Long-wave infrared double-layer non-interval stacked achromatic superlens and preparation method thereof

Abstract

The application provides a long-wave infrared double-layer non-interval stacked achromatic superlens and a preparation method thereof, which comprises a substrate, a first microstructure array arranged on the upper surface of the substrate, the first microstructure array comprising a plurality of first silicon rectangular columns with a first preset height, a filling layer composed of filling material filled in the gap between the first silicon rectangular columns, the upper surface of the filling layer being flush with the upper surface of each first silicon rectangular column, the filling material in the filling layer being magnesium fluoride, and a second microstructure array arranged on the upper surface of the filling layer, the second microstructure array comprising a plurality of second silicon rectangular columns with a second preset height, and the achromatic focusing in the long-wave infrared wave band being realized through each first silicon rectangular column and each second silicon rectangular column. The superlens has the advantages of high phase control freedom, efficient achromatic focusing capacity, good structural stability and easy preparation in the long-wave infrared wave band.

Description

Technical Field

[0001] This invention relates to the technical field of long-wave infrared superlenses, and more specifically, to a long-wave infrared double-layer stacked achromatic superlens and its fabrication method. Background Technology

[0002] The long-wave infrared band is an important atmospheric window and corresponds to the peak wavelength of human thermal radiation, possessing irreplaceable key application value in fields such as night vision, infrared remote sensing, security monitoring, and autonomous driving. However, traditional long-wave infrared optical systems mainly rely on refractive lens groups composed of materials such as germanium, zinc selenide, and chalcogenide glass, which generally suffer from problems such as large size, complex structure, and heavy overall weight, making it difficult to meet the development requirements of miniaturization, lightweighting, and high integration of optical systems.

[0003] In recent years, metalenses, as a novel planar diffractive optical element based on metasurfaces, have been regarded as a revolutionary technology with the potential to replace traditional infrared optical systems due to their advantages such as miniaturization, lightweight, high integration, and multifunctional control. Metalenses utilize a series of subwavelength artificial microstructures, and by precisely controlling the geometric parameters of these microstructures (such as height, diameter, and period), they can manipulate the phase, amplitude, and polarization state of light waves. However, metasurface-based optical devices generally suffer from severe chromatic aberration, significantly reducing imaging quality under broadband illumination conditions. Therefore, achieving efficient achromatic focusing in the long-wavelength infrared band is a core challenge that urgently needs to be overcome in this field.

[0004] To reduce chromatic aberration in superlenses, current techniques typically rely on designing nanoscale unit structures with specific phase and dispersion responses. By constructing a phase library, the desired phase distribution and dispersion compensation conditions are simultaneously met within the target wavelength range. While some advanced design methods, such as topology optimization and reverse engineering, can achieve relatively high focusing efficiency to a certain extent, their applications are mostly concentrated in the mid-infrared band or polarization-sensitive superlenses. For polarization-insensitive superlenses, their microstructure design usually needs to meet higher symmetry requirements (such as cylindrical, toroidal, and square pillars). Therefore, isotropic or structural units with specific symmetries are often used, which limits the degree of freedom in phase modulation and thus restricts further improvements in energy utilization efficiency and achromatic aberration capabilities.

[0005] To address these issues, some researchers have attempted to employ double-layer or multi-layer stacked superlens architectures to provide greater freedom in phase modulation. However, existing double-layer stacking schemes still have significant drawbacks: First, some schemes involve a substrate or spacer layer between the two microstructures, which introduces interface reflection, substrate absorption, and Fabry-Perot (FP) cavity effects, significantly reducing optical efficiency. Second, some schemes use alternating stacks of high- and low-refractive-index materials, which can improve the equivalent refractive index and reduce the aspect ratio to some extent, but the fabrication process is complex, and the dimensions of the upper and lower layers are usually the same, limiting the freedom in phase modulation. Third, in the long-wave infrared band, to achieve the required phase modulation, the microstructure often requires a high aspect ratio, making the structure prone to mechanical collapse during fabrication and use, severely restricting the reliability and practicality of the device.

