An electromagnetically induced transparent device and method based on magnetic field excitation

Abstract

This invention discloses a magnetic field-excited electromagnetically induced transparency-like device and method. The device includes two opposing FR-4 dielectric substrates and a metal-etched resonant structure fixed to the surface of the FR-4 substrates. The metal resonant structure includes a copper double U-shaped ring resonant structure and a double circular ring resonant structure. Both the double U-shaped ring resonator and the double circular ring resonator are excited by incident electromagnetic waves. The incident electric field direction is symmetrical to the structure, and the incident magnetic field direction is perpendicular to the surface of the dielectric substrate. Both the double U-shaped ring structure and the double circular ring structure are excited by the incident magnetic field, but with different coupling strengths, forming a bright-mode-bright-mode coupling. This invention features a bright-mode-bright-mode channel coupling method with simultaneous magnetic field excitation. By using two resonant structures with different coupling strengths to the electromagnetic field, a two-layer electromagnetically induced transparency-like device with large group time delay and high sensitivity is obtained.

Description

Technical Field

[0001] This invention belongs to the field of metamaterials, and particularly relates to an electromagnetically induced transparent device and method based on magnetic field excitation. Background Technology

[0002] Electromagnetic induced transparency (EIT) is a quantum interference effect that occurs in three-level atomic systems, producing a clear transmission window over a wide absorption spectrum. Simultaneously, within this window, the phase exhibits extremely strong dispersion changes, resulting in a slow-light effect. A typical configuration involves two atomic states that can be independently excited to the same final state, but transitions between them are forbidden. The importance of EIT lies in its significant enhancement of nonlinear magnetic susceptibility in the induced transparency spectral region, and its association with steep dispersion. It is important to note that achieving EIT in three-dimensional atomic systems requires demanding experimental conditions, such as extremely low temperatures and high-intensity lasers, which greatly limits its application.

[0003] In 2008, X. Zhang's research group at the University of California, Berkeley, achieved electromagnetic induction (EIT) in the terahertz band using electromagnetic metamaterials, without requiring harsh experimental conditions such as low temperatures and high-intensity lasers. Therefore, EIT based on electromagnetic metamaterials has become a research hotspot. The electromagnetically induced transparency (EIT) proposed by X. Zhang's group consists of a dielectric substrate and three metal cross-sections. Modes that can be directly excited by incident electromagnetic waves are called bright modes, while those that cannot are called dark modes. One metal cross-section is placed vertically, and the other two are placed horizontally aligned. When the electric field of an incident electromagnetic wave is incident along the vertical metal cross-section, it can excite an electric resonance in the vertical cross-section, which is selected as a bright mode. However, it cannot excite resonance in the two horizontally placed metal cross-sections, which are selected as dark modes. The energy of the excited electric resonance in the vertical cross-section is coupled to the two horizontally placed metal cross-sections through near-field coupling, inducing magnetic resonance in the two horizontally placed metal cross-sections. The correlation coupling between the vertically placed transverse tangent electric resonance and the horizontally placed magnetic resonance of two metal transverse tangents induces an electromagnetically induced transparency (EMI) transmission peak. EMI obtained using this coupling method does not require harsh experimental conditions such as low temperature and high-intensity laser, simplifying the experimental conditions for EMI generation and advancing its engineering applications. Since then, EMI based on metamaterials has received considerable attention.

[0004] Different types of electromagnetically induced transparency (EMT) can be obtained depending on the coupling method of the resonant units. Published EMT coupling methods include bright-mode-bright-mode coupling and bright-mode-dark-mode coupling. For bright-mode-bright-mode coupling, the coupling between the two resonators is bright-mode, and the near-field coupling strength is weak, which is not conducive to the generation of strong slow light effects. For bright-mode-dark-mode coupling, in order to obtain a strongly coupled bright-mode-dark-mode channel, the bright and dark modes need to be close to each other, which is not conducive to obtaining a large coupling distance and a large group refractive index. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a magnetic field-excited electromagnetically induced transparent device and method. The excitation of both metal resonant structures in this device is magnetic field excitation, and it is a bright mode-bright mode coupling method, which can produce significant slow light effect and group refractive index. At the same time, through structural design, it can be applied in the field of sensors.

[0006] An electromagnetically induced transparent device based on magnetic field excitation includes a dielectric plate and a metal resonant structure fixed on the surface of the dielectric plate without contact between them. The metal resonant structure includes a double U-shaped ring resonator and a double circular ring resonator. The two dielectric plates are arranged in parallel, and the surface of the dielectric plates is perpendicular to the magnetic field direction of the incident electromagnetic wave. The double U-shaped ring resonator and the double circular ring resonator are on opposite surfaces of the two dielectric plates. The opening direction of the double U-shaped ring resonator and the axis of symmetry between the two rings of the double circular ring resonator are both perpendicular to the electric field direction of the incident electromagnetic wave.

