Multi-frequency-point terahertz synchronous and asynchronous dual-mode switch

Abstract

The invention discloses a multi-frequency-point terahertz synchronous and asynchronous dual-mode switch which structurally comprises a first graphene strip, a second graphene strip, a third graphene strip, a fourth graphene strip, a first hexagonal graphene pattern, a second hexagonal graphene pattern and a silicon substrate. The graphene of different structures can interact to generate a plasma induced transparency effect under the irradiation of terahertz waves, so that two-frequency-point synchronous switching, three-frequency-point synchronous switching and four-frequency-point asynchronous switching can be realized by adjusting the Fermi level of the graphene. The multi-frequency-point terahertz synchronous and asynchronous dual-mode switch has the advantages of being simple in structure, high in controllability, small in size, low in cost, easy to integrate and the like, and meets the requirements of application in the fields of terahertz wave communication and the like.

Description

Technical Field

[0001] The invention relates to terahertz technology, and in particular to a multi-frequency terahertz synchronous and asynchronous dual-mode switch. Background Art

[0002] Terahertz (THz) refers to electromagnetic waves with a radiation frequency range of 0.1 to 10 THz and a wavelength of 30 μm to 30 mm. It is located between microwaves and infrared radiation in the electromagnetic spectrum. Due to the development limitations of terahertz sources and terahertz functional devices, compared with microwave and infrared radiation bands that have been maturely applied in various fields, the terahertz band is called the terahertz gap. In recent years, the vigorous development of low-scale semiconductor-related technologies has promoted the rapid development of terahertz wave technology. In addition, thanks to the advantages of terahertz waves such as high transmittance, low energy, water absorption, and transient properties, terahertz wave technology has been widely used in various fields, such as terahertz security imaging, terahertz nondestructive testing, and terahertz biomedical testing. Most materials in nature do not respond to the terahertz wave band, which is also an important reason for the slow development of terahertz wave functional devices. Due to the rapid development of terahertz wave technology applications, related terahertz functional devices have become increasingly important in the basic applications of terahertz wave technology, such as terahertz filters, terahertz switches, terahertz modulators, etc. As the application and promotion of terahertz technology becomes increasingly mature, it is of great significance to study high-efficiency, high-performance, and low-cost terahertz devices.

[0003] In recent years, terahertz switches have attracted extensive attention from researchers. Most current research focuses on single-frequency terahertz switches. Once the device structure is determined, the operating frequency is fixed and most cannot be dynamically adjusted. Therefore, controllable multi-frequency terahertz switches have become a hot topic in current research, but there are few studies on multi-frequency terahertz switches. This is due to strict constraints, and it is challenging to achieve the optimal setting between multiple frequencies and simple structures. A multi-frequency, simple-structured, dynamically adjustable terahertz switch has important application significance for meeting the needs of terahertz communication and its multiplexing system. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art, such as difficulty in integration, complex structure, difficulty in actual production and high cost, and to provide a multi-frequency terahertz synchronous and asynchronous dual-mode switch.

[0005] In order to achieve the above object, the technical solution of the present invention is as follows:

[0006] A multi-frequency terahertz synchronous and asynchronous dual-mode switch, which is formed by unit structures arranged continuously and periodically on a plane; each unit structure comprises a silicon substrate and a graphene pattern formed by graphene material attached to the surface of the silicon substrate; the graphene pattern comprises a first graphene strip, a second graphene strip, a third graphene strip, a fourth graphene strip, a first hexagonal graphene pattern and a second hexagonal graphene pattern; the first graphene strip, the second graphene strip, the third graphene strip and the fourth graphene strip are respectively arranged close to the four sides of the square surface of the silicon substrate, the first hexagonal graphene pattern and the second hexagonal graphene pattern are arranged inside the enclosed area of ​​the four graphene strips, and each has and only has one endpoint overlapping the center of the square surface of the silicon substrate; the graphene pattern on the surface of the silicon substrate is both mirror-symmetrical and centrally symmetrical.

[0007] Preferably, the first graphene strip, the second graphene strip, the third graphene strip and the fourth graphene strip are all rectangular in shape with the same size, and the length of the rectangle is 3.5 μm to 4 μm, and the width is 0.5 μm to 1.0 μm.