[0006] Therefore, how to provide a superlens that combines high phase control freedom, high efficiency achromatic focusing capability, good structural stability and ease of fabrication in the long-wave infrared band has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] The technical problem to be solved by this invention is how to realize a superlens that has high phase control freedom, high efficiency achromatic focusing capability, good structural stability and easy fabrication in the long-wave infrared band. In order to overcome the above-mentioned defects of the prior art (or related technology), this invention provides a long-wave infrared double-layer uninterrupted stacked achromatic superlens and its fabrication method.

[0008] This invention provides a long-wave infrared double-layer uninterrupted stacked achromatic superlens, comprising: A substrate; A first microstructure array is disposed on the upper surface of the substrate, the first microstructure array comprising a plurality of first silicon rectangular pillars having a first preset height; A filling layer is formed by filling material filling the gaps between each of the first silicon rectangular pillars, the upper surface of the filling layer is flush with the upper surface of each of the first silicon rectangular pillars, and the filling material in the filling layer is magnesium fluoride; A second microstructure array is disposed on the upper surface of the filling layer. The second microstructure array includes a plurality of second silicon rectangular pillars with a second preset height. Achromatic focusing is performed in the long-wave infrared band by each of the first silicon rectangular pillars and each of the second silicon rectangular pillars.

[0009] Compared with existing technologies, the long-wave infrared double-layer uninterrupted stacked achromatic superlens of this invention has the following advantages: This invention employs a double-layer, uninterrupted stacked structure composed of a first microstructure array and a second microstructure array. The preset heights of the first and second silicon rectangular pillars in the upper and lower layers can be independently designed. Compared to a single-layer superlens, this structure provides a richer phase library, significantly improving phase modulation capabilities while maintaining polarization insensitivity. This solves the problem of insufficient modulation freedom caused by structural symmetry constraints in existing polarization-insensitive superlenses, resulting in high phase modulation freedom. Furthermore, through the synergistic effect of the upper and lower microstructure arrays, broadband achromatic focusing can be achieved in the long-wave infrared band. Simultaneously, the gaps between the first silicon rectangular pillars are filled with a filling material at the same height, providing a flat upper surface to facilitate the fabrication of the second layer of microstructures and forming mechanical support for the bottom first microstructure array. This effectively avoids the problem of high aspect ratio microstructures being prone to collapse, improving reliability and manufacturability.

[0010] In one possible implementation, the substrate is made of barium fluoride.

[0011] Compared with existing technologies, the above technical solution can utilize barium fluoride's extremely high transmittance and extremely low absorption loss in the long-wave infrared band, while also possessing stable chemical properties and a well-matched coefficient of thermal expansion. This provides an ideal substrate platform for the upper-layer second microstructure array, ensuring overall optical efficiency.

[0012] In one possible implementation, the first preset height is 7.8 μm and the second preset height is 6 μm.

[0013] Compared with existing technologies, by adopting the above technical solution, under this height combination, by scanning the side length (0.5~2.5μm), the first microstructure array can provide a phase delay covering 0~2π, while the second microstructure array can provide additional compensation phase. Both heights are controlled within a reasonable aspect ratio range, avoiding processing difficulties and structural collapse risks caused by excessive structure height, and achieving the best balance between phase control capability and process feasibility.

[0014] In one possible implementation, the long-wave infrared band is 8-12 μm.

[0015] This invention also provides a method for fabricating a long-wave infrared double-layer uninterrupted stacked achromatic superlens, applied to the aforementioned long-wave infrared double-layer uninterrupted stacked achromatic superlens, comprising the following steps: Step S1: Construct a first phase library and a second phase library. The first phase library contains first phase response data of the first microstructure array at multiple characteristic wavelengths under different structural parameters. The second phase library contains second phase response data of the second microstructure array at multiple characteristic wavelengths under different structural parameters. Step S2, first stage optimization: Based on the center wavelength, calculate the target phase of the superatom at each of the characteristic wavelengths according to the target phase distribution formula, and perform error matching between the target phase and the first phase response data, and select the structural parameter with the smallest error as the structural parameter of the first microstructure array; Step S3, Second stage optimization: An optimization algorithm is used to perform collaborative optimization on a set of phase constants. Each phase constant corresponds to a characteristic wavelength. In each optimization individual, the target phase distribution formula is updated according to the current phase constant. Based on the updated target phase distribution formula, the optimal structural parameters of the second microstructure array are matched for each superatom in the second phase library. At the same time, the global weighted phase error is calculated. Step S4: Iteratively execute step S3 until the global weighted phase error converges, and output the optimal combination of phase constants and the structural parameters of the second microstructure array for fabrication of the long-wave infrared double-layer uninterrupted stacked achromatic superlens.

