Sub-wavelength infrared antenna based on bismuth telluride metasurface nanopore array structure

Abstract

The invention discloses a sub-wavelength infrared antenna structure based on a bismuth telluride metasurface nanopore array and a preparation method of the sub-wavelength infrared antenna structure, and relates to the field of metasurface antenna design and infrared band application. According to the structure, bismuth telluride is used as a core material, and a 12 * 12 metasurface nanopore array is prepared through a high-energy electron beam in a transmission electron microscope to serve as a sub-wavelength infrared antenna. The antenna is excited by a dipole source in the center of an array, and full-wave time domain finite difference simulation optimization design is adopted. In the infrared band, the directional coefficient of 15 dBi, the gain of 14.5 dBi and the radiation efficiency of 93% are achieved, and the sub-wavelength size design is achieved due to the high refractive index characteristic of bismuth telluride. The problems that a traditional metal metasurface antenna is large in ohmic loss and large in size in the infrared band are solved, miniaturization, high directivity and adjustable radiation characteristics are achieved, and the polarization adjustable potential is achieved. The method can be widely applied to the fields of infrared communication, sensing, imaging and the like.

Description

Technical Field

[0001] This invention relates to the field of infrared antenna technology, specifically to a subwavelength infrared antenna structure based on a bismuth telluride metasurface nanopore array. It achieves high directional radiation and miniaturization in the infrared band through a low-loss dielectric metasurface, and is suitable for infrared communication, infrared sensing, infrared imaging and other scenarios. Background Technology

[0002] In the infrared band, antenna performance is particularly sensitive to material properties: traditional metasurface antennas mostly rely on metal components, but their inherent ohmic loss will significantly reduce radiation efficiency, and metal structures are difficult to balance size and performance at the subwavelength scale; although existing dielectric metasurface antennas can reduce loss, they lack highly adaptable material designs for the infrared band, making it difficult to simultaneously achieve the comprehensive requirements of "high directivity, high radiation efficiency, and subwavelength size".

[0003] Existing technology 1 (All-dielectric metasurface for high-performance structuralcolor, Nature Communications, 11:1864 (2020)) uses silicon to achieve structural color in the visible light band. Although the color gamut and brightness are improved through a refractive index matching layer, silicon has significant absorption loss in the infrared band, and its refractive index (n≈3–4) is much lower than that of bismuth telluride, resulting in a large resonator size, which is difficult to directly apply to the miniaturization requirements of infrared antennas. In addition, the structure of existing technology 1 is a nanodisk array, and its resonance mechanism depends on electric dipole and magnetic dipole modes. Existing technology 2 (Light passing through subwavelength apertures, Rev. Mod. Phys., Vol. 82, No.1, January–March 2010) uses a metal-based subwavelength aperture array, such as gold or silver thin films. The anomalous optical transmission (EOT) phenomenon mainly depends on the excitation of plasmon polaritons (SPP) on the metal surface, but it is limited in the infrared band by the high ohmic loss and limited field localization capability of the metal. The silicon nanodisks and nanospheres and tellurium nanocube arrays in existing technology 3 (Advanced Optical Materials, 2015, 3: 813-820; Nature Communications, 2014, 5: 3402; Physical review letters, 2012, 108:097402) are all based on solid nanoparticles. These solid morphologies mainly scatter and resonate with incident electromagnetic waves through their outer boundaries, and their field enhancement regions are mostly located on the outside or surface of the structure.

[0004] Bismuth telluride (Bi₂Te₃), as a high-refractive-index dielectric material (n=7~8 in the range of 2~10µm), exhibits low-loss characteristics, and its refractive index advantage can reduce resonator size. Simultaneously, Bi₂Te₃'s topological insulator properties (conductive surface states can optimize current distribution) and anisotropy (which can be used for polarization control) provide potential for improving antenna performance. Currently, there are no reports on constructing subwavelength infrared antenna structures based on Bi₂Te₃ metasurface nanopore arrays in known metasurface antenna designs. Summary of the Invention

[0005] Technical Problem: To address the issues of high ohmic loss, insufficient directivity, and large size in the infrared band of traditional metallic metasurface antennas, as well as the lack of targeted material design for existing dielectric metasurface antennas, this invention provides a subwavelength infrared antenna structure based on a bismuth telluride metasurface nanopore array. This structure utilizes the low loss and high refractive index characteristics of Bi₂Te₃ and the coherent radiation advantages of the metasurface nanopore array to achieve high directivity, high radiation efficiency, and subwavelength size in the infrared band, while also possessing polarization control potential.

