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A novel design method of large-aperture metalens and investigation of electrical focus-tuning mechanism with phase shifter structures
Author(s): Ruo-Qian Gao; Qi Song; Jin-Bo Gao; Hai Liu; Xiao-Yi Wang; Xiao-He Chen; Jin-Song Gao
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Paper Abstract

A metalens is the flat and ultrathin surface made of billions of sub-wavelength elements and can bend light like traditional optical lens, which make it attract enormous interests. However, two fundamental issues need to be addressed before metalens can replace traditional lens. First, a large diameter (up-to-cm) metalens is extremely difficult to simulate and optimize, due to the large area, lack of periodicity, and multiple parameters on billions of sub-wavelength elements. Second, to obtain a high-quality image within certain distance, a variable focus length is highly desired in most of modern optical system. In this work, we develop an analytical model based on an optical phased array antenna with the focusing phase profile, and accurately predict the far field radiation pattern for a large-area metalens with significant low computational cost. The beam-width of system and depth-of-focus (DOF) are given with respect to wavelength, element spacing and aperture size. To realize the focus tuning function on silicon metalens, the cascaded PIN junction phase shifters enhanced by Fabry-Perrot cavity are attached to metalens to enable the 2π phase variation. At last, a silicon metalens with a diameter of 400um and a focus of 93um, at 1.55um wavelength is verified in FDTD simulation. The results show that the beam-width, DOF and focus tuning range agree well with the analytical model result. The f/10 axial displacement is achieved with a carrier injection of 1019 cm-3. This focus tuning mechanism could be deployed to many attractive near-infrared applications, such as fluorescence microscopy and LIDAR.

Paper Details

Date Published: 25 October 2018
PDF: 10 pages
Proc. SPIE 10823, Nanophotonics and Micro/Nano Optics IV, 1082307 (25 October 2018); doi: 10.1117/12.2500902
Show Author Affiliations
Ruo-Qian Gao, Changchun Institute of Optics, Fine Mechanics and Physics (China)
Qi Song, Suzhou Institute of Biomedical Engineering and Technology (China)
Soleilware LLC (United States)
Jin-Bo Gao, Changchun Institute of Optics, Fine Mechanics and Physics (China)
Hai Liu, Changchun Institute of Optics, Fine Mechanics and Physics (China)
Xiao-Yi Wang, Changchun Institute of Optics, Fine Mechanics and Physics (China)
Xiao-He Chen, Suzhou Institute of Biomedical Engineering and Technology (China)
Jin-Song Gao, Changchun Institute of Optics, Fine Mechanics and Physics (China)


Published in SPIE Proceedings Vol. 10823:
Nanophotonics and Micro/Nano Optics IV
Zhiping Zhou; Kazumi Wada, Editor(s)

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