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Multilayer-superstructure-surface-based method for constructing broadband achromatic super-structural optical lens group

A technology of metasurfaces and construction methods, applied in optical components, instruments, optics, etc., can solve problems such as low convergence efficiency, small numerical aperture, and complex metaunit construction.

Active Publication Date: 2019-10-25
NANJING UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, the existing achromatic planar metalenses are mainly based on a single-layer metaplane, and there are problems such as complex construction of metaunits, relatively small numerical aperture, and low convergence efficiency.

Method used

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  • Multilayer-superstructure-surface-based method for constructing broadband achromatic super-structural optical lens group
  • Multilayer-superstructure-surface-based method for constructing broadband achromatic super-structural optical lens group
  • Multilayer-superstructure-surface-based method for constructing broadband achromatic super-structural optical lens group

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0148] 1. Unit construction

[0149] Construct superunits working between 400nm and 700nm. The unit has two structures: (1) dielectric gallium nitride (GaN) cylinder, located in dielectric sapphire (Al 2 o 3 ) above the substrate, such as image 3 (a) shown; (2) dielectric GaN cylinder is wrapped in dielectric Al 2 o 3 inside the substrate, such as image 3 (d) shown. The construction requirements are: the transmission coefficient is greater than 0.9 in the entire frequency band, and the compensation phase covers 0-2π. A transmission coefficient greater than 0.9 is not a necessary condition for this construction method, but in order to improve the transmission efficiency of the entire device, it is recommended to select a superunit with a relatively high transmission coefficient. By optimizing the period of the unit, the height of the dielectric column, and the radius of the dielectric column, two unit structures that meet the requirements are finally constructed: the pe...

Embodiment 2

[0156] The ideal focal length f of the double-layer achromatic lens group to be constructed g = 36 μm. Select the focusing metalens sample library GroupⅠ and the diverging metalens sample library GroupⅡ, and determine that the distance variation range between the optimal focusing metalens and the diverging metalens is 0.5μm≤d≤5μm, and then follow step 4 to solve The optimal value of the lens group of the chromatic aberration relationship, that is, the combination of the best focusing metalens and the diverging metalens that satisfy achromatic dispersion.

[0157] The programming completes the optimization solution process of formula (14), and finally obtains the focal length f of the focusing metalens 1 =15.6μm, the focal length f of the diverging metalens 2 =-26.7 μm, the distance d between the diverging metalens and the focusing metalens = 2 μm. Then, the focusing metalens and the diverging metalens are combined to form a double-layer broadband achromatic metalens group, ...

Embodiment 3

[0159] The ideal focal length f of the double-layer achromatic lens group to be constructed g = 36 μm. Select the focusing metalens sample library GroupⅠ and the diverging metalens sample library GroupⅢ, determine that the distance variation range between the optimal focusing metalens and the diverging metalens is 0.5μm≤d≤5μm, and then follow step 4 to solve The optimal value of the lens group of the chromatic aberration relationship, that is, the combination of the best focusing metalens and the diverging metalens that satisfy achromatic dispersion.

[0160] The programming completes the optimization solution process of formula (14), and finally obtains the focal length f of the focusing metalens 1 =15.6μm, the focal length f of the diverging metalens 2 =-26.7 μm, the distance d=2 μm between the diverging metalens and the focusing metalens, n 1 -n 5 The material of the dielectric layer is Al 2 o 3 , n 5 The thickness of the dielectric layer is 1 μm. Then, the focusing...

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Abstract

The invention discloses a multilayer-superstructure-surface-based method for constructing a broadband achromatic super-structural optical lens group. The method comprises: constructing a super unit and carrying out simulation to obtain a transmission coefficient and phase change curve of a uniform array corresponding to the super unit; constructing a focused super-structure lens and a divergent super-structure lens, generating a focused super-structure lens sample and a divergent super-structure lens sample, and calculating Abel constants of the focused super-structure lens sample and the divergent super-structure lens sample based on dispersion characteristics; solving an optimization problem to obtain the combination with the minimum dispersion of the focused super-structure lens and thedivergent super-structure lens; and then with full-wave simulation, acquiring dispersion characteristics of the broadband achromatic super-structural optical lens group, comparing the lens group witha single-layer dispersion super-structural optical lens, and evaluating the chromatic aberration improvement condition of the broadband achromatic super-structural optical lens group. Therefore, thecomplexity of processing of the broadband achromatic device is reduced and the integration and reliability of the broadband achromatic device are enhanced.

Description

technical field [0001] The invention belongs to the field of electromagnetic wave metamaterials, in particular to a construction method of a broadband achromatic metalens group based on a multilayer metasurface. Background technique [0002] Various types of lenses are widely used in radar imaging, optical imaging, photoelectric sensing and other fields. The recently emerging planar metalens uses a planar metasurface instead of a curved surface. Compared with traditional lenses, it can not only effectively eliminate spherical aberration, but also has the advantages of small size, strong integration, and batch processing and preparation using semiconductor technology. Therefore, it has attracted extensive attention in many application fields. In the early days, the design of planar metalenses generally only focused on one of the convergence efficiency, numerical aperture or working bandwidth, and the current design began to focus on two or more parameters. Recently, improvi...

Claims

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Application Information

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IPC IPC(8): G02B27/00
CPCG02B27/0012
Inventor 俞叶峰李帅帅李猛猛陈如山
Owner NANJING UNIV OF SCI & TECH
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