Light-operated terahertz metasurface modulator with ultrahigh Q value

Abstract

The invention discloses a light-operated terahertz metasurface modulator with an ultrahigh Q value. The light-operated terahertz metasurface modulator comprises a transmission substrate layer and a frequency control structure, the frequency control structure is stacked on the upper surface of the transmission substrate layer; the frequency control structure comprises a surface periodic structure; the surface periodic structure is composed of a plurality of transmission units arranged in a regular matrix. External laser is controlled to apply laser pulses to the light-sensitive material layer of the modulator, so that the light-sensitive material layer generates a large number of optical excitation free carriers, a periodic unit resonator is formed, and the quality factor Q value of transmitted terahertz waves under a specific frequency band is regulated and controlled. Compared with the prior art, the ultra-narrow band-pass filter can realize and regulate ultra-high quality factors under ultra-narrow frequency, is suitable for different occasions, and is simple in structure and convenient to operate.

Description

Technical Field

[0001] The present invention relates to the field of terahertz control devices and wireless communications, and in particular to a light-controlled ultra-high Q-value terahertz metasurface modulator. Background Art

[0002] Recently, with the rapid development of network communication technology, 5G communication technology has matured and gradually commercialized, and basic theoretical research on 6G communication technology with a wider communication spectrum and faster transmission rate has been gradually carried out around the world. Terahertz communication technology is expected to achieve data transmission of up to 1Tbit / s, and is expected to become the main working frequency band of 6G communication, which is one of the best solutions for realizing 6G communication technology.

[0003] As a key basic component in terahertz communication technology, the terahertz ultra-high Q modulator can achieve fast modulation in the terahertz band due to its ultra-high Q value, supporting higher data transmission rates. This is very critical for terahertz communication systems, especially future wireless communication and data exchange technologies.

[0004] At present, terahertz modulators mainly use metal composite controllable materials to design resonant structures, and achieve amplitude control through electrical control modulation or thermal control modulation. However, terahertz modulators using electrical control modulation require a power source to be directly connected to the modulator, and terahertz modulators using heating control require the heating source to be close to the modulator, which to some extent limits the application scenarios of the modulators. Summary of the invention

[0005] The purpose of the present invention is to solve the problems in the background technology and to propose a light-controlled ultra-high Q-value terahertz metasurface modulator.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A light-controlled ultra-high Q-value terahertz metasurface modulator comprises a transmissive substrate layer and a frequency control structure; the frequency control structure is superimposed on the upper surface of the transmissive substrate layer;

[0008] The frequency control structure includes a surface periodic structure;

[0009] The surface periodic structure is composed of a plurality of transmission units arranged in a regular matrix;

[0010] Each of the transmission units is composed of two silicon dioxide patches and a light regulating material patch (22), and the two silicon dioxide patches are respectively a left silicon dioxide patch and a right silicon dioxide patch;

[0011] The left silicon dioxide patch is a fan-shaped silicon dioxide patch, and the right silicon dioxide patch is a fan-shaped silicon dioxide patch;

[0012] The left silicon dioxide patch and the right silicon dioxide patch have the same shape and the same size;

[0013] The left silicon dioxide patch and the right silicon dioxide patch are respectively located on two opposite sides, and there is a gap between the left silicon dioxide patch and the right silicon dioxide patch;

[0014] The two light-regulating material patches are respectively a left light-regulating material patch and a right light-regulating material patch;

[0015] The left light regulating material patch is a fan-shaped patch made of light regulating material, and the right light regulating material patch is a fan-shaped patch made of light regulating material;

[0016] The left light-regulating material patch and the right light-regulating material patch have the same shape and are equal in size;

[0017] The left light regulating material patch and the right light regulating material patch are respectively located on two opposite sides, and there is a gap between the left light regulating material patch and the right light regulating material patch;

[0018] The radius of the left silicon dioxide patch and the right silicon dioxide patch and the radius of the left light regulating material patch and the right light regulating material patch are equal;

[0019] The upper straight edge of the left silicon dioxide patch is connected to the lower straight edge of the left light regulating material patch;

[0020] The upper straight edge of the right silicon dioxide patch is connected to the lower straight edge of the right light regulating material patch;

[0021] The central angles of the left silicon dioxide patch and the left light regulating material patch are complementary;

[0022] The central angles of the right silicon dioxide patch and the right light regulating material patch are complementary.

