VO2- and Metamaterial-Based Current-Modulated Terahertz Devices and Systems

Abstract

The present invention provides a current-modulated terahertz device, a terahertz wave modulation system, and an information encryption system based on VO2 and metamaterials. Among them, the current-modulated terahertz device includes: a substrate transparent to terahertz waves; a VO2 layer formed on the substrate; a microresonator formed on the VO2 layer; the microresonator includes: a current positive terminal and a current negative terminal, which are formed on the VO2 layer, are symmetric about the left and right, and are used for loading a bias current; N×M resonant units, which are formed on the VO2 layer, are symmetric about the left and right, are arranged in an array inside the current positive terminal and the current negative terminal, N≥2, M≥2; the resonant unit has a split-ring structure with an LC resonance mode, the M resonant units in each row are connected in series in turn, and the two ends of the N rows of resonant units are respectively connected to the current positive terminal and the current negative terminal. Compared with methods such as laser irradiation, voltage regulation, and traditional thermal control, the present invention has the advantages of simple operation and being more easily integrated with current integrated circuit technology.

Description

Technical Field

[0001] The present invention relates to the field of metamaterials and terahertz functional devices, and particularly to a current-modulated terahertz device, a terahertz wave modulation system, and an information encryption system based on VO2 and metamaterials. Background Art

[0002] Metamaterials have obtained many unusual properties, such as negative refraction, perfect lens, superlens, and invisibility, by designing periodic unit structures to achieve special responses to electromagnetic waves. However, these metamaterials are passive because their optical responses cannot be dynamically changed after manufacturing.

[0003] Vanadium dioxide (VO2), as a phase change material, exhibits insulator-metal transition (IMT) behavior near room temperature. During the phase change process, VO2 undergoes reversible resistance changes between the high-temperature metallic tetragonal phase and the low-temperature insulating monoclinic phase. The conductivity can change by several orders of magnitude, accompanied by thermal hysteresis characteristics. These excellent properties make VO2 materials suitable for many promising applications, such as smart windows, optical switches, and phase change memories.

[0004] However, when thermally controlling devices based on VO2 and metamaterials, expensive and bulky heating equipment needs to be used, which brings inconvenience to experimental operations and further loses the opportunity to develop into integrated devices. Summary of the Invention

[0005] (I) Technical Problems to be Solved

[0006] In view of this, the present invention expects to solve at least one of the above technical problems in part.

[0007] (II) Technical Solutions

[0008] To achieve the above object, according to the first aspect of the present invention, a current-modulated terahertz device based on VO2 and metamaterials is provided, including: a substrate transparent to terahertz waves; a VO2 layer formed on the substrate; a microresonator formed on the VO2 layer; the microresonator includes: a current positive terminal and a current negative terminal, which are formed on the VO2 layer, are symmetric about the left and right, and are used for loading a bias current; N×M resonant units, which are symmetric about the left and right, are arranged in an array on the inner sides of the current positive terminal and the current negative terminal formed on the VO2 layer, N≥2, M≥2; wherein, the resonant unit has a split-ring structure with an LC resonance mode, the M resonant units in each row are connected in series in sequence, and the two ends of the N rows of resonant units are respectively connected to the current positive terminal and the current negative terminal.

[0009] In some embodiments of the present invention, in the horizontal direction, the resonant unit is symmetric up and down, including: a closed loop; a left extension arm and a right extension arm respectively passing through the left and right sides of the closed loop; the left side of the left extension arm is connected to the positive current terminal or the right extension arm of the previous resonant unit; the right side of the right extension arm is connected to the left extension arm of the next resonant unit or the negative current terminal; a rectangular opening area is formed between the left and right extension arms.

[0010] In some embodiments of the present invention, it includes: S×T microresonators formed on the VO2 layer and arranged in an array, where S≥2 and T≥2; for each microresonator, the structural parameters of N×M resonant units are the same, and N = M; the period p of the resonant unit is between 40 μm and 60 μm; the closed loop is a closed square loop, and its side length l is between 30 μm and 40 μm; the line width w is between 3 μm and 6 μm; the line widths of the left and right extension arms are the same as the line width of the closed loop; the height h of the rectangular opening area is between 5 μm and 15 μm, and the width g is between 2 μm and 8 μm.

[0011] In some embodiments of the present invention, the thickness of the VO2 layer is between 5 nm and 100 nm.

[0012] In some embodiments of the present invention, the bias current applied to the inner N rows of resonant units at the positive current terminal and the negative current terminal is between 0 and 0.7 A.

[0013] In some embodiments of the present invention, in the thickness direction, the resonant unit includes: a viscous metal layer formed on the VO2 layer; a conductive layer formed on the viscous metal layer, the thickness of the viscous metal layer is between 5 nm and 100 nm, and the thickness of the conductive metal layer is between 100 nm and 300 nm. The closed loop and the left and right extension arms are formed by the viscous metal layer and the conductive metal layer.

[0014] In some embodiments of the present invention, in the horizontal direction, the period of the resonant unit is 50 μm; the side length l of the closed loop is 36 μm, and the line width w is 4 μm; the height h of the rectangular opening area between the left and right extension arms is 10 μm.

[0015] In some embodiments of the present invention, in the vertical direction, the substrate is a sapphire substrate; the thickness of the VO2 layer is 10 nm; the viscous metal layer is a chromium thin film with a thickness of 20 nm; the conductive metal layer is a gold thin film with a thickness of 200 nm.

[0016] In some embodiments of the present invention, the current modulation terahertz device serves as a terahertz wave active modulator or an information encryption memory.

[0017] To achieve the above object, according to the second aspect of the present invention, a terahertz wave modulation system is provided, including: the current modulation terahertz device as above, which serves as a terahertz wave active modulator; a bias current source, the two ends of which are connected to the positive current terminal and the negative current terminal of the microresonator in the terahertz wave active modulator; wherein, the bias current source loads an encoded current carrying encoded information to the positive current terminal and the negative current terminal of the microresonator in the terahertz wave active modulator to regulate the terahertz wave transmittance of the microresonator.

[0018] In some embodiments of the present invention, the encoded information carried in the terahertz wave transmittance is 2-bit information encoding; the terahertz wave modulation system is defined as follows: when the terahertz wave transmittance is greater than or equal to the transmittance threshold, it carries the binary code "1"; when it is less than the transmittance threshold, it carries the binary code "0".

[0019] In some embodiments of the present invention, the terahertz wave active modulator includes: S×T microresonators arranged in an array, S≥2, T≥2. For each microresonator, the structural parameters of N×M resonant units are the same; for different microresonators, the structural parameters of the internal resonant units are different, and the bias current source can provide different bias currents for different microresonators.

