A vector light generation system based on metasurface

Abstract

The present invention discloses a vector light generation system based on a metasurface, which includes a plurality of artificial atomic structures in an M×M array arranged along horizontal and vertical planes, each artificial atomic structure including a first metal layer, a dielectric layer, and a second metal layer in sequence along the vertical direction; the first metal layer, the dielectric layer, and the second metal layer are square structures, and the side lengths are all p, and the vertical heights are h1, h2, and h3 in sequence; the first metal layer is penetrated by a first metal seam extending in the longitudinal direction, the first metal seam is arranged parallel to the first side of the first metal layer adjacent to it, the distances between the first metal seam and the center of the first metal layer in the transverse and longitudinal directions are Dlta1x and Dlta1y respectively, the width of the first metal seam in the transverse direction is a1, and the width in the longitudinal direction is a2; the second metal layer is penetrated by a second metal seam.

Description

Technical Field

[0001] The present invention relates to the field of electronic technology, and in particular to a vector light generation system based on a metasurface. Background Art

[0002] Traditional optical systems typically consist of discrete optical components with different functions, such as laser sources, lenses, polarizers, and detectors. These components have significant limitations when generating vector light fields, primarily in terms of size, functionality, stability, flexibility, and integration. While these optical components still play an important role in many applications, their shortcomings in generating complex light fields, particularly in the control and generation of vector light fields, have exposed certain shortcomings and restricted their widespread use in high-end optical applications.

[0003] First, traditional optical devices are often bulky and complex in structure. In order to generate a vector light field, multiple discrete optical devices are usually required, such as lenses, polarizers, optical fibers, etc., which need to be precisely matched and adjusted with each other. As the complexity of the optical system increases, these discrete optical components not only take up a lot of space, but also require extremely fine adjustment and alignment. In many applications, such a design not only increases the weight and volume of the system, but also reduces the convenience and reliability of the system. Especially in some applications with strict requirements on volume and weight, such as aerospace, communications and miniaturized equipment, the limitations of traditional optical devices are particularly prominent.

[0004] Secondly, traditional optical devices have significant functional limitations. Although these devices can achieve basic optical regulation and light field control, their functions are usually insufficient when it comes to generating and regulating vector light fields. The modulation of vector light fields involves precise control of multiple dimensions such as the amplitude, phase, and polarization of the light field, and traditional optical devices are often unable to flexibly and efficiently implement these complex operations. In order to generate different types of vector light fields, it is usually necessary to combine multiple devices, which not only increases the complexity of the system, but also makes the light field generation process cumbersome and time-consuming.

[0005] Furthermore, traditional optical devices suffer from poor stability, especially over long-term use. Optical devices are extremely sensitive to environmental conditions (such as temperature, humidity, and mechanical vibration). These external factors can adversely affect device performance, leading to reduced stability in light field generation or even performance degradation. For example, the material of a lens can be affected by temperature fluctuations, causing its focal length to shift, which in turn affects the accuracy and stability of the light field. Furthermore, it is difficult to maintain perfect precision during adjustment of discrete optical devices, resulting in traditional optical devices often failing to achieve ideal repeatability and long-term stability. Flexibility is another major shortcoming of traditional optical devices. While some optical devices can generate simple vector light fields, they lack flexibility when faced with complex and evolving application requirements. Generating a specific light field for varying requirements may require replacing different device types or performing fine manual adjustments, which is time-consuming, labor-intensive, and inefficient in practice. In applications requiring rapid response and dynamic adjustment, such as high-speed communications and information processing, the adaptability and adjustment efficiency of traditional devices are clearly insufficient.

[0006] Furthermore, traditional optical systems suffer from a low level of integration. Discrete optical components often cannot be efficiently integrated on a single physical platform, resulting in limited system integration, larger size, and more complex design. As the scale and complexity of optical systems increase, traditional optical design methods are increasingly unable to meet the demands for high integration, high precision, and high stability. The emergence of integrated optics technology has made it possible to integrate multiple optical functions on a single chip, effectively resolving the problems of low integration, large size, and dispersed functionality faced by traditional optical systems.

[0007] In summary, while traditional optical devices can perform some basic tasks when generating vector light fields, their limitations are becoming increasingly apparent in increasingly complex optical applications. This is particularly true in areas requiring precise control, volume, and stability. With the advancement of micro-nanofabrication and integrated optics technologies, light field generation technologies based on integrated photonics platforms have emerged as effective solutions to overcome these problems. These emerging technologies not only enable more efficient and precise light field control, but also significantly improve the integration and stability of optical systems, providing stronger support for a wide range of high-end optical applications.

[0008] Metasurfaces, as a new type of planar light field manipulation device, hold promise for addressing the issue of efficient coupling between on-chip optical devices. Metasurfaces are composed of a series of subwavelength artificial atoms (meta-atoms) arranged in a specific two-dimensional macroscopic sequence. When external light strikes the metasurface, each artificial atom can be considered a sub-wave source radiating outward. According to the Huygens principle, by manipulating the parameters of the artificial atoms at local locations, their radiation polarization and phase response can be adjusted, thereby achieving efficient manipulation of both near- and far-field electromagnetic waves. For example, when the metasurface's transflection phase gradient is less than the wave vector k0 of light in a vacuum, functions such as anomalous reflection and focusing can be achieved. By distributing the polarization of the artificial atoms, spatial light fields, such as spatial vector light fields, can also be realized.

