Terahertz metamaterial device for realizing EIT-like phenomenon by coupling bright and dark modes

Abstract

The invention discloses a terahertz metamaterial device for realizing an EIT-like phenomenon by coupling a bright mode and a dark mode, and belongs to the technical field of terahertz application. The terahertz metamaterial device comprises a substrate layer and patterned resonator layers which are periodically arranged on the substrate layer. The patterned resonator layer is formed by combining a bright mode resonator of a cross structure and four strip-shaped short arm structure dark mode resonators, electromagnetic fields are enabled to generate destructive interference through near-field coupling between a bright mode and a dark mode so as to realize an EIT-like phenomenon, and a transparent window with the transmissivity of 86.5% is generated at 1.588 THz. One patterned resonator layer and the substrate layer form a structure period, one structure period P is 25 [mu] m, and the terahertz metamaterial device is an array formed by splicing a plurality of structure periods. The optical device can be used as a four-frequency asynchronous optical switch device, a sensor, a modulator, a slow light device and other optical devices.

Description

Technical Field

[0001] The present invention relates to the field of terahertz application technology, and in particular to a terahertz metamaterial device that realizes EIT-like phenomenon by coupling bright and dark modes. Background Art

[0002] Terahertz (THz) waves refer to electromagnetic waves with a frequency range of 0.1THz-10THz and a wavelength range of 0.03mm-3mm. The THz band is located between the microwave and infrared bands in the electromagnetic spectrum. It has good penetration and can penetrate materials such as paper and plastic. It also has strong penetration, high resolution and low energy. These characteristics make THz waves have broad application prospects in the fields of biomedicine, food safety, safety testing, etc. Metamaterials (MMS) are a specially designed artificial synthetic structure with very special electromagnetic properties, such as negative conductivity and negative dielectric constant. By artificially adjusting the unit structure and size parameters of metamaterials, different electromagnetic responses can be generated, thereby realizing electromagnetic phenomena that cannot be produced in many natural materials, such as negative refractive index. Terahertz metamaterial devices control electromagnetic waves by designing specific periodic structures, but lack dynamic adjustability after fixing the structure in ordinary metal materials, and can only manipulate electromagnetic waves within a predetermined frequency range. Compared with other metal materials, graphene has the advantage of being tunable. Its electronic properties can be adjusted by applying bias voltage or chemical doping to achieve dynamic tuning of the electromagnetic response of terahertz metamaterial devices, thereby dynamically controlling terahertz waves. In practical applications, the Fermi level can be regulated by applying bias voltage. An ion gel layer with a dielectric constant of 1.82 is laid on top of the graphene layer and a gold gate is deposited on the ion gel layer. The Fermi level of graphene can be regulated by applying bias voltage control.

[0003] Electromagnetically induced transparency (EIT) is a quantum interference phenomenon between atomic states caused by the interaction between coherent electromagnetic fields and multi-level systems. This phenomenon reduces the absorption of light by metamaterials at the atomic resonance frequency, thereby producing a transparent window. In the transparent window, light transmission exhibits strong dispersion characteristics, which can be used to control the incident speed of light and is applied in the fields of optical storage, slow light transmission, and biosensing. However, the conditions for realizing the EIT effect in atomic systems are extremely harsh, such as extremely low temperatures and relatively strict rare gas experimental conditions. In recent years, researchers have begun to use metamaterials to simulate the EIT phenomenon, which is called electromagnetically induced transparency (EIT-like). EIT-like reduces the strict requirements for working conditions and expands the ideas for people to study the EIT effect and develop applications. At present, there are generally two ways to realize the EIT-like phenomenon: bright mode coupling and bright-dark mode coupling. When an electromagnetic wave is incident on a metamaterial structure, the bright mode resonator can be directly excited by the incident electromagnetic wave, while the dark mode resonator cannot be directly excited by the incident electromagnetic wave but can be excited by the near-field coupling of the bright mode resonator. Bright mode coupling is achieved by the weak coupling of two or more bright mode resonators, which causes the electromagnetic field to produce destructive interference, thereby producing an EIT-like phenomenon. Bright and dark mode coupling, on the other hand, is caused by the near-field coupling between the bright mode and the dark mode, which transfers the electromagnetic energy of the bright mode to the dark mode and produces destructive interference, thereby forming a transparent window in the transmission spectrum and realizing the EIT-like phenomenon. However, few existing EIT-like phenomena can achieve the excellent performance of sensors and switches at the same time. Therefore, there is an urgent need to develop terahertz metamaterial EIT-like devices that integrate dynamically tunable modulators, high-performance sensors, and excellent performance switch devices. Summary of the invention

