Actively tuned electromagnetically induced transparent device based on solid-state plasma

Abstract

The active tuning electromagnetically induced transparent device based on solid-state plasma adopts a hybrid structure of metal and solid-state plasma, and realizes active tuning of the transparent window by switching the state of solid-state plasma; it is composed of a square patch with grooves and a metal cross-section, and the solid-state plasma is integrated into the metamaterial unit; by adjusting the working state of the solid-state plasma: when in state I, the solid-state plasma at the end of the cross-section is in an unexcited state, and the solid-state plasma in the square patch gap is excited; when in state II, the solid-state plasma at the end of the cross-section is in an excited state, and the solid-state plasma in the square patch gap is unexcited; when freely switching between the two states, the transmission window can be switched in a larger range. The present invention adopts a fine structural design, and can realize actively tuned electromagnetically induced transparency in the terahertz frequency range without changing the physical size parameters, and the tuning range can reach 403GHz.

Description

Technical Field

[0001] The present invention belongs to the field of metamaterials, and in particular relates to an actively tuned electromagnetically induced transparent device based on solid-state plasma. Background Art

[0002] Electromagnetically induced transparency (EIT) is a quantum destructive interference that occurs in a three-level atomic system, producing a clear transparent window over a wide absorption spectrum. This phenomenon can be enhanced when the frequency of the incident light matches the frequency of the atomic transitions during resonance. On the other hand, quantum interference effects are difficult to produce because they require harsh experimental conditions, such as low temperatures and high-intensity lasers. Because electromagnetically induced transparency avoids the harsh experimental conditions in atomic systems, the use of metamaterials to achieve the EIT effect has received widespread attention.

[0003] Coupling between modes with similar resonant frequencies is a necessary condition for obtaining classical EIT in metamaterials. Modes directly excited by external electromagnetic waves are called bright modes. In contrast, dark modes can only couple with bright modes in the near field. There are two main coupling methods to achieve quasi-EMI transparency: bright-dark mode coupling and bright-bright mode coupling. In practical applications, passive modulation and active modulation are common methods to obtain tunable EIT. The former requires changing the physical geometry to achieve dynamic adjustment of quasi-EMI transparency, which limits its flexibility in practical applications and hinders the further application development of quasi-EMI transparency. Summary of the invention

[0004] In response to the existing passively modulated frequency-adjustable electromagnetic induced transparency, the present invention proposes an actively tuned electromagnetic induced transparency device based on solid-state plasma, which can achieve active modulation within a certain frequency range by changing the working state of the solid-state plasma without changing the geometric parameters of the device.

[0005] An active tuning electromagnetically induced transparent device based on solid-state plasma, comprising a dielectric substrate at a lower layer and cross-cutting lines and square patches at an upper layer, characterized in that:

[0006] The transverse lines and the square patches are arranged on a dielectric substrate;

[0007] Solid plasma is arranged at the ends of both sides of the cross-section line, and a gap is provided in the square patch to embed the solid plasma;

[0008] By changing the working state of solid-state plasma, actively tuned electromagnetically induced transparency in the terahertz frequency range is achieved.

[0009] Furthermore, the dielectric substrate is made of polyimide material.

[0010] Furthermore, the cross-cutting lines and the square patches are made of gold material.

[0011] Furthermore, the square patch is provided with strip-shaped slits in four directions based on the four sides. In order to minimize the influence of the direction of the incident electromagnetic wave on the square patch, the four strip-shaped slits are distributed around the patch in a centrally symmetrical manner. In addition, the shape and size of the square patch slits mainly affect the current path of the square patch, and thus affect its resonant frequency. The design of the slits needs to make the resonant frequency of the square patch and the resonant frequency of the cross-section close in both working states of the device, so that the two can couple with each other before and after the state switching, realizing adjustable electromagnetically induced transparency.

[0012] Furthermore, the device includes state I and state II. When the device is in state I, the solid plasma at the end of the cross-section is in a closed state, and the solid plasma in the square patch gap is in an open state; when the device is in state II, the solid plasma at the end of the cross-section is in an open state, and the solid plasma in the square patch gap is in a closed state.