[0016] The method for fabricating a long-wave infrared double-layer uninterrupted stacked achromatic superlens of the present invention has the following advantages compared with the prior art: This invention fully utilizes the rich phase library of the upper and lower microstructure arrays, whose sizes can be independently varied, to optimize structural parameters, significantly improving design flexibility and achieving better achromatic performance under polarization-insensitive conditions. Furthermore, by introducing an optimization algorithm in the second stage to collaboratively optimize the phase constants of multiple characteristic wavelengths and using the global weighted phase error as the fitness function for iterative convergence, it can effectively escape local optima and obtain globally optimal structural parameters, ensuring that the superlens simultaneously meets the target phase distribution and dispersion compensation requirements across a wide wavelength range.

[0017] In one possible implementation, the characteristic wavelengths in step S1 are 8μm, 9μm, 10μm, 11μm and 12μm, respectively.

[0018] Compared with existing technologies, the above-mentioned technical solution can uniformly cover the working band of the long-wave infrared band with five characteristic wavelengths, which can fully characterize the dispersion characteristics of the superlens in the broadband range. Using these discrete characteristic wavelengths as the design benchmark, and then using the optimization algorithm for interpolation compensation, stable achromatic focusing performance can be guaranteed in the continuous working band.

[0019] In one possible implementation, in step S2, the coordinate data of the grid position where the superatom is located is obtained, and the target phase is calculated based on the coordinate data, the characteristic wavelength, the preset focal length, and the phase constant corresponding to the characteristic wavelength.

[0020] Compared with existing technologies, the above-mentioned technical solution can independently calculate the required spatial phase distribution for each characteristic wavelength through the target phase distribution formula, providing a clear physical target for subsequent phase library matching and global weighted phase error calculation, and is the theoretical basis for realizing broadband achromatic focusing.

[0021] In one possible implementation, in step S3, the global weighted phase error is calculated based on the position weight of each superatom position in the superlens mesh, the actual phase value matched from the second phase library, and the target phase calculated by the target phase distribution formula.

[0022] Compared with existing technologies, the above-mentioned technical solution can quantify the sum of the deviations between the actual phase value and the target phase at all characteristic wavelengths and all superatomic positions as the global weighted phase error. Using this global weighted phase error as the fitness function in the optimization algorithm can guide the search process to converge toward the direction of optimal phase matching, thereby ensuring that the final design has high-precision phase control capability in both spatial and wavelength dimensions.

[0023] In one possible implementation, the location weights are configured such that the weight of the central region of the superlens is greater than the weight of the edge region, and the central region, which occupies 70% of the aperture, has a weight of 10.0, while the edge region, which occupies 30% of the aperture, has a weight of 1.0.

[0024] Compared with existing technologies, the above technical solution takes into account that the central region plays a decisive role in the quality and energy concentration of the focused spot in the imaging optical system. By giving the central region a higher weight, the optimization algorithm will prioritize the phase matching accuracy of the superatoms in the central region, thereby significantly improving the peak intensity and imaging clarity at the focal point. At the same time, the edge region can still be effectively optimized, achieving a balance between overall focusing performance and computational efficiency.

[0025] In one possible implementation, the optimization algorithm used in step S3 is a genetic algorithm or a particle swarm optimization algorithm, and when a genetic algorithm is used, the parameters are configured as follows: the population size is set to 120, the number of evolution iterations is set to 80 generations, and the optimization range of the phase constant is set to [-π, π].

