Electric control terahertz double-frequency phase modulator

Abstract

The invention relates to an electric control terahertz double-frequency phase modulator which comprises a sapphire substrate and a metasurface structure resonance array located on the surface of the sapphire substrate. Each resonance unit comprises a T-shaped metal resonator, an inverted T-shaped metal resonator and a square split ring resonator. The middle electric control phase change patch is embedded in a gap between the T-shaped resonator and the inverted T-shaped metal resonator, and the right electric control phase change patch is embedded in an opening of the split ring resonator. The two sides of the metasurface structure resonance array are each fixedly provided with an electrode which is connected with the positive electrode and the negative electrode of the direct-current power source. The phase modulator provided by the invention can realize dual-band, large-bandwidth and more than 100-degree phase modulation through power-on, and the adjustable maximum phase exceeds 140 degrees. The terahertz dual-frequency phase modulator has a wide application prospect in the fields of terahertz phased array radar, terahertz communication, terahertz imaging and the like.

Description

Technical Field

[0001] The invention relates to the field of terahertz functional devices, and in particular to an electrically controlled terahertz dual-frequency phase modulator. Background Art

[0002] The frequency range of terahertz (THz) waves is 0.1THz to 10THz, which is between microwaves and infrared rays. It is the frequency band to be used in the future sixth-generation (6G) ultra-wideband wireless communication. Modulators that can actively manipulate the phase of terahertz waves have important application value in the fields of terahertz communication, imaging, and sensing. With the development and promotion of terahertz technology, the demand for terahertz wave phase modulation devices is increasing rapidly. However, most natural materials only exhibit weak electromagnetic responses and therefore cannot be used to control the phase of terahertz waves. At the same time, due to the characteristics of terahertz waves, phase modulators in the millimeter wave band and visible light band cannot be used directly. Therefore, people have invested a lot of energy to develop adjustable terahertz phase modulators based on different principles and methods.

[0003] The emergence of metamaterials has greatly improved our ability to manipulate electromagnetic waves. Metamaterials can be used to build terahertz phase modulators. By actively regulating the electromagnetic properties of metamaterials and changing the resonance characteristics of metaatoms, the phase of terahertz waves can be modulated. However, most existing terahertz phase modulators can only modulate in one frequency band, which still cannot meet many application requirements. How to achieve terahertz dual-band and large phase modulation has become a difficulty in the terahertz field. Summary of the invention

[0004] The purpose of the present invention is to disclose an electrically controlled terahertz dual-frequency phase modulator, which can realize dual-frequency rapid and dynamic regulation of terahertz wave phase through electrical control, and the amplitude modulation depth can reach more than 90%.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] An electrically controlled terahertz dual-frequency phase modulator is composed of a sapphire substrate and a metasurface structure resonant array located on the surface of the sapphire substrate. The metasurface structure resonant array is composed of periodically distributed resonant units, each of which includes a T-shaped metal resonator, an inverted T-shaped metal resonator, a square open ring resonator and two electrically controlled phase change patches. The left and right sides of the metasurface structure resonant array are electrode leads, which are respectively connected to the positive and negative poles of a DC power supply. The electrode leads are respectively connected to the leftmost column and the rightmost column of resonant units in the metasurface structure resonant array.

[0007] The invention discloses an electrically controlled terahertz dual-frequency phase modulator, comprising a sapphire substrate and a metasurface structure resonance array located on the surface of the sapphire substrate, wherein the area of ​​the metasurface structure resonance array is 1.0 to 2.0 times the cross-sectional area of ​​a beam formed on the array surface by an incident terahertz wave; the terahertz wave is incident from above the metasurface structure resonance array and is emitted after passing through the sapphire substrate.

[0008] The T-shaped metal resonator and the inverted T-shaped metal resonator of the resonance unit are symmetrical about the center of the unit, and a vertical rectangular gap is formed at the center.

[0009] The square open ring resonator is located in the center of the resonance unit, and the opening is located in the middle of the right arm of the resonator; the horizontal bars of the square open ring resonator intersect with the vertical bars of the T-shaped metal resonator and the inverted T-shaped metal resonator respectively.

[0010] An intermediate electrically controlled phase change patch is embedded in the gap between the T-shaped resonator and the inverted T-shaped metal resonator.

[0011] Another electrically controlled phase change patch on the right is embedded in the opening of the square split ring resonator.