[0009] However, the generation of space vector light fields using metasurfaces has been limited to a few aspects. For example, most metasurfaces currently generate space vector light fields by first generating left-handed circularly polarized light and right-handed circularly polarized light, then combining these two beams. This is not straightforward or convenient, and their thickness is often greater than half the operating wavelength. The question of how to make these metasurfaces ultrathin and quickly and easily generate space vector light fields remains to be explored and designed.

[0010] The above content is only used to assist in understanding the technical solution of the present invention and does not constitute an admission that the above content is prior art. Summary of the Invention

[0011] The main purpose of the present invention is to provide a vector light generation system based on a metasurface, aiming to solve the above-mentioned technical problems in the prior art.

[0012] To achieve the above objectives, the present invention provides a metasurface-based vector light generation system, comprising a plurality of artificial atomic structures arranged in an M×M array along a horizontal and vertical plane, each artificial atomic structure vertically comprising a first metal layer, a dielectric layer, and a second metal layer;

[0013] The first metal layer, the dielectric layer, and the second metal layer are square structures, and the side lengths are all p, and the vertical heights are h1, h2, and h3 respectively;

[0014] A first metal seam extending longitudinally is formed through the first metal layer. The first metal seam is arranged parallel to the first side of the first metal layer adjacent to the first metal seam. The distances between the first metal seam and the center of the first metal layer in the transverse and longitudinal directions are Dlta1x and Dlta1y, respectively. The width of the first metal seam in the transverse direction is a1, and the width in the longitudinal direction is a2.

[0015] A second metal seam is formed through the second metal layer. The distances between the second metal seam and the center of the second metal layer in the transverse and longitudinal directions are Dlta2x and Dlta2y respectively. The angle between the extension direction of the second metal seam and the transverse direction is θ. The length of the second metal seam in the extension direction is a4. The width of the second metal seam is a3.

[0016] Among them, the phase of each artificial atomic structure needs to satisfy formula (1), and the phase gradient of each artificial atomic structure needs to satisfy formula (2):

[0017] ; (1)

[0018] ; (2)

[0019] The polarization angle of the second metal slit of each artificial atomic structure needs to satisfy formula (3):

[0020] ; (3)

[0021] Among them, (x k ,y k ) is the position coordinate of the i-th artificial atomic structure, x k and y k The value range of is [-M / 2, M / 2];

[0022] ph k (x k ,y k ) is the phase of the kth artificial atomic structure;

[0023] ζ is the phase gradient of the artificial atomic structure;

[0024] is the polarization angle of the second metal slit of the kth artificial atomic structure;

[0025] θ k is the turning angle of the second metal seam of the kth artificial atomic structure.

[0026] Preferably, in the metasurface-based vector light generation system, the M×M array of artificial atomic structures is divided into multiple areas of equal angular size according to the geometric center, and each area is provided with an artificial atomic structure with a different polarization direction. Each artificial atomic structure is excited by an x-polarized electromagnetic wave, and the phase of the transmitted electromagnetic wave needs to satisfy formula (1).

[0027] Preferably, in the metasurface-based vector light generation system, the M×M array of artificial atomic structure is divided into 12 areas of equal angular size according to the geometric center, and the rotation angles of each area are 0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 300°, and 330° respectively.

[0028] Preferably, in the metasurface-based vector light generating system, the vector light generating system generates a transmissive tightly focused vector light beam by normally incident an x-polarized electromagnetic wave onto the surface of the vector light generating system.

[0029] Preferably, in the metasurface-based vector light generation system, the method for determining each parameter in the metasurface-based vector light generation system is as follows:

[0030] Step S210, according to the ω of the two resonance modes s 、ω a , based on the FDTD metasurface simulation model, h1, h2, and h3 are obtained;

[0031] Step S220, according to the obtained h1, h2, h3, determine the initial values ​​of a1, a2, a3, a4, Dlta1x, Dlta1y, Dlta2x, Dlta2y; and according to the initial values ​​of a1, a2, a3, a4, Dlta1x, Dlta1y, Dlta2x, Dlta2y, based on the FDTD metasurface simulation model, determine the parameters in formula (4); wherein, a1 p / 2,a3 p / 2,a2 p,a4 p,

[0032] Dlta1x p / 3,Dlta1y p / 3,Dlta2x p / 3,Dlta2y p / 3;

[0033] Step S230: Calculate the transmission phase t according to the following formula (4): phase ;

[0034] ; (4)

[0035] Step S240: sequentially obtain the phase of the artificial atomic structure and compare the obtained phase of the artificial atomic structure with the transmission phase t phase Are the sizes equal to each other and get the judgment result;