[0023] Preferably, each of the transmission units is symmetrical about its longitudinal center axis.

[0024] Preferably, the transmission substrate layer is made of a terahertz high-transmittance material such as high-resistance silicon, mica substrate, and sapphire substrate;

[0025] The silicon dioxide patch is made of high-resistance silicon, silicon nitride, polyimide and other terahertz high-transmittance materials;

[0026] The light regulating material patch is made of terahertz photosensitive materials such as photosensitive silicon, transition metal sulfide and vanadium dioxide.

[0027] Preferably, the area covered by the surface periodic structure is larger than the area of ​​the terahertz beam spot irradiated on the modulator body.

[0028] Preferably, the area covered by the surface periodic structure is 1.5 to 2.5 times the area of ​​the terahertz beam spot irradiated on the modulator body.

[0029] Preferably, the spot area of ​​the laser is greater than or equal to the coverage area of ​​all periodic transmission units of the frequency control structure.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention designs a terahertz metasurface with C2 symmetry by using silicon dioxide material. Under C2 symmetry, the symmetry of the structure ensures that the propagation characteristics of terahertz waves in different directions are symmetrical, and the coupling with the radiation mode is suppressed. When the metasurface structure has C2 symmetry, the radiation channel of the resonant mode is closed, and the structure cannot effectively radiate energy at this time, forming a bound state. In this state, the local electromagnetic field on the metasurface can be accurately controlled and localized, and the energy will not escape through the external radiation channel, resulting in no energy loss in the resonant state, and the Q value of the transmission transmission curve is infinite at this time. When vanadium dioxide phase change material is added to the metasurface, the original C2 symmetry is destroyed, and the continuum bound state mode is transformed into a quasi-continuum bound state mode. The formation of high Q value mainly stems from the low radiation loss in the quasi-continuum bound state mode. In the quasi-continuum bound state mode, the resonant mode of the metasurface hardly generates radiation, so that the energy stays in the resonant cavity for a long time. This ultra-long energy retention time leads to the generation of ultra-high Q value. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic diagram of the three-dimensional structure of a light-controlled ultra-high Q-value terahertz metasurface modulator;

[0033] Figure 2 A top view of a light-controlled ultra-high Q-value terahertz metasurface modulator;

[0034] Figure 3 is a schematic diagram of the structure of a transmission unit;

[0035] Figure 4 It is a schematic diagram of the terahertz wave transmittance curve of the present invention when not excited by pump light and when excited by pump light.

[0036] In the figure: 1 transmission substrate layer; 2 frequency control structure; 21 silicon dioxide patch; 22 vanadium dioxide patch. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0038] See also Figure 1 A light-controlled ultra-high Q-value terahertz metasurface modulator includes a modulator body, which is composed of a transmissive substrate layer 1 and a frequency control structure 2. The transmissive substrate layer 1 can be a terahertz high-transmittance material such as high-resistance silicon, mica, and sapphire. The shape of the transmissive substrate layer 1 can be circular, square, or polygonal, etc., and it only needs to be able to accommodate the frequency control structure 2. In a preferred embodiment of the present invention, the transmissive substrate layer 1 is rectangular, and the thickness of the transmissive substrate layer is 10μm. The frequency control structure 2 is superimposed on the upper surface of the transmissive substrate layer 1.

[0039] See also Figure 2 , the frequency control structure 2 includes a surface periodic structure.

[0040] The surface periodic structure is located in the middle of the frequency control structure 2 and is composed of a plurality of transmission units arranged in a regular matrix. Figure 3 As shown, the whole is symmetrical about its longitudinal central axis. Each transmission unit is composed of two silica patches 21 and a light regulating material patch 22. In a preferred embodiment of the present invention, the thickness of the silica patch 21 is 1 to 4 μm, and the thickness of the light regulating material patch 22 is 0.2 to 4 μm. The silica patch can be a terahertz wave high transmittance material such as high-resistance silicon, silicon nitride, polyimide, etc.; the light regulating material patch can be a photosensitive material such as photosensitive silicon, transition metal sulfide and vanadium dioxide.

