An electrically controlled terahertz unimodal-bimodal-broadband polarization conversion filter

Abstract

The application discloses a terahertz single-peak-double-peak-broadband polarization conversion filter with electric heating control, wherein two direct current power supplies are used to respectively apply voltages to metal patches of a first polarization control structure layer and a second polarization control structure layer, electrically induced Joule heat is generated to trigger phase transition of a heat-induced phase transition patch, and the heat-induced phase transition patch is converted from an insulating state to a metal state; meanwhile, a nano thermal insulation layer is added between a first insulating layer and a second insulating layer, so that the reconfigurable metasurface of the first polarization control structure layer and the second polarization control structure layer is independently controlled, and thus dynamic control and switching of three working states (single-peak-double-peak-broadband polarization conversion transmission) of terahertz waves are realized. Experiments show that the transmittance of the single-peak and double-peak can reach more than 50%, and the broadband transmittance can reach more than 40%, and the application is suitable for fields such as terahertz polarization multiplexing communication.

Description

Technical Field

[0001] This invention relates to the field of terahertz polarization conversion filter technology, specifically to an electrothermal controlled terahertz single-peak-double-peak-wideband polarization conversion filter. Background Technology

[0002] Recently, with the rapid development of network communication technology, 5G communication technology has matured and gradually become commercialized, while 6G communication technology has become a key area of ​​research for countries around the world. Terahertz communication technology, with its data transmission rate of up to 1Tbps, has become one of the core technologies for the development of 6G communication technology. Terahertz polarization conversion filters achieve multi-band communication modulation through polarization conversion transmission in different frequency bands, and are one of the key components in realizing terahertz communication technology. Currently, most terahertz polarization conversion filters use metal composite phase change materials to design resonant structures to achieve polarization conversion from a single frequency point to multiple frequencies. However, these types of terahertz polarization conversion filters can only switch between two polarization states and cannot switch between multiple terahertz frequencies, which greatly limits the application range of polarization conversion modulation devices. Summary of the Invention

[0003] The present invention aims to solve the problem that existing terahertz polarization conversion filters cannot achieve multiple polarization conversion filtering, and provides an electrothermally controlled terahertz single-peak-double-peak-wideband polarization conversion filter.

[0004] To solve the above problems, the present invention is achieved through the following technical solution:

[0005] A thermo-controlled terahertz single-peak-double-peak-wideband polarization conversion filter includes a high-resistivity silicon substrate layer, a first polarization control structure layer, a first insulating layer, a nano-thermal insulation layer, a second insulating layer, and a second polarization control structure layer stacked from bottom to top along the Z-axis. The first polarization control structure layer consists of two first electrode patches and N first transmission units. The two first electrode patches are elongated strips extending along the X-axis and are relatively parallel in the Y-axis direction. The N first transmission units are arranged in a matrix along the X and Y axes, positioned between the two first electrode patches. The first transmission units in the same column along the Y-axis are sequentially connected, with their two ends connected to the two first electrode patches respectively. The second polarization control structure layer consists of two second electrode patches and N second transmission units. The two second electrode patches are elongated strips extending along the Y-axis and are relatively parallel in the X-axis direction. The N second transmission units are arranged in a matrix along the X and Y axes, positioned between the two second electrode patches. The second transmission units in the same row along the X-axis are sequentially connected, with their two ends connected to the two first electrode patches respectively. After the elements are connected in sequence, their two ends are connected to two second electrode patches respectively; the matrix arrangement of the N first transmission units of the first polarization control structure layer is exactly the same as the matrix arrangement of the N second transmission units of the second polarization control structure layer, and the N first transmission units and N second transmission units are one-to-one opposite in the Z-axis direction; the two first electrode patches of the first polarization control structure layer are respectively connected to the positive and negative terminals of the first DC power supply, and the two second electrode patches of the second polarization control structure layer are respectively connected to the positive and negative terminals of the second DC power supply; the terahertz wave is incident from above the second polarization control structure layer along the Z-axis direction; when the first DC power supply and the second DC power supply are both turned off, the polarization conversion filter realizes the single-peak polarization conversion filtering function of the terahertz wave; when the first DC power supply and the second DC power supply are both turned on, the polarization conversion filter realizes the double-peak polarization conversion filtering function of the terahertz wave; when the first DC power supply is turned on and the second DC power supply is turned off, the polarization conversion filter realizes the broadband polarization conversion filtering function of the terahertz wave; N is a positive integer greater than 1.