[0007] Furthermore, the dual U-ring resonator includes two U-rings with opposite openings, distributed on a dielectric substrate in such an opposite manner.

[0008] Furthermore, the dual-ring resonator comprises two single rings, which are placed side by side on another dielectric substrate.

[0009] The surface of the dielectric substrate is perpendicular to the magnetic field direction of the incident electromagnetic wave, and the opening direction of the double U-shaped rings is perpendicular to the electric field direction of the incident electromagnetic wave. This prevents the double U-shaped ring metal resonance from being excited by the electric field, but it can be excited by the magnetic field, accompanied by a large Q value. The axis of symmetry between the two rings is perpendicular to the direction of the incident electric field, preventing the double rings from being excited by the electric field of the incident electromagnetic wave. However, since the dielectric substrate is perpendicular to the magnetic field direction of the incident electromagnetic wave, it can also be excited by the incident magnetic field, accompanied by a small Q value. Electromagnetically induced transparency is generated between the two metal resonant structures through bright-mode coupling.

[0010] A method for generating electromagnetically induced transparency using a magnetic field-excited electromagnetically induced transparency-like device includes the following steps:

[0011] Step 1: The incident electromagnetic wave excites the two resonant structures on the dielectric substrate, namely the double U-ring resonator and the double circular resonator. The two metal resonant structures have different coupling strengths with the incident field and different Q values, so they will couple with each other and form a bright mode-bright mode coupling, which induces an electromagnetically induced transparent transmission peak.

[0012] In step 2, the two excited metal resonant structures in step 1 are coupled in the near field to form a bright mode-bright mode coupling, which induces an electromagnetically induced transparent transmission peak with a large group delay and a group index of 1500.

[0013] Furthermore, the excited metal resonant structure is a double U-shaped ring resonator and a double circular ring resonator.

[0014] The beneficial effects of this invention are as follows: The structure employed in this invention features a bright-mode-bright-mode channel coupling method with simultaneous magnetic field excitation, resulting in a large coupling distance. Through two resonant structures with different coupling strengths to the electromagnetic field, a strong slow-light effect can be generated, accompanied by a large group delay and high sensitivity, which also has potential application value in the field of sensors. Furthermore, the use of a double-layer opposing structure to achieve electromagnetically induced transparency enriches the methods for obtaining electromagnetically induced transparency. Attached Figure Description

[0015] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0016] Figure 1 and Figure 2 These are schematic diagrams of the two structural parts of the present invention;

[0017] Figure 3 Figures a and b are three-dimensional schematic diagrams and transmission spectra of electromagnetically induced transparency generated using the device described in this invention;

[0018] Figure 4 The small figure in the middle (a) shows the phase of the electromagnetically induced transparent transmission window generated using the device described in this invention, and the small figure (b) shows the corresponding group index.

[0019] Figure 5 The transmission spectra of the double U-shaped rings (DURs) and double circular rings (DCRs) described in this invention are as follows when the electric field direction of the incident electromagnetic wave is along the x-axis; and the transmission spectra of the combined structure of double U-shaped rings and double circular rings.

[0020] Among them, 1-first copper-clad dielectric substrate, 2-double U-shaped ring resonator, 3-double circular ring resonator, 4-second copper-clad dielectric substrate. Detailed Implementation

[0021] like Figure 1 and Figure 2 As shown, the present invention discloses a unit structure of a magnetic field-excited, open-mode coupled electromagnetically induced transparent device. The device includes a first copper-clad dielectric substrate 1, a double U-shaped ring resonator 2, a double circular ring resonator 3, and a second copper-clad dielectric substrate 4. The double U-shaped ring resonator 2 and the double circular ring resonator 3 are non-contact metallic resonant structures, respectively fixed to the surfaces of the first copper-clad dielectric substrate 1 and the second copper-clad dielectric substrate 4. The surface of the first copper-clad dielectric substrate 1, i.e., the plane containing the double U-shaped ring resonator 1, is perpendicular to the magnetic field direction of the incident electromagnetic wave. The double U-shaped ring resonator 2 uses two U-shaped ring openings placed opposite each other. When the electric field direction of the incident electromagnetic wave is along the x-axis, due to the symmetrical structure, the double U-shaped ring resonator 2 will not be excited by the electric field of the incident electromagnetic wave. Furthermore, since the magnetic field of the incident electromagnetic wave is perpendicular to the first copper-clad dielectric substrate 1, the double U-shaped ring resonator 2 will be strongly excited by the incident magnetic field.