[0041] The two silica patches 21 are respectively a left silica patch 21 and a right silica patch 21. The left silica patch 21 and the right silica patch 21 are both fan-shaped and made of the same terahertz wave high transmittance material such as high-resistance silicon, silicon nitride, polyimide, etc. The left silica patch 21 and the right silica patch 21 have the same shape and size; the left silica patch 21 and the right silica patch 21 are respectively located on opposite sides, and there is a gap between the left silica patch 21 and the right silica patch 21. In a preferred embodiment of the present invention, the central angle of the silica patch 21 is 60° to 87°.

[0042] The two light regulating material patches 22 are respectively a left light regulating material patch 22 and a right light regulating material patch 22. The left light regulating material patch 22 and the right light regulating material patch 22 are both the same fan-shaped patch made of materials such as photosensitive silicon, transition metal sulfide and vanadium dioxide. The left light regulating material patch 22 and the right light regulating material patch 22 have the same shape and are equal in size. The left light regulating material patch 22 and the right light regulating material patch 22 are respectively located on opposite sides, and there is a gap between the left light regulating material patch 22 and the right light regulating material patch 22.

[0043] The radius of the left silica patch 21 is equal to that of the right silica patch 21 and the left light regulating material patch 22 and the right light regulating material patch 22. The upper straight edge of the left silica patch 21 is connected to the lower straight edge of the left light regulating material patch 22. The upper straight edge of the right silica patch 21 is connected to the lower straight edge of the right light regulating material patch 22. The central angles of the left silica patch 21 and the left light regulating material patch 22 are complementary. The central angles of the right silica patch 21 and the right light regulating material patch 22 are complementary.

[0044] When in use, the terahertz wave is incident directly from directly above the modulator, that is, directly above the surface periodic structure. And it passes through the frequency control layer and the lower surface of the transmission substrate layer. In order to allow the terahertz beam on the modulator to pass through without obstruction, the surface periodic structure, that is, the area covered by all the transmission units, is larger than the area of ​​the terahertz beam spot irradiated on the modulator, which is 1.5 to 2.5 times the area of ​​the terahertz beam spot; the terahertz wave is vertically incident from the upper surface of the frequency control layer. In order to ensure the excitation (pumping) effect of the laser on the modulator, the spot area of ​​the laser is greater than or equal to the coverage area of ​​all periodic transmission units of the frequency control layer. In the present invention, the spot area of ​​the laser is 2 to 3 times the coverage area of ​​all periodic transmission units of the frequency control layer, and the laser is obliquely pumped from the upper surface of the frequency control layer. The laser used in the present invention has a wavelength of 800nm ​​to 1064nm and a power of 0.5W to 1.5W.

[0045] The present invention has the following two working states:

[0046] The first working state: when there is no laser pumping on the upper surface of the frequency control layer, the light control material in the frequency control layer will not undergo photoelectric effect, and will not generate photoexcited carriers. The light control material is in a non-metallic state. At this time, the silica material and the non-metallic light control material jointly form a quasi-continuum bound state mode, and its resonant mode generates almost no radiation. The energy stays in the resonant cavity for a long time, and the ultra-long energy residence time produces an ultra-high Q value. Figure 4 Schematic diagram of the terahertz wave transmittance curve of the present invention when not excited by pump light and when excited by pump light, Figure 4It can be seen that within the ultra-narrow frequency band of 701.625 GHz to 702.125 GHz, the terahertz wave transmittance is 46%, and the transmission curve quality factor Q value is 2314.75.

[0047] The second working state: when there is laser pumping on the upper surface of the frequency control layer, the optical control material of the frequency control layer will undergo a photoelectric effect, generate light-excited carriers, and the optical control material will transform into a metallic state. At this time, the silicon dioxide material and the metallic optical control material together form a quasi-continuum bound state mode, and its resonance mode is enhanced compared to when the optical control material is in a non-metallic state, the terahertz wave transmittance is reduced, and the Q value is increased. Figure 4 In the ultra-narrow frequency band of 701.625 GHz to 702.125 GHz, the terahertz wave transmittance is 38%, and the transmission curve quality factor Q value is 3588.02.