[0013] Furthermore, for the on state, the solid plasma frequency is 2.90×10 14 rad / s.

[0014] Furthermore, for the off state, the solid plasma frequency is set to 2.90×10 8 rad / s.

[0015] Furthermore, the device uses a dielectric substrate with a thickness of 10μm and a size of 300μm*300μm, the total length of the cross-section is 240μm, the size of the square patch is 110μm*110μm, the size of the gap embedded in the solid plasma on the four sides is 25μm*60μm, and the distance between the cross-section and the square patch is 20μm.

[0016] The beneficial effects achieved by the present invention are:

[0017] 1) A hybrid structure of metal and solid-state plasma is adopted to realize active tuning of the transparent window by switching the state of solid-state plasma. The implementation method is intuitive and stable.

[0018] 2) There is no need to change the physical geometric structure to achieve dynamic adjustment of electromagnetically induced transparency, which has high flexibility and better adaptability and is suitable for various occasions and environments.

[0019] 3) The present invention adopts a sophisticated structural design, which can achieve actively tuned electromagnetically induced transparency in the terahertz frequency range without changing the physical size parameters, and the tuning range can reach 403 GHz. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1Schematic diagram of the resonance unit when the device works in state I in an embodiment of the present invention.

[0021] Figure 2 It is the transmission spectrum of the quasi-electromagnetic induced transparency generated when the device works in state I in the embodiment of the present invention, including the resonance curve corresponding to the resonance unit and the transmission curve of the combination unit;

[0022] Figure 3 Schematic diagram of the resonance unit when the device works in state II in an embodiment of the present invention.

[0023] Figure 4 It is the transmission spectrum of quasi-electromagnetic induced transparency generated when the device works in state II in the embodiment of the present invention, including the resonance curve corresponding to the resonance unit and the transmission curve of the combination unit;

[0024] Figure 5 : is the spectrum diagram of the device at different incident angles in the embodiment of the present invention. a is the intensity diagram of the transmission peak changing with the incident angle when the device is working in state I; b is the intensity diagram of the transmission peak changing with the incident angle when the device is working in state II.

[0025] Figure 6 It is the phase and group delay of the device between two states in the embodiment of the present invention. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings.

[0027] Figure 1 This is a schematic diagram of the structure of an actively tuned electromagnetically induced transparent unit based on solid-state plasma when it works in state I. The lower layer is a polyimide dielectric substrate with a thickness of 10μm and a size of 300μm*300μm, and the upper layer is a cross-section and a square patch. The total length of the cross-section is 240μm, the size of the square patch is 110μm*110μm, the size of the gap where the solid-state plasma is embedded on the four sides is 25μm*60μm, and the distance between the cross-section and the square patch is 20μm. The solid-state plasma at the end of the cross-section is in the off state, and the solid-state plasma embedded in the gap of the square patch is in the on state. The bias voltage is used to affect the frequency of the solid-state plasma, causing it to enter the on / off state.

[0028] Figure 2is the transmission spectrum of the device when it is working in state I. Assuming that when the incident electromagnetic wave is along the x-axis, the incident electromagnetic wave will simultaneously excite the upper cross-section line and the square patch. Since the two resonant units have similar resonant frequencies, the mutual interference between the two constitutes the bright-bright mode coupling, generating a quasi-electromagnetic induced transparent transmission peak. In the figure, the two resonant frequencies are close and the transmission angle has a significant deviation, indicating the difference in the quality factor value, which is the key factor to achieve the quasi-electromagnetic induced transparent effect. Figure 2 The transmission spectrum of the combined structure shown in shows that there is an obvious transparent window at 0.833 THz, and the phase changes sharply within the transmission window.

[0029] Figure 3 This is a schematic diagram of the structure of the active tuning electromagnetically induced transparent unit based on solid-state plasma when it works in state II. The solid-state plasma at the end of the cross-section is in the on state, and the solid-state plasma embedded in the square patch gap is in the off state.

