• Opto-Electronic Engineering
  • Vol. 49, Issue 11, 220258 (2022)
Kun Zhang1、2, Zijie Ma1、2, Yi Zhou1、2、*, Gaofeng Liang1、2, Zhongquan Wen1、2, Zhihai Zhang1、2, Zhengguo Shang1、2, and Gang Chen1、2
Author Affiliations
  • 1College of Optoelectronic Engineering, Chongqing University, Chongqing 400044, China
  • 2Key Laboratory of Optoelectronic Technology and Systems Ministry of Education, Chongqing University, Chongqing 400044, China
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    DOI: 10.12086/oee.2022.220258 Cite this Article
    Kun Zhang, Zijie Ma, Yi Zhou, Gaofeng Liang, Zhongquan Wen, Zhihai Zhang, Zhengguo Shang, Gang Chen. Silicon-based super-resolution metalens with weak sidelobe[J]. Opto-Electronic Engineering, 2022, 49(11): 220258 Copy Citation Text show less

    Abstract

    Overview: Optical super-resolution lenses have shown great potential in super-resolution microscopic systems and nano-fabrication systems. With the decrease of the focusing spot of the super-resolution lens, it is inevitable that large sidelobes and sidebands will be generated, which will lead to a limited field of view and imaging artifacts. Therefore, when designing super-resolution optical devices, it is necessary to adopt a balanced strategy between focusing spot and side lobe according to the practical applications. Metasurface is a planar structure composed of nanoscale meta-atoms, which can flexibly regulate the amplitude, phase and polarization of the optical field, being beneficial to construct complex super-resolution optical fields. The PB phase meta-atom is comparatively easy to fabricate due to its simplicity. Using Finite-Difference Time-Domain (FDTD) solutions to optimize the size of the meta-atom, we can get a structure with high transmittance. By rotating the angle of the meta-atom, we can achieve linear phase control. The application of PB phase metasurface has been demonstrated in the field of super-resolution focusing devices with suppressed sidelobe. Based on the vector angular spectrum method and particle swarm optimization (PSO) algorithm, a super-resolution point focusing lens with a large numerical aperture and weak sidelobe is optimally designed with a 32-valued phase control at the wavelength of λ=632.8 nm. Based on the silicon-based PB phase metasurface, our metalens was fabricated by electron beam lithography and orthoplastic etching. The lens radius Rlens=57λ, focal length zf=20λ, corresponding to the numerical aperture of NA=0.944. The optical field distribution of the super-resolution metalens was measured experimentally by a large-numerical-aperture microscopy system. The results show that, at the focal plane, the FWHM of the focal spot is 0.45λ, which is less than the diffraction limit of 0.53λ (the diffraction limit is 0.5λ/NA), the side-lobe ratio SR is 0.07, and the depth of focus is 0.4λ. Our proposed metalens can achieve a small depth of focus, a weak sidelobe ratio, and super-resolution point focusing. Our proposed super-resolution metalens bears the potential to realize the miniaturization, lightweight, and integration of super-resolution optical devices or systems.Metasurface is a spatially varying ultrathin nanostructure that has been widely studied and used in optical super-resolution focusing, either in lenses or in systems. However, with the decrease of the focal spot size of the metalens, large sidelobes are inevitably generated, limiting the field of view and potential applications of the lens. In this paper, a method for producing super-resolution metalens with a large numerical aperture (NA=0.944) and weak sidelobe is presented. For a circularly polarized light with the wavelength of λ=632.8 nm, a super-resolution point-focusing with a weak sidelobe is realized based on PB phase regulation of silica-based metasurface. Experimental results show that the FWHM (full-width at half maximum) of our focusing spot is 0.45λ, which is less than the diffraction limit of 0.53λ (the diffraction limit is 0.5λ/NA), and the sidelobe ratio (SR) is 0.07. Our proposed super-resolution metalens bears the potential to realize the miniaturization, lightweight and integration of super-resolution optical devices or systems.
    Kun Zhang, Zijie Ma, Yi Zhou, Gaofeng Liang, Zhongquan Wen, Zhihai Zhang, Zhengguo Shang, Gang Chen. Silicon-based super-resolution metalens with weak sidelobe[J]. Opto-Electronic Engineering, 2022, 49(11): 220258
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