[0008] Preferably, the first hexagonal graphene pattern has a length of 1 μm to 3 μm and a width of 0.5 μm to 1.5 μm, and one set of opposite sides of the six sides of the first hexagonal graphene pattern has a length of 0.2 to 0.3 μm, and the other two sets of opposite sides have a length of 0.8 to 1.2 μm.

[0009] Preferably, the second hexagonal graphene pattern has a length of 1 μm to 3 μm and a width of 0.5 μm to 1.5 μm, and one set of opposite sides of the six sides of the second hexagonal graphene pattern has a length of 0.2 to 0.3 μm, and the other two sets of opposite sides have a length of 0.8 to 1.2 μm.

[0010] Preferably, the distance from the first hexagonal graphene pattern to the nearest graphene strip is 0.1 μm to 0.5 μm.

[0011] Preferably, the distance from the second hexagonal graphene pattern to the nearest graphene strip is 0.1 μm to 0.5 μm.

[0012] Preferably, the silicon substrate has a dielectric constant of 11.9 and a thickness of 0.1 μm to 0.2 μm.

[0013] Preferably, the period P of the unit structure in the x direction is x 5μm~20μm, the period P in the y direction y 5μm~20μm.

[0014] Preferably, the entire multi-frequency terahertz synchronous and asynchronous dual-mode switch consists of 36 unit structures periodically arranged in a 6×6 rectangular array.

[0015] Preferably, when an x-polarized terahertz wave is incident, the switching device is controlled to transmit the terahertz wave on and off by adjusting the graphene Fermi level, thereby realizing dual-frequency synchronous switching, triple-frequency synchronous switching and quad-frequency asynchronous switching.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] The present invention provides a multi-frequency terahertz synchronous and asynchronous dual-mode switch, the structure of which includes a first graphene strip, a second graphene strip, a third graphene strip, a fourth graphene strip, a first hexagonal graphene pattern, a second hexagonal graphene pattern, and a silicon substrate. Since graphenes of different structures can interact with each other under terahertz wave irradiation to produce a plasma-induced transparency effect, the multi-frequency terahertz synchronous and asynchronous dual-mode switch of the present invention can realize the functions of a two-frequency synchronous switch, a three-frequency synchronous switch, and a four-frequency asynchronous switch by adjusting the Fermi level of the graphene. The present invention has the advantages of simple structure, small size, low cost, and easy production. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a three-dimensional schematic diagram of the periodic structure of multi-frequency terahertz synchronous and asynchronous dual-mode switching;

[0019] Figure 2 It is a three-dimensional schematic diagram of the unit structure of a multi-frequency terahertz synchronous and asynchronous dual-mode switch;

[0020] Figure 3 It is a schematic diagram of the planar structure of a multi-frequency terahertz synchronous and asynchronous dual-mode switch;

[0021] Figure 4 The multi-frequency terahertz synchronous and asynchronous dual-mode switch at 5.12 THz is shown as a dual-frequency synchronous switch, (a) electric field distribution in the on state, (b) electric field distribution in the off state;

[0022] Figure 5 The multi-frequency terahertz synchronous and asynchronous dual-mode switch at 7.91 THz is manifested as a dual-frequency synchronous switch, (a) electric field distribution in the on state, (b) electric field distribution in the off state;

[0023] Figure 6 It is the performance curve of the multi-frequency terahertz synchronous and asynchronous dual-mode switch in the dual-frequency synchronous switching state;

[0024] Figure 7The multi-frequency terahertz synchronous and asynchronous dual-mode switch at 5.31 THz is shown as a three-frequency synchronous switch, (a) the electric field distribution in the on state, (b) the electric field distribution in the off state;

[0025] Figure 8 The multi-frequency terahertz synchronous and asynchronous dual-mode switch at 6.77 THz is shown as a three-frequency synchronous switch, (a) the electric field distribution in the on state, (b) the electric field distribution in the off state;

[0026] Fig. 9 The multi-frequency terahertz synchronous and asynchronous dual-mode switch at 8.20 THz is shown as a three-frequency synchronous switch, (a) the electric field distribution in the on state, (b) the electric field distribution in the off state;