[0020] To achieve the above object, according to the third aspect of the present invention, an information encryption system is provided, including: the current modulation terahertz device as above, which serves as an information encryption memory; the microresonator serves as a pixel of the information encryption memory; wherein, the structural parameters of the microresonator in the information encryption memory carry encrypted information, and a specific terahertz wave frequency and a specific bias current loaded to the positive current terminal and the negative current terminal of the microresonator are used as keys. Among them, the specific terahertz wave frequency used as the key is selected from the resonance peak or resonance valley of the microresonator.

[0021] In some embodiments of the present invention, the information encryption memory includes: S×T microresonators arranged in an array, where S≥2 and T≥2. Each microresonator serves as a pixel of the information encryption memory. For each microresonator, the structural parameters of N×M resonant units are the same; for different microresonators, the structural parameters of their internal resonant units are different. In the information encryption system, a correspondence between a preset terahertz wave transmittance and color is set. The encrypted information carried by a pixel is represented as the corresponding color obtained from the terahertz wave transmittance under the conditions of a specific terahertz wave frequency and a specific bias current. The encrypted information carried by the information encryption memory is represented as a pattern formed by the arrangement and combination of S×T pixel color blocks, and the pattern is in the form of letters, numbers, and / or symbols. On the decryption side, the information encryption system further includes: a decryption module for separately applying a specific bias current to each microresonator in the information encryption memory and irradiating the information encryption memory with terahertz waves of a specific frequency; a color demodulation module arranged at the rear end of the optical path of the information encryption memory for decrypting the terahertz wave transmittance of each pixel in the information encryption memory into the corresponding color according to the preset correspondence between the terahertz wave transmittance and color, and forming a pattern by arranging and combining the S×T pixel color blocks.

[0022] (III) Advantageous Effects

[0023] As can be seen from the above technical solutions, the present invention has at least one of the following advantageous effects compared with the prior art:

[0024] (1) In the present invention, a current positive terminal and a current negative terminal are symmetrically arranged on both sides of the microresonator, and the VO2 material below is heated by the electric field generated when the bias current passes through the microresonator. The structure of the microresonator results in a highly localized phase change of VO2 and the distribution of electrical current filaments attached to the microresonator. Such a design can not only ensure a relatively consistent heating effect when the bias current flows through each resonator, but also utilize the differences in gaps to control the resonant spectral response of terahertz waves and adjust the transmission spectral lines.

[0025] Compared with the control method using laser irradiation, the present invention is more conducive to the integration with the mainstream current integrated circuit technology, and at the same time avoids interference between the laser light source and the terahertz wave source.

[0026] Compared with the control method using voltage, the present invention adopts a current modulation method. Experiments have proved that current adjustment is more direct and effective, and the current can be used as an additional modulation parameter to expand the application range of the device. At the same time, it is more conducive to combining with the current integrated circuit technology.

[0027] Compared with the traditional modulation methods for thermally controlling the VO2 phase transition, the present invention abandons the bulky external heater and adopts a flexible electrical regulation method, reducing the complexity of actual operation and providing convenience for the development of integrated devices.

[0028] Compared with the modulation method of heating the VO2 material by forming a p-n junction between the VO2 layer and the underlying material, the present invention utilizes the metallic properties of the metamaterial to generate Joule heat after being energized, heating the VO2 layer, thereby changing the conductivity of the VO2 material and reducing the terahertz wave transmittance. The process is more direct and effective, with lower energy consumption, and at the same time reduces the impact on other components of the integrated circuit caused by doping the substrate material.

[0029] Compared with forming a phase change material region only at the split ring opening using VO2 powder, the present invention has the following advantages: First, the whole VO2 layer fabricated by the epitaxial growth method has higher crystallinity and better consistency, thus the reliability of the device is higher; Second, the controllability of the overall coating process is better, and the manufacturing cost is lower, which is more conducive to industrial production; Third, it is more conducive to the integration with the mainstream technologies of current integrated circuits.

[0030] (2) Compared with the asymmetric resonant units in the prior art, in the present invention, whether it is the symmetric arrangement of the positive and negative current terminals in the microresonator, the array arrangement of the resonant units, or the internal structure of the resonant unit, they are all set to be symmetrically arranged. Such a symmetric setting compared with the asymmetric resonant units in the prior art makes the electrical and thermodynamic properties of the whole device more stable.

[0031] (3) Each microresonator is an array of split ring resonator unit structures with different sub-wavelength sizes fabricated on the same substrate and is independently controlled by applying an external current. The different threshold current magnitudes and resonance responses required for each microresonator enable the microresonator to be used as a spatially selective terahertz modulator according to actual needs.

[0032] (4) The split ring structure with an LC resonance mode is used to construct the microstructures of the terahertz metasurface layer. The LC resonance mode makes the spectral lines exhibit a sharp and high-quality factor line shape, which has a high sensitivity to the external field response. It can enhance the response of terahertz waves to the change in conductivity during the VO2 phase transition and improve the modulation sensitivity of the spectral curve to the VO2 phase change.

[0033] (5) In the terahertz metasurface microstructure, the internal gap sizes of the resonator unit structures are 8, 6, 4, and 2 μm respectively; among them, the microresonator with the smallest gap has the LC resonance mode with the strongest response, so it shows the sharpest resonance valley spectral line shape in the spectrum and the highest sensitivity in the phase transition modulation of VO2. When fully modulated, the reduction of the gap reduces the operating current of the device from 0.62 A to 0.38 A, effectively reducing the operating threshold of the device.

[0034] (6) Based on the high modulation depth and hysteresis characteristics exhibited by the current-modulated terahertz device, a terahertz wave modulation system based on the transmission spectrum was developed. Based on the erasable characteristics and different electro-induced non-volatile multi-level conductance states, multiple microresonator arrays can all achieve the rewritable function, and can perform arbitrary combination outputs on the output binary codes, providing exciting opportunities for the development of photon memories and terahertz communication devices.

[0035] (7) Utilizing the separated transmittance hysteresis loops generated by different resonator unit structure arrays, an information encryption system with frequency-selectable dynamic tunable color pattern display is further provided in the terahertz frequency band. By presetting the correspondence between the terahertz wave transmittance and colors, information encryption and multi-image reproduction can be achieved using the current and terahertz wave frequency as decryption keys. Description of the Drawings

[0036] Figure 1A It is a three-dimensional schematic diagram of the current-modulated terahertz device according to an embodiment of the present invention.

