Common-aperture super grating array based on medium doping

Abstract

The invention discloses a common-caliber super grating array based on medium doping, and relates to the technical field of super grating arrays, the common-caliber super grating array comprises a first super grating array and a second super grating array, the first super grating array sleeves the second super grating array, and the second super grating array sleeves the first super grating array. The center line of the first super grating array and the center line of the second super grating array are collinear, a gap exists between the first super grating array and the second super grating array, and each of the first super grating array and the second super grating array comprises an upper dielectric layer, a super grating layer, a lower dielectric layer and a metal layer which are sequentially stacked from top to bottom. According to the invention, by introducing the common-caliber design and the medium doping design, the ultra-wideband OAM vortex beam and the mode multiplexing OAM vortex beam can be generated by changing parameters, and the design of the ultra-wideband and mode multiplexing OAM vortex beam is realized.

Description

Technical Field

[0001] This application relates to the technical field of super-grating arrays, and particularly to a co-aperture super-grating array based on dielectric doping. Background Art

[0002] Currently, a variety of methods for generating broadband vortex beams have been proposed. However, most of these methods can only generate vortex beams with a single mode order, and the research in the field of broadband vortex beam mode multiplexing is relatively limited. Moreover, most of the existing vortex beam mode multiplexing technologies mainly focus on the switching between different mode orders or generating vortex beams with different mode orders in different directions. The research on generating multimode superposition vortex beams that can carry multiple mode orders simultaneously in the same direction is still very scarce. Due to the orthogonality between different OAM mode orders, it is allowed to simultaneously transmit vortex beams carrying different mode orders on the same physical channel, which can significantly improve the data transmission capacity, alleviate the increasingly tense spectrum resources, and is applicable to high-density wireless communication scenarios. In addition, with the continuous development of wireless communication technologies, a variety of spectrum resources have been developed and utilized, and the demand for broadband and multi-band communication is getting higher and higher. Therefore, developing ultra-wideband vortex beams can cover multiple frequency bands simultaneously, which is beneficial to cost reduction.

[0003] Based on this, there is an urgent need for a technology that can generate ultra-wideband and mode multiplexing OAM vortex beams. Summary of the Invention

[0004] The purpose of this application is to provide a co-aperture super-grating array based on dielectric doping, which can realize the design of ultra-wideband and mode multiplexing OAM vortex beams.

[0005] To achieve the above purpose, this application provides the following solutions:

[0006] In the first aspect, this application provides a co-aperture super-grating array based on dielectric doping. The co-aperture super-grating array based on dielectric doping includes: a first super-grating array and a second super-grating array. The first super-grating array is sleeved outside the second super-grating array. The center lines of the first super-grating array and the second super-grating array are collinear, and there is a gap between the first super-grating array and the second super-grating array.

[0007] The first super-grating array includes a first upper structure and a first lower structure which are stacked in sequence from top to bottom. The first upper structure includes a first upper dielectric layer, and the first lower structure includes a first super-grating layer, a first lower dielectric layer, and a first metal layer which are stacked in sequence from top to bottom. The second super-grating array includes a second upper structure and a second lower structure which are stacked in sequence from top to bottom. The second upper structure includes a second upper dielectric layer, and the second lower structure includes a second super-grating layer, a second lower dielectric layer, and a second metal layer which are stacked in sequence from top to bottom.

[0008] The thickness and dielectric constant of the first upper structure are equal to those of the first lower structure, and the thickness and dielectric constant of the second upper structure are equal to those of the second lower structure. Both the first super-grating layer and the second super-grating layer are sub-wavelength gratings, and the upper surfaces of the first super-grating layer and the second super-grating layer are coplanar.

[0009] When the co-aperture super-grating array based on dielectric doping is used to provide an ultra-wideband OAM vortex beam, the thickness of the first upper structure is different from that of the second upper structure, and the mode orders corresponding to the first super-grating layer and the second super-grating layer are the same.

[0010] When the co-aperture super-grating array based on dielectric doping is used to provide a mode multiplexing OAM vortex beam, the thickness of the first upper structure is the same as that of the second upper structure, and the mode orders corresponding to the first super-grating layer and the second super-grating layer are different.

[0011] Optionally, when the co-aperture super-grating array based on dielectric doping is used to provide an ultra-wideband OAM vortex beam, the thickness of the first upper structure is 3 mm, and the thickness of the second upper structure is 1.5 mm. At this time, the frequency range of the ultra-wideband OAM vortex beam is 8.9 - 50 GHz.

[0012] Optionally, when the co-aperture super-grating array based on dielectric doping is used to provide a mode multiplexing OAM vortex beam, the mode order corresponding to the first super-grating layer is greater than that corresponding to the second super-grating layer.