[0006] This application relates to a subwavelength infrared antenna structure based on a bismuth telluride (Bi₂Te₃) metasurface nanopore array. Utilizing the high refractive index (n≈7–8) and low loss characteristics of bismuth telluride, combined with the subwavelength resonant design of the nanopore array, high directivity, high gain, and high radiation efficiency in the infrared band are achieved. Specifically, bismuth telluride has an extremely high refractive index in the 2–10 μm infrared band, which can effectively localize the electromagnetic field and reduce the resonator size. Simultaneously, its topological insulator properties help optimize the surface current distribution and reduce ohmic losses. The core morphology of this application creatively employs a nanopore array structure. Compared with common solid nanostructures in the prior art (such as nanodisks, nanocubes, or nanospheres), the morphological advantage of the nanopore array lies in its hollow structure, which can more effectively guide and localize the electromagnetic field.

[0007] Technical solution:

[0008] According to a first aspect of the present invention, a subwavelength infrared antenna based on a bismuth telluride metasurface nanopore array structure is provided. Two-dimensional bismuth telluride (Bi₂Te₃) material is used as the substrate, and a metasurface nanopore array is constructed on the surface of bismuth telluride using a high-energy converging electron beam. The present invention can realize the function of a subwavelength infrared antenna.

[0009] In some embodiments of the present invention, the two-dimensional bismuth telluride material is a multilayer (preferably no more than 10 layers, for example, 5-6 layers) bismuth telluride material; in some embodiments of the present invention, the two-dimensional bismuth telluride material has an exceptionally high refractive index (n≈7-8) in the mid-infrared band of 2-1µm. In one embodiment of the present invention, the two-dimensional bismuth telluride material is prepared by a tape-peeling method, that is, by repeatedly mechanically peeling off bulk crystals and separating them by adhesive tape, thereby obtaining a very simple preparation technique for single-layer or few-layer two-dimensional materials.

[0010] In some embodiments of the present invention, the thickness of the two-dimensional bismuth telluride material is 2 to 10 nm, for example, 6 nm.

[0011] In some embodiments of the present invention, the antenna structure comprises an array containing at least 10 × 10 bismuth telluride nanopores, wherein the nanopore diameter is 3-5 nm and the spacing between the nanopores is approximately 10-20 nm. In some embodiments of the present invention, the array period of the bismuth telluride nanopores is smaller than the subwavelength scale, forming a resonator array. In some specific embodiments, the array may contain, for example, 12 × 12 or 18 × 18 nanopores.

[0012] In some embodiments of the present invention, the nanopore array can be constructed using a transmission electron microscope (TEM), wherein the electron accelerating voltage is set to 200-300 kV.

[0013] In some embodiments of the present invention, a central dipole near-field excitation method is used during performance testing: coherent radiation of the metasurface nanopore array is coupled and excited through a point dipole source located at the geometric center of the array to form a directional radiation beam.

[0014] Performance verification: In some embodiments of the present invention, the full-wave finite-difference time-domain (FDTD) method is used to simulate antenna performance, and the simulation configuration uses perfectly matched layer (PML) boundary conditions to absorb emitted radiation in order to accurately evaluate radiation characteristics.

[0015] Key performance parameters: In some embodiments of the present invention, in the infrared band, the simulated directivity coefficient is 15 dBi, the simulated gain is 14.5 dBi, and the radiation efficiency is 93%; the radiation pattern is the end-fire characteristic of the main lobe along the z-axis.

[0016] According to a second aspect of the present invention, the present invention provides a method for fabricating a subwavelength infrared antenna based on a bismuth telluride metasurface nanopore array structure as described in the first aspect. A two-dimensional bismuth telluride thin film is prepared as a metasurface substrate by a tape-tearing method, and the substrate is placed in a transmission electron microscope to construct a nanopore array structure on the metasurface substrate using a converging electron beam.

[0017] A dipole source is placed at the center of the array, and the excitation frequency is set to 30-60 THz to excite the resonant radiation of the nanopore array.

[0018] In some embodiments of the present invention, the transmission electron microscope is set to an accelerating voltage of 200-300 kV for electrons.

[0019] In some embodiments of the present invention, a converging electron beam is used to construct 12×12 or 18×18 initial nanopores with a diameter of 3~5 nm on the sample.

[0020] According to a third aspect of the present invention, the present invention provides an application of the subwavelength infrared antenna based on the bismuth telluride metasurface nanopore array structure described in the first aspect, for use in infrared communication, biosensing, thermal imaging and high-precision infrared detection systems.

[0021] Beneficial effects: This invention achieves highly efficient electromagnetic control in the infrared band by designing a subwavelength structure, such as a 12×12 bismuth telluride (Bi2Te3) metasurface nanopore array (nanopore diameter approximately 3~5nm), combined with the high refractive index (n=7~8) and low loss characteristics of bismuth telluride. Its directivity coefficient reaches 15dBi, gain reaches 14.5dBi, and radiation efficiency reaches 93%, which is significantly better than traditional metal antennas. Meanwhile, the high refractive index of bismuth telluride enables a significant reduction in resonator size, solving the miniaturization problem of infrared antennas. Furthermore, the surface state characteristics of topological insulators provide a new approach to polarization control, which can be extended to the design of tunable polarized antennas.

