the GST225 pattern layer 1. The inner radius of the circular inner ring... The value range is 2~6μm, and the outer radius is... The value range is 5~10μm, and the inner radius of the circular inner ring is... The value range is 12~18μm, and the outer radius is... The value range is 15~20μm, and the side length of the outer ring of the open square is... The value range is 45~49.5μm, and the ring width is... The value ranges from 2 to 5.5 μm, and the aperture spacing is... The value range is 8~14μm; like Figure 3 As shown, the thickness of the GST225 pattern layer 1 It is 0.3μm.

[0035] Both the first dielectric layer 2 and the second dielectric layer 5 adopt The dielectric constant is 3.75, and the thickness of the first dielectric layer 2 is... The thickness of the second dielectric layer 5 All are 15μm.

[0036] In this scheme, parameters such as the thickness, relative permittivity, and tangent loss angle of the first dielectric layer 2 and the second dielectric layer 5 all affect the operating frequency and performance of the multifunctional terahertz metamaterial device. Therefore, the material and specific structural parameters of the dielectric layers can be determined according to actual needs. The first dielectric layer 2 and the second dielectric layer 5 can also be made of... Materials such as...

[0037] The GST225 patternless layer 3 serves as a function switching layer, and its size is the same as that of the first dielectric layer 2 and the second dielectric layer 5; the thickness of the GST225 patternless layer 3 is... It is 0.3μm.

[0038] like Figure 4As shown, the polarization conversion metal layer 4 consists of two completely symmetrical metal structures, forming a 135° angle with the horizontal plane. The axisymmetric spacing between the two metal structures is... The diameter is 4 μm, and each metal structure consists of three semi-circular arched metals, wherein the inner radius of each semi-circular arched metal is 4 μm. The value range is 3~8μm, and the outer radius is... The value range is 9~11μm.

[0039] The metal backplate layer 6 serves as the reflective backplate of the converter, and its size is the same as that of the first dielectric layer 2 and the second dielectric layer 5.

[0040] In this scheme, the metal structure in the polarization conversion metal layer 4 and the metal backplate layer 6 can be made of high-conductivity metals such as gold, aluminum, and copper, and the thickness is determined according to requirements and actual conditions. In this embodiment, the metal structure in the polarization conversion metal layer 4 and the metal backplate layer 6 are made of gold, and the thickness of the metal structure in the polarization conversion metal layer 4 is... The thickness of the metal backing layer 6 is 0.2 μm. It is 0.3μm.

[0041] The periodic arrangement of the unit structure adopts a square cell arrangement; the length and width of the unit structure are both periodic. Furthermore, they are arranged periodically in both length and width directions.

[0042] In this scheme, the periodic arrangement of the unit structure can also take the form of triangular cell arrangement, hexagonal cell arrangement, etc.

[0043] In this embodiment, the CST microwave studio simulation software is used to simulate the multifunctional terahertz metamaterial device, wave vector. k and The axis is parallel and perpendicular to the structural plane of the multifunctional terahertz metamaterial device, and the magnetic and electric fields are parallel to the axis. shaft and axis, The boundary conditions along the axis are set to open boundary conditions. and The boundary conditions in the axial direction are set to periodic boundary conditions.

[0044] When GST225 is in the amorphous state, a-GST225 exhibits insulating properties. Therefore, the GST225 patterned layer 1 and GST225 unpatterned layer 3 in the multifunctional terahertz metamaterial device can be regarded as low-loss dielectric layers. The multifunctional terahertz metamaterial device is mainly formed by the combined action of the polarization conversion metal layer 4, the second dielectric layer 5 and the metal backplate layer 6 to realize a multifunctional multi-band polarization converter. like Figure 5 As shown, when the multifunctional terahertz metamaterial device provided in this solution is used as a multifunctional multi-band polarization converter, the first cross-polarization reflection coefficient... Second cross-polarization reflection coefficient The corresponding curves coincide, and the first copolarized reflection coefficient Second copolarized reflection coefficient The corresponding curves coincide, and within the frequency ranges of 0.98THz-1.95THz and 3.795THz-3.95THz, the first cross-polarization reflection coefficient... Second cross-polarization reflection coefficient The first copolarized reflection coefficient exceeds 0.9. Second copolarized reflection coefficient Below 0.3. In the range of 0.98THz-1.96THz, there are three resonant points with center frequencies of 1.084THz, 1.3THz, and 1.75THz, respectively. Meanwhile, in the range of 3.795THz-3.95THz, there is a resonant point at 3.88THz.

