Particle swarm optimization algorithm-based stretchable super-structure lens with high infrared band focusing efficiency and adjustable focus

Abstract

The invention discloses a stretchable super-structure lens with an adjustable focus and high infrared band focusing efficiency based on a particle swarm optimization algorithm. The stretchable metamaterial lens is composed of periodic structures, each periodic structure comprises a substrate (1), and a plurality of metamaterial lens basic unit structures (2) are stacked on the substrates (1). The substrate (1) is made of a stretchable material PDMS, and the meta-lens basic unit structure (2) is made of a GaN material. The super-structure lens is simple in structure, simple in preparation process and low in material cost, the super-structure lens achieves the stretchable effect with the period ranging from 450 nm to 650 nm within the wave band of 780 nm to 880 n, the obtained focal lengths are 50.38 microns, 69.05 microns, 88.45 microns, 107.34 microns and 130.03 microns respectively, and the expected target focal length can be well achieved. Under the wave band of 780 nm to 880 nm, incident light of different wavelengths can be concentrated on one point, the super-structure lens shows good focusing performance, the super-structure lens can reach the focusing efficiency of 60% or above within the wave band of 780 nm to 880 nm, and the super-structure lens has a great progress space compared with an existing stretchable super-structure lens; the focus-adjustable stretchable super-structure lens provides an effective method for application of stretchable devices, and provides a new direction for design of future super-structure lenses, such as application in next-generation three-dimensional imaging, holographic projection and astronomical telescope systems.

Description

Technical Field

[0001] This invention belongs to the field of focus-adjustable stretchable metalenses, specifically relating to a focus-adjustable stretchable metalens with high focusing efficiency in the infrared band based on particle swarm optimization algorithm and its design method. Background Technology

[0002] Traditional lenses, used in cameras, microscopes, and telescopes, are made of glass or other transparent plastic materials. They have a curved surface and a fixed focal length. Everyday cameras consist of many lenses to address chromatic aberration or other aberrations and to provide the energy for zooming. Therefore, to achieve good image quality, traditional imaging systems are inevitably large, bulky, and inefficient. With the gradual development of metasurfaces, we have gained a more powerful method of phase control. By changing the shape and size of the structure designed on the substrate, we can adjust the amplitude, phase, and polarization of the light beam. With the discovery and verification of PDMS (Potentially Spectrophotometers), we can gradually achieve corresponding focus-adjustable functions by stretching PDMS. Using relevant technologies, we have designed a stretchable metasurface lens with high focusing efficiency and adjustable focus in the infrared band.

[0003] Based on the phase control of metasurfaces and the stretchability of PDMS, this invention designs a stretchable metalens with high focusing efficiency in the infrared band based on particle swarm optimization algorithm. The structure includes a substrate (1), on which many basic metalens structural units (2) are stacked. Both the substrate (1) and the basic unit structure (2) adopt a cuboid structure. This invention has a simple structure and a simple fabrication process, making it easier to manufacture. In the 780nm-880nm band, this metalens achieves a stretchable effect with a period from 450nm to 650nm, and the obtained focal lengths are 50.38μm, 69.05μm, 88.45μm, 107.34μm, and 130.03μm, which can well achieve the expected target focal length. In the 780nm-880nm wavelength range, incident light of different wavelengths can be focused onto a single point, and this metalens exhibits excellent focusing performance. Within the 780nm-880nm wavelength range, this metalens can achieve a focusing efficiency of over 60%, representing a significant improvement over previous stretchable metalenses. This focus-adjustable stretchable metalens provides an effective method for the application of stretchable devices and offers a new direction for the design of future metalenses, such as applications in next-generation 3D imaging, holographic projection, and astronomical telescope systems. Summary of the Invention

[0004] This invention presents a high-focusing-efficiency, focus-adjustable stretchable metalens in the infrared band based on particle swarm optimization algorithm and its design method. This design method and the realization of the metalens provide an effective approach for the application of stretchable devices and offer new directions for the design of future metalenses, such as applications in next-generation three-dimensional imaging, holographic projection, and astronomical telescope systems.

[0005] The objective of this invention is achieved as follows:

[0006] To achieve the objective of this invention, the following technical means are used to realize a metalens: a stretchable metalens with adjustable focus and high focusing efficiency in the infrared band based on a particle swarm optimization algorithm. The periodic structure includes a substrate, on which multiple metalens unit structures are composed, and the metalens unit structure is a cube structure.

[0007] Furthermore, a periodic array is formed using the aforementioned meta-lens structure units.

[0008] Furthermore, the height of the aforementioned meta-lens is H, where H = 1.5 μm, and the length L ranges from 0.05 μm to 0.25 μm. Similarly, the width W ranges from 0.05 μm to 0.25 μm.

