Topology optimization of freeform large-area metasurfaces

We demonstrate optimization of optical metasurfaces over 10⁵–10⁶ degrees of freedom in two and three dimensions, 100–1000+ wavelengths (λ) in diameter, with 100+ parameters per λ². In particular, we show how topology optimization, with one degree of freedom per high-resolution “pixel,” can be extend...

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Bibliographic Details
Main Authors: Lin, Zin, Liu, Victor, Pestourie, Raphael, Johnson, Steven G
Other Authors: Massachusetts Institute of Technology. Department of Mathematics
Format: Article
Published: The Optical Society 2020
Online Access:https://hdl.handle.net/1721.1/123826
Description
Summary:We demonstrate optimization of optical metasurfaces over 10⁵–10⁶ degrees of freedom in two and three dimensions, 100–1000+ wavelengths (λ) in diameter, with 100+ parameters per λ². In particular, we show how topology optimization, with one degree of freedom per high-resolution “pixel,” can be extended to large areas with the help of a locally periodic approximation that was previously only used for a few parameters per λ². In this way, we can computationally discover completely unexpected metasurface designs for challenging multi-frequency, multi-angle problems, including designs for fully coupled multi-layer structures with arbitrary per-layer patterns. Unlike typical metasurface designs based on subwavelength unit cells, our approach can discover both sub- and supra-wavelength patterns and can obtain both the near and far fields.