[0012] The transverse width of a resonance unit in the metasurface structure resonance array is 60 μm to 80 μm, and the longitudinal length is 90 μm to 110 μm, and the longitudinal length is 1 to 1.8 times the transverse width.

[0013] The materials of the T-shaped metal resonator, the inverted T-shaped metal resonator and the square open ring resonator in the metasurface structure resonant array are gold, copper, aluminum and the like, with a thickness of 0.1 μm to 0.5 μm and a width of 4 μm to 10 μm.

[0014] The horizontal bar length of the T-shaped metal resonator and the inverted T-shaped metal resonator is 60 μm to 80 μm, and the vertical bar length is 25 μm to 40 μm.

[0015] The side length of the square split ring resonator is 30-60 μm, and the opening length is 10-20 μm.

[0016] The middle electrically controlled phase change patch and the right electrically controlled phase change patch are long strips made of vanadium dioxide material and have a thickness of 0.05 μm to 0.5 μm.

[0017] The phase change characteristics of the electrically controlled phase change patch are controlled by an external current. When the patch temperature exceeds 68°C, vanadium dioxide changes from an insulating phase to a metallic phase, and the resistivity changes by 3-5 orders of magnitude, thereby achieving modulation of the terahertz wave phase.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: an electrically controlled terahertz dual-frequency phase modulation device is provided, which generates Joule heat through an external current to trigger the phase change of the electrically controlled phase change patch, so that it changes from an insulating state to a metallic state, thereby realizing dynamic regulation of the terahertz wave phase. When vanadium dioxide is in an insulating state, two resonance peaks are generated at 0.33THz and 0.75THz by two T-shaped metal resonators and a square open ring resonator; when vanadium dioxide is in a metallic state, a new resonance peak is generated in the middle of the dual-frequency resonance, and the amplitude modulation depth of the terahertz wave before and after the phase change can reach more than 90%. In the dual frequency bands of 0.33-0.49THz and 0.61-0.75THz, the adjustable phase is between 100 and 140 degrees; the phase modulation reaches 100 degrees within the working bandwidth of 300GHz.

[0019] Therefore, this electrically controlled terahertz dual-band phase modulator has potential application value in the fields of terahertz imaging, variable-focus terahertz lenses and phased array antennas. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a periodic structure array diagram of an electrically controlled terahertz dual-frequency phase modulation device according to an embodiment of the present invention;

[0021] Figure 2 for Figure 1 Schematic diagram of the AA section;

[0022] Figure 3 for Figure 1 Schematic diagram of a resonant unit structure;

[0023] Figure 4 for Figure 1 A top view of a resonant unit structure;

[0024] Figure 5 is a curve diagram showing the variation of terahertz wave transmittance with frequency when an electrically controlled terahertz dual-frequency phase modulator according to an embodiment of the present invention is powered on and powered off;

[0025] Figure 6 The present invention is a graph showing the change of terahertz wave phase with frequency when an electrically controlled terahertz dual-frequency phase modulator is powered on and powered off.

[0026] Numbers in the figure: 1-sapphire substrate layer; 2-metasurface structure resonant array; 3-electrode; 21-T-shaped metal resonator; 22-inverted T-shaped metal resonator; 23-square open ring resonator; 24-middle electrically controlled phase change patch; 25-right electrically controlled phase change patch. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with specific embodiments, but the embodiments of the present invention are not limited thereto. It should be noted that the directional terms mentioned in the examples, such as "upper", "lower", "middle", "left", "right", "front", "back", etc., are only referenced to the directions of the drawings. Therefore, the directions used are only used for illustration and are not used to limit the scope of protection of the present invention.

[0028] An electrically controlled terahertz dual-frequency phase modulator, such as Figure 1 and 2 As shown, it includes a sapphire substrate 1 and a super-surface structure resonant array 2 located on the surface of the sapphire substrate; in a preferred embodiment of the present invention, the sapphire substrate 1 is rectangular and has a thickness of 0.5 mm.

[0029] In this example, the area of ​​the metasurface structure resonance array 2 is 1.0 to 2.0 times the cross-sectional area of ​​the beam formed by the incident terahertz wave on the array surface; the length and width of the sapphire substrate 1 are both larger than the length and width of the metasurface structure resonance array 2; the terahertz wave is incident from above the metasurface structure resonance array 2 and is emitted after passing through the sapphire substrate 1.

