Metasurface equilibrium three-valued 3-line-1-line encoder based on graphene and vanadium dioxide materials

Abstract

The invention discloses a metamaterial equilibrium three-valued 3-line-1-line encoder based on a graphene plasma induced transparency (PIT) effect and a vanadium dioxide phase change characteristic, and belongs to the technical field of terahertz communication modulation. The structure is composed of a vanadium dioxide substrate, a silicon dioxide dielectric layer, a silicon pattern layer, a rectangular graphene pattern layer, a silicon dioxide pattern layer and a top graphene pattern layer. Based on a graphene plasma induced transparency effect and a vanadium dioxide phase change characteristic, a vanadium dioxide state, a state of applying a bias voltage to a cross-like graphene pattern layer and a state of applying a bias voltage to a triangular graphene pattern layer are respectively used as three input quantities of the encoder; therefore, a 3-line to 1-line coding function of a certain frequency point in the terahertz wave band can be realized. The work fills the gap of the terahertz logic function device on the device.

Description

Technical Field

[0001] The present invention relates to the field of terahertz modulation technology, and in particular to a terahertz metasurface device with a 3-line-1-line coding function and an operation scheme. Background Art

[0002] In recent years, researchers have used the tunable properties of graphene materials to design metamaterial modulation devices, such as the terahertz metasurface 2-bit encoder based on graphene plasma-induced transparency (PIT) and the terahertz metasurface 3-bit encoder based on graphene dual plasma-induced transparency. These devices can achieve modulation functions by simply applying voltage without changing their structural dimensions or internal doping. The emergence of such logic function modulators is of great significance in practical design. However, the above terahertz devices are only binary encoders, that is, binary logic devices.

[0003] With the development of terahertz communication technology, the demand for multi-valued logic functional devices has also increased. Compared with binary logic, three-valued logic can handle more signal conversions. Currently, it is known that there are 3-wire-1-wire encoders based on three-valued memristors to regulate the output voltage results. However, there are no three-valued logic devices in the terahertz band. In order to fill this technical gap, it is particularly important to develop a balanced three-valued 3-wire-1-wire encoder in the terahertz band. Summary of the invention

[0004] In order to solve the above problems, the present invention discloses a super-surface balanced ternary 3-line-1-line encoder based on graphene and vanadium dioxide materials.

[0005] The present invention is achieved through the following technical scheme: a super-surface balanced three-value 3-line-1-line encoder based on graphene and vanadium dioxide materials, comprising a vanadium dioxide substrate 1, a silicon dioxide dielectric layer 2, a silicon layer 3, a silicon dioxide layer 4, a rectangular graphene layer, a cross-shaped graphene layer and a right-angled triangle layer with four sides; the dielectric layer 2 is located on the upper surface of the substrate layer 1, the silicon layer 3 and the rectangular graphene layer are both on the upper surface of the dielectric layer 2, the silicon dioxide layer 4 is located on the upper surface of the vertical rectangular graphene layer, and the cross-shaped graphene layer and the right-angled triangle layer with four sides are respectively located on the upper surfaces of the layer 4 and the layer 3.

[0006] In the above scheme, the thickness of the substrate 1 is 0.3 μm; the thickness of the dielectric layer 2, the layer 3 and the layer 4 is 2 μm; and the thickness of the graphene layer is 1 nm.

[0007] The above-mentioned supersurface balanced three-value 3-line-1-line encoder based on graphene and vanadium dioxide materials is characterized in that: when the conductivity of the vanadium dioxide substrate 1 is set to 200S / m, when voltage is applied to the rectangular graphene layer, the cross-like graphene layer and the right-angled triangle layer on the four sides, the phenomenon of dual plasma induced transparency is presented in the terahertz band through the coupling of light and dark modes.

