Design method of large-diameter broadband achromatic and spherical-aberration-eliminating super lens
Through the combination of periodic dispersion control and new phase formulas, combined with geometric phase design and group delay elimination of chromatic aberration problems of ultralens under wideband incident light and finite long light source conditions, the high-quality imaging effect is achieved.
Patent Information
- Application Number
- CN202411762331.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-03
- Publication Date
- 2025-03-07
AI Technical Summary
The chromatic aberration problem introduced by existing superlenses in the case of wideband incident light is more significant, and the introduction of off-axis aberration under the condition of finite long light sources, resulting in poor imaging quality.
By introducing periodic dispersion control, the group delay is stopped passively; the new phase formula is adopted to consider the phase difference caused by off-axis incident of finite distance light sources; the geometric phase design method is used to improve resolution; the group delay elimination of chromatic difference components of the unit structure is constructed; the electromagnetic propagation process of the ultralens is simulated by the finite time domain differential method to verify the design performance.
The design of a large-size wideband achromatic ultralens is realized, which meets the application of finite-high light sources and infinite-high light sources scenes, improves imaging quality and suppresses off-axis aberration.
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Figure CN119575643A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of achromatic and aplanatic metalens, and in particular to a design method of a large-diameter broadband achromatic and aplanatic metalens. Background Art
[0002] Compared with conventional lenses, superlenses have an extremely thin sub-wavelength thickness, which enables them to be miniaturized. In addition, superlenses have excellent capabilities in electromagnetic regulation, so they have a wide range of applications in the field of optics, including precise control of the phase and polarization of light. However, since the refractive index of the material varies with the wavelength, the focusing position of the light at different wavelengths of the superlens will shift, resulting in chromatic aberration. Especially in the case of broadband incident light, the chromatic aberration problem introduced by superlenses is more significant than that of conventional lenses. On the other hand, existing research on broadband achromatic superlenses rarely considers the focusing problem under the condition of finite light sources, and the object distance of finite light sources is short, causing the light to no longer present a completely single on-axis incidence, but also off-axis incidence. At this time, the wavefront is spherical, so off-axis aberrations, also known as spherical aberrations, are introduced. This problem causes the focusing effect of conventional superlenses to decrease, which manifests as poor imaging quality in the optical system. Summary of the invention
[0003] In view of the above problems or problems existing in the prior art, the present invention is proposed.
[0004] Therefore, the purpose of the present invention is to provide a large-scale broadband achromatic and aplanatic metalens design method, which can solve the large-scale problem of a single-chip broadband achromatic lens, and at the same time, combined with the characteristics of aplanatic aberration, make the single-chip large-scale broadband achromatic metalens meet the application of both finite and infinite light source scenes.
[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: a large-diameter broadband achromatic and aplanatic metalens design method, which includes introducing periodic dispersion control to stop the group delay from passively increasing;
[0006] Through the innovation of phase formula, the phase difference caused by off-axis incidence of finite light source is introduced;
[0007] By adopting the geometric phase design method, higher resolution is obtained;
[0008] By using the method of eliminating chromatic aberration components through group delay, a database of group delay and geometric parameters of the unit structure is constructed;
[0009] The electromagnetic propagation process of the superlens is simulated by the finite time-domain difference method to verify the design performance of the superlens.
[0010] As a preferred solution of the large-diameter broadband achromatic and aplanatic metalens design method of the present invention, the periodic dispersion control achieves control of the group delay by periodically adjusting the geometric parameters of the unit structure so that the group delay required by the arranged unit structure no longer increases with the diameter of the metalens.
[0011] As a preferred solution of the large-scale broadband achromatic and aplanatic metalens design method of the present invention, the new phase formula, under the condition of a finite light source, the spherical shape of the incident light wavefront will cause off-axis aberration, affecting the imaging quality, and its formula is as follows:
[0012]
[0013] in, represents the phase at the (x, y) position, w min represents the minimum angular frequency in a narrowband wavelength, C is the speed of light, S is the object distance, and F is the focal length.