[0030] The metasurface structure resonance array 2 in this example includes two parts: a surface periodic structure and an extraction structure; the surface periodic structure is located in the center of the metasurface structure resonance array 2, and is composed of a plurality of resonance units arranged in a regular matrix. The extraction structure is located on the relatively outer side of the metasurface structure resonance array 2, and is composed of two electrodes 3, which are respectively connected to the positive and negative poles of a DC power supply. It can be understood that the number of resonance units in the actual metasurface structure resonance array 2 is large, so in order to make the picture clear, only the resonance units are shown in FIG. Figure 1 5×3 resonant units are shown in the figure.

[0031] like Figure 3 and 4 As shown, the resonance unit in this example includes a T-shaped metal resonator 21, an inverted T-shaped metal resonator 22, a square split ring resonator 23, a middle electrically controlled phase change patch 24 and a right electrically controlled phase change patch 25. A resonance unit has a length of a=70 μm and a width of b=100 μm.

[0032] The T-shaped metal resonator 21 and the inverted T-shaped metal resonator 22 of the resonance unit in this example are symmetrical about the unit center, and a vertical rectangular gap is formed at the center. The lateral length of the T-shaped metal resonator 21 and the inverted T-shaped metal resonator 22 in this example is equal to the length of the resonance unit, which is a=70μm, the width is c=6μm, and the distance between the two T-shaped metal resonator horizontal bars is h=78μm; the length of the vertical rectangular gap between the T-shaped metal resonator 21 and the inverted T-shaped metal resonator 22 is g=20μm.

[0033] In this example, the square split ring resonator 23 is located in the center of the resonant unit, and the opening is located in the middle of the right arm of the resonator; the horizontal strips of the square split ring resonator 23 intersect with the vertical strips of the T-shaped metal resonator 21 and the inverted T-shaped metal resonator 22. In this example, the side length of the square split ring resonator 23 is l = 54 μm, and the length of the split ring is g = 20 μm.

[0034] In this example, the middle electrically controlled phase change patch 24 is embedded in the vertical rectangular gap between the T-shaped resonator 21 and the inverted T-shaped resonator 22. The middle electrically controlled phase change patch 24 is a vanadium dioxide patch with a thickness of 0.1 μm, a length of g=20 μm, and a width of w=8 μm.

[0035] In this example, the right electrically controlled phase change patch 25 is embedded in the opening of the square open ring resonator 23. The right electrically controlled phase change patch 25 is a vanadium dioxide patch with a thickness of 0.1 μm, a length of g=20 μm, and a width of w=8 μm.

[0036] In this example, the lead-out structure is located on the relatively outer side of the surface periodic structure and is composed of two electrodes 3. The two electrodes 3 are both long strips made of metal materials, the first electrode is connected to the left side of the metasurface structure resonance array 2, and the second electrode is connected to the right side of the metasurface structure resonance array 2.

[0037] In this example, when the switch connecting the electrode 3 to the DC power supply is disconnected, the metasurface structure resonant array 2 connected thereto is powered off, and the middle electrically controlled phase change patch 24 and the right electrically controlled phase change patch 25 are both low conductivity. The dual-band phase modulator resonates with the T-shaped metal resonator 21, the inverted T-shaped metal resonator 22 and the square open ring resonator 23, generating two resonance peaks at 0.33THz and 0.75THz. At this time, the curves of the terahertz wave transmittance and phase change with frequency incident on this phase modulator are as follows: Figure 5 , 6 The solid line curve in .

[0038] When the switch of the electrode 3 is closed, all the connected metasurface structure resonance arrays 2 are energized, and the middle electrically controlled phase change patch 24 and the right electrically controlled phase change patch 25 embedded in each resonance unit of the metasurface structure resonance array 2 generate Joule heat-triggered phase change due to the addition of current, causing it to change from an insulating state to a metallic state, thereby realizing dynamic regulation of the terahertz wave phase. Based on this principle, a new resonance peak will be generated between the two resonance peaks, and the amplitude modulation depth of the terahertz wave before and after the phase change can reach more than 90%. In the dual frequency bands of 0.33-0.49THz and 0.61-0.75THz, the adjustable phase is between 100 and 140 degrees, and the phase modulation reaches 100 degrees within the working bandwidth of 300GHz. At this time, the curves of the transmittance and phase of the terahertz wave incident on this phase modulator as a function of frequency are shown as follows: Figure 5 , 6 As shown by the dashed curve in .