[0027] Fig.10 It is the performance curve of the multi-frequency terahertz synchronous and asynchronous dual-mode switch in the three-frequency synchronous switching state;

[0028] Fig.11 The multi-frequency terahertz synchronous and asynchronous dual-mode switch at 6.24 THz is manifested as a four-frequency asynchronous switch, (a) electric field distribution in the on state, (b) electric field distribution in the off state;

[0029] Fig.12 The multi-frequency terahertz synchronous and asynchronous dual-mode switch at 6.77 THz is manifested as a four-frequency asynchronous switch, (a) electric field distribution in the on state, (b) electric field distribution in the off state;

[0030] Fig.13 The multi-frequency terahertz synchronous and asynchronous dual-mode switch at 7.39 THz is manifested as a four-frequency asynchronous switch, (a) the electric field distribution in the on state, (b) the electric field distribution in the off state;

[0031] Fig.14 The multi-frequency terahertz synchronous and asynchronous dual-mode switch at 8.20 THz is manifested as a four-frequency asynchronous switch, (a) the electric field distribution in the on state, (b) the electric field distribution in the off state;

[0032] Fig.15 It is the performance curve of the multi-frequency terahertz synchronous and asynchronous dual-mode switch in the four-frequency asynchronous switching state. DETAILED DESCRIPTION

[0033] In order to make the above-mentioned purpose, features and advantages of the present invention more obvious and easy to understand, the specific implementation mode of the present invention is described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. The technical features in each embodiment of the present invention can be combined accordingly without conflicting with each other.

[0034] In the description of the present invention, it should be understood that the terms "first" and "second" are only used for the purpose of distinguishing descriptions, and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features.

[0035] like Figure 1 As shown, the present invention provides a multi-frequency terahertz synchronous and asynchronous dual-mode switch, which is composed of unit structures arranged continuously and periodically on a plane. All unit structures are arranged continuously in a rectangular array to form a four-sided continuous switch device whose plane size can be adjusted according to actual conditions. Figure 1 A multi-frequency terahertz synchronous and asynchronous dual-mode switch composed of 36 unit structures arranged periodically in a 6×6 rectangular array is shown. Of course, in other embodiments, the specific number of periods and arrangement form can be adjusted according to actual needs.

[0036] like Figure 2As shown, the shape of each unit structure in the entire switch device is the same. Each unit structure includes a silicon substrate 7 and a graphene pattern formed by graphene material attached to the surface of the silicon substrate 7. The graphene pattern includes a first graphene strip 1, a second graphene strip 2, a third graphene strip 3, a fourth graphene strip 4, a first hexagonal graphene pattern 5 and a second hexagonal graphene pattern 6; the first graphene strip 1, the second graphene strip 2, the third graphene strip 3 and the fourth graphene strip 4 are respectively arranged close to the four sides of the square surface of the silicon substrate 7, and the long side of each graphene strip is parallel to one of the sides of the square surface, and the long sides of the four graphene strips are respectively parallel to the four sides of the square surface. The first hexagonal graphene pattern 5 and the second hexagonal graphene pattern 6 are arranged inside the enclosed area of ​​the four graphene strips. The first hexagonal graphene pattern 5 and the second hexagonal graphene pattern 6 each have and only have one endpoint overlapped, and the overlap point is located at the center of the square surface of the silicon substrate 7. The graphene pattern on the surface of the silicon substrate 7 is both mirror-symmetrical and centrally symmetrical. There are two mirror-symmetrical center lines of the graphene pattern, which are two vertical center lines on the square surface passing through the above-mentioned overlap point. The central symmetry point of the graphene pattern is the above-mentioned overlap point.