[0045] For linear-to-linear polarization, the polarization conversion ratio (PCR) is usually used to quantify the conversion efficiency of orthogonal linear polarization conversion during linear-to-linear polarization.

[0046] like Figure 6 As shown, polarization and When the incident wave is polarized, the curves corresponding to the first polarization conversion rate PCRx and the second polarization conversion rate PCRy almost completely overlap. In the frequency ranges of 0.98 THz-1.946 THz and 3.8 THz-3.94 THz, the PCR values ​​are all greater than 90%. The PCR values ​​at the resonant points of 1.084 THz, 1.3 THz, 1.75 THz, and 3.88 THz are 0.999, 0.9995, 0.9986, and 0.998, respectively. Therefore, the multifunctional terahertz metamaterial device provided by this invention can effectively perform… Polarized waves and Polarized waves, and Polarized waves and The conversion between polarized waves enables dual-frequency line-to-line polarization conversion, thus serving as a dual-frequency line-to-line converter.

[0047] like Figure 7 As shown and Figure 8 As shown, x polarization and y Phase difference of multifunctional terahertz metamaterial devices when polarized incident waves and ellipticity The curves highly overlap, combined Figure 5 It was found that the reflection coefficient of the multifunctional terahertz metamaterial device is within the range of 0.86 THz-0.94 THz and 3.6 THz-3.7 THz. The phase difference is approximately With an ellipticity less than -0.9, the multifunctional terahertz metamaterial device achieves the conversion from linearly polarized waves to right-handed circularly polarized waves. Within the frequency ranges of 2.08 THz-2.43 THz and 3.98 THz-4.05 THz, the reflection coefficient... The phase difference is approximately The ellipticity is greater than 0.9, indicating that the multifunctional terahertz metamaterial device has achieved the conversion from linearly polarized waves to left-handed circularly polarized waves.

[0048] The performance of circularly polarized waves can also be described by the axial ratio (AR). When AR is less than 3 dB, the reflected wave can be regarded as a circularly polarized wave.

[0049] like Figure 9 As shown, polarization and When polarized incident waves are observed, the AR value is less than 3dB in the ranges of 0.86THz-0.94THz, 3.6THz-3.7THz, 2.08THz-2.43THz, and 3.98THz-4.05THz. The multifunctional terahertz metamaterial device provided by this invention has good line-to-circle conversion function in these frequency bands, that is, it can be used as a multi-frequency line-to-circle converter.

[0050] This shows that, and Under normal incident polarization conditions, the polarization conversion rate, ellipticity, and axial ratio curves of the multifunctional terahertz metamaterial device provided by this invention almost completely overlap, indicating that the multifunctional terahertz metamaterial device is polarization insensitive.

[0051] When GST225 is in a crystalline state, h-GST225 exhibits metallic properties. The multifunctional terahertz metamaterial device mainly consists of a GST225 patterned layer 1, a first dielectric layer 2, and a GST225 unpatterned layer 3 to realize a dual-frequency absorber.

[0052] like Figure 10 As shown, the multifunctional terahertz metamaterial device exhibits an absorption rate greater than 90% in the frequency bands of 1.66THz-3.19THz and 7.35THz-8.53THz, indicating that the device has good absorption performance in these two frequency bands.

[0053] like Figure 11As shown, in the ranges of 1.66THz-3.19THz and 7.35THz-8.53THz, the real part of the equivalent impedance fluctuates around 1, and the real part of the equivalent impedance fluctuates around 0. According to impedance matching theory, the equivalent impedance and free space impedance are matched within the aforementioned dual-frequency bands, thereby achieving the absorption function.