[0036] Step S250: When the judgment result is no, continue to execute step S220 to enter the next loop until all artificial atomic structures are traversed, and a1, a2, a3, a4, Dlta1x, Dlta1y, Dlta2x, and Dlta2y at this time are taken as the final values;

[0037] Step S260: When the judgment result is yes, continue to execute step S240 to enter the next loop until all artificial atomic structures are traversed, and a1, a2, a3, a4, Dlta1x, Dlta1y, Dlta2x, and Dlta2y at this time are taken as the final values;

[0038] in,

[0039] X is the far-field coupling strength between mode a and mode s, and is calculated as follows:

[0040] ;

[0041] d 1s Take the complex conjugate;

[0042] d 2s Take the complex conjugate;

[0043] d 1s is the coupling coefficient between the first port and the sth mode;

[0044] d 1a is the coupling coefficient between the first port and the ath mode;

[0045] d 2s is the coupling coefficient between the second port and the sth mode;

[0046] d 2a is the coupling coefficient between the second port and the ath mode;

[0047] t0 is a constant, set to 0;

[0048] W a is the operating frequency in mode a;

[0049] W s is the operating frequency in s mode;

[0050] ;

[0051] ω is 2πf, f is the frequency;

[0052] is the radiation damping of the ath mode;

[0053] is the radiation damping of the sth mode;

[0054] is the absorption damping of the sth mode;

[0055] Absorbing damping for the ath mode;

[0056] ω a is the operating frequency of mode a;

[0057] ω s is the operating frequency of mode s.

[0058] Preferably, in the metasurface-based vector light generation system, the first metal layer and the second metal layer are made of gold.

[0059] Preferably, in the metasurface-based vector light generation system, the dielectric layer is made of plastic.

[0060] Preferably, in the metasurface-based vector light generating system, M is 21.

[0061] Preferably, in the metasurface-based vector light generating system, the vertical thickness of the metasurface-based vector light generating system is λ / 30, where λ is the operating wavelength.

[0062] Preferably, in the metasurface-based vector light generation system, the operating wavelength is 750 um.

[0063] The present invention has at least the following beneficial effects:

[0064] The present invention provides a metasurface-based vector light generation system, which includes a plurality of artificial atomic structures in an M×M array arranged along a horizontal and vertical plane, each artificial atomic structure vertically including a first metal layer, a dielectric layer, and a second metal layer; the first metal layer, the dielectric layer, and the second metal layer are square structures, and the side lengths are all p, and the vertical heights are h1, h2, and h3 respectively; the first metal layer is penetrated by a first metal seam extending in the longitudinal direction, the first metal seam is arranged parallel to the first side of the first metal layer adjacent to it, and the first metal seam is parallel to the center of the first metal layer. The horizontal and vertical distances are Dlta1x and Dlta1y respectively, the width of the first metal seam in the horizontal direction is a1, and the width in the vertical direction is a2; the second metal layer is penetrated by a second metal seam, the horizontal and vertical distances between the second metal seam and the center of the second metal layer are Dlta2x and Dlta2y respectively, the angle between the extension direction of the second metal seam and the horizontal direction is θ, the length of the second metal seam in the extension direction is a4, and the width of the second metal seam is a3; wherein, the phase of each artificial atomic structure needs to satisfy equation (1), and the phase gradient of each artificial atomic structure needs to satisfy equation (2). In this way, an ultra-thin, easy-to-integrate, and convenient on-chip vector light field generator can be formed.

[0065] Furthermore, the metasurface-based vector light generation system provided by the present invention differs from conventional optical devices that require a large space, and from previous metasurfaces that require the superposition of multiple beams to generate a vector light field. The present invention only requires x-polarized electromagnetic waves to illuminate the vector light generation system to generate a vector light field.

[0066] Furthermore, the present invention provides a metasurface-based vector light generating system, which generates a transmissive tightly focused vector light beam by incidenting an x-polarized electromagnetic wave normally onto the surface of the vector light generating system. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 A schematic diagram of a single artificial atom structure in a metasurface-based vector light generation system provided by the present invention is shown;

[0068] Figure 2 for Figure 1 A top view of the first metal layer of a single artificial atomic structure;

[0069] Figure 3 for Figure 1 A top view of the second metal layer of a single artificial atomic structure;

[0070] Figure 4 The schematic diagram of the vector light generation system based on the metasurface provided by the present invention is shown;

[0071] Figure 5 The schematic diagram of generating a vector light field in the prior art is shown;

[0072] Figure 6 The schematic diagram shows the principle of generating a vector light field by the metasurface-based vector light generation system provided by the present invention;

[0073] Figure 7 Indicated Figure 6 A diagram showing the relationship between the polarization angle of the middle arrow and the rotation angle θ of the second metal seam of the second metal layer;

[0074] Figure 8 The schematic diagram of the structure principle of generating vector light field in the prior art is shown. Figure 8 (a) shows that the related technology uses the Bosch process to etch deep grooves in the medium. Figure 8 (b) shows the schematic diagram of the top of the medium after etching using the related technology. Figure 8 (c) shows the bottom of the medium after etching.