[0006] In the above scheme, each first transmission unit includes a first metal patch and a first thermally induced phase change patch; the first metal patch is composed of two inverted T-shaped metal patches; the first thermally induced phase change patch is composed of one Z-shaped thermally induced phase change patch and one straight thermally induced phase change patch; the two inverted T-shaped metal patches are arranged in a mirror image relative to each other in the X-axis direction; the Z-shaped thermally induced phase change patch and the straight thermally induced phase change patch are both located between the two inverted T-shaped metal patches; the straight thermally induced phase change patch passes through the middle of the Z-shaped thermally induced phase change patch along the X-axis direction; the two ends of the straight thermally induced phase change patch are respectively connected to the two inverted T-shaped metal patches, and the two inverted T-shaped metal patches and the straight thermally induced phase change patch form an H-shape.

[0007] In the above scheme, each second transmission unit includes a second metal patch and a second thermally induced phase change patch; the second metal patch consists of two straight metal patches and one L-shaped metal patch; the second thermally induced phase change patch consists of one straight thermally induced phase change patch; the two straight metal patches are arranged relatively parallel in the Y-axis direction; both the straight thermally induced phase change patch and the L-shaped metal patch are arranged between the two straight metal patches; the straight thermally induced phase change patch is close to the upper straight metal patch, and the L-shaped metal patch is close to the lower straight metal patch; the upper end of the straight thermally induced phase change patch is connected to the upper straight metal patch, and the lower end of the straight thermally induced phase change patch is suspended.

[0008] In the above scheme, the first metal patch and the second metal patch are made of metal materials.

[0009] In the above scheme, the first thermally induced phase change patch and the second thermally induced phase change patch are made of thermally induced phase change material.

[0010] In the above scheme, the voltages of the first DC power supply and the second DC power supply are the same.

[0011] In the above scheme, the coverage area of ​​the first polarization control structure layer and the coverage area of ​​the second polarization control structure layer are equal, and the coverage area is greater than or equal to the irradiation area of ​​the terahertz wave.

[0012] Compared with existing technologies, this invention applies voltages to the metal patches of the first and second polarization control structure layers using two DC power supplies, respectively, generating electro-induced Joule heating to trigger a phase transition in the thermally induced phase change patch, causing it to transform from an insulating state to a metallic state. Simultaneously, a nano-thermal insulation layer is added between the first and second insulating layers, allowing for independent control of the reconfigurable metasurfaces of the first and second polarization control structure layers. This enables dynamic control and switching of the three operating states of terahertz waves (single-peak, double-peak, and broadband polarization conversion transmission). Experiments show that this invention achieves transmittance exceeding 50% in single-peak and double-peak modes and exceeding 40% in broadband mode, making it suitable for applications such as terahertz polarization multiplexing communication. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the three-dimensional structure of a thermo-controlled terahertz single-peak-double-peak-wideband polarization conversion filter.

[0014] Figure 2 This is a top view of the first polarization control structure layer.

[0015] Figure 3 This is a top view of the first transmission unit.

[0016] Figure 4 This is a top view of the second polarization control structure layer.

[0017] Figure 5 This is a top view of the second transmission unit.

[0018] Figure 6 This is a schematic diagram showing the transmittance of terahertz waves as a function of frequency under electrode energization and de-energization conditions according to the present invention.

[0019] The following labels are used in the figure: 1. High-resistivity silicon substrate layer; 2. First polarization control structure layer; 21. First metal patch; 22. First thermally induced phase change patch; 23. First electrode patch; 3. First insulating layer; 4. Nano-insulating layer; 5. Second insulating layer; 6. Second polarization control structure layer; 61. Second metal patch; 62. Second thermally induced phase change patch; 63. Second electrode patch. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific examples and the accompanying drawings. It should be noted that the directional terms mentioned in the examples, such as "up," "down," "middle," "left," "right," "front," and "back," are only for reference to the directions in the accompanying drawings. Therefore, the directions used are for illustrative purposes only and are not intended to limit the scope of protection of this invention.