[0054] like Figure 12 As shown, when the polarization angle of the incident electromagnetic wave varies from 0° to 90°, the absorption rate curves almost completely overlap. Therefore, the change in polarization angle will not affect the performance of the absorber. The multifunctional terahertz metamaterial device provided in this solution has good stability in response to polarization angle and high practical application value when used as a dual-frequency absorber.

[0055] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A multifunctional terahertz metamaterial device, characterized in that, It includes several unit structures with two-dimensional periodicity; The unit structure includes, from top to bottom, a GST225 patterned layer (1), a first dielectric layer (2), a GST225 unpatterned layer (3), a polarization conversion metal layer (4), a second dielectric layer (5), and a metal backplate layer (6). The multifunctional terahertz metamaterial device can switch between the functions of a multifunctional multi-band polarization converter and a dual-frequency absorber by changing the phase transition characteristics of GST225 in the patterned layer (1) and the unpatterned layer (3) of GST225.

2. The multifunctional terahertz metamaterial device according to claim 1, characterized in that, The GST225 in the patterned layer (1) and the unpatterned layer (3) undergoes a reversible phase transition between crystalline and amorphous states under external temperature stimulation; When GST225 in the patterned layer (1) and the unpatterned layer (3) is in an amorphous state, the multifunctional terahertz metamaterial device acts as a multifunctional multi-band polarization converter. When GST225 in the patterned layer (1) and the unpatterned layer (3) is in a crystalline state, the multifunctional terahertz metamaterial device acts as a dual-frequency absorber.

3. The multifunctional terahertz metamaterial device according to claim 2, characterized in that, The pattern in the GST225 pattern layer (1) includes an open square outer ring, a circular middle ring, and a circular inner ring. The geometric centers of the open square outer ring, the circular middle ring, and the circular inner ring are all located at the center of the GST225 pattern layer (1), and the inner radius of the circular inner ring is... The value range is 2~6μm, and the outer radius is... The value range is 5~10μm, and the inner radius of the circular inner ring is... The value range is 12~18μm, and the outer radius is... The value range is 15~20μm, and the side length of the outer ring of the open square is... The value range is 45~49.5μm, and the ring width is... The value ranges from 2 to 5.5 μm, and the aperture spacing is... The value range is 8~14μm; The thickness of the GST225 patterned layer (1) It is 0.3μm.

4. The multifunctional terahertz metamaterial device according to claim 3, characterized in that, Both the first dielectric layer (2) and the second dielectric layer (5) are made of The dielectric constant is 3.75, and the thickness of the first dielectric layer (2) is... The thickness of the second dielectric layer (5) All are 15μm.

5. The multifunctional terahertz metamaterial device according to claim 4, characterized in that, The GST225 patternless layer (3) serves as a function switching layer, and its size is the same as that of the first dielectric layer (2) and the second dielectric layer (5); the thickness of the GST225 patternless layer (3) is... It is 0.3μm.

6. The multifunctional terahertz metamaterial device according to claim 5, characterized in that, The polarization conversion metal layer (4) consists of two completely symmetrical metal structures, which are at a 135° angle to the horizontal plane. The axisymmetric spacing between the two metal structures is... The diameter is 4 μm, and each metal structure consists of three semi-circular arched metals, wherein the inner radius of each semi-circular arched metal is 4 μm. The value range is 3~8μm, and the outer radius is... The value range is 9~11μm.

7. The multifunctional terahertz metamaterial device according to claim 6, characterized in that, The metal backplate layer (6) serves as the reflective backplate of the converter and is the same size as the first dielectric layer (2) and the second dielectric layer (5).

8. The multifunctional terahertz metamaterial device according to claim 7, characterized in that, The periodic arrangement of the unit structure adopts a square cell arrangement; the length and width of the unit structure are both periodic. Furthermore, they are arranged periodically in both length and width directions.

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