[0075] Figure 9 The phase coverage diagram of the metasurface-based vector light generation system provided by the present invention is shown;

[0076] Figure 10 A flowchart illustrating a method for determining various parameters in a vector light generation system based on a metasurface provided by the present invention is shown;

[0077] Figure 11 The effect verification diagram of the vector light generation system based on the metasurface provided by the present invention is shown; wherein, Figure 11 (a) is a schematic diagram of the electromagnetic wave incident on the black metasurface from the -z direction; (b) is a schematic diagram of the electromagnetic wave incident on the black metasurface from the -z direction; Figure 11 (a) is a schematic diagram of a cross section taken from the middle of the image; (c) is a schematic diagram of a cross section taken from the middle of the image; Figure 11 (a) is a schematic diagram of a cross section taken from the middle of the image; (d) is a schematic diagram of a cross section taken from the middle of the image; Figure 11 Schematic diagram of a cross section taken from the middle of (a);

[0078] Figure 11a for Figure 11 Enlarged schematic diagram of (a);

[0079] Figure 11b for Figure 11 Enlarged schematic diagram of (b);

[0080] Figure 11c for Figure 11 Enlarged schematic diagram of (c);

[0081] Figure 11d for Figure 11Enlarged schematic diagram of (d).

[0082] 1-first metal layer, 11-first metal seam, 2-dielectric layer, 3-second metal layer, 31-second metal seam.

[0083] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0084] The technical solutions of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments. It should be noted that the embodiments of the present invention and the features therein may be combined with each other unless there is a conflict.

[0085] In embodiments of the present invention, the term "and / or" describes the association relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0086] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0087] In the embodiments of the present invention, the term "plurality" refers to two or more than two, and other quantifiers are similar.

[0088] In the present invention, unless otherwise specified, the directional words used, such as "up, down, top, bottom", usually refer to the directions shown in the drawings, or to the components themselves in the vertical, perpendicular or gravity direction; similarly, for ease of understanding and description, "inside and outside" refer to the inside and outside relative to the outline of each component itself, but the above directional words are not used to limit the present invention.

[0089] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, it will be understood by those skilled in the art that in the embodiments of the present invention, many technical details are provided to enable the reader to better understand the present invention. However, even without these technical details and the various changes and modifications based on the following embodiments, the technical solutions claimed in the present invention can be implemented. The division of the following embodiments is for convenience of description and should not constitute any limitation on the specific implementation of the present invention. The various embodiments can be combined with each other and referenced to each other under the premise that there is no contradiction.

[0090] In order to solve the above problems, Figures 1 to 3 The present invention provides a vector light generation system based on a metasurface, which includes a plurality of artificial atomic structures in an M×M array arranged along a horizontal and vertical plane (which can be understood as an XY plane), and each artificial atomic structure includes a first metal layer 1, a dielectric layer 2, and a second metal layer 3 in sequence along the vertical direction (which can also be understood as the Z direction). The first metal layer 1, the dielectric layer 2, and the second metal layer 3 are square structures with side lengths p and vertical heights h1, h2, and h3 respectively; the first metal layer 1 is penetrated by a first metal seam 11 extending in the longitudinal direction, and the first metal seam 11 is arranged parallel to the first side of the first metal layer 1 adjacent to it, and the distances between the first metal seam 11 and the center of the first metal layer 1 in the horizontal and vertical directions are Dlta1x and Dlta1y respectively, and the width of the first metal seam 11 in the horizontal direction is a1, and the width in the vertical direction is a2; the second metal layer 3 is penetrated by a second metal seam 31, and the distances between the second metal seam 31 and the center of the second metal layer 3 in the horizontal and vertical directions are Dlta2x and Dlta2y respectively, the angle between the extension direction of the second metal seam 31 and the horizontal direction is θ, the length of the second metal seam 31 in the extension direction is a4, and the width of the second metal seam 31 is a3.

[0091] In some embodiments, p = 328.6 μm, h1 = 60 nm, h2 = 25 μm, and h3 = 60 nm. M is set to 21, and the phase gradient ζ can be calculated from p to be 0.285 k0.

[0092] is the wave vector of the operating frequency, defined as 2π / , is the working wavelength.

[0093] In some embodiments, the first metal layer 1 and the second metal layer 3 are made of gold, and the dielectric layer 2 is made of plastic.

[0094] Among them, the phase of each artificial atomic structure needs to satisfy formula (1), and the phase gradient of each artificial atomic structure needs to satisfy formula (2):

[0095] ; (1)

[0096] ; (2)

[0097] The polarization angle of the second metal seam 31 of each artificial atomic structure needs to satisfy formula (3):

[0098] ; (3)

[0099] Among them, (x k,y k ) is the position coordinate of the i-th artificial atomic structure, x k and y k The value range of is [-M / 2, M / 2];

[0100] ph k (x k ,y k ) is the phase of the kth artificial atomic structure;

[0101] ζ is the phase gradient of the artificial atomic structure;

[0102] is the polarization angle of the second metal slit 31 of the k-th artificial atomic structure;

[0103] θ k is the turning corner of the second metal seam 31 of the kth artificial atomic structure.