[0013] Optionally, when the co-aperture super-grating array based on dielectric doping is used to provide a mode multiplexing OAM vortex beam, the thicknesses of both the first upper structure and the second upper structure are 4 mm.

[0014] Optionally, when the medium-doping-based co-aperture super-grating array is used to provide a mode-division multiplexing OAM vortex beam, the ratio of the area of the upper surface of the first upper structure to the area of the upper surface of the second upper structure is equal to the ratio of the purity of the OAM vortex beam generated by the first super-grating array to the purity of the OAM vortex beam generated by the second super-grating array.

[0015] Optionally, the duty cycles of the first super-grating layer and the second super-grating layer are both 0.3-0.6.

[0016] Optionally, the duty cycles of the first super-grating layer and the second super-grating layer are both 0.41.

[0017] Optionally, both the first super-grating array and the second super-grating array are cylindrical.

[0018] Optionally, the first upper dielectric layer, the first lower dielectric layer, the second upper dielectric layer, and the second lower dielectric layer all use a dielectric material, and the dielectric material includes F4B material;

[0019] Both the first metal layer and the second metal layer use a metal material.

[0020] Optionally, the dielectric constant of the F4B material is 2.85.

[0021] According to the specific embodiments provided by the present application, the present application has the following technical effects:

[0022] The present application provides a co-aperture metasurface grating array based on dielectric doping, including: a first metasurface grating array and a second metasurface grating array. A co-aperture design is introduced, with the first metasurface grating array sleeved outside the second metasurface grating array. The centerlines of the first metasurface grating array and the second metasurface grating array are collinear, and there is a gap between the first metasurface grating array and the second metasurface grating array. A dielectric doping design is introduced. The first metasurface grating array includes a first upper structure and a first lower structure stacked in sequence from top to bottom. The first upper structure includes a first upper dielectric layer, and the first lower structure includes a first metasurface grating layer, a first lower dielectric layer, and a first metal layer stacked in sequence from top to bottom. The second metasurface grating array includes a second upper structure and a second lower structure stacked in sequence from top to bottom. The second upper structure includes a second upper dielectric layer, and the second lower structure includes a second metasurface grating layer, a second lower dielectric layer, and a second metal layer stacked in sequence from top to bottom. The thickness and dielectric constant of the first upper structure are equal to those of the first lower structure, and the thickness and dielectric constant of the second upper structure are equal to those of the second lower structure. Both the first metasurface grating layer and the second metasurface grating layer are sub-wavelength gratings, and the upper surfaces of the first metasurface grating layer and the second metasurface grating layer are coplanar. Based on the above co-aperture design and dielectric doping design, when the thickness of the first upper structure is different from that of the second upper structure and the mode orders corresponding to the first metasurface grating layer and the second metasurface grating layer are the same, an ultra-wideband OAM vortex beam is generated. When the thickness of the first upper structure is the same as that of the second upper structure and the mode orders corresponding to the first metasurface grating layer and the second metasurface grating layer are different, a mode multiplexing OAM vortex beam is generated. At this time, a multi-mode superposition vortex beam carrying multiple mode orders in the same direction can be generated. By introducing the co-aperture design and dielectric doping design, the present application can realize the design of ultra-wideband and mode multiplexing OAM vortex beams by changing parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0024] Figure 1 It is a schematic structural diagram of a metasurface grating unit provided in Embodiment 1 of the present application.

[0025] Figure 2 It is a schematic diagram of the performance comparison of the simulated and calculated metasurface grating units provided in Embodiment 1 of the present application, where Figure 2 (a) in is |r xx |, |r yy| and the comparison result with PD (Phase Difference), Figure 2 (b) in Figure 2 is |r ll | and |r rl The comparison result of |, Figure 2 (c) in Figure 2 is the comparison result of PCR (Polarization Conversion Ratio).

[0026] Figure 3 It is a schematic diagram of the PCR of the super-grating unit with different medium thicknesses provided by Embodiment 1 of the present application for simulation and calculation.

[0027] Figure 4 It is a schematic diagram of the structure of the common-aperture extreme ultra-wideband super-grating array provided by Embodiment 1 of the present application.

[0028] Figure 5 It is a schematic diagram of the far-field intensity distribution and far-field phase distribution of the vortex beam generated by the simulated common-aperture extreme ultra-wideband super-grating array provided by Embodiment 1 of the present application.

[0029] Figure 6 It is a schematic diagram of the mode purity of the vortex beam generated by the simulated common-aperture extreme ultra-wideband super-grating array provided by Embodiment 1 of the present application.

[0030] Figure 7 It is a schematic diagram of the structure of the common-aperture mode multiplexing super-grating array with different area ratios provided by Embodiment 1 of the present application. Among them, Figure 7 (a) in Figure 7 is S l＝－4 : S l＝－2 = 2.8:1 structure, Figure 7 (b) in Figure 7 is S l＝－4 : S l＝－2 = 1:2.8 structure, Figure 7 (c) in Figure 7 is S l＝－4 : S l＝－2 = 1:1 structure.