[0022] This structure is suitable for infrared communication, biosensing, thermal imaging and high-precision infrared detection systems, and has the advantages of compactness, high directionality and low power consumption.

[0023] Compared to prior art 1, the nanopore array in this application achieves more efficient radiation coupling in the infrared band through hole resonance, and the low-loss characteristics of bismuth telluride further avoid the high ohmic loss problem of metal antennas in the infrared band. This application solves the technical bottlenecks of miniaturization, high efficiency, and tunability of infrared antennas through material innovation (bismuth telluride replacing traditional silicon or metal) and structural optimization (nanopore array replacing nanodisks). Experimental simulations show that its directivity reaches 15 dBi, gain is 14.5 dBi, and radiation efficiency is as high as 93%, significantly outperforming the potential performance of silicon-based structures in the infrared band in prior art 1.

[0024] Compared to prior art 2, this application uses bismuth telluride as the dielectric material. Its high refractive index effectively compresses the resonant wavelength, enabling deep subwavelength resonant units. Simultaneously, its topological insulator properties optimize surface current distribution, significantly reducing losses. Furthermore, bismuth telluride exhibits superior low absorption characteristics in the infrared band compared to metals, contributing to improved radiation efficiency. In terms of morphology design, the nanopore array in this application generates directional beams through coherent radiation under dipole excitation by controlling the aperture period and arrangement. The principle is similar to EOT in prior art 2, but thanks to the material advantages of bismuth telluride, higher field enhancement and lower propagation loss can be achieved in the same wavelength band. Therefore, this application not only inherits the array synergy effect of prior art 2 but also breaks through the performance bottleneck of traditional metals in the infrared band through material innovation, demonstrating clear progress and feasibility.

[0025] Compared to prior art 3, the nanopore array of this application introduces subwavelength holes within a single resonant unit. When electromagnetic waves are incident, this hole morphology can excite a stronger localized field enhancement effect and concentrate energy inside and at the edges of the hole, thereby achieving more efficient electromagnetic field confinement. Furthermore, the nanopore array, through its periodic arrangement, can excite stronger coherent coupling between structures, forming a directional radiation beam—a mechanism difficult to achieve with solid particle arrays. Therefore, this unique hollow morphology of the nanopore is one of the key principles for achieving high directivity and high radiation efficiency antennas in this application. Compared to traditional solid nanoparticle morphologies, it has inherent advantages in electromagnetic field localization and radiation control. Attached Figure Description

[0026] Figure 1 The image shows the transmission electron microscope (TEM) characterization of the bismuth telluride nanopore array in the subwavelength infrared antenna structure based on the bismuth telluride metasurface nanopore array in Example 1. The array layout is labeled as 12×12 and the nanopore diameter is 3~5nm.

[0027] Figure 2 The following is a simulation diagram of the beam direction of the metasurface array antenna in Example 1. (A) Three-dimensional radiation pattern when φ=60° and θ=0°; (B) Two-dimensional cross-sectional view along the z-axis.

[0028] Figure 3 The image shows the transmission electron microscope (TEM) characterization of the bismuth telluride nanopore array in the subwavelength infrared antenna structure based on the bismuth telluride metasurface nanopore array in Example 2. The array layout is labeled as 18×18 and the nanopore diameter is 3~5nm.

[0029] Figure 4 The following is a simulation diagram of the beam direction of the metasurface array antenna in Example 2: (A) Three-dimensional radiation pattern when φ = 60° and θ = 0°; (B) Two-dimensional cross-sectional view along the z-axis. Detailed Implementation

[0030] Materials: The two-dimensional bismuth telluride thin film prepared by the tape-tearing method in the examples consists of approximately 5-6 layers.

[0031] Example 1:

[0032] A two-dimensional bismuth telluride thin film (approximately 6 nm thick) was prepared as a metasurface substrate using a tape-tearing method. Under transmission electron microscopy (TEM) with an electron acceleration voltage of 300 kV, a focused electron beam was used to construct 12 × 12 initial nanopores with diameters of approximately 3–5 nm on the sample, forming a nanopore array structure with a spacing of approximately 18 nm. Figure 1 As shown.

[0033] A point dipole source was placed at the center of the array. The dipole source was made of gold / platinum nanowires (diameter ≈50 nm), deposited on the Bi₂Te₃ surface via FIB (Focused Ion Beam) excitation. The excitation frequency was set to 30 THz (corresponding to an infrared wavelength of 10 μm), and the resonant radiation of the nanopore array was excited by a coplanar waveguide feeding method. Simulations were performed using the full-wavelength finite-difference time-domain (FDTD) method, with perfectly matched layer (PML) boundary conditions set to absorb the emitted radiation and avoid boundary reflection interference. Simulation results show ( Figure 2 The FDTD simulation software extracted the directivity coefficient of the antenna from the radiation pattern data through numerical analysis. The gain was 14.5 dBi and the radiation efficiency was 93% at a frequency of 30 THz. The main lobe of the radiation pattern is along the z-axis (end-fire direction), which meets the high directivity requirement.