[0104] The present invention provides a metasurface-based vector light generation system, which includes a plurality of artificial atomic structures in an M×M array arranged along a horizontal and vertical plane, each artificial atomic structure vertically including a first metal layer 1, a dielectric layer 2, and a second metal layer 3; the first metal layer 1, the dielectric layer 2, and the second metal layer 3 are square structures, and the side lengths are all p, and the vertical heights are h1, h2, and h3 respectively; the first metal layer 1 is penetrated by a first metal seam 11 extending in the longitudinal direction, the first metal seam 11 is arranged parallel to the first side of the first metal layer 1 adjacent to it, and the first metal seam 11 is parallel to the center of the first metal layer 1. The horizontal and vertical distances are Dlta1x and Dlta1y respectively. The width of the first metal seam 11 in the horizontal direction is a1 and the width in the vertical direction is a2. The second metal layer 3 is penetrated by a second metal seam 31. The horizontal and vertical distances between the second metal seam 31 and the center of the second metal layer 3 are Dlta2x and Dlta2y respectively. The angle between the extension direction of the second metal seam 31 and the horizontal direction is θ. The length of the second metal seam 31 in the extension direction is a4. The width of the second metal seam 31 is a3. The phase of each artificial atomic structure needs to satisfy equation (1), and the phase gradient of each artificial atomic structure needs to satisfy equation (2). In this way, an ultra-thin, easy-to-integrate, and convenient on-chip vector light field generator can be formed.

[0105] Furthermore, the metasurface-based vector light generation system provided by the present invention differs from conventional optical devices that require a large space, and from previous metasurfaces that require the superposition of multiple beams to generate a vector light field. The present invention only requires x-polarized electromagnetic waves to illuminate the vector light generation system to generate a vector light field.

[0106] Furthermore, the rotation angle of the second metal slit 31 of the artificial atomic structure determines the polarization direction of the transmitted electromagnetic wave, thereby forming a vector light field with different electric field polarizations in the spatial cross section.

[0107] Figure 4 The schematic diagram of the vector light generation system based on the metasurface provided by the present invention is shown. Figure 4 When an electromagnetic wave is incident on the metasurface-based vector light generation system, it first strikes the first metal slit 11 on the first metal layer 1, exciting Mode 1 in the upper layer. Mode 1 then excites Mode 2 in the lower layer (the second metal slit 31 on the second metal layer 3) through near-field coupling, which then exits the system. Both Mode 1 and Mode 2 are evanescent wave modes, meaning they decay rapidly with increasing distance. Therefore, the thickness of the metasurface-based vector light generation system is crucial, and near-field coupling plays a decisive role in this process. If the thickness of the metasurface-based vector light generation system increases, the near-field coupling weakens or even disappears. Consequently, Mode 1 cannot excite Mode 2, and the electromagnetic wave cannot penetrate the structure. By utilizing the aforementioned metasurface-based vector light generation system structure and near-field coupling, the present invention achieves a thickness unattainable by previous devices with the same functionality. Specifically, the present invention can achieve a thickness of 1 / 30 of a wavelength, where λ is the operating wavelength. In some embodiments, the operating wavelength is 750 μm.

[0108] Figure 5 The schematic diagram of the principle of generating a vector light field in the related art is shown. Figure 6 The schematic diagram shows the principle of the vector light generation system based on the metasurface provided by the present invention to generate a vector light field. Figure 5 and Figure 6 As shown, the related art requires superposition of left-handed circularly polarized light and right-handed circularly polarized light (LCP+RCP) to generate a vector light field, typically requiring two devices to generate the LCP and RCP, respectively. However, the present invention simply divides the vector light field into multiple regions according to its requirements and generates them directly, requiring only a single device. Furthermore, the vectors generated by the present invention are more accurate.

[0109] More specifically, if Figure 6 As shown in Figure 1, the artificial atomic structure of the M×M array is divided into multiple areas of equal angular size according to the geometric center. Each area is equipped with an artificial atomic structure with a different polarization direction. Each artificial atomic structure is excited by an x-polarized electromagnetic wave, and the phase of the transmitted electromagnetic wave needs to satisfy Equation (1).

[0110] Assuming M is 21, the metasurface-based vector light generation system includes 441 artificial atomic structures in a 21×21 array. For example, the system is divided into 12 regions of equal angle according to the geometric center. Figure 6 , the polarization direction of the 441 artificial atomic structures in the 21×21 array is arranged according to the requirements of the vector light field, so that when the electromagnetic wave irradiates the 21x21 structure, a vector light field will appear at the transmission end. Specifically, the 21×21 array structure is divided into 12 areas, each area is as follows Figure 6 The polarization direction indicated by the arrow is filled in. The M×M array of artificial atomic structures is divided into 12 regions of equal angle size according to the geometric center. The rotation angles of each region are 0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 300°, and 330° (from Figure 6 In some embodiments, the rotation angle may be defined as positive in the counterclockwise direction and negative in the clockwise direction, starting from the rightmost yellow arrow in the image.