[0004] The purpose of the present invention is to provide a terahertz metamaterial device that realizes EIT-like phenomenon by coupling bright and dark modes, so as to solve the key problems existing in the terahertz metamaterial device in the background technology, such as non-tunability and difficulty in simultaneously achieving excellent performance of sensors and switches.

[0005] The present invention provides a terahertz metamaterial device that realizes EIT-like phenomenon by coupling bright and dark modes, and its structure comprises: a substrate layer and a patterned graphene resonator layer periodically arranged on the substrate layer. The patterned graphene resonator layer is composed of a bright mode resonator with a cross structure and four dark mode resonators with strip-shaped short arm structures. The surface of the resonator layer is the front side of the terahertz metamaterial device that realizes EIT-like phenomenon by coupling bright and dark modes.

[0006] Preferably, a structural period P of the terahertz metamaterial device for realizing EIT-like phenomenon by bright and dark mode coupling is 25 μm, and the terahertz metamaterial device includes an array formed by splicing multiple structural periods.

[0007] Preferably, the thickness of the substrate layer is 100 nm, and the substrate layer material is silicon dioxide (SiO2) material, and its relative dielectric constant ε is 3.9.

[0008] Preferably, the material of the patterned resonator layer is a single-layer graphene, the thickness of the single-layer graphene is 0.34 nm, and the initial value of the graphene Fermi level is set to E F =1.0eV, its conductivity is determined by the intra-band and inter-band conductivity, which can be calculated by the classic Kubo formula.

[0009] Preferably, the length L1 of the horizontal and vertical bars of the cross-structure bright mode resonator is 23 μm, and the width W is 2 μm; the length L2 of the short arms of the four strip-shaped short-arm dark mode resonators is 12.5 μm, and the width W is also 2 μm; the spacing G between the cross-structure resonator and the four strip-shaped short-arm resonators is 2 μm. The cross-structure resonator and the four strip-shaped short-arm resonators are combined to form a patterned resonator layer.

[0010] The present invention provides a method for using a terahertz metamaterial device that realizes an EIT-like phenomenon by coupling bright and dark modes as follows: an incident wave is vertically incident on the front side of the resonator layer, resonates with the terahertz metamaterial device, and generates a transparent window with a transmittance of up to 86.5% at 1.588 THz.

[0011] The present invention uses the above-mentioned bright and dark mode coupling to realize the terahertz metamaterial device of EIT-like phenomenon, and its beneficial effects are as follows:

[0012] (1) The terahertz metamaterial device described above designs a bright mode structure and a dark mode structure to generate bright and dark mode coupling, realizing the EIT-like phenomenon. The cross-structure resonator as a bright mode can be directly excited by the incident wave, and the four strip-shaped short arm resonators as dark modes cannot be directly excited by the incident wave but can be excited by the near-field coupling of the bright mode structure. The near-field coupling between the bright and dark modes causes the electromagnetic field to produce destructive interference and a transparent window with a transmittance of 86.5% is generated at 1.588 THz.

[0013] (2) The terahertz metamaterial device that realizes the EIT-like phenomenon by coupling the bright and dark modes can also be used as a four-frequency asynchronous optical switch device. The transmittance thresholds of the "on" and "off" states are set to 80% and 10% respectively. At the four frequency points of 1.037THz, 1.277THz, 1.588THz and 1.956THz, when E F =0.6eV and E F =1.0eV, the "on" and "off" states are completely opposite, realizing the quad-frequency asynchronous optical switch function.