[0034] Example 2:

[0035] A two-dimensional bismuth telluride thin film (approximately 6 nm thick) was prepared as a metasurface substrate using a tape-to-surface method. Under transmission electron microscopy (TEM) with an electron acceleration voltage of 300 kV, a focused electron beam was used to construct 18 × 18 initial nanopores (approximately 3–5 nm in diameter) on the sample, forming a nanopore array structure. Each array period consists of 6 × 6 nanopores with a period length of approximately 90 nm. Figure 3 As shown.

[0036] A point dipole source, employing CdSe / ZnS core-shell quantum dots (approximately 3 nm in size), was placed at the center of the array. The excitation frequency was set to 60 THz, and a femtosecond laser pulse with a wavelength of 800 nm was used to trigger carrier oscillation in the quantum dots, generating an equivalent dipole moment and exciting resonant radiation from the nanopore array. Simulations were performed using the full-wavelength finite-difference time-domain (FDTD) method, with perfectly matched layer (PML) boundary conditions set to absorb the emitted radiation and avoid boundary reflection interference. The simulated directional gain was 17.2 dBi, and the radiation efficiency was 91%. The simulated beam direction is shown in the figure below. Figure 4As shown, with the increase of the number of array elements, it can be seen from the two-dimensional radiation pattern that the main lobe width of the array beam narrows and the amplitude ratio of the main lobe to the side lobe increases significantly. This indicates that the pointing accuracy of the directionality is positively correlated with the ratio of the main lobe to the side lobe and the array size, and can be further expanded.

[0037] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A subwavelength infrared antenna based on a bismuth telluride metasurface nanopore array structure, wherein a two-dimensional bismuth telluride material is used as the substrate material, and a metasurface nanopore array is constructed on the surface of bismuth telluride by a high-energy converging electron beam.

2. The subwavelength infrared antenna based on a bismuth telluride metasurface nanopore array structure according to claim 1, wherein the two-dimensional bismuth telluride material is a multilayer bismuth telluride material; And / or, the refractive index n of the two-dimensional bismuth telluride material is 7–8 in the mid-infrared band of 2–10 µm.

3. The subwavelength infrared antenna based on a bismuth telluride metasurface nanopore array structure according to claim 1, wherein the thickness of the two-dimensional bismuth telluride material is 2~10 nm.

4. The subwavelength infrared antenna based on a bismuth telluride metasurface nanopore array structure according to claim 1, wherein the antenna structure is composed of an array containing at least 10×10 bismuth telluride nanopores; And / or, the nanopore diameter is 3~5 nm and the nanopore spacing is 10~20 nm.

5. A method for fabricating a subwavelength infrared antenna based on a bismuth telluride metasurface nanopore array structure as described in claim 1, wherein a two-dimensional bismuth telluride thin film is used as a metasurface substrate, which is placed in a transmission electron microscope, and a nanopore array structure is constructed on the metasurface substrate using a converging electron beam.

6. According to the method of claim 5, a dipole source is placed at the center of the array, and the excitation frequency is set to 30-60 THz to excite the resonant radiation of the nanopore array.

7. The method according to claim 5, wherein the transmission electron microscope is set to an accelerating voltage of 200-300 kV for electrons.

8. The method according to claim 5, wherein 12×12 or 18×18 initial nanopores with a diameter of 3~5 nm are constructed on the sample using a converging electron beam.

9. According to the method of claim 5, a two-dimensional bismuth telluride film with a thickness of 6 nm is prepared as a metasurface substrate by the tape tearing method. The substrate is placed in a transmission electron microscope with an electron acceleration voltage of 300 kV. A converging electron beam is used to construct 12×12 initial nanopores with a diameter of 3~5 nm on the sample to form a nanopore array structure with a nanopore spacing of about 18 nm. Alternatively, a two-dimensional bismuth telluride film with a thickness of nm can be prepared as a metasurface substrate using the tape-tearing method. The substrate is placed in a transmission electron microscope with an electron acceleration voltage of 300 kV. A converging electron beam is used to construct 18×18 initial nanopores with a diameter of about 3~5 nm on the sample to form a nanopore array structure. Among them, 6×6 nanopores form one array period with a period length of about 90 nm.

10. The use of the subwavelength infrared antenna based on the bismuth telluride metasurface nanopore array structure as described in claim 1, for use in infrared communication, biosensing, thermal imaging and high-precision infrared detection systems.

Images