[0037] Figure 1B is Figure 1A a cross-sectional view of the current-modulated terahertz device shown.

[0038] Figure 2 is Figure 1A a schematic diagram of one of the resonator units of each of the four resonators in the current-modulated terahertz device shown.

[0039] Figure 3A 、 Figure 3B 、 Figure 3C 、 Figure 3D are respectively Figure 1A the terahertz transmission spectrum curves of the four resonators in the current-modulated terahertz device shown under current modulation.

[0040] Figure 4 is Figure 1A the surface current and electric field distribution diagrams of the fourth resonator with an internal gap g = 2 in the current-modulated terahertz device shown at the first resonance valley.

[0041] Figure 5 is Figure 1AComparison diagram of the modulation depth of the transmittance of the second, third, and fourth microresonators in the shown current-modulated terahertz device varying with current at the first resonance valley.

[0042] Figure 6 Schematic diagram of the conversion and output from the continuous spectrum to digital information of four microresonators in the current-modulated terahertz device of the present invention varying with current.

[0043] Figure 7 Schematic diagram of the multi-state characteristics of the transmittance realized by the terahertz wave modulation system of the embodiment of the present invention and the binary coding corresponding to the multi-states.

[0044] Figure 8A 、 Figure 8B is Figure 7 Schematic diagram of the flexible arbitrary coding function using programmable current pulses realized by the fourth resonator in the shown terahertz wave modulation system.

[0045] Figure 9A Demonstrates the schematic diagram of the information encryption memory composed of four microresonators.

[0046] Figure 9B Schematic diagram of the color display varying with current under the wrong decryption keys of -0.87 and 1.01 THz.

[0047] Figure 9C Schematic diagram of realizing information decryption and image reproduction using various terahertz wave frequencies and bias currents as decryption keys. Detailed implementation manners

[0048] In the present invention, a technical solution is proposed to modulate the VO2 layer using the Joule heat generated by current and utilize the phase change characteristics of VO2 to achieve related functions. Compared with methods such as laser irradiation, voltage regulation, and traditional thermal control, it has advantages such as simple operation and being more easily integrated with current integrated circuit technology.

[0049] To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with the specific implementation manners and with reference to the accompanying drawings.

[0050] I. Current-modulated terahertz device

[0051] In the first exemplary embodiment of the present invention, a current-modulated terahertz device based on VO2 and metamaterials is provided. Through the optimization of the modulation method and the design of the microstructure of the metasurface layer, a spectral line shape sensitive to the external field is obtained, improving the consistency and stability of the entire device and increasing the compatibility with current integrated circuit technology.

[0052] Figure 1A Schematic three-dimensional diagram of the current-modulated terahertz device of the embodiment of the present invention.Figure 1B is Figure 1A a cross-sectional view of the current-modulated terahertz device shown. As Figure 1A and Figure 1B shown, the current-modulated terahertz device of this embodiment includes:

[0053] a substrate transparent to terahertz waves;

[0054] a VO2 layer formed on the substrate;

[0055] four microresonators etched on the VO2 layer and arranged in a 2×2 array.

[0056] The current-modulated terahertz device of this embodiment will be described in detail below, especially the VO2 layer and the microresonators, which are the key parts of the present invention.

[0057] In this embodiment, the substrate is a 430-μm-thick sapphire substrate (Sapphire), which is transparent to terahertz waves. The sapphire substrate has the advantages of mature technology, low cost, and good transparency. In addition to the sapphire substrate, other substrates with lattice parameters matching those of the VO2 material can also be used in the present invention to fabricate the VO2 layer.

[0058] In this embodiment, the VO2 layer is grown on the substrate by pulsed laser deposition (PLD). The thickness of the VO2 layer is 10 nm, which covers the entire substrate rather than only in the resonator region. Those skilled in the art should understand that in addition to PLD, other thin-film epitaxial deposition methods can also be used. In addition, in other embodiments of the present invention, the thickness of the VO2 layer ranges from 5 nm to 100 nm, and the present invention can also be realized.

[0059] The test results show that the VO2 layer epitaxially grown on the sapphire substrate in this embodiment has high-quality epitaxy and a relatively smooth surface, and the resistance shows a three-order-of-magnitude mutation near the transition temperature, providing a large contrast and higher stability for electro-control modulation.

[0060] It should be noted that in the prior art, there has been a technical solution of using VO2 powder to coat the split-ring opening to form a phase-change material region. Compared with it, the present invention has the following advantages: First, the whole VO2 layer fabricated by epitaxial growth has higher crystallinity and better consistency, so the reliability of the device is higher; Second, the overall coating process has better controllability and lower manufacturing cost, which is more conducive to industrial production; Third, it is more conducive to the integration with the current mainstream integrated circuit technology.

[0061] Please continue to refer to FIG. 1. In this embodiment, a microstructured metasurface layer composed of four microresonators is fabricated on the VO2 layer by an etching method. The four microresonators are uniformly distributed on the VO2 layer in a 2×2 pattern, and the spacing between each microresonator in the horizontal and vertical directions is 2 mm. For ease of description, the resonators in the upper left, upper right, lower left, and lower right are named the first resonator, the second resonator, the third resonator, and the fourth resonator, respectively.

[0062] Those skilled in the art should understand that in the present invention, each microresonator is an array of split-ring resonator unit structures with different sub-wavelength sizes fabricated on the same substrate and is independently controlled by applying an external current. The different threshold current magnitudes and resonance responses required for each microresonator enable the microresonator to be used as a spatially selective terahertz wave active modulator according to actual needs.

[0063] In other embodiments of the present invention, the current-modulated terahertz device may include S×T independent microresonators, where S≥2, T≥2, and S and T may be the same or different. In this embodiment, S = T = 3.

[0064] For each microresonator, it includes: a current positive terminal and a current negative terminal that are formed on the VO2 layer, are symmetric about the left and right, and are used to load a bias current, and are connected to a bias current source; 3×3 resonator units that are arranged in an array inside the current positive terminal and the current negative terminal. Among them, the 3×3 resonator units of each microresonator are connected by gold wires and connected to the current positive terminal and the current negative terminal on the left and right sides to form a path for independent current modulation. In other words, each microresonator serves as an independent current modulation unit.

[0065] In other embodiments of the present invention, the resonator unit array constituting the microresonator may include N×M units, where N≥2, M≥2, and N and M may be the same or different. Preferably, in order to minimize the anisotropy of detection as much as possible, the number of unit structures in the horizontal and vertical directions is the same, that is, N = M. In addition, preferably, in order to ensure the detection signal strength, the area covered by the unit structure array should be equal to or greater than the area covered by the terahertz wave in the terahertz time-domain spectroscopy system.