[0026] Compared with existing technologies, the above-mentioned technical solution can achieve stable convergence of the global weighted phase error within a reasonable time overhead by setting parameters, and output the optimal combination of phase constants and the structural parameters of the second microstructure array. At the same time, limiting the phase constants to the range of [-π, π] conforms to the phase periodicity characteristics, avoids redundant search, and improves optimization efficiency. Attached Figure Description

[0027] Figure 1 This is a front view schematic diagram of the long-wave infrared double-layer uninterrupted stacked achromatic superlens of the present invention; Figure 2 This is a schematic diagram of the 45-degree side view of the long-wave infrared double-layer uninterrupted stacked achromatic superlens of the present invention. Figure 3 This is a flowchart of the preparation method of the present invention; Figure 4 This is a schematic diagram of the phase response data of microstructure arrays with different side lengths at different characteristic wavelengths according to the present invention. Figure 4 In the diagram, (a) represents the phase response of the first microstructure array with different side lengths at different characteristic wavelengths. Figure 4 In the figure, (b)-(f) represent the phase response of the first and second microstructure arrays with different side lengths in the 8-12μm long-wave infrared band; Figure 5 The xz-plane light field intensity diagrams of the long-wave infrared double-layer uninterrupted stacked achromatic superlens of the present invention at different wavelengths are shown. Figure 6 The following are the focusing efficiency and diffraction efficiency curves of the long-wave infrared double-layer uninterrupted stacked achromatic superlens of the present invention at different wavelengths. Figure 7 This is a focal length distribution curve of the long-wave infrared double-layer uninterrupted stacked achromatic superlens of the present invention. Explanation of reference numerals in the attached figures: 1. Substrate; 2. First silicon rectangular pillar; 3. Filling layer; 4. Second silicon rectangular pillar. Detailed Implementation

[0028] First, those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention. Those skilled in the art can make adjustments as needed to adapt to specific application scenarios.

[0029] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0030] See Figure 1 and Figure 2 This invention discloses a long-wave infrared double-layer uninterrupted stacked achromatic superlens, comprising: Substrate 1; A first microstructure array is disposed on the upper surface of substrate 1. The first microstructure array includes a plurality of first silicon rectangular pillars 2 with a first preset height. A filling layer 3 is composed of a filling material filling the gaps between each first silicon rectangular pillar 2. The upper surface of the filling layer 3 is flush with the upper surface of each first silicon rectangular pillar 2. The filling material is magnesium fluoride. A second microstructure array is disposed on the upper surface of the filling layer 3. The second microstructure array includes multiple second silicon rectangular pillars 4 with a second preset height. Achromatic focusing is performed in the long-wave infrared band by each first silicon rectangular pillar 2 and each second silicon rectangular pillar 4. Should Figure 1 and Figure 2 The example only shows a simplified structure of a single first silicon rectangular pillar 2 and a single second silicon rectangular pillar 4. In actual applications, the first silicon rectangular pillar 2 and the second silicon rectangular pillar 4 can be laid out in a plane.

[0031] In this embodiment of the invention, substrate 1 is a square barium fluoride substrate with a side length of Based on the aperture of the superlens, in this embodiment, the aperture of the superlens, i.e., the distribution area of ​​the first microstructure array, is 200μm × 200μm. Both the first and second microstructure arrays are arranged periodically with a period of 2.8μm. The height of the first silicon rectangular pillar 2... It is 7.8 μm, and its side length is The scanning variation is within the range of 0.5~2.5μm; the height of the second silicon rectangular pillar 4 It is 6μm, and its side length is Similarly, the magnesium fluoride filling layer 3, which is composed of magnesium fluoride as the filling material, completely fills the gap between the first silicon rectangular pillars 2. Its upper surface is precisely flush with the upper surface of the first silicon rectangular pillars 2 through chemical mechanical polishing or etching back process, so as to provide a flat substrate for the fabrication of the second microstructure array.

[0032] In this embodiment of the invention, the substrate 1 is made of barium fluoride, the first preset height of the first silicon rectangular pillar 2 is 7.8 μm, the second preset height of the second silicon rectangular pillar 4 is 6 μm, and the long-wave infrared band is 8-12 μm. It should be noted that the above-mentioned size parameters (height, period, aperture) and material selection (barium fluoride substrate 1, silicon rectangular pillar, magnesium fluoride filling layer 3) are all optimized solutions for the 8-12 μm long-wave infrared band. In actual implementation, each parameter can be appropriately adjusted on the premise of ensuring that the phase modulation range covers 0~2π. However, barium fluoride and silicon have high transmittance and high refractive index contrast in the long-wave infrared band, and magnesium fluoride, as a low refractive index filling material, can effectively reduce interface reflection. These material selections have significant advantages.