[0039] In summary, the present invention can achieve the dual-band and large-phase modulation effect of terahertz waves by electrifying electrodes, is suitable for different occasions, has a simple structure, and is easy to operate.

[0040] The above embodiments are only specific examples for further describing the purpose, technical solutions and beneficial effects of the present invention, and the present invention is not limited thereto. Any modification, equivalent replacement, improvement, etc. made within the scope of the disclosure of the present invention are included in the protection scope of the present invention.

Claims

1. An electrically controlled terahertz dual-frequency phase modulator, comprising a sapphire substrate (1) and a metasurface structure resonant array (2) located on the surface thereof, wherein the area of ​​the metasurface structure resonant array (2) is 1.0 to 2.0 times the cross-sectional area of ​​the beam formed by the incident terahertz wave on the array surface; the terahertz wave is incident from above the metasurface structure resonant array (2), passes through the sapphire substrate (1) and then exits. The sapphire substrate (1) is 0.5 mm thick; and is characterized in that: The metasurface structure resonant array (2) is composed of periodically distributed resonant units, each of which includes a T-shaped metal resonator (21), an inverted T-shaped metal resonator (22), a square open ring resonator (23), a middle electrically controlled phase change patch (24) and a right electrically controlled phase change patch (25); The T-shaped metal resonator (21) and the inverted T-shaped metal resonator (22) of the resonance unit are symmetrical about the center of the unit, and a vertical rectangular gap is formed at the center; The square split ring resonator (23) is located in the center of the resonance unit, and the opening is located in the middle of the right arm of the resonator; the horizontal bars of the square split ring resonator (23) intersect with the vertical bars of the T-shaped metal resonator (21) and the inverted T-shaped metal resonator (22) respectively; The intermediate electrically controlled phase change patch (24) is embedded in the gap between the T-shaped resonator (21) and the inverted T-shaped metal resonator (22); The right electrically controlled phase change patch (25) is embedded in the opening of the square open ring resonator (23); The relatively outer side of the metasurface structure resonance array (2) is a lead-out structure and is composed of two electrodes (3) which are respectively connected to the positive and negative poles of a direct current power supply; the electrodes (3) are respectively connected to the leftmost column and the rightmost column of resonance units of the metasurface structure resonance array (2).

2. The electrically controlled terahertz dual-frequency phase modulator according to claim 1, characterized in that: The transverse width of a resonance unit in the super-surface structure resonance array (2) is 60 μm to 80 μm, and the longitudinal length is 90 μm to 110 μm, and the longitudinal length is 1 to 1.8 times the transverse width.

3. The electrically controlled terahertz dual-frequency phase modulator according to claim 1, characterized in that: The materials of the T-shaped metal resonator (21), the inverted T-shaped metal resonator (22) and the square open ring resonator (23) are gold, copper, aluminum and the like, with a thickness of 0.1 μm to 0.5 μm and a width of 4 μm to 10 μm.

4. The electrically controlled terahertz dual-frequency phase modulator according to claim 1, characterized in that: The horizontal bar length of the T-shaped metal resonator (21) and the inverted T-shaped metal resonator (22) is 60 μm to 80 μm, and the vertical bar length is 25 μm to 40 μm.

5. The electrically controlled terahertz dual-frequency phase modulator according to claim 1, characterized in that: The side length of the square open ring resonator (23) is 30 μm to 60 μm, and the opening length is 10 μm to 20 μm.

6. The electrically controlled terahertz dual-frequency phase modulator according to claim 1, characterized in that: The middle electrically controlled phase change patch (24) and the right electrically controlled phase change patch (25) are long strips made of vanadium dioxide material and have a thickness of 0.05 μm to 0.5 μm.

7. The electrically controlled terahertz dual-frequency phase modulator according to claim 1, characterized in that: The length of the middle electrically controlled phase change patch (24) is 4 μm to 10 μm, and the width is 10 μm to 20 μm; the length of the right electrically controlled phase change patch (25) is 4 μm to 10 μm, and the width is 10 μm to 20 μm.

8. The electrically controlled terahertz dual-frequency phase modulator according to claim 1, characterized in that: The voltage of the DC power supply is 12V to 24V.

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