[0066] As Figure 1A shown, in this embodiment, the resonator unit has a split-ring structure with an LC resonance mode, and the 3 resonator units in each row are connected in series in turn, and both ends of the 3 rows of resonator units are respectively connected to the current positive terminal and the current negative terminal. Figure 2 For Figure 1A a schematic diagram of one of the resonator units of each of the four resonators in the current-modulated terahertz device shown.

[0067] Among them, Figures (A), (B), (C), and (D) are Figure 1A the resonant units in the first, second, third, and fourth microresonators. The following will introduce the resonant unit in this embodiment in conjunction with Figure 1A , Figure 1B and Figure 2 .

[0068] Please refer to Figure 1B . In the thickness direction, the resonant unit includes: a chromium layer formed on the VO2 layer; a gold layer formed on the chromium layer. Among them, the thickness of the chromium layer is 20 nm, and the thickness of the gold layer is 200 nm. Among them, the main function of the chromium layer is to ensure the adhesion of the gold layer to the substrate. The chromium layer and the gold layer are etched to form the planar structure of the resonant unit.

[0069] Those skilled in the art should be clear that the chromium thin film can also be replaced by other adhesive metal materials that can provide high adhesion, such as titanium, etc.; the gold microstructure can also be replaced by other similar metal materials, such as silver, copper, etc. In addition, the thicknesses of the chromium thin film and the gold microstructure can also be adjusted as needed. Preferably, the thickness of the chromium thin film is between 5 nm and 100 nm. The thickness of the gold thin film is between 100 nm and 300 nm.

[0070] In this embodiment, the resonant unit structures in the four microresonators are the same, and the only difference is the split gap size g. Please refer to Figure 1A and Figure 2 . In the horizontal direction, the resonant unit is symmetric up and down, including: a closed square ring; a left extension arm and a right extension arm respectively passing through the left and right sides of the closed square ring; the left side of the left extension arm is connected to the positive current terminal or the right extension arm of the previous resonant unit; the right side of the right extension arm is connected to the left extension arm of the next resonant unit or the negative current terminal; a rectangular opening area is formed between the left and right extension arms.

[0071] Specifically, in this embodiment, the period p of the resonant unit is between 40 μm and 60 μm; the side length l of the closed square ring is between 30 μm and 40 μm; the line width w is between 3 μm and 6 μm; the line widths of the left and right extension arms are the same as the line width of the closed square ring; the height h of the rectangular opening area is between 5 μm and 15 μm, and the width g is between 2 μm and 8 μm. The period of the resonant unit is 50 μm; the side length l of the closed square ring is 36 μm, the line width w is 4 μm; the height h of the rectangular opening area between the left and right extension arms is 10 μm.

[0072] Those skilled in the art should understand that although the present embodiment is described by taking a closed square ring as an example, in other embodiments of the present invention, a closed ring such as a closed circular ring or a closed rectangular ring may also be used. At the same time, the structural parameters of the closed ring, such as the side length, line width, opening size, etc., may also be adjusted as needed.

[0073] It should be noted that in order to enhance the sensitivity of the spectral line shape of the current modulated terahertz device of this embodiment to the VO2 phase change, the values ​​of the parameter g of the resonant units in the four resonators determined in the experiment after adjusting the resonance response are 8, 6, 4, and 2 μm respectively.

[0074] The current-modulated terahertz device of this embodiment is configured in this way because the phase change of VO2 is highly localized and depends on the distribution of electrical current filaments attached to the microresonator. This design can not only ensure that the bias current produces a relatively consistent heating effect when flowing through each microresonator, but also can utilize the difference in gaps to achieve the control of the resonant spectral response of the terahertz wave and the adjustment of the transmission spectrum lines.

[0075] Furthermore, the present invention uses a split ring structure with an LC resonance mode to construct a terahertz super surface layer microstructure. The LC resonance mode makes the spectrum line show a sharp line shape with a high quality factor, which has a high sensitivity to external field response, can enhance the response of THz waves to the change of conductivity during the VO2 phase transition, and improve the modulation sensitivity of the spectrum curve line shape to the VO2 phase transition.

[0076] In addition, it can be seen from the above structure that compared with the asymmetric resonance unit in the prior art, the symmetrical arrangement of the positive current terminal and the negative current terminal in the microresonator, the array arrangement of the resonance unit, and the internal structure of the resonance unit in the present invention are all arranged symmetrically. Compared with the asymmetric resonance unit in the prior art, such a symmetrical arrangement makes the electrical and thermodynamic characteristics of the entire device more stable.

[0077] Figure 3A , Figure 3B , Figure 3C and Figure 3D The transmission spectrum curves of the first, second, third and fourth microresonators in the current modulated terahertz device shown in Figure 1 are changed with the applied current. The horizontal axis is the frequency (Frequency), the unit is terahertz (THz); the vertical axis is the transmittance (Transmission). Figure 3A As shown in the figure, the transmission spectrum under static state (I=0A) does not show obvious resonant absorption. When I gradually increases, the amplitude transmittance begins to decrease and drops to the lowest value as a whole when the current value is large enough. When the current decreases to 0A, the transmission spectrum returns to the state of static current, indicating that the resistance change of VO2 is reversible.Figure 3A Under the modulation of small current, the change of the spectral line is not obvious.

[0078] In order to improve the sensitivity of the microresonator to the electro-control response, the present invention has conducted a systematic study on the design of the surface resonator unit structure. By fixing the external connection structure in the resonator unit structure and only reducing the gap size g value to tune the impedance and reduce the loss, a resonance line shape with a high quality factor and a narrow bandwidth in the frequency spectrum is obtained. When the g value in the resonator unit structure is reduced to 6, 4, and 2 μm respectively, the corresponding electro-tunable transmission spectra measured experimentally are as Figure 3B , Figure 3C and Figure 3D shown. The figure shows that as g decreases, both the resonance frequency and amplitude in the frequency spectrum change. The resonance frequency at static state shifts to the low frequency and at the same time a resonance with a sharper line shape is generated.

[0079] Figure 4 Shows the surface current and electric field distribution diagrams of the fourth resonator at the first resonance valley. The current is a circular current, indicating that the microresonator has an LC resonance mode. The electric field is mainly localized at the gap and has a strong intensity.