[0008] The above-mentioned super-surface balanced three-value 3-line-1-line encoder based on graphene and vanadium dioxide materials can realize the 3-line-1-line encoding function; it is characterized in that: the state of applying bias voltage to the rectangular graphene layer is used as the enable terminal S, the metallic state or insulating state of vanadium dioxide is used as the logic input X2, the state of applying bias voltage to the cross-shaped graphene layer is used as the logic input X1, and the state of applying bias voltage to the four-sided triangular graphene layer is used as the logic input X 0。 When the enable terminal S=1 is valid, X2X1X0 can input "100", "010", or "001" as required to realize the 3-line-1-line encoding function at two frequency points.

[0009] In the above scheme, according to the state of the terahertz wave after it enters the device, the low transmittance of the electromagnetic wave at this frequency point (the valley of the PIT phenomenon) is the logic output "0", the high transmittance of the electromagnetic wave at this frequency point is the logic output "1", and the high reflectance of the electromagnetic wave at this frequency point is the logic output "-1". Among them, the logic output "0" only exists in the PIT phenomenon, and the low transmittance in other cases is not used as the logic output "0".

[0010] That is, as described above, the present invention obtains a 3-line-1-line encoder in the terahertz band by changing the three input quantities of the metasurface structure. The present invention has the characteristics of novel functions, flexible tunability, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a schematic diagram of the unit structure of a super-surface balanced three-value 3-line-1-line encoder based on graphene and vanadium dioxide materials.

[0012] Figure 2 This is a top view of the unit structure of a super-surface balanced three-value 3-line-1-line encoder based on graphene and vanadium dioxide materials.

[0013] Figure 3 The transmission spectrum of dual plasma induced transparency phenomenon is realized for a metasurface balanced ternary 3-line-1-line encoder based on graphene and vanadium dioxide materials.

[0014] Figure 4The reflection and transmission spectra of a supersurface balanced ternary 3-line-1-line encoder based on graphene and vanadium dioxide materials to realize the 3-line-1-line encoding function. ; DETAILED DESCRIPTION

[0015] In order to describe the solutions and advantages of the present invention in more detail, the present invention will be further explained below with reference to the accompanying drawings and in combination with embodiments. The following embodiments are only part of the embodiments, not all of the embodiments.

[0016] An implementation example of a supersurface balanced ternary 3-line-1-line encoder based on graphene and vanadium dioxide materials Figure 1 As shown. A 2μm thick silicon dioxide dielectric layer 2 is laid on a 0.3μm thick vanadium dioxide substrate 1, and then a rectangular graphene layer is plated at the center of the upper surface of the dielectric layer 2, and a 0.2μm thick silicon layer 3 is laid on the four corners of the upper surface of the dielectric layer 2, and then a 0.2μm thick cross-shaped silicon dioxide layer 4 is laid on the rectangular graphene layer, and finally, graphene layers of the same shape are plated on the upper surfaces of layers 3 and 4 respectively; in this example, the dielectric constant of silicon dioxide is 3.9, the dielectric constant of silicon is 11.9, and the conductivity of vanadium dioxide is 200S / m or 200000S / m.

[0017] A unit structure top view of a super-surface balanced three-value 3-line-1-line encoder based on graphene and vanadium dioxide materials is shown in FIG. Figure 2 As shown. The structure is axially symmetrical, with a unit structure period of P = 5μm. The right angles of the four isosceles right triangles are fixed at a = 1.77μm; the base length and waist length of the isosceles triangles in the cross-shaped pattern are fixed at b = 1.3μm and c = 3.95μm respectively; the width of the rectangular graphene is fixed at d = 0.2μm.

[0018] A metasurface balanced three-value 3-line-1-line encoder based on graphene and vanadium dioxide realizes the transmission spectrum of dual plasma induced transparency phenomenon. Figure 3 As shown. When the rectangular graphene layer acts alone, it is in dark mode; when the cross-shaped graphene layer and the quadrilateral triangular graphene layer act alone, they are both in bright mode. The rectangular graphene layer and the cross-shaped graphene layer produce dip1 and dip2 through the coupling of the bright-dark mode, and the cross-shaped graphene layer and the quadrilateral triangular graphene layer produce dip3 through the bright-bright mode coupling, which causes the inclination angle produced by the single quadrilateral triangular layer to shift. When the three act together, the dual plasma induced transparency phenomenon is formed.