[0111] Figure 7 Indicated Figure 6 The polarization angle of the middle arrow and the rotation angle θ of the second metal seam 31 of the second metal layer 3 k The relationship diagram between . Figure 7 It can be seen that the second metal seam 31 of the second metal layer 3 is rotated to form a corresponding rotation angle θ k , we can get the corresponding polarization angle φ k .

[0112] The present invention provides a metasurface-based vector light generation system that generates a transmissive, tightly focused vector beam by injecting an x-polarized electromagnetic wave normally onto the system's surface. Specifically, a phase-gradient metasurface serves as a bridge, and after the incident light passes through the metasurface, a tightly focused vector beam is formed.

[0113] Furthermore, the metasurface-based vector light generation system provided by the present invention achieves a phase coverage of 2π on the basis of being ultra-thin (the thickness of the vector light generation system can be less than 1 / 30 of the wavelength). Figure 8 and Figure 9 As shown, Figure 8 It can be seen that if the relevant technology wants to achieve 2π phase coverage while ensuring a certain transmittance, then its thickness must be sacrificed. For example, the previous high aspect ratio dielectric column is very thick, about 1 wavelength. Figure 8It can be seen that the process of the related technology finally produced a dielectric column with a high aspect ratio, which is conducive to producing 360-degree phase coverage and further creating conditions for generating a vector light field; then, the electromagnetic wave is incident from the top of it, and the two beams of light LCP and RCP are finally emitted to synthesize to generate a vector light field; however, the defect of this method of the related technology is that the thickness of the device is very large, reaching one wavelength; secondly, the vector light field must be generated by synthesizing the two beams of light LCP and RCP, and if there is a slight difference in phase between LCP and RCP, the synthesized vector light field effect cannot be very ideal.

[0114] like Figure 9 As shown, the metasurface-based vector light generation system provided by the present invention has two modes (Mode 1 and Mode 2), thus achieving a 2π phase coverage while being ultra-thin. (The 2π phase coverage is important because it is required when establishing a phase gradient.)

[0115] Figure 10 The figure illustrates a flow chart of a method for determining various parameters in a vector light generation system based on a metasurface provided by the present invention.

[0116] like Figure 10 As shown, at step S210, according to the ω of the two resonance modes s 、ω a , based on the FDTD metasurface simulation model, h1, h2, and h3 are obtained.

[0117] It should be noted that the frequencies ω of the two resonance modes s 、ω a It can be the frequency point you want to work at, and the specific frequency can be determined according to your needs. s Take 7GHz, ω a Take 8GHz.

[0118] When the vector light generating system includes two resonant modes, s can be 1 and a can be 2, that is, one mode has a frequency ω s , the other mode is ω a Since s and a are two modes in total, the vector light generation system defaults to two ports. The vector light generation system has two external ports and two resonant modes.

[0119] The frequency ω s 、ω a By inputting the FDTD (Finite-Difference Time-Domain) metasurface simulation model, h1, h2, and h3 can be obtained.

[0120] Step S220, according to the obtained h1, h2, h3, determine the initial values ​​of a1, a2, a3, a4, Dlta1x, Dlta1y, Dlta2x, Dlta2y; and according to the initial values ​​of a1, a2, a3, a4, Dlta1x, Dlta1y, Dlta2x, Dlta2y, based on the FDTD metasurface simulation model, determine the parameters in formula (4); wherein, a1 p / 2,a3 p / 2,a2 p,a4 p,

[0121] Dlta1x p / 3,Dlta1y p / 3,Dlta2x p / 3,Dlta2y p / 3.

[0122] According to h1, h2, and h3, the initial values ​​of a1, a2, a3, a4, Dlta1x, Dlta1y, Dlta2x, and Dlta2y can be selected. They can be selected randomly or according to a certain rule, and no specific restrictions are made here.

[0123] Substituting these values ​​into the FDTD-based metasurface simulation model, we can obtain the parameters in formula (4), such as d 1s d 1a d 2s d 2a 、W a 、W s Based on these parameters, the transmission phase t can be calculated. phase .

[0124] Step S230: Calculate the transmission phase t according to the following formula (4): phase ;

[0125] ; (4)

[0126] in,

[0127] X is the far-field coupling strength between mode a and mode s, and is calculated as follows:

[0128] ;

[0129] d 1s Take the complex conjugate;

[0130] d 2s Take the complex conjugate;

[0131] d 1s is the coupling coefficient between the first port and the sth mode;

[0132] d 1a is the coupling coefficient between the first port and the ath mode;

[0133] d 2s is the coupling coefficient between the second port and the sth mode;

[0134] d 2a is the coupling coefficient between the second port and the ath mode;

[0135] t0 is a constant, set to 0;

[0136] W a is the operating frequency in mode a;

[0137] W s is the operating frequency in s mode;

[0138] ;

[0139] ω is 2πf, f is the frequency;

[0140] is the radiation damping of the ath mode;

[0141] is the radiation damping of the sth mode;

[0142] is the absorption damping of the sth mode;

[0143] Absorbing damping for the ath mode;

[0144] ω a is the operating frequency of mode a;

[0145] ω s is the operating frequency of mode s.