[0014] As a preferred solution of the large-scale broadband achromatic and aplanatic metalens design method of the present invention, the theoretical value of the metalens group delay is obtained based on the new phase formula, which is used to describe the group delay requirements that need to be met at various positions when achieving achromatism. The formula is as follows:
[0015]
[0016] Wherein, GD(x, y) represents the group delay at position (x, y) on the metalens; mod represents the modulo operation; C is the speed of light; S is the object distance; F is the focal length; represents the straight-line distance from the light source to the point (x, y) on the metalens; represents the straight-line distance from the point (x, y) on the metalens to the focus; Δphase is the phase difference; w max and w min They represent the maximum and minimum angular frequencies within the operating wavelength range respectively; ΔGD represents the range of change of group delay.
[0017] As a preferred solution of the large-diameter broadband achromatic and aplanatic metalens design method of the present invention, the variation range of the group delay ΔGD is the variation range of the minimum period group delay, and its calculation formula is as follows:
[0018]
[0019] Here, 2π is a constant used to convert changes in angular frequency into changes in phase. In optics, phase is usually measured in radians, and 2π radians equals one complete cycle.
[0020] As a preferred solution of the large-scale broadband achromatic and aplanatic metalens design method of the present invention, the geometric phase design obtains the modulation phase by rotating the angle of the subwavelength medium structure when the incident light is circularly polarized light.
[0021] As a preferred solution for the design method of a large-scale broadband achromatic and spherical aberration metalens of the present invention, the group delay elimination method of the chromatic aberration component obtains the phase of the unit structure by simulating electromagnetic propagation using the finite time-domain difference method, and obtains the phase change at different frequencies by frequency scanning the unit structure under different geometric parameter forms, thereby constructing a database of group delay and geometric parameters of the unit structure.
[0022] As a preferred solution of the large-diameter broadband achromatic and aplanatic metalens design method of the present invention, the limiting group delay calculation formula of the unit structure is as follows:
[0023]
[0024] Among them, Group Delay is the group delay, phase is the phase, and w is the angular frequency.
[0025] As a preferred solution of the large-scale broadband achromatic and aplanatic metalens design method of the present invention, the finite time-domain difference method is a numerical simulation method used to simulate the propagation of electromagnetic waves in space. The performance of the metalens under actual working conditions is simulated by the finite time-domain difference method.
[0026] As a preferred solution of the large-scale broadband achromatic and aplanatic metalens design method of the present invention, the metalens is composed of a substrate and a subwavelength medium structure, the subwavelength medium structure is arranged on one side of the substrate, and the substrate provides support for it. The broadband wave is emitted from the object side light source, passes through the substrate and is regulated by the subwavelength medium structure, and the metalens focuses the light to the image side focus.
[0027] Beneficial effects of the present invention: By introducing periodic dispersion control, the present invention makes the group delay of the required unit structure no longer continue to expand with the expansion of the metalens diameter, and can meet the design requirements of a monolithic large-diameter broadband achromatic metalens. At the same time, in view of the problem of off-axis aberration of a finite light source, a new phase formula is proposed, and the consideration of the phase difference caused by the off-axis incidence of the finite light source is introduced, and the off-axis aberration is successfully suppressed, so that the large-diameter broadband achromatic metalens can be successfully applied to the scene of the finite light source, while meeting the scene of the infinite light source. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:
[0029] Figure 1 Schematic diagram of the metalens structure for the design method of a large-diameter broadband achromatic and spherical metalens.
[0030] Figure 2 Schematic diagram of the design performance of the metalens related to the design method of a large-diameter broadband achromatic and spherical metalens.
[0031] Figure 3 Schematic diagram of the comparison of group delay compensation for large-diameter broadband achromatic and spherical metalenses design methods.
[0032] Figure 4 Schematic diagram of the comparison of focusing effects of the phase formula for the design method of large-diameter broadband achromatic and spherical metalens.
[0033] Figure 5 Schematic diagram of the comparison of achromatic performance at different wavelengths of the design method of large-scale broadband achromatic and spherical metalens.
[0034] Figure 6 Schematic diagram of the horizontal axis resolution of each wavelength for the design method of a large-scale broadband achromatic and spherical metalens. DETAILED DESCRIPTION
[0035] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.
[0036] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.
[0037] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.