[0014] (3) The terahertz metamaterial device that realizes the EIT-like phenomenon by coupling the bright and dark modes can also be used as a sensor. The EIT-like spectrum has a transmission peak and two transmission valleys. The changes of these three characteristic peaks can be used as key indicators for the EIT-like device to detect substances. By monitoring their frequency and amplitude changes, the EIT-like device has the potential to be used as a sensor. The terahertz metamaterial device proposed in the present invention has two transmission valleys. 1 (1.227THz), dip 2 The sensitivities at the three frequency points are dip (1.956THz) and transmission peak (1.588THz) respectively. 1 =707GHz / RIU, dip 2 =842GHz / RIU and peak=1132GHz / RIU, and can still maintain a high transmittance when the incident angle is greater than 70°. Therefore, the terahertz metamaterial device proposed in the present invention has excellent sensing performance such as high sensitivity and insensitivity to changes in the incident angle.

[0015] (4) The terahertz metamaterial device that realizes the EIT-like phenomenon by coupling the bright and dark modes can be used as a modulator. The conductivity of the graphene surface can be manipulated by changing the Fermi level. The Fermi level of graphene can be adjusted by an external voltage to achieve modulation of the EIT-like transparent window. The maximum modulation depth of the terahertz metamaterial device proposed in the present invention reaches 97.5%, which overcomes the problem that the terahertz metamaterial device can only manipulate electromagnetic waves within a predetermined frequency range after preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of a three-dimensional structure of a terahertz metamaterial device for realizing EIT-like phenomenon by coupling bright and dark modes provided by the present invention;

[0017] Figure 2 This is a front view of a terahertz metamaterial device for realizing EIT-like phenomenon by coupling bright and dark modes provided by the present invention;

[0018] Figure 3 It is a transmission spectrum diagram of a terahertz metamaterial device that realizes EIT-like phenomenon by coupling bright and dark modes provided by the present invention;

[0019] Figure 4 It is a schematic diagram of the electric field distribution of a terahertz metamaterial device that realizes EIT-like phenomenon by coupling bright and dark modes provided by the present invention.

[0020] Figure 5 It is a three-level system principle diagram of a terahertz metamaterial device for realizing EIT-like phenomenon by bright and dark mode coupling provided by the present invention.

[0021] Figure 6 It is a transmission curve diagram of a terahertz metamaterial device that realizes EIT-like phenomenon by bright and dark mode coupling provided by the present invention as a four-frequency asynchronous optical switch device.

[0022] Figure 7 The present invention provides a terahertz metamaterial device that realizes EIT-like phenomenon by coupling bright and dark modes, and detects transmission curves corresponding to objects to be tested with different refractive indices.

[0023] Figure 8 The transmission spectrum diagram at different incident angles of a terahertz metamaterial device for realizing EIT-like phenomenon by bright and dark mode coupling provided by the present invention.

[0024] Fig. 9 It is a transmission curve diagram of different Fermi energy levels of a terahertz metamaterial device for realizing EIT-like phenomenon by bright and dark mode coupling provided by the present invention.

[0025] Fig.10 It is a group delay curve diagram of a terahertz metamaterial device that realizes EIT-like phenomenon by bright and dark mode coupling provided by the present invention.

[0026] Reference numerals

[0027] 1. Patterned graphene resonator layer; 2. Silicon dioxide substrate layer; 3. Ion gel layer; 4. Gold gate; 5. Incident wave. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific implementation examples, but is not limited thereto. Other embodiments obtained by modifying or equivalently replacing the technical solution of the present invention without creative work all belong to the protection scope of the present invention. Any adjustment of the structure, modification of the proportional relationship or change of the size can be applied to the technical scope of the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0029] The present invention provides a terahertz metamaterial device that realizes EIT-like phenomenon by coupling bright and dark modes. The device includes a silicon dioxide substrate layer and a patterned graphene resonator layer periodically arranged on the substrate layer. A patterned resonator layer and the substrate layer form a structural period. The terahertz metamaterial device is an array formed by splicing multiple structural periods. The spliced ​​array is as follows: Figure 1 As shown. In actual situations, there are N structural periods, N is generally greater than 3. Figure 1 The schematic diagram of the array is composed of 9 periodic structures. The surface where the patterned graphene resonator layer is located is the front side of the terahertz metamaterial device. Figure 2 As shown, the bottom of the substrate layer is the reverse side. The patterned graphene resonator layer is composed of a cross structure and four strip-shaped short arm structures. A silicon dioxide substrate layer and a group of patterned graphene resonator layers on the substrate layer form a structural period. A structural period P is 25 μm, the thickness of the silicon dioxide substrate layer is 100 nm, and the length and width of a silicon dioxide substrate layer are both 25 μm. The material of the periodically arranged patterned resonator layer on the substrate layer is graphene, which is a two-dimensional material. The thickness of a single layer of graphene is 0.34 nm, and the Fermi level of graphene is E F The initial value of is set to 1.0 eV. The length L1 of the cross structure is 23 μm, the width W is 2 μm, the length of the short arm is 12.5 μm, the width is also 2 μm, and the spacing G between the short arm and the cross structure is 2 μm. The cross structure and the four strip short arm structures are combined to form a patterned graphene resonator layer, and are deposited on the silicon dioxide substrate layer to form a structural period. The terahertz metamaterial device described in the present invention is an array formed by splicing multiple structural periods.