[0146] Step S240: sequentially obtain the phase of the artificial atomic structure and compare the obtained phase of the artificial atomic structure with the transmission phase t phase It should be noted that in the initial state, k=1, that is, the phase of the first artificial atomic structure is equal to the transmission phase t phase In the second cycle, the phase of the second artificial atomic structure is compared with the transmission phase t phase Compare the sizes to see if they are equal, ... until the phases of all artificial atomic structures are equal to the transmission phase t phaseThe total number of artificial atomic structures is M×M. Taking M as 21 as an example, the phases of 441 artificial atomic structures need to be compared with the transmission phase t phase Size comparison.

[0147] When the judgment result is equal, step S240 is continued to enter the next loop, and at this time k=k+1.

[0148] When the judgment result is not equal, continue to execute step S220 to readjust the values ​​of a1, a2, a3, a4, Dlta1x, Dlta1y, Dlta2x, and Dlta2y and enter the next cycle, at which time k=k+1.

[0149] In step S250, if the result is negative, determine whether k is less than M*M (e.g., 21*21=441). If k is less than M*M, continue with step S220 to enter the next loop. If k is equal to or greater than M*M, proceed to step S270.

[0150] In step S260, if the result is negative, determine whether k is less than M*M (e.g., 21*21=441). If k is less than M*M, continue with step S240 to enter the next loop. If k is equal to or greater than M*M, proceed to step S270.

[0151] Step S270, when k is greater than or equal to M*M, use a1, a2, a3, a4, Dlta1x, Dlta1y, Dlta2x, and Dlta2y at this time as the final values.

[0152] More specifically, taking M as 21 as an example, the method for determining the parameters in the metasurface-based vector light generation system includes:

[0153] S1, according to the two resonance modes ω s 、ω a , based on the FDTD metasurface simulation model, h1, h2, and h3 are obtained.

[0154] S2, according to the obtained h1, h2, h3, determine the initial values ​​of a1, a2, a3, a4, Dlta1x, Dlta1y, Dlta2x, Dlta2y; and according to the initial values ​​of a1, a2, a3, a4, Dlta1x, Dlta1y, Dlta2x, Dlta2y, based on the FDTD metasurface simulation model, determine the parameters in formula (3);

[0155] S3, according to formula (3), calculate the transmission phase t phase ;

[0156] S4, compare the phase of the kth artificial atomic structure with the transmission phase t phaseAre the sizes equal to each other and get the judgment result;

[0157] S5, when the judgment result is no, when k is 441, jump directly to S7, otherwise continue to execute step S2 to re-determine a1, a2, a3, a4, Dlta1x, Dlta1y, Dlta2x, Dlta2y, enter the next round of loop, k=k+1;

[0158] S6, when the judgment result is yes, when k is 441, jump directly to S7, otherwise continue to execute step S4 to enter the next loop, k=k+1;

[0159] S7, when k is 441, take a1, a2, a3, a4, Dlta1x, Dlta1y, Dlta2x, and Dlta2y at this time as the final values.

[0160] Figure 11 The diagram shows the effect verification of the vector light generation system based on the metasurface provided by the present invention. Figure 11 In (a), an electromagnetic wave is incident on the black metasurface from the -z direction. The light beam that appears below is a hollow light beam with a green center (green represents a light intensity of 0). This is a characteristic of a vector light field. A non-vector light field will not have a hollow light beam. Figure 11 (b) is in Figure 11 Taking a cross section in the middle of (a) (7314 μm away from the metasurface) and observing the components of Ex, we can see that along the x-direction, Ex is divided into two lobes, left and right. This is also the characteristic of the vector light field. If it is not a vector light field, the displayed image is a uniform circular spot. Figure 11 (c) is in Figure 11 Taking a cross section in the middle of (a) (7314 μm away from the metasurface) and observing the components of Ey, we can see that along the y direction, Ey is divided into two lobes, upper and lower. This is also a characteristic of the vector light field. If it is not a vector light field, the displayed image is a uniform circular spot. Figure 11 (d) is in Figure 11 A cross section taken in the middle of (a) (7314 μm from the metasurface) shows the polarization direction of the electric field. The polarization arrows point radially from the center, which is consistent with the behavior of a vector light field. This further demonstrates that the metasurface-based vector light generation system provided by this invention can directly generate vector light fields.

[0161] Obviously, the embodiments described above are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, those skilled in the art may make other different forms of changes or modifications without making any creative work, and all of these should fall within the scope of protection of the present invention.