[0037] For the convenience of description, the present invention has been Figure 3 The relative spatial position relationship of the unit structure is described by the up, down, left, and right directions in the figure. Therefore, the specific materials and parameters of the multi-frequency terahertz synchronous and asynchronous dual-mode switch are as follows:

[0038] The first graphene strip 1, the second graphene strip 2, the third graphene strip 3, and the fourth graphene strip 4 are all rectangular in shape with the same size, and the length of the rectangle is 3.5 μm to 4 μm, and the width is 0.5 μm to 1.0 μm. The long sides of the first graphene strip 1, the second graphene strip 2, the third graphene strip 3, and the fourth graphene strip 4 are respectively parallel to and close to the upper edge, the lower edge, the left edge, and the right edge of the square surface of the silicon substrate 7, and each has the same distance from the closest edge. The length of the first hexagonal graphene pattern 5 (the maximum length of the pattern, i.e., the distance between the upper and lower vertices in the hexagon) is 1 μm to 3 μm, and the width (the maximum width of the pattern, i.e., the distance between the left and right opposite sides in the hexagon) is 0.5 μm to 1.5 μm, and the length of one group of opposite sides among the six sides of the first hexagonal graphene pattern 5 (a group of opposite sides not connecting the above-mentioned overlapping points, i.e., the two opposite sides on the left and right sides) is 0.2 to 0.3 μm, and the lengths of the other two groups of opposite sides are 0.8 to 1.2 μm. The length of the second hexagonal graphene pattern 6 (the maximum length of the pattern, i.e., the distance between the upper and lower vertices in the hexagon) is 1 μm to 3 μm, and the width (the maximum width of the pattern, i.e., the distance between the left and right opposite sides in the hexagon) is 0.5 μm to 1.5 μm, and the length of one set of opposite sides (a set of opposite sides not connecting the above-mentioned coincidence points, i.e., the two opposite sides on the left and right sides) among the six sides of the second hexagonal graphene pattern 6 is 0.2 to 0.3 μm, and the lengths of the other two sets of opposite sides are 0.8 to 1.2 μm. The distance from the first hexagonal graphene pattern 5 to the nearest graphene strip, i.e., the distance from the first hexagonal graphene pattern 5 to the first graphene strip 1, is 0.1 μm to 0.5 μm. The distance from the second hexagonal graphene pattern 6 to the nearest graphene strip, i.e., the distance from the second hexagonal graphene pattern 6 to the second graphene strip 2, is 0.1 μm to 0.5 μm. The dielectric constant of the silicon substrate 7 is 11.9, and the thickness is 0.1 μm to 0.2 μm. Figure 3 As shown, the period P of the above unit structure in the x direction is x 5μm~20μm, the period P in the y direction y 5μm~20μm.

[0039] When an x-polarized terahertz wave is incident on the multi-frequency terahertz synchronous and asynchronous dual-mode switch, the on-off function of the transmitted terahertz wave of the switch device can be controlled by adjusting the graphene Fermi level, thereby realizing two-frequency synchronous switching, three-frequency synchronous switching and four-frequency asynchronous switching.

[0040] The above-mentioned multi-frequency terahertz synchronous and asynchronous dual-mode switch is applied to a specific example to demonstrate its technical effect.

[0041] Example 1

[0042] In this embodiment, the shapes of the components of the multi-frequency terahertz synchronous and asynchronous dual-mode switch are as described above. Figure 1 to Figure 3 , I will not go into details here. However, the specific parameters of each component are as follows:

[0043] The first graphene strip 1, the second graphene strip 2, the third graphene strip 3, and the fourth graphene strip 4 are all rectangular shapes of the same size, with a length of 3.7 μm and a width of 0.7 μm. The length of the first hexagonal graphene pattern 5 is 2 μm and a width of 1 μm, and the length of one set of opposite sides of the six sides of the first hexagonal graphene pattern 5 is 0.27 μm, and the lengths of the other two sets of opposite sides are 1 μm. The length of the second hexagonal graphene pattern 6 is 2 μm and a width of 1 μm, and the length of one set of opposite sides of the six sides of the second hexagonal graphene pattern 6 is 0.27 μm, and the lengths of the other two sets of opposite sides are 1 μm. The distance from the first hexagonal graphene pattern 5 to the nearest graphene strip is 0.1 μm. The distance from the second hexagonal graphene pattern 6 to the nearest graphene strip is 0.1 μm. The dielectric constant of the silicon substrate 7 is 11.9 and the thickness is 0.15 μm. The period P of the unit structure in the x direction is x The period P in the y direction is 6 μm. y The entire multi-frequency terahertz synchronous and asynchronous dual-mode switch is composed of a periodic arrangement of unit structures with a period number of 6×6.