[0019] A supersurface balanced ternary 3-line-1-line encoder based on graphene and vanadium dioxide material realizes 3-line-1-line encoding function. Figure 4By changing the input logic input, the 3-wire-1-wire encoding function at 2.572THz and 4.231THz can be realized. The truth table of the designed metamaterial 3-wire-1-wire encoder is shown in the following table, where S is the enable terminal, X2, X1 and X0 are logic inputs, and Y is the logic output.

[0020]

[0021] The described super-surface balanced ternary 3-line-1-line encoder based on graphene and vanadium dioxide materials uses a rectangular graphene layer as an enable end S, S=0, that is, the Fermi level of the layer is set to 0eV, S=1, that is, the Fermi level of the layer is set to 1.4eV; the state of the vanadium dioxide substrate is used as the input quantity X2, X2=0, that is, the vanadium dioxide is in an insulating state (the electrical conductivity is 200S / m), and X2=1, that is, the vanadium dioxide is in a metallic state (the electrical conductivity is 200000S / m); the Fermi level of the cross-shaped graphene layer is used as the input quantity X1. X1=0, that is, the Fermi level of the layer is set to 0eV, and X1=1, that is, the Fermi level of the layer is set to 1.4eV; the Fermi level of the quadrilateral triangle graphene layer is used as the input quantity X0. X0=0, that is, the Fermi level of the layer is set to 0eV, and X0=1, that is, the Fermi level of the layer is set to 1.4eV.

[0022] In this embodiment, it is defined that when the transmittance of the coding frequency point is higher than 50%, it is defined as the logic output state Y=1, otherwise it is defined as the logic output state Y=0; it is defined that when the coding frequency point achieves "complete reflection", it is defined as the logic output state Y=-1. That is, when the terahertz wave can "completely" penetrate the device, it is defined as Y=1, when the terahertz wave cannot "completely" penetrate the device, it is defined as Y=0, and when the terahertz wave is "completely" reflected back, it is defined as Y=-1. Among them, it is stipulated that the logic output Y=0 only exists in the PIT phenomenon, and the low transmittance in other cases is not regarded as the case of the logic output Y=0.

[0023] like Figure 4 As shown, when the Fermi level of the rectangular graphene layer is set to 1.4 eV, the vanadium dioxide substrate is set to a metallic state (conductivity is 200,000 S / m), and the Fermi levels of the cross-shaped graphene layer and the quadrilateral triangular graphene layer are both set to 0 eV, the logic input is X2X1X0=100, then the logic outputs at 2.572 THz and 4.231 THz are both Y=-1, and the reflectivity at the two frequency points is 93.4% and 93.1%, respectively.

[0024] like Figure 4As shown, when the Fermi level of the rectangular graphene layer is set to 1.4ev, the vanadium dioxide substrate is set to an insulating state (conductivity is 200S / m), the Fermi level of the cross-shaped graphene layer is set to 1.4eV, and the Fermi level of the quadrilateral triangular graphene layer is set to 0eV (at this time, the rectangular graphene layer and the cross-shaped graphene layer produce a single PIT phenomenon through the coupling of the light-dark mode), the logic input is X2X1X0=010, then the logic outputs at 2.572THz and 4.231THz are both Y=0, and the transmittances at the two frequency points are 5.1% and 12.3%, respectively.

[0025] like Figure 4 As shown, when the Fermi level of the rectangular graphene layer is set to 1.4ev, the vanadium dioxide substrate is set to an insulating state (conductivity is 200S / m), the Fermi level of the cross-shaped graphene layer is set to 0eV, and the Fermi level of the quadrilateral triangle graphene layer is set to 1.4eV, the logic input is X2X1X0=001, then the logic outputs at 2.572THz and 4.231THz are both Y=1, and the transmittances at the two frequency points are 99.6% and 97.1%, respectively.