[0030] Example 1

[0031] The present invention provides a terahertz metamaterial device for realizing EIT-like phenomenon by coupling bright and dark modes, and a method for using the device: an incident wave is vertically incident from the surface of a patterned graphene resonator layer, and through the near-field coupling between the bright and dark modes of a cross-structure resonator and four strip-shaped short-arm structure resonators, the electromagnetic field produces destructive interference, thereby generating a transparent window with a transmittance of 86.5% at 1.588 THz.

[0032] The basic working principle of a terahertz metamaterial device that realizes the EIT-like phenomenon by coupling bright and dark modes is as follows: when the incident wave is incident on the surface of the terahertz metamaterial, the metamaterial structural unit resonates with the incident wave within a specific frequency range, which causes the local electric and magnetic fields to be enhanced or weakened. In order to better explain the physical mechanism of the present invention to achieve EIT-like, a single cross structure, four strip short arm structures and a structure combining the two will be studied below. The resonator layer of a single cross structure will directly couple with the incident wave as a bright mode, resonate at 1.660 THz to form a transmission valley, such as Figure 3 As shown by the dotted line, the four short-arm strip structures as dark modes cannot directly couple with the incident wave and do not form strong resonance, as shown in Figure 3 As shown by the dashed line in the middle, the combination of the two can produce destructive interference in the electromagnetic field through the near-field coupling between the bright and dark modes, and produce a transparent window with a transmittance of 86.5% at 1.588 THz, realizing the EIT-like phenomenon, such as Figure 3 In addition, two transmission valleys are given. 1 (1.227THz), dip 2 The electric field diagram at the transmission peak (1.956THz) and the transmission peak (1.588THz) is further explained, as shown in Figure 4 As shown. Obviously, at these three frequency points, the dark mode alone is not excited by the direct incident wave, and there is no electric field energy accumulation. However, in the bright mode alone, the electric field energy accumulates at the vertical bars of the cross, resulting in dipole resonance, and resonance occurs at 1.660 THz to form a transmission valley. In the structure combining the two, the electric field energy accumulates mainly at 1.227 THz and 1.956 THz. Since the electric field accumulation at 1.956 THz is more obvious, the transmittance is lower than that at 1.227 THz. At 1.588 THz, the bright and dark modes produce destructive interference in the electromagnetic field through near-field coupling, and there is no electric field energy accumulation, realizing an EIT-like phenomenon. In order to further explain this phenomenon, the most classic three-level Λ-type system is introduced to illustrate, as shown in Figure 5 As shown. In an atomic system with Λ-type structure, there are usually three quantum states: ground state, metastable state and excited state, which are represented by |1>, |2> and |3> respectively. The dark mode corresponds to the metastable state |2> in the atomic system, and the bright mode corresponds to the excited state |3> in the atomic system. When only the detection light exists, if the detection light frequency (ω p ) matches the transition frequency from the ground state to the excited state, the probe light will be absorbed by the atomic system, causing the electrons to transition from the ground state to the excited state. c), the pump light will stimulate the transition from |2> to |3>, but because the two transition paths are in opposite phases, the energy they generate cancels each other out, causing the electrons in |1> to be unable to transition to |3>, resulting in a transparent window. The electron transition from energy level |1> to energy level |3> can be completed directly, and some of the detection light photons are absorbed, forming a transmission valley on the transmission spectrum, such as Figure 3 As shown by the dotted line, the energy of the electron transition from energy level |2> to energy level |3> is insufficient to be completed directly. Through the near-field coupling of the bright and dark modes, the energy of the electron transition from energy level |3> to energy level |1> is transferred to energy level |2>. After energy level |2> obtains energy, it can complete the electron transition from energy level |2> to energy level |3>. The destructive interference between the bright and dark modes limits the absorption of the incident electromagnetic wave by the bright mode, thus forming an EIT-like window.