[0031] Figure 8 It is a schematic diagram of the simulation result of the common-aperture mode multiplexing super-grating array with the area ratio S l＝－4 : S l＝－2 = 2.8:1 provided by Embodiment 1 of the present application. Among them, Figure 8 (a) in Figure 8 is the far-field intensity and phase distribution, Figure 8 (b) in Figure 8 is the mode purity.

[0032] Figure 9 It is a schematic diagram of the area ratio S l＝－4 : S l＝－2Schematic diagram of simulation results of a co-aperture mode multiplexing super-grating array with an area ratio of 1:2.8. Among them, Figure 9 in (a) is the far-field intensity and phase distribution, Figure 9 in (b) is the mode purity.

[0033] Figure 10 The area ratio S provided in Embodiment 1 of the present application l＝－4 : S l＝－2 Schematic diagram of simulation results of a co-aperture mode multiplexing super-grating array with an area ratio of 1:1. Among them, Figure 10 in (a) is the far-field intensity and phase distribution, Figure 10 in (b) is the mode purity.

[0034] Figure 11 Schematic diagram of the co-aperture super-grating array prototype provided in Embodiment 1 of the present application. Among them, Figure 11 in (a) is the lower-layer structure, Figure 11 in (b) is the upper-layer structure.

[0035] Figure 12 Schematic diagram of the customized measurement system in the anechoic chamber provided in Embodiment 1 of the present application.

[0036] Figure 13 Schematic diagram of the comparison between the simulation and measurement results provided in Embodiment 1 of the present application. Among them, Figure 13 in (a) is the comparison result at 9 GHz, Figure 13 in (b) is the comparison result at 12 GHz, Figure 13 in (c) is the comparison result at 16 GHz. Detailed implementation manners

[0037] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0038] Embodiment 1

[0039] This embodiment is used to provide a co-aperture super-grating array based on dielectric doping. The co-aperture super-grating array based on dielectric doping includes: a first super-grating array and a second super-grating array. The first super-grating array is sleeved outside the second super-grating array. The center lines of the first super-grating array and the second super-grating array are collinear, and there is a gap between the first super-grating array and the second super-grating array. In this embodiment, after the first super-grating array is prepared, the first super-grating array can be hollowed out, and the second super-grating array can be placed in the hollowed-out area of the first super-grating array to form a co-aperture super-grating array. Among them, the first super-grating array and the second super-grating array can be of any shape. In this embodiment, the first super-grating array and the second super-grating array can be specifically selected to be cylindrical.

[0040] The first super-grating array includes a first upper structure and a first lower structure stacked in sequence from top to bottom. The first upper structure includes a first upper dielectric layer. The first lower structure includes a first super-grating layer, a first lower dielectric layer, and a first metal layer stacked in sequence from top to bottom. The second super-grating array includes a second upper structure and a second lower structure stacked in sequence from top to bottom. The second upper structure includes a second upper dielectric layer. The second lower structure includes a second super-grating layer, a second lower dielectric layer, and a second metal layer stacked in sequence from top to bottom.

[0041] The thickness and dielectric constant of the first upper structure are equal to those of the first lower structure. The thickness and dielectric constant of the second upper structure are equal to those of the second lower structure. The first upper structure is in contact with the first lower structure, and the second upper structure is in contact with the second lower structure. The preparation method of the first upper structure and the second upper structure can be: prepare a metal-dielectric-metal PCB board, and strip the upper and lower layers of metal. The preparation method of the first lower structure and the second lower structure can be: prepare a metal-dielectric-metal PCB board, and prepare a super-grating array structure on the upper layer of metal, which can be specifically prepared by laser engraving to form a super-grating layer.

[0042] The first upper dielectric layer, the first lower dielectric layer, the second upper dielectric layer, and the second lower dielectric layer all use dielectric materials. The dielectric materials can be any dielectric materials. For example, the dielectric material is F4B material (a composite material based on polytetrafluoroethylene), and the dielectric constant of the F4B material can be 2.85. The first super-grating layer and the second super-grating layer are both sub-wavelength gratings, that is, the grating stripe period is less than 1 wavelength, and the upper surfaces of the first super-grating layer and the second super-grating layer are coplanar. The duty cycles of the first super-grating layer and the second super-grating layer are both 0.3 - 0.6. Preferably, the duty cycles of the first super-grating layer and the second super-grating layer are both 0.41. At this time, the working bandwidth of the super-grating layer is the widest and the performance is better. The first metal layer and the second metal layer both use metal materials. The metal materials can be any metal materials.