[0021] See Figure 1 A thermo-controlled terahertz single-peak-double-peak-wideband polarization conversion filter consists of a high-resistivity silicon substrate layer 1, a first polarization control structure layer 2, a first insulating layer 3, a nano-thermal insulation layer 4, a second insulating layer 5, and a second polarization control structure layer 6 stacked from bottom to top in the Z-axis direction.

[0022] The high-resistivity silicon substrate 1, the first insulating layer 3, the nano-thermal insulation layer 4, and the second insulating layer 5 are all sheet-like, and can be square, polygonal, circular, or other regular or irregular sheet shapes. They only need to accommodate the first polarization control structure layer 2 and the second polarization control structure layer 6. The high-resistivity silicon substrate 1 is made of high-resistivity silicon material, i.e., silicon with a resistivity greater than or equal to 10000 Ω·cm. In this embodiment, it is made of high-resistivity silicon material commonly used in existing polarization conversion filters, and its thickness is 0.5 mm. The first insulating layer 3 and the second insulating layer 5 are made of insulating material. In this embodiment, they are made of polyimide material. The thickness of the first insulating layer 3 is 20 μm, and the thickness of the second insulating layer 5 is 15 μm. The nano-thermal insulation layer 4 is made of nanomaterials. In this embodiment, it is made of SiO2-Al2O3 material, and its thickness is 10 μm. The first polarization control structure layer 2 and the second polarization control structure layer 6 are both surface pattern structures of polarization conversion filters. The first polarization control structure layer 2 is attached to the lower surface of the first insulating layer 3, and the second polarization control structure layer 6 is attached to the upper surface of the second insulating layer 5. The coverage area of ​​the first polarization control structure layer 2 and the coverage area of ​​the second polarization control structure layer 6 are equal.

[0023] See Figure 2 The first polarization control structure layer 2 consists of two first electrode patches 23 and N first transmission units. The two first electrode patches 23 serve as the leads of the first polarization control structure layer 2, and the N first transmission units serve as the surface periodic structure of the first polarization control structure layer 2, where N is a positive integer greater than 1. Both first electrode patches 23 are elongated strips extending along the X-axis and are arranged relatively parallel to each other in the Y-axis direction. The two first electrode patches 23 are made of a metallic material, such as gold, copper, or aluminum. In this embodiment, both first electrode patches 23 are made of aluminum, with a thickness between 0.2 and 0.8 μm. The N first transmission units have the same structure and size and are arranged in a matrix in the X-axis and Y-axis directions, positioned between the two first electrode patches 23. When the N first transmission units are arranged in a matrix, their number of rows and columns can be equal (e.g., forming a 4×4 square matrix) or unequal (e.g., forming a 6×5 rectangular matrix). In this embodiment, N first transmission units form a square matrix with an equal number of rows and columns, which is a 4×4 square matrix. Each first transmission unit includes a first metal patch 21 and a first thermally induced phase change patch 22, such as... Figure 3As shown. The first metal patch 21 is made of a metal material, such as gold, copper, or aluminum. In this embodiment, the first metal patch 21 is made of aluminum, and its thickness is between 0.2 and 0.8 μm. The first thermochromic phase change patch 22 is made of a thermochromic phase change material, such as vanadium dioxide (VO2), germanium-antimony-tellurium alloy (Ge2Sb2Te5), and germanium telluride (GeTe), which are materials whose conductivity is regulated by heat. In this embodiment, the first thermochromic phase change patch 22 is made of vanadium dioxide, and its thickness is between 0.8 and 1 μm. The first metal patch 21 consists of two inverted T-shaped metal patches. The first thermochromic phase change patch 22 consists of one Z-shaped thermochromic phase change patch and one straight thermochromic phase change patch. The two inverted T-shaped metal patches are arranged in a mirror image relative to each other in the X-axis direction. The Z-shaped thermochromic phase change patch and the straight thermochromic phase change patch are both located between the two inverted T-shaped metal patches. A linear thermochromic phase change patch is inserted through the middle of a Z-shaped thermochromic phase change patch along the X-axis. The two ends of the linear thermochromic phase change patch are connected to two inverted T-shaped metal patches, forming an H-shape with the two inverted T-shaped metal patches and the linear thermochromic phase change patch. In the N first transmission units, the inverted T-shaped metal patches of the first transmission units in the same column along the Y-axis are connected end-to-end, and their two ends are connected to two first electrode patches 23.