[0033] Example 2

[0034] The present invention provides a method for using a terahertz metamaterial device that realizes an EIT-like phenomenon by coupling between bright and dark modes as a four-frequency asynchronous optical switch device: the incident wave is vertically incident from the surface of the terahertz metamaterial device, coupled with the patterned graphene resonator layer to generate resonance, and the Fermi level of the graphene is changed while keeping other structural parameters unchanged to achieve switch state conversion. Therefore, the graphene Fermi level can be regulated by applying an external bias voltage, and an ion gel layer with a dielectric constant of 1.82 is laid on the top of the graphene layer, and a gold gate is deposited on the ion gel layer. By applying an external bias voltage V gs Control the Fermi level of graphene. The transmittance thresholds of the "on" and "off" states are set to 80% and 10% respectively, that is, when the transmittance is greater than 80%, the terahertz metamaterial device is in the "on" state at the corresponding frequency point, and when the transmittance effect is 10%, the terahertz metamaterial device is in the "off" state at the corresponding frequency point. The corresponding four frequency points are 1.037THz, 1.227THz, 1.588THz and 1.956THz, respectively. The transmission spectrum is shown in the figure below: Figure 6 As shown. When the Fermi level E F =0.6eV, the transmittance of the device at 1.037THz and 1.588THz is less than 10%, which is in the "off" state, corresponding to OFF 1 and OFF 3 state, while the transmittance at 1.277THz and 1.956THz is greater than 80%, which is in the "on" state, corresponding to ON 2 and ON 4 state. And when E F =1.0eV, the transmittance at 1.037THz and 1.588THz is greater than 80%, which is in the "on" state, corresponding to ON 1and ON 3 state, while the transmittance at 1.277THz and 1.956THz is less than 10%, which is in the "off" state, corresponding to OFF 2 and OFF 4 Status, and E F =0.6eV, the "on" and "off" states are completely opposite, realizing a four-frequency asynchronous optical switch. The performance of the optical switch can be calculated by the corresponding modulation depth MD = |T on -T Off | / T on And insertion loss IL = -10lg (T on ) was evaluated. The MD at 1.037THz was calculated. 1 90.4%, IL 1 =0.85dB, at 1.227THz MD 2 94.6%, IL 2 =0.64dB, at 1.588THz MD 3 91.6%, IL 3 =0.63dB, at 1.956THz MD 4 97.4%, IL 4 =0.69 dB. This indicates that the terahertz metamaterial device for realizing EIT-like phenomenon by bright and dark mode coupling proposed in the present invention is a four-frequency asynchronous optical switch device with lower insertion loss and greater modulation depth.