[0080] It should be noted that when the internal gap size g value in the resonator unit structure decreases, the change of the spectral line at a small current value also becomes sensitive, and the terahertz transmission amplitude of the fourth resonator decreases rapidly with the increase of the current. In order to more strongly demonstrate that the microresonator with a sharp line shape resonance increases the response to the modulation current, the variation of the modulation depth of the resonance amplitude of the second, third, and fourth microresonators at the first resonance valley with the current value is extracted, as Figure 5 shown. The results show that as g decreases, the saturation current of the LC resonance modulation drops from 0.32 A to 0.22 A. This shows that by reducing the internal gap size of the resonator unit structure, the response of terahertz waves to the change of conductivity during the VO2 phase transition is successfully enhanced, the sensitivity of the spectral curve line shape to the small current regulation is improved, and the working current is reduced.

[0081] In the present invention, a current positive terminal and a current negative terminal are symmetrically arranged on both sides of the microresonator, and the VO2 material below is heated by the electric field generated when the bias current passes through the microresonator. The structure of the microresonator results in a highly localized phase transition of VO2 and the distribution of electrical current filaments attached to the microresonator. Such a design can not only ensure a relatively consistent heating effect when the bias current flows through each resonator, but also utilize the differences in the gaps to control the resonance spectral response of terahertz waves and adjust the spectral line of the transmission spectrum.

[0082] As can be seen from the above description, in the present invention, a current positive terminal and a current negative terminal are symmetrically arranged on both sides of the microresonator, and the VO2 material below is heated by the electric field generated when the bias current passes through the microresonator. The structure of the microresonator results in a highly localized phase transition of VO2 and the distribution of electrical current filaments attached to the microresonator. Such a design can not only ensure a relatively consistent heating effect when the bias current flows through each resonator, but also utilize the differences in the gaps to control the resonant spectral response of terahertz waves and adjust the transmission spectral lines. The following will illustrate the differences and advantages of the current-modulated terahertz device of the present invention compared with the VO2 control methods in the prior art:

[0083] (1) Compared with the control method using laser irradiation, the present invention is more conducive to the integration with the mainstream technologies of current integrated circuits, and at the same time avoids the interference between the laser light source and the terahertz wave source.

[0084] (2) Compared with the control method using voltage, the present invention adopts a current modulation method. Experiments have proved that the current adjustment is more direct and effective, and the current can be used as an additional modulation parameter to expand the application scope of the device. At the same time, it is more conducive to the combination with the current integrated circuit technology.

[0085] (3) Compared with the modulation method of heating the VO2 material by forming a p-n junction between the VO2 layer and the underlying material, the present invention utilizes the metallic properties of the metamaterial to generate Joule heat after being energized, heating the VO2 layer, thereby changing the conductivity of the VO2 material and reducing the terahertz wave transmittance. The process is more direct and effective, with lower energy consumption, and at the same time reduces the impact on other components of the integrated circuit caused by doping the substrate material.

[0086] (4) Compared with the traditional modulation method of thermally controlling the phase transition of VO2, the present invention abandons the bulky external heater and adopts a flexible electrical control method, reducing the complexity of actual operation and providing convenience for the development of integrated devices.

[0087] (5) Compared with using only VO2 powder to form a phase change material region only at the split ring opening, the present invention has the following advantages: First, the monolithic VO2 layer fabricated by the epitaxial growth method has higher crystallinity and better consistency, thus the reliability of the device is higher; Second, the overall coating process has better controllability and lower manufacturing cost, which is more conducive to industrial production; Third, it is more conducive to the integration with the mainstream technologies of current integrated circuits.

[0088] In this embodiment, the four microresonators correspond to different transmission spectral lines within the experimentally measurable frequency range (0.25 - 2.25 THz). Based on this, a function of converting continuous spectral information into digital information is developed, and two applications are specifically proposed: a terahertz wave active modulator and an information encryption memory.

[0089] II. Terahertz Wave Modulation System

[0090] In the second exemplary embodiment of the present invention, a terahertz wave modulation system is provided. Please refer to Figure 1A , the terahertz wave modulation system of this embodiment includes:

[0091] The current modulation terahertz device as described above, which serves as a terahertz wave active modulator;

[0092] A bias current source, the two ends of which are connected to the current positive terminal and the current negative terminal of the microresonator in the terahertz wave active modulator;

[0093] Wherein, the bias current source loads the coding current carrying coding information to the current positive terminal and the current negative terminal of the microresonator in the terahertz wave active modulator to regulate the terahertz wave transmittance of the microresonator.

[0094] In this embodiment, it is defined that (1) when the transmittance in the spectrum is greater than 0.3, the output digital signal is "1"; (2) when the transmittance in the spectrum is less than 0.3, the output digital signal is "0". In this way, the continuous spectrum can be represented by 8 binary codes at intervals of 0.25 THz to represent the transmittance within the spectrum range. Referring to the international ASCII code, the 8 binary codes are combined into corresponding digital information. The digital signal outputs corresponding to the spectral lines of the four microresonators in different current modulation states are as shown in Figure 6 the upper left corner. When no current is applied, the VO2 thin film is in an insulating state. At this time, the signal conversion and output of the four microresonators respectively correspond to the 4 curves from top to bottom. For example: for the first microresonator, the transmittance exceeds 0.3 within the range of 0.5 - 2.0 THz, so this frequency band is represented by 6 binary codes of 1, while the transmittance in other frequency bands is less than 0.3, so it is represented by 0. In this way, the numerical signal corresponding to the entire frequency band is "01111110", and the corresponding coding information output by referring to the international ASCII code is the symbol "~"; the figure also respectively shows the coding information outputs of the other 3 microresonators at rest, all realizing the conversion and output from continuous spectral information to digital information.

[0095] Changing the magnitude of the applied bias current can change the transmission spectral line shape, thereby changing the coding output information. Figure 6As guided by the arrow direction, it respectively shows the encoded output information of four microresonators when the current is increased to 0.34 A, and when 0.7 A causes the VO2 thin film to be completely in the metallic state and then the bias current is decreased to 0.34 A. It can be found that with the change of the applied current, the output information of the same microresonator varies with the change of the transmission spectrum. During the entire current modulation process, the first resonator outputs a total of two symbol information, the second resonator outputs a total of three symbol information, while the third and fourth resonators with smaller g values output a total of four symbol information. In the insulating and metallic states, the spectral line shapes of each microresonator are significantly affected by current modulation, and different encoded information is output.

[0096] It should be noted that when the current stops at 0.34 A twice, due to the inherent hysteresis characteristics of VO2, the microresonators present different encoded information. Based on this, the arbitrary encoding function of the current-modulated terahertz device is developed.