[0009] Furthermore, with varying stretching effects on the substrate, the substrate periods were 0.45 μm, 0.50 μm, 0.55 μm, 0.60 μm, and 0.65 μm, respectively.

[0010] Furthermore, the substrate of this metalens is made of stretchable PDMS material, and the unit structure of the metalens is made of GaN.

[0011] Furthermore, after selecting the material, the performance parameters of the metalens unit structure are optimized using the finite difference time-domain method. Once the expected performance is achieved (the metalens unit structure can satisfy a phase delay of (2π / 2) for the corresponding incident wavelength), the desired performance is achieved. The metalens structure unit is constructed based on the wavefront reconstruction equation. Then, the position distribution and size of the corresponding metalens structure unit are obtained by the particle swarm optimization algorithm. Finally, the metalens is constructed, simulated and its function is verified based on the data.

[0012] Compared with existing technologies, this invention has the following advantages: the metalens unit uses a cuboid directly stacked on the substrate, simplifying the fabrication process and enabling fabrication via nano-imprinting. Furthermore, by controlling the height of the cuboid, the phase delay performance of the metalens can be better achieved. Simultaneously, due to the relatively simple structure, the final metalens has a relatively high integration density. Attached Figure Description

[0013] Figure 1 This is a three-dimensional structural diagram of a stretchable metalens with adjustable focus and high focusing efficiency in the infrared band.

[0014] Figure 2 This is a structural diagram and top view of a stretchable metalens unit with adjustable focus and high focusing efficiency in the infrared band.

[0015] Figure 3 This is a focusing effect diagram of a stretchable meta-lens with adjustable focus and high focusing efficiency in the infrared band, located in the 780nm-880nm range.

[0016] Figure 4 The image shows the xy focal energy distribution and full width at half maximum (FWHM) plot of a stretchable metalens with adjustable focal point and high focusing efficiency in the infrared band.

[0017] Figure 5 (a) is a graph showing the relationship between the focal length and full width at half maximum (FWHM) of this structure in the 780nm-880nm range; Figure 5 (b) is a graph showing the average focal length, average transmittance, and average focusing efficiency.

[0018] Figure 6 (a) is a graph showing the relationship between the focal length and period of this structure in the 780nm-880nm range; Figure 5 (b) is a graph showing the relationship between focal length and wavelength in the 780nm-880nm range. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0020] like Figure 1 , 2 As shown, this invention proposes a stretchable metalens with high focusing efficiency in the infrared band based on a particle swarm optimization algorithm. The metalens includes a substrate (1), on which a multi-layered meta-structural unit (2) is placed, forming the stretchable metalens with high focusing efficiency in the infrared band. The basic unit structure of the metalens is composed of cuboids. In this invention, with subsequent gradual stretching of the PDMS, the radius of the metalens gradually becomes 13.5 μm, 15 μm, 16.5 μm, 18 μm, and 19.5 μm; the specific unit structure on the metalens is determined by the structure (2).

[0021] In this invention, the meta-lens structure unit (2) is located at the center of the substrate (1). As the substrate (1) is gradually stretched, the period of the substrate (1) gradually becomes a cuboid with P=0.45μm, 0.50μm, 0.55μm, 0.60μm, and 0.65μm. The meta-lens unit structure (2) is a cube structure with a height of H=1.5μm and a length L ranging from 0.05μm to 0.25μm. Similarly, the width W ranges from 0.05μm to 0.25μm.

[0022] The material of the meta-lens structure unit (2) is GaN. Considering the stretchability of the material, PDMS is selected as the material of the substrate structure unit (1).

[0023] Based on the simulation calculation of transmittance and corresponding optimization, the height of the meta-lens structure unit (2) is selected as H=1.5μm.

[0024] The basic structural design principle of a metalens is as follows: Utilizing the PB phase principle, the phase of the incident wave is modulated by changing the dimensions of the metalens's structural units. The incident wave requiring phase modulation is determined by the optical path difference between each point on the metalens's surface and the focal point. The core formula is... , ,in, f represents the incident wavelength, and f represents the focal length. Let (x, y) represent the phase difference, and (x, y) represent the position coordinates of the metalens unit. In the calculation, the surface of the metalens is divided into several periods using the finite-time difference method. To simplify the calculation time, only the position of the center point in each period is taken and substituted into the above formula to calculate the phase value. When the phase adjustment of all basic unit structures in the metalens satisfies the above formula (1.1), the metalens can achieve focusing at the focal point.

[0025] The fabrication process of this metalens is as follows: After selecting the material structure, the basic structural unit of the metalens can be simulated and optimized using the finite-domain time-difference method (FDTD). Through structural optimization, the phase delay can be achieved to 2... Then, the basic structural unit (2) of the metalens is constructed according to equation (1.1). Subsequently, the position of each basic structure of the metalens is calculated by the particle swarm optimization algorithm, and the metalens is constructed according to this position.