[0026] like Figure 4 As shown, for the logic output Y=0 and Y=1, the modulation depth MD of the transmittance is calculated according to the corresponding formula to be 99.9% and 99.8% respectively, the extinction ratio ER is 12.9dB and 9.08dB respectively, and the insertion loss IL is 0.02dB and 0.15dB respectively, indicating that the 3-line-1-line encoder has excellent performance.

[0027] The above specifically describes an embodiment of a tunable device based on graphene plasma induced transparency, but the present invention is not limited to the embodiment. The contents not described in detail in this specification belong to the prior art known to professionals in the field.

Claims

1. A supersurface balanced ternary 3-line-1-line encoder based on graphene and vanadium dioxide materials, characterized in that: First, a dielectric layer 2 is laid on the upper surface of substrate 1, and four isosceles right triangle layers 3 are laid on the four corners of the upper surface of 2, and a rectangular graphene layer is plated at the center of the upper surface of 2, and then a cross-shaped layer 4 is laid on the surface of the rectangular graphene layer, and finally, graphene layers of the same shape are plated on the upper surfaces of layers 3 and 4. Substrate 1 is vanadium dioxide with a conductivity of 200S / m or 200000S / m and a thickness of 0.3μm; dielectric layer 2 and layer 4 are silicon dioxide with a dielectric constant of 3.9 and a thickness of 2μm; layer 3 is silicon with a dielectric constant of 11.9 and a thickness of 2μm; and the graphene layers are all 1nm. The right-angled sides of the isosceles right triangles at the four corners of the dielectric layer 2 are fixed at a=1.77μm; the cross-shaped layer 4 laid on the rectangular graphene layer is composed of an isosceles triangle rotated 90°, 180° and 270° and superimposed, and the base length and waist length are fixed at b=1.3μm and c=3.95μm respectively; the width of the rectangular graphene is fixed at d=0.2μm; the structure is an axisymmetric figure in a top view, and the side length P of the unit structure is 5μm.

2. The supersurface balanced ternary 3-line-1-line encoder based on graphene and vanadium dioxide material according to claim 1, characterized in that: The 3-line-1-line encoder is a multi-valued logic device having three different encoding output states. According to the state after the terahertz wave is incident on the device, the electromagnetic wave is in a low transmittance at this frequency point (the valley of the PIT phenomenon) as the logic output "0", the electromagnetic wave is in a high transmittance at this frequency point as the logic output "1", and the electromagnetic wave is in a high reflectance at this frequency point as the logic output "-1"; the 3-line-1-line encoder uses the state of applying a bias voltage to the rectangular graphene layer as the enable terminal S, and uses the vanadium dioxide state, the state of applying a bias voltage to the cross-shaped graphene layer, and the state of applying a bias voltage to the triangular graphene layer as three logic inputs X2X1X0 respectively. When the enable terminal S=1 is valid, and the logic inputs X2X1X0 are "100", "010", and "001" respectively, three logic output results can be obtained at a certain frequency point.

3. The supersurface balanced ternary 3-line-1-line encoder based on graphene and vanadium dioxide material according to claim 1, characterized in that: The rectangular graphene in the 3-line-1-line encoder structure is in dark mode, and the cross-shaped and triangular graphene are both in bright mode. The device can achieve dual plasma induced transparency through the light-dark coupling mechanism.

4. The supersurface balanced ternary 3-line-1-line encoder based on graphene and vanadium dioxide material according to claim 1, characterized in that: The 3-line-1-line encoder achieves 3-line-1-line encoding function at 2.572THz and 4.231THz, with reflectivity of 93.4% and 93.1% respectively, modulation depth MD of transmittance of 99.9% and 99.8% respectively, extinction ratio ER of 12.9dB and 9.08dB respectively, and insertion loss IL of 0.02dB and 0.15dB respectively.

Images