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Proceedings Paper

High efficiency metasurfaces based on topology optimization (Conference Presentation)
Author(s): Jonathan A. Fan
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Paper Abstract

Metasurfaces are thin-film optical devices that use nanoscale geometric designs to shape the wavefront of electromagnetic waves. In this talk, we discuss how adjoint-based inverse design can be used to produce high efficiency metasurfaces that can efficiently respond to a broad range of incident wave inputs. We discuss two classes of devices. First, we demonstrate periodic dielectric metasurfaces that can support ultra-high efficiency (>90%) anomalous refraction for nearly arbitrary combinations of incident and outgoing angles. Both polarization dependent and independent device configurations can be realized, and the achieved metrics exceed the capabilities of conventional metasurfaces and diffraction gratings based on Littrow mounting by a large margin. Second, we discuss a route towards aperiodic devices. Our general design strategy is to sub-divide the desired phase profile into wavelength-scale sections and use topology optimization to design each of these sections individually. Compared to design schemes that focus on optimizing the entire device at once, our method has clear advantages in scalability and computational efficiency. We show that with our design approach, we can theoretically and experimentally produce high efficiency, high numerical aperture lenses. All of the devices presented here utilize dielectric nanostructures that support strong near-field optical interactions with neighboring structures and non-trivial optical mode dynamics, thereby extending their functionality beyond that of discrete phase shifters.

Paper Details

Date Published: 17 September 2018
Proc. SPIE 10719, Metamaterials, Metadevices, and Metasystems 2018, 107190V (17 September 2018); doi: 10.1117/12.2321232
Show Author Affiliations
Jonathan A. Fan, Stanford Univ. (United States)

Published in SPIE Proceedings Vol. 10719:
Metamaterials, Metadevices, and Metasystems 2018
Nader Engheta; Mikhail A. Noginov; Nikolay I. Zheludev, Editor(s)

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