[0033] See Figure 3This invention also discloses a method for fabricating a long-wave infrared double-layer uninterrupted stacked achromatic superlens, applied to the aforementioned long-wave infrared double-layer uninterrupted stacked achromatic superlens, comprising the following steps: Step S1: Construct a first phase library and a second phase library. The first phase library contains first phase response data of the first microstructure array at multiple characteristic wavelengths under different structural parameters. The second phase library contains second phase response data of the second microstructure array at multiple characteristic wavelengths under different structural parameters. Step S2, first stage optimization: Based on the center wavelength, calculate the target phase of the superatom at each characteristic wavelength according to the target phase distribution formula, and perform error matching between the target phase and the first phase response data. Select the structural parameter with the smallest error as the structural parameter of the first microstructure array. Step S3, second stage optimization: The optimization algorithm is used to perform collaborative optimization on a set of phase constants. Each phase constant corresponds to a characteristic wavelength. In each optimization individual, the target phase distribution formula is updated according to the current phase constant. Based on the updated target phase distribution formula, the optimal structural parameters of the second microstructure array are matched for each superatom in the second phase library. At the same time, the global weighted phase error is calculated. Step S4: Iterate through step S3 until the global weighted phase error converges to less than the target value, and output the converged combination of phase constants and the structural parameters of the second microstructure array.

[0034] In this embodiment of the invention, in step S1, electromagnetic simulation is performed using the Finite-Difference Time-Domain (FDTD) method or Rigorous Coupled-Wave Analysis (RCWA). For the first phase library: the height of the first silicon rectangular pillar 2 is fixed at 7.8 μm, and its side length is scanned at equal intervals from 0.5 μm to 2.5 μm (e.g., step size 0.05 μm). The transmission phase response at five characteristic wavelengths of 8 μm, 9 μm, 10 μm, 11 μm, and 12 μm is calculated and recorded as the first phase response data. For the second phase library: the height of the second silicon rectangular pillar 4 is fixed at 6 μm, and considering that the first microstructure array has been determined (i.e., the first microstructure array and its filling layer 3 already exist), the side length of the second silicon rectangular pillar 4 is scanned (also in the range of 0.5~2.5 μm), and the overall phase response (including the total phase delay of the upper and lower silicon rectangular pillars and the filling layer 3) at the same set of characteristic wavelengths is calculated and recorded as the second phase response data. See details below. Figure 4 , Figure 4 In the diagram, (a) represents the phase response of the first microstructure array with different side lengths at different characteristic wavelengths. Figure 4 In the diagram, (b)-(f) represent the phase response of the first and second microstructure arrays with different side lengths in the 8-12 μm long-wave infrared band.

[0035] In this embodiment of the invention, the center wavelength is selected as 10 μm, and the preset focal length is... The aperture of the superlens (200 μm) is 600 μm. First, the aperture of the superlens is divided into discrete grid points, each grid point corresponding to a superatom (i.e., a silicon rectangular pillar and its surrounding periodic units). The grid spacing is the period of 2.8 μm. For each superatom position... The target phase at a wavelength of 10 μm is calculated based on the target phase distribution formula. Then, the phase response data corresponding to all side lengths in the first phase library are traversed to find the structural parameter whose actual phase value is closest to the target phase at a center wavelength of 10μm. This side length is used as the side length of the first silicon rectangular pillar 2 at that position. By traversing all grid positions, the initial design of the first microstructure array is completed.

[0036] In this embodiment of the invention, the core of the second-stage optimization lies in introducing a set of variable phase constants. , , , , These correspond to five characteristic wavelengths, and each optimized individual contains these five phase constants. The initial values ​​can be set to 0 or random values. For each optimized individual, the updated target phase distribution formula is first used (i.e., substituted into the current...). (Value) Recalculate the target phase of each superatom at five characteristic wavelengths. Then, for each superatomic position, a search is performed in the second phase library to find the side length of the second silicon rectangular pillar that minimizes the overall error between the actual phase values ​​of the five characteristic wavelengths and the target phase. This matching process can use the weighted least squares method. The minimum global weighted phase error at the superatomic position is recorded, and the global weighted phase errors of all superatomic positions are accumulated according to the characteristic wavelength and spatial position, and multiplied by the position weight. The global weighted phase error of the optimized individual is obtained. The global weighted phase error As a fitness function, it is used to evaluate the quality of an individual for optimization.