[0044] When x-polarized terahertz waves are incident on this multi-frequency terahertz synchronous and asynchronous dual-mode switch device, the device can control the on-off function of transmitting terahertz waves by adjusting the graphene Fermi level, realizing dual-frequency synchronous switching, triple-frequency synchronous switching, and quad-frequency asynchronous switching. When the graphene Fermi level switches between 1.2eV and 1.7eV, the device can realize dual-frequency synchronous switching. The graphene Fermi level is E f =1.2eV, terahertz waves with frequencies of f1 = 5.17THz and f2 = 7.91THz can pass through the device, no electric field energy is generated on the structure, and the switch is on; the Fermi level of graphene is E f =1.7eV, terahertz waves with frequencies of f1 = 5.17THz and f2 = 7.91THz cannot penetrate the device, and electric field energy is generated on the structure, and the switch behaves as off, such as Figure 4 and Figure 5 As shown. When the graphene Fermi level is E f =1.2eV, the terahertz wave transmittances of f1 = 5.17THz and f2 = 7.91THz are 0.874 and 0.974 respectively, and the switch is on; the graphene Fermi level is adjusted to E f=1.7eV, the transmittances of terahertz waves with frequencies of f1 = 5.17THz and f2 = 7.91THz are 0.011 and 0.057 respectively, and the switch behaves as off. The performance curve is as follows Figure 6 As shown. When the graphene Fermi level switches between 0.2eV and 1.8eV, the device can achieve triple-frequency synchronous switching function. f =0.2eV, terahertz waves with frequencies of f1 = 5.31THz, f2 = 6.77THz, and f3 = 8.20THz can pass through the device. No electric field energy is generated on the structure, and the switch is on. The Fermi level of graphene is E f =1.8eV, terahertz waves with frequencies of f1 = 5.31THz, f2 = 6.77THz, and f3 = 8.20THz cannot penetrate the device, and electric field energy is generated on the structure, and the switch behaves as off. Figure 7 , Figure 8 and Fig. 9 As shown. When the graphene Fermi level is E f =0.2eV, the transmittances of terahertz waves with frequencies of f1 = 5.31THz, f2 = 6.77THz, and f3 = 8.20THz are 0.970, 0.985, and 0.981, respectively, and the switch is on; the graphene Fermi level is adjusted to E f =1.8eV, the transmittances of terahertz waves with frequencies of f1 = 5.31THz, f2 = 6.77THz, and f3 = 8.20THz are 0.008, 0.081, and 0.051, respectively. The switch is off. The performance curve is as follows Fig.10 As shown. When the graphene Fermi level switches between 1.5eV and 1.8eV, the device can achieve a four-frequency asynchronous switching function. f =1.5eV, terahertz waves with frequencies of f1=6.24THz and f3=7.39THz cannot pass through the device, electric field energy is generated on the structure, and the switch is off; at the same time, terahertz waves with frequencies of f2=6.77THz and f4=8.20THz can pass through the device, no electric field energy is generated on the structure, and the switch is on. The Fermi level of graphene is E f =1.8eV, the terahertz waves with frequencies of f1=6.24THz and f3=7.39THz pass through the device, no electric field energy is generated on the structure, and the switch is on; at the same time, the terahertz waves with frequencies of f2=6.77THz and f4=8.20THz cannot pass through the device, and electric field energy is generated on the structure, and the switch is off, as shown in FIG. Fig.11 , Fig.12 , Fig.13 and Fig.14 When the graphene Fermi level is E f=1.5eV, the transmittances of terahertz waves with frequencies of f1 = 6.24THz and f3 = 7.39THz are 0.090 and 0.083 respectively, and the switch is off; at the same time, the transmittances of terahertz waves with frequencies of f2 = 6.77THz and f4 = 8.20THz are 0.911 and 0.939 respectively, and the switch is on. f =1.8eV, the transmittances of the terahertz waves with frequencies of f1 = 6.24THz and f3 = 7.39THz are 0.904 and 0.943 respectively, and the switch is on; at the same time, the transmittances of the terahertz waves with frequencies of f2 = 6.77THz and f4 = 8.20THz are 0.081 and 0.051 respectively, and the switch is off. The performance curves are shown in Fig.15 This shows that the designed multi-frequency terahertz synchronous and asynchronous dual-mode switch can switch on or off the two-frequency, three-frequency and four-frequency terahertz waves, and has excellent performance.

