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      Arrayed waveguide lens for beam steering

      1 , 2 , 1 , 3 , 4 , 1 , 2
      Nanophotonics
      Walter de Gruyter GmbH

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          Abstract

          Integrated planar lenses are critical components for analog optical information processing that enable a wide range of applications including beam steering. Conventional planar lenses require gradient index control which makes their on-chip realization challenging. Here, we introduce a new approach for beam steering by designing an array of coupled waveguides with segmented tails that allow for simultaneously achieving planar lensing and off-chip radiation. The proposed arrayed waveguide lens is built on engineering the evanescent coupling between adjacent channels to realize a photonic lattice with an equi-distant ladder of propagation constants that emulates the continuous parabolic index profile. Through coupled-mode analysis and full-wave numerical simulations, we show that selective excitation of waveguide channels enables beam steering with large field-of-views of ∼60°. The proposed arrayed waveguide lens can serve as a compact component in integrated photonic circuits for applications in imaging, sensing, and metrology.

          Most cited references38

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          Light propagation with phase discontinuities: generalized laws of reflection and refraction.

          Conventional optical components rely on gradual phase shifts accumulated during light propagation to shape light beams. New degrees of freedom are attained by introducing abrupt phase changes over the scale of the wavelength. A two-dimensional array of optical resonators with spatially varying phase response and subwavelength separation can imprint such phase discontinuities on propagating light as it traverses the interface between two media. Anomalous reflection and refraction phenomena are observed in this regime in optically thin arrays of metallic antennas on silicon with a linear phase variation along the interface, which are in excellent agreement with generalized laws derived from Fermat's principle. Phase discontinuities provide great flexibility in the design of light beams, as illustrated by the generation of optical vortices through use of planar designer metallic interfaces.
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            Metalenses at visible wavelengths: Diffraction-limited focusing and subwavelength resolution imaging.

            Subwavelength resolution imaging requires high numerical aperture (NA) lenses, which are bulky and expensive. Metasurfaces allow the miniaturization of conventional refractive optics into planar structures. We show that high-aspect-ratio titanium dioxide metasurfaces can be fabricated and designed as metalenses with NA = 0.8. Diffraction-limited focusing is demonstrated at wavelengths of 405, 532, and 660 nm with corresponding efficiencies of 86, 73, and 66%. The metalenses can resolve nanoscale features separated by subwavelength distances and provide magnification as high as 170×, with image qualities comparable to a state-of-the-art commercial objective. Our results firmly establish that metalenses can have widespread applications in laser-based microscopy, imaging, and spectroscopy.
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              Dielectric metasurfaces for complete control of phase and polarization with subwavelength spatial resolution and high transmission

              Metasurfaces are planar structures that locally modify the polarization, phase and amplitude of light in reflection or transmission, thus enabling lithographically patterned flat optical components with functionalities controlled by design. Transmissive metasurfaces are especially important, as most optical systems used in practice operate in transmission. Several types of transmissive metasurface have been realized, but with either low transmission efficiencies or limited control over polarization and phase. Here, we show a metasurface platform based on high-contrast dielectric elliptical nanoposts that provides complete control of polarization and phase with subwavelength spatial resolution and an experimentally measured efficiency ranging from 72% to 97%, depending on the exact design. Such complete control enables the realization of most free-space transmissive optical elements such as lenses, phase plates, wave plates, polarizers, beamsplitters, as well as polarization-switchable phase holograms and arbitrary vector beam generators using the same metamaterial platform.
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                Author and article information

                Contributors
                (View ORCID Profile)
                Journal
                Nanophotonics
                Walter de Gruyter GmbH
                2192-8614
                August 17 2022
                July 12 2022
                September 01 2022
                August 17 2022
                August 03 2022
                September 01 2022
                : 11
                : 16
                : 3679-3686
                Affiliations
                [1 ]Department of Physics , Queens College of the City University of New York , Queens , 11367 , New York , USA
                [2 ]Physics Program , The Graduate Center of the City University of New York , New York , 10016 , NY , USA
                [3 ]Microsoft Research, Microsoft Corporation , Seattle , WA , USA
                [4 ]Department of Electrical Engineering , The City College of New York , New York , NY , USA
                Article
                10.1515/nanoph-2022-0198
                f56fb0c9-3713-418a-acfe-cb4458488935
                © 2022

                http://creativecommons.org/licenses/by/4.0

                History

                Nanomaterials,Nanotechnology,Nanophysics,Industrial chemistry,Materials science
                Nanomaterials, Nanotechnology, Nanophysics, Industrial chemistry, Materials science

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