[0097] In this embodiment, the frequency with a monotonic change and a large amplitude of transmittance with current modulation is selected to achieve the arbitrary encoding function. Figure 7 It is a schematic diagram of the multi-state characteristics of the transmittance and the binary encoding corresponding to the multi-states realized by the terahertz wave modulation system of the embodiment of the present invention. Figure 7 In it, first, the transmittance of four microresonators at 1.425 THz is extracted, and the change curve of the whole process with current regulation is made, corresponding to the longest cyclic curve in the figure. It can be seen that the transmittances of different microresonators respond differently to the applied current. The structural design brings differences in the terahertz electromagnetic response of the resonators and also makes the hysteresis loop adjustable. From top to bottom, corresponding to the decrease of the gap g value inside the unit structure, the operating current value of the microresonator moves towards the small current direction. At the same time, the current value I at the maximum hysteresis corresponding to each microresonator is found h ( Figure 7 the vertical dotted line in it), the transmittance difference is the largest at this current, which is more conducive to signal discrimination and state reading. Obviously, I h also decreases with the decrease of the gap, and the I h values corresponding to the decrease of the gap are 0.45, 0.34, 0.3, and 0.26 A respectively. Further, in order to realize the multi-state memory function of VO2, the applicant applies current cyclic curves with different end current values to the microresonators, and realizes three clearly visible cyclic curves of transmittance changes, as shown in Figure 7 represented by the three complete cyclic curves in each microresonator; there are four different transmittance magnitudes corresponding to I h here, which are defined as the 4 states of VO2, and are respectively represented by the 2-bit encoding "00, 01, 10, 11" states.

[0098] In this embodiment, the applicant applies a programmable series of pulsed currents to the fourth resonator to demonstrate any encoding function. As Figure 8A shown, the h value of 0.26 A is used as the "read" current input for obtaining the transmittance state process, and the "write" and "erase" inputs are achieved by applying different short pulsed currents. The "write" input is set to 0.5 A with a pulse width of 4 s, and the "erase" input is set to 0 A with a pulse width of 10 s. First, if one wants to achieve Figure 6 the information "|" of the binary encoded output of the fourth resonator at 0 A without current in Figure 8A the programmable pulse sequence in the above figure, where the "write" current is encoded as 0.29 - 0.5 - 0.5 - 0 A, one can obtain the same binary sequence "01111100" and its corresponding encoding as Figure 6 the result; in addition, arbitrary encoding of other sequences can also be performed, such as Figure 8B where the write current sequence is 0 - 0.5 - 0.35 - 0 A, and the same output information as when the current in Figure 6 drops to 0.34 A can be obtained. It should be noted that this device can not only repeat Figure 6 the full-spectrum fixed encoding in its own structure in

[0099] For those skilled in the art, it should be understood that for a terahertz wave active modulator including S × T microresonators, where S ≥ 2 and T ≥ 2, for each microresonator, the structural parameters of N × M resonant units are the same; for different microresonators, the structural parameters of the internal resonant units are different, and the bias current source can provide different bias currents for different microresonators. Through the method of this embodiment, various modulation options can be provided.

[0100] It can be seen that in the present invention, based on the erasable characteristics and different electro-induced non-volatile multi-level conductance states, multiple microresonator arrays can all achieve the rewritable function, and can perform arbitrary combination outputs of the binary encoding of the output, providing an exciting opportunity for the development of photon memories and terahertz communication devices.

[0101] III. Information Encryption System

[0102] According to the third aspect of the present invention, an information encryption system is also provided. The information encryption system of the embodiment of the present invention includes:

[0103] The current modulation terahertz device as described above, which serves as an information encryption memory; the microresonator serves as a pixel of the information encryption memory;

[0104] Among them, the structural parameters of the microresonators in the information encryption memory carry encrypted information, and a specific terahertz wave frequency and a specific bias current applied to the positive and negative current terminals of the microresonators are used as keys. Preferably, the specific terahertz wave frequency used as the key is selected from the resonance peaks or valleys of the microresonators.

[0105] For the information encryption memory, it includes S'×T' microresonators. Each microresonator serves as a pixel of the information encryption memory. For each microresonator, the structural parameters of N×M resonance units are the same; for different microresonators, the structural parameters of the internal resonance units are different. It should be noted that here S' and T' are used to represent the number of rows and columns of the microresonators in the information encryption memory respectively, aiming to distinguish from Figure 1A the number of rows S = 2 and the number of columns T = 2 of the microresonators in the current modulation terahertz device shown, and there is no other meaning.

[0106] In the information encryption system, the corresponding relationship between the preset terahertz wave transmittance and the color is set; when the encrypted information carried by the pixel is in the form of a specific terahertz wave frequency and a specific bias current, the corresponding color obtained from the terahertz wave transmittance; the encrypted information carried by the information encryption memory is represented as a pattern formed by the arrangement and combination of S'×T' pixel color blocks, and the pattern is in the form of letters, numbers, and / or symbols.

[0107] Figure 9A shows a schematic diagram of an information encryption memory composed of four microresonators combined. In Figure 9A the shown information encryption memory, the distinguishable hysteresis characteristics of four microresonators with different gap sizes (g) - the first resonator, the second resonator, the third resonator, and the fourth resonator - are used for the spatial arrangement design of the array device, expanding its application in the field of dynamic display that is lacking in the terahertz range.

[0108] In Figure 9A , each square corresponds to a pixel, that is, a microresonator. The numbers 1, 2, 3, and 4 respectively represent the positions of the above-mentioned first, second, third, and fourth microresonators in the information encryption memory. The gray scale represents the pseudo-color gray scale corresponding to the transmittance of each microresonator when the bias current value rises from 0 A to 0.34 A at a frequency of 1.425 THz.

[0109] In this embodiment, the color representation is pseudo-color. The encryption principle is as follows: The "Colormap" option in the function plotting software Origin is used to associate the terahertz wave transmittance values of pixels with pseudo-colors. The range of values corresponds to the range of colors, and finally the transmittance magnitude is represented by colors, so that the color composition at the special terahertz frequency of the microresonator forms a letter pattern. Each microresonator is arranged as a pixel unit of the information encryption memory, and the composed letter pattern is the encrypted information.

[0110] In Figure 9A it, S' = 16 and T' = 16. An encrypted information of 16×16 pixels is composed of four microresonators, that is, the letter "EROI". It should be noted that the grayscale here is only for more clearly showing the encryption process. In actual operation, only the device composed of 16×16 microresonators can be seen in this step, without grayscale display. However, at this time, the letter information has been encrypted, and the information already exists in the memory.