[0043] When a co-aperture metagrating array based on dielectric doping is used to provide an ultra-wideband OAM vortex beam, the thickness of the first upper structure is different from the thickness of the second upper structure, and the mode order corresponding to the first metagrating layer is the same as the mode order corresponding to the second metagrating layer.

[0044] Wherein, the thickness of the first upper structure can be 3 mm, and the thickness of the second upper structure can be 1.5 mm. At this time, the frequency range of the ultra-wideband OAM vortex beam is 8.9 - 50 GHz.

[0045] When a co-aperture metagrating array based on dielectric doping is used to provide a mode multiplexing OAM vortex beam, the thickness of the first upper structure is the same as the thickness of the second upper structure, and the mode order corresponding to the first metagrating layer is different from the mode order corresponding to the second metagrating layer.

[0046] Wherein, the thickness of the first upper structure and the thickness of the second upper structure can both be 4 mm. The mode order corresponding to the first metagrating layer is greater than the mode order corresponding to the second metagrating layer, or the mode order corresponding to the first metagrating layer is less than the mode order corresponding to the second metagrating layer. Preferably, the mode order corresponding to the first metagrating layer is greater than the mode order corresponding to the second metagrating layer, which can improve the space utilization rate. The ratio of the area of the upper surface of the first upper structure to the area of the upper surface of the second upper structure is equal to the ratio of the purity of the OAM vortex beam generated by the first metagrating array to the purity of the OAM vortex beam generated by the second metagrating array. Thus, by adjusting the area ratio, purity customization can be achieved.

[0047] This embodiment makes full use of the dual-band characteristics of the metagrating unit. Through the co-aperture scheme, the frequency band between the dual bands is added, so that the co-aperture metagrating array can generate high-quality and high-purity OAM vortex beams in the ultra-wide frequency band of 8 - 50 GHz. Utilizing the characteristic that the aperture size of the metagrating array is insensitive to frequency, by filling a low-order metagrating array in the middle of a high-order metagrating array or filling a high-order metagrating array in the middle of a low-order metagrating array, multi-mode multiplexing is realized within the same aperture, and OAM vortex beams with multi-mode superposition carrying different mode orders can be generated simultaneously in the same direction. Moreover, it is found that by controlling the aperture size of the co-aperture metagrating array, the purity ratio between different OAM mode orders can be controlled, thus realizing the customized design of mode purity. This embodiment also fabricated a co-aperture mode multiplexing metagrating array prototype and conducted tests.

[0048] This embodiment first analyzes the performance of the metagrating unit to guide the subsequent design of the co-aperture metagrating array as follows:

[0049] If the super-grating array is directly simulated, due to the complex structure of the super-grating array, the simulation time will be too long. Considering that the super-grating array is composed of countless super-grating units arranged, therefore, the super-grating unit is simulated, as Figure 1 shown, which is a schematic structural diagram of the super-grating unit. Dielectric doping with equal thickness and equal dielectric constant is used to achieve the best performance, that is, the thickness h1 and dielectric constant of the upper layer structure in the super-grating unit are equal to the thickness h2 and dielectric constant of the lower layer structure. The upper dielectric layer in the upper layer structure and the lower dielectric layer in the lower layer structure can both use the F4B material with a dielectric constant of 2.85. In order to study the performance of the super-grating array in the low-frequency band, therefore, the thickness of the super-grating unit is increased. The finally adopted optimized parameters are h1 = h2 = 4mm, and the duty cycle q (that is Figure 1 the ratio of the width of the pink part along the y-axis to the width p of the yellow part along the y-axis in

[0050] ) = 0.41, and p = 1mm. xx |, the co-polarization reflection coefficient |r yy | in the y direction, the phase difference PD between x polarization and y polarization, the circular polarization co-polarization reflection coefficient |r ll |, the cross-polarization reflection coefficient |r rl |, and PCR. The comparison results of simulation and calculation are as Figure 2 shown. It can be observed that in the broadband range, |r xx | ≈ |r yy | ≈ 1, and the phase difference |arg(r xx ) - arg(r yy )| ≈ π (that is, the phase difference PD ≈ π) can cover approximately 6.0 - 16.0 GHz and 28.0 - 37.0 GHz, which confirms that the super-grating unit has dual broadband characteristics. Similarly, the circular polarization co-polarization reflection coefficient |r ll | and PCR can also approximately cover the dual broadband of 6.0 - 16.0 GHz and 28.0 - 37.0 GHz. The simulation results and the calculation results have good consistency.