[0048] By changing the laser power pumping on the upper surface of the frequency control layer, the quality factor of the transmitted terahertz wave can be modulated. Figure 4 It can be seen that within the ultra-narrow frequency band of 701.625 GHz to 702.125 GHz, the transmitted terahertz wave can achieve a quality factor Q value ranging from 2314.75 to 3588.02.

[0049] The present invention controls an external laser to apply laser pulses to the photosensitive material layer of the modulator, so that a large number of light-excited free carriers are generated to form a periodic unit resonator, thereby realizing the regulation of the quality factor Q value of the transmitted terahertz wave under a specific frequency band. Compared with the prior art, the present invention can achieve and regulate the ultra-high quality factor under ultra-narrow frequency, is suitable for different occasions, has a simple structure, and is easy to operate.

[0050] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A light-controlled ultra-high Q-value terahertz metasurface modulator, characterized in that: It comprises a transmissive base layer (1) and a frequency control structure (2); the frequency control structure (2) is stacked on the upper surface of the transmissive base layer (1); The frequency control structure (2) comprises a surface periodic structure; The surface periodic structure is composed of a plurality of transmission units arranged in a regular matrix; Each of the transmission units is composed of two silicon dioxide patches (21) and a light regulating material patch (22), and the two silicon dioxide patches (21) are respectively a left silicon dioxide patch (21) and a right silicon dioxide patch (21); The left silicon dioxide patch (21) is a fan-shaped patch made of silicon dioxide material, and the right silicon dioxide patch (21) is a fan-shaped patch made of silicon dioxide material; The left silicon dioxide patch (21) and the right silicon dioxide patch (21) have the same shape and the same size; The left silicon dioxide patch (21) and the right silicon dioxide patch (21) are respectively located on two opposite sides, and there is a gap between the left silicon dioxide patch (21) and the right silicon dioxide patch (21); The two light regulating material patches (22) are respectively a left light regulating material patch (22) and a right light regulating material patch (22); The left light regulating material patch (22) is a fan-shaped patch made of light regulating material, and the right light regulating material patch (22) is a fan-shaped patch made of light regulating material; The left light regulating material patch (22) and the right light regulating material patch (22) have the same shape and the same size; The left light regulating material patch (22) and the right light regulating material patch (22) are respectively located on two opposite sides, and there is a gap between the left light regulating material patch (22) and the right light regulating material patch (22); The radii of the left silicon dioxide patch (21) and the right silicon dioxide patch (21) and the left light regulating material patch (22) and the right light regulating material patch (22) are equal; The upper straight edge of the left silicon dioxide patch (21) is connected to the lower straight edge of the left light regulating material patch (22); The upper straight edge of the right silicon dioxide patch (21) is connected to the lower straight edge of the right light regulating material patch (22); The central angles of the left silicon dioxide patch (21) and the left light regulating material patch (22) are complementary; The central angles of the right silicon dioxide patch (21) and the right light regulating material patch (22) are complementary.

2. The optically controlled ultra-high Q-value terahertz metasurface modulator according to claim 1, characterized in that: Each of the transmission units is symmetrical about its longitudinal center axis.

3. The optically controlled ultra-high Q-value terahertz metasurface modulator according to claim 1, characterized in that: The transmission substrate layer (1) is made of a terahertz high-transmittance material such as high-resistance silicon, a mica substrate, or a sapphire substrate; The silicon dioxide patch (21) is made of a terahertz high-transmittance material such as high-resistance silicon, silicon nitride, polyimide, etc.; The light regulating material patch (22) is made of terahertz photosensitive materials such as photosensitive silicon, transition metal sulfide and vanadium dioxide.

4. The optically controlled ultra-high Q-value terahertz metasurface modulator according to claim 1, characterized in that: The area covered by the surface periodic structure is larger than the area of ​​the terahertz beam spot irradiated on the modulator body.

5. The optically controlled ultra-high Q-value terahertz metasurface modulator according to claim 2, characterized in that: The area covered by the surface periodic structure is 1.5 to 2.5 times the area of ​​the terahertz beam spot irradiated on the modulator body.

6. The optically controlled ultra-high Q-value terahertz metasurface modulator according to claim 4, characterized in that: The spot area of ​​the laser is greater than or equal to the coverage area of ​​all periodic transmission units of the frequency control structure.

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