[0038] Example 1
[0039] Reference Figure 1 to Figure 6, is an embodiment of the present invention, which provides a design method for a large-scale broadband achromatic and aplanatic metalens, which can solve the large-scale problem of a single-chip broadband achromatic lens, and at the same time, combined with the characteristics of aplanatic aberration, enables the single-chip large-scale broadband achromatic metalens to meet the application of both finite-distance light source and infinite-distance light source scenarios.
[0040] Specifically, by introducing periodic dispersion control, the group delay stops passively increasing;
[0041] Through the innovation of phase formula, the phase difference caused by off-axis incidence of finite light source is introduced;
[0042] By adopting the geometric phase design method, higher resolution is obtained;
[0043] By using the method of eliminating chromatic aberration components through group delay, a database of group delay and geometric parameters of the unit structure is constructed;
[0044] The electromagnetic propagation process of the superlens is simulated by the finite time-domain difference method to verify the design performance of the superlens.
[0045] Furthermore, the periodic dispersion control periodically adjusts the geometric parameters of the unit structure so that the group delay required by the arranged unit structure no longer increases with the diameter of the superlens, thereby achieving control over the group delay.
[0046] Furthermore, under the condition of a finite light source, the spherical shape of the incident light wavefront will cause off-axis aberration, affecting the imaging quality. The formula is as follows:
[0047]
[0048] in, represents the phase at the (x, y) position, w min represents the minimum angular frequency in a narrowband wavelength, C is the speed of light, S is the object distance, and F is the focal length.
[0049] It should be noted that the phase formula of the superlens can be used to control the phase of the incident light, thereby changing the shape of the incident light wavefront. According to the phase formula, the phase is arranged at the corresponding (x, y) position as The sub-wavelength unit structure can achieve the incident angle frequency w at the object distance S. min The spherical wavefront light is focused to a focal point with a focal length of F.
[0050] Furthermore, the theoretical value of the metalens group delay is obtained based on the new phase formula, which is used to describe the group delay requirements that need to be met at various positions when achieving achromatism. The formula is as follows:
[0051]
[0052] Wherein, GD(x, y) represents the group delay at position (x, y) on the metalens; mod represents the modulo operation; C is the speed of light; S is the object distance; F is the focal length; represents the straight-line distance from the light source to the point (x, y) on the metalens; represents the straight-line distance from the point (x, y) on the metalens to the focus; Δphase is the phase difference; w max and w min They represent the maximum and minimum angular frequencies within the operating wavelength range respectively; ΔGD represents the range of change of group delay.
[0053] It should be noted that for the (x, y) position, it is theoretically necessary to arrange the unit structure that meets the target group delay GD(x, y). By searching the database of geometric parameters and group delay, the unit structure closest to the target group delay GD(x, y) is obtained. Since the geometric phase is used, according to the phase formula Adjust the rotation angle of the unit structure.
[0054] The relationship between angular frequency w and frequency f is w=2πf.
[0055] Furthermore, the variation range of the group delay ΔGD is the variation range of the minimum periodic group delay, and its calculation formula is as follows:
[0056]
[0057] Here, 2π is a constant used to convert changes in angular frequency into changes in phase. In optics, phase is usually measured in radians, and 2π radians equals one complete cycle.
[0058] Furthermore, the geometric phase design obtains the modulation phase by rotating the angle of the sub-wavelength medium structure when the incident light is circularly polarized light.
[0059] It should be noted that the shape of the subwavelength medium structure is an elliptical cylinder, a rectangular parallelepiped, a cylinder, etc., and this embodiment adopts a rectangular parallelepiped shape. The size of the substrate needs to cover all subwavelength medium structures, and its shape includes rectangular parallelepiped, cube, cylinder, etc. This embodiment adopts a cylindrical shape. Regarding the phase control method of the superlens for electromagnetic waves, there are transmission phase, geometric phase, resonance phase and mixed phase control methods. This embodiment adopts the design method of geometric phase. When the incident light is circularly polarized light, the modulation phase can be obtained by rotating the angle of the subwavelength medium structure. Since polarization information is introduced during the light transmission process, a higher resolution can be achieved at this time.
