A method of realizing broadband achromatic metalens based on fork structure
A superlens and achromatic technology, applied in the field of optical metamaterials, can solve the problems of low focusing efficiency of superlenses, and achieve high focusing efficiency and high conversion efficiency
Active Publication Date: 2022-03-04
SOUTH CHINA NORMAL UNIVERSITY
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[0003] In view of this, in order to solve the problems of limited NA and low focusing efficiency of the superlens in the prior art, the present invention proposes a method for realizing a broadband achromatic superlens based on a fork structure, by controlling the handedness of nanorods of different wavelengths , then different wavelengths can achieve 0-2π phase coverage to focus on the same focus, and all wavelengths in between can be focused on the same focus; because each wavelength can cover 0-2π by controlling the rotation direction of the nanorods The phase change range will be able to break through the limitation of the aspect ratio of the wavelength unit structure based on the transmission phase chromatic aberration, and realize high-efficiency wide-band achromatic aberration
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[0021] The method of realizing the broadband achromatic superlens based on the fork structure in the present invention adopts FDTD simulation. The following implementation steps take the optimized structure with a waveband of 650-790nm and the 660nm and 780nm structures selected when optimizing a single structure as an example to illustrate the specific effects of the method of the present invention. The unit structure is Si (refractive index n=3.4), and the substrate is SiO 2 . When simulating a single structure, for the calculation of transmittance and phase difference, the light sources are TE and TM plane waves respectively, the periodic boundary conditions are selected for the x and y directions, and the PML boundary conditions are used for the z direction; for the calculation of the polarization conversion efficiency, the light source is selected For left-handed polarized light composed of two plane waves, periodic boundary conditions are selected for the x and y direct...
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Abstract
The invention discloses a method for realizing a wide-waveband achromatic superlens based on a fork structure, which belongs to the field of optical metamaterials. Firstly, the geometric structure of rod 1 and rod 2 is optimized so that the polarization conversion efficiency is the highest, and then the phase of rod 1 is passed. Information control wavelength λ 1 Focusing on the target focal point, the phase of rod 2 controls the wavelength λ 2 Focusing on the target focal point, the phase information of the fork structure composed of rod 1 and rod 2 controls the wavelength λ 1 nearby wavelength, λ 2 Near wavelength and wavelength λ 1 ‑λ 2 The wavelength in the broadband range is focused on the focal point of the target, so that the broadband chromatic aberration is eliminated. Finally, the metalens composed of the fork structure realizes high-efficiency broadband achromatic aberration, and the phase is controlled by rotating the structure. There is no requirement for the aspect ratio of the structure. Therefore, a metalens with a large numerical aperture can be designed, which solves the problems of large chromatic aberration, low focusing efficiency and small numerical aperture of the previously designed metalens.
Description
technical field [0001] The invention relates to the technical field of optical metamaterials, in particular to a method for realizing a broadband achromatic superlens based on a fork structure. Background technique [0002] Metasurface is a two-dimensional ultra-thin planar structure composed of many subwavelength structural units, which can change the phase, amplitude and polarization of light waves arbitrarily according to requirements, so as to achieve the regulation of light field. Based on the research of metasurface planar optics, it has broad application prospects in holographic imaging, vortex beams, deflectors, polarization conversion and control, and lens imaging. Chromatic aberration is a serious problem for the wideband focusing of metalens. Recently, a sub-area achromatic method has been proposed to control the focusing of different wavelengths through different areas, but this method cannot achieve broadband achromatic, and the efficiency is very low; in addit...
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IPC IPC(8): G02B1/00G02B27/00
CPCG02B1/002G02B27/0012G02B27/0075
Inventor 吴立军冯前斌陈俊逸李强吴杰鹏朱彦霖吴钰段尧明
Owner SOUTH CHINA NORMAL UNIVERSITY