[0037] In this embodiment of the invention, in step S4, a genetic algorithm is used to perform iterative optimization. The population size is set to 120 individuals, and the genes of each individual are encoded as five phase constants (with values ​​ranging from -π to π). In each generation, the global weighted phase error of each individual is calculated. Excellent individuals are selected for crossover and mutation in order of increasing global weighted phase error to generate the next generation population. After 80 generations of evolution, the global weighted phase error tends to converge. At this time, the combination of phase constants corresponding to the globally optimal individual is output, as well as the side length distribution of the second microstructure array matched under the optimal combination of phase constants. Thus, the complete design of the long-wave infrared double-layer uninterrupted stacked achromatic superlens is completed.

[0038] In this embodiment of the invention, the target phase distribution formula used in step S2 is: ; in, Indicates the characteristic wavelength; Indicates the target phase; This represents the x-coordinate of the grid position where the superatom is located; This represents the y-coordinate of the grid position where the superatom is located; Indicates the preset focal length; This represents the phase constant corresponding to the characteristic wavelength.

[0039] In this embodiment of the invention, the formula for calculating the global weighted phase error in step S3 is as follows: ; in, This represents the globally weighted phase error; Represents the first in the superlens mesh line, number The superatomic positions of the column; This represents the actual phase value obtained from the matching of the second phase library; This represents the target phase calculated according to the target phase distribution formula; This indicates the position weight.

[0040] In this embodiment of the invention, the configuration standard for position weights is that the weight of the central region of the superlens is greater than the weight of the edge region, and the central region, which occupies 70% of the aperture, has a weight of 10.0, while the edge region, which occupies 30% of the aperture, has a weight of 1.0.

[0041] In this embodiment of the invention, the optimization algorithm used in step S3 is a genetic algorithm or a particle swarm optimization algorithm. When a genetic algorithm is used, the parameters are configured as follows: the population size is set to 120, the number of evolution iterations is set to 80 generations, and the optimization range of the phase constant is set to [-π, π].

[0042] In this embodiment of the invention, to further verify the technical effect of the method of the present invention, a simulation was performed on the long-wave infrared double-layer uninterrupted stacked achromatic superlens designed and prepared using the above method. Figure 5 The light field intensity distribution in the xz plane of this long-wave infrared double-layer stacked achromatic superlens at different wavelengths (8μm, 9μm, 10μm, 11μm, 12μm) is shown. It can be seen that the focused light spot of each characteristic wavelength is located near the preset focal length. Figure 6 The curves showing the changes in focusing efficiency and diffraction efficiency with wavelength are given. Figure 6 The average diffraction efficiency is 94.69%, and the average focusing efficiency is 67.2%. Figure 7 The relationship between the actual focal length and the characteristic wavelength was shown, and the maximum focal length offset coefficient was calculated to be only 1.7%, indicating that the long-wave infrared double-layer uninterrupted stacked achromatic superlens prepared by the method of the present invention has excellent achromatic performance while maintaining high efficiency.

[0043] In this embodiment of the invention, as an alternative implementation, substrate 1 can also be made of other materials that are transparent in the long-wave infrared band, such as zinc selenide, chalcogenide glass, etc., but barium fluoride is preferred due to its extremely low absorption coefficient. The cross-sectional shape of the silicon rectangular pillar is not limited to a square, and can also be circular, cross-shaped or other isotropic shapes to meet the polarization insensitivity requirement. In addition to magnesium fluoride, other dielectric materials with a refractive index lower than silicon and transparent in the long-wave infrared band, such as yttrium fluoride, ytterbium fluoride, etc., can also be used as filling materials. The preset height of the upper and lower microstructure arrays can also be finely adjusted on the premise of ensuring the phase modulation range. For example, the first preset height can be selected between 7.5 and 8.0 μm, and the second preset height can be selected between 5.8 and 6.2 μm. These alternative solutions all fall within the protection scope of this invention.