[0060] Furthermore, the group delay elimination method of chromatic aberration components obtains the phase of the unit structure by simulating electromagnetic propagation using the finite time-domain difference method, and obtains the phase change at different frequencies by frequency scanning the unit structure in different geometric parameter forms, thereby constructing a database of group delay and geometric parameters of the unit structure.
[0061] Furthermore, the calculation formula of the limiting group delay of the unit structure is as follows:
[0062]
[0063] Among them, Group Delay is the group delay, phase is the phase, and w is the angular frequency.
[0064] Furthermore, the finite time-difference method is a numerical simulation method used to simulate the propagation of electromagnetic waves in space. The performance of the metalens under actual working conditions is simulated by the finite time-difference method.
[0065] Furthermore, the superlens is composed of a substrate and a subwavelength medium structure. The subwavelength medium structure is arranged on one side of the substrate, and the substrate provides support for it. The broadband wave is emitted from the object side light source, passes through the substrate and is regulated by the subwavelength medium structure. The superlens focuses the light to the image side focus.
[0066] Specifically, for a broadband wavelength light source with a bandwidth of 50 nm from 480 nm to 530 nm, a metalens with a diameter of 27 μm, an object distance of 26 μm, and an image distance of 26 μm is designed, and an achromatic and aplanatic metalens example with an NA value of 0.46 is designed.
[0067] Among them, the sub-wavelength dielectric structure uses Al2O3 as the substrate material and TiO2 as the unit column material. Figure 2 (A) shows the relationship between the unit structure geometric parameters and group delay, that is, the transmittance information obtained by scanning the geometric parameters at a wavelength of 525nm, and the unit structure group delay information under wavelength scanning, and the database information of geometric parameters and group delay is established. In order to achieve the focusing of the metalens, the theoretical phase distribution required is as follows Figure 2 As shown in (B), due to the geometric phase modulation method, the phase of the unit structure is determined by its 2 times rotation angle relative to the X-axis, so the theoretical phase distribution can be perfectly realized, thereby achieving the focusing of light.
[0068] Since the narrowband light source is not a single wavelength, the unit structure that constitutes the metalens will show different refractive indices, thereby introducing chromatic aberration interference, making it impossible for conventional metalens to focus to the same position at different wavelengths. Based on the calculation results of the theoretical value of the metalens group delay, the ideal group delay distribution of this metalens example is obtained, such as Figure 2As shown in (C), the unit structure geometric parameters close to the ideal group delay are set in the corresponding unit cell area. After traversing the entire metalens, the actual group delay distribution achieved is as follows Figure 2 (D) as shown.
[0069] According to the above examples, the relevant performance is verified through the design of experiments, including large size, spherical aberration performance, chromatic aberration performance, and lateral resolution. The specific verification is as follows:
[0070] Large size verification:
[0071] The parameters of the metalens are designed to have a diameter of 200μm, and the focal length and object distance are both 100μm. The fundamental way to achieve achromatism is to use a unit structure to cancel the group delay. For traditional dispersion control methods, such as using the following formula:
[0072]
[0073] like Figure 3 (A) shows the group delay that needs to be met in the traditional way, such as Figure 3 (B) shows the group delay required by the present invention. It can be seen that the conventional group delay control method requires the group delay to be approximately 200 to 500 fs, while the present invention only maintains the group delay at 0 to 20 fs, which can be satisfied by common materials.
[0074] Spherical aberration performance verification:
[0075] The finite time-domain difference method is used to simulate the electromagnetic propagation process of the metalens to achieve the purpose of simulating the performance of the metalens in real scenes. First, when the incident wavelength is 525nm, when facing a light source at a finite distance, the focusing effect obtained by the conventional metalens phase formula is as follows: Figure 4 As shown in (A), it can be seen that there are multiple focal points, and the focal points are not on the ideal focal plane; the focusing effect of the phase formula derived by this scheme is as follows Figure 4 As shown in (B), there is only one focus, which shows that the focusing effect of the present design is better and is almost located at the ideal focal plane. It can be seen that the phase formula designed by the present invention can well solve the off-axis aberration problem caused by the finite light source.
