Reconfigurable continuous-zoom metalens in visible band

Yuan Cui; Guoxing Zheng; Ming Chen; Yilun Zhang; Yan Yang; Jin Tao; Taotao He; Zile Li

doi:doi:10.3788/COL201917.111603

Chinese Optics Letters, 2019, 17 (11): 111603, Published Online: Sep. 12, 2019

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Yuan Cui ¹Guoxing Zheng ^1,2Ming Chen ³Yilun Zhang ³Yan Yang ⁴Jin Tao ²Taotao He ¹Zile Li ^1,2,*

Author Affiliations

¹ Electronic Information School, Wuhan University, Wuhan 430072, China

² NOEIC, State Key Laboratory of Optical Communication Technologies and Networks, Wuhan Research Institute of Posts and Telecommunications, Wuhan 430074, China

³ Photonics Research Centre, Guilin University of Electronic Technology, Guilin 541004, China

⁴ Integrated Circuit Advanced Process Center, Institute of Microelectronics of Chinese Academy of Sciences, Beijing 100029, China

Figures & Tables

Fig. 1. (a) Working principle of a continuous-zoom metalens. (b) Diagram of a nanobrick unit structure. Each nanobrick was designed with length $L = 140 nm$ , width $W = 70 nm$ , height $H = 350 nm$ , and cell size $C = 300 nm$ at an operation wavelength of 633 nm. $ϕ$ is the orientation angle of the nanobrick, and the incident light propagates along the $z$ -axis direction. (c) Schematic diagram of one of the designed GEMSs. (d) The co-polarization and cross-polarization transmissivities of a nanobrick. The simulation was run by normally illuminating a nanobrick with a beam of CP light and under the boundary condition of a period.

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Fig. 2. Focal length of the metalens as a function of the mutual rotation angle between two GEMSs. With LCP incident light, the metalens acts as a positive zoom lens and its focal length changes from +∞ to nearly zero like the blue curve. When the incident light is switched to RCP, the metalens becomes a negative one, and its focal length ranges from −∞ to nearly zero. In this example, the metalens dimension is $30.3 μ m \times 30.3 μ m$ , the constant $a$ is $0.1 {μ m}^{- 2}$ , and the operation wavelength is 633 nm.

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Fig. 3. Simulation of a zoom metalens. Full-wave numerical simulations were performed by FDTD Solutions for the propagation of LCP incident light. (a)–(c) Intensity of the electric field along the direction of light propagation ( $z$ axis) corresponding to $θ = 30 °$ , 45°, and 75°, respectively. The back surface of the metalens is placed at $z = 0 μ m$ .

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Fig. 4. Simulation results at the focal plane of the metalens. (a)–(c) Intensity of the electric field at the cross-section of the focal plane corresponding to $θ = 30 °$ , 45°, and 75°, respectively. The Airy disks marked by white curves are calculated with the diffraction limit principle, and their radii are 2.42 μm ( $θ = 30 °$ ), 1.61 μm ( $θ = 45 °$ ), and 0.97 μm ( $θ = 75 °$ ), respectively.

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Fig. 5. Simulation of a zoom metalens. (a), (b) The simulation domains show the distribution of phase along the direction of light propagation ( $z$ axis) for $θ = 75 ° (f = - 37.9 μ m)$ and $θ = 30 ° (f = - 94.8 μ m)$ , respectively. (c), (d) Compared with the negative focal length case, the simulation domains show the phase distribution of $θ = 75 ° (f = 37.9 μ m)$ and $θ = 30 ° (f = 94.8 μ m)$ with LCP light incidence.

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Fig. 6. A variation tendency of the focal length for the corrected metalens. (a)–(d) Intensity of the electric field along the direction of light propagation ( $z$ axis) corresponding to $θ = - 90 ° (f = + \infty)$ , $θ = - 45 ° (f = 63.1 μ m)$ , $θ = 0 ° (f = 31.5 μ m)$ , and $θ = 45 ° (f = 21.0 μ m)$ , respectively. The corrected metalens is illuminated by a beam of LCP incident light.

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Yuan Cui, Guoxing Zheng, Ming Chen, Yilun Zhang, Yan Yang, Jin Tao, Taotao He, Zile Li. Reconfigurable continuous-zoom metalens in visible band[J]. Chinese Optics Letters, 2019, 17(11): 111603.

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