[0044] In the description of this invention, the references to "one embodiment," "some embodiments," "in this embodiment," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0045] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for fabricating a long-wave infrared double-layer uninterrupted stacked achromatic superlens, characterized in that, This is applied to a long-wave infrared double-layer uninterrupted stacked achromatic superlens, the long-wave infrared double-layer uninterrupted stacked achromatic superlens comprising: A substrate (1); A first microstructure array is disposed on the upper surface of the substrate (1), the first microstructure array comprising a plurality of first silicon rectangular pillars (2) having a first preset height. A filling layer (3) is formed by filling material filling the gap between each of the first silicon rectangular pillars (2). The upper surface of the filling layer (3) is flush with the upper surface of each of the first silicon rectangular pillars (2). The filling material in the filling layer (3) is magnesium fluoride. A second microstructure array is disposed on the upper surface of the filling layer (3). The second microstructure array includes a plurality of second silicon rectangular pillars (4) with a second preset height. Achromatic focusing is performed in the long-wave infrared band by each of the first silicon rectangular pillars (2) and each of the second silicon rectangular pillars (4). The method for fabricating the long-wave infrared double-layer uninterrupted stacked achromatic superlens includes the following steps: Step S1: Construct a first phase library and a second phase library. The first phase library contains first phase response data of the first microstructure array at multiple characteristic wavelengths under different structural parameters. The second phase library contains second phase response data of the second microstructure array at multiple characteristic wavelengths under different structural parameters. Step S2, first stage optimization: Based on the center wavelength, calculate the target phase of the superatom at each of the characteristic wavelengths according to the target phase distribution formula, and perform error matching between the target phase and the first phase response data, and select the structural parameter with the smallest error as the structural parameter of the first microstructure array; Step S3, Second stage optimization: An optimization algorithm is used to perform collaborative optimization on a set of phase constants. Each phase constant corresponds to a characteristic wavelength. In each optimization individual, the target phase distribution formula is updated according to the current phase constant. Based on the updated target phase distribution formula, the optimal structural parameters of the second microstructure array are matched for each superatom in the second phase library. At the same time, the global weighted phase error is calculated. Step S4: Iteratively execute step S3 until the global weighted phase error converges, and output the optimal combination of phase constants and the structural parameters of the second microstructure array for fabrication of the long-wave infrared double-layer uninterrupted stacked achromatic superlens. In step S3, the global weighted phase error is calculated based on the position weight of each superatom position in the superlens mesh, the actual phase value matched from the second phase library, and the target phase calculated by the target phase distribution formula.

2. The method for fabricating a long-wave infrared double-layer uninterrupted stacked achromatic superlens according to claim 1, characterized in that, The substrate (1) is made of barium fluoride.

3. The method for fabricating a long-wave infrared double-layer uninterrupted stacked achromatic superlens according to claim 1, characterized in that, The first preset height is 7.8 μm, and the second preset height is 6 μm.

4. The method for fabricating a long-wave infrared double-layer uninterrupted stacked achromatic superlens according to claim 1, characterized in that, The long-wave infrared band is 8-12μm.

5. The method for fabricating a long-wave infrared double-layer uninterrupted stacked achromatic superlens according to claim 1, characterized in that, The characteristic wavelengths in step S1 are 8μm, 9μm, 10μm, 11μm and 12μm, respectively.

6. The method for fabricating a long-wave infrared double-layer uninterrupted stacked achromatic superlens according to claim 1, characterized in that, In step S2, the coordinate data of the grid position where the superatom is located is obtained, and the target phase is calculated based on the coordinate data, the characteristic wavelength, the preset focal length, and the phase constant corresponding to the characteristic wavelength.

7. The method for fabricating a long-wave infrared double-layer uninterrupted stacked achromatic superlens according to claim 1, characterized in that, The configuration standard for the position weights is that the weight of the central region of the superlens is greater than the weight of the edge region, and the central region is the region that occupies 70% of the aperture, with a weight of 10.0, while the edge region is the region that occupies 30% of the aperture, with a weight of 1.

0.

8. The method for fabricating a long-wave infrared double-layer uninterrupted stacked achromatic superlens according to claim 1, characterized in that, The optimization algorithm used in step S3 is a genetic algorithm or a particle swarm optimization algorithm. When a genetic algorithm is used, the parameters are configured as follows: the population size is set to 120, the number of evolution iterations is set to 80 generations, and the optimization range of the phase constant is set to [-π, π].

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