[0024] See Figure 4 The second polarization control structure layer 6 consists of two second electrode patches 63 and N second transmission units. The two second electrode patches 63 serve as the leads of the second polarization control structure layer 6, and the N second transmission units serve as the surface periodic structure of the second polarization control structure layer 6, where N is a positive integer greater than 1. Both second electrode patches 63 are elongated strips extending along the Y-axis and are arranged relatively parallel to each other in the X-axis direction. The two second electrode patches 63 are made of a metallic material, such as gold, copper, or aluminum. In this embodiment, both second electrode patches 63 are made of aluminum, with a thickness between 0.2 and 0.8 μm. The N second transmission units have the same structure and size and are arranged in a matrix in the X-axis and Y-axis directions, positioned between the two second electrode patches 63. When the N first transmission units are arranged in a matrix, their number of rows and columns can be equal (e.g., forming a 4×4 square matrix) or unequal (e.g., forming a 6×5 rectangular matrix). In this embodiment, N first transmission units form a square matrix with an equal number of rows and columns, which is a 4×4 square matrix. Each second transmission unit includes a second metal patch 61 and a second thermally induced phase change patch 62, such as... Figure 5As shown. The second metal patch 61 is made of a metal material, such as gold, copper, or aluminum. In this embodiment, the second metal patch 61 is made of aluminum, and its thickness is between 0.2 and 0.8 μm. The second thermotropic phase change patch 62 is made of a thermotropic phase change material, such as vanadium dioxide (VO2), germanium-antimony-tellurium alloy (Ge2Sb2Te5), and germanium telluride (GeTe), which are materials whose conductivity is regulated by heat. In this embodiment, the second thermotropic phase change patch 62 is made of vanadium dioxide, and its thickness is between 0.8 and 1 μm. The second metal patch 61 consists of two straight metal patches and one L-shaped metal patch. The second thermotropic phase change patch 62 consists of one straight thermotropic phase change patch. The two straight metal patches are arranged relatively parallel to each other in the Y-axis direction. Both the straight thermotropic phase change patch and the L-shaped metal patch are disposed between the two straight metal patches. A linear thermochromic phase change patch is positioned close to the upper linear metal patch, and an L-shaped metal patch is positioned close to the lower linear metal patch. The upper end of the linear thermochromic phase change patch is connected to the upper linear metal patch, while the lower end of the linear thermochromic phase change patch is suspended. In the N second transmission units, the linear metal patches of the second transmission units in the same row along the X-axis are connected end to end, and their two ends are respectively connected to two second electrode patches 63.

[0025] The matrix arrangement of the N first transmission units in the first polarization control structure layer 2 is exactly the same as the matrix arrangement of the N second transmission units in the second polarization control structure layer 6. The coverage dimensions of the first and second transmission units are the same, and the center positions of the N first transmission units and the N second transmission units are one-to-one in the Z-axis direction.

[0026] In use, the terahertz wave is incident from above the second polarization control structure layer 6 along the Z-axis. To ensure unobstructed passage of the terahertz wave on the polarization conversion filter, the irradiation area, i.e., the spot area, must be less than or equal to the coverage area of ​​the N first transmission units of the first polarization control structure layer 2 and the coverage area of ​​the N second transmission units of the second polarization control structure layer 6. In this embodiment, the coverage area of ​​the N first transmission units of the first polarization control structure layer 2 and the N first transmission units of the second polarization control structure layer 6 are equal, and this coverage area is 1.5 to 2.5 times the spot area of ​​the terahertz wave. The two first electrode patches 23 of the first polarization control structure layer 2 are connected to the positive and negative terminals of the first DC power supply, respectively, and the two second electrode patches 63 of the second polarization control structure layer 6 are connected to the positive and negative terminals of the second DC power supply, respectively. The voltages of the first and second DC power supplies are the same, ranging from 12 to 24V. When the first DC power supply and / or the second DC power supply are turned off, the first thermo-phase change patch 22 of the first polarization control structure layer 2 and / or the second thermo-phase change patch 62 of the second polarization control structure layer 6 are de-energized, and the first thermo-phase change patch 22 and / or the second thermo-phase change patch 62 do not undergo phase change, exhibiting an insulating state. When the first DC power supply and / or the second DC power supply are turned on, the first thermo-phase change patch 22 of the first polarization control structure layer 2 and / or the second thermo-phase change patch 62 of the second polarization control structure layer 6 are energized, and the first thermo-phase change patch 22 and / or the second thermo-phase change patch 62 undergo phase change, exhibiting a metallic state. The nano-insulation layer 4 is located between the first insulating layer 3 covered by the first polarization control structure layer 2 and the second insulating layer 5 covered by the second polarization control structure layer 6, so as to realize the individual phase change regulation of the first polarization control structure layer 2 and the second polarization control structure layer 6. Based on this principle, the polarization conversion filter of the present invention has the following four operating states, such as Figure 6 As shown:

[0027] When both the first and second DC power supplies are turned off, the polarization conversion filter performs single-peak polarization conversion filtering of terahertz waves. In this embodiment, the center frequency of the single peak is 0.8 THz.

[0028] When the first DC power supply and the second DC power supply are turned on simultaneously, the polarization conversion filter realizes the dual-peak polarization conversion filtering function of terahertz waves. In this embodiment, the center frequencies of the two peaks are 0.8THz and 1.19THz, respectively.

[0029] When the first DC power supply is turned on and the second DC power supply is turned off, the polarization conversion filter performs broadband polarization conversion filtering of terahertz waves. In this embodiment, the broadband range is 0.69THz to 1.29THz.

[0030] When the first DC power supply is off and the second DC power supply is on, the polarization conversion filter performs terahertz wave dual-peak polarization conversion filtering. However, since the transmittance of both peaks is low in this state, the dual-peak polarization conversion filtering effect is poor. Therefore, this state is discarded in this invention and is not considered.

[0031] The change of the first center frequency of the polarization conversion filter can be achieved by adjusting the total length (length in the X-axis direction) of the linear thermo-phase change patch of the first polarization control structure layer 2. In this embodiment, the total length of the linear thermo-phase change patch is 30 μm, and the corresponding center frequency is 0.8 THz. The change of the second center frequency of the polarization conversion filter can be achieved by adjusting the total length (length in the Y-axis direction) of the linear thermo-phase change patch of the second polarization control structure layer 6. In this embodiment, the total length of the linear thermo-phase change patch is 40 μm, and the corresponding center frequency is 1.19 THz. Due to the asymmetry of the first thermo-phase change patch 22 of the first polarization control structure layer 2, a broadband polarization conversion filtering phenomenon can be generated. The change of the broadband range of the polarization conversion filter can be achieved by adjusting the total length (the sum of the lengths in the two X-axis directions and the length in the one Y-axis direction) of the zigzag thermo-phase change patch. In this embodiment, the length of the Z-shaped thermal phase change patch in the X-axis direction is 35 μm, and the length of the Z-shaped thermal phase change patch in the Y-axis direction is 49 μm, that is, the total length of the Z-shaped thermal phase change patch is 119 μm, and the corresponding broadband range is 0.69 THz to 1.29 THz.

[0032] This invention achieves multiple functional adjustments to transmittance in a specific frequency band by controlling the on / off state of the first polarization control structure layer 2 and the second polarization control structure layer 6, and by adding a nano heat insulation layer 4 between the two insulating layers. It can realize three functional switching of single passband (single peak), double passband (double peak), and broadband polarization conversion filtering. It is suitable for fields such as terahertz polarization multiplexing communication, and features simple operation and stable performance.

[0033] It should be noted that although the embodiments described above are illustrative, they are not intended to limit the invention. Therefore, the invention is not limited to the specific embodiments described above. Any other embodiments obtained by those skilled in the art under the guidance of this invention without departing from its principles are considered to be within the protection scope of this invention.