[0051] If new frequency bands can be introduced to cover the frequency band between the two widebands, the dual-wideband characteristics of the metagrating unit will be fully exploited, and it is promising to achieve a metagrating unit with an extremely ultra-wideband, and then it is promising to achieve an extremely ultra-wideband OAM vortex beam. According to this idea, since the thickness of the metagrating unit is different, the frequencies are different. As Figure 3 shown, the PCR of the metagrating units with h1 = h2 = 1.5 mm and h1 = h2 = 3.0 mm was simulated and calculated. It can be observed that the working bandwidth with PCR > 0.97 for the two combined reached approximately 8.9 - 50.0 GHz.

[0052] Based on the above findings, in this embodiment, two metagrating arrays with different thicknesses are combined together through a shared aperture strategy to generate an ultra-wideband high-performance OAM vortex beam. In this embodiment, further simulation of the co-aperture metagrating array for generating an extremely ultra-wideband OAM vortex beam is as follows:

[0053] When h1 = h2 = 1.5 mm and h1 = h2 = 3.0 mm, the PCR of the two metagrating units combined can achieve an extremely ultra-wideband. The dual-wideband characteristics of the metagrating unit with h1 = h2 = 3.0 mm are utilized. Therefore, the high-frequency band performance when h1 = h2 = 3.0 mm needs to be considered. The value of the local spatial frequency K0 of the grating strip is closely related to the position r and the topological charge m. When r is larger, K0 is smaller, the local period of the grating is larger, and the width of the grating strip is larger. To achieve a high-performance vortex beam and avoid the occurrence of Wood anomalies (sharp or sudden changes in the spectral intensity of the grating at a certain wavelength), the maximum period of the grating strip cannot exceed the wavelength corresponding to the highest frequency. Therefore, in the modeling process, the width of the widest grating strip of the metagrating array with a thickness of h1 = h2 = 3.0 mm should be less than the width of the widest grating strip of the metagrating array with h1 = h2 = 1.5 mm. The two metagrating arrays can still use the F4B material with a dielectric constant of 2.85 and a loss tangent of 0.002. The upper structure of both is a pure F4B dielectric, and the lower structure is a metal-dielectric-metal structure. The upper surface of the lower structure is the metagrating layer, the middle is the F4B dielectric, and the lower surface is the metal ground plane.

[0054] The metagrating array structure with the mode order l = ±2 is selected to verify the effectiveness of the co-aperture scheme. Considering the easy processability of the structure, the middle of the metagrating array with a thickness of h1 = h2 = 3.0 mm is hollowed out, and the metagrating array with h1 = h2 = 1.5 mm is placed in the hollowed-out area. Different from the traditional metasurface scheme, since the metagrating array has the characteristics of being insensitive to the aperture size and working frequency, this co-aperture method will not significantly affect the performance of the metagrating array. As Figure 4As shown, a co-aperture metasurface array with \(l = \pm2\) is given. Among them, the pink part is the metasurface array of the low-frequency and high-frequency bands with a diameter \(R\) s \(= 300\) mm and \(h1 = h2 = 3.0\) mm. A hollowing treatment is done in the middle, and then the hollowed part is filled with a metasurface array with \(R\) s1 \(= 210\) mm and \(h1 = h2 = 1.5\) mm in the middle frequency band (about 19 - 38 GHz). There is a gap \(g1 = 1\) mm between the two arrays, and the whole forms a quasi-continuous co-aperture metasurface array.

[0055] The co-aperture metasurface array with \(l = \pm2\) is simulated using the CST MWS Studio simulation software. By setting the LHCP (left-handed circular polarization) plane wave to excite the metasurface array, a super-wideband OAM vortex beam with \(l = -2\) can be generated. Figure 5 The simulation far-field intensity distribution and far-field phase distribution results of the co-aperture metasurface array with \(l = \pm2\) are given. It can be observed that the far-field intensity distribution of the vortex beam generated by the proposed co-aperture metasurface array can maintain an approximately ideal doughnut-shaped far-field intensity distribution within the extremely wide frequency range of 8 - 50 GHz. The energy distribution is mainly concentrated in the main lobe, and the side lobes are very low. In terms of the phase distribution, within the extremely wide frequency range of 8 - 50 GHz, along a circumference on the main lobe of the far-field intensity distribution, the phase changes continuously from 0 to \(4\pi\) and shows a clockwise spiral phase distribution. Outside the main lobe, the phase distribution is discontinuous, which reveals the generation of a high-performance OAM vortex beam with \(l = -2\).

[0056] As Figure 6 shown, the mode purity calculation results of the OAM vortex beam in the 8 - 50 GHz frequency band are given. From the mode purity calculation results, it can be seen that within the frequency band of 8 - 50 GHz (144.8%), the mode purity of the vortex beam with \(l = -2\) exceeds 0.85. Within the frequency bands of 9 - 50 GHz (139.0%) and 14 - 50 GHz (112.5%), the mode purities exceed 0.92 and 0.95 respectively, and the maximum mode purity reaches 0.9981. These results indicate that the proposed co-aperture metasurface array can generate high-performance OAM vortex beams with extremely high mode purity and extremely low mode crosstalk within the extremely wide frequency range, which is suitable for ultra-wideband application scenarios, achieving the widest OAM vortex beam bandwidth so far and refreshing the record of the widest OAM vortex beam bandwidth.