[0111] On the decryption side, the information encryption system further includes: a decryption module for respectively applying a specific bias current to each microresonator in the information encryption memory and irradiating the information encryption memory with terahertz waves; a color demodulation module arranged at the optical path rear end of the information encryption memory for decrypting the terahertz wave transmittance of each pixel in the information encryption memory into the corresponding color according to the preset correspondence between the transmittance of terahertz waves at a specific frequency and colors, and arranging and combining the color blocks of S'×T', that is, 16×16, pixels to form a pattern.

[0112] In this embodiment, the decryption module selects three frequencies, namely the LC resonance valley (1.01 THz) in the fourth resonator and its two side resonance peaks (0.87 THz and 1.425 THz) for dynamic display and decryption demonstration. The transmittance related to the current is represented by pseudo-colors.

[0113] Figure 9B shows the graphic displays at 0.87 and 1.01 THz respectively. When the VO2 thin film is in the insulating state without an externally applied current, the transmittances of the four microresonators at 0.87 THz are approximate, and the color difference is small. At 1.01 THz, only the fourth resonator has a very low transmittance due to the resonance valley, which will result in a huge difference in color display compared with the other three microresonators. However, when the current is increased to 0.7 A, it can be observed that the images at these two frequencies are almost the same under dark blue, because in the metallic state, the transmittances of all hybrid microresonators are significantly attenuated by the VO2 thin film. Thus, Figure 9BDynamic imaging at different frequencies and different current values is shown. However, it should be noted that since the frequency and current values are not the decryption keys, the demonstrated graphs are not the encrypted letter information "EROI". It can be seen that as long as one of the terahertz wave frequency and the bias current does not match, the encrypted information cannot be decrypted.

[0114] Figure 9C It is a schematic diagram for realizing information decryption and image reproduction using a variety of terahertz wave frequencies and bias currents as decryption keys. As Figure 9C shown, the function of the array at a frequency of 1.425 THz is demonstrated. In the initial state of 0 A, the transmittances of the four microresonators are all the highest, but the differences are not significant. The result is shown in red (state I), and the encrypted letter pattern information cannot be seen, and decryption cannot be achieved. When the current increases to 0.34 A, the pattern is consistent with the encrypted letter information "EROI" (state II), indicating that at this terahertz wave frequency and this bias current, the decryption process has been completed, and the letter information stored in the information encryption memory has been successfully reproduced, and the decryption is successful. To more clearly demonstrate the importance of the bias current as a key, when the bias current is further increased to 0.7 A, it is found that the letter information is hidden in the blue background (state III), and decryption cannot be completed. In addition, if the bias current is used as the key and the application order is incorrect, decryption cannot be completed. For example, when the bias current is selected to gradually decrease from the maximum current of 0.7 A to 0.34 A, although the current values are the same, the graph display is very different from that in state II, showing that the letter information is converted into the prominently red "FPCL" (state IV), and the decryption fails. Importantly, this opens up a new way for using the bias current as a decryption key, using current modulation of terahertz devices to achieve information encryption, and realizing the application of multicolor dynamic display in terahertz imaging.

[0115] It can be seen that in the present invention, by using the separated transmittance hysteresis loops generated by different resonator unit structures in the array, an information encryption system with frequency-selectable dynamic adjustable color pattern display is further provided in the terahertz band. Using the current and terahertz wave frequency as decryption keys can achieve information encryption and multi-image reproduction.

[0116] So far, the embodiments of the present invention have been described in detail with reference to the accompanying drawings. Based on the above description, those skilled in the art should have a clear understanding of the present invention.

[0117] It should be noted that for some implementation manners, if they are not the key content of the present invention and are well-known to those of ordinary skill in the art, they are not described in detail in the accompanying drawings or the main body of the specification. In this case, reference can be made to the relevant prior art for understanding. It should be understood that the purpose of providing these embodiments is only to make the present invention meet legal requirements, and the present invention can be implemented in many different forms and should not be construed as limited to the above embodiments.

[0118] In addition, the above definitions of each element and method are not limited to the specific structures, shapes or manners mentioned in the embodiments. Those of ordinary skill in the art can make simple changes or substitutions thereto. For example:

[0119] (1) The size of the resonant unit structure in the microresonator can be slightly adjusted;

[0120] (2) The spacing between each unit cell in the resonant unit array can be set as needed;

[0121] (3) In the current modulation terahertz device, the thicknesses of the substrate and the VO2 layer can be slightly adjusted.

[0122] In summary, the present invention provides a current modulation terahertz device based on VO2 and metamaterials. Through improvements in aspects such as the resonant unit structure, planar arrangement of the resonator, modulation method, etc., it enhances the response of the line shape to the change in conductivity during the VO2 phase transition, reduces the operating current of the current modulation terahertz device, and develops applications in terahertz wave modulation systems and information encryption systems, providing a new method for constructing a revolutionary platform with VO2 integrated devices and having good application prospects.

[0123] It should also be noted that the directional terms mentioned in the embodiments, such as "upper", "lower", "front", "rear", "left", "right", "inner", "outer", etc., are only references to the directions in the accompanying drawings and are not used to limit the protection scope of the present invention. Throughout the accompanying drawings, the same elements are represented by the same or similar reference numerals. And, the shapes and sizes of the components in the figures do not reflect the actual sizes and proportions, but only illustrate the content of the embodiments of the present invention. Additionally, in the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

[0124] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "connected" and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0125] Unless otherwise expressly indicated to the contrary, the numerical parameters set forth in the specification and claims of the present invention may be approximate values and can vary depending on the content of the present invention. Specifically, all of the numbers expressing the contents of components, reaction conditions, etc. recited in the specification and claims should be understood to be modified in all instances by the term "about", which is intended to mean that the recited value includes variations of ±10% in some embodiments, ±5% in some embodiments, ±1% in some embodiments, and ±0.5% in some embodiments.

[0126] Furthermore, the word "comprising" does not exclude the presence of elements or steps not recited in the claims. The word "a" or "an" preceding an element or step does not exclude the presence of a plurality of such elements or steps.

[0127] The ordinal numbers such as "first", "second", "third", "primary", "secondary", as well as Arabic numerals, letters, etc. used in the specification and claims to modify the corresponding elements or steps are intended only to clearly distinguish one element (or step) having a certain name from another element (or step) having the same name, and do not mean that the element (or step) has any ordinal significance, nor does it represent the order of one element (or step) relative to another element (or step).