Claims

1. A thermo-controlled terahertz single-peak-double-peak-wideband polarization conversion filter, characterized in that, The structure includes a high-resistivity silicon substrate layer (1), a first polarization control structure layer (2), a first insulating layer (3), a nano-thermal insulation layer (4), a second insulating layer (5), and a second polarization control structure layer (6) stacked from bottom to top in the Z-axis direction. The first polarization control structure layer (2) consists of two first electrode patches (23) and N first transmission units; the two first electrode patches (23) are both elongated strips extending along the X-axis and are arranged relatively parallel in the Y-axis direction; the N first transmission units are arranged in a matrix in the X-axis and Y-axis directions and are located between the two first electrode patches (23); the first transmission units in the same column in the Y-axis direction are connected in sequence, and their two ends are connected to the two first electrode patches (23) respectively; The second polarization control structure layer (6) consists of two second electrode patches (63) and N second transmission units; the two second electrode patches (63) are both elongated strips extending along the Y-axis and are arranged relatively parallel in the X-axis direction; the N second transmission units are arranged in a matrix in the X-axis and Y-axis directions and are located between the two second electrode patches (63); the second transmission units in the same row in the X-axis direction are connected in sequence, and their two ends are connected to the two second electrode patches (63) respectively; The matrix arrangement of the N first transmission units in the first polarization control structure layer (2) is exactly the same as the matrix arrangement of the N second transmission units in the second polarization control structure layer (6), and the N first transmission units and the N second transmission units are in one-to-one correspondence in the Z-axis direction. The two first electrode patches (23) of the first polarization control structure layer (2) are connected to the positive and negative terminals of the first DC power supply, respectively, and the two second electrode patches (63) of the second polarization control structure layer (6) are connected to the positive and negative terminals of the second DC power supply, respectively; the terahertz wave is incident from above the second polarization control structure layer (6) along the Z-axis direction; when the first DC power supply and the second DC power supply are turned off at the same time, the polarization conversion filter realizes the single-peak polarization conversion filtering function of the terahertz wave; when the first DC power supply and the second DC power supply are turned on at the same time, the polarization conversion filter realizes the double-peak polarization conversion filtering function of the terahertz wave; when the first DC power supply is turned on and the second DC power supply is turned off, the polarization conversion filter realizes the broadband polarization conversion filtering function of the terahertz wave. N is a positive integer greater than 1.

2. The electrothermally controlled terahertz single-peak-double-peak-wideband polarization conversion filter according to claim 1, characterized in that, Each first transmission unit includes a first metal patch (21) and a first thermally induced phase change patch (22); the first metal patch (21) consists of two inverted T-shaped metal patches; the first thermally induced phase change patch (22) consists of one Z-shaped thermally induced phase change patch and one straight thermally induced phase change patch; Two inverted T-shaped metal patches are arranged in a mirror image relative to each other in the X-axis direction; a Z-shaped thermo-phase change patch and a straight thermo-phase change patch are both located between the two inverted T-shaped metal patches; a straight thermo-phase change patch is inserted through the middle of the Z-shaped thermo-phase change patch along the X-axis direction; the two ends of the straight thermo-phase change patch are respectively connected to the two inverted T-shaped metal patches, and the two inverted T-shaped metal patches and the straight thermo-phase change patch form an H-shape.

3. The electrothermally controlled terahertz single-peak-double-peak-wideband polarization conversion filter according to claim 1, characterized in that, Each second transmission unit includes a second metal patch (61) and a second thermally induced phase change patch (62); the second metal patch (61) consists of two straight metal patches and one L-shaped metal patch; the second thermally induced phase change patch (62) consists of one straight thermally induced phase change patch; Two straight metal patches are arranged parallel to each other along the Y-axis. A straight thermal phase change patch and an L-shaped metal patch are both positioned between the two straight metal patches. The straight thermal phase change patch is closer to the upper straight metal patch, and the L-shaped metal patch is closer to the lower straight metal patch. The upper end of the straight thermal phase change patch is connected to the upper straight metal patch, and the lower end of the straight thermal phase change patch is suspended.

4. The electrothermally controlled terahertz single-peak-double-peak-wideband polarization conversion filter according to claim 1, characterized in that, The voltages of the first DC power supply and the second DC power supply are the same.

5. The electrothermally controlled terahertz single-peak-double-peak-wideband polarization conversion filter according to claim 1, characterized in that, The coverage area of ​​the first polarization control structure layer (2) is equal to that of the second polarization control structure layer (6), and the coverage area is greater than or equal to the irradiation area of ​​the terahertz wave.

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