[0022] When the electric field direction of the incident electromagnetic wave is along the x-axis, since the double-ring metal resonator 3 is symmetrical with respect to the electric field direction of the incident electromagnetic wave, the incident magnetic field is perpendicular to the surface of the second copper-clad dielectric substrate 4, which can excite the double-ring metal resonator 3 to resonate. The double-ring metal resonator 3 is selected as the bright mode. At the same time, the double-U-shaped metal resonator 2 is also excited by the incident electromagnetic wave and also acts as a bright mode. Through ingenious design, the double-U-shaped metal resonator 2 and the double-ring metal resonator 3 are placed face to face on the first copper-clad dielectric substrate 1 and the second copper-clad dielectric substrate 4, respectively. At the same time, the energy of the excited double-U-shaped metal resonator 2 is coupled to the double-ring metal resonator 3 through near-field coupling, and similarly, the energy of the double-ring metal resonator 3 is coupled to the double-U-shaped metal resonator 2, forming a bright mode-to-bright mode channel. The mutual coupling between the two induces an electromagnetically induced transparent transmission peak with a large group delay and a large refractive index.

[0023] like Figure 3 (a) and Figure 3 As shown in (b), this is a three-dimensional schematic diagram and transmission spectrum of electromagnetically induced transparency based on simultaneous magnetic field excitation and bright-bright mode coupling, generated using the device described in this invention. Figure 3 As can be seen in (b), when the electric field of the incident electromagnetic wave is incident along the x-axis, a distinct electromagnetically induced transparent transmission window appears in the 5-8 GHz transmission spectrum. Figure 4 (a) and Figure 4 As can be seen in (b), the phase changes sharply within the transmission window and is accompanied by a large group exponent, which reaches 1500. Therefore, this device can be used in the fields of slow light devices and sensors. Figure 5This refers to the transmission spectra of the double U-ring metal resonator 2, the double circular metal resonator 3, and the combined structures of the double U-ring metal resonator 2 and the double circular metal resonator 3, when the incident electric field direction is along the x-axis and the incident magnetic field direction is along the z-axis. Figure 5 As can be seen from the data, the electric field of the incident electromagnetic wave is along the x-axis, and the incident magnetic field is along the z-axis, which can excite the double U-ring metal resonator 2 and the double circular ring metal resonator 3 to resonate. Therefore, the double U-ring metal resonator 2 and the double circular ring metal resonator 3 are selected as the bright mode. Combining the EIT curve, it can also be seen that... Figure 5 As can be seen from the black solid line, a narrow transparent window appears over a wide frequency range. This is because the resonant frequencies of the double U-ring metal resonator 2 and the double circular metal resonator 3 are relatively close and their Q factors differ by orders of magnitude, thus fulfilling the necessary conditions for obtaining electromagnetically induced transparency.

[0024] The present invention discloses a magnetic field-excited, bright-mode coupled electromagnetically induced transparent device. The distance between the two dielectric plates of the double-layer structure, i.e., the coupling distance, is more adjustable than that of the single-layer structure. Since the designed structure has a large group index of about 1500, and the group index is proportional to the group delay, the designed structure has a large group delay, producing a strong slow light effect.

[0025] The above description is merely a preferred embodiment of the present invention and is not intended to further limit the present invention. All equivalent changes made based on the description and drawings of the present invention are within the protection scope of the present invention.

Claims

1. A magnetic field excitation based electro-magnetic induced transparency like device comprising a dielectric plate and metallic resonant structures fixed on the surface of the dielectric plate without contact between them, characterized in that, The metal resonance structure comprises a double-U-shaped loop resonator and a double-circle loop resonator, the two dielectric plates are arranged in parallel and the surfaces of the dielectric plates are perpendicular to the magnetic field direction of the incident electromagnetic wave, the double-U-shaped loop resonator and the double-circle loop resonator are arranged on the opposite surfaces of the two dielectric plates respectively, the plane where the double-U-shaped loop resonator is arranged is perpendicular to the magnetic field direction of the incident electromagnetic wave, and the axis symmetry lines between the openings of the double-U-shaped loop resonator and the axis symmetry lines between the two circle loops of the double-circle loop resonator are both perpendicular to the electric field direction of the incident electromagnetic wave; The incident electromagnetic wave excites the double-U-shaped loop resonator and the double-circle loop resonator on the dielectric plates, the coupling strength of the double-U-shaped loop resonator and the double-circle loop resonator with the incident field is different, the double-U-shaped loop resonator and the double-circle loop resonator have different Q values, coupling occurs between the double-U-shaped loop resonator and the double-circle loop resonator, and a bright mode-bright mode coupling is formed, thereby inducing a kind of electromagnetic induced transparency transmission peak; The near-field coupling of the excited double-U-shaped loop resonator and the double-circle loop resonator forms a bright mode-bright mode coupling, thereby inducing a kind of electromagnetic induced transparency transmission peak with large group delay; The double-U-shaped loop resonator comprises two U-shaped resonator loops with opposite openings and is arranged horizontally on a dielectric plate. The double-circle loop resonator comprises two single circle loops and is arranged horizontally on another dielectric plate.

2. A magnetic field excitation based electro-magnetically induced transparency like device according to claim 1, wherein, The excited double-U-shaped loop resonator and the double-circle loop resonator are excited by the magnetic field of the incident electromagnetic wave, and the excited double-U-shaped loop resonator and the double-circle loop resonator are arranged face to face on two oppositely arranged dielectric plates.

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