[0030] Figure 4 It is the transmission spectrum of the device when it works in state II. Assuming that when the incident electromagnetic wave is along the x-axis, the incident electric field will simultaneously excite the upper cross-section line and the square patch, forming a bright-bright coupling between the two, generating a quasi-electromagnetically induced transparent transmission peak. Figure 4 In the experiment, the resonant frequency is reduced to 0.482 THz and the frequency of the transmission window is moved to 0.430 THz with a larger group delay.

[0031] The switching of the solid-state plasma working state changes the current path inside the cross-section and the square patch to a certain extent, causing the resonant frequency to redshift, thereby reducing the electromagnetically induced transparent transmission peak frequency caused by the mutual interference between the two, thus achieving active modulation.

[0032] Figure 5 is the transmission spectrum of the device working at different incident electromagnetic wave angles. Where a is when the device is working in state I, the solid plasma at the end of the transverse line is closed, and the equivalent current path of the transverse line is sensitive to the incident angle of the electromagnetic wave. As the incident angle increases, the current equivalent path becomes shorter, which in turn affects the generated electromagnetically induced transparency, causing the frequency of the transmission peak to gradually decrease. When the device works in state II, the angle of the incident electromagnetic wave increases from 0° to 30°, and the transmission peak stabilizes near 0.430 THz, which is less affected by the incident angle.

[0033] Figure 6It is the phase and group delay of the device between two states. In state I, a steep phase change can be found at the transparent window, and the group delay at 0.827THz reaches 10.75ps. The group delay of the device changes with the state change. When working in state II, the group delay reaches 8.56ps, and the slow light capability of the overall structure changes. When the device state switches from I to II, the group delay region shows an obvious red shift. Therefore, it can be seen that when the device switches between two different conditions, the active modulation of the group delay is completed, and the dynamic control of the slow light effect is realized. When the entire device switches from state I to state II, the frequency offset is 403GHz, achieving a large frequency offset.

[0034] The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiment. Any equivalent modifications or changes made by ordinary technicians in this field based on the contents disclosed by the present invention should be included in the protection scope recorded in the claims.

Claims

1. An actively tuned electromagnetically induced transparent device based on solid-state plasma, comprising a dielectric substrate at a lower layer and cross-section lines and square patches at an upper layer, characterized in that: The transverse lines and the square patches are arranged on a dielectric substrate; The ends of both sides of the transverse line are closely connected with a first solid plasma, and the square patch is provided with a gap to embed a second solid plasma; By controlling the solid-state plasma frequency through bias voltage and changing the working state of the two solid-state plasmas, actively tuned electromagnetically induced transparency can be achieved within the terahertz frequency range.

2. The active tuning electromagnetically induced transparent device based on solid-state plasma according to claim 1, characterized in that: The dielectric substrate is made of polyimide material.

3. The active tuning electromagnetically induced transparent device based on solid-state plasma according to claim 1, characterized in that: The cross-cuts and square patches are made of gold.

4. The active tuning electromagnetically induced transparent device based on solid-state plasma according to claim 1, characterized in that: The square patch has strip-shaped gaps that are centrally symmetrically distributed on the four sides.

5. The active tuning electromagnetically induced transparent device based on solid-state plasma according to claim 1, characterized in that: The device includes state I and state II. When the device is in state I, the first solid plasma is in a closed state and the second solid plasma is in an open state; when the device is in state II, the first solid plasma is in an open state and the second solid plasma is in a closed state.

6. The active tuning electromagnetically induced transparent device based on solid-state plasma according to claim 5, characterized in that: For the on state, the solid plasma frequency is 2.90×10 14 rad / s.

7. The active tuning electromagnetically induced transparent device based on solid-state plasma according to claim 5, characterized in that: For the off state, the solid plasma frequency was set to 2.90 × 10 8 rad / s.

8. The active tuning electromagnetically induced transparent device based on solid-state plasma according to claim 1, characterized in that: The device uses a dielectric substrate with a thickness of 10μm and a size of 300μm*300μm, a total length of a cross-section of 240μm, a square patch size of 110μm*110μm, a gap size of 25μm*60μm for embedding solid plasma on four sides, and a distance of 20μm between the cross-section and the square patch.

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