[0026] like Figure 3The image shows the focusing efficiency of a high-focusing, adjustable, stretchable metalens in the infrared band within the 780nm-880nm range, with focal lengths of 50.38μm, 69.05μm, 88.45μm, 107.34μm, and 130.03μm. The image demonstrates that this metalens exhibits excellent focus adjustment. For the smallest focal length, this metalens can achieve a stretching effect of up to 160%.

[0027] like Figure 4 As shown in the figure, the xy focal energy distribution and half-maximum width at half-maximum (FWHM) plot of the stretchable metalens with high focusing efficiency in the infrared band are shown. It can be seen from the figure that the stretchable metalens has good imaging capabilities.

[0028] Figure 5 (a) is a graph showing the relationship between the focal length and full width at half maximum (FWHM) of this structure in the 780nm-880nm range. As can be seen from the graph, the focal length gradually decreases while the FWHM gradually increases with increasing wavelength. Figure 5 (b) is a graph showing the average focal length, average transmittance, and average focusing efficiency. It can be seen from the graph that as the stretching distance increases, the focal length of the meta-lens gradually increases, and during the stretching process, the focusing efficiency and transmittance of the meta-lens both exceed 50% and 95%, respectively.

[0029] Figure 6 (a) is a graph showing the relationship between the focal length and period of this structure in the 780nm-880nm range. Under the condition of constant incident wavelength, it can be seen from the graph that the focal length gradually decreases as the stretching distance increases; Figure 5 (b) shows the relationship between focal length and wavelength in the 780nm-880nm range. Under the condition of constant stretching period, it can be seen that the focal length of the metalens gradually decreases as the wavelength increases.

[0030] It should be noted that although the embodiments described above are illustrative, they are not intended to limit the invention. Therefore, the invention is not limited to the specific embodiments described above. Any other embodiments obtained by those skilled in the art under the guidance of this invention without departing from its principles are considered to be within the protection scope of this invention.

Claims

1. A high-focusing-efficiency, focus-adjustable stretchable metalens for the infrared band based on particle swarm optimization algorithm. The high-focusing-efficiency, focus-adjustable stretchable metalens is characterized by comprising a substrate (1), on which an infrared-band focus-adjustable metalens composed of multiple metalens structural units (2) is disposed, wherein the metalens structural unit (2) has a cubic structure.

2. The high-focusing-efficiency, focus-adjustable stretchable metalens based on particle swarm optimization algorithm according to claim 1, characterized in that: The complex array is composed of the meta-lens structure unit (2).

3. A high-focusing-efficiency, focus-adjustable stretchable metalens based on particle swarm optimization algorithm according to any one of claims 1-2, characterized in that: The meta-lens structure unit (2) has a height H = 1.5 μm, a length L ranging from 0.05 μm to 0.25 μm, and a width W ranging from 0.05 μm to 0.25 μm.

4. A stretchable metalens with adjustable focus and high focusing efficiency in the infrared band based on particle swarm optimization algorithm, as described in any one of claims 1-2, characterized in that: The periodicity of the substrate (1) is 0.45μm-0.65μm.

5. A stretchable metalens with adjustable focus and high focusing efficiency in the infrared band based on particle swarm optimization algorithm according to claims 3-4, characterized in that: The substrate (1) is made of PDMS, and the meta-lens structure unit (2) is made of GaN.

6. The design method of a stretchable metalens with high focusing efficiency in the infrared band based on particle swarm optimization algorithm according to claim 1, wherein the design method is as follows: after selecting the metalens material and the basic unit structure of the metalens, the performance parameters of the basic structural unit of the metalens can be optimized by simulation using the finite difference time-domain method, so that the structural unit can meet the requirement of a phase delay of 2. First, the metalens structure unit is constructed based on the wavefront reconstruction equation. After the metalens structure unit is constructed, the position and size of the metalens structure unit (2) are calculated according to the particle swarm optimization algorithm. Then, the overall metalens is constructed based on the phase and size of each obtained metalens unit structure.

7. A stretchable metalens with adjustable focus and high focusing efficiency in the infrared band based on particle swarm optimization algorithm according to claim 1, characterized in that: Between 780nm and 880nm, this meta-lens achieves a stretchable effect with a period ranging from 450nm to 650nm, and the resulting focal lengths are 50.38μm, 69.05μm, 88.45μm, 107.34μm, and 130.03μm, which can well achieve the expected target focal length. In the 780nm-880nm wavelength range, this metalens achieves a focusing efficiency of over 60%, representing a significant improvement over previous stretchable metalenses. This focus-adjustable stretchable metalens provides an effective method for the application of stretchable devices and offers new directions for future metalens design, such as applications in next-generation 3D imaging, holographic projection, and astronomical telescope systems.

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