[0128] Similarly, it should be understood that, in order to streamline the present invention and assist in understanding one or more of the various inventive aspects, in the foregoing description of the exemplary embodiments of the present invention, the various features of the present invention are sometimes grouped together in a single embodiment, figure, or description thereof. However, the methods of the invention should not be construed as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as reflected in the claims, the various inventive aspects lie in less than all of the features of the preceding single embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into the detailed description, with each claim standing on its own as a separate embodiment of the present invention.

[0129] The specific embodiments described above have elaborated in detail the objectives, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only specific embodiments of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A current-modulated terahertz device based on VO2 and metamaterials, characterized in that, Comprising: A substrate transparent to terahertz waves; a VO2 layer formed on the substrate; A microresonator formed on the VO2 layer; The microresonator includes: a current positive terminal and a current negative terminal, which are formed on the VO2 layer, are symmetric left and right, and are used for loading a bias current; N×M resonant units, which are symmetric left and right, are arranged in an array, are formed on the VO2 layer inside the current positive terminal and the current negative terminal, and N≥2, M≥2; Wherein, the resonant unit has a split-ring structure with an LC resonance mode, the M resonant units in each row are connected in series in sequence, and the two ends of the N rows of resonant units are respectively connected to the current positive terminal and the current negative terminal; Wherein, in the horizontal direction, the resonant unit is symmetric up and down, and includes: a closed loop; a left extension arm and a right extension arm respectively passing through the left and right sides of the closed loop; the left side of the left extension arm is connected to the current positive terminal or the right extension arm of the previous resonant unit; the right side of the right extension arm is connected to the left extension arm of the next resonant unit or the current negative terminal; a rectangular opening area is formed between the left and right extension arms; Wherein, the closed loop is one of the following forms: a closed square loop, a closed circular loop, a closed rectangular loop.

2. The current-modulated terahertz device according to claim 1, wherein Comprising: S×T microresonators, which are formed on the VO2 layer, are arranged in an array, S≥2, T≥2, and S=T; For each microresonator, the structural parameters of the N×M resonant units are the same, and N = M; The period p of the resonant unit is between 40μm and 60μm; the closed loop is a closed square loop, and its side length l is between 30μm and 40μm; the line width w is between 3μm and 6μm; the line widths of the left and right extension arms are the same as the line width of the closed loop; the height h of the rectangular opening area is between 5μm and 15μm, and the width g is between 2μm and 8μm.

3. The current-modulated terahertz device according to claim 2, wherein The thickness of the VO2 layer is between 5nm and 100nm; and / or The bias current loaded on the inner N rows of resonant units by the current positive terminal and the current negative terminal is between 0 and 0.7A; And / or In the thickness direction, the resonant unit includes: a viscous metal layer formed on the VO2 layer; A conductive metal layer formed on the viscous metal layer, the thickness of the viscous metal layer is between 5nm and 100nm, the thickness of the conductive metal layer is between 100nm and 300nm, and the closed loop and the left and right extension arms are formed by the viscous metal layer and the conductive metal layer.

4. The current-modulated terahertz device according to claim 3, wherein In the horizontal direction, the period of the resonant unit is 50μm; the side length l of the closed loop is 36μm, and the line width w is 4μm; the height h of the rectangular opening area between the left and right extension arms is 10μm; and / or In the vertical direction, the substrate is a sapphire substrate; the thickness of the VO2 layer is 10nm; the viscous metal layer is a chromium thin film, and its thickness is 20nm; the conductive metal layer is a gold thin film, and its thickness is 200nm.

5. The current-modulated terahertz device according to claim 1, characterized in that, The current modulation terahertz device serves as a terahertz wave active modulator or an information encryption memory.

6. A terahertz wave modulation system, characterized in that, It includes: The current modulation terahertz device according to any one of claims 1 to 4, which serves as a terahertz wave active modulator; A bias current source, whose two ends are connected to the positive current terminal and the negative current terminal of the microresonator in the terahertz wave active modulator; Wherein, the bias current source loads an encoded current carrying encoded information to the positive current terminal and the negative current terminal of the microresonator in the terahertz wave active modulator to regulate the terahertz wave transmittance of the microresonator.

7. The terahertz wave modulation system according to claim 6, wherein The encoded information carried in the terahertz wave transmittance is 2-bit information encoding; the terahertz wave modulation system is defined as follows: when the terahertz wave transmittance is greater than or equal to the transmittance threshold, it carries the binary code "1"; when it is less than the transmittance threshold, it carries the binary code "0"; and / or The terahertz wave active modulator includes: S×T microresonators arranged in an array, S≥2, T≥2. For each microresonator, the structural parameters of N×M resonant units are the same; for different microresonators, the structural parameters of the internal resonant units are different, and the bias current source can provide different bias currents for different microresonators.

8. An information encryption system, characterized in that, It includes: The current modulation terahertz device according to any one of claims 1 to 4, which serves as an information encryption memory; The microresonator serves as a pixel of the information encryption memory; Wherein, the structural parameters of the microresonator in the information encryption memory carry encrypted information, and a specific terahertz wave frequency and a specific bias current loaded to the positive current terminal and the negative current terminal of the microresonator are used as keys. Among them, the specific terahertz wave frequency used as the key is selected from the resonance peak or resonance valley of the microresonator.

9. The information encryption system according to claim 8, wherein The information encryption memory includes: S×T microresonators arranged in an array, S≥2, T≥2. Each microresonator serves as a pixel constituting the information encryption memory. For each microresonator, the structural parameters of N×M resonant units are the same; for different microresonators, the structural parameters of the internal resonant units are different; In the information encryption system, a corresponding relationship between a preset terahertz wave transmittance and a color is set; when the encrypted information carried by the pixel is in the form of a specific terahertz wave frequency and a specific bias current, the corresponding color obtained from the terahertz wave transmittance; the encrypted information carried by the information encryption memory is in the form of a pattern formed by the color block arrangement and combination of S×T pixels, and the pattern is in the form of letters, numbers and / or symbols; On the decryption side, the information encryption system further includes: a decryption module for applying a specific bias current to each of the microring resonators in the information encryption memory and irradiating the information encryption memory with terahertz waves of a specific frequency; a color demodulation module disposed at the optical path rear end of the information encryption memory for decrypting the terahertz wave transmittance of each pixel in the information encryption memory into a corresponding color according to the preset correspondence between the terahertz wave transmittance and the color, and arranging and combining the color blocks of S×T pixels to form a pattern.

Images