[0035] Example 3

[0036] The present invention provides a method for using a terahertz metamaterial device that realizes an EIT-like phenomenon by coupling a bright and dark mode as a sensor: an incident wave is vertically incident from the surface of the terahertz metamaterial device, and is coupled with a patterned graphene resonator layer to produce resonance. When the refractive index of the surrounding medium changes, the equivalent dielectric constant and equivalent magnetic permeability of the terahertz metamaterial device will change, thereby affecting the coupling strength between the bright mode and the dark mode. This change in coupling strength will cause the frequency and width of the EIT-like window to change, so that the refractive index of the surrounding medium can be detected by monitoring the change in the EIT-like window. Sensitivity is one of the main performance parameters of a terahertz metamaterial sensor, and the higher the sensitivity, the better the sensing performance. During detection, a test object with a certain thickness is placed above the terahertz metamaterial device, and the terahertz wave is vertically incident on the surface of the terahertz metamaterial device to detect and analyze the target substance by detecting the signal change. The sensitivity of a terahertz metamaterial sensor is defined as the offset of the resonant frequency when the refractive index changes per unit. Its specific value can be calculated using the formula S=Δf / Δn, where Δf is the change in the resonant frequency of the sensor object when the refractive index changes, and Δn is the change in the refractive index of the object. In order to explore the sensing performance of the terahertz metamaterial device proposed in the present invention, different objects to be tested are placed above the terahertz metamaterial device. The objects to be tested are selected to be biological molecules and cells with a refractive index between 1.2 and 1.6. The refractive index n of the object to be tested is changed from n=1.2 to n=1.6, with an interval of 0.1 each time. The corresponding transmission spectrum also changes. The transmission spectrum is as follows: Figure 7 As shown in the figure. When the refractive index of the object under test changes, the resonant frequency of the terahertz metamaterial device shifts, and the shift amount of the object under test with different refractive index is different. The two transmission valleys dip are calculated by the formula. 1 (1.227THz), dip 2 The sensitivities of dip (1.956THz) and transmission peak (1.588THz) are 1 The peak is 707GHz / RIU, the dip is 842GHz / RIU 2 The incident angle is 1132GHz / RIU. Considering that there may be experimental errors in the experiment, which may cause the incident angle to shift, it is necessary to study the impact of the incident angle on the entire metamaterial device. The incident angle of the electromagnetic wave is taken as θ, which represents the angle between the incident direction and the z-axis. The transmission spectrum is obtained when the incident angle changes from 0° to 80°, as shown in the figure below. Figure 8As shown in the figure, it can be seen that the incident angle has little effect on the metamaterial device proposed in the present invention, and the transmittance can still be kept high when the incident angle is greater than 70°, indicating that the proposed metamaterial device is insensitive to the change of the incident angle. Therefore, it can be further shown that the terahertz metamaterial device proposed in the present invention that realizes the EIT-like phenomenon by coupling the bright and dark modes can be used as a high-performance sensor with high sensitivity and high stability.

[0037] Example 4

[0038] The present invention provides a method for using a terahertz metamaterial device that realizes an EIT-like phenomenon by coupling a bright and dark mode as a modulator: an incident wave is vertically incident from the surface of the terahertz metamaterial device, and couples with a patterned graphene resonator layer to generate resonance. The terahertz metamaterial device controls the incident electromagnetic wave by designing a specific periodic structure. However, the fixed-structure terahertz metamaterial device lacks dynamic adjustability, and its physical structure cannot be changed after manufacturing. Therefore, the fixed-structure terahertz metamaterial device can only manipulate electromagnetic waves within a predetermined frequency range. Compared with other metal materials, graphene has the advantage of tunable conductivity. Through an external electric field or chemical regulation, graphene can realize dynamic frequency response and function regulation of terahertz metamaterial devices, making it an ideal material for realizing tunable terahertz metamaterial devices. The present invention controls the Fermi level of graphene by an external bias voltage method. A layer of ion gel with a dielectric constant of 1.82 is laid on the graphene layer, and a gold gate is deposited on the ion gel layer. The bias voltage V gs Controlling the Fermi level of graphene. By controlling the Fermi level of graphene, the transmission curve of the terahertz metamaterial device can be frequency tuned. The resonant frequency increases with the increase of the Fermi level of graphene, such as Fig. 9 As shown, the Fermi level E of graphene F Adjusting between 0.5eV-1.0eV can still maintain a high transmittance and still produce EIT-like phenomenon, with a maximum modulation depth MD MAX =97.5%. This indicates that the terahertz metamaterial device for realizing EIT-like phenomenon by bright and dark mode coupling proposed in the present invention can be used as a frequency modulator for terahertz incident waves.

[0039] Example 5

[0040] The present invention provides a method for using a terahertz metamaterial device that realizes the EIT-like phenomenon through bright and dark mode coupling as a slow light device: the incident wave is vertically incident from the surface of the terahertz metamaterial device, and couples with the patterned graphene resonator layer to produce resonance, thereby generating an EIT-like effect. When the EIT-like effect occurs, the refractive index of the system changes dramatically with frequency, causing the speed of the detection light pulse to slow down when propagating in the medium, thereby generating a slow light effect, that is, the group velocity of the detection light pulse is reduced. The slow light effect reduces the transmission speed of light during the generation, transmission and other propagation processes of the optical signal, thereby effectively controlling the optical signal. The strength of the slow light effect can be measured by the group delay generated. The definition of group delay is where ω is the angular frequency, is the transmission phase. By calculation, it can be obtained that when the graphene Fermi level is 1.0 eV, the group delay of the proposed terahertz metamaterial device is 1.52 ps, as shown in Fig.10 As shown, it is shown that the present invention provides a terahertz metamaterial device that realizes EIT-like phenomenon by coupling bright and dark modes and can be used as a slow light device with high group delay.