Claims

1. A vector light generation system based on a metasurface, characterized in that: The invention comprises a plurality of artificial atomic structures in an M×M array arranged along a horizontal and vertical plane, wherein each artificial atomic structure comprises a first metal layer, a dielectric layer, and a second metal layer in sequence along the vertical direction; The first metal layer, the dielectric layer, and the second metal layer are square structures, and the side lengths are all p, and the vertical heights are h1, h2, and h3 respectively; A first metal seam extending longitudinally is formed through the first metal layer. The first metal seam is arranged parallel to the first side of the first metal layer adjacent to the first metal seam. The distances between the first metal seam and the center of the first metal layer in the transverse and longitudinal directions are Dlta1x and Dlta1y, respectively. The width of the first metal seam in the transverse direction is a1, and the width in the longitudinal direction is a2. A second metal seam is formed through the second metal layer. The distances between the second metal seam and the center of the second metal layer in the transverse and longitudinal directions are Dlta2x and Dlta2y respectively. The angle between the extension direction of the second metal seam and the transverse direction is θ. The length of the second metal seam in the extension direction is a4. The width of the second metal seam is a3. Among them, the phase of each artificial atomic structure needs to satisfy formula (1), and the phase gradient of each artificial atomic structure needs to satisfy formula (2): ；（1） ；（2） The polarization angle of the second metal slit of each artificial atomic structure needs to satisfy formula (3): ；（3） Among them, (x k ,y k ) is the position coordinate of the kth artificial atomic structure, x k and y k The value range of is [-M / 2, M / 2]; ph k (x k ,y k ) is the phase of the kth artificial atomic structure; is the phase gradient of the artificial atomic structure; is the polarization angle of the second metal slit of the kth artificial atomic structure; θ k is the turning angle of the second metal seam of the kth artificial atomic structure; The artificial atomic structure of the M×M array is divided into multiple regions of equal angle size according to the geometric center, and each region is provided with an artificial atomic structure of different polarization direction. Each artificial atomic structure is excited by an x-polarized electromagnetic wave, and the phase of the transmitted electromagnetic wave needs to satisfy formula (1); the artificial atomic structure of the M×M array is divided into 12 regions of equal angle size according to the geometric center, and the rotation angles of each region are 0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 300°, and 330° respectively; the vector light generating system generates a transmission-type tightly focused vector light beam by normally incidenting the x-polarized electromagnetic wave onto the surface of the vector light generating system.

2. The metasurface-based vector light generation system according to claim 1, wherein: The method for determining the parameters in the metasurface-based vector light generation system is as follows: Step S210, according to the ω of the two resonance modes s 、ω a , based on the FDTD metasurface simulation model, h1, h2, and h3 are obtained; Step S220: Determine the initial values ​​of a1, a2, a3, a4, Dlta1x, Dlta1y, Dlta2x, and Dlta2y based on the obtained h1, h2, and h3; and determine the parameters in formula (4) based on the FDTD metasurface simulation model based on the initial values ​​of a1, a2, a3, a4, Dlta1x, Dlta1y, Dlta2x, and Dlta2y; Among them, a1 p / 2,a3 p / 2,a2 p,a4 p, Dlta1x p / 3,Dlta1y p / 3,Dlta2x p / 3,Dlta2y p / 3; Step S230: Calculate the transmission phase t according to the following formula (4): phase ; ；（4） Step S240: sequentially obtain the phase of the artificial atomic structure and compare the obtained phase of the artificial atomic structure with the transmission phase t phase Are the sizes equal to each other and get the judgment result; Step S250: When the judgment result is no, continue to execute step S220 to enter the next loop until all artificial atomic structures are traversed, and a1, a2, a3, a4, Dlta1x, Dlta1y, Dlta2x, and Dlta2y at this time are taken as the final values; Step S260: When the judgment result is yes, continue to execute step S240 to enter the next loop until all artificial atomic structures are traversed, and a1, a2, a3, a4, Dlta1x, Dlta1y, Dlta2x, and Dlta2y at this time are taken as the final values; in, X is the far-field coupling strength between mode a and mode s, and is calculated as follows: ； d 1s Take the complex conjugate; d 2s Take the complex conjugate; d 1s is the coupling coefficient between the first port and the sth mode; d 1a is the coupling coefficient between the first port and the ath mode; d 2s is the coupling coefficient between the second port and the sth mode; d 2a is the coupling coefficient between the second port and the ath mode; t0 is a constant, set to 0; W a is the operating frequency in mode a; W s is the operating frequency in s mode; ； ω is 2πf, f is the frequency; is the radiation damping of the ath mode; is the radiation damping of the sth mode; is the absorption damping of the sth mode; Absorbing damping for the ath mode; ω a is the operating frequency of mode a; ω s is the operating frequency of mode s.

3. The metasurface-based vector light generation system according to claim 1, wherein: The first metal layer and the second metal layer are made of gold.

4. The metasurface-based vector light generation system according to claim 1, wherein: The medium layer is made of plastic.

5. The metasurface-based vector light generation system according to claim 1, wherein: M is 21.

6. The metasurface-based vector light generation system according to claim 1, wherein: The vertical thickness of the metasurface-based vector light generation system is λ / 30, where λ is the operating wavelength.

7. The metasurface-based vector light generation system according to claim 6, wherein: The operating wavelength is 750um.

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