[0076] Among them, the phase modulation formula used here is obtained based on the above phase formula:
[0077]
[0078] The resolution calculation formula is as follows:
[0079]
[0080] Among them, d is the resolution, which indicates the minimum detail size that the metalens can resolve; λ is the wavelength of the light wave, which is an important property of the light wave and determines the diffraction limit of the light wave; NA is the numerical aperture, which is a parameter that measures the ability of an optical system to receive light and is defined as NA = n·sin(θ), where n is the refractive index of the medium and θ is the angle of incidence.
[0081] Achromatic performance verification:
[0082] The focal points of the finite light source at different wavelengths in the narrowband wavelength are tested to obtain the focal shift and evaluate the achromatic performance of this design. The focal positions at 488nm, 505nm, and 525nm are tested respectively, and two sets of experiments are set up for verification. Figure 5 As shown in (A), finite-distance light sources with wavelengths of 488nm, 502nm and 525nm are used respectively, wherein the upper figure is a focusing effect diagram without achromatic control; the lower figure is a focusing effect diagram of the present invention; Figure 5 (B) shows that three wavelengths of 488nm, 502nm and 525nm are used respectively. The upper figure shows the intensity distribution of the light along the z-axis under the control of no chromatic aberration; the lower figure shows the intensity distribution of the light along the z-axis of the axis of the present invention. Figure 5 (A) As shown in the figure above, the focal points are located at 29.78μm, 27.92μm, and 25.41μm respectively. Figure 5 (B) As shown in the figure above, it can be seen that there is an obvious focus shift. As the wavelength increases, the focus shifts inward. At 488nm and 525nm wavelengths, the focus shift is 4.37μm, which is 16.8% of the ideal focal length. After adding dispersion control, the focus is located at 24.96μm, 24.38μm, and 23.35μm respectively. It can be seen that the focus shift at 488nm and 525nm wavelengths is 1.61μm, which is reduced by 63%. It can be seen that it has excellent achromatic performance.
[0083] Lateral resolution verification:
[0084] For the horizontal axis information of the focal plane, its half-height full width value is obtained as its lateral resolution. At this time, when the wavelength of the finite element light source is 488nm, 502nm and 525nm, the resolution is 0.64μm, 0.64μm and 0.61μm respectively, as shown in Figure 6 (A), (B), and (C) show the lateral resolution at wavelengths of 488nm, 502nm, and 525nm, respectively, which shows that it achieves a sub-micron theoretical resolution.
[0085] In summary, the present invention introduces periodic dispersion control so that the group delay of the required unit structure no longer continues to expand with the expansion of the metalens diameter, and can meet the design requirements of a monolithic large-diameter broadband achromatic metalens. At the same time, in view of the problem of off-axis aberration of a finite light source, a new phase formula is proposed, which introduces the consideration of the phase difference caused by the off-axis incidence of the finite light source, and successfully achieves the suppression of off-axis aberration, so that the large-diameter broadband achromatic metalens can be successfully applied to the scene of the finite light source, while meeting the scene of the infinite light source.
[0086] Importantly, it should be noted that the construction and arrangement of the present application shown in a plurality of different exemplary embodiments are only exemplary. Although only a few embodiments are described in detail in this disclosure, it should be readily understood by those who refer to this disclosure that many modifications are possible without substantially departing from the novel teachings and advantages of the subject matter described in the application (e.g., mounting arrangements, use of materials, color, changes in orientation, etc.). For example, the element shown as integrally formed may be composed of a plurality of parts or elements, the position of the element may be inverted or otherwise changed, and the nature or number or position of the discrete element may be altered or changed. Therefore, all such modifications are intended to be included within the scope of the present invention. The order or sequence of any process or method steps may be changed or reordered according to an alternative embodiment. In the claims, any "bracket plus function" clause is intended to cover the structure of the execution function described herein, and is not only structurally equivalent but also equivalent structure. Without departing from the scope of the present invention, other replacements, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments. Therefore, the present invention is not limited to a specific embodiment, but extends to a variety of modifications that still fall within the scope of the appended claims.
[0087] Additionally, in an effort to provide a concise description of example embodiments, all features of an actual implementation may not be described.