[0045] The above-described embodiment is only a preferred solution of the present invention, but it is not intended to limit the present invention. A person skilled in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A multi-frequency terahertz synchronous and asynchronous dual-mode switch, characterized in that: The invention is formed by continuously and periodically arranging unit structures on a plane; each unit structure comprises a silicon substrate (7) and a graphene pattern formed by graphene material attached to the surface of the silicon substrate (7); the graphene pattern comprises a first graphene strip (1), a second graphene strip (2), a third graphene strip (3), a fourth graphene strip (4), a first hexagonal graphene pattern (5) and a second hexagonal graphene pattern (6); the first graphene strip (1), the second graphene strip (2), the third graphene strip (3) and the fourth graphene strip (4) are respectively arranged close to four sides of the square surface of the silicon substrate (7); the first hexagonal graphene pattern (5) and the second hexagonal graphene pattern (6) are arranged inside the enclosed area of ​​the four graphene strips, and each has only one endpoint that overlaps at the center of the square surface of the silicon substrate (7); the graphene pattern on the surface of the silicon substrate (7) is both mirror-symmetrical and centrally symmetrical.

2. The multi-frequency terahertz synchronous and asynchronous dual-mode switch according to claim 1, characterized in that: The first graphene strip (1), the second graphene strip (2), the third graphene strip (3), and the fourth graphene strip (4) are all rectangular in shape with the same size, with a length of 3.5 μm to 4 μm and a width of 0.5 μm to 1.0 μm.

3. The multi-frequency terahertz synchronous and asynchronous dual-mode switch according to claim 1, characterized in that: The first hexagonal graphene pattern (5) has a length of 1 μm to 3 μm and a width of 0.5 μm to 1.5 μm, and one set of opposite sides of the six sides of the first hexagonal graphene pattern (5) has a length of 0.2 to 0.3 μm, and the other two sets of opposite sides have lengths of 0.8 to 1.2 μm.

4. The multi-frequency terahertz synchronous and asynchronous dual-mode switch according to claim 1, characterized in that: The second hexagonal graphene pattern (6) has a length of 1 μm to 3 μm and a width of 0.5 μm to 1.5 μm, and one set of opposite sides of the six sides of the second hexagonal graphene pattern (6) has a length of 0.2 to 0.3 μm, and the other two sets of opposite sides have lengths of 0.8 to 1.2 μm.

5. The multi-frequency terahertz synchronous and asynchronous dual-mode switch according to claim 1, characterized in that: The distance between the first hexagonal graphene pattern (5) and the nearest graphene strip is 0.1 μm to 0.5 μm.

6. The multi-frequency terahertz synchronous and asynchronous dual-mode switch according to claim 1, characterized in that: The distance between the second hexagonal graphene pattern (6) and the nearest graphene strip is 0.1 μm to 0.5 μm.

7. The multi-frequency terahertz synchronous and asynchronous dual-mode switch according to claim 1, characterized in that: The silicon substrate (7) has a dielectric constant of 11.9 and a thickness of 0.1 μm to 0.2 μm.

8. The multi-frequency terahertz synchronous and asynchronous dual-mode switch according to claim 1, characterized in that: The period P of the unit structure in the x direction x 5μm~20μm, the period P in the y direction y 5μm~20μm.

9. The multi-frequency terahertz synchronous and asynchronous dual-mode switch according to claim 1, characterized in that: The entire multi-frequency terahertz synchronous and asynchronous dual-mode switch consists of 36 unit structures arranged periodically in a 6×6 rectangular array.

10. The multi-frequency terahertz synchronous and asynchronous dual-mode switch according to claim 1, characterized in that: When x-polarized terahertz waves are incident, the switching device is controlled to transmit terahertz waves by adjusting the graphene Fermi level, thereby realizing two-frequency synchronous switching, three-frequency synchronous switching and four-frequency asynchronous switching.

Images