[0041] It can be illustrated from the above embodiments that the terahertz metamaterial device of the present invention can be used as optical devices such as quad-frequency asynchronous optical switch devices, sensors, modulators and slow light devices, which can provide great convenience for the integration and miniaturization of terahertz metamaterial devices. With the rapid development of photonics technology and metamaterial technology, the preparation of terahertz metamaterial devices based on graphene is feasible. There are many methods for preparing uniform single-layer graphene, such as micromechanical peeling and chemical vapor deposition (Chemical Vapor Deposition, CVD). Among them, CVD method is a commonly used method for preparing graphene. CVD technology is used to grow a large uniform single-layer graphene on silicon dioxide, and then a patterned graphene layer is obtained by electron beam lithography. From the above, it is shown that the terahertz metamaterial device proposed by the present invention that realizes EIT-like phenomenon by light and dark mode coupling is feasible for preparation.

[0042] It should be noted that the above-described embodiments are further explanations of the technical solutions of the present invention, rather than limitations. Those skilled in the art should understand that this description should not be interpreted as a substantial limitation on the technical details. Without affecting the effects that can be produced by the present invention and the purposes that can be achieved, any adjustment to the structure, modification of the proportional relationship or change in size can be applied to the technical scope of the present invention. All various equivalent modifications or changes that belong to the relevant technical field and are completed without departing from the core concepts and technical ideas disclosed by the present invention should be included in the scope of the claims of the present invention.

Claims

1. A terahertz metamaterial device that realizes EIT-like phenomenon by light-dark mode coupling, wherein the terahertz metamaterial device comprises a substrate layer and a patterned resonator layer periodically arranged on the substrate layer. The surface of the patterned resonator layer is the front side of the terahertz metamaterial device that realizes EIT-like phenomenon by light-dark mode coupling.

2. The terahertz metamaterial device for realizing EIT-like phenomenon by coupling bright and dark modes according to claim 1, characterized in that: The thickness of the substrate layer is 100 nm, and the length and width are both 25 μm. The material used for the substrate layer is silicon dioxide material.

3. The terahertz metamaterial device for realizing EIT-like phenomenon by coupling bright and dark modes according to claim 2, characterized in that: The patterned resonator layer periodically arranged on the substrate layer is a patterned structure composed of graphene material, and the patterned structure consists of a bright mode resonator with a cross structure and four dark mode resonators with strip-shaped short arm structures.

4. The terahertz metamaterial device for realizing EIT-like phenomenon by coupling bright and dark modes according to claim 3, characterized in that: The length of the horizontal and vertical bars of the cross-structure bright mode resonator is L1=23μm, and the width W is 2μm; the length of the short arms of the four strip-shaped short-arm dark mode resonators is L2, and the width is also W=2μm; The spacing G between the cross-structure resonator and the four strip-shaped short-arm resonators is 2 μm, and the cross-structure resonator and the four strip-shaped short-arm resonators are combined to form a patterned resonator layer.

5. The terahertz metamaterial device for realizing EIT-like phenomenon by coupling bright and dark modes according to claim 4, characterized in that: The material used for the patterned resonator layers is graphene material, and the thickness of a single layer of graphene material is 0.34 nm.

6. The terahertz metamaterial device for realizing EIT-like phenomenon by coupling bright and dark modes according to claim 5, characterized in that: A structural period of the terahertz metamaterial device comprises a silicon dioxide substrate layer and a patterned graphene resonator layer on the substrate layer, a structural period P is 25 μm, and the terahertz metamaterial device comprises an array formed by splicing a plurality of structural periods.

7. A terahertz metamaterial device that realizes EIT-like phenomenon by coupling bright and dark modes according to claims 1-6, characterized in that: The incident wave is vertically incident on the front side of the resonator layer, resonates with the terahertz metamaterial device, and generates a transparent window with a transmittance of 86.5% at 1.588 THz.

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