[0088] It should be understood that in the development of any actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort may be complex and time-consuming, but for those of ordinary skill having the benefit of this disclosure, the development effort will be a routine task of design, fabrication, and production without undue experimentation.
[0089] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.
Claims
1. A design method for a large-diameter broadband achromatic and aplanatic metalens, characterized by: include, By introducing periodic dispersion control, the group delay stops passively increasing; Through the innovation of phase formula, the phase difference caused by off-axis incidence of finite light source is introduced; By adopting the geometric phase design method, higher resolution is obtained; By using the method of eliminating chromatic aberration components through group delay, a database of group delay and geometric parameters of the unit structure is constructed; The electromagnetic propagation process of the superlens is simulated by the finite time-domain difference method to verify the design performance of the superlens.
2. The method for designing a large-diameter broadband achromatic and aplanatic metalens according to claim 1, characterized in that: The periodic dispersion control achieves control of the group delay by periodically adjusting the geometric parameters of the unit structure so that the group delay required by the arranged unit structure no longer increases with the diameter of the super lens.
3. The method for designing a large-diameter broadband achromatic and aplanatic metalens according to claim 2, characterized in that: The new phase formula, under the condition of finite light source, the spherical shape of the incident light wavefront will cause off-axis aberration, affecting the imaging quality. The formula is as follows: in, represents the phase at the (x, y) position, w min represents the minimum angular frequency in a narrowband wavelength, C is the speed of light, S is the object distance, and F is the focal length.
4. The method for designing a large-diameter broadband achromatic and aplanatic metalens according to claim 2, characterized in that: The theoretical value of the metalens group delay is derived based on the new phase formula, which is used to describe the group delay requirements that need to be met at various positions when achieving achromatism. The formula is as follows: Wherein, GD(x, y) represents the group delay at the position (x, y) on the metalens; mod represents the modulo operation; C is the speed of light; S is the object distance; F is the focal length; represents the straight-line distance from the light source to the point (x, y) on the metalens; represents the straight-line distance from the point (x, y) on the metalens to the focus; Δphase is the phase difference; w max and w min They represent the maximum and minimum angular frequencies within the operating wavelength range respectively; ΔGD represents the range of group delay variation.
5. The method for designing a large-diameter broadband achromatic and aplanatic metalens according to claim 4, characterized in that: The variation range of the group delay ΔGD is the variation range of the minimum period group delay, and its calculation formula is as follows: Here, 2π is a constant used to convert changes in angular frequency into changes in phase. In optics, phase is usually measured in radians, and 2π radians equals one complete cycle.
6. The method for designing a large-diameter broadband achromatic and aplanatic metalens according to any one of claims 3 to 5, characterized in that: The geometric phase design obtains the modulation phase by rotating the angle of the sub-wavelength medium structure when the incident light is circularly polarized light.
7. The method for designing a large-diameter broadband achromatic and aplanatic metalens according to claim 6, characterized in that: The group delay elimination method of the chromatic aberration component obtains the phase of the unit structure by simulating electromagnetic propagation using the finite time-domain difference method, and obtains the phase change at different frequencies by performing frequency scanning on the unit structure under different geometric parameter forms, thereby constructing a database of the group delay and geometric parameters of the unit structure.
8. The method for designing a large-diameter broadband achromatic and aplanatic metalens according to claim 7, characterized in that: The calculation formula of the limiting group delay of the unit structure is as follows: Among them, Group Delay is the group delay, phase is the phase, and w is the angular frequency.
9. The method for designing a large-diameter broadband achromatic and aplanatic metalens according to any one of claims 7 or 8, characterized in that: The finite time-difference method is a numerical simulation method used to simulate the propagation of electromagnetic waves in space. The performance of the metalens under actual working conditions is simulated by the finite time-difference method.
10. The method for designing a large-diameter broadband achromatic and aplanatic metalens according to claim 9, characterized in that: The superlens is composed of a substrate and a subwavelength medium structure. The subwavelength medium structure is arranged on one side of the substrate, and the substrate provides support for it. A broadband wave is emitted from an object-side light source, passes through the substrate and is regulated by the subwavelength medium structure. The superlens focuses the light to the image-side focus.