An electrically controlled terahertz dual-frequency phase modulator

Abstract

The present invention is an electrically controlled terahertz dual-frequency phase modulator, comprising a sapphire substrate and a metasurface structure resonant array located on the surface of the sapphire substrate. Each resonant unit comprises a T-shaped metal resonator, an inverted T-shaped metal resonator and a square open-ring resonator. The middle electrically controlled phase change patch is embedded in the gap between the T-shaped resonator and the inverted T-shaped metal resonator, and the right electrically controlled phase change patch is embedded in the opening of the open-ring resonator. An electrode is fixed on each side of the metasurface structure resonant array, which is respectively connected to the positive and negative poles of a DC power supply. The phase modulator provided by the present invention can achieve dual-band, large bandwidth, and phase modulation of more than 100 degrees by powering on, and the maximum adjustable phase exceeds 140 degrees. This terahertz dual-frequency phase modulator has broad application prospects in the fields of terahertz phased array radar, terahertz communication, terahertz imaging, etc.

Description

Technical Field

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

[0002] Terahertz (THz) waves have a frequency range of 0.1THz to 10THz, lying between microwaves and infrared radiation. They are the frequency band that will be used in future sixth-generation (6G) ultra-wideband wireless communications. Modulators that can actively manipulate the phase of THz waves have important applications in THz communications, imaging, and sensing. With the development and widespread application of THz technology, the demand for THz wave phase modulation devices is rapidly increasing. However, most natural materials exhibit only weak electromagnetic responses and therefore cannot be used to control THz wave phase. Furthermore, due to the characteristics of THz waves, phase modulators in the millimeter wave and visible light bands cannot be directly used. Therefore, considerable effort has been invested in developing tunable THz phase modulators based on various principles and methods.

[0003] The emergence of metamaterials has greatly enhanced our ability to manipulate electromagnetic waves. They can be used to construct terahertz phase modulators. By actively controlling the electromagnetic properties of the metamaterials and altering the resonant properties of metaatoms, the phase of terahertz waves can be modulated. However, existing terahertz phase modulators are mostly limited to a single frequency band, which still cannot meet the needs of many applications. Achieving dual-band, large-phase modulation in terahertz has become a challenge 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 consists of a sapphire substrate and a metasurface structure resonant array located on the sapphire substrate surface. 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 split-ring resonator, and two electrically controlled phase change patches. Electrode leads are located on the left and right sides of the metasurface structure resonant array, connecting to the positive and negative poles of a DC power supply, respectively. These electrode leads are connected to the leftmost and rightmost columns of resonant units in the metasurface structure resonant array, respectively.

[0007] The present invention designs an electrically controlled terahertz dual-frequency phase modulator, comprising a sapphire substrate and a metasurface structure resonant array located on the surface of the sapphire substrate. The area of ​​the metasurface structure resonant array 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 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 split 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 split 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 to 60 μm, and the opening length is 10 to 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 existing technology, the present invention has the following advantages: it provides an electrically controlled terahertz dual-frequency phase modulation device. By applying an external current to generate Joule heat, it triggers the phase change of an electrically controlled phase change patch, causing it to transition from an insulating state to a metallic state, thereby achieving dynamic control of the terahertz wave phase. When the vanadium dioxide is in the insulating state, two resonant peaks are generated at 0.33THz and 0.75THz by two T-shaped metal resonators and a square split-ring resonator. When the vanadium dioxide is in the metallic state, a new resonant 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 over 90%. In the dual frequency bands of 0.33-0.49THz and 0.61-0.75THz, the adjustable phase ranges from 100 degrees to 140 degrees, and the phase modulation reaches 100 degrees within the 300GHz operating bandwidth.

[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 diagram of a periodic structure array 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 middle 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 This is a graph showing the variation of terahertz wave transmittance with frequency when the electrically controlled terahertz dual-frequency phase modulator is powered on and powered off according to an embodiment of the present invention;

[0025] Figure 6 This is a graph showing the change of terahertz wave phase 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.

[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 will be described in further detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto. It should be noted that directional terms such as "upper," "lower," "center," "left," "right," "front," and "back" mentioned in the examples are merely references 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 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 metasurface 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 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 length and width of the sapphire substrate 1 are both larger than the length and width of the metasurface structure resonant array 2; the terahertz wave is incident from above the metasurface structure resonant array 2 and is emitted after passing through the sapphire substrate 1.

[0030] The metasurface structure resonant 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 resonant array 2 and is composed of a plurality of resonant units arranged in a regular matrix. The extraction structure is located on the relatively outer side of the metasurface structure resonant array 2 and is composed of two electrodes 3, which are respectively connected to the positive and negative poles of the DC power supply. It is understandable that the number of resonant units in the actual metasurface structure resonant array 2 is large. In order to make the picture clear, only the number of resonant units is shown in FIG. Figure 1 5×3 resonant units are shown in the figure.

[0031] like Figure 3 and 4 As shown, the resonant 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 resonant unit has a length a = 70 μm and a width b = 100 μm.

[0032] The T-shaped metal resonator 21 and the inverted T-shaped metal resonator 22 of this resonant unit are symmetrical about the unit's center, with a vertical rectangular gap formed at the center. The horizontal 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 resonant unit, a = 70 μm, and the width is c = 6 μm. The distance between the two T-shaped metal resonators is h = 78 μm. The length of the vertical rectangular gap between the T-shaped metal resonator 21 and the inverted T-shaped metal resonator 22 is g = 20 μm.

[0033] In this example, the square split-ring resonator 23 is located in the center of the resonant unit, with the opening 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 split 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 outside of the surface periodic structure and consists of two electrodes 3. Both electrodes 3 are long strips made of metal material. The first electrode is connected to the left side of the metasurface structure resonant array 2, and the second electrode is connected to the right side of the metasurface structure resonant 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 to it is powered off, and the middle electrically controlled phase change patch 24 and the right electrically controlled phase change patch 25 both have 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 of the incident terahertz wave are shown as follows: Figure 5 、 6 The solid line curve in .

[0038] When the switch of the electrode 3 is closed, all the metasurface structure resonance arrays 2 connected to it are energized, and the middle electrically controlled phase change patch 24 and the right electrically controlled phase change patch 25 nested 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 control 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 degrees 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 as follows: Figure 5 、 6 The dotted curve in .

[0039] In summary, the present invention can achieve dual-band and large-phase modulation effects 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 to further illustrate the purpose, technical solutions and beneficial effects of the present invention, and the present invention is not limited thereto. Any modifications, equivalent replacements, improvements, etc. made within the scope of the disclosure of the present invention are included in the scope of protection 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 of the sapphire substrate, wherein the area of ​​the metasurface structure resonant array (2) is 1.0 to 2.0 times the cross-sectional area of ​​a beam formed by an 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 is emitted; the sapphire substrate (1) has a thickness of 0.5 mm; 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 split 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 resonant 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); 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 DC 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 metasurface 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, etc., 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 split 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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