[0057] In this embodiment, the co-aperture metasurface array is further simulated for generating ultra-wideband mode multiplexing OAM vortex beams as follows:

[0058] According to the structure of the metagrating unit, the metagrating array for realizing OAM mode multiplexing vortex beam consists of two layers of F4B dielectric substrates with a thickness of 4.0 mm. From the expression of the local spatial frequency K0 of the grating strip, it can be seen that when the topological charge m increases, as the position r decreases, the value of K0 increases exponentially, and then the width of the grating strip decreases exponentially, resulting in inability to identify and model. Therefore, for the metagrating array structure for realizing high-order OAM vortex beam, in order to complete the modeling and simulation and processing applications, a part of the central region of the metagrating array structure always needs to be hollowed out. For the metagrating array structure for realizing low-order OAM vortex beam, by reasonably setting the initial value of the grating period, the central region of the array does not need to be hollowed out or only needs to be slightly hollowed out. Therefore, the mode order corresponding to the first metagrating layer is set to be greater than the mode order corresponding to the second metagrating layer to improve the space utilization rate. In order to evaluate the ability of the common-aperture metagrating array to generate multi-mode superimposed vortex beams, metagrating arrays with l = ±4 and l = ±2 are selected. Among them, the metagrating array with l = ±2 is located in the hollowed-out region in the middle of the metagrating array with l = ±4. By flexibly adjusting the size of the hollowed-out region, the spatial ratio (i.e., the area ratio) of the metagrating array with l = ±2 and the metagrating array with l = ±4 is adjusted, and the influence of different area ratios on the multi-mode superimposed vortex beam is analyzed.

[0059] Figure 7 Shows three OAM mode multiplexing common-aperture metagrating array structures. The final structural parameters are: R = 400 mm, R1 = 200 mm, R2 = 200 mm, R3 = 200 mm, g2 = 2.0 mm, g3 = 1.0 mm, g4 = 2.0 mm, and the area ratio of the metagrating array with l = -2 and the metagrating array with l = -4, that is, S l＝－4 : S l＝－2They are 2.8:1, 1:2.8, and 1:1 respectively. Then, the CST MWS Studio simulation software is used to model and simulate these three structures. Set the LHCP plane wave to excite the co-aperture super-grating array, and finally an OAM vortex beam formed by the superposition of two modes with l = -2 and l = -4 is generated in the normal direction. That is, the reflected vortex beam contains information about two mode orders. Since the phase distributions of l = -2 and l = -4 are different, the far-field intensity and far-field phase distribution of the superposed OAM vortex beam will no longer be the standard doughnut-shaped intensity distribution and the helical phase change of 2πl respectively. Therefore, the mode order information contained in the real vortex beam cannot be completely resolved by observing the far-field intensity and phase distribution of the vortex beam after mode superposition. Therefore, it is necessary to calculate the energy spectrum distribution of the vortex beam, that is, calculate the purity of the OAM mode order to resolve the mode proportion of the OAM vortex beam with mode superposition. It is worth mentioning that since the far-field intensities of the vortex beams with l = -2 and l = -4 are both close to 0 at the center point, the intensity at the center point of the far-field intensity distribution after their superposition should also be close to 0.

[0060] Figure 8 , Figure 9 and Figure 10 respectively show the simulated far-field intensity and phase distribution of the co-aperture super-grating array with area ratios S l＝－4 : S l＝－2 = 2.8:1, S l＝－4 : S l＝－2 = 1:2.8, and S l＝－4 : S l＝－2 = 1:1, as well as the mode purity calculated from the far-field data. Two phenomena can be summarized from the results. First, after the far-field superposition of the vortex beams with l = -2 and l = -4, the far-field intensity and phase distribution have changed significantly compared to the results of a single mode order. The far-field intensity distribution is no longer the standard doughnut shape, and the far-field phase distribution shows different phase parts according to different area ratios. When S l＝－4 : S l＝－2 = 2.8:1, the phase changes approximately from 0 to 8π within a circle, and at this time the phase distribution of the 4th-order OAM vortex beam dominates. When S l＝－4 : S l＝－2 = 1:2.8, the phase distribution of the 2nd-order OAM vortex beam dominates. When S l＝－4 : S l＝－2When the ratio is 1:1, the phase of the approximate inner circle as a whole changes approximately from 0 to 4π, while the phase of the outer circle changes approximately from 0 to 8π. Generally speaking, however, it is still difficult to distinguish the mode ratio by observing the far-field intensity and phase distribution. Second, from the perspective of the calculated mode purity, the mode ratio can be clearly judged, and there is also a certain pattern. For example, the ratio of the mode purity of l = -2 and l = -4 is almost the same as the area ratio of the super-grating array structure of l = -2 and l = -4. When S l＝－4 : S l＝－2 = 2.8:1 (S l＝－4 : S l＝－2 = 1:2.8), the mode purity of l = -4 (l = -2) is approximately 2.8 times that of l = -2 (l = -4). When S l＝－4 : S l＝－2 = 1:1, the mode purity of l = -4 and l = -2 is almost the same. This reveals that by designing the area ratio of the structure, the mode purity ratio can be customized, so as to realize the customized design of the mode purity. By carefully calculating the mode purity, it is found that the mode superimposed vortex beam generated by the proposed co-aperture super-grating array also has a very high mode purity, and the purity of the mode superimposed vortex beam generated by the co-aperture super-grating arrays with three different area ratios (the sum of the purities of l = -4 and l = -2) exceeds 0.9 in the ultra-wideband range. In addition, the scheme adopts a shared-aperture design, which can transmit or receive signals of multiple OAM modes simultaneously without increasing the volume of the device, and does not require multiple feed excitations or additional electronic tuning, with significant low-cost characteristics.

[0061] Finally, a prototype test is carried out in this embodiment as follows:

[0062] Figure 11 Shows the processed co-aperture super-grating array prototype with an area ratio of S l＝－4 : S l＝－2 = 1:1, including a super-grating array structure layer (i.e., the lower structure) and a doped dielectric layer (i.e., the upper structure). The aperture sizes of the two are the same, and the thickness of both is 4 mm. Figure 12 Shows the test system in the microwave anechoic chamber. To facilitate the comparison of the test results with the simulation results, Figure 13 Shows the measured and simulated far-field amplitude and phase distributions, where, Figure 13For (a), (b), and (c) in [reference], the left side shows simulation results and the right side shows test results. It can be observed that there is good consistency between the measured far-field intensity distribution and the simulation results. However, there is a certain gap between the measured far-field phase distribution and the simulation results, but the measured results also show a certain trend. The large gap between the test and simulation results is mainly due to the following factors: First, the customized system framework will jitter during the near-field scanning process, resulting in amplitude and phase acquisition errors. Second, the sampling probe will block the feed, which has a greater impact on the proposed common-aperture scheme. This is mainly because the middle of the super-grating array is a super-grating array structure with l = -2, while the outer ring is a super-grating array structure with l = -4. The occlusion of the sampling probe will significantly affect the reflected vortex beam with l = -2, while having a smaller impact on the vortex beam with l = -4, resulting in a larger superposition phase error in the far field. Finally, there are also errors caused by the feed not being an ideal LHCP plane wave, the polarization of the sampling probe not being perfectly LHCP, as well as various factors such as environmental noise and alignment errors.

[0063] In this embodiment, the expressions of the grating functions g(r, φ) of the first super-grating layer and the second super-grating layer are as follows:

[0064]

[0065] where r is the position of the grating strip; φ is the phase constant; r0 is the initial position of the grating strip; Λ0 is the initial local period of the grating strip; φ0 is the initial phase constant; m is the topological charge.

[0066] Through the above formula, a Lee-type binary grating array with any integer mode order can be generated. Among them, the Lee-type binary can be derived as follows:

[0067] t(x, y) = U s (η) = U s (cos(g) - cos(πq));

[0068] where t(x, y) is different positions in the super-grating array structure; U s (η) is the unit step function of the Lee-type binary grating, and the intermediate variable η = cos(g) - cos(πq); g is the grating function; q is the duty cycle.

[0069] U s (η) is defined as follows:

[0070]

[0071] When forming the meta-grating array, if t(x, y) = 1, it represents the area of the metal grating strip, and when t(x, y) = 0, it represents the dielectric area. Therefore, this is actually a binary description of the grating function g, called the Lee-type binary grating, which means that the meta-grating array can be regarded as composed of countless binary pixels. When the modeling accuracy is high enough, the structure of the meta-grating array presents a continuous state. When the modeling accuracy is low, the narrow grating stripe area may become blurred or even unrecognizable.

[0072] This embodiment proposes two types of co-aperture meta-grating arrays. First, by making full use of the dual-bandwidth characteristics of the meta-grating unit, a new working frequency band is introduced through the co-aperture design scheme of meta-grating arrays with different thicknesses, covering the frequency band between the dual bandwidths, so that the co-aperture ultra-wideband array realizes high-quality and high-purity OAM vortex beams in the ultra-wide frequency band of 8 - 50 GHz. Second, a low-order meta-grating array structure is embedded in the hollowed-out part of the high-order meta-grating array, or a high-order meta-grating array structure is embedded in the hollowed-out part of the low-order meta-grating array, realizing multi-mode multiplexing within the same aperture, and multiple OAM vortex beams with different mode orders can be generated simultaneously in the same direction. In addition, research shows that by adjusting the ratio of the aperture area occupied by meta-grating arrays with different mode orders, the purity ratio of different OAM mode orders can be controlled, and thus the customized design of mode purity can be realized. Finally, the processing of the OAM mode multiplexing meta-grating array prototype is completed and tested and verified.

[0073] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use, and processing of relevant data need to comply with relevant regulations.

[0074] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as within the scope described in this specification.

[0075] Specific examples are used in this article to elaborate on the principle and implementation manner of this application. The description of the above embodiments is only used to help understand the method and its core idea of this application; at the same time, for those of ordinary skill in the art, based on the idea of this application, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to this application.

Claims

1. A co-aperture super-grating array based on dielectric doping, characterized in that, The co-aperture super-grating array based on medium doping includes: a first super-grating array and a second super-grating array. The first super-grating array is sleeved outside the second super-grating array. The center lines of the first super-grating array and the second super-grating array are collinear, and there is a gap between the first super-grating array and the second super-grating array. The first super-grating array includes a first upper structure and a first lower structure stacked in sequence from top to bottom. The first upper structure includes a first upper dielectric layer. The first lower structure includes a first super-grating layer, a first lower dielectric layer, and a first metal layer stacked in sequence from top to bottom. The second super-grating array includes a second upper structure and a second lower structure stacked in sequence from top to bottom. The second upper structure includes a second upper dielectric layer. The second lower structure includes a second super-grating layer, a second lower dielectric layer, and a second metal layer stacked in sequence from top to bottom. The thickness and dielectric constant of the first upper structure are equal to those of the first lower structure. The thickness and dielectric constant of the second upper structure are equal to those of the second lower structure. Both the first super-grating layer and the second super-grating layer are sub-wavelength gratings, and the upper surfaces of the first super-grating layer and the second super-grating layer are coplanar. When the co-aperture super-grating array based on medium doping is used to provide an ultra-wideband OAM vortex beam, the thickness of the first upper structure is different from that of the second upper structure, and the mode orders corresponding to the first super-grating layer and the second super-grating layer are the same. When the co-aperture super-grating array based on medium doping is used to provide a mode multiplexing OAM vortex beam, the thickness of the first upper structure is the same as that of the second upper structure, and the mode orders corresponding to the first super-grating layer and the second super-grating layer are different.

2. The co-aperture super-grating array based on dielectric doping according to claim 1, wherein When the co-aperture super-grating array based on medium doping is used to provide an ultra-wideband OAM vortex beam, the thickness of the first upper structure is 3 mm, and the thickness of the second upper structure is 1.5 mm. At this time, the frequency range of the ultra-wideband OAM vortex beam is 8.9 - 50 GHz.

3. The co-aperture super-grating array based on dielectric doping according to claim 1, wherein When the co-aperture super-grating array based on medium doping is used to provide a mode multiplexing OAM vortex beam, the mode order corresponding to the first super-grating layer is greater than that corresponding to the second super-grating layer.

4. The co-aperture super-grating array based on dielectric doping according to claim 1, wherein When the co-aperture super-grating array based on medium doping is used to provide a mode multiplexing OAM vortex beam, the thickness of both the first upper structure and the second upper structure is 4 mm.

5. The co-aperture super-grating array based on dielectric doping according to claim 1, wherein When the co-aperture super-grating array based on medium doping is used to provide a mode multiplexing OAM vortex beam, the ratio of the area of the upper surface of the first upper structure to the area of the upper surface of the second upper structure is equal to the ratio of the purity of the OAM vortex beam generated by the first super-grating array to the purity of the OAM vortex beam generated by the second super-grating array.

6. The co-aperture super-grating array based on dielectric doping according to claim 1, wherein The duty cycle of the first super grating layer and the duty cycle of the second super grating layer are both 0.3 - 0.

6.

7. The co-aperture super-grating array based on dielectric doping according to claim 6, characterized in that, The duty cycle of the first super grating layer and the duty cycle of the second super grating layer are both 0.

41.

8. The co-aperture metasurface grating array based on dielectric doping according to claim 1, wherein The first super grating array and the second super grating array are both cylindrical.

9. The co-aperture super-grating array based on dielectric doping according to claim 1, wherein The first upper dielectric layer, the first lower dielectric layer, the second upper dielectric layer, and the second lower dielectric layer all use dielectric materials, and the dielectric materials include F4B materials; The first metal layer and the second metal layer both use metal materials.

10. The co-aperture super-grating array based on dielectric doping according to claim 9, wherein The